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

  • Is the basic reproduction number of at least one strain of all infectious microorganisms available?

    I can easily find the basic reproduction number of deadly, or serious infectious microbes such as HIV, Ebola, rubella, TB, and MRSA. However, it is more difficult to find it for other microbes. So, is the basic reproduction number of at least one strain of all infectious microorganisms available? if yes, what is the most reliable reference collecting them; if no, what is the criteria upon which we decide we should estimate the basic reproduction number. Also, for known basic reproduction number of different strains of a single species, are they significantly different (for instance, MRSA , VRSA, and other sensitive staph. aureus do they have a different R0). Thank you

  • Andrew G King added an answer in Scoliosis:
    Do you routinely use antithrombotic prophylaxis in scoliosis surgery for children and adolescents ?

    This issue is very controversially or undiscussed at all in the pertinent literature. On the one hand this kind of surgery may last for hours, and on the other hand this prophylaxis is not commonly used in children. What is your approach and practical experience ?

    Andrew G King · Louisiana State University Health Sciences Center New Orleans


    I am interested in the idea of micro embolism during pedicle screw tapping and passage . Do you have any data on that?

  • Can I explore the association between two continuous variables using simple regression?

    Is it fine to explore the association by applying simple linear regression as I could visualize the positive association on regression line using scatter-plot? Also, this analysis would help me to treat one variable as a predictor and another as an outcome variable, it would also help to demonstrate how much variance is explained in the latter by the former. I have rarely encountered this way of analyzing the relationship between two variables, most scholars employ correlation analysis.

    Emmanuel Curis · Université René Descartes - Paris 5

    @ Timothy : check for « equivalence tests » and you will have exactly what you're asking for.

    @ Biba: the ability to use or not regression strongly depends not only on your data (linear relationship or not, normality and so on), but also and more importantly on the problem you are studying. If it is meaningful (or imposed by the experimental design) to consider one variable as a predictor and the other as predicted, you can use regression. If, in the contrary, it is meaningless and you have to consider the two variables in your problem simultaneously, then you cannot use regression and must use correlation and related techniques. The fact that in the most simple case (linear regression/correlation), the formula are the same is very misleading on that point...

  • Kymbra Clayton added an answer in SPSS:
    Is PCA a good method to analyse very skewed survey data of 93 items?

    I am attempting to analyse data in SPSS version 17. I have 93 items dealing with ethical dilemmas faced and wish to work out if there are differences for those in rural versus city. Principal Components was suggested, and I have run this many times but I am concerned that the 'variables produced through this end up with residuals >3 and removal of these individuals, then rerunning the PCA means components change and there are 'new residuals'.

    any help would be appreciated. 

    Kymbra Clayton · Charles Sturt University

    Hello Alvaro,

    Thankyou for your response. The data was properly obtained, and the outliers are those who experienced more issues...hence are also what I am interested in.. that said though, the PCA did give 3 factors...and using the saved variables from the PCA, Anovas suggests differences for these across some independent variables such as location... 

    Was I right to use the saved regression variables from the PCA and use these in the Anova's? There seems to be a variety of ways individual create variables after running the PCA....

    your help is really appreciated

  • Laura Cardús Font added an answer in Sociology:
    Could you suggest me fundamental literature which focuses on the concept of "community"?

    I am particularly interested in works stemming from the field of anthropology/sociology. Thanks.

    Laura Cardús Font · University of Barcelona

    "Imagined Communities", by Benedict Anderson.

  • How significant is the discovery of Kepler-186f, an earth-sized habitable zone planet?
    Kepler-186f is the first earth-sized planet located in the habitable zone of another star that has been discovered. With this discovery, the search for life on other planets has entered into a new zone of discovery.

    I remember to the probability discourse in the 1960's on the emergence of life elsewhere that was based on the science of the time and now there is almost no doubt that the probability of emergence of life are high and not even exclude in this solar system.  For intelligence life, the probability discourse is pessimist now but It will change.

