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  • Can anybody help me on AAS instrument?

    we are analyzing Sodium in steam water which OEM spec fall in ppb range. calibration graph is plotted using method of standard addition. please kindly explain me how sample concentration is calculated with using absorbance values for standards and reagent blank and how we can decide whether its times to plot a new calibration graph that mean what happens to a graph when we use it for long period of time. 

    R.Girijan Menon · Toshvin Analytical Pvt.Ltd.

    Hi, Madurika,

    Method of Standard Addition is a very popular technique in AAS. This is a very valuable technique especially if you observe interference due to matrix. The procedure of standard addition is already discussed by Mr. Najib and hence I am not repeating it. Once you plot the graph, you see whether it is passing through origin(0,0). If the plotted line is passing through origin, then your sample does not have that target element. If your sample contains the target element, then the plotted line will not pass through origin and it will have a Y-intercept. You can then extrapolate the graph and it will touch the X-axis on the negative side. Since the X-axis is the concentration axis, you can easily read the concentration of the element in your sample. I hope this is clear to you. For any further info, please write to me on : rgirijan@toshvin.com.   

  • Kaleem Ullah added an answer in Refractive Index:
    How can I calculate imaginary refractive index?

    How can I find imaginary refractive index for the wavelength range of 400 nm to 700 nm for calcium carbide?

    Kaleem Ullah · Nanjing University of Science and Technology

    but the other people not even some time ..so i am using that refrence..hehehe  I am new in this field my background is of power electronics and solid state physics.  

    Recently i define Calcite in FDTD it shows the 0.98 RMS error. i have put data from the book of Palik.. But material data is not matched with FDTD model... 

  • Writing answers instead of recording in in-depth interviews. Is it methodologically sound?

    In an in depth interview for a qualitative data collection, we faced difficulty in recording the interview due to social causes. Is it possible to write the answers by an assistant data collector.

    David Schmidt · University of Sydney

    Title: Research in Health Care: Concepts, Designs and Methods

    Authors: Julius Sim, Chris Wright

    Publisher: Nelson Thornes, 2000

    This text discusses the value of handwritten notes vs recordings in the chapter on "Recording and organizing data from exploratory studies". They point out that handwritten notes can be quite beneficial where you may have suspicion from participants about every word being recorded. This may be a factor in your study from what you have described.

  • Rahimi Ali added an answer in Mass Communication:
    Who and when the author (year) presented Desentization thoery in Mass Communication?

    I need full theory with reference, journal name or book name.

    Rahimi Ali · Bangkok University

    Dear Sajjad ,

    this is it:


    Good luck with your research.

  • S. Sampath added an answer in SPSS:
    Is there any difference in formula when calculating Skewness manually and using SPSS software?

    When I calculate Skewness manually, i get that the value of Skewness is 1.26, but when I calculate in SPSS program, the value of Skewness is 0.000. What am i doing wrong in this calculation? Is there any correction in SPSS software for this value or is it something else?

    Mean = 6

    Median = 2

    Standard deviation = 3.16

  • Haider M. Zwain asked a question in VSS:
    What do Total Dissolved Solids (TDS) represent in the anaerobic system?

    I am working on anaerobic baffled reactor to treat paper mill wastewater. I have noticed that the concentration of Total Dissolved Solids (TDS) in the effluent (wastewater after treatment) has increased in compare to the influent (wastewater before treatment).

    Hence, I want the understand what do TDS's mean in the anaerobic system? whats the source? what are the key factors which control the concentration?

    For example, the VSS may represent the concentration of biomass or microorganisms.

  • L. Velazquez added an answer in Molecular Dynamics:
    In Molecular dynamics, which ensemble is better to use: NVE or NVT?

    We use different ensembles in MD, which one is preferred to use?

