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Everything posted by SMF

  1. Sidd. Because religious answers are much more circular than scientific explanations, I presume you have some alternative that you didn't mention. SM
  2. Apricimo: I am a retired scientist and I have both written and reviewed a fair number of successful research articles and NIH grants. The Ph.D. program in question had a Biomedical Sciences degree. This was a bit more general in an attempt to give graduating students a chance of ultimately (after a postdoc in their specialty) being more attractive as a job candidate to different departments on the basis of being able to teach in more than one specialty. This was accomplished by requiring students to take some coursework outside of their department and to take my scientific teaching skills course. The student in question was in the Microbiology Department but had taken my Microscopic Anatomy course, the Cell and Molecular Biology course, in which I was a lecturer, and had participated in some journal clubs in which I also participated, so he chose me as the required outside (of his) department general science member of his committee. The student got his degree and a good postdoc, and I assume that he is doing well somewhere as an independent researcher and teacher. Asking science question is what this forum is about, and I often answer questions here in my area of knowledge because I don’t have to do a lot of research. I am quite able to do my own research when I have a question that is of great interest to me but otherwise, like everyone else, just ask when there might be expertise here for a quick answer. In this case there was someone. Now aren’t you embarrassed for your long and inappropriate rant when you could have just asked me about what a general science Ph.D. committee member might be? SM
  3. Pretty nifty and I am also not an engineer. SM
  4. Here is one paper- http://www.jabs.org.uk/pages/hepb6.pdf Here is the Google Scholar search where I found the above- http://scholar.google.com/scholar?q=Hepatitis+B+vaccine+polyneuropathy&hl=en&btnG=Search&as_sdt=1%2C5&as_sdtp=on
  5. A not so fun addition to the dynamite comments. I believe that there have been several instances of individuals that thought they were playing a joke on friends that enacted a suicide by putting a pistol against their head and firing a blank and killed themselves from the concussion.
  6. Re the topographic map on the cortex: If you were to electrically stimulate a small region anywhere on the body surface, there would be a corresponding set of cortical neurons within the map (homunculus) of the somatosensory cortex. You could record this activity in just the right spot. It is not a one to one connection, but it is pretty close. If you stimulated this cortical spot in a person, they would report touch sensation in the corresponding spot on the body. Note that the sensory pathways pass through the thalamus for processing prior to reaching the sensory cortex. If you were to electrically stimulate just a few cortical neurons in the primary motor cortex, mapped for a finger, there would be a corresponding twitch in a few motor units within one of the muscles in the forearm that is involved in controlling the specific finger, and there would be a corresponding very small movement of the finger. Location in the brain corresponds to location on the body. Is this what you wanted to know? Re the spinal cord constituents: The cord carries a variety of long (and some shorter) nerve tracts consisting of bundles of axons, but at each segment that is associated with a specific dermatome there will be neuron cell bodies. Sensory neuron cells are in or near the dorsal horn, and motor neurons are in the ventral horn. These neurons project axons out to the periphery in the peripheral nerves, while others send (sensory) or receive (motor) activity to/from the brain via long tracts of axons in the cord. The spinal cord actually does some neural processing, so there are quite a few interneuron circuits in the dorsal and ventral horns. Re current noninvasive microstimulation and recording technology: I haven't really kept up with this. So, if you find my information useful I would, in exchange, appreciate a short piece in this thread regarding what you find out about this. Once you get your search terms down, be sure to use Google Scholar to find the real science (e.g. primary literature and scientific reviews). Re spinal nerves: First, be careful with terminology. A "nerve" is a component of the peripheral nervous system that consists of a bundle of individual "axons" contained in a connective tissue sheath. There is a tendency to use nerve and axon interchangeably, but this can cause confusion. A bundle of axons in the central nervous system (CNS= brain and spinal cord) is a "tract," or "commissure" when it crosses the midline (there are other descriptions, but this is safe). Axons projecting to the periphery from the dorsal and ventral horns collect together outside of the cord into a single nerve. Sensory and motor axons branch into smaller and smaller nerves that are all named and their terminal fields are pretty well known, although there is quite a surprising amount of variability. I am pretty sure that axons that are going to branch together stay together. Isn't that nice? However, the path that axons take within a peripheral nerve tends to weave about, so that any topography that might exist would be hard to reliably demonstrate. I hope this helps. SM
