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  • Jia Ning asked a question in Liver Microsomes:
    Does anyone know where to find the liver microsome/S9 from Chinese population?

    I want to do risk assessment for Chinese population. Therefore I need to use the liver microsome and S9 from Chinese donors. However, I found many companies that they only sold liver microsome/S9 from Caucasian. Does anyone know how to solve my problem?


  • Proceso Fernandez asked a question in Equation of State:
    Is it possible to reconstruct the adjacency matrix of a graph using the diagonals of its powers?

    Let G=(V,E) be a simple undirected graph with n vertices, and let A be the adjacency matrix representing G.

    It is a known property that in A^k (i.e., the kth power of A), the element at row i column j has a value equal to the number of k-length paths from vertex i to vertex j. Thus, the ith diagonal entry of A^k is the number of k-length paths from vertex i to itself.

    Does anyone know if it is possible to reconstruct the adjacency matrix A, i.e., determine all the values at every row and column, if the diagonals from a sufficient number of powers of A is known?

    Why this may be possible: 

    - The graph reconstruction is equivalent to solving for the values of a_(i,j), for all i < j in the adjacency matrix A. (Since the graph is simple and undirected, then a_(j,i)=a_(i,j) and a_(i,i)=0).  Thus there are n(n-1)/2 variables to be computed, each of which is either 0 or 1

    - Each element in the diagonal of A^k corresponds to an equation involving the the a_(i,j) variables.  This is because each of the powers of A^k can be expressed as dot products from A.

    - Thus in principle, if m powers of the adjacency matrix A is known, where m=ceiling( (n-1)/2 ), then there would be at least n(n-1)/2 equations from which all the unknown variables can be computed.

    Why this may be not possible: It is not obvious however (to me, at least) if the n(n-1)/2 equations stated above are sufficient. This is because it may be possible (unless proven otherwise) that some equation can be derived from other equations, e.g., a linear combination of some other equations. 

    I would appreciate any help, either an answer to this question, or at least  some directions that I may explore.  Thanks!

  • Sadeeq Ur Rahman added an answer in Codon Optimization:
    What is the best method to find out codon optimizaiton?

    I am trying to optimize gene (click beetle luciferase) expression in Listeria (gram+), how and what is the best method to do codon optimization, finding out rare codon etc. is there any good software ?

    Sadeeq Ur Rahman

    Thanks Ishiaq sab and happy to see your good contribution in science. I guess i had met you during a conference at LUMS in Pakistan.

  • Alan Short added an answer in Gamification:
    What are the benefits of using technology and/or gamification in conjunction with outdoor explorations?

    My focus is on middle school, although I feel that I can learn from any age-level experience.  I'm looking at technology or gamification and how it can assist environmental education, place-based education, or field investigation/ exploration.

    Alan Short

    Major benefits of technology:

    1) Real time data capture and communication (for surveys etc). Photos, notes, databases (e.g. Cybertracker)

    2) vast amount of data (e.g. field guides, maps) available in a single device (several field guides now have excellent electronic versions which include far more information than the print field guide)

    3) Citizen science involves ordinary members of the public in research, and has an effect on the enthusiasm and participation of ordinary people. Science becomes something not just done by boffins. Most modern citizen science relies strongly on technology

    4) Social networks allow nature enthusiasts to quickly share photos and their thoughts to others, which can cause others to become more enthusiastic

    5) Bring nature closer to people who may have less access to it.

    6) Apps like Google Maps can illuminate landscape processes while students are studying local processes. Zooming in and out allows fine detail to be observed, as well as the greater topography and context (e.g. distance from urban encroachment, patterns of wetlands). This can be powerful in the field

    7) Today's kids are incredibly innovative and may be inspired to create new apps, tools or technology to assist with recording or conserving nature. Using technology in the field allows them to see the possibilities and that nature is not incompatible with technology

    Major benefits of gamification:

    1) Present complex concepts in a simple form which allows people to better understand causes, consequences and linkages. Much media presentation of natural phenomena is incredibly oversimplified.

