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

  • Deepak Sridhar added an answer in Capacitance-Voltage:
    How can I calculate the capacitance from charge - discharge curves by the attached file?

    Can anyone help for calculation of capacitance from  the Charge discharge curve as attached file. I used the EC-lab for calculation dv/dt ( slope) and (I.dt/dv.m) but found the value of capacitance too small( 7 F/g) .moreover, this CV of same potential was around 300 F/g . the active mass electrode is 0.00044-0.00074

    please let me to know the way of calculation in detail from curve. 

    Deepak Sridhar

    Prof. George Zheng Chen

    But will the result really change if the potential window of CD is different that observed potential in CV. I always thought,  in CD the galvanostat considers as delta V and not V!! Please clarify


  • Eric Baird added an answer in Quantum Gravity:
    Is there any theory of quantum gravity which is fully constructive, i.e. explains curved space-time?

    Does any current candidate theory of quantum gravity aim to, or claim to, construct or explain the curvature of space-time?

    My understanding is that quantum gravity theories are classified as background dependent or independent, according to whether they are formulated such that the depend on the shape of space-time or not.  This is *not* what I am asking.  I am asking whether they give an account of the cause of curvature of space-time.

    Eric Baird

    Robert (page 2): " ... I tend to believe QM a more fundamental level of explanation of nature than GR, a preference which I've become acutely aware some friends of mine might argue with.  So I would prefer to see gravity emerge from quantum phenomena. ... "

    Yep, me too.

    The problem is that when we try this, we seem to end up with something other than the current general theory.

  • Ilian Peruhov added an answer in Photons:
    How can you explain a possible inconsistency with the Bohr atom model?

    It is well known that Bohr model is not totally right. But I recently discovered a very curious inconsistency (if I am right) which I haven't seen explained anywhere.

    The first postulate of Bohr theory is that the Orbital momentum of the electron is quantized L=mvr=nh  (where h  means the Dirac constant). This means that if there is a transition between level n=5  to n=1  (Balmer series) the orbital momentum changes by 4h  !!! Based on this rule and his second postulate Bohr finds the right energy for this transition (and all others as well). But this transition is a release of just one photon and a photon has spin 1h  . It can add to L as (h,0,−h)  . So it can change the orbital momentum with 1,0  or −1  and not by 4.  I'm very surprised to make such conclusion.

    Am I wrong here?

    Ilian Peruhov

    I don't how are you refuting my statement at all.

    First Heisenberg formalism wasn't invented when Bohr model was presented. So I don't see any necessity to rely on it. Just turn back to that time. And check the angular momentum law. Is it fulfilled or not? Is the nucleus momentum concerned or not?

    Secondly from QFT viewpoint what is the field you are talking about? Because EM has spin 1 and can not fit in the picture.

  • Louis Brassard added an answer in Neuroscience:
    What contemporary visual artists are applying principles from fields like neuroscience, neuroaesthetics, and visual perception?
    Scientific research has shed much light on how we see, and on how visual art resonates in our minds. I am interested in reading about contemporary visual artists who have applied this information in their creative processes.
    Louis Brassard

    Guess editorial by Jan Koenderink:   Visual art and visual perception


  • Paul Milham added an answer in Soil Chemistry:
    How can I calculate silicon content of the soil?

    Basically under indian subcontinent conditions there is limited resources to conduct research. The availablity of xray fluorescent spectroscopsy is rare. So anyone can tell me other instruments and method from which we could estimate the silicon content of soil?

    Paul Milham

    The extraction and measurement of soil Si is well treated by previous contributors, However, if you want to measure available soils Si, at some tine you must measure Si in plants, which is what I address.  First I say that XRF is still a good technique for plant Si; however XRF must be calibrated using chemical measures.  Many plant species do not contain sufficient Si concentrations for gravimetric methods to be practical; consequently most plant Si measurements are done using the silicomolybdate reaction on extracted Si.  Unless you use HF during acid digestion, Si recovery is low and variable.  Ashing, followed by fusion with an alkaline flux such as Na2CO3 can give good recovery in the hands of experienced analysts. However, suspension of ground plant material in dilute HCl, with added HF, in a polythene bottle with warming (say overnight) is convenient and effective.  For safety, XS HF is converted to fluoroborate by adding  boric acid solution to the reaction bottle before colorimetry.