  • What are common sources of administrative data that could be used as auxiliary data?

    In the U.S., it may be more difficult to obtain good administrative data for an entire population than in many other countries. Partial data may be useful, but some may try to use it for substitution-type imputation, and that seems problematic. The real value in administrative data is in its use as auxiliary data for model-assisted design-based estimation, such as found in Särndal, C.-E., Swensson, B. and Wretman, J. (1992), Model Assisted Survey Sampling, Springer-Verlag, or as noted in Särndal, C.-E., and Lundström, S., (2005), Estimation in Surveys with Nonresponse, Wiley.

    Also, if administrative data on an entire population can be obtained, it may be used as regressor data in strictly model-based estimation.

    For official statistics, particularly for establishment surveys, one may have an infrequent census that could be used as auxiliary/regressor data for a more frequent sample on the same data items. But if such auxiliary or regressor data are not available, administrative data could be very useful. From Särndal, and Lundström (2005), it seems that such administrative data may be more commonly available in Europe than in the US.

    A major use of auxiliary/regressor data may be in various uses of ratios in estimation, as shown in the paper at the first link below.

    What sources of administrative data have you used or noted for any such survey? Where might such data be obtained? How did you find it? This would be highly dependent on the subject matter, but may stimulate/inspire ideas in others as to how to obtain administrative data for their use. Such efficient use of available information may be very helpful for many organizations. 

    James R Knaub · Energy Information Administration

    Regarding official use, the major problem with obtaining administrative records in the US appears to be that in the US, the various agencies are greatly restricted from sharing information with each other, and even within an agency.  In contrast, I've heard that is not such a problem for, say, Statistics Canada.  


  • What is the legality of shipping arthropods across state lines?

    I have not been able to find a concrete list of exactly what species are illegal to ship across state lines. Whenever I am purchasing arthropods online for research purposes, I see websites that say "We cannot ship to Florida or Hawaii," but I haven't been able to find anything explaining this in writing other than a few people telling me that they think it's illegal to ship some insects to those states but they don't know which ones.

    Some websites I see say that you need an import permit for EVERY arthropod species you plan to bring across state lines. And that it is always illegal to ship any non-U.S. native insect or millipede across state lines! I find this hard to believe... for example, I know that many people purchase Dubia Roaches online to feed their reptiles, and get them shipped across the country. Dubia Roaches are native to South America, however there are thousands of people who sell them in the U.S. including legitimate businesses like DubiaRoaches.com.

    I am worried that I will think I've got all the laws sorted out based on what people say, then I will go ship some of my extra research specimens to someone in another state and the USDA will pound on my door! Any help would be appreciated, thanks!

    Tracey Emmerick Takeuchi · California State Polytechnic University, Pomona

    Email Kathy Kosta at the CDFA for permits and permit information. kathy.kosta@cdfa.ca.gov

  • Mesenchymal stem cell isolation from rats: what are the differences between old and young rats?

    I am doing the mesenchymal stem cell isolation from rats. I wonder whether there are differences between cells extracted from neonatal rats and from those from older rats. First of all, I found that older rats have bigger cells than the younger one by looking under microscope. Do you think it is true in general? And are there any other differences between neonatal MSC and "old MSCs"? Thanks a lot for your sharing.

    Saleh Alkarim · King Abdulaziz University


    There are many studies that provided evidence of that there are age-related changes in MSCs derived from the bone marrow of old rodents with regard to plasticity and basic stem cell biology.

    see the article in attachment

    Good Luck 

  • Peter T Breuer added an answer in Matrix:
    How do I use CULASpare function culaSpareCudaDcsrGmresJacobi correctly?

    I want to solve a linear equation like A*x=b where A is symmetrical but not positive definite matrix stored in a spare matrix format and x and b are vectors . So I choose  a iterative solver called GMRES. b is a spare vector with only one value b(300)=2.3 and I get a correct solution. But when I only change b(300) to 17.8 , the solution is false. I don't know if I get the right way or the solver has its drawback . Dose anyone has a suggestion ?

