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

  • Tobias Willem Shinyemba asked a question in Data:
    How can I merge Household database and to Women data base in the DHS data using "stata"?

    I am trying to merge these two files in "stata" and I am failing to do so since the files do not have a common identifier.

  • Stam Nicolis added an answer in Special Relativity:
    When it comes to simultaneity is Einstein correct or is Dingle correct?

    Albert Einstein claimed in 1905 that a single event can occur simultaneously at different times within two inertial reference frames moving relative to one another. In 1950 Herbert Dingle argued that different times cannot be simultaneous. I have analysed this conflict by deriving the Lorentz equations using both points of view. According to this analysis Dingle must be correct. See youtube presentation of this analysis at  https://youtu.be/4XLYzhHQ64Y

    Stam Nicolis · University of Tours

    Lorentz transformations don't have anything to do with clocks being synchronized in any particular manner. They pertain to mathematics and, as the term indicates, they are transformations, which means, in particular,  that they can be composed. What does the term ``isochronous clocks of the same indication'' mean, beyond, ``synchronized, identical, clocks''? One consequence of the covariance of the wave equation under Lorentz transformations is that ``isochronous clocks of the same indication do not necessarily link the same real time instant.''.  

  • Mustafa Ozkan Baltaci added an answer in Dyes:
    Is there a dye which changes colour in contact with bacteria?

    Could anybody suggest dye that changes colour in contact with bacteria or pus?

    Mustafa Ozkan Baltaci · Ataturk University

    http://en.wikipedia.org/wiki/Resazurin you should look this one.

  • Nata Kuzlo added an answer in Civil Engineering:
    Can anyone help me with any articles or other information on the analysis of professional discourse?

    I mean structure and principles of analysis of professional discourse, especially any civil engineering discourse (any construction projects specifically). But if not, I would be grateful for any materials concerning analysis of any professional discourse.

    Nata Kuzlo · National university of water management and nature resources use, Ukraine, Rivne


  • Why does the PCR not work occasionally?

    Dear collegues!

    we extracted RNA from apple peel. We need clean RNA without DNA contamination, so we check our RNA samples by PCR. Samples are fresh. and reagents are the same. BUT one time PCR works another time - no band in DNA control. Only thing we change is the electrophoresis chamber. We have no idea what can it be? Do you have such a problem? Please write your suggestions about this. Thank you in advance. looking forward to hearing from you soon.

    David Rincón Fernández-Pacheco · University of Cordoba (Spain)

    As Peter said, it is possible that the problem is in the number of samples, if you are making a lot tubes at the same time there are some problems that could be affecting your PCR. When do you add the polymerase to the tube? Polymerases usually have exonuclease activity, so it should be possible that during the preparation of so many tube polymerase was destroying the primers. Is the polymerase a hotstart enzyme?

    If it isn't a complicate PCR, it should be useful to change the PCR kit and try with a mastermix all in one tube. This way, you only have to add water, primers, template and mastermix. More steps, more time, more possibilities to make mistakes, easier to fail.

  • Tobias Willem Shinyemba asked a question in Databases:
    How can I merge Household database to Women database in the DHS data using "stata"?

    I am trying to merge these two files, and I am failing to do so since the don't have a common identifier.

  • Igor Goliney added an answer in Complex Networks:
    How can we write wave equation on complex network?

    Dmitri Krioukov et al suggest that the univse resembles a complex network. See http://arxiv.org/pdf/1203.2109v1.pdf. Now the question is whether it is possibl the wave equation on complex network. What do you think?

    Igor Goliney · Kiev Institute for Nuclear Research

    You are good. 

  • Petre Ianakiev added an answer in RNA-Seq:
    Does anyone have experience with strand specific RNA sequencing?

    Does anyone have experience with one of the following kits, used to do cDNA synthesis and strand specific sequencing?

    • http://www.clontech.com/US/Products/cDNA_Synthesis_and_Library_Construction/Next_Gen_Sequencing_Kits/Total_RNA-Seq/Strand-Specific_RNA_Seq_Illumina

    • https://www.neb.com/products/e7420-nebnext-ultra-directional-rna-library-prep-kit-for-illumina
    • http://www.biooscientific.com/next-gen-sequencing/illumina-stranded-rna-seq-library-prep-kits/nextflex-rapid-directional-rna-seq-kit

    I've found three companies that offer this kind of kit, but am wondering how good they work and if they really are better than cDNA synthesis and subsequent Nextera library prep?

