Electron microscopic observations of SiO2 precipitates at dislocations in silicon

The precipitation of oxygen from silicon single crystals has been examined. It has been found that oxygen precipitates are formed preferentially at dislocations. This finding enabled the formation of zones with high particle density and with large particles, which aided identification. It was then shown that the precipitates consisted of crystalline - and -SiO₂ grown in a manner partially coherent with the Si lattice. Some of the precipitates are hexagonal prisms with the longitudinal axis in the 110 direction of the Si-matrix.     

Organic Semiconductors based on Dyes and Color Pigments

Organic dyes and pigments constitute a large class of industrial products. The utilization of these compounds in the field of organic electronics is reviewed with particular emphasis on organic field‐effect transistors. It is shown that for most major classes of industrial dyes and pigments, i.e., phthalocyanines, perylene and naphthalene diimides, diketopyrrolopyrroles, indigos and isoindigos, squaraines, and merocyanines, charge‐carrier mobilities exceeding 1 cm² V^?1 s^?1 have been achieved. The most widely investigated molecules due to their n‐channel operation are perylene and naphthalene diimides, for which even values close to 10 cm² V^?1 s^?1 have been demonstrated. The fact that all of these π‐conjugated colorants contain polar substituents leading to strongly quadrupolar or even dipolar molecules suggests that indeed a much larger structural space shows promise for the design of organic semiconductor molecules than was considered in this field traditionally. In particular, because many of these dye and pigment chromophores demonstrate excellent thermal and (photo‐)chemical stability in their original applications in dyeing and printing, and are accessible by straightforward synthetic protocols, they bear a particularly high potential for commercial applications in the area of organic electronics.     

Growth modes of epitaxial copper films on c-sapphire

Usually copper grows on c-sapphire with orientation Cu(111)Al₂O₃(0001) with Cu[2 ] along Al₂O₃[2 0]. In the present work an additional orientation is described. To understand this orientation, a microscopic model of roughness of the substrate crystal is proposed and verified.     

Stability of polynomials under coefficient perturbation

Let the real polynomiala_{0}x^{n} + a_{1}x^{n-1} + ... + a_{n-1}x + a_{n}be stable and let the real numbersb_{k}, c_{k} geq 0, 0 leq k leq n, be given. We present a simple determinant criterion for finding the largestt_{0} geq 0such that the polynomialalpha_{0}x^{n} + alpha_{1}x^{n-1}+ ... +alpha_{n-1}x + alpha_{n}is stable for allalpha_{k} in (a_{k} - b_{k}t_{0}, a_{k} + C_{k}t_{0}) cup {a_{k}}, 0 leq k leq n. Several further observations allow us to reduce the computational cost considerably.     

Changing patterns of self-poisoning in a UK health district

Details of admissions to a dedicated district poisons treatment unit in South Glamorgan were analysed to assess changes in self-poisoning patterns between 1987-1988 and 1992-1993. Self-poisoning rates increased in both men and women, with male rates showing a relatively larger increase, resulting in a fall in female to male ratio for person-based rates from 1.33:1 to 1.13:1. The highest age-specific rates in both period were found in 15-19-year-old females. Paracetamol was the most commonly ingested poison in 1992-1993, with 43.4% of episodes involving its use, compared with 31.3% of episodes in 1987-88. Antidepressant involvement in self-poisoning also increased from 11.3% of episodes in 1987-1988 to 17.6% of episodes in 1992-1993. Repetition of self-poisoning was relatively common, with 18% of admissions per year in 1992-1993 representing repeats. Although hospital admission increased in this health district over the study periods, this was not reflected in an increase in in-patient all-cause mortality, which was only 0.5% in 1987-1988 and 0.1% in 1992-1993.