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
  • Carmen María Pérez added an answer in Food Access:
    What governs the speed of food production?
    Food production around the world does not seem to be in proportion with the population size. For example africa, a resource rich continent deals with hunger and subsidy based agriculture while developed countries flourish beyond their need. What governs the speed of food production. What is the rationale behind it?
    Carmen María Pérez · University of Puerto Rico, Medical Sciences Campus

    Dear Dr. Balaji:

    Agriculture as you know produces the world’s food. In agriculture, control of the biophysical aspects of food production shifted from a theoretical ambition to an attainable goal due to three interconnected developments: (1) the liberalization of the agrarian markets following the debt crisis in the 1970s, (2) the acceleration and expansion in the use of biotechnologies to control the production and reproduction of life, and (3) the privatization of nature through the extension of intellectual property rights to agriculture products. In order to have a better answer for your question, you should examine how the corporate management of food (agribusiness) folds into bio-political strategies for managing life and how their commercial interests supplant human needs.

  • Mizanur Rahman asked a question in Consolidation:
    How can I estimate consolidation parameters (cv & mv) from a conventional triaxial consolidation test?

    Tri-axial isotropic consolidation is not K0; how do these boundary conditions affect consolidation parameters compared to oedometer test?  It would be interesting to see some theories and publications.

  • Maxwell Ofosuhene added an answer in Urban Planning:
    What could be some barriers for increasing residential density within a metropolitan area?

    Outdated government policies? Ingrained ideologies within the population? etc...

    Maxwell Ofosuhene · Trinity Western University

    1. Lack of public consultation - involving the public and businesses in the density decision making process.

    2. Lack of political will to carry out such density project.

    3. Neighborhoods resistance to change of cityscape

    4. Urban decay - hence people and businesses try to avoid the neighborhood

    5. Affordability - land and house prices 

  • n.t Spence added an answer in ANSYS:
    With regards to the picture in my profile, how would I go about calculating stress, deflection and von mises calculations?

    This model was designed for calculations to be made on Ansys-something which I am currently struggling with as I am new to the program and am used to CAD.

    I wanted to find out if possible how I would model the FORCES and MESHES on Ansys as well as how first principles would be approached. I should look to take it from there. I have values for poissons ratio (0.27), youngs modulus (220E6), yield stress (200E6), material thickness (2mm) and of course dimensions.

    Any assistance with manual calculations would be grand!

    n.t Spence · Aston University

    Thank you Prabhakar, you are too kind. Very useful!

  • Martin Forde added an answer in Ethanol:
    How can I explain great siRNA transfection efficiency but no knockdown with validated positive controls?

    I'm performing reverse transfection on SH-SY5Y using Viromer Green, and I get wonderful transfection efficiency (90+%). See picture (RFP labeled siRNA fluorescence overlapped on phase contrast image).

    However, when I qPCR for KO I see no knockdown for any of my siRNAs. It's odd, because I had previously validated this protocol for two of my siRNAs and they worked fine (>50% KO with low standard errors, replicated across multiple biological replicates, at multiple time points, with a clear and significant dose response curve). So I know that at-least two are targeting my transcript fairly well.

    For qPCR, I'm using TaqMan chemistry with best coverage primer probe sets. I'm extracting total RNA with Directzol (column-based RNA separation from Trizol reagent), and cDNA synthesis with MultiScribe.

    Almost everything in my protocol is identical to what I performed in the validation. The only thing that is different is that I forgot a step in the RNA extraction process. In particular, Directzol indicates to homogenize cells in Trizol, add an equal volume of ethanol to the homogenate, run through column, DNase treatment on column, several ethanol washes, and elute in water. This time around, I forgot to add ethanol to the homogenate. Stupid move on my part, I know. Obviously, it precipitates the nucleic acids out of solution, so that they more readily interact with the column. However, I still recovered a good deal of pure RNA, which was lower though roughly consistent with my yields from the validation. So I reran my extraction protocol with the ethanol addition and my yields were somewhere between 1.5-2x greater. 

