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
  • Mohammad Hasan Gerami added an answer in Organic:
    Does somebody know what this organism is?

    Found in Coastal Waters

    Mohammad Hasan Gerami · Gonbad Kavous University

    if you found it in Hormozgan coastal waters, it is not sea slug.

    I think it is a kind of ray.

    but it covered with a black substrate. could you specify geographical information?

  • Matts Roos added an answer in Theoretical Physics:
    Could time or radial dilation prevent the formation of black holes?

    As we get close in time to the formation of an event horizon, then in the vicinity of the location where that event horizon will form in the future, time dilation becomes very large. The formation of the event horizon must depend on continued entry of material from beyond the radius where the event horizon will form, otherwise it would have already formed. A tiny differential instant before it forms time dilation approaches infinity.

    Of course in the proper time of an observer at that location, there is no time dilation and the black hole forms. But has anyone considered that in the reference frame of a more distant observer in the normal universe there may be no event horizon ever really existing in that observer's reference frame?

    9/26/2014 I extended this question to include radial effects.  For example, if one plots the radius in Schwarzschild coordinates, which I call Rs, vs the radius in distant observer coordinates (plain R) using units where c=G=1 and assuming M=1, the Schwarzschild coordinate radius declines less slowly than the distant observer coordinate radius, and past a value of three rises.  At 2 it rises to infinity.  In other words, not only is time slowed down, but the in falling object has further to to, and eventually infinitely further.

    The above is all within standard GR.  One contributor suggested arbitrarily setting R=0 at the event horizon and that nothing was within.  That has an interesting relation to the (1+φ/c2) potential which can be derived using equivalence and the Newtonian φ=GM/r.  When this is converted into Schwarzschild-like coordinates (defining Rs=C/2π) we get 1/(1-φ/c2) and further Rs = R ( 1 + GM/rc2 ) indicating that the zero origin of the observer coordinate R is in fact at the event horizon (for this non-standard case) and so there is no "real" space past the event horizon.  It appears in observer coordinate space as a point.

    Matts Roos · University of Helsinki

    Adding to my previous comment, let me just say that the situations discussed may be too restrictive, i.e. restricted by the need for simplest theoretical/mathematical description. Some day we may obtain new information about black holes from the observation of black hole evaporation by Hawking radiation, and of BH-BH,  NS-NS and BH-NS mergers, and gravitational radiation.

  • Ajay Singh added an answer in Regularization:
    How much do you spend on 'personal improvement'? Is it useful in achieving your personal/professional goals?

    We all spend at least some time on social media activities. Do you spend regular time (or/and money) on your personal improvement, i.e., gym membership, learning additional language(s), joining yoga classes, reading good self-help books, regular pleasure trips, attending motivational seminars, meditation etc. or a simple morning/evening walk.

    I believe these activities are useful for becoming a 'better' person, to have a 'better' life, and to have 'better' skills.

    What is your opinion on this?

    Your contribution is very welcome.

    Ajay Singh · IIT Kharagpur

    Dear dear @Miranda for your good comment and nice greenery.

  • Ridvan Kizilkaya added an answer in Sodium Azide:
    How much sodium azide should I use to kill the microbes in my soil?

    Each flask I have contains 20g of soil (very little organic matter) and 200 mL of synthetic surface water.

    Ridvan Kizilkaya · Ondokuz Mayıs Üniversitesi

    Hello Molly,

    A stock solution of sodium azide (NaN3) can be added to soil samples contained in glass beakers, flasks and vials that can later be sealed. The final concentration of sodium azide is usually between 1 and 10% (Trevors, 1996). In my lab. we are using 2,5% NaN3 solution (mL per g soil) for inhibition of microbial activity in soil. 

    Regards,

    Ridvan

  • Can anyone suggest how to find the transition state with different functional?

    I have a problem to find transition state with PBE functional. I have already used the scan process and use the opt=(ts,calcfc,noeigentest) and redundant option 4 5 D to optimize the transition state. But I can't find any imaginary frequency. Then I tried use qst3 calculation to find the transition state, but I found the transition state with BLYP functional. Is there any way to find out the transition state or some suggestion to do this calculation?

