Q&A

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

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
  • Chokri Bayoudh asked a question in Fees and Charges:
    Can I find a laboratory dealing with leaf in vitro tissue culture of pears (Pyrus communis L.)?

    I have a Ph-D student looking for a collaboration with a specialized team in in vitro tissue culture of pears to establish and optimize a protocol of plant regeneration of Tunisian local pears from leaves (via organogenesis or somatic embryogenesis). I am very grateful to the hosting team. Travel and accommodation fees are in charge of our laboratory. We are in an urgent need to this collaboration...

  • Ane Ripoll-Zarraga added an answer in Stochastic:
    How can I calculate technical efficiency of each household in the STATA?

    I used sfcross command to estimate stochastic frontier of production function.

    The example of STATA command :
    sfcross lnYield lnLand lnChemfer lnLaborloc lnMachineryh if Typology==0
    predict e,u

    I wonder if the value of e represent the technical efficiency? I really doubt it.

    Ane Ripoll-Zarraga · The London School of Economics and Political Science

    You can also use sfpanel (please see Federico Belotti's paper). This command refers to making different assumptions regarding the error term. It is assumed that a part of the error is explained by technical inefficiency and other part cannot be explained (noise, etc.)

    You will generate u first (techical inefficiency) and then you can generate the TE based on the assumptions you choose for the inefficiency term.

    For example, with this command you could predict TE following Battese & Coelli (1988; 1992; 1995) or Kumbhakar (1990)

    It is really important to test the distribution of the inefficiency term (u) and not to assume that all the error is caused by inefficiency. In other words, managers may not always be able to reduce this.

    I wish it helps

    Ane

  • Bhaskar Ghosh added an answer in Piezoelectricity:
    Is piezoelectricity observable or at least, significant in disordered materials?

    I keep thinking that since in a disordered material, there is no periodicity, thus random orientation of dipoles may result to an average of zero. 

    Is there any journals I could read that could help enlighten me?

    Bhaskar Ghosh · Central Mechanical Engineering Research Institute

    This may not be a journal but I think it will help your research on Piezoelectricity up to some extent.
    You may also refer to the following book

    "Piezoelectricity" by Walter Guyton Cady (Vol1 and Vol.2).

    The book might help you regarding your quest. :)

  • Mahmoud Abouseoud added an answer in Anaerobic Culture:
    Can anyone suggest what is the simplest technique to maintain anaerobic conditions in dissolution medium other than passing gas?

    I am working on microbially triggered drug delivery system so I want to do dissolution studies for tablet.

    Mahmoud Abouseoud · Dr. Yahia Fares University of Médéa

    commercial jars are better

  • Héctor Cuevas-Vargas added an answer in Organizational Theory:
    Challenge question about one of the hottest issues in research methodology?

    Please guys I need your help


    In an organizational research, Assume there are two independent variables named X and Y; and the research aims to study the effect of X and Y on the dependent Variable named Z.

    Till now, doing such study has no problem; but the question is:

    Can I combine X and Y (items) and study the effect of both of them together at the same time on Z.

    IF yes, which theory can cover such this methodology?

    IF no, please Justify why

    Thank you

    Héctor Cuevas-Vargas · Autonomous University of Aguascalientes

    I agree with Noor, you can try a second order CFA by taking both factors  X and Y as a construct as a high level factor by appliying a SEM

  • Rajat Pradhan added an answer in Foundations of Physics:
    Do the effects of mind on matter as demonstrated in the experiments of Radin et al (Physics essays 2012 & 2013) herald a new scientific paradigm ?

    This refers to the recent experiments of Radin et al :

    1) D. Radin, L. Michel, K. Galdamez, P. Wendland, R Rickenbach and A. Delorme
    Physics Essays, 25, 2, 157 (2012).
    2)  D. Radin, L. Michel, J. Johnston and A. Delorme, Physics Essays, 26, 4, 553 (2013).

    These experiments show that observers can affect the outcome of a double slit experiments as evidenced by a definite change in the interference pattern.

    It requires urgent attention from the scientific community, especially Physicists.

    If these observed effects are real, then we must have a scientific theory that can account for them.

