The chemistry of Venus' atmosphere

A model for the Venus atmosphere involving photochemistry of oxygen, hydrogen, chlorine and sulfur species is presented. Sulfur reaction schemes and hydrogen and chlorine reaction schemes were included. The impact of sulfur on the oxygen budget and the subsequent production of H2SO4 molecules for the Venus cloud deck were explored. A major new reaction scheme for production of H2SO4 molecules involving sulfur and oxygen chemistry was established shown to dominate over the odd hydrogen scheme proposed earlier. The efficiency of the scheme in formation of H2SO4 is only about 50%, with the remaining sulfur residing in SO2 molecules. The calculated downward flux of H2SO4 may be sufficient to maintain a steady state sulfuric acid cloud if the resident time of H2SO4 droplets in the cloud is as long as a few years. If however, the resident time is half a year or shorter, additional chemistry capable of more efficient conversion of SO2 to SO3 is required

Electronic Interface Reconstruction at Polar-Nonpolar Mott Insulator Heterojunctions

We report on a theoretical study of the electronic interface reconstruction (EIR) induced by polarity discontinuity at a heterojunction between a polar and a nonpolar Mott insulators, and of the two-dimensional strongly-correlated electron systems (2DSCESs) which accompany the reconstruction. We derive an expression for the minimum number of polar layers required to drive the EIR, and discuss key parameters of the heterojunction system which control 2DSCES properties. The role of strong correlations in enhancing confinement at the interface is emphasized.Comment: 7 pages, 6 figures, some typos correcte

Electrical transport across Au/Nb:SrTiO3 Schottky interface with different Nb doping

We have investigated electron transport in Nb doped SrTiO$_3$ single crystals for two doping densities. We find that the resistivity and mobility are temperature dependent in both whereas the carrier concentration is almost temperature invariant. We rationalize this using the hydrogenic theory for shallow donors. Further, we probe electrical transport across Schottky interfaces of Au on TiO$_2$ terminated n-type SrTiO$_3$. Quantitative analysis of macroscopic I-V measurements reveal thermionic emission dominated transport for the low doped substrate whereas it deviates from such behavior for the high doped substrate. This work is relevant for designing devices to study electronic transport using oxide-semiconductors.Comment: 10 Pages, 3 Figure

A micro-mechanics model for imperfect interface in dielectric materials

The interface between two dielectric bodies is considered imperfect if there are defects (micro-voids and micro-cracks) present on the interface. For such interface, the perfect continuity condition across the interface is no longer valid and its use in analysis becomes questionable. To account for this imperfection, we propose a micro-mechanics model based on the self-consistent scheme, leading to the establishment of a constitutive relationship between the electric displacement and potential discontinuity across the imperfect interface. © 2001 Elsevier Science Ltd.postprin

Fibromatosis of the neck causing airway obstruction managed effectively with weekly low-dose methotrexate and vinblastine

Fibromatosis is a rare disease with benign histology. Its infiltrative growth pattern may prevent complete resection. We report a case of a 40-year-old woman with fibromatosis of the neck requiring an emergency operation for acute upper airway obstruction. Gross residual tumour was left behind but excellent tumour shrinkage was achieved by using weekly low-dose methotrexate and vinblastine. Despite the use of newer agents such as imatinib, cytotoxic chemotherapy remains an efficacious treatment for inoperable fibromatosis.published_or_final_versio

Spintronics for electrical measurement of light polarization

The helicity of a circularly polarized light beam may be determined by the spin direction of photo-excited electrons in a III-V semiconductor. We present a theoretical demonstration how the direction of the ensuing electron spin polarization may be determined by electrical means of two ferromagnet/semiconductor Schottky barriers. The proposed scheme allows for time-resolved detection of spin accumulation in small structures and may have a device application.Comment: Revised version, 8 two-column pages, 5 figures; Added: a comprehensive time dependent analysis, figures 3b-3c & 5, equations 6 & 13-16 and 3 references. submitted to Phys. Rev.

Superconducting Quantum Point contacts and Maxwell Potential

The quantization of the current in a superconducting quantum point contact is reviewed and the critical current is discussed at different temperatures depending on the carrier concentration as well by suggesting a constant potential in the semiconductor and then a Maxwell potential. When the Fermi wave length is comparable with the constriction width we showed that the critical current has a step-like variation as a function of the constriction width and the carrier concentration.Comment: 13 pages, 8 figures, some figures are clarified; scheduled to appear in an issue in MPLB Vo.21, (2007