    Yazid Meftah · Université de Biskra

    thank you Taye B. Demissie,Oleg B. Gadzhiev

    the problem isn't the magnitude. i try QST3 by using the structure from BLYP taransition state but i found TS with PBE1PBE1 ,B3LYP,M06 with PBE i found other transition state.(other forming bound)

  • Fahad Alsweleh added an answer in Tooth Bleaching:
    Is there proof that tooth bleaching affects the quality / quantity of calcium in enamel ?

    Does bleaching, especially home bleaching either with Carbamyl or Hydrogen Peroxide cause calcium loss or degradation in tooth enamel?

    Fahad Alsweleh · King Saud University

    can you read the followings studies

    1-

    J Contemp Dent Pract. 2014 Jul 1;15(4):392-8.
    Influence of Fluoride Concentration and pH Value of 35% Hydrogen Peroxide on the Hardness, Roughness and Morphology of Bovine Enamel.
    Nascimento WC, de Lima Gomes Ydo S1, Alexandrino LD1, Costi HT, Silva JO Jr, Silva CM.

    2-

    Sichuan Da Xue Xue Bao Yi Xue Ban. 2014 Nov;45(6):933-6, 945.
    [Effects of vinegar on tooth bleaching and dental hard tissues in vitro].
    [Article in Chinese]
    Zheng LW, Li Di-ze, Lu JZ, Hu W, Chen D, Zhou XD

    3-

    Oper Dent. 2014 Dec 23. [Epub ahead of print]
    Effects of the Concentration and Composition of In-office Bleaching Gels on Hydrogen Peroxide Penetration into the Pulp Chamber.
    Mena-Serrano A, Parreiras S, Nascimento ED, Borges C, Berger S, Loguercio A, Reis A.

    4-

    .J Esthet Restor Dent. 2014 Dec 20. doi: 10.1111/jerd.12123. [Epub ahead of print]
    Evaluation of Novel Microabrasion Paste as a Dental Bleaching Material and Effects on Enamel Surface.
    Bağlar S, Çolak H, Hamidi MM

    5-

    J Int Oral Health. 2014 Jul;6(4):18-24.
    Microhardness and roughness of enamel bleached with 10% carbamide peroxide and brushed with different toothpastes: an in situ study.
    Melo CF, Manfroi FB, Spohr AM

    6-

    Eur J Dent. 2014 Jul;8(3):320-5. doi: 10.4103/1305-7456.137634.
    Effects of a bleaching agent with calcium on bovine enamel.
    Alexandrino L, Gomes Y, Alves E, Costi H2, Rogez H, Silva C1.

    7-

    BMC Oral Health. 2014 Sep 6;14:113. doi: 10.1186/1472-6831-14-113.
    Does post-bleaching fluoridation affect the further demineralization of bleached enamel? An in vitro study.
    Kemaloğlu H, Tezel H, Ergücü Z.

    8-


     
    See comment in PubMed Commons belowOper Dent. 2015 January/February;40(1):96-101. Epub 2014 Aug 19.
    Effect of Hydrogen Peroxide Concentration on Enamel Color and Microhardness.
    Borges A, Zanatta R, Barros A, Silva L, Pucci C, Torres C.

    9-


     
    See comment in PubMed Commons belowActa Clin Croat. 2013 Dec;52(4):419-29.
    Surface changes of enamel and dentin after two different bleaching procedures.
    Klarić E, Marcius M, Ristić M, Sever I, Prskalo K, Tarle Z.

  • Michael Durtnall added an answer in Coccyx:
    What is the management of coccydynia other than the ultrasound?
    Coccydynia is a condition common in postpartum, ultrasound helps to relieve the pain but the condition comes back after some time, is there any other ways to manage the pain? I have found core stabilisation helps out in certain patients but could not find the reason, can anybody suggest some reasons and any other treatment options for coccydynia?
    Michael Durtnall · University College London

    I have added links to my ideas on coccyx treatment, some of my statistics and the testimonials page of Coccyx.org with 60 patients' opinions on my approach to coccydynia ... not scientific, but interesting.

