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

  • Gautam Ray added an answer in Cirrhosis:
    Why does spider angioma appear only on a skin of the upper part of a trunk in cirrhosis?

    Have you seen other location of this sign?

    Gautam Ray · B.R.Singh Railway Hospital, Kolkata, India

    Spider angiomas on skin correspond to gastropathy, enteropathy, colopathy that occur internally in the GI mucosa in cirrhosis and portal hypertension and the pathogenesis are the same i.e.increased amount of large number of vasodilators in the portal circulation that are not metabolised by the cirrhosed liver. Most probable cause of location in the superior vena cava drainage area in that maximum blood in the portal circulation that cannot go through the liver due to fibrosis reach the systemic circulation through the SVC as has been documented in the pathogenesis of esophageal varices in addition to the vasodilation.

  • Sand Saiy asked a question in Heavy Metals:
    What does the negative sign mean in Langmuir's isotherm?

    This is langmuir' equation

    Qe = QmbCe / (1+bCe) 

    where as  Qe=  heavy metal adsorbed to adsorbent (mg/g)
    Qm = maximum adsorption capacity (mg/g)
    b= langmuir 's constant
    Ce =equilibrium concentration of heavy metal solution (mg/)

    when i set it as LINEAR 

    1/Qe = 1/Qm + (1/bQm)(1/Ce)

    when i plot 1/Qe againt with 1/Ce 
    i got  y = 81.6X -6.8

    and i am wondering
    1.what does it mean with this negative sign (-6.8) 

    when calculate the intercept Y  = 1/Qm
    2. i need to calculated
    intercept Y = 1/Qm = 1/-6.8  so Qm = -0.14??     or only 1/6.8

    Thank you for you help :))

  • Is there any pre-layout method to determine the bitlines/wordlines capacitances of a SRAM cell/Array for a given technology node ?

    Since sometimes we don't have layout drawing tool for the given technology node (say 22 nm or 16 nm) .

    And also it is very difficult to draw layout to determine these capacitance especially when we only concentrate on spice simulation of the circuit. Is there any analytical method  

    Ahmed Ahmed Shaaban Dessouki · Port Said University

    Please refer to the book in Title: CMOS VLSI Design: A Circuits and Systems perspective

    By: Neil E. Weste and David M. Harris

    Chapter 2 and 4

  • Marc Tessera 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.


    There is clearly a misunderstanding between us.

    I didn't ask you for references supporting your specific hypothesis that thalamus is a 'center of consciousness' or even "the central receiver for sensory input , the central hub that directs etc".

    I asked you for references supporting the hypothesis that there could be a 'center of consciousness'.

    But, now, you say you no more support it (!).

    So, the discussion is over now.

  • Umar Younas added an answer in Quantile Regression:
    How to run a quantile regression with instrumental variable but the endogeneous variable is not a dummy in STATA?

    When using the quantile regression to estimate the effect of the number of bidders on final price in online auctions, the number of bidder is an endogeneous variable. I decide to use the duration of auction and peak time dummy as the instrument variables. How to run such  quantile regression in STATA when the endogeneous variable does not take the value of 1 or 0?

    Umar Younas · International Islamic University, Islamabad

    there are two methods first you solve the IV problem in OLS frame work then use QR other method is direct in QR using stata

  • How can I extract a biosurfactant produced by bacteria in a suspension? How do I test the activity of this biosurfactant?

    this bacterial suspension is grown on MSM liquid added to the crude oil (1%)

    Farzaneh Fakharian · Shahid Beheshti University

    Hi, I agree with Mr. Haytham M. M. Ibrahim, but i want to add some point. :

    First we have to remove the bacterial cells by centrifugation (10,000 rpm 4oC, 20 min ) then add 6N HCl to reduced the pH of supernatant to approximately 2.0 this will precipitate the biosurfactant. Keep the the acidified suspension in the refrigerator  4oC overnight. then centrifuge again and keep the mass ( partially purified biosurfactant) remained at the bottom of tube. now you can dissolve it in ethyl acetate and start thin layer chromatography with different solvent systems including hexane/ ethyl acetate or chloroform/ methanol/distilled water.

