The Influence of Natural Convection and Radiation Heat Transfer on Sintering of Polycarbonate Powders

The influence ofsurface radiation and natural convection on sintering of polycarbonate powders processed under non-isothermal conditions is investigated. These modes of heat transfer affect local powder temperatures and thus local sintering rates which in turn influence part growth (uncontrolled sintering). This paper presents a 2-dimensional sintering simulation of powder whose free surface exchanges energy with the surrounding enclosure surfaces. Modeling is accomplished using a commercial finite element code (FIDAP) in conjunction with a model for viscous sintering.Mechanical Engineerin

Reliability of Transcriptional Cycles and the Yeast Cell-Cycle Oscillator

A recently published transcriptional oscillator associated with the yeast cell cycle provides clues and raises questions about the mechanisms underlying autonomous cyclic processes in cells. Unlike other biological and synthetic oscillatory networks in the literature, this one does not seem to rely on a constitutive signal or positive auto-regulation, but rather to operate through stable transmission of a pulse on a slow positive feedback loop that determines its period. We construct a continuous-time Boolean model of this network, which permits the modeling of noise through small fluctuations in the timing of events, and show that it can sustain stable oscillations. Analysis of simpler network models shows how a few building blocks can be arranged to provide stability against fluctuations. Our findings suggest that the transcriptional oscillator in yeast belongs to a new class of biological oscillators

Being Mum’s Confidant, a Boon or Bane? Examining Gender Differences in the Association of Maternal Disclosure with Adolescents’ Depressive Feelings

This article reports on a longitudinal study investigating gender differences in the association between maternal disclosure and adolescents’ depressive symptoms. Little research has examined the relationship of parental disclosure to adolescents’ depressive symptoms and research on sex differences is particularly lacking. In a sample of 428 families with a mean age of 13.36 (52% female) of the target adolescents, maternal and children’s disclosure and depressive symptoms were assessed twice with an interval of 4 years. Controlling for the quality of the parent–child relationship and levels of maternal depressive symptoms, the analyses revealed an interaction effect for child’s gender, moderating the effect of maternal disclosure on adolescents’ depressive symptoms. Higher levels of maternal disclosure were accompanied by lower levels of depressive symptoms in girls and higher levels of depressive symptoms in boys. Gender differences in socialization, communication, individuation and social networks might explain why daughters and sons are differently affected by maternal disclosure

Isolation in Globalizing Academic Fields: A Collaborative Autoethnography of Early Career Researchers

This study examines academic isolation – an involuntary perceived separation from the academic field to which one aspires to belong, associated with a perceived lack of agency in terms of one’s engagement with the field – as a key challenge for researchers in increasingly globalized academic careers. While prior research describes early career researchers’ isolation in their institutions, we theorize early career researchers’ isolation in their academic fields and reveal how they attempt to mitigate isolation to improve their career prospects. Using a collaborative autoethnographic approach, we generate and analyze a dataset focused on the experiences of ten early career researchers in a globalizing business academic field known as Consumer Culture Theory. We identify bricolage practices, polycentric governance practices, and integration mechanisms that work to enhance early career researchers’ perceptions of agency and consequently mitigate their academic isolation. Our findings extend discussions on isolation and its role in new academic careers. Early career researchers, in particular, can benefit from a deeper understanding of practices that can enable them to mitigate isolation and reclaim agency as they engage with global academic fields

High Resolution X-Ray Spectroscopy with a Microcalorimeter

Energy-dispersive spectrometry (EDS) is often the preferred choice for X-ray microanalysis, but there are still many disadvantages associated with EDS, the most significant of which is the relatively poor energy resolution, which limits detection sensitivity and the ability to distinguish among closely spaced spectral features, limiting even qualitative analysis. A new type of EDS detector that operates on the principle of microcalorimetry has the potential to eliminate this shortcoming, reaching resolutions an order of magnitude better. The detector consists of an absorber in thermal contact with a transition edge sensor (TES). An X-ray from the specimen hits the absorber and manifests itself as a change in temperature. Because the system is kept at 80 mK, the heat capacity is low and the temperature spike is observable. The TES responds to the increase in temperature by transitioning from its superconducting to its normal conducting state, thus sharply raising the overall resistance of the circuit. The circuit is kept at a constant voltage, so the increase in resistance is manifested as a decrease in current flow. This decrease in current is measured by a superconducting quantum interference device (SQUID), and by integrating the current over time, the energy of the incident X-ray is determined. The prototype microcalorimeter was developed by NIST, and this technology is now available commercially through a partnership between Vericold Technologies and EDAX International. ORNL has received the first of these commercial microcalorimeters in the United States. The absorber in this detector is gold, and the TES consists of a gold-iridium bilayer. It is designed to offer spectral resolution of 10-15 eV at a count rate of ~150 s-1. The goal of this project was to analyze and document the performance of the detector, with particular attention given to the effects of an X-ray optic used to improve collection efficiency, the multiple window system and any other sources of spectral artifacts. It was found that the detector is capable of distinguishing many Lα and Lβ spectral lines, with a resolution between 13 and 17 eV. It was also observed that the background has an unusual shape, and this is largely being attributed to the variable transmission coefficient of the X-ray optic. These preliminary results suggest that the microcalorimeter has a high potential for use in microanalysis, but more work to quantify its capabilities must still be done

