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  • Kenza Drissi asked a question in Fibrocartilage:
    Is there a mathematical model for ligament-to-bone attachment regarding the gradation of Young modulus?

    Some sources explain there are 4 areas composing the ligament-to-bone or tendon-to-bone insertion, namely bone- calcified fibrocartilage - uncalcified fibrocartilage- ligament. I would like to know if someone knows about the gradation of the Young modulus across each of these sections and how it behaves under loading

  • Jaime Jimenez asked a question in Aesthetics:
    Is aesthetics a discipline of study for art?

    Is aesthetics an actual discipline of study? Is art its proper object of study?

  • Tarek Ben Mahmod added an answer in Tungsten:
    How do I calculate the coating density for ASTM G65 test ?

    I have substrate of law carbon steel (AISI 1018 ) with thickness of 10 mm, only one face of the substrate is coated by HVOF method (high velocity Oxy fuel), the coating type is Tungsten Carbide Nickel chromium (WC-Ni-Cr) , the coating thickness is about 250 -300 micrometer.
    Is there any easy way to calculate or to measure the density of such this coating, because I am doing ASTM G65 test ( Dry wheel test)?.and the required density in the G65 standard formal it should be the coated density NOT as the powder density.

    I tried different ways , but in each time I got different result, also I tried ASTM B 311-13 test.

    Thank you 

    Tarek Ben Mahmod

    Many Thanks to all for replay to  my question,

    Unfortunately I forgot to measure the weigh of the steel before the coating process,

     I am trying now to split small layer of the coating so I can get the mass and then the volume of small segment ,is this work??

    Professor  William,  regarding to the porosity method it will be difficult to etching the coating, I tried that but does not work  

  • Raphaël Royauté added an answer in Mixed Models:
    Any advice on mean trait values or BLUPs in a repeated measurements experiment?


    In a repeated measurements experiment (several behaviors measured multiple times), I found that traits are repeatable (interindividual consistency). Now I need to pick one single value per individual (as representative of all replicates) for further analysis (i.e. to correlate with other variables). Would it be better to get the mean of all replicates, or a BLUP obtained from the mixed model used to estimate repeatability (which includes some covariates as well)? Any other alternative?


    Raphaël Royauté

    Hi David,

    The answer may depend on your sample size and whether you need to correct for other fixed effects or not. In general, it is discouraged to use "stats on stats" approaches because of propagation of error problems. I would strongly suggest you to look into multivariate mixed model approaches allowing to estimate among-individual (i.e. behavioral syndromes) & within-individual correlations (i.e. correlated plasticities). These methods are also very flexible allowing for different tyoes of distributions and inclusion of fixed effects. Dingemanse & Dochtermann (2014) provides a great starting point, especially the supplementary materials.

    One caveat though, among-individual correlation require high sample sizes to be detected (see Fig 1 in Dingemanse & Dochtermann 2014), but the alternative of using means or BLUPs is not necessarily better. See for example Hadfield et al. 2010 for how using BLUPs as point estimates can be problematic.

    Ultimately, I think if you have the sample size to estimate among-individual correlation, you should go for it! At the moment it is the best way to test for behavioral correlations and allows to considers multiple levels of correlations. If your study suffers from low sample sizes however, the decision is less clear cut and there are advantages and inconvenients in using each of these methods.

    Hope this helps!



    Dingemanse, Niels J., and Ned A. Dochtermann. "Quantifying individual variation in behaviour: mixed‐effect modelling approaches." Journal of Animal Ecology 82.1 (2013): 39-54.

    Hadfield, Jarrod D., et al. "The misuse of BLUP in ecology and evolution." The American Naturalist 175.1 (2010): 116-125.

  • Demetric Armstead asked a question in Quantitative Research:
    How do you select sample size in relation to population size?

    In quantitative research

  • Vini Gautam asked a question in PLL:
    Reasons for dead cells in primary hippocampal culture???

