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

  • John F Watts added an answer in Electron Impact:
    Is there any reviews or original papers on energy sharing between two final state electrons upon electron impact ionization of atoms?

    This energy sharing is very asymmetric according to our calculations. We have found some old papers that predicted this assymetry based on the analyses of classical trajectories. I am sure there shuold be a lot of studies on this subjects.

    John F Watts

    Not that I am aware of.


  • Paul Sacco added an answer in Latent Class Analysis:
    What is the best statistical approach to make subgroups from factors identified by a CFA?

    We are attempting to validate or revise a theoretical model. The model groups etiological risk factors that variously lead to problem gambling. We started with 120 items and reduced them through EFA and used CFA to obtain six psychometrically strong factors. We now want to see how these factors break out into groups (that is, what constellation of factors combine to form each subgroup)? Do we use latent class analysis or some other technique to devise these groups? no agreement among the stats folks. Thanks in advance

    Paul Sacco

    Dear Dr. Nower: 

    One option would be to use factor mixture modelling. You could use the factor model that you have developed already and then derive latent classes based on the factor scores. 

    Lubke, G. H., & Muthén, B. (2005). Investigating population heterogeneity with factor mixture models. Psychological methods, 10(1), 21.

    Hope this Helps,


  • Subhendu Sekhar added an answer in Power Generation:
    Is it economically justifiable to generate reactive power by DFIG?
    Reactive Power Generation using DFIG
    Subhendu Sekhar


  • Gordon Lee added an answer in Gold Nanorods:
    Why do some long chain molecules (in this case MPEG-SH) prefer to attach itself to the end of a nanoparticle (nano-rod) where the curvature is higher?


    I am following the method published in this paper (link: http://pubs.acs.org.libproxy1.nus.edu.sg/doi/suppl/10.1021/cm101155v).

    Why do some long chain molecules (in this case MPEG-SH) prefer to attach itself to the end of a nanoparticle (nano-rod) where the curvature is higher, while the shorter chain molecules (CTAB) prefers to attach to the side where it is more flat. 

    Gordon Lee

    thank you all for sharing your knowledge with me. I still don't quite understand why higher energy at the edges will make it more attractive to larger molecules. Does larger molecules help to lower the energy and makes it more stable?

  • Jean-Michel Rubillon added an answer in PID Control:
    Which has better performance and speed: Hardware PID or a software-programmed PID ?

    Which is better in terms of performance and speed: (options 1, 2 or 3)

    1: A (commercially available) hardware auto-tune fuzzy-PID controller (for example, see the link 1 below) having thermocouple input and solid-state relay (SSR) output, or

    2. A PID controller programmed using softwares like LabVIEW or MATLAB/SIMULINK (link 2-4) and interfaced (by a Data-acquisition card) to thermocouples for temperature (input) and SSR for controller action (output). I want to have precise temperature control of a custom-made electrical furnace for example.

    3. For implementing complex "Ramp-soak" temperature profiles, I am thinking to *program* the above hardware PID controller through MODBUS RTU/ASCII (whatever it supports) on a PC (using LabVIEW). i.e. I can read PV (process variable) and write SV (set variable) into the controller. Rest all is same as case 1. 

    I have access to all options above (hardwares and licensed softwares).

    Please share your *practical* experiences.


    + 3 more attachments

    Jean-Michel Rubillon

    You might only be interested in precise temperature control but you also mentioned ramp-soak temperature profiles in your initial query.
    I would still use Matlab/Simulink for the sheer flexibility of the set-up. Also you will be able to "play" with different control strategies which you wouldn't necessarily be able to do with a hardware PID controller.
    Another solution might be to use a PLC to do the control of the rig and provide a software interface to Matlab for more advanced control algorithms before implementing them in the PLC itself.
    More food for thought...

  • Katharina Tondera added an answer in Wastewater:
    Does anyone know a publication mentioning the uncertainty level for COD in a wastewater sample?