    Peter T Breuer · Birmingham City University

    Check the matrix is non-singular, and if it is singular, check that b is in its image space?

  • Javad Azizabadi added an answer in Type Systems:
    How can I design a back stepping controller?

    Hi everybody,

    How can I design a back stepping controller for this system? h1 and h2 are states of the system and q is the input.

    Because, in Khalil's book, design is said for specific type of systems.

    Javad Azizabadi · Shahrood University of Technology

    Hello. i implementation the all of the slotin nonlinear book using matlab software.

    in the attached file. the matlab simulation files is added. download that and see how that designed. you can design your problem with this simulation.(similar way)

    three problem is simulated.

  • What are the differences between uncertainty principal for photons and fermions?

    The uncertainty principle is one of the basics of quantum mechanics. I want to know are there any differences in applying it to bosons like photons and fermions like electrons?

    The speed of light in vacuum is well defined, Does this make the uncertainity for photons lesser than electrons because their speeds are not well defined at least in vacuum in comparison with photons?

    Johan Frans Prins · Sage Wise 66 (Pty) Ltd

    A V Uryson,

    "The uncertainty principle says that we cannot simultaneously know the exact position x and the exact momentum p of a particle. "

    What do you mean by "know"? We do not need to be able to measure 100% accurately what the actual position and momentum of an entity with a centre-of-mass is, to know that they manifest simultaneously with 100% accuracy.  If they do not do so, then we cannot calculate anything, including Schroedinger's equation; as wel as Heisenberg's so-called uncertainty relationship: Which HAS NOTHING to do with "uncertainty" at all!!!!.

  • What is your opinion on the use of business vocabularies (glossaries) in various information systems/software projects?
    As you may have noticed, inclusion of business vocabularies (also referred to as glossaries) into the project activities is trending, yet this process is often lacking objective feedback and consolidated opinion from the experts and industry. Do we really need specialized/additional solutions for that? If you are working in the field of business analysis, business modeling, requirements engineering, IS design or development, I would like to hear your opinion!

    Or better yet, please consider filling out an anonymous five minute survey that is being conducted by the Center of Information Systems Design Technologies of Kaunas University of Technology and is available at
    On the last page of the survey, there is an option to leave extended feedback, if you wish to do so. Each answer is extremely valuable to us!

    We would appreciate your response by March 24th. Feel free to also forward it to your fellow colleagues, both academicians and practitioners. And big thanks to all of those who have already contributed!

    I must also add that this survey is part of research that we plan to publish in the form of a paper, if we get enough feedback (which is harder to achieve than we thought). So you will be the first to know when it happens!
    Kestutis Kapocius · Kaunas University of Technology

    Just a brief update: the paper has been made available on IEEE Xplore. Just search my last name, there won't be much to choose from. And if you can't access this database but still want to see the paper, let me know.

  • Vanja Vucicevic Boras added an answer in Neuralgia:
    How would you interpret unexplained pain in upper and lower gingiva?

    OPG clear, no bone loss, no pockets on clinical exam, 

    patient undergoes perio surgery twice suspecting gingival origin but no relief

    no caries with teeth, 

    blood reports normal 

    no pain in TMJ and associated areas.

    neurological evaluation done by neurologist and he ruled out any nerve involvement and any neuralgia

    no relief by pain killers, 

    I suspect a form of MPDS

    what systemic diseases can cause gingival pain alone?

    Vanja Vucicevic Boras · University of Zagreb

    if everything regarding oral cavity is Ok, I would consider atypical orofacial pain, referral to neurologist although she went and amytriptiline.maybe to  consult the book : Orofacial pain by Joanna Zakrzewska,

  • Sylvester Adejo added an answer in Langmuir:
    Is it possible to have an adsorption system that does not follow Langmuir or Freundlich isotherm models?

