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  • Valesca Anschau added an answer in Ames Test:
    Why does the NAD+ 340nm absorbance increase without the addition of substrate during enzyme assay?

    I got another weird observation with my enzyme assay. The control reaction containing just NAD+ and my enzyme sample without the addition of substrate displays consistent signal increase at 340nm. I am testing a polyol dehydrogenase, before I suspect that it may be due to the glycerol I added to for long term enzyme storage. However, this observation persists after I freshly purify the protein again without the use of glycerol.

    Anyone has any idea how this could happen? Could it be DTT reducing NAD+? The purification buffer I used is 100mM Tris-HCl, 0.5M NaCl, 1mM DTT and imidazle for 6his purification. Why could the 340nm absorbance increase without the addition of any substrate. This is only a problem with some of my proteins  I am working on, while others are fine. Help please! 

    Valesca Anschau · University of São Paulo

    My suggestion because I have worked with protein a long time is to change the protein buffer ( the same buffer without Dtt and imidazole ). If you need to work with your protein reduced, you add Dtt before you start the experiment. 

    Imidazole is used in buffer just you purified it. Just it.

    I recommend you to change the buffer after you purified it.

    Imidazole causes interferences during the experiment and  increase absorbance as well.

    I hope it's help. Keep touch

  • Yu Ming asked a question in Odds Ratio:
    What is the difference between incident rate ratio IRR and Odds ratio?

    To my knowledge, if the new event is a rare occurrence, these two can be considered as equal? or these are two different terms for different study design?

  • Arturo Geigel added an answer in Science Communication:
    Why Joachim Pimiskern leads netwotk in score ?

    He has the highest score, which stays at 184.80 and grooving He is the unique person on RG, having this highest score without even 1 published paper.

    Joachim is a Professional Librarian, which allows him to be aware and understanding science on the broad bases. He provides his services for 7 million members, consulting and sending the links about question posted. 

    Thus, he helps  to entre science community, his help is highly appreciated by his peers, who upvote his answers

    Thus, he is highest rated RG member as voted by pears.

    I personally take my hat off, and congratulate Joachim . with his achievement.  

    Arturo Geigel · Polytechnic University of Puerto Rico

    I will also congratulate him on such an excellent contribution to RG. I have seen posts in areas particular to my area of expertise and he is very accurate with the answers that I have seen that he gives.

  • Jonah Mutua added an answer in Mathematics Education:
    How does students' competencies in solving fractions and quadratic equations affect their ability to pass college algebra?

    Hello Scholars,

    I would like to do a quantitative study on how does students' competencies in solving fractions and quadratic equations affect their ability to pass college algebra? 

    I needed your advise/opinion  on the necessary variables and the best way to collect data.

    Data Collection.

    a). I am weighing between administering a test (20 questions, 10 questions on fractions and 10 questions on quadratic equations). All questions will be picked from previous exams.


    b). Print students' previous exams and evaluate how they performed on fractions and quadratic equations problems.

    I welcome your suggestions & advise.



    Jonah Mutua · Texas State University

    Can you please explain your suggestion more. Thanks.

  • Balasubramani pk added an answer in Stem Cell Culture:
    Is it feasible to obtain 100 Million Mesenchymal Stem Cell in a 2 Layered Cell Factory?

    I would be using 2 layered cell factory (1272cm2) for Mesenchymal stem cell culture.

    Source - P1 Umbilical cord Mesenchymal Stem Cell.

    If it is feasible to culture and arrive at the  magical number (I100 Million mesenchymal stem cell ). what would be the ideal media to use, Supplement ( FBS % and bFGF concentration ) and Seeding density ?

    Balasubramani pk · Cryo Stemcell pvt ltd

    Thanks Diaz for your valuable inputs it is really helpful indeed.

  • George Bekas asked a question in Syntax:
    How can I recall the inputs of a nested function in Matlab?

    Suppose that I have a main function with many variables and a nested function whose inputs depend on the variables of the main function. The variables have a form as follows: x(1), x(2), x(4), x(7), x(8), x(9) etc. When inserting these variables in the nested function that has a form as follows: function c = evaluate(A, B, C) c = 2*A + 5*B - C end x(1), x(2), x(4), are considered A, B, C and then I want x(7), x(8), x(9) to be considered A, B, C again. Suppose that I have a working code for inserting x(1), x(2), x(4), x(7), x(8), x(9) etc. and for all the operations within the nested function, with what kind of syntax can I make sure that the desired variables that are inserted in the nested function, will be considered A, B and C?

