Q&A

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

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
  • How to determine trace levels of soil available boron by colorimetry?

    Colorimetric determination of soil boron through Azomethine-H method is the most popular one. However, it's detection limit is not very low, as I guess. Can anyone suggest me any recent modification of the method so that I can determine the boron content of B-deficient soils?

  • Mohammadjavad Paydar added an answer in Dyes:
    Which gel loading dye is suitable for DGGE?

    Hi, I am using promega master mix without dye so that equal concentration of PCR product can be loaded to DGGE. Now i did not understand which dye can be used before loading the sample. Can i used Gel Loading Dye, Blue (6X) from BioLabs? Please tell me the dye, what concentration and quantity should be used for loading?

    Mohammadjavad Paydar · University of Malaya

    Hi. Yes you can use Gel loading dye, Blue (6x).  Bromophenol blue is the standard dye for DGGE.

    0.05 g bromophenol blue in 10 ml 1* TAE

  • Ayuba Fasasi added an answer in Nanotechnology:
    Does anyone know of a physical method to obtain nanoparticles?
    There are several chemical methods to synthesize nanoparticles of gold, silver, and iron oxide, as co-precipitation or thermal decomposition. But physical methods either are not widely known or publicized. There is the laser ablation in a liquid medium, which can obtain any type of nanoparticles, but lasers for this technique are expensive. Does anyone know a way to make it cheaper or other physical process to obtain nanoparticles?
    Ayuba Fasasi · Phillips 66

    Have you tried Physical vapor deposition(PVD)?

  • Laurie Betts added an answer in THP-1:
    How can I get suspension cells to adhere to the coverslips?

    Has anyone ever mounted naive THP-1 cells on coverslips for confocal imagining? I want to image THP-1 cells without polarizing them to M0 macrophages, but I have had problems getting them to adhere to the coverslips. 

    Laurie Betts · University of North Carolina at Chapel Hill

    I use fibronectin coated cover slips for THP-1 cells.  sigma-aldrich sells solutions and has a recipe.

  • How to do reproductive toxicity testing in vitro and in vivo?

    I want to evaluate the reproductive toxicity of chemicals. Which guideline should I follow to test reproductive toxicity in vivo and in vitro?

    Muhd Hanis Md Idris · National University of Malaysia

    Thanks Andrea. But for in vitro study, is there any guidelines to follow? Or is there any standard procedure to use?

  • Alain J P Alix added an answer in Cancer Biology:
    Conserved sequences within promoter region
    Is it common to find some conserved sequences (homologous alignment of human, rat, mouse) of a gene of interest within the promoter region?
    Alain J P Alix · Université de Reims Champagne-Ardenne

    absolutely it is very common; 

  • Jack M. Gallup added an answer in Primer:
    How do I average multiple amplification efficiencies (i.e. 6 standard curves) for the same qPCR primers?

    The geometric mean is used standard for this problem but why is this the case and are there alternatives?

    Jack M. Gallup · Iowa State University

    That is a tricky calculation, took me a while to crack the code, but it goes like this:

    EAMP over n rxns:10(1/avg(1/log(EAMP1),1/log(EAMP2),1/log(EAMP3),1/log(EAMP4),1/log(EAMP5),1/log(EAMP6)))
    That equation will calculate what you are asking.

    In Excel: e.g., if your six Eamp values are: 1.92, 1.87, 1.945, 1.892, 1.776 and 1.959, the equation in excel would look like the following:
     = 10^(1/AVERAGE(1/LOG(1.92),1/LOG(1.87),1/LOG(1.945),1/LOG(1.892),1/LOG(1.776),1/LOG(1.959)))

    The result would be:  1.88939 meaning:  88.939% efficiency

    But, hopefully you don't have Eamp values that vary like I have stated above - the above is just a theoretic example.  Hopefully the 6 standard curves you're 'exponentially inverse log averaging' don't vary in efficiency more than 2 or 3% away from one another... (perhaps that is even too much) but... you could consider throwing out the outlier curve or curves if they 'seem out of whack.'

    Good luck~!
     
     
     
     

  • Junjiong Shao added an answer in Photosynthesis:
    How can one obtain leaf temperature data in a photosynthesis model?

    In photosynthesis model (Farquhar), the leaf temperature is used to relate some variables (e.g., Vcmax, Jmax) at certain temperature to those at a reference temperature. I wonder how the leaf temperature data was generated, because usually we can only get fine temporal scale air temperature data. So, does anyone know how to calculate the leaf temperature according to the air temperature? Or just use air temperature in the model?

    Junjiong Shao · Fudan University

    Thank you very much, Dr. Bongi. Your answer and recommended literature really help me. I will check whether I have enough data to calculate the leaf temperature.

  • Can you recommend protocols for removing bound RNA that may co-purify with recombinant proteins?

