Science topics: Chemistry
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Chemistry - Science topic

Chemistry is the science of matter, especially its chemical reactions, but also its composition, structure and properties. Chemistry is concerned with atoms and their interactions with other atoms, and particularly with the properties of chemical bonds.
Questions related to Chemistry
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I am writing my thesis about metabolomics, and after reading about metabolites and proteins and how these have been measured through time for characterization and kinetics, I think metabolomics could be the one analytical technique that enables universal measurement of all intracellular, and possibly extracellular molecules. Even proteins with intact protein mode, for example. Maybe I'm too naive and inexperienced, and saving for some differences to enable separation (column chemistry), and ionization (ESI v APCI v direct injection), what are your thoughts on this statement?
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Hi Luis, metabolomics studies the metabolome in a top-down, experimental manner. The metabolome comprehends the whole ensemble of small molecules, with grey limits within biological oligomers. Proteins, genes, transcripts, are not part of the metabolome, neither lipids or glycans in my opinion. While MS or NMR can/will 'virtually' be able to obtain information about any molecule, for sure it will not be in a high-throughput manner, measuring everything at the same time. In fact, metabolomics is the least high-throughput omic technique where robust bioinformatic pipelines are still under development when compared to proteomics, genomics, etc. Many analytical techniques are 'the true' technique to answer the problem to which the technique is focused to retrieve data valuable to be evaluated.
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I understand vaguely that the first author is supposed to be the one who "did the most work", but what counts as "work" in this comparison? Does "most" mean "more than all the other coauthors together" or just "more than any other coauthor"? What happens when the comparison is unclear? How often is "did the most work" the actual truth, versus a cover story for a more complex political decision?
I realize that the precise answer is different for every paper. I'm looking for general guidelines for how an outsider (like me) should interpret first authorship in your field. Pointers to guidelines from journals or professional societies would be especially helpful.
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As the contributions in this thread are documenting, there are obviously some highly emotional aspects concerning author's lists...
In my field, typically the first author is the one who did most of the work and I never really understood the discussions about the ranking after place 1. I am always happy if everyone is included who contributed with anything and alphabetical order is ok for me.
The world would probably better if we could put away our vanity more often.
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Considering the context of the COVID-19 pandemic that requires remote teaching activities. In the case of Chemical Education, which requires a high degree of abstraction and the use of visualizations can effectively contribute to the student's learning process, how does the teacher deal with the relationship of macro, micro and symbolic representations, in online teaching?
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I agree with your suggestion Yacine Lafifi , I think having an experience with MOOC helps to understand the online teaching process and can focus on specific aspects of the chemistry content. We can also be combined with face-to-face activities when possible. Exploring different visual aids.
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kindly give the software details and download link
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Endnote
Mendely
Origin
ChemDraw
Docking
Rstudio
Matlab
there are many soft wares, it depends on your work.
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Much has been said about the differences between physics and mathematics, but less attention has been paid to the differences between physics and chemistry.
The question is, where does physics and chemistry work?
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After reviewing the answers so far:
The question was interesting but ignored.
I still like this question.
It would be interesting to explore the differences between physics and chemistry.
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As a requirment in my project, I have to synthesize Formamidinium bromide (FABr). According to the protocols which are mentioned in the articles, I've synthesized this material but I think there is an error in my work?
Does anyone has the experience of this synthesis?
Because in the articles, the authors don't express all the steps, I want to know if there is any critical strategy during the synthesis of FABr and specially in the purification stage of this process.
I would appreciate if you point out a reliable article which has mentioned all the stages of this synthesis with it's details.
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Dear Reads Nima Tabatabaei Rezaei,
Have you tried the way I propose to go ahead for the same? Just try it.Somebody has done and successfully got some very interesting synthesis results.
Because of the good thermal stability and superior carrier transport characteristics of formamidinium lead trihalide perovskite HC(NH2)2PbX3 (FAPbX3) has been considered to be a better optoelectronic material than conventional CH3NH3PbX3 (MAPbX3). The FAPbBr3 photodetector’s responsivity to two-photon absorption with an 800-nm excitation source can reach 0.07 A W−1, which is four orders of magnitude higher than that of its MAPbBr3 counterparts. Materials such as Formamidine acetate, lead bromide (PbBr2, > 98%) and hydrobromic acid (48 wt% in water), Gamma-butyrolactone (GBL) and N,N-dimethylformamide (DMF) may required for synthesis.
Formamidinium iodide (FAI) and formamidinium bromide (FABr) can be synthesised by dissolving formamidinium acetate powder in a 2x molar excess of 57%w/w hydroiodic acid (for FAI) or 48%w/w hydrobromic acid (for FABr). FABr can be synthesized by slowly dropping 10 mL hydrobromic acid into 50 mmol (5.205 g) formamidine acetate in a flask, accompanied by continuous stirring at 0 °C for 2 h under argon atmosphere. The product FABr was formed once the solvent was removed using a rotary evaporator at 70 °C. The crude white powder was dissolved in ethanol and subsequently reprecipitated in diethyl ether. Then, the filtered product was dried at 60 °C in a vacuum oven for 24 h for further use.
Ashish
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Hello,
I need to impregnate the pores of a MOF with cu(acac)2, which I will then reduce under vacuum to copper nanoparticles. I plan on using the incipient wetness approach to do so. However, my MOF will not be in a powder form, but rather a self supported, fibrous mat form ( ). According to my current research, the solid support catalyst (MOF) is typically stirred as the metal precursor solution in chloroform (or other solvent) is added to it, yielding a paste. However, I cannot stir my fibrous mat. Will simple immersion of my mat in the metal precursor solution be sufficient to impregnate the pores of the MOF with the precursor? Or would a drop-wise method of adding my solution work without stirring the MOF? Is there another way around this issue?
Thank you for any answers!
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Claire Boyer I think that simply soaking the fibrous mat in a solution of Cu(acac)2 in dichloromethane over night will be sufficient to impregnate the pores of the MOF with the copper precursor. As suggested earlier, use dichloromethane instead of chloroform to dissolve you Cu(acac)2.
P.S. When other RG members help you by answering your questions, it is polite and a good practice on RG to recommend their answers.... 😎
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Does anyone know of, or use, commercially produced surfaces for contact measurements (control material)? As an example, is there a producer of PTFE discs with highly controlled surface roughness and chemistry that I can purchase? I have not found any....
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Dear Michael Pujari-Palmer, why don't you use directly AFM for contact measurement? My Regards
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Several studies on combustion of bio diesel/petroleum fuel blends in IC engines and other power generation / combustion devices discussed extensively about the influence of fuel unsaturation on NOx emissions. A fundamental question arises on how we quantify fuel unsaturation?
I would like to start a discussion on the topic - How to quantify fuel unsaturation ? what would be an appropriate index to quantify unsaturation irrespective of the family of origin of fuels - like methyl esters, ether, alcohol , alkanes, alkenes, alkynes or aromatics or a weighted combination of aforementioned categories.
Our research group's take on this -
We have established a parameter - Degree of unsaturation that serves as a common platform across different fuel families (esters/alkanes/aromatics) to quantify the effects of fuel unsaturation, particularly with petroleum/bio-diesel blends. DOU can be evaluated based on the average molecular formula of the fuel alone without involving complex and expensive experimental procedures such as those involved in the measurement of iodine number and bromine number.
If interested, please follow the link to access the research work we have conducted at our laboratory to investigate the effect of fuel unsaturation on nitric oxide emissions.
Message me to get a copy of this article.
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Dear Ana
If you intend to determine all double bonds (including aromatic, carbonyl and etc) I recommend using the NMR analysis, although you will need a specific lab, this equipment is usual in chemical departments.
Some articles may help you with this problem.
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I am wondering why some stains do not work by themselves and absolutely need to be paired with a counterstain to work. What is the chemistry behind this process? Is there a nice book that explains this process in depth?
Thank you very much for your answer in advance.
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Hi Alida, this is a really good question. I think that the basis for this is the combination of basic and acidic dyes to stain acidic/basophilic, and basic/acidophilic molecules in tissue, respectively. I realize that your question is really asking why some stains won't work without their counterpart. I know that you must use basic dyes before acidic dyes, and alcohol before aqueous, otherwise staining will not work. I suggest Animal tissue techniques (A Series of books in biology) 3rd ed. by Gretchen L Humason. It was published in 1972, but is still one of the best histology books I've ever seen. You can get it on amazon for about $10, ISBN-10: 9780716706922 .