  • I Wayan Supartha added an answer in Parasitoids:
    Key for the identification of Plutella xylostella and its parasitoids?

    key for the identification of Plutella xylostella and its parasitoids?

    I Wayan Supartha · Udayana University

    Good information given by Hill and Rouse, you'd better follow the both articles

  • Tatiana Albarracin asked a question in Antifungal Activity:
    Microdilution methods for evaluation of antifungal activity?

    I want to know for microdilution methods of antifungal activity, which is the best method?. Because I read about the use of McFarland standard, but I don't how good it it for MIC. Another method is using MTT, do you know other reagent?

    other good method to search the MIC by microdilution?

    Thank you

  • Armin S. Coronado asked a question in Cultivation:
    Can anyone have a literature and/or journal about the cultivation of Dunaniella in laboratory condition? Can anyone provide me a copy?

    medium used for the lab cultivation

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

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

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

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

    Personally, I agree with Stanislas Dehaene's opinion.

    Louis Brassard ·


    The multiverse story is as wrong in its new version than in its old version. There is not more evidence for the new one than for the old ones.  India has so many sacred texts that whatever we will invent in the future we can be sure to find an old one in the billion of sacred stories.  But saying everyting is as far as prediction goes  almost not better than saying nothing.

  • Donggyu Jang asked a question in EMI:
    Is there unwanted effect of double shielding of EMI source in Faraday cage?


    I have a plan to make new version of Faraday cage for gas discharge circuit. Unlikely to current cage in which radiation sources such as Thyratron and capacitor are just proximate to some electronics related to discharge triggering, This new box will have additional shielding room for these sources as seen in the attached images.

    At this moment, I don't know which is good way to get more effective shielding. one image (1st case) shows additional shielding room shares one side to whole Faraday cage while the another (2nd case) is isolated type which is connected to inner surface of the cage via wire.

    In 1st case, What I'm worrying is the possibility that EMI directly hits the cage thus cages are all fluctuated in voltage if EMI is severe.

    Actually EMI is severe. When we enclose the capacitor with aluminum foil, foil is shaken!

    Could you tell me anything about these two design?

    In 2nd case, does external surface of the isolated shielding room keep itself equipotent no matter what happens inside?

  • Rakesh Yashroy added an answer in Philosophy:
    Does certainty or absolute truth exist?
    Our means of perceiving reality through our senses make us vulnerable to distortions and biases. But with scientific methodologies, can we claim that perception of objective reality is indeed possible? OR objective reality only in the context of known knowledge of the time/period?
    Rakesh Yashroy · Indian Veterinary Research Institute

    How can anyone observe 'something', which is infinity (no beginning, no middle and no end), without becoming a part of that Absolute Truth? Like, we fall (not rise) in love, there is no alternative but to fall into Absolute by shedding false pride of innumerable identities of pure temporary nature and then be infinity ourselves - concludes God in Bhagwad Gita.

  • Bhoj R Singh added an answer in Cell Culture Techniques:
    What is the permissible fungal colony (contamination) count (on a YPD agar plate) in a tissue culture lab?

    I ve spotted a few colonies growing on Yeast extract, Peptone and dextrose (YPD) agar medium, which is exposed to a fumigated room for 3.5 hours and incubated at 30 degrees centigrade for 41 hours. But I am not able to find the permissible count for the same. I wish to know whether I can start working in that room or do another fumigation. I request you all to suggest and clarify me.

    Bhoj R Singh · Indian Veterinary Research Institute

    I think you used settle plate count, it depends on the time for which you kept your plate open, in practice I used one hour. There should be no colony count on Blood agar as well as YPD agar plates, do it in triplicate. To get rid of contamination perform humidified fumigation than dry or just fumes in a dry room.

  • AR Reddy added an answer in Signal Process:
    I am planning to work in layered modulation(Hierarchical modulation) techniques, what are possible ways to mitigate inter layer interference?

    1. what are possible ways to mitigate inter layer interference?