    Nucleic acid enzymes and binding proteins expressed in E. coli can have bound RNA as well as DNA. Are there specific methods for removing RNA versus DNA?

    Adam B Shapiro · AstraZeneca

    If this is a problem, the solution is just to use a bigger column (or a smaller sample). Ion exchange chromatography can be scaled up easily.

  • Wan-jun Zhang added an answer in Spectinomycin:
    What antibiotic concentration of Streptomycin or Spectinomycin that I use to transform E. coli DH5α and Agrobacterium tumefaciens strains?

    I have a plasmid vector derived from pPZP200 with the gene aadA that confers resistance to spectinomycin and streptomycin.
    So, what antibiotic concentration of Streptomycin or Spectinomycin, that I use to transform E. coli DH5α and Agrobacterium tumefaciens strains: EHA 105, LBA1126 e AGL-1?

    Is there an advantage to use spectinomycin than streptomycin?

    Can anyone help with this?

    Wan-jun Zhang · China Agricultural University

    I use 100mg/l each for E.coli, and 300 mg/l each for Agro.

  • Geng Ouyang asked a question in Mathematics:
    What is number? Why and how does it come, how does it exist,… ?

    No mathematics without numbers; so, we have many different kinds of number forms in our mathematics --------we use numbers to cognize things in universe including infinite related things.


    But when we look at the number spectrum (system) in our mathematics, we can see a serious defect: lack of infinite related number forms. Why?

  • Lithium disilicate - restorative material with multiple options?
    I am working on a project regarding this subject. Any opinions will be very valuable.
    Carlos Araújo Queiroz · New University of Lisbon

    A review focusing glass-ceramics developed for biomedical applications that mentions lithium disilicate based glass-ceramics developed as dental biomaterials was included as Chap. 1 of: C.M.G.A. Queiroz, "Cristalização de Biomateriais Vitrocerâmicos e Mineralização em Meio Fisiológico Simulado", Ph.D. Thesis, Universidade de Aveiro, 2005 (in Portuguese; cf. pp. 18 and 21 and references quoted herein): https://www.researchgate.net/publication/231157960_Cristalizao_de_Biomateriais_Vitrocermicos_e_Mineralizao_em_Meio_Fisiolgico_Simulado

  • Narasim Ramesh added an answer in Nucleotides:
    Who can use software that generates maximally disordered sequences on the integers?

    I have taken effort to produce such software and am seeking persons who have suitable application for such sequences.  Currently, the software will compute shustrings on the integers and the nucleotides but will generate maximally (or uniformly) disordered sequences only on the integers; the nucleotides is coming, as is binary and a user selectable symbol set.  For now, understanding the application areas for such sequences, and the provision of same to interested parties, with the hope that users will provide feedback, is solicited.

    This software generates sequences in integral powers of ten, up to length one hundred million digits.  A sequence of one hundred million digits takes just 30 seconds to produce.

    Narasim Ramesh · Sri Jagadguru Chandrasekaranathaswamiji Institute of Technology

    It looks very intriguing and promising .It would be nice if following could be considered.

    1.Would it be feasible to give a simple example

    2. Is it possible to invert it ? ie if we start with a known sequence

    can we get back the original sequence

    3. Does it require a seed ?

    4. What happens if applied sequentially?

    5. Can we think of it as a sort of integer  chaotic result ? ie complex integer sequence?

    6. Does maximally disordered mean same as uniform distribution?( max entropy )

    It seems that with the above we could see many applications such as

    cryptography , image enhancements , artificial creativity etc..

    Cheers

  • Tamara Heredia asked a question in Keratinocytes:
    If I have cultured keratinocytes expressing only K14 gene, is it possible that under certain conditions, they become activated and express K16??

    If I have cultured keratinocytes expressing only K14, treated with IL-1ß, is possible that they become activated and therefore they express K16?? (that happens in basal keratinocytes, but I am not sure if "cells that express only K14 gene" means that all the other genes are not there, or they are only "turned off" and evetually they could be "turned on")

  • If you could fix one thing about science publication, what would it be?

    Issues have been raised about peer review, open access, costs, reviewer bias and quality, fairness, and efficiency among other things. If you could change just one thing about research publications what would you change? 

    Vitaly Voloshin · Troy University

    I would say that this is present implicitly in the journal citation index.

  • Kelly-Anne Masterman asked a question in Lysis Buffer:
    Recipe for Red Blood Cell Lysis buffer without Ammonium Chloride?

    Hi,

    ACK lysis buffer is great for non-nucleated RBCs, but not good for nucleated ones. Birds, reptiles and fish have nucleated RBC so the traditional ACK doesn't work well (nor does water alone or BDFacsLyse). I found a recipe on research gate making it with MgCl2 and sucrose etc and a quick a dirty suggested it might work. I was wondering if anyone could confirm the recipe and tell me how it is used (time, temperature, diluent post lysis stage...), cheers!