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Hello researchers,
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Hello everyone,
I do calculations on compounds with about 25-30 atoms (hydrogen, carbon, oxygen) and about 110 electrons in a water solvent (SMD solvation model). These are optimizations and frequency calculations. I'm searching for the best reference method I could compare results with. These systems are being calculated with B3LYP/6-311**G(d,p), B3LYP/aug-cc-pVDZ and B3LYP/aug-cc-pVTZ.
I was thinking about CIS/6-311++G(d,p) but have found it's not the best pick - it's barely accurate when calculating frequencies. So I came up with an idea to recruit CCSD/cc-pVTZ, though three things are running through my head:
  1. I don't want calculations to run for more than 1 week (I do use 4 processors and 40GB; can try to increase it slightly)
  2. Because of the number of hydrogen bonding I find diffusion function necessary, though adding them to the reference method may demand much more time and computational resources in order to be calculated. How to bypass this problem?
  3. Maybe just use CCD/aug-cc-pVTZ? However, how long will it be calculating?
  4. Or just use optimized geometry from B3LYP/aug-cc-pVTZ level as a starting one, and then perform CCSD(T)/aug-cc-pVTZ with frequency and optimization calculations.
The main problem arises from the technical features of the computer I'm using and time. What's is your opinion? Maybe use something completely different?
Thank you.
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If you were using Gaussian09, you might wanna try b97d3 or wb97xd functional which includes a better dispersion correction.
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Morpholine acetate is one of the ionic liquids I need to know about, but I couldn't find it. Is there anybody who can help me?
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Try Zinc15 or VulcanChem (https://www.vulcanchem.com/) Or a vendor listed on PubChem. They are usually more responsive than others found on the Internet.
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Dear Scholars
I was wondering if anyone can recommend a publication on crude oil chemistry - particularly on SARA (Saturates, Aromatics, Resins, and Asphaltenes) classifications.
Thanks.
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I am working for PEM fuel cell cathode material. I am confused regarding the onset potential determination for my catalyst (CV attached, fig 1 is complete CV while fig 2 is its zoom image for clear understanding of change in reduction curve direction) and also why the reduction starts from 0.8e-4 A instead of 0 A. I performed this CV in calomel electrode under oxygen in 0.5M H2SO4.
i) If I use Argon and overlap both the graphs then probably the curves start to separate at around 0.58V.
ii) I have read in some discussions to consider the onset potential at which current density approaches 0.1mA/cm2 while in other discussion, I have read to consider 20microA/cm2 as onset potential. If I plot LSV curve for current density (instead of current) vs potential , then in first case (0.1mA/cm2), it would be 0.785V while in second case (20microA/cm2), it would be 0.775V
iii) If I only consider the point from where curve starts to change the direction of reduction peak, it would be o.64V or 0.56V
iv) if I draw tangents then this would be around 0.5V.
So please help me in i) analyzing onset potential ii) guide me why there is positive current in the reduction peak iii) i also don't know what does the background correction mean and should I need to do it for my CV? All potentials are measured in SCE.
So please help me to analyse onset potential in the best way and also guide me why there is positive current in the reduction peak. All potentials are measured in SCE.
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@Muhammad Shoaib thanks for asking this question. The answers here my mind to a greater extent.thanks
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In our field of research (chemistry), successful PhD research often requires a lot of experimental work in the laboratory. The completion of a PhD usually takes between 3 and 5 years. What's the duration of a PhD in your area?
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It depends on the topic and process of the university and the cooperation of supervisors as well.
Approximately 3-4.
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As you know, a time crystal shows oscillations with a period longer than the driving force. Is it possible to use this feature in molecular machine synthesis? Does this provide any advantages to molecular machines?
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With precise oscillatory pattern much less perturbed by external stimuli, it can act as precise "timing" device without any internal electronics and piezoelectrics (only external laser pulses would be enough). The molecular machines with sustained fixed rotational speeds (e.g. molecular analogue of synchronous motor) can be made this way. If time crystal is made of quantum-entangled particles, the entanglement would be more robust and less prone to decoherence instead of external perturbations, using them as quantum level memory element- but rather the memory would be volatile-as continuous external energy has to be applied to keep the time-crystal tendency going. The pulse, if can be coupled with delocalized electron system of an organic molecule, can provide pulsating electronic excitation (which may be tailored by attenuation/amplification with certain functional groups). Samely, phase modulation of pulses can create a much robust and compact phased array, that is far more thermal oscillation insensitive and more importantly, can circumvent centrosymmetry constraints and requirement of enough molecules to construct a reasonable periodicity of a piezoelectric crystal. However, if pulsating device with a few molecules can be constructed, then this aspect of time crystals can be greatly diminished. Last but not the least, some very common biochemically relevant ionic compounds (e.g. Monoammonium phosphate) show time-crystal behaviour, such crystal surrounded in hydrophobic (inside) transparent micelle (possibly overall amphiphilic) in presence of a biological or external optoelectronic field can drastically alter standing waves-system in-vivo, possibly in an unexpected manner (note constructive and destructive interference are only half/quarter wavelengths apart). A nano-phased array of optical system can modify such response quite dramatically. (such time crystal can be designed to keep working on harnessing nonequilibrium biochemical environment as well)
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So I have some pH = {4, 7, 10} standard buffer solutions from Fisher Scientific. But they must have went bad or I must have contaminated them because when I try to calibrate my pH meter to 4 using the pH 4 standard buffer solution, it calibrates the pH meter to 2 which obviously isn't right because it should be 4 so I can't trust the standard buffer solutions!!!
I need to do some experiments which require that I accurately calibrate the pH meter which means I can't titrate the standard buffers with HCl or NaOH. I have to know the exact quantities. Might seem a little over-the-top, but I want to be really certain about the math.
I intend to prepare my own calibration standards using exact quantities of chemicals. Total concentration should be 0.1 M, volume needs to be 100 mL. I think 0.1 M is a good choice because that should have low ionic strength and not much crazy debye-huckel variations in pH.
I am pretty certain that I know how to prepare a pH = 4 standard buffer solution using acetic acid and sodium acetate. But I am not quite sure how to prepare a pH 7 standard.
First of all, is this exactly how I should prepare a 0.1 M acetate buffer in 100 mL?
According to pubchem the pKa of acetic acid is 4.76. I have a chem textbook which tells me that the pKa is 4.74. Not much difference so I will assume pubchem is right.
HA + H2O --> A- + H3O+
Acetic Acid + H2O --> Acetate + H3O+
Henderson-Hasselbalch Equation: pH = pKa + log([A-] / [HA])
pH = pKa + log([Acetate] / [Acetic Acid])
= 4.76 + log([Acetate] / [Acetic Acid])
For the total concentration:
[Acetic Acid] + [Acetate] = 0.1 M
The simultaneous solution to these equations is about:
[Acetic Acid] = 0.0852 M
[Acetate] = 0.0148 M
pH = 4.76 + log(0.0148 / 0.0852) = 3.9998 etc ... Pretty much exactly 4!
I have glacial acetic acid and sodium acetate.
Glacial Acetic acid is a pure liquid so its concentration is its density / (Formula Weight)
[Glacial Acetic Acid] = [(1.05 g/mL) / (60.05 g/mole)] * (1000 mL / 1 L) = 17.5 M
Basic Dilution Equation:
Initial Volume = (0.0852 M / 17.5 M) * 100 mL = 0.487 mL glacial acetic acid in 100 mL total volume.
Sodium Acetate --> Na+ (aq) + Acetate- (aq)
grams sodium acetate = (0.0148 moles sodium acetate / L) * (82.03 grams sodium acetate / 1 mole sodium acetate) * (1L / 1000 mL) * 100 mL = 0.121 grams sodium acetate
So I can exactly prepare a pH = 4 is 0.1 M acetate solution by adding 487 microliters of glacial acetic acid & 0.121 grams sodium acetate to 100 mL volumetric flask, and bring the volume up to 100 mL with ultrapure deionized water? Swirl to mix.
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I am confused about how to prepare an exactly pH = 7 phosphate buffer solution.
I know the step wise dissociation of Phosphoric Acid. But the problem is that I am not certain about the second dissociation constant.
