Science topics: Chemistry
Science topic

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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Using DFT, I have a graphene system with Nitrogen doping. It is well known that the nitrogen covalent bonds with 3 sp2 hybridized carbon atoms. When placing this system on top of an Silica which contains Si surface atoms having sp3 hybridization (Si has one free electron), the Nitrogen creates a covalent bond with Si.
My question is, what happens to the lone pairs in nitrogen ? How can it bind with the electron in Si even though it has lone pairs.
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Thank you for your Response Robert Lawrence
I looked at this bonding type but here the Si contains a free electron so both atoms are contributing to the covalent bonding.
In some instances DFT models represent a view of what happens in simple chemical bonds and I was wondering if my case can be explained.
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Hello Ali, the most important tip for preparing the nanoparticle core-shell is that the core should be made of magnetized elements: iron, cobalt, and nickel.
This keeps them fused as a capsule for as long as possible.
And this is when the ball and the shell are elements, but if the ball is a polymer or an antibiotic... Here the situation changes
My greetings
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The molecule shown in the image is known as Argyrin G3, please propose a retrosynthetic analysis diagram showing disconnections and reasons for the disconnections. also please provide a synthetic route for the forward synthesis of Argyrin G3 including reagents and amounts. please provide sources as well if possible.
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Your cyclic peptide also includes a thiazole.
Check
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in the matter of measuring the content of a certain component in botanical chemistry
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The dry weight of the plant is determined based on the certain amounts of live/wet plant biomass and is variable (the physical, chemical and biomechanical processes are carried out in its content). The dry extract of the plant will undergo a physical phase change after the initial extraction based on a series of special post-processing in accordance with the relevant protocols.
Regards
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How many grams of K2Cr2O7 to dissolve it in 1 liter Distilled water to obtain 50 ppm of Chromium? to become aqueous solution, Is there a specific equation to apply? Thanks
Ali
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Errami Ahmed answer is correct. 52 is the atomic weight of Cr and 294.18 is the molecular weigh of potassium dichromate. 2 is the stechiometric conversion factor.
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Is there any good chemistry book about heavy metal precipitation/ extraction via chemical / chelate method?
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Besides classic analytical chemistry textbooks that cover complexometry, the signalled book references also may help to identify suitable masking/demasking agents or procedures:
D.D. Perrin, "Masking and Demasking of Chemical Reactions: Theoretical Aspects and Practical Applications (Chemical Analysis)", Series: Chemical Analysis (vol. 33), Wiley-Interscience, New York, 1970.
Eugene W. Berg, "Physical and Chemical Methods of Separation", McGraw-Hill, New York (etc.), 1963, sections 18.3 & 18.4.
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is it possible to calculate photoelectron Circular dichroism (PECD) using quantum chemistry?
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Photoelectron circular dichroism (PECD) is a phenomenon that occurs when a molecule is irradiated with circularly polarized light, resulting in a difference in the yield of photoelectrons emitted from the molecule depending on the handedness of the circular polarization. PECD can be used to study the chiral properties of molecules, and is sensitive to the electronic and geometric structure of the molecule.
To calculate PECD using quantum chemistry, one can use a multi-reference configuration interaction (MRCI) approach, which is a method for treating electron correlation in molecules. MRCI calculations can be used to calculate the transition dipole moments for different electronic states, which are needed to calculate the PECD signal.
Another approach is time-dependent density functional theory (TD-DFT) which is a first-principle method to calculate PECD signal. TD-DFT can be used to calculate the transition dipole moments, and the PECD signal can be calculated by comparing the transition dipole moments for different electronic states.
It is important to note that the PECD signal is usually very small and difficult to measure experimentally and so it is important to use high level of theory and a good basis set to obtain accurate results.
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Hello,
I need to take the sodium nucleotide salts I have available in my lab and modify them to instead contain some more exotic counterions. Can I do this by binding my nucleotides to a strong anion exchange resin, washing, and eluting with a salt of my preferred counter ion?
Thanks very much!
Nikhil
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You can do either of two things:
1. First, convert a Dowex cation exchanging resin, H+ form, to the desired ionic form by washing with 0.5-1M solution of a salt containing the desired cation followed by the extensive washing of the resin with water. Next, pass, at a slow flow rate, an aqueous solution of your nucleotide through a column containing min. 10-fold excess of the resin prepared as above and wash the column with several volumes of water to complete the elution of the nucleotide. Freeze-drying will give you your nucleotide in the desired ionic form.
2. If your nucleotide is retained on a C18 reverse phase column, you can dissolve the nucleotide in a solution containing the desired cation and apply the solution to the column. Next, wash the column with 3 volumes 0.1 M aqueous solution of the salt containing the desired cation. Next, wash the column with water, min 1 column volume. Finally, elute the nucleotide with 10-15% aq acetonitrile and evaporate the eluate to dryness. It would be advantageous to monitor the UV absorbance of all eluates by an on-line detector and collect only the UV-absorbing fractions. Not all nucleotides are retained by C18 reverse phase, particularly in the step of washing with water. If you decide to use this method make sure to check all eluted fractions.
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I want to prepare 2% solution of chitosan using 0.5 M acetic acid but need to adjust pH to 4. How can I do that? I added NaOH to the chitosan solution, precipitates were formed in chitosan solution.
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In case you want to consider an acetic acid / sodium acetate buffer solution:
The pKa of acetic acid is 4.75, from what we can only expect fair pH buffering effect between approx. 3.75 to 5.75. The pH of acetic acid / sodium acetate buffer solutions can be simply calculated based on the Henderson-Hasselbalch equation, after the molar concentrations of acetic acid (Ca) and sodium acetate salt (Cs) at the buffer solution: pH = pKa + log10(Cs/Ca); what can be generally expected to hold for Ca > 100Ka. A possible derivation for this equation, along with a justification for the stated minimum concentration limit for its validity, can be found elsewhere at this forum: https://www.researchgate.net/post/pH_calculation_of_a_mixture_of_formic_acid_NaOH_and_water
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Some Oxford Nanopore kits have Primers with 5 ' modification that provide ligation to adapters without the need for ligases (ligase-free method), as in 16S barcoding kits. Does anyone know what modification this is or the chemistry involved in the process? I'm very grateful if anyone can help me with this information. Thanks.
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I'm also concerned about this because the Nanopore's Barcode recognition often goes wrong
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If I want to synthesize the product shown in the image, would it be faster to use option A as the starting material or option B. My goal is to synthesize the product in the space of 4-5 hours, which is the best option to use? also what reagents should be used for the synthesis? i was thinking of mixing the starting material with dry methanol and then adding TMSCl while the solution is in an ice bath then removing the mixture from the ice bath and stirring till the reaction is complete. the issue I have is that this reaction usually would take much longer to complete. what is the best way to approach this problem?
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Hi, the starting material doesn't matter. I would use the unprotected amino acid (its way more cheaper), add dry methanol and at least 5 eq of TMSCl. Starting with an ice bath and after 30 min stirring raise to 40 °C for 2-3 h. Check the reaction progess via TLC. Good luck.
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Some researchers say the type of surface electrical charges effects on pH value of the reaction medium and thus the adsorption and removal process , when pH value increases, the overall surface electrical charge on the adsorbents become negative and adsorption process decreases, while if pH value decreases, surface electrical charge become positive and adsorption process increases
Malkoc, E.;Nuhoglu, Y. and Abali,Y. (2006). “Cr (VI) Adsorption by Waste Acorn of Quercus ithaburensis in Fixed Beds: Prediction of Breakthrough Curves,” Chemical Engineering Journal, 119(1): pp. 61-68.