    Rajat Pradhan · Utkal University

    Coming back again to the original question and my analysis based on psychophysical interpretation:

    One interesting conclusion from my analysis is that it requires 109 observers that is a thousand crores meditators with perfect ability to concentrate one one of the paths to force the photon to follow that path, assuming that perfect concentration is assigned the value 1 and perfect non-concentration (no thought at all of the path) is assigned the value 0.

    The effect being so small no wonder that we have so far missed it (i.e. any subjective influence) in Laboratory experiments.

  • Larry A Distiller added an answer in OGTT:
    What test do you recommend for screening of undiagnosed diabetes in a rural setting?

    I was reading the ADA guidelines, which say that HbA1c diagnoses fewer cases of undiagnosed diabetes than fasting plasma glucose (FPG), which in turn diagnoses less cases than oral glucose tolerance test (OGTT). Shall we go for all three FPG, HbA1c and OGTT in the first go? What would you do if you do not want to leave any patient of diabetes undiagnosed?

    Larry A Distiller · Centre For Diabetes And Endocrinology

    That's fine in an ideal world - maybe a suburban clinic in Boston. And possibly for Vivek's research project where funding and resources seem to be available. I was referring to a generic screening programme for underdeveloped rural communities..

  • Justin Lemkul added an answer in Gromacs:
    Which vector in GROMACS has forces for the system?

    I am trying to implement scaled potential replica exchange in GROMACS. I need to scale forces for that too. How do I scale forces?

    Justin Lemkul · University of Maryland, Baltimore

    You won't find either in an .xtc because it only saves coordinates. Forces are written to the .trr file, if nstfout != 0. Energies have to be written to the .edr file.

  • jean claude Dutailly added an answer in Theoretical Physics:
    Can Quantum 'Mechanical' Description of Physical Reality be considered Completed?

    Simplicity is the key to the interpretation of physics. Nothing more simple in the analysis than supposing the existence of some parameter "hidden," invisible and not measurable which is an integral part of a pair of photons and that tells at the time of their creation: "you are oriented east" or "you are oriented to the west. "This analysis requires us to introduce "hidden variables", a process which in physics is debatable, but allows in a very elegant way to explain everything in realistic terms. The pair of photons has its own objective reality that can describe them completely. Part of this reality is unknowable but never mind, the problem is only human, nature is safe.

    We have two options: 1) quantum mechanics is inherently probabilistic; 2) quantum mechanics is not inherently probabilistic, but deterministic. The first position is that of the so-called "Copenhagen interpretation", still very accredited by physicists, while the second was that of Einstein-Podolsky-Rosen (EPR) and of the "hidden variables". Subsequently, Bell showed that the hidden variables can not be there. John Bell in 1964 pointed the way for an experimental verification of the existence of hidden variables, but subsequent experiments, especially the French group of Alain Aspect, have shown the full validity of quantum mechanics.

    Then, the second theoretical position is no longer sustainable. Instead it is if we consider the fact that the "ontological materiality" turns out to be greater than the "physical". There are no additional variables that may enter into the physic calculation, but there are physical materials that physics fails to consider which have an impact on theorizing. These factors determine the overall behavior of matter which, therefore, appears inherently probabilistic. It can be said that Einstein was right: the hidden variables exist, only that they lurk outside of physics, in ontology.

    Many physicists (Einstein leading) have always refused that indetermination be an inherent feature of physical reality. Consequently, they preferred to assume that the description provided by quantum mechanics was simply incomplete. Their reasoning, in practice, consists in saying: even at the microscopic level physical reality continues to be deterministic, only that we can not know the exact values of the state variables and so we are forced to an indeterministic description. To explain this failure many proponents of determinism (starting from Einstein himself) introduced the so-called "hidden variables". At the microscopic level, there would be some factor that is not yet known which would prevent us from a deterministic description. The moment we knew, we could provide a description of these factors completely deterministic

    For many years the debate between the advocates of the hidden variables and the promoters of intrinsic indeterminism remained on a purely metaphysical level. In 1964, however, the physicist J.S. Bell derived a famous inequality (Bell's theorem) that allowed to transfer experimentally what until then had been a metaphysical discussion. Such inequality, in practice, led us to expect different experimental results depending on whether had been true the hypothesis of hidden variables (at least limited to the so-called "local theories") or not.