    2) often can tap into people's competitive instincts so that they want to "win" - in the process learning far more lessons than by other methods (I've seen this with kids especially).

    Disadvantages: technology can be overused and separate us from nature. Nothing replaces experiencing and handling nature in person, especially with a knowledgeable mentor.

    Bottom line: technology is a powerful supplement to nature learning, but not a replacement

  • Vladimir Dusevich added an answer in Academic Writing:
    Citing Wikipedia?
    While Wikipedia is more and more popular with students, professors discourage them from using it and bar them from citing it. What are reasons (to cite or) not to cite Wikipedia?
    Jul 31, 2012
    Vladimir Dusevich

    Citing Wikipedia - or any other encyclopedia - makes author looking dumb enough to reject his/her paper immediately. At least in all the cases when paper is not about encyclopedias. 

  • Mostafa Sahebdel added an answer in Finite Volume Method:
    Can you help me to find a good refrence about FVM?

    I need a good and easy to explain reference about Finite Volume Method except Leveque. I'm greateful about helping me to find it.

    Mostafa Sahebdel

     Thanks a lot dears, for answering my question and offering the useful references.
    Dears, I am looking for references that explain different types of slope limiters that use in Finite volume or Finite difference methods when we encounter to shock.
    Thanks alot

  • Camille Hallez added an answer in Antibody Detection:
    Do you know a good antibody against HBV capsid for western blotting ?

    Hi all,

    I am currently searching for a good antibody to detect HBc proteins in western blotting (and why not in immunofluorescence). I tested an antibody from Santa Cruz but I'm not really convinced. For now, I especially need something for western blotting to prove that I do have viruses after purification (I'm interested in proteins inside the capsid, I detect them in WB, but i lack the control...)

    Thanks for your help !

    Camille Hallez

    Tnahks you. I saw that Abcam proposes antibodies to HBV core but I didn't know what was the best (because they have 2 or 3 different antibodies) ! So I hoped somebody had already tested them, because technical sheets can be beautiful but far from truth...

  • Guy Brachya asked a question in Cryopreservation:
    How can I cryopreserve activated natural killer (NK) cells?


    Does anyone have experience in cryopreserving activated NK cells?

    I've tried multiple freezing and thawing methods but the cells die within a few hours after thawing.

    The cells source is healthy human PBMN and activation was done with IL-15 supplemented culture medium for two weeks.

    Thank you,


  • Andrew Duncan added an answer in Satellite Data:
    Could somebody guide me to know calibration algorithm between satellite rainfall and gauge data in the case of TMPA and GSMap data?

    I am comparing the satellite rainfall data and ground gauge data in some countries of Africa and South America. I understand the satellite rainfall value is calibrated (rescaled) based on some gauge data, usually monthly value, except CMORPH . So when I try to compare the satellite data and gauge data, I think i should know actually which gauge data for the specific area were used for the product of satellite rainfall such as TPMA and Gsmap, etc. I think the availability of gauge data in Africa and South America is different. Could somebody guide me to learn from papers about this ? Thank you in advance. 

    Andrew Duncan

    I would suggest that this problem is analogous to merging of radar rainfall estimates and raingauge data, since the radar is represented by a grid of values (similar presumably to the satellite?) and the gauge observations are spot values at different x-y locations within the grid, not necessarily at the nodes.

    Therefore I would suggest you look at kriging or co-kriging methods as a way of combining the two data fields and producing a calibrated joint estimate. Early papers tended to regard the gauge data as "ground truth" and arrange to correct the radar data, but more recently it has beome obvious that both sets of observations have (different) errors and that a way of combining so as to minimise the errors is needed.

    The following papers may be of use in this regard...

    Krajewski, W.F., 1987. Cokriging radar-rainfall and rain gage data. J. Geophys. Res. Atmospheres 1984–2012 92, 9571–9580.

    Ochoa-Rodriguez, S., Wang, L.-P., Grist, A., Allitt, R., Onof, C., Maksimović, Č., 2013. Improving the applicability of radar rainfall estimates for urban pluvial flood modelling and forecasting, in: Urban Drainage Group Autumn Conference and Exhibition.

