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

  • Ayman El Ansary added an answer in Concrete Material Technology:
    How can modulus of elasticity be calculated using a stress-strain Curve?

    I am looking for practical references to show me how to find modulus of elasticity in UHPC. 

    Ayman El Ansary

    I do agree with Roger that in the elastic limit, modulus of elasticity is simply the slope of the stress-strain line. Considering the non linear curve, there are to methods for calculating the modulus of elasticity either tangent modulus or the secant modulus,

  • Pyare mohan Tiwari added an answer in Sliding Mode Control:
    How can actuator saturation be addressed in higher order sliding mode control design?

    In a higher-order sliding mode control design for a system with relative degree two, how can system stability be proved in the presence of actuator saturation?

    Pyare mohan Tiwari

    Dear Prof. Kada

    In attitude control design taking quaternion parameter, I started with

    sliding variable s=qv (vector quaternion). Obviously, \ddot{s}=f(q,\omega,u)+u. Therefore, \dddot{s}=ff(q,\omega,u)+\dot{u}

    To eliminate chattering, I am proposing for \dot{u}. So ,whether saturation problem is automatically eliminated or not?

  • Sugirtharan Muthucumaran added an answer in Water Quality Management:
    What are the possible management strategies against fluctuating salinity in lagoon?

    Water quality monitoring in the lagoon level shows fluctuation of salinity from 2 ppt to 33 ppt. Opening of barmouth during rainy season allows salt water intrusion in the later part of rainy season. That might be the direct cause for the salinity level in the lagoon.  So what are the options and remedies for salinity problem to include during the preparation of water quality management plan?  

    Sugirtharan Muthucumaran

    dear researchers, thanks for your valuable comments and if you  have any more ideas when you are reading literature please suggest... thanks

  • Ajay Padmawar added an answer in Curcumin:
    How do I make nanoparticle of curcumin?

    I want to make nano particle of curcumin. I have curcumin 95% which is derived from turmeric. Please suggest me simple laboratory method to make nano particles.

    Ajay Padmawar

    Thank you very much  Mythili, Suparno and Hossieni.for this valuable information.

  • Chelsie Rohrscheib asked a question in Statistical Testing:
    What statistical test can I use to determine if successful Drosophila mating is due to male behaviour or female choice?

    How do I test if mate success is dependent on males or the female? 

    We wanted to investigate how certain mutations affect male mating success. 

    Male conditions (4 total):

    1.) mutant 1

    2.) mutant 2

    3.) wild type 1

    4.) wild type 2

    Female Conditions (3 total):
    1.) mutant 1

    2.) mutant 2

    3) wild type 


    Two males of different mutation conditions (see above) are placed into an arena with one female of a specific mutation status. The male that successfully mates with the female is given a score of 1. The loser receives a score of 0. 

    Examples of some combinations we might test:

    Female (Mutant 1) x Male (Mutant 1) x Male (Mutant 2)
    Female (Mutant 2) x Male (Mutant 1) x Male (Wild Type 1)
    Female  (Wild Type) x Male (Mutant 2) x Male (Mutant 2)

    .. etc. etc. until all possible combinations have been explored (14 combinations in total)

    I have already run the pairwise comparisons between the males and it is fairly obviously that the mutations are influencing mate success (ie some mutants mate more successfully than other), however I still have to control for effects of females. 

    What statistical test can I preform to rule out the possibility that mating success is based on female mate preference and not male mating behaviour? 

  • Roozbeh Hesamamiri added an answer in Strategic Management:
    What experiential exercises can be used for teaching strategic management?

    I would like to know what experiential team-based exercises are recommended for teaching strategic management in Msc classes. For example, to introduce vision, mission, strategy, values, policies, etc.

    Roozbeh Hesamamiri

    Thanks a lot for your answers. I appreciate your coordination. 

  • Jill Muhling added an answer in Sorting:
    Is estimation of viral titre an unavoidable step in Transduction experiments?

