From afraniocd from gmail.com Sun Feb 1 07:23:30 2009 From: afraniocd from gmail.com (afraniocd@gmail.com) Date: Sun Feb 1 12:54:22 2009 Subject: [Neuroscience] Re: Alzheimer Research References: <0934ec9a-d07b-462c-8723-57c1eebc9d1b@e25g2000vbe.googlegroups.com> <24KdnbeBGusDYhnUnZ2dnUVZ8hednZ2d@westnet.com.au> Message-ID: <7b099804-7d08-4e5f-9e66-25d187d03ea4@o24g2000yqf.googlegroups.com> On Jan 31, 11:40?pm, "John Hasenkam" wrote: > http://www.alzforum.org/ > > wrote in message > > news:0934ec9a-d07b-462c-8723-57c1eebc9d1b@e25g2000vbe.googlegroups.com... > > > > > Good Afternoon, > > Does anyone in this group works with alzheimer research?- Hide quoted text - > > - Show quoted text - Thanks for the information, but I would like to discuss protocols used in research with Alzheimer's, techniques for staining of brain tissue in mice .... Does this site you can get this information? Thank you From connelly.bill from gmail.com Sun Feb 1 17:30:33 2009 From: connelly.bill from gmail.com (Bill) Date: Sun Feb 1 18:06:16 2009 Subject: [Neuroscience] Making a dummy cell - where to get 1GOhm variable resistors? Message-ID: <266ce687-9ca6-4b9e-9a8e-6b42d7cf6ad1@v18g2000pro.googlegroups.com> Hey, I'm wanting to build a dummy cell with variable resistors and capcitors, to modulate series resistance and whole-cell capcitance (and a place to record over the "cell" to show voltage errors). However I'm having a hard time finding variable resistors in the 2-20 MOhm range, let alone the 1GOhm max for the input resistance. Does anyone know a good source for potentiometers in that range that will ship to the Antipodes? Thanks. From johnh from goawayplease.com Mon Feb 2 20:29:44 2009 From: johnh from goawayplease.com (John Hasenkam) Date: Mon Feb 2 20:50:00 2009 Subject: [Neuroscience] Re: Alzheimer Research References: <0934ec9a-d07b-462c-8723-57c1eebc9d1b@e25g2000vbe.googlegroups.com> <24KdnbeBGusDYhnUnZ2dnUVZ8hednZ2d@westnet.com.au> <7b099804-7d08-4e5f-9e66-25d187d03ea4@o24g2000yqf.googlegroups.com> Message-ID: Can't answer your question. I suggest you look at that site, note the relevant researchers, and contact them. On this forum there are a number of bods that provide good info re protocols etc but I have not seen anything in relation to Alz mentioned here. John. wrote in message news:7b099804-7d08-4e5f-9e66-25d187d03ea4@o24g2000yqf.googlegroups.com... On Jan 31, 11:40 pm, "John Hasenkam" wrote: > http://www.alzforum.org/ > > wrote in message > > news:0934ec9a-d07b-462c-8723-57c1eebc9d1b@e25g2000vbe.googlegroups.com... > > > > > Good Afternoon, > > Does anyone in this group works with alzheimer research?- Hide quoted > > text - > > - Show quoted text - Thanks for the information, but I would like to discuss protocols used in research with Alzheimer's, techniques for staining of brain tissue in mice .... Does this site you can get this information? Thank you From jopower from yahoo.com Wed Feb 4 11:27:45 2009 From: jopower from yahoo.com (polly jo) Date: Wed Feb 4 15:43:29 2009 Subject: [Neuroscience] Re: Alzheimer Research In-Reply-To: <7b099804-7d08-4e5f-9e66-25d187d03ea4@o24g2000yqf.googlegroups.com> Message-ID: <856529.87271.qm@web65706.mail.ac4.yahoo.com> --- On Sun, 2/1/09, afraniocd@gmail.com wrote: > From: afraniocd@gmail.com > Subject: [Neuroscience] Re: Alzheimer Research > To: neur-sci@magpie.bio.indiana.edu > Date: Sunday, February 1, 2009, 5:53 PM > On Jan 31, 11:40 pm, "John Hasenkam" > wrote: > > http://www.alzforum.org/ > > > > wrote in message > > > > > news:0934ec9a-d07b-462c-8723-57c1eebc9d1b@e25g2000vbe.googlegroups.com... > > > > > > > > > Good Afternoon, > > > Does anyone in this group works with alzheimer > research?