Transition-metal silicides lattice-matched to silicon

We have used a systematic search to determine all the possible transition-metal silicides that are geometrically lattice-matched to either the (100), (110), or the (111) face of silicon. A short table with the best possible matches is presented here, and a more comprehensive table including slightly worse matches is deposited with the editor

Dark Matter and Pseudo-flat Directions in Weakly Coupled SUSY Breaking Sectors

We consider candidates for dark matter in models of gauge mediated supersymmetry breaking, in which the supersymmetry breaking sector is weakly coupled and calculable. Such models typically contain classically flat directions, that receive one-loop masses of a few TeV. These pseudo-flat directions provide a new mechanism to account for the cold dark matter relic abundance. We discuss also the possibility of heavy gravitino dark matter in such models.Comment: 16 pages, 2 figures. v2: comments, refs adde

Lattice match: An application to heteroepitaxy

We define the concept of lattice match for any pair of crystal lattices in any given crystal direction, allowing for a periodic reconstruction of the interface. An algorithm for a systematic search for all possible matches is developed, and some examples of nonstandard lattice matches are given for CdTe on GaAs and sapphire to illustrate the method. For the case of CdTe on GaAs, our results agree with published results, both with respect to growth plane and orientation for CdTe(111) on GaAs(100). For CdTe on sapphire, our results agree with published results with respect to growth plane

Temporal Variability of Urinary Phthalate Metabolite Levels in Men of Reproductive Age

Phthalates are a family of multifunctional chemicals widely used in personal care and other consumer products. The ubiquitous use of phthalates results in human exposure through multiple sources and routes, including dietary ingestion, dermal absorption, inhalation, and parenteral exposure from medical devices containing phthalates. We explored the temporal variability over 3 months in urinary phthalate metabolite levels among 11 men who collected up to nine urine samples each during this time period. Eight phthalate metabolites were measured by solid-phase extraction–high-performance liquid chromatography–tandem mass spectrometry. Statistical analyses were performed to determine the between- and within-subject variance apportionment, and the sensitivity and specificity of a single urine sample to classify a subject’s 3-month average exposure. Five of the eight phthalates were frequently detected. Monoethyl phthalate (MEP) was detected in 100% of samples; monobutyl phthalate, monobenzyl phthalate, mono-2-ethylhexyl phthalate (MEHP), and monomethyl phthalate were detected in > 90% of samples. Although we found both substantial day-to-day and month-to-month variability in each individual’s urinary phthalate metabolite levels, a single urine sample was moderately predictive of each subject’s exposure over 3 months. The sensitivities ranged from 0.56 to 0.74. Both the degree of between- and within-subject variance and the predictive ability of a single urine sample differed among phthalate metabolites. In particular, a single urine sample was most predictive for MEP and least predictive for MEHP. These results suggest that the most efficient exposure assessment strategy for a particular study may depend on the phthalates of interest

Transoral trans-stomal microdebrider excision of tracheal papillomatosis

Objectives: To describe a technique for surgical removal of recurrent respiratory papilloma in the distal trachea in patients with an indwelling tracheostomy tube. Methods: A transoral trans-stomal technique for removal of distal tracheal papilloma using a modified ventilating bronchoscope setup and a microdebrider with a rotatable Skimmer blade (XOMED Products, Jacksonville, Florida, USA). Results: Surgical removal of papillomas in the distal trachea is a challenging procedure, involving potentially competing demands for visualization, instrumentation, and ventilation. Previously described methods for management of these challenging cases provide limited ability to deliver continuous oxygenation and ventilation during the procedure. The transoral trans-stomal technique overcomes these limitations in patients who have an existing tracheostomy. Conclusions: This technique allows for precise removal of papilloma in the distal trachea, while providing for excellent visualization and continuous oxygenation and ventilation of the patient. Laryngoscope, 2009Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62137/1/20163_ftp.pd

Fermi-level position at a semiconductor-metal interface

We have investigated the phenomenon of Fermi-level pinning by charged defects at the semiconductor-metal interface. Two limiting cases were investigated. In the first case we modeled an infinitely thick metallic coverage. In the second case we modeled a submonolayer coverage by using a free semiconductor surface containing defects. In both cases we assumed that most of the defect-induced interface states are localized inside the semiconductor, not more than a few angstroms away from the metal. Under these conditions we have estimated the difference in Fermi-level position between n- and p-type semiconductors to be less than 0.05 eV in the case of a thick metallic coverage. This difference was shown to be the maximum possible one, and it occurs only when there is no pinning. When there is pinning, this difference is even smaller. No such upper bound on the difference in Fermi-level position exists in the case of submonolayer coverage. We have also found that the defect density required to pin the Fermi level is ∼10^14 cm^-2 in the case of a thick metallic coverage, but only ∼10^12 cm^-2 in the case of a submonolayer coverage