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  • Do I need to chloride a concentric electrode for electrophysiology?

    I am putting together a stimulating electrode for electrophys. recording. Do I need to chloride a concentric electrode the same way I would a bipolar electrode?

    Thank you! 

    Serguei N Skatchkov · Central University of the Caribbean

    Dear Greg,

    if you do not cover your Ag-wire (reference electrode or in patch pipette), you will have tremendous and unpredictable shifts of electric potential which will produce potentially wrong data in electrophysiological experiments measuring DC currents/voltages. So, it is necessary to use stable electrodes. Ag-AgCl is mostly used, however there others such as (i) copper-copper sulfate electrode (Cu-CuSO4) or (ii) mercury electrode (Hg-HgCl2, called calomel electrode) that we used as well. All depends on particular design of the experiments. 

    Dr. Akopian suggested simple method how to cover rapidly your silver wire making Ag-AgCl elecrode. We also used successfully not electrochemical (cathode covering, using electric current) but just chemical procedures as Dr. Akopian suggested, but different methods:

    1. CuSO4+NaCl solution method

    2. fire melted AgCl coating

    Both methods produce harder surface of coated wire and thus more mechanically stable.

    Very cordially, Serguei.

  • Soheil Soroushnia added an answer in Abaqus:
    How do I find the input parameters for Mohr-Coulomb analysis on concrete in Abaqus ?

    Can somebody help me with something. I am doing a Mohr-Coulomb analysis on concrete in Abaqus. But I can't figure it out how do I calculate the input parameters. Friction angle, Dilation angle, Cohesion Yield Stress  

  • Ariel Linden added an answer in Maximum Likelihood:
    How do I inflate a small sample through time series data?

    Hi everyone!

    In a few words, ma question is: Can I increase the number of cases of a small sample by considering these cases at several points in time ?

    In more detail: I have a sample of 26 cases (which is actually the universe), concerned by a given policy. This policy covers a period of 7 years. Is my sample big enough if I take those 26 cases in seven different points in time?

    Recently I have read this article that holds that small samples may not be too big an issue if one conducts Maximum Likelihood Regression instead of Least Squares. More specifically, the author posits that Type I errors are not a problem, Type II error may be more porblematic. If I combine the maximum likelihood method with cross section data in a time series, would my 26 cases still be a problem?

    thank you so much for your attention,

    Ariel Linden · University of Michigan

    Yes, if you have data measured repeatedly over time you want to assess the stability of time series. You can certainly use a longitudinal model and then look at the within group (and perhaps even the between group) variances. Which model type to use will depend on what your outcome variable is. If it is a count, then you can consider a Poisson. If it's overdispersed, then a negative binomial is more suitable.

  • Serdar Badoğlu asked a question in Pcm:
    SMD or what else?

    Hi all. I'm a bit confused. For Gaussian 09, when one evaluate an optimization and frequency calculation in solvation phase by selecting PCM (which is in fact IEFPCM) is it computed by using SMD model or not? If not, which model is in use in such a case?

  • Guilherme Maia Santos asked a question in SIESTA:
    Why don't appear the electric density of Al in my simulation?

    Ab initio calculations in the AlFeO3 compound have been performed using the SIESTA program package. Calculations of atomic geometry and electronic structure were performed within first-principles of Dendity-Functional Theory (DFT) under the generalized gradient approximation (GGA) of Perdew, Burke, and Ernzerhof (PBE) including spin polarization. A 490 Ry cutoff was employed for the plane wave basis, and integrations over the Brillouin zone of the orthorhombic crystal were sampled with a 5 X 5 X 5 k-points mesh.

    My question is, Why don't appear the electron density for the Al?

    Appear for the O, and Fe... but not for the Al!!

    Anyone can help me with this issue?!

  • Christina R Bourne added an answer in Gyrase:
    Are you familiar with expression clones for DNA gyrase?

    We have been trying to overexpress and purify full length gyrase A from E coli, but we seem to have a knack for getting a cleaved product, even during expression.  We've tried a few different clones, but not the "original" Hallett et al plasmids.  Would anyone know where we could source JMtacA and JMtacB?  Alternatively, if anyone knows a trick for gyrA I'd love to hear it!
    Thanks in advance

    Christina R Bourne · University of Oklahoma

    Previous publications have been successful with E coli, and it is a bacterial protein.  I don't think mammalian cells are the way to go.....   thanks for your help though!

  • Robert Neil Leong asked a question in ps:
    How can I statistically classify curves?

    Dear colleagues,

    I am currently working on classifying certain objects which are (visually) represented as waves/curves. I am wondering whether there is a way to characterize the curves so as to be able to build classification rules which can then be used to classify the curves.

    P.S. I have 3 pre-defined classes of curves.

  • Amir Abbas Talebi asked a question in Power:
    How to calculate the power short-circuit?

    How to calculate the power short-circuit?

  • Radhwan Alnaimi added an answer in X-Ray Sources:
    How can I count X-ray source intensity?