H3PO4 --> H2PO4- (aq) + H+ (aq)
H2PO4- (aq) --> HPO42- (aq) + H+ (aq)
If I know the second dissociation constant of phosphoric acid I could figure out exactly how to make a pH = 7 standard 0.1 M phosphate buffer solution using phosphate salts.
My undergrad general chem text book is telling me the second Ka is 6.2 * 10^(-8) or the pKa is 7.208 and pubchem is telling me the second the second pKa is 7.09.
Thus I could use the Henderson-Hasselbalch Equation again with the total concentration to figure out the exact quantities. But I am not certain about what the second pKa of phosphoric acid is! Are undergrad chem textbooks just wrong? That's too much of a margin of error.
pH = pKa + log[(K2HPO4) / (KH2PO4)]
Also I was wondering if a 0.1 M solution of NaCl would have a pH of EXACTLY 7? Would it be more or less accurate than making the phosphate buffer?
NaCl is formed by the titration of a strong acid HCl with a strong base NaOH. Therefore the equivalence point of the titration of a strong acid and strong base should yield a pH 7 of neutrality forming NaCl.
So if I dissolved NaCl in water to yield a 0.1 M concentration would the pH be just as good as making that phosphate buffer solution?
I also need to figure out how to make a pH = 10 standard buffer solution.
Any advice? Can you make my life easier?
Thanks so much!
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There must be some problem with the pH meter then.. U should show it to a technician so that it can be fixed.
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We are planning to extract phosphorus from biochar by organic acids. If anyone has some procedure (concentration of organic acids & steps) please inform.
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@ Chandra, please have a look of the attached file.
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#COVID-19
Coronavirus Covid-19: Current Research. Open Access Publications Chemistry in Coronavirus Research: A Free to Read Collection from the American Chemical Society
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Can have a look - on the attached manuscripts
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I have extracted Manganese dioxide from zinc-carbon battery in order to prepare Manganese fertilizer . but it never dissolve , Why ??
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Please check the following link, I hope this can help:
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A biosafety level is the level of the biocontainment precautions required to isolate dangerous biological agents in an enclosed facility. The levels of containment range from the lowest biosafety level 1 to the highest at level 4. In the United States, the Centers for Disease Control and Prevention (CDC) have specified these levels. In the European Union, the same biosafety levels are defined in a directive. Sabanci University is following the same directive in accordance with Turkish biological safety regulation.
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I've made a synthesis in French a few months ago. Hope it will help.
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I recently read:
"The perovskite solution for the solvent quenching method (MAPI) recipe was prepared by dissolving 553.2 mg PbI2 and and 181.23 mg MAI in 1 ml anhydrous DMF/DMSO (4:1, v:v) to obtain a 1:0.95 molar ratio solution (PbI2:MAI) with a concentration of 42.96 wt %."
How can one get 553.2 mg of PbI2 and 181.23 of MAI (CH3NH3I) to be dissolved in 1 ml solution to obtain a 1:0.95 molar ration solution when the molar mass for PbI2 and MAI are 461.01 g/mol and 158.97 g/mol respectively.
I am confused. Thanks for the help in advance.
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I highly agree with the opinion reported by Frank T. Edelmann
Regards
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I'm interested in reading about popular research being conducted in the organic chemistry world. Any ideas where to start?
May we design intelligent reactions or intelligent reactant?
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some the hottest topics right now in organic chemistry research :
Synthesis of Chemical lead compounds to control COID-19
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Some studies reveal that SARS-CoV-2 virus activity can be mitigated at the alkaline pH medium (above pH= 7.5). Any explanation about the mechanism or the Chemistry behind this phenomenon.
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The virus uses several protease enzymes, they are particularity sensitive to pH changes .
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Cheers Everyone.
I was seeing some uses of ionic exchange to recover NH4 by ionic exchange with other cations in a specific matrix. And it brought me to question what drives an ionic exchange to be better towards an ion in solution and not so good to another?
I thought maybe the charge of the cation would influence but maybe is not so relevant as here K and Ca are ahead of Na and Mg. Maybe the hydration radius as an important role in it instead? And can pH of the solution where ionic exchange is done affect also the selectivity of the ionic exchange knowing it can affect the lattice charge of the matrix?
Is there a way we can estimate this? or just by trial?
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Mostly pH is affected.
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I need to download a chemistry book the original version in English and translated into Arabic that can help me , it is very importante
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Dear crystallographers I have synthesized and crystallized a compound but after the XRD study i found out that the crystal structure of this compound already exists (the attached file A is my structure B is that of literature) but i noticed some differences :
- My structure's volume is large by around 7.6 A - some minor difference in cell parameters. - Clear difference in R1 (mine is better). - Difference in number of asymmetric units Z'.
My questions are: - Is my structure considered as a new structure ? - Can i publish it ? i have another structure (3rd one ) of the same compound but with a solvent inside the cell - Can i publish both structures (A and the 3rd structure ) in same article as new polymorphs ? ps: attached files: projection along the C axis of both structures with parameters Thank you in advance
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Dear Oussama,
From this picture I cannot state with certainty if it is the same structure (= the same molecule with the same crystal packing) or not, because the representation is different. The coordinates of the atoms are chosen differently with respect to the origin in A and B. You can probably shift your atoms in the unit cell so that the two structures look more similar.
From the unit cell it seems the same structure: the difference in volume is "negligible" and the different reported Z, Z' is likely due to a different definition of the moiety formula or sum formula.
But, in principle, the unit cell is not enough to decide if it's the same structure. As suggested, you can compare the simulated powder patterns. I also suggest to carefully compare the crystal packing by analyzing the intermolecular contacts and examining a bigger packing range (like for example 2x2x2 unit cells). Some programs also allow to overlay two crystal structures, to visually compare them.
In any case, you can most probably publish your structure along with the solvated form, with more focus on this latter, as it is new. Compare if there are real differences with the literature structure, for example, were they measured at the same temperature? Any conformational differences? I suggest you adopt the same atom labelling names and the most similar setting to the published structure, in order to facilitate the comparison both for you and for the readers.
Best wishes,
Arianna
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In the age of Covid19, is there a basic conflict between science and superstition in the discipline of medical knowledge? Are there some simple, sensible, robust and reasonable ways to distinguish a scientific statement (or fact) from a superstitious statement?
To stay focused, the topic will concentrate on science versus superstition in the scientific discipline of medicine. We will try our very best to stay focused and not stray off track. it is very easy to wander off message and be all over the map. i will try to summarize the key conclusions from time to time.
In the age of the Corona Virus, there are so many statements out there. The statements may not be scientific. But if they are not scientific, are they false? Are they fake? Are they simply statements based on superstition.
What should we do if people believe in statements that are not based on science? Should we be polite and tolerate their beliefs?
As long as people do not harm others, then from society’s point of view, the fact that people hold non-scientific hypotheses is probably benign. However, the trouble starts when the same people act these beliefs, and then cause harm to others. The question arises: what should society do in this case?
Based on the discussion, there are two assumptions and four categories.
Assumption1: Beliefs cannot be justified or unjustified.
Assumption2: hypotheses can be disproven
Scientific hypotheses that are based on justified facts in natural causation. Or scientific hypotheses have not been disproven (I prefer the negative formulation because we may never be able to prove anything but we are unable to disprove it.)
Since science cannot give a definitive answer, there are many competing answers that merit our attention, and we may not be able to select among them.
Non-scientific hypotheses are unjustified facts that may be “proven” in the future with better evidence and facts.
Pseudo-scientific hypotheses: not sure where these fit in?
Superstitions are unjustified beliefs in supernatural causation.
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Joseph Tham, thanks for a thought provoking question. I think we should tolerate and respect beliefs and ideas that are not considered scientific. Our intolerance of such beliefs and ideas could be the result of a lack of understanding of the science behind them. We should therefore subject them to rigorous testing using the scientific method. A practical example is the fact that the World Health Organization has not dismissed out of hand the herbal remedy from Madagascar that is claimed to prevent illness from COVID-19. Instead the remedy is going to be tested using established scientific principles. The null hypothesis can then be rejected or accepted. This is how Indigenous Knowledge Systems contribute to scientific advancement.
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chemistry is one of an interesting science in the world. but in most developing country student is nit prefer to learn chemistry. i mention the most two cases: in developing country mostly no laboratory accumulation, and there is no reference materials and so on.