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I admitted as an undergraduate to multiple universities in Arizona and Colorado! I have been actively looking for admission to the university to continuously prepare me as an investigator/innovation scientist in mineral exploration by building my foundational knowledge in metallurgy, chemistry, control systems engineering, geochemistry, geophysics, etc. These might be included in my coursework. My focus may be on "control system engineering" compared to "geoscience," as I want to spend my effort investigating sensor innovation using metallurgy, geophysics, chemistry, etc. for mineral exploration. Precisely, investigative research will be on creating "detection technology for purposing of Mining exploration and extraction" So, I'm confused with two queries: 1. Which university would be the best option based on my research interests? 2. Which major and region for internship/ real time research job corresponds to what I'm actually looking for?
Hope you already understand I’ve applied many universities with getting rejection that didn’t also find exact research team yet I’m looking. Thank you so much.
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Dear Saifur Rahman Khan and Al,
lI wish you Happy New Year: success in your spiritual achievement, good health and prosperity for it!
I found the next on the facbook (https://www.facebook.com/USGSVolcanoes):
'A volcanologist is a person who studies volcanoes, but there are many different specialties within the field of volcanology. Which interests you and what steps should you take to achieve your goal? Find out more in #VolcanoWatch.
Earthquakes are one primary tool used to study volcanoes. A volcano seismologist studies the earthquakes that are generated as magma moves through Earth’s crust.
A volcano geodesist studies the deformation, or change in shape, of a volcano caused by the movement of magma and gases beneath the surface. Many features of volcanoes can be studied from space, as well, using satellite sensors. Tools like these provide clues about the state of the volcano.
Geologists and geochemists study the composition of lavas and gases to understand the source and style of the eruption. Measuring gas emissions is especially important, as the vog (volcanic air pollution) caused by toxic volcanic gases can contribute to breathing problems, acid rain, and agricultural problems downwind, especially during long-lived eruptions.
If you are interested in becoming a volcanologist, you’ll need to work toward a bachelor’s degree, preferably in a STEM field (Science, Technology, Engineering, and Math). Volcanologists frequently pursue degrees in geology, chemistry, physics, and/or mathematics, but that is not always the case. Oceanography, computer science, engineering, environmental science are all potential pathways, and the list goes on. Explore different fields to find what interests you most.
After achieving a bachelor’s degree, consider options for advanced degrees like a Masters or Doctorate. Many advanced degree programs in the sciences are funded, meaning tuition may be waived, and you might get a stipend for doing the work. Basically, you get paid instead of having to pay for school, and you gain valuable work experience at the same time.
You might consider working for the USGS or other agencies and companies. You have seen many photos of HVO scientists working during the eruptions of Mauna Loa and Kīlauea. The National Park Service also offers a variety of positions for people with either bachelor’s or advanced degrees, such as park geologists, archaeologists, botanists, guides, interpretive rangers, and law enforcement rangers. Science writing and journalism are also excellent ways to explore the excitement of volcanology, natural disasters, and cutting-edge science, while encouraging those passions in others. Similarly, eco- and geo-tourism are great ways to get close to the action and work outdoors, while also meeting, educating, and inspiring people from all over the world. Careers in emergency management will have you helping people stay informed during crises.
Check out usajobs.gov for positions within the federal government. There is even a special section for students and recent grads.
Volcano Activity Updates
#MaunaLoa is not erupting. Webcam imagery shows weak, residual incandescence intermittently in the inactive Northeast Rift Zone fissure 3 lava flow at night. Seismicity remains low and ground deformation rates have decreased. Sulfur dioxide (SO2) emission rates are at background levels. For Mauna Loa monitoring data, see: https://www.usgs.gov/volcanoes/mauna-loa/monitoring-data.
#Kilauea is not erupting. Lava supply to the Halemaʻumaʻu lava lake in Hawai‘i Volcanoes National Park ceased on December 9. Sulfur dioxide emission rates have decreased to near pre-eruption background levels and were last measured at approximately 200 tonnes per day (t/d) on December 14. Seismicity is elevated but stable, with few earthquakes. Over the past week, summit tiltmeters recorded several deflation-inflation (DI) events. For Kīlauea monitoring data, see https://www.usgs.gov/.../past-week-monitoring-data-kilauea.
There were three earthquakes with 3 or more felt reports in the Hawaiian Islands during the past week: a M3.3 earthquake 14 km (8 mi) S of Fern Forest at 7 km (4 mi) depth on Dec. 27 at 4:33 a.m. HST, a M3.4 earthquake 7 km (4 mi) WSW of Volcano at 2 km (1 mi) depth on Dec. 24 at 8:31 p.m. HST, and a M2.5 earthquake 1 km (0 mi) S of Mountain View at 11 km (7 mi) depth on Dec. 24 at 9:57 a.m. HST.
In the photo, an HVO technician adjusts a volcanic gas analysis instrument that was specifically designed for this Unoccupied Aircraft System (UAS) unit, which carries three one-liter analysis bags. The instrument transmits gas concentration information in real-time during the flight at Kīlauea summit. USGS has special use permits from the National Park Service to conduct official UAS missions as part of HVO's mission to monitor active volcanoes in Hawaii, assess their hazards, issue warnings, and advance scientific understanding to reduce impacts of volcanic eruptions. Launching, landing, or operating an unoccupied aircraft from or on lands and waters administered by the National Park Service within the boundaries of Hawai‘i Volcanoes National Park is prohibited under 36 CFR § 1.5 - Closures and public use limits.
USGS image taken January 14, 2022 by M. Warren.
#USGS #HVO #HawaiianVolcanoObservatory'
Maybe it can help you!
Regards,
Laszlo
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Hello All! I am working on a project that uses stable isotope analysis (C and N) to look at the diets of California reef fishes. I am going to be collecting Liver and White muscle tissue. It was suggested to me to use 20ml borosilicate glass scintillation vials (urea caps with polyurethane lined caps/not foil lined) for my tissues. I will be freezing the tissue samples in the vials and drying them in a 65C drying oven in them as well. The issue I am running into is that every brand of vials are back ordered for about 4 months no matter where I look.
So I wanted to see if 1. Anyone in the southern California/greater LA Area had vials I could buy off of them to use. Or 2. If anyone knew of a substitute I could use. It has been suggested that I could hand make aluminum foil packets, pre combust them, and store/dry the tissue in those. However, I would prefer the glass vials for both, organization/storage sake as well as I will eventual be grinding the powder into a powder and vials would be less likely to fail with the powder.
Thank you in advance for any advice!
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It is not uncommon for certain lab supplies to be in high demand or backordered due to various reasons such as an increase in demand for certain types of research or supply chain disruptions. In such cases, it may be helpful to try reaching out to the manufacturer or distributor directly to see if they can provide any information on when the vials will be back in stock. Additionally, you can try looking for alternative suppliers or checking with local scientific supply companies to see if they have any borosilicate glass vials in stock.
Alternatively, you could consider using other types of containers for storing and drying your tissue samples. For example, you could use pre-combusted aluminum foil packets as you mentioned, or you could try using pre-combusted tin capsules or pre-combusted glass vials. It is important to ensure that the containers you use are properly combusted and clean to avoid contamination of your samples.
It is also worth noting that the type of container you use may depend on the specific requirements of your stable isotope analysis method. It is always a good idea to consult with your laboratory or the manufacturer of the stable isotope analysis equipment to ensure that the container you choose is suitable for your specific application.
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Greeting,
When I tried to remotely accessed the scopus database by login into my institution id, it kept bring me back to the scopus preview. I tried cleaning the cache, reinstall the browser, using other internet and etc. But, none of it is working. As you can see in the image. It kept appeared in scopus preview.
Please help..
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To reach the Scopus document search module, you should use academic IPs. If your institute has been listed in the Scopus database, you have permission to search documents in Scopus. It is not free of charge, and your university should pay its share to Scopus to provide this service for its academic researchers.
