Fabrication of large tungsten structures by chemical vapor deposition

Process is accomplished by reducing tungsten hexafluoride with hydrogen. Metallic tungsten of essentially 100 percent purity and density is produced and built up as dense deposit on heated mandrel assembly. Process variations are building up, sealing or bonding refractory metals at temperatures below transition temperatures of base metal substrates

The application of remotely sensed data to pedologic and geomorphic mapping on alluvial fan and playa surfaces in Saline Valley, California

Arid and semiarid regions yield excellent opportunities for the study of pedologic and geomorphic processes. The dominance of rock and soil exposure over vegetation not only provides the ground observer with observational possibilities but also affords good opportunities for measurement by aircraft and satellite remote sensor devices. Previous studies conducted in the area of pedologic and geomorphic mapping in arid regions with remotely sensed data have utilized information obtained in the visible to near-infrared portion of the spectrum. Thermal Infrared Multispectral Scanner (TIMS) and Thematic Mapping (TM) data collected in 1984 are being used in comjunction with maps compiled during a Bureau of Land Management (BLM) soil survey to aid in a detailed mapping of alluvial fan and playa surfaces within the valley. The results from this study may yield valuable information concerning the application of thermal data and thermal/visible data combinations to the problem of dating pedologic and geomorphic features in arid regions

Why Do U.S. Firms Hold So Much More Cash Than They Used To?

The average cash to assets ratio for U.S. industrial firms increases by 129% from 1980 to 2004. Because of this increase in the average cash ratio, American firms at the end of the sample period can pay back their debt obligations with their cash holdings, so that the average firm has no leverage when leverage is measured by net debt. This change in cash ratios and net debt is the result of a secular trend rather than the outcome of the recent buildup in cash holdings of some large firms. It is concentrated among firms that do not pay dividends. The average cash ratio increases over the sample period because the cash flow of American firms has become riskier, these firms hold fewer inventories and accounts receivable, and the typical firm spends more on R&D. The precautionary motive for cash holdings appears to explain the increase in the average cash ratio.

Quantifying structure in networks

We investigate exponential families of random graph distributions as a framework for systematic quantification of structure in networks. In this paper we restrict ourselves to undirected unlabeled graphs. For these graphs, the counts of subgraphs with no more than k links are a sufficient statistics for the exponential families of graphs with interactions between at most k links. In this framework we investigate the dependencies between several observables commonly used to quantify structure in networks, such as the degree distribution, cluster and assortativity coefficients.Comment: 17 pages, 3 figure

Mirror formation control in the vicinity of an asteroid

Two strategies are presented for the positioning and control of a spacecraft formation designed to focus sunlight onto a point on the surface of asteroid, thereby sublimating the material and ejecting debris creating thrust. In the first approach, the formation is located at artficial equilibrium points around the asteroid and controlled using the force from the solar radiation pressure. The second approach determines the optimal periodic formation orbits, subject to the gravitational perturbations from the asteroid, the solar radiation pressure and the control acceleration derived from a control law

Molecular diagnostic yield of exome sequencing in patients with congenital hydrocephalus: A systematic review and meta-analysis

IMPORTANCE: Exome sequencing (ES) has been established as the preferred first line of diagnostic testing for certain neurodevelopmental disorders, such as global developmental delay and autism spectrum disorder; however, current recommendations are not specific to or inclusive of congenital hydrocephalus (CH). OBJECTIVE: To determine the diagnostic yield of ES in CH and whether ES should be considered as a first line diagnostic test for CH. DATA SOURCES: PubMed, Cochrane Library, and Google Scholar were used to identify studies published in English between January 1, 2010, and April 10, 2023. The following search terms were used to identify studies: congenital hydrocephalus, ventriculomegaly, cerebral ventriculomegaly, primary ventriculomegaly, fetal ventriculomegaly, prenatal ventriculomegaly, molecular analysis, genetic cause, genetic etiology, genetic testing, exome sequencing, whole exome sequencing, genome sequencing, microarray, microarray analysis, and copy number variants. STUDY SELECTION: Eligible studies included those with at least 10 probands with the defining feature of CH and/or severe cerebral ventriculomegaly that had undergone ES. Studies with fewer than 10 probands, studies of mild or moderate ventriculomegaly, and studies using genetic tests other than ES were excluded. A full-text review of 68 studies was conducted by 2 reviewers. Discrepancies were resolved by consensus. DATA EXTRACTION AND SYNTHESIS: Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and Meta-Analysis of Observational Studies in Epidemiology guidelines were used by 2 reviewers to extract data. Data were synthesized using a random-effects model of single proportions. Data analysis occurred in April 2023. MAIN OUTCOMES AND MEASURES: The primary outcome was pooled diagnostic yield. Additional diagnostic yields were estimated for specific subgroups on the basis of clinical features, syndromic presentation, and parental consanguinity. For each outcome, a 95% CI and estimate of interstudy heterogeneity (I2 statistic) was reported. RESULTS: From 498 deduplicated and screened records, 9 studies with a total of 538 CH probands were selected for final inclusion. The overall diagnostic yield was 37.9% (95% CI, 20.0%-57.4%; I2 = 90.1). The yield was lower for isolated and/or nonsyndromic cases (21.3%; 95% CI, 12.8%-31.0%; I2 = 55.7). The yield was higher for probands with reported consanguinity (76.3%; 95% CI, 65.1%-86.1%; I2 = 0) than those without (16.2%; 95% CI, 12.2%-20.5%; I2 = 0). CONCLUSIONS AND RELEVANCE: In this systematic review and meta-analysis of the diagnostic yield of ES in CH, the diagnostic yield was concordant with that of previous recommendations for other neurodevelopmental disorders, suggesting that ES should also be recommended as a routine diagnostic adjunct for patients with CH