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Sometimes it is just but a misconception and a result of peer pressure. Such students require alot of motivation for a positive attitude to the subject.
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When a piece of copper foil is placed in a test tube of iron(III) chloride solution? Fe goes from Fe3+ to Fe2+ and Cu2+ goes to Cu. Both are being reduced?
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Dear
Bram Kuijer
, in such redox reactions, it is not possible that all reagents are being reduced. Oxidation and reduction must always take place simultaneously. In this case., the metallic copper is oxidized by iron(III) chloride, i.e. FeCl3 is the oxidizing agent which is itself being reduced to Fe2+. On the other hand, you start with metallic copper (Cu0), which is the reducing agent. During the reaction, Cu0 is oxidized to Cu2+, i.e. the copper foil slowly dissolves.
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I come across many reactions like A + B --> products.
How to consider "products" as a species and solve the kinetics in simulation/modelling, as such the reaction is unbalanced by logic of chemistry.
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Hi there,
Additionally to Fache Axel answer please check the paper: A Kinetic Study of OH Radical Reactions with Methane and Perdeuterated Methane by James R. Dunlop & Frank P. Tully.
Best
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Any thoughts and recommendations on good articles, textbooks and resources on the topic of permanent magnet materials (e.g. neodymium) in terms of phenomena associated with their ageing and degradation under temperature, chemical, mechanical and electrical/electromagnetic stressing.
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Herbst, J. F., and J. J. Croat. "Neodymium-iron-boron permanent magnets." Journal of magnetism and magnetic materials 100, no. 1-3 (1991): 57-78.
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Hello everybody
I want to simulate MXene by means of molecular dynamics method. But it seems that I need the Mxene atomic structure as a file in .cif, .pdb, or .mol format.
Is it possible for anyone to tell me how I can get the files or how I can build the atomic structure of MXene?
Thank you so much
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Hi Saeed,
If you have the top view and side view of the MXene, with dimensions present on the figure, you can make the system. The top view and side view of relaxed MXene systems should be available online.
Also, if you have the atomic coordinates for a unit cell, you can use the lattice vectors to make large supercells.
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Biological techniques are methods or procedures that are used to study living things. They include experimental and computational methods, approaches, protocols and tools for biological research.
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At both very high and very low water activities, lipid oxidation rates are high compared to the rate at intermediate water activities. What can explain this trend?
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The relationship between rates of lipid oxidation and moisture is complex. The amount of water, the water activity and the state of water in a food, along with other factors, must all be considered.
For most fresh or tissue foods that have moisture contents between 60 - 95% have a water activity very close to 1.T he mode of deterioration at this water activity is generally microbial or enzymatic in nature. Direct lipid oxidation (i.e. not enzyme-mediated) is not an important source of deterioration at this high water activity since other modes of degradation will deteriorate the food first.
Concentration, freezing, and drying are mechanisms by which the water activity of food can be reduced. Such processes may bring the food into the intermediate moisture or low-moisture region where direct lipid oxidation becomes a more important mode of degradation. Also, during dehydration, free radicals can be formed which accelerates lipid oxidation. Freezing can also lead to the acceleration of lipid oxidation rates through the concentration of substrates and catalysts in the unfrozen portion of the system.
On the other hand, Chou et al. (1973) found that water activity primarily affects matrix swelling and thus substrate/reaction site availability as well as catalyst mobility.
Hereinbelow the tow common theories related to the relationship between water activity/content and lipid oxidation are briefly discussed:
Monolayer theory
Unlike most aqueous chemical reactions, the rate of lipid oxidation that takes place in the oil phase is observed to increase as water activity is decreased below the monolayer (i.e. water molecules that are bound tightly to the food surface). This can be explained by considering the role of water in this reaction. It has been suggested that the monolayer of water—or rather, the water saturation of polar groups in lipids—is necessary to cover the surface of the lipid, preventing it from direct exposure to air. This monolayer is essentially “bound” water with limited mobility and is assumed to not participate in chemical reactions. Several studies have found that a variety of foods are most stable to lipid oxidation at a relative humidity or aw consistent with the monolayer.
On the other hand, water can form a hydration sphere around metal catalysts such as Cu, Fe, Co, and Cd. In the dry state, the metal catalysts are most active. As water activity increases, the metals may hydrate which may reduce their catalytic action thus slowing the rate of lipid oxidation.
This monolayer theory, however, cannot be applied universally.
Glass transition theory
According to the glass transition theory, one important function of water is its ability to act as a plasticizing agent. The plasticization of a matrix involves swelling of the polymer matrix when moisture is increased. The resulting increase in free volume might allow for faster diffusion of substrates in the aqueous phase which may lead to faster reaction rates. Plasticization may also increase the contact of the absorbed aqueous phase with the lipid phase. The number of catalytic sites increases such that the rate of lipid oxidation increases.
The above discussion shows that water plays both protective and prooxidative roles in lipid oxidation. In some foods at low aw near the monolayer moisture content, water is protective, presumably because it provides a barrier between the lipid and oxygen.
While the classic food stability map proposed by Labuza et al. (1972) shows lipid oxidation having a U-shaped relationship to aw, no U-shape was also observed; lipid oxidation actually slowed as aw increased as the case of freeze-dried food.
Overall, monolayer and glass transition concepts might not effectively predict lipid oxidation reactions in some foods if oxidation is primarily occurring in the lipid phase and thus would not be significantly impacted by water and the physical state of proteins and carbohydrates. On the other hand, water can play a major role in lipid oxidation chemistry if reactions are primarily promoted by water-soluble prooxidants such as metals. Unfortunately, the causes of lipid oxidation in low-moisture foods are poorly understood, which could be why measurements of water activity, monolayers, and glass transitions do not consistently predict lipid oxidation kinetics.
Sources:
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12 answers
Many efforts are spent to prevent, treat and stop COVID-19 spread.
but I think these efforts are fragmentary and not organized.
there is no platform for a scientific collaboration that could shorten the time of interesting findings, some nations hide some facts are a privilege of authorship or for other political reasons.
I think that all countries should a global platform for scientific collaboration.
Personally I have some ideas that could be proposed for the treatment of COVID-19 based on scientific facts but with the innovative mode of application, how and where can I try to apply them?
All nations should avoid wasting their time to find a solution for COVID-19 without international collaboration.
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Thats a very good idea to unite and make joint efforts to defeat the pandemic the world is suffering.
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4 answers
How to deal with this problem?
Example I have 10 sample, and I use duplo method. And we have a target for our sample's CV is under 5%
In the 7th sample, the coefficient of variance is more than 5%, but it happened only in the 7th sample. In this case, another sample is fine (CV less than 3%).
Do you have any idea what is going on?
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Flow measurement can be performed with different methods. Accuracy of reading may depend on different factors like samples water etc.
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37 answers
The SARS-CoV-2 genome was rapidly sequenced by Chinese researchers. It is an RNA molecule of about 30,000 bases containing 15 genes, including the S gene which codes for a protein located on the surface of the viral envelope (for comparison, our genome is in the form of a double helix of DNA about 3 billion bases in size and contains about 30,000 genes).
Comparative genomic analyses have shown that SARS-CoV-2 belongs to the group of Betacoronaviruses and that it is very close to SARS-CoV, responsible for an epidemic of acute pneumonia which appeared in November 2002 in the Chinese province of Guangdong and then spread to 29 countries in 2003.
A total of 8,098 cases were recorded, including 774 deaths. It is known that bats of the genus Rhinolophus (potentially several cave species) were the reservoir of this virus and that a small carnivore, the palm civet (Paguma larvata), may have served as an intermediate host between bats and the first human cases.
Since then, many Betacoronaviruses have been discovered, mainly in bats, but also in humans. For example, RaTG13, isolated from a bat of the species Rhinolophus affinis collected in China's Yunan Province, has recently been described as very similar to SARS-CoV-2, with genome sequences identical to 96 percent.
These results indicate that bats, and in particular species of the genus Rhinolophus, constitute the reservoir of the SARS-CoV and SARS-CoV-2 viruses.
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The Sarbecoviruses (SARS and SARS-related beta coronaviruses) are a faily diverse clade of coronaviruses. Merbecoviruses (MERS and MERS-related beta coronaviruses) are another clade with similar diversity. The SARS-CoV-1 and SARS-CoV-2 sarbecoviruses are quite distant from each other.