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Hey,
I'm looking for an article that explains that inductive and resonative effects are components of pi bonds. That is what my PI claims.
Thanks.
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We have a substance. We study it using physical methods and determine that its molecules have a dipole moment , they are polarized under the action of an external electromagnetic field ... We determine the structure of the molecule. We compare with other molecules and come to the conclusion that in some molecules the electron density shifts under the action of a magnetic field along a chain of sigma bonds (inductive effect). For other molecules, the electron density shifts along the chain of pi bonds (resonant effect). Bonds between atoms in molecules are primary, while inductive and resonant effects are secondary.
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Hi everyone!
I project to measure levels of total phenolic compounds in peppers following the method of the Folin-Ciocalteu's reagent, and I am going to calculate them by reading absorbance using gallic acid as a standard.
Nevertheless, I am confused about what wavelenght should be setted: while some authors read absorbance at 765 nm (Dogan et al., 2018; Kupina et al., 2018); others read it at 760 nm (Ghasemnezhad et al., 2011); 750 nm (Toledo-Martín et al., 2015; Lwin et al., 2022) or even 725 nm (Vega-Gálvez et al., 2009).
I would be grateful if someone could give me some light about this.
Thanks to everyone in advance.
Pablo
Literature cited:
Dogan, A.; et al. (2016). Comparison of pesticide-free and conventional production systems on postharvest quality and nutritional parameters of peppers in different storage conditions. Scientia Horticulturae 207: 104-116.
Ghasemnezhad, M.; et al. (2011). Variation in phenolic compounds, ascorbic acid and antioxidant activity of five coloured bell pepper (Capsicum annum) fruits at two different harvest times. Journal of Functional Foods 3: 44-49.
Kupina, S.; et al. (2018). Determination of total phenolic content using the Foling-C assay: Single-Laboratory validation, First Action 2017.13. Journal of AOAC International 101 (5): 1466-1472.
Lwin, H.P.; et al. (2022). Perforated modified atmosphere packaging differentially affects the fruit quality attributes and targeted major metabolites in bell pepper cultivars stored at ambient temperature. Scientia Horticulturae 301: 111131.
Toledo-Martín, E.M; et al. (2015). Application of visible/near-infrared reflectance spectroscopy for predicting internal and external quality in pepper. Journal of the Science of Food and Agriculture 96: 3114-3125.
Vega-Gálvez, A.; et al. (2009). Effect of air-drying temperature on physico-chemical properties, antioxidant capacity, colour and total phenolic content of red pepper (Capsicum annuum, L. var. Hungarian). Food Chemistry 117: 647-653.
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From the one hand, the use of suitable solvents in the mobile/mobility phase coupled with sample preparation instructions, using the column and the detector related to the type of secondary metabolite and the degree of polarity and non-polarity of the solvent particles and the resulting bonds should be considered. On the other hand, having the standards of considered compounds helps the process of isolation and identification of compounds phenolics and flavonoids. Eventually, It should be noted that setting the appropriate temperature program and effective wavelengths (280-320) must also be applied till would be made the best result.
Regards
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I will use DFT calculation tool, MedeA VASP, for calculating Gibbs free energy of gas phase and solid phase.
I know that gas phase calculation using VASP may be uncorrect. But I can't use Gaussian because of the budget.
MedeA VASP Phonon module gives below data
1)Cv : vibrational heat capacity at constant volume 2)E_vib(T)=E(T)-E(0) : the change in vibrational internal energy from 0 K, where E(0) = E_elec + ZPE is the electronic energy of formation E_elec plus the zero point energy ZPE 3)S(T) : the vibrational entropy at temperature T 4)-(A(T)-E(0)) : the change in the vibrational Helmholtz free energy from 0 K 5)E(T) : the electronic energy of formation plus the vibrational internal energy, so this term is E_elec + ZPE + E_vib(T)
6)A(T) : the electronic plus vibrational Helmholtz free energy, E(T) - T.S(T)
and my questions are
1)How can I calculate Gibbs free energy for gases and solids from these data?
(I know that in a gas we can regard the internal energy as the sum of the electronic, translational, rotational, and vibrational energies. And We just get electronic and vibrational energy. Also, How can I consider PV term?)
2)How accurate is the VASP transition state and thermodynamic calculation for gas?
(I will calculate reactions for CVD reaction. ex)SiH4+SiH4->SiH6+H2, Si(wafer)+SiH4->Si+H2, etc.)
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As you mentioned it. The gas phase in VASP may be incorrect. An easy way to do the solid phase and gas phase could be:
1. Solid phase: compute the vibrational frequencies of the system. With that, you could calculate the enthalpy=U+KbT+H_vib., and then the Gibss as H-TS ( )
2. Gas phase: You could follow the tutorial of ORCA (free software: https://www.orcasoftware.de/tutorials_orca/prop/thermo.html). You must construct a good (and representative) model of your system in gas phase.
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Usually, plant phenols are best extracted with solvents like methanol and ethanol. But I would like to know if the extraction is carried out with water, how much usually is the efficiency of that extraction??
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alcohols like methanol and ethanol are the best solvents to extract phenolic compounds. but these can also be extracted with water but it depends on the part of the plant drug used (leaves, flowers, roots ........) you must also do a bibliographic research on the optimization of the various extracts used on your plant in order to obtain the best yield in polyphenols. good luck
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Irrational numbers are uncomputable with probability one. In that sense, numerical, they do not belong to nature. Animals cannot calculate it, nor humans, nor machines.
But algebra can deal with irrational numbers. Algebra deals with unknowns and indeterminates, exactly.
This would mean that a simple bee or fish can do algebra? No, this means, given the simple expression of their brains, that a higher entity is able to command them to do algebra. The same for humans and machines. We must be able also to do quantum computing, and beyond, also that way.
Thus, no one (animals, humans, extraterrestrials in the NASA search, and machines) is limited by their expressions, and all obey a higher entity, commanding through a network from the top down -- which entity we call God, and Jesus called Father.
This means that God holds all the dice. That also means that we can learn by mimicking nature. Even a wasp can teach us the medicinal properties of a passion fruit flower to lower aggression. Animals, no surprise, can self-medicate, knowing no biology or chemistry.
There is, then, no “personal” sense of algebra. It just is a combination of arithmetic operations.There is no “algebra in my sense” -- there is only one sense, the one mathematical sense that has made sense physically, for ages. I do not feel free to change it, and did not.
But we can reveal new facets of it. In that, we have already revealed several exact algebraic expressions for irrational numbers. Of course, the task is not even enumerable, but it is worth compiling, for the weary traveler. Any suggestions are welcome.
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We need to be optimistic, because that is the lesson from nature. An animal can self-medicate, obeying natural laws in chemistry that are unknown to animals. A tree grows when pruned, so we can see this pandemic as an opportunity. Let's grow, nature is not a zero-sum game!
Irrational numbers and mathematical real-numbers are uncomputable, with probability 1.
But irrational numbers can be calculated exactly in algebra a and that is how animals are able to calculate-- in a network of thoughts.
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In the following article's ESI, it seems that in situ decomposition of 2,5-Dihydroxy-1,4-benzoquinone (DHBQ) lead to the formation of oxalate under hydrothermal conditions.
Can someone explain the mechanism/pathway behind it?
Ref.: Science 374, 1464 (2021)
Please correct me if I am wrong by any chance.
Thanks in advance.
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You may also see the retrosynthesis pathway from scifinder
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I want to apply Post-doc Chemistry in Turkey. Can anyone suggest me a University in Turkey???
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Koç university, Sabancı university (more suitable for interdisciplinary subjects), Boğaziçi university and METU.