- Hide quoted text - > > > > - Show quoted text - > > Thanks for the information, but I would like to discuss > protocols used > in research with Alzheimer's, techniques for staining > of brain tissue > in mice .... Does this site you can get this information? > Thank you Well, I do work in Alzheimer's for the moment. However, it depends on which techniques you are looking for, for there are various ones.... if you are interested in plaques/ tangles/oligomers/ neurons/spines and so on.... You could give more details, and you could also look up papers that give the techniques. Best Pow > _______________________________________________ > Neur-sci mailing list > Neur-sci@net.bio.net > http://www.bio.net/biomail/listinfo/neur-sci From nin from neurohost.org Thu Feb 5 16:01:37 2009 From: nin from neurohost.org (Jose Guzman) Date: Thu Feb 5 17:06:59 2009 Subject: [Neuroscience] intracellular AMPAR blocker for in vivo experiments. Message-ID: Hi everybody there, I have been looking in the pubmed for a long time, and I did not find any AMPARs blockers for intracellular application (apart from the polyamines). The problem is that while extracellular stimulation in vivo is quite straightforward, we still do not if this response is uniquely excitatory. Applying the drugs extracellularly is difficult due to the nature of the experiments (in vivo recordings). Does anybody of you know something related with that?. The idea would be to discard the AMPAR component of a EPSC in the granule cells of the hippocampus upon entorinal cortex stimulation. Thank you very much in advance. Jose. From rkmishra from cbcs.ac.in Thu Feb 5 14:59:40 2009 From: rkmishra from cbcs.ac.in (Ramesh Mishra) Date: Thu Feb 5 17:07:03 2009 Subject: [Neuroscience] Re: Neur-sci Digest, Vol 45, Issue 4 In-Reply-To: <200902051705.n15H5s823615@net.bio.net> References: <200902051705.n15H5s823615@net.bio.net> Message-ID: <939e39190902051159r4c10c55btbe669058b4981ad5@mail.gmail.com> Hi Does anyone work with eye movements? I would like to discuss some analysis procedures. I use a SMI High speed eye tracking system ( 1250 Hz). Regards On Thu, Feb 5, 2009 at 10:35 PM, wrote: > Send Neur-sci mailing list submissions to > neur-sci@net.bio.net > > To subscribe or unsubscribe via the World Wide Web, visit > http://www.bio.net/biomail/listinfo/neur-sci > or, via email, send a message with subject or body 'help' to > neur-sci-request@net.bio.net > > You can reach the person managing the list at > neur-sci-owner@net.bio.net > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of Neur-sci digest..." > > > Today's Topics: > > 1. Re: Re: Alzheimer Research (polly jo) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Wed, 4 Feb 2009 08:27:45 -0800 (PST) > From: polly jo > Subject: Re: [Neuroscience] Re: Alzheimer Research > To: neur-sci@magpie.bio.indiana.edu, "afraniocd@gmail.com" > > Message-ID: <856529.87271.qm@web65706.mail.ac4.yahoo.com> > Content-Type: text/plain; charset=us-ascii > > --- On Sun, 2/1/09, afraniocd@gmail.com wrote: > > > From: afraniocd@gmail.com > > Subject: [Neuroscience] Re: Alzheimer Research > > To: neur-sci@magpie.bio.indiana.edu > > Date: Sunday, February 1, 2009, 5:53 PM > > On Jan 31, 11:40 pm, "John Hasenkam" > > wrote: > > > http://www.alzforum.org/ > > > > > > wrote in message > > > > > > > > news:0934ec9a-d07b-462c-8723-57c1eebc9d1b@e25g2000vbe.googlegroups.com. > .. > > > > > > > > > > > > > Good Afternoon, > > > > Does anyone in this group works with alzheimer > > research?- Hide quoted text - > > > > > > - Show quoted text - > > > > Thanks for the information, but I would like to discuss > > protocols used > > in research with Alzheimer's, techniques for staining > > of brain tissue > > in mice .... Does this site you can get this information? > > Thank you > > Well, I do work in Alzheimer's for the moment. However, it depends on which > techniques you are looking for, for there are various ones.... if you are > interested in plaques/ tangles/oligomers/ neurons/spines and so on.... > You could give more details, and you could also look up papers that give > the techniques. > > Best > Pow > > _______________________________________________ > > Neur-sci mailing list > > Neur-sci@net.bio.net > > http://www.bio.net/biomail/listinfo/neur-sci > > > > > > > ------------------------------ > > _______________________________________________ > Neur-sci mailing list > Neur-sci@net.bio.net > http://www.bio.net/biomail/listinfo/neur-sci > > End of Neur-sci Digest, Vol 45, Issue 4 > *************************************** > -- Ramesh Kumar Mishra PhD Centre for Behavioural and Cognitive Science ( CBCS) University of Allahabad Allahabad 211002 India Email:rkmishra@cbcs.ac.in Ph-91-0532-2460738 ( work) Mob-91-9451872007 Fax-91-0532-2460738( work) Personal page: http://www.cbcs.ac.in/~rkmishra.htm Home page: www.cbcs.ac.in From peter.wallace24 from gmail.com Sat Feb 7 12:06:04 2009 From: peter.wallace24 from gmail.com (peter.wallace24@gmail.com) Date: Sat Feb 7 16:34:12 2009 Subject: [Neuroscience] Weizmann Institute Scientists Create Working Artificial Nerve Networks Message-ID: <5cd29758-a148-44be-ac17-23e8e0a92a52@w39g2000prb.googlegroups.com> Scientists have already hooked brains directly to computers by means of metal electrodes, in the hope of both measuring what goes on inside the brain and eventually healing conditions such as blindness or epilepsy http://www.theanalystmagazine.com/pr/feb2009/808068.html From connelly.bill from gmail.com Mon Feb 9 20:31:23 2009 From: connelly.bill from gmail.com (Bill) Date: Mon Feb 9 21:33:12 2009 Subject: [Neuroscience] Re: intracellular AMPAR blocker for in vivo experiments. References: Message-ID: <8286423c-74f7-4a56-ba09-eedc25151252@r37g2000prr.googlegroups.com> That is a problem! If you weren't at such a deep location I would say just apply high strength CNQX to the cortex (works when you're in cerebellar granule cells). I have looked for the exact same thing in the more mundane situation of patching in slices, and I couldn't find anything. However, I wonder if it would be possible to find a non-selective sodium channel antagonist. I say this because you can apply DIDS intracellularly to block GABAA receptors, and it is just a Cl- channel blocker, mostly used by epithelia researchers. What do you think you're chances are if you picospritzed the drug on? You should be able to get a drug application electrode in their first, and the blowing of CNQX shouldn't distrupt your patch very often (it doesn't in slices). Sorry I couldn't be more help. On Feb 6, 10:01?am, Jose Guzman wrote: > Hi everybody there, > > I have been looking in the pubmed for a long time, and I did not find > any AMPARs blockers for intracellular application (apart from the > polyamines). > > The problem is that while extracellular stimulation in vivo is quite > straightforward, we still do not if this response is uniquely > excitatory. Applying the drugs extracellularly is difficult due to the > nature of the experiments (in vivo recordings). > > Does anybody of you know something related with that?. The idea would be > to discard the AMPAR component of a EPSC in the granule cells of the > hippocampus upon entorinal cortex stimulation. > > Thank you very much in advance. > > Jose. From usenet02 from out-of-phase.de Tue Feb 10 19:24:22 2009 From: usenet02 from out-of-phase.de (Christian Wilms) Date: Wed Feb 11 00:52:21 2009 Subject: [Neuroscience] Re: intracellular AMPAR blocker for in vivo experiments. References: <8286423c-74f7-4a56-ba09-eedc25151252@r37g2000prr.googlegroups.com> Message-ID: <1iuy6ak.px3o8u1odflfcN%usenet02@out-of-phase.de> > What do you think you're chances are if you picospritzed the drug on? > You should be able to get a drug application electrode in their first, > and the blowing of CNQX shouldn't distrupt your patch very often (it > doesn't in slices). Spritzing deep in the tissue can get seriously complicated. Since you're lacking visual feedback, handling two pipettes is difficult and collisions likely. While there are labs doing dual patch recordings in vivo, there aren't many and even they tend to find it difficult ... Just my 2 cents - sorry it's not more positive. Cheers, Christian From deniseingebo from gmail.com Wed Feb 11 10:12:29 2009 From: deniseingebo from gmail.com (Denise Ingebo) Date: Wed Feb 11 12:58:07 2009 Subject: [Neuroscience] Introducing "Impulsing in the Nervous System" a new model in Neuroscience Message-ID: Invitation to Critique New ModelBased on the member's of this forum's interest in the neural correlates of consciousness, I'd like to introduce you to a new model called "Impulsing in the Nervous System" ... a new way of following activity in the Nervous System. As a theorist, I'm not a recognizable professional, but the concepts are sound. Please view the featured video at www.youtube.com/impulsing. Your comments, if you'd like to respond, will be carefully reviewed. The website is www.impulsing.org. Thank you, Denise Ingebo Introducing "Impulsing in the Nervous System" a new model in Neuroscience From connelly.bill from gmail.com Fri Feb 13 20:16:27 2009 From: connelly.bill from gmail.com (Bill) Date: Sat Feb 14 12:45:11 2009 Subject: [Neuroscience] Op Amps - The Voltage Follower Circuit Message-ID: <9d7d358d-02a2-4451-bf33-34a6f85a4114@w1g2000prm.googlegroups.com> I'm having a hard time understanding the classical Voltage Follower Circuit made by a single op amp. I wont bother trying to draw it in ASCII, just have a look here if you don't know what I'm talking about: http://hyperphysics.phy-astr.gsu.edu/Hbase/electronic/opampvar2.html This is who I'm thinking about it (which I'm sure is wrong): 1) Lets imagine you have a 1mV input to the + input. 2) At the instant this is switched on the - input is 0, so the op amp outputs 1mV 3) Now the + input still gets 1mV and - input gets 1mV, so the amp outputs 0mV, sending us back 1) I appriciate that the op amp works 'instantaneously' so you don't get oscillations like I described, but I still don't know how one can conceptualize op amps without getting into these kind of oscillations. Thanks for anyone who can tell me the correct way to think about this From r_s_norman from _comcast.net Fri Feb 13 22:02:18 2009 From: r_s_norman from _comcast.net (r norman) Date: Sat Feb 14 12:45:16 2009 Subject: [Neuroscience] Re: Op Amps - The Voltage Follower Circuit References: <9d7d358d-02a2-4451-bf33-34a6f85a4114@w1g2000prm.googlegroups.com> Message-ID: On Fri, 13 Feb 2009 17:16:27 -0800 (PST), Bill wrote: >I'm having a hard time understanding the classical Voltage Follower >Circuit made by a single op amp. I wont bother trying to draw it in >ASCII, just have a look here if you don't know what I'm talking about: > >http://hyperphysics.phy-astr.gsu.edu/Hbase/electronic/opampvar2.html > >This is who I'm thinking about it (which I'm sure is wrong): >1) Lets imagine you have a 1mV input to the + input. >2) At the instant this is switched on the - input is 0, so the op amp >outputs 1mV >3) Now the + input still gets 1mV and - input gets 1mV, so the amp >outputs 0mV, sending us back 1) > >I appriciate that the op amp works 'instantaneously' so you don't get >oscillations like I described, but I still don't know how one can >conceptualize op amps without getting into these kind of oscillations. > >Thanks for anyone who can tell me the correct way to think about this You forget that the op amp is really an amplifier with a very high gain. Lets suppose it has a gain of one thousand. Actually it is normally higher than that but this will do for calculation. When you put 1 mv on the input, it responds by putting an output not of 1 mv, but only about 999 microvolts, 1/1000 less than the desired 1 mv. Then there is 1 millivolt on the + input and 0.999 mv on the - input for a difference of 0.001 mv which, times the 1000 gain, would produce an output of 1 mv. Remember, I said "about" 999 microvolts. The difference is the approximation error. To be precise, if the gain is G, then the output is G times the difference between the + and - inputs. Let the output be y and the input x. Then y = G(x - y) since the output is applied to the - input. Solve that to get y = x * G/(1+G). If G is very large, then G/(1+G) is very close to one. Oscillations are an entirely different story. For that you have to describe the output in terms of the LaPlace (or