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5 answers
Hello,
So I have conducted an experiment looking at the size of silica nanoparticles. However, the results I obtained showed that at a lower mass concentration of SiO2, the volume and radius of individual particles are greater than that of higher SiO2 mass concentration.
I can't seem to find an explanation regarding this and was thinking that at lower mass concentration the individual particles colliding somehow caused them to agglomerate together causing the bigger particle size.
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It may be due to aggregation, use stabilizing agents to reduce aggregation.
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4 answers
Dear researchers,
I have some salt solution analysis.
I want to know is there any software to estimate the scale deposition thickness in a specific time period on a metal plate at a known temperature (like a stainless steel heat exchanger)
I want to predict the scaling thickness in evaporative and non-evaporative condition.
Thanks.
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I see some very good answers - we do the estimation by measuring the change in thermal conductivity of the space. The measurement can be more meaningful if you know the composition of the mineral deposit. The thermal conductivity of common water system scales is known. If the accumulation is, in fact, deposited, not grown in place - then the thermal conductivity model would be more relevant within repeated accumulation/settling of solids in that location.
Thermal conductivity is an accurate means of measuring the relative thickness but the results are more material with repeated measures or an accurate knowledge of the physical and chemical composition of the matter of interest.
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Seems like a silly question but I'm having trouble with searching for CIF files via https://www.ccdc.cam.ac.uk. I've used it before but I was on university campus so I think I was able to use more than just the simple search function. I think I used structure search before and I was able to type in the compound name and the structural formula to get a CIF file, but now as I'm working from home, I don't have a CCDC licence and so I'm restricted to just the simple search. I've tried just typing in the compound name and no results come up. Will I need to search compound names with a paper that potentially has a CIF referenced? Or have I just misremembered how to use CCDC! Any and all help appreciated, thanks!
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Hi Annie, you can try to search the CIF file you need at COD (crystallographic open database - http://www.crystallography.net/cod/) or Materials Project ( https://materialsproject.org/) database. They are free of charge.
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3 answers
Column chromatography with Silica Gel columns with inbuilt UV detector.
Compound structure is mainly poly unsaturated fatty acids and analogs without UV handles.
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You have answered your own question. Proper chromatography methods require detection methods which are applicable to the samples under analysis. You may want to review the types of instruments, detectors, columns and materials available at your school before deciding on a final approach. Have someone in the school's analytical instrument lab assist you.
For HPLC samples with weak or no chromaphore, you will need to use a detector that does not rely on wavelength based light absorbance such as an RID, ELSD, CAD or MS, to name a few. Put a little time into researching this basic question so you will better understand the uses and limitations of these methods and detectors. I often suggest my students start with a keyword search on the web (GOOGLE or BING) to find examples and articles to review. This is one of the best ways to learn. Once you have familiarized yourself with the basics, be sure to ask your teacher for help in setting up and running some example methods.
BTW: You may also be able to derivatize some of your samples and use GC/FID or GC/MSD as an alternative to HPLC (only if the samples are appropriate).
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Assume a solution with acidic pH, which consists of 2 and 3 valent iron ions. With increasing the pH, iron content will precipitate.
Do ferric and ferrous precipitate in an equal pH? If no, at what pH will precipitation happen for these ions?
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I read that after leaching of oxidized zinc concentrates with sulfuric acid, the resulting solution is purified from harmful impurities like iron, copper, cobalt, nickel. And with a weakly acidic medium, pH = 5.2–5.3 iron ions are practically precipitated by the formation of hydroxides.
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3 answers
Hello,
I am looking an all solid state halogenide ion conductor (conducting halogenides, not necessarily based on them) especially iodide ions for a solid state battery.
Poorly the research seems almost exclusively on monovalent cations like Na+/K+/Li+.
Also the ion conductor should have approximately 10^3- 10^-2 S/Cm at room temperature.
any ideas?
thanks a lot
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6 answers
basically scholar is having maths and statistics background but he is doing research in fluid mechanics. he is interested but difficulty is finding problem and doing paper publications.
so we need some suggestions. how to develop knowledge on this research area being a mathematics scholar.
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If a person is good in mathematics and has command over it, that means he has good logic aptitude and grasping ability. If now he want to do research in Fluid mechanics of course he can. He should start with reading the basic physics books and gradually increase the level to engineering fluid mechanics. Which, at this stage, should be a matter of not more than 6 focused months. after that he will be able to do like masters. Do not run behind paper publication from the start it will a by product of your focused learning and problem solving.
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Hi everybody!
I am PhD in analytical chemistry and I make part of a multidisciplinary team working on the development of a web based solution focusing mainly on treatment and management of environmental chemistry data. But in order be more acertive in this project I need to interview researchers worldwide to trace a more realistic picture on how they deal with their environmental data.
Could any of you please help me by giving me a 40 minute interview? We could make it via WhatsApp or Hangouts (or other choice).
Messages in private to more details are welcome!
Thank you all very much in advance.
Yours sincerely
Gilson
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Dear Dr Gilson
I am ready to help if I could and be grateful to do something due to make progress!
I think many valuable media and journals could be useful for you such as:
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My lab has hydrazine sulphate. I need to convert it to hydrazine hydrate. How can I do this?
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Hydazine hydrate solution in water is basic (pH=11) but the solution of Hydrazinesulfate in water is acidic (pH = 3). So to get the hydrazine hydrate from hydrazine sulfate , the pH of the hydrazine sulfate solution has to be tuned to pH= 11.
Here the procedure:
Dissolve the Hydrazinesulfate in water ( 1 g in 30 ml), check the pH (then add Ambersep 900 hydroxide from resin (or any other OH from resins) and adjust its pH to 11. Filter the solution to obtain Hydrazine hydrate.
I have used this procedure recently, it works very well.
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I want built a small biochemistry lab for research purpose ( Phytochemical Study).
Phytochemical screening
 It refers to the extraction, screening and identification of the medicinally active substances found in plants. Some of the bioactive substances that can be derived from plants are flavonoids, alkaloids, carotenoids, tannin, antioxidants and phenolic compounds.
Please give me some guideline and references for built a small laboratory.
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Hi,
as
Sebastian Schmitt
mentioned, it is indeed necessary to provide a more specific question in this case. Depending on the machines available in your lab it could be possible to perform an analysis more than another. Of course some basic chemicals are in every lab, but to avoid misleading you it could be better to receive more information about the type of research you want to carry.
Please have a look at the following link:
Best regards
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1 answer
What are the oil based inputs for production of bio-polyamides for application in textile sector?
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Mostly adipic acid, manufactured from hexane, and also 1,6 Hexane Diamine, also made from hexane. Or Caprolactam made from hexane.
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When comparing different Li-ion cells (no cooling) , what is the general trends in cycle life vs temperature? Across different Li-ion chemistries (NMC622, 532, NCA etc), is there a generic trend.
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3 answers
Hi everyone,
I'm not able to find the correct citation style for Rubber Chemistry and Technology (ACS). I'm using the Endnote plug-in "Cite while you write" for Microsoft word.
The references should be superscript, listed by appearance order and edited using first name, surname. Such as:
R. B. Fox, RUBBER CHEM. TECHNOL. 68, 547 (1995). doi:10.5254/1.3538755
P. J. Nieuwenhuizen, J. M. van Veen, J. G. Haasnoot, and J. Reedijk, RUBBER CHEM. TECHNOL. 72, 27 (1999); 72, 43 (1999).
The "ACS-no title" citation style seems to be ok, but in the list, the surname appears before the name (as usual) and it is wrong.
Fox R. B., RUBBER CHEM. TECHNOL. 68, 547 (1995). doi:10.5254/1.3538755
Thanks for any advice,
francesco valentini
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It looks like neither the journal nor EndNote provide a style file, thus you will have to edit an existing style (perhaps ACS). If you have EndNote on your computer (not the plug-in but the stand alone program), go to Edit/Output Style/Edit "ACS"/Bibliography/Templates. Edit the journal article template, then save the edited style with a new name. When you reopen Word, you should see it when you "Select another style".
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We used the one step method in the lab to obtain FAME for our GC analysis.
Many time we see varying degrees of evaporation of solvent (BF3 and internal standard) from our test tube during the 1 hour heating.
We tried putting PTFE tape around the thread of the test tube but we have varying success rate.