    Many thanks for your input!

    Petre Ianakiev · Beckman Coulter Inc.

    Thumbs UP Alexander! I love what you have done. 

  • Is it proper to change your research model after factor analysis?

    Let you started with a research model based on some theoretical insights and collected data.

    You run a factor analysis and observed different factors. 

    What ways can be followed?

    Marija Topuzovska Latkovikj · Ss. Cyril and Methodius University

    You can continue with your factors-observed, as these findings give you the characteristics for your specific target population/national context. 

  • Sachida Barik asked a question in Print:
    How to exchange the position of words in a file using c ? for example the word is " i am a boy" and i want to print "am i a boy"??
    how to exchange the position of words in a file using c ? for example the word is " i am a boy" and i want to print "am i a boy"
  • What solvent can I use to solubilize the SEBS block copolymer (different to dichloroethane) ?

    I need to make the casting of the copolymer of styrene-ethylene-butylene-styrene ( SEBS ) and I wonder what I could use as solvent (different to dicloroethane)

    Alejandra Tapia Sierra · Servicio Nacional de Aprendizaje SENA

    Thanks for your suggestions

  • Sachida Barik added an answer in SWAP:
    How to swap the content position of a file using c lanuage....?

    how to swap the content position of a file using c lanuage.... i want to interchange words in a file content...plz help me to get the code..

    Sachida Barik · KIIT University

    thanks for your answer....but i want to exchange the position like " i am a boy " to "am i  boy a"...is it possible...then plz help..

    how to exchange the position of words in a file using c ? for example the word is " i am a boy" and i want to print "am i a boy"

  • Evan Jordan added an answer in Tourism Development:
    What is the opposite of stress?

    I've recently been conducting research about how tourism development causes stress for individuals in tourism host communities. I've been grappling with the fact that most conceptualizations of stress are inherently negative, even when the experience of stress leads to successful coping actions and positive outcomes. I'd like to find a way to measure some type of positive affect that contrasts stress in this context to provide a balanced view of some of the psychological impacts of tourism development.

    Evan Jordan · University of Hawaiʻi at Mānoa

    Thank you to everyone who has provided valuable input - this sounds like an area that deserves a great deal of further inquiry. I think several of you made an important point that much of society imparts a negative connotation to stress, essentially equating stress with distress rather than eustress. One question that remains for me is: In the context of residents of a tourism host community, can you think of an example of eustress? Perhaps tourism development results in an individual getting a new job that results in eustress...but that seems like a bit of a stretch. 

  • Arnab Halder added an answer in Nano:
    How to prepare graphene nano sheets?

    By simple relatively methods

  • Is there any mailing-list, community or forum for researchers studying Visual Sociology?

    I would like to contact with other researchers on Visual Sociology, do you know if is there any mailing-list, community or forum?

    I appreciate your advice

    Manuel Van Hoben · ISCTE-Instituto Universitário de Lisboa

    I have found this association, don't know if you knew it

  • Charlotte Récapet added an answer in Sperm:
    How to assess the sexual maturation in wild long-lived birds when ageing is not possible??

    Cloacal or blood sampling? What kind of biomarker (testosterone, sperm, other hormones...) ?

    Charlotte Récapet · Claude Bernard University Lyon 1

    Dear Fabrizio,

    I know about using cloacal anatomy in the poultry industry, but I could not find any serious reference about it!

    Could you be more precise as to which species you are planning to study? I would expect the reproductive hormones to have very different dynamics depending on the seasonality or not of their breeding cycle. I would think comparing the hormones dynamics over a year on a good sample of individuals of known stage might allow you to differentiate differnt types of dynamics or hormones levels between stages. I do not know about any such study on wild long-lived birds, but you might find something on domestic birds to get a first idea of the interest or not of the measure.