  7. There are topographic maps in the cortex that correspond to touch in somatosensory cortex, and motor units (a specific group of muscle cells) within various muscles in motor cortex (look up motor and somatosensory homunculus). The position within these maps is a primary part of the code that distinguishes different body regions. For somatosensory cortex, the highest resolution for discrimination between two points is called the two point threshold which can be pretty fine in areas like the tips of the fingers, lips, and tongue. The spinal cord carries information for the body, but not the head, and because motor axons from motor cortex peel off at their approximate appropriate level and sensory information enter the cord at approximately adjacent levels (look up dermatome map), your supposition regarding what is above and below any cord level is correct and this is why serious spinal cord damage causes loss of sensation and motor control below the damage. The motor and sensory pathways in the spinal cord are separate and take very different routes and, except for spinal reflexes, interact only very indirectly. Also, ascending and descending axons in the spinal cord are laid down in an orderly topographical manner. For example, a small cut on the surface of the somatic touch pathway at a specific level will predict a specific region of sensory loss, while small penetrating wound at the same level will result in a different region of loss. It is possible to put long term microelectrodes in nervous tissue (e.g. look up cochlear implants) that can record electrical activity from, or stimulate, small regions. I know that there are problems of formation of scar-like tissue that can cause problems, but scientists are working on it. There has been quite a bit of experimentation with a brain interface via macro electrodes that can just be fastened to the scalp, but this reduces the number of electrodes because the areas of brain they can record from are so large. SM
  8. I think we need James Randi to explain this.
  9. I knew a Ph.D. student whose thesis was on the function of one HIV protein. He had manipulated and combined genes from three inactivated strains available from the NIH to get the model he needed to do his research. I was the general science advisor on his committee and during his thesis defense I asked him if the virus could be manipulated to be more infectious or less detectible for the purpose of bioterrorism. He said that this was possible. I would like some confirmation of this anecdotal evidence from an expert. SM
  10. Bottoming out is a clear concept. What of the obvious hole in the bottom piece, could this have been drilled for an (not so) Easy Out extraction? If broken on tightening it would require a non-threaded portion as Xitten says. It could be broken on extraction with a completely threaded hole, but I have never had this happen with a solid Allan head bolt. Usually the Allan wrench twists off and there is no sign of a Vise Grip (or other) assist to the Allan wrench. If the hole through the bottom piece is preexisting then this could explain the breakage because the screw would be weak at the top of this section. I am stumped. SM
  11. Hal_2011, you say: I say that your posts are not clear to me. SM
  12. Hal_2011 I am having a problem with what you are saying because I don't think anyone is saying that a theory can be true like a mathematical proof. In fact, I don't believe science asserts any proofs. Who or what are you objecting to? SM
  13. Much of what is said in the popular media regarding right brain versus left brain function, in a normal brain, is not supported by neuroscience research. SM
  14. Sonnysingh, quick answers: 1. Why is not a good question for biological devices. An intelligent engineer could design a heart with a single chamber that would be more efficient. It is just the result of the way this mechanism was developed naturally by the evolutionary process. 2. The right atrium contracts first and the activity spreads to the left. 3. Valves are passive and thus open and close from pressure and flow. 4. Action potentials do not dissipate; they are an all or none phenomenon. In the heart, action potentials spread in the muscle from cell to cell and where there are no further cells to spread to the activity stops. However, The spread of activity from the S-A node, across the right ventricle, eventually triggers cells in the A-V node by the spread of action potentials. 5. Same answer as number 3. 6. This is a fluid dynamics question that some physicist should answer. From a simpler perspective, consider that when you blow air through a single small straw it takes a lot of pressure to get a good volume of flow, but if you could get 20 straws in your mouth there would be hardly any resistance at all and the pressure for good air flow would be low. The capillary bed that makes up the inter-alveolar septa is very, very large and is also very delicate. See this other post for a description and simple illustration of heart electrophysiology- http://www.scienceforums.net/topic/56489-overview-of-the-heart/page__view__findpost__p__601257 SM
  15. SMF

    E.coli or e.Coli?

