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  • Brandon Lavery added an answer in Perovskite Solar Cells:
    What other metals are being tried for perovskite solar cells?

    Have researchers begun trying different metals in perovskite solar cells? I've seen tin and lead published, but what about copper, zinc, magnesium, calcium, or any other +2 metal?

    Brandon Lavery

    Thank you everyone. I suppose I should have been more specific. I know of the inorganic varieties of perovskites but I am interested in the ones used for solar cells which are commonly of the organometal halide variety. 

  • Hywel Owen added an answer in Chaotic Dynamics and Applications:
    How does one find the region of stability for an iterated map?
    I come from the field of particle storage rings, where an electron or other charged particle circulates many times around a ring, confined to an orbit by appropriate magnets. One can represent the net effect of the ring by a polynomial map, and the dynamical system consists of iterating this map over and over. The dynamics are chaotic, and there is a stable region and an unstable region. I am curious if there is any recent progress in this problem, i.e. how to find the stability region given the map? Is there any way besides simply tracking each initial condition many times?
    I am also curious if there are any other applications in which this same problem is encountered, so we might learn from that literature.
    Hywel Owen

    Looks there is still no answer to this question?

  • Bachir Achour added an answer in Reservoir Engineering:
    How can I calculate the water residence time in reservoir?

    When I calculate the average water residence time in reservoir according to this relationship Tr= reservoir volume/annual discharge, is what I consider the dam is full to 100%, in this case I consider the total capacity storage, or just 67% of this end  according to the study vorosmarty et al 2003. 

    Bachir Achour

    Dear Mahrez,

    The residence time is the ratio of the reservoir volume and the amount of input or output stream (zero water balance). It is better to use the sum of inflows as there may be losses and outflows not taken into account. It is necessary for the calculation, consider the total water volume in the reservoir.

    With my best regards

    Prof. Bachir ACHOUR

  • Kawther Jasim asked a question in SSR:
    How to use R software to analyze SSR marker?

    Dose anyone know, how to use R software to analyze SSR marker?

  • Alaa Khedr added an answer in LC-MS:
    As can proceed to the analysis of pharmaceuticals submit NaOH, HCl and Fe +2 and H2O2 by LC-MS?

    As can proceed to the analysis of pharmaceuticals submit NaOH, HCl and Fe +2 and H2O2 by LC-MS? I need analize degradation products in pharmaceuticals by LC-MS. lc-ms it is compatible with these agents?

    Alaa Khedr

    HCl/NaOH; acid base catalyzed forced degradation, you should neutralized the media sample before injection. HCl excess shall denature the LC column, also excess NaOH is harmful. Ferrous ions shall precipitated on the ESI ion source as black spots. H2O2 excess shall decomposed at ESI.

    Inject blank experiment to identify the gust peaks due to reagent or reaction byproducts of reagent with column stationary phase.

  • Salim Y Hanna added an answer in Carbapenems:
    What is the best solvent for carbapenem antiobiotics? Water or DMSO?

    A very basic query regarding the solubility, stability and storage of carbapenems antibiotics such as Meropenem trihydrate or Imipenem monohydrate. I have known to dissolve them in DMSO in higher concentration for short storage periods but can we use water for the same? Does water affect the stability due to storage in the long run at -20 degree Celsius?

    Salim Y Hanna

    Hi Mr. Singh, You can try different percent mixture of water :DMSO , then see which one is good for your study. 

  • Fateme Fard asked a question in Microvesicles:
    What is a suitable protocol of microvesicle RNA extraction?

    I'm trying to extract RNA from microvesicles.I used ordinary  protocol contains: adding RNAXplus , chloroform after that put it in -20 for 1hour then added cold isopropanol, ethanol80% ...

    I wonder if you know suitable protocol for RNA extraction from microvesicles.

  • Yoav Lubelsky added an answer in Molecular Biological Techniques:
    Can anyone suggest tell his/her experience with a histone extraction kit?

    We are using EpiQuick histone extraction kit from Epigentek, but we want to know if anyone can suggest any other kit as well as any recommendation... Although this kit leads obtaining histones really fast, we are having several problems, specially when loading the samples into the gel (samples sometimes become yellow when adding the loading buffer for the acidic properties of histones). Thanks for your help!

