Q&A

ResearchGate Q&A lets scientists and researchers exchange questions and answers relating to their research expertise, including areas such as techniques and methodologies.

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  • Edwin Gnanadhas added an answer in Regional Tourism:
    Do you think the classic travel agencies will eventually disappear from the market due to the use of Internet in business?
    Will the increasing use of the Internet and the emergence of online travel agencies positively or negatively affect classical travel agencies? Will classical travel agencies therefore disappear from the market?
    Edwin Gnanadhas · Scott christian college

    dont think that all the people in india are having internet facilities. only few percentage having net connection. out of this only few percentage are able to use the facilities. So my opinion the classic travel agencies will flourish.

  • Mostafa Eidiani added an answer in Frequency:
    How do I model the harmonic impedance of the network?

    Is it possible to consider the frequency dependency of the short-circuit impedance of the network for the harmonic load flow and frequency sweep analysis?

    Mostafa Eidiani · Khorasan Institute of Higher Education

    For being able to consider frequency dependent network impedance you must use the Voltage Source element instead of the External Network. The short circuit impedance must here be defined by R and X in Ohms.
    On the Harmonics-page, frequency characteristics for R and L could be defined.
    For more information about the Voltage Source, refer to the technical reference of the element AC Voltage Source (ElmVac).

  • Scott Russell added an answer in Meaning:
    Does philosophy need a language that admits of no contradictions?
    Some philosophers/mathematicians (e.g., Tarski) laid some emphasis on construing a language that does not admit of contradictions, and were even ready to pay the price (if you want to call it thus) of excluding semantic terms and the like. I came to ask myself if it is actually a problem (rather than an advantage) of a language that it is able to express many things (including contradictions). What do you think?
    Scott Russell · University of Michigan-Flint

    Would synonymy exist in such a language, Cameron?

  • Burt Browne added an answer in Coastal Engineering:
    How do I assess the likely settlement of a breakwater?

    In a European/UK context.

    Burt Browne · Royal HaskoningDHV

    I do not understand what you need

  • Social media: Downvoting and degrading in social networks – What are the reasons? - What are the reactions?
    We have recently seen a lot of down-votings in some threads. We also saw different kinds of reactions on this phenomenon. I would like to ask a question about these reactions.

    First I assume that there are several possible reasons for downvotings: dissent – misunderstandings – misuse of buttons without knowing it– a social scientist who writes a paper about the reactions – a test carried out by RG – some technical problem, etc.

    I would like to have a discussion about the reactions on the part of researchers. We have seen calls to ban down-voters or to cancel their anonymity. Elections in democracies are anonymous and there are good reasons for this. I think most of us agree about some basic traits of democracy, the right to stay anonymous is among them. What about these basics in social media?
  • Zoltan Varallyay added an answer in Interpolation:
    How do you show result on an unstructured mesh grid with Matlab?

    I used to interpolate the result to structured grid and display with 'mesh' or 'surf' functions, but sometimes the interpolated data was outside of the boundary. I have tried different interpolation method, but it doesn't help.

    Zoltan Varallyay · Furukawa Electric

    Interpolation data will appear outside of the boundary if you have a complex shape with concave geometry. Probably you did it with the meshgrid function. The only solution I know is to fill your array with NaNs or zeros in those unwanted points. Obviously you have to know the geometry in this case and write a few additional lines with the necessary conditions.

  • Is the economic potential of invasive pines getting explored and exploited in any part of the world?

    Many invasive pines have huge economic potential which can contribute a lot in the sustainable development of the area. How far this is tapped in the global perspective?

    Gustavo Javier Chacón · Universidad del Azuay (UDA)

    Dear Gautam,

    It will be great to discuss these issues in detail. We will have a newer report by the end of October in Spanish that I can send it to you. Is Spanish a problem for you? I will eventually translate it into English...

    Regards...

  • Isabel Ferreiro asked a question in Proximate Analysis:
    Can anyone help me in a matter concerning contents of lignin, cellulose and hemicellulose?

    I am trying to predict the contents of lignin, hemicellulose and cellulose from the elemental/proximate analysis through correlations. Until now I have found one article with this kind of information (Sheng and Azevedo, 2002), but I would like to compare this method with another. Does anyone know any other method, that can be shared?

    best regards

  • Stefano Gennai added an answer in Meta-Analysis:
    How big is the risk for regression in a single group meta-analysis?

    I'm performing a single group meta-analysis with continuous data. Data are from different follow-up  points as efficacy evaluation of a single surgical intervention. How big is the risk for regression to the mean creating effect?

