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

  • Are all frames of reference truly equivalent?

    In cosmology, the rest frame for the cosmic microwave background (CMB) appears to be a preferred frame of reference. For example, galaxies tend to have an average speed of zero relative to their local CMB rest frame. If an observer is traveling at a relativistic speed relative to the local CMB rest frame, the galaxy density would not appear homogeneous in all directions. Also there would be a substantial CMB anisotropy (unequal photon pressure) which opposes motion relative to the local CMB rest frame.

    Now, ignoring the anisotropic effects of the CMB, is there any reason to believe that the laws of physics would not be the same in all frames of reference? For example, if a fundamental particle has relativistic kinetic energy exceeding Planck energy (about 2×109 J), then its de Broglie wavelength viewed from the CMB rest frame would be less than Planck length. Is this possible? Is it possible that experiments conducted in such an extreme frame of reference would find noticeable differences in the laws of physics? For example, would QED and QCD operations which depended on virtual particle creation and destruction be affected?

    Ilja Schmelzer · Independent Researcher

    Charles, of course "CMB-preferred system of coordinates" would be, of course, more accurate, but, as it often happens, the shorter but less accurate "CMB frame" is the established notion. Which is not that problematic, because these CMB-preferred coordinates define, everywhere, locally (where SR is applicabla) a frame in which the CMB radiation is isotropic. 

  • Alaa Kareem Niamah added an answer in Mastitis:
    How specific is milk cytology for diagnosing mastitis in bitch?

    Hy, I would like to know if bitch milk cytology and pH assays are relevant in diagnosing subclinical mastitis in bitches?

    Alaa Kareem Niamah · University of Basrah

    you can look of attach file 

  • Arun Prabhu Dhanapal added an answer in Variance:
    What does it mean when heritability is larger than 1?

    I have a half-sibling design with a partly selfing but mainly outcrosser plant. My design includes families within populations and I measured several functional traits. I calculate heritability as 4Vf/PV, where Vf is family variance and PV is phenotypic variance. In some instances, I obtain heritabilities that are larger than 1.

    Is this due to maternal effects or to selfing (or both)? Most importantly, what can be done?

    Thank you.

    Arun Prabhu Dhanapal · University of Missouri

    This Heritability number can range from 0 (no genetic contribution) to 1 (all differences on a trait reflect genetic variation)
    If you do not raise the plants in independent environments, the estimate of H2 would be too large if calculating the individuals in same environments and could even exceed 1 if the observed phenotypic correlation were also greater than 0.5.

  • Thokozane Ngcongwane added an answer in Arthropods:
    Do lunar eclipses affect any typical mammalian behaviours?

    The effects of eclipses, particularly lunar eclipses, have been noted mostly in nocturnal arthropods and mammals, in terms of their behaviours. However, except for bats, not a lot has been done for other nocturnal mammals. I'm trying to find out the behavioural differences that occur in nocturnal mammals during lunar eclipses. Any help is much appreciated. 

    Thokozane Ngcongwane · University of the Free State

    Yes, the feasibility of the research is somewhat ambiguous, given the frequency of these events. Total lunar eclipses, and even more so total solar eclipses, happen once every so often and this puts a real stranglehold on the research of these behavioral mechanisms. I value the input, thank you! 

  • How can I individually dispersed a gold nanoplate on HOPG?

    I want to study Gold nanoplates by STM and I need to individually disperse on conductive substrate similar to HOPG.
    How can I dispersed gold on HOPG?

    Tanya Dahms · University of Regina

    I was not suggesting to try glass or mica, just to be clear!

  • Does transformation of microfinance institutions into regulated financial institutions increase accessibility of financing to the low income class?

    Most microfinance institutions were founded as non-profit organizations with main mission of providing financial services to the low income class or financially excluded people, mostly women. Although, it appears that transformation of microfinance institutions into regulated financial institutions comes with many benefits such as influx of new capital, deposit mobilization, increase outreach and improved management and governance among others. There is fear that transformed microfinance institutions may deviate from their original mission to serve the low income class and alleviate poverty. More specifically, some observers believe that the transformation of microfinance institutions into regulated financial institutions may encourage profit motive over social impact of alleviating poverty.

    Rafael S. Trueta · Universidad Nacional Autónoma de México

    Tricky question!:

    A lot depends on the country in which the transformation happens, subjects as regulatory framework, institutional infrastructure and other particularities of the financial system will play a major role in the outcome of the transformation 

  • Victor Christianto added an answer in Gravitation:
    Is it possible to re-derive Einstein's equations from vacuum fluctuation?
    • One of often-cited paper by A. Sakharov described how Einstein's equations may be re-derived from vacuum fluctuations (see http://ufn.ru/ufn91/ufn91_5/Russian/r915i.pdf). One example here is H. Puthoff who proposes vacuum polarization model of gravitation.