    Yoav Lubelsky

    Sample buffer turning yellow is common when doing acidic extractions. Just neutralize it with ammonia vapor (hold the tube open next to the mouth of an ammonia bottle for a few seconds until it turn blue) and continue with loading the gel.

  • Asok Mukhopadhyay added an answer in Western Blot:
    Has anyone the protocol for using mouse serum / plasma on western blot?

    I've got serum samples from WT and KO mice and would like to check cytokine on western blot, I tried to mix serum with sample buffer but having precipitate after boiling, anyone have a detail protocol on that?

    Asok Mukhopadhyay

    Cytokines are present in pg/ng level in serum, it will be wasteful effort to identify them in WB. The better approach will be ELISA that will provide you quantitative data. Alternatively, if you so keen in WB, remove albumin using UF cut 20 KD- 30 KD, concentrate the filtrate 10 folds and then run  WB (I  will not do  that).  All the best.

  • Gamal el shallaly added an answer in Acute Cholecystitis:
    Is diagnostic laparoscopy justified in acute cholecystitis in order to determine operability (lap/open)?

    Timing of cholecystectomy is controversial. Sometimes the inflammation is too advanced for patient's history of pain.

    Gamal el shallaly

    Yes the intention is for Laparoscopic cholecystectomy but when one finds out the inflammation is too advanced even conversion would have a high risk of complications and one loses the magnification advantage of the laparoscope

  • Gregory James Buchan added an answer in Plaque Assay:
    How accurate are plaque assays?


    I am in a pharmacology lab and started studying influenza. I found that "standard plaque assays" are used the majority of the time to determine the infectious viral burden from cell culture as well as tissue homogenates. It is also used to determine the MOI for cell experiments and mouse infection. I have contacted several people and for the most part the reason I get for its accuracy is "If you count between 30-300 plaques, it just works". 

    Recently I have begun running plaque assays in tandem to my cell experiment to determine the Pfu/mL at the time of the experiment (rather than titering once batch of influenza and using that Pfu/mL for subsequent experiments) and the results are confounding.

    If I grab a batch of flu that is 10^7 pfu/mL and use this to calculate the MOI=2, it is actually closer to MO1=0.02 or MOI=0.2 (due to thawing?). I am wondering if people take this into consideration or even do this at all for the experiments. The literature will only ever give you the MOI or "we did standard plaque assay" with no further explanation.

    Thank you for reading.


    Gregory James Buchan

    Hi Dani,

    Thank you for your response. I use MDCK cells to determine the titer of the virus. I base my MOI calculations off of this value (which seems to be the way everyone does it) and use it for various experiments in either RAW, MDCK, A549, etc... IN the "tandem" plaque assay I perform a plaque assay in MDCK cells while I am performing an experiment in other plates to try and get the most accurate reading of the Pfu/mL of the virus I am applying to those cells. I have noticed that if say you bought a vial of influenza at 8*10^7 pfu/mL from ATCC or some other source and used that to calculate your MOI during your experiments...it can be completely wrong.

  • M. A. Awadallah added an answer in ANFIS:
    What can I do to reduce the mean square error in anfis?

    Currently i am using the dataset (https://www.researchgate.net/publication/281449157_USDvINR_rate) to predict the future rate of INR against USD. The current training and testing mean square error are in the range of 0.0201 to 0.0235. The training set uses 5670 and test set uses 1170 random records from the dataset. What can be done to reduce the MSE further (approx 0.0001 to 0.0005)

    For further info about the implementation refer to - https://www.researchgate.net/publication/280698216_FOREX_rate_prediction_using_a_Hybrid_System

    + 1 more attachment

    M. A. Awadallah


    You can do a lot of things. But, remember that lower error (especially on the training data) does not ALWAYS mean that your system performs better since ANFIS may become only a MEMORY remembering the training data behavior. In this case, ANFIS performance on the testing data may not be as much good. Keep in mind that you need to experiment on many factors till you obtain satisfactory results.

    Here is what you can do.

    1. Try different MF although they tend not to change the results much. If this is the case, I would stick to the Gaussian MF as it gives least number of adaptable parameters.

