Hydrogen contamination in Ge-doped SiO[sub 2] thin films prepared by helicon activated reactive evaporation

Germanium-doped silicon oxidethin films were deposited at low temperature by using an improved helicon plasma assisted reactive evaporation technique. The origins of hydrogen contamination in the film were investigated, and were found to be H incorporation during deposition and postdeposition water absorption. The H incorporation during deposition was avoided by using an effective method to eliminate the residual hydrogen present in the depositionsystem. The microstructure, chemical bonds, chemical etch rate, and optical index of the films were studied as a function of the deposition conditions. Granular microstructures were observed in low-density films, and were found to be the cause of postdeposition water absorption. The granular microstructure was eliminated and the film was densified by increasing the helicon plasma power and substrate bias during deposition. A high-density film was shown to have no postdeposition water absorption and no OH detected by using a Fourier-transform infrared spectrometer

Identifying the best Pichia pastoris base strain using functional genomics

Market sizes for novel breakthrough therapies and growing demand for existing treatments in emerging markets promise to challenge the current capacity for production of biologics. These trends dictate the need for a concomitant paradigm shift in biomanufacturing toward greater productivity for lower cost. Strain engineering is a promising means to realize the greatest returns by increasing the product titer going into downstream processes. Current cellular hosts are approaching saturation of optimal productivity due to lack of deep biological understanding or limitations of the host’s intrinsic secretion capacity. We demonstrate an approach informed by functional genomics to understand key performance differences between interchangeably-used variants of the host, Pichia pastoris. Genomic variant calling on all USDA-banked and commercially-available strains revealed varying numbers of SNPs relative to the WT strain, Y-11430. Combining transcriptomics and traditional phenotypic assays, the functional impact of these SNPs can inform which host strain is best suited for a given application. Taken together, we have identified key, beneficial SNPs that can be introduced into a WT background to create an IP-free host primed for optimal protein production

Arteriovenous fistulae complicating cardiac pacemaker lead extraction: Recognition, evaluation, and management

AbstractTransvenous pacemaker lead extraction has become a commonly performed procedure that is associated with a small but significant risk. We report two cases where lead extraction was complicated by arteriovenous fistulae between branches of the aortic arch and the left brachiocephalic vein. Presenting signs and symptoms included severe chest or back pain, persistent or copious bleeding from the venous puncture site, unexplained hypotension or anemia, superior vena cava syndrome, and signs of central venous hypertension or acute heart failure. One patient whose injury was not recognized immediately and who did not undergo repair died rapidly, whereas the other patient who was diagnosed quickly underwent successful repair. Immediate diagnosis with arteriography and rapid intervention with surgery or percutaneous techniques are indicated and may prevent mortality. (J Vasc Surg 2000;32:1225-8.

No evidence for high atmospheric oxygen levels 1,400 million years ago

Zhang et al. (1) recently proposed atmospheric oxygen levels of ∼4% present atmospheric levels (PAL) based on modeling a paleoenvironment reconstructed from trace metal and biomarker data from the 1,400 Ma Xiamaling Formation in China. Intriguingly, this pO2 level is above the threshold oxygen requirements of basal animals and clashes with evidence for atmospheric oxygen levels <<1% PAL in the mid-Proterozoic (2). However, there are fundamental problems with the inorganic and organic geochemical work presented by Zhang et al. (1)

Evaluation of air oxidation and internal stresses induced by quenching of partially Cr-coated and uncoated optimized ZIRLO part I:Materials characterization

It is critical to develop technologies that minimize risk of nuclear reactor failure. Coated claddings present an opportunity to preserve fuel rod integrity in the case of a loss of coolant accident. In this work, the material evolution of quenched Optimized ZIRLO (OPZ) rings and Cr-coated OPZ rings is studied at temperatures up to 1000 °C, until full oxidation in air is uncovered through a variety of microstructural characterization techniques, including optical analysis and X-ray diffraction. A number of microstructural reorienting and complex, multi-stage oxidation mechanisms are found to play a role in the structural and material changes. At 1000 °C, the primary failure mode of uncoated ZIRLO is breakaway oxidation; however, the introduction of a single-sided Cr coating protects ZIRLO from oxygen penetration through the exterior surface. The material is seen to undergo several microstructural reorientations from 315° to 900°C while remaining in the α-Zr phase. At 900 °C, Cr-coated OPZ begins the α to β phase transition, and the chromium diffuses into the substrate layer. When both events are present, the Cr phase change can lead to the formation of a Cr-β-Zr eutectoid, and subsequent eutectic temperature at 1332 °C. For uncoated samples, a new phenomenon of iron-rich oxide (rust) development along the ring center in air at 1000 °C is unveiled and explained as an extension of spinodal decomposition. This study is Part I of a two-part series regarding the behavior of Cr-coated and uncoated OPZ at high temperatures. Part II investigates the internal stresses and other mechanical behaviors induced by metallic restructuring and oxide development

