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  • Is it necessary to use Quick change for site-directed mutagenesis kit?

    when making a mutation in a gene by mutated primers, is it necessary to use Quick change site -directed mutagenesis kit or it can be using A master mix PCR kit with mutated primers?

    Hêro Akrayi · Salahaddin University - Erbil

    Thanks so much for your answer David and Irshad

  • What is the current understanding of the atherosclerosis risk factors?

    I remember reading somewhere that not only a chronic hypertension but also a short-lasting bouts of high blood pressure can contribute to the atherosclerosis development due to small damages to the arterial endothelium. 

    I am aware that the atherosclerosis is also called an inflammatory disease and that antioxidants can help preventing the risk and development. I also know that atherosclerosis and hypertension do not have to be both present at the same time or prevalent in the population at once. 

    For example, as it was discussed in the 7 countries study, the Japanese had quite a thin blood but high blood pressure. They suffered low rates of coronary heart disease but had a high incidence of brain hemorrhage: consuming very little animal (saturated) fat but having a high salt and unsaturated fats intake. 

    When I read about the Finns and how they enjoy frequent sauna, the short-term hypertension and its link with the atherosclerosis were somehow put together in my mind and I started to think whether the enhanced vasodilation in the Finnish sauna and then a sudden vasoconstriction of the peripheral circulatory system, re-directing the blood into the body core, could somehow contribute to a high prevalence of atherosclerosis and the coronary heart disease in Finns (in addition to a high animal fat intake and low intake of antioxidants, including low selenium, lacking in their soils and/or a high iron intake)? I did not read the whole 500 volume of the 7 countries study, just some extract freely available online which mentioned these details. 

    My main point here was whether the physiological stress due to the sauna could actually contribute to the endothelial injury and therefore to the atherosclerosis?

    Vilemar Magalhaes · Faculdade Kurios

    Well said Dr Max. There are many other factors too. According to Dr. Kilmer McCulley, homocistein is another important agent to this condition.

  • Hanno Krieger added an answer in Writing:
    Does writing quality in a first language corellates with writing quality in a second language?

    I am just wondering if ESL learners who write well in their first language will be able to write in the same quality in a second language. Are there any relationships between the writing quality in both languages?

    Hanno Krieger · retired from Justus-Liebig-Universität Gießen

    Thats the point dear Joseph, thinking in the language you actually use. Good formulation!

  • Victor Christianto added an answer in Population:
    Are there evidences that all humans descended from a single population of ancestors in Africa?

    I read somewhere concerning this hypothesis. Do you know any evidence?

    Victor Christianto · University of New Mexico

    @David, Maria, William: while i am no specialist in genetics or genomic, i think i can accept the idea that there is one common ancestor of all human being, be it from africa or elsewhere. But frankly speaking, i cannot swallow the idea of single last universal common ancestor (LUCA). 

  • David L Morgan asked a question in Scaling:
    How to help people create simple scales?

    One of the most frequently asked topics I come across is how to create simple scales from Likert-scored items. Apparently there are a lot of beginning researchers who have learned how to use Likert-style items in questionnaires, but never got any advice about how to analyze the resulting data.

    Hence, I would like to put together a thread here that people can refer to whenever this question gets asked.

    Please remember that this is advice for beginning researchers who generally want to run basic regressions, so there is no point in recommending complex procedures such as Item Response theory or Structural Equation Modeling.

    Instead, I would to find sources for things like how to use Cronbach's alpha effectively and how to do the most straightforward kind of Factor Analyses (almost certainly Exploratory rather than Confirmatory).

    The overall goal is to help beginners get started with scaling, so who can suggest some resources?

  • Abebe Genetu Bayih added an answer in Freezing:
    Does anybody know a freeze-thawing method to isolate crude protein from parasites?

    Does anybody familiarize with the freeze thawing method to isolate proteins? what is the normal yield of protein we can get from it?

    Abebe Genetu Bayih · The University of Calgary

    We extract crude Leishmania proteins using freeze-thawing in liquid nitrogen. Wash the cells in PBS and centrifuge at 4oC. Then, resuspend the cells (pellet) with PBS in the presence of cocktails of protease inhibitors and snap freeze in liquid nitrogen and thaw in ice. Repeat the freeze thawing three to five times. You can also sonicate it after the freeze thawing. Good luck! 

  • Vedvyas Dwivedi asked a question in ADD:
    Why do we add a constant while integrating a quantity?

    Why not we subtract?

  • Hocine Osmani added an answer in Hardness Tests:
    How can I calculate fracture toughness?

