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  • Witold Orlik added an answer in Mplus:
    Can we do model testing in path analysis?

    When applying path analysis on observed variables to study mediation, can we go for model testing also (chi-square, CFI, RMSEA, or BIC). I have come across many research papers with pathanalysis on observed variables, but they have not tested the model fit. But the software packages utilized for the purpose do provide with the same (like AMOS, Mplus).

    Witold Orlik

    Hello there,

    The simpler the model, the higher likelihood that you will get indication that your model fits perfectly the data.

    You can compare nested models and  then AIC, BIC indices are useful (the lower the better model) usually you use several fit indices and it is a bit of an art to decide which one is the best. 

    Best wishes

  • Elman Shahverdiev added an answer in Real Functions:
    Suppose f(x) is negative and increasing whiles g(x) is positive and decreasing. Can we conclude that the product f(x)g(x) is decreasing?

    Let f(x) and g(x) be real functions defined for x>0 such that f is negative and increasing, whiles g is positive and decreasing. Can we conclude that the product f(x)g(x) is decreasing? or What condition(s) will make this product decreasing? Your comments will be appreciated.

    Thank you.

    Elman Shahverdiev

    Dear Kwara,

    I totally agree with prof.Fernando Lobo Pimentel.

  • Mahamad Nabab Alam added an answer in PSAT:
    How can I get MVA Ratings of the Generators connected in IEEE 24 Bus test system ?

    Basically, according to IEEE 24 RTS data available i have MWs rating available for the Generators connected in that system. But, as i am working in PSAT Tool in Matlab , i need to enter the values of MVA & kV ratings of Generators connected at several buses. Check the attachment figure.

    Mahamad Nabab Alam

    Dear Mayur Sailor,

    go through the following link..




  • Karthikeyan Rajagopal added an answer in Mesenchymal Stem Cell:
    What are the markers for rabbit PDLSc to confirm their identity by flow cytometry?

    In Human PDLSc CD 73, CD 90 and CD105 has been confirmed and supported the Dominici criteria to be called as multipotent. However, what about rabbit PDLSCs?

    these markers are absent in rabbit MSCs (Comparison of Surface Markers between Human and Rabbit Mesenchymal Stem Cells)

    Can somebody put a light on it?

    Karthikeyan Rajagopal

    As per this article 


    Vimentin stained 95% positive but not for cytokeratin....  So u can give a try with vimentin.

  • Sofia Cividini added an answer in Network Meta-Analysis:
    Is it possible to make a network meta-analysis of RCTs, by including also evidence from observational studies?

    Dear all,

    until now, I have always seen network meta-analyses of RCTs. But, I would like to ask you if it is possible to make a network meta-analysis of RCTs, by including also evidence from observational studies. Or, if it makes sense to do a network meta-analysis, by using observational studies only.

    Many thanks.

    Sofia Cividini

    I agree with you, Patricio. Thanks again.

  • Dominic Evangelista added an answer in Historical Biogeography:
    Could anyone please suggest the best method to know the ancestral geographic range in a phylogeny?

    Hi everyone, I want to know the ancestral geographic range in a phylogeny of an insect genus. The genus includes three allopatric species endemic from three different islands. Could anyone please suggest the best method to achieve this goal? I have both nuclear and mitochondrial DNA sequences for two populations in one species and four populations for each of the remaining species.

    Thanks in advance    

    Dominic Evangelista

    A software called "Legrange".

  • Ilaria Barletta asked a question in 5G:
    What are the potential applications and benefits from the use of 5G mobile technologies within manufacturing facilities?

    Dear researchers,

    In am interested in the potential applications/benefits/barriers of implementing the 5G tech within manufacturing facilities/companies. 

    I will particularly appreciate sources reporting previous scientific studies, market reports which may forecast such applications, and outcomes from case/pilot studies (if they exist).

    You can also bring your own view and experience within mobile technologies, wireless systems and their integration in manufacturing environments.

    Thank you!

  • Neil J Calkin added an answer in Matrix Analysis:
    Anyone familiar with rank deficient matrix?