    I'm looking for a published uncertainty level (in percentage) that occurs when a random sample is taken from wastewater at a WWTP or in stormwater. There are values for the lab uncertainties, but I'm particularly interested in the uncertainty that occurs before that.

    Katharina Tondera

    Hello Jeremy,

    > "There is a lot of implicit trust in the values returned from a full-scale sampling exercise."

    That puts my experience with this topic in precise words. Thank you for the long and very detailed answer and sorry for replying so late. I will keep you posted if I make progress on this topic.

  • Augusta Jamin added an answer in Protocols:
    Molarity of Primers for ChIP qPCR?

    Dear All,

    What should be the Molarity of Primers for a qPCR after ChIP, the final concentration in a 25ul reaction. Some protocols suggest using 10uM stocks of each primer (0.5ul each), while other protocols suggest using 5uM each primer (o.5ul each) in a 25ul reaction. Which one is the best?

    Thank you


    Augusta Jamin

    Hi Ikram,

    In my opinion, the best concentration should be one that you have tested in your hand and works. For my ChiP assay, I usually use 1uM final concentration for each primer and this can be considered high but it has been working well for me. I would suggest testing a number of concentrations and based on the raw Ct for each primer concentration, you can choose which particular concentration would work best for your experiments.


  • Daniel Cavaller added an answer in Database Management:
    What is suitable Database to store the OpenStack Ceilometer?

    Does anyone know about the which Database or Management Database System suitable to store OpenStack Ceilometer monitoring information for future processing? 

    Thanks to all.

    Daniel Cavaller

    what 's going to use this?

  • Amanda Stranks asked a question in Th2 Cells:
    Best way to stimulate PBMCs for IL-4 detection?

    I'm looking for a positive control for IL-4 secretion in a 5 - 7 day PBMC proliferation.  Currently I'm stimulating the cells with CD3 (0.2 ug) in the presence of IL-2 (10 ng) for the culture with further stimulation with PMA/ionomycin/BrefA on the final day (around 6) hours and then attempting to detect IL-4 in Th2 cells.  So far very little IL-4 signal (lots of IFNg), and I'm not sure if my stimuli or staining protocol is the main problem.  Any thoughts on either would be welcome!

  • Ali Mahmood Humada added an answer in Pattern Recognition:
    Does anyone know of any ISI journals that respond quickly?
    Most journals respond in around 6 - 12 months. I am looking for a journal in the field of Computer Vision, Pattern Recognition or Image Processing which have a short time response.
    Ali Mahmood Humada

    Dear Mohamad Ivan Fanany,

    This is very interesting informations, however can you list, please, the same tables regarding the electrical engineering. thanks

  • Suvanka Dutta asked a question in Photo:
    How the presence of different solvent can affect on photo-luminescence of photo catalyst?

    I like to know about the effect of different solvent on photo-luminescence of semiconductor photo catalyst. some solvent can act as sacrificial electron donor in  photo catalysis process. I want to how they can affect photo-luminescence. 

  • Sergio Scanu added an answer in Principal Component Analysis:
    Can someone suggest a good free software for Principal Component Analysis?

    There is lot of interest for Principal Component Analysis among researchers in sciences. What would be a good free software for use of this community?

    Sergio Scanu


  • Abhishek Vats added an answer in Reference Genes:
    Why do I see a late amplification at ~37 cycles for the cytokine genes?


    I am trying to standardise certain cytokines' m-RNA expression in glial cells, but the amplification happens at ~35-40 cycles. Considering that the cytokines are lowly expressed in physiologically normal cells, a low copy number is obvious, but i have read that reactions beyond ~35 cycles are not much acceptable. Any inputs? I have changed the primers and taqman probes twice, the result being the same. Can ~40 cycles be considered permissible?
    Just FYI: I have been successfully running singleplex and duplex reactions in the same samples with different not-so-low expressed genes, with ~100+_1 % efficiency, comparable with the reference gene. so:

    The C-DNA is working well

    Reaction mixture/ buffer/machine are working fine. Same samples in duplex give a proper signal for 18 s gene.

    there does appear amplification, albeit late; and taqman probes will ensure specificity, so can be speculated that the amplification is actually happening, only the copy no. might be low.