    It is well known that fracture toughness can be detected using special devices and instruments. But if I want to calculate fracture toughness [for ceramics materials] from hardness test instead of using those devices, can I do that? and how?

    Hocine Osmani · Ferhat Abbas University of Setif

    yes you can determine the tenacity by measuring the lengths of cracks on the arrested Vickers imprint
    there are several formulas
    either for radial cracking mode or Palmquist
    For this see the articles by K. liang or gilbert fantozzi
    see RG hocine osmani, I have some articles

    Article: Interaction between indentation cracks in sodalimesilica glass
    Malou Z, Hamidouche M, Madjoubi M.A, Loucif K, Osmani H, Bouaouadja N

  • Steingrimur Stefansson added an answer in SDS-PAGE:
    Urine Proteomics: what is an efficient way to resuspend proteins post precipitation?

    We use Acetone precipitation to concentrate /clean-up proteins from urine samples. However, it's difficult to fully resuspend samples post precipitation. We've tried many different solubilization buffers including additives such as SDS or Urea but always get left with a cloudy solution which contains significant amount of protein (checked by running pellets on SDS-PAGE). Has anyone experienced this issue? 

    Steingrimur Stefansson · HeMemics Biotechnologies Inc

    Hi Stoyan, albumin binds many peptides. If you precipitate albumin out of the mixture, you might also lose whatever is bound to albumin.


  • Does anyone know about this lost reference on soil classification?

          I have been looking for a reference for a long time, and I am annoyed that I cannot find it again. Perhaps someone on this list could help me...
         About 30 years ago, I remember reading an article, by a British scientist if I recall correctly, talking about soil maps. The author said that soil maps without a well-defined practical purpose don't make a lot of sense. He (or she?) discussed the example of a soil map useful to a fisherman. That map only needs to have two classes: soils with earthworms and soils without earthworms...
          I have always thought that this paper was right, in so many ways... And for the last few years, I have tried desperately to find it again, to cite it in a reflection on the usefulness of soil maps that I would like to write... We seem to spend so much time and energy making maps, including now digital maps, and so little time thinking about what information soil maps should contain to be useful, or what precise purpose maps serve. As a result, most of the information that current soil maps provide is almost entirely useless or misleading for a wide range of situations... 
    Anyway, if someone could tell me what the reference to this article is, I would be eternally grateful.

    Luis Daniel Olivares · Universidad Nacional Autónoma de México

    I guess I recently read this text, but I can't remember if it was on Soil genesis and classification by Buol et al. or within the memories of a tropical soils congress of the 70's. I'll look for the sentence hoping to find it out.

    However, this idea is the first step in any soil survey book, for example I'll recommend you to see:
    – Dent, D. and Young, A., 1981 Soil survey and land evaluation. London, England: George Allen &Unwin.

  • Is rapid change in mobile technologies good for world economy?

    The large number of countries have yet to set 3G networks still in the same country vendor are looking for 4G markets. It forces some countries to unnecessarily invest before time in my opinion. Your comments are requested.

    Vedvyas Dwivedi · C U Shah University Wadhwan City, Surendranagar, Gujarat, India

    in my view in short 'no'

  • How do I troubleshoot Nystatin partitioning in 80%POPC/20% Cholesterol Liposomes (MLV)?

    I've been trying to develop my technique as a graduate student and am attempting to partition the antifungal drug Nystatin into a liposome preparation consisting of 80% POPC/ 20% cholesterol. I've used literature to find a protocol for making the liposomes. Calculated volumes of POPC and Cholesterol in Chloroform were combined in a tube and dried under Nitrogen followed by overnight vacuum. I then used 50 mM Tris, 10 mM EDTA Buffer to dissolve the lipid film at 37 degrees Celsius for 3 minutes. This was followed by 3 rounds of 30 minutes at 37 degrees and 30 minutes at 4 degrees Celsius. Liposomes were then flushed with argon, wrapped with teflon tape and parafilm before use. My experiment consisted of preparing various concentrations of liposome using Tris buffer to dilute, followed by adding Nystatin to a final concentration of 10 uM. These solutions were incubated for one hour in a water bath at 37 degrees. A fluorometer with excitation slit width 1 nm, emission slit width 8 nm was used to take measurements of fluorescence. Excitation beam was 315 nm, emission was 415 nm with a quartz cuvette. All samples were prepared in parallel with references to which no drug was added. The literature suggests that there should be a significant enhancement of fluorescence that corresponds to partitioning of the drug in the membrane with respect to references, but I have not been able to accomplish this. Any suggestions for troubleshooting?