    The rank of a matrix A is the dimension of the vector space generated by its columns. It shows the dependent and independent column of matrix A.

    Suppose I have a nxn matrix A with rank n/2. As a specific example, let A =[3 1 3 1;1 4 1 4;3 1 3 1;1 4 1 4] with the two eigenvalues 4.7639, 9.23361 and the other two zero. Matrix A is 4x4 but its rank is 2. In other words, matrix A is actually 2D but it is represented in 4D.

    My question is how to get actual 2D representation of matrix A (Eigenvalue in 2D and 4D should be same)? Since matrix A consist of four similar 2x2 matrices, can I take the 2x2 matrix as its representation in 2D(This matrix has eigenvalue half that of matrix A)? Or I have to do projection or something?
    Please help!

    Neil J Calkin


    An mxn matrix is sometimes best regarded as the representation of a linear transformation of an n-dimensional vector space with basis B_1 to an m-dimensional vector space with basis B_2.  So, what you are really asking for, in your example, is to find two bases, each with 2 vectors in R^4, with respect to which the matrix is a 2x2 matrix of full rank. If there are two distinct non-zero eigenvalues, then using the corresponding eigenvectors will work.  (Things can get more complicated, in particular, there might not be any non-zero eigenvalues, but this should be enough to get you started thinking about this).


  • Khalid Ali Khan added an answer in EDTA:
    I want to prepare a stock solution of 0.5 M EDTA . Can I use simple EDTA instead of disodium EDTA salt?

    I am going to prepare 5X Stock Solution of TBE Buffer for Gelelectrophoresis. In protocols EDTA disodium salt is used to prepare stock solution of EDTA. Can I use simple EDTA instead of disodium EDTA salt? 

    Khalid Ali Khan

    Dear Chara Spanou and Dominique Liger,

    I prepared the EDTA solution through its free acid form. Your valuable suggestions helped me a lot. Really thanks both of you.



  • Capt. David Williams added an answer in Dolphins:
    Why do dolphins strand themselves on beaches?

    I haven't found yet any reasonable explanations for this.

    Capt. David Williams

    Answers to objections by A. G. Gordon::

    1. Sorry but you are mistaken. Sinus air acts underwater by reflecting returning biosonar clicks in a fashion to enable echonavigation. A tear in the membrane of a sinus will leak air into the cranium and cause the leaking sinuses to collapse, which in turn disables the reception of echoes. Non-navigating whales ALWAYS swim downstream in the path of least drag and certainly not round in circles.

    2. Any effort to examine air chambers in the middle ear destroys the evidence of the injury. Besides, one must look specifically for this type of injury. This has not been done due to that lack of funding.

    3. Sinus barotrauma is the most common injury in scuba divers. In fact, it is the most common injury in all marine mammals.

    4. Why would barosinusitis in one whale exclude the possibility of similar injuries in 100 diving whales? If the pressure disturbance surrounds the entire pod, all of the diving whales would be injured in the same fashion.

    Dr. Gordon, I think you fail to see the danger to diving whales because you are aware of the serious hazard that undersea earthquake present to both marine mammals, surface ships, and even nuclear submarines.

    I suggest you read an article published by US Navy's Maritime Safety Division that reveals the dangers of catastrophic seafloor disturbances (see link below). The US Navy clearly states therein that seaquakes can kill marine life and sink ships. This article will help you understand the hazard diving mammals face when exposed to waterborne seismic p-waves.

    Thank you for your comments, 

  • Callebaut Marc added an answer in Embryo Culture:
    How can I store fruits for longer duration for embryo cultures? What is the result on its viability?

    I have tried storing the fruits at -20 degrees for few days  but when i did embryo culture of the stored fruits,  it did not showed any response.

    Callebaut Marc

    For chicken and quail blastoderms we used  for culture in vitro, a mixture of 25 ml egg white and a gel made of 150 mg Bactoagar (Difco, Detroit, Mi) in 25 ml Ringer's solution. Boil this solution and cool at room temp., than add the egg white.This semi-solid medium allowed microsurgery and further culturing on the same substrate.