  • Mohamed El Naschie added an answer in Science, Technology & Society Studies (STS):
    Is there still a gulf between scientists and ‘intellectuals’? Which of them have more influence on people’s worldviews?

    Traditional intellectuals –thinkers, writers, political and social commentators, and artists- have historically played a major role in the diffusion of the ideas that shape the ways people see the world and their own society and lives

    In the prominent book The Third Culture (1995), John Brockman claimed that these kinds of intellectuals have “become increasingly marginalized”. They are being replaced by scientists who, “through their work and expository writing”, communicate directly with the general public. These “third-culture intellectuals” would be represented by the likes of Paul Davies, Martin Rees, Richard Dawkins, Steve Jones, Daniel C. Dennett, Brian Goodwin, W. Daniel Hillis, Nicholas Humphrey and many others.  

    The culture of traditional intellectuals, says Brockman, “dismisses science”, is “often nonempirical”, uses “its own jargon”, and “is chiefly characterized by comment on comments, the swelling spiral of commentary eventually reaching the point where the real world gets lost”.

    The idea of a Third Culture has its origin in C.P. Snow’s influential “Two Cultures”   essay (1959), in which the British scientist and novelist deplored the “mutual incomprehension” –“sometimes hostility”-- between science and the arts. Scientists shared a “culture” –no matter their political, religious, social class and even disciplinary differences-, with common attitudes, standards, approaches, assumptions and patterns of behavior, At the opposite pole, attitudes were more diverse, but the total incomprehension gave an “unscientific flavor” –often almost “antiscientific”— to the whole “traditional culture”. Moreover, scientists largely overlooked traditional literature, which they perceived as irrelevant to their interests, while most intellectuals were unable to describe something as basic as the Second Law of Thermodynamics.

    Snow saw such disconnection and polarization as a “sheer lose” to society and stressed the need to build bridges between the sides. In a second essay, published in 1963, he suggested that the gap would be closed by a “Third Culture” that would eventually emerge. In his version of this new culture, intellectuals would communicate with scientists.    

    Not long ago, a column in Scientific American stated that Snow’s vision “has gone unrealized” (see Krauss, Lawrence M.: “An Update on C.P. Snow’s ‘Two Cultures’”, August 17, 2009).

    What is your opinion? Is there such a cultural divide? Are intellectuals scientifically illiterate? Do scientists ignore the basics of the humanities? Which of them have more influence on the public? What kind of Third Culture –if any- is emerging?

    + 4 more attachments

    Mohamed El Naschie


  • Alessandro Vasciaveo asked a question in Virus Integration:
    Where I can find public available datasets about virus integration sites?

    For example, one source is here: http://variation.osu.edu/rtcgd/

  • Xuebin Wei added an answer in Google Analytics:
    Is anyone working with social media data?

    or using google analytics or other tools? any recommendation please?

    I am working with social media data, one of the chapter of my PhD. Facebook, Twitter,Instagram, Google +,Thumbl etc. I want to know the best way to gather my data. Thank you 

    Xuebin Wei

    You can use my website to extract and download Facebook or Twitter data for free: www.lbsocial.net

    And here is my blog if you are interested in extracting Facebook or Twitter by yourself: blog.lbsocial.net

  • Marc Tessera 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.

    Marc Tessera


    Well, your speech is so long and unclear that it is nearly impossible to discuss it.

    Perhaps it is its purpose.

    You repeat, "The current approach is objective, I told you so many times".

    Repetition is not argumentation.

    Please, can you explain why the approach that uses the self subject's report as the reference for validating any correlate of consciousness is "objective" and not just rational and relevant precisely because it takes into account the first person subjectivity?

    In other words in what sense is the approach "objective", i.e., independent of the subject's individual biases, interpretations, feelings, and imaginings?

