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Notizen: Abstract: Northern blot analysis determined whether multiple α4 transcripts for neuronal nicotinic receptors in rat brain could be detected as distinct bands. When poly(A)+ RNA was isolated from brain regions and hybridized with a Hinfl fragment of α4-1 cDNA containing a sequence shared by both α4-1 and α4-2, but little homology with other α or β subunits, bands at 6.0, 4.6, and 2.6 kb were obtained. When a Taql fragment with selectivity for α4-1 was used, a single band was present at 6.0 kb. The 6.0-kb band was least abundant in all brain regions; the 2.6-kb band was most abundant in frontal cortex, hippocampus, striatum, basal forebrain, and thalamus, whereas the 4.6-kb band was most abundant in midbrain and cerebellum. Nicotine (3.6 µmol/kg, s.c., twice daily) increased the abundance of the 4.6-kb transcript in frontal cortex significantly by 28% following 2.5 days of injections; the 6.0- and 2.6-kb transcripts were unchanged. Nicotine did not affect α4 transcripts in other brain regions. Results suggest that increased mRNA levels may mediate the nicotine-induced up-regulation of receptors in cerebral cortex.

Notizen: Abstract: The objective of these experiments was to determine whether the chronic administration of nicotine, at a dose regimen that increases the density of nicotine binding sites, alters the nicotine-induced release of [3H]dopamine ([3H]DA), [3H]norepinephrine ([3H]NE), [3H]serotonin ([3H]5-HT), or [3H]acetylcholine ([3H]ACh) from rat striatal slices. For these experiments, rats received subcutaneous injections of either saline or nicotine bitartrate [1.76 mg (3.6 µmol)/kg, dissolved in saline] twice daily for 10 days, and neurotransmitter release was measured following preloading of the tissues with [3H]DA, [3H]NE, [3H]5-HT, or [3H]choline. Chronic nicotine administration did not affect the accumulation of tritium by striatal slices, the basal release of radioactivity, or the 25 mM KCl-evoked release of neurotransmitter. Superfusion of striatal slices with 1, 10, and 100 µM nicotine increased [3H]DA release in a concentration-dependent manner, and release from slices from nicotine-injected animals was significantly (p 〈 0.05) greater than release from saline-injected controls; release from the former increased to 132, 191, and 172% of release from the controls following superfusion with 1, 10, and 100 µM nicotine, respectively. Similarly, [3H]5-HT release increased in a concentration-related manner following superfusion with nicotine, and release from slices from nicotine-injected rats was significantly (p 〈 0.05) greater than that from controls. [3H]5-HT release from slices from nicotine-injected rats evoked by superfusion with 1 and 10 µM nicotine increased to 453 and 217%, respectively, of release from slices from saline-injected animals. The nicotine-induced release of [3H]NE from striatal slices was also concentration dependent but was unaffected by chronic nicotine administration. [3H]ACh release from striatal slices could not be detected when samples were superfused with nicotine but was measurable when tissues were incubated with nicotine. The release of [3H]ACh from slices from nicotine-injected rats was significantly (p 〈 0.05) less than release from controls and decreased to 36, 83, and 77% of control values following incubation with 1, 10, or 100 µM nicotine, respectively. This decreased [3H]ACh release could not be attributed to methodological differences because slices from nicotine-injected rats incubated with nicotine exhibited an increased [3H]DA release, similar to results from superfusion studies. In addition, it is unlikely that the decreased release of [3H]ACh from striatal slices from nicotine-injected rats was secondary to increased DA release because [3H]ACh release from slices from hippocampus, which is not tonically inhibited by DA, also decreased significantly (p 〈 0.05) in response to nicotine; hippocampal slices from nicotine-injected rats incubated with 1 and 10 µM nicotine decreased to 42 and 70%, respectively, of release from slices from saline-injected animals. Results indicate that the chronic administration of nicotine increases the ability of nicotine to induce the release of [3H]DA and [3H]5-HT and decreases the ability of nicotine to evoke the release of [3H]ACh but does not alter the nicotine-induced release of [3H]NE from brain slices.

Notizen: By using a microwave cavity tuned oscillator (MCTO), the relative dielectric constant ε of nonpolar dielectric fluid was measured with high accuracy. The theory of this technique was studied in detail. A new formula for evaluating the uncertainty of the measured ε was derived. From the formula, we have found that MCTO has a locking characteristic and therefore only operates in certain discrete regions. We have also found that a higher resonant frequency f of the MCTO, a longer delay time of the delay line, and a higher quality factor of the cavity Q lead to a higher accuracy of the measurement. When the values of the above parameters are taken properly, the uncertainty measured ε by the MCTO may become as small as an order of 10−5. The ε of saturated liquid nitrogen was measured by this approach and the experimental results agree very well with the values calculated by our formula. © 1996 American Institute of Physics.

Notizen: Rapid removal of photoresist assisted by a large-area electron beam in oxygen atmosphere has been performed. The removal rate depended upon the pressure, flow rate of oxygen, and the power density of the electron beam. The maximum removal rate of 2500 nm/min for photoresist was one order of magnitude higher than that of conventional plasma processes.

Notizen: Diamond films were grown on turbostratic carbon (TC) pregrown on Cu substrates by hot filament chemical vapor deposition. Auger electron spectroscopy, Raman spectroscopy, x-ray diffraction, infrared absorption spectroscopy, and scanning electron microscopy were used to characterize both the TC and the diamond films. It was shown that the TC films could form on Cu at low temperatures (≈650 °C) with the catalysis of Mo and that diamond crystallites rapidly formed on TC in less than 10 min at higher temperature (≈1000 °C). The sp3 bonds were found to coexist with sp2 bonds in TC. The sp3 bonds in TC provide nucleation sites for diamond crystals and improve the nucleation rate at the early stage of deposition of diamond on TC.

Notizen: The downstream near afterglow region of a hydrogen plasma is used to decompose and convert trimethylarsine (TMAs) into methylarsine homologs [(CH3)3−xAsHx, where x=1,2,3] including that of arsine (x=3). Approximately 30%, 17%, and 10% of the TMAs is converted into dimethylarsine (DMAs), monomethylarsine (MMAs), and arsine, respectively, while 28% remains undecomposed. Hydrogen is replaced by deuterium to isotopically verify that the origin of the arsenic hydrogenation occurring during gas conversion arises from both the plasma gas and fragmented hydrogen from the TMAs. Deuterium tagging of the MMAs, DMAs, and hydrocarbon byproducts is consistent with TMAs decomposition via plasma initiated CH3 radical removal and explains why the predominant light stable hydrocarbon produced is methane while ethane and acetylene account for the main higher hydrocarbons.

Notizen: An analysis is carried out of the physical origin of thermal instability that can trigger a catastrophic vacuum breakdown event in vacuum microelectronic devices based on flat diamond emitters. The temperature rise in a diamond film will enhance internal field emission across metal–diamond interface. This effect can lead to a regenerative process that can initiate a breakdown event at temperature lower than the melting point of an emitter. A set of equations has been developed. These theoretical findings are successfully applied to explain the instability of field emission from the nondoped diamond films. © 1999 American Institute of Physics.

Notizen: The magnetocaloric effect in La1.6Ca1.4Mn2O7 polycrystal with the layered Sr3Ti2O7-type perovskite structure has been studied. It is found that the magnetic entropy change of La1.6Ca1.4Mn2O7 is comparable to that of Gd, but smaller and more broadened than that of La0.8Ca0.2MnO3. © 1999 American Institute of Physics.