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  • David L Thorn added an answer in Reactors:
    How can I clean up the borazine byproducts (white powder) in the reactor?

    I have used borazine liquid for hBN growth. After many experiments, there are white powder left in the tube and finally it was blown into the quartz reactor. I dont know exactly what the white powder is. As borazine itself is highly reactive and can not contact with water. Anyone can give any suggestions how to remove these white powder and clean the quartz tube. Thank you.  

    David L Thorn

    The white powder may be boric acid per Rafik's suggestion; if so then aqueous ammonia or sodium hydroxide should remove it easily.  It may also be a polyborate, if so then aqueous ammonia or sodium hydroxide should remove it eventually but it may take several hours or days.  It may also be a polyborazalene which may resist treatment with aqueous ammonia / NaOH, if so then you might try dilute aqueous HF or ammonium fluoride - be immensely careful handling these, avoid skin/eye contact.

  • Thierry Wambo added an answer in Carbonic Anhydrase I:
    Which of PH-sifted assay or esterase assay is the most accurate?

    I am not very familiar with techniques used in experiments when it comes to find Ki of a ligand. For a protein such as carbonic anhydrase, I realized (from litterature review) that the reported Ki for the same molecule will generally vary if the PH-sifted assay is used instead of the esterase assay. Apparently PH-sifted assay usually gives lower values than the other technique. Which of these techniques should be most trusted or is more accurate?

    Thank you!

    Thierry Wambo

    Dear Adam,

    Thank you for your explanations.

  • Lotfi Zeghadnia added an answer in Computer:
    How to compute Lambert Function (W)?

    Lambert function has been proposed by Jean-Henri Lambert, some times called Omegat function (W).

    the equation can be written as following:

     xexp(x) = z  this means that x= W0(z)

    So the question is , how can i compute W0?

    Lotfi Zeghadnia

    Dear Mykola Kozlenko:

    The doc is interesting, thank you So much  for your contributions.

  • Mozafar Karamian added an answer in Gravitational Field:
    Is the non locality of the gravitational field energy a serious problem for General Relativity (GRT)?



    "Although there is no room for such a thing in the energy–

    momentum tensor T, it is clear that there are situations where a ‘disembodied’

    gravitational energy is actually playing a physical role.

    Imagine  two massive bodies (planets, say). If they are close together (and we can

    suppose that they are instantaneously at rest relative to each other), then

    there will be a (negative) gravitational potential energy contribution which

    makes the total energy, and therefore the total mass, smaller than it would

    be if they are far apart.  Ignoring much tinier energy effects,

    such as distortions of each body’s shape due to the gravitational tidal field

    of the other, we see that the total contributions from the actual energy–

    momentum tensor T will be the same whether the two bodies are close

    together or far apart. Yet, the total mass/energy will differ in the two cases,

    and this difference would be attributed to the energy in the gravitational

    field itself (in fact a negative contribution, that is more sizeable when the

    bodies are close than when they are far apart)." 


    The same problem was also rised by Thirring, Kalman and Feynman in the FGT theory, they inserted the gravitational energy in the tensor equations...

    It is a problem of paramount importance which prevents the General relativity theory from describing any motion in which the hamiltonian is time dependent or rather in case of non isolated systems, or in case of non stationary interactions between different bodies.

    The attempt to model a free falling body in a gravitational field for GRT seems impossible.

    GRT has been tested  only for static or stationary systems where there is not a net exchange of energy (excluding gravitational radiation)

    Don't we need another GRAVITATIONAL THEORY which includes the results give by GRT in order to explain with a better accuracy the simple phenomenon like the free falling of a mass in a gravitational field?

  • Vassilis Doucas added an answer:
    In simplistic terms Banach tarski theorem means we can get something from nothing ,is it not?

    if true then nothing is  a source not only of Einstein equations but also for every thing. This is in perfect agreement with set thory

    Vassilis Doucas

    Dear Mohamed,

    I do not know a lot about Banach Tarski theorem but the field is very intriguing. To my opinion, the answer consists of positioning one point and then creating infinite points. For the moment that we need to create and to introduce geometrical notions in a philosophical conception then we assume that there is something. So, nothing can the source of something if we accept that something has nothing as an origin.