    2. Try different number of MF per input. The rule of thumb is that the higher the number of MF per input, the better the results. However, you may find different behavior for your ANFIS depending on the nature of your training data.

    3. Try different Sugeno models (linear vs. constant) although the linear model tends to give better results usually.

    4. Increase the number of training epochs as long as the error decreases. Stop training once the error stagnates. To reduce the error further, you need to adjust the design of your ANFIS as more training may not help.

    5. Change the number of data points and selection criteria in your training/testing datasets.

    It is a tedious process of various experiments, but hopefully, one of these suggestions may help you. Good luck.


  • Saurabh Chauhan asked a question in Hole Transporting Materials:
    How is diffusion length in organic-inorganic lead halide solar cells calculated?

    After reading the first few articles ( stranks et. al and xing et. al), I understood that they use one dimensional diffusion model to fit the carrier population decay rate as,

    dn/dt = D d2n/dx2 -k n;

    Now I understand where the diffusion term is coming from. But the second term is attributed to decay of excited state population by electron or hole quenching in presence of electron transport material and hole transporting material respectively. So I am assuming they modeled it as:

    electrons + ETM -------- ETM-

    dn/dt = -k'n [ETM]; assuming [ETM] doesn't change, 

    dn/dt = -kn

    however, have they taken account of electron hole recombination within the perovskite layer which would also decrease the excited state population. Recently, Kamat et. al showed that excited state decay mostly via electron hole bimolecular recombination or,

    e- + h+ ---- [eh]

    dn/dt = k'' n2 ; (assuming same number of electrons and holes)

    So shouldn't the overall equation be:

    dn/dt = D d2n/dx2 -k n - k'' n2  to calculate the diffusion coefficient D.

    And then use L = sqrt (D*lifetime of perovskite films)

    Or is it, exciton relaxation rather than electrons and hole bimolecular recombination, which suggests,

    (e-------h+) ---------(eh)

    So dn/dt = k'' n

    and then dn/dt = D d2n/dx2 -k n - k'' n = D d2n/dx2 -k' n;

    I am not sure if I interpreted the model right. Can anyone please explain if I am not thinking it right?? Thank you!

    Saurabh Chauhan

  • Daniel Isac Escobedo Beceiro added an answer in Data Stream Mining:
    Which algorithm is better for classification and clustering among svm and k-means ?

    data and stream mining

    Daniel Isac Escobedo Beceiro

    Svm is very good algorithm

  • Viktor Baranov added an answer in Chironomidae:
    Does anyone know of any publications on Chironomidae from the Republic of Moldova?

    I am supposed to have new species of Chironomidae for Moldova according to Fauna Europaea database, but I want to be completely sure and looking for any papers concerning Chironomidae for this country. Could you help me?

    Viktor Baranov

    You have to check weather you can get Toderash dissertation. And never mind if Fauna Europea missing any records - Martin dont have enough time to put all the data there, especially only occuring in old soviel literature. I will send you a Zelentsov et al (1994) paper, as for the othe records, check the world chironomidae catalouge by Ashe (2009,2012).

  • Aurora Sanchez added an answer in LISREL:
    Anybody knows a good book for SEM (using LISREL) to assess mediation and moderation.?

    I am doing a research where I need to use  some moderating and mediating variables  and I would like to see some examples using LISREL.

    Aurora Sanchez

    Thank you Witold for your suggestion

  • Marina Mainas added an answer in Nanocomposites:
    Is it possible to prepare transparent silicate ceramics?

    As we know, there are many studies and applications about transparent ceramics, including AlN, PLZT, sesquioxide (Y2O3 and Lu2O3) and aluminate (Y3Al5O12 or MgAl2O4). But there is no report about fabricate transparent silicate ceramics. So, is it possible to prepare transparent silicate ceramics?

    Marina Mainas

     I think that using sol -gel method starting with TEOS for O-si-O-  precursor, and adding nitrate precursors of metals, in H2O/EtOH solution, controlling drying and calcination temperature together with pH and H2O/EtOH ratio, you could obtain a transparent gel and then a transparent ceramic. You can try forexample choosing 60°C for drying and 1000_ 1100°C for calcination.  