    L. Velazquez · Universidad Católica del Norte (Chile)

    Actually, I am speaking about the observation of anomalous response functions such as negative heat capacities, dependence of fluctuations and other related behaviors on the enviromental influence, such as correlation functions and critical phenomena, criteria of thermodynamical stability, etc. I and my coleague Curilef have discussed these questions with more details in the following paper: 


    or http://iopscience.iop.org/1742-5468/2011/06/P06021

    Precisely, dependence of thermodynamical description on statistical ensembles are better explained by fluctuation theorems that relate fluctuations of system macroscopic observables under influence of an enviroment and its response functions, such as the well-known canonical fluctuation relation that relates energy fluctuations and the heat capacity. For a more general context, such a flutuation relation should include thermal fluctuations of enviromental temperature, which makes possible the observation of states with negative heat capacities.  Canonical ensemble (an environment with constant temperature)  is unable to describe these states, which means that this conventional ensemble cannot be employed to study phase coexistence phenomena during discontinuous phase transitions. 

  • Rajivgandhi Sundaram added an answer in Elution:
    How can I purify protein with 27 KDa from GST ?

    Dear colleagues, i am trying to purify a protein with 26 kDa size that is expressed as a GST fusion protein. When i have done  on column GST cleavage in the flow through both GST and my protein of interest coming together. Even i tried Superdex 200 SEC there also proteins are co-eluting. My protein pI is 4.54 and GST pI is 6.09 so i did ion exchange (mono q) with buffer pH 6.5 i eluted by gradient elution with 1M NaCl but here also both the protein coming together. Please suggest some idea to purify the protein. I need this protein for crystallization and structural studies.

    the image i have given is MONOQ profile in 18% SDS gel 

    Rajivgandhi Sundaram · The National Institute of Science Education and Research

    Thank you dear Csaba and yann your comment is really usefull for me  i wil try 

  • Bharat Bhushan Negi asked a question in Life Cycle:
    What does the "Sterile Immunity" means in case of Malaria Vaccine development ?

    The blood stage is the only stage in the parasite life cycle that causes disease, a vaccine against this stage of the parasite life cycle would prevent or reduce severity and complications of the disease, and perhaps eliminate malaria if sterile immunity could be achieved. What does Sterile Immunity means in this case ?

  • Mohthash Musambil added an answer in Xanthomatosis:
    Can any one explain what "Atheroeruptive xanthoma" is?

    Can any one explain what "Atheroeruptive xanthoma" is?

    Mohthash Musambil · King Saud University

    What makes Atheroeruptive xanthoma different from eruptive xanthoma?

  • Ralph Trancoso asked a question in Feature Selection:
    What is the best approach to select input variables in Artificial Neural Networks (ANNs)?

    The selection of input variables is critical in order to find the optimal function in ANNs. Studies have been pointing numerous algorithms for input variable selection (IVS). They are generally classified in three different groups: (1) dimension reduction, (2) variable selection, and (3) filter. Each group holds several algorithms with specific assumptions and limitations.

    If a researcher decides to use ANN, he might be happy to know...

    1) Which approach is the most recommended to select ANN input variables? 

    2) What are the advantages and drawbacks of your choice in regard to other strategies? 

    3) Is the algorithm implemented in any statistical package (R or other free ones are more approachable)? 

  • Phil Wang added an answer in Optogenetics:
    Should I use AAV serotype 2 or 5 for expression of ChR2 in the ventral tegmental area?

    Leaning toward serotype 5. I have read that serotype 5 is better in adult rodents. That was outlined here

    Han X. Optogenetics in the nonhuman primate. Progress in brain research. 2012;196:215-233. doi:10.1016/B978-0-444-59426-6.00011-2.

    Seeing if anyone has experience handling these vectors and injecting them.

    Phil Wang · Georgia Regents University

    This may be out of your question and I beg your pardon if it is. We got great expression using AAV9 to transduce DA neurons in VTA. We injected 0.5 microliter of diluted AAV9 with a titer about 10 to the 10th. Almost all DA neurons showed expression of GFP-ChR2.

  • Muhammad Wasif Umar asked a question in Power Supply:
    DC current regulation?

    Hello All,

    Can anyone tell me about DC current regulation using switch mode power supply?

  • DNA isolation troubleshooting help?

    I have used an in-house DNA extraction protocol to isolate DNA from young leaf tissues and even though i can see the DNA on the Agarose without much degradation, the bands are not intact (slightly spread). Can any one point to me how i can troubleshooting this to get intact DNA bands?