    Now, the Heisenberg principle would not only establish our inability to learn at the same time the values ​​of the position and momentum of a particle. These values are established, before a measurement be made, they are absolutely and inherently indeterminate.

    Einstein's objections to quantum mechanics made sense because he was perfectly aware that quantum mechanics is incompatible with determinism. However, his views obstinately deterministic and his attempts to defend them (hidden variables) have not stood the test of facts.

    The microscopic reality is inherently indeterminate. However, what is surprising is that the macroscopic reality is instead largely deterministic. To explain this apparent contradiction is a fascinating challenge in theoretical physics. An interesting attempt at a solution appears that provided by three Italian physicists G. Ghirardi, A. Rimini and. T. Weber (in Physical Review D 34, 470, 1986).

    So, in this context it became obvious that the description of the states of a physical system offered by quantum mechanics was incomplete and that such an incompleteness was responsible for the indeterministic character of the theory. In other words, it has been assumed that quantum mechanics is indeterministic only because our level of knowledge does not put us in a position to "see" some additional variable, able to "complete" the description of the physical system provided by quantum mechanics. According to this conjecture, if we were able to identify these new variables, currently "hidden", we would recuperate a level of description deeper than the quantum level and at that level determinism could be recovered. "

    In fact, the enigma of the "hidden variables" was not solved by a logical-deductive approach, as Popper might have wished, or was it only partially.

    As already said, “in 1964 the issue was a crucial turning point: J. Bell showed that for a large family of theories and hidden variables, the so-called local theories, it is impossible to reproduce with media operations on hidden variables all the predictions of quantum mechanics. "" the result of Bell had the great merit of showing on the experimental ground the theme of possible deterministic completions of quantum mechanics, and a great interest aroused for the realization of experiments sensitive to discrepancies between the predictions of quantum mechanics and that of the local theories of hidden variables . "(Enrico Beltrametti)

    In 1981, Alain Aspect was able to realize the first of a series of experiments of high quality. In practice, the experiment showed that Einstein had been wrong in suggesting the idea of hidden variables.

    As for Popper, we could say that he lost a game: the one with LQ,

    Criticism of Popper was wrong from a logical point of view, but in many ways it had some basis. Popper did not want to admit a weakness of logic explicit in theory LQ. For Popper's logic was to remain an ‘a priori’ science, having as main feature the absolute independence from any content. Therefore, he refused to consider the possibility of choosing logics different from the logic, most suitable than this to the empirical character of particular situations.

    Already in the Logic of Scientific Discovery, which was finished in 1934, then prior to the writing of Birkhoff and von Neumann, Popper anticipated: "... replacing the word" true with "the word" likely "and the word" false  with "the word" unlikely ", nothing is gained.

    However Popper earned another no less important point. The revolutionary discovery of Bell and Aspect was not from a pure inductivism, but from experiments carried out in the light of a theory already formulated ‘a priori’, then from a hypothesis to be subjected to strict scrutiny, identifying the elements and data that could refute it. At least on this ground, Popper took an important rematch.

    At the time of the article in Einstein's death, the controversy was still strong and "philosophical" issues had a great weight, so much so that an American physicist was the victim of McCarthyism and lost his job for supporting a deterministic model with hidden variables. Today we tend to minimize the importance of our imperfect knowledge on the subject; theories are used as they are reaping the fruits without worrying about a coherent understanding of the underlying laws. Most physicists do not interpret more the principle of indeterminism  in a metaphysical way. It is considered as a simple impossibility of knowing at the same time position and momentum of the particles in a system still felt completely deterministic. After all, beyond the supposed wave-particle duality, also in the macroscopic world there is a kind of uncertainty: for example, I can not measure my speed with accuracy higher than my reaction time to press the button on the timer.

    jean claude Dutailly

    Following Charles Francis' post,

    I do not intend to say that I agree or disagree, only that he brings up many subtle points which I wish to comment.

    1. How an "element of reality" shows in a theory ? There are two obvious criteria : an element of reality is related to a physical phenomenon (something defined perhaps in vague terms, but which can be part of a narrative in the theory) on one hand, and is related to measures on the other hand. And in Physics, where the formalism used is mathematical, this element of reality is a variable.

