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
  • Esen Bellur added an answer in Alkylation:
    How can one bring about N- alkylation of any N-heterocycle?

    How can one bring about N- alkylation of any N-heterocycle specially benzothiazole

    Esen Bellur · DEVA Holding

    Alkyl halides could be used for N-alkylation. By conducting such a reaction using benzothiazole you would end up with corresponding tertiary amine halide salt. For example, if the reaction is carried out by using benzothiazole and iodomethane in acetonitrile at room temperature (min. 24 h), the product will be N-methyl-benzothiazolium iodide.

  • How can I find if the time series has additive Gaussian noise?

    I have a time series data. I want to find out if the data has been corrupted by additive white Gaussian noise or what is the characteristic of noise present in that data ?? How can that be done .

    Abdelhalim Zekry · Ain Shams University

    Dear Sharda,

    From the the information you gave about the signal, i get out that it is a single variable statistical problem and this is the frequency of a power system.

    So, you can calculate its probability distribution function by using the well statistical methods. The most probable value it that with highest probability distribution. The deviation from this value is noise. If the distribution is Gaussian, the most probable value will be the average value. After articulating the pdf you can compare it THAT OF GAUSSIAN. 

    If the noise is white then you can separate the signal from from the noise by performing fast Fourier transform FFT on the signal. The noise will be seen as a signal floor laying under the signal.

    In summary, you can separate the signal from noise by making statistical analysis

    or by FFT.

    wish you success. 

  • Are there any free data-sets I can use to practice disease mapping?

    Hello,

    I am new to spatial epidemiology and looking for datasets that can be used freely to practise disease mapping and maybe disease clustering. I would also like to use the data later on in lectures to give students a basic understanding of the geographical or spatial perspective. Any suggestions or recommendations are greatly appreciated.

    Thanks in advance,

    Fabian

    Fabian Erdsiek · Technische Universität Chemnitz

    Thanks to you all. While the datasets used on spatialepidemiology.net were not really fitting for my purposes, especially the NTD mapper and Snow's Cholera study look very promising.

  • Thanh Do asked a question in Dynamic Analysis:
    Frame elements in simulation of structures?

    I am trying to simulate a frame structure under some loading conditions, e.g. push-over analysis, dynamic analysis, etc. Which frame elements are available in the literature that can capture the plasticity as the element approaches the nonlinear range? Can you please advice? Thank you.

  • Zmicer Gavrilenko added an answer in Peritonitis:
    What do you use for diagnosis of spontaneous bacterial peritonitis in cirrhosis in your clinic: the manual counting or an automated cell counter?

    How often you meet false negative results at the relatively low but pathological levels of PMN in ascitic fluid (for example, polymorphonuclear cell count <500 cells/mm3)?

    Zmicer Gavrilenko · Gomel State Medical University

    Dear Dr. Shinozaki, Thanks for your comments!

    Best regards!

  • Anyone know the research on cognitive training for older adults in the context of compensatory changes in the aging brain (e.g. HAROLD, PASA)?

    I'm looking for the research verifying if the training-induced changes in cognitive task performance are connected with the changes in human brain, in terms of compensatory patterns, as PASA or HAROLD (or some other).

  • Rion Lerm asked a question in Dendrogram:
    Which clustering method to use for comparing to to ANOVA results?

    I performed cluster analysis in R (using hclust under vegan package) to find relationships between habitats based on species. A dendrogram/tree was derived from Bray-Curtis sim. matrix. Cluster methods are Ward, Ward.D2, Single, Complete, Average etc.

    However, when I perform an ANOVA with post-test, the significant differences between pairs of habitats do not represent the differences observed in the dendrogram, when using a variety of methods. E.g. ANOVA computed that A was different from C, but the cluster analysis showed that A is similar to C.

    ANOVA was performed using species abundances and cluster analysis using Bray-Curtis which converts to binary/presence-absence.

    Any ideas?

  • Simon Cottle added an answer in Content Analysis:
    Recently I read few papers for content analysis and the approach appealed me a lot. Could anyone please suggest reference material for a beginner?

