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

  • Does anyone know, how can I assess the impact of climate change on water balance in river basin using monthly input data?

    I conduct study that aim to assess the impact of climate change on water balance in river basin. My data are monthly (Temp, PPT, and Runoff) for number of stations spread all over the basin for the period 1960-2012.

    Henrique de A. Pereira · WayCarbon

    Dear Ismaiel, also keep in mind that climate models often deliver results for distant periods in the future (2020, 2050 and 2100). A lot can change in a basin in such periods: land use and cover, population / economical growth, regulations, etc. Those variables can also have correlations with variations (+/-) in water balance in the future. 

  • Surya Gautam added an answer in Liposomes:
    How can one prepare a tablet of pre-liposomes to govern in situ formation of liposomes?

    Dear All, 

    I have seen many Research Articles starting with the topic "Tablets of pre-liposomes govern in situ formation of liposomes"

    Can anyone share the open access of such article? 

    If not can anyone share me how to prepare the pre-liposomes? 

    Your valuable suggestion is really appreciated. 

    Thanks in advance

    Surya Gautam · CT Institute of Pharmaceutical Sciences

    follow the link to access the article


  • Yannis P. Papastamatiou added an answer in Tuna:
    Has anyone worked on Fish Aggregating Devices (FADs) and can you write your experience ?

    In India we have deployed Fish Aggregating Devices at Andaman & Nicobar Islands and Lakshadweep group of Islands for the benefit of Fishermen community as requested by the respective Fisheries Administration. According to the Lakshadweep fishermen the Tuna aggregation is nearer FADs and they are getting a good catch. Please share your experience. I can provide more details whenever required. Thank you.  

    Yannis P. Papastamatiou · University of St Andrews

    Also contact Kim Holland (kholland@hawaii.edu) and Dave Itano (daveitano@gmail.com ) who have done a lot of work on fish behaviour and movements at FADs all over the Pacific.

  • Denis Melnikov added an answer in Angiosperms:
    Taxonomy of angiosperms: what are the modern trends and techniques?

    Angiosperm represents the largest as well as the most successful group of plants within the Plant Kingdom. Taxonomy of Angiosperms started with two approaches viz. empirical and interpretative approach. But with the advent of science and technology different methods and techniques are considered for better understanding and better approaches of taxonomy works. 

    So, what are the modern techniques that can be applied in angiosperm taxonomy and why?

    Denis Melnikov · Russian Academy of Sciences

    I should note that at the moment, due to the high resolution chemical analysis methods, virtually disappeared marker compounds that would be typical for this or that group of plants. In this connection Chemotaxonomy not answer the question of taxonomists.

  • Is anyone familiar with dry powder yeast preparation?

    I'm working with yeast in a dry powder form. What is the best protocol to prepare yeast cells before we treat with stress conditions (high pH, salinity) ?.

    Please let me know the details. Thank you.

    Wahauwouélé Hermann Coulibaly · Université Nangui Abrogoua/trainee to National Institute of Applied Sciences of Toulouse (France); member of the Inter-graduate school of food (AUF)

    I think that you must begin to rehydrate your yeast powder, and to do a pre-culture in YPD medium and you inoculate your yeast suspension in the YPD liquid and you use the orthophosphoric acid for ajuste the pH and you do viability study for example

  • Can someone help me with Protein Purification using Ni-NTA?

    I am working on a protein, that I tried to express in BL-21 cells. This protein is an integral membrane protein, so I tried harsh buffer conditions to take out this protein in soluble form. The gene responsible for this protein has been cloned in pET28 vector. I am using Ni-NTA to purify this protein, but I am not able to purify it. After purification, I am getting three more proteins of 45, 47 and 47 kDa, with my protein, that is 41kDa. I have used 500uM imidazole for elution, but I didn't get any protein, so I tried 250mM imidazole for elution. Please suggest me, what else I can do to purify it. I can not go for western blot, as we lost this protein primary antibody.

    Priyanka Srivastava · The Energy and Resources Institute

    Thankyou Amit for the valuable suggestion.

  • Ritika Joshi asked a question in Red-shift:
    What is the reason for fluorescence enhancement of any probe on addition of dna when excited at the formers abs wavelength?

    there is only negligible red shift in the emission maxima of the probe with fluorescent enhancement

  • How do you calculate vertical detachment energy for a "Dipole Bound Anion"?