    I have been trying to grow primary culture from isolated hippocampi from rat pups. Sometimes the cells survive while most other times they strangely land up dead like debris after 3-4 days. I have tried changing different things but cant get to a consistent healthy culture. Can someone please help? I am quite frustrated! Below are the details:

    The age of the pups is usually between 0-2 days. I dissect the hippocampus out and dissociate it in papain based solution. I then gently triturate the tissue pieces in pre-warm culture medium (no centrifuge), count the cells in Haemocytometer, and then plate them at 20*10^4 /ml onto glass coverslips kept in a 24-well plate. The coverslips are coated with poly-L-lysine (MW>150kDa) mixed with or without collagen.

    Now, most of the times I can see healthy cells (e.g. neurons with long processes) when I count them in haemocytometer. So I presume there is nothing wrong with my trituration. But after plating, the cells dont grow - next day they dont have processes anymore, the glia doesnt grow, basically nothing happens. I guess they dont die either (because they appear phase bright at least for next 2 days). But then after 3 days, they start to die, and after 4-5 days, its just debris left over in the wells.

    Is it the coating? I clean the coverslips with acid, wash them and coat PLL or PLL/Collagen as per the instructions. I tried ornithin/Laminin too, but no improvement..

    Is it the medium? I tried DMEM with FBS, B27, glutamine as well as Neurobasal-A with FBS, B27, glutamine. The medium pH after preparing is usually 7.4-7.6 and the osmolarities range between 280-310.

    Please help!!! I cant think of anything more! Thank you very much.

  • Trevor John Kenchington added an answer in Fisheries Biology:
    Should I use geometric mean values for 'a & 'b' from fishbase when calculating the weight of a particular genus of fish using the formula W = a × Lb?

    here is an example for the genus Diodon, is it ok if i use the geometric mean values as circled below?

    Trevor John Kenchington


    Estimating weights from lengths, using values of the a and b parameters that did not come from the same samples of fish, cannot give you accurate results. The value of a can change with season, for example. Combining data across species within each genus will add to the uncertainties. Some species are deeper-bodied than others, which means more weight for the same length and so higher a. b may be more stable, though the examples you have taken from FishBase vary from a little more than 2 up to 3.

    If you need weights, if you have no weight data and if you can accept the uncertainty, then go ahead and make your estimates. However, there is no point in trying for high precision in the parameter values. They won't make your estimates any more accurate.

    Do you really need weight estimates? You could use CPUE expressed as numbers of fish caught per unit effort. If you are worried about catches of many small fish confusing the CPUE estimates, you could use a CPUE index based on the sum of the cubes of the lengths of the fish caught, per unit effort. That would give you a weight-like measure without making any assumptions about a. It would effectively assume that b=3 but it might be better to use an obvious approximation than to pretend to have an accurate value.

    However, if you want to compare CPUE between genera, such a simple index would not help.

  • Behzad Vaziri Hassas asked a question in Atomic Force Microscopy:
    What is the best organic solvent for cleaning the gold coated cantilever?

    I am trying to glue a colloidal tip on a gold coated AFM cantilever. When the location of tip is not the one I want, I need to wash out the glue with an organic solvent and try another particle. Since Ethanol oxidizes the gold I noticed that the gold covered side of cantilever goes bad when I use Ethanol for cleaning. I am looking for a solvent that does not have any effect on either cantilever or its coating (Al or Au). I appreciate comments and suggestions.

  • Jonathon Little added an answer in Confirmatory Factor Analysis:
    How do I calculate factor scores while running formative construct under factor analysis?

    Could you please let me know that how to calculate Factor scores while running formative construct under factor Analysis?

    Jonathon Little

    This is an old question so I apologize if I'm too late.  Your question is a little unclear to me but I will have a guess at where you are comming from.  As you are probably aware we can't use CFA with formative measures however if you are looking for a way around the identification problem and want to get a formative score you can play with you may find the following article helpful....

    Treiblmaier, H., Bentler, P. M., & Mair, P. (2011). Formative Constructs Implemented via Common Factors. Structural Equation Modeling: A Multidisciplinary Journal, 18(1), 1–17. doi:10.1080/10705511.2011.532693

    Best of luck


  • Gonzalo Olivares added an answer in Salmo salar:
    Is there any quantitative estimation of parr-smolt transformation impact on energy budget of Salmo salar?