    Sinclair, S., Pegram, G., 2005. Combining radar and rain gauge rainfall estimates using conditional merging. Atmospheric Sci. Lett. 6, 19–22.

    Wang, L.-P., Ochoa-Rodríguez, S., Simões, N.E., Onof, C., Maksimović, Č., others, 2013. Radar-raingauge data combination techniques: a revision and analysis of their suitability for urban hydrology. Water Sci Technol 68, 737.

  • Kimia Kim asked a question in Hamiltonian:
    How can I write Hamiltonian by considering screening effect?

    Can you please let me know how I can write Hamiltonian by considering screening effect? Which book I can find formula:

  • C.A. (Kees) Kan added an answer in Pesticides:
    Is there any proven toxic impact of organochlorine pesticides on humans?


    C.A. (Kees) Kan

    In the 1960's Hexachlorobenzene (HCB) caused mass intoxications a.o. porphyria in humans in Turkey.

  • Geziel Aguilar added an answer in Primer:
    Is it possible to fuse two mCherry sequences (identical DNA sequences) by overlap extension PCR using unique linker regions?

    I am trying to generate a 2x mCherry sequence using overlap PCR. The first reaction generates good fragments with overhanging sequences (linkers) but the following 'fusion reaction' does not work. Any ideas why the second reaction does not work? It is important to say that the two fragments I want to fuse (mCherry sequence) have identical sequences apart from the designed overhanging linkers.

    Here is what I do:

    Primer 1: 5'-(25bp nesting region 1)ATGGTGAGCAAGGGCGAG-3'



    Primer 4: 5'-CTTGTACAGCTCGTCCATGC(25bp nesting region 2)-3'

    Primer 5 and 6: 25bp nesting regions in primer 1 and 2, respectively.

    I generate two fragments using primer pairs 1+2 and 3+4. I purify these fragments and use it in a second reaction where I use nested primers (5+6) to amplify the larger fragment. This second reaction does not work. 

    Geziel Aguilar

    Dear Jie,

    I am testing the effect of different molecular weight (size) in my experiments. Hence the double mCherry.  :-)

  • Ramesh Prasad Bhatt added an answer in Dehydrogenation:
    What are the best substrates between TTC or INT to measure the dehydrogenase activity in a tropical soil (French Guiana) ?

    Hi all, 

    I am looking for  DH activity protocol in a re-forested area of french Guiana. I just need an advice for selecting the best substrate !

    Thanks for reading

    Ramesh Prasad Bhatt

    some support from the web www.solid-earth.net has best describe soil microbial properties and enzymatic activities

  • Nils Ross asked a question in Sentaurus:
    In Sentaurus TCAD, how can I define thin film RayTraceBC conditions on a device surface without declaring the outside air in sde?

    I'm using Sentaurus TCAD to simulate thin film solar cells in two dimensions. Using the natively one-dimensional TMM solver produces some convergence difficulties: presumably a single dimensional optical generation profile is insufficient in my structure.

    I can successfully introduce light into my system using Raytracing(), but I'd like to be able to at least try to include the thin film interference effect from my top layer (200 nm Zinc Oxide).

    Using RayTraceBC{ TMM () } is straightforward for internal interfaces. But since ZnO is my top layer, I have no 'reference=' material to provide the TMM boundary condition.

    I have not defined the outside air explicitly when I build my structure in sde. I have at one stage tried to add a layer of material="Gas" above the ZnO (and its cathode contact), but doing so seems to open up another round of convergence or simulation issues [the issue is unclear but I have no helpful error message, just a generic failure message].

    The Raytracing solver itself understands that the surrounding material is air, by default. Does this default region have an internal region or material name that can be used as the 'Reference=' material in the TMM RayTraceBC? Or is there some other way to declare device-surface thin film interference effects in the Raytracing optical solver?

  • Wissem Gallala added an answer in Diatomaceous Earth:
    How can I separate sulfur from siliceous compounds?

