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.

Size-Controlled Synthesis of Nanoparticles. 2. Measurement of Extinction, Scattering, and Absorption Cross Sections

Abstract: Extinction, scattering, and absorption cross sections and efficiencies were experimentally measured for chemically clean silver nanoparticles in water for 16 different sizes ranging from 29 to 136 nm. The measured efficiencies indicate that particles interact with light 4−10 times stronger than the geometric cross section suggests. Absorption and scattering components of the plasmon resonance were separately measured across the visible spectral range. A method, termed standard subtraction, is suggested for the simple and reliable determination of particle concentrations independent of their size, shape, and aggregation state.

Evidence for General and Domain‐Specific Elements of Teacher–Child Interactions: Associations With Preschool Children's Development

Abstract: This study evaluates a model for considering domain-general and domain-specific associations between teacher-child interactions and children's development, using a bifactor analytic strategy. Among a sample of 325 early childhood classrooms there was evidence for both general elements of teacher-child interaction (responsive teaching) and domain-specific elements related to positive management and routines and cognitive facilitation. Among a diverse population of 4-year-old children (n = 1,407) responsive teaching was modestly associated with development across social and cognitive domains, whereas positive management and routines was modestly associated with increases in inhibitory control and cognitive facilitation was associated with gains in early language and literacy skills. The conceptual and methodological contributions and challenges of this approach are discussed.

Two-Stage DEA: Caveat Emptor

Abstract: This paper examines the wide-spread practice where data envelopment analysis (DEA) efficiency estimates are regressed on some environmental variables in a second-stage analysis. In the literature, only two statistical models have been proposed in which second-stage regressions are well-defined and meaningful. In the model considered by Simar and Wilson (J Prod Anal 13:49–78, 2007), truncated regression provides consistent estimation in the second stage, where as in the model proposed by Banker and Natarajan (Oper Res 56: 48–58, 2008a), ordinary least squares (OLS) provides consistent estimation. This paper examines, compares, and contrasts the very different assumptions underlying these two models, and makes clear that second-stage OLS estimation is consistent only under very peculiar and unusual assumptions on the data-generating process that limit its applicability. In addition, we show that in either case, bootstrap methods provide the only feasible means for inference in the second stage. We also comment on ad hoc specifications of second-stage regression equations that ignore the part of the data-generating process that yields data used to obtain the initial DEA estimates.

Formation Rates of Black Hole Accretion Disk Gamma-Ray Bursts

Abstract: The cosmological origin of at least an appreciable fraction of classical gamma-ray bursts (GRBs) is now supported by redshift measurements for a half-dozen faint host galaxies. Still, the nature of the central engine (or engines) that provide the burst energy remains unclear. While many models have been proposed, those currently favored are all based upon the formation of and/or rapid accretion into stellar-mass black holes. Here we discuss a variety of such scenarios and estimate the probability of each. Population synthesis calculations are carried out using a Monte Carlo approach in which the many uncertain parameters intrinsic to such calculations are varied. We estimate the event rate for each class of model as well as the propagation distances for those having significant delay between formation and burst production, i.e., double neutron star (DNS) mergers and black hole-neutron star (BH/NS) mergers. One conclusion is a 1-2 order of magnitude decrease in the rate of DNS and BH/NS mergers compared to that previously calculated using invalid assumptions about common envelope evolution. Other major uncertainties in the event rates and propagation distances include the history of star formation in the universe, the masses of the galaxies in which merging compact objects are born, and the radii of the hydrogen-stripped cores of massive stars. For reasonable assumptions regarding each, we calculate a daily event rate in the universe for (1) merging neutron stars: ~100 day-1; (2) neutron star-black hole mergers: ~450 day-1; (3) collapsars: ~104 day-1; (4) helium star black hole mergers: ~1000 day-1; and (5) white dwarf-black hole mergers: ~20 day-1. The range of uncertainty in these numbers, however, is very large, typically 2-3 orders of magnitude. These rates must additionally be multiplied by any relevant beaming factor (fΩ < 1) and sampling fraction (if the entire universal set of models is not being observed). Depending upon the mass of the host galaxy, one-half of the DNS mergers will happen within 60 kpc (for a galaxy with a mass comparable to that of the Milky Way) to 5 Mpc (for a galaxy with negligible mass) from the Galactic center. The same numbers characterize BH/NS mergers. Because of the delay time, neutron star and black hole mergers will happen at a redshift 0.5-0.8 times that of the other classes of models. Information is still lacking regarding the hosts of short, hard bursts, but we suggest that they are due to DNS and BH/NS mergers and thus will ultimately be determined to lie outside of galaxies and at a closer mean distance than long complex bursts (which we attribute to collapsars). In the absence of a galactic site, the distance to these bursts may be difficult to determine.

Emotional Exhaustion in a High Stress Organization

Abstract: This study develops the concept of emotional exhaustion, an extremely affective and chronic type of work-related strain. Sources of emotional exhaustion were investigated in a police organization t...