    I'm trying to figure out the energy cost of parr-smolt transformation and the subsequent introduction of smolts into the sea. If there is an increase in specific energy demand, how is it compared to the parr demand? Is it a transient change or a permanent one? Is there any (dynamic) energy model that explicitly incorporates this process?

    Gonzalo Olivares

    Thanks, Trygve. If there is more info about the growth potential you mentioned, don't you think it may be easier estimate the putative change in energy demand from the change in the potential for growth?. I will search for that kind of info in the literature. By the way, I agree with you. Biology is much more complicated, but also more interesting!!

    Thanks again.

  • Jaya Kumar added an answer in Microinjection:
    How do I conduct molecular analysis (Western Blot and RT-PCR) in the brain region I microinjected with drugs?

    I am planning to microinject a drug into the lateral (LA) and central amygdala (CeA) of male wistar rats and observe their behavior. Following that, I want to conduct a western blot and RT-PCR analysis. I realise that I have to validate the microperfusion in the LA and CeA through staining of the brain. So, how do I extract the LA and CeA nuclei from these experimental animals for WB and RT-PCR analysis? Do I need a separate group of rats? The problem is the drug can’t be administered via systemic injection as it doesn’t pass through the blood brain barrier.

    Jaya Kumar


    Thank you for the prompt reply and such a informative answer. 

  • Alex Russell added an answer in Data Aggregation:
    SPSS cannot compute Spearman's Rank because one of the variables is constant. How do I proceed?

    Hello all,

    I want to use Spearman's Rank Correlation to to measure association between two constructs - Culture and Ethics. I have coded  the Likert Scale data and aggregated the responses from the several questions in the questionnaires into two sets (Culture and Ethics) using the median values of responses from each question. However, in one of the Construct of 7 questions the median values are the same number (2). Now SPSS will not perform Spearman's Rank Correlation for the two Construct because 'one of the variable is constant'. Am I right to have used median values? What did I do wrong? How do I remedy this?

    Many thanks! 

  • Anne Schreiber asked a question in Spinal Cord:
    I am going to make a rat prostate homogenate to label TRPM8 by western blot. I dont know which sample buffer is the best, or if PBS is sufficient?

    To standardize TRPM8 expression in spinal cord samples, we intend to first verify TRPM8 presence at prostate tissue (from rat). I would like to know what type of processing is needed in this tissue (abcam  primary anti TRPM8 ab104569).

  • Antonio Fluminhan added an answer in Date Palm:
    Is this photo of the callus of a date palm, a root or stem?

    this is a photo for a callus of date palm (phoenix dactylifera), in this treatment the cal developed a forms like roots, but these forms go upwards not down.

    Antonio Fluminhan

    It is not surprising to see roots growing upwards, during plant regeneration from monocot tissue cultures. You can verify if these formations are roots if you leave the calli under lights. Normally, root tissue do not show differentiation from proplasts to chloroplasts. So, they should remain white coloured even after some days or weeks.

  • Jonathon Little added an answer in Confirmatory Factor Analysis:
    Factorial analysis in a questionnaire based in a theory of personality: procrustean rotation or a confirmatory factor analysis?

    If i want to perform a factorial analysis in a questionnaire based in a theory of personality, which has constructs very close conceptually and empirically, the best choice is a procrustean rotation or a confirmatory factor analysis.

    Jonathon Little

    You may wish to consult the literature on personality testing using Exploratory Structural Equation Modelling.  Many would now argue that CFA is not suitable as this constraints non-target loadings to zero, while EFA with procrustean rotation is probably an out-of-date approach and does not allow you to impose any constraints in your model in the way that Exploratory Structural Equation Modelling can.  Have a look at...

    Marsh, H. W., Lüdtke, O., Muthén, B., Asparouhov, T., Morin, A. J. S., Trautwein, U. &
    Nagengast, B. (2010). A new look at the big-five factor structure through exploratory structural equation modeling. Psychological Assessment, 22, 471-491.



