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Notes: Abstract: Evidence that neurosteroids are potent modulators of the action of GABA at GABAA receptors has prompted the investigation of the mechanism that controls brain neurosteroid synthesis by glial cell mitochondria in vivo. In vitro studies suggest that the interaction of the diazepam binding inhibitor (DBI)—a polypeptide that is abundant in steroidogenic cells—with glial mitochondrial DBI receptors (MDRs) is a crucial step in the physiological regulation of neurosteroid biosynthesis. MDRs bind 4-chlorodiazepam (4′-CD), N,N-di-n-hexyl-2-(4-fluorophenyl)-indol-3-acetamide (FGIN-1–27), and the isoquinoline carboxamide PK 11195 with high affinity, and these ligands have been used to investigate whether the stimulation of glial MDRs increases brain pregnenolone production in vivo. Adrenalectomized and castrated (A-C) male rats (to eliminate peripheral sources of pregnenolone) were pretreated with trilostane (to prevent pregnenolone metabolism to progesterone), and the pregnenolone content in brain regions dissected after fixation with a 0.8-s exposure to microwave irradiation focused to the head was determined by HPLC followed by specific radioimmunoassay. The forebrain and cerebellum of A-C rats contained 4–7 ng of pregnenolone/g of tissue, and the olfactory bulb contained 10–14 ng/g. These concentrations of brain pregnenolone are only 30–40% lower than those of shamoperated rats. In contrast, the plasma pregnenolone content of sham-operated rats was 2–3 ng/ml, but it was only 0.15–0.20 ng/ml in the plasma of A-C rats. In A-C rats, treatment with the MDR ligands 4-CD and FGIN-1–27 increased the pregnenolone content in the brain but failed to change the plasma or peripheral tissue content of this steroid. The effect of 4′-CD on brain pregnenolone content was maximal (70–100% increase) at the dose of 18 μmol/kg, 5–10 min after intravenous injection. The effect of oral administration of FGIN-1–27 on brain pregnenolone content was maximal (80–150% increase) at doses of 400–800 μmollkg and peaked at ∼ 1 h. That this effect of FGIN-1–27 was mediated by the MDR was documented by pre-treatment with the MDR partial agonist PK 11195 (100 μmol/kg, i.p.). PK 11195 did not affect basal brain pregnenolone content but prevented the accumulation of brain pregnenolone induced by FGIN-1–27. FGIN-1–27 and 4-CD failed to increase the brain concentration of dehydre epiandrosterone in A-C rats. These data suggest that glial cell MDRs play a role in neurosteroid biosynthesis in vivo.

Notes: Tight-binding molecular dynamics has been used to simulate vibrationally excited Si–H and Si–D modes. Simulations find that vibrationally excited Si–D bending modes decay much more rapidly than Si–H bending modes, resulting in SiD bonds having much higher stability than SiH bonds. This provides a viable mechanism for reduced degradation in deuterated metal–oxide–semiconductor transistors and deuterated amorphous silicon devices. © 1998 American Institute of Physics.

Notes: Light-induced metastable defects in a-Si:H are proposed to be silicon dangling bonds accompanied by pairs of hydrogen atoms breaking a silicon bond, forming a complex with two Si-H bonds. This supports the model of Branz. These defects are the analog of the H2* defect in c-Si and their energy correlates with the bond-angle strain. Several features of the annealing are well described by this defect complex. © 1998 American Institute of Physics.

Notes: Textural changes of canned biscuit wheat dough during microwave and conventional baking were described and contrasted using empirical methods. Drastic increases of specific volume and modulus of elasticity were observed in the beginning and the ending periods of both baking processes. Weight loss showed a significantly (p 〈 0.001) linear relationship with baking time for both baking methods, but the weight loss rate constant for microwave baking was 0.36%/s significantly (p〈0.01) higher than conventional baking. Multi-dimensional Scaling showed that microwave baking for 50 s best resembles the textural characteristics of wheat dough under conventional baking for 10 min. Stress relaxation modeling indicated that microwave baking produced higher viscosity and modulus of elasticity values which translates into baked biscuits with undesirable tougher texture.

Notes: Residence time distribution (RTD) of fluid and particles was measured in the holding tube of an aseptic processing system. A unique injector device instantaneously injected a large number of particles at one time without interruption of flow. A fraction collector device sampled exiting fluid at 1-sec intervals. Exiting particles at specific lapsed times from injection, were counted from those collected. RTD of fluid was determined by dye injection. RTD of fluid and particles under turbulent flow fitted a normal distribution function. Mean residence time of fluid was 0.975 times that calculated from volumetric flow rate with standard deviation ± 4.16%. Mean residence time of particles was 1.032 times that of the fluid, standard deviation was ± 4.62%.