Arizona’s Rising STEM Occupational Demands and Declining Participation in the Scientific Workforce: An Examination of Attitudes among African Americans toward STEM College Majors and Careers

According to the Bureau of Labor Statistics (2008), science, technology, engineering, and math (STEM) occupations constitute a growing sector of Arizona’s economy. However, the number of African Americans earning degrees related to these occupations has not kept pace with this growth. Increasing the participation of African Americans in STEM education fields and subsequent related occupations in Arizona is vital to growing and maintaining the state’s economic stature. This objective is made even more compelling given that each year, from 2008– 2018, there are 3,671 projected job openings in STEM fields in Arizona. This study explores the extent to which the attitudes held by African Americans in Arizona toward STEM related majors and careers influence their likelihood of joining the state’s scientific workforce. Our analyses reveal the importance of career consideration, confidence in one’s ability to be successful in a STEM related field, and family support of the pursuit of STEM education and careers.Educatio

A comparison of spectrophotometric and denuder based approaches for the determination of gaseous molecular iodine

The presence of molecular iodine in the atmosphere is thought to have implications for both climate and human nutritional health, but measurement of the gas at low concentrations requires technically demanding techniques that are not widely accessible. Here, amylose coated denuder tubes and solvent traps coupled with spectrophotometric detection are evaluated and compared as relatively cheap and straightforward methods to measure gaseous molecular iodine at environmentally relevant concentrations. Denuder tubes were found to give unacceptably low and highly variable recoveries of molecular iodine from a test gas source, with values ranging from 1 to 62%. Blank concentrations were also high, being equivalent to a gas phase concentration of 5 pptv under typical operating conditions. Ethanol and hexane solvent traps gave much better performance. Optimisation of the hexane solvent trap method gave 100% recovery and an atmospheric limit of detection of 70 pptv, which is within the range of concentrations observed in the coastal marine atmosphere

Molecular transport junctions: Current from electronic excitations in the leads

Using a model comprising a 2-level bridge connecting free electron reservoirs we show that coupling of a molecular bridge to electron-hole excitations in the leads can markedly effect the source-drain current through a molecular junction.In some cases, e.g. molecules that exhibit strong charge transfer transitions, the contribution from electron-hole excitations can exceed the Landauer elastic current and dominate the observed conduction.Comment: 4 pages, 2 figures, submitted to PR

Casimir Force between a Dielectric Sphere and a Wall: A Model for Amplification of Vacuum Fluctuations

The interaction between a polarizable particle and a reflecting wall is examined. A macroscopic approach is adopted in which the averaged force is computed from the Maxwell stress tensor. The particular case of a perfectly reflecting wall and a sphere with a dielectric function given by the Drude model is examined in detail. It is found that the force can be expressed as the sum of a monotonically decaying function of position and of an oscillatory piece. At large separations, the oscillatory piece is the dominant contribution, and is much larger than the Casimir-Polder interaction that arises in the limit that the sphere is a perfect conductor. It is argued that this enhancement of the force can be interpreted in terms of the frequency spectrum of vacuum fluctuations. In the limit of a perfectly conducting sphere, there are cancellations between different parts of the spectrum which no longer occur as completely in the case of a sphere with frequency dependent polarizability. Estimates of the magnitude of the oscillatory component of the force suggest that it may be large enough to be observable.Comment: 18pp, LaTex, 7 figures, uses epsf. Several minor errors corrected, additional comments added in the final two sections, and references update

Measuring the quantum efficiency of single radiating dipoles using a scanning mirror

Using scanning probe techniques, we show the controlled manipulation of the radiation from single dipoles. In one experiment we study the modification of the fluorescence lifetime of a single molecular dipole in front of a movable silver mirror. A second experiment demonstrates the changing plasmon spectrum of a gold nanoparticle in front of a dielectric mirror. Comparison of our data with theoretical models allows determination of the quantum efficiency of each radiating dipole.Comment: 4 pages, 4 figure

GEM-AQ, an on-line global multiscale chemical weather system: model description and evaluation of gas phase chemistry processes

International audienceTropospheric chemistry and air quality processes were implemented on-line in the Global Environmental Multiscale model. The integrated model, GEM-AQ, has been developed as a platform to investigate chemical weather at scales from global to urban. The model was exercised for five years (2001?2005) to evaluate its ability to simulate seasonal variations and regional distributions of trace gases such as ozone, nitrogen dioxide and carbon monoxide on the global scale. The model results presented are compared with observations from satellites, aircraft measurement campaigns and balloon sondes

Analysis of satellite-derived Arctic tropospheric BrO columns in conjunction with aircraft measurements during ARCTAS and ARCPAC

We derive tropospheric column BrO during the ARCTAS and ARCPAC field campaigns in spring 2008 using retrievals of total column BrO from the satellite UV nadir sensors OMI and GOME-2 using a radiative transfer model and stratospheric column BrO from a photochemical simulation. We conduct a comprehensive comparison of satellite-derived tropospheric BrO column to aircraft in-situ observations of BrO and related species. The aircraft profiles reveal that tropospheric BrO, when present during April 2008, was distributed over a broad range of altitudes rather than being confined to the planetary boundary layer (PBL). Perturbations to the total column resulting from tropospheric BrO are the same magnitude as perturbations due to longitudinal variations in the stratospheric component, so proper accounting of the stratospheric signal is essential for accurate determination of satellite-derived tropospheric BrO. We find reasonably good agreement between satellite-derived tropospheric BrO and columns found using aircraft in-situ BrO profiles, particularly when satellite radiances were obtained over bright surfaces (albedo \u3e0.7), for solar zenith angl

Anisotropic flow in 4.2A GeV/c C+Ta collisions

Anisotropic flow of protons and negative pions in 4.2A GeV/c C+Ta collisions is studied using the Fourier analysis of azimuthal distributions. The protons exhibit pronounced directed flow. Directed flow of pions is positive in the entire rapidity interval and indicates that the pions are preferentially emitted in the reaction plane from the target to the projectile. The elliptic flow of protons and negative pions is close to zero. Comparison with the quark-gluon-string model (QGSM) and relativistic transport model (ART 1.0) show that they both yield a flow signature similar to the experimental data.Comment: 4 pages, 3 figures, Accepted for publication in Phys. Rev.

Dissipative effects on finite-Larmor-radius modified magnetohydrodynamic ballooning modes

Finite-ion-Larmor-radius (FLR) effects provide a band of additional stability for values of ..beta..(exactly equal to plasma pressure/magnetic pressure) exceeding the limit predicted for ideal magnetohydrodynamic (MHD) ballooning modes. We examine the effect of particle collisions on the stable modes of the FLR modified ideal theory that exist in this range of ..beta.. values