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.

Browse by research topic to find out what others in your field are discussing.

Browse Topics

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
  • Rosie Delaney asked a question in Area Studies:
    German research proposal?

    We've been asked to do a 700 word research proposal on anything related to Germany. Can anything think of anything maybe GDR related? I picked that as my area to study but I'm having difficulties narrowing it down and finding a proper title.

  • What does it mean to the fractional calculus if the constant is equal to zero in some definitions and not equal to zero in another's definition?
    Riemann–Liouville fractional derivative & Caputo fractional derivative & Modified Riemann–Liouville
  • Khaldi Brahim added an answer in Mobile Learning:
    What are the differences/similarities between personalized learning systems, learning recommender systems, and adaptive learning systems?
    One of the most important issues in the context of mobile computer supported collaborative learning is not only to provide information anywhere and anytime, but also to allow the mobile learners to find the most suitable information (and/or activities) and collaborate with the right persons. the systems mentioned above represent a good solution, so, what are the differences and similarities between them, and which one is more advisable to the m-learner group formation problem?
    Khaldi Brahim · Université des Sciences et de la Technologie d'Oran Mohamed Boudiaf

    you must know how does each one of them work, its features to get up differences and similarities, :)

  • Ute Hellmich added an answer in HSQC:
    How does NMR sample impurity impact HSQC quality?

    Hello , everyone! I have one question. I have one NMR protein with 10KDa with a degradation about 5% . Can I acquire such sample NMR spectra for structure calculation?
    Besides this, I want to know,how many percent NMR sample impurity can be tolerate in NMR HSQC. I saw one paper said that if a impurity is a very larger protein when target protein only 10KDa, it can be ignore? Is it reasonable?
    For such impurity, I think that it will affect our assign signal. Maybe sometimes, very low percent impurity can give some peak strong intensity. Thanks a lot!

    Ute Hellmich · Johannes Gutenberg-Universität Mainz

    Dear Chengkun, NMR is generally a pretty insensitive technique, so a little bit of protein degradation or impurities can indeed be tolerated. HOWEVER, it is almost impossible to make a general statement such as "5% degradation is still ok" because this will depend a lot on the specific details of your sample. One issue is that unfolded protein regions tend to give very sharp and intense peaks. These can overlap with peaks that are from the folded protein. When your impurity is a very large protein, it is possible that its tumbling rate is so unfavorable, that the linewidth are broad enough to essentially disappear. Again, this does not have to mean that ALL regions of this impurity are invisible in your spectra. If this second protein has a mobile loop for example, it may still show up as perfectly well resolved resonances. Secondly, when you have protein degradation of your target protein, it is not clear that the amount of degraded protein should always remain the same throughout the 2D and 3D experiments required for the assignment of your sample. The amount could initially be low enough but build up over multiple days of running experiments (depending on what kind of experiments you are doing). If you have impurities/degraded protein throughout your prep, I think it'd be worthwhile to optimize your sample preparation to get rid of these. If degradation occurrs during the NMR measurement, consider changing the temperature, maybe the buffer or salt composition or potentially add a ligand that could stabilize your protein? 

    I hope this helps a little bit and good luck with your project!

  • Aya Azam added an answer in Nanofiltration:
    Can we remove the pesticide residues from the milk by nano-filtration?

    Is it possible?

    Will the physical and chemical properties of milk change?

    Aya Azam · Benha University

    THANKS FOR ALL OF YOU

    BUT WHAT DO YOU MEAN BY ULTRA-FILTRATION ? ITS TYPE OF NANOTECHNOLOGY.

  • Robabeh Aeinehvand asked a question in Inversion:
    Can I use something else instead water in inverse miniemulsion polymerization?

    Can I use something else instead water in inverse miniemulsion polymerization?

  • Igor Novak asked a question in Chemical Grafting:
    What type of discharge plasma (i.e. barrier, radio-frequency, microwave...) can be best used for anti-bacterial treatment of polymer surfaces?

    Surface modification of polymers (e.g. polyolefin) is a straightforward strategy to render anti-adherence quality which deters the susceptibility to bacterial

    adhesion. This can be achieved by deposition of thin antibacterial

    layers tethered to the surface of polymeric support already

    chemically grafted with a spacer of a brush-like pattern. This

    multistep approach has aroused great interest thanks to several

    advantages such as convenient and controllable introduction of

    biocidal species with a high surface density together with precise

    localization and long stability of the grafted layers.

