Modifying Fragility and Collective Motion in Polymer Melts with Nanoparticles

We investigate the impact of nanoparticles (NP) on the fragility and cooperative string-like motion in a model glass-forming polymer melt by molecular dynamics simulation. The NP cause significant changes to both the fragility and the average length of string-like motion, where the effect depends on the NP-polymer interaction and the NP concentration. We interpret these changes via the Adam-Gibbs (AG) theory, assuming the strings can be identified with the "cooperatively rearranging regions" of AG. Our findings indicate fragility is primarily a measure of the temperature dependence of the cooperativity of molecular motion.Comment: To appear in Physical Review Letter

Relationships between surface and column aerosol radiative properties and air mass transport at a rural New England site

Chemical, physical, and radiative properties of surface and vertical column aerosols were measured at a rural site in southern New Hampshire from July 2000 to September 2001. The primary objective was to determine how intensive and extensive aerosol properties vary in air masses originating in different upwind regions. The data set also allows for an investigation of some of the relationships between surface and column aerosol properties at the site, and provides an estimate of direct radiative forcing by aerosols during the study period. Extensive properties (e.g., optical depth and chemical concentration) were at maximum values during times of south-southwest (S-SW) transport, while minimum values were seen during north-northeast (N-NE) transport. Certain intensive properties such as fine particle mass scattering efficiency did not vary significantly between times of transport from different source regions. Mean optical depth (wavelength = 500 nm) was 0.24 during S-SW transport, compared to 0.10 during N-NE transport. The study period average scattering efficiency for (NH4)2SO4 was 6.54 ± 0.26 m2 g−1 (± standard error) and 3.36 ± 0.49 m2 g−1 for organic carbon, while the absorption efficiency of elemental carbon was 12.85 ± 0.80 m2 g−1. Top of the atmosphere aerosol direct radiative forcing was −0.35 ± 0.83 Wm−2 (±1 standard deviation) in winter 2000–2001 and −9.06 ± 3.77 Wm−2 in summer 2001, differences that can be primarily attributed to seasonal changes in surface reflectance (high in winter, low in summer) and the relatively low values of single scatter albedo observed in winter. The annual average direct radiative forcing was −5.14 ± 4.32 Wm−2. We generally observed a moderate correlation between surface and column aerosol light extinction, suggesting that vertical column aerosol radiative properties measured by surface-based radiometers should be supplemented by boundary layer measurements of aerosol chemical, physical, and radiative properties to help understand the mechanisms contributing to global aerosol variability

Electrothermal rockets having improved heat exchangers Patent

High resistance cross flow heat exchangers for electrothermal rocket engine

Obituary: Ross McDonald Parish (1928 - 2001)

Teaching/Communication/Extension/Profession,

In the Absence of Scrutiny: Narratives of Probable Cause

This Article reports on a set of roughly thirty interviews with federal magistrate judges. The focus of the interviews was the impact of the Supreme Court case, United States v. Leon, on the behavior of magistrate judges. Leon, famously, put in place the good faith exception for faulty warrants that were obtained by the officers in good faith. The insertion of this exception diminished significantly the incentive for defendants to challenge problematic warrant grants. That effect, in turn, could have diminished the incentive for magistrate judge scrutiny of the warrants at the front end of the process. We do not find any indication of diminished scrutiny. What we do find, however, is a highly ritualized and formalistic process for the evaluation of warrants where calculations of probabilities are viewed through a legalistic rather than a pragmatic lens

The Fayet-Iliopoulos D-term and its renormalisation in the MSSM

We consider the renormalisation of the Fayet-Iliopoulos D-term in a softly-broken supersymmetric gauge theory with a non-simple gauge group containing an abelian factor, and present the associated beta-function through three loops. We also include in an appendix the result for several abelian factors. We specialise to the case of the minimal supersymmetric standard model (MSSM), and investigate the behaviour of the Fayet-Iliopoulos coupling for various boundary conditions at the unification scale. We focus particularly on the case of non-standard soft supersymmetry breaking couplings, for which the Fayet-Iliopoulos coupling evolves significantly between the unification scale and the weak scale.Comment: 18 pages, Revtex, 2 figures. Expanded version including general results for gauge groups with several abelian factors. Minor typos correcte