    Calculating vertical detachment energy or electron affinities for a "Dipole Bound Anion" is not as straightforward as the "Valance Bound Anion".  I was wondering if anyone had experience with  "Dipole Bound Anion". It is usually in the order of few Milli-electron volts.


    Piotr Skurski · University of Gdansk

    If the electronic stability of a dipole-bound anion is small (and this is usually the case), one must be very careful while performing the calculations. There are two main issues: the choice of basis set and the choice of method. The latter is simple as the CCSD(T) method usually performs very well in those cases (correlation contribution dominates the excess electron binding energy). The choice of basis set is more difficult. I suggest reading our paper "How to Choose a One-Electron Basis Set to Reliably Describe a Dipole-Bound Anion" by P. Skurski, M. Gutowski, J. Simons, published in Int. J. Quantum Chem. 80, 1024-1038 (2000). 

  • Raphael Baudoin added an answer in Chemistry:
    Does pressure sensitive paint (PSP) work in water?
    I am wondering if pressure sensitive paint will work under water or if it will will work with a limited amount of oxygen available. Or more specific: does oxygen quenching 'consume' the oxygen?
    Raphael Baudoin · Ecole Centrale Paris

    I would also thank M. Henne for the answer.

    However I recently found an interesting Nasa's paper on Water based PSP you might be interested in :http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20100014071.pdf

  • Can COMPUSYN calculate synergism for cytoprotective in vitro expriments? What factors should I consider while calculating drug synergism in compusyn?

    I can see a significant cytoprotection in the combination(1:10) drug doses than the individual doses (approx. >17%, MTT assay values). I now need to find the CI values and DRI values along with relevant plots for further study. Can compusyn assist me with the job?

    Enrique Barrajón-Catalán · Universidad Miguel Hernández de Elche

    Of course, as any pharmacological effect, cytoprotection can be used with Compusyn software. You only have to stablish the right control for cytoprotection and use good desogn for measure the activity (chekerboard disign for example).

  • Christian Cantos added an answer in Primer:
    How can I clone a PCR generated 9 kb amplicon in a 7.8kb vector?

    I am trying to clone a full length gene with flanking sequences (a total size of 9 kb) in the Drosophila expression vector pCaSpeR4. I had constructed primers with sites for BamHI and KpnI in the Forward and Reverse primers respectively to clone the gene directionally. On lack of results, I tried non-directional cloning using primers bearing restriction sites for the same enzyme, but in vain. My inserts and vectors are both clean, and ratios of vector : insert which I have tried are 1:1, 1:3, 1:5, 1:10. Is it a ligation problem?

    Christian Cantos · International Rice Research Institute

    Like what Pietro said, try doing Gibson Assembly, it can ligated in single reaction large fragments and very straight forward to. I did not have any problems with this system just make sure you have right overhangs, right components and competent bacterial cells. here is the link to learn more:


  • Peter S. Young asked a question in Osteoclast:
    What is the best marker for assessing osteoclast maturity activity?

    I am currently looking at osteoclast differentiation on varying polymer surfaces, can anyone tell me which would be the best analysis method for osteoclast maturity and actual activity?

  • Nicolas Salliou added an answer in Social Capital:
    What is the importance of institutions and their network at the community level in the context of social capital?
    I am looking for studies done focusing on how formal and informal institutions at the community level aid towards enhancing efforts towards collective action and hence social capital.
    Nicolas Salliou · French National Institute for Agricultural Research

    You should read Putnam who is a major source for social capital and communities research: "Bowling Alone: America's Declining Social Capital" and "Bowling Alone. The Collapse and Revival of American Community"

  • Mudhir Sabir Shekha added an answer in Wistar Rats:
    What is the laboratory rats diet composition?

    We have a pellet maker in our animal house at college. Which raw materials can we use for making pellet for Laboratory rats?

    Mudhir Sabir Shekha · Salahaddin University - Hawler

    Thank  you Mireille Kameni and Sakire Pogun 

  • I need help with factor analysis?

    Is it okay to include a factor that shows a coefficient alpha below .7 in exploratory factor analysis but shows above .7 in confirmatory factor analysis?

    Gideon P. De Bruin · University of Johannesburg

    Hi Reynan

    I make the assumption that in the exploratory factor analysis you identify items with loadings above a certain threshold (perhaps > |.30|) and then calculate coefficient alpha for those items as if they constitute a scale. I also make the assumption that in the confirmatory factor analysis the items that constitute the factor (scale) are selected a-priori and all of them have satisfactory loadings. It is possible that the items identified by the EFA can differ from those in the CFA, which could lead to different reliabilities.