  • Haralampos N. Miras added an answer in Sugar:
    How can I improve the analysis of UV-Vis if the contaminant present absorbs the same wavelength that we used to determine the analyte?

    I want to determine the sugar content of a solution at wavelength 450nm using UV-Vis, but the contaminant present and absorb same wavelength. What should i do to improve the analysis?

    Uv-vis analysis.

  • Vijayashree Achar Achar asked a question in Fluorescence:
    Is HS buffer compatible to use for absorbance read?

    HS buffer from life tech is used for fluorescence read on qubit 2.0 to quantify DNA. We are trying to have one buffer and take both absorbance and fluorescence from the same tube. Can we use HS buffer to absorbance reads?

  • Mohammad Asad asked a question in T Lymphocytes:
    Will total mice splenocytes will proliferate in in-vitro culture?


    I am studying purified mice CD4 T cells, CD8 T cells and DCs etc proliferations in vitro labelled with CFSE. But total splenocyes are NOT showing proliferation. How can I observe splenocytes proliferation in culture. I am using both the ways for stimulating splenocytes either by specific antigen or anti-CD3 & anti-CD28 or ConA stimaution.

  • Jamail Lu asked a question in Trypan Blue:
    Have you seen these tiny things in your cell culture flasks?

    Researchers, Pls check the attached video clip which was taken during cell counting. Round big ones were cells but we still see some small dots, stained with trypan blue and some were not. However, obviously they were moving, some active swimming and some were tilting only at around its place. What were those tiny moving things? Bacteria? or else?

    My culture media did not turn to cloudiness. These tiny guys can only be seen under 20X and more clearer under 40X. 

    I have cultured the contaminated media on MHA agar, nothing was grown. Contaminated media was sub-cultured with MH broth but the media hasn't turn to cloudiness even after a week too. What are those guys in the media? Pen/strep did not help to stop. Cipro made reduce but not eradicated them. 

  • Charles Francis added an answer in Gravitational Field:
    Is the non locality of the gravitational field energy a serious problem for General Relativity (GRT)?



    "Although there is no room for such a thing in the energy–

    momentum tensor T, it is clear that there are situations where a ‘disembodied’

    gravitational energy is actually playing a physical role.

    Imagine  two massive bodies (planets, say). If they are close together (and we can

    suppose that they are instantaneously at rest relative to each other), then

    there will be a (negative) gravitational potential energy contribution which

    makes the total energy, and therefore the total mass, smaller than it would

    be if they are far apart.  Ignoring much tinier energy effects,

    such as distortions of each body’s shape due to the gravitational tidal field

    of the other, we see that the total contributions from the actual energy–

    momentum tensor T will be the same whether the two bodies are close

    together or far apart. Yet, the total mass/energy will differ in the two cases,

    and this difference would be attributed to the energy in the gravitational

    field itself (in fact a negative contribution, that is more sizeable when the

    bodies are close than when they are far apart)." 


    The same problem was also rised by Thirring, Kalman and Feynman in the FGT theory, they inserted the gravitational energy in the tensor equations...

    It is a problem of paramount importance which prevents the General relativity theory from describing any motion in which the hamiltonian is time dependent or rather in case of non isolated systems, or in case of non stationary interactions between different bodies.

    The attempt to model a free falling body in a gravitational field for GRT seems impossible.

    GRT has been tested  only for static or stationary systems where there is not a net exchange of energy (excluding gravitational radiation)

    Don't we need another GRAVITATIONAL THEORY which includes the results give by GRT in order to explain with a better accuracy the simple phenomenon like the free falling of a mass in a gravitational field?

    Charles Francis

    Luiz, I know from your previous discussions that you are not much interested in physics, but only in ranting and hurling abuse, but in this case you miss the mark twice, first because I have already said that physical law is fundamentally local, and that invariant quantities are locally define, and second, because that does not preclude global solutions like the Friedmann equation, or observed cosmological phenomena like red shift.

  • Ron Reiserer added an answer in HMDS:
    Can anybody suggest priming agents or processes to promote adhesion between an EBL photoresist and borofloat glass?