  • Morteza Vafadar added an answer in XRD Analysis:
    What is the interpretation of humps (broad peaks) in a XRD pattern which repeat themselves in a exact range?

    We are using RF magnetron sputtering for coating VANADIUM (30-50nm) on various types of substrate. After obtaining the XRD results, there are two humps with wide range. Despite their different intensity in different samples, they have quite exact points for rising and falling in every cases. So I don't think that they are due to amorphous property of sample. These humps also are independent of grain size of coated vanadium since the AFM images shows different grain sizes for different samples, while there is no change in the hump ranges.

     Attached, there is a XDR pattern of one of the samples to show these humps.

    Later attached: XRD patterns for naked Si, SiO2/Si substrates and XRD system configuration details.

    Morteza Vafadar · Ataturk University

    Maykel, we are not using the GIXRD analysis. Our system works with conventional θ/2θ scanning method.

  • Paolo Ialongo asked a question in Harmonic scalpel:
    What is your experience about devices for dissection of liver parenchyma ?

    What about Harmonic scalpel, Ligasure, Radiofrequency, Cavitron ? Which do you prefer ? Why ? and When ?

  • Višnja Kukoč added an answer in Spatial Planning:
    Can anyone suggest the bibliography for relation between national spatial planning and urban expansion?

    I am interested by the postcommunism evolution.

    Višnja Kukoč · University of Split

    Thank you, but for the moment I am engaged in sveral project with topics not related to topical issue.

    All the best.

    Višnja Kukoč

  • How do countries promote their heritage tourism through GIS applications?

    The discussion is about GIS applications used by different countries for promoting their heritage tourism. Everybody is welcome to share opinions and expertise. 

  • Mehdi Hedayatpour asked a question in Power Systems:
    Controlling any non-zero active or reactive power during short circuit conditions?


    when we used the droop control method for power sources, controlling any non-zero active or reactive power during short circuit (grid voltage equals zero) results in infinitely high currents,  which is avoided when controlling the active and reactive current directly.

    dose any one explain difference between the active and reactive power control in contrast to active and reactive current control?

  • Ramadan Sabra added an answer in Leptospirosis:
    Can anyone help me with the construction of Lyapunov function for non-linear systems of differential equations?

    I am currently working on my masters thesis "Mathematical modelling of Leptospirosis". I have this serious problem with the construction of lyapunov function to investigate the stability of the system, as it is known that there is no exact method for the construction of lyapunov for non-linear systems. Thanks

    Ramadan Sabra · Jazan University

    Could you give more details please!

  • Prakash Kumar Sahoo added an answer in ELISA:
    How can I normalize an ELISA?

    I used positive and and negative serum for optimizing an ELISA, but there is a difference between each sample. The total antibody content is different from person to person.

    So, it is not convenient to compare direct absorbance values obtained for serum samples. The values should be normalized for analysis. How can I normalize the OD values obtained for different serum samples?

    Prakash Kumar Sahoo · Indian Council of Medical Research

    Actually I want to know , What is your aim?  In an ELISA you are taking Positive and Negative serum Sample. Titre of both and many other will differ. If you want to normalize the 'titre'" you have to take a control pool serum (that should from all category) in all plate and convert OD in to ELISA unit. If you want to declare positive or negative from the OD value you have select a cut off value negative. That can be done by pooling 10-12 mean OD + 2SD of negative samples. Further if you want to quantify the antibody, you have to take a known (quantitatively identified) serum. Then you convert then to quantity as ng/ml or pg/ml. 

  • Ram Nath Mishra added an answer in pCREB:
    Are there any calcineurin pathway studies in prion infected laboratory animals?