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Hello! What are the oldest literary sources you know that would mention pharmaceutical salts? I am aware of the first cocrystal [benzoquinone + hydroquinone] (1:1) investigated in 1844, but I could not find any mention of the first (or even the first described) pharmaceutical salt (Wohler, F. Untersuchungen über das Chinon / F. Wohler // Ann. Chem. Pharm. – 1844. – V. 51. – P. 145-163). If you know of such sources, please share them. Thanks in advance
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Interesting situation. As soon as I write a question here, I immediately find the answer. Here are some papers on pharmaceutical salts (responding to my comment above): 1) 10.1016/j.ijpharm.2021.120993; 2) 10.1016/j.jddst.2021.102913
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I would like to generate a *.sdf file like those posted NIST Chemistry Webbook from a *.log or *.chk Gaussian 16 file and cannot immediately find how to do this. Many thanks for helping me.
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Hi Ioan, Gaussview can help you.
Best wishes,
Quang
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Which software is best for making high-quality graphs? Origin or Excel? Thank you
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origin
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Mehlich-3, 20 L final volume:
0.2 M acetic acid (230 mL concentrated glacial acetic acid, ACS)
0.25 M NH4NO3 (400 g ammonium nitrate, ACS)
0.015 M NH4F (11.1 g ammonium fluoride, ACS)
0.013 N HNO3 (16.5 mL concentrated nitric acid, ACS)
0.001 M EDTA (5.85 g EDTA free acid, ACS)
Purpose: Soil nutrient extraction for boron, copper, zinc, phosphorus, iron, manganese, magnesium, potassium, calcium, and sulfur to be measured by ICP-OES.
Once all compounds are combined and dissolved, my Mehlich-3 extractant has a pH of approximately 3.2 instead of the pH 2.5 the SOP I'm following indicates the extractant should be. Should the unadjusted pH of the extractant be 2.5 and, if not, what acid would be appropriate to adjust the pH without impacting extractant performance?
Some preparation instructions suggest making a 3.75 M NH4F + 0.25 M EDTA free acid stock solution and adding a volume of that rather than adding NH4F and EDTA directly to the extractant as I'm doing above but I've never managed to get the EDTA to dissolve after dissolving the NH4F using that approach.
Thank you!
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Formic Acid maybe. It is used in LC-MS.
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Good day,
If anyone can assist me, please. How do you measure ammonium and nitrogen from urine? what is the best simple method for someone who is new in chemistry if you can recommend the site where I can find the experiment of measuring ammonium and nitrogen would really appreciate it.
Thanks
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Hello,
in order to determine ammonium, i find that the Nessler method of determining ammonium should be suitable for you. As suggested in Paul Milham's answer, it is a colorimetric assay. It has the advantage of being easy to perform (no need to heat, for urine there should be no need to correct the pH and the reaction is fast) and sensitive. Don't hesitate to ask if you have any questions. Good luck.
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How long does it take to a journal indexed in the "Emerging Sources Citation Index" get an Impact Factor? What is the future of journals indexed in Emerging Sources Citation Index?
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Clarivate announced that starting with 2023 ESCI-indexed journals will also be assigned an impact factor. See: https://clarivate.com/blog/clarivate-announces-changes-to-the-2023-journal-citation-reports-release/
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We can test an antagonist e.g. at 10uM with varying concentrations of agonist. We can then use Schild/gaddum equation to find a KD (also known as KB) for the antagonist.
If i was to change antagonist concentration to some other concentration like 100nM, but test with same agonist, will the KD calculated for the antagonist change or not
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The Ki value of a ligand is normalized by the affinity of the radioligand for the protein of interest (Cheng Prusoff equation). Likewise, the functionally calculated Kb value is normalized to the EC50 of the agonist and the concentration of agonist used (described by Cheng in the Power Issue article that Tomasz referred to). In this case, it's best to run the EC50 calculation for each independent assay as a control. As long as the IC50 is well defined by complete competition, the calculated Ki or Kb value should be robust and consistent across varying concentrations of radioligand or agonist.
Ideally, though, you wouldn't want a completely saturating concentration of radioligand or agonist (stick to ~Kd/EC50) to ensure full competition.
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If someone is granted with utility model can he/she claim it to be granted a Patent?
Is it legally acceptable?
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It would depend on the jurisdiction because patents are national rights as are utility models. Many countries don't have utility models and there are some which have what are called "petty patents" which are like utility models. I am only qualified to advise on UK law (and it would be a criminal offense under the UK Patent Act to mark a product so as to claim to have a UK patent if you didn't have a UK patent), but the rule of thumb for every jurisdiction must be to act honestly and reasonably. So if you have a German Utility Model then say you have a German Utility Model, if you have an Indian Patent Application, then claim you have an Indian Patent Application, etc etc
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Data augmentation techniques drastically improved AI models while dealing with images and text, however, it is not so obvious how to translate these approaches to chemistry and materials science. What methods do you know and how legal do you think they are?
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When I was looking into data augmentation techniques, I came across SMILES enumeration for molecules.
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I have some flyash and want to leach out Al2O3 and SiO2 using NaOH. IS there any additive which can help me to improve rate of leaching or dissolution .
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Under some circumstances there are a few organic acid ions such as oxalate, glycolate that marginally assist in silicate leaching but I am not sure if they would work in your case. However, if you find nothing else, they might be worth investigating.
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We talk about the round oval shape objects. Grid is 15 um. We supossed some kind of drug crystals, but patient has no special medication.
Chemistry:
blood 2+
leukocytes 2+
pH 7.0
SG 1.009
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Fat droplets? Check with polarized light. https://www.labce.com/spg2087066_oil_or_fat_droplets.aspx
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Hello everyone. I need a little help here.
can we use essential oils to reduce chlorinous odor in a hypochlorous acid solution without decreasing free chlorine or pH value? any toughts and propositions are much appreciated
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The reduction in odor is likely due to chlorination of essential oil constituents. Why are you using hypochlorite? As biocide pH should be ~6.5. Are you measuring av Cl ?
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Hi, I need to make an optical window 0.5 - 1mm thick and 6 mm in diameter from PMMA. I would really want to master the skill of production instead of buying some slug or film sheet because later would need to modify the shape ( make a wedge instead of a plane window ) and so on.
I am planning to make a mold using a 3d printed circular part ( see the drawing attached ) wedged between two microscope slides.
We gave it a try and made a sample, but at that time we didnt have the vacuum chamber and poured the pmma into the could mold. ( see the picture attached )
The problem is that the fist sample was quite large and separated from the glass rather easily, which is not the case for smaller sample. The second problem is bubbles.
Could you please suggest the exact step by step scheme to follow ( the concentration, temperature mode, time frames and so on ) to improve our results and obtain bubble free sample which can be safely parted from the mold after the hardening.
What I have:
1. Methyl methacrylate (CAS Number: 80-62-6) from sigmaaldrich
2. Azobisisobutyronitrile (CAS Number:78-67-1) from sigmaaldrich
3. magnetic stirrer hot plate, beakers, vacuum chamber, heating chamber
Thanks a lot in advance.
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Hello Georgy,
the first step is to produce a prepolymer with short chains of pmma. You have to figure out your iniator yield to get reproductive bubble free polymers. There are numerous literatur about these topic. At first glance I would recommend a smaller amount of AIBN for prepolymerisation and a thorough degassing of the slightly thickening batch (stirring, vacuum, cooling, ...).
With best regards
Carsten
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I have synthesized cerium oxide nanoparticles (CeO2 NPs) using the combustion method. My attempts to functionalize the NPs using the APTES have failed so far. After APTES functionalization, the particles are not stable; they settle rapidly. I would greatly appreciate it if someone could propose a solution and reason to the problem.
#Nanoparticles #chemistry.
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Nadir chami, Thank you for the response.! Please suggest any reference for that protocol.