    In an EFA it is common practice to include all items with  loadings greater than the set threshold in a scale and to then calculate coefficient alpha for this scale. But if one or more of these items have relatively low loadings in comparison to the remaining items it can lead to a reduction in the size of coefficient alpha (adding items can lead to a reduction in reliability if the item is weak). Coefficient alpha is based on the assumption of tau-equivalence (i.e. the unstandardized factor loadings of all the items are the same). If this assumption is not met alpha will underestimate the reliability. A better indicator of reliabillity in this case is to use McDonald's coefficient omega, which is calculated directly from the results of a factor analysis.

    I hope this helps.

  • Gustavo Cabrera added an answer in Chitosan:
    What are the alternating horizontal lines in my my pure chitosan SEM image?

    Please help me out. I am unable to understand this image. I have prepared pure chitosan by adding 5g chitosan powder into 500mL acetic acid

    Gustavo Cabrera · Center for Research, Develpment and Innovation (CIDI), Grupo Hijuelas

    Dear Jahan,

    You can also try to add some plasticizer to your chitosan mixture in order to improve film flexibility and separation. There are a lot of papers dealing with this topic in chitosan film preparation.

    You can also use some recipe  made of teflon (or with surface recovered with teflon) in order to avoid such issue or a device with a highly polished surface. 

    If you are going to work for long time with this system you will have to create your own toolbox.

    best regards,


  • Why do we use 90 min equilibrations of isolated aortic rats?

    After that, rings were placed under a resting tension of 2 g and equilibrated for 90 min before starting the experimental protocols.

    If less or more than 90 min what occurs?

    Mudhir Sabir Shekha · Salahaddin University - Hawler

    Thank you Stephen J Ives

  • Soheil Soroushnia added an answer in SeismoStruct:
    How to model Masonry Infill using Seismostruct?

    For Non-Linear Static Analysis, I am currently using Seismostruct. I developed two model for RC structure (One is Bare frame and other is with infill). When I go for analyzing Infill model, a problem occurring "unable to apply permanent load". Why I am getting such problem?

  • Can anybody suggest me research articles on dislike button/ dislike article/ dislike post etc.?

    Can anybody suggest me research articles on dislike button/ dislike article/ dislike post etc.?

    Thank you!

    Venkata Kongara · Sri Krishnadevaraya University

    Hey Nikos,

    I have found some information from other sources

    Please go through some of the references from this article, you will get an idea on how to proceed further., all the best for your study

  • Mudhir Sabir Shekha added an answer in Organ Bath:
    When we add a drug in an isolated 10 ml organ bath must the dilution be not more than 1:20?

    We have Isolated tissue bath, we work on it, herbal, drug blocker....etc

    If our krebs solution in organ is 10 ml, I read paper it said you can not adding more than 0.5 ml , is eqaul to 10.5 ml

    If more than 0.5 all results become ERROR

    Can any one help me ?

    Mudhir Sabir Shekha · Salahaddin University - Hawler

    Thank you Stephen J Ives 

  • Alessandro Lugari added an answer in Remote Sensing:
    How to rectify Band Issues using Quickbird Satellite data?

    I have procured data from DigitalGlobe -Quickbird Satellite data for different periods hence some data having different band combination. How can one rectify this problem? or how can I switch default true color band ?

    I have attached an example image to show the problem.

    I am looking for your guidance. Thanks in advance

  • Jan Mischke added an answer in Ohmic Contacts:
    How can I achieve ohmic contacts to p-GaN core-multishell nanowires?

    I am trying to contact core-multishell GaN nanowires with a n-doped core and a p-doped multishell radial around the core via E-Beam lithopraphy. To characterize them I tried to realize ohmic contacts with Ni/Au to the p-doped GaN-shell. Because of the geometry of the wires I need to vapor deposit 30nm Nickel/300nm Gold to make sure, that the contact path doesn't ripp off the wire after the evaporation. Does anyone have experience with contacting p-GaN nanowires with Ni/Au and the formation of ohmic contacts? I tried several temperature steps in the RTA without any big impact on the results (up to 590°C). Thank you very much

    Jan Mischke · University of Duisburg-Essen

    Yeah the doping concentration could also be a (or the) limiting factor for achieving an ohmic contact. Would be good to know the doping concentration. We are working on that issue :)

  • Ritika Joshi asked a question in Fluorophore:
    What is the reason for hyperchromism of probes abs peak on subsequent titration with DNA?