    Despite the fact that this paper has been cited by many physicsts, it is also debatable whether that is what Sakharov himself wants to say.

    So what do you think? Is Sakharov's assumption correct? Is it possible to re-derive Einstein's equations from vacuum fluctuation? Your comments are welcome.

    Victor Christianto · University of New Mexico

    @Rogier: thank you so much for this link. Yes i was looking for the english version of Sakharov's paper while i found only the russian version. Best wishes

  • Antioxidant in topical formulation whether it acts on the surface of skin or it need to penetrate the Stratum Corneum Layer?

    We know that there are lot of antioxidant topical creams in the market. These antioxidant help to reduce the radicals and prevents for oxidative stress and aging. But I am confused whether these antioxidants act on surface of skin or it need to penetrate into the skin (stratum corneum) to act. Anyone aware about this can help me out. Thanks in advance.

    Hi Ramkumar

    Well I can't say if the attached paper and link are good/bad because the subject does not fit with my interest field, please check them.
    With my best regards

  • Kelvyn Jones added an answer in Constructivism:
    What is the difference between constructivism and pragmatism philosophical approaches in drawing on quantitative methods of data collection?

    Due to the nature of my research question which evaluate the impact of a particular educational programme on advancing students skills, I found my self adopting both qualitative and quantitative lines of inquiry. This mixed methods have led me to pragmatism as potential philosophical assumption & interpretive frameworks of my work that allow the researcher to use both methods. However , there was a voice inside of me that saying that pragmatism is not the appropriate paradigm. Then I shifted my thinking to constructivism since most of my work will be exploratory. I found it real hard to justify the quantitative data collection based on the fact the most of research books associate constructivism  with qualitative method of inquiry. However, I recently found this paper by Machenzie and Knipe (2006) in their discussion of the dilemmas associated with paradigms, methods and methodology:

    "The constructivist researcher is most likely to rely on qualitative data collection methods and analysis or a combination of both qualitative and quantitative methods (mixed methods). Quantitative data may be utilised in a way, which supports or expands upon qualitative data and effectively deepens the description. (p.3)" http://www.iier.org.au/iier16/mackenzie.html

    so the question that popped to my mind is why research books advocate pragmatism for mixed methods without pointing out to this possibility of drawing on both Qaul and Quan in constructivism paradigm? and what criteria exist to the extent of using Quantitative methods in constructivism.

    Kelvyn Jones · University of Bristol

    You may want to have a look at this


    I specifically attempt to provide a  not - too- -demanding look at the philosophical underpinnings of modern quantitative methods and contrast a rigid positvism with more pragmatic scientific realism - I also argue against unbridled constructivism in which anything goes and we construct the world as we go along.

    I am also impressed by Jason Seawright's arguments


    Things are undoubtedly  getting better but the rapprochment than I often see in mixed methods is not very sophisticated quantitative work.

  • Franc Dimc added an answer in Atomic Clock:
    What is the timing accuracies among GPS receivers?

    Known primarily as a navigation system, the global positioning system is also used to disseminate precise time, time intervals, and frequency. The GPS
    carrier signals originate from on-board atomic clocks monitored by ground control stations. GPS satellites transmit time signals with each subframe of data modulated onto the carrier. While navigation and survey receivers use GPS time
    to aid in computation of position solutions, time and frequency receivers use GPS satellite transmissions to control timing signals and oscillators.

    Franc Dimc · University of Ljubljana

    Accuracy of timing disseminated from L1 GPS receivers on determined positions is about 30 nanoseconds (@95% probability level) @ one satellite in view. Employment of more complex methods may bring accuracy to even less than 1 nanosecond.

  • Jayne R Pivik added an answer in Child Development:
    What evidence is there of housing and living conditions affecting child academic achievement?

    What I'm interested in is pulling together all potential influences, not just psychological but also architecture, health, social housing and the like.

    Achievement can, in this sense, means either specifically (e.g. their homework) or generally (over time), and directly (e.g. concentration) or indirectly (e.g. time spent in hospital). Living conditions could be viewed in terms of healthy-environment (e.g. damp, cramped).

    Jayne R Pivik · University of British Columbia - Vancouver

    I reviewed this area in a paper entitled "Environmental scan for school readiness and health: Definitions, indicators, determinants and interventions", See https://independent.academia.edu/JaynePivik

  • Thecla Mutia asked a question in Accreditation:
    Any papers out there on arsenic concentration in Kenyan Rift valley soils?

    very suspicious values from my lab analysis --which is accredited

  • How do I could measure or record dislocations movements inside material grain?

