Clemson University

About: Clemson University is a education organization based out in Clemson, South Carolina, United States. It is known for research contribution in the topics: Population & Control theory. The organization has 20556 authors who have published 42518 publications receiving 1170779 citations. The organization is also known as: Clemson Agricultural College of South Carolina.

Orientation of ECM protein deposition, fibroblast cytoskeleton, and attachment complex components on silicone microgrooved surfaces.

Abstract: The microfilaments and vinculin-containing attachment complexes of rat dermal fibroblasts (RDF) incubated on microtextured surfaces were investigated with confocal laser scanning microscopy (CLSM) and digital image analysis (DIA). In addition, depositions of bovine and endogenous fibronectin and vitronectin were studied. Smooth and microtextured silicone substrata were produced that possessed parallel surface grooves with a groove and ridge width of 2.0, 5.0, and 10.0 μm. The groove depth was approximately 0.5 μm. CLSM and DIA make it possible to visualize and analyze intracellular and extracellular proteins and the underlying surface simultaneously. It was observed that the microfilaments and vinculin aggregates of the RDFs on the 2.0 μm grooved substrata were oriented along the surface grooves after 1, 3, 5, and 7 days of incubation while these proteins were significantly less oriented on the 5.0 and 10.0 μm grooved surfaces. Vinculin was located mainly on the surface ridges on all textured surfaces. In contrast, bovine and endogenous fibronectin and vitronectin were oriented along the surface grooves on all textured surfaces. These proteins did not seem to be hindered by the surface grooves since many groove-spanning filaments were found on all the microgrooved surfaces. In conclusion, it can be said that microtextured surfaces influence the orientation of intracellular and extracellular proteins. Although results corroborate three earlier published hypotheses, they do not justify a specific choice of any one of these hypotheses. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 291–300, 1998.

The Physics of Proto-Neutron Star Winds: Implications for r-Process Nucleosynthesis

Abstract: We solve the general-relativistic steady-state eigenvalue problem of neutrino-driven proto-neutron star winds, which immediately follow core-collapse supernova explosions. We provide velocity, density, temperature, and composition profiles and explore the systematics and structures generic to such a wind for a variety of proto-neutron star characteristics. Furthermore, we derive the entropy, dynamical timescale, and neutron-to-seed ratio in the general relativistic framework essential in assessing this site as a candidate for r-process nucleosynthesis. Generally, we find that for a given mass outflow rate (), the dynamical timescale of the wind is significantly shorter than previously thought. We argue against the existence or viability of a high entropy (300 per kB per baryon), long dynamical timescale r-process epoch. In support of this conclusion, we model the proto-neutron star cooling phase, calculate nucleosynthetic yields in our steady-state profiles, and estimate the integrated mass loss. We find that transonic winds enter a high-entropy phase only with very low (1 × 10-9 M☉ s-1) and extremely long dynamical timescale (τρ 0.5 s). Our results support the possible existence of an early r-process epoch at modest entropy (~150) and very short dynamical timescale, consistent in our calculations with a very massive or very compact proto-neutron star that contracts rapidly after the preceding supernova. We explore possible modifications to our models, which might yield significant r-process nucleosynthesis generically. Finally, we speculate on the effect of fallback and shocks on both the wind physics and nucleosynthesis. We find that a termination or reverse shock in the wind, but exterior to the wind sonic point, may have important nucleosynthetic consequences. The potential for the r-process in proto-neutron star winds remains an open question.

r-process nucleosynthesis in the high-entropy supernova bubble

Abstract: We show that the high-temperature, high-entropy evacuated region outside the recent neutron star in a core-collapse supernova may be an ideal r-process site. In this high-entropy environment it is possible that most nucleons are in the form of free neutrons or bound into alpha particles. Thus, there can be many neutrons per seed nucleus even though the material is not particularly neutron rich. The predicted amount of r-process material ejected per event from this environment agrees well with that required by simple galactic evolution arguments. When averaged over regions of different neutron excess in the supernova ejecta, the calculated r-process abundance curve can give a good representation of the solar-system r-process abundances as long as the entropy per baryon is sufficiently high. Neutrino irradiation may aid in smoothing the final abundance distribution.

Self-Control and Crime/Deviance: Cognitive vs. Behavioral Measures

Abstract: Using survey data, various measures of self-control, based respectively on cognitive and behavioral indicators, are compared in their ability to predict eight measures of crime/deviance. The results show that either type of measure produces supportive evidence for the theory, and the behavioral measures provide no better prediction than do the cognitive measures. Unlike cognitive type indicators, and contrary to the implications of the theory, different types of crime-analogous, imprudent behaviors are not highly interrelated, making it difficult to develop reliable behavioral measures. These results suggest that general support for self-control theory would likely not be any greater if all researchers had used behaviorally based measures, as recommended by the authors of the theory. Improving the level of prediction to the point where self-control could claim to be the master variable, as envisioned by its proponents, does not seem to rest on a shift to behaviorally based measures. Instead, improvements in the theory itself, particularly the incorporation of contingencies, appears to offer more promise.

Temperature dependence of radial breathing mode Raman frequency of single-walled carbon nanotubes

Abstract: Recent high-temperature studies of Raman-active modes in single-walled carbon nanotube (SWNT) bundles report a softening of the radial and tangential band frequencies with increasing sample temperature. A few speculations have been proposed in the past to explain the origin of these frequency downshifts. In the present study, based on experimental data and the results of molecular dynamics simulations, we estimate the contributions from three factors that may be responsible for the observed temperature dependence of the radial breathing mode frequency $[{\ensuremath{\omega}}_{\mathrm{RBM}}(T)].$ These factors include thermal expansion of individual SWNTs in the radial direction, softening of the C-C (intratubular) bonds, and softening of the van der Waals intertubular interactions in SWNT bundles. Based on our analysis, we find that the first factor plays a minor role due to the very small value of the radial thermal expansion coefficient of SWNTs. On the contrary, the temperature-induced softening of the intra- and intertubular bonds contributes significantly to the temperature-dependent shift of ${\ensuremath{\omega}}_{\mathrm{RBM}}(T).$ For nanotubes with diameters $(d)g~1.34\mathrm{nm},$ the contribution due to the radial thermal expansion is \ensuremath{\leqslant}4% over the temperature range used in this study. Interestingly, this contribution increases to \ensuremath{\geqslant}10% in the case of nanotubes having $dl~0.89\mathrm{nm}$ due to the relatively larger curvature of these nanotubes. The contributions from the softening of the intra- and intertubular bonds are approximately equal. These two factors together contribute a total of about \ensuremath{\sim}95% and 90%, respectively, for SWNTs having $dg~1.34\mathrm{nm}$ and \ensuremath{\leqslant}0.89 nm.