Mechanism of error-free replication across benzo[a]pyrene stereoisomers by Rev1 DNA polymerase.

Benzo[a]pyrene (BP) is a carcinogen in cigarette smoke which, after metabolic activation, can react with the exocyclic N amino group of guanine to generate four stereoisomeric BP-N -dG adducts. Rev1 is unique among translesion synthesis DNA polymerases in employing a protein-template-directed mechanism of DNA synthesis opposite undamaged and damaged guanine. Here we report high-resolution structures of yeast Rev1 with three BP-N -dG adducts, namely the 10S (+)-trans-BP-N -dG, 10R (+)-cis-BP-N -dG, and 10S ( - )-cis-BP-N -dG.

Gradient and shim technologies for ultra high field MRI.

Ultra High Field (UHF) MRI requires improved gradient and shim performance to fully realize the promised gains (SNR as well as spatial, spectral, diffusion resolution) that higher main magnetic fields offer. Both the more challenging UHF environment by itself, as well as the higher currents used in high performance coils, require a deeper understanding combined with sophisticated engineering modeling and construction, to optimize gradient and shim hardware for safe operation and for highest image quality. This review summarizes the basics of gradient and shim technologies, and outlines a number of UHF-related challenges and solutions.

A coupled finite-element, boundary-integral method for simulating ultrasonic flowmeters.

Today's most popular technology of ultrasonic flow measurement is based on the transit-time principle. In this paper, a numerical simulation technique applicable to the analysis of transit-time flowmeters is presented. A flowmeter represents a large simulation problem that also requires computation of acoustic fields in moving media.

Finite element simulation of nonlinear wave propagation in thermoviscous fluids including dissipation.

A recently developed finite element method (FEM) for the numerical simulation of nonlinear sound wave propagation in thermoviscous fluids is presented. Based on the nonlinear wave equation as derived by Kuznetsov, typical effects associated with nonlinear acoustics, such as generation of higher harmonics and dissipation resulting from the propagation of a finite amplitude wave through a thermoviscous medium, are covered. An efficient time-stepping algorithm based on a modification of the standard Newmark method is used for solving the non-linear semidiscrete equation system.

[Pneumothorax in vertical infraclavicular block of the brachial plexus. Review of a rare complication].

A 50 year old female patient received anaesthesia of the arm by the vertical infraclavicular blockade of the plexus brachialis (VIP). Postoperatively an ipsilateral pneumothorax occurred complicated by pleural effusion and a contralateral bronchopneumonia, which resolved completely after treatment. The blockade of the plexus was performed correctly, failures in determining the correct point of needle insertion could be excluded.