    My question is would this necessarily be a causative issue with the lack of KO in the TaqMan experiment? I'm testing this hypothesis in the next couple days, but I would like your input to see if this reasoning is solid. If it's not then maybe I can save some reagents. I just find it odd that I got a decent quantity of high quality RNA from the extractions without the ethanol precipitation. Plus, when I run the cDNA from these batches I still get good amplification curves (all thresholding between 15-25 cycles) with little variability between technical and biological replicates. So I don't think it's an issue with cDNA synthesis or the assay itself. Could the lack of ethanol precipitation bias my pool of total RNA? Wouldn't any bias that results from RNA loss in the extraction process be relatively random? In turn, shouldn't I still be able to see my KO effects at the mRNA level? Or could the lack of ethanol precipitation cause the total RNA pool to be of lower quality or integrity? I've ran samples on both nanodrop and qubit, and both my 260/280 & 260/230 are consistently between 2-2.1.

    Any ideas or questions to help me work through this would be greatly appreciated?

    Marty

    Martin Forde · University of Chicago

    So the issue was with the RNA extraction mistake afterall. I nanodroped new samples today, and had close to 3x the yield. Moreover, I ran the assay, and the got the expected KO I was looking for.

  • Francis Jake Docog Galeon added an answer in ICT:
    How can I measure the economic impact of ICT in the context of developing countries?

    Is anybody aware of a tool or a framework or a theory which can be used to quantify the ICT impact on economic growth and development in the context of developing countries?

    I am just wondering that since economies in developing countries have different natures and attributes than those in developed or transition countries, we can not use the same principles to quantify economic impact of ICT. Do you agree?

    Any advice?

    Francis Jake Docog Galeon · University of Asia and the Pacific

    I think you can assess the impacts of ICT in the economy using a Computable General Equilibrium (CGE) Model. Another possible method is through an Input-Output (I-O) Analysis.

    Check these papers for your reference:
    CGE Model Approach
    http://econpapers.repec.org/paper/ekd002672/4731.htm

    Input-Output Analysis:
    http://article.sciencepublishinggroup.com/pdf/10.11648.j.jwer.20130202.11.pdf

  • Hazwani Noor added an answer in Herbal Plants:
    Is there any differences if we used different concentrations of solvent to extract the plant?

    For example, if I used 40% of methanol, 60% of methanol and 80% of methanol to extract the herbal plant, is there any difference? Is it true if the higher concentration of solvent can extract more chemicals compound from the plant? Can anyone here provide me the references. thank you.

    Hazwani Noor · University of Science Malaysia

    Thanks for the answers. By the way, can we state that 80% of methanol extracted more chemical compounds compare to 40% methanol?

  • Nicholas Meyler asked a question in 3D Printing:
    Are there any 3D Printing Scientists online looking for a great job?

    Harrisburg, PA is the location:  http://app.streamsend.com/ss/1/u4Kt/ttnszl1ae5 

  • Elizabeth Martin added an answer in Ethics:
    When is an ethical clarification needed in research experiments?

    I've submitted a research article that deals with new biomarkers, and is based on samples received from cancer patients. The patients didn't give the blood for this project, however they consented to use the samples for research purposes. The journal asked me an ethical clarification, because I'm working with human material. Can anyone help me with this? If there is any document for exception of ethical clarifications please send it to me.

    Maybe you can look at the case of Havasupai Indian Tribes of the Grand Canyon. This case is one of ethic

  • Sandip Maurya added an answer in PDMS:
    Does an ultrasonic bath with isopropanol destroy a surface grafting of PEG or PAA on PDMS?

    I want to use this method too make sure that the grafting is on a chemical level and is not removable through ultrasonic bath or alcohol. I activated the surface with oxygen plasma before grafting.

    Sandip Maurya · Gwangju Institute of Science and Technology

    You didnot mentioned the procedure of grafting.

    If you have grafted PEG by radical grafting then it should not be detach from surface, however, it may swell in alcohol.

  • Marc Verhaegen added an answer in Metatarsus:
    Your thoughts on the Ontogeny - Phylogeny Evolution Model?

