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[1] Obeid I, Nicolelis MA, Wolf PD, A low power multichannel analog front end for portable neural signal recordings.J Neurosci Methods 133:1-2, 27-32 (2004 Feb 15)

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ref: -1977 tags: polyethylene surface treatment plasma electron irradiation mechanical testing saline seawater accelerated lifetime date: 04-15-2017 06:06 gmt revision:0 [head]

Enhancement of resistance of polyethylene to seawater-promoted degradation by surface modification

  • Polyethylene, when repeatedly stressed and exposed to seawater (e.g. ships' ropes), undergoes mechanical and chemical degradation.
  • Surface treatments of the polyethlyene can improve resistance to this degradation.
  • The author studied two methods of surface treatment:
    • Plasma (glow discharge, air) followed by diacid (adipic acid) or triisocyanate (DM100, = ?) co-polymerization
    • Electron irradiation with 500 kEV electrons.
  • Also mention CASING (crosslinking by activated species of inert gasses) as a popular method of surface treatment.
    • Diffuse-in crosslinkers is a third, popular these days ...
    • Others diffuse in at temperature e.g. a fatty acid - derived molecule, which is then bonded to e.g. heparin to reduce the thrombogenicity of a plastic.
  • Measured surface modifications via ATR IR (attenuated total reflectance, IR) and ESCA (aka XPS)
    • Expected results, carbonyl following the air glow discharge ...
  • Results:
    • Triisocyanate, ~ 6x improvement
    • diacid, ~ 50 x improvement.
    • electron irradiation, no apparent degradation!
      • Author's opinion that this is due to carbon-carbon crosslink leading to mechanical toughening (hmm, evidence?)
  • Quote: since the PE formulation studied here was low-weight, it was expected to lose crystallinity upon cyclic flexing; high density PE's have in fact been observed to become more crystalline with working.
    • Very interesting, kinda like copper. This could definitely be put to good use.
  • Low density polyethylene has greater chain branching and entanglement than high-density resins; when stressed the crystallites are diminished in total bulk, degrading tensile properties ... for high-density resins, mechanical working loosens up the structure enough to allow new crystallization to exceed stress-induced shrinkage of crystallites; hence, the crystallinity increases.

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ref: -0 tags: serial electron microscopy Lichtman reconstruction nervous tissue date: 01-17-2017 23:32 gmt revision:0 [head]

PMID-26232230 Saturated Reconstruction of a Volume of Neocortex.

  • Data presented at Cell "Big Questions in Neuroscience", perhaps the most impressive of the talks.

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ref: -0 tags: Charles Lieber syringe-injectable electronics SU-8 chronic flexible date: 10-14-2016 23:30 gmt revision:1 [0] [head]

PMID-27571550 Stable long-term chronic brain mapping at the single-neuron level.

  • Fu TM, Hong G1, Zhou T1, Schuhmann TG, Viveros RD2, Lieber CM.
  • 8 months with only 800nm of Su-8 (400nm of insulation!!). This is both surprising and very impressive; we have to step up our game!
  • In a mouse, too - their surgical technique must be very good. Mice only live ~ 2 years anyway.
  • Figure 3 -- stability -- incredible.
  • Recording sites were bare platinum, 20um diameter; stimulation sites were also bare Pt, 150um dia.
    • No plating or mircowire-fets, so far as I can see; electrode impedances were stable at 200 - 600k (supplementary figure 12).

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ref: -0 tags: optical neural recording photon induced electron transfer date: 01-02-2013 04:25 gmt revision:2 [1] [0] [head]

PMID-22308458 Optically monitoring voltage in neurons by photo-induced electron transfer through molecular wires.

  • Photoinduced electron transfer.
    • About what you would think -- a photon bumps an electron into a higher orbital, and this electron can be donated to another group or drop back down & fluoresce a photon.
  • Good sensitivity: ΔF/F of 20-27% per 100mV, fast kinetics.
  • Not presently genetically targetable.
  • Makes sense in terms of energy: "A 100-mV depolarization changes the PeT driving force by 0.05 eV (one electron × half of 100-mV potential, or 0.05 V). Because PeT is a thermally controlled process, the value of 0.05 eV is large relative to the value of kT at 300 K (0.026 eV), yielding a large dynamic range between the rates of PeT at resting and depolarized potentials.
  • Why electrochromic dyes have plateaued:
    • "In contrast, electrochromic dyes have smaller delta G values, 0.003 (46) to 0.02 (47) eV, and larger comparison energies. Because the interaction is a photochemically controlled process, the energy of the exciting photon is the comparison energy, which is 1.5–2 eV for dyes in the blue-to-green region of the spectrum. Therefore, PeT and FRET dyes have large changes in energy versus their comparison energy (0.05 eV vs. 0.026 eV), giving high sensitivities; electrochromic dyes have small changes compared with the excitation photon (0.003–0.02 eV vs. 2 eV), producing low voltage sensitivity."