    I have tried different primer/probe concentrations, different temperature range... not to much avail. Increasing concentration too, doesn't sound good, for even upon increasing the concentration of cDNA from 1 ng/ul to 10 ng/ul, the Cq shift is not more than ~2-3 cycles.

    Any suggestion is very much welcome.

    Thanks .

    Abhishek Vats

    Are you a Dr. T.R. Raju student.

  • Arhan Sthapit added an answer in Papers:
    What are the most preferred motivation techniques in organisations? Could you please advise me good papers?

    I'm working on exploring the motivation technique (one from the techniques related to financial, recognition, participation, promotion, etc.) that is most preferred by officials, across the countries; particularly in your individual country.

    Arhan Sthapit

    I express my sincere gratitude to Prof. Dr. Edwin A. Locke. My sincere thanks also to Khaliq Ahmad sir, Anup Bhurtel, Steven Reiss sir, and BK Punia sir for sharing their invaluable insights with me. 

  • Yousef Tamsilian added an answer in Polyacrylamide:
    How do I perform DLS particle size measurement of an inverse emulsion of polyacrylamide dispersed in cyclohexane in the presence of surfactant?

    Could someone offer advice on how to DLS particle size measurement of a inverse emulsion of polyacrylamide dispersed in cyclohexane in the presence of surfactant? As some literature said, I take a droplet from this inverse emulsion and dilute it by mixture of cylohexane-surfactant into a glass vial for DLS analysis. But, I cannot obtain a routine results from it. Z-average and also PDI are very high.

    Is there any method to measure the size inaddition of SEM and TEM?

    Yousef Tamsilian

    No, once I can do the analysis with 100-200 nm and another ones faced to error (large PDI).

  • Alejandro Gómez-Aristizábal asked a question in Trizol:
    Does anyone know a good way to isolate cartilage RNA, DNA and glycosaminoglycans? Can it be done with trizol?

    I am thinking of being able to get RNA for qRT-PCR; the glycosaminoglycans to quantify them and further understand the RT-PCR data; and the DNA to normalize the GAG content. I know I can isolate both RNA, DNA and protein with the trizol method, but I was wondering whether the glycosaminoglycans, e.g. aggrecan would be within the protein phase or not.

  • Georgianne W. Moore added an answer in Ecology:
    Can anyone help with this terminology in ecology: process vs mechanism and function vs role?
    What are the respective meanings of:
    - ecological processes vs. ecological mechanisms?
    Does a process includes several mechanisms, like a strategy includes several tactics?

    -ecological function vs ecological role.
    For instance, we can find "the nursery role of salt marsh " as well "the nursery function of slat marsh".

    If there is not difference in terms of meaning, is the preference for one term over the other dependent on the context and/or the audience?
    Georgianne W. Moore

    Hello Pierre and Zubairu,

    Its great to break it down and think of specific examples. I also agree with Neil's comments and Zebra example. But there are clear differences between these terms that are perhaps becoming more blurred. Allow me to try again to delineate them.

    Use the term "mechanism" to refer to HOW the change or event happened. As Neil pointed out, it could be an isolated event or something more fundamental. In plant ecophysiology, we reserve the term mechanism for phenomenon that recur in some type of repeatable/predictable way. The mechanism explains the pattern! So a 'density-dependent mechanism', as mentioned before, would refer to instances where we explain HOW something happened differently, using density to differentiate the multiple mechanisms.

    Use the term "process" to refer to WHAT is happening. As mentioned before by Thomas, processes tend to have rates (growth rates, mortality rates, rates of consumption by predators/herbivores). Therefore, I disagree that size is a process, it isn't. It is an attribute (or factor) we use as a point of reference to determine a process (e.g., size at time 1 compared to size at time 2 determines growth), but alone we cannot use size as a proxy for process. Another example: vegetation productivity at the landscape scale is measured with NDVI (infers greener parts of the landscape are more productive), but until we know how it changed, such predictions are likely wrong! We therefore must understand the link between greenness and biomass, and then how much it changed over time to predict growth.