  • What is the best way to get RNA from distinct skin immune cell populations for gene array analysis?

    We would like to first obtain mouse skin, then isolate immune cells (e.g. gd T cells, macrophages, overall T cells) and then purify RNA and do microarrays. In addition, we would like to use the negative fraction (other skin-resident cells) as control. Has anybody done microarrays on e.g. gd T cells sorted from mouse skin in comparison to other skin cells and could share a protocol? Or any alternative ways to do such an analysis? Thank you!

    Daniel H Gonzalez Maglio · National Scientific and Technical Research Council

    Hi.

    In order to obtain different skin immune cell population it is useful to treat whole skin samples with dispase 25 mg/ml (2h, 37°C) to cleanly and easily separate epidermis from dermis, ans subsequently obtain epidermal and dermal immune cells independently by cell sorting. Unfortunely, I've never used cell sorting and I've studied whole epidermal and dermal RNA samples looking for cytokines, chemokines and other molecules.

  • Sahar Shojaei asked a question in Organic Food:
    How is organic farming in your countries? Do people want to use organic products?

    Traditional farming (of many particular kinds in different eras and places) was the original type of agriculture, and has been practiced for thousands of years. All traditional farming is now considered to be "organic farming" although at the time there were no known inorganic methods. For example, forest gardening, a fully organic food production system which dates from prehistoric times, is thought to be the world's oldest and most resilient agroecosystem. After the industrial revolution had introduced inorganic methods, some of which were not well developed and had serious side effects, an organic movement began in the 1940s as a reaction to agriculture's growing reliance on synthetic fertilizers and pesticides. The history of this modern revival of organic farming dates back to the first half of the 20th century at a time when there was a growing reliance on these new synthetic, inorganic methods (http://en.wikipedia).

  • Zoë Gaffen added an answer in Epinephrine:
    How to best detect catecholamines HPLC?

    Hey guys,

    I am currently working in a lab trying to detect catecholamines such as epinephrine, norepinephrine, dopamine and seratonin using HPLC. Although we have been able to detect these catecholamines we are having trouble quantifying due to having low efficiency levels when running and quantifying known standards to compare to. I am hoping that by describing our general set up someone may have more advice on better columns to use or maybe how to modify our mobile phase.
    We use a C18 ion pairing column with an acetate buffer at pH 4, a PBA spin column as the stationary phase and a glassy carbon electrode as the detector.

    Thanks for any and all possible help. Not the best with HPLC just trying to help solve our low efficiency levels...

    -Adam

    Zoë Gaffen · King's College London

    I was involved in detecting catecholamines in saliva samples, back in the late 1980s/early 1900s, for a sports physiology research project that some of our medical students had chosen to do. We derivatised the samples with OPT/Thiol, just 60 seconds prior to injection, to produce their Vicinal-diols, which were then detected quantitatively (for a range of catecholamine standards), although the physiological levels in 1ml saliva samples were in the femtomolar range, so most were qualitative estimations. At the time, I did not have a coulometric detector, we used a BAS electrochemical detector, measuring by 'current drop' on passing over a glassy carbon electrode. We mixed β-mercaptoethanol plus o-phthalaldehyde together then, 1 min prior to injection, we opened a switch connected to the integrator, mixed the sample 1:1 with this mixture, and loaded the 20ul injection loop, injecting onto the 30cm C18 reverse-phase column, and injected on the "t=0secs" signal, simultaneously closing the switch and marking the injection event on the recording.

    I don't think the data was published, as it was not quantified and it was an 'in-house' project within King's College, London, Chelsea campus.

  • Alfredo Pereira Junior asked a question in LTP:
    Is it a coincidence that in LTP methylation of the DNA of neurons is mediated by calcium ion entry through N-Methyl-d-Aspartate membrane receptors?

    Recently molecular biologists have recognized the importance of DNA methylation in epigenetic processes, confering a degree of plasticity to all cellular functions. This mechanisms operate in all living cells, tissues and systems.

    In the brain, one of the most powerful mechanisms of plasticity is long-term potentiation (LTP), which is induced by calcium ion entry through a membrane channel that contains the same kind of molecule.

    Is it just a coincidence or there is an evolutionary process that begins with the plasticity of single cells and develops to brain tissue plasticity, allowing register, storage and cognitive computation with more complex information patterns?