    In my original paper in Signal coordination at the cellular level, I have said that: ‘It could be hypothesized that the build-up of subnuclear space might contribute to “reactivation” of its components in such a way that it is coding of units compartmentalization and an embodiment of the subnuclear space “collective memory”. As the compartmentalization of the molecules transforms the subnuclear space into a domain of new experience, the subnuclear space, in the very process of its production, might become a means of control through its multiplicity of networks”.

    To my mind before “the build-up of subnuclear space” exists nothing as there is no space. At the moment that we accept the build-up of space then we obtain something because we create a memory and a coding-system.  That is very critical in biological sciences – I think.  

    Your question resembles in a way to the 'chicken and the egg' conundrum for life’s beginnings.  An egg could be consider the nothing and the chicken the something or the vice versa.  Both are simple points. They become something as we create memory and a coding system, if not they we will be nothing for ever. / If, we reorganize the scattering points of an egg or a chicken we can obtain a chicken or an egg – depends the order. I think this is life. Best, Vassilis

  • Farhan Younas added an answer in Protein Denaturation:
    Urea as protein denaturant?

    Do you know If the urea is quite more efficient than SDS as a protein denaturant?  I always experience a smear in my SDS-PAGE and I thought Urea may help me in getting rid of this smear.

    Farhan Younas

    Well, normally i donot have problems in using excess of the SDS dye, but what you can try is to dilute the sample in pbs or tris then try running the gel after adding dye. what could also help is that if your sample is having some debris, then after adding the dye and denaturing it, centrifuge the sample for 2 mins at max speed, then load the supernatant on the gel.


  • Peter D Southon added an answer in Phase Change:
    Any suggestions on a phase-change temperature-calibration material?

    I'm looking for a material with a solid-solid phase change in the range -40 and 20 C, for calibrating the temperature in a diffraction experiment. I can't use a melting point as the material is under gas flow. All the standard materials I can find are too high (KNO3) or too low (Rochelle salt, etc). Any suggestions?

    Peter D Southon

    Thank you Helena, that table from Snell is just what I was after!

  • Adam B Shapiro added an answer in Detergents:
    Can any body advise about detergent extraction of difficult membrane proteins and common detergents used ?

    please suggest common detergents used in extraction of difficult membrane proteins.

    Adam B Shapiro

    If you don't need the proteins to be in a native state, you can use SDS. If you don't want to denature the proteins, you could try Triton X-100, sulfobetaine detergents such as Zwittergent 3-12 or 3-14, dodecylmaltoside, octylglucoside, and CHAPS.

  • Adam B Shapiro added an answer in PLGA Nanoparticles:
    I cant calculate protein encapsulation in PLGA nanoparticles?

    my blank NP absorbency in BCA method is higher than NP contain protein. it s maybe because PVA in blank NP or i dont have protein encapsulation. i confuse, also i used NaoH 1M and urea 10M+ SDS 2% and pbs for dissolve protein in pellet. please guide me if you have same experience,

    Adam B Shapiro

    Please consult the list of compatible substances for the BCA assay.


    You may have added too much of one or more interfering substances, such as urea (3 M is maximum). The pH may also be too high because of the NaOH. The combination of NaOH, urea, and SDS may be causing interference.

  • Samah Fathy asked a question in Immunology:
    How long can I store serum and plasma and what is better to preserve for longer time?

    Physiology or Immunology researchers

  • Jan Baxa added an answer in Aortic Dissection:
    Is there any possibility that contrast agents may trigger the rupture of thoracic aortic dissection (Stanford A type)?

    Actually, I am concerned with the association between the use of contrast agents and rupture of thoracic aortic dissection (Stanford A type).

    Here is the case I experienced recently. A 57-year-old male with a history of hypertension and atrial fibrillation visited our department with a complaint of chest pain. His consciousness was clear and his systolic blood pressure was 100 mmHg. TTE revealed dilated ascending aorta along with moderate aortic regurgitation. Immediately, contrast-CT was performed. Contrast enhanced CT revealed Stanford A type aortic dissection. There was no retention of pericardial effusion. Within a few minutes after that, he fell into CPA. TEE revealed massive retention of pericardial effusion. PCPS was introduced. However, PCPS did not work efficiently probably because of collapse in the right heart. Immediately, pericardial drainage was performed; drainage was not effective because of coagulated blood.

