Effects of the transversely nonuniform plasma density in a blowout regime of a plasma wakefield accelerator.

We present an analytical study on the effects of the transverse plasma gradient in the blowout regime of a plasma wakefield accelerator. The analysis departs from a simple ballistic model of plasma electrons and allows us to derive a complete analytic solution for the pseudopotential and, consequently, for the wakefield. We demonstrate that the transverse plasma gradient modifies the bubble shape and affects the wakefield; namely, the dipole plasma gradient results in a dipole component of the wakefield.

Suppression of Deflecting Forces in Planar-Symmetric Dielectric Wakefield Accelerating Structures with Elliptical Bunches.

Wakefield based accelerators capable of accelerating gradients 2 orders of magnitude higher than present accelerators offer a path to compact high energy physics instruments and light sources. However, for high gradient accelerators, beam instabilities driven by commensurately high transverse wakefields limit beam quality. Previously, it has been theoretically shown that transverse wakefields can be reduced by elliptically shaping the transverse sizes of beams in dielectric structures with planar symmetry.

Electron emission projection imager.

A new projection type imaging system is presented. The system can directly image the field emission site distribution on a cathode surface by making use of anode screens in the standard parallel plate configuration. The lateral spatial resolution of the imager is on the order of 1-10 μm.

Cherenkov radiation from short relativistic bunches: general approach.

In recent years new interest in Cherenkov radiation has arisen based on progress in its new applications like biomedical imaging, photonic structures, metamaterials, and beam physics. These new applications require Cherenkov radiation theory of short bunches to be extended to rather more complicated media and structures than considered originally. We present a new general approach to the analysis of Cherenkov fields and loss factors for relativistic short bunches in arbitrary slow wave guiding systems.

The effects of a protein osmolyte on the stability of the integral membrane protein glycerol facilitator.

Osmolytes are naturally occurring molecules used by a wide variety of organisms to stabilize proteins under extreme conditions of temperature, salinity, hydrostatic pressure, denaturant concentration, and desiccation. The effects of the osmolyte trimethylamine N-oxide (TMAO) as well as the influence of detergent head group and acyl chain length on the stability of the Escherichia coli integral membrane protein glycerol facilitator (GF) tetramer to thermal and chemical denaturation by sodium dodecyl sulphate (SDS) are reported. TMAO promotes the association of the normally tetrameric α-helical protein into higher order oligomers in dodecyl-maltoside (DDM), but not in tetradecyl-maltoside (TDM), lyso-lauroylphosphatidyl choline (LLPC), or lyso-myristoylphosphatidyl choline (LMPC), as determined by dynamic light scattering (DLS); an octameric complex is particularly stable as indicated by SDS polyacrylamide gel electrophoresis.

Terahertz radiation from an ultra-relativistic charge exiting the open end of a waveguide with a dielectric layer.

We analyze radiation produced by an ultrarelativistic charge as it exits the open end of a cylindrical waveguide with a dielectric lining. The end of the waveguide can be either orthogonal to the structure axis or skewed. To obtain terahertz radiation from waveguides with centimeter or millimeter radii, we consider high order TM(0m) modes driven by the beam.

Experimental demonstration of energy-chirp compensation by a tunable dielectric-based structure.

A tunable energy-chirp compensator was used to remove a correlated energy chirp from the 60-MeV beam at the Brookhaven National Laboratory Accelerator Test Facility. The compensator operates through the interaction of the wakefield of the electron bunch with itself and consists of a planar structure comprised of two alumina bars with copper-plated backs separated by an adjustable beam aperture. By changing the gap size, the correlated energy chirp of the electron bunch was completely removed.

Dissecting electrostatic interactions in Bacillus circulans xylanase through NMR-monitored pH titrations.

NMR-monitored pH titration curves of proteins provide a rich source of structural and electrostatic information. Although relatively straightforward to measure, interpreting pH-dependent chemical shift changes to obtain site-specific acid dissociation constants (pK (A) values) is challenging. In order to analyze the biphasic titrations exhibited by the side chain (13)C(γ) nuclei of the nucleophilic Glu78 and general acid/base Glu172 in Bacillus circulans xylanase, we have revisited the formalism for the ionization equilibria of two coupled acidic residues.

Structure, dynamics, and ionization equilibria of the tyrosine residues in Bacillus circulans xylanase.

We have developed NMR spectroscopic methods to investigate the tyrosines within Bacillus circulans xylanase (BcX). Four slowly exchanging buried tyrosine hydroxyl protons with chemical shifts between 7.5 and 12.

Circular permutation of Bacillus circulans xylanase: a kinetic and structural study.

The 20 kDa Bacillus circulans Bcx is a well-studied endoxylanase with a beta-jellyroll fold that places its N- and C-termini in salt bridge contact. Initial experiments verified that Bcx could be circularly permuted by PCR methods to introduce new termini in loop regions while linking its native termini directly or via one or two glycines. Subsequently, a library of circular permutants, generated by random DNase cleavage of the circularized Bcx gene, was screened for xylanase activity on xylan in Congo Red-stained agar.

[Agamospermy in outbred crosses of Fragaria vesca L. (Rosaceae)].

The seed progeny obtained in European wood strawberry Fragaria vesca L. (2n = 2x = 14) via outbred crosses proved to include matromorphic diploid plants, whose proportion varied from 10.0 to 21.

Stability of the glycerol facilitator in detergent solutions.

Understanding membrane protein folding and stability is required for a molecular explanation of function and for the development of interventions in membrane protein folding diseases. Stable aqueous detergent solutions of the Escherichia coli glycerol facilitator in its native oligomeric state have been difficult to prepare as the protein readily unfolds and forms nonspecific aggregates. Here, we report a study of the structure and stability of the glycerol facilitator in several detergent solutions by Blue Native and sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE), circular dichroism (CD), and fluorescence.

[Identification of the apomixis in Poa pratensis L. using SDS-electrophoresis of endosperm reserve proteins].

To determine the characteristics of variability of seed reproduction in the Kentucky bluegrass (Poa pratensis), individual seed variability with respect to the composition of endospermal reserve proteins was studied. Comparative analysis of caryopses obtained by self-fertilization and free fertilization of plants I1 (no. 2-4) and I2 (no.

[Prolonged peridural block in the overall treatment of the infectious-allergic form of bronchial asthma].

The authors describe the treatment of 23 patients with a severe form of infectional-allergic bronchial asthma by continuous peridural blockade. Positive results of the peridural injection of the anesthetic drug was observed in cases with localization of the autosensibilization in the broncho-pulmonary system. The peridural blockade was not found to be effective for the treatment of bronchial asthma against the background of chronic diseases of otorhinolaryngologic organs.