    2. How do we understand "the possibility to predict the element of reality with certainty without disturbing the system" ? The issue raised by EPR is clearly related to the Dirac's impossibility to measure simultaneously some quantities at the atomic scale. But actually predict the outcome of an experiment (and so the value of an element of reality) is not the same as the knowledge of the value of this element of reality at any time during the experiment, so the issue of "without disturbing the system" is not relevant. Take a gun : knowing the initial conditions, one can predict accurately the location where the shell falls, without bothering with its speed and location during its trajectory.

    3. The last point is related to the way Physics deals with "predictions" and checks the validity of laws by experiments. We start with a model, where elements of reality are represented by variables, the laws are relations between the variables, they enable to compute the outcome of an experiment, and the check is done by the comparison between the computed and the measured value. So we have an initial state, a prediction, and a final state. What happens between the beginning and the end of the experiment does not matter, from the point of view of the measures, but is usually crucial for the computation (if the process is assumed to be continuous the prediction is based on continuous variables).  Similarly, whenever the elements of reality are represented by variables which, from a mathematical point of view, can take values in a uncountable infinite set the measure can provide only an estimate. So there is an unavoidable discrepancy (not related to the imprecision of the measures) between the way we understand the checking of a theory, and the way we can physically check it.

    4. 'In a complete theory there is an element corresponding to each element of reality."

    This is a far reaching requirement. No experiment can physically include "each element of reality" (known or hidden). We can just expect to include all the elements which are deemed significant, but even then some elements are missing. An example : in relativity, as it is commonly understood, all material bodies are assumed to follow a world line, a path in a 4 dimensional universe. The big issue is then : what is the engine which powers this incredible motion ? The natural answer is gravitation (and I have suggested some way to deal with that). And we cannot escape this effect, but so far it is totally absent of the usual models.

  • Subhash C. Kundu added an answer in Information Technology:
    Without the use of modern information technologies to conduct research work possible?

    Dear collegues,thank you very much in advance.

    Subhash C. Kundu · Guru Jambheshwar University of Science & Technology

    Technology and Research Insights

    Technology is at the heart of our business. Ericsson engineers, researchers and scientists around the world are working on what’s next in information, communications and telecommunications (ICT). Find out more about our advances in technology and the thoughts of the people who make it happen.

  • Payel Chaudhuri added an answer in Culture:
    Can Hofstede's Cultural Distance Dimensions be used to study regional cultures within national boundary?

    I want to know if the dimensions of Hofstede's Cultural distance model be taken as the parameters to understand the regional cultural differences.

    Are there any research papers which have used the same?

    If this framework is rejected to study regional cultures, please suggest which cultural distance model would be more helpful or what could be the way forward

    Payel Chaudhuri · KIIT University

    First, I earnestly thank all of you for your valuable inputs. From the discussion I gather using Hofstede framework for studying the regional culture influences might not explain the differences in true sense. Then for studying the same, what should be my approach? Am I missing on any model that is already there for regional culture studies? is it advisable to take up variables by studying the history of the region like role of government, importance of education, gender diversity, etc and not taking up any particular established model of culture? I would like to add that is related to my doctoral thesis so clarification on this is utterly important for me. Please help.

  • Antonios Georgantzoglou added an answer in Point Clouds:
    What algorithms are available for for finding simple 2D geometry in 3D space?

    I am looking for any algorithms that can find simple 2D geometry such as square\rectangle\hexagon in a 3D point cloud. Point clouds never contain more than around 50 points.

    I have looked at RANSAC but this doesn't suite my solution, basically all the shapes will have points only were the vectors change angle. For instance a square will contain 4 points, hexagon 6 points and octagon 8 points.   

  • Manoharsinh Zala added an answer in Rice:
    How can we effectively control rice stem borer?

    It's rice harvest season here in Leyte, Philippines and many farmers have been complaining of a very low harvest because of stem borer infestation. The hybrids planted later in June this year are the ones highly affected.

    Manoharsinh Zala · Anand Agricultural University

    Thanks

  • Lutz von Wangenheim added an answer in Oscillators:
    Does the Barkhausen criterion for oscillation apply for linear circuits only?