    I x-ray patients standing and/or sitting using low-dose, closely-collimated digital imaging to see the state and position of the joints. Secondly, I accurately palpate and assess the ranges of movement of each joint and mobilise to regain mobility and function. Patients also need specific, very regular physical exercises to get them back to physical health. This is not just a joint problem but often unilateral muscular thickening due to antalgic sitting sideways over months or years can lead to pudendal neuralgia. I have treated c. 1,000 coccyx and pelvic pain patients - many were stressed with misery and pain but none were 'psychosomatic'. 

  • Lipsy Chopra added an answer in Triton X-100:
    Can protein sample be made 2% Triton X-100 free?

    The protein I am purifying needed an elution buffer with 2% Triton X-100. I formulated the elution buffer not keeping the CMC in mind. My goal is to make my protein sample triton free to check its stability and quantify its concentration. Lately, I learnt that micelles can be broken down upon dilution. So, I've diluted my protein sample below triton's CMC and tried concentrating it using Sartorius Vivaspin 5K (PES resin). I loaded 500 ul of diluted sample and was left with 100 ul after concentration using vivaspin. But, this sample gave an abnormal reading of above 3 OD after blanking against the buffer it is in. I presume, triton's interference is causing these discrepant readings.

  • Elham Mahmoudian added an answer in Primer Design:
    What is the best tool to design primers for Real-time PCR online?

    I was used to design primers from the genscript site. Does anyone have a better suggestion for primer design for the Real-time PCR ?

    http://www.genscript.com

    Elham Mahmoudian · Azarbaijan Shahid Madani University

    Thank you so much dear friends for your answer and helpful guides.

  • Sameh Shenawy added an answer in Coordination:
    How does one define equality of two vectors in the space-time geometry of Minkowski?

    There are two versions of this definition (1) vectors AB and CD are equal, if their coordinates in inertial coordinate system are equal, (2) vectors AB and CD are equal, if scalar product (AB.CD} =|AB| |CD| and |AB|=|CD|. This definitions are equivalent for timelike vectors, but they are different for spacelike vectors. For instance, if AB1 =(r,r,0,z),  AB2 =(r,0,r,z),  CD=(0,0,0,z), then AB1=CD, AB2=CD, but AB1 is not equal to AB2.

    Sameh Shenawy · Modern Academy

    Both definitions are equivalent in Riemannian and hence Euclidean case.  But in pseudo-Riemannian they are not.

    The first definition considers vectors as elements of a vector space and the second considers vectors as geometric objects that have length and angle in between.

    I  think the main definition is the first one as they are elements of a vector space and in Euclidean sense there are many equivalent definitions like the second one.

    I have no good defense to choose the first, but it does make sense.

  • Joaquim Mª Rius Bartra added an answer in Spectrum:
    Can anybody help me with the Theoritical calculation using DFT theory ?

    I want the steps to calculate the theoritical IR spectrum , UV spectrum  for a compound using gaussian 03 program . 

    Joaquim Mª Rius Bartra · Autonomous University of Barcelona

    Hello Hossam,

    1)First thing to do is the optimization of structure, and I think that it is important to add symmetry (you will see it group it is correct and you can do all modifications that you need going to point group. 

    2) Go to calculate opt+freq. With this you will obtain the raman, polarized graph and IR.

    3) With the result molecule, do an other only energy calculus. In this case, TD for example. With this method you will calculate the excitation states and then you will obtain UV-VIS spectra.

    I think I follow all steps, but I always think that reasergate is only a little help to know which is the way.

    I hope it helps you and feel free to contact me.

    Joaquim Mª Rius Bartra

    Universitat Autònoma de Barcelona

  • Pouria mi added an answer in Lifting:
    How do I create a mathematical model to predict reciprocal influences of two horizontally close Clark Y airfoil on each other?