  • Stefano Rovetta added an answer in Time Series Analysis:
    Which activation function should be used in a prediction model?
    I want to develop a prediction model (like time series forecasting) with BPNN. The sigmoid function is mostly used as activation functions in BPNN but the sigmoid function gives an output between 0 to 1. If my expected output is like 231.54 then how to calculate the error & go for training? In short, I want my network to produce values like 231.54. What should the activation function for the hidden and the output layer then be?
  • Mauricio Maldonado added an answer in Coordination:
    How can I fix the error "Error in internal coordinate system'' while opt=qst2 calculation for locating a transition state?

    I am performing TS calculation for a system using QST2 method. But repeatedly i am getting the error as ''Error in internal coordinate system.''

    The last few lines of the output file are as:

    Berny optimization

    NTrRot=   -1NTRed=     7NAtoms=    3NSkip=    4   IsLin=F

    Error in internal coordinate system

    Error termination via Lnk1e in /opt/g09/l103.exe

    Mauricio Maldonado

    Try opt=(ts,cartesian)

  • Paul Milham added an answer in Soil Organic Carbon:
    How do I convert organic carbon (%) of soil for value & interpretation into available nitrogen (Kg/Ha) & rating?

    Say in my area soil organic carbon measured is 0.28, 0.30, 0.18 %

    as per soil fertility rating it is low in organic carbon or low in nitrogen (Kg/Ha)

    now for all my data like above I want to convert into available nitrogen (Kg/Ha)

    so what will be any formulae ?

    Paul Milham

    Gentlemen, As a matter of curiosity, below what C concentration would you consider that the benefit was not worth the effort?  Paul

  • Giuseppe Cotellessa added an answer in Doppler:
    Is the Doppler Radar or loop of radiation fully explained with the Lorentz Transformations?

    A loop of radiation is a radiation starting from the RF of an emitter, bouncing on another relative moving object (RF1) and returning to the same RF of the emitter.

    Such radiation loop is the same as the implementation of the Doppler Radar.

    Only using the twice the forward LT transformation is possible to account for the frequency ratio of the Doppler Radar...

    The loop of radiation does obviously not belong to a Transformation Group.

    Some doubts raise about the applicability of LT in case of systems exchanging radiation.

    • Source
      [Show description] [Hide description]
      DESCRIPTION: A radiation loop is a closed loop of radiation between reciprocally moving bodies, it comes out as simple application of the Relativistic Doppler Effect (RDE) which was derived from the Lorentz transformations (LT). The forward LT have to be applied twice to justify the loop frequency ratio so that the radiation loop does not belong to a transformation group. The RDE loop can deal with the case of non-accelerated Reference Frames (RF) exchanging radiation.
    Giuseppe Cotellessa

    I have to underline the original approach of patent procedurecould be  applied also to theoretical approach, started by experimental applied research. It is not based only on theoretical hypotesis. There was 8 years before it has had official registration!

    Best regards.

    Giuseppe Cotellessa

  • Ginés R. Pérez Teruel added an answer in Invariant Theory:
    Did Einstein obtain field equations directly from the principle of equivalence?

    "THE MEANING OF RELATIVITY” is a description of General Relativity by Einstein.


    Einstein wrote: "It is evident that the formulation of the general theory of relativity assumes a generalization of the theory of invariants and the theory of tensors; the question is raised as to the form of the equations which are co-variant with respect to arbitrary point transformations. The generalized calculus of tensors was developed by mathematicians long before the theory of relativity. Riemann rst extended Gauss's train of thought to continua of any number of dimensions; with prophetic vision he saw the physical meaning of this generalization of Euclid's geometry. Then followed the development of the theory in the form of the calculus of tensors, particularly by Ricci and Levi-Civita. This is the place for a brief presentation of the most important mathematical concepts and operations of this calculus of tensors". Page 68.

    Many have claimed that in 1915 Hilbert discovered the correct field equations for general relativity before Einstein but never claimed priority. Following article shows that this view is in error.