    I have been working with 3rd generation lentiviral vectors. The problem is that the transduction efficiency is very low and GFP signal is expressed atleast after 72 hours (although the expression is under the control of CMV promoter). 

    And in this duration normally cells take atleast 2 divisions and then the population for sorting becomes more difficult to analyze and sort through FACS.

    Is there anyother way to select transduced cells or I can start with low cell density and high viral load without doing titre and then sort them through FACS. Any suggestions please.

    Jill Muhling

    500ul of concentrated virus sounds like a LOT. Ok, after you produce your virus, add 1ul of virus to one well of a 24-well plate containing 293T cells at 50-70% confluency. After 2-3 days, count the number of green cells. You can then work out your virus titre. If you don't know your titre then you don't know where your problem might be.

  • Ashwini Kumar added an answer in XRD Analysis:
    What do we exactly get from XRD analysis of polymeric films?

    Almost all the publications regarding preparation and application of polymeric films have XRD analysis as one of the methods. What information do we exactly obtain by performing XRD of the polymeric films? Why do we need this particular study?

    Ashwini Kumar

    Thanks a lot sir for your kind help. 

  • Ron Reiserer added an answer in Incubators:
    Does anyone know of a hypoxia incubator (170L or larger) that can be used with a single tank of pre-mixed gas?

    We want to conduct cell culture in a hypoxic environment, however we don't have a nitrogen line in the lab and can't get one installed. We have a premixed gas (2%O2, 5%CO2, 93% N) but have been told it's not compatible with our HeraCELL 240 incubator. Does anyone know of an incubator that can achieve hypoxic conditions using a premixed gas mixture? Thanks for your help in advance.

    Ron Reiserer

    It will be hard to find a commercial single gas incubator that will allow hypoxic conditions. Typically the single gas is intended to be pure CO2, not a mixture. You could try to see if your CO2 incubator will flow enough of the mixed gas to keep the chamber hypoxic. The mixed gas will not hurt anything. The controller should just keep injecting gas to try to keep the CO2 at 5%. You may find that you use a large volume of gas each day that may be difficult to manage. Another possible problem will be humidification. Mixed gases are usually completely dry and if you are putting a large volume of dry air into the incubator, you may find that the humidity is low in the incubator which can also cause your CO2 sensor to read erroneous levels.

  • Dinesh Kumar added an answer in Superconductors:
    For the estimation of Hc2(0) in superconductors, we use WHH equation, what does the factor 0.692 in the WHH equation stand for?

    In the equation

    Hc2(0)=-0.692*Tc*dHc2/dT at T=Tc, why does 0.692 comes into picture?

    Dinesh Kumar

    @Eric Krage

    Thank you for pointing that out, I should have checked it. Now can you please tell me why ln2 factor is multiplied?



  • Anais Legrand asked a question in Histological Analysis:
    Student T-test versus Wilcoxon rank-sum?

    Hi all!

    I would like to compare the vessels density between to samples (control versus treatment, so 2 groups) of healed skin wounds, based on histological analysis. In each group I have 30 measurement datas. At the beginning I was thinking about a simple Student t-test, but I have also found other papers using the Mann-Whitney (=Wilcoxon rank-sum test). Any idea about what is the most suitable?

    Thank you!

  • Mahmoud Omid added an answer in Validation:
    Would you agree that a «How...?» question is asking for a scientific explanation, whereas a «Why...?» question asks for a phylosophical answer?

    I wonder...

    Just the other day, as I told this to my students, I stopped for a while, and then I added. «...But isn't Phylosophy a Science ???»

    I should like to know your approach to this. 

    Isn't Phylosophy of Sciences a valid and valuable field of the scientific matter?

    Mahmoud Omid

    Yes dear Maria

    A common element between the philosophy and science is that they try to explain situations and find answers. Philosophy does this by using logical argumentation while science uses empirical data. On the other hand, the main difference is how they work and treat knowledge. Philosophy examines the 'why', whereas science examines the 'how'.

    The famous Bertrand Russell has once said "Science is what you know. Philosophy is what you don't know."