    I am working on my 4th year final thesis, which is to model a conjoint pressure distribution around two horizontally close ( sequentially close ) Clark Y airfoil. The target is to see how total lift condition changes when the distance between the foil changes. I need help to model this.

    Pouria mi · Beijing University of Technology

    sorry,i am not working airfoil.my thesis is radiation from nozzle`plume .

  • Vishal Srivastava added an answer in His-Tag:
    How can one solve the problem of getting expression bands lower than expected size?

    I am working with a protease gene which is his-tagged at c-terminal and is ~50Kda size. I transformed the recombinant construct (pET23b+Gene) in Rosetta DE3 pLysS. When I am trying to check induction I am getting results like that n given SDS PAGE. 

    The conditions are:

    Induction with 0.6mM IPTG when od reaches 0.6 

    Lane-2 marker (97.4kda, 66kda 43 kda 29kda 20.1 kda and 14 kda)

    lane-3 uninduced cells 200ul

    lane-4 induction of 2 hours 

    lane-5 induction for 4 hours

    lane-6 induction for 6 hours

    lane-7- blank

    lane-8 20 hour induction.

    As you can see the gel image expression is going on but its giving band of much lower size than expected.  I have done sequencing/ primer walking of my gene, they are intact and 100% correct.

    Vishal Srivastava · Indian Institute of Technology Delhi

    ' am planning. To do mass finger print..  if I will add protease inhibitor then my protein will also not work

  • Iftikhar Hussain added an answer in Trapping:
    What is the most efficient and fast way of live trapping of Norway rats?

    I need to trap alive dozens of wild Norway rats for my research. What kinds of places and what ways of live trapping would you recommend? I have used many kinds of traps and baits and I have tried out many kinds of places (barns, cowsheds, sewers, basements, landfills etc.). It always takes days or weeks and the success is usually limited to a few individuals. The remaining rats develop trapshyness and the 'hunting' is over - usually for weeks. Any hints or tips appreciated.

    Iftikhar Hussain · PMAS - Arid Agriculture University

    Give access by pre-baiting the traps for at least 3 consecutive nights to overcome neophibia and trap-shyness and then set the trap-on on the 4th night. Give 3-4 weeks gap to repeat trapping at any particular habitat.

  • Lipsy Chopra added an answer in SDS-PAGE:
    I am getting vertical streaking in my SDS-PAGE. Is there any method to remove them?

    Thanks in advance for your replies.

  • Tillmann Krauss added an answer in Hafnium:
    Increase of the crystallization temperature of hafnium oxide?

    Amorphous structure have led researchers to alloy hafnium oxide with silicon or aluminium, which were found to increase the crystallization temperature of hafnium oxide. Why does it matter? What are the benefits?

    Tillmann Krauss · Technical University Darmstadt

    I guess, this translates to a higher thermal budget for the processes after the hafnium deposition. Compare a gate-last and gate-first process flows for HKMG - there you will find the benefits of a higher budget.

    Best,
    Till

  • David Horgan added an answer in Nonlinear:
    Is there any numerical solution to solve nonlinear coupled PDEs?

    Is there any numerical solution to solve nonlinear coupled PDEs?

    David Horgan · King's College London

    Hi Mohsen, in that case we'll need to know more about exactly which equations you want to solve. There is no one way fits all for systems of PDEs, the methods used depend on the Type (elliptical, hyperbolic ..), boundary conditions and so on. Let us know and we'll have a look. Which coding language do you want to use? c++, python 

    ...

  • Jesús Izco added an answer in Phytosociology:
    Does anybody know anything about the ecology and phytosociology amplitude of Galium murale and Trifolium suffocantum?

    I am particularly interested in the syntaxonomic focus of this species. In which classes and orders do they occur?

    Literature and websites would be very helpful.

    regards,

    bernd

    Jesús Izco · University of Santiago de Compostela

    Galium murale is an annual species that forms part of herbaceous (annual or perennial ) comunities, typical of rocky habitats , weakly nitrophilous , preferably in Mediterranean climates.