    Belated Decision in the Hilbert-Einstein Priority Dispute

    According to the commonly accepted view, David Hilbert completed the general theory of relativity at least 5 days before Albert Einstein submitted his conclusive paper on this theory on 25 November 1915. Hilbert's article, bearing the date of submission 20 November 1915 but published only on 31 March 1916, presents a generally covariant theory of gravitation, including field equations essentially equivalent to those in Einstein's paper. A close analysis of archival material reveals that Hilbert did not anticipate Einstein. The first set of proofs of Hilbert's paper shows that the theory he originally submitted is not generally covariant and does not include the explicit form of the field equations of general relativity.


    If equivalence principle was origin of general relativity, how Einstein have obtained Field equations?

    Ginés R. Pérez Teruel


    Thanks for mentioning my paper. Regarding the scape velocity, I would like to comment that, according to my work, the scape velocity at the Schwarzschild radius of a gravitational source turns out to be lower than the speed of light by a 20%. See eqs. (20-21) of my paper:


    In this sense, I think that the event horizon is a very problematic concept and I am not the only one, many theoretical physicist are starting to be skeptical about it (Hawking among others). In particular, there are serious concerns that such a concept could be incompatible with quantum mechanics. I think that some current modifications of Einstein´s theory are promising, specially the Palatini theories of gravity, where the connection is independent of the metric (unlike General Relativity, where the Levi-Civita connection derives from it). In these theories the geometry is essentially non-Riemannian,however, at low energies we recover the full Einstein´s equations (with a cosmological constant). Essential singularities like those of black holes are replaced by finite geometrical structures that have particle properties like geons. I recommend the articles of Gonzalo Olmo for example, which are very interesting.

  • Hicham Chairi added an answer in Competent Cells:
    What are the possible reasons of getting very low or no transformants during cloning?

    Is it okay to heat shock the E. coli competent cells at 45°C for 50 minutes?

    Hicham Chairi

    normally if you use industrial competent bacteria you should get good results but when preparing ourselves these bacteria with such a TSS protocol we obtained a low yield

  • Rafik Karaman added an answer in Pharmacology:
    Does anyone understands the various pharmacological experiments?

    i want to better understand the pharmacological experiments one can conduct. kind give an explanation citing examples.

    Rafik Karaman

    Dear Harrison,

    Attached please find three files that fully cover the answer to your question.

    Hoping this will be helpful,


    + 2 more attachments

  • Dhruv Bhatia added an answer in IMS:
    How do I solve this S-CSCF error?

    I am trying to find out maximum registration rate that my S-CSCF can handle in a defined period say 10 minutes. I am trying to register about 24000 users on my Open IMS core. My rate currently is 10 registrations per second. But whne I try to send registrations I am able to successfully register about 3800 users but after that my S-CSCF starts giving me an error (see attached file) and I only see an increasing number of 1st register and then some unexpected messages. My wireshark shows me 600 busy everywhere message from the S-CSCF. It also says that unable to forward it to S-CSCF.

    Note: Though when I restart my S-CSCF my process continues from where it stopped. I start getting an increasing no. of registrations and 200 oks. But this is not what I want. I dont want my S-CSCF to stop and start giving me errors.

    + 1 more attachment

    Dhruv Bhatia


    This link probably has the answer to increase the memory.

    This is what this guy wrote. We both have exactly the same issue.
    I think I got rid of the
    problem by running SER with increased memory limits (-m 1024). Now I can register 20000 users without crashing. SER memory usage is 150MB per process and Java 1GB.

    But I do not understand how did he do this. Could you help me out with this please.

  • Mauricio Maldonado added an answer in Methylation:
    What are good conditions for the demethylation on aromatic methyl ethers?

    what is the good condition for de methylation on aromatic methyl ethers?

    Mauricio Maldonado

    Boron tribromide In dichloromethane.

  • Awadh Alkhaldi asked a question in Thermal Properties:
    How to measure thermal properties of a wall using acoustics?

    I am wondering if there is a way to measure the thermal resistance of an envelope using acoustics?

  • Sergei A. Ostroumov added an answer in Aquatic Ecology:
    What is the cost of good freshwater?