    Can anyone suggest some Antibiotics that alters calcineurin levels in brain?or any drug that can change levels of pCREB and pBAD levels in brain?

    Ram Nath Mishra · Independent Researcher

    PLoS Pathog. 2010 Oct; 6(10): e1001138.
    Published online 2010 Oct 7. doi: 10.1371/journal.ppat.1001138
    PMCID: PMC2951383
    Calcineurin Inhibition at the Clinical Phase of Prion Disease Reduces Neurodegeneration, Improves Behavioral Alterations and Increases Animal Survival
    Abhisek Mukherjee et al

    Prion diseases are a group of infectious neurodegenerative disorders producing a rapid and devastating clinical deterioration. The disease is 100% fatal and affected patients usually die within one year from the appearance of the first clinical alterations. Currently there is no treatment available for these diseases. The main goal of this study was to show that inhibition of the brain phophatase calcineurin is a therapeutic target for prion diseases. We show that calcineurin is hyperactivated as a consequence of endoplasmic reticulum stress produced by accumulation of misfolded prion protein. Treatment of animals showing the symptoms of prion disease with the calcineurin inhibitor FK506 resulted in a substantial decrease in the severity of clinical signs, an increase in animal survival and a reduction in brain degeneration. These findings indicate that calcineurin might play an important role in prion-induced neurodegeneration and inhibition of this phosphatase might represent a promising novel approach for prion disease therapy.

  • Is there any information on linear ordered topological structures?

    Could linear ordered topological structures, I am looking forwards to expertise this fileld which became actual since falling past XX, be related to your subject I believe, differential geometry? Just can find Differential Manifolds, Brickell F. and Clark, R. S. in my library say, times where I was a student ... Thank you.

    Nuno Freire · CIMA-Universidade de Évora

    Thank you, dear Yuriy, I believe I possibly can obtain the paper. I found an application of Schauder basis, linear funct. analysis, to a difficult problem in general topology. Wickstead, Vector and Banach Lattices I could obtain the pdf. through the google

  • Is there a solid counter-argument against Dingle's old objection to Relativity Theory?
    Herbert Dingle's argument is as follows (1950):

    According to the theory, if you have two exactly similar clocks, A and B, and one is moving with respect to the other, they must work at different rates,i.e. one works more slowly than the other. But the theory also requires that you cannot distinguish which clock is the 'moving' one; it is equally true to say that A rests while B moves and that B rests while A moves. The question therefore arises: how does one determine, 3 consistently with the theory, which clock works the more slowly? Unless the question is answerable, the theory unavoidably requires that A works more slowly than B and B more slowly than A - which it requires no super- intelligence to see is impossible. Now, clearly, a theory that requires an impossibility cannot be true, and scientific integrity requires, therefore, either that the question just posed shall be answered, or else that the theory shall be acknowledged to be false.
    Stefano Quattrini · Ordine degli ingegneri della provincia di Ancona

    Yes there is not carrier at all in the QE.

  • Marcia Gasis added an answer in Tissue Embedding:
    Can anyone suggest me a good Ab to stain CYP11A1 (cytochrome P45011a1) on tissue?

    Good morning.

    I have a problem. I'm trying to stain CYP11A1 on Mouse tissues embedded in parrafin or frozen but I can't find a good Ab.

    I tryed 3 different Ab on mouse testis and adrenal gland (positive control) embedded in paraffin or frozen in OCT . I changed many protocols (antigen retrival, blocking, Ab concentration, washing buffers, timing, etc etc) I wrote to all techical support and to authors of papers who used the same Ab but I never was able to obtain a good and specific staining (low signal and high background).

    These are the Ab I used:

    1. Abcam cyp11a1 ab 75497
    2. Santa cruz cyp11a1 (D-16) sc18040
    3. Proteintech 133663-1-AP

    Can you suggest a different Ab to use?

    Marcia Gasis · Heinrich-Heine-Universität Düsseldorf

    Hello Elisa.