Thank you
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Hello Scholars,
I am an undergraduate at the University of Cross River State, Nigeria currently pursuing a microbiology program. For familiarity and enhanced understanding of the course, I wish to seek recommendations on the virtual/simulation laboratory software that would be very helpful to me and my colleagues. With my interest in research too, I will be pleased if a research simulator is recommended to help widen my understanding of Microbiological research.
Your recommendations would go a long way to significantly contribute to my academic career as well as my colleagues.
Thank you
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Thermofisher Scientific has a virtual lab training option on cell culture. You can check here: https://www.thermofisher.com/bd/en/home/global/forms/cell-culture-basics.html
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I'm finding some cationic molecules like below.
I tried finding on www.sigmaaldrich.com , but couldn't find anything.
Where can I buy some molecules like this?
ref)Ikeda, Taichi, and Yoshitaka Matsushita. "Tetrahedral Tetra-cationic ionic liquids." Chemistry Letters 49.1 (2020): 14-16.
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if you got the cas you can try http://www.chemexper.com/ they search over different chemical companies, but such kind of systems can get quite expensive.
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I will be working on a slow-release fertilizer for my undergraduate thesis, but I am confused about how other authors measure cumulative nitrogen release for a time interval (including the instruments and calculations)?
More exactly how they measure the exact nitrogen released each time.
Please provide a step-by-step process for a rapid water test.
-Thank you for helping a chemistry student.
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Not something I've done but the idea is to have a stirred cell which contains the fertiliser suspended in water, and continuous/timed sampling connected to an analysis system (e.g., spectrophotometer, conductivity cell ....)
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I wonder if the removal of pi bond and the addition of heteroatoms such as halogens would increase or decrease the energy gap between the ground state and excited state of the electrons.
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After the first step of an electrophilic addition reaction an intermediate (carbonium ion) is formed (with a much higher energy). There are no more pi-electons.
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We are living in a world where recently Artificial intelligence is being used in many applications for prediction of many events and things. We all know that the amount and balance of certain Chemicals in the brain have a role in causing us think creative , feel emotional or happy etc. I would like to learn the valuable opinions of Scientists on what specific roles Chemistry would have in creating human conciousness ?
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Thank you Jerry, very helpful reference and information
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Salt has an ionic bond. It's chemically bonded. So, when it dissolves in water, the ionic bond is somewhat lost. But, people argue that it is a physical change because-:
a) The mixture of salt and water can be separated by evaporation.
b) No new substance is formed.( how though? isn't salty water completely different from just water or salt alone?)
c) There is no energy produced. (but then again when we tear paper, the ripping creates some energy...so how is there no energy in a physical change?)
Thank you in advance,
B.P.
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Dissolution can cause hydration reaction with creation of charged and uncharged complexes. Example: gypsum dissolution
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thanks in advance on sharing the method
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Please find the attached article - Determination of Chloride Content in Cementitious Materials. (It may be helpful)
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I am evaluating the options, especially in the true open-source world, for making reliable calculations with high-accuracy using quantum correlation methods.
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You might want to consider ORCA or PSI4 depending on what you want to do. ORCA is very good for high accuracy correlated methods.
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I synthesized a molecule. I want to know what are the self-assembled structures possible for it through hydrogen bonding.
If possible, please suggest me some free software available (installation-based or online)
Any relevant suggestions are highly appreciated. Thanks.
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Using GROMACS to perform molecular dynamics simulation is a very good choice. GROMACS is quite fast, flexible and meantime freely available.
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Hello, I recently discovered via GC-MS that my sample contains crown ether. This was really unexpected. I would like to know how to isolate these compounds for further analysis. I appreciate any paper suggestions or personal tips!
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In aqueous media? I'd try solid phase extraction onto reverse phase. Wash with water, then wash with steps of increasing concentration of acetonitrile in water.
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Who is your nominate for the chemistry and physics Nobel prize?
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My guess in the field of tissue engineering is Robert Langer from MIT. For the Chemistry Nobel Prize.
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Chemistry question: I've received compounds to dissolve at 10uM. They sent MW, FW, and mg amts for each. Some cpds MW=FW, but others have "salts" added, and those have FW>MW. Should I use MW or FW to convert the mg amt to moles for calculations to achieve uM solutions?
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It depends on what the experiment is determining. For instance if the experiment required analyzing perchlorate (anion) and you were given sodium perchlorate salt to dissolve you would need to "subtract" the sodium to determine the uM concentration of perchlorate anion in the solution. In the above example if you were not to correct for the salt and just used the MW to determine perchlorate concentration in your solution you would be ~19% off. 0.1231g of NaClO4 is equivalent to 0.1000g of ClO4 anion. So it makes a big difference - especially if you are using the solution for an analytical standard, or for instrument calibration. We could dive into this deeper if you gave us more information. You can always calculate it both ways as well, unless the experiment requires a specific concentration - then you would need to know up front if you should prepare the solution based on the anion concentration.
regards and hope you come up with the correct solution :)
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Please Suggest me research topic for bachelor degree of chemistry
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Nischal
Do you have a mentor/professor to guide you? You should!
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self‐assembly in the crystalization process.
The origin and the first study in the field of self‐assembly
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Dear Mohammad,
I suggest to clearly define what you mean by "self-assembly".
The problem is that this term has been very often used in completely non-specific way, just to boost the importance of a paper or report. I call this buzz-wording. Imho this term should not be used for:
1) the assembly of ions in a crystal lattice
2) any simple bond formation of a coordinative or covalent bond
Personally, I find the term "self" misleading as in many cases, the researchers are driving the assembly clearly in just one way. Or there is only one way of aggregation of the ions or molecules.
I would use the term "selective assembly" if there are more than one possibility to form an aggregate or a crystal or a complex and one way is selective over the others.
If there is only one way how the particles (ions, ligands, molecules) can assemble, then there is no extra word like "self" needed, and we should call this specifically "coordination", "forming of H bond", "crystallisation" depending what forces finally keep the particles together.
Best
AXEL
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Hello everyone, I have a question about COD (Chemical Oxygen Demand) electrolysis of organic compounds. When doing the COD analysis of the initial sample before treatment, why did it produce a high COD level? what factors in the COD level caused the initial COD level to be very high?
Meanwhile, after being electrolyzed (after treatment), the COD level decreased, what caused the COD level to decrease and were there any structural changes that occurred related to the reagents in the electrolysis process (organic compounds, electrolyte, additional H2O2, COD reagents) .
So, for example, the sample is acetaminophen
Before treatment (acetaminophen + aquades), why was the COD level of the acetaminophen sample so high? what causes the high value? and why after treatment, the COD level of acetaminophen decreased? what causes the COD level of acetaminophen decrease? Are there any structural changes that occur in acetaminophen related to the reagents associated with the electrolysis process after treatment? if there is a change, what kind of change and how?
Thanks in advance.
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to answer your question well I want to know how you do the electrolysis? is it by electrocoagulation?
