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  • Napoleon Ono Imaah added an answer in Slum Tourism:
    Is there any research comparing different types of pro-poor tourism?

    For example comparing the results of slum tours run by a community versus run by an outside company. Comparisons of volunteer tourism and educational slum tourism. Comparisons between volunteer eco-tourism, and educational but not volunteer related eco-tourism. Thanks. 

    Napoleon Ono Imaah · Rivers State University of Science and Technology

    I inadvertently deleted part of a discussion. is it possible to retrieve it?

  • Marilyn J. Smith added an answer in Jet Propulsion:
    How does the dissipation of a supersonic under expanded jet depend on grid fineness and aspect ratio ?

    I have recently tried to simulate the acceleration due to friction in the a micro channel flow. I find that even though the peak mach numbers match up with previous experiments, the jet breakdown occurs much sooner than expected.

    This gives birth to the question on whether the making the grid finer near the nozzle exit and continuing till the boundary would help carry on the jet further, how influential would this be.

    In my understanding, having a high aspect ratio cell would lead to more dissipation, can anyone help me in understanding how much effect would the cell aspect ratio would have on the jet breakdown.


    Marilyn J. Smith · Georgia Institute of Technology

    This is a multi-fold question.  The primary issue is the type of turbulence modeling you are using - LES is best, but perhaps not practical.  From your problem description, you should be using at minimum a 2-equation model such as Menter's SST (fully 3D).  Even better would be a hybrid URANS-LES approach - even DES would help. Next is your spatial scheme and its inherent dissipation.  If you are using a commercial CFD code, watch out as dissipation is added for code robustness, but it can interfere with your solution. With respect to the mesh, it depends on the problem.  A grid study is typically necessary, and I recommend it here, though you can do a rapid assessment in 2D steady to determine the mesh dependency before moving to 3D unsteady.  Make sure that your y+ at the wall is less than 1 and your stretching ratio gives you 35-50 points in the boundary layer.  For aspect ratios, obviously a 1:1:1 is optimum, but usually not practical.  Do that mesh refinement study (halve the mesh in each direction and compare convergence and important quantities until they change less than what you can tolerate in your simulation). Set any dissipation terms to the lowest you can set them without loss in stability.

  • Asif Khan asked a question in Stigma:
    Is there any method to induce invitro flowering in Saffron (Other than using phytohormones) ?

    I am working on saffron and my project is to in vitro induce flowering in saffron. In literature i didnt find any successful flower induction in this specie instead stigma or stigma like structures are reported. I want to know is there any method that can induce flowering in saffron or let say monocots? (Using different combinations of PGR is the first one but none of them got successful results)

  • Fatma Meligy added an answer in Contamination:
    How can I prevent cell culture contamination?

    we usually used HEK293 cell line for analysis our results, but for last few weeks I suffer a lot of cell contamination. Characteristics of contamination is also unique. To prevent contamination I changed my cell line, medium but there is no positive outcome. Every time when I divide my cell there is no contamination, but after 1st cycle when I again divide my cell some cells are contaminated some are not, but after 2nd cycle most of the cell become contaminated. Under microscope there is many black spot and this become visible in 3rd cycle, a hazy white suspension. I cleaned my incubator, change medium several time, autoclave each and every bottle, every time before work rinse work station with ethanol. Moreover my other lab mates have not this problem.

    I really can not understand this situation. Can any one help me with their experience.

    Fatma Meligy · Assiut University

    I think it is better to use antibiotic anti mycotic  and before opening or closing any bottles especially freezing vials expose the openings to a flame

  • Hussam El-Gayar asked a question in Pharmacological Research:
    I have a new natural compound and I would like to start LD50 in vivo . I have only IC50. From any dose I start?

    Pharmacology researchers

  • Erkki J. Brändas added an answer in Theoretical Physics:
    Is the concept of field the proper way to describe physical processes?

    What is a field? Everywhere around a 'source' of the field, if we put a 'test particle', then a 'force' will be applied to it, coming from the source.
    This definition has a critical drawback:

    • if you calculate, using volume integrals, the total energy of the field , then you will find it infinite. Is this acceptable?