  • Nicole Byrne added an answer in Bilingualism:
    Code-Mixing: Strategy or an unconscious skill in bilingual stroke patients (Aphasia)?
    Just 2 days ago there was a discussion about code-switching skills and strategies in healthy controls; so I wanted to add an addendum to that. What is code-switching and mixing in people with stroke?
    Nicole Byrne


    Representation of first and second languages in the brain differ, Different languages are represented in the brain differently and Aphasia in bilingual speakers offers means to research the representation of language in the brain.
    I'd suggest you look at work of Micael Paradis (1977)

    Types of impairment & patterns of recovery in bilingual aphasia





    Paradis, M. (2000). Generalizable outcomes of bilingual aphasia research. Folia Phoniatrica et Logopaedica, 52, 54-64.

    Paradis, M. (2004). A neurolinguistic theory of bilingualism. Amsterdam: John Benjamins.

    Fabbro (2001) Language recovery of 20 bilingual Friulian-Italian aphasics was investigated.

    Thirteen patients (65%) showed a similar impairment in both languages (parallel recovery),
    four patients (20%) showed a greater impairment of L2,
    three patients (15%) showed a greater impairment of L1.
    Despite the many hypotheses advanced to account for nonparallel recovery, none of them seems to provide satisfactory explanations.
    The study of bilingual aphasics with parallel impairment of both languages allows us to verify the hypothesis whereby grammatical disorders in aphasia depend on the specific structure of each language.
    As far as rehabilitation programs for multilingual aphasics are concerned, several questions have been raised, many of which still need a satisfactory answer.

    The Bilingual Brain: Bilingual Aphasia. Available from: https://www.researchgate.net/publication/11642142_The_Bilingual_Brain_Bilingual_Aphasia [accessed Jun 1, 2015].


    • Source
      [Show abstract] [Hide abstract]
      ABSTRACT: Since most people in the world know more than one language, bilingual aphasia is an important line of research in clinical and theoretical neurolinguistics. From a clinical and ethical viewpoint, it is no longer acceptable that bilingual aphasics be assessed in only one of the languages they know. Bilingual aphasic patients should receive comparable language tests in all their languages. In the present work, language recovery of 20 bilingual Friulian-Italian aphasics was investigated. Thirteen patients (65%) showed a similar impairment in both languages (parallel recovery), four patients (20%) showed a greater impairment of L2, while three patients (15%) showed a greater impairment of L1. Despite the many hypotheses advanced to account for nonparallel recovery, none of them seems to provide satisfactory explanations. The study of bilingual aphasics with parallel impairment of both languages allows us to verify the hypothesis whereby grammatical disorders in aphasia depend on the specific structure of each language. As far as rehabilitation programs for multilingual aphasics are concerned, several questions have been raised, many of which still need a satisfactory answer.
      Brain and Language 12/2001; 79(2):201-10. DOI:10.1006/brln.2001.2480
  • Jonathon Little added an answer in Factor Analysis:
    How do I do Factor Analysis with One Set of Variables and Two Sets of Data?

    I am trying to do a data analysis with 41 variables. The problem is that I got two sets of data: one set is before I made certain intervention to the participants, and one is after the intervention. I conducted factor analysis to the "before" data and "after" data respectively, and got different results. So I got confused should I do it respectively or just combine the two sets of data together to conduct the factor analysis? Thanks!

    Jonathon Little

    Manuel Heinrich said it best - I second his answer.  A good example of a longitudinal CFA is 

    Marsh, H. W., Scalas, L. F., & Nagengast, B. (2010). Longitudinal Tests of Competing Factor Structures for the Rosenberg Self-Esteem Scale: Traits, Ephemeral Artifacts, and Stable Response Styles. Psychological Assessment, 22, 366-381.

    What you want is a CFA model that reflects the correlation between observations at each time wave.  To get your head around this see Little ( 2013) as a good start.

    Little, P. T. D. (2013). Longitudinal structural equation modeling. Guilford Press.

