Formation of Nanocrystalline Transition-Metal Ferrites inside a Silica Matrix

Nanocrystalline transition-metal ferrites were synthesized inside an amorphous silica matrix by the sol–gel method. The formation of spinel ferrites began above 400°C, giving fine particles of about 10 nm at 800°C. This is associated with a specific role of the silica matrix, which facilitates the diffusion of the reacting cations, enhancing the ferrite formation. Above 1000°C the MnFe₂O₄ and CuFe₂O₄ nanoparticles lost their fine nature. The dried gels and crystalline materials were characterized by X-ray diffraction, thermal, FTIR, and BET analyses as well as by high-resolution scanning transmission electron microscopy.     

Pattern of [–1–4C]2-deoxyglucose concentration associated with potentiation of reproductive behavior by prostaglandin E?.

One indication of receptive behavior of the female leopard frog, Rana pipiens, is absence of a release call during tactile stimulation of the trunk. Prostaglandin E? (PGE?) inhibits this call. This experiment demonstrates a different pattern of [–1–4C]2-deoxyglucose concentration in brains of 5 receptive females silenced by 1 μg/g PGE? compared with that in 3 unreceptive, vocalizing controls injected with deionized water. –1–4C concentrations were measured in areas important for vocalization in frogs, in limbic system structures and in parts of the brain that receive somatosensory input. There was high activity relative to the rest of the brain in the receptive, silent PGE?-treated females in the caudal part of the anterior preoptic nucleus, in the dorsal habenula, and in the dorsal tegmental area of the medulla lateral to the pretrigeminal nucleus. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prevalence and determinants of Helicobacter pylori infection in preschool children: a population-based study from Germany

Branching enzyme (BE) belongs to the amylolytic family which contains four highly conserved regions. These regions are proposed to play an important role in catalysis as they are thought to be necessary for catalysis and/or binding the substrate. Only one arginine residue was found to be conserved in a catalytic center at the same position in all known sequences of BEs from various species as well as in the alpha-amylase enzyme family. In mBEII, a conserved Arg residue 384 is in catalytic region 2. We have used site-directed mutagenesis of the Arg-384 residue in order to study its possible role in BE. Previous chemical modification studies (H. Cao and J. Preiss, 1996, J. Prot. Chem. 15, 291-304) suggest that it may play a role in substrate binding. Replacement of Arg-384 by Ala, Ser, Gln, and Glu in the active site caused almost total inactivation. However, a conservative mutation of the conserved Arg-384 by Lys resulted in some residual activity, approximately 5% of the wild-type enzyme. The kinetics of the purified mutant R384K enzyme were investigated and no large effect on the Km of the substrate amylose for BE was observed. Thus, these results suggest that conserved Arg residue 384 in mBEII plays an important role in the catalytic function of BEs but may not be directly involved in substrate binding.     

Mismatch losses in multiply tapped SAW convolvers

An analysis procedure is given for calculating the output mismatch loss in a multiply tapped SAW convolver. The analysis takes into account the lossy transmission-line properties of convolvers and includes realistic values for the parasitics due to bonding pads and wires. Results illustrating trade-offs between bandwidth and insertion loss for a convolver with six taps are given, which provide guidelines for the design of broadband output matching networks.     

Demonstration of low voltage field emission

The authors describe field emission from a thin-film field emitter array. The process used to fabricate the field emitters is based on the mold technique described by H.F. Gray and R.F. Greene (US patent 4,307,507). Each emitter chip consists of a 10×10 square array of field emitter tips and associated lead bonding pads. There is a 10-μm spacing between emitter tips. The bare chips were packaged by mounting to an alumina substrate, four to eight chips per substrate. The chips were tested in a demountable vacuum system equipped with a movable anode. The testing apparatus makes it possible to accurately measure currents as low as 100 nA at low duty. Fowler-Nordhein-like current-voltage characteristics were measured for most of the chips tested, indicating field emission. Substantial emission currents were observed at less than 20 V. The emitted current was collected almost entirely at the anode: the measured gate current was 1 to 5% of the emitted current     

Cooccurrence of C-24 alkylated Δ7- and Δ5-Sterols in the leaves ofBeta vulgarisin the leaves ofBeta vulgaris

The 4-desmethylsterols from the leaves ofBeta vulgaris are a mixture of Δ⁷-sterols (71%) and Δ⁵-sterols (29%). The Δ⁷-sterols isolated are spinasterol (24α-ethylcholesta-7,22-dien-3β-ol; 45%), 22-dihydrospinasterol (24α-ethylcholest-7-en-3β-ol; 24%), and avenasterol (24-ethylcholesta-7,24(28)-dien-3β-ol; 1.5%). The Δ⁵-sterols isolated are sitosterol (24α-ethylcholest-5-en-3β-ol; 15%), 24ζ-ethylcholesta-5,22-dien-3β-ol (7.5%), and 24ζ-methylcholest-5-en-3β-ol (7%).     

Relation between 22-kHz ultrasonic signals and sociosexual behavior in rats.

The copulatory performance of male rats, tested in a large seminaturalistic environment, was assessed to determine the relation between 22-kHz ultrasonic vocalizations and a range of sociosexual behaviors. The 7 sexually experienced Charles River male rats were tested until sexual exhaustion. Ultrasonic signals were shown to occur in a wider range of sociosexual circumstances than previously reported; for example, the calls occurred in particular social circumstances during the preejaculatory period as well as during the postejaculatory interval. There was no consistent evidence that the emission of this call during the postejaculatory period consistently functions to keep the female away from the male. The nature and occurrence of postejaculatory ultrasonic signals showed increasing variability in successive ejaculatory series. The results of this and previous studies are interpreted within a semiotic theory of communication. The 22-kHz call is described as a message that makes available the information that the sender is in a socially depressed and withdrawn state. (14 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)