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  • Martin A Thomas added an answer in BET:
    Why is langmuir surface area always higher than BET surface area?

    In any sample I observe same scenario, why so?

    Martin A Thomas

    Both the Langmuir equation and the Brunauer Emmett Teller (BET) equation model the adsorption behavior of a gas (on the surface of a solid) in terms of the monolayer capacity (and hence both can be used for surface area measurement based on that assumption).

    However, the Langmuir equation is derived around the monolayer being the limit of adsorption (and thus cannot be exceeded - which we know to be untrue in real physisorption systems with a freely accessible surface), whereas the BET equation models partial and multilayer adsorption in terms of the monolayer (at least up to a point).  Therefore, when applying the Langmuir equation to data which is not strictly limited to a monolayer, e.g. "type II" or "IV" isotherm - and not a "type I" (here I am using the IUPAC nomenclature) it is not surprising that the Langmuir can over-estimate the surface area! This is often very evident by lack of linearity in the Langmuir plot if using the same calculation range as BET. Yet for many materials one can find reasonable agreement if the relative pressure (P/Po) points used for the Langmuir are taken at much lower P/Po than for the BET (i.e. corresponding to P/Po before the so-called "knee" of the isotherm).

    One can perhaps appreciate the difference between the two approaches from the equations themselves. At first they do not appear to be so different since both are of the form

    A = B + D, or more exactly

    A = 1/kQm + (k'/Qm)(P/Po)

    where A = (P/Po)/Q (Langmuir) or 1/Q((Po/P)-1) (BET)... i.e. simple expression of the data pairs Q (amount adsorbed) and P/Po.

    When we turn our attention to the right side of the equation, the term B is effectively the same, being proportional to 1/Qm, Qm being the monolayer quantity, k being related to the heat of adsorption. However, the second term on the right, 'D' is where the difference lies. In the Langmuir equation k' = 1, but in the BET equation k' = (k-1)/k. In the BET equation k is usually given the symbol C.

    Tough to follow I know, so to clarify... the Langmuir equation only considers the heat of adsorption in the B term not in both B and D, and that's basically the difference between monolayer (Langmuir) and monolayer+multilayer (BET) models.

    Note: both Langmuir and BET can yield surface area values grossly in error when applied to microporous materials, even though the isotherm might be of type I which exhibits a very obvious plateau (limiting value of amount adsorbed). This is simply due to the fact that in physisorption of gases in a purely microporous solid, the limiting value is not due to the formation of a monolayer (all adsorbate molecules in kinetic (ads<->des) equilibrium with adsorptive (in this sense adsorbate = immobilized molecules on the surface and adsorptive = mobile gas phase above the surface). Rather, the plateau is due to micropore volume filling... which has a limiting value when the micropores are filled!

    Probably time to stop here rather than continue with a full length thesis. For further reading I would direct those interested to books by Rouquerol & Sing, or by Lowell et al.

  • Martyn Lloyd-Kelly added an answer in Cognitive Architectures:
    Other than Kosslyn, are there any other prominent researchers concerned with visual-spatial reasoning?


    I develop and maintain the CHREST (Chunking Hierarchy and REtrieval STructures) cognitive architecture and have recently developed functionality to allow the architecture to use coordinate-based visual-spatial reasoning to "plan ahead" along with other behaviours.  In doing this I've become interested in how the mind actually handles visual-spatial reasoning, particularly coordinate-based visual-spatial reasoning.  I'm looking for research that details human data with regard to this topic with a view to having CHREST "fit" this data and see if any predictions can be made by the architecture.

    Many thanks for any help that anyone can provide! 

    Martyn Lloyd-Kelly


    Sure! I was given a book by my PI called "Image and Brain" by Kosslyn that appears to tie together a lot of his work. Its a little overtly technical at times but its been a great source of information for me thus far!

  • Jean-Luc Bertrand-Krajewski added an answer in WaterCAD:
    How do I model intermittent flow in water network with house roof storage?

    In many cities like Amman, water is supplied to households one or two days per week. All households have storage tanks on their roof to store water for the whole week (storage size 2-6 cubic meter per family). In addition, many families do their excessive water use during their running water days.

    I need some ideas how to  better model this system using of the water distribution networks solvers (watercad etc.). 