    2. Which modulation techniques will be good to be used?

    AR Reddy · Madanapalle Institute of Technology & Science
    1. Hierarchical modulation is the signal processing techniques for multiplexing and modulating multiple data streams into one single symbol stream, where base-layer symbols and enhancement-layer symbols are synchronously overplayed before transmission.
    2. Hierarchical modulation suffers from serious inter-layer interference (ILI) with impact on the achievable symbol rate.
    3. Offset hierarchical QAM modulation: Layered offset hierarchical QAM modulation scheme  enhances the high priority stream error performance by reducing the intersymbol interference from the superimposed symbols of the low priority stream. The scheme shifts the symbols of the two priority layers by half the symbol duration, whereas the detector performs multi-stage maximum-likelihood detection with interference cancellation.
  • Mahboubi Chikh Younes added an answer in Bioturbation:
    Please can you help me to know about this bioturbation which I found it in lower callovien of algeria?

    please can you help me to know about this bioturbation which I found it in lower callovien of algeria

    Mahboubi Chikh Younes · University of Oran

    Dear keith 

    is preserved in Micrite limestone 

  • ِAbdelrahman Halim Hussein asked a question in Work Stress:
    How to eliminate air bubbles in cast epoxy dog bone sample for tensile testing?

    I am performing mechanical testing with epoxy polymer. The problem that I am facing is that most of the samples contain trapped air bubbles, which work as stress concentration points in the mechanical testing. I use Epon 828 with DETA curing agent (12 phr) and cure at 40 C for one hour. I tried vacuum degassing, but it resulted in even larger bubbles. 

  • Shane douglas Muldoon added an answer in Grounded Theory:
    Have you come across any studies where Grounded Theory and Case based method was used together?

    I am doing my doctorate. The nature of my problem required me to gather bounded project cases (with proper problem statement, options and resolution in each case). Over 100 in-depth interviews I have conducted are all bounded projects. I am using grounded theory for driving my data collection with theoretical sampling. Coming to data analysis, I am using constant comparison method between interviews. I am wondering if here multiple case studies based analysis is also applicable. Have you seen any such study in which Grounded Theory and case based analysis was used together to form the theory? Please provide some guidance and references.  

    Shane douglas Muldoon · New Age People Research Consultancy, Melbourne, Victoria, Australia

     well perhaps if you want to follow a purist GTM approach Ali is correct. however, i do still believe GTM and case studies are quite compatible. you might want to draw on the essence of GTM - ie, inductive understanding and interpretation of data and drawing out concepts  etc through that process rather than imposing preconceptualisations on the case data - and qualify/explain your methodological work. be very careful in putting forward your list of examiner names that you do not include any who would critique your work for its imaginative use of GTM or any other research methods/approaches. please also list solid references in detail for your methodological arguments. 

  • Paramjit Singh Dhot added an answer in Stem Cell Transplantation:
    Haploidentical transplants or Cord blood transplants ,is a raging debate in the Stem Cell Transplant community, which one is better and why.?

    All experts on Stem cell transplants, haematologists., oncologists

    Paramjit Singh Dhot · LifeCell

    There is a btrend for Haploidentical transplants, but Cord Blood transplants remain a mainstay in over 80 disorders

  • Arif Jawaid added an answer in Patient Safety:
    What are the resons that prohibit patient safety criteria?

    What can we do to overcome the barriers of patient safety in hospitals?

    Arif Jawaid · Linton University College

    Hi Nader

    I think this problem is arising from lack of Policy document and  implementation of SOPs (Standard Operating Procedures). There is definitely requirement of Safe and Secure Environment Policy Document. The management should ensure that these SOPs are 100% implemented. It will be travelling down from whole and holistic system (comprising vision and mission focusing on patients). It needs details, of course, perhaps some time later. Good luck!

  • Bernard Ochieng' Ogongo added an answer in Seaweed:
    Can anyone identify this specimen?

    the specimen was collected from the rocky shore of the spray zone of north kerala while sampling seaweeds. the stem like structure is hard and many originates from the same base. can anyone help?

    Bernard Ochieng' Ogongo · Kenya Marine and Fisheries Research Institute (KMFRI)

    Jania has no woody stem that is longer to that magnitude, and because of that; I suggested two options and requested for more closely taken photos for confirmation.

  • Houssam Nahilia added an answer in Wind Power and Power Systems:
    Does anyone know about models of DFIG in power system transient stability?

    I want to study the impact of DFIG based wind generator. what's is the best model to choose?! please help. 