    I believe that the adage - ontogeny recapitulates phylogeny - embodies the 'smoking gun' (e.g., in determining the ancestrally lineage of homo sapiens).

    The etiology of the two abnormal foot structures that I have written about (PreClinical Clubfoot Deformity and Primus Metatarsus Supinatus foot structure) can be easily understood when one studies the normal embryological development of the human foot.

    During embryogenesis, first the fetal foot bud emerges, then it develops into the the Clubfoot Structure, then as it continues to develop, it becomes a PreClinical Clubfoot Structure, then a Primus Metatarsus Supinatus Foot Structure, and finally the Plantargrade Foot.

    Using this same methodology (e.g., the Ontogeny - Phylogeny Evolution Model), I believe we can trace back our homo sapien prototypes. That is, our earliest ancestors (who were bipedal obligates) would have the PreClinical Clubfoot Structure (twisted calcaneus and talar head). This would rule out A. afarensis. The A. sebida fossil's do have the twisted calcaneus.

    The PreClinical Clubfoot Structure/deformity forces the foot to hyperpronate. If the Laetoli footprints indicate that foot did not hyperpronate, following the above methodology, that upright walker would not be in our direct prototype, but rather a divergent line.

    I believe this line of reasoning will help uncomplicate our understanding of hominine taxonomy; which is consistent with my own research. That is, the closer you get to the truth, the easier it becomes to understand.

    Marc Verhaegen · Study Center Anthropology

    Ontogeny indeed often seems to recapitulate phylogeny: when evolutionary changes happen earlier in ontogeny, they're more likely to result in serious distortions of the normal development & hence to be selected out.

    I'm no sure what you mean by "our earliest ancestors who were bipedal obligates"? IMO this is at best vague, and at worst wrong. It's often said by traditional anthropologists who still believe that we had apelike ancestors who left the forests to run on the African plains, whereas there's evidence that the early hominoids already lived in swamp forests (cf lowland gorillas in forest bais), where they waded bipedally & climbed vertically arms overhead (vs monkeys) in the branches above the swamp, and that early-Pleistocene Homo populations dispersed intercontinentally along African & Eurasian coasts (S.Munro 2010 "Molluscs as ecological indicators in palaeoanthropological contexts" PhD thesis Austr.Nat.Univ.Canberra), beach-combing, wading bipedally & shallow-diving for littoral foods (S.Cunnane 2005 "Survival of the fattest: the key to human brain evolution" World Scient.Publ.Comp.Singapore).

    "It is often stated that human locomotion was an adaptation to running on the open plains, which is illustrated by expressions such as 'Savannahstan', 'endurance running', 'born to run', 'le singe coureur' etc., even on the cover of the most influential scientific journals. Verhaegen et al. (2007) disproved in detail all endurance running arguments (Bramble & Lieberman, 2004) that our Homo ancestors during most of the Pleistocene were adapted to running over open plains. When we analyse human locomotion into more elementary components, the running 'explanation' appears to be a just-so interpretation (cherry-picking): Bramble & Lieberman (2004) interpret every locomotor trait in humans as having evolved 'for' running, without even considering possible wading or swimming scenarios. A comparative approach shows that, for each trait, semi-aquatic scenarios provide more parsimonious explanations (google ‘econiche Homo’ table 4), and that extant human running is a secondary and conspicuously imperfect adaptation which evolved late in the human past, e.g. we run maximally 40 km/hr over short and 20 km/hr over long distances, about half as fast as typical open plain mammals." (Hum.Evol.28:237-266, 2013).

    Whatever, your observations on australopith feet look very interesting, Brian. Can you please send me your publications on this, m_verhaegen at skynet.be?

  • Nor fadhilah Kamaruzzaman added an answer in FACS:
    What is a suitable compound that can arrest cell division for 12hrs?

    I need to measure retention of nanoparticle in skin cell. In order to do so, I will incubate nanoparticles with cells for 2 hours, remove the medium, add new fresh medium and leave cell for 12hrs. after 12 hrs I will do facs to see whether the nanoparticle has been washed out from the cells. My worry is that cell multiplication can introduce bias. Is there any suggested compound I should use to arrest cell multiplication for 12hrs? Thank you.