    In this case,

    Should we have performed pericardiotomy to save this patient?

    May contrast agents trigger the rupture of thoracic aortic dissection (Stanford A type)? Actually, I know several cases that thoracic aortic dissection ruptured immediately after contrast CT. I want a paper discussing this point.  

    Jan Baxa

    There is evidence, that CM administration could increase the heart rate, but I don't know about influence on BP. On the other hand, it is questionable if the small volume (cca 150 ml...CM + saline) injected in short time could jump the BP. Despite it can not be excluded, I am convinced that there is no direct relation. 

  • Adam B Shapiro added an answer in Glutamate:
    Why absorbance is not stabilized in an end-point enzymatic assay?

    Hi everyone,

    I'm having problems with a classic end-point enzymatic assay. It is the measure of glutamine and glutamate using the Lund method, based on the conversion of glutamate to 2-oxoglutarate by the enzyme glutamate dehydrogenase, so the increment in absorbance can be measured at 340 nm since NADH is generating from this reaction. Glutamine has been previously converted to glutamate using the glutaminase reaction.

    In the protocol it is said to incubate for 40 min and then measure the absorbance until it's constant. The problem is in my case the absorbance doesn't stop increasing, even with the standards after almost 2 hours. Normally is just the third decimal the one who changes, but if it doesn't stop increasing, the change at the end is considerable high. Indeed, there's a point where this absorbance is higher than the expected for the standard concentration (for example, if I apply the formula the protocol gives with a 90 min-absorbance for glutamate 0,2 mM I obtain 0,24 mM or so).

    Anyone has any idea what i'm doing wrong?

    Thanks !

    Adam B Shapiro

    If the reaction is slow to reach the endpoint, it may be because the enzyme concentration is too low or the enzyme has lost some of its activity. Try a fresh sample of glutamate dehydrogenase.

  • Rafik Karaman added an answer in Enzymes:
    What is the difference between fast digest and conventional restriction enzymes?

    The difference between fast digest enzymes and conventional ones is just in their buffers or the enzymes are different too?

    Rafik Karaman

    Dear Touraj,

    176 FastDigest enzymes available (ThermoFisher)
    A unique system of 176 FastDigest restriction enzymes formulated to have 100% activity in a single buffer.

    All FastDigest enzymes are 100% active in the universal FastDigest
    and FastDigest Green buffers and are able to digest DNA in 5-15
    minutes. This enables any combination of restriction enzymes to
    work simultaneously in one reaction tube and eliminates the need
    for sequential digestions. As an added convenience, the FastDigest
    Green Buffer allows for direct loading of the reaction mixture on gels.
    FastDigest enzymes are qualified for complete digestion of plasmid
    DNA, genomic DNA, viral DNA and PCR products. Digestion time
    and protocols are experimentally proved and provided for each of
    the FastDigest enzyme on each of the templates


    Conventional Restriction Enzymes—Thermo Scientific

    A system Containing 190 enzymes. Five Buffer System ensures the optimum reaction conditions for each restricton enzyme.


    For more details please access the two links indicated above.

    Hoping this will be helpful,


  • Oladotun Afolabi Oluwajana added an answer in Basin Modeling:
    How do I estimate Bottom Hole Temperature for 2 wells?

    I am trying to develop 1-D basin models for 4 wells in the same basin. Only 2 wells have Bottom Hole Temperature and there is no formation temperature for the four wells. How do I assume or estimate BHT value from nearby well.

    Oladotun Afolabi Oluwajana

    Thanks James.

    Well JW-1, Depth is (8691ft) and BHT (220F). The second well J-1, Depth is (6387 ft) and BHT (175F).

  • Mahlomola Mosala asked a question in Insulation:
    RE: Transformer Winding Insulation... How do I calculate the Interlayer Insulation thickness?

    Transformer Winding Insulation

  • Kenneth M Towe added an answer in Calcium Carbonate:
    How can we purify limestone which contain some impurities?

    what we want are the calcium carbonate only of Limestone.

  • Emmanuel Mogaji added an answer in Twitter:
    How to perform "frames in perception" content analysis and sampling of face book comments?