    Jean-Luc Bertrand-Krajewski


    If you need / wish a more detailed modelling of each tank at short time scale, simulating individual water uses in each household may be an option. This is what we used for a different purpose (generating stochastically wastewater pulses based on individual water uses in households). More information in the attached file. A more detailed paper in under preparation.

    Best regards,


  • Hugh Lachlan Kennedy added an answer in Human Behavior:
    Have you ever thought about temptation as a mathematical function for stimulating the behavior of a robot ?

    Maybe Afforts to create a model for human behavior and movements and even feelings and reactions based on a mathematical equations is one of my interests in my future research life.
    So I wanna see if there were any clues on this area which help me to make robats that just act like a human do on different situations to start my investigation on it??

    Hugh Lachlan Kennedy

    ... That's an interesting idea. With AI, we are so busy trying to make algorithms perfect. But to emulate human intelligence I guess we should focus on other behaviours - temptation, jealousy, lust, greed, etc. 

    I think "forgetting" is a good example - it is generally considered to be undesirable, but I'm pretty sure it is an essential part of intelligence and the learning process. 

  • Arnold Trehub 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.

    Arnold Trehub

    Respect must be granted to all sincere expressions, but agreement depends on the personal understanding, often in conflict with others, of each involved person.

  • Serah Yim added an answer in Immunohistochemical Staining:
    My primary antibody stopped producing stains. What can cause an antibody to suddenly stop working?

    An F4/80 antibody I've been using for immunohistochemistry was consistently producing good stains. But the past couple times, it hasn't worked! I haven't changed the protocol at all. I ran some experiments with the F4/80 and another antibody that marks the same cell type (macrophages) with the same steps. The other antibody worked but the F/80 didn't. 

    Recently the refrigerator where the F4/80 is stored was cleaned out. When we put the antibodies back, the refrigerator was too cold so some of the reagents stored in there (1% BSA, hydrogen peroxide, etc) froze. I'm wondering if maybe the antibodies froze too and now they're damaged? But I didn't think one freeze/thaw cycle could ruin antibodies like that! 

    Thank you in advance! 

    Serah Yim

    Hi Steven,

    Maybe you already know, but apparently F4/80 is widely known to be troublesome. According to the researcher who's helping me, none of his colleagues who've worked with F4/80 know why this happens. Sorry I couldn't be of more help. Good luck!

  • Jacob Hyler asked a question in Coaching:
    How long to a full text will be added after a request?

    I sent a request in for a full text: 

    Home advantage in soccer - A matter of expectations, goal setting and tactical decisions of coaches?

  • Brett Oppegaard added an answer in QR Codes:
    Can you think of any ways that the use of QR codes has enhanced your experience of a place?

    Any particular places you've visited (museums, restaurants, tours, etc.) that made use of QR codes in a way that enhanced your experience?

    Can you think of any places that do not currently make use of QR codes that might benefit from implementing them?

    Brett Oppegaard

    Really interesting story, Yi; I particularly appreciated the background history and ways in which you pushed yourself as a storyteller.

  • Afshin Rahimi asked a question in Data Model:
    Fault Classification/Identification Methods?

    I am trying to look into innovative ways to do fault identification/classification. It looks to me that most of the literature available is dealing either with the data or the model and I am wondering if there is anything in particular available that can help with the combination of both.

    I am more specifically working on a Reaction Wheel (RW) model. If anyone has seen a work related to this topic or has done anything in this area, it would be appreciated to share that with me.

  • Jahangheer Shaik added an answer in Bacterial Genomics:
    Can anyone help me with converting genbank to fasta (KAAS input file)?

    Hello every one.

    Hope you can help me. The task seems to be rather easy. I have a set of bacterial draft genomes in .gbk format and I want to used them as input into KEGG Automatic Annotation Server to assign KO numbers and extract main pathways. The problem is that the system require to input multi-fasta files.

    I've already tried to find some tools by web searches but couldn't' found a proper one yet. So if you know any tool that would allow me to input large data sets (>5Mb) to convert genbank to fasta files would be a great help.

    Thank you in advance.


    Jahangheer Shaik

    May be a little too late for responding. Just use Seqret command in Emboss. By far the easiest way to deal with this conversion.

  • Ann Aitken Worth added an answer in Spearman Correlation:
    How do I find out if participants' ranking of a scale correlates with the orginal scale?