    Dear Sirs and Madams,

    We are having an issue with adhesion between ma-N 2403 EBL photoresist and borofloat glass. We have tried spincoating HMDS but it proved unsuccessful.

    SurPass was suggested (cationic primer) but we do not have access to it - does anybody know its composition?

    Any suggestions are welcomed. Thank you in advance.


    Ron Reiserer

    Can you vapor prime instead of spin the HMDS? Etch the glass in piranha before priming. You may need to do some optimization for the parameters of the resist as well. Some resists are very sensitive to humidity as well as adsorbed water on the substrate so a dehydration bake may also improve adhesion.

  • Marcel Balçık added an answer in Nanoparticles:
    How may I explain the shift in peak positions in radial distribution functions?

    I am doing classical MD simulations of crystalline-like FCC nanoparticles at finite temperatures. When analyzing the peak positions of the averaged radial distribution functions over 1000 snapshots at equilibrium, I found the positions of the first peaks (bond length) decreased as T increased, while those of the second, third and fourth peaks increased as T increased. The same trends were observed at two particle sizes. The calculated average bond length (pair-wise distances within cutoff) increased as T increased. So I couldn't think of a reason for the opposite trends of 1st peak vs. others. Would you please shed light on this issue? Thank you very much.

    Marcel Balçık

    While one can say there is a shifting in peak positions, i am not sure if this shifting means anything statistically as it is really small. Considering atoms tend to move much much faster, the behaviour may not be "that" unexpectable. I mean, if all peaks had increased, where these atoms would go? :)

  • Ade Kujore added an answer in HPLC Analysis:
    What are the best concentrations for preparing standard curve for carbofuran in HPLC?

    Dear All

    I am working on photocatalytic degradation of carbofuran. Please, what are the best concentrations for preparing standard curve in HPLC?


    Ade Kujore

    Dear Amal, 

    In order to help, it would be useful to have details of your method, of the instrument settings and to see some copies of the chromatograms.

    Kind regards,

    Ade Kujore


    Cecil Instruments Limited

    Milton Technical Centre, Cambridge CB24 6AZ

    United Kingdom

    email:- ade.kujore@cecilinstruments.com

    telephone:- +44 (0) 1223 420821

    fax.:- +44 (0) 1223 420475

    web site:- www.cecilinstruments.com

  • Mark West added an answer in Social Media Research:
    Which type of risk am I perceiving when using social media as a medical professional?

    To my knowledge, there are different facets of perceived risk on social media, such as physical, financial, social, time, etc.

    When I am using social media, I am concerned that I may violate professional code of conduct as a medical professional. I have concern on privacy, confidentiality, professional image, etc.

    Is there any conceptual definition for such type of perceived risk? Is it appropriate to name it "perceived professional risk"?

    Mark West

    I gather that your perception of the risk of using social media as a medical profession involves more than merely professional risk.  Codes of ethics are multifactoral, so to speak; they involve risks which are moral, and risks which are professional.  As such, Dr. Fox touches on two potential risks in professional communication (reputation risk, confidentiality risk). Then there would be risks which would arise from communication as a result of the profession itself, which would be detailed in the profession's code of ethics.  Then, there are risks inherent in communicative situations per se; see Waldron, V. R., & Kassing, J. W. (Eds.). (2010). Managing risk in communication encounters: Strategies for the workplace. Sage.     Thus your question raises, I suspect, three sources of communicative risk (profession-specific, risks generic to communication by professionals, and communicative risks per se.)  

  • Mehrdad Taheran added an answer in Activated Carbon:
    Is there any expert in analyzing XRD of activated carbon?

    I have two XRD pattern of biochar. one before activation (BC-M) and the other after activation (AC-M). Now I need help for interpretation. As I know, the structure of biochar before activation is graphite-like sheets in highly disordered form. therefore no serious peaks are expected except a small peaks at around 2theta=26 . But after activation two peaks at around 2theta=26 and 2theta=41 are formed which indicate the turbostratic structure. Can anyone put a more precise interpretation on it?

    thanks in advance

    + 1 more attachment

    Mehrdad Taheran

    Thanks again Mr Migorod

    Your second comments is so interesting for me. Can you please give me a reference that confirms your comments just for putting in my paper? 