    Here is the distinction between process and mechanism...we can measure something repeatedly to monitor growth. But if we knew the mechanisms for growth well enough (solar radiation, soil moisture), we can model growth fairly well. Such is called a "mechanistic model", because it uses a priori knowledge of HOW growth occurs to predict growth. "Process-based models" refer to a similar set of models, but they may require measures of growth as inputs, while mechanistic models only require, for example, light and moisture.

    I do not see these as hierarchical, but could be convinced otherwise. 

    Looking forward to hearing what others think of this!

    --Georgianne Moore

  • Mohammad Asad asked a question in Real Time:
    How to choose proper control for the Knock out mice?

    While knocking out a gene from the mice, some un-calculated stressed must have been developed in the mice (for sure) due to the process of knock out. In that situation, how much it is honest and justified conclusion that all the changes in mice phenotype is ONLY due to the gene knock out but not because of the process of knock out? If the process of knock out also leaves an impact on the resulting mice, than what should be the proper control? Whether any other gene could be knocked out (as we use house keeping gene in Real time PCR) for control?Thanks in anticipation.

  • Volker Maiwald asked a question in Differential Evolution:
    Can someone point me please to C++ code for optimization algorithms, Multi Start, Threshold Accepting and Differential Evolution?

    I am currently trying to create a tool for trajectory calculations (low-thrust) and want to apply the three mentioned algorithms for that. While the algorithms are not complicated and could code them myself, I would prefer already existing (free) code, which is validated/ verified.

    My search only resulted in very large libraries, which would be overkill for my purpose. Thank you already!

  • Nikos Stravelakis added an answer in Autonomics:
    Where can I find an analysis of bifurcations in the 4D vector field associated with a Jacobian with the following normal form?

    I have a system of autonomous differential equations whose dynamical behavior I wish to analyze. The matrix is {{0,-omega,0,0},{omega,0,0,0},{0,0,0,0},{0,0,0,0}}. A reference would be very helpful, or even a name for the associated bifurcations. Another case of interest would be {{0,-omega,0,0},{omega,0,0,0},{0,0,-1,0},{0,0,0,0}}

    Nikos Stravelakis

    CONVERGENCE ALMOST EVERYWHERE* the paper is available online. the idea therein is whether the elements on the main diagonal are non positive (competitive) or non negative (cooperative). On these grounds it discusses the types of bifurcations.  

  • Abiramy Krishna asked a question in Leadership:
    Which is the best questionnaire for female leadership ? responden will be the teacher's who works for the female leader?

    respondents will be the teacher and will they will evaluate their leader

  • Fred Bernhard Hesser added an answer in HEC-RAS:
    Do you have any suggestions for public domain flood modeling software except HEC-RAS and LISFLOOD?

    Any suggestions for public domain flood modeling software except HEC-RAS and LISFLOOD?

    Fred Bernhard Hesser

    Started in Hamburg, the open source modeling system Kalypso is gaining more and more users from universities, consulting engineers and agencies.

    You can find it here:


  • Nicolas Delpierre added an answer in Picea:
    Which papers report both dark respiration and nitrogen content for different needle cohorts in European conifers (Picea / Pinus) ?

    I find only a few papers addressing the question, usually reporting data only for the current (y) and y-1 cohort. Any reference is welcome. Thanks in advance.

    Nicolas Delpierre

    Dear Jiquan, dear Frida,

    thanks for you answers. I went through the references you mentioned but did not find the dark respiration (Rd) and N content data throughout several needle age classes. Such data are difficult to find are rarely published indeed. The reasons are:

    - Separating measurements among different age classes is a hard task and old cohorts usually photosynthesize and respire less than the newest one. Hence most studies report data only for the latest (at best two latest) cohort.