  • Khalid Hassan added an answer in Adaptive Evolution:
    What are units of selection in evolutionary biology?
    What entities will evolve through the process of natural selection? The units that are reproduced (e.g. genes, accepting true replication truly exists) or the units that allow reproduction (e.g. individuals having abilities to produce offspring constituting next generations)?
    Khalid Hassan

    Genes represent the units transmitted from one generation to the next generation , and the genotype of individual broke down to genes during gametogenesis and distribute on gametes and through fertilization process new set of genotypes appear in the next generation.

    Good Luck

  • Fernanda mo added an answer in Salmonella:
    Why are bacteria on XLD yellow with black center but after subculture yellow without black center?

    i isolated salmonella from vegetable and water after enrichment the sample on XLD agar the suspected colony are yellow with black center but after sub culture the bacteria are yellow without black center can any body tell me what hap and what i must do ????? thanx

    Fernanda mo

    Dear Abdallah: I suggest you check time of incubation. Chronologically, salmonella first uses xylose, during which time the medium is acidified and therefore its color will be yellow. Once exhausted xylose, Salmonella metabolizes lysine, which generate alkalis (here the medium should become red). On the other hand, and for all the above, you must also make sure that actually try to salmonella (this because you bacteria comes from a non axenic culture and you can have bacteria with similar methabolic characteristics like salmonella). Finally, if it is salmonella, your colonies should be red with black center.

    Best regards,

    Fernanda Mo.

  • Fred Mutunga added an answer in Potential Energy Surfaces:
    How do I calculate potential energy surface with ZPE appended?

    I have computed single point energies along the potential energy surface using CCSD(T). I also have DFT calculated ZPEs for the stationary point (this is an isomerization reaction cis-A ->trans-A) how do I append Zero point energies to generate more accurate PES?

    Fred Mutunga


    I am interested in points along the PES including stationary points. Most paper don't actually mention how they have included the ZPEs (it might seem a common sense!). Thanks. I will have a look at this paper hopefully I will get an idea.


  • Amanpreet Cheema added an answer in Culture Cells:
    Why do primary liver cells isolated from porcine not attaching to the plate?

    I isolated primary liver cells from porcine by two step collagenase method. I am using RPMI 1640 medium for culturing the cells on collagen coated plates (collagen coating is done by myself). The cells are not attaching even it is 10 to 14 days old, but they are viable and forming clusters. Please suggest me any method to have cell attachment

  • Tim Brodribb added an answer in Hydraulics:
    What is the best (easiest, cheapest) way to get degassed water to run some hydraulic measuremts? A vaccum pump takes some time and it is very noisy.

    What is the best (easiest, cheapest) way to get degassed water to run some hydraulic measurements? I currently use a vacuum pump but it takes some time and it very noisy.

    Tim Brodribb

    I just bought a degasser that delivers 1L per minute. It is quiet and fast and removes more gas than the quick and dirty syringe method. I can find you the details if you are interested.

  • David Arndt added an answer in HDAC inhibitors:
    Has anyone intravenously injected Trichostatin A (TsA) into a rat with saline and 10% DMSO solution serving as vehicle? Any pH issues to be aware of?

    We are planning on injecting Trichostatin A intravenously into a rat for a maximum of 20 daily injections.  Just wondering if injecting this HDAC inhibitor has any unwanted side effects or pH issues to be aware of when administered iv.  Thanks for your input!

    David Arndt

    Thank you for passing along that paper, Mushtaq, I had not seen that article in my searching, so that was helpful.  Thanks.

  • Kelvyn Jones added an answer in P Value:
    Can I reject the constant from dynamic panel model?

    P-value for constant is very high. When I reject it, p-values for other variables are changing (are very different from the previous ones)..

    Kelvyn Jones

    I would not remove the constant - if you remove it you are fitting a repression through the origin model 


    and that is a big constraint to impose.

     Also remember that the intercept is the value of Y when all the X's are zero - why do you expect this estimate to be zero?

  • Carl A Wesolowski added an answer in Body Surface Area:
    Is it suitable to index renal and many other physiologic function for Body Surface Area ?