    No shift is observed in abs spectra for the fluorophore but hypochromism is seen even though I am adding dna

  • Ashley Sproul added an answer in Pharmacy Education:
    Does any pharmacist researcher wish to join a multicenter study about pharmacy education in colleges of pharmacy?

    Please provide provisional willingness to participate in an international pan-multicenter study in pharmacy education.

    Ashley Sproul · Horizon Health Network, canada, waterville


    I am interested in helping! Can you send me additional information as to what is involved?



  • Can I add Pen/strep to my hESC cultures?


    I was just wondering whether I can add antibiotics to avoid contamination into my human embryonic stem cell cultures without interfering with the cells. Any suggestion? concentrations?

    Thanks a lot!

    Faisal Alzahrani · King Abdulaziz University

    Hi Vinc :) 

    According to Stemgent protocol, they recommend ( as optional step) adding 5 ml of Pen/Strep(100x) for each 500 ml of medium. 

    Pen/strep available at GIBCO   cat No# 15070-063

  • Gotzon Aurrekoetxea added an answer in Dendrogram:
    What is the best cutting of the Clustering?

    Cutting Clustering analysis or dendrogram is essential to project the output into the map. In geolinguistics many people use clustering and project the output into the maps, but nobody explains what is the best cutting place or level.

    Gotzon Aurrekoetxea · Universidad del País Vasco / Euskal Herriko Unibertsitatea

    Thanks you very much

  • Michael Voice asked a question in Glucose-6-Phosphate:
    We are seeing inhibition of some CYP isoforms by the G-6-P in the NADPH generating system, particularly CYP4A11. Has anyone else seen this?

    We noticed a loss of activity when reassaying some CYP4A11 products and after a fair bit of investigative work narrowed it down to the glucose-6-phosphate in the NADPH generating system.  We had good activity when using NADPH and this was inhibited by the addition of G-6-P.  Generating system using an old lot of G-6-P which had been frozen for a while as part of another product development project also worked fine.  We found the G-6-P from at least two suppliers is inhibitory to CYP4A11 and a couple of other isoforms to a lesser extent.   Has anyone else noticed this and, if you are seeing low activity with some CYP isoforms and use a generating system for the NADPH, perhaps this could be the cause.

  • Fredrick Johnson J asked a question in Dll:
    Anybody using the latest FTDI's IC FT4222H I2C/SPI to USB Bridge as a Master or a Slave in the Evaluation Board i.e. UMFT4222H ?

    I am using a FTDI's IC FT4222H, a programmable one which was released few months back. It's used for interfacing I2C/SPI based slave or master devices and acquire the signals or data. I am using the Evaluation module of the same IC to act as a I2C Master and communicate with a EEPROM 24LCB16 for reading and writing the data from and to it respectively.

    I am using LabVIEW to communicate with the FTDI IC through USB. I am not using the Virtual COM port whereas I am importing the FT4222H .dll into vi and executing the program such a way. 

    I find the device is listed properly in the VI, it is getting recognize as FT422H. The mode selected is Mode 3 where the I2C Master/Slave, SPI Master/Slave is enabled and the GPIOs are disabled. So it is listed as FT4222H. 

    Even then the device is getting opened and doesn't through error from FT_Status till the device is initialized. Here I have configured the device as I2C Master and in the next step I am reading the data from EEPROM. But the following errors are listed.

    1. Initialize- 1000( FT_STATUS)

    2.Read device - 3 

    3. Un initialize- 3

    4. Close status-1.

    The DWORD are listed under the Appendix of datasheet.

    If someone can reason out the solution for this kindly help me out to go ahead. Its almost done only the write and read operation has to be performed.

    I have attached the Zip file of VI and Sub-VIs that I am executing. If you find any errors in those please let me know.  

  • Is it possible to coat silver nanoparticles onto an aluminum foil by using an inkjet printer?

    I just tried electro spinning but it is only for fiber type. I need a better and more cost effective method.

    Farid Touaiti · Åbo Akademi University

    Hi Rafik,

    It is quit hard to answer but i guess there are many methods to coat or print films. 

    Lets see first are you sure you gonna have strong adhesion between the silver particles  and the Aluminium substrate. if yes then i suggest to use simple a doctor blade coating method it is cheap and you can get a thickness as low as 20 um (attachment 1: doctor blade). You can also use the apparatus in Attachemnt 2 

    For further information check the publications on the website of Functional printing materials center 


    you can 

    I hope i was of some help