    On the contrary, there exists the interaction from a distance view, where a force is applied to the test particle only when it is being present in the neighborhood of the source. So, we have not any kind of infinite energy here.
    Which approach do you believe that is correct and why? 

    Erkki J. Brändas · Uppsala University


    There must be some unnecessary and clever fudging going on to "repair" the violation of the exact canonical commutation relations between conjugate quantities imparted by finite space representations. Conjugate operators with absolutely continuous spectra are particularly unsuited for a traditional finite space analysis.

  • Will K Reeves added an answer in Flavivirus:
    Can Aedes albopictus cell lines be used for Rhabdovirus?


    Will K Reeves · Air Force Research Laboratory

    Yes they support some of the Rhabdoviridae.  Vesiculovirus grows on some of the cell lines quite nicely.  I doubt you could get Lyssavirus to live in insect cell lines however.  There is a good chance that Ephemerovirus would also grow on Aedes cell lines but I don't have direct experience with the genus so I'm not sure.

  • Monica Patrascu added an answer in Functional Equations:
    Could it be possible implementing the fitness function of GA code in matlab to work with simulation rather than equations?

    I chose the GA for optimization by writing the program using ga code in matlab. This program is ok if I put the terms of fitness function as equations; for example:
    When I run the program the ga graphs and results is fine, and par=10.
    However, when I put these equations as a model in simulation, the ga graphs (best value) is constant (line) which is incorrect.
    My issue is that I need to import y1 from the simulation and y2 from data results to estimate par.
    Really I got stuck in this point which is how can I use ga with simulation.
    Moreover, I can share the knowledge with who is interested in.


    Monica Patrascu · Polytechnic University of Bucharest

    Oh, hello again. I forgot to check the questions, sorry, I don't get notifications. Here is an already implemented example of GA and simulink models: http://www.mathworks.com/matlabcentral/fileexchange/51072-gaot-ecm--extension-for-control-and-modeling

    I hope it's not too late!

  • Hanin Beidas asked a question in Motor Learning:
    What are the available tasks for testing motor sequence learning in children ( 5-7 years old)?


    I am looking for a simple task that tests procedural motor learning performance in children (ages 5.5- 7 years old). Thank you. 

  • Moiseev K. G. added an answer in Fractal Dimension:
    Is it possible spectral fractal dimension be used in calculations of the surface structure or volume?


    Is it possible spectral fractal dimension be used in calculations of the surface structure or volume?


    Moiseev K. G. · Research Institute of Agrophysics, Russian Academy of Agricultural Sciences

    A pleasure to read, thanks again.

  • 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 · University of Massachusetts Amherst


    Your I! Is always involved in your conscious processes, including the construction, expression, and neuronal storage of your mental propositions. But not all of your propositions are constructed with a synaptic link to your I-token -- your I!, a neuron representing your core self. This requires an understanding of the self image -- one's personal narrative -- as distinct from one 's core self. I 'll try to give some examples later.

  • Luisiana Cundin added an answer in Mathematics:
    Is there a method for calculating zero-derivative points without using derivative?

    Characterizations of zero-derivative points of C1 functions in several variables, which do not explicitly require derivative, are known, see, e.g. "On the behavior of functions ..." Inter. J. Opt: Theory, Methods, Applications 1(2009), available on Google.They are also mentioned in some answers to the ongoing  RG question "Is there a book in English..." These results have been found useful for verifications of optimality, in sensitivity theory, operations research, economics, etc. How can  they be used to actually  calculate zero-derivative points?

    Luisiana Cundin · Die Wand : leben heißt kampf

    One more point: once algebraically carrying out the terms, for at least polynomials, the leading term is the derivative, if you realize all other terms, minus one, equal zero near the neighborhood of x* -> 0. Finally, the one undesirable term that remains has a pole and that can be discarded for it does not contribute to the real part of the solution.

    e.g. x^5 => ((x+x*)^5-x*^5)/x* = 5 x^4 +x^5/x* + 10 x^3 x* + 10 x^2 x*^2 + 5 x x*^3,

    By inspection, in the limit of x* -> 0, all terms can be disregarded, except 5 x^4. The reason for seeking that limit is that is where the function is flat, with regard to the variable x*. Lastly, the pole contributes in the imaginary plane and can be disregarded for our purposes.