    Nor fadhilah Kamaruzzaman · Royal Veterinary College

    i am wondering if i introduce serum deprivation will it kill the cell? thanks.

  • Brian Portugais added an answer in Traffic Flow:
    What are the current theories in modeling traffic flow?

    Suggest some papers regarding the recent theories in modeling traffic flow. Thank you.

     

    Brian Portugais · Boise State University

    I would start with:

    1. FHWA's Revised Monograph on Traffic Flow Theory. It can be downloaded by chapter at https://www.fhwa.dot.gov/publications/research/operations/tft/.

    It is an update to the TRB Special Report 165, "Traffic Flow Theory," published in 1975.  

    "The report consists of ten chapters, representing the most updated and unique compilation of knowledge in the field of traffic flow theories. These chapters are: (1) Introduction, (2) Traffic Stream Characteristics, (3) Human Factors, (4) Car Following, (5) Continuum Flow Models, (6) Macroscopic Flow Models, (7) Traffic Impact Models, (8) Unsignalized Intersections, (9) Signalized Intersections, (10) Traffic Simulation. Chapters 3 and 5 are two completely new chapters in this report."

    In addition to the above mention of Kerner, I would suggest :

    2. Treiber, Martin, and Arne Kesting. 2013. Traffic flow dynamics data, models and simulation. Heidelberg: Springer. http://dx.doi.org/10.1007/978-3-642-32460-4.

    Lily Elefteriadou (UF) has a new book out that is somewhat watered-down but may be a good primer and is a short book:

    3. Elefteriadou, Lily. 2014. An introduction to traffic flow theory. http://dx.doi.org/10.1007/978-1-4614-8435-6.

    As mentioned above if you narrow the question, I can suggest more.  What is the model's application?

  • Olivier Serrat added an answer in Digital Strategy:
    What steps might an organization take to develop a digital strategy?

    A typical, not necessarily linear, methodology for developing a digital strategy is to (i) identify key business challenges and needs in the digital space translate objectives into actionable recommendations; (ii) evaluate digital products and services against requirements and develop new digital initiatives and plans to improve user experiences and drive value; (iii) collaborate with cross-functional teams to plan, deliver, and execute digital campaigns; (iv) educate and inspire personnel on digital opportunities, latest technologies, and best practices; and (v) ensure alignment between the digital strategy and the organization's overall knowledge management strategy. Can you suggest other steps and give concrete examples of digital strategies?

    Olivier Serrat · Asian Development Bank

    Thank you, Paul. A clear and powerful vision of the future can certainly help find common ground for constructive action and enlist commitment in support of that. An article on a related system-wide strategic planning tool is at http://www.adb.org/publications/future-search-conferencing.

  • How to add header and footer in unix based latex report?

    In report preparation, header and footer are necessary.  Which style file to include for adding header and footer in a report? 

    Daniel Robert Franklin · University of Technology Sydney 

    Use the fancyhdr package (replaces fancyheadings which is obsolete):

    http://www.ctan.org/tex-archive/macros/latex/contrib/fancyhdr

    This lets you customise headers and footers with an enormous amount of flexibility and sophistication; it is well-documented.

  • Ba AlShammari asked a question in Acids:
    Why 120 c usually used for acid treatmeny of CNTs. ?

    Acid is mix from sulfric and nitric. 

    Thankd

  • John Salatas added an answer in Conversion:
    Can anyone suggest text to phoneme conversion algorithm ?

    I want to convert any word into it's phoneme. So,is there any algorithm or technique available for conversion of text to phoneme.

    John Salatas · University of California, Irvine

    I have implemented that feature for the cmusphinx project.
    I believe you will find the following links interesting. 

  • How can I use MATLAB to calculate the size of crystals?

    I'm producing a lot of crystals with needle-like shape. Currently, I used optical microscope to manually measure the length and the width of the crystals. Can MATLAB do this task?

    Siti kholijah Abdul mudalip · Universiti Malaysia Pahang

    yes. i would like to do it in an automated fashion. I will check on that paper. 