    Suggestion for some good reference book or online resource would be highly appreciated.

    Simon Cottle · Cardiff University

    Hi,

    In my view the clearest, straight-forward account of content analysis as method and how to operationalise it in practice is Anders Hansen chapter in Mass Communication Research Methods, co-authored by A.Hansen, R.Negrine, S.Cottle and C.Newbold (1998) (Macmillan). Hope this helps. Simon

  • What is your preferred method for mounting Si samples for thermal evaporation?

    I am interested in methods for mounting Si samples for thermal evaporation.

    I tried using S1813 photoresist to adhere my Si samples to microscope slides (ensuring no air bubbles before hardbake) then used a microscope slide clamp to mount them into the thermal evaporator (picture attached). However, during evaporation some of the samples began to tilt due to the photoresist swelling.

    Unfortunately my process is quite restrictive in the sense that I need to cut my samples before carrying out following processes.

    Any suggestions would be much appreciated.

    Jules

  • P. Matic added an answer in Induction Motor:
    Why are star delta starters preferred with induction motors?

    Why star delta starter is preferred with induction motor?

    P. Matic · University of Banja Luka

    As said previously, this is very simple method for decreasing starting current, applicable for motors in D-connection with all six terminals available. By using Y-D starter, IM starting line currents and starting (pull - out) torque are reduced three times. However, those are also the main drawbacks of this method.  In some applications, this 1/3 current reduction is not sufficient, and from the other hand,  starting torque in Y connection may be not enough to start heavy loaded drive. As conclusion, the method is applicable in drives which do not require high starting torques, and in which 1/3 reduction in starting line current is  acceptable.

  • Aoife Lawton added an answer in Reference Manager:
    Hi. Which software would you advise for an Institutional Repository?

    Currently we are using Zotero Reference Manager to keep track of publications produced by our scientists. However, I feel Greenstone or DSpace would be better suited to house our repository. Most of our publications are published Open Access, though there are some from years gone by that are not OA and so only have links to the publisher's page. I would like to develop a collection that is :

    a. easily accessible online

    b.easily used for reference purposes

    c. whose bibliographic details can be easily extracted and exported

    Any ideas?

    Aoife Lawton · Health Service Executive

    Hi we use Open Repository hosted by BioMed Central.  I've written a paper about it (you'll get it on my profile).  I ran 2 focus groups and a needs analysis.  It is really important to get buy-in from people who will use and contribute to the repository from the start.  Ideally before you decide which system to go for.  This worked well at our institution.  All stakeholders should be involved in the decision about which system to select, that helps to give them a sense of ownership of the repository going forward.  In our organisation, we opted for Open Respository.  But Digital Commons was also liked and ePrints, ArchivalWare. 

    We branded ours and BioMed Central have been good at customizing options for customers.  It is based on a DSpace platform.  I can confirm that it is possible to batch export references using common tools like Endnote, Refworks, etc.  You can have a look at it at www.lenus.ie

  • Anyone who is interested in developing a full body model for Vicon using clusters?

    Dear all,

      Greetings, I am interested in creating a full body model for Vicon (With Marker set) using the clusters to find the joint center unlike the plug in gait model which has got individual and wand markers.

    The idea is to find the reliable joint center for all the major joints thereby reducing the error percentage in the 3D motion analysis (especially in terms of angle interpretations).

    While post capturing the same data can be imported into matlab to find the angles and associated graphs for the same.

    I will be more than happy to go on with a collaborative study on this. 

    Pietro Cerveri · Politecnico di Milano

    Dear Vasanth

    plese take a look to an early approach based on kinematic models and kalman filters I studied more than 10 years ago.

    Cerveri P., Pedotti A., Ferrigno G., Robust recovery of human motion from video using Kalman filters and virtual humans, Human Movement Science, 22(3):377-404, 2003.

    If you are interested, I could provide you some matlab-based source code.

    Pietro

  • Graft İn stent carotid artery restenosis;What are your opinion with this case?