    Although, this still is taking the derivative, essentially, but does remove a lot of the formality usually associated. 

  • Miłosz Wieczór added an answer in Gromacs:
    How do I correctly install a force field on GROMACS for phosphorylation?

    I've been trying to install this new ffG54a7 GROMACS force field for post-translational modifications : http://vienna-ptm.univie.ac.at/?page_id=100

    I copied the downloaded folder into the "gromacs_installation/share/top" folder, and the force field seems to be installed fine since it appears on the list of available force fields when I use pdb2gmx, and it can be used and works without crashing for standard sequences.

    However, whenever I use it on a sequence that has, say, a Y2P residue (which is a phosphorylated tyrosine), from a PDB file generated by the PTM tool on their website, I get a
    Fatal error: Residue 'Y2P' not found in residue topology database

    So I went to check the .rtp files, and there exists a Y2P entry in the gromos54a7.ff/aminoacids.rtp file. There also is one in the aminoacids.dat and residuetypes.dat files in the same directory.

    I contacted the forcefield team and they can't see where the problem comes from. I tried with Gromacs 4.6.3 and 4.6.7, on two local computers and a cluster and get the same problem.

    Is there something I'm not seeing ?


    Miłosz Wieczór · Gdansk University of Technology

    If you make a slight change in your .rtp file in the working case, does it affect the resulting topology? This way you can make sure that your pdb2gmx recognizes the right .rtp.

    For me, the most plausible source of your error is that the file residuetypes.dat should be in the *parent* directory (that is, .../share/gromacs/top) and not in the .ff directory. They might have put it in the .ff folder to avoid overwriting any pre-existing custom version of the file, and apparently assumed that you'll mv it by yourself.

  • Thomas Adejoh added an answer in Radioactivity:
    Is it dangerous for the staff, inpatients or outpatients at a hospital to care for radioactively contaminated patients or to be near them?

    researcher who has experience in radiation 

    Thomas Adejoh · Nnamdi Azikiwe University Teaching Hospital, Nnewi, Nigeria

    Thanks, Hanno  Krieger  for  the  update.

  • Paul John Wells added an answer in UV Radiation:
    Does anyone have experience in analysis in visible range using CE7100 agilent systems?

    We have tried to replace UV lamp with a LED system, but the intensity of the source is not enough. Does anyone known commercial visible source suitable with CE7100?

    Thank you 


    Paul John Wells · Broadcom Corporation


    You could use a fibre optic bundle to get the light in.  That way you could have the laser outside the CE7100.

  • Josef Loeffl added an answer in Roman History:
    Did veteran colonies founded by Augustus have their own urban militia for self defence?

    I've read much about Augustus' placement of veteran colonies in places like Antioch in Pisidia.  There was clearly an intent to use the placement of these colonies for regional defence and pacification.  I have found much on the social organisation of the colonies, and their role in providing army recruits.

    I can find little on how the colonies were defended.  Were they simply reliant on the nearest Roman army units?  Did they have army cohorts stationed at them?  Or did they also maintain their own militias both for self defence and for the training of young men for later army service?

    Advice on any academic papers on this subject would be appreciated.  Thanks

    Josef Loeffl · University of Applied Sciences Coburg

    The question of (self?-)defence of Augustan colonies has perhaps a connection to a Lex de Vi Publica...

  • Artur Braun added an answer in Silver:
    How can I fabricate a Ag/AgCl reference electrode?

    In silver/silver chloride reference electrode, If electrons flow from the copper wire through the silver wire to the electrode AgCl pellet, they convert the AgCl to Ag atoms and the Cl - ions become hydrated and enter the solution. If electrons flow in the reverse direction, Ag atoms in the silver wire that is coated with AgCl give up their electrons (one electron per atom) and combine with Cl –ions that are in the solution to make insoluble AgCl. [http://www.bionanotec.org/Lectures/Membranes/Contents/IBioelectricityIonsinsolution8/ibioelectricityionsinsolution8.htm]. 