    I'm fitting my isotherm data to linearized langmuir and freundlich isotherm models. But they didn't have a good fit with these models. But data showed a good fit with dubinin-radushkevich and Temkin isotherm models is it possible?

    Sylvester Adejo · Benue State University, Makurdi

    Yes, it is very possible. Quite a number of adsorption systems especially in solution do not obey Langmuir.   You can also check some of my publications on this issue. The papers are there on my page within this community.

    If I may ask what was the basis of your fitting?


  • Do you think it will be possible to graph the comparisson between people who don't go to Church and seek God/ to those who are faithful to Church?

       From the time of Freud, has anyone, referring to Psychology of Religion, researched groups of people who attend minimal/no Church vs those who are faithful? What are the differences in the lifestyles: stressors, depression, anxiety and anger (etc) are dealt with?  

    Mary Latela · Sacred Heart University

    Nicole, thanks for finally clarifying. Now, thanks for sharing that you have a position as a member of a religious group - that being fully attentive at services means people are good "believers." This is a perception. One cannot measure interiority.

    The question, "Are you a believer?" itself is confusing. Believe in what/whom?  In the 1980s people would come up to you and ask "Are you saved?" which was a way of asking if you were a born-again Christian. Christians who did not know what this meant or didn't care about the "born again" phenomenon could not relate.

    My point is that you can only measure quantifiable things. A few years ago, it was found (in survey) that people who attend church are more likely to say they believe in Jesus. But people never like to put into writing something that might cause shame later.

    Still, good wishes. What kind of ministry are you looking at, I'm curious. ML

    p.s. you simply can't transfer this amount of data into your own research pile. You will need to do the hard work!

  • Isam Basheir added an answer in Image Processing:
    How can I extract a triangle shape from an image?

    Suppose I have an image of a geographical region. I want to extract a triangle from that region that covers a certain features (knowing that the image is RGB).

    Isam Basheir · United Nations World Food Programme

    Hallo guys thank you for reply. I want to use MATLAB in this issue.

  • Shilpi Goenka added an answer in Serum:
    Should one use standard serum or low serum (0.5%) for running coculture experiments for up to 6 days?

    I am wondering if one is doing coculture experiments with two cell types, should one use serum free, low serum (0.5%) or the standard 5% serum? I want to coculture for upto a week and few papers use low serum. Which is better?

    Shilpi Goenka · Stony Brook University

    But my question is can't I use standard serum (10%) and grow the cells for upto 5-6 days. using low or no serum is not physiological and I am not planning to do long term culture.

  • Does “spin” imply physical rotation?

    The “spin” of an electron or other fundamental particle is often described as “intrinsic angular momentum”. This terminology is required because a point particle or Planck length vibrating string cannot possess ½ ħ of angular momentum. Larger objects such as molecules or electrons in atomic orbitals possess quantized angular momentum which can be demonstrated to involve physical rotation. For example, a carbon monoxide molecule in a vacuum can only rotate at integer multiples of 115 GHz which is integer multiples of ½ ħ. Therefore, do you believe that fundamental particles have a physical angular momentum that is currently not understood? Alternatively, is "intrinsic angular momentum" an accurate description of spin because it is a quantum mechanical property that does not involve physical rotation?

    Richard Gauthier · Santa Rosa Junior College

    Hello Yuri,

     Thank you for your positive response to the question "does spin require physical rotation?", based on analyzing the Dirac equation. Please take a look at my model of a Dirac electron that is modeled as a circulating charged photon at https://www.researchgate.net/publication/267922850_The_Electron_Is_a_Charged_Photon  and https://www.researchgate.net/publication/269932279_The_Charged-Photon_Model_of_the_Electron_the_de_Broglie_Wavelength_and_a_New_Interpretation_of_Quantum_Mechanics . Dirac claimed in his Nobel prize lecture that the electron moves at an unobservable speed of light with an unobservably small  amplitude but the electron's observable speed is less than the speed of light. My Dirac electron model is based on this claim and has a helical light-speed motion with a longitudinal velocity v of the electron, and finds that the charged photon model fits the relativistic electron's energy-momentum equation E^2 = p^2 c^2 + m^2 c^4 , and also predicts (in the second article above) the relativistic de Broglie wavelength of a moving electron. With your expertise on the Dirac equation you should be able to say if my proposed charged-photon model of a free electron is consistent with the Dirac equation for a free electron, and if not why not. Thank you. 