    When I asked this question, nobody gave me a clear answer.

    Key words: water quality, water supply, monetary assessment, economics of natural resources, aquatic ecology, unsolved problems, water reslources, freshwater

    Sergei A. Ostroumov

    Prof. Bachir ACHOUR, thank you. May I vote you up. However it not the final answer.

    You gave a nice answer about the PRICE of water. However it is not its COST.

    Look, after treatment of wastewater it is not potable. Its quality is not restored to the initial level of potable water. If you restore it up to the level of potable quality, you will spend a lot of monery for 1 cubic meter. I am interested how much it will cost to restore it up to the level of drinkable quality. Can anybody answer this question?

    Another question is, why in Denmark it is 6 euro, and in France it is 3 euro?

  • Ray Simpkin added an answer in Dielectric Constant:
    How do I calculate/find values for the relative permittivity of buffers?

    Hey fellow researchers,

    I am trying to find the relative permittivty /dielectric constant of different buffers. Does anyone have an idea where to look? Or is there a formula with which you can calculate that value maybe as a mean value or sum of the components' relative permittivities?



    Ray Simpkin

    Hi Natalie,

    I take it that you're interested in the dielectric properties of liquids used as buffers. There are suitable dielectric probes available for use with vector network analysers that can be used at low frequencies for liquids. The software that comes with the probe calculates the complex permittivity from measurements of the reflection coefficient. Can you tell me what buffers you're interested in? I think your question was also aimed at what happens to the permittivity when you mix different fluids together. In this case, as long as the mixture of two or more fluids does not result in any new chemical species being formed, you can usually use Lichtenecker's logarithmic mixture law to calculate the complex permittivity of the mixture from the permittivities of its constituents.

    Hope this helps,


  • Debra Sharon Ferdinand added an answer in Intelligence:
    In your opinion, which variables influence students' motivation?

    I am working on the development of a workshop designed to teachers about how to motivate students to study. Implicit theories of intelligence is, undoubtedly, an important topic to discuss with them! In your opinion, which variables influence motivation towards study?

    Debra Sharon Ferdinand

    This year's theme for the 16th Annual Conference on Scholarship of Teaching and Learning (SoTL) was "Motivation". I am attaching my conference paper that can show how "debating" can motivate both teacher and student.

    Best regards,


    • Source
      [Show abstract] [Hide abstract]
      ABSTRACT: The Debate (i.e., arguing for or against the topic, giving reasons to support or oppose it) is a dynamic teaching tool (for both f2f and online classes) that engages high school/university students’ critical thinking, communication, collaborative, and research skills, in mastering the course content across subject disciplines (O’Mahoney, 2015). A good debate topic (moot) is topical, relating to students’ prior reading, experience, or societal/global issue in motivating students to participate to win. The debate usually has three rounds: (1) Students make an initial argument for or against the moot, clarifying key concepts; (2) Convincingly rebut their opponents’ arguments; and (3) Summarize their arguments, rebutting or defending key points. Teachers are motivated by students’ enthusiastic exchanges, noting improvements in their understanding and mastery of the course content (Akerman & Neale, 2011). Students’ debate assessment include quality of their collaborative debating strategy, debating arguments, and presentation (includes eye contact and oratory skills).
      The 16th Annual Midwest Scholarship of Teaching and Learning (SoTL) Conference, Indiana University South Bend, Indiana, U.S.A.; 04/2015
  • Naïrouz Benzeggouta asked a question in Drugs:
    Why number of diseases is increasing ?

    Drugs "treat" or "cure" diseases ?  What's the difference ? 

  • Andrew Bateman added an answer in Rasch:
    School climate scale: could a Rasch 'speaking' psychometrician please advise me?

    I read the attached presentation by Bergh and Fokuoka with interest - I am designing a study using the School climate measure - and wondered what is meant by "The precision of measurement could be improved by inclusion of additional items of appropriate severity" (slide 50). I think it means the construct isn't well enough covered but does it need easier or more difficult items to endorse? Thank you.