Arcjet exploratory tests of ARC optical window design for the AFE vehicle

Tests were made in the 20 MW arc jet facility at the NASA ARC to determine the suitability of sapphire and fused silica as window materials for the Aeroassist Flight Experiment (AFE) entry vehicle. Twenty nine tests were made; 25 at a heating rate about 80 percent of that expected during the AFE entry and 4 at approximately the full, 100 percent AFE heating rate profile, that produces a temperature of about 2900 F on the surface of the tiles that protect the vehicle. These tests show that a conductively cooled window design using mechanical thermal contacts and sapphire is probably not practical. Cooling the window using mechanical thermal contacts produces thermal stresses in the sapphire that cause the window to crack. An insulated design using sapphire, that cools the window as little as possible, appears promising although some spectral data in the vacuum-ultra-violet (VUV) will be lost due to the high temperature reached by the sapphire. The surface of the insulated sapphire windows, tested at the 100 percent AFE heating rate, showed some slight ablation, and cracks appeared in two of three test windows. One small group of cracks were obviously caused by mechanical binding of the window in the assembly, which can be eliminated with improved design. Other cracks were long, straight, thin crystallographic cracks that have very little effect on the optical transmission of the window. Also, the windows did not fall apart along these crystallographic cracks when the windows were removed from their assemblies. Theoretical results from the thermal analysis computer program SINDA indicate that increasing the window thickness from 4 to 8 mm may enable surface ablation to be avoided. An insulated design using a fused silica window tested at the nominal AFE heating rate experienced severe ablation, thus fused silica is not considered to be an acceptable window material

Twirling and Whirling: Viscous Dynamics of Rotating Elastica

Motivated by diverse phenomena in cellular biophysics, including bacterial flagellar motion and DNA transcription and replication, we study the overdamped nonlinear dynamics of a rotationally forced filament with twist and bend elasticity. Competition between twist injection, twist diffusion, and writhing instabilities is described by a novel pair of coupled PDEs for twist and bend evolution. Analytical and numerical methods elucidate the twist/bend coupling and reveal two dynamical regimes separated by a Hopf bifurcation: (i) diffusion-dominated axial rotation, or twirling, and (ii) steady-state crankshafting motion, or whirling. The consequences of these phenomena for self-propulsion are investigated, and experimental tests proposed.Comment: To be published in Physical Review Letter

Characterization of a Homozygous Deletion of Steroid Hormone Biosynthesis Genes in Horse Chromosome 29 as a Risk Factor for Disorders of Sex Development and Reproduction

Disorders of sex development (DSD) and reproduction are not uncommon among horses, though knowledge about their molecular causes is sparse. Here we characterized a 200 kb homozygous deletion in chromosome 29 at 29.7-29.9 Mb. The region contains AKR1C genes which function as ketosteroid reductases in steroid hormone biosynthesis, including androgens and estrogens. Mutations in AKR1C genes are associated with human DSDs. Deletion boundaries, sequence properties and gene content were studied by PCR and whole genome sequencing of select deletion homozygotes and control animals. Deletion analysis by PCR in 940 horses, including 622 with DSDs and reproductive problems and 318 phenotypically normal controls, detected 67 deletion homozygotes of which 79% were developmentally or reproductively abnormal. Altogether, 8-9% of all abnormal horses were homozygous for the deletion, with the highest incidence (9.4%) among cryptorchids. The deletion was found in 4% of our phenotypically normal cohort, 1% of global warmblood horses and ponies, and 7% of draught breeds of general horse population as retrieved from published data. Based on the abnormal phenotype of the carriers, the functionally relevant gene content, and the low incidence in general population, we consider the deletion in chromosome 29 as a risk factor for equine DSDs and reproductive disorders

Superior Vena Cava Defibrillator Coils Make Transvenous Lead Extraction More Challenging and Riskier

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Molecular engineering improves antigen quality and enables integrated manufacturing of a trivalent subunit vaccine candidate for rotavirus

Background Vaccines comprising recombinant subunit proteins are well-suited to low-cost and high-volume production for global use. The design of manufacturing processes to produce subunit vaccines depends, however, on the inherent biophysical traits presented by an individual antigen of interest. New candidate antigens typically require developing custom processes for each one and may require unique steps to ensure sufficient yields without product-related variants. Results We describe a holistic approach for the molecular design of recombinant protein antigens—considering both their manufacturability and antigenicity—informed by bioinformatic analyses such as RNA-seq, ribosome profiling, and sequence-based prediction tools. We demonstrate this approach by engineering the product sequences of a trivalent non-replicating rotavirus vaccine (NRRV) candidate to improve titers and mitigate product variants caused by N-terminal truncation, hypermannosylation, and aggregation. The three engineered NRRV antigens retained their original antigenicity and immunogenicity, while their improved manufacturability enabled concomitant production and purification of all three serotypes in a single, end-to-end perfusion-based process using the biotechnical yeast Komagataella phaffii. Conclusions This study demonstrates that molecular engineering of subunit antigens using advanced genomic methods can facilitate their manufacturing in continuous production. Such capabilities have potential to lower the cost and volumetric requirements in manufacturing vaccines based on recombinant protein subunits