    In several documents it is claimed that Barkhausens (necessary) criterion for a feedback circuit to oscillate applies to linear active circuits only (example:https://en.wikipedia.org/wiki/Barkhausen_stability_criterion).

    For my opinion, this requirement is wrong.

    In contrary, stable "sinusoidal" oscillations require a smooth non-linearity of the loop gain function. Otherwise, a hard-limiting (clipping) of the oscillation amplitude (which also is a non-linear effect) occurs.

    Shouldn`t we recommend a rewording in wkipedia?

    Lutz von Wangenheim · Hochschule Bremen

    To B. Gilbert:

    You nicely have summarized the basic considerations for designing a "linear" oscillator - and, I suppose, everybody knows why I have used quotation marks since there are no linear circuits in reality. But we assume linearity - and this works. And we also know that oscillator circuits do oscillate if the non-linearity is even visible (example: tanh characteristic of the diff. amplifier).

    That was the background of my question.

    More than that, of course I agree that - as an engineer - we should "understand our circuits from the most fundamental considerations, certainly not by applying somecriteria found in a text-book.".

    On the other hand, students use textbooks and are asking questions about the oscillation criterion. Is it really sufficient or is it only a necessary one? And what about the requirement for linearity?  Hence, in this case, one cannot simply ignore textbook contents and the criteria to be found in it.

    _____________________________________

    Finally, a technical question:

    Quote: Any analysis that neglects the role of noise in oscillator behaviour is incomplete.

    I do not fully agree to the mentioned importance of noise. Don`t you think, that the voltage step caused by the power switch-on is the main reason for starting the oscillation? I have made many inverstigations in this context. Even in low-Q circuits (WIEN oscillator) one can show that the step response after applying power to the circuit causes a safe and quick start of oscillations. - much faster than the noise can do.

  • Helena Pestana added an answer in International Migration:
    What solutions do you propose for the reception of immigration to current Europe ?

    Due to the wave of immigration to Europe that has become more pronounced in recent times, what solutions do you propose for the reception of emigration to Europe ?

    Your answer will be greatly appreciated.

    Helena

    Helena Pestana · ISCTE-Instituto Universitário de Lisboa

    Hi Ricardo, 

    For me the help humans make up whatever their race, religion, political party (I am not affiliated in any), culture, beauty, etc ... are human beings who deserve all our respect and help.
    In Portugal in the north of my country they help in the integration of some immigrant families, which I find to praise.
    We only understand the suffering of others if we are treated very badly or if we have nothing to feel honored and respected.
    Dear Colleague, I think that you need more sensitively, because you never know if one day you will not be the person who needs understanding from others. For me, I will be here to help if you need to and within my abilities.
    If I put this question on immigrants was precisely because I consider relevant and because I wanted to know more, because for knowledge to be endless, i feel the need to know more about  this matter.
    Have a nice day...and we all  should open  our heart to humanity like Pope Francisco.

    Helena

  • Ahmed Raslan added an answer in Zebrafish:
    How can I remove the background in young zebrafish embryos in situ hybridization?

    I am doing in situ hybridization for zebrafish bud , 3-somite, 6-somite, 10-somite, 14-somit and 18-somite stages  embryos I am always facing problem of background after detection even with different probes. I am using digoxigenin-label probes and detection with NBT/BCIP substrate. please any suggestions to avoid this problem and also to remove the background after detection?..Thanks in advance.

    Ahmed Raslan · Kangwon National University

    Thanks Dr.Michelle

  • Lorenza Ferro asked a question in Illumina Sequencing:
    PCR with DNA mixtures?

    Hi! Is it possible to amplify one gene starting from a mixture of different DNAs? I am asking because I want to determine the population of algae in some water samples through a metagenomic approach. But for Illumina sequencing I first have to produce a pool of amplicons with adapters.

    So, let's say, if I have 10 different algal species in my sample, and I extract the DNA of all of them, I will have a mixture of 10 different DNAs. Then I want to amplify one gene of interest with specific primers, for all of the species. is this possible with a routine PCR?

    The PCR products obtained will be then sequenced through Illumina and used for taxonomy classification.

    Thank you in advance.

  • Ane Ripoll-Zarraga added an answer in Financial Audit:
    Do you professional skepticism to the Auditor of recent trends in auditing?