Protein Kinase C BetaII Peptide Inhibitor Exerts Cardioprotective Effects in Rat Cardiac Ischemia/Reperfusion Injury

Ischemia followed by reperfusion (I/R) in the presence of polymorphonuclear leukocytes (PMNs) results in a marked cardiac contractile dysfunction. A cell-permeable protein kinase C (PKC) betaII peptide inhibitor was used to test the hypothesis that PKC betaII inhibition could attenuate PMN-induced cardiac dysfunction by suppression of superoxide production from PMNs and increase NO release from vascular endothelium. The effects of the PKC betaII peptide inhibitor were examined in isolated ischemic (20 min) and reperfused (45 min) rat hearts with PMNs. The PKC betaII inhibitor (10 microM; n = 7) significantly attenuated PMN-induced cardiac dysfunction compared with I/R hearts (n = 9) receiving PMNs alone in left ventricular developed pressure (LVDP) and the maximal rate of LVDP (+dP/dt(max)) cardiac function indices (p \u3c 0.01). The PKC betaII inhibitor at 10 microM significantly increased endothelial NO release from a basal value of 1.85 +/- 0.18 pmol NO/mg tissue to 3.49 +/- 0.62 pmol NO/mg tissue from rat aorta. It also significantly inhibited superoxide release (i.e., absorbance) from N-formyl-L-methionyl-L-leucyl-L-phenylalanine-stimulated rat PMNs from 0.13 +/- 0.01 to 0.02 +/- 0.004 (p \u3c 0.01) at 10 microM. Histological analysis of the left ventricle of representative rat hearts from each group showed that the PKC betaII peptide inhibitor-treated hearts experienced a marked reduction in PMN vascular adherence and infiltration into the postreperfused cardiac tissue compared with I/R + PMN hearts (p \u3c 0.01). These results suggest that the PKC betaII peptide inhibitor attenuates PMN-induced post-I/R cardiac contractile dysfunction by increasing endothelial NO release and by inhibiting superoxide release from PMNs

Protein kinase C ßII peptide inhibitor exerts cardioprotective effects in rat cardiac ischemia/reperfusion injury

Ischemia followed by reperfusion (I/R) in the presence of polymorphonuclear leukocytes (PMNs) results in a marked cardiac contractile dysfunction. A cell-permeable protein kinase C (PKC) ßII peptide inhibitor was used to test the hypothesis that PKC ßII inhibition could attenuate PMN-induced cardiac dysfunction by suppression of superoxide production from PMNs and increase NO release from vascular endothelium. The effects of the PKC ßII peptide inhibitor were examined in isolated ischemic (20 min) and reperfused (45 min) rat hearts with PMNs. The PKC ßII inhibitor (10 µM; n = 7) significantly attenuated PMN-induced cardiac dysfunction compared with I/R hearts (n = 9) receiving PMNs alone in left ventricular developed pressure (LVDP) and the maximal rate of LVDP (+dP/dtmax) cardiac function indices (p \u3c 0.01). The PKC ßII inhibitor at 10 µM significantly increased endothelial NO release from a basal value of 1.85 ± 0.18 pmol NO/mg tissue to 3.49 ± 0.62 pmol NO/mg tissue from rat aorta. It also significantly inhibited superoxide release (i.e., absorbance) from N-formyl-L-methionyl-L-leucyl-L-phenylalanine-stimulated rat PMNs from 0.13 ± 0.01 to 0.02 ± 0.004 (p \u3c 0.01) at 10 µM. Histological analysis of the left ventricle of representative rat hearts from each group showed that the PKC ßII peptide inhibitor-treated hearts experienced a marked reduction in PMN vascular adherence and infiltration into the postreperfused cardiac tissue compared with I/R + PMN hearts (p \u3c 0.01). These results suggest that the PKC ßII peptide inhibitor attenuates PMN-induced post-I/R cardiac contractile dysfunction by increasing endothelial NO release and by inhibiting superoxide release from PMNs