    The question bases on the wide criticism  by which measuring and estimating the body surface area (BSA) are questioned. Within  the many doubts, it  was emphasized  the inadequate methods to measure and to estimate the body surface, the frequent change of the weight, on which are based practically all the formulae stated to estimate the body surface, and the criteria followed for indexation according to the equation : variable N x 1,73/BSA, where the standardized measure of 1,73 square meters was the average body surface  in 1927 , a measure that increased very much during the past years, at present attaining 1,97 square meters, this inducing an underestimation of the measure function, being 1,73/1,97  = 0,878, that is to say a reduction of about 12 %.

    Carl A Wesolowski

    Body surface area does not form urine. Even if it did, the BSA estimating formulas would not be BSA, but functions of weight to a power and height to a power. When some of us tested the statistical validity of using height in such a formula for correlation to a one exponential term model of 99m-Tc-DTPA clearance, we found that including height to a power and weight to a power decreased the correlation to GFR that would be achieved using a power of weight alone. That is, BSA is spuriously correlated to GFR (Look up "spurious correlation' as a search term, if you have not seen this before) . Much more accurate body scaling can be obtained using fractal geometry for which GFR is proportional to the 99m-Tc-DTPA volume of distribution to the 2/3 power and weight to the 1/4 power.

    [See Wesolowski CA, Babyn PS, and Puetter RC. An improved method for determining renal sufficiency using volume of distribution and weight from bolus 99mTc-DTPA, two blood sample, paediatric data. Nuclear Medicine Communications 27(12): 961-968, 2006 and

    Wesolowski CA, Babyn PS, and Puetter RC. A Power Law for Determining Renal Sufficiency Using Volume of Distribution and Weight from Bolus 99mTc-DTPA, Two Blood Sample, Pediatric Data. Nuclear Science Symposium Conference Record, 2006 IEEE, pp. 1986-1994, 2006.]

    For those interested in body scaling, there are papers and books on the subject that have gone unnoticed by many. I might mention the work of West GB, Brown JH, Enquist BJ. The fourth dimension of life: fractal geometry and allometric scaling of organisms. Science 1999;284:1677-9, among many other papers. And the extensive review Agutter PS, Wheatley DN. Metabolic scaling: consensus or controversy? Theor Biol Med Model. 2004;1:13.

    Now if one uses Kleiber's law namely GFR is proportional to weight to 3/4 power, better results are to be had (see publications above). However, GFR is not endogenous creatinine clearance. Because muscle mass increases as roughly the 1.08 power of weight, the creatinine clearance should use a lower power of weight for body scaling than GFR, and endogenous creatinine clearance is only roughly related to GFR, and, to make matters more confusing, the experimentally obtained power of weight for scaling creatinine is 0.69, and that for scaling inulin 0.77.

    [See Adolph EF. Quantitative relations in the physiological constitutions of animals. Science. 1949;109:579-85.]

    Finally, what do you want to use body scaling for? Errors in GFR measurement are proportional, Thus, the logarithm of GFR for a patient should be compared to a later logarithm of GFR of the same patient as logarithm of GFR errors are homoscedastic. However, taking logarithms does not normalize GFR (That is, convert GFR values into a normal distribution). For such, a different GFR transform is needed (information withheld, unpublished).

    Normalization for drug dosimetry is an entirely different problem. For example, blood volume is approximately the first power of weight. That is, to calculate a dose of a vasoactive drug administered by intravenous infusion (example dipyridamole) one uses weight because independent of the body size of mammals, blood volume is roughly 5% of weight. This contrasts to dosing furosemide that I would dose by metabolism, that is, using for example

    Pediatric dose = Adult dose * (W/70)^0.75

    Next problem, how does one measure GFR? The best method is not affected by alterations in body fluid and would require few samples drawn over the shortest time possible. That is, as far as some of us can tell, the Tk-GV method

    [Wesolowski CA, Puetter RC, Ling L, Babyn PS. Tikhonov adaptively regularized gamma variate fitting to assess plasma clearance of inert renal markers. J Pharmacokinet Pharmacodyn. 2010;37:435-74.