    Do you professional skepticism to the Auditor of recent trends in auditing?

    Ane Ripoll-Zarraga · The London School of Economics and Political Science

    Absolutely, professional skepticism is the key to detect areas of risk and material misstatement. It is a skill earned with professional experience.

  • Hind Al belushi asked a question in Ecm:
    What is the best way to quantify growth factors on decellularised Porcine trachea?

    I am interested at quantifying Growth factors in decellularised porcine ECM scaffold? what is the best way to do so and can any one advice on a kit to do so as I have never done it before?

  • Farideh Badichi Akher added an answer in Gromacs:
    Can anyone help with AMBER-FF in Gromacs for protein-ligand complex MD?
    I am trying to simulate my Protein-ligand complex using AMBER-FF. I tried all 94,96,99SB, GS etc in Gromacs. However, the ligand atoms like OM is not there. So I have added the required atoms in atomtypes.atp and ffnonbonded.itp as referred in Gromacs site. Now grompp is not firing any errors in recognizing atom-types. And EM is successfully completed. However, in Position-restrained steps I am getting errors like too large bond lengths between atoms, charged group moved too far etc. I have simulated these complexes in Gromos53a6-ff. There is no problem. But, in amber, even in OPLS/AA (earlier), I had faced such errors. If anybody has the corrected or higher amber-ff that can run Protein-ligand complex successful, kindly share with me for which I will be grateful.
    Farideh Badichi Akher · University of Sistan and Baluchestan

    HI. I am working with autodock and gromacs too. First, I performed docking corresponding to ligand-protein. Then, I use gromacs for MD of complex (ligand-protein) but when I used command pdb2gmx, I faced with this error:

    Residue 'ligand' not found in residue topology database

    Then, I searched for this error, I found that we can use of Amber tool for generation topology file for ligand. Thus, I downloaded it and installed on linux. But I cant how work with it for generation topology file. Please guide me.

    With regards,

    F. Badichi

  • Harold Gómez-Estrada added an answer in Amides:
    Would an amide group attached at the c terminal of a PDZ domain affect binding to it?

    I am running a peptide based array and my peptides have an amide group attached to the c terminal end of them. One of my peptides contains a PDZ binding domain at its C terminus and I was wondering if this would have an effect upon its ability to interact with other proteins as it should do. 

    Harold Gómez-Estrada · Universidad de Cartagena

    Hello, you should consider possible electrostatic interactions. You must design an energy assessment study between the peptide and protein in order to investigate the most important interactions. I wish success.

  • Roland Cochard added an answer in Clusiaceae:
    Can anyone help with the identification of these plants?

    I suspect Clusiaceae and Crassulaceae species, but I am not too sure.

    Roland Cochard · ETH Zurich

    O.K. so these are mangroves (I'd thought savanna species)..., right? The first is probably Avicennia germinans. But check the herbarium in any case.

  • Marcus Fraga Vieira added an answer in Motion Analysis:
    How we can calculate body sway (which is usually reported in the stability papers) from data of displacement of cop in ML and AP?

    How we can calculate body sway (which is usually reported in the stability papers) from data of displacement of cop in ML and AP?

    Marcus Fraga Vieira · Universidade Federal de Goiás

    Hi Amirhossein,

    From displacement of COP you can extract several variables to describe/evaluate postural/stability control. However, it is not easy to relate these variables to physiological mechanisms. A summary of these variables and related references can be found in Vieira et al., 2015. Effects of four days hiking on postural control. PlosOne. 

  • Ricardo Duchesne added an answer in Democracy:
    What are the consequences of seeking/requesting or not seeking/requesting data on racial origin when conducting social science research?