  • Ján Kozempel added an answer in Graphite Oxide:
    Can anyone help me getting a method that can make graphene oxide bonded to the surface of the quartz crystal?

    I want to replace gold electrode with  graphene in QCM .Can anyone help me getting a method that can make graphite oxide bonded to the surface of the quartz crystal? Thanks!

    Ján Kozempel · Czech Technical University in Prague

    That may be good choice. 

  • Can anyone recommend several references about the experimental study on the production of syenitic melts from crustal rocks ?

    The syenites can be produced by the mantle-derived melts via fractional crystallization or mixing with crust-derived magma. This is common for most syenites. But, is it possible that meltng of crustal rocks can produce syenitic melts ? Dose anybody know some experimental petrology studies on this problem?

    Yu Sheng Zhu · Chinese Academy of Sciences

    Dear all,

    Thanks. I agree with that special crustal rocks may generate syenitic melts. For most igneous syenites, mantle rocks seem to be their source materials. Episyenite is new for me as i always work on the igneous rocks. But, this remonds me to pay attention to the influence of post-magmatic alteration. Thanks again.

  • Swati Goel asked a question in Protein Hydrolysates:
    Desalting of protein hydrolysate??

    I am hydrolysing my proteins with 6 N HCl to peptides, followed by neutralisation with 2 N NaOH. Can anyone suggest the best way to remove salts without removing peptides. Since my peptide of interest are less than 1 Kda and I do not want to do loose them. 

  • Gert Nolze added an answer in X-ray Diffraction:
    Are crystallite size and particle size are the same?

    Are crystallite size and particle size are the same?

     If not, then how can particle size be calculated from XRD data?

    Gert Nolze · Bundesanstalt für Materialforschung und -prüfung

    As Harry ten Brink already mentioned there are already several questions touching this topic. Nevertheless, a short answer.

    As the terminology already explains a particle is assymed to be a homogeneous object, but it can consist of many subobjects like crystals of the same or different phases, amorphous as well as crystalline. A crystallite however is a single-crystalline individuum of a very small size. Crystal and crystallite are terms expressing the somehow the same. The later only points out that the (small) size of a specific characteristic.

  • How does one stimulate biogas productivity by Cd and Pb?

    Does anyone know something about stimulation biogas production by Cd and Pb. Ofcourse both are heavy metals so its obvious that higher doses are inhibiting biogas production, but in some small doses the effect is opposite.

    Henrik Rasmus Andersen · Technical University of Denmark

    The mechanism could be that your methane bacteria are partially inhibited by sulfide. Lead and Cadmium will precipate as sulfide salts which will decrease the concentration of sulfide in the digester liquid.

    I worked with iron sludge addition to digesters and we found a similar effect in our range finding experiment, but in the published final experiment the sulfide concentration in the control was lower and we could not see any stimulation of methane production by low iron sludge doses.

    If you are running experiments with metals addition to methane developing systems I think I can suggest an experiment that will distinguish between hormesis and reduced sulfide toxicity.

  • Saadat Majeed added an answer in Fluorescence:
    How do you get the integrated peaks in Fluorescence spectra?

    In fluorescence studies the FL peaks are obtained with varies fluorescent intensity. Can anyone guide me on how to obtain the integrated fluorescent intensity?

    Saadat Majeed · Hannover Medical School

    Thank you Robert ,for valuable suggestion.I am sure it will help me.

  • Steingrimur Stefansson added an answer in Proteins:
    Does anyone know if anyone sells unconjugated protein A or protein G?

    Most of the protein A/G that I find are conjugated either to agarose or sepharose beads.  Does anyone company sell just plain protein A or G?

    Steingrimur Stefansson · HeMemics Biotechnologies Inc

    ...or Sigma

    http://www.sigmaaldrich.com/catalog/product/sigma/p6031?lang=en&region=US

    http://www.sigmaaldrich.com/catalog/product/sigma/p4689?lang=en&region=US

  • Temitope Olawunmi Sogbanmu added an answer in Agar:
    Please suggest the relevance of using Normal Melting Point Agar and Low Melting Point Agar while doing comet assay?