    Phytosociological syntaxonomy : Class Parietarietea Rivas- Martínez in Rivas Goday 1964 , Order Parietarietalia muralis ( Rivas- Martínez 1960 ) Rivas Goday 1964. The species is considered characteristic of the Alliance Parietarion judaicae - Centhrantion rubri Rivas- Martínez 1960 (= Parietario - Galion muralis Rivas-Martínez ex Rivas Goday 1964).


    Trifolium suffocatum (sic) is an annual plant that is part of herbaceous perennials, dense, communities, developed under the influence of grazing sheep. These communities have no edaphic preferences and live both on acid substrates as basic.

    Phytrosociological syntaxonomy. Class Poetea bulbosae Goday Rivas & Rivas-Rivas-Martínez Martínez in 1978, Order Poetalia bulbosae Goday Rivas & Rivas-Martínez in Rivas-Martínez et Ladero 1970.

  • How can a Fabry Perot Interferometer (FPI) measure pm (pico-meter) displacements, using a mirror made of atoms with sizes of nm?

    The Bohr structure of atom consists of a nucleus (~fm), surrounded by electrons cloud (~ nm).  Now, having a scale graduated in " nm" due to uncertainty in electron position in the cloud (ie resolution), how can one measure 1000  times  (ie pm) or better measurements using FPI?

    Jeremias Seppä · Centre for metrology and accreditation MIKES

    I think a key point is that we measure the average position of huge number of atoms on the mirror surface, and also do averaging on the time axis -- picometre-range resolution can be done also with michelson interferometry (have done it), in addition to frequency measurement and fabry-perot (which can go to below pm?)

  • What is Lipchitz Criteria for stability?

    For testing the stability of system in which Sliding Mode controller is applied Lipchitz criteria is used. I am unable to understand the criterion.Kindly explain.

    Vijay Bhaskar Semwal · Indian Institute of Information Technology Allahabad

    it is used to measured the stability of non linear system. there is one more technique is  Lyapunov-like functions which basically consider the kinetic and potential energy

    A control-Lyapunov function is a function V:D\rightarrow\mathbf{R} that is continuously differentiable, positive-definite (that is V(x) is positive except at x=0 where it is zero), and such that


    \forall x \ne 0, \exists u \qquad \dot{V}(x,u)=\nabla V(x) \cdot f(x,u) < 0.

  • Does anyone know examples of cytochrome P450 enzymes, which produce fluorescent or colored small molecule?

    What I'm looking for is the cytochrome P450 enzyme, which accepts electron from adrenodoxin (or analogue), and produces fluorescent or colorful compound. For example, I already know about CYP106A2, which produces steroids, which in order are fluorescent at strong oxidative conditions. I also know about mammalian cytochrome assay for producing luciferin-like molecules, which than accepted by luciferaze as a substrate. I'd like to learn of more examples. Thanks!

    Michel Kranendonk · New University of Lisbon

    Colleagues above indicated several assays for P450 enzyme kinetic assays. I would like to add to be cautious with the final solvent concentration in the assays. Majority of P450 substrates are quite hydrophobic and need to be solved in DMSO, EtOH, MeOH or ACN. However P450 isoforms are quite sensitive for these solvents which can inhibit, differentially and quite strongly P450 activity, see Busby et al., 1999 Drug Metab Dispos

  • Yu I Kantor added an answer in Terminology:
    Where can I find a published glossary of terms that defines 'riblets' as a sculpture for mollusk shells?

    I want to cite a formal work that has properly defined the term 'riblet' - as in a form or molluscan sculpture- in a paper and can't seem to find anything apart from secondary sources on the web. Does anyone know of a thorough glossary for molluscan terminology that might have this?

    Yu I Kantor · Severtsov Institute of Ecology and Evolution

    There is an excellent glossary of gastropod shell (in many cases it is applicable to other groups) published by R.N.Kilburn as an appendix to the book of South African Molluscs. I have a PDF and can send a complete reference. it just says: RIBLET: small rib

  • Dino King Donayre added an answer in Organic Manure:
    Whether organically grown crops really have good quality parameters?