    Directly using telomere length to estimate chronological age would also require a good calibration and in most species, the variation in initial telomere length and telomere dynamics among individuals prevents using telomere length as a direct marker of chronological age : http://www.ncbi.nlm.nih.gov/pubmed/21429128 Some more sophisticated methods have been developped but they require an intensive lab and data analysis workload per sample: http://www.ncbi.nlm.nih.gov/pubmed/21585768

    Whether they relate to sexual maturation, I am not sure. If interested, you should get in touch with Mark Haussman from Bucknell who did a lot of work on telomeres and life-histories in birds : http://www.bucknell.edu/academics/majors-and-minors/biology/faculty-and-staff/mark-haussmann.html

    Good luck!

  • What is your experience in creating knowledge in process improvement projects within organizations/companies?

    Process improvement starts with assessing processes in an organization and proposing potential improvements. During these activities knowledge that exists in an organization might be discovered and systematized .

    What is the difference between large and small companies regarding this issue?

    Zeljko Stojanov · University of Novi Sad

    Dear Borut
    thank you for answer. Actually, I completed assessment and improvement project in one small software company, and my next endeavor is systematization of knowledge discovered during the project. There is a lot of available books and articles, but opinion of people from the practice is invaluable.

  • Is there any software available for multiple regression analysis?

    Can you please suggest suitable software? Thanks.

    Gabriel Arguello · University of Zulia

    Statgraphics is a good tool if you do not want to do operations.  I prefer MATLAB, because I can use it in learning process.

  • Justin Ugochukwu Ogbu added an answer in Malawi:
    Could anyone help me identify this plant with photos from Malawi Africa?

    Photos were taken in a small town in Malawi Africa. This plant is commonly used to treat backache via local people.

    Justin Ugochukwu Ogbu · Federal College of Agriculture, Ishiagu

    Scadoxus multiflorus is the plant. It is naturally distributed in most part of sub-Saharan Africa. I do come across it some times in the bush where it grows wild in my country Nigeria.In addition to its medicinal value it is also used as poison for fishing. Of course the plant is classified as an ornamental spp in Plant Resources of Tropical Africa (PROTA) Basic list of species and Commodity grouping publication (2002).

  • Is it routine in your intensive care unit to perform ultrasound-guided central venous catheterization?

    Is it routine in your intensive care unit to perform ultrasound-guided central venous catheterization?

    Eliska Potlukova Horakova · Universitätsspital Basel

    At our ICU we do all insertions with ultrasound. I suppose few doctors would be able to do it without, as they already learn to do it ultrasound-guided.

  • What do you think about the measures of macroprudential policy effectiveness? Do you know any tools for assessing such an effectiveness?
    I am thinking of comparing the effectiveness of different arrangements in relation to macroprudential policy, but I am afraid that there is no possibility to measure effectiveness after such a short term of implementing and using MP. I perceive lack of experience as a main barrier in assessing MP. Please, advise!
    Benali Abdelghani · Université 20 août 1955-Skikda

    Maybe you can use   financial stress 

    There is a report in detail in Chapter 4 : Appendix about Data and Methodology this appendix  explain how to use this indicator of financial stress.

    at this web


    there is also the financial stability map 

    The Global Financial Stability Map was developed as a tool to interpret the risks and conditions that impact financial stability in a graphical manner. It complements other existing tools for assessing financial stability, and seeks to overcome some of the drawbacks of earlier approaches. This paper provides the motivation for the tool, a detailed discussion of its construction, including the choice of risk factors and conditions, a description of the underlying indicators, and a discussion on how the final assessment is determined. When applied to past events of financial instability, the Global Financial Stability Map performs reasonably well in signaling risks to stability, as well as in characterizing the depth of crisis episodes.

    source: https://www.imf.org/external/pubs/cat/longres.cfm?sk=23947.0 

    On my research, I am looking how to link between financial stress and macroprudential policy 

  • Hasan el moumni added an answer in Printing:
    What is 3-D printing?

    I see some news and competitions about 3-D printing?

    Can someone explain this? Thanks!

    Hasan el moumni · Cadi Ayyad University

    you can look to this link


  • What is the ideal participation rate in observational studies? Is there any good references on this topic?

    Trial participation rate can give additional informations on patient representativeness. No consensus on this indicator have been published since it seems to have no ideal rate. However, some people says that by convention, a participation rate lower than 80% may increase the risk of selection bias.