  • Jean-Lou Justine added an answer in Water Supply:
    How much do you pay for 1 cubic m of water (please specify your location)?

    I want to compare prices for freshwater...

    Jean-Lou Justine

    For France, all is here:

  • Mary Frances Rice added an answer in Narrative Inquiry:
    Narrative inquiry: can anyone direct me to an example of a narrative interview guide?

    I have developed a narrative interview guide drawing on Clandinin et al's  (2007) three commonplaces but it would be useful to see other examples.  Plus in narrative inquiry does anyone have a link to literature about giving the interview schedule to the participant prior to interview?  I thought I would but have no evidence to support this. helen

    Mary Frances Rice
    I like Carol Gilligan's Listening Guide. It is not fully "narrative" but it has the kind of edges that I think you might be interested in.
  • Matthew Rhodes-Purdy added an answer in Structural Equation Modeling:
    How are survey constructs measured within a model?

    I would like to understand the math behind how survey constructs are measured within a model. For example, if there is a construct C with 3 correlated indicators A, B, and C, what is the equation tying these together?

    On one hand, it would make sense that Y would be a reflective construct, in which case each indicator I would have its own equation as follows:

    I = Beta(Y) + error

    On the other, it would also make sense knowing that indicators are correlated that the construct would be their sum:

    Y = A + B + C

    Are either of these correct? I am looking to use these within a structural equation model.

    Matthew Rhodes-Purdy

    I'd approach this using Confirmatory Factor Analysis; if you have strong theoretical reasons to assume structural relationships between the indicators and the latent construct, its often better to use CFA than more exploratory techniques like EFA or PCA. It depends on if the indicators reflect or "cause" the latent construct. For example, three indicators of socioeconomic status (occupation, income, and education) are often thought to "cause" or form the construct, in which case you'd have the equation in Dr. Morgan's answer. If they reflect the latent construct (effect indicators), then you have three separate equations:

    A = b1A + e1

    B = b2B + e2

    C = b3C + e3

    If you use them as "cause" indicators, you have a MIMC model, and you need at least two arrows "away" from the latent construct; in other words, you need to simultaneously estimate equations for two effect indicators or other dependent variables to indentify the model. Try Bollen 1989 (Structural Equations with Latent Variables) for a guide.

  • Javeed Ali Shah added an answer in Heat Maps:
    I want to create a heat map of flowcytometric data, please suggest the best software for that.

    I want to create a heat map of flowcytometric data, please suggest the best software for that.
    Please find the attached PDF for relevant information. The software given in that was not working.

    Javeed Ali Shah

    You could also try funkycells.org, which is a nice web based tool for flow analysis.  For statistical analysis of complex flow data, COMPASS is a great R package that we have used int the past.  We have also used SPICE as a data mining tool  Hope this helps.

  • Lucien Wald added an answer in MENA:
    What is the residence time of dust aerosols over the MENA region (below 1.5km, near surface)?

    I am trying to estimate the residence time of dust aerosol over the MENA region. I have tried to compute it using the equation T=fct(radius, normalized_radius,Twet). But, Twet varies with the meteorology (3*1e5, 6.91*1e5). From literature, residence time of dust  is : 1) varying between ~2 and 8 days, 2) varying between ~2.4 and 12.9 days, 3) global mean is ~2.7 days, 3)  average of ~4days, …

    Anyone can suggest more precise season specific residence time for the MENA region. 

    You help is greatly appreciated. 

    Lucien Wald

    Dear Imen, I am afraid that there is no simple answer. The MENA region is very large with various climates. Dust in UAE has not the same properties than dust in Lybia and the meteorological systems differ, too. My answer does not help much but means that there is a variety of scales. Maybe, you can restrict your domain by looking at the scales of interest.

  • Douglas Nuttall added an answer in Ecosystem Services:
    How can I try to appraise the value (euro or dollars) of the Ecosystem Service of a runnig water exposed to risk of loss of ecological functionality ?

     I need the procedure to estimate the damage on river ecosystem. In particular I need to estimate the loss of ecologiocal functionality caused by diversion of water for mini hydropower plant

    Douglas Nuttall

    Good question.