    The notion of race is contentious, and, yet, with the manifestation of racism it is clear that researchers cannot pretend that the social construction of race--peoples' lived realities based on race, not the biological configurations previously used to create a scientific hierarchy--does not exist. How should researchers address this sensitive conundrum? Should researchers identify their racial affiliations, and underscore the pertinence of such demographic information, or should they just ask for the information without providing such background? Or should the topic be avoided, and no data gathered? What are the ethical, moral and professional responsibilities of researchers conducting research on race or on topics that involve a racial dimension, which includes most social science research? Having conducted several studies related to the experiences, perceptions and perspectives of educators in relation to democracy and education, in which I and the research group have included demographic questions on gender, birth place, parental occupation, educational experience, and racial origin among other variables, we have found that it would be irresponsible to not try and understand how racialization may or may not play a role in how one experiences democracy, for example, regardless of the context. Our research has confirmed that the usually 15% or so of each sample (of which there have been many in Canada, the USA, Australia and about a dozen countries around the world) which is non-White presents us with some interesting insight into experiences with normative, relativistic and hegemonic notions of democracy. I would be interested to know how colleagues address this issue, and the importance of signifying racial positions, identities and postures.

    Ricardo Duchesne · The University of New Brunswick, Saint John

     Let me make this simple for you: you can use racial categories if you are identifying non-whites as "victims" of white racism, or if you are identifying whites as "racists," or if you are writing about the great achievements of non-whites.

    But don't you ever use racial categories if you are writing, for example, about the disproportionate number of crimes committed by blacks in the US in comparison to whites and Asians. And don't you ever use racial categories if you are writing about white achievements.

    If you follow these double standards, you will be OK. 

  • Antonios Georgantzoglou added an answer in Microbeam:
    How can i model a 3D fixed-fixed microbeam by Physics of general form PDE?

    I have modeled a 3D fixed-fixed microbeam by Physics of general form PDE, to calculate the deflection on the length, but i get error.

    the pics of PDE equation and parameters and the error is attached

    I will be grateful  if someone help me on this.

  • Sara Liyuba Vesely added an answer in Maxwell's Equations:
    What is the relationship between Maxwell equations and an emitted photon?

    This is not something you can find clearly stated.

    If photon is a particle then it should be not applicable, but in the double slit experiment a photon interferes with itself. But if this is the case it must be propagating in all directions but it clearly doesn't.

    Sara Liyuba Vesely · itb cnr

    As George Van Hoesen suggests, the relationship between Maxwell's electromagnetic field and emitted/absorbed photons was probably established by Einstein. To me it seems that all the interesting answers to Andrew Wutke's question don't clearly point out that there are also differences between Maxwell's field conception and Einstein's contribution, which in my opinion could be of some interest.

    Maxwell's solutions describe a classical field of forces over the whole “physical space” – by which is meant the luminiferous aether carrying the forces. Stam Nicolis points out that there are classical propagating waves among the solutions of Maxwell's equations.

    Einstein focuses rather on the matter-field interaction, which in modern parlance corresponds to production and detection (observation) of electromagnetic signals. As pointed out in this thread, Einstein didn't associate any message conveying information with signals, but gave them a solid mass-like structure.

    The difference I wish to point out is the following. Whereas Maxwell tried hard to substitute Newton's metaphysical space with a physical entity – the aether – Einstein posited that rational mechanics is a faithful description of Nature, and that it is equipped with an inherent concept of space. In fact, then it was commonly accepted that the laws of physics match “dynamical space”. Maxwell himself, besides modeling electromagnetic fields geometrically, also gave a Lagrangian interpretation of electromagnetism. Today, experimental verification of a geometry is no longer required. The “configuration space” of the quantal description is actually a sample space. Summing up, Maxwell thought that a geometrical representation is unavoidable to grasp his theory, whereas the photon picture takes over intuitive representations from electromagnetism or mechanics, if at all.

  • Ahmad Mohammad asked a question in Software:
    Eidors software problem... Can anyone help me in run eidors software?

    eidors software problem... Can anyone help me in run eidors software?

  • Nick O'Leary added an answer in Teaching Methods:
    What are the best methods available to teach large classes?

    Large group teaching is a most challenging one for everybody. Need to get their response throughout the whole session. There should be some best methods which can be easily implemented. 

    Nick O'Leary · University of Wolverhampton

    This is a wide ranging question  but being the 'sage on the stage' attempting to instruct from the front is likely to be extremely challenging and will ultimately lead to the development of passive learners. I would suggest you become the 'guide on the side' using indirect teaching approaches such as cooperative learning and group work. This will develop active learners; allow you to facilitate learning by observing and giving feedback through open ended questioning. Be prepared for considerable planning for such approaches to be effective.