ResearchGate Q&A lets scientists and researchers exchange questions and answers relating to their research expertise, including areas such as techniques and methodologies.

Browse by research topic to find out what others in your field are discussing.

Browse Topics

  • Francisco T Tirol added an answer in Varicose Veins:
    What is your approach in patients with uncomplicated varicose veins who are scheduled for elective abdominal surgery?
    Would you will treat varicose veins before, simultaneously, or after abdominal intervention?
    Varicose veins are generally considered to be a risk factor for venous thrombotic complications in general surgery.
    Francisco T Tirol · Wound Care Center at PMHD

    I agree with Dr. Heretzman

  • Could anybody help me to find best vector in order to get transient transfection into human fibroblast?

    I would like to perform transient transfection into human primary fibroblast with gata4 mef2c and tbx5. I do not want to perform viral transfection. 

    Could you give me some suggest? 

    Vuong Tuan Anh · Sungkyunkwan University


    My lab using pcDNA3.1 or  as backbone plasmid and for stable cell line we select with puromycin.

  • Is it the time to move to new cryptography methods?
    We need new cryptographic algorithms and information security techniques to rise our life security in the future.
    Nicolae Constantinescu · University of Craiova

    in asymmetric encryption it is necessary a new algorithm, in symmetrical encryption OTP still rules

  • During electrodeposition of Ni-Co a thick semi-adherent black film was formed on the anode. What is this layer and how can we stop its formation?

    The electrolyte was the typical Watts bath (240 g/l NiSO4+ 35 g/l NiCl2 + 30 g/l H3BO3) with 24 g/l CoSO4. temperature, and pH were 58C and 4 respectively. The current density was 4 A/dm2. The working electrode was copper (1.2 cm2) and the anode was Platinum (6 cm2). After about 300 s, a gradual drop in potential was observed ( I suppose it is the time when the anode's black film formation had started) and after about 50 s, the potential becom constant at more negative potentials. What is this black film formed on anode, and how can it be stopped?

    prof V.S Muralidharan · Central Electrochemical Research Institute

    GOOD  - it is very difficult  to oxidise sulphides to sulphates in the present pH and plating conditions

  • Md. Nazmul Hasan added an answer in Scintillation:
    What is the process of measuring activity of enzyme(radio-enzymatic assay) using liquid scintillation counter?

    Is there anyone here who is familiar with calculation of enzyme activity using a radio-enzymatic assay? I am working on enzymes inhibitory activity and I am planning to use radioisotopes. I am getting count per five minutes data in the end after counting the product form by a liquid scintillation counter. Any biochem expert here. need help

    Md. Nazmul Hasan · Kyushu University

    Thanks to Maria Grazia Tozzi and Marcin Nowicki for their valuable advise. It will help me to solve my problem.

  • What is the digital signature? Can you differentiate between physical and digital signatures?

    What is digital signature? Differentiate between physical and digital dignature

    Nicolae Constantinescu · University of Craiova

    digital signature basic principle where explained above

    digital declaration is the next step of it; elliptic curves provide better performance rate

  • Jacob L. H. Mclaughlin added an answer in SSCP:
    Why does my amplification of ssDNA fragments not work?

    Hey guys, I have separated ssDNA fragments (purified from dsDNA PCR amplicons by Lamda-exonuclease digestion) by SSCP (basically a PAGE assay) and want to reamplify the single bands of the SSCP gel for Sanger sequencing (which usually works fine in our lab also with that specific primer pair). However, from my last two gels I can not reamplify the ssDNA fragments, neither with the primers I used for the first PCR nor with primers that are located within the amplicon sequence. I've checked the PCR for inhibition by the gel matrix and the elution buffer we have used: there was no inhibition. Does anybody has  some experience in sequencing ssDNA from SSCP or DGGE and can tell me what might be the problem?!

    Jacob L. H. Mclaughlin · National Measurement Institute

    Hi René,

    Here are some things that I can think of that might help you to determine where your problem lies:

    Check for Secondary Structure:
    One of the most important things to consider when you are amplifying from a ssDNA template is secondary structure formation, particularly if the GC content is high. Strong secondary structure formation will prevent your primers accessing the template which will prevent that template from being copied by the polymerase in that cycle.