    CharonY, I started out my career in science with a mechanical typewriter (old habits). SM
  16. DrmDoc. Except for apologies for my typo on Hobson's name I think I will let my statements stand for reasons I have already mentioned. For others, I recommend, again, that those interested in the basic science of sleep and the theories that have been looked at in the past regarding the functions of dreams, REM and nonREM (NREM), sleep read the recent Nature review by Hobson- http://www.culturacientifica.org/textosudc/sueno_01.pdf This review is clearly and extensively referenced with citations to previous research to help a reader pursue the science and it clears up many of the problems with this thread, and makes it clear that this general area of research is in a state of flux, but also proposes a hypothesis for future research. I love a good scientific review article. SM
  17. If debating these options in any way suggests that it has to be an either/or choice, I would debate this notion. Also, I think that conservation should be included as the low hanging fruit for solving future energy problems. SM
  18. With apologies, I pasted one incorrect link above. The first is actually the website for the expectation fulfillment theory that hasn't really received much attention. The link to the Solms research that provides evidence that Hobson's activation synthesis theory won't work is- http://www.ncbi.nlm....pubmed/11515144 I couldn't find this as a free full text article but I did find a book of collected articles that has it. For the book advertisement, access is provided with only a couple of pages from the Solms article missing- http://books.google....O00AIclGlxByTv4 - v=onepage&q&f=false Finally, in looking around I found a recent review of dream science by Hobson's as a free PDF. This is well done and I think it would be a good start for anyone coming to this thread to learn what the science is about. In addition to the review he is presenting his new REM sleep-dream protoconsciousness hypothesis- http://www.culturaci...dc/sueno_01.pdf SM
  19. SMF

    E.coli or e.Coli?

    The genus name is capitalized and the species name is not. Further they both should be italicized or underlined. SM
  20. DrmDoc, this is a response to your post #19 and it may also apply to what ThinkerJeff has been talking with you about. Your answers to my first two questions were that I didn't understand what you were saying. I will accept this, but with the addition that if you wish responsive comments perhaps you need to work on making your assertions more understandable and provide citations on the spot. Your answer to my question about rigorous support for statement that "Dreaming is an interpretive brain process" was initially a series of studies on REM sleep and PGO waves. I know what PGO waves are, I have recorded them with microelectrodes as mass action potentials and as single cell recordings in the Lateral Geniculate nucleus of experimental animals, and they have no relationship to any theory of dreams or any interpretive brain process. This was disappointing and a big waste of time for anybody here who wishes to gain some understanding. I was very happy to see the reference to the 1981 Hoffman research paper that did a test of his activation-synthesis hypothesis. Some real relevant science! So I did a search for information on this. What I found is that Hoffman's theory, originally published in 1977, has been pretty much disassembled by subsequent research. See for example this study by Solms (2000) that separates REM sleep from Dreaming mechanisms- http://www.why-we-dr...hertheories.htm . To his credit, Hoffman has adapted to the research disproving his theory by adapting. His current version is referred to as input-output gating, modulation (AIM) theory. I also found that there have been several other theories that have been tested and found wanting including Freud's wish fulfillment theory, the we dream to forget theory by, of all people, Francis Crick, the we dream to remember (memory consolidation) theory, and the expectation fulfillment theory (no real subsequent support). In addition to all the speculations by psychologists and psychiatrists, what this all suggests to me is that nobody really knows what dreams are about and nobody has a coherent theory that has, or is, surviving post publication peer review. That is, there is no construct by which the science is progressing at this time. I was hoping for something new regarding the "thalamic stage of evolution" comment. In fact the triune brain idea put forward by MacLean in the 1960's has nothing to do with any thalamic stage. Further, research left this idea behind a long time ago. See this paper for example- http://rstb.royalsoc.../1485/1585.full . Here is a quote (my bolding)- This is now just pop culture. I, and I don't think anybody here, is going to try to follow up on your giant copy paste of your book research bibliography. For me, it is just too information poor relative to trying to understand what you are trying to relate. I suggest, at least for me, that for a good scientific discussion, especially when it involves such a diffuse topic, that it is best to make a coherent statement and then provide a citation or two that are specifically relevant, not a whole bunch that includes a lot of irrelevant information. In this way readers can look at the science and then discuss specific points. SM