    Andrew Bateman

    In the Bond and Fox book (Applying the Rasch Model) (btw have you seen the new 3rd edition?) there's a super figure (3.1,3.2) that draws the items and respondents as stepping stones (of varying sizes) and this image is always worth glancing at to help make sense of precision that might be determined both by the size of the stepping stones (measurement error of each item) and how far apart they are quickly makes sense of how accurately you can place your respondents on the continuum you are investigating..

  • Antonio Seijas-Macias added an answer in Normal Distribution:
    How can I fit a Gaussian to dependent distributions?

    Hi All,

    I have three 1D normal distributions (A,B, and C) with ux, varx and nx being the mean, variance and number of samples of each distribution.

    I would like to know what it is meant by saying "fitting a 3D Gaussian to these distributions".

    Does it mean, defining the normal distribution which is characterized by,

    mean vector = [uA uB uC]and

    covariance matrix =

    [  varA                  covar(A,B)       covar(A,C)

       covar(B,A)        varB                 covar(B,C) 

       covar(C,A)        covar(C,B)       varC   ]?

    Thank you in advance for your inputs.

    Antonio Seijas-Macias

    As I understand you have three normally distributed random variables and you are interested in constructing a multivariate distribution of then. In Kenney, J. F. and Keeping, E. S, Mathematics of Statistics, Princenton (1951), you have the mathematical fundamentals for two variables, but it's very simple to extend to n variables. 

    If you use the Wolfram's sofware "Mathematica" in this page you can see an introduction to the process with references to the commands that you might use in that software ( http://mathworld.wolfram.com/BivariateNormalDistribution.html).

  • Wes Raykowski added an answer in Infinity:
    Can we really have many different definitions with different natures for the concept of “infinite” in human science?

    Since “infinite” concept came into our science, the “infinite” related concepts and theories such as “potential infinite”, “actual infinite”, “countable infinite”, “uncountable infinite”, “infinity”, “infinitesimal”, “infinite set”, “variables” were introduced; still, some other mathematicians (such as G. Kantor and A. Robinson) have tried to develop some different “infinite” theories specially (only) for set theory or analysis …. The question of “What is potential infinite and actual infinite?” has been analyzed, discussed and debated and this situation is sure to be “endless” in present classical science theory frame--------our science history strongly proved!

    Our studies prove that when facing and treating the “infinite related beings” in present cluttered, unsystematic classical “infinite” theory system, we are unavoidable to meet following two unexplainable arguments: (1) what on earth are “infinite”, “potential infinite”, “actual infinite”, “higher infinite”, “lower infinite”, “the ‘infinite’ of more infinite”, …? Can we really have many different definitions for “infinite”? Are different definitions for “infinite” the same mathematical things in our science? Why? (2) What kind of “infinite related number forms” should we have to demonstrate and cognize so many different “infinites”? Can we use just one kind of “infinite number form” forthem (several “infinite related number forms” in Harmonic Series Paradox is a typical example)? Why? Cardinality, continuum hypothesis and non-standard analysis theories help nothing here.

    Our science history since Zeno’s time tells us clearly: there are serious fundamental defects in present infinite related classical science theory system-------both in philosophy and mathematics. Our science history since Zeno’s time also proved that not matter how we have tried, all the paradoxes and troubles produced by present infinite related classical science theory system are impossible to be solved (unsolvable) inside this very system itself.

    For some small defects, the diminutive mendings are very much ok; but for the serious fundamental defects, those diminutive mendings do not only of no help but produce more troubles------errors plus other errors. So, the challenge is: to be or not to be staying in the foundation of present infinite related classical science theory frame.

    Wes Raykowski

    Hi Vadim and all others, 

    Regarding: “I am very sorry, that plenty of erroneous posts in the present discussion do not let you find the right answer to your question. But this answer was in this thread. It was my answer.”

    I admire your confidence, but I think you are barking up the wrong tree. You, Geng, and many others pay too much attention to the ancient division between potential and actual infinity, and give too little credit to the issue of operations on infinities.