    I have a 10-level scale. I gave the participants text descriptions of each level of the scale and asked them to rank all of them in order from one to 10. I want to know if these participant rankings correlate to the original ranking of the scale.

    I know a previous researcher asking the same question used Spearman's correlation - and came up with a single, significant correlation for the entire scale, not level by level -  but I can't for the life of me figure out how.

    I can't even figure out how to organise my data in SPSS. At the moment I have my data in separate columns for each level of the scale. So in relation to this question each participant has 10 columns, named up the top with the label of the original level.

    And yes, it's entirely possible the answer to this is simple, as psychology statistics are not my friend.

    Ann Aitken Worth

     Thanks for these suggestions. It definitely helped - I now have results that make sense and can talk about in a meaningful way. I'm still wondering why I decided to do a quantitative masters, but that's neither here nor there ...!

  • Manuel Alberto M. Ferreira added an answer in IR Theory:
    How do different IR theories explain Russia's recent bombings in Syria?

    There is little agreement about why Russia is bombing targets in Syria at this particular time. Is there a rationalist explanation, such as to retain Assad in power or to force western countries to collaborate with Russia as a step out of isolation of perhaps get rid of sanctions? Or is it more because of identity and prestige, like constructivism would predict? 

    Manuel Alberto M. Ferreira

    I think that the real motive, for the moment,is to keep moving and to stand  a position. Other motives only will be patent in a near future.

  • Kristian E Swearingen asked a question in Streptavidin:
    Do urea or SDS interfere with the capture of biotin by streptavidin?

    Several sources indicate that, once bound, the streptavidin-biotin complex can withstand up to 2% SDS and 6M urea (at room temperature). However, I can't find any discussion on whether the presence of SDS or urea in the sample buffer would inhibit binding in the first place. There is some evidence that urea weakly binds the streptavidin binding site. Most protocols reduce SDS to 0.1% or less, and I have found none that include urea.

  • Sam Tonddast-Navaei added an answer in Computer Aided Drug Design:
    Does anyone have experience with pharmacophore modelling for two same ligands in same binding pocket?
    I have a protein (crystal structure) complexed with two molecules of the same ligand (inhibitor). I am trying to build a pharmacophore model for searching potential hits. But the problem is that two molecules are bound in same binding pocket but in different conformation (image attached). Both the molecules are interacting with hydrophobic interaction. The binding pocket consists of exclusively hydrophobic residues. Could some one please suggest me how can I develop a pharmacophore model by using these? Shall I straightforwardly consider any one of the ligand molecules? I was thinking of merging two similar pharmacophore features to make one point. But the problem is that the binding conformation of both the inhibitor molecules is different.
    Also, if I want to do docking of several inhibitors in the same site before going for pharmacophore modelling (for building common pharmacophore model), how should I do this?
    Please help me in solving this. Thanking you in anticipation.
    Sam Tonddast-Navaei

    Dear Nutan, I was wondering if there a chance that you could reveal the ligand's name?

  • Richy Jérôme asked a question in Chemical Etching:
    How to increase the surface roughness of an alumina substrate above 2 µm?

    I am looking for a method to enhance the roughness of alumina substrate (10 x 10 x 0.5 mm with Ra = 2 µm). I already used chemical etching in a sodium hydroxyde solution (2 mol/L to 6 mol/L , up to 24h), but Ra only decreases. I could change the acid, and use HF etching for example. Do you think it could work, or do you know another method (physical or chemical) to increase Ra (< 10µm)?


  • Fernando Fogliano added an answer in Beauty:
    I want to do a review on beauty. Could my colleagues express their opinion on who is considered beautiful in their part of the world?

    I want to do a review on beauty. Therefore I would like to ask my colleagues from different countries of the world if they would like to express their view on who is considered a beautiful woman in their part of the world.

    Fernando Fogliano

    A possible routing for your search you can find in the book of Nacy Etcoff , The survival of the pretiest . Another source is the Book of Mario Livio , The Golden Ratio: The Story of PHI , the World 's Most Astonishing Number. Livio brings an interesting discussion of how organisms are organized in terms in the golden ratio. To find beautiful faces near you I suggest the use of Dr Marquardt`s masks at the following link: http://www.beautyanalysis.com/.

  • Marc Guyon added an answer in Piles:
    Does anyone have or have access to noise measurement data from underwater piling in a river?

    I'm interested in the piling noise.