    I am using a photo diode with known quantum efficiency to measure the intensity of my x-ray source. The diode's signal is measured in volts on a scope with known impedance.

    Can anyone help with, how to calculate the counts per second for the photons of the x-ray source.

    Many thanks,


    Radhwan Alnaimi · Imperial College London

    Hi Rodolfo,

    I am using a photodiode type AXUV20A with a known responsivity  to the wavelength emitted from the the source. If I am right so I am using the formula

    No. of Photons =  Power / photon energy

    where P = Voltage value/ (responsivity x oscilloscopes impedance).

    Power is taken in J/s and photons energy is taken in joules.

  • Lila Nath Sharma added an answer in Biodiversity:
    How to test whether two species accumulation curves are different or not?

    I obtained species accumulation curve by using accucomp in Biodiversity R package. I obbtained desired curves. Now I am looking for some methods to test whether these two curves are significantly different or not.

    Thank you for considering my issue

    Lila Nath Sharma · University of Bergen

    Thank you, Sebastian for indicating interesting paper. Unfortunately I do not have Access to full paper. I Guess there is theoritical answer to my question.

    My current concern is comparing two species accumulation curves that we get from accumcomp funcation in Biodiversity R. I think its simple technical thing for someone who is expert in R.

  • Chengjun Yu added an answer in Battery:
    Have A grade of glass microfiber filters (GF/A) been used as Na ion battery separator?

    why have F grade of glass microfiber filters (GF/F) frequently been using  as Na ion battery separator and not another grade of them.

    Chengjun Yu · Université de Picardie Jules Verne

    It just to seperate the cathode and anode in physical way.

  • Deisi Yunga added an answer in Vocational Education:
    Do you think that the transfer of a Vocational Education and Training System from one country to another is possible?

    Background: Since the 1950s the german ministry tries to transfer the dual VET system - with very, very limited success. Do you know successful examples of transfer (also other systems, not only the dual system)?

    Deisi Yunga · Universidad Técnica Particular de Loja

    I think it's possible, in my country we are starting a VET structure that takes as a example the dual system in Europe, we are working on that slow because as we all know something that is successful in one country can be a total disaster in another country, but if you adapt the system to your reality and take the necessary measures to minimize negative effects it can be done. One project I like that work in transference of knowledge is http://www.u-rpl.eu/project-partners because the administrators took a lot of time and effort into managing the differences (context, culture, etc) within the countries involved in the project.

  • Amir Abbas Talebi asked a question in Connectivity:
    What is the connection definite purpose?

    What is the connection definite purpose?

  • Daniel Davis asked a question in Wittgenstein:
    Is is possible to view space as a substance, on a par with material substances, distinct in its nature but also possessing causal efficacy?

    Following Kant Hume, Wittgenstein and most Western philosophers, the majority view is that this effort would be foolish metaphysical speculation, flights of fancy that we might want to pursue but should not.

    I argue that their epistemology-based approach leads Western culture to overlook the space between things, as it focuses on the details of the observables and ignores the ubiquitous, non-material substance with which all particular things must coincide. 

  • Jose Caballero added an answer in Umbilical Hernia:
    At what age do you repair an uncomplicated umbilical hernia in a child?

    A large proportion of umbilical hernias will self resolve with age. At what stage do you tell the parents that their child's hernia will not improve further, and you would consider a repair for cosmetic reasons.

    Jose Caballero · Hospital Regional Docente de Trujillo

    Me too 5 years old

  • Arnold Trehub added an answer in Cognitive Systems:
    Is Chalmers' so-called "hard problem" in consciousness real?

    In his 2014 book "Consciousness and the Brain: Deciphering How the Brain Codes Our Thoughts" Stanislas Dehaene wrote "Chalmers, a philosopher of the University of Arizona, is famous for introducing a distinction between the easy and the hard problems. The easy problem of consciousness, he argues, consists in explaining the many functions of the brain: how do we recognize a face, a word, or a landscape? How do we extract information form the senses and use it to guide our behavior? How do we generate sentences to describe what we feel?

    “Although all these questions are associated with consciousness,” Chalmers argues, “they all concern the objective mechanisms of the cognitive system, and consequently, we have every reason to expect that continued work in cognitive psychology and neuroscience will answer them. By contrast the hard problem is the “question of how physical processes in the brain give rise to subjective experience … the way things feel for the subject. When we see for example, we experience visual sensations, such as that of vivid blue. Or think of the ineffable sound of a distant oboe, the agony of an intense pain, the sparkle of happiness or the meditative quality of a moment lost in thought … It is these phenomena that poses the real mystery of the mind”."

    Stanislas Dehaene's opinion is "that Chalmers swapped the labels: it is the “easy” problem that is hard, while the “hard” problem just seems hard because it engages ill-defined intuitions. Once our intuition is educated by cognitive neuroscience and computer simulations, Chalmers’ “hard problem” will evaporate".

