Leadership is in the eye of the beholder

Introduction to teaching & learning: Social responsibility in the management classroom

Pensions seminar: Buy-out or cop-out?

Energy Losses in Cross Junctions

Energy losses occurring in pipe junctions have been studied for many years. Head loss coefficients (K) are commonly used to characterize losses across elbows, tees, crosses, valves, and other pipe fittings. When accurate values of K are used, the flow rate and corresponding total head at any location in a pipe network can be calculated. While K is well defined for most pipe junctions and fittings, the literature has limited documentations of K for crosses. This study was commissioned to determine K for a wide range of flow combinations in a pipe cross with equal diameter pipes and varied flow combinations. This study provides and innovatively presents over 1,000 experimental values of K for designing and analyzing equal diameter pipe crosses.

Thermal links for the implementation of an optical refrigerator

Optical refrigeration has been demonstrated by several groups of researchers, but the cooling elements have not been thermally linked to realistic heat loads in ways that achieve the desired temperatures. The ideal thermal link will have minimal surface area, provide complete optical isolation for the load, and possess high thermal conductivity. We have designed thermal links that minimize the absorption of fluoresced photons by the heat load using multiple mirrors and geometric shapes including a hemisphere, a kinked waveguide, and a tapered waveguide. While total link performance is dependent on additional factors, we have observed net transmission of photons with the tapered link as low as 0.04%. Our optical tests have been performed with a surrogate source that operates at 625 nm and mimics the angular distribution of light emitted from the cooling element of the Los Alamos solid state optical refrigerator. We have confirmed the optical performance of our various link geometries with computer simulati...

Spacecraft Materials in the Space Flight Environment: International Space Station—May 2002 to May 2008

The performance of ISS spacecraft materials and systems on prolonged exposure to the low‐Earth orbit (LEO) space flight are reported in this paper. In‐flight data, flight crew observations, and the results of ground‐based test and analysis directly supporting programmatic and operational decision‐making are described. The space flight environments definitions (both natural and induced) used for ISS design, material selection, and verification testing are shown, in most cases, to be more severe than the actual flight environment accounting, in part, for the outstanding performance of ISS as a long mission duration spacecraft. No significant ISS material or system failures have been attributed to spacecraft‐environments interactions. Nonetheless, ISS materials and systems performance data is contributing to our understanding of spacecraft material interactions with the spaceflight environment so as to reduce cost and risk for future spaceflight projects and programs.

A membrane basis for bacterial identification and discrimination using laser-induced breakdown spectroscopy

Nanosecond single-pulse laser-induced breakdown spectroscopy (LIBS) has been used to discriminate between two different genera of Gram-negative bacteria and between several strains of the Escherichia coli bacterium based on the relative concentration of trace inorganic elements in the bacteria. Of particular importance in all such studies to date has been the role of divalent cations, specifically Ca2+ and Mg2+, which are present in the membranes of Gram-negative bacteria and act to aggregate the highly polar lipopolysaccharide molecules. We have demonstrated that the source of emission from Ca and Mg atoms observed in LIBS plasmas from bacteria is at least partially located at the outer membrane by intentionally altering membrane biochemistry and correlating these changes with the observed changes in the LIBS spectra. The definitive assignment of some fraction of the LIBS emission to the outer membrane composition establishes a potential serological, or surface-antigen, basis for the laser-based identifi...

Comparison of the MODIS Collection 5 Multilayer Cloud Detection Product with CALIPSO

CALIPSO, launched in June 2006, provides global active remote sensing measurements of clouds and aerosols that can be used for validation of a variety of passive imager retrievals derived from instruments flying on the Aqua spacecraft and other A‐Train platforms. The most recent processing effort for the MODIS Atmosphere Team, referred to as the Collection 5 scream, includes a research‐level multilayer cloud detection algorithm that uses both thermodynamic phase information derived from a combination of solar and thermal emission bands to discriminate layers of different phases, as well as true layer separation discrimination using a moderately absorbing water vapor band. The multilayer detection algorithm is designed to provide a means of assessing the applicability of 1D cloud models used in the MODIS cloud optical and microphysical product retrieval, which are generated at a 1 km resolution. Using pixel‐level collocations of MODIS Aqua, CALIOP, we investigate the global performance of multilayer cloud ...

Temperature Dependence of Radiation Induced Conductivity in Insulators

This study measures Radiation Induced Conductivity (RIC) of Low Density Polyethylene (LDPE) over temperatures ranging from ∼110 K to ∼350 K. RIC occurs when incident ionizing radiation deposits energy and excites electrons into the conduction band of insulators. Conductivity was measured when a voltage was applied across vacuum‐baked, thin film LDPE polymer samples in a parallel plate geometry. RIC was calculated as the difference in sample conductivity under no incident radiation and under an incident ∼4 MeV electron beam at low incident fluxes of 10−4–10−1 Gr/sec. The steady‐state RIC was found to agree well with the standard power law relation, σRIC = kRIC⋅DΔ between conductivity, σ and adsorbed dose rate, D. Both the proportionality constant, kRIC, and the power, δ, were found to be temperature dependant above ∼250 K, with behavior consistent with photoconductivity models developed for localized trap states in disordered semiconductors. Below ∼250 K, kRIC and Δ exhibited little change. The observed ...

Photoelectrochemical etching of p-type GaN heterostructures