    P.S.: This question was discussed in RG sometimes ago.

  • Waqas Qureshi added an answer in Internal Medicine:
    How I can calculate the dose of ferrous sulfate to anemic patient with iron deficiency anemia?

    I want to calculate the appropriate dose of ferrous sulfate for anemic patient depending on MCV, HB level and his diet ?

    Waqas Qureshi

    currently there is no specific data suggesting this approach. This is because the intestinal receptor density changes as the need for iron increases so even 1 tablet of ferrous sulfate is better absorbed when the iron stores are depleted in the body. Which means that it doesnot matter how much Iron you give, what matters is how much iron depletion is there and even 1 tablet suffices for that purpose. 

  • Mehrdad Taheran asked a question in Chitosan:
    How to dissolve chitosan in DMF?

    I want to produce electrospum fibers from PAN/Chitosan composite. The problem is that PAN is soluble in organic solvents like DMF but chitosan is not. I know that chitosan should be modified to be soluble but I do not know the easiest and strightforward method for dissolving in DMF. What do you suggest?

  • Anand S. Kale added an answer in Coastal Geomorphology:
    Any idea what this rock type occurring on the beaches of Maldives?

    These structures are about a meter in diameter, displaying striking laminated structure.

    Anand S. Kale
    1. Definately an algal structure. Resembles what are now described as micro-biolites, of algal origin. These are prolific reservoirs in the pre-salt of Brazilian continental margin.
  • Chao-Dong Zhu asked a question in Insects:
    Are you interested in interdisciplinary studies on insects?

    Are you interested in interdisciplinary studies on insects? Use your mobile to scan and join the wechat group organized by some young entomologists in China.


  • Krishnan Umachandran added an answer in Faculty:
    What strategies do you use to address late attendance in classes?

    While we have policies on attendance at our Universities, it seems late coming is not explicitly addressed, leaving faculty to use their own strategies to deal with late comers. ironically, the issue becomes even more complicated when you have to try and bring the late-comer into the "present" without keeping back the rest of the class. How do you deal with late coming and late comers in the classroom?

    Many thanks,


    Krishnan Umachandran

    Being strict holds good only when everyone in the system sticks to it. The common practice is that the student does not get their attendance when they are not available when the 'Roll call or attendance is called" , some lenience also happens when they are present before the register is taken away, mostly 5 or 10 minutes within the start of the session.

    The problem here is when the student is marked absent, they go to the administration department and try to make it up through some means, else in some cases the management, before semester exams collects some penalty fees for "attendance regularization" and settles it. In such cases the teacher is a laughing stock. We need to understand situations before taking actions and suitably find innovative ways to handle classroom discipline.

    I apply PEER CONTROL TECHNIQUES, so that team takes care of the communication with their members on the regularity and contribution through activities, were performance and transparent evaluation is practiced.

  • Sakshi Kanagala added an answer in Water Purification Technologies:
    How do I reduce organic loading rate of wastewater?

    I want to check the efficiency of my treatment model for varying organic load, which method should I adopt to reduce the organic loading rate of influent?

    Sakshi Kanagala

    we can still reduce the organic loading rate by either increasing surface area or adopting different films to it.the efficiency always depends upon the type of organic loading you are giving to the treatment model.research have shown that giving smaller doses of organic matter rather than whole at a time will increase the efficiency allowing for the application of higher hydraulic and organic loading rates. hope this helped!

  • Sibnarayan Datta added an answer in DNA Sequencing:
    How to make double stranded DNA from single stranded DNA products?

    I'm trying to make double stranded DNA from large single stranded DNA products. How to make these double stranded again?

    Sibnarayan Datta

    Dear Thuur 

    Use random hex in a Klenow reaction to make dsDNA from ssDNA.


  • Bernardo B. S. Niebuhr added an answer in Animal Movement:
    Should I worry about residuals when fitting non-normal (generalized) linear models?

    I am fitting exponential and Weibull models to animal movement data.