    Can anone suggest research papers?

    Marc Guyon

    Hello Francesca,

    There are these documents exist:




    There is also some information in the after documents




    All the best


  • Kai Fauth added an answer in Induction Heating:
    What is the best RF frequency for inductively heating a graphite susceptor?

    I want to grow epitaxial semiconductor films on wafers heated to 700-1200C on a graphite susceptor.

    Kai Fauth

    I get your point. Also, for entire wafers, tremendous DC currents would be needed. Have no experience with inductive heating, though. I imagine that optimum frequency might rather be a functin of geometric setup (in conjunction with graphite properties) than of graphite (as such and alone). In the end, what I guess you will be doing is impedance matching. If resonance conditions are to be met for optimum coupling then I would try to figure out the equivalent circuit.

    Hope you will find someone able to give more specific advice. Good luck!

  • Ahmed Hemdan asked a question in Pricing:
    What is the price of the alcalase enzyme ?

    What is the price of the alcalase enzyme ?

  • Shahid Mahmood added an answer in Animal Science:
    Anyone, can you provide me a best protocol for crude protein extraction from poultry meat.!?

    Dear Science heads,

    As i am new to animal science division, it will be of great help from you, if you can share me a best working protocol for Whole Protein extraction from Poultry Meat. It will be of great help. Thank you.

    Shahid Mahmood

    I do not know why you call it crude way. If your hypothesis is to relate something with animal physiology, then you have to flash freeze the muscle (in liquid nitrogen) and store it at -80C. Then you can grind the sample using a super-chilled (in liquid nitrogen) mortar and pestle. The ground sample should be stored at -80 until they are used. Weight the desired quantity (may be 1 g) and homogenize with an extraction buffer. The extraction buffers are different for different types of protein analysing techniques e.g. for 2-D gel one can use Urea and Chaps...but in the case of Elisa you may not use Chaps and Urea..Here i am sending you a link of a document but its better to read some papers so you can have a better idea about the composition of the extraction buffer depending upon the proteins you want to analyze.

    1. Tissue Homogenization Procedures for use with ELISA

    2. http://www.abcam.com/protocols/elisa-sample-preparation-guide-1

    After extraction, you have to measure total protein concentrations using an appropriate method. You may use 2-D quantitative kit but you have to check if the composition of your extraction buffer allows this or not.  

  • C.A. (Kees) Kan added an answer in Pollution:
    I want research about the adverse effect of resources and their pollution on environment?

    can anybody help me for this title and tell some article about this title

    C.A. (Kees) Kan

    This question is far to broad to provide you with a meaningful answer. Search yourself on the internet or in websites like pubmed to find relevant articles. Then reformulate your question.

  • Benjamin Cassen Macneille added an answer in QIIME:
    Qiime: alpha diversity and default mc2?

    To calculate alpha diversity and rarefaction curves, singleton counts should be included, but qiime's default removes them in pick_open_reference. Does qiime treat the doubletons as singtons for the rarefaction curve?


    Benjamin Cassen Macneille

    Thanks, Ahmed! I ended up using the mc2 file because the thresholds to accept singletons seemed fairly rigorous, though the extent to which is not very clear to me.

  • François-Xavier Gillet added an answer in DNA Ligase:
    I'm looking for a plasmid or E.coli strain to produce recombinant DNA ligase. Can someone help me?

    I have a request. As many labs, we produce and purify basics recombinants proteins of interest in molecular biology. For instance, we produce the pfu and RNAseA obtained from addgene. One protein of interest for us is the T4 DNA ligase. I'm trying to find the plasmid or the E.coli strain to but without success. An idea?

    François-Xavier Gillet

    I found a company that sell a pET with the T4 DNA ligase for 900$... however I guess that, for some plasmids or strains, the patent expired since many years and it would be possible to diffuse it free of charge. 

  • Wiliam Ferreira da Cunha added an answer in Conducting Polymers:
    Will conducting polymers display superconductive properties?

    In my view if conducting polymers shows DC conductivity than they shows the property of superconductivity.

    Thanks in advance.

    Wiliam Ferreira da Cunha

    I believe you are familiar with the work from Little in the mid 60's - Phys. Rev. 134 6A (1994).  Although no such polymer has been synthesized to this date, I can't  see superconductivity in polymers as being impossible. As long as the  polymer goes through a small Peirls distortion, I do believe superconductivity is a possibility. Actually, I'm currently looking for experimental organic chemistry groups to work together in this field. I'd be delighted to discuss this further if anyone is interested; thank you for the question.