How would you effectively prevent evaporation of solvent in a screw-capped test tube during heating in a water bath?
See here for the simplified method we used: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2593112/
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Dont worry. Dr Kafferlein. We are all here for discussion. That's no wrong or right answers. Thank you so much for your contribution.
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4 answers
Using DCM as a solvent for functionalizing a gold/silicon substrate with a self assembled monolayer by immersion. I noticed that after while, the solution is turning cloudy. Why does that happen?
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Please observe what happens when CH2CL2 , taken in a separating funnel, is shaken with a little bit of water and then allow the mixture to get separated in to two layers.
Collect the organic layer, and observe the layer keenly and add anhydrous Mg(SO4)2 to the organic layer. The layer on becoming dry, should turn into a transparent liquid after becoming dry.
Now, the following would be my comments.
(a) Absorbed moisture can impart turbidity to organic solvents. This is specially so with low-boiling liquids like CH2CL2 and diethyl ether.
(b) Anhydrous solvents normally have a great tendency towards absorbing moisture, when kept exposed to a moist environment.
(c) Please do keep in mind that chlorinated hydrocarbons are normally avoided due to their toxicity.
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Hello! I am working with short-single walled carbon nanotubes dispersed in water. There is .3g in 30ml of water. I need concentrations of 10ug/ml, 20ug/ml, 30ug/ml, and 40ug/ml.
I was told that since the CNTs are already dispersed that we basically need to take X amount of our stock solution and dilute it with X volume of water and we will have our desired concentrations.
I am a horticulture major and this is my first venture into a project of this magnitude. I can't seem to find a chemist or bio professor to help me, can anybody help me out? Would really appreciate it.
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Daniel Jackson yes, you are right, you need made serial dilutions from the primary solution. I recomend you this video to understand the method.
Regards.
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5 answers
We have a solution with an oxygen concentration of 6.5 ppm. How to Calculate Oxygen Pressure in a Solution Using Oxygen Concentration?
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Hello Mr. Ulrich Deiters
My solvent is water.
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4 answers
Ethyl Benzoate protonates with HCl to form protonated Ethyl Benzoate and Cl- (Screenshot Attached). After the Ethyl Benzoate is protonated with HCl(non aqueous) in a non aqueous solution, would the protonated Ethyl Benzoate then serve as a cation, and the solution's PH can then be measured by a standard electrode?
Would the H ion pop back off of the oxygen in the presence of an electrode? Essentially I am looking for a way to measure the PH (or relative PH) of this non aqueous solution.
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5 answers
Adsorption is sub wed in science chemistry surfaces..it is two types : physical adsorption and chemical adsorption....eta
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Dear Ihab Asaad Altameemi
I hope you feel well today. I will write what I understand from your equation. In really adsorption presence is separation method or transfer containment from liquid or gas phase to the solid phase. Therefore, there are products waste as solid can control it for disposal or reuse. All treatment processes need an energy source for work but adsorption does not want that. The low cost of operation and the initial cost of adsorption is the advantage. On the other hand, we use the adsorption process for removal of the low initial concentration of the heavy metal that can't be removed from water by precipitation. Today, the researcher tries to find now mater that has high adsorption capacity at the same time made this material from waste ( the name of adsorbent is super-adsorbent ) such as metal-organic network , nanoparticle, polymer, and hydrogel.
I hope I write what do you look for.
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4 answers
Alginate is an anionic polymer and on the other hand Rhodamine B is a cationic dye. Theoretically these two should be boned by ionic bond. Does it happen? More suggestions and experience are greatly appreciated. Advanced thanks!!
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You might be able to couple the rhodamine carboxyl to an alginate hydroxyl with a water soluble diimide coupling reagent.
Or use a different dye....
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7 answers
When weighing powder substances, static tend to cause unstable reading on an analytical balance, and most annoyingly, causing sample to stuck and disperse around the mouth of test tube.
How do you overcome this problem?
I know company like Shimadzu has a static remover block for this purpose, but it's too expensive to get one.
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You may not want to use the following advice if you are weighing hazardous substances: don't wear gloves. They are a big source of static. Check with the lab head whether this is permissible if you want to try it. Wash your hands afterwards.
Otherwise, minimize static by avoiding a lot of motion of the solid in its container. In other words, avoid shaking or tapping the container. Use metal spatulas, not plastic ones. If you are not weighing the solid directly into the final container, use glassine weighing paper rather than a weighing boat. Use the smallest feasible piece of weighing paper, not necessarily a whole one.
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3 answers
The HC gas upstream T,P is known and downstream P is know. A cooling effect is likely to occur since moving from a high pressure to low pressure across the control valve. One of the things I am not sure how to estimate is the Joule-Thomson coefficient.
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Thank you gentlemen for your assistance, really appreciate it.
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3 answers
This nomenclature has confused me for years, and I have been told different answers. Does 1:1 25 mM AmBic/50% ACN refer to
A) a final concentration of 25 mM AmBic and 50% ACN,
B) equal amounts of 25 mM AmBic and 50% ACN mixed (final 12.5 mM AmBic and 25% ACN) or C) something else entirely?
If A, Then what do you do with recipes that call for 1:1 25 mM AmBic/ACN (implying 100% final concentration)?
Thanks for the clarification!
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Hi Ryan,
I think that B is the correct answer. Usually Mixing solvents with statement 1:1 means equivolume mixing of components, (1+1=2volumes diluted finally x2) which finally yields halved concentrations of constituents. This should be premixed if used as Hplc mobile phase and degased, and pumped through special pH basic resistant column matrix.
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9 answers
1.Looking for easy comprehensive and authentic books on analytical chemistry
I am already using
G.D christian
Harris Quantitative chemical analysis
Skoog and west
I just want to explore some book other than these!
2. Do tell me some good precise and easy to understand books on spectroscopy?
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Spectrometric identification of organic compounds I Robert M Silverstain
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4 answers
For example, which is more likely to oxidise to the equivalent phosphate, triethylphosphite or tris(2,2,2-trifluoroethyl)phosphite?
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Yes, if electron withdrawing groups are prsent in near or conjugation to phosphrus, then n then only chance for more labile oxidation. but any phosphites are highly undergoes to oxidation so inert atmosphere is needed.
thank you
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2 answers
A plasma bonded PDMS device to glass slide when treated with pluronic, will make the surface hydrophobic? I know that pluronic is used to avoid deposition on surfaces, but what does it really do to make the surfaces deposition free.
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Hydrophobic and in layman's terms slippery!
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18 answers
I would like to start a project for the construction of rockets as a project for high school students. Starting with the development of a solid fuel (KNO3 + sugar) which is the safest method for the production? What additives can I use? I have seen from very simple elaborations, to more elaborate methods with the same components. Heat the mixture and manipulate it how dangerous it is? How do I estimate efficiency?
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I have experience with r-candy propellants, and its not very dangerous as other solid propellants (for example APCP). If you apply the basic safety procedures you will be very safe (lab coats, safety googles, masks etc). If you make the propellant by heating method, then you must be carefull with the burners, because when you put the propellant in the mold through casting method, its very important to ensure that the propellant will not fall on the burner by mistake. Because you have to make the propellant with students, I will recommend to you to mix well the KNO3 with sugar as raw materials and do not use the heating method.
Also, you have to consider that these propellants are not easy to ignite them, so be sure that you will ignite the propellant from far, using ignition wires, not with lighter.
If you want to increase the burning rate, you can decrease the KNO3 particle size or you can add a small quantity of Fe2O3 red iron oxide as catalyst. But if you do that, you have to keep in mind that it will be more dangerous.
It is very good to learn to your students the significance of safety.
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10 answers
The unit of Tafel slopes are mV/decade (for cathodic and anodic slopes).
What mean the decade?!
is it (log scale) only ?!
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Dear Dr. Haider Abdulkareem Al-Mashhdani,
in a previous question relating to this topic here in ResearchGate, Dr. @Angel Cuesta, gave the following, very clear, explanation.