    We had  reported  the case of a 57-year-old male patient with a history of acute amaurosis fugax. Carotid angiography was performed as blood pressure differed between his left and right arms and there was a pan-systolic murmur on the left common carotid artery. Total occlusion of the proximal right brachiocephalic artery and a thrombus occluding 90–99% of the left internal carotid artery were detected by carotid angiogram. We decided to place a graft-covered stent through the lesion first, and contain the plaque and thrombus between the stent and the lumen. Therefore, a graft covered stent (5×13, Direct) was implanted with 12 atm pressure. After removing the distal blockingbased protection system, we opened the selfexpanding stent (7×10×30, Cristallo) (figure 3) and dilated the stent using a post-dilatation balloon5×20, Tarcomgrande).

    A self-expanding graft-covered stent was successfully implanted and there were no complications. This case  published in BMJ Case Journal “ Covered stents may provide extra protection during carotid artery stenting in high risk patients with an excessive thrombus burden”, Tatli E, et al. BMJ Case Rep 2013. doi:10.1136/bcr-2013-010258.

     However , the patient presented transient  ischemic attacks after three years. DSA angiography show 99% instent restenosis in the  overleap segment of   the both stent.

    What are your opinion with  this case ?

    Francesco Antonucci · radiologie am graben

    The patient was  relatively young when the decision of stenting was made.The brachiocepahlic artery was occluded. The left carotid severely stenotic. Despite hese severe angiografic findings  his only symptoms were those concerning the amaurosis ( I presume on his left eye): No further clinical informations are available. Cardiological Status? Carcinoma or other diseases?  I wonder who took, with these angiografic findings, the decision of stenting . If his general conditions were extremely poor I may understand the decision but he is still living three years after stenting, in this case the stenting was not a decision for the patient but for the interventionalist . I can't believe that an experienced  surgical team would have agreed to stent the "patient". Carotid surgery should have been first choice ( no clinical informations available). Now? You need a good surgeon, an even better anesthesist and  a good intensive care unit. In the future? More humility. Best regards

  • Pencho Mihnev added an answer in E-Learning:
    Which software do you use to create SCORM compliant online learning materials (and why)?

    I'm considering Adobe Captivate and Articulate Storyline 2. Any helpful comments about these or other alternatives? 

    Pencho Mihnev · Sofia University "St. Kliment Ohridski"

    Dear David,

    You can look also at the iSpring eLearning suite and (or some of) its components. Easy to use and handy. There is also free parts, in order to test its usability and functionalities (with more limited functionalities).

    http://www.ispringsolutions.com/

    Best regards,
    Pencho Mihnev

  • Ahmad Rayan added an answer in Bipolar Disorder:
    Can depressive symptoms differ between people?

    Signs and symptoms of depression in mothers of children with autism are frequently reported. However, based on extensive clinical observations and self reported data, I constantly observed that these mothers report specific depressive symptoms more than others. I did not observe this phenomenon in patients with schizophrenia or bipolar disorders. Is there any evidence supports this??? or it is a merely chance?  

    Ahmad Rayan · Zarqa University

    It is a small sample, but there is a clear constant pattern, I will try to enlarge the sample size and make further investigations.

  • Can any one share with me the best technique to analyze anaerobic microbial community ?

    I want to evaluate microbial community interaction and mutual action

  • Nilesh Singh added an answer in Student Engagement:
    What is the differences between students' engagement and students' motivation in learning activities?

    Is there any difference between students' engagement and students' motivation in the context of students' learning? Do you have any theory of these terms? Thanks

    Nilesh Singh · University of the South Pacific

    Both kinds of motivation will result in engagement. During engagement motivation is also needed.

    Best wishes.

    Nilesh

  • David Cox added an answer in Electromigration:
    How thick should Ti adhesion layer be?

    Making 100 nm wide nanowires to break controllably using electromigration, see DR Strachan et al. for example.

    Previously I've used 2 nm Ti adhesion layer and 14 nm Au; I use ebeam evaporation to deposit the metals in vacuum, into a PMMA negative from EBL. I am concerned however that a 2 nm film of Ti is not continuous, and that 4 nm would be safer.