  • Is there any possibility for HPMA monomer to get polymerized without adding initiator to the reaction medium?

    I just synthesized HPMA monomer under the condition that Ulbrich et.al. did. In the first run, I get crystalline monomer but in the second run, I just get a sticky mass.I wonder if the monomers get polymerized?

    the reference based on which I worked is:

    Ulbrich K, Subr V, Strohalm J, Plocova D, Jelinkova M, Rihova B. (2000) Polymeric drugs based on conjugates of synthetic and natural macromolecules I. Synthesis and physicochemical characterisation. J. Controlled Release 64(1-3), 63-79.

    Rajesh Krishnan Gopalakrishna Pnaicker · Polytechnique Montréal

    Hi Prabhu,

    When it comes to polymers you remove remaining solvents by the methods you described. But Sahar is synthesizing a monomer. She is trying to purify it by recrystallization and she is not getting crystalline material because there may be some impurity and/or solvent. If she do the recrystallization as described in the manuscript she will get crystalline material. She already did it before. Recrystallization generally remove small amount of impurities. Now it is amorphous because it is impure. If you read the reference cited by Sahar you can see they have a stringent condition for recrystallization.  

  • Atef Oreiby asked a question in Immunoassay:
    I am searching for a good source to read about lateral flow immunoassay manufacturing, which source do you recommend?

    I am searching for a good source to read about lateral flow immunoassay manufacturing, which source do you recommend?

  • Vanja Vucicevic Boras added an answer in Xerostomia:
    What is the most effective method to screen for dry mouth (xerostomia/hyposalivation) in general dental practice?

    There is need for effective diagnostic criteria and functional tests in order to detect those individuals with oral dryness who may require oral treatment, such as alleviation of discomfort and/or prevention of disease (Lofgen et al., 2012).

    - Xerostomia Inventory schort form (SXI-D)
    - Index for symptoms of xerostomia (bother index)
    - Clinical oral dryness score for clinical signs (CODS)
    - Sialometry, the measurement of whole salivary flow rates

    Vanja Vucicevic Boras · University of Zagreb

    salivary flow rate is most objectively measured when patient sits in the chair and spits out saliva during five minutes in calibrated test tubes (0,1 ml). if salivary flow rate is lower than 2,0 ml in five minutes i.e. 0,4 ml in one minute this can be consider as xerostomia better hyposalivation. xerostomia is a subjective feeling of dry mouth unlike hyposalivation which is objective one. However, published literature is full of mistakes regarding subjective and objective dry mouth feeling.

  • Brian Hanley added an answer in Herpes Virus:
    Can anybody provide the sequence of envelope Glycoprotein B?

    (Sequence from India). I am working on herpes virus in my project so I need it.

    To avoid preventing you from learning how to search, I'll suggest that you use scholar.google.com for that. You also need to know which HSV it is. And learn to use Genbank and RCSB. And don't you have an adviser to ask questions of?

  • Erik Martin added an answer in Cancer Cells:
    What would you add or change for a complete list of the hallmarks of cancer?

    The concepts published on the hallmarks of cancer (Hanahan D, Weinberg RA, The hallmarks of cancer Cell. 2000 Jan 7;100(1):57-70) and its update (Hanahan D, Weinberg RA, Hallmarks of cancer: the next generation Cell. 2011 Mar 4;144(5):646-74. doi: 10.1016/j.cell.2011.02.013) have been very influential in forming our ideas about the nature of cancer and reasonable approaches to improved interventions. Do these published hallmarks completely capture current ideas or would you add or change them from your results and understanding?

