SLS Processing Studies of Nylon 11 Nanocomposites

Selective Laser Sintering (SLS) is widely used for rapid prototyping/manufacturing of nylon 11 and nylon 12 parts. This processing technique has not been explored for nylon nanocomposites. This study investigates the technicalities of processing nylon 11-clay and nylon-carbon nanofiber nanocomposites with SLS. Microstructural analyses of the SLS powders and parts were conducted under SEM. Results suggest that SLS processing is possible with the new nylon 11 nanocomposites. Yet the SLS parts built have inferior properties relative to those of injection molding, suggesting that more fine tuning for the processing is required.Mechanical Engineerin

Formation of a large, complex domain of histone hyperacetylation at human 14q32.1 requires the serpin locus control region

The human serine protease inhibitor (serpin) gene cluster at 14q32.1 is a useful model system to study cell-type-specific gene expression and chromatin structure. Activation of the serpin locus can be induced in vitro by transferring human chromosome 14 from non-expressing to expressing cells. Serpin gene activation in expressing cells is correlated with locus-wide alterations in chromatin structure, including the de novo formation of 17 expression-associated DNase I-hypersensitive sites (DHSs). In this study, we investigated histone acetylation throughout the proximal serpin subcluster. We report that gene activation is correlated with high levels of histone H3 and H4 acetylation at serpin gene promoters and other regulatory regions. However, the locus is not uniformly hyperacetylated, as there are regions of hypoacetylation between genes. Furthermore, genetic tests indicate that locus-wide controls regulate both gene expression and chromatin structure. For example, deletion of a previously identified serpin locus control region (LCR) upstream of the proximal subcluster reduces both gene expression and histone acetylation throughout the ∼130 kb region. A similar down regulation phenotype is displayed by transactivator-deficient cell variants, but this phenotype can be rescued by transfecting the cells with expression cassettes encoding hepatocyte nuclear factor-1α (HNF-1α) or HNF-4. Taken together, these results suggest that histone acetylation depends on interactions between the HNF-1α/HNF-4 signaling cascade and the serpin LCR

Risk of cancer in small and diminutive colorectal polyps

The prevalence of cancer in small and diminutive polyps is relevant to “resect and discard” and CT colonography reporting recommendations. We evaluated a prospectively collected colonoscopy polyp database to identify polyps <10 mm and those with cancer or advanced histology (high-grade dysplasia or villous elements). Of 32,790 colonoscopies, 15,558 colonoscopies detected 42,630 polyps <10 mm in size. A total of 4790 lesions were excluded as they were not conventional adenomas or serrated class lesions. There were 23,524 conventional adenomas <10 mm of which 22,952 were tubular adenomas. There were 14,316 serrated class lesions of which 13,589 were hyperplastic polyps and the remainder were sessile serrated polyps. Of all conventional adenomas, 96 had high-grade dysplasia including 0.3% of adenomas ≤5 mm in size and 0.8% of adenomas 6–9 mm in size. Of all conventional adenomas, 2.1% of those ≤5 mm in size and 5.6% of those 6–9 mm in size were advanced. Among 36,107 polyps ≤5 mm in size and 6523 polyps 6–9 mm in size, there were no cancers. These results support the safety of resect and discard as well as current CT colonography reporting recommendations for small and diminutive polyps

Heat transfer of an 0.006-scale thin-skin thermocouple space shuttle model (50-0, 41-T) in the NASA-Ames Research Center 3.5-foot hypersonic wind tunnel at Mach 5.3 (IH28), volume 2

For abstract, see N76-32230

Heat transfer test of an 0.006-scale thin-skin thermocouple space shuttle model (50-0, 41-T) in the NASA-Ames Research Center 3.5-foot hypersonic wind tunnel at Mach 5.3 (IH28), volume 1

Data obtained from a heat transfer test conducted on an 0.006-scale space shuttle orbiter and external tank in the NASA-Ames Research Center 3.5-foot Hypersonic Wind Tunnel are presented. The purpose of this test was to obtain data under simulated return-to-launch-site abort conditions. Configurations tested were integrated orbiter and external tank, orbiter alone, and external tank alone at angles of attack of 0, + or - 30, + or - 60, + or - 90, and + or - 120 degrees. Runs were conducted at Mach numbers of 5.2 and 5.3 for Reynolds numbers of 1.0 and 4.0 million per foot, respectively. Heat transfer data were obtained from 75 orbiter and 75 external tank iron-constantan thermocouples

Innovative Selective Laser Sintering Rapid Manufacturing using Nanotechnology

The objective of this research is to develop an improved nylon 11 (polyamide 11) polymer with enhanced flame retardancy, thermal, and mechanical properties for selective laser sintering (SLS) rapid manufacturing (RM). A nanophase was introduced into nylon 11 via twin screw extrusion to provide improved material properties of the polymer blends. Atofina (now known as Arkema) RILSAN® nylon 11 injection molding polymer pellets was used with three types of nanoparticles: chemically modified montmorillonite (MMT) organoclays, nanosilica, and carbon nanofibers (CNF) to create nylon 11 nanocomposites. Wide angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM) were used to determine the degree of dispersion. Fifteen nylon 11 nanocomposites and control nylon 11 were fabricated by injection molding. Flammability properties (using a cone calorimeter with a radiant flux of 50 kW/m2 ) and mechanical properties such as tensile strength and modulus, flexural modulus, elongation at break were determined for the nylon 11 nanocomposites and compared with the baseline nylon 11. Based on flammability and mechanical material performance, five polymers including four nylon 11 nanocomposites and a control nylon 11 were cryogenically ground into fine powders for SLS RM. SLS specimens were fabricated for flammability, mechanical, and thermal properties characterization. Nylon 11-CNF nanocomposites exhibited the best overall properties for this study.Mechanical Engineerin

Business Students Perception Of University Library Service Quality And Satisfaction

The main purpose of this study is to examine the college students perception of library services, and to what extent the quality of library services influences students satisfaction. The findings depict the relationship between academic libraries and their users in todays digital world and identify critical factors that may sustain a viable library-user relationship on campus

Cardiovascular magnetic resonance with an MR compatible pacemaker

Abstract Magnetic resonance imaging (MRI) within FDA guidelines for the MRI-conditional pacemaker precludes placing the heart at the center of the magnet’s bore. This in effect appears to preclude cardiovascular MR. In this manuscript, we describe a protocol for cardiovascular MR of patients with a Revo pacemaker system while operating within FDA guidelines, and the first US case of cardiovascular MR in a patient with a Revo MRI-conditional pacing system despite position constraints.</p