    I suggest sourcing the cited Marsh article and looking at their discussion of correlated uniquenesses as this is often overlooked in longitudinal CFA.  It's a lot to get your self up to speed on but thankfully both texts are fairly accessible at the graduate level.  

    Goodluck with it.

  • Ilya Tsyrlov added an answer in siRNA:
    Does anyone know what the half life of FIH-1 (factor inhibiting HIF1a) is?

    Trying to reduce FIH-1 protein expression using siRNA, but the initial experiment I performed with the siRNA didn't lead to any changes in FIH-1 levels. If the FIH-1 protein has a long half-life, then the lysates I acquired after 72h siRNA treatment might still have FIH-1 present that was expressed from before I added the siRNA. So I may need to treat the cells for longer with siRNA before lysate acquisition, however I need to know what the half-life of FIH-1 so I know how long the cells need to be treated for. Tried finding out what the half life of FIH-1 was online, but couldn't see it anywhere. 

    This may be because I acquired the lysates too soon (after 72h lysate treatmet) 

    Ilya Tsyrlov

    Hi James,

    Inasmuch as I dn’t know an exact half-life value of FIH-1 (think nobody does), an answer might be that FIH-1 has rather LONG half-life than otherwise. Why? Rachelle S. Singleton in her paper in JBC (286, 39:33784–94, 2011) logically indicated that the levels of hydroxylation on proteins examined under specific conditions should be an accurate reflection of the activity (and the turnover) of FIH-1. Thus measurements of the decay of hydroxylated species following the catalytic inhibition of FIH-1 demonstrated near identical decay of hydroxylation and hydroxylated protein species for both HIF1-CAD and ARD proteins, revealing that hydroxylation of these proteins is not significantly reversed, at least under the experimental conditions examined. Together with evidence from Singleton’s and other studies that the catalysis of asparaginyl hydroxylation at these sites is entirely dependent on FIH-1 (i.e. the enzyme is nonredundant). Because FIH-1 plays more important role in other processes not directly related to cellular metabolism, including neural differentiation and vasculogenesis,  understanding of the regulation of FIH-1 expression, its half-time and the consequences for HIF-1 activity warrants further investigation.

    Best wishes,


  • Can Kiessling added an answer in SYBR Green:
    Can I use the SYBR green to detect U6 snRNA during qPCR of miRNA detection?

    I would like to measure miRNA expression by stem-loop RT PCR.

    I case of normalizer, I would like to use U6 snRNA by using SYBR green system. That's it possible. 

    Can Kiessling

    I have used a SYBR-green based PCR assay, although it must be noted that it was using the biorad IQ supermix which may perform differently to home made mixes. You can avoid using ROX if you do a panel of reference genes. In fact, it would be wise to validate your reference gene unless others have shown that it is stable in your conditions. The following link may clarify some concepts


  • Bhupinder Singh added an answer in Sputtering:
    How can we deposit Gold ( Au ) layer using sputtering on a Nafion polymer membrane ?

    I want to deposit an Gold layer on a nafion membrane by sputtering and I need good adhesion between these two layers. How can I get good adhesion of sputtered Au with nafion flm?

    Bhupinder Singh

    Hi Ashwani

    I havent worked with nafion myself, so I am not an expert. having said that I would like to mention that it is a very common practice to have an adhesion layer to make gold stick better. Try sputtering ~ 5 nm of chromium or titanium followed by gold. Gold sticks better to Cr/ Ti. Also, what kind of sputter system are you using?

    let me know if you have further questions.


  • Christian Lipfert added an answer in Heterologous Expression:
    Can anyone tell me what I can do to improve the expression?

    I expressed protein in E.coli and the vector is pET22b. However, no matter the temperature or concentration of IPTG was changed, the soluble and insoluble expression were still very low and were just identified by WB.  Who can tell me what I can do to improve the expression?

    Christian Lipfert

    Hi Wang, I totally agree with the prior answers, there can be a lot of parameters that have influence on your expression. Tags can also be critical. I would start with core problems first. If your stock is too old or the cells can't handle some rare codons then temperature, concentrations and expression time wont help you much.