    Can we use NMPA (Normal Melting Point Agar) instead of LMPA?

    Temitope Olawunmi Sogbanmu · University of Lagos

    LMPA (0.75%) is best to use.

  • John Macken added an answer in General Relativity:
    What physically changes when a particle is elevated and gains gravitational potential energy?

    We frequently speak of an object having gained gravitational potential energy when work is done in lifting a mass from a lower elevation to a higher elevation. However, what exactly has physically changed? Where is this gravitational potential energy stored? When a photon propagates from a lower elevation to a higher elevation, we say that it has undergone a gravitational redshift. However, this is entirely due to the gravitational change in the rate of time. Local clocks at the two elevations are running at different rates of time giving the perception of a lower frequency at the higher elevation. The photon appears to have lost energy but there is no change in frequency if adjustments are made for the different clock rates. If an electron is perceived as a point particle with no internal structure, then it is impossible to assign any change in the internal energy of an electron at two different elevations. Therefore, where is gravitational potential energy stored when an electron or other particle is elevated?

    John Macken · Saint Mary's College of California

    Rajat: You say that "the potential energy always resides in the space between the objects". I am going to use one of Einstein’s thought experiments to disprove this. Suppose that there is a star with one planet in a highly elliptical orbit. When the planet is at its apogee it has the lowest kinetic energy and the greatest gravitational potential energy. At its perigee it has the opposite condition – the lowest gravitational potential energy and the highest kinetic energy. So, the first point is that the greatest potential energy occurs when the gravitational field is weakest between two masses. Second and most important, this is a closed system since energy is not being added or lost. Therefore, the average gravitational acceleration produced by this system does not change.  This is easiest to see at a distance large compared to the orbit.

    Now, the kinetic energy of the planet clearly resides within the mass of the planet. If the internal energy of the particles that make up the planet does not change inversely to offset the change in kinetic energy, then the total energy of the planet would continuously change over its orbital path. Actually, it can be shown that the gravitational effect on the rate of time does produce many other changes. One of these changes is that a unit of energy such as 1 Joule decreases in gravity when the measurment uses an absolute scale that incorporates a constant rate of time.  

    For example, the energy of an electron appears to be constant in gravity or zero gravity if the measurement is made locally. However, there is a difference if the measurement always uses the standards of zero gravity. This difference exactly offsets the change in kinetic energy of a mass in free fall in a gravitational field. The implication is that the local rate of time produces a physical change within the particles which affects internal energy.

  • Dorian Aur added an answer in Cognitive:
    What is the best approach to study the Problem of Consciousness?

    The Problem of Consciousness:

    http://www.imprint.co.uk/chalmers.html

    Cognitive approaches:

    http://www.mind.ilstu.edu/curriculum/consciousness_sci_of/cognitive_approaches_to_consc.php

    Are there any other approaches?

    Dorian Aur · Stanford University

    No need to  have "the role of compression in air"  electromagnetic waves travel  through the vacuum, the analogy with acoustic waves is an issue. Nunez is right. You assimilate easily  what Buzsaki is telling, probably a far closer background.There are standing and travelling waves as Nunez describes and far more other complex phenomena since  excitable structures are inside.

    Please, notice that I only reply since you  strongly insisted.

    My view in no different than  Max Planck quote" A scientific truth does not triumph by convincing its opponents and making them see the light...."
    and also that "we ourselves are a part of the mystery that we are trying to solve"

  • Fulvio M. Rivano added an answer in Bulk Density:
    How can I test soil water-filled pore space?

    Hi, I am doing soil  water-filled pore space (WFPS). I don't know why researchers tend to make soil bulk density at 1.1 g/cm3 during the test? Besides, what factors will affect the results of WFPS? Is WFPS the constant for a specific soil?

    Thank you very much.

  • Tatyana Sysoeva asked a question in His-Tag:
    Is it possible that a protein missing His-tag binds to Ni-NTA resin?

    I work with a protein that appears to weakly bind to Ni-resin. It binds with some efficiency under 10 mM Imidazole and starts eluting at about 50-60 mM.