    Stefano Gennai · Università di Pisa

    Dear Emilie,

    thank you very much for your prompt response.

    Data derived from the control groups of different studies, you can take a look at the file I'm attaching you to better understend the disegn of the meta-analysis. You can look here for the risk to the mean definition  http://en.wikipedia.org/wiki/Regression_toward_the_mean .

    Best Regards

  • Mahfuz Judeh asked a question in Teamwork:
    How to build a teamwork culture in universities?

    Building a conductive environment to teamwork in universities is a process requiring a plan and specific activities to support the teamwork solidarity.

  • Omar Fergani added an answer in Machining:
    What is the effect of machining temperature on grain size?

    People have been studying machining effect on microstructure and especially the average grain size. Most of the results are specific to grain refinement. Recently, I have been observing a grain growth on the machined surface in some specific cases. Does anybody have a comment about the physics behind such a behavior?

    In fact, diffusion based grain growth can be the source, however, the temperature rise was observed in a very short time.


    Omar Fergani · Georgia Institute of Technology

    Hi,

    This is exactly what I was thinking when started working on some of these aspect. I suspected that although people have been presenting papers based on the assumption that refinement alone will happen was to be verified. 

    What we see after investigation and using conditions where the cutting will generate high temperature is that we definitely have refinement, but this refinement is reduced due to the temperature that is responsible of other phenomena, such as dislocation relaxation, or atoms diffusion that will definitely lead to grain growth. Experimental investigation were performed on two materials: AA7075, where we observed a slight refinement on the machined surface due to the growth of the precipitates. While in Ti64,  we are trying to use TEM to see if there are some nano scale grains on the surface otherwise, we will have to make the same conclusion as for Aluminum.

    I totally agree with your guess!

    Sincerely,

  • Evans Wabwire added an answer in Climate Change:
    What is the best model to use when analysing climate variability and rural adaptation?

    I am looking for a best model to assess climate variability (rainfall and temperature) and its implication on rural adaptations.

    Evans Wabwire · The Catholic University of Eastern Africa

    Thank you Rajiv Pandey, the papers are so helpful.

  • Oriana Gava added an answer in Food Supply:
    What indicator can you use to asses biodiversity conservation in wheat to bread chain?

    To assess multiple dimensions of sustainability in traditional vs industrial food supply chains.

    Oriana Gava · Università di Pisa

    thanks

  • Vera B Dugina added an answer in HaCaT:
    Any ideas on the 'best' culture medium composition for HaCaT?

    We're trying to get a HaCaT cell culture going for the first time in our lab. However, opinions on the optimal medium composition seem to differ. In general it's DMEM + 10% FCS + 1%Pen/Strep. But what about DMEM? With or without Glutamax? And how about glucose levels, L-glutamine levels, essential amino acids, insulin etc. 

    Vera B Dugina · Lomonosov Moscow State University

    Immortalized keratinocytes HaCaT are going well and keep good ("normal") morphology in DMEM (see Clark) with glutamine as well as DMEM with glutamax. These cells are better without F-12 and even in 5%FBS.

  • What determines the number of layers in an artificial neural network application?

    Resources say that 2 layers are sufficient for most applications. But I've also heard the more the number of layers in the ANN, the more complex calculation it will be able to perform. How do you exactly know how many layers to include in your application? Is there any way to theoretically determine the optimum number of layers?

    Ali Naderi · Semnan University

    Optimal number of the neurons in the hidden layer and number of hidden layers determine by trying different networks. It is found that, best structure of the ANN model has minimum value of performance function (MSE, MRE and MAE and etc).

    In addition, you can combine ANN and optimization methods ( GA ,PSO and etc) to choose best number of hidden layers and neurons.

    Good luck

  • Mary T Silcox added an answer in Zooarchaeology:
    Can you answer my question on specimen Counts in Paleontology (and Zooarchaeology)?

    Most abundance counts in paleontology and zooarchaeology use one of two major methodologies, Number of Identified Specimens (NISP) or Minimum Number of Individuals (MNI). However, in many situations, I have seen fossils from a given locality catalogued as several different specimens, even if it is obvious they belong to a single individual. For example, in several cases, a complete mammal skull will have the cranium be given one specimen number, the left dentary a second, and the right one a third, even if the jaws were found in occlusion. In these situations, especially if the counts are being done on a locality where elements are not found close to one another and therefore two given specimens are normally unlikely to belong to the same individual (e.g., a multi-square kilometer outcrop of a geological formation), does one count associated and articulated parts as a single "specimen"?