Fourier) transform of its "transfer function". But control theory tells you exactly how to do it and to build a circuit that does not produce oscillations. From jalegris from sympatico.ca Fri Feb 13 23:29:30 2009 From: jalegris from sympatico.ca (J.A.Legris) Date: Sat Feb 14 12:45:21 2009 Subject: [Neuroscience] Re: Op Amps - The Voltage Follower Circuit References: <9d7d358d-02a2-4451-bf33-34a6f85a4114@w1g2000prm.googlegroups.com> Message-ID: <59528a1e-fec0-4cc0-b7b4-b84d3e87ad76@l37g2000vba.googlegroups.com> On Feb 13, 8:16?pm, Bill wrote: > I'm having a hard time understanding the classical Voltage Follower > Circuit made by a single op amp. I wont bother trying to draw it in > ASCII, just have a look here if you don't know what I'm talking about: > > http://hyperphysics.phy-astr.gsu.edu/Hbase/electronic/opampvar2.html > > This is who I'm thinking about it (which I'm sure is wrong): > 1) Lets imagine you have a 1mV input to the + input. > 2) At the instant this is switched on the - input is 0, so the op amp > outputs 1mV > 3) Now the + input still gets 1mV and - input gets 1mV, so the amp > outputs 0mV, sending us back 1) > > I appriciate that the op amp works 'instantaneously' so you don't get > oscillations like I described, but I still don't know how one can > conceptualize op amps without getting into these kind of oscillations. > > Thanks for anyone who can tell me the correct way to think about this Recommended reading: http://www.analog.com/library/analogDialogue/archives/39-05/Web_ChH_final.pdf -- Joe From kedar from kedarghimire.com Sun Feb 15 04:46:30 2009 From: kedar from kedarghimire.com (kedar Ghimire) Date: Sun Feb 15 15:13:53 2009 Subject: [Neuroscience] Blocking a transmembrane ATPase but not on the sarcoplasmic reticulum Message-ID: Dear Bio.net friends, Due to conflicting results of my experiment, I need to know whether the ATPase on the cell membrane is contributing to Autophagy or the one on the sarcoplasmic reticulum namely SERCA. How can i block the ones on the cell membrane and still keep the ATPases on the sarcoplasmic reticulum unblocked? and then i want to observe the situation of autophagy in drosophila cells. I generated homzygous clones for the relevant gene but i have a feeling it will act on all ATPases on the cells and wouldn't be specific to those on the membrane of SR/ER thanks, Kedar From connelly.bill from gmail.com Sun Feb 15 03:48:56 2009 From: connelly.bill from gmail.com (Bill) Date: Sun Feb 15 15:14:02 2009 Subject: [Neuroscience] Re: Op Amps - The Voltage Follower Circuit References: <9d7d358d-02a2-4451-bf33-34a6f85a4114@w1g2000prm.googlegroups.com> Message-ID: <7c526ac8-a3fa-4284-8def-d0eea3efd3ea@u18g2000pro.googlegroups.com> Yes, I see how without the G term in that equation, it breaks down to output = input/2, i.e. halfway between those osscillation i described above. And so this is the importance of the "infinite open-loop gain" that the perfect op amp has. On Feb 14, 4:02?pm, r norman wrote: > On Fri, 13 Feb 2009 17:16:27 -0800 (PST), Bill > > > > wrote: > >I'm having a hard time understanding the classical Voltage Follower > >Circuit made by a single op amp. I wont bother trying to draw it in > >ASCII, just have a look here if you don't know what I'm talking about: > > >http://hyperphysics.phy-astr.gsu.edu/Hbase/electronic/opampvar2.html > > >This is who I'm thinking about it (which I'm sure is wrong): > >1) Lets imagine you have a 1mV input to the + input. > >2) At the instant this is switched on the - input is 0, so the op amp > >outputs 1mV > >3) Now the + input still gets 1mV and - input gets 1mV, so the amp > >outputs 0mV, sending us back 1) > > >I appriciate that the op amp works 'instantaneously' so you don't get > >oscillations like I described, but I still don't know how one can > >conceptualize op amps without getting into these kind of oscillations. > > >Thanks for anyone who can tell me the correct way to think about this > > You forget that the op amp is really an amplifier with a very high > gain. ?Lets suppose it has a gain of one thousand. ?Actually it is > normally higher than that but this will do for calculation. > > When you put 1 mv on the input, it responds by putting an output not > of 1 mv, but only about 999 microvolts, 1/1000 less than the desired 1 > mv. ?Then there is 1 millivolt on the + input and 0.999 mv on the - > input for a difference of 0.001 mv which, times the 1000 gain, would > produce an output of 1 mv. ?Remember, I said "about" 999 microvolts. > The difference is the approximation error. > > To be precise, if the gain is G, then the output is G times the > difference between the + and - inputs. ?Let the output be y and the > input x. ?Then y = G(x - y) since the output is applied to the - > input. ?Solve that to get y = x * G/(1+G). ?If G is very large, then > G/(1+G) is very close to one. > > Oscillations are an entirely different story. ?For that you have to > describe the output in terms of the LaPlace (or Fourier) transform of > its "transfer function". ?But control theory tells you exactly how to > do it and to build a circuit that does not produce oscillations. From jalegris from sympatico.ca Sun Feb 15 08:51:58 2009 From: jalegris from sympatico.ca (J.A.Legris) Date: Sun Feb 15 15:14:06 2009 Subject: [Neuroscience] Re: Op Amps - The Voltage Follower Circuit References: <9d7d358d-02a2-4451-bf33-34a6f85a4114@w1g2000prm.googlegroups.com> <7c526ac8-a3fa-4284-8def-d0eea3efd3ea@u18g2000pro.googlegroups.com> Message-ID: On Feb 15, 3:48?am, Bill wrote: > On Feb 14, 4:02?pm, r norman wrote: > > > On Fri, 13 Feb 2009 17:16:27 -0800 (PST), Bill > > > wrote: > > >I'm having a hard time understanding the classical Voltage Follower > > >Circuit made by a single op amp. I wont bother trying to draw it in > > >ASCII, just have a look here if you don't know what I'm talking about: > > > >http://hyperphysics.phy-astr.gsu.edu/Hbase/electronic/opampvar2.html > > > >This is who I'm thinking about it (which I'm sure is wrong): > > >1) Lets imagine you have a 1mV input to the + input. > > >2) At the instant this is switched on the - input is 0, so the op amp > > >outputs 1mV > > >3) Now the + input still gets 1mV and - input gets 1mV, so the amp > > >outputs 0mV, sending us back 1) > > > >I appriciate that the op amp works 'instantaneously' so you don't get > > >oscillations like I described, but I still don't know how one can > > >conceptualize op amps without getting into these kind of oscillations. > > > >Thanks for anyone who can tell me the correct way to think about this > > > You forget that the op amp is really an amplifier with a very high > > gain. ?Lets suppose it has a gain of one thousand. ?Actually it is > > normally higher than that but this will do for calculation. > > > When you put 1 mv on the input, it responds by putting an output not > > of 1 mv, but only about 999 microvolts, 1/1000 less than the desired 1 > > mv. ?Then there is 1 millivolt on the + input and 0.999 mv on the - > > input for a difference of 0.001 mv which, times the 1000 gain, would > > produce an output of 1 mv. ?Remember, I said "about" 999 microvolts. > > The difference is the approximation error. > > > To be precise, if the gain is G, then the output is G times the > > difference between the + and - inputs. ?Let the output be y and the > > input x. ?Then y = G(x - y) since the output is applied to the - > > input. ?Solve that to get y = x * G/(1+G). ?If G is very large, then > > G/(1+G) is very close to one. > > > Oscillations are an entirely different story. ?For that you have to > > describe the output in terms of the LaPlace (or Fourier) transform of > > its "transfer function". ?But control theory tells you exactly how to > > do it and to build a circuit that does not produce oscillations. > Yes, I see how without the G term in that equation, it breaks down to > output = input/2, i.e. halfway between those osscillation i described > above. > And so this is the importance of the "infinite open-loop gain" that > the perfect op amp