    Diatomaceous earths are used for acid filtration, however after few time the pores will be clogged by sulfur. We search minerallurgical techniques in order to reuse Diatomaceous earths.

    Wissem Gallala

    Dear Sayan,

    Does Carbon Tetrachloride and Sulfur Dioxide can dissolve sulfur.


  • Daniele Sasso added an answer in Quantum Physics:
    Why has the classical electron radius generally been rejected in quantum physics?

    There is a very close and accurate agreement between the classical electron radius, alpha, the electron Compton wavelength and the Bohr radius. such that:

    re = alpha. lambdae /2pi = alpha2 a0

    Given the great accuracy ascribed to alpha in particular, this would suggest that the classical electron  radius is valid.  

    Daniele Sasso

    Corpuscolar nature of a particle is due to its small sizes. In the event of massive particles (electron, proton, etc..) the size is caused by the mass density of particle. In the event of energy particles (photons, gamma rays, delta rays, etc..) the size is caused by the wavelength of electromagnetic nanowave that represents the quantum. It is possible to associate an equivalent wavelength to a a massive particle that can be De Broglie's wavelength or Compton's wavelength according to necessities. It is possible also to associate an equivalent mass to an energy particle. It is manifest that an electron at low speed has a De Broglie's greatest equivalent wavelength while Compton's wavelength is independent of speed. We cannot think mass of a massive particle (for instance electron) and mass of a iron ball have the same physical nature. On this account for elementary particles, whether leptonic or baryonic,  in the Theory of Reference Frames I defined electrodynamic mass that is different from inertial mass and gravitational mass of ordinary bodies like an iron ball. Electrodynamic mass changes with the speed according to the relation  m=mo(1-v2/2c2), it follows that electron and massive elementary particles are subject to internal transmutations whether because of interactions with other particles (for instance positron) or when they are accelerated by a force field. Electron diffraction is a physical phenomenon that is studied and explained also in the Theory of Reference Frames in which electron diffraction is due to the electrodynamic nature of particle and not only to its equivalence with an electromagnetic nanowave.

  • Fabrice Clerot added an answer in Multiple Linear Regression:
    B value multiple linear regression vs. B value simple linear regression?

    Why do we get B value in the multiple linear regression higher than the B value in the simple linear regression for the same dimension? How can I justify this?

    Fabrice Clerot


    there might be plenty of reasons ...

    for one "usual suspect", see the section "suppressor variable" below ;



  • Angel Nyirenda added an answer in Thermoluminescence:
    How can we interpret the shift of TL glow peak as a function of post-irradiation anneal at different temperatures?

    Tmax shift

    Angel Nyirenda

    Can you clarify your question a bit? Do you irradiate your sample after the post irradiation anneal then take a TL measurement or else you take a TL measurement immediately after an anneal? For the latter, the answer posted by Chen explains the shifting.

  • Hector Espinos Morato added an answer in Passive Sampling:
    What could be the relation between odours units and concentrations of several wastewater compounds? Works for comparing results??

    I am trying to related the odour units with the hydrogen sulphide and ammonia concentrations levels measured with passive sampling.

    I'm publishing emmissions rates (in g/s) of several wastewater treatment plants and I like compare my results with others works!.

    Hector Espinos Morato

    Could you give me reference?

    An odour unit is a sensory measurement of the concentration of a mixture of odorous compounds in a sample of odour.
    The concept of odour concentrations, as odour units per cubic metre,
    is based on a correlation between a physiological
    response that is when odour is detected by the nose, and exposure to a particular sample at a specific concentration. The results of this
    assessment are expressed in terms of a single number. The odour sample assessed can be one of many individual odorous substances or a complex mixture of many substances, and so the odour unit or concentration will vary between test samples.
    An odour at a strength of 1ouEm-3 is in reality so weak that it would
    not normally be  detected outside the controlled environment of an odour laboratory by the majority of the population ( that is individuals with odour sensitivity in the “normal” range)
    But I want to distinguished the sources of the odour. For managiming he processes you must know the source and what compound provoke them. You can have the number of units of odours in a zone, but which provoke them? Hydroge sulphide, ammonia, no2,....