    George Schreiber · Plasma Protein Therapeutics Association


    Agreed for therapeutic trials. Participation rates are not critical, more important is how close the various arms are in the study.  Unfortunately, I am not a French speaker so might not fully appreciate your comments.  I do know that in the RCT often we have fairly low participation rates, often due to the stringent inclusion/ exclusion criteria.  True too, as you point out, frequently the results of these trials are not extrapolable to the general population as we often see in a phase III or IV study.  You made some very important points. Thanks.

  • Ankit Jha added an answer in ANSYS:
    How can we model liquid sloshing in a closed container in ANSYS?

    I am trying to model liquid sloshing inside a closed container with acceleration following a sine function. I am interested in finding the stress distribution in the container under earthquake.

    Ankit Jha · Indian Institute of Technology (Banaras Hindu University) Varanasi


    I have not yet reached that stage of modelling. I still need to know the steps to assign sinosoidal velocity to the container for my simulation.

    Also I don't have much experience with CFX/CFD/Fluent modelling and have limited knowledge about the applicability of displacement or potential based elements. It would be nice if you could help me out with early stage hurdles.

  • Can any one suggest me up to what extent aseptic conditions are required during plant gDNA isolation?

    what are the necessary measures to be taken to maintain aseptic conditions during plant genomic DNA isolation and purification from different samples?

    Yuan-Yeu Yau · Northeastern State University

    To try to avoid gDNA contamination from one plant to another plant, when we isolated gDNA from putative individual transgenic plants, we used different set of pestle and mortar, which were wash-cleaned and autoclaved, for liquid N2 tissue grinding.

  • Critical thinking vs. truth in education?

    Many educators claim critical thinking as one of the major skills for 21st century students. Students may challenge any 'fact' to construct their own body of knowledge. 

    On the other hand, educators have to build on some truths (e.g., in maths we use axioms) in their teaching. This can be overwhelming students. How do you, as a teacher, find the right balance?

    Rafael Resendiz Ramírez · Autonomous University of Baja California

    I believe that critical thinking is always necessary, for any student. While it is true that to build knowledge itself must resort to facts or concepts, the creation or re-creation together with our own peers, is necessary. The consensus is a priority not only for the development of new ideas, trends or theories, but also for their own generation. I explain it as follows, the starting point is always an axiom, which is built around it and no, it is a postulate, a corollary, an assumption, conjecture or theory. At this point we must not forget that even what we regard as critical thinking is an axiom, which fails if its intention is to analyze another axiom, just look at the definition.
     But if you analyze a theory or concept, then you can find some gaps in argumentation, in theoretical construction or in experimental design, since no theory or law is perfect or universal strictly. Therefore, the student should be able to find gaps in knowledge, to construct their own knowledge, but without forgetting what this building is actually a reconstruction of a previous knowledge of external origin.

  • Dannielle S. Green asked a question in Two Way:
    In asymmetrical anova: fixed and orthogonal, which term is the Control vs others tested over?

    I have an experiment with two fixed and orthogonal factors (dose and concentration) and one control. I thought I knew how to do it, but have found contrasting literature on how to carry out the asymmetrical anova and most papers do not declare the details of how the analyses were done. Also most of the papers refer to designs with random factors, such as those in Glasby and Underwood etc and mine are all fixed. I have carried out two separate anovas, (1) one way with all treatments including control and (2) two way with dose x concentration without control. When I construct the asymmetrical anova from the two analyses, I am not sure whether to test control vs others against the res from analysis (1) or from the combined residual from (1) and (2). Any suggestions?

  • What is the more reliable EXPERIMENTAL method to determine the (activation) energy distribution for the pyrolysis of biomasses?

    interested in deconvolution of f(E)biomass with few parameters from f(E) Cell, Lign,Hemi

    Ramón Piloto-Rodríguez · Instituto Superior Politécnico José Antonio Echeverría

    In my opinion, the thermogravimmetry and differential thermal analysis. Throughout these and knowing or estimating the kinetic models for the thermal decomposition of the biomass, you can applying Vyazovkin, Coast-Redfern or others know the accurate vale of the activation energy but other kinetic parameters.