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ref: Obeid-2004.02 tags: Wolf BMI recording electronics telemetry Obeid date: 12-31-2011 18:27 gmt revision:4 [3] [2] [1] [0] [head]

PMID-14757341[1] A low power multichannel analog front end for portable neural signal recordings.

  • have an interesting section on CMRR, quote: Although we use a precision differential amplifier with a CMRR of 110 dB, we were unable, in practice, to measure CMRRs greater than not, vert, similar42 dB. This can be accounted for by the device tolerances in the preamplifier stage; using ±0.1% resistors and ±5% capacitors in the preamplifier, the expected worst case CMRR at 1 kHz is 39.2 dB


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ref: notes-0 tags: nordic pinout nRF24L01 spark fun electronics date: 10-09-2007 19:59 gmt revision:5 [4] [3] [2] [1] [0] [head]

nordic semi links:

here is the connection list for the nRF24L01 module made by sparkfunelectronics
  1. VCC
  2. CE
  3. CSN
  4. SCK
  5. MOSI
  6. MISO
  7. IRQ
  8. GND
(1 is by the voltage regulator, obviously.) reversed:
  1. GND
  2. IRQ
  3. MISO
  4. MOSI
  5. SCK
  6. CSN
  7. CE
  8. VCC

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ref: bookmark-0 tags: DARPA projects quantum electron spin date: 04-04-2007 20:39 gmt revision:0 [head]


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ref: physics notes-0 tags: plasma mercury vapor lamp electron ozone date: 04-03-2007 15:23 gmt revision:3 [2] [1] [0] [head]

ok, so i just (19 Feb 2007) did some simple experiments with the small (100W) mercury vapor lamp that i have + a hard-drive magnet + a solenoid.

  1. magnet splits the plasma into two paths, depending on the direction of the AC plasma current. The split is strongest when at the transition between north and south poles on the HD rare-earth magnet, as here the field lines are going in short loops with the vertical part approximately intersecting the plasma, and hence exerting the lorentz force towards or away from the magnet.
    1. it is possible to extinguish the bulb by moving the plasma too close! I think that this forces the electrons to collide with the quartz tube, cooling them too much.
  2. I also built a solenoid out of a small spool of 14 gauge magnet wire attached to my buzz box arc welder. The current was set at ~50 amps, (not sure how accurate that setting was) - enough to get the small coil pretty hot rather quickly. When placed inside the AC-energized coil, the plasma arc was forced to spiral around the walls of the quartz tube.
    1. This is most likely because the mean velocity of the electrons is pretty low, hence the lamour radius is high in the relatively-weak magnetic field. I notice that at the beginning of igniting the mercury-vapor lamp, far more ozone is produced (as gauged by smell) than is produced when it is hot and the plasma current is high. This accompanies a shift from a very blue emission spectra to a whiter emission, I think this is because the pressure becomes higher inside the tube, hence the mean free path of the electrons is lower, hence they have less energy to excite the hard-UV bands of mercury ions once the lamp is hot. http://en.wikipedia.org/wiki/Planck's_constant --> E=hv, where v is the frequency --> 250nm approximately equals 5 eV. lamour radius: mv/qB. 5ev ~= 1.33e6 m/s. @ B= 0.1T, lamour radius = 7.5e-5m = 0.07mm (what?) ok, more reasonable: B = 0.005T, r = 1mm - still smaller than observed! Need to check this magnetic field. B=mu n I. I = 50A, n = 3 * 2/0.064) = 93 turns, mu (air) = 4*pi*10^-7 --> B ~= 0.005T. (as a first approximation). If the electron velocity is lower, then the radius will be smaller; it is the opposite for the magnetic field strength.
    2. of course, we are disregarding thermal interactions, as well as drift - will have to look at the textbook for this.
  3. Feb 23 2007 - I made a larger-diameter solenoid out of the 14 gauge copper wire & turned the buzz-box welder current up to 100A (or so it says, don't know how much in practice) - enough to get the coil very hot very quickly. I put this current loop around the broken 400W metal-halide lamp - the one originally from the blacklight cannon. As it is still being driven from the same low-wattage power supply, it remains cool, the bulb voltage is low (21V) and much UV (and ozone) is produced - generally indicating that the pressure in the bulb is low and the electron velocity/mean free path is higher.
    1. well, actually: when the blub pressure is low, much energy below 240nm is produced. Apparently this is what is required for ozone production:
    2. HBO lamps do not generate ozone, because owing to the self-absorption in the cooler outer arc regions, all radiation below 240nm is trapped within the discharge. However during run-up before pressure increases, some ozone is produced.
    3. When I turned the solenoid on around the ignited bulb, the concentration of plasma in the center noticably increased, and the luminous intensity increased also. I'm not sure if this was due to AC pumping of plasma current; I doubt it, as most of the magnetic flux should have went around the plasma.
    4. The bulb voltage went to 23 - 24V; I do not know the current, I will have to measure it (perhaps with an oscilloscope?)
    5. The plasma became less uniform, too, perhaps because the solenoid was not aligned to the E-field with any accuracy.