    Maybe the link below is helpful for you to find an appropriate antibody:


    Regarding the ab´s you tested:

    - The abcam-ab is reactive in human tissue only. Maybe that´s the reason why you can´t establish it on mouse tissue. Usually Abcam antibodies are good and their technical support is also helpful.

    - Personally, I don´t like santa cruz abs. They tend to be unspecific. So I wouldn´t spend more time in establishing this one...

    - The Proteintech ab, has not been tested in IHC as stated on their website. It could be difficult to get this one to work.

    Good luck!

  • Could anyone help me with Huntington's disease dataset or at best ,where can i get dataset.?

    I completed my academic master's project.......I designed a small tool for Huntington disease prediction. I need Huntington dataset containing age and age of onset to proceed validation or modelling using fuzzy neurons.....could you help me with dataset or at best ,where can i get dataset.
    Thanks and Regards,

    Ram Nath Mishra · Independent Researcher

    Genotyping and clinical examination determined that 171 participants were presymptomatic gene carriers (PSGCs) and 414 participants were non-gene carriers (NGCs). The PSGCs performed significantly worse when compared with the NGCs on the digit symbol, picture arrangement, and arithmetic subscales of the WAIS-R (p<0.02) and for the physiological measures: button tapping, auditory reaction time, visual reaction time with decision, and movement time with and without decision (p<0.05). Although no PSGCs had sufficient neurological findings to warrant a diagnosis of Huntington's disease on clinical examination, the PSGCs had more frequent possible or definite abnormality for oculomotor function, chorea, muscle stretch reflexes, gait, and station stability, and rapid alternating movements (p⩽0.02)


    J Neurol Neurosurg Psychiatry 2000;69:773-779 doi:10.1136/jnnp.69.6.773
    Subtle changes among presymptomatic carriers of the Huntington's disease gene
    S C Kirkwooda et al


  • There are studies that analyze the dynamics of fluids in the carotid arteries?

    Even through computational analysis, comparing patients with or without carotid plaque? Thanks

  • Sajid Ali asked a question in Malondialdehyde:
    How can we calculate malondialdehyde (MDA) contents ?

    I have noted absorbance at 600, 532 and 450 nm for MDA, but, unable to calculate it. Would anyone please like to guide me based on information provided ?

  • Mathew Baite added an answer in DNA Extraction:
    Can anyone help me with DNA not dissolved in water when extracted from Ascochyta?

    Whenever I do DNA extraction from Ascochyta, at a stage when I want to dissolve the DNA in water, the DNA is partially or do not dissolve at all. Anyone may help me? 

    Mathew Baite · Indian Agricultural Research Institute

    @ michael, i will try ur suggestions might help.

    @ Irfan, what you are saying is at the last step of DNA isolation, where TE buffer is used and stored as such. but my problems starts before that. after precipitating alcohol washing, and the dissolving with pure water. Here my DNA doesnt dissolve and face difficulty in subsequent RNAse treatment.

  • Shian-Loong Bernard Lew added an answer in Music:
    Concerning research in emotional responses to music, has someone done a study correlating musical devices and mental states in performance?

    In my submission "A Brief History of Modulation in Musical Rhetoric and Brahms'  Harmonic Ambiguity ", I identify the need for a study to correlate musical devices and mental states. The first step is to develop[ a catalog of such devices. These include among many effects, modulation (shifts in tonicity), silence, unison, changes in rhythmic texture etc.

    By using the term "mental states", I choose a broader field than mere "emotion".

    With an understanding of composition/improvisation (generative), there are a great many possibilities. Just within modulation, Max Reger has developed an extensive catalog of the devices, alas no mention is made of effect on an  audience. Rameau in his treatise on Harmony discusses very briefly an emotional response to chromatic modulation (please see my article for the citation specifics; Reger is not cited in this paper yet. It remains in an unfinished form: more than a few citations TBD.