    Wesolowski CA, Ling L, Xirouchakis E, Burniston MT, Puetter RC, Babyn PS, Giamalis IG, Burroughs AK. Validation of Tikhonov adaptively regularized gamma variate fitting with 24-h plasma clearance in cirrhotic patients with ascites. Eur J Nucl Med Mol Imaging. 2011;38:2247-56. doi:10.1007/s00259-011-1887-9.

    Wickham, Fred; Burniston, Maria Teresa; Xirouchakis, Elias; Theocharidou, Eleni; Wesolowski, Carl Adam; Hilson, Andrew J W; Burroughs, Andrew Kenneth. Development of a modified sampling and calculation method for isotope plasma clearance assessment of glomerular filtration rate in patients with cirrhosis and ascites. Nucl Med Commun 34:1124–1132, doi:10.1097/MNM.0b013e32836529ab, 2013

    And shortly, Surajith N. Wanasundara, Michal J. Wesolowski1, Mark C. Barnfield, Michael L. Waller, Anthony W. Murray, Maria T. Burniston, Paul S. Babyn, Carl A. Wesolowski1, Accurate and precise plasma clearance measurement using four Tc-99m-DTPA plasma samples over four hours, In press in Nuclear Medicine Communications, Sept. 9, 2015]

    In summary, BSA is appropriate for estimating percentage damage of body surface area for burn victims as a guide to fluid replacement, but, there are few other situations for which I would not use a better estimator.

  • Michael Päch added an answer in Polymer Synthesis:
    I am synthesizing phenol formaldehyde resins that are slightly yellow and transparent. How do I get them colourless?

    I have been using formulations from the 1920's and 30's from the patent literature to create the resole prepolymer.  There were a couple of cases that addressed this colour issue.  One that I found on my own was the use of a nitrogen purge throughout the prepolymer synthesis, which helped a lot.  It still gets slightly yellow and darkens upon curing.  Other methods have involved the use of neutralizing acid for the sodium hydroxide catalyst; lactic acid was used but this did not give clear resins.  Other concoctions have been suggested to bleach the resin with no help.

    Michael Päch

    As N2 purge did help, one might surmise, that oxidation reactions leading to some sort of quinoid structures are causing the yellow colour. That said, it seems likely, that the addition of antioxidants might suppress the yellowing further. I would refrain, though, from the commonly used ones (e.g. BHT; H2Q) as the give rise to yellow oxidation products themselves. How about phosphites, phosphinates, tin(II)ethylhexanoate or ascorbyl palmitate?

  • Amiya K. Pani added an answer in Finite Difference Method:
    How finite difference method is used in cubic spline collocation method for non linear ordinary differential equation?

    Suggest me How i solve given problem with cubic spline or finete difference method or finite difference method with cubic spline.


    B.C. f(0)=constant , f'(0)=0  and f'(infinity)=1 ?

    Amiya K. Pani

    First of all, we have to write problem in a bounded domain using say artificial boundary condition.  Sometimes, if theoretically one can not  prove the error committed by artificial boundary condition is small, one can do so by varying the right hand boundary condition and see its effect numerically.  Then the problem is posed on a bounded domain.  One can take say $f' =u$ and obtain a nonlinear two point boundary value problem and apply fdm which may give rise to nonlinear system and solve .

    But why did you want to apply numerical method. May be try to do it analytically

    after obtaining $u$:  one finds : $u''+ (u^2/2)'=0$ Then integrate  from 0 to \eta. Then

    and possibly one can integrate again.

  • D.B. Jani added an answer in Building Simulation:
    How can I determine the air change rate for building simulation?

    How can I determine the air change rate for building simulation? Simulation of desiccant cooling system.

    D.B. Jani

    Thank you for the answer.

  • Farid Fathi asked a question in Pedigree:
    What are the causes of wrong in pedigree information?

    Two kinds of pedigree errors can influence the results of breeding value estimation - incorrect pedigree information (i.e. wrong parentage) and missing pedigree information (i.e. parentage unknown).

  • Nadjia El Saadi added an answer in Chagas Disease:
    Where can I find real values for transition probabilities from juvenile stages to adult stage in vectors of Chagas disease ?

    In fact, I need such values especially for T. Sanguisuga   for a simulation study. 

    Nadjia El Saadi

     The paper is interesting. Thank you very much.