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How can a correlation be obtained from subatomic to superatomic? Why does the subatomic behave differently than the superatomic? Why does something that makes something behave differently from what it creates? Let's give an example to this first: Let's think of H2o water, hydrogen and oxygen: Here, hydrogen and oxygen atoms will behave differently from the water they form. So why is this? Is this due to the change in chemical structure? This means that the change in the chemistry of atoms under matter ensures that matter itself exists on matter. So what provides this? So what is it that changes the chemistry? How is it changing? So why does the thing that brings together this changing chemistry (structure) become matter? If the chemistry changes in the atoms under matter, what do we say if this matter is different from the substance itself, and since the submatter will normally form the above matter logically? If atomic chemistry, that is, subatomic, changes, it becomes supermaterial and they behave differently. Here we reach something: In contrast to atoms, there is something else under matter. In other words, apart from quantum, there is a structure under matter that interacts with atoms under matter and forms the upper part of matter. What should we call this:? Should we call it such a thing that it interacts with atoms and changes their structure and turns them into normal matter? So let it act in classical physics. So what makes atoms move in classical physics? Let's ask this. How do we determine whether something is in quantum or classical physics? If something moves relative to atoms, it's quantum. If there is something directly related to matter itself, it is classical physics. So what is it that differentiates atoms from what is directed directly at matter itself? Let's first explain the quantum theory: An atom could be in more than one place at the same time. So this would mean that an atom cannot be in more than one place at the same time when it interacts and changes chemistry. But what does it do? What kind of thing makes atoms lose this quality? What kind of thing in the universe loses the function of a particle being in two places at once? First of all, let's ask this: Being in two places at the same time;. It means being able to copy yourself and be able to influence at different points. So this thing, the thing that changes the chemistry, must have a function that destroys this quality. What thing in the universe reduces or eliminates influence at different points? What is the most influential thing in the universe? Matter is the answer, which occurs through this space-time warping. So as a result, Isaac Newton's m1.m2/r'2 formula gives us the output. As the distance between the objects increases; gravity (ie, space-time warping), that is, the twist by matter would decrease. In that case, as the distance between matter increases in the universe, the relationship that a substance establishes with submaterial and supermaterial brings us the existence of the supermaterial. Thank you.
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Hakan,
Perhaps my article `Subquantum leapfrog` will give you some thoughts on this topic
I'm talking about quantum mechanics and molecules.
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In electrofenton, there is one method, namely electrochemical peroxidation, what are the advantages of this method so that it can degrade organic compounds? How is it different from electrocoagulation? what makes electrofenton/electrochemical peroxidation better than electrocoagulation?
Also, there are electrocoagulation and traditional coagulation, what makes electrocoagulation better than traditional coagulation? as well as the electrofenton and traditional fenton, why is the electrofenton better than the traditional fenton? What is the effect of Fe and H2O2 in degrading organic compounds? why when an electric current is applied the results are better? if there is no electricity, is it also good to degrade organic compounds?
Thanks in advance
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Electrochemical treatment on real wastewater or contaminated water works best, but in the water/wastewater pH band of 6 to 8 only, with or without aid.
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What parameters play a role in the ability of amines to be protonated in water? Can the base strength of amines be a sufficient measure to compare the protonation ability of two amines? For example, is the protonation ability of n-butylamine more than morpholine?
Thank you
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I would say yes, but you have to remember not to extrapolate it to another solvent. pKas varies from solvent to solvent. So, one amine can be more basic in one specific solvent, and less basic in another one.
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Hi everybody. I have a question about study kinetics. So, I did electrolysis by dissolving organic compounds with aquades as a sample under acidic conditions with Na2SO4 as electrolyte, with additional H2O2 (Fenton reaction) using iron as anode and graphite as cathode. In discussing the study of kinetics, I found that if the kinetic graph that R2 close to one or almost linear is in pseudo-second order graph, what does this pseudo-second order mean? what does pseudo-second order actually mean? i was told that "the pseudo explains that something is involved but doesn't appear in the rate law, for example the solvent or there is usually the fraction of the reactant that matters" is that true? So, if what is meant by second order is that there are two reagents that have an effect in this case, for example H2O2 and Na2SO4, but in pseudo-second order something is involved but it doesn't appear, what is it? also, if you also know, what kind of reaction mechanism that produces the pseudo?
Thanks in advance
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Send your email address to me, dgamble@ns.sympatico.ca. I can send my published comments about second order kinetics.
Best regards,
Donald Gamble
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Hello everyone!
I want to simulate a premixed combustion case with Hydrogen/air (or oxygen) chemistry.
I know simulating a non-premixed combustion case with hydrogen/air detailed chemistry means injecting hydrogen as fuel and air as oxygen at a particular temperature and pressure and using any available chemical mechanism (GRI, UCSD, etc...).
But, what is meant by simulating premixed combustion with detailed chemistry?
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Thanks for your answer. It is very helpful
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:I don`t understand this bold part
The mono- and bidentate bonding are formed via protonation of the surface hydroxyl group and releasing one water molecule, leading to a strong P-O-M bond.
Article title:Organic Hole Transport Layers for Efficient, Stable and Scalable Inverted Perovskite Solar Cells
doi:10.1002/adma.202203794
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P-O-M is simply phosphorous-oxygen-metal bond. In other words, the linkage between the metal based substrate.
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I saw this sentence .Hydroxyl group and amino group are the both nuclephilic. So no reaction will take place
I have prepared a sample and apparent physical properties show excellent coverage, but I do not how to explain. can anyone help me?
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What kind of reaction?
surface Si-OH is relatively acidic.
amine is basic
so Si-OH + R3N -> Si-O- + R3N-H +
ionic forces will hold them together.
but if you wash with water they may desorb
if you wash with acidic water at a low enough pH to protonate Si-O- it will definitely desorb.
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I am carrying out a Research on the effect of blended learning on senior secondary school students achievement and retention in Chemistry. Could someone
help me with materials?
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Thanks so much Mr. Faroum. Am grateful
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Hi there,
would like to learn more about appropriate material for the application of PPE in Epidemiology.
As all the material seems to be Polyethylene/Polypropylene, would love to learn, whether it is possible to use Polyamide material instead? Are the properties sufficient?
If Polyamide does the job, are normal Snowboarding and Fishing Overalls an alternative to the ordinary Hazmats?
Cherish your feedback.
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The chemical nature of Polyamides, with potential reactive chemical groups, make it more susceptible to contamination than inert PE/PP in an Epidemiology environment. Physical properties are OK.
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Defining the dilution factor is very important when we are working at the level of ppb (parts per billion) or ppt (parts per trillion). Other day, I was working on plant biomass samples to analyze available Si (Silicon) in plant biomass. I have gone through several steps of dilution and became so confused about what is DILUTION FACTOR. I did several dilutions at several steps (digestion, adding chemicals, again diluting to come up with the range of AAS) and it became so complicated. As always, I approached Dr. Rafael Santos and he solved this problem very easily, I would say just in 10 minutes when I was struggling for an hour. Finally, Dr. Santos made a good explanation with their whiteboard and step by step he came up with the solution. Again, doing a Ph.D. is not just collecting and analyzing data but also needs to understand the chemistry happening in between. If you don't know how to do it then seek help. Asking someone doesn't mean your basics are not strong, asking someone means you know what you're looking for but you don't know how to approach it. I am thankful to have Dr. Santos as my mentor, peer and guide. PS: Here's complex whiteboard solution in the picture :) #ppb #ppt #help #academia #PhD #chemistry #data #AAS
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Asking for guidance is the best learning method after attempting a solution.
Sounds like you have a great mentor.
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Research chemists continue in their slow uptake of preprints. I've lately suggested one key reason for this unique behaviour of scholars in the basic sciences in two OA studies, one published by Publications:
and another by Insights:
What is your opinion on the origin of this delay? Has your team recently embraced preprint publishing? What are your favorite preprint repositories?
Thank you in advance for your insight.
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Dear Prof. Mario Pagliaro, Preprints are defined as an author’s version of a research manuscript prior to formal peer review at a journal, which is deposited on a public server. ResearchGate (RG) said about "Preprints": early-stage research. On the other side, RG is not a publisher and, in turn, uploaded unpublished text is not regarded as a publication. Hence, a preprint is an author's own original or draft version of their paper before any peer review has taken place and before it is published.