    Gee, how do I put a citation here? - simple footnote:

    Max Reger: Modulation (Dover Books on Music) Paperback 2007
    ISBN 048645732X

    Jean-Philippe Rameau: Treatise on Harmony Dover 1971

    ISBN 0-486-22461-9

    Shian-Loong Bernard Lew · Taylor's University

    Study in the link seems to confirm the belief that music is a universal language.A language containing semantic structures that are comprehensible to a wide and diverse range of individuals.Musical devices are definitely an important unit of analysis in the analysis of a piece of music's semantic structure. Musical devices especially those related to the Baroque era may have a universal impact on the mental states with regards to "movement planning, memory and attention". Especially music's role in helping the brain to " foreshadow".

  • Any scientific research on self-determination theory (Deci & Ryan, 2000 ?

    I'm working on an introduction program voor students at the age of 14/ 15 years old in Veldhoven Holland. I use the self-determination theory (Deci & Ryan, 2000) as my fundament in the program. Is there any scientific research that proves that their concept is working. It is evident based, but I can't find any proof.

    Antoon van Wolferen


    Antoon van Wolferen · Hogeschool Fontys

    Thank you very much I will read them 

    have  a nice weekend


  • Is 63.5% the optimal acid concentration for isolation of cellulose nanocrystals from MCC?

    According to Bondeson, that used response surface methodology for optimization of the acid hydrolysis procedure for preparation of CNWs from MCC, the optimized treatment condition  is as follows:

    63.5% acid concentration (sulphuric acid)

    temperature= 45 C

    time= 130 min

    however, some researchers believe that MCC will dissolve at this high acid concentration  and as a result amorphous particles are formed and the yield is low. In an article, acid concentration 57-60 % and time 40-60 minute has been proposed as the optimal codition for the acid hydrolysis process. 

    any suggestions?

  • Andrei Rogoza added an answer in Silk:
    Anyone familiar with diazonium coupling of silk?

    I have done diaotization of light chain silk for modification of tyrosine present in it. I tried H1-NMR and ATR-FTIR on these modified silk. But no peak was observed, from dizonium salts in both of these characterization, Is there any technique to determine that silk material is diotized and %diaotization done after completion of experiment?  

    Andrei Rogoza · Irkutsk Institute of Chemistry of the Russian Academy of Sciences

    Diazonium salts with aliphatic substituent ( like in tyrosine) are unstable and rapidly lost nitrogen with building of alcohol (in water media). This is good method of R-NH2 -> R-OH transformation.
    Dry diazotization (via Ar-NH2 -> Ar-N=S=O + NO+BF4- -> Ar-N≡N+ BF4- )  is known in aromatics but to be explored in aliphatics.

  • Marković G. Đoko added an answer in Hermeneutics:
    What is the relationship between hermeneutics, dialogue and multiculturalism in the context of modernity?

    I need information on these issues and their conceptual relationship.

    Marković G. Đoko · University of Montenegro

    Hermeneutics, as the art of interpretation of the phenomenon helps us to appreciate the essence and explain the importance of dialogue and multiculturalism in the context of modernity.

  • Alaa Al-Afeef added an answer in Aperture:
    How do coded apertures improve imaging resolution?

    Why is it that we get a better resolution when using coded apertures as opposed to pixel-by-pixel imaging?

    Alaa Al-Afeef · University of Glasgow

    coded apertures are a Deconvolution technique, which uses a prior knowledge about the reconstructed signal. 

    see attached link for example.

  • Paolo Ialongo added an answer in Liver Surgery:
    Liver surgery: What is optimal simultaneous or staged liver resection?

    Up to 15% of patients with colorectal cancer have synchronous liver metastases. Wich is optimal timing of hepatectomy ?

    Paolo Ialongo · Università degli Studi di Bari Aldo Moro

    Thank you dear colleagues for your comments. The  variety of your considerations underline the importance of experience as well as results reported in literature