Langlands-shahidi method and poles of automorphicL-functions II

We use Langlands-Shahidi method and the observation that the local components of residual automorphic representations are unitary representations, to study the Rankin-SelbergL-functions of GL _k × classical groups. Especially we prove thatL(s, σ ×τ) is holomorphic, except possibly ats=0, 1/2, 1, whereσ is a cuspidal representation of GL _k which satisfies weak Ramanujan property in the sense of Cogdell and Piatetski-Shapiro andτ is any generic cuspidal representation of SO_2l+1. Also we study the twisted symmetric cubeL-functions, twisted by cuspidal representations of GL₂. Partially supported by NSF grant DMS9610387.     

SYNTHESIS AND OPTICAL PROPERTIES OF POLY (THIENYLACETYLENES)*

3 -Ethynyl-4-(trimethylsilyl)thiophene (1a) and 3 -ethynyl-4-bromothiophene (1 b ) selectivelyundergo acetylene polymerizations in the presence of the MoCl_5- and WCl_6-Ph_3SiH catalysts to give soluble,high-molecular-weight poly(thienylacetylenes) (2) (M_w up to 602000) in high yields (up to 100%). Lighttransmission spectra of THF solutions of 2 continuously red-shift with increasing concentration. Theconcentratochromism shows a logarithmic concentration dependence; that is, the optical transitions of 2 arepredictably tunable by simply changing their concentrations.     

Reaction of 4,5-diamino-3-methyl-1-phenylpyrazole with 3-dimethylaminopropiophenones. Synthesis of new 4-aryl-6-methyl-8-phenyl-2,3-dihydropyrazolo[3,4-b]diazepines and 4-aryl-8-methyl-6-phenyl-2,3-dihydropyrazolo[4,3-b]diazepines

New 4-Aryl-6-methyl-8-phenyl-2,3-dihydropyrazolo[3,4-b]diazepines and 4-aryl-8-methyl-6-phenyl-2,3-dihydropyrazolo[4,3-b]diazepines were obtained from the reaction of 4,5-diamino-3-methyl-1-phenylpyrazole 1 with one equivalent of the 3-dimethylaminopropiophenones 2 in absolute ethanol. The structures of 4-aryl-6-methyl-8-phenyl-2,3-dihydropyrazolo[3,4-b]diazepines 3 and 4-aryl-8-methyl-6-phenyl-2,3-dihydropyrazolo[4,3-b]diazepines 4 were determined by detailed nmr measurements.     

HREELS of H/GaN(0001): evidence for Ga termination

Two issues relevant to the growth and processing of GaN are the termination of the GaN(0001) surface and its reaction with hydrogen. We have used high-resolution electron energy loss spectroscopy (HREELS), low-energy electron diffraction (LEED), and Auger electron spectroscopy (AES) to study the adsorption of hydrogen on MOCVD-grown GaN(0001). LEED of the sputtered and annealed surface shows evidence of facetting. No adsorbate vibrations are observed on the clean surface by HREELS, only Fuchs–Kliewer phonons at intervals of 700 cm⁻¹. Following exposure of the clean GaN surface to hydrogen atoms, HREEL spectra show adsorbate loss peaks at 2580, 3280, and 3980 cm⁻¹. The Ga–H stretching vibration at 1880 cm⁻¹ becomes evident when the HREEL spectrum is deconvoluted to remove the phonon multiple-loss peaks. We assign the 2580, 3280, and 3980 cm⁻¹ peaks to combination modes of the Ga–H stretch and phonon(s). Upon dosing with deuterium, the Ga–D bending mode is observed at 400 cm⁻¹. No vibrational peaks due to N–H (N–D) species are observed after H (D) exposure. We conclude that sputtered and annealed GaN(0001) is Ga-terminated.     

Peak effect and oxygen ordering in YBa2Cu3O7−δ single crystals

We have investigated the second magnetization peak in pure YBa₂Cu₃O_7−δ single crystals with various oxygen contents (6.91<7−δ<6.97) and degrees of oxygen vacancy ordering, as achieved by low (1 bar) and high (100 bar) oxygen pressure annealing. Although the position of the peak changes drastically with oxygen stoichiometry, no dependence on the distribution of oxygen vacancies has been found for temperatures below 70 K. For T>70 K, however, ordering effects become important as demonstrated by the disappearance of the peak for the high pressure annealed samples. These results suggest that while at low temperatures, pinning of the vortex system by clusters or a more homogeneous distribution of oxygen vacancies is similar, at elevated T, the former are much stronger pinning sites leading to larger hysteresis and the presence of the peak.     

Double modulation Fourier transform infrared photoluminescence of InSb

The near-gap photoluminescence of the narrow gap semiconductor, InSb, has been measured near 5.3m at low temperatures excited with argon laser light using a modified commercial Fourier transform infrared spectrophotometer. Both conventional and double modulation techniques were used for removing the effect of the thermal background radiation. Three peaks were observed in the spectrum of which the first and second were assigned to band-to-band emission, band-to-impurity emission, and the third, hitherto unreported, peak to an acceptor-bound exciton transition.     

Potential analytical applications of lysenin channels for detection of multivalent ions

Transmembrane protein transporters possessing binding sites for ions, toxins, pharmaceutical drugs, and other molecules constitute excellent candidates for developing sensitive and selective biosensing devices. Their attractiveness for analytical purposes is enhanced by the intrinsic amplification capabilities shown when the binding event leads to major changes in the transportation of ions or molecules other than the analyte itself. The large-scale implementation of such transmembrane proteins in biosensing devices is limited by the difficulties encountered in inserting functional transporters into artificial bilayer lipid membranes and by the limitations in understanding and exploiting the changes induced by the interaction with the analyte for sensing purposes. Here, we show that lysenin, a pore-forming toxin extracted from earthworm Eisenia foetida, which inserts stable and large conductance channels into artificial bilayer lipid membranes, functions as a multivalent ion-sensing device. The analytical response consists of concentration and ionic-species-dependent macroscopic conductance inhibition most probably linked to a ligand-induced gating mechanism. Multivalent ion removal by chelation or precipitation restores, in most cases, the initial conductance and demonstrates reversibility. Changes in lipid bilayer membrane compositions leading to the absence of voltage-induced gating do not affect the analytical response to multivalent ions. Microscopic current analysis performed on individual lysenin channels in the presence of Cu²⁺ revealed complex open–closed transitions characterized by unstable intermediate sub-conducting states. Lysenin channels provide an analytical tool with a built-in sensing mechanism for inorganic and organic multivalent ions, and the excellent stability in an artificial environment recommend lysenin as a potential candidate for single-molecule detection and analysis.