    1. Should I worry about residual normality or anything like that?
    (it seems to me that this is not important, since I do not assume normality)

    2. Anyway, how should I analyze residuals to get a picture whether my fit is good or not?

    Just for note, my model looks like:

    y[i] ~ dexp(lambda[i])
    lambda[i] = f(x[i]) (linear function)

    Thanks in advance!

    Bernardo B. S. Niebuhr

    Yes, I am trying to model animal movement using random walks, and trying to associate it with landscape and environmental variables, though using models simpler than Langrock's ones. But the idea is similar.

    I am not using BUGS (I just used a similar notation), I am using a MLE approach directly in R, with bbmle package. I am comparing alternative models and selecting them using AIC; in a certain way, it seems to me that this is already a measure of relative "goodness-of-fit" of the models. However, I wonder how should I perform residual diagnostics for a better understanding of model fit.

    I have found some references on GLM residual analysis (e.g. James Fox, "An R and S-Plus Companion to Applied Regression" - https://us.sagepub.com/sites/default/files/upm-binaries/38503_Chapter6.pdf), but code already implemented on R does not accept mle2 models.

    I still have not found clear references on how to properly calculate residuals (or which residual formula is more straightforward to interpret) for non-normal models, nor how to interpret residual fitting.

  • Shahzad Hassan added an answer in Wireless Sensor Network:
    Anyone familiar with Random Number Generation in WSN?

    Hello , 

    I am writing a code for event detection in WSN. Generally we generate random number between (0,1) and we set a certain threshold (e.g temperature) or any randomly generated threshold .  I am having trouble with the threshold value . Beside (0,1) and temperature range . Is there any alternate method for setting the threshold value .


    Shahzad Hassan

    HI , Andrea ,

    Many thanks for answering . I will check it out. Thanks

  • Ron Reiserer added an answer in HMDS:
    Can anybody suggest priming agents or processes to promote adhesion between an EBL photoresist and borofloat glass?

    Dear Sirs and Madams,

    We are having an issue with adhesion between ma-N 2403 EBL photoresist and borofloat glass. We have tried spincoating HMDS but it proved unsuccessful.

    SurPass was suggested (cationic primer) but we do not have access to it - does anybody know its composition?

    Any suggestions are welcomed. Thank you in advance.


    Ron Reiserer

    Do you have access to vapor priming? I have had much better adhesion with vapor priming than spin coating HMDS when using other resists.

  • Shubha Likitha added an answer in Lactobacillus plantarum:
    How can Lactobacillus plantarum survive in simulated gastric fluids at pH 2?

    I tested viability of L. plaatarum NCIMB 8826 at simulated gastric fluids. My SGF was prepared by using 2 g NaCl, 3 g of Pepsin and 7 mL of conc, HCl. Distilled water was then added to get 1 L. After that pH was adjusted to 2 by 1 M NaOH. SGF was sterilized by a syringe filter (0.2 um). One mL of culture was added into SGF and incubate for 2 h.

    After incubation, I did dilution in saline solutions and used pour plate method.

    I and my labmate repeated in couple times. The cell counts were higher that 6 log CUF/mL. The results reported by other papers showed that the cells could not survive after 2 h at pH 2. 

    Can anyone suggest what happen with my result or what I did wrong?   

    Thank you in advance. 

    Shubha Likitha

    Dear ,

    Did u check for the viability of cells after encapsulation (before simulation). U also ckeck foe the compatibility of pectin used at pH 2.

  • Sibnarayan Datta added an answer in Viral Load:
    Can anyone suggest the best HBV viral load positive control for real time PCR along with the full details of company providing this?

    Hello Frnds,

    I want to get HBV viral load positive control for real time PCR so that I can easily Plot the LJ chart of the sample results. so please suggest me which is the best?...

    Sibnarayan Datta

    Dear Shaifali,

    I recommend you to go for the 3rd WHO International Standard for Hepatitis B Virus for Nucleic Acid Amplification Techniques (NIBSC code: 10/264). You can refer to the links and references provided below for more detailed information on this standard and NIBSC website for purchase enquiry.