    Input your sequence into MFold (linked below) using the Mg2+ concentration of your mastermix (if known) and set the temperature parameter to your annealing temperature, then repeat for your denaturation temperature.

    Check if there are any strong stem-loops in your primer binding areas, particularly at your denaturation temperature. If there are, you can increase your denaturation or annealing temperature to minimise this. (Don't worry about thermal degredation of your template, it is well protected in PCR buffer, see second link).

    Check your 5' phosphorylated primers:
    Check that only one of your primers has a 5' phosphate, because if they both have a 5' phosphate you will degrade everything (personal experience).

    Check your digestion:
    Lambda Exonuclease has some dsDNA endonuclease activity, so maybe you are over-digesting your template. Try doing a time series of digestion duration.

    Check your purification:
    Purify some of the dsDNA bands as well and try to amplify those, you might just be having a really low yield in your purification.

    If I think of anything else I will add it in. Let me know if I have made an incorrect assumption about your procedure and I will try to fix it.


  • Yinsheng Zhang added an answer in Epistemology:
    Is Control-Knowledge the Strongest Form of Knowledge?

    Many years ago, when I was still a student, one of my professors occasionally said that we would have only then "really understood something", if we would be able to /implement/ "it" technically or algorithmically.

    In more philosophical terms, the professor's aphorism amounts to the question whether Control-Knowledge (or: Instrumental Knowledge) is the /strongest/ and /deepest/ possible form of knowledge, or ---even more bold and radical!--- if Control-Knowledge is perhaps even the /only/ epistemic entity which truly and rightly deserves the label "Knowledge" at all?

    Or, more concisely: What is the right understanding of "Understanding"?

    This difficult question I would like to discuss with Epistemologists, Gnoseologists, Hermeneuticists, Philosophers of Science, and Philosophers of Mind.


    Yinsheng Zhang · Institute of Scientific and Technical Information of China

    I don‘t think control-kowledge has any prior rank .On contrary, it behind the primary knowlege. You make a lift following you know the direction of gravity. If you now all the knowledge ,you can make a frog!

  • Khaliqur Rahman asked a question in BOD:
    Relationship between toxicity and BOD of textile mill effluent

    Anyone knows a relationship?

  • Papungkorn Sangsawat asked a question in Protein BLAST:
    Purified chicken breast peptide sequecing by LC/MS/MS

    I got 4 peptide sequences from researcher including TEL, LTE, VEL and DDL. They were digested by intestinal enzyme digestion and purified already.

    How can find the position of these peptide, where are they release or digest from chiccken protein?.

    I can't use Standard Protein BLAST of NCBi program because this program want amino acid sequence more than 3.

    Standard Protein BLAST of NCBi very good for finding, it have CHICKEN database but I can't use this program.

    I want to know my peptides derived from what protein for example actin part and/or  myosin part etc.

    Can you help me for this case?, thanks you very much.

  • How can I apply a single neuron pid controller for a twin rotor mimo system?

    There is an inbuilt pid controller which i want to change to a single neuron pid controller as my project work. i want guideline about how to design and simulate single neuron network in matlab

    Felipe Nascimento Martins · Instituto Federal de Educação, Ciência e Tecnologia do Espírito Santo (IFES)

    If I understood correctly, you need to implement in Simulink the equations shown in the paper. The article shows some Simulink models that you can built. If you are going to use a single neuron, you could build it yourself using regular Simulink blocks. But, maybe it is a good idea to use the NN Toolbox because you would have tools that would help on the training phase.

  • Yuan-Yeu Yau added an answer in Phytoremediation:
    Is there anyone aware of plant species used industrially for phytomining, or could you please tell me about a well known phytoremediator species?

    What are the well known plants using in Phytoremediation?