    Abhishek Jha · Nirma University

    Plz tell me the calculation to decide the weight of lipids i.e. lecithin and cholesterol if i want to take them respectively in 7: 3 molar ratio.

    i m very confused in this calculations. first of all how to decide the weight of these lipids in 7: 3 :lecithin: cholesterol ratio? and second if the value comes in mg, then is it for per ml or how much quantity of both organic solvent and water

  • Why displacement current is necessary in Ampere's law?

    Maxwell modified the ampere's law by the introduction of displacement current and was presented as 4th of the famous Maxwell equations. But I am always not clear about this term. Can any one help in this regard?

    Vedvyas Dwivedi · C U Shah University Wadhwan City, Surendranagar, Gujarat, India

    Dear Mr Gyan, Displacement current and Ampere's Current Law are well inter-relatively explained by all these scholars. I am mostly agreed with Vladimir Lvovich Bychkov.

  • Abhishek Jha asked a question in Lecithins:
    Plz tell me the calculation to decide the weight of lipids i.e. lecithin and cholesterol if i want to take them respectively in 7: 3 molar ratio.

    i m very confused in this calculations. first of all how to decide the weight of these lipids in 7: 3 :lecithin: cholesterol ratio? and second if the value comes in mg, then is it for  per ml or how much quantity of both organic solvent and water

  • Ilya V Kublanov added an answer in NCBI:
    Where can I get the reference sequence for 16S rDNA?

    I have analyzed gut flora of Helicoverpa and found B. pumilius, with some strain identification by 16S rDNA analysis.

    I want to check these strains via nucleotide diversity by DNA sp software. I am looking reference sequences of 16S rDNA of those strains. Can you please suggest other than NCBI data base for getting reference sequences for diversity analysis of these strains?

    Ilya V Kublanov · Winogradsky Institute Of Microbiology

    BTW, Venkatachalam, EZ-taxon (ezbiocloud now) is a special database for valid species and common uncultured clones (the modern verison). LPSN - is a database of valid taxa, not sequences. Thus, both useful for understanding whether your microbe new or not.

  • In programming, what exactly do you mean by a top down and bottom up approach?

    In layman's terms, how would you explain the concept of top down and bottom up approach. If we have to explain these concepts to a laymen who is for the first time studying programming how will you explain this term to that person.

    Raphaël Couturier · University of Franche-Comté

    Did you read the explanation in wikipedia?

  • Have someone tried Experiential Learning in higher education (at undergrad. and graduate levels)?

    Can you advise me a report or paper on Experiential Learning in (Sustainability) Higher Education? Or another evolution of this approach to education and learning? 

    Maciej Laskowski · Lublin University of Technology


    I've tried some gamification in higher education (simple gamification techniques, applicable to all kinds of courses). Here are some publications I may suggest:

  • Adil Hussain added an answer in Drought:
    What are the criterion to delineate the drought prone regions of India?

    There are different types of droughts. Along with rainfall what are the other criterions for the delineation of drought prone regions of India.

    Adil Hussain · International Islamic University, Islamabad

    Climate and meteorological data or Remote sensing technology  may be the primary sources for the identification of the occurrence, severity,and distribution of drought in different regions.

  • How can we use the GMRES algorithm for the following system?

    good morning
    I read the article titled 'SINRD Circuits Analysis with WCIP' we can solve the equation system (10) by the GMRES algorithm
    So to use the GMRES we must put the system in the form of equation (11) something I've already done that is to say the system is like this we have: A*x = b
    my question is how can we write equation (11) in matlab to use the GMRES
      thank you

    Raphaël Couturier · University of Franche-Comté

    I didn't read the paper, only the equation (11). If the part in parenthesis represents a matrix and if Az is the unknown, you should be able to represent this equation in  matlab.

  • Are there any alternative for CastP?

    Can't access CastP(an online tool for surface analysis of protein) from links i've found through google(http://cast.engr.uic.edu/castp/calculation.php, http://sts.bioengr.uic.edu/castp/)

    I guess their server is down or i'm trying the wrong URL. Please suggest me any alternative.

    Ruhshan Ahmed Abir · Shahjalal University of Science and Technology

    Thanks Danish Jasnaik, that was really helpful.

  • What difference is there between design frequency and operating frequency regarding Microstrip antenna?

    What is difference between design frequency and operating frequency regarding Microstrip antenna. What is the role of design frequency for designing of antenna.

    Vedvyas Dwivedi · C U Shah University Wadhwan City, Surendranagar, Gujarat, India

    Sundaram and Enrique are in my opinion correct.

    Dr. Amipara has explained technically. Still if any confusion, please do write me at provc.cushahuniv@gmail.com  

  • Xuezhong He added an answer in Rattan:
    Can rattan be a carbon material by heating up to 1000C?

    can rattan be a carbon material by heating up to 1000C?