  • Hasi Ray added an answer in Triacetin:
    Convert to Units in Lipolytic activity assay?

    I have assayed the lipolytic activity of lactic acid bacteria isolated from olives by spectrophotometric method. I used lipase from porcine (Sigma) to generate a standard curve.  I tested bacteria but I can't convert the results from microgram to Units.

    The lipase box says following:

    Lipase from porcine pancreas
    Type II, 100-500 units/mg protein (using olive oil (30 min incubation)), 30-90 units/mg protein (using triacetin)

    So, 1 microgram/miligram = How many Units? I couldn't calculate this. Please help.

    Hasi Ray

    I think that you need to read more the standard books to learn the subject.

    If that is not true then I think I donot understand your subject at all. According to my knowledge - your question

    1 microgram/milligram = .001

    Please inform me if it is useful to you or not?

  • Bhupinder Singh added an answer in Thin Film Coatings:
    How can I prepare a sample for elemental analysis (ICP -MS) from thin films ?

    We have prepared oxide thin films from spray pyrolysis method. we need to analyze the ICP measurement for our prepared film. we don't know how to sample prepare from the thin film coated on glass substrate. kindly suggest my problem.

    Bhupinder Singh

    Hi Raja

    I am total agreement with Hilal that you would have to be VERY VERY careful to avoid any possible contamination form your sample preparation step/s. The logical way would be to scrape off your coatings and digest them in aqua regia, filter it using glass filter paper and dilute it to make samples for ICP-MS.

    Note that ICP-MS is very sensitive (down in ppt to ppb range for some elements). While using ICP-MS, i usually dilute my samples a 1000 times to get concentrations in ppb range. You should make the calibration solutions accordingly. Also, to be statistically sound, make sure you do everything in triplicate and calculate the LOD and LOQ of all the metals that you are looking for. Report the concentrations only if they are above the LOQ of respective elements. 

    If you want to be sure about any contamination introduced during your sample preparation step, do a spike and recovery experiment. 

    I am just throwing our everything that I can think of (which you probably already know).

    Let me know if you have any further questions.


  • Hugo Alonso-Cantabrana added an answer in Plant Molecular Biology:
    How many genes one can transfer successfully to a plant tissue in a single transformation?

    I want to ask a question that, Currently, how many genes one can already transfer successfully to a plant tissue in a single transformation? Thank you and waiting for the answer soon !.

    Hugo Alonso-Cantabrana

    More recent technologies like GoldenGate plasmids allow gene stacking in one single plasmid. I don't know what is the maximum number, but 5 genes seems quite standard now.

  • Oluwafemi Samson Balogun added an answer in Biostatistics:
    Can anyone help with materials on application of panel data on biostatistics?

    Please i need materials on application of panel data on biostatistics

    Oluwafemi Samson Balogun

    Thanks Prof

  • David Rinaldi asked a question in Growth:
    How small can PbSe nanoparticles be made?

    I have documentation that under a certain conditions PbSe nc's can be made 3-5nm by ways of growth time 5 min, injection temp: 150 C, and growth temp: 115 C.

    To make my particles smaller, should I adjust my growth time (shorter time) or change any other variables?  

  • Heng Liu added an answer in Work-Environments:
    Can scales reliably help to identify output control and clan control?

    I am referring to organizations which make use of teleworking. For this kind of work environments I am looking for scales to determine if output control and clan control is in place. May be even to determine the intensity and/or quality of their use. Any hints are very welcome. At the moment I am aware of the work of Kirsch and as well of Henderson & Lee, but I try to find out if I missed scales which were developed in this field.

    Heng Liu

    This paper may be helpful.

    Snell, S.A. Control theory in strategic human resource management: The mediating effect of administrative information [J]. Academy of Management Journal,


  • Ilse Ruyssen asked a question in Probit Model:
    We are working on an estimator for probit models with a binary endogenous regressor and binary sample selection. Anyone knows of an application?

    Note that the dependent in both the selection and the outcome equation should be dichotomous.