Before answering this valuable question, please let me give my own opinion about the preprint dilemma (مُعضلة ما قبل الطباعة):
I have a different perspective on uploading any preprint anywhere before it has been published. Why do you let others know about your insights and methodologies before publication? You should avoid telling the other researchers about the details of any one of your papers until it has been published and seeing your name by yourself. You may say that I am somewhat old-fashioned, but I have a different perspective on uploading any preprint anywhere before it has been published by your name. My advice is not to put your research anywhere until it is published. It is a security issue:
  • Your manuscript may be copied and then published by others before you can do that. This stealing of your paper might be happening. So, you must wait until the paper is accepted and then published in that journal. Then, upload that research item on any platform you wish.
  • A journal may have automated plagiarism software to check the paper before admitting it to the reviewing process. There are chances that your paper can get a rejection at any point. Thus, to avoid this problem. Publish the preprint after you got the paper as "ACCEPTED".
  • There may be a "cold war" between the professors of a given department. They do not like to discuss ideas as others will "steal" them and publish an article on them without giving credit to the one from whom they got the idea. My suggestion is to keep your work "private" and share it only with those who are really interested.
  • Academic publishing remains a competitive process. If someone else has recently published a paper very similar to mine, mine is less likely to be accepted. So although I may share my topic, I prefer to keep my methodology, findings, and discussion private, until published in a peer-reviewed journal. So. there is a high chance that someone may claim your idea as theirs!
  • Preprint gives a false feeling of security. Personally, I would always wait until the paper is accepted by the editor of a journal. After that, I can post it as a regular research item on any platform you wish.
Finally, for the coming future, do not upload any paper anywhere until it is published with your name. Even if it is a "preprint"! For the time being, If you had done something like that as a "preprint", for instance, I advise you to delete the preprint from any elsewhere and wait for two months before sending the paper to any journal.
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Does anyone has an experience with sodium tert-butoxide? How dangerous it actually is?
Do I need to use a glovebox while weighting and handling it?
Do I have to dissolve it in THF at -30C or room temperature will also do?
How do you store it after the can is opened?
We have 100g of sodium tert-butoxide in total, the planned amount for my synthesis is ca. 1.5 g.
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Do not breathe dust/fume/gas/mist/vapours/spray. Avoid breathing dust/fume/gas/mist/vapours/spray. Use only outdoors or in a well- ventilated area.
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This is a graphical abstract image from one of the paper of eminent total synthesis chemist KC Nicolaou. Can anyone tell me how I can draw such type of image?
Please comment
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Hi everyone!
I am working on different polymers and modifying them chemically and I want to write the chemical reaction. If I want to confirm whether the proposed chemical reaction is right or wrong, is there any software or something?
Thanks for your help!
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You can use the :-
- ChemReaX (is a free web app for modeling and simulating basic chemical reactions)
- Molecular Workbench
Best Wishes...
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Hi all,
To set things clearly: I am a PhD student working on the process implications of electryfing the ammonia production by replacing conventional SMR with Water Electrolysis. A part of my preliminary work is to assess the difference in theoretical minimum energy consumption. To do so, I have calculated a first approximation by summing up the reactions (SMR, Water gas shift, Haber-Bosch,...) and calculating the enthalpy of the resulting "total" reaction. I have done this for the "Water Electrolysis + Haber-Bosch scenario" and validated the minimum with values from the literature.
However, for the conventional "SMR + Haber-Bosch scenario", values from the literature are different. To be more specific, here is the energy minimum calculated in the following conference paper:
(...) the theoretical minimum of energy consumption for the process itself (represented by LHV of methane) is 22.2 GJ/t NH3 (...)
So here is my question: Why use the LHV of methane (instead the enthalpy of reactions) to calculate the energy minimum ? I feel like this is incorrect as I do not take into account the synthesis of methane.
Thanks in advance for any answers,
Antoine
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The paper you cited also includes the combustion of methane to provide the energy needed to account for the endothermic reaction as well as bringing the reaction temperature to that where the reaction occurs (850 C). For the combustion reaction, the LHV of methane is appropriate, where as for the SMR reaction, the heat of formation is appropriate. The reactor(s) consist of tubes packed with catalyst where the SMR, WGS, and HB reactions occur. On the outside of the tubes, CH4 is burned using either air or pure O2 to provide the energy needed for the process.
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Dear all
Hope you are doing well!
What are the best books in Materials Science and Engineering (Basics and Advanced)? Moreover, what are the best skills (or materials topic related) that materials scientists have to develop and to acquire?
Thanks in advance
^_^
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Dear all, following a list of interesting books. My Regards
- Fundamentals of Materials Science and Engineering: An Integrated Approach, William D. Callister, David G. Rethwisch, 5th Edt (2015).
- Materials Science and Engineering: An Introduction, 10e WileyPLUS NextGen Card with Loose-Leaf Print Companion Set, Callister Jr., William D., Rethwisch, David G. 10th Edt (2018).
- The Science and Engineering of Materials, Donald R. Askeland, Wendelin J. Wright. 7th Edt (2014).
- Materials Science and Engineering: A First Course, V. Raghavan, (2004).
- Foundations of Materials Science and Engineering, Willaim Smith, Javed Hashemi, 6th Edt (2019).
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This statement is claimed by
Simplistic notion of law of mass action or common ion effect cannot explain it . So what is the reason?
Please do not refer to the references on the paper
Kron I, Marshall SL,
May PM, Hefter G, and Konigsberger E (1995) The ionic product of water
in highly concentrated aqueous electrolyte solutions. Monatshefte für
Chemie 126: 819–837.
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At initial concentration, atoms of the salt molecules have not ionized to form part of the solution. The already auto-ionized water ions(H+ & OH- ) tend to interact with the salt molecules until complete ionization can take place.
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Dear all,
what are the possible instruments to use to obtain the purity of a powder (NaCl sold in a pellet form) (has 99% purity or above)?
the cheapest instrument to the expensive one if possible according to your experience
Thank you in advance
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Purification of chemicals is a large branch of chemical technology, with a large number of non-universal methods. In the case of NaCl, it is sufficient to simply recrystallize it from an aqueous solution.
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0.1 N concentration solution of both was taken, with HCl as titrant abd HPh as indicator. After reaching the endpoint of colourless condition, the colour reappears after continous shaking for 5 mins. even sometimes after 15 mins. How to be sure of that this much time is enough, for shaking to confirm completion of titration?
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in case of titration, 0.1 N sodium carbonate solution the required hcl concentration is concentrated or 0.1 N solution used.
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Good day,
i have a general question about tissue culture.
I have found the following recipe for Epipremnum Aureum "Marble Queen":
Leaf Explant: MS Medium + 4.54 µM TDZ + 1.07 µM NAA (Thidiazuron in Micropropagation of Aroid Plants by Chen and Wei (2018), p. 105, DOI: 10.1007/978-981-10-8004-3_4)
Specifically, I have the following questions.
1) Do i only need to autoclave the agar with distilled water (I use a pressure cooker for this) and when the agar has cooled down a bit just add the MS, TDZ and NAA and mix it or do i need to autoclave the MS as well?
2) Will the TDZ dissolve in the agar water at all and how hot can the agar water be to add the MS, TDZ and NAA?
3) Is it even necessary to autoclave the water incl. agar (in the pressure cooker) if I clean all the jars with NaClO (sodium hypochlorite)?
Thank you in advance!
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In general, all things associated with tissue culture need to be properly sterilized. For me, I autoclave the complete media (MS, hormones(I use 2.4-D, NAA, BAP, Kinetin), and agar) along with the culture vessel (petri dish or test tube). But it is better to filter sterilize (.2 micron) the hormones and vitamins (of the media) and add them to MS media (agar mixed) when the temperature drops to about 50 degrees celcius.
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Kindly discuss your ideas and viewpoints on the origin of life and the RNA world hypothesis.
What are the contradictory views on why researchers are still unsure about the origin of life through RNA or such analogous molecular intermediate pre-cursors preceding its existence?