  • Rogerio Maestri added an answer in History:
    Are there any Relevant Similarities between Post-Colonial Africa and West-Europe after the Collapse of the West-Roman Empire?

    Approximately around the year 500 (A.D.), the West-Roman Empire collapsed. Thereafter it took about 300 years before, around the year 800 (A.D.), the Germanic-Franconian emperor Carolus Magnus had (alas not without armed violence) established a new social and political order in West-Europe of such sufficient stability that quite "rapid" cultural growth ---"rapid" by the standards of those olden days--- could follow soon: New towns and cities, courts and market-places (etc.) were built, and the first West-European universities were established around the end of the 11th Century (A.D.)

    Now my Questions to Expert Historians:

    1. Do you see ---yes or no--- any relevant structural-systematic similarities between between West-Europe immediately after the collapse of the West-Roman Empire, and Africa immediately after its Decolonization in the second half of the 20th Century?

    2. IF your answer to the first question was "yes", then: Do you believe that any "historic lessons" could possibly be learned from West-Europe's "intermediate years" (500-800) for the sake of Post-Colonial Africa's further development towards a prosperous future?

    Rogerio Maestri · Universidade Federal do Rio Grande do Sul

    Dear Rob.

    .
    I am extremely pleased to hear from anyone who understands a matter that we are not as erroneous so.
    .

    Many times we answer something that is not our specialty in order to help, but this help can damage, but we cannot omit our opinion since it is clear that is from someone who is not an expert.
    .

    But from the question and the answers will venture out and give an opinion, that is incorrect I ask for you to do the fix.
    .

    In history there is a great desire to draw parallels between civilizations to understand its evolution; however I think the bias adopted by many is wrong, I find it easier to understand the civilizing process in place of looking for similarities search the differences!
    .

    Let me explain, if we look at Roman and Celts civilizations before the Roman domination we come across many similar conditions between both, like in terms of technological development, similarities in terms of cosmological view of the world, similar in many ways, but the explanation why one could gain dominion another may be much easier to explain the differences (which I will not here put them in respect to you).
    .

    This is a sort of transference difference in evolution between people analyzing their microcosm, it can be almost equal in terms of intelligence, work capacity and opportunities to another person, but one personality characteristic can define completely antagonistic future. With civilizations think the same, no similarities that have or a religious difference or a social difference or any materials define completely different evolutions.

    .

  • Vivek Morya added an answer in Jatropha:
    What is the method for isolating Jatropha (Jatropha curcas) leaf-degrading microorganisms from soil in the laboratory?

    1- Soil is sandy loam.

    2- Jatropha leaves are buried in soil inside leaf bags.

    3- Jatropha leaf litter around Jatropha trees.

    Vivek Morya · Inha University

    Organic loaded soil is very good consortia of microorganism, However you are interested in leaf degrading microorganism/s which is little tough. as leaf biomass is more complex it have variety of bio molecules. and degradation  also depends on moisture temperature and pH of soil. Usually in natural condition a several types of microbes simultaneously involved in degradation of biomass. Another limitation is only culturable microbes can be isolate which requires a series of media including leaf as a sole source of nutrition. In my opinion better to  focus on functional targets. Any way the following thesis can help you in designing of your experiments ...

    http://scholarworks.sjsu.edu/cgi/viewcontent.cgi?article=4034&context=etd_theses

    http://theses.cz/id/b36pql/downloadPraceContent_adipIdno_6921

    http://edoc.ub.uni-muenchen.de/8554/1/Koch_Isabella_H.pdf

    Good luck...

  • Unilateral Pulmonary Edema after Minimally Invasive Right Thoracotomy Mitral Valve Approach, possible mechanisms and solutions?

    Right lung edema has been observed in minimally invasive right thoracotomy mitral valve procedures, requiring extracorporeal membrane oxygenation in some patients. Proposed mechanisms have included right lung manipulation, ischemia/reperfusion, and reexpansion edema.

  • Kenneth M Towe added an answer in Vehicle Emissions:
    Are solid characterization factors available for particulate matter to CO2 equivalent (Global Warmining Potential) ?

    I would like to convert Particulate Matter from vehicle emissions into CO2 equivalent, but I am not able to find solid characterization factors for Italy (or Southern Europe at least...).

  • How do I get the age range (95% HPD) displayed at each node of an MCC tree in Figtree?

    I have a maximum clade credibility tree drawn and I am trying to get the age range at each node but I don't seem to get it right. How do I get that? I have the node bars displayed but I need the range displayed in years at the node as well. Or how do I interpret [10, 24.58] displayed at the node of my tMRCA?

    Hi Chantal,
    Displaying "height_95%_HPD" instead of "Node ages" will give you the 95%HPD age for each node.
    Cheers,
    Thomas

  • Who has info about disaster medicine/management education of undergraduates in local medical schools?