  • Ahmed Samir added an answer in Interface Design:
    Should interface design specifications be considered in the development of a mobile application for entertainment use while driving?

    Que especificações de desenho de interface deverão ser consideradas no desenvolvimento de uma aplicação móvel para entretenimento, utilizada durante a condução?

    Ahmed Samir

    Dear Jan,

    Thank you for detailed answer. As I understood from the question, andr

  • Remi Cornwall added an answer in Entropy:
    Is anihilation isentropic?

    Is the anihilation of matter and antimatter isentropic process? All the mass is converted to energy, without any entropy? Is it completly reversible without any lost of energy? Is therefore no entropy produced?

  • Rodrigo Lopez Leal added an answer in Extracellular Vesicles:
    I've come across the inhibitor 'GW4869' where it was described as exosome inhibitor - how specific is this?

    In the sense that does it inhibit release of other types of extracellular vesicle?


    Rodrigo Lopez Leal

    I know that this drug inhibit the ceramide synthesis, and the ceramide is a essencial lipid for a subtype of exosome biogenesis in multivesicular bodies. 

  • James R Knaub added an answer in Cluster Sampling:
    In stratified random sampling, can the researchers based selection of strata on equal number of the strata not proportion?

    What are the distinctions between stratified random sampling and cluster sampling? Is the difference in the number of subgroups? Is it possible to have equal strata in stratified random sampling?

    In my research, i have selected my participants from two universities, the selection of universities have been on convenient sampling, though almost equal number of subgroups(EFL undergraduates, EFL post graduates,  non-EFL undergraduates and non-EFL post graduates) from the two universities were randomly selected. Is this cluster sampling or stratified random sampling?

    James R Knaub

    Elahe -

    In my first response I asked what kind of data you have.  Assuming you have appropriate quantitative data, you could estimate proportional and also cost optimum allocation between strata, but you need to have variance estimates by strata.  That is important information for you anyway.  Thus it is another reason that a pilot study may often be useful.

    There are a number of survey statistics textbooks which include the proportional allocation technique, and other useful information.

    For stratified random sampling, you could see Chapter 5 and 5a in Cochran, W.G(1977), Sampling Techniques, 3rd ed., John Wiley & Sons.

    Also, Chapter 5 in
    Blair, E. and Blair, J(2015), Applied Survey Sampling, Sage Publications
    covers stratified random sampling.

    Both of those books also cover cluster (random) sampling.

    An insightful and well written book, but perhaps harder to borrow as it may be expensive, would be the following:

    Lohr, S.L(2010), Sampling: Design and Analysis, 2nd ed., Brooks/Cole.

    Of the books above, the least expensive, and perhaps more elementary would be Blair and Blair.

    Of course, these are my opinions from my experience, and there are many other sampling textbooks.

    Best wishes - Jim 

  • C. Allen added an answer in Geophysics:
    What is the cause of this warming?

    In Sept. 2015, Ukrainian Central Geophysical Observatory  fixed just three temperature records in Kyiv.

    1)            Maximum temperature+35,7°C  was in Sept. 2.  This day was the warmest September since 1881.

    2)            Also on this day on 6,5°C was exceeded and pre-historical significance of the average daily temperature, which was fixed in 1938. The average temperature reached +29.1°C.

    3)            In addition, 3 September in Kiev was fixed very warm night of 1881 to that date. Night temperature is not dropped below + 20,6 ° C and thus on exceeding 3,1°C prior to the historical significance of this day in 1899.

    P.S. Most water wells disappeared. This has not been a long time !!!

    C. Allen

    Dear Kenneth,

    Yes Dr.

    Yes population IS the key problem, but that is politically distasteful and solutions are seen as draconian. Tim Flannery has a new book out that purports hope (that is in the title), and he stated a good argument, but I would not hold my breath as it does not address population growth.

    I would love to have the paper advertised, promoted, read, cited, etc., it was initially condoned and had my workplace name on it but politics changed (internal/external) and just after peer review, but prior to publication that was withdrawn and I was asked not to publicise it in any form, even as a private citizen. I thus can not reveal more of my identity or link it to my other papers.