    Mary T Silcox · University of Toronto

    In answer to the question asked, if there is a very good reason to believe that material belongs to one individual, standard curatorial practice would be to catalogue them with one specimen number.  But if there is any doubt, it would likely be preferable to catalogue them with separate numbers, perhaps with a note in the catalogue indicating a possible association.

  • Bharat Kumar asked a question in Formulations:
    Why relativistic formulation is better than non-relativistic formulation in nuclear physics ?

    Can any one explain briefly? Why this is needed?

  • Marco Ceia added an answer in Python:
    An open source high level package for GPR processing and visualization?

    What is the best Matlab (or Python) - open source high level - package for GPR processing and visualization - to work on as an user, or to software development?
    What about OpenDtect/Madagascar - again - for GPR processing and visualization - to work on as user, and to develop? Is there enough available plugins?

    Marco Ceia · Universidade Estadual do Norte Fluminense

    If you can save your GPR data in SEG-Y format, you can use MATLAB with Crewes scritps (www.crewes.org) for processing and visualization of 2D data.

  • Michael Linnebacher added an answer in Mycoplasma:
    What are the most effective ways to control mycoplasma contaminations in tissue culture?

    Helpful hints to better control mycoplasma contaminations in the tissue culture.

    Michael Linnebacher · University of Rostock

    There are two possibilities:

    either you want to eradicate them with the risk of loosing your culture. Then Plasmocin (as Sreekumar suggested), MRA (from BioRad) or similar agents are worth trying. The basic for these agents are antibiotics: fluoroquinolones, tetracyclins, pleuromutilins, and macrolides. There is a genius protocol from the DSMZ: look into PMID:
    24733241 from Uphoff and Drexler.

    However, there are several heavily-contaminated cell lines that will look like mucoplasma-free after hard treatments but later on, the infection comes back! Be aware of the need to repeat testing regularly.

    The second possibility is to make novel cells - of course this depends on the tissue origin of your cells.

    Finally, it is wise to have contaminated or treated cell cultures separated from the ones that are (or at least should be) free of mycoplasma.

    Good luck.

  • Mário Rui Castro added an answer in Arabidopsis:
    How can I obtain Arabidopsis leaves that are big enough for an LI-COR chamber?

    I am measuring leaf conductance in Columbia plants and the chamber area is 6 cm and no Arabidopsis leaf would ever reach this size!

    What can I do to get accurate readings? Modify the chamber? or manipulate growth conditions to obtain bigger leaves?

    Mário Rui Castro · Universidade da Beira Interior

    Hello Radwa Mohamed,

    It looks like you have an all around chamber. Its good for much everything, but not specific enough for your job. Well, Li-Cor has chambers that are specific to Arabidopsis. Please see here: http://www.licor.com/env/products/photosynthesis/chambers/arabidopsis.html

    Also, I believe you do not need to fill the entire chamber with leaf. I worked with pine trees and the chamber was 2x6cms. Each pine needle was 2mm broad at max. Try testing the chamber with other size leafs (other species) and see if you get similar results.

    Regards

  • Sivanandam S. added an answer in Neuropathy:
    Does anyone knows whether during exercise heart rate is higher in patients with diabetes who have also an autonomic neuropathy?

    as compared to healthy people in a similar way as what can be observed at rest?

    Sivanandam S. · SRM University

    Dear Maria,

    Yes, when a healthy adult exercises itself, the heart rate will increase; further, the diabetic subjects are highly vulnerable to increased blood pressure as either the arteries of the subject might might have lost it's contractility or may be weak to adjust for the physical as well as physiological demands.

    The inflammation of the artery and the bad cholesterol deposits in the inner lining of the artery would have attained the advanced stage by the time of onset of the diabetes and the same will be diagnosed only during the presence of possible symptoms; by that time an irrecoverable damage would have caused in all the major arteries (ex. tibial, femoral, Carotid artery to brain, coronary artery etc.,) and minor arteries ( ex. that supply blood to the skin, eyes, ears, kidney, upper & lower extremities etc).

    Thereby, in a diabetic subject without neuropathy, the above said factors may have increased chances of shoot up in the blood pressure during exercises  and undoubtedly, the query results will be true for the diabetic subjects with neuropathy complications.

    Regards,

    S.Sivanandam

  • Andrés Cardona added an answer in MCF-7 Cells:
    How much FBS do I need to add to the medium in order to prevent cell division in 96-well plates?