    Heermann KH, Gerlich WH, Chudy M, Schaefer S, Thomssen R.
    Quantitative detection of hepatitis B virus DNA in two international reference
    plasma preparations. Eurohep Pathobiology Group. J Clin Microbiol.

    Fryer JF, Heath AB, Wilkinson DE, Minor PD and the collaborative study
    group. Collaborative study to evaluate the proposed 3rd WHO International
    Standard for hepatitis B virus (HBV) for nucleic acid amplification technology
    (NAT)-based assays. WHO ECBS Report 2011; WHO/BS/2011.2170.



  • Ashish Gupta added an answer in Surface Acoustic Waves:
    What is the optimum number of the IDT finger to get 50 Ohm?

    Dear All,

    I am not sure how can I calculate the number of IDT finger in order to achieve 50 ohm resistance. Let's say my strip width is 50 micron.
    what should be the number of IDT finger for 50 micron strip width ?

    Best Regards,
    Yannapol S.

    Ashish Gupta

    There is no hard and fast rule to calculate the finger width and length of IDC. it is quitely depending on your structure... u mast hv to optimize it in order to get the best results.. however u can initialize the optimization by taking the width and gap = 0.2 mm....

  • Monika E Schloder added an answer in Physical Activity:
    What are the functions of mechanical efficiency in physical activity?

    Wich are the funtions to the mechanical efficiency in themphysical activity in the differents ages groups.

    Monika E Schloder

    In Prevention and Recovery… you want to get the Coach work book and the Reference book (excellent resource). Tell Wayne that I gave you his email.

  • Dimitris N Tatakis added an answer in Pathogens:
    What are the most recent gingival crevicular biomarkers for oxidative stress?

    Gingival crevicular fluid is an invasive and reliable source of multiple diseases & underlying pathogenic mechanisms, among these pathogenic mechanisms is the oxidative stress. 

  • Istkhar Rao added an answer in Entomopathogenic Nematodes:
    What will be the correct decision when results of molecular Identification of EPNs revealed from COI gene oppose the results of ITS and D2D3 regions?

    I am working on the identification of entomopathogenic nematodes (EPNs). During the molecular identification of the species, I found 100% similarity of the studied EPN isolates with Steinernema abbasi based on ITS and D2D3 regions whereas the COI  gene showing a distance matrix of 1.3 and phylogenetic tree (MP, ML and NJ) placed the specimen into a new clade. what could be the concluded remarks? Is it a different species or an isolate of S. abbasi? Is it better to use COX I gene or the identification based on ITS and D2D3 is sufficient? Out of all these three genes, which one is the best suited genes for molecular identification? Kindly suggest. Thanks in Advance.

    Istkhar Rao

    Lal Ramliana Sir, its not about the ITS its about the COI gene. The ITS has complete set of ITS1-5.8S-ITS2. Problem is related to COI gene. why there is a variation in COI genes of compared species??Is it mean that we should not use COI gene in phylogenetic analysis?

  • Nagarjuna Sivaraj added an answer in HEPES:
    Which is the alternative buffer for HEPES?

    I am trying to do a  colorimetric assay for measuring phospholipase A2 at physiological pH. and I got an article in that they used HEPES buffer but it is not available with me, So please suggest any other buffer.

    Nagarjuna Sivaraj

    Noura S. Dosoky, the protocol that you suggested is nice but their is no references for that protocol and also what to measure is not specified i.e., whether assay is measuring the absorbance of lysolecithine  or a fatty acid

  • Yuan-Yeu Yau added an answer in Crop:
    Where can i get data on global production and adoption of transgenic crops or GM crops?

    Agrobiotechnology, agricultural policy development researchers 

    Yuan-Yeu Yau

    Hi Hudu,

    ISAAA is a good place to look. It contains a lot of information about GM plants, including a GM approval database. Please go to this website at:  http://www.isaaa.org/