Optimization Studies for the Gas Atomization and Selective Laser Melting Processes of Al10SiMg alloy

Selective laser melting (SLM) is an additive manufacturing technology that can fabricate complex engineering components using a scanning laser beam to melt consecutive layers of powders with characteristics that significantly influence material properties. Present work investigates both the gas atomization and SLM processes for the Al10SiMg alloy with a focus on establishing the relationships among atomization parameters, powder characteristics, SLM parameters and materials properties. Al10SiMg alloy powders (Al-10wt.%Si-0.5wt.%Mg) were batch-produced through gas atomization by systematically varying the melt flow rate (0.012 - 0.037 kg/s), gas pressure (1.4 - 3.1 MPa), and melt temperature (850C -1000C). The highest yield of 80 wt.% was accomplished for powders with particle size smaller than 75um, considered suitable for SLM, utilizing gas pressure of 2.7 MPa, melt flow rate of 0.020 kg/s, and melt temperature of 950C. Investigations for the SLM process were carried out to identify the optimal particle size distribution (PSD) and critical reuse limit for Al10SiMg powders. Five distribution ranges ( \u3c 45µm, 20µm \u3c x \u3c 63µm, \u3c 75µm, \u3c 106µm, 75µm \u3c x \u3c 106µm), and five sets of recycled powder (new, one, five, ten and over twenty uses) were used to build SLM samples for metallographic and mechanical characterization. Archimedes\u27 method, optical, scanning electron microscopy and mechanical testing in tension were employed to assess the influence of powder feedstock on part density, microstructure and mechanical properties, respectively. All PSDs examined in this study produced samples with over 99% relative density, but samples built with size range of 75µm \u3c x \u3c 106µm yielded the highest tensile and yield strengths of 448 MPa and 265 MPa, respectively. Results from recycling demonstrated that Al10SiMg alloy powders can be reused in SLM without sacrificing quasi-static tensile properties

Knee Joint Peri-articular Hardware Sawbones Study

Study of discovering the effect of instrumentation after open reduction internal fixation on knee contact pressures was conducted with sawbones. Four sawbones were utilized, although only two of those, #3172 and #3181, were analyzed for this study because the other two lacked data to compare with the control. For sample #3172, uniaxial loading with average body weight of women and 2.5 times the body weight was done in two conditions: before fixation and with fixation. The process was repeated with sample #3181, which also employed the two types of loading to account for the load variability on knee while walking. In comparison to sample #3172, additional measurements were taken for sample #3181 after removing the plate, to examine if the contact pressure restored its value after the removal. Peak cartilage pressures and the histograms in different conditions were compared to observe the change in pressure with changing conditions. The results of sample #3172 were capricious and ambiguous to conclude whether the fixation had an impact on the contact pressure. Nevertheless, comparison of the pressure of sample #3181 at initial condition with that after the fixation showed a clear increase in contact pressure. With body weight force, the maximum pressure of medial pressure increased from 2.4 MPa to 3.48 MPa. Also, an extra increase in pressure after removal of the plate was noted, which was not as expected. With body weight force, the maximum contact pressure increased from 3.48 MPa to 4.03 MPa. This shows that instrumentation of hardware increases stress on the knee, and retention of hardware does not restore back the pressure. Some sources of error include damage in the sensors, inconsistent location of the sensors, and discrepancy in contact surfaces between the condyles during instrumentation

Inae Sharon Lee, Violin; Junsoo Park, Violin

Sonata for Violin and Piano in D minor, Op. 75 / Camille Saint Saens; Por Una Cabeza / Carlos Garde

Inae Sharon Lee, Violin; Junsoo Park, Violin

Sonata for Violin and Piano in A major, Op. 13 / Gabriel Faure; Histoire du Tango for Violin and Guitar / Astor Piazzolla; Sonata for Two Violins in C Major, Op. 56 / Sergei Prokofie

Elastic theory of unconstrained non-Euclidean plates

Non-Euclidean plates are a subset of the class of elastic bodies having no stress-free configuration. Such bodies exhibit residual stress when relaxed from all external constraints, and may assume complicated equilibrium shapes even in the absence of external forces. In this work we present a mathematical framework for such bodies in terms of a covariant theory of linear elasticity, valid for large displacements. We propose the concept of non-Euclidean plates to approximate many naturally formed thin elastic structures. We derive a thin plate theory, which is a generalization of existing linear plate theories, valid for large displacements but small strains, and arbitrary intrinsic geometry. We study a particular example of a hemispherical plate. We show the occurrence of a spontaneous buckling transition from a stretching dominated configuration to bending dominated configurations, under variation of the plate thickness

Measurement error affecting web- and paper-based dietary assessment instruments: Insights from the Multi-Cohort Eating and Activity Study for Understanding Reporting Error