    Trying to get a picture on existing programs (voluntary or obligatory) in DM education on medical schools.

  • Tamara Heredia asked a question in Keratinocytes:
    If I have cultured keratinocytes expressing only K14 gene, is it possible that under certain conditions, they become activated and express K16??

    If I have cultured keratinocytes expressing only K14, treated with IL-1ß, is possible that they become activated and therefore they express K16?? (that happens in basal keratinocytes, but I am not sure if "cells that express only K14 gene" means that all the other genes are not there, or they are only "turned off" and evetually they could be "turned on") 

  • Joseph A. Wonderlich added an answer in Alcohol:
    What are the best predictors of alcohol relapse following treatment?

    What are the best predictors of alcohol relapse following treatment?

    Joseph A. Wonderlich · George Mason University

    Two of the best predictors of relapse are severity of use prior to treatment and negative interpersonal relations established prior to treatment.

    (McLellan, Alterman, Metzger, Grissom, Woody, Luborsky, O'Brien, 1994)

    Alcoholic relapse, life events, and behavioral theories of choice: A prospective analysis.
    Vuchinich, Rudy E.; Tucker, Jalie A.
    Experimental and Clinical Psychopharmacology, Vol 4(1), Feb 1996, 19-28. http://dx.doi.org/10.1037/1064-1297.4.1.19

  • According to you, which one is the biggest innovations in science and technology for the year 2014?

    Biggest innovations of the year

  • Do Toan added an answer in Simulation and Modeling:
    Does anyone use COMSOL Multiphysics for simulation?
    Is anyone working in this area - Electromagnetism, Heat transfer and CFD.
    Do Toan · Yuan Ze University

    Does anyone use COMSOL for the simulation of Plasma Electrolytic Oxidation?

  • Rakesh Kumar Tekade added an answer in Thiols:
    How can one break a gold-thiol bond?

    Just curious, if a moiety has been attached to gold surface via thiol bond; then:

    1. under what conditions it can be separated?

    2. Is this bonding strong?

    Thank you Miss Moraima. Can I please ask if you came across any specific reference or any literature available.

    Kind Regards,

    Rakesh 

  • Theresa Groth added an answer in Validation:
    How have others addressed a large number of 'Not applicable' answers in survey responses?

    I have a number of variables being used in the development of a scale. In my survey analysis I've deemed the 'Not applicable' (NA) selections as missing so they are not used in the analysis - other responses are based upon a 5 pt Likert score.

    There are 3 separate groups of interest. I'm wondering if I need to modify the cases in Grp 1 somehow to increase the number of valid cases:

    Group number / valid cases / missing cases
    Grp 1 / 35 / 107
    Grp 2 / 171 / 58
    Grp 3 / 321 / 81


    Only those cases in which all variables were answered, and not including any NA responses, are included in the valid cases count. Of these invalid cases there are about 100 in which there are numerous NA's selected. Of those 100ish, it looks like 85-90% of those individuals with multiple NA's are from Grp 1, with the remaining 10-15% from Grp 2. 

    There are about another 25 cases in which there may be 1 or 2 NA's selected.

    All in all there are 529 valid cases and 265 missing cases. The respondent needed to have answered all questions contained in the scale and not have responded with a 'Not Applicable'. Does this low valid cases count for Grp 1 pose problems? Bias?

    I'm wondering what others have done to account for NA's in survey analysis. Do you acknowledge the low count and proceed with analysis? In my reading I'm generally finding information on how to account for truly missing data - and that's not exactly the case here.

    Theresa Groth · Charles Sturt University

    Hi David,

    You are correct in that my question/explanation was not entirely clear. Yes, all 3 groups are answering the same exact 12 variables included in the scale. The original survey data was based upon a 6 pt Likert scale (6 being the NA) with a 'neutral' option in the center. So in deeming the NA's as 'missing' I'm left with a 5 pt Likert scale. Perhaps in keeping the NA's included, I should consider recoding the scale so that the  6 (NA) would become a 1 (currently 'strongly disagree') and the current 5 ('strongly agree) would become the 6. Does this information change the advice you would give?

  • Rocky Talchabhadel added an answer in Interpolation:
    Do we need to take into account of elevation while interpolating temperature data spatially?

    While interpolating spatially how can we consider elevation or simply topographically effects? Though my country Nepal is small in size, the elevation of the country varies from 60 m a.m.s.l. in the south to 8848 m a.m.s.l. in the north within a horizontal distance of less than 200 km.

    Rocky Talchabhadel · Ministry of Science, Technology and Environment

    Thank you all for overwhelming responses. I do have small query on regression krigging. I think i understand the process and am quite clear about regression and calculation of residuals. Talking about interpolation of residuals can we try some other options other than kriging?