    Yuan-Yeu Yau · Northeastern State University

    Hi Elham,

    Recently I had a chance to communicate with Dr. Rufus Chaney. He is an expert working in the field of phytomining at USDA. He has just attended an 'Phytomingng Workshop' in Australia this July. He mentioned a handful companies have licensed the technology of using Hyperaccumulator Alyssum species for Ni. I attached his 2014 Conference paper for your reference. Please see page 10, the paragraph "PHYTOMINING OF NI AS A COMMERCIAL TECHNOLOGY".

  • Suharsh Shah added an answer in Gene Expression:
    Can anyone please suggest a way to transfect plasmid DNAs into the U266 cell line?

    I am trying to transfect plasmid DNAs into the U266 cells. I tried Amaxa electroporation, Lipofectamine, and ViaFect. None of these techniques is working. Can anyone please suggest a better way to get DNA into the U266 cells?

    Suharsh Shah · The University of Calgary

    Try using lipofectamine 2000 from invitrogen along with your DNA (1:1 ratio).

  • Jogender Singh added an answer in Disulfides:
    How to use Ellman's reagent (DTNB) for determination of Tm of disulfide?

    I have a beta barrel protein with a single interior disulfide. I would like to use Ellman's reagent (DTNB) to determine at what temperature the disulfide breaks via the absorbance of TNB at 412 nm.  Since I know the protein doesn't start unfolding until close to 50° C, I would expect relatively little change in absorbance at 412 nm until that temperature, then a significant increase when the disulfide breaks followed by little change in absorbance following complete denaturation of the disulfide, resulting in a sigmoidal curve of absorbance at 412 nm versus temperature.  However, I get something that looks more like an exponential curve. What could be causing this?

    Jogender Singh · Tata Institute of Fundamental Research

    Dear Brian,

    I agree with Adam, increase in temperature itself should not lead to breakage of the disulfide bond. If the disulfide bond is intact then ideally you should not see any change in absorbance as you change the temperature.

    Reason for exponential curve: If you carry out a labeling reaction on a free cysteine, then you will get an exponential curve. So cysteine in your case might be free, and that is why you get the exponential curve. So please check the oxidation status of your protein first.

    If your aim is to determine Tm of the protein, why don't you use circular dichroism (CD) measurements. CD measurements will give you good measure of Tm. If you have a buried tryptophan in the folded protein, you can also try tryptophan fluorescence as a probe to calculate the Tm for your protein. Differential scanning calorimetry could be another option.



  • Ye Yu added an answer in PDMS:
    What hints would you give for sputtering gold on glass for making band electrodes for microfluidic systems?

    I'm trying to sputter gold on glass substrate in order to make band electrodes for microfluidic system. Since I need to attach and detach PDMS from glass multiple times, I need the gold band electrode to stay on the glass. What are the crucial steps to be taken to enhance the durability of the band electrode? Can you give me some hints? Thank you in advance :)

    Ye Yu · Jilin University

    Well, I've done almost exactly the same thing before and I fail to find a way to make it stay on glass. PDMS will peel the gold film straight off. It is just a one-shot device...And yes I've tried Cr and Ti adhesion layer, and plasma treatment. Sorry...

    But maybe you can try ITO glass, it is far more stable on glass than Au does.

  • How to test the strength of a symmetric key encryption?

    Now a days a large numbers of papers are being published on symmetric key cryptography, how to decide which one is best?

    Nicolae Constantinescu · University of Craiova

    input: the algorithm, the implementation of it

    tests: chosen text, poor text (as input)

    these are techniques for cryptanalysts

  • Does Ackermann function belong to Mu-recursive function?

    Some books say that a function can be Turing-computed if and only if it is a Mu-recursive function [1] . So Ackermann function should be Mu-recursive,Here,Mu-recursive is defined by primary recursive functions by composition or recursion schemes.

    Meanwhile, it is proved that Ackermann function is not primary recursive function, so it should not be Mu-recursive, which is contradictive to the above proposition.

    Then, does Ackermann function belong to Mu-recursive function after all?


    [1]Thomas A Sudkamp.Languages and Machine:An Introduction to the Theory of Computer Science,Third Edition, Pearson Education, Inc.,2006,pp.415-416.