    I need to design an experiment to measure or record dislocation movements inside material grain under different strain conditions.  

    Lawrence Margulies · University of Guelph

    Here are some links for x-ray topography:

    Bowen, Keith and Tanner, Brian: High Resolution X-Ray Diffractometry and Topography. Taylor and Francis (1998).

    It is even possible to get information on the 3D spatial distribution using topo-tomography:

    W. Ludwig, P. Cloetens, J. Härtwig, J. Baruchel, B. Hamelin and P. Bastie: Three-dimensional imaging of crystal defects by `topo-tomography'. J. Appl. Cryst. (2001) 34, 602-607.

    P. Mikulík, D. Lübbert, D. Korytár, P. Pernot, and T. Baumbach. Synchrotron area diffractometry as a tool for spatial high-resolution three-dimensional lattice misorientation mapping. J.Phys. D:Appl. Phys. (2003) 36(10), A74-A78.

  • Robert H. Eibl added an answer in Cancer Biology:
    Are there specific cell markers to identify metastatic cancer cells?
    Does a primary tumor contain specific cancer cells that can leave the tumor and cause metastasis? Or are these changes triggered by the tumor microenvironment after the cancer cell has left the tumor?
    Robert H. Eibl · Universität Heidelberg

    Simple answer: No, to my understanding and until now, there is no single marker, which could identify a metastatic cell. The same seems to be true for stem cells, although thousands of labs appear to use different ways to identify their stem cells, cancer stem cells or metastasis initiating cells. There are so many different cancer types, which might be seen as very different groups (but very different groups may share alsmost identical pathways which should open same treatment for very different subgroups), therefore it is not likely to ever find a specific marker for metastasis. And, at least some cancers may have all the tools to metastasize from the beginning of the cancer, like stem cell can easily migrate to distant sites. I tried to look for mechanisms of metastasis ressembling the physiologic steps involved in leukocyte migration, especially lymphocyte homing: cell adhesion receptors mediate rolling and sticking and chemokines can activate the stronger binding against the blood stream. In fact, I could identify some and confirm other adhesion receptors for such rolling events in cancer cells outside the leukocyte-like cell populations, but found the chemokine activation only on lymphoid tumor cells, i.e. although I had written a research grant in 1999 when I was at STanford university, to check for example breast cancer biopsies for expression of CXCR4 and CCR7, I did not get the grant. Others from the Stanford area published later a Nature paper with my postulates, but the mechanism of action is probably not what I postulated. I later found that even normal tissue of the breast can express CXCR4 and CCR7 receptors, therefore, such markers may not serve as metastasis markers, but could be used for tumor cells to metastasize, if already expressed.

  • T. Karthick added an answer in Oscillators:
    What should I do when i get oscillator strength values more than 1?

    I have performed absorption calculations for some molecules using TD-DFT in Gaussian 09 program. As I know oscillator strength values should be in the range of  0-1, but when I performed absorption spectra calculations I have observed oscillator strength values more than one. What I am supposed to do to get accurate oscillator strength values? Please suggest me regarding this. Thank you.

    T. Karthick · KSR Institute for Engineering and Technology

    Dear Sai Sudhakar,

    What basis set was used in your calculation? some times lower basis set in DFT calculations yields poor results. If you don't mind, send the output file and molecular structure.



  • Kai Fauth added an answer in Graphene:
    How can I make a gamma detector with graphene?

    I want to detect gamma by using of graphene. One way that I think about is to make a three dimensional structure of graphene. I think that I use hundreds of graphene layers to construct a grid of layers. I choose a substrate and put one layer of graphene on it then I put one layer of a special material on it then I put the second layer of graphene on the special material then I repeat this action for one hundred layers. The goal is to maintain the specific features of single-layer graphene in the constructed grid. If this approach responds well, then what material should I use to fill between the layers of graphene?

    What's your opinion about this approach?

    Another way of detecting gamma with graphene is to use graphene in the junctions between silicon for increasing the speed.

    Can I make a photodiode based on graphene?

    Than you

    Kai Fauth · University of Wuerzburg

    Why would you want to use graphene for this purpose? Do look up the attenuation length in carbon materials for em rays of the energy of your interest (Henke tables at the link below). And hundreds of graphene layers... wouldn't that just amount to a chunk of graphite?

  • T. Bui added an answer in Coding:
    Can anyone help with fountain codes implementation in Matlab?

    Recently I am working on Fountain codes specially on LT and Raptor classes.

