Structure of self-implanted silicon annealed under enhanced hydrostatic pressure

Implantation of any ions at a sufficiently high dose and energy (E) into single-crystalline Si leads to the creation of amorphous Si (aSi), with damages peaking near the projected range (R _p) of implanted species. Enhanced hydrostatic pressure (HP) at a high temperature (HT) influences the recrystallization of aSi. The structure of self-implanted Czochralski silicon (Si⁺ dose, D=2×10¹⁶ cm^?2, E=150 keV, R _p=0.22 μm) processed for 5 h at 1400 or 1520 K under HPs up to 1.45 GPa was investigated by X-ray, secondary ion mass spectrometry and photoluminescence methods. The implantation of Si produces vacancies (V) and self-interstitials (Si_i). Vacancies and Si_is form complex defects at HT–HP, also with contaminants (e.g. oxygen, always present in Czochralski silicon). The mobility and recombination of V and Si_i as well as the kinetics of recrystallization are affected by HP, thus processing at HT–HP affects the recovery of aSi.     

Progress in high-temperature and radiation-resistant strain-gage development

This paper covers the performance characteristics of bonded resistance strain gages in high-temperature and nuclear-radiation environments. Typical electrical properties of ceramic-bonded strain gages are given for various environmental conditions. The methods used to minimize errors induced by the extreme environments are fully discussed.     

Surface Coarsening on High-Tc Superconducting Single Crystals

Surface coarsening on high T_c superconducting single crystals is proposed to be due to the effect of impurity adsorption on the collective motion of growth steps. Differential interference contrast microscopy (DICM), scanning tunneling microscopy (STM), and polarized optical microscopy (POM) were used for the surface phenomena observations.     

Bromination at C-5 of Pyrimidine and C-8 of Purine Nucleosides with 1,3-Dibromo-5,5-dimethylhydantoin

Treatment of the protected and unprotected nucleosides with 1,3-dibromo-5,5- dimethylhydantoin in aprotic solvents such as CH(2)Cl(2), CH(3)CN, or DMF effected smooth bromination of uridine and cytidine derivatives at C-5 of pyrimidine rings as well as adenosine and guanosine derivatives at C-8 of purine rings. Addition of Lewis acids such as trimethylsilyl trifluoromethanesulfonate enhanced efficiency of bromination.     

Fluoride-promoted cross-coupling of chloro(mono-, di-, or triphenyl)germanes with aryl halides in "moist" toluene. Multiple transfer of the phenyl group from organogermane substrates and comparison of the coupling efficiencies of chloro(phenyl)germanes with their corresponding stannane and silane counterparts

The trichlorophenyl-, dichlorodiphenyl-, and chlorotriphenylgermanes undergo Pd-catalyzed cross-couplings with aryl bromides and iodides in the presence of tetrabutylammonium fluoride in toluene with addition of the measured amount of water. One chloride ligand on the Ge center allows efficient activation by fluoride to promote transfer of one, two, or three phenyl groups from the organogermanes. The corresponding chlorophenylstannanes were found to be more reactive than chlorophenylsilanes, which in turn were more effective than chlorophenylgermanes. One chloride ligand on the Ge or Si center allows efficient activation by fluoride to promote transfer of up to three aryl groups from germane or silicon. However, no haloligand was necessary to be present on the Sn center, since tetraphenyltin efficiently transferred up to four phenyl groups during fluoride-promoted couplings with aryl halides. (19)F NMR studies suggested formation of the fluorophenylgermanes and the hypervalent germanate species as possible intermediates.     

On discrete and continuous quotient Riesz spaces

Order properties of quotient Riesz spaces E/N(f) by null ideals N(f) are investigated. We show relationships between properties of a Riesz space E and its order dual E ^~ and properties of quotients E/N(f) where f runs over some subspaces of E ^~. A characterization of metrizable locally convex topological Riesz spaces whose all quotients (by proper closed ideals) are discrete is also given.     

Synthesis of 1‐Amino‐5,6‐diaryl‐3‐cyano‐1H‐pyridin‐2‐ones and 6,7‐Diaryl‐4‐cyano‐3‐hydroxy‐1H‐[1,2]diazepines from Isoflavones

The one‐step cyclocondensation of substituted isoflavones (=3‐phenyl‐4H‐1‐benzopyran‐4‐ones) with cyanoacetohydrazide in the presence of KOH afforded a mixture of 1‐amino‐5,6‐diaryl‐3‐cyano‐1H‐2‐pyridin‐2‐ones and 6,7‐diaryl‐4‐cyano‐3‐hydroxy‐1H‐[1,2]diazepines.     

A bifunctional tRNA for in vitro selection

In vitro selection is a powerful approach for generating novel aptamers and catalysts. Currently, several methods are being developed to extend this technique to proteins. In principle, selection methods could be applied to any library whose members can be replicated. Here, we describe a bifunctional tRNA that fuses translation products to their mRNAs. The utility of peptide-tRNA-mRNA fusions for in vitro selection was illustrated by the selective enrichment of tagged peptides-together with their mRNAs-by affinity chromatography. Our system can generate libraries larger than 10(11). Because library members can be copied and amplified, they provide a means for applying in vitro selection procedures to peptides and proteins. Furthermore, because the system is amenable to translation with misacylated tRNAs, a wide range of unusual monomers could be used to make libraries of nonstandard polymers for selection experiments.     

Defect-related light emission from processed He-implanted silicon

Photoluminescence (PL) from He⁺-implanted Si (Si:He, He⁺ dose—2×10¹⁶ cm⁻², at 150 keV) is related to its microstructure; it has been tuned by processing at 720-1400 K under hydrostatic Ar pressure (HP, up to 1.2 GPa). Processing of Si:He at 720 K for 10 h results in an appearance of the D2 and D3 dislocation-related PL lines, these last of the highest intensity. Only the D1 dislocation-related line of intensity increasing with HP has been detected after processing at 920-1070 K. The D1 (of the highest intensity), D2 and D3 PL lines are observed after the treatment at 1270 K. No dislocation-related PL has been detected for Si:He processed at 1400 K. The treatment of Si:He at 720-1270 K under HP makes it possible to produce Si:He of specific microstructure resulting in strong PL at 0.81, 0.87 or 0.94 eV.     

Crystal growth and surface morphology of Pb,Bi, Sr,Ca, Cu,O, high T c superconductors

Two types of Pb, Bi, Sr, Ca, Cu, O superconducting single crystals: plate with a flat surface and bulk mica-like were successfully grown by a slow cooling method. As-grown crystal dimensions up to 1 cm² have been obtained. Magnetization and resistivity measurements indicate that the as-grown single crystals have a superconducting transition temperature at 85–90 K. Surface morphology observations by means of differential interference contrast microscope (DICM) and scanning tunneling microscope (STM) are reported.