    Peter T Breuer · Birmingham City University

    Dear Yinsheng - there is nothing complex here. I am just quoting Google on the matter. You can look it up too.

    As to g(x,y) = mu z. [f(x,y)=z], I pointed out that the first form I gave does not have a mu-operator on the outside. It is the composition of two functions, both mu-recursive. One is the lookup function, and the other is the table of the Ackermann function. Composition is the simplest way to do it, in my view.

    If you want to look at a form with the mu-operator on the outside, then you need to look at the second form I gave, which I only gave at your insistence, so I cannot see why you now choose to look instead at the first form and ignore the second.

    As to ∀p<-dom(c),p=<x,y>→c<x,y>=R(c,x,y)/\<M,N><-dom(c) , that is a perfectly ordinary mathematical statement and you should code it up for yourself accoding to your own preference. It says, in natural language, that c is a partial table of the Ackermann function including at least the <M,N>th entry. You may program that as you prefer in whatever formal language you are using.

    Written out longhand, it says "for all pairs p in the domain of c, the pth entry in c is R(c,x,y) where p=<x,y> and <M,N> is in the domain of c". That is, "c is a partial table of the Ackermann function including at least the <M,N>th entry". Use whatever code you prefer there. As the Google quote says, R(c,x,y) is the right hand side of the Ackermann equations. I wrote that out formally for you at some stage too.

    As to your question "If [the] Acke[r]mann function uses [the] Mu-operator, why it can't be expressed in a mathematic[al] formula in accordance with Mu-operator?", the answer is that there is no a priori reason why it should be expressible with the mu-operator on the outside, any more than there is any reason that a house built with bricks should have the bricks on the outside (rather than the concrete or plaster facade). 

    But Kleene's theorem says that it can always be reexpressed with the mu-operator on the outside. So I did that for you. Now you are ignoring that :-(.

  • Suharsh Shah added an answer in Cell Signaling:
    What is the best method to transfect shRNA clones into myeloma cell lines, RPMI8226 and U266?
    I am trying to transfect shRNA clones into myeloma cell lines RPMI 8226 and U266 cells. I have tried different sorts of lipid based transfection reagents. I am now trying nucleofection. Tried Amaxa recommended program X-05, but it killed all my cells. Can anyone suggest the best transfection method for these cell lines?
    Suharsh Shah · The University of Calgary

    Try transfecting them using serum free medium.

  • Can 2D filter bank use in ground penetrating radar signal processing?

    We have obtained several ground penetrating radar B-scan image but we do not know how to use 2D filter bank to extract useful information from the image. Can you help me? Thank you very much.

  • Qi Wang asked a question in Rainwater Harvesting:
    Rainwater harvesting with ridges and furrows in semiarid areas

    I had more than 20 year’s experiences on teaching and experiments on irrigation with nitrate leaching in arid areas and rainwater harvesting with ridges and furrows in semiarid areas China. I got 2 projects in rainwater harvesting from Chinese Central government. Who would like to work with me or provide an employment in this area?

    I look forward to hearing from you

  • Mariadoss Arokia Vijayaanand asked a question in DMBA:
    Why we are not used female hamster as a experimental model for oral carcinogenics?

    Male golden hamster is a  well established model for the induction DMBA induced experimental oral carcinogenics. what about female.

  • Is it possible to get large number of colonies from PCR product after performing site directed mutagenesis on ampicillin containing plates?
    I have got large number of colonies (100-200 approx.) after transforming and plating my PCR product on ampicilllin containing plates. At the same time, I have no colony on negative control (Template -ve and DNA Polymerase -ve) after DpnI digest. Is it possible to have so many colonies from newly created mutant plasmid? If yes, what can be the reason?
    Brian Stoveken · University of Texas Health Science Center at San Antonio

    Wow, that does seem high, and large colony counts after SDM are somewhat unusual in my experience.  I've been doing SDM recently and have seen a variation in colony numbers anywhere between 0-50 after transforming DH5a cells.  Still, this isn't impossible in principle.