    I am implementing the Fountain codes coding and decoding algorithms using Matlab and would like to create a platform for their use in wireless communications.

    I would strongly appreciate any help towards this.

    T. Bui · Sungkyunkwan University

    Do you read this document. It is very useful for me. Let me know if you have any problem with implementation base on it 


  • Emergency MAD (Maximal Anal Dilatation) for acute fissure in ano. Is it still the practice ?

    Most cases of acute anal fissure don't respond to conservative measures.

    José Joaquim Ribeiro da Rocha · University of São Paulo

    I have no experience with anal dilatation for ACUTE ANAL FISSURE, but I see no sense in strectching the sphincteres for such disease. In our country (Brasil)  it's not used at all. The conservative management for superficial fissures has high success rate. Our surgical approach is lateral sphincterotomy associated with curetter and cauterize the bed of the fissure.

  • Mujahed Thneibat added an answer in Storage:
    What are the effects of water storage and its impact on urban distribution system?

    There are severe water rationing practices that have resulted in consumers opting for storage than waiting for the next supply. This storage in turn has its effects on the water distribution system of a community.

    Mujahed Thneibat · Purdue University

    Thanks for bringing this up. Besides the quality concerns, storage is seen as a compensatory strategy by households to accommodate with supply deficits. I think it has both, social and economic perspectives.  

    The economic aspect is the main determinant to adopt this strategy. This means that high consumption is more likely expected from storage tanks' owners.

    More importantly, this can mislead policy makers in measuring the social equity of the water system, which harms planners interested in  sustainable water systems.

  • William E. Asher added an answer in Ocean:
    Surface ocean pCO2 maps?


    I am trying to find global maps of surface ocean pCO2 (uatm) and aqueous [CO2] (umol/kg) (NOT pCO2 flux between the ocean and the atmosphere, c.f. Takahashi  et al., among others)...

    Aside from the SOCAT gridded data viewer (which shows measured fCO2 for cruise tracks), I cannot seem to find anything... Does anyone have any suggestions of references/ websites?

    Thanks, Clara

    William E. Asher · University of Washington Seattle

    Have you looked here:

  • Bodo Hattendorf added an answer in Bacillus:
    What would be the reason if ICP/MS doesn't detect the Cr(III) after the biosorption process?

    I am studying the biosorption of Cr(III) (100 ppm) from water using a novel strain of Bacillus. After centrifuging the samples, ICP/MS couldn't detect Cr!

    What are the reasons?

    Bodo Hattendorf · ETH Zurich

    I am not sure what exactly the problem is. Do you analyse the bacillus or the supernatant? What method do you apply for eliminating the potential ArC+ interference?

    It would be helpful to have some more information about the experimental set up. There are many different possibilities why ICPMS may not detect a particular isotope.They are mostly related to insufficient signal / noise (e.g. low concentration or spectral interference) or loss of the analyte before analysis.

    Best regards


  • Do single photons propagate at the same speed as beams of light?

    When we measure the speed of light, we measure a beam or pulse. Are we correct to extrapolate this speed to single photons?  Are we correct to infer that single photons have any definite speed, at all?

    In QED, a definite speed is assumed.

    Miguel Carrion Alvarez · Grupo Santander

    @Oscar: in quantum mechanics you cannot really speak of "velocity vector as a rate of change of position with respect to time", only of time-of-flight measurements. And that's for "thought experiments". For real experiments you have to be a little more imaginative, as in the paper Lawrence shares in which you use a process emitting two photons, use one to determine the "time of emission" and the detection of the second photon defines the "time of flight".

  • Yoonos Pirzad added an answer in Mass Customization:
    What are the differences between customerization and customization?

    Do you think that mass customization means customerization?

    Yoonos Pirzad · University of Tehran

    customization is product oriented

    but customerization is customer oriented and market driver

  • Daniela Campeche added an answer in Aquaculture:
    Does anyone has any knowledge about aquaculture production using salty water well?

    We are interest in research of aquaculture production system in semi arid region using salty water well. There are some producers using it to raise shrimp, but we have never seen any study about its manegement. I´d appreciate if I could hear something about it. Thank you!

    Daniela Campeche · Brazilian Agricultural Research Corporation (EMBRAPA)

    Thank you so much everyone for the answers! This will be a new study for my research group and any contribution is more than welcome. I understood that each region has its own particularity that needs to be cared about. As brazilian semi arid has also social economics issues, it will be important for us a production systems easy enough for small producers to work with. If anyone is willing to work as an international networking in this subject  my reasearch group is opened for a conversation.