    Does it mean that I have to have an unchloridized portion of the silver wire dipped into the chloride solution of the reference electrode so that it can be converted into silver chloride when electron is flowing in the reverse direction? Or I can simply chloridize the whole silver. 

    Assuming it's okay to chloridize the whole silver wire, all the Ag/AgCl reference electrodes I have seen so far have a portion of bare silver without silver chloride coating- what is the function of this portion?

    Artur Braun · Empa - Swiss Federal Laboratories for Materials Science and Technology

    ok, makes sense, thank you.

  • Narayanan Bhattathiri added an answer in Personality:
    Does the digital personality die when a person dies himself?

    Many of people have a legacy of scientific, literary, photographs and correspondence within the digital world (such as e-mail). When a person dies, who has the right to access  his legacy and personal correspondence?

     Are there laws specify who can accessed or owned the legacy after the death of the person?

    Narayanan Bhattathiri · Sansar

    Dear Qasim

    I never thought of this, and the info given by Sudev was very revealing.

    If a person dies and later becomes very famous, FB, Google Drive, Google pHotos, Whatsapp, etc., may become the owners of his digital personality.

    This sure brings out the need for definite National/International laws.

    May each of us is selling off ourselves to these Giants by signing the agreements.

    What is the policy of ResearchGate in this regard I wonder. Does anyone know?


  • Mohamed El Naschie added an answer in Dark Matter:
    What are you thinking about that old conflict of theories by Nikola Tesla and Albert Einstein?

    It gets new meaning with the introduction of dark matter.

    And also how little attention did the works of Dr. Tesla drew.

    Mohamed El Naschie · Alexandria University Alexanderia Egypt


  • John c Frain added an answer in Econometric Modeling:
    What is the frequently used software package for econometrics modeling?

    Econometric modeling software those are popular and user-friendly for researchers.

    John c Frain · Trinity College Dublin

    http://www.autobox.com/pdfs/econometrics.pdf is a compendium of econometric software. Each package is described by the authors. https://en.wikipedia.org/wiki/Comparison_of_statistical_packages is a comparison of various statistical packages. 

    A correct answer to your question depends on what kind of econometric analysis you wish to do.  I have used gretl (http://gretl.sourceforge.net) for a lot of my analyses. It is easy to use and has a good graphical user interface (gui).  Commands issued  through the gui can be saved, edited and rerun in a parallel batch system. It also has very good data import/export  and graphics facilities.  I use R for more advanced work.  For simulation of economic models I would recommend Octave or Matlab. Gretl, R and Octave have the advantage that the are free.

    I have used RATS, Oxmetrics, Microfit, Stata, Mathematica. I used SPSS and SAS on mainframes about 35 years ago and have not used them since so I can not comment on the current programs.    

  • Upasna Rai added an answer in Activated Carbon:
    What is the Boehm Back Titration Procedure on Activated Carbon Samples?

    When it is performed, with the reactant solutions containing the bases to determine the acidic groups against NaOH, to what pH is it run down?

    Upasna Rai · University of Florida


  • Fernando Cardoso Cotelo asked a question in GLUT:
    Who has already had the opportunity to play GIROS/GLUT, a pedagogical game to teach the workings of land markets and what did you think about it?

    I had the opportunity to play it with a group of Latin American professionals in Montevideo in June 2015 and it was a very interesting experience. The Game was idealized by Martim Smolka from Lincoln Institute of Land Policy and Carlos Morales from Erasmus University.

  • Titus Sobisch added an answer in Material Characterization:
    How do I measure the density of small quantities of material (glass)?

    I need to measure the density of glasses, which unfortunately I got in very limited and small quantities: around 50 mg, both in powder form and in bulk. I have been trying so far: Archimedes's method for determining the density (in ethanol - water sensitive material - and in air), Guy-Lussac pycnometer (the smallest I could find - 5ml - encountered problems with this also because of the liquid medium: ethanol/isopropanol, due to rapid volatillization). I have access to helium pycnometer as well, but to my knowledge, I need at least 2 g of sample for accurate determination. If somebody encountered this problem likewise, I would like to hear about a solution. Thank you in advance.