    I am wary of going too thick however, as when the gap breaks via electromigration, I try to trap a molecule in the gap, connecting two Au electrodes. the Ti can be problematic for two reasons:

    1. If the exposed Ti, which is presumably not oxidized because it was protected by the Au, does not also electromigrate then it will short the ends. Some recent work suggests that Ti can electromigrate however so it is possible that it would do so.
    2. If the Ti does electromigrate, a Ti-Ti tunnel junction would not likely contain the molecule (I use thiolated molecules to form self-assembled monolayers on the Au).

    Previous work, my favorite of which is from Takhee Lee et al. has used 1-2 nm of Ti or Cr, so I am further hesitant to go thicker. It is difficult to test this matter as well.

    Thanks in advance for any advice.

    David Cox · University of Surrey

    In our experience with Ti on both Si and SiO2 we tend to aim for 3 to 5nm, (so about 4nm on average) and I'm not aware of us ever having problems with this thickness, although of course we are not doing your experiment. One thing I will say is how often do you check the deposition rate of your system and what thicknesses do you check if it all? They all tend to drift around a bit over time and even if you have a set recipe it will change due to system pressure variation, if the target has a bit of oxide on it, the energy and current of the e-beam drift and many other subtle variations, all of which might make the difference of aiming for 2nm and getting a bit less that might make for a continuous film or not. We tend to test ours at few difference target thicknesses such as 5nm 10nm 20nm about once every couple of months even if we thing it is working as it should. Basically don't trust the machine, it may be in error and you can't afford much of error with 2nm.

  • Chen Ziheng added an answer in Text Analysis:
    Can anyone help me in getting mapping tool for concepts which are extracting from a text dataset (Topic Mapping)?

    Hello,

    I'm working with text clustering/topic extraction, the outputs are lists of phrases/terms which represent the concepts of my dataset.

    I would like to draw the cncepts(phrases and terms) to a map(Graphical interface). als each concept has related documents in the  Lucene Index. 

    Is anyone knows any free software to d that? 

    Thanks in advance.

    Darsh

    Chen Ziheng · Renmin University of China

    Hi, there are two R packages may be useful for you 

    1

    Rwordseg:  it can count the word frequency and get the document matrix.

    2

    wordcloud : it can help depict the wordclod.

    3

    http://nlp.stanford.edu/software/tmt/tmt-0.4/

    in this website, there are some packages that can help you use lda model and other topic models.

    good luck!

  • Neha Patel added an answer in Text Mining:
    Can anyone help me in getting financial text mining datasets?

    i need a finanical text minig datasets  whatever news or documents

    Neha Patel · Charotar University of Science and Technology

    https://www.quandl.com/ (I recommended).

  • Lipofectamine plasmid amount for lentivirus production?

    I am using lipofectamine to transfect plasmids to produce lentiviruses in 293T cells. The vectors I am using belong to the second generation of lentivectors, pMD2.G (envelope plasmid) and psPAX2 (packaging plasmid) + pLenti6/V5-D-TOPO modified to be 9kb long. the protocol I was told to use is>

    OMEN + plasmids to a final volume of 500 uL

    OMEN + lipofect. 16ul to a final vol. of 500 uL

    incubate 2 min + mix + vortex

    incubate 15 min

    aspirate old mediom frim 10 cm dish and and 3ml of fresh medium

    +add solution to dish

    change medium after 5+7 hours

    Anyway I do not know which amunt of plasmids I should use. From a previous trial with calcium phosphate transfection I used 22.5 ug of clonned construct, 7.9 ug envelope plasmid and 14.6 packaging plamid but I am not sure if it will be correct for this method.

  • Jill Muhling added an answer in Codon Optimization:
    Has anyone tried CrispR/Cas9 in CEM-CCRF cell lines?

    Has anyone tried CrispR/cas9 in CEM-CCRF cell lines? I am trying to express human codon optimized Cas9-2A-GFP which is under the control of Cbh or CAG promoters and so far, no luck. I am using neucleofection and my positive control plasmid, pMAX-GFP (which is under the control of CMV promoter)  works fine with up to 30% GFP+ cells.  I am suspecting mostly promoter issue or cleavage of 2A peptide???.Any suggestions much appreciated.