has. > The oscillations you described are a byproduct of your discrete, step- by-step characterization of the op-amp. Real op-amps do not make instantaneous changes. Rather, the voltage on the output rises or falls until equilibrium is established through the feedback to the (-) input. This all happens very quickly of course, but it is still a continuous process. Oscillations occur when the delay and overall gain of the feedback loop "reinforce" particular frequencies. It is possible to get an op-amp to oscillate between discrete states, but this requires special techniques, such as non-linear circuit elements or topologies. -- Joe From r_s_norman from _comcast.net Sun Feb 15 10:32:31 2009 From: r_s_norman from _comcast.net (r norman) Date: Sun Feb 15 15:14:11 2009 Subject: [Neuroscience] Re: Op Amps - The Voltage Follower Circuit References: <9d7d358d-02a2-4451-bf33-34a6f85a4114@w1g2000prm.googlegroups.com> <7c526ac8-a3fa-4284-8def-d0eea3efd3ea@u18g2000pro.googlegroups.com> Message-ID: On Sun, 15 Feb 2009 00:48:56 -0800 (PST), Bill wrote: >Yes, I see how without the G term in that equation, it breaks down to >output = input/2, i.e. halfway between those osscillation i described >above. >And so this is the importance of the "infinite open-loop gain" that >the perfect op amp has. You got it! >On Feb 14, 4:02?pm, r norman wrote: >> On Fri, 13 Feb 2009 17:16:27 -0800 (PST), Bill >> >> >> >> wrote: >> >I'm having a hard time understanding the classical Voltage Follower >> >Circuit made by a single op amp. I wont bother trying to draw it in >> >ASCII, just have a look here if you don't know what I'm talking about: >> >> >http://hyperphysics.phy-astr.gsu.edu/Hbase/electronic/opampvar2.html >> >> >This is who I'm thinking about it (which I'm sure is wrong): >> >1) Lets imagine you have a 1mV input to the + input. >> >2) At the instant this is switched on the - input is 0, so the op amp >> >outputs 1mV >> >3) Now the + input still gets 1mV and - input gets 1mV, so the amp >> >outputs 0mV, sending us back 1) >> >> >I appriciate that the op amp works 'instantaneously' so you don't get >> >oscillations like I described, but I still don't know how one can >> >conceptualize op amps without getting into these kind of oscillations. >> >> >Thanks for anyone who can tell me the correct way to think about this >> >> You forget that the op amp is really an amplifier with a very high >> gain. ?Lets suppose it has a gain of one thousand. ?Actually it is >> normally higher than that but this will do for calculation. >> >> When you put 1 mv on the input, it responds by putting an output not >> of 1 mv, but only about 999 microvolts, 1/1000 less than the desired 1 >> mv. ?Then there is 1 millivolt on the + input and 0.999 mv on the - >> input for a difference of 0.001 mv which, times the 1000 gain, would >> produce an output of 1 mv. ?Remember, I said "about" 999 microvolts. >> The difference is the approximation error. >> >> To be precise, if the gain is G, then the output is G times the >> difference between the + and - inputs. ?Let the output be y and the >> input x. ?Then y = G(x - y) since the output is applied to the - >> input. ?Solve that to get y = x * G/(1+G). ?If G is very large, then >> G/(1+G) is very close to one. >> >> Oscillations are an entirely different story. ?For that you have to >> describe the output in terms of the LaPlace (or Fourier) transform of >> its "transfer function". ?But control theory tells you exactly how to >> do it and to build a circuit that does not produce oscillations. From letizia.polito from gmail.com Sun Feb 15 18:29:48 2009 From: letizia.polito from gmail.com (letizia polito) Date: Sun Feb 15 23:56:46 2009 Subject: [Neuroscience] paper Message-ID: Hi everybody. Could anybody access to J Neuropathol Exp Neurol and send me a pdf copy of 'Sirtuin 1 reduction parallels the accumulation of tau in Alzheimer disease' vol 68 n?1, january 2009 pp48-58. Thank a lot From hind2007 from gmail.com Mon Feb 16 05:15:39 2009 From: hind2007 from gmail.com (hind2007@gmail.com) Date: Mon Feb 16 13:07:17 2009 Subject: [Neuroscience] Analytical and numerical solutions Message-ID: <39598eda-58c9-45ac-9a6a-95469411574d@v38g2000yqb.googlegroups.com> I need to understand what's the difference between analytical solution via Laplace transform for example, and numerical solution? Thank you From h.w.tse from live.co.uk Wed Feb 18 18:01:55 2009 From: h.w.tse from live.co.uk (HW) Date: Wed Feb 18 19:01:13 2009 Subject: [Neuroscience] compound solubility Message-ID: <41d880a2-10c0-4b32-8390-66a7b9af4410@b16g2000yqb.googlegroups.com> Does anyone work in the glutamate area and find compounds like kynurenic acid, DL-AP5, RS-MCPG, CHPG etc. hard to dissolve in just water, and basically go through the hassle of working out how much NaOH is needed to dissolve it, well life is easier as you can get these compounds as the sodium salt...check it out http://www.ascentscientific.com/searchLatestJAW.php?searchterm=glutamate From brendonfish from gmail.com Thu Feb 19 02:56:26 2009 From: brendonfish from gmail.com (brendonfish@gmail.com) Date: Thu Feb 19 12:36:09 2009 Subject: [Neuroscience] PhD in Brain Science, Institute of Statistical Science, Academia Sinica (Taipei) --Extensive experience with Flex 3 needed Message-ID: <61c3107d-873a-466f-85dd-9fdbe7cf3363@b8g2000pre.googlegroups.com> Research team at the Institute of Statistical Science, Academia Sinica seeks applicants for graduate research assistantship. Research opportunities are in several different areas of brain science. Research will involve EEG/MEG data processing and source localization, structure images, functional MRI and 4D PET image analyses. Ideal candidates will need a strong background in computer science and be really interested in working with and studying in brain science. Applicants must have a MS degree in computer sciences, applied mathematics or related areas. As far as programming skills are concerned, both of the followings are needed: -Extensive experience with Flex 3 and ActionScript 3 -Experience designing modular, object-oriented Flex 3 applications -Familiar with Flex component life cycle (extending and creating custom components), styling and skinning -Please provide past flex works and source code for review Research assistantships include a monthly stipend, health benefits, scientific supervisor and tuition remission. Please contact Dr. Arthur Tsai at arthur@stat.sinica.edu.tw From connelly.bill from gmail.com Fri Feb 20 01:24:34 2009 From: connelly.bill from gmail.com (Bill.Connelly) Date: Fri Feb 20 11:58:50 2009 Subject: [Neuroscience] Re: Analytical and numerical solutions References: <39598eda-58c9-45ac-9a6a-95469411574d@v38g2000yqb.googlegroups.com> Message-ID: Numerical solutions are essential simulations, analytical methods involve an equation. In neuroscience, classical examples are calculating the membrane potential of a cell the NEURON modelling package. Here you do not calculation the membrane potential for any given point of time, you calculate it over time, using the last known value. This is a numerical solution. Figuring out the reversal potential of an ion channel using the Nernst equation, this is an analytical equation. On Feb 16, 11:15?pm, hind2...@gmail.com wrote: > I need to understand ?what's the difference between analytical > solution via Laplace transform for example, and numerical ?solution? > > Thank you From lookforheadstage from gmail.com Tue Feb 24 17:53:20 2009 From: lookforheadstage from gmail.com (J Yu) Date: Tue Feb 24 18:51:00 2009 Subject: [Neuroscience] used Axoclamp2A headstage Message-ID: <372bb850902241453y4f9c96e9p4ff306c999f78f21@mail.gmail.com> Dear all, I would like to buy a secondhand patch-clamp headstage to go with our Axoclamp2A amplifier. The one I am looking for is HS-2 or HS-2A and the current-passing gain is 0.1. If you happen to have a spare one, please write me an email (lookforheadstage@gmail.com). It would be really helpful to my project as my current one deforms a little. Thanks you! John