  • Jan Szulejko added an answer in Global Warming:
    Will recent warming hiatus with respect to mean temperature continue or not?

    2014 became the warmest year on record, without a strong El Niño. The so-called global warming hiatus (1998-2012) are widely concerned. In the following decade, global mean temperature warming will continue to slow down, or will rise much more rapidly than in the "slowdown" period? What are main physical causes responsible for inter-decadal changes of mean temperature?

    Jan Szulejko · Hanyang University

    The 18-year global warming hiatus will be likely following by global cooling at an average rate of 0.01 C per year for the next 20 years or so followed by global warming at an average rate of ~0.01 C per year for the next 40 years or so. Then the 60-year cycle will repeat. Since ca. 1600 (the end of Little Ice Age), the Earth has been warming at a linear rate of 0.6 C per century. Superimposed on this linear trend is a 61-year periodic variation of amplitude 0.2 C.

  • What can cause sodium to turn black in a glove box?

    I use sodium metal in a MBraun Ar-filled glovebox (H2O < 0.1 PPM, O2 <0.1 PPM). For some reason fresh cuts into a piece of sodium turn immediately black. This hasn't happened before. Does anyone have an idea what might cause that? Solvent vapours? Thank you. Ronald.

    Ioannis Samaras · Aristotle University of Thessaloniki

    dear Ronald (Väli)

    let me add one more minor detail. The cutting tool may have some traces of Na-alloys on the surface from a previous (some days before) cutting of Na.  So, next time, please, make some more Na-pieces (i.e. Na1, Na2, Na3,...) with the same cutting tool. After some hours, note if there are any differences between the 1st (Na1) piece and the last Na-piece since you have already regenerated your glovebox.

  • Enrico Predazzi added an answer in Particle Physics:
    Is there a Dirac equation for the Proton or Neutron?

    To the best of my knowledge, because the Dirac equation explains very well the gyromagnetic ratio of the Electron, it is typically considered to be an equation for the Electron. There seems to be no such thing as the Dirac equation for the Proton or Neutron despite them being spin-1/2 particles. After the calculation that I conducted in the present paper, I would like to believe that the Dirac equation can be thought of as an equation for any general spin-1/2 particle. I certainly will be happy to hear your thoughts on this very important matter.

    Enrico Predazzi · Università degli Studi di Torino

    Strong interactions (i.e. the fact that they are composite particles) spoils the extension of Dirac's considerations to proton and neutron which, in fact, have an anomalous magnetic moment. This, clearly, doesn't imply that there are no antiparticles which are, in fact, perfectly well known to exist and are commonly produced in high energy accelerators

  • Diego F. Aranha added an answer in Elliptic Curves:
    Given elliptic curve E over a binary field with parameters æ and ß. Is there a relation between these parameters and the number of points on E?

    I want to determine the number of points on E in terms of æ and ß. For example:

    For Koblitz curves one can compute this cardinality using a Lucas sequence but I am working in Elliptic curves over F_{2n} (not necessary Koblitz curves) given by the equation Y2 + XY = X3 + æX2 + ß where æ and ß are elements in F_{2n} and Tr(æ) = 1.

    Diego F. Aranha · University of Campinas

    Yes, there is a relation between the order of the group of points, the size of the base field (check Hasse's condition) and the curve coefficients. You can use a point counting algorithm like Schoof-Elkies-Atkin (SEA) to determine the order. This algorithm is usually already implemented in software like Sage or MAGMA.

  • Joseph Gbertyo added an answer in Langmuir:
    How do I plot a langmuir Isotherm?

    When trying to plot the data for my adsorption of protein to the surface of a polymer I am having a hard time solving for the K value in the langmuir isotherm in the equation  theta=K*c/(1+Kc). I am not sure how I can use my data to come up with a value for K that will fit my data. I can plug in individual points to determine the value, but they are different throughout the data series. Trying to average them didn't give me a good fit either.

    Joseph Gbertyo · Benue State University, Makurdi

    A paper was presented in Boston, US (July, 2013) by an expert in adsorption and titled "proposing a new adsorption isotherm known as Adejo-Ekwenchi isotherm in an international symposium and a similar one in Ghana (Africa) by the same author. If you can access, it has valuable information to your challenge. Just as Azam Taufik has said, a lot of errors will not agree to be buried in linearlizing non-linear isotherms. It is safer to explore polymaths software. You just type in your equation and send your data.