The Tafel slope simply tells you how much you have to increase the overpotential to increase the reaction rate by a factor ten. This will be determined by the magnitude of the change in the activation energy for a given increase in overpotential (when you change your potential 1 V, the Gibbs energy of the process will change by 1 eV per electron transferred, but the activation energy will only change by a fraction of this, and this fraction determines the Tafel slope). In a reaction involving only one step with one electron transfer, the Tafel slope will be determined by the symmetry factor, which is usually 0.5 (corresponding to a Tafel slope of 120 mV). In a more complex reaction involving several steps and several electron transfers, the Tafel slope will be determined by the rate-determining step and by the number and nature (i.e., involving an electron transfer or not) of the preceding steps. So, essentially, from the Tafel slope you can deduce whether your rate-determining step involves an electron transfer or not, as well as the number of electrochemical (involving an electron transfer) and chemical (not involving an electron transfer) steps that precede it. If you propose a reaction mechanism, you can calculate what the corresponding Tafel slope should be and, if it does not coincide with the experimental one, the mechanism cannot be correct.
For more details, you can have also a look at the following notes:
-Tafel Plot and Evans Diagram
By Palm Sens
- Quantitative Corrosion Theory
By Gamry
Best regards, Pierluigi Traverso
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10 answers
I have performed a demethylation reaction using BBr3 and neutralized it with sodium bicarbonate solution and removed the water by lyophilization. Now, I want to separate my product from reaction mixture. My product is soluble in methanol and water. Could anybody help me to give idea for separation of the product?
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Hi
How do i separate powder it contains sodium bicarbonate,tartaric acid and citric acid by HPLC or only organic acid ?
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5 answers
What happens when HF and SiO2 react? Will other toxic / hazardous substances be created as a side product? Thanks!!
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SiF4 gas will appear and take in consideration that SiF4 is toxic and corrosive. In moist air it fumes, whereby it is easily hydrolyzed to give H2SiF6 and SiO2. However, in my opinion the most toxic / hazardous substance in this system is certainly HF. Utmost care must be exercised when working with HF, especially if it is a concentrated solution (40%) or even anhydrous. It easily penetrates the skin and can lead to serious injuries
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4 answers
I have to do few toxicity tests in which silver is involved. To do that i have to prepare a stock solution using silver nitrate (AgNO3) salt. The concentration of exposure in the tests is referred to silver itself, not to the compound. I need to know how much silver nitrate salt i need to have the concentration of 5 g/L of Ag. I would be really glad if someone could also explain/show the mathematical and logical reasoning behind the answer.
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You're welcome. I just noted a typing error in my answer. 0.786 g AgNO3 is of course 4.63 mmole, not 6.63 mmole. It must be the same as the mmole amount of Ag.
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7 answers
I am removing carbonates from clay and sand samples. So, I treat the sediments with H2O2. I need to wash the sediments to remove acid residues. I am thinking of heating the sediments with ultra-pure water over hot plate and subsequent evaporation. The process can be repeated for 3-4 times over hot plate. Will it work and act as an alternative method of centrifuge washing?
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Ashok - H2O2 is used to remove organic matter from sediments - not carbonates. If you are trying to remove carbonates, but wish to leave any clay minerals unaffected, you should use a buffered sodium acetate/acetic acid solution (pH 5.3). If you aren't concerned about the clay minerals, dilute HCl would be fine. E-mail me if you would like the method.
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7 answers
Needed for review
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Saida, If you have a look at a Dieke diagram it'll be apparent to you that the energy states of La are well separated (gs and es) way above its bandgap so no emission line will fall in the visible region. And La doesn't have 4f electrons as the other lanthanide ions do. Also, other emissive lanthanide ions which are often used as emitters, have energy levels that are separated by energies falling in the visible range. However, due to the inner shell configuration of these 4f ions, it's very unlikely that you can directly excite a 4f-4f transition in these- so you'll see little-to-no emission intensity. However, if you have La in the material it can absorb the incident energy and efficiently transfer it to the emitting lanthanide ion in an indirect way. But this energy transfer is strong enough that it populates the emissive states of your lanthanide activator and you'll see the fluorescence occurring from them. That's why you see an increase in luminescence efficiency in the presence of La.
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See above
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I agree with Neeraj K. Sethiaya
Just the the second method, you cant use methanol to isolate the alkaloids,
you most make two immesible layers , like chloroform and polar solvet,
Best regards for all
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7 answers
Dear Community,
as i want to find out the impact of ceramide on my cells in DMEM-F12 medium. I dissolved C16-CER in Ethanol and added it to my medium. After having a look through the microscope, i see that it precipitates. 
Does anyone have a solution for my problem?
And do you know if C2-CER is easier to use?
Thanks,
Konstantin
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Working with C2-Ceramide it obviously had an effect on the treated cells in our publication ( ). Therefore, I think it is increasing solubility and subsequently effectivity of the compound. For the preparation of a C2-CER BSA mixture you can follow the instructions by ENZO. It worked well for me.
Best
Konstantin
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5 answers
Is anybody can help me to prpapre dual buffer system viz. Histidine-acetat, Histidine-phosphate, Histidine-citrate, arginine-acetat, Arginine-citrate
How can we select a dual buffer for particular pH reasons behind that.
In dual buffer how theory weak acid or weak base and its conjugate would work and chemistry behind if that
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I also recommend
Ellis, KJ et al. Methods in Enzymoloigy, Vol. 87.
and
Dawson, RMC et al. In: Data for Biochemical Research. Chapter 20.
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8 answers
Whenever I pyrolyzed NaH2PO2, I am facing difficulties in cleaning the white left over residue (may be phosphates) in the tube.
So, I am looking for any effective cleaning protocols to get rid of this issue.
Thanks.
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Yes Mr.
Curtis Guild
Actually, when we try for the annealing of potassium niobate, we suffer from those cracks on the tube. The niobium gets reacted with Si and forms Niobium Silicate. Those cracks are at inner surface of the tube. And cracks get propagated and unfortunately that tube get damaged.
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I am currently proposing a study about the formation of free PUFAs (EPA and DHA) in raw oysters treated with acidic sauces. Based on a study by Sajiki et al. (1994), free PUFA formation may be caused by the activation of lipolytic enzyme in the oysters treated with acetic acid. However, I am confused regarding this mechanism since the oysters are not alive. Can this explanation be used for dead oysters? Is there a better explanation for the formation of free PUFAs?
Here is Sajiki's study if you are interested:
Any answer or literature will be appreciated, thank you!
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I agree with C.A. (Kees) Kan
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Hey all
Technical papers or not
Is there one search engine that embraces all the detailed procedures and guidlines for lab scale processes and synthesis methods
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Dear Gabris Mahamid, Such a database aggregated and sorted at this stage is being developed. It has not been tested and therefore cannot be seen. The development is of large companies such as: Web of Science, Scopus, Google Scholar and Google Academia, Microsoft Academic, Semantic Scholar and others. There is only a partial finding at this stage of these data companies on specific topics in specific areas. Wishing you success in research. Emil Yankov
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Branch of chemistry
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Study of diseases and the pharmacological potential and mode of action of drugs
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As well known
In almost all papers the experimental section is so short and not detailed for instance no clear weights setup and so on
Where can we find expanded detailed narration of experiments and methods
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Dear all, some journal use the experimental details in a separate file with a specific DOI. It is named 'Supplement file'. It is mentionned in the first page mother file. Generally it is free downloadable. My Regards
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While I am looking for academic positions in Canada, they are constantly asking for a research proposal in NSERC format. I never had an experience of making a proposal in that format.
Hence, I am requesting the research community here in to share their proposals. If you want to share with me only, please send it as a message. I will keep it confidential.
Any sample of proposal (awarded/non-awarded) in that format will be great help for me to fasten up and amend my proposal. I am very much grateful if someone can share their sample proposals.
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Thanks for your message Priya Dharshana.
I am looking for a sample not for a template.
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Hello,
I will soon start a new project in which electrochemistry is applied in organic chemistry. It will be totally new for me and for the group where I work. Do you have some tricks or advise for this topic?
Thank you very much
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Hi;
The electrosynthesis provides a better environment for the generation of reactive species by dissociation or bond forming processes. The reactive carbon species are used in various synthetic transformations, essentially C-C bond formations. Oxidation and reduction of functional groups are also important reactions in organic synthesis. A major advantage of electrosynthesis is the reduced formation of side products.
With my best regards
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Journal, Magazines and Letters publish scientific articles. What is technical difference between these articles and their recognition?
Writing Style, technical soundness, number of words etc.