    Titus Sobisch · LUM GmbH

    Heavy liquid - polytungstate solution is commercially available and this wets glass. So proceed according to Archimedes as others suggested.

  • Henna Iqbal added an answer in BN-PAGE:
    Which can detect a stronger protein-protein interaction of the 3 ? Co-IP, BN-PAGE analysis or proximity ligation assay ?

    I have already done a Co-IP experiment to show that my protein of interest pulls down another protein in my bacterium, that is a part of an Outer Membrane complex. I need to verify this IP finding with another assay. I prefer in-vivo, since these are huge proteins and I don't know what part of each protein interact. I need suggestion if Blue-native gel could help equally ? Or in other words, can a blue native gel detect weaker or stronger or similar binding affinities as CO-IP ? Or would you think something like a Proximity ligation assay may work better than BN-PAGE ?



    Henna Iqbal · University of Oklahoma Health Sciences Center

    Thanks Vincent and Matthias. I like the diversity of ideas here!

  • Khalil El-Saghir added an answer in Urdu:
    Is it necessary to have bilingual experts (with formal education) for translating a questionnaire?

    While testing a questionnaire for its validation and cross-cultural adaptation, is it necessary to have bilingual experts with formal education? E.g translation of Nordic questionnaire into Urdu (is it necessary that the translators have a formal level of education/degree in Urdu or English?)

    Could it be done by someone who is brilliant at both languages but does not have formal education? 

    Secondly, how is the sample size selected for translation-based studies like this? Inclusion and exclusion criteria and number of participants etc...

    Thanks in anticipation.

    Khalil El-Saghir · Wayne State University

    My concern would be with how "brilliant" is measured (e.g., level of expertise in both L1 and L2, knowledge of the subject matter and the scope of the treatment, etc) and whether or not such bilingual translator is capable of ensuring the validity of the questionnaire, as per Dr. Yaghoubi-Notash.

  • Helene M van Ettinger-Veenstra added an answer in Resting State fMRI:
    At which point in time it might be best to do a resting state fMRI?

    At which point in time it might be best to do a resting state fMRI? I asked myself , should i do the resting state before or after the fMRI Task? What are the Advantages and Disadvantages?

    Helene M van Ettinger-Veenstra · Linköping University

    Gregory Kroliczak, regarding the training effect on resting state, what is the literature you base your statement on about 3 pre- and 3 post-scans? I would be obliged if you would like to share some references.

  • John Oluwafemi Olla asked a question in Information Science:
    I need thesis topic from the combination of Education, Economics and information science?

    I need thesis topic from the combination of Education, Economics and information science

  • Charles Anukwonke added an answer in Landscape:
    Can anyone provide literature on landscape Conservation and Management?

    I am in dire need of useful literature on landscape conservation and management to enable me develop and actualize a task. Thanks

    Charles Anukwonke · Anambra State University

    Thanks alot colleagues

  • Bruce Weaver added an answer in Logistic Regression:
    How can I adjust age and gender in spss using logstic regression?

    logistic regression

    Bruce Weaver · Lakehead University Thunder Bay Campus

    If you have age in years, treat it as a covariate, as Basheer suggested.  But note that this forces a linear relationship between age and the fitted log-odds.  You might want to investigate the possibility of a non-linear relationship.  To relax that constraint, and allow a U- or inverted U-shaped function, include Age and Age2.  To relax the constraint even further, allowing  a cubic relationship (i.e., 2 changes in direction) include Age, Age2 and Age3

  • Muhammet Samet Kılıç added an answer in Amperometric Biosensors:
    What are the major advantages of p-Benzoquinone using as mediator in amperometric biosensor ?

    Redox mediators such as the ferricyanide ion, p-benzoquinone, or
    dimethylferrocene can be used as electron carriers allowing redox
    events within the cell to be monitored.

    Muhammet Samet Kılıç · Bülent Ecevit Üniversitesi

    I used p-benzoquinone as a mediator for enzymatic fuel cell. Maybe this publication (below) can help you.