    Several parallel points:

    1)  Development is usually done by converting community wealth (often unquantified and unquantifiable) into individual wealth (often quantified only as cash).  We trust good planning to ensure the loss of community wealth is minimized, and we trust greed to ensure that the gain in individual wealth is maximized.  But there is currently no calculus that ensures the loss in community wealth is significantly less than the gain in community wealth.  Not all development is good development.  Were we actually doing Sustainable Development, there would be no net loss of wealth in the long term.

    2) Ecological Economics attempts to quantify the value of ecological services.  However, many ecological services can not be replaced with alternatives, so they can not receive a replacement value.  If I can not control access to an ecological service, or I can't replace the benefit that the service provides, then the concept of value breaks down.  How does one price Gravity?  Or Photosynthesis?  There must be an economic concept of 'Sacred' vs 'Mundane', and using the precautionary approach, all ecological services must be considered Sacred until they have been proven that they can be controlled and replaced, and thus Mundane.

    3) Normally, the buyer will purchase a service if the value of the service to the buyer is greater than the price, and the seller will sell a service if the value of the time to the seller is less than the price.  But with ecological services, the seller doesn't speak up - nature doesn't make you pay up front for the services, but rather you pay after the fact by the absence of the service.  So 'authorities' will try to set a price (like setting a price on pollution with Carbon Taxes) in the absence of Nature being at the negotiating table.  But since these authorities are not omniscient, omnipotent, or infinitely wise, they will always get it wrong.  Again, the precautionary principal implies that it must be assumed that the Authority will always underestimate the value of natural services.

    In your case,  I would consider the Triple Bottom Line approach, using different scenarios of flow diversion, and from that determine what fraction of flow the developer can extract that ensures an acceptable balance is maintained.

    Alternatively, if there is sufficient data available, you could consider the time/resource curve for your community, and determine under what conditions the Actualize Quality of Life would be increased.  Harder to do, normally.

  • Daniela Pacheco added an answer in Crosslinking:
    Is there a cytocompatible hydrogel with polymerization time in the range of seconds?

    Looking for a hydrogel with properties like...

    - very fast crosslinking procedure, in the range of seconds,

    - cytocompatible before and after crosslinking (cell won't be encapsulated within the gel but they would be in contact with it for long term),

    - non-degradable under physiological conditions/ in-vivo,

    - low viscosity prior to crosslinking, like PEG-DA solutions for example,

    - high strength and elasticity after crosslinking

    Until now, I was curing PEG-DA solutions under visible light with Eosin Y and TEA. I did not use any catalyst like 1-vinyl-2-pyrrolidone since it is assumed to be cancerogenic. Furthermore, I don't want to use UV light for the same reason. Without catalyst the polymerization lasts 2 min which is still too long.

    Thank you in advance for you help!

    Daniela Pacheco

    Dear Marius Köpf,

    I would suggest you Gellan Gum hydrogels, which are quite versatile in terms of cross linking agent, meaning that you can crosslink them with temperature variations, Calcium Chloride, PBS and in case of methacrylation procedure it also enables photocrossliking. The time gelation window is 20 s in case of ionic cross linking, as you can confirm at:
    - http://www.sciencedirect.com/science/article/pii/S0378517314008485;
    - http://online.liebertpub.com/doi/abs/10.1089/ten.TEA.2009.0117?url_ver=Z39.88-2003&rfr_id=ori%3Arid%3Acrossref.org&rfr_dat=cr_pub%3Dpubmed.

    It is highly proposed for regenerative medicine and tissue engineering applications, therefore its cytocompatibility is being confirmed by many studies. 

    Even not being fully understand, its degradation occurs through hydrolysis however up to a certain degree not being fully degraded.

    Its viscosity prior to crosslinking is temperature dependent, while its mechanical properties are dependent on both material processing and cross linking agent, which you can find on the follow paper:
    - http://www.ncbi.nlm.nih.gov/pubmed/20663552

    Hope it is helpful!
    Warm Regards,

    Daniela P. Pacheco