  • Hamid Radmard Rahmani asked a question in Abaqus:
    How can we perform a simple implicit dynamic analysis in abaqus with specific damping?

    The problem is that in Dynamic Implicit analysis, Abaqus considers a damping for the system which is not adjustable.

    I find a free vibration respond to a puls load on a simple structure with a specific damping using implicit analysis (Not Explicit!).

    Any idea?

  • P. Pardha-Saradhi added an answer in Beer Lambert Law:
    What alternative law to Beer-Lambert could we use to determine the absorbance of Methylene Blue ?

    How can I explain the fact that methylene blue doesn't follow the Beer-Lambert law and what law could I use instead?

    P. Pardha-Saradhi

    Dear Peter,

    Can you please explain what is applicable to solutions of chemicals like methylene blue, when they do not obey the Beer-Lambert law? Many of us are aware of limitations and complications associated with the Beer-Lambert law, that is the precise reason why Safia asked this question. To the best of my knowledge and based on our experiences, I feel that Adams furnished valid answer. 

    I know, you are fortunate to have been trained by best teachers and many of us are not fortunate to have such teachers. Many times some of us find it difficult to understand complicated formulae. Therefore, I humbly request you to furnish appropriate answer to Safia's question, preferably in a language that is easily understandable by every one.

    To my understanding aim/goal of ResearchGate is to give freedom to individuals to clarify their doubts [this I feel is a good means to educate each other]. Something, which is simple to you could be complicated for me and something which I find simple could be complicated for you. 

    Hoping to receive an apt answer to Safia's question.

  • Caner Yıldırım added an answer in Patch-Clamp Electrophysiology:
    How can I distinguish neurons from neuroglia when I try to work with cohlear nucleus neurons and patch clamp electrophysiology techniques?

    Hi, I new started patch clamp electrophysiology techniques and I m working in the cohlear nucleus neurons but I cant distinguish neurons and neuroglia in this area. I realize that most of cells which I did seal is glial cells. What could be reason for it?HowHow do I overcome it. Also would you give me some references /resources for current clamp analysis. thanks.

    Caner Yıldırım

    Dear professor; Thank you very much for your interest in also for taking your time for me .. in fact I'm trying to patch clamp is approximately 1 year and I can receive recordings in current clamp, but I'm talking about the subject it scared me and I thought I made a huge mistake somewhere.  I hope that I develop myself.. I took note that author and  important points that you mentioned. I will search them.Thank you so much. Best regards.

  • Cynthia Grant added an answer in Questionnaire:
    How can I calculate response-rate in a Delphi-study?

    I am interested in your opinions on this issue;

    In the study I asked 136 person (the total population) of their interest in participating. This was done by e-mail. Only 36 agreed to participate in a response e-mail, and later received the first questionnaire. After three rounds 24 had answered all three questionnaires. I had heard arguments for calculating the response rate as 24/130. However those 136 did not receive a questionnaire only a question whether they were interested in participating or not. I have calculated the response rate as 24/36. As they actually participated in the study. I am very interested in your opinions on this. All the best / Mats Holmberg, Sweden

    Cynthia Grant

    I had a similar challenge-- lots of inquiries went out to obtain participants, but then some dropped off with each phase of the study.  I wrote this up just as it occurred (and probably a little lengthy, but it was clear).  This was not a published study, but an internal report for our agency. 

    The initial recruitment email was distributed to (let's say for ease of example) 100 people. There were 25 potential respondents who expressed an interest in participating, yielding an overall response rate of 25%. One hundred percent of these 25 participants completed phase one and 24 of 25 participants (96%) completed phase two. However, only 21 of the 25 respondents (84% of the initial sample) were able to participate in all three rounds of the Delphi study.

  • Harekrishna Misra added an answer in Entrepreneurship:
    Do cooperative organisations have entrepreneurial potentials?

    entrepreneurship is a key factor that stimulate economic development and am currently working on how cooperative organization can key into this potential.