    - Rd is actually not easy to measure (it is true for all gas exchanges)

    Up to now, my best references on the subject are (in case you are interested), for European species :

    - Wallin et al. 1990 (New Phytol)

    - Grassi & Minotta 1990 (Tree Physiol)

    - Niinemets 2002 (Tree Physiol)

    A very interesting and recent paper on the subject for a north American species (P. mariana) has just been published in Annals of Botany: Jensen et al. 2015 (AoB).

    Any other idea is welcome !



  • Pegah Hafiz asked a question in Sampling:
    How to redo classification using Adaboost.M1 method with 1NN as weak learner?


    I've implemented Adaboost.M1 algorithm using 1NN as weak learner and apply it on my data set. The number of iteration is 30 or more. However, in some iterations the classification error in Adaboost, that is the some of distributions of misclassified samples, is more than 0.5 and I should redo the 1NN classification on training data set that is randomly chosen from N training data samples and the data distribution is the probability of each sample (just like what Adaboost do).

    The problem is that redoing classification doesn't lead to an error less than 0.5 and this process repeats infinitely. What should I do to solve this problem?


  • Shafqat Rehmani 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.


    Shafqat Rehmani

    Dear Greg, 

    You are right the results vary, just like vitro and in vivo. The Newcastle disease virus even if it gives 107pfu in chicken fibroblast cell line it may not be able to kill the chicken with the higher dose. Just because the nature of the virus its not virulent form. in case of virulent form the size of the plaques  will  be bigger dia and a very low dose will kill the chickens. so the CLD50 will be higher int his case. contrary to the small plaques where no infection can be seen in chickens with the same dose, ( reason is the virulent nature of the virus). 


  • Paul Whybrow added an answer in Content Analysis:
    In a qualitative study, how do you content analyze response that has both positive and negative statement; that contains the "BUT" or "DEPENDS"?

    For example, on a topic of whether reward can encourage a person to share his/her knowledge, an informant said: "Yes it can. But rewards should not be exercised because it encourage people to be "subsidized" to do good things". OR

    "Depends but not always. Most crucial is the environment, peers and relationship".

    So, in the analysis, it would be easy to categorize the solid "YES" and "NO" response. But where and how the above case should go in?

    Hope anyone can share their view and knowledge on this. Thanks!

    Paul Whybrow

    I agree with Roberta's suggestion. Just to add to this, part of the reason for qualitative investigations is to draw out and question some of the taken-for-granted ideas and categories. So, if you think about it, the fact that your respondents have given ambiguous answers already suggests that there is more here than rewards for knowledge. As Roberta suggests, reread with fresh eyes - how do they see the issue? Why don't they think it is that simple? Code for meaning-rich words to help you make comparisons across cases.

  • Tomasz Jaroń added an answer in Rietveld Refinement:
    Any advice on Rietveld refinement of Li1.2Ni1/3Co1/3Mn1/3O2?

    Could you please help? I want to refine the following compound Li1.2Ni1/3Co1/3Mn1/3O2  by using full prof software. This compound is isostructural with LiNiO2 layered structure , hexagonal (space group R3m). Li in the 3a site (0,0,0.5), while Ni, Mn and Co in the 3b site (0,0,0), O in the 6c site (0,0,0.25). In addition, Li/Ni  partially replacement is possible. Furthermore, Ni can be present in two oxidation state Ni3+ as well as Ni2+. So, I want to know the exact position of every atom in the structure. I am confused about B and Occ values, what are they mean? how to calculate them. I am beginner to Full Prof.

    Looking forward for your kind reply.

    Tomasz Jaroń

    Dear Mohammed,

    I do not know Fullprof software (I use mainly Jana for Rietveld refinement), but I think you have problem with description of profile. You should start from LeBail refinement (free intensities of reflections) to have the profile refined.

    Do you have the measured pattern of good quality? You can paste the picture here.