    I am asking this question because even though when we apply organic manures to plants it takes in inorganic form itself. Then in what way the quality is going to improve. if anybody have information pertaining to improvement in quality parameters  please discuss.

    Dino King Donayre · Philippine Rice Research Institute

    Hi Dr. Sunil. I hope this paper can help your query on organic crop's quality. (Arvin Paul Tuaño, Zhimin Xu, Michelle B. Castillo, Cezar P. Mamaril, Rosaly V. Manaois, Marissa V. Romero, Bienvenido O. Juliano. 2011. The Philippine Agricultural Scientist. 94(2):211-216.)

  • Luis Fonseca asked a question in ISO 9001:
    Do you agree ISO 9001:2015 will be a right step for Quality?

    Hi everyone.

    Do you support that the future ISO 9001:2015 International Standard should have major benefits for Quality Management Systems with less emphasis on documentation and new/reinforced approaches like consideration of organizational Context and (relevant) Stakeholders, Risk Based thinking and Knowledge Management;

    or

    - Do you think it should be more prescriptive and will be to generic to bring value to the organization?

    Many thanks for your inputs.

    Best Regards

    Luis Fonseca 

  • Henk-jan Schoonbeek added an answer in Agarose Gel:
    How to differentiate primer dimer signal and amplification (Gene of interest) signal??

    When I perform real time PCR for my gene of interest, I am getting the signal. However, when I run agarose gel (1%) I am not getting any band. My product length is 180-200bp. I want to know whether the signal because of primer dimer. If in that case how to differentiate?? 

    Henk-jan Schoonbeek · John Innes Centre

    And you could increase the agarose concentration to 2% so that any band you have will be more defined and easier to distinguish + run appropriate marker...

  • Elham Mahmoudian added an answer in DNA Extraction:
    Waht are the best methods for sample collection and storage for DNA extraction?

    Hello! We are preparing an study for molecular diagnosis in different type of spicemen: blood, feces and urine. The samples are collected in a different country and we want to avoid the cold chain. Can Anyone sugest any protocol or literature for this purpose?

    Thanks

    Elham Mahmoudian · Azarbaijan Shahid Madani University

    This is my question too.

    R.P. Achterberg

     thank you so much for your answer.

  • Lipsy Chopra added an answer in FPLC:
    Can FPLC destroy protein structure to many oligopeptides which can be not detected by SDS-PAGE electrophoresis?

    I purify by FPLC by Hitrap SP FF column. I have 4 fractions and all of them were being collected. I take an SDS-PAGE electrophoresis, and get some things below:

    - Percentage of target protein in Sample lane and sole lane which have target protein are 60%, 98% respectively.

    - Flowthrough lane doesn't have target protein. This demonstrates that all target protein was bound onto column. They would be eluted in the next step.

    - Wash lanes have a little other proteins but doesn't have target protein.

    - 3 rest fractions don't have target protein.

    - Performance of purification is 45%.

    - After fractions, I wash column with NaCl 2M buffer to take column clean. It doesn't have any protein.

    Something is wrong. All of the target protein was to be collected in one sole fraction but the performance is so low. Where is the 55% rest protein? Did FPLC destroy the protein structure to many oligopeptides?

  • Abdelkader BOUAZIZ added an answer in Tin:
    What is the lowest temperature at which I can polymerize caprolactone with tin octoate catalyst via ring opening?

    What is the lowest temperature for ring opening polymerization of caprolactone with tin (II) octoate? It can be with or without co-catalysts.

    Regards

    Abdelkader BOUAZIZ · Univ. Ibn Khaldoun Tiaret

    Dear all,

    these attached files mentioned a variety of polymerization temperatures. Regards

  • Alcides Simão added an answer in Birefringence:
    Is there a material with high Verdet constant and in the same time strong linear birefringent?

    I know that quartz possess linear birefringent as well as optical activity, but with low Verdet constant. Is there a material with high Verdet constant and in the same time strong linear birefringent?

    Alcides Simão · University of Coimbra

    Optical fibers exhibit such characteristics.