"The general notion of an “RNA World” is that, in the early development of life on the Earth, genetic continuity was assured by the replication of RNA and genetically encoded proteins were not involved as catalysts. There is now strong evidence indicating that an RNA World did indeed exist before DNA- and protein-based life. However, arguments regarding whether life on Earth began with RNA are more tenuous. It might be imagined that all of the components of RNA were available in some prebiotic pool and that these components assembled into replicating, evolving polynucleotides without the prior existence of any evolved macromolecules. A thorough consideration of this “RNA-first” view of the origin of life must reconcile concerns regarding the intractable mixtures that are obtained in experiments designed to simulate the chemistry of the primitive Earth. Perhaps these concerns will eventually be resolved, and recent experimental findings provide some reason for optimism. However, the problem of the origin of the RNA World is far from being solved, and it is fruitful to consider the alternative possibility that RNA was preceded by some other replicating, evolving molecule, just as DNA and proteins were preceded by RNA." - Robertson and Joyce
[This is as per the explanation by Michael P Robertson and Gerald F Joyce in the article: "The origins of the RNA world." published in the Cold Spring Harb. Perspect. Biol. 4, a003608 (2012).]
The scientific community must resolve this contradicting conjecture through rational discussion and debate backed by strong experimental evidence on what must be the pre-cursor molecule to the Origin of Life if it is not RNA!
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One of the issues that is holding the concept of an RNA world back from being more scientifically useful - irrespective of whether there ever was such a thing - is that we don't use the idea in the scientific way it was intended. Just like any other prebiotic scenario, it is not (nor has it ever been) a scientific hypothesis. In fact, scenarios are usually not intended as such. Scenario authors from all niches (including RNA world) have pointed out that scenarios themselves are untestable. However, they guide thinking and allow to conceive of hypotheses that are testable. If we go through the old literature we find very explicit passages to support this fact.
For the specific authors advanced in the question, G.F. Joyce and L.E. Orgel, we have a passage from 1999 in "prospects for understanding the origins of the RNA world". (The RNA World 2nd ed. 49-77).
"The presumed RNA World should be viewed as a milestone, a plateau in the early history of life on earth. So too, the concept of an RNA World has been a milestone in the scientific study of life's origins. Although this concept does not explain how life originated, it has helped to guide scientific thinking and has served to focus experimental efforts."
You can find this point of view expressed in foundational work for all niches related to the popular scenarios today. But you can also find it for scenarios most people in origins have never heard of. E.g. the idea that celllular life started with terpenoids found in G. Ourisson and Y. Nakatomi's "the terpenoid theory of the origin of cellular life: the evolution of terpenoids to cholesterol. (1994) Chem & Biol. 1 11-23".
"The hypothesis provides an attractive way of ordering the terpenoids: like all evolutionary theories, it cannot be tested directly. The ideas summarized here do, however, suggest a multitude of experiments having some bearing on the fundamental and fascinating question: how did the first cells appear? We hope to carry out some of them."
A related line of thought - but highly influential - is the exposition by Harold J. Morowitz from 1992 in his book "Beginnings of Cellular Life: Metabolism Recapitulates Biogenesis". If we go to the conclusion, we find this explicit clarification on the distinction between a genuine scientific theory and a scenario:
"at this stage of the thought process, it is important to focus on the hypothesis that intermediary metabolism recapitulates prebiotic chemical evolution. This hypothesis is not a strictly vulnerable theory in the Popperian sense, but it does provide us with a valuable heuristic method for using modern knowledge of biochemistry to search for events that have left their trace. If the intermediary metabolism of autotrophs does not recapitulate biogenesis, then the discontinuities will have to be explained."
More than 2 decades back, many authors made a clear distinction regarding this nuance. Scenarios are here to help: they guide thinking and design experiments. They only guide thinking in a scientifically meaningful direction as long as we can easily abondon scenarios and enthusiastically continue replacing them with new, more informed scenarios. A situation where a scenario gets entrenched and where researchers treat it as a scientific hypothesis is - by construction - hard to escape.
In fact, this is exactly the situation that many researchers have described around the 80s, when criticism mounted against the prebiotic broth scenario. The passage from Wächtershäuser's 1988 "Theory of a Surface Metabolism" is telling:
"The prebiotic broth theory has received devastating criticism for being logically paradoxical (11, 135), incompatible with thermodynamics (11, 144, 160), chemically and geochemically implausible (134, 136, 144), discontinuous with biology and biochemistry (160), and experimentally refuted (135, 160). The reason for the tenacity with which it is retained as accepted dogma has been forcefully and clearly stated by Scherer (126): "If this rejection is substantiated, there will remain no scientifically valid model of the selforganization of the first living cells on earth."
Clearly, the broth scenario had overstayed its welcome. One reason for this is that its 'claims' (which for a scenario can only be speculations) were too much in contradiction with claims from fields of science that do not suffer the same restrictions when it comes to testing and refuting their theories. One example of a very controversial idea that can be found in Haldane's formulation of a broth scenario, is the purported necessity of a long, highly functional protein randomly emerging from a soup, as an extremely rare event: we expect this to be prohibitively unlikely and hence a far from parsimonious explanation.
Quite a few of the critiques voiced against the prebiotic broth scenario are equally valid critiques of some scenarios we have today, including RNA world.
The RNA world is an old and multifaceted concept. There are contrasting formulations that make different claims (to be interpreted as speculations) about history. As with the prebiotic broth scenario (and any scenario), it has raised genuine scientific objections. These have remained largely unadressed, in spite of its long dominance.
It is instructive to bear in mind that scenarios don't come from nowhere. They're fairly detailed speculations about purported historical events. To make them, each author makes assumptions. Some of these concern speculations that later became testable, e.g. about chemistry and physics. You will find different scenario authors make different assumptions and different arguments (and flaws therein). There's an inevitable bias here with respect to the fields an author is trained in. Some of the foundational assumptions in popular scenarios like RNA world are at least 50 years old, but some unchallenged assumptions date back to a literature that is more than a century old. A time before IUPAC, modern quantum mechanics, genetics, and so forth.
That has been enough time to forget that scenarios like RNA world are by construction not testable hypotheses and that they were not intended as such. Scenarios are here to guide thinking, to inspire experiments. The best thing a scenario can do for us, is generate insights that spur us to change the way we think and thereby necessitate replacing our old scenarios with new ones, and repeat the cycle. The science coming out of the community today is a lot more conducive to doing that than previously.
The same cannot be said for the rather myopic RNA-centric framing of a question in the cited passage, which attempts to elevate RNA world to more than a scenario. Rather than forcing ourselves to think about the rather narrow and outdated proposal by Joyce and Robertson, ("consider the alternative possibility that RNA was preceded by some other replicating, evolving molecule"), it is more productive to critically revisit all the things that have been assumed and argued when the concept of an RNA world was conceived and how which of these premises are considered valid or plausible today, and which ones back then. Is there a formulation of RNA world for abiogenesis that is logically sufficient? And if so is it logically necessary that abiogenesis proceeded this way?
It is also instructive to check how much of the logic was sound. e.g. the rhetorical tricks employed in RNA world introduce all sorts of hidden assumptionsm.
As an example of the latter: some still justify an RNA world by the party trick 'chicken-and-egg' question 'protein or RNA, which came first?', only to conclude with 'RNA, it encodes proteins' and hastily conclude with an even stronger 'RNA-first' for abiogenesis. 'chicken-and-egg' fallacies are nothing new in origins. In fact, they were already identified as such long ago. E.g. in chapter 8 of "Seven Clues to the Origin of Life (1985)" by Cairns-Smith, there's an illustrated passage detailing that these types of paradoxes in origins frame the question in a manner that prevent us from considering scaffolds.