    Houssam Nahilia · University of Science and Technology Houari Boumediene

    yes, i totally agree with you, but sometimes, lot of assumptions have to be made. In fact, in litterature we find a variety of model, and by mistake, we may have some problems, that's why i'm asking about models for studying transient stabilty.

  • Soo-Jin Jeong added an answer in Abaqus:
    What is the reason for unexpected large strain in abaqus modeling?

    Hi my Friends,

    I am doing abaqus run for a copper specimen under hydrostatic pressure. The magnetude of pressure is in order of several Giga Pascals. In my material definition, I have defined stress-strain flow up to strain of 0.4. But as you can see in attached photo, some elements show very large deformation (considerably larger than 0.4). Knowing that I have not defined stress strain behaviour for srain greater than 0.4, how this can be occure? Unfortunately, niether adaptive meshing nor element deletation were not eliminate this issue!!

    Best Thanks

    Soo-Jin Jeong · Korea Automotive Technology Institute

    As above researcer mentioned, key is the range of stress-strain curve( >=0.4). Beyond that point(0.4), as it stands, excessive stress may be computed, resulting in large deformation.

  • Kwamina Ewur Banson added an answer in Rural Sociology:
    What is the best approach to measure the activity profile of rural dwellers?

    Roles played by individuals vary based on gender and other factors. 

    Kwamina Ewur Banson · University of Adelaide

    The systems thinking approach is can be used to measure the activity profile of rural dwellers. Systems thinking is a way to conceptualize and act towards the integration of social, environmental and economic dimensions of sustainability. This supports communities to address the challenges of improving both human and ecosystem well-being. 

  • Anthony Parrington added an answer in Geopolymer Concrete:
    I want to know the mix design for various ingredients for obtaining good geo-polymer concrete mix. Please suggest your views?

    Geopolymer Concrete mix design

    Anthony Parrington · University of New South Wales

    No problems Shriram, glad that my answer was of assistance.

  • Bhoj R Singh added an answer in ESBL:
    How I detect for beta lactamase?

    Hi all

    I am trying to detect beta lactamase by combine disk test with ceftazidime,ceftazidime/clavulanete and cefotaxime, cefotaxime/clavulanate as described at CLSI. I don't see any zone at some of my isolates. it means Esbl positive isolate. or this is false result

    Bhoj R Singh · Indian Veterinary Research Institute

    Dual disc (ampicillin and ampicillin subactam and or amoxycillin and amoxyclav) testing is also good indicator and now several molecular tests based on PCR are available. Better consult CLSI 2014 Guidelines.

  • Luisiana Cundin added an answer in Fractional Derivative:
    What are the geometric interpretation of fractional derivative operator (i.e Saigo-Maeda operator)?

    Fractional integration and fractional differentiation are generalizations of notions of integer-order integration and differentiation, and include nth derivatives and n-fold integrals (n denotes an integer number) as particular cases.Because of this, it would be ideal to have such physical and geometric interpretations of fractional-order operators, which will provide also a link to known classical interpretations of integer-order differentiation and integration

    Luisiana Cundin · Die Wand : leben heißt kampf

    There is no consensus on what they mean geometrically. Here are a few papers



    The upshot is that fractional derivatives have greater and wider dependencies on the space they live on...this implies they are highly directional or very sensitive to direction.

  • Agasthya Thotagamuwa asked a question in Tigers:
    What parameters to study to findout suitability of tiger beetles as indicators of environmental health?

    I'm trying to use tiger beetles as indicators of Environmental health. But I feel the soil and climatic parameters along is not sufficient to support the topic. I would be grateful if you could provide some ideas.

    Thank you


    Climatic-Temp,solar rd,humidity

  • Latreuch Zinelaabidine added an answer in Finite Difference:
    Can we calculate the the anti-difference operator of exponential functions?

    There are many functions whose anti-derivatives (primitives), even though they exist, cannot be expressed in terms of elementary functions (like exponential functions, logarithms, trigonometric functions, inverse trigonometric functions and their combinations). I want to ask if it was the same for anti-difference operator of some functions. In other words , can we express the anti-difference operator exponential functions "exp(P(x))" in terms of elementary functions?

    Latreuch Zinelaabidine · Université Abdelhamid Ibn Badis Mostaganem

    Can you explain me more Dr Kelly.