    Personally, I agree with Stanislas Dehaene's opinion.

    Arnold Trehub · University of Massachusetts Amherst


    Please give us some examples of stimuli which cannot be consciously perceived.

  • Younes Fathabadi added an answer in Magnetic Field:
    If residual magnetism of a shunt generator is destroyed accidentally can it be restored by connecting its shunt field?

    to a DC source. !
    to an AC source.!

    Younes Fathabadi · Khorasan Institute of Higher Education


    You have to connect it to a dc source for sure. But you have to pay attention on the polarity! the machine has to be keept on the previous polarity, therefore the magnetic polarity must be the same.

  • Francisco T Tirol added an answer in Appendectomy:
    Unexpected Cecal Mass during Appendectomy - What can I do now?

    I had an appendectomy on a 25 years old man with an unexpected mass in cecum. I did a right hemicolectomy at that stage. Now I have the pathologic result: Esosinophilic entropathy! Is there any guideline for unexpected masses in cecum during appendectomy? Was my procedure right?

    Francisco T Tirol · Wound Care Center at PMHD

    Refer to recent publication with photograph  of cecocolic mass, 2.5 cm hypertrophic  thick wall, benign, secondary to chronic recurrent torsion with spontaneous resolution:Congenital Hyperrotated Colon, F.T.Tirol, Abdominal Surgery, Winter/Spring, 2015, Figure 12.

  • Amir Abbas Talebi asked a question in Network:
    What is the purpose of the network maneuver?

    What is the purpose of the network maneuver?

  • Imalka Jayawardena added an answer in PEDOT:PSS:
    How does PEDOT:PSS act as a hole extractor/electron blocking layer in organic solar cells?

    Is it only the work function and relevant HOMO LUMO  energy level alignment that makes a pedot:pss layer act as a hole extracting layer? In that case, with different energy level alignment can it extract electrons as well? or is there an additional mechanism for blocking the electrons? For example how the hole mobility and electron mobility of pedot:pss would compare?

    Thank you.

    Imalka Jayawardena · University of Surrey

    I think the above two comments have more or less answered the question. PEDOT:PSS is preferred due to several reasons. When there are no other additives (such as IPA, DMSO) PEDOT:PSS has a sufficiently high work function to form and Ohmic contact to P3HT enabling hole extraction. The energy level difference between the LUMO of PCBM and the PEDOT work function is too high resulting in a barrier for charge extraction. I am not sure as to whether PEDOT:PSS can be considered as a preferential hole transporter. placed between two metal contacts such as Au, the transport should be due to electrons. This is also seen in the case of ITO where it can act either as the anode or cathode contact depending on the nature of the layer in contact with it. So, the reason for using PEDOT:PSS as an HTL is more likely due to its work function. 

  • Younes Fathabadi added an answer in Low-Voltage:
    How can I design a high frequency transformer for isolated bidirectional full bridge dc dc converter?

    This bidirectional dc dc converter can power flow in both direction one is high voltage side and other one is low voltage side. Low voltage side is current fed and high voltage side is voltage fed.

    Younes Fathabadi · Khorasan Institute of Higher Education


    You have to connect it to a dc source for sure. But you have to pay attention on the polarity! the machine has to be keept on the previous polarity, therefore the magnetic polarity must be the same.

  • Amir Abbas Talebi asked a question in Operations:
    What is the purpose of the operation post?

    What is the purpose of the operation post?

  • Tasseled cap greenness for landsat 8, interpretation from which technique will better?

    Remote sensing 

  • Sajid Hussain added an answer in Raw Materials:
    How to construct price index of raw material for cross section data?

    i have different items in raw material. i need price of raw material for my translog cost function. please guide me.

    Sajid Hussain · University of Lahore


    Could you elaborate your answer? to my information i can not do that as my data is cross section.

  • Fatima Shaheen asked a question in Gradient PCR:
    Does anybody know the reason of disappearance of a band during gel extraction and purification?

    I did gradient PCR using cDNA as a template. Then I used these PCR products in a new PCR as templates. I ran the new PCR products in 2% agarose gel in order to extract and purify the desired bands. I got 2 bands, the first one was very bright while the second one was faint. I started cutting the gel with the bright band. When I wanted to cut the faint band, it disappeared (like it wasn't visible under UV light) as well as the ladder bands started to disappear, too. So does anyone have any idea about the reason of this disappearance? 

  • Amir Abbas Talebi asked a question in Network:
    The network control mean?

    The network control mean?

  • Who can give me information about power conference

    Who can give me information about power conference?

    Sri Nikhil Gupta Gourisetti · Pacific Northwest National Laboratory

    Most prestigious one: http://www.pes-gm.org/2015/

    for circuits and systems: https://www.engr.colostate.edu/mwscas2015/

  • Sajjad Nazidizaji asked a question in Cities:
    How can accessibility in the cities help the tourism industry in city ?

    I mean , high or less accessibility in cities how can help or hurt the growth of tourism in that city specially in economic way .