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A magazine is definitely not the same as a Journal. Magazines normally carry popular articles, not original work. A Scientific Journal publishes original scientific work not published elsewhere. 'Letters' or 'Notes' are of shorter length. It may include a comment on an already published recent paper by the author or someone else. Normally, Editor takes decisions on 'Letters' and 'Notes'. Seldom are they are sent to reviewers.They get published quickly. A full length paper in a reputed Journal has to undergo peer review process and may take up to an year or so to get published.
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A resazurin-based assay was produced with ampicillin against E.coli , negative control was just LB media and E.coli and the positive being ampicillin and E.coli, with resazurin for the readings. Plate readings were taken initially and then every 30 minutes for 2 hours. The only data I have is the plate readings and the initial concentration of ampicillin added. How would I work out the final concentration of ampicillin?
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I want to mix Graphdiyne into NDP-V that is non-fullerene polymer and seldom used as electron transport layer. could you please predict its chemical properties or kindly send some research articles of someone already did it.
Thanks in Advance
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Dear colleagues,
At the brink of curricular reform in Czechia, we stand before the question how, if ever, to exit the traditional structure of lower-secondary chemistry curriculum.
We found several resources describing such initiatives, but so far nothing we could use to support our ideas during the talks with the policy-makers. Could you please refer us to some resources?
Thank you in advance.
Best,
Martin
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There have been a lot of initiatives to include active learning exercises in both lecture and lab. Many have observed good results in information retention and elimination of misconceptions. I have observed some of these results firsthand, and active learning is something I think is quite valuable. Here are a few resources, but there's lots of info out there:
For curriculum, I have noticed a shift towards an "atoms first" approach, but I haven't seen anything conclusive on its effectiveness. My feeling is that it works well for some students, not for others (just like any approach). I have yet to see any good methods on stoichiometry excepting certain teachers who have a knack for explaining it well.
This article suggests focusing on training teachers and developing innovating learning material:
This blog suggests directing chemistry towards things people will actually use and encounter (cooking for example):
The American Chemical Society has a small guidebook on what should be explored:
(See also attached pdf)
I hope the resources will help you.
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I was once told that stable isotopes of lighter elements such as H, N C , etc are found in stars, planets, etc. Can anyone suggest any literature which talks about the formation of these isotopes?
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The lightest elements (mainly hydrogen and helium and in trace amounts lithium and beryllium) were formed about 100 seconds after Big Bang through the Big Bang nucleosynthesis (this process lasted up to 20 minutes after Big Bang).
After the formation of stars new elements, from helium to iron, are produced in stellar nucleosynthesis (thermonuclear fusion: CNO cycle, proton–proton chain reaction and triple-alpha process) during stellar evolution.
Elements higher than iron are produced in supernovae through the r-process and s-process.
A very good book about this and generally about properties of stellar interiors and the structure and evolution of stars is: "The Physics of Stars" A. C. Phillips.
About the nuclear physics of stars, you can see also a book of Christian Iliadis "Nuclear Physics of Stars".
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Hello sir
I am looking for a collaboration working for a synthesis project in organic chemistry.
Regards
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i am work about antibacterial activity of material and synthesis of nanomaterial
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I am using 1g/L stock solution of Copper and Zinc prepared from Copper Sulphate pentahydrate and Zinc Chloride, respectively. I am using the stock solution to prepare standard solutions of concentrations between 0.1 mg/L to 10 mg/L by dilution. I am preparing the standard solutions everyday by dilution from the stock solution to calibrate the Atomic Absorption Spectrophotometer.
My question is that is it OK if I store the standard solutions, which are of quite low concentration and use them for future use instead of preparing everyday from the stock solution? If yes, what is the maximum storage period for which I can use them?
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Store the stocks in the fridge, i.e. cool and dark, and they should last for months. What tends to happen is that they slowly concentrate due to evaporation. So use good containers. The more dilute solutions are more stable in acid. Even 1 mg/L is quite concentrated beside the solutions used to calibrate ICP-MS so it should be OK for a few days. Beyond that rely on testing for yourself.
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Yesterday on December 5th, 2019 at 3:45 p. m. a full bottle of our homemade brandy on the small kitchen table on our kitchen spontaneously exploded. I am a retired university professor in chemistry and very knowledgeable in physics but I do not understand how could it happen?
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Can you tell if it exploded (pressure build up) or imploded (sealed while warm and bottle was flawed)?
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I have been looking into MSDS of KOH of 0.1 M, and it says use proper ventilation area while working. But in my lab, we don't have fume hood to work with. And I am not able to find any safety sheet on 0.001 M KOH solution. I would also like to know about any possible health effects of this.
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Only concentrated KOH is dangerous (Caustic soda). But solutions of 10 - 15 % (that is around 2 mol/l) are medically used for topical application.
I can find safety data for a KOH solution of 0.1 M at a Sigma-Aldrich site
NO STATEMENT for special ventilation is given for 0.1 M KOH
But for 0.001 M, their could be no harm at all (except do not swallow ..). No need for special ventialtion or fume hood.
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I need to find a proper method to prepare sample solution by digestion for Pt-Pd-Rh elements from spent automotive catalysts. Any suggestion except application of microwave-assisted digestion would help me.
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What about try acid digestion?. Normally people to determine the metals by ICP-MS using HCl:H2SO4: HClO4.
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hello every one
I want to synthesis the CuInSexS2-x QDs and as I am elementary in chemistry, I want to know that how to determine the sub x in such structure in practice (mean in the synthesis of CuInSexS2-x QDs in Lab) ? and could you introduce me a source for more study about this fundamental issue in chemistry? thanks
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You can measure the stoichiometry of a sample using X-ray photoelectron spectroscopy, although XPS is normally very surface sensitive so there may be some difference between the measured st. and the bulk of the QD depending how small it is.
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Good evening.
I am working on my bachelor’s thesis and i need some informations about water solubility of Drotaverine HCl.
I couldn’t find something usefull not even on chemistry websites.
Thank you for your help !
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Drotaverine is sparingly soluble in water. In DMF/PBS 1:5, the solubility is 0.16 mg/mL. See https://www.caymanchem.com/pdfs/20944.pdf
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Do there exist any compounds, fluorophores, dyes, quantum dots, phosphors etc that can emit or fluoresce non-linearly without needing ultra-high intensity illumination (such as pulsed femtosecond laser)? That is, with a UV led for example and with this non-linear emission being dominant?
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Dear Sammy,
Prof. A. Tikhonov already nicely summarised the most important issues concerning up-conversion. As far as phosphors are concerned, there are a couple of materials that can show rather efficient NIR to VIS up-conversion at moderate irradiation levels. These are: NaGdF4:Er,Yb; Gd2O2S:Er,Yb; BaY2F8:Er,Yb and YOCl:ErYb.
All of these materials make us of the mechanism of Sensitised Energy Transfer Up-conversion (S-ETU), while Yb3+ is the sensitiser and Er3+ the green or red emitter. Important is that the host material has solely low phonon energies, otherwise the process is easily quenched by electron-phonon coupling. Good luck!
Thomas
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Hi all, working on a task where HF acid gas may be present due to Li-ion battery combustion (faulty batteries, over-changing, transport/vibration) in a container. Curious how one would design a filter or neutralize this gas in order to lessen damage to humans and surroundings? I imagine this may be a chemical engineering question, which I have no experience with. Thank you!
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When we want to trap hydrogen fluoride on a filter in order to estimate its concentration in the atmosphere we use filters soaked with sodium carbonate. I think you could try to adapt this method to your issue. You can see an exmple of the use of this method here:
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I'm dissolving PCL in TFE for electrospinning purposes, and the paper I'm following has detailed how to do a 10% w solution by dissolving 0.4 g PCL in 4 mL TFE, but this doesn't seem right to me based on previous training I've received on how to calculate a w% solution which required me to dissolve 0.763 g PCL in 5 mL TFE. I'm feeling like the latter method is really a w/v%, but it always produced good results, so for future purposes which calculation should I go with?
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Christian Chavis Christian Chavis In pharmacy, a w% or more commonly w/w% is the number of parts by weight of the solute (or active ingredient) contained in a hundred parts by weight of the final preparation. so to get a 10% W/W solution you have to dissolve 0.5 gm of your solute (PCL) in 4.5 gm of the solvent (TFE, you can convert this to volume of TFE by dividing 4.5 by the density of TFE). I hope this is of use. Best wishes.