Subnormal subgroups of the groups of rational points of reductive algebraic groups

We prove that for a reductive algebraic group over an infinite field the group of rational points does not contain any noncentral finitely generated normal subgroups.

     

Connection establishment in high-speed networks

Protocols for establishing, maintaining, and terminating connections in packet-switched networks have been studied, and numerous standards have been developed to address this problem. The authors reexamine connection establishment in the context of a high-speed packet network, introduce a protocol for connection establishment/takedown that is appropriate for such a network, and explain its advantages over previously proposed protocols. The main features of the proposed protocol are: fast bandwidth reservation in order to avoid as much as possible reservation conflicts, guaranteed release of the reserved bandwidth even under modal and link failures, and soft recovery from processor failures, which allows the maintenance of existing connections under processor failure provided the switch and links do not fail. The underlying model that is used is the PARIS/plaNET network, but the protocol can be adapted to other fast packet networking architectures as well     

Crystal structure and absolute configuration of yohimbine hydrochloride,C21H27ClN2O3

Yohimbine (C₂₁H₂₆N₂O₃) is an important indole alkaloid found in the Indian snake rootrauwolfia serpentina, and is very closely related to reserpine. Yohimbine hydrochloride (C₂₁H₂₇ClN₂O₃) is orthorhombic:P2₁2₁2₁,a = 11·54,b = 24·88,c = 7·00 Å,Z = 4. X-ray diffraction data to a Bragg angle of 80 ° were collected on a G.E. diffractometer using CuK radiation. The structure was solved by direct methods, and refined to a reliability index of 9·9 % by the block-diagonal least-squares method. Yohimbine has a ring system very similar to that of reserpine, though the conformations of the ringsC andD about the C—N bond are different in the two molecules. The absolute configuration of the molecule, determined by X-ray anomalous scattering, confirms the 3, 15, 20 configuration assigned earlier by conformational analysis.     

Use of novel carbon-nanofiber-doped carbon liquid crystals as suitable adsorbents for hydrogen storage

Over the last few years a number of groups have been exploring the possibilities and limitations associated with using adsorption on newly developed materials for the storage of hydrogen. Here we report the results of hydrogen adsorption investigations on a newly synthesized form of carbon nanofiber-doped carbon liquid crystals. This material shows a marked increase in specific surface area upon activation with water vapor, leading to activated samples that are capable of adsorbing hydrogen upto 3.5% by weight at 77.3 K, at moderate pressures. The possibility of higher adsorption (6.5 wt.%) in these materials is also discussed. PACS 68.43.-h; 68.43.De; 68.60.-p     

High-intensity-laser-driven Z pinches

Experiments were performed in which ultrahigh intensity laser pulses (I>5 x 10(19) W cm(-2)) were used to irradiate thin wire targets. It was observed that such interactions generate a large number of relativistic electrons which escape the target and induce multimega ampere return currents within the wire. MHD instabilities can subsequently be observed in the pinching plasma along with field emission of electrons from nearby objects. Coherent optical transition radiation from adjacent objects was also observed.     

Elastic and total cross-sections for electron scattering by acetylene in the intermediate energy range

We present a joint theoretical-experimental study on electron scattering by C₂H₂ in the intermediate energy range. We report calculated elastic differential, integral, and momentum-transfer as well as total (elastic + inelastic) and absorption cross-sections at impact energies ranging from 10 to 500 eV. Also, experimental absolute elastic cross-sections are reported in the (50-500)-eV energy range. A complex optical potential is used to represent the electron-molecule interaction dynamics. The iterative Schwinger variational method, combined with the distorted-wave approximation, is used to solve the scattering equations. Experimentally, the angular distributions of the scattered electrons are converted to absolute cross-sections using the relative flow technique. The comparison of our calculated with our measured results, as well as with other experimental and theoretical data available in the literature, is encouraging.Received: 26 August 2004, Published online: 5 October 2004PACS: 34.80.Bm Elastic scattering of electrons by atoms and molecules     

The electronic spectrum of silicon monotelluride radical

In the electronic spectrum of silicon monotelluride which has been produced in microwave discharges through sealed tubes, a large number of new bands belonging to theA ¹Π-X ¹Σ⁺ system (3100–3900 Å) and theE ¹Σ⁺-X ¹Σ⁺ system (2800–3100 Å) of Si¹³⁰Te has been observed. The vibrational structure analyses of these band systems have resulted in the determination of improved vibrational constants in all the three electronic states involved in these transitions. An error in the previous determination of the vibrational constants of theE ¹Σ⁺ state has been corrected. An upper limit for the dissociation energy of the silicon monotelluride has been determined to be 40,000 cm^?1.     

A rapid microwave protocol for Heck vinylation of aryl chlorides under air

In modern high-throughput chemistry, the overall workflow is a crucial factor and much work is devoted to speeding up the process of chemistry development. Since automated microwave-based synthesizers are known to streamline the compound production and to accelerate slow organic transformations, this technology was implemented for Heck reactions with sluggish aryl chlorides. Furthermore, homogeneous palladium-catalyzed Heck vinylations of aryl chlorides can be performed under air under optimized conditions. Based on this finding, controlled microwave heating was utilized to accelerate model reactions down to 30 min employing a mixture of ionic liquid and 1,4-dioxane as solvent.     

Absorption and emission spectral studies of Sm and Dy doped alkali fluoroborate glasses

Absorption and photoluminescence spectra of Sm³⁺ and Dy³⁺ doped alkali fluoroborate glasses of the composition 90.5% B₂O₃+4% AlF₃+5% MF+0.5% LnF₃ (M=Li, Na, K and Ln=Sm, Dy) have been reported. On excitation, with , the Sm³⁺ glasses are found to be orange fluorescent in color and richness of that color is high in the Na+ glass, compared to Li⁺ and K⁺ glasses. Similarly, on excitation with , the Dy³⁺ glasses are fluorescent yellow in color and that color is richer in the K⁺ glass.