    I am looking to perform "frames in perception" analysis of face book comments. I am looking for helpful articles which could guide my research. Are there any identified "frames in perception" in social media specifically face book or twitter for that matter? 

    Secondly, the sampling of comments is another area of concern. As face book posts in those communities which are selected for this study usually have comments exceeding 5000. Is there any guideline regarding appropriate selection of sample?

    Thirdly, to perform aforementioned two tasks, Is there a better software?

    Emmanuel Mogaji

    Actually now aware of  "frames in perception" though I have qualitatively explored Facebook comments, please keep me posted of your research.

  • Analjyoti Basu asked a question in Research Papers:
    If there are any ways to measure individual entrepreneur's entrepreneurial intensity?

    If there are any ways to measure individual entrepreneur's entrepreneurial intensity? If yes kindly provide some research papers regarding it.

  • Mateusz Mrukiewicz added an answer in Birefringence:
    Is it a rule that Nematic LC must always show optical birefringence or there is any exception?

     I had not been able to detect any birefringence in one LC compound in my experiment using thin prism technique.

    Mateusz Mrukiewicz

    Yes,  it could be. 

  • Morton E. O'Kelly added an answer in Atmospheric Correction:
    How do I know the longitude and latitudes to use in the NASA's atmospheric parameter calculator using Landsat 5, 7 and 8?

    I am trying to make use of the NASA's Atmospheric Correction Parameter Calculator (http://atmcorr.gsfc.nasa.gov/). Which coordinates should I use in the calculation? There seems to be only one coordinate to be specified for the calculation. Would any coordinate which falls within a Landsat scene suit the estimation?

    Morton E. O'Kelly

    From reading the data entry page, it seems that it is going to do a calculation for each integer lat and long, and it will interpolate for "real" values. So, you could do this request for each integer lat and long in your scene.

  • Alexa Wu asked a question in Spiders:
    These are human MSC I've cultured, what do you think?

    Hi! This is my first time to culture MSC(from MDS patients' BM), I notice there are three kinds of MSC: 1. stretched and big,irregular in shape,with sandy granule near nucleus,  most frequently seen  2. thin and long,spindle-like. 3. flat and faint in color,with spider like reticulate structure in cytoplasm. These can form extraordinarily orginaized structure can they are confluent, some expand as colonies, with adipocytes in the center. What do you think of these cell,are they typical MSC in morphology? Do the different morphology signify anything? Thanks!

    + 3 more attachments

  • Lisbeth Nilsson added an answer in Occupational Therapy:
    Are there any studies on the inclusion of stereotype threat by occupational therapists in their practice?

    I'm an french occupational therapist and I study in master of education science and my thesis for my master is about stereotype threat and occupational therapy.

    If somebody can help me a little because i don't found a lot of article about this.

    Lisbeth Nilsson

    Dear Renaud Janet, do I understand it right that you study OT's stereotype threat towards clients/patients/relatives? Do you focus a specific OT practice, group of clients or diagnosis? What kind of method do you use? a litterature study? or some other method?

    It would be interesting to hear your opinion of how conscious aware we are of our own stereotype threats towards other people in our professional and private life.

    Good luck with your study.

  • James R Knaub added an answer in Econometric Methods:
    How do I compare countries statistically in terms of their history and development phases?

    I am looking for a statistical/econometric method that could be used to compare 6 countries w.r.t. to their historical and developmental phases. 

    James R Knaub

    Nandini  - 

    Perhaps you could compare per capita GDP graphically?  

    Whatever you decide to compare, you should check first into the accuracy of the statistics, to see that differences between countries are meaningful.  I worked for many years at a statistical agency, which produces official statistics on the energy industry, and it seemed to me that often data users might assume greater accuracy than was present, and think of a difference as being meaningful, when it wasn't.  So you want to look into both sampling and nonsampling error, bias and variance. Official Statistics often are accompanied by technical notes that provide metadata, or at the very least, some standard errors.

    Best wishes - Jim

  • Nicholas Youngblut asked a question in Typing:
    Could any type of nuclease be biased for 12C-DNA versus 13C-DNA?

    If so, how much bias do you think is possible?

  • Mary Jensen asked a question in Love:
    Any one have papers on counseling jail inmates?

    May be going to work at a city jail as a counselor and would love some papers to read on the subject.