    Upendra Kumar Devisetty · University of California, Davis

    This is after RNAase treatment and clean up after the treatment. No i haven't used silica based method. i just used custom protocol

  • Bharathi Raja A asked a question in R:
    Priority queue in R?

    Is it possible to implement priority queue in R? how to implement?

  • Stephanie Assmann added an answer in Trade:
    Is a high dependency on food imports really a problem?

    I have been researching Japan's high dependency on food imports. Japan imports 60% of his foodstuffs which has become an issue of concern among Japanese citizens and for the Japanese government. In this context, the low food self-sufficiency rate of 40% has been discussed as a problem, in particular in the context of the expansion of free trade negotiations Japan has been involved in. I have been asked several times by students whether a low food self-sufficiency rate is really a problem, or if it is portrayed as a problem in order to promote domestic foodstuffs more strongly? Can anybody recommend materials in which the significance of a high food self-sufficiency is not a given but is more critically discussed? Thanks!

    Stephanie Assmann · Hokkaido University

    Thank you, Patricia and Richard, for your answers and for alerting my attention to very valuable sources!

  • Subhash Chandra added an answer in Likert Scale:
    Is it mandatory to have the value of Cronbach's alpha above .70?

    In my study using questionnaire survey, I have four variables and job satisfaction is one independent variable. I measured job satisfaction with a 3-item scale. Responses were captured in a 5-point LIkert scale. The value of Cronbach's alpha is .65. However, the value of Cronbach's alpha for other variables (captured with  5-point Likert scale are above .70. Can I use the data (with job satisfaction having alpha value below .70) to test my hypotheses? 

    Subhash Chandra · Department of Economic Development

    Arjun - what is the hypothesis you intend to test? That Cronbach's alpha should be >0.70 is absolutely arbitrary. 

  • Khozema Ahmed Ali added an answer in Photocatalysis:
    How does light intensity and wavelength, (UV light vs visible light) effects product yield for photocatalysis process?

    How can we relate the light source to the product yield? I found a few papers that briefly explains that UVC light emits higher power that visible light, thus product yield will decrease with increase in light wavelength. Is there any better and detailed explanation on this?

    Khozema Ahmed Ali · University of Science Malaysia

    thank you very much to all for the help on this matter

  • Asutosh Kar added an answer in Image Compression:
    How can I get an example on Back propagation ANN for image compression training and testing?

    How can I get an example on Back Propagation ANN for image compression training and testing?

    Asutosh Kar · International Institute of Information Technology, Bhubaneswar

    Dear Mr. Ali,

                         Thanks for your question. I think I should go for a subjective answer rather than objective for your concern. This is a well known research area and I believe if you go through the below mentioned links you will surely get some valuable examples for this issue. If you have any doubts in these papers please feel free to ask more.


    Dr. Kar





  • INNOVATION SYSTEMS Application to Educational Quality?

    Would like to understand the status of eductional quality and employability of fresh graduates and application of Innovation Systems Model... Unable to find and have my handle onit from my searches... Is any one of the Learned Scholars in RG is working on this? I will be grateful if I get a pointer.

    Thank you in advance

    Kindest Regards


  • Marković G. Đoko asked a question in Mathematics:
    Does anyone know how the writer Rhind papyrus famous Egyptian priests Ahmess solved linear equations?

    Ahmes Papyrus (known as Rindov papyrus), written around 1800. g. BC, is one of the oldest monuments of human culture. Here's a little view this decrypted text:,, lesson, how to achieve knowledge of obscure (difficult) things,,, all the secrets that conceal things ... Ahmes writer wrote this... From old manuscripts ...  Rhind Mathematical Papyrus contains a series of tasks that modern mathematics solve using the equation of the first degree. Ahmes them solves the way to over next 3000 years represent the main proceedings for solving similar tasks, the so-called. ,, method of false position. The Egyptians then had to mark unknown special character and name, the last is pronounced,, hua "or,, aha" and translates word,, bunch. "

  • Niraj N Mahajan asked a question in Sterilization:
    Is Female sterilization by Pomeroy's Technique justified in all cases?