    Xuezhong He · Norwegian University of Science and Technology

    Yes, you used vacuum, N2 and CO2 as purge gas for carbonization. If the carbonized materials can have porous microstructure. That will be useful, the main concern is the mechanical strength. It will be brittle Alain?

  • Vedvyas Dwivedi added an answer in Waveguides:
    Which mode is used in dielectric circular wave guide ?

    Which mode is used in dielectric circular wave guide ?

    Vedvyas Dwivedi · C U Shah University Wadhwan City, Surendranagar, Gujarat, India

    agreed with Respected Raymond.

  • Vedvyas Dwivedi added an answer in Massive MIMO:
    Can the EM wave hazards be reduced in massive mimo because of using low power antennas?

    In massive mimo large number of low power antennas are used at the base station. Because of this low power transmission, do the hazards get reduced or not?

    Vedvyas Dwivedi · C U Shah University Wadhwan City, Surendranagar, Gujarat, India


  • Ljubomir Jacić added an answer in Research Papers:
    Can we define an expiration date or useful age for our papers?
    Is it reasonable to use these terms?
    A number of papers have been published a long time ago, but still have many citations.
    If it is possible, then is it predictable?
    Is citation can be a suitable measure to judge the useful age of a paper?
    Which papers have more useful lifetime or long expire date?

    Thanks for your inputs.
    Ljubomir Jacić · Technical College Požarevac

    "Journal articles are an outdated way of sharing scientific research, says open-access advocate." This is fine article!

    Research results stay for ever, the way of their dissemination change!

  • Hesham Saeed Amer asked a question in Healthcare:
    Is there any questionnaire that can be used to measure healthcare workers performance?

    I need a questionnaire that can be used to measure healthcare workers performance in general .

  • Hazem Y. Abdelwahed added an answer in Tinnitus:
    Could you give your experience regarding Patulous (abnormal patency) Eustachian tube, diagnosis & management?

    From time to time, i meet different patients of tinnitus (HF-SNHL, Menier's disease, thyroid dysfunction, vascular) but in other patients no complaint except intermittent tinnitus during breathing (inspiration/expiration) & after excluding other causes of tinnitus, i diagnosed patulous ET. Please, you would give your experience regarding Patulous Eustachian tube, diagnosis & management.  

    Hazem Y. Abdelwahed · King Saud University

    Thanks Ranjit for your sharing. Would you mention any published article which supports your opinion.

  • Vedvyas Dwivedi added an answer in HFSS:
    Are there any companies that design microstrip patch antennae from HFSS?


    Vedvyas Dwivedi · C U Shah University Wadhwan City, Surendranagar, Gujarat, India

    we at our university do it.

  • David L Morgan added an answer in Likert Scale:
    How can I do data analysis of the Likert scal?

    I have prepared a questionnaire which contains the Likert scale. Respondents are in four different age groups and there are 20 questions asked using the likert scale. Can I use 1 way ANOVA?

    David L Morgan · Portland State University

    I assume that age is your independent variable and that the Likert scored items go together to make up one or more dependent variables, is that correct?

    If so, the first question I would ask you is whether you expect the effects of age to be linear or non-linear. Entering them into an ANOVA as an independent variable treats them as categorical variables and thus ignores the idea that the effect may be linear across age groups.

    To test for a linear effect, recode each age group to the midpoint of that age range, which effectively convert ages to a continuous, interval-level variables. That will allow you to use the age variable in correlations and regressions.

    The next question I have is whether the 20 items that have Likert scores can be combined into one or more scales. For example, are all of them designed to measure the same theoretical concept? If so, then you can use Cronbach's alpha statistic to determine whether  all 20 of your items can be added together to form a continuous measure of that concept. (or, if you have two 10-item scales, you can examine each of the separately, and so on).

    Creating a single scale from a set of Likert-scored items is standard practive in many fields. The analogy is like a bundle of sticks: any one of the items may be weak by itself, but combined into a larger set they are much stronger.

    Note that the alternative to creating scales is to do 20 analyses, each of which is essentially testing the same thing with a comparatively weak measure.

    Here is a link to a tutorial about using SPSS to calculate Chronbach's alpha, but you really should begin by doing some reading on how to create scales.


  • Joerg Kampmann added an answer in Solar Cells:
    Why did the best band gap for solar cell lye close to 1.5 eV ?

    In several papers I found that the optimized band gap for solar cells is close to 1.5 eV. This value corresponds to a wavelength of about 830 nm, in infrared. Is it due to the fact that we use more silicon or silicon-like devices ?