  • Cornelia Monzel added an answer in Data:
    With only 6 data, which method is the most suitable method to model out the data?

    From glance, it looks like it follows gamma or normal distribution.

    Cornelia Monzel

    With only 6 data points statistics are difficult as you can not surely say what type of distirbution it follows. Always determine the median and work with box plots.

  • Stephen Cranwell asked a question in Endothelial Progenitor Cells:
    Is there a universal exocytotic tag or sequence for proteins?

    I am a masters student and have a presentation of theoretical applications of regenerative medicine. I need a xenoenzyme to be exocytosed from an endothelial progenitor cell. I thought there would be a know tag/ sequence that could be incorporated to tell the cell to export the protein but I have had no luck finding any. How would you go about ensuring this protein is secreted by the cell?

    Any help is much appreciated. Thanks!

  • Chithan C Kandaswami added an answer in Antioxidant Assays:
    In vitro antioxidant assays-waste of money and time?

    Dear All,

    Recently, I have attended two conferences in Europe (EuroFedLipid, Florence, Italy and EuroFoodChem, Madrid, Spain). During many presentations on ANTIOXIDANTS, I have observed that, many researchers have repeatedly highlighted in vitro antioxidant studies are really useless and it does not have any 'real' significance! They have argued that the results will never have any significant correlation with in vivo studies.

    We can find thousands of studies on  in vitro antioxidant assays of plant extracts, synthetic compounds, nanoparticles, so on. I am sure there are so many researchers are working on it and writing their papers. 

    What is your opinion? We must stop such assays and spend our time and energy on other aspects of science?

    Chithan C Kandaswami

    The aspect of mutagenicity (paper by H. Stich et al on ascorbate and mammalian mutagenicity) was simply mentioned here in the light of Dr. Nobosse’s comments above (Paracelsus and the issue of toxicity). I was not trying to make a point on mutagenicity here.

    It is known that flavonoids possessing vicinal hydroxyl groups can autoxidize in aqueous media at biologically relevant pH and radicals subsequently generated can cause strand scission of DNA. This could explain the observed effects of these compounds on the frequency of chromosomal aberrations caused in cultured cells exposed to these flavonoid constituents. Bacterial mutagenicity studies on plant flavonoids, which have generally employed pharmacologic concentrations of the compounds, are known to have yielded highly complex, inconsistent and contradictory results. Certain studies have reported weak mutagenic activity (or minimal mutagenic activity) of some (hydroxylated) flavonoids. In the investigations of MacGregor and Jurd, and of MacGregor and Wilson, the same flavonoid compounds showed different mutagenic effects in different tester strains of Salmonella typhimurium. The mutagenic response was reported to be  greatly dependent on the absence of excision repair and the presence a certain plasmid. Other authors have reported on the mutagenic effects of flavonoids tested in Salmonella typhimurium strains, TA 98, TA 100 and TA 102; quercetin was mutagenic only in TA 98. Taxifolin (dihydroquercetin, a pentahydroxy compound), a flavonone in which the middle ring, the heterocyclic C-ring of the flavone, lacks a 2,3-double bond was only weakly mutagenic in tests with Salmonella typhimurium strains. Taxifolin possesses vicinal hydroxyl groups (amenable for autoxidation and redox cycling) in its B-ring (3’-4’). Quercetin and another flavonoid, kaempferol, were studied for their mutagenic effects on cultured mammalian cells. They produced point mutations only at pharmacologic concentrations.

    MacGregor JT, Wilson RE. Flavone mutagenicity in Salmonella typhimurium:dependence on the pKM101 plasmid and excision-repair deficiency. Environ MolMutagen. 1988;11(3):315-22. PubMed PMID: 3281825.  MacGregor JT, Jurd L. Mutagenicity of plant flavonoids:structural requirements for mutagenic activity in Salmonella typhimurium. Mutat Res. 1978 Dec;54(3):297-309. PubMed PMID: 368618. 


  • Ihsan Ates added an answer in Cardioprotection:
    Are serum calcium and serum lipid levels cardioprotective before any type of myocardial infarction?

    Also do we recommend restriction of calcium or else normal intake of calcium in the dietary schedules of patients who recently underwent coronary stunting and why?

    Ihsan Ates

    we do not recommend for the development of atherosclerotic plaque