    Erik Martin · University of Maryland, Baltimore

    A future addition to the hallmarks of cancer may be the acquired plasticity associated with tumorigenesis, or in other words the enhanced ability of a tumor (or clonal population) to quickly adapt and respond to therapeutic interventions, or other insults, through genetic mutations, signaling, and modulations of differentiation status, etc relative to non-transformed cells. 

  • Are we living in a world consolidating epistemic and symbolic violence?

    My problem-oriented debate comes from questioning Gypsy / Roma inclusion. Governmental inclusion is based in fact on the exclusion of differences. From my recent ethnographic research on Gypsies in Romania  I  found that they do not want to hear about inclusion. Inclusion means subordination. Inclusion means symbolic violence.

    Magnus Pharao Hansen · Brown University

    I think this is very common, and is a standard finding in literature about cultural minorities in relation to nation state majorities. Inclusion means assimilation and that equals that cultural minorities cease to exist as distinct cultural and political collectives.  This is the symbolic violence of conforming to the nation state - and it is the other side of the double sided sword that is democracy. The same is found in the relation to Saami minorities in Sweden and Norway, to immigrant groups all over Europe, to indigenous peoples in post-colonial nations in Latin America etc. 

  • Is abnormal movement (behavior) an endpoint for ecological risk assessment?

    I am exploring technology that can result in a low cost, onsite assessment of aquatic invertebrate behavior (movement) as an endpoint for ecological risk assessment.  If statistical analysis can confirm a difference between movements of individual aquatic invertebrates upstream, in, and below stream of point discharge, would this be of use for phase 1 or other studies of risk assessment?  Thanks, Lou

    Louis Macovsky · Dynamic BioSystems, LLC & RxSim, Inc.

    Thank you Azubuike and Xiaowei.  Papers like that one are for what I search.

    Do regulatory agencies like EPA here in America accept abnormal movement (behavior) as an endpoint at least in scoping or phase 1 of risk assessments?

  • Have you sure that there is a direct relationship between risk and return?

    Textbooks assume that there is a direct relationship between risk and return, thus if a company has more risk it is expected a higher profitability. Have you ever checked this relationship?

  • William K Peters added an answer in Absorbance:
    What is the natural frequency of a molecule in the context of light absorption?

    When the frequency of light is equal to the natural frequency of a molecule, molecule absorbs light.

    My question is whether the molecule can have only one natural frequency? If thats the case why the natural frequency should match the energy gap between the ground and excited state.

    William K Peters · University of Colorado at Boulder

    I'm curious where you came across the concept of the natural frequency; that would help with interpretation. However, usually when I come across the concept, it is in the context of a Lorentz model for optical response. In this model we apply more-or-less classical mechanics to an electron bound by a harmonic force to derive things like absorption line shapes, index of refraction vs frequency, etc. The natural frequency is then the harmonic frequency of the electron, root(k/m). The spring constant is basically arbitrary here.

    When applying this model to reality, you'll use any resonant frequency of the molecule as the "natural frequency", usually the closest resonance to the spectral range you're considering. So in the visible, the frequency of the HOMO-LUMO transition will take the place of the natural frequency. In the IR or microwave, you could use vibrational or rotational frequencies. However, the Lorentz model is less useful in these spectral ranges, as it is mainly valuable when you can  pretend the response is dominated by a single frequency.

  • Terezinha Pinto added an answer in Ethyl Acetate:
    Does 0.1% acidified ethyl acetate kill all bacteria?

    I was doing N-Acyl homoserine lactone (AHL) extraction from bacteria using 0.1% acidfied ethyl acetate. Wondering does certain bacteria tolerance to this so that I might leave bacteria broth and acidfied ethyl acetate mixtures for extended time so that better yield of AHLs?

    Terezinha Pinto · University of São Paulo

    Considering the diversity of resistence, depending on different bacterias, Dr. Ramanujam consideration is completely adequated.