    Jill Muhling · GSEx viral vector core, University of Adelaide

    Sounds like a plasmid issue rather than a specific CRISPR problem. The 2A peptide is meant to be cleaved but even if it cleaves poorly you'd still get a Cas9-GFP fusion protein so you'd still see some GFP. Where did you get the Cas9 plasmid from? Does it work in other cell lines?

  • Vasiliki Milpani asked a question in Teaching:
    How can we teach in a way of get high respond of the studentsin a classroom ?

    methods of qualitave research that we can help us to have an good contuct with our students

  • Varsha Shinde added an answer in T-RFLP:
    Is there any way to find out the bacterial abundance from environmental samples other than T-RFLP and ARISA?

    I am isolating bacteria from tarball samples and want to know if I can see the bacterial species abundance on the basis of number of isolates which I will get after doing their identification by 16S rRNA sequencing.

    Varsha Shinde · National Institute of Oceanography

    thank u very much Karin for your suggestion. As I am planning to extract the DNA from tarballs in future, the suggestions of you guys will definitely help me. 

  • Jiansheng Wei added an answer in Alloys:
    How many twins can be introduced into one grain?

    Acting as a barrier for the movement of dislocations, twin boudaries can improve strength of alloys. If this is true for most of the alloys, seems finding a way to put more twins into one grain is a way for strengthening, if it could be done. Here comes my questions: (1) how many twins can be pumped into one grain in real work no mater what kind of metal it is; (2) Is there a theory on this

    Any direct answer or link is appreciated.

    Jiansheng Wei · Central South University

    Dear M.L. Fares

    Thanks for the link, working on it right now.

  • Does anyone have information about hydraulic calculation for closure works in tidal regions?

    Does anyone have information about hydraulic calculation for closure works in case of hydraulic structures in tidal regions?

    Van Van Than · Aix-Marseille Université

    Thank you,

  • Jitin Makker added an answer in REDCap:
    Do you know how to add Excel APIs in REDCAP ?

    We have REdcap projects and trying to add excel sheets in the survey for easy allocation of matrix type of data,

    Any one used this as an API? 

    Thank you

    Bismi

    Jitin Makker · University of California, Los Angeles

    Can you please elaborate on what you are trying to achieve?

    You can convert excel sheets to redcap data and import easily using data dictionary.

  • What is the best method to isolate circulating tumor cells in mice?

    In order to determine the efficacy of the drug on liquid tumors, circulating tumor cells isolation is necessary. Is there any way to isolate the circulating tumor cells?

    Rathindranath Baral · Chittaranjan National Cancer Institute

    I also believe that it is possible by tumor cell adherence from total PBMC preparation. However, at that time some other cells will be adhered, like, macrophages. Stain these cells. If tumor marker is not known, you can stain other cells, like mac and DCs. So unstained cells may be counted keeping morphology of all cells in mind. Decrease represents drug response. Is it?

  • Artur Braun added an answer in Electrodes:
    How do I prepare working electrode using nanoparticles which is stable and does not peel off of the electrode?

    We have tried making nanoparticle based electrodes in two different ways (1) electrophorosis on a Ni-foam and (2) pressing a composite on the Ni-foam. In either case, upon performing electrochemistry, the deposited film peels off of the Ni-foam. I will appreciate if somebody can provide a detailed information for preparing a stable electrode using nanoparticles.

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

    Maybe you can use the same approach like we did with dye sensitized solar cells with TiO2 nanoparticles, using PLURONIC as binder which you can burn off at 140°C.

    Semicond. Sci. Technol. 26 (2011) 045007 (6pp) doi:10.1088/0268-1242/26/4/045007
    Low-temperature roll-to-roll coating
    procedure of dye-sensitized solar cell
    photoelectrodes on flexible polymer-based
    substrates

  • Thanh Do asked a question in Structural Engineering:
    Damage models with applications in structural engineering in literature?

    I was wondering if you could point out to me some damage models that have applications in structural engineering? By damage model, I mean those that have degradation in the model response. Thank you.