    My MCF-7 cells are dividing in 5% medium, but I need to keep them alive and prevent them from division...

    Andrés Cardona · Instituto Tecnológico Metropolitano

    I also think that you could reducing it to 2%. I have maintained HepG2 and SkHep1 cells in basal medium supplemented with 2% FSB, when I need a low rate of cell prolifetion.

    With 2% FBS you can increase the "time needed" to cell division at cell culture, like a slow growing

    regards

  • John L Hostetler added an answer in SIEMENS:
    Can anyone help with; Thin film conductivity measurement ?

    I am working on thin films. I want to measure thin film conductivity. I have some result about thin film resistance in (Ohm/square) Unit, which collected by Four Point (Jundel rm3-ar) analyzer, and i don't know how to convert this figures to (Siemens/Meter) Unit. 

    John L Hostetler · United Silicon Carbide

    Graphene is definitely anisotropic, so conduction through the film vertically will be different than along the film laterally.  Sounds like an interesting experiment.  

  • GC-MS derivatization in Mumbai or anywhere in India?
    Does anyone know, where in Mumbai or in India, sample derivatization is being done for Gas Chromatographic detection?
    Varoon Singh · Defence Research and Development Organisation

    You can use many derivatization techniques for derivatization like methylation by using diazomethane, silylation by using BSTFA, MTBSTFA, TMSCl, TBDMSCl etc. search sigma aldrich guide on silylation on google you will find all the reagents available for derivatization and their mechanism also.

    You can have a look on papers published by our group which deals with the derivatization and extraction then analysis by GC-MS.

  • Manuel Schnabel added an answer in Fermi Level:
    Can I calculate the quasi Fermi levels in a p-n junction solar cell in the case of the absorption of a single photon?

    We know that the "driving force" that separates photo-generated charge carriers in a solar cell is not merely the built-in potential of the junction, but the gradient of the electrochemical potential which takes into account both electrostatic potential and concentration gradient of charge carriers.

    If we consider now the absorption of a single photon within the space charge region of a solar cell p-n junction, this locally creates a small increase of charge carrier concentrations and thereby also a splitting of the quasi Fermi energies (=electrochemical potentials, Fn,p) of electrons and holes. Is it possible to draw the quasi Fermi levels, for example under short-circuit conditions?

    My problem is that I do not understand how a separation of the e-h pair can happen when considering the electrochemical potentials. I am aware that, since the excitation takes place within the built-in electric field of the junction, the carriers will drift into their respective majority regions. But from the electrochemical point of view, there should only appear a "delta-like" peak in Fn and Fp, and since there is no gradient of the quasi Fermi levels, no directed current can result..

    Manuel Schnabel · Fraunhofer Institute for Solar Energy Systems ISE

    If you're interested in cells where absorption takes place in the depletion region you can look at the literature on a-Si:H solar cells. These usually have a p-i-n structure because the inbuilt field is needed to improve the carrier extraction process. I am also unsure how that works without consuming some of the electrochemical driving force but maybe you can find the answer by reading the literature on these cells. I think there are some good transport mechanism papers by Crandall and Merten.

  • Can anyone suggest a simple protocol of esterification/transesterification of a glyceride using n-butanol as the solvent, as well as the catalyst?
    For a high yield of an ester, a catalyst that will give an optimum yield is needed in the esterification reaction.
  • Andrea Vannini added an answer in Glyphosate:
    What is the simplest way to extract Glyphosate /AMPA from soil samples?

    I am learning to use an HPLC in with a UV detector.

    Andrea Vannini · Università degli Studi di Siena

    This is a very simple method!!!

  • Baldwin Pine asked a question in MODIS:
    What is the best way of dealing DEM and NDVI (Vegetaion cover) with different spatial resolution?

    I am doing erosion modelling, two of the parameters needed would be C factor Map ( ill be using MODIS time series which is 250 x 250 m) . DEM is 5 meters. How will i deal with this. And any idea/methods how can I extract C-factor from NDVI.? Thanks in advance.

  • Problems in sample derivatization for gas chromatography?
    I have a plant extract, for which I tried derivatization using MSTFA and pyridine. But I did not get any derivatives. Can you please suggest something?
    Varoon Singh · Defence Research and Development Organisation

    Remember one thing when you dry pyridine on KOH make sure you use it after distilling it because there are chances some of the KOH might remain in the Pyridine in dissolved form.

    If you are intereseted in other derivatizing agents, you can check the papers of our group in which aminoalchols are derivatized by using HMDS at room temp.