    How much template do you use?  If you start with a lot of template (i.e. >25-50ng as recommended), then even a linear reaction such as that which occurs in "quickchange" SDM could give you a lot of product with the desired mutation.  This could translate into many colonies if you're using sufficiently high efficiency cells.

    Only sequencing or a restriction digest (assuming you've added/ablated a site) will tell you if it worked.  Might as well pick a few colonies and see what turns up.

  • xi Song added an answer in Genomic DNA:
    Genomic DNA can't be digested by BamH1-HF. What is the reason for this?

    Genomic DNA from fungi mycelium was extracted by classic CTAB method, but can't be digested in 37°C overnight. I also tried the High salt DNA extraction method. The DNA can't be digested too.

    Enzyme 1ul
    DNA 8ug(26-15 ul)
    10*buffer 3ul
    ddH2O 0-11 ul
    Total 30 ul

    The protocols are listed and also the gel pictures before and after digestion. When I finish the southern blot, there are only lines around the genomic lines.

    xi Song · China Agricultural University

    Other enzyme like Ecor1 can cut the dna.  Will 1-2 ug DNA per reaction work for southern blot. The minimum is 8 ug DNA per reaction recommanded by the protocal.

  • What is the method of security provision in core network (home environment) in 3G mobile communication networks - Encryption or Encoding?
    In order to security provision in radio access network of mobile communication networks we use encryption methods, I was wondering what method is used to keep confidentiality in core network.
    Nicolae Constantinescu · University of Craiova

    according with standards, is encryption

  • What is the difference between the two terms 'Tectonic Geomorphology' and 'Morphotectonics'?

    Add your Knowledge about

    1- Analysis Methods

    2- Terminology History

    3-  Scale of Geomorphic Indices involved

    So I see it interchangeably term but I doubt from the geomorphological point of view....

    Meelad Hussein · Marine Science Center

    I`m appreciated your answers Ahmad Nourbakhsh and Siddhartha Kumar Lahiri.... I see the textbooks for the (Ollier, C.D., 1985) and ( Burbank and Anderson, 2001) and (Adrian Scheidegger, 2004)... was titled their books withe tow terms... So it seems the morphotectonics have global scale like continents and local scale like river drainage basin, lake basin shore or coast line than the tectonic geomorphology that certainly stressed on the relation between the tectonics and geomorphology.....

    I`ll traced the terms in all publications (Books, Journals, Theses) 

    Mr. Siddhartha Kumar Lahiri. I couldln`t  download your paper http://dx.doi.org/10.1016/j.geomorph.2014.04.032

    and I`m happy to read the discussion about the 2nd link.... this add to me more comprehension about the subject.....


  • What is the relation between coding theory and cryptography?
    For real life which one should we apply first? To transform digital information we apply coding theory, and for security we apply cryptography. Which one should we apply first? Is cryptography applied before coding or after coding or both?
    Nicolae Constantinescu · University of Craiova

    The most important difference (mathematical point of view) if that in codding theory we have f(x)=y, where f is the codding function, x is the plain information and y is encoded information and in cryptography we have a key k, and the transformation become

    f(x,k)= y

    From these we have:

    in codding theory the secret consist on algorithm

    on cryptography the algorithm is considered to be public (even it is not published) but the secret is the key k

  • Eddie Seva See added an answer in Accounts:
    I think we've become obsessed with RG account

    I think I've become obsessed with RG account!

    How many answer my question? What is the new question? How I can answer the question?
    Every half hour, I need to see my site.
    Please help!

    Eddie Seva See · Bicol University

    When you ENJOY being in RG, it is no longer working or studying. It is fun. Just enjoy what you do while it is still fun.

  • How can I dry a methanolic extract?

    I want to test a methanolic extract on cell line..however, my extract is not dry enough..the extract is still wet after being concentrated by rotovap..some people suggest just put it in oven at 60 degrees C but I am afraid the extract will be spoilt..please help

    Abdul rahman Zulkiflli · National University of Malaysia

    wow guys..really appreciate all your responses..very much thank you =)