    As per rule/law, at least in India, we have to perform female sterilization with Pomeroys technique. But over the years, I came across several cases, where I feel this technique should not be used in some cases. For example
    Previous 3/4 cesarean section
    Previous rupture uterus and scar dehiscence this time
    Scar dehiscence without labour in previous one scar
    If we perform pomeroy's technque in these cases, there is a little chance of spontaneous recanalization, and surgical recanalization is never intended or advised in such cases.

  • M N Manoj added an answer in Parasitemia:
    What affects PCR efficiency?

    I made a 10-fold serial dilution of malaria parasite and tested it using PCR. I did a 10 dilutions from 1:10 until 1:10e-10. with a start up parasitemia of 2%. dilutions number 1:10e-7 and 1:10e-8 amplified at the same cycle! any explanations why?

    M N Manoj · Bigtec Labs

    Are you diluting a parasite culture or blood? Then be cautious that different RBC's have varying amount of parasite genome and this also depends on the stage of growth. Assuming that your PCR conditions are perfect, this can cause variations in Ct.

  • Dhanunjaya dm added an answer in Object Recognition:
    Can any one explain about steps in object recognition? with one example?

    i need to know about object recognition steps can any one help me, with an example.

    Dhanunjaya dm · Birla Institute of Technology and Science Pilani

    Refer opencv documentation link pasted below.It gives c++ example for face recognition. You can train classifier for other object detections also.

  • Alban Grastien added an answer in NP-complete:
    Is anyone familiar with NP Hard problems?

    Please I have a question, 

    How will I know if an optimization problem is NP-hard or NP-complet? 

    (Many papers just say that the optimization problem they have is NP hard and propose heuristics...)

    Alban Grastien · National ICT Australia Ltd

    Thanks for your clarifications Antonis.

  • Anil Panigrahi added an answer in Tissue:
    Looking for technique to study protein changes in tissue??

    Hi, I have to find out six proteins change due aging in muscle tissue. I am performing western blot right now.  Is there another technique available to get accurate protein concentration?  I don't have purified proteins to use as standers so can't perform ELISA. 

    Anil Panigrahi · Baylor College of Medicine

    If you do not have a pure protein of interest, you cannot obtain its "accurate" concentration.

    It is not clear if you wanted "six techniques to study protein changes" or "changes to six proteins". If it is the former, there are many techniques that address many properties of proteins; some require pure preps while others don't. Over aging, many changes can occur to a protein: the level of expression, post-translational modifications (these can be simply numerous), folding, proteolysis etc. If you know what exactly you are looking for, it will be easier for you to find a way.

  • What is the difference between "value chain" and "supply chain"?

    Are there any acknowledged definitions of "value chain" and "supply chain" in the literature that allow us to clearly understand where they do differ?

    Or, is there a work addressing exactly this issue and clearly explaining the differences among them? (and maybe suggesting how to use them)?

    Despite the existence of particular studies, considerations and reflections supported by previous experiences are always welcome.

    Hamidreza Panjehfouladgaran · Putra University, Malaysia

    in my point of view, supply chain leads to value for the companies and supply chain members. Therefore, supply chain is pre-requisite for the value chain and value chain creates by supply chain

  • Aashish Basnet added an answer in Social Exclusion:
    Does anyone know about the sources related to Social Exclusion in India and other texts or research books at international level?

    I'm working on Dalit women and Social Exclusion: A study of the Chamar Women in Post colonial Uttar Pradesh. I want suggestions, sources related to Dalit women in Uttar Pradesh, material / texts Social Exclusion and Chamar women related sources in Historical perspective. 

    Aashish Basnet · Tribhuvan University

    Hi Santosh,

    some  time back i had read, Memory, Trauma and World Politics: Reflections on the Relationship Between Past and Present. Palgrave MacMillan, London, in which there is an essay on Partition and Trauma:Repairing India and Pakistan. Why not go through it? 

  • Kisalaya Basu added an answer in Standard Deviation:
    How problematic is it if the standard deviation of the dependent variable is marginally higher than the mean?

    Is it really problematic to have standard deviation of the dependent variable marginally higher than the mean?

    Kisalaya Basu · Health Canada

    I think I just have to take log, Subrata Chakraborty. If you know the answer to my new question, it will be helpful. The new problem is this: I have same percentile distribution for my dependent variable until 90 percentile for both years for the treatment group. Is it ok to continue with difference-in-differences model?