  21. With a little web research I have gleaned a little additional information regarding what CaptainPanic and I have been talking about that I feel I should add for accuracy, and that might be interesting to you all. The ISS actually has a pretty big PV solar power array. The station has eight 23KW arrays, so the power input is much bigger than a large system for an expensive California home that I mentioned previously for comparison. This much energy is more in the range of PV systems in my area that have been erected on a brewery, a winery, and a local community college to save money on electricity. This is still miniscule relative to the heat generated by a commercial gigawatt nuclear plant that would require a large and prohibitively expensive radiative cooling system that would have to be lifted to and assembled in orbit. SM
  22. CaptainPanic, I strongly agree with your attitude regarding nuclear power generation in space, but my interest in the heat radiation problem is still not satisfied. This is because it seems to me that the International Space Station only has to deal with waste heat from electrical devices that are powered by a solar panel array that one could find on a very opulent solar home in California. The amount of heat from a sizable commercial reactor/generator would be, I think, somewhere around three orders of magnitude of what is generated on the ISS. This would probably require piping and radiators that would be too massive to even think about putting into orbit. I think the problem is practical, not theoretical, but there may be something I don't understand. SM
  23. Here are a few things I would like citations for. You say- Just because the brain is as active during dreaming sleep as it is in a waking brain does not, by itself, indicate that dreams are not an integral component of sleep. Please justify your assertion with citations. I am not asking for research on brain activity, but for a scientific paper where these data are analyzed and the dreaming activity was declared not a component of sleep. This statement is very unclear, but it seems to say that dream images are memories. I would be very interested in seeing some published data. By what method was this established what is being interpreted, and who did the work? What is the proper mental context, what was the clear meaning and relevance that was discovered, and where is it published? Also please elaborate on the "thalamic stage of evolution." Who coined this term? SM
  24. IRzilla. Here is a short bit on how the muscle contractions of the heart are organized to make it an effective pump. I presume you already know about how the heart is actually two separate pumps, but both pumps (left and right sides) are controlled together. There are no neurons in the heart for initiating and controlling muscle contraction. The components that act like neurons, the sino-atrial (S-A) node, the atrio-ventricular (A-V) node, and the atrio-ventricular bundle are made of modified muscle cells that can conduct electrical activity (action potentials) between them by electrical synapses in a manner similar to some neural circuits. These control mechanisms and all of the heart muscle cells have a natural repetitive rhythm of action potentials that will occur without any neural input, and how they all are connected together results in well-organized heart contractions. The S-A node rate of action potentials is the fastest, so it is the initiator of contraction and its activity can be regulated by the nervous system. A in the illustration- A contraction cycle starts when the S-A node cells produce a coordinated action potential (the little spark in the drawing). The stippling indicates that this electrical activity is spreading from the node into the muscle of the Right Atrium and progressing across it. B-The contraction spreads onto the Left Atrium as well C- When the contraction reaches the A-V node there is a slight pause while all the cells become active, then its activity spreads to down the A-V bundle. D- When the activity reaches the ends of the bundle at the bottom of the heart it starts contraction in both ventricles. E- The contraction spreads up both ventricles. F- Contraction has been completed and the S-A node begins another cycle. Note that the way that the contraction spreads from cell to cell in the atria and ventricles makes for the unique wringing action of the muscle of the pumps that, in turn, make for an efficient pump. Also note that this well organized and complicated behavior is simply due to how all the muscle cells of the heart are connected together. Many heart contraction problems involve disruptions of this organization. SM
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