  • Moustapha Thiam added an answer in ArcMap:
    How can we determine the error of interpolation by the natural neighbor with ArcMap 10?

    With several boreholes localited, we could determine a spatial interpolation of different geological layer. Would it be possible to determine the errors associated with the interpolation. I used ArcMap 10.0

    Moustapha Thiam · Université de Thiès

    Thanks a lot for all these informations!

  • Alex Eckert added an answer in Business:
    Can anyone refer me to a study on the history of consolidations standards relative to U.S. GAAP and IFRS convergence?

    I want to better understand the controversy between the IASB and FASB on the business combinations standard.  In the end the FASB and IASB could not agree on the definition of control.  Is there a study that discuss this controversy in detail? Please share this citation with me.  Thanks.

    Jenice

    Alex Eckert · Universidade de Caxias do Sul (UCS)

    the attached file may help you.

  • Dev Thacker added an answer in Bioinformatics:
    Can anyone recommend a textbook on bioinformatics?

    Ideally, it should provide a good general introduction to the subject - probably aimed at BSc/MSc level students - and be clearly written with informative illustrations. It needs to be something that someone would enjoy opening up and reading, yet providing sufficient depth and breadth to serve as a value lab resource. It also needs to be reasonably up to date (i.e. not more than five years old). Thanks!

    Dev Thacker · Indian Institute of Technology Bombay

    In my opinion, essentials of bioinformatics by Jin Xiong is the ideal book to start out with from the basic level. I really enjoy reading the book and have taken to it many times when I've been in doubt. Once you're clear with the fundamentals you can refer to books like Baxevanis or David Mount.

  • How is it possible to prevent a PTFE membrane blockage while vacuum filtering multiwalled carbon nanotubes?
    In functionalizing MWCNTs using HNO3, I used vacuum filtration with a PTFE membrane but in a couple of seconds the solution stopped passing through the membrane and the rate became almost zero. I know that this blockage of membranes with CNTs is common in this sense but would you please help me how to overcome this problem?
    Pira Mahes · Queen Mary, University of London

    Hi guys,

    I am also trying to filter acid treated carbon nanotubes. Once I wash the nanotubes on the membrane with watee, the nanotubes go straight through the membrane into the filtrate. I am using a hydrophobic 0.6 um membrane. What do you think is the problem?

  • Evan Chiswick added an answer in FACS:
    Does anyone have experience with abdominal lavage after CLP?

    We are currently facing the problem that we can't do FACS analysis on isolated cells because they clot together after doing lavage with PBS and 3%FCS. How can we avoid that?

    Thanks for you help

    Evan Chiswick · Boston University

    Yes, I'm well acquainted with the pains of trying to recover cells post-CLP, and then using the cells for functional assays! We do not use FCS for lavage; cold Hbss or PBS with 1mM EDTA or 10U/mL of heparin works fine. Strain the cells through a cell strainer to help remove cecal contents. Wash with Hbss/PBs with 0.5% BSA. There are ways to get rid of the bacteria and dead cells too.

  • Brijesh B. Mehta added an answer in Hadoop:
    Is there any common test bed to compare performance of Hadoop cluster and HPC cluster?

    In the following survey paper I found a comparison of some horizontal scaling platform and some vertical scaling platform. Now I want to make performance analysis of these platforms but I don't know whether there is any test bed available for such analysis.

    Brijesh B. Mehta · Sardar Vallabhbhai National Institute of Technology

    Hello Felix,

    Thanks for sharing this information. I am going to study your paper and try to find something relevant to my problem.

  • Tamás Váczi added an answer in Graphene:
    How can I process raman mapping data?

    In graphene research field, raman spectra is an useful method to characterize graphene properties. If we got few raman data we can analyze these data by origin. But the data size is huge in raman mapping. It is inefficient to manually process these data. Is there any software to process raman mapping data?

    BTW: I have two kinds of data format-- .txt and .ngc. 

  • SILAS DERENZO added an answer in Rifampicin:
    Is there any correlation between Rifampicin (raw material) color (reddish brown or brownish red) with thermal profile (polymorphism)?

    I'm doing thermal analysis Rifampicin with different color of rifampicin in raw material and I found the different thermal profile, but I'm not sure those rifampicin have different polymorph because it coming from the same manufacturer. Thank you

    SILAS DERENZO · Instituto de Pesquisas Tecnológicas

    I think that these articles can help you.