  • Carl B. Mcgowan added an answer in Collaboration:
    Are you interested in collaborating on work on residential property markets in Australia and China?

    I am looking for academics interested in residential property markets in Australia and China.



    Carl B. Mcgowan · Norfolk State University

    I was asking Justine. 

  • Mohan Lal asked a question in Domestic Violence:
    Do you think Domestic violence is still a serious concern in developing Counteries.?

    If so, role of public health experts to reduce risk of this medico-social problem.

  • Monika Tomar asked a question in STD:
    How to use error bar in fold induction plot?


    I am doing a qpcr analysis, where I used 3 biological replicates for control and for treatment.I calculated the mean and std dev from replicates.Thne using mean values I converted control values as 1 and treatment as fold induction compare to control.Now I am bit unsure about how to plot error bars on my fold induction plot.Because the std dev used for error bar is based on raw values and we plotted graph in fold induction.Kindly suggest how should I make it right.Thanks 


  • Lawrence Margulies added an answer in Scattering:
    What type of vial or bottle should be used to avoid absorption and scattering for an x-ray experiment with a liquid?

    I need to conduct an experiment using x-rays. The test sample is in the form of a liquid and I need to use a small vial or bottle; but what exactly should the material be to avoid not only absorption but scattering from the vial or bottle?

    In other words, the vial is just facilitating keeping my liquid in front of the x-ray window.

    Lawrence Margulies · University of Guelph

    For SAXS I would definitely use a low Z crystalline holder. Beryllium oxide is very good since it has very few peaks and none in the SAXS range. Toxicity is not a problem in the oxide state (unless it is ground into a powder and inhaled). It is not like Be metal which you should never even touch. Graphite is also good as well as Boron Nitride, 

  • Khadidja Belattar added an answer in Source Coding:
    Is anyone familiar with Content Based Image Retrieval with Relevance Feedback?

    Relevance Feedback (RF) in CBIR consists to select iteratively the returned (from image retrieval process) positive and negative images according to the image user query, until the the retrieved images are improved.

    The attached a CBIR with RF source code  written in MATLAB, i would like firstly understand How they do the Relevance feedback,how the compute relevance score, correct the errors to use the code in my context?

    Thank you a lot for your help.

    Khadidja Belattar · Université Constantine 2

    Hi  Abdul Hameed, 

    Thank you for your reponse.

    I would like to  know how does the Relevance  Feedback work in the attached code .

  • Louis Brassard added an answer in Cognitive Systems:
    Is Chalmers' so-called "hard problem" in consciousness real?

    In his 2014 book "Consciousness and the Brain: Deciphering How the Brain Codes Our Thoughts" Stanislas Dehaene wrote "Chalmers, a philosopher of the University of Arizona, is famous for introducing a distinction between the easy and the hard problems. The easy problem of consciousness, he argues, consists in explaining the many functions of the brain: how do we recognize a face, a word, or a landscape? How do we extract information form the senses and use it to guide our behavior? How do we generate sentences to describe what we feel?

    “Although all these questions are associated with consciousness,” Chalmers argues, “they all concern the objective mechanisms of the cognitive system, and consequently, we have every reason to expect that continued work in cognitive psychology and neuroscience will answer them. By contrast the hard problem is the “question of how physical processes in the brain give rise to subjective experience … the way things feel for the subject. When we see for example, we experience visual sensations, such as that of vivid blue. Or think of the ineffable sound of a distant oboe, the agony of an intense pain, the sparkle of happiness or the meditative quality of a moment lost in thought … It is these phenomena that poses the real mystery of the mind”."

    Stanislas Dehaene's opinion is "that Chalmers swapped the labels: it is the “easy” problem that is hard, while the “hard” problem just seems hard because it engages ill-defined intuitions. Once our intuition is educated by cognitive neuroscience and computer simulations, Chalmers’ “hard problem” will evaporate".

    Personally, I agree with Stanislas Dehaene's opinion.


    ''My answer is that a conscious body is a living body with a brain that can represent the world from a privileged egocentric perspective.''

    There are many other answers as you know. I personally departs from your above answer with the word ''represent''.  I disagree that our brain represent the world.  Why our brain would bother with ''Re-present'' .  IOur  nervous system is controling our bodily interaction with the world, it is part of our body,  The body (which include our nervous system) IS  the ''I' in interaction'' .  Our entire body structure is a reflection of the world we interact with.  It does not need to create a little space within it where the world is re-presented because the whole body is in the image of this interaction and is constantly modified while our interaction (insight) evolves.  In a few words, our approaches depart right at the beginning. Lets say I agree that God (the world) created (evolution as mirroring) humans at his own image.