    I agree with you that anything defined as never ending can never be bounded – this is a tautology. But this does not mean that one cannot handle/use/operate /etc on an unbounded sets or processes. As I said before (under the name of Untangling Math), we do this every day. 

    Imagine a point moving forever and ever (what you might call “potential infinity”) around a circle. Can anyone move such a circle, change its shape, multiply it, or operate on it in other ways without affecting the movement of the point? Now think of an area made of points. Can you mathematically (or physically) operate on an area made of infinitely many points? Then think of a never ending line? Can you intersect it with another infinite line, turn it around, multiply it, etc.? Now think of the set of natural numbers? Can you add it to another set, multiply the result, or operate on it in some other way? It is very likely that you agree with me that one can operate at least in some ways on all infinities defined in this way.

    The problem you (and Geng) created for yourself involves a view of mathematics as reflecting our everyday ideas and notions. In one of your earlier messages you said (I quote) “In the second case there is no limit and, hence, there is no resulting object.” It looks that you understand the term “mathematical object” literally as any everyday object.

    My perspective of mathematics is more technical. The way I see it, mathematicians make a series of technical assumptions (mostly procedural) and then operate on them logically. They treat infinities the same way as other mathematical objects. 

    In summary, other than the common name, mathematical concepts of infinity have very little in common with the concept of infinity we use every day. The discussion about existence of actual infinity reminds me the theological discussions about how many angels can dance on the sharp end of a pin. 

  • Arnold Windeler added an answer in Social Theory:
    What are the criteria for a robust social theory?

    I would like to find out more about the criteria for a robust social theory, since I am currently developing a theory on water research.

    Arnold Windeler

    Dear all,

    I agree with Ivo, Giddens' Structuration Theory is one of the most fruitful social theories today. And you can really use it for empirical studies (references to some studies I did usind the structuraion approach to be found at my contributions.

    To your question on robustness:

    Jen defines robustness as the ability of a system to
    maintain certain features when subject to internal or external perturbations.

    Jen, E. (2006). Robust design: A repertoire
    of biological, ecological, and engineering case
    studies. Oxford: Oxford University Press.

    Good examples for robustness in the social sciences are to be discussed in:

    1. The robustness of the innovation cluster "Silicon Valley"

    Ferrary, Michel/Granovetter, Mark (2009): The role of venture capital firms in Silicon Valley's complex innovation network. In: Economy and Society 38 (2), S. 326-359.

    2. Robust action of the Medici in Florence:

    Padgett, John F./Ansell, Christopher K. (1993): Robust action and the rise of the Medici, 1400-1434. In: American Journal of Sociology 98 (6), S. 1259-1319.



  • Sébastien Poncet added an answer in Fluid Flow:
    For modeling fluid flow in tube of a chimney with flat plate and Re=800, can the flow be laminar or turbulent?

    diameter of flat is 2/3 of tube diameter.

    Sébastien Poncet


    for natural convection, you need to calculate the Rayleigh number and found the critical value in all books about heat transfer.

    The Richardson is just to know if you are in natural, fixed or forced convection regime.

  • Cássio Prinholato da Silva added an answer in Genome Editing:
    Can genome editting technologies such as CRISPR/CAS9 be used on non-cycling cells?

    Genome editting technologies, such as CRISPR/CAS9, rely on either non-homologus end-joining and homologous recombination.  My understanding is that homologous recombination is specifically required for site-directed muatgenesis and only occurs when cells are cycling. Does this mean that genome editting tools is limited to non-specific mutagenesis, which requires NHEJ,in quiescent cells, such as resting T cells or is it possible to introduce site-specific mutations in these cells?

    Cássio Prinholato da Silva

    maybe theses articles will be useful




  • Hassan Zaidi added an answer in Primer Sequences:
    Designing primers for qRT-PCR (SYBRGREEN) ?

    Is it compulsory to consider only those primer sequences which lies within cds region when designing gene specific primers for qRT-PCR ?

    Hassan Zaidi

    Thanks brother. If the both said properties are present in primers, lies in cds region and showing single band  on GEL, then what could be the cause of dimers &  peaks below threshold line in qPCR ?