Few biomarker-based validation studies have examined error in online self-report dietary assessment instruments, and food records (FRs) have been considered less than food frequency questionnaires (FFQs) and 24-hour recalls (24HRs). We investigated measurement error in online and paper-based FFQs, online 24HRs, and paper-based FRs in 3 samples drawn primarily from 3 cohorts, comprising 1,393 women and 1,455 men aged 45-86 years. Data collection occurred from January 2011 to October 2013. Attenuation factors and correlation coefficients between reported and true usual intake for energy, protein, sodium, potassium, and respective densities were estimated using recovery biomarkers. Across studies, average attenuation factors for energy were 0.07, 0.07, and 0.19 for a single FFQ, 24HR, and FR, respectively. Correlation coefficients for energy were 0.24, 0.23, and 0.40, respectively. Excluding energy, the average attenuation factors across nutrients and studies were 0.22 for a single FFQ, 0.22 for a single 24HR, and 0.51 for a single FR. Corresponding correlation coefficients were 0.31, 0.34, and 0.53, respectively. For densities (nutrient expressed relative to energy), the average attenuation factors across studies were 0.37, 0.17, and 0.50, respectively. The findings support prior research suggesting different instruments have unique strengths that should be leveraged in epidemiologic research

The Properties of Type Ia Supernova Host Galaxies from the Sloan Digital Sky Survey

We investigate the properties and environments of Type Ia Supernova (SN Ia) host galaxies in the Stripe 82 of the Sloan Digital Sky Survey-II Supernova Survey centered on the celestial equator. Host galaxies are defined as the galaxy nearest to the supernova (SN) in terms of angular distance whose velocity difference from the SN is less than 1000 km s^{-1}. Eighty seven SN Ia host galaxies are selected from the SDSS Main galaxy sample with the apparent r-band magnitude m_r < 17.77, and compared with the SDSS Main galaxies. The SN Ia rates for early and late-type galaxies are 0.81 +- 0.19 SN (100yr)^{-1} and 0.99 +- 0.21 SN (100yr)^{-1}, respectively. We find that the host galaxies have a color distribution consistent with that of the Main galaxies, regardless of their morphology. However, host galaxies are on average brighter than the Main galaxies by ~ 0.3 mag over the range of -18.3 > M_r > -21.3. But the brighter ends of their luminosity distributions are similar. The distribution of the distance to the nearest neighbor galaxy shows that SNe Ia are more likely to occur in isolated galaxies without close neighbors. We also find that the SN Ia host galaxies are preferentially located in a region close to massive galaxy clusters compared to the Main galaxies.Comment: 10 pages, 8 figures, accepted for publication on Ap

p21 is decreased in polycystic kidney disease and leads to increased epithelial cell cycle progression: roscovitine augments p21 levels.

BackgroundAutosomal dominant polycystic kidney disease (ADPKD) is a common genetic disease with few treatment options other than renal replacement therapy. p21, a cyclin kinase inhibitor which has pleiotropic effects on the cell cycle, in many cases acts to suppress cell cycle progression and to prevent apoptosis. Because defects in cell cycle arrest and apoptosis of renal tubular epithelial cells occur in PKD, and in light of earlier reports that polycystin-1 upregulates p21 and that the cyclin-dependent kinase inhibitor roscovitine arrests progression in a mouse model, we asked whether (1) p21 deficiency might underlie ADPKD and (2) the mechanism of the salutary roscovitine effect on PKD involves p21.Methodsp21 levels in human and animal tissue samples as well as cell lines were examined by immunoblotting and/or immunohistochemisty. Apoptosis was assessed by PARP cleavage. p21 expression was attenuated in a renal tubular epithelial cell line by antisense methods, and proliferation in response to p21 attenuation and to roscovitine was assessed by the MTT assay.ResultsWe show that p21 is decreased in human as well as a non-transgenic rat model of ADPKD. In addition, hepatocyte growth factor, which induces transition from a cystic to a tubular phenotype, increases p21 levels. Furthermore, attenuation of p21 results in augmentation of cell cycle transit in vitro. Thus, levels of p21 are inversely correlated with renal tubular epithelial cell proliferation. Roscovitine, which has been shown to arrest progression in a murine model of PKD, increases p21 levels and decreases renal tubular epithelial cell proliferation, with no affect on apoptosis.ConclusionThe novelty of our study is the demonstration in vivo in humans and rat models of a decrement of p21 in cystic kidneys as compared to non-cystic kidneys. Validation of a potential pathogenetic model of increased cyst formation due to enhanced epithelial proliferation and apoptosis mediated by p21 suggests a mechanism for the salutary effect of roscovitine in ADPKD and supports further investigation of p21 as a target for future therapy