    Solid-state characterization of rifampicin samples and its biopharmaceutic relevance.
    Agrawal S1, Ashokraj Y, Bharatam PV, Pillai O, Panchagnula R. Eur J Pharm Sci. 2004 Jun;22(2-3):127-44.

    Rifampicin Dissolution: Polymorphism or Crystal Defects Ramesh Panchagnula, Sonia Bedi, and Ashokraj Yasvanth informahealthcare.com/doi/.../10601330600718939 - ,2006

    2006, Vol. 23, No. 2 , Pages 71-83

  • What is iodine number in terms of activated carbon? what is the significance of iodine number? how to find it?

    In many paper, people are talking about Iodine number of activated carbon. What really Iodine number is? what is the significance of iodine number? how to find it?

    Sureshkumar Ayyalusamy · National Institute of Technology Rourkela

    Dear prince,

    Thanks for your time and guidance... 

  • Jörg Vogt added an answer in Mass:
    Where can I find a database with the ratio between the mass of DNA and total cell (or tissue) mass of cells of various animal and plant species?

    I need to extract very large amounts of DNA and I want to reduce waste and impurities. So I'm looking for the most suitable species for the purpose.

    Jörg Vogt · Julius Kühn-Institut

    Hello.

    I am not experienced in detail with this topic ...

    I don't think, that there is too much interest in creating such a database. I cannot imagine a very important use of it (to spend much time and tousants of Euro/dollars to create and maintain the db).

    But it's surely done thousands of times. It might be necessary to mine publications to find some data. I know that it was done for several apple species in "Genome Size Variation in Malus Species" (Monika Höfer and Armin Meister). And it was done with many strawberry species and cultivars in the same department. But I'm not sure if this data of strawberry is published. In the article of Höfer you might find some cross references or even not. I don't read it, but the abstract seems to deal with your question. 

    btw: Plants  do have sometimes many repetetive elements, therefore they might have a very big genome (DNA per cell). If it does not matter, which sequences the DNA consits of, consider of plants as a ressource (Fritellaria assyrica: 124 000 Mbp) or use polyploid oraganisms, which predominantly occur in the plant kingdom.

    Hope I got the question right.

    Regards. J

  • Adeel Javed added an answer in Omnet++:
    Which simulator should I use for working on source location privacy preservation in wireless sensor networks?

    I am working on a source location privacy preservation in wireless sensor networks. Should I use NS3 or Omnet++ as both are used in articles? Can someone guide me?

    Adeel Javed · University of Otago

    my vote is also for omnet++ as i found it easy and quick to learn.

  • Donald Mcmiken added an answer in Physical Activity:
    Glucose levels on intermittent activity?

    Hey, Im doing a piece of research regarding the effects of intermittent activity on glucose levels, is there much previous research on this area?

    thanks

    Charles

    Donald Mcmiken · University of Texas at Austin

    There is a lot of work being done in this area. My question is this: Why can't you find it through the usual channels? Are you just taking the lazy route to research a paper? Second, which glucose levels are you taking about: blood, interstitial, muscle, CNS, or perhaps liver glycogen as a source of blood glucose? What specific exercise are you talking about? What species of animal: biologists don't always assume the human animal? There are many variables here, you'll need to expand you query and be specific to get a specifically serious answer.

  • Felix Timischl added an answer in Signal Analysis:
    How to hook up the output of a PMT to a PC for time dependent signal analysis?

    I like to hook up the output of a PMT (R928 Hammamatsu) to a PC to see time dependent optical signal. Could you please suggest me the possible options? Any help would be really appreciated.

    Felix Timischl · JEOL Technics Ltd.

    The following URL is a link to an extensive but easy-to-read documentation on PMTs and their applications.
    https://www.hamamatsu.com/resources/pdf/etd/PMT_handbook_v3aE.pdf
    Chapter 5.3 (“Connection to an External Circuit”) describes several possibilities depending on the amplifier you want to choose, including the required math.
    If you want to observe slowly changing signals (sampling in the order of several hundreds of ms or slower), connecting the output amplifier (low output impedance) to a data logger might be the easiest way to obtain data you can directly transfer to your computer and process in Excel. If you want to observe high-speed signals, a digital oscilloscope is a straightforward approach.