    Harekrishna Misra

    Cooperative organizations display better entrepreneurial acumen.  Follow Url: www.amuldairy.com/ as an example...

  • Sabino Aurelio Bufo added an answer in Column Chromatography:
    Is it possible to separate an analyte and its salt simultaneously by HPLC?

    I am asking about the possibility of separation of an analyte like pseudophedrine and its salt pseudophedrine hydrochloride using HPLC simultaneously i.e using the same method?

    If it is not possible, any suggestions for determination of the two compounds in one sample?.

    Sabino Aurelio Bufo

    Dear Fuad

    pseudoephedrine and pseudoephedrine hydrochloride can be coeluted both as pseudoephedrine when when you use a C18 column at any pH value (compatible with your column). The salt is rapidly dissolved in water as the two separate components (pseudoephedrine and chloridric acid). You can try to separate them using an ion exchange column and amperometric detection under pH 

  • Anji BABU Kapakayala added an answer in Gnuplot:
    How does plot bandstructure in GNUPLOT from VASP calculation ?

    How does plot good looking publishable bandstructure from VASP calculation.

    I have tried p4vasp but we can not modify graph in p4vasp. Any other suitable method for plotting bandstructure from VASP calculation.

    Anji BABU Kapakayala

    Hi Shilendra Kumar Sharma,

    I did not get you question . Please clarify this , what do you mean by shift label to zero ????........

    If you are asking about why valance band in your band structure lies bellow the fermi level?? i don't have answer for that. it depends on your material. Valance band always need not to be at fermi level, Please check the literature.

    Accoring to me , your band structure looks pretty and you will have a direct band gap at Gamma point.

    If it is not the proper answer to your question , please write again with clarity.


    Anji Babu

  • Natalia Oliveira asked a question in Stock Solution:
    How can I perform ion exchange with a 37bp DNA sequence?

    Which dialysis tube and procedure is more suitable for a buffered sample with this size? I just want to remove any salt that it`s left on the stock solution of DNA and then perform ITC analysis with a target diluted in the same buffer..

  • Sönke Weinert added an answer in Elastomers:
    How to measure the strain in a tensile test for elastomers using ImageJ ??

    I had tested several specimens of rubber using the standard test method ASTM D412 (tensile test for elastomers). I don't used an extensometer, so I painted two points in the gage length and I recorded the test in a video.

    I want to know how I can process the video and get the distance between the points painted for each photograma of the video using ImageJ.


    Fabian Hernandez

    Sönke Weinert

    Hi Fabian,

    can you provide 2-3 typical images that I can think about thresholding your marks in ImageJ. To speed the process up.

    Best Soenke

  • Thomas Rowe added an answer in Plaque Assay:
    How accurate are plaque assays?


    I am in a pharmacology lab and started studying influenza. I found that "standard plaque assays" are used the majority of the time to determine the infectious viral burden from cell culture as well as tissue homogenates. It is also used to determine the MOI for cell experiments and mouse infection. I have contacted several people and for the most part the reason I get for its accuracy is "If you count between 30-300 plaques, it just works". 

    Recently I have begun running plaque assays in tandem to my cell experiment to determine the Pfu/mL at the time of the experiment (rather than titering once batch of influenza and using that Pfu/mL for subsequent experiments) and the results are confounding.

    If I grab a batch of flu that is 10^7 pfu/mL and use this to calculate the MOI=2, it is actually closer to MO1=0.02 or MOI=0.2 (due to thawing?). I am wondering if people take this into consideration or even do this at all for the experiments. The literature will only ever give you the MOI or "we did standard plaque assay" with no further explanation.

    Thank you for reading.


    Thomas Rowe

    you are correct, freeze/thawing will affect the titer of the virus.  You will generally lose between 0.5 and 1 log of virus every time you freeze thaw.  We will make several aliquots of virus and perform PFU on an aliquot and then use one of the others for testing.  Thus, each vial should have roughly the same PFU since they are stored under the same conditions.  Also, when performing your PFU, you will need to run replicate wells and get an average PFU.