Development of high efficiency solar cells on silicon web

Web base material is being improved with a goal toward obtaining solar cell efficiencies in excess of 18% (AM1). Carrier loss mechanisms in web silicon was investigated, techniques were developed to reduce carrier recombination in the web, and web cells were fabricated using effective surface passivation. The effect of stress on web cell performance was also investigated

Selling Out: Musicians, Autonomy, and Compromise in the Digital Age

Charges of “selling out” and debates about the boundaries of cultural autonomy have played a pivotal role in the development of popular music as a legitimate and “serious” art form. With promotional strategies and commercial business practices now practically inseparable from the core activities previously associated with music making, the relevance of such concepts and the values that underpin them are questioned by industry experts, musicians, and fans. In this article, we explore how popular music making and perspectives on selling out have been shaped by digitalization, promotionalism, and globalization

A Magnetically-Switched, Rotating Black Hole Model For the Production of Extragalactic Radio Jets and the Fanaroff and Riley Class Division

A model is presented in which both Fanaroff and Riley class I and II extragalactic jets are produced by magnetized accretion disk coronae in the ergospheres of rotating black holes. While the jets are produced in the accretion disk itself, the output power still is an increasing function of the black hole angular momentum. For high enough spin, the black hole triggers the magnetic switch, producing highly-relativistic, kinetic-energy-dominated jets instead of Poynting-flux-dominated ones for lower spin. The coronal mass densities needed to trigger the switch at the observed FR break power are quite small ($\sim 10^{-15} g cm^{-3}$), implying that the source of the jet material may be either a pair plasma or very tenuous electron-proton corona, not the main accretion disk itself. The model explains the differences in morphology and Mach number between FR I and II sources and the observed trend for massive galaxies to undergo the FR I/II transition at higher radio power. It also is consistent with the energy content of extended radio lobes and explains why, because of black hole spindown, the space density of FR II sources should evolve more rapidly than that of FR I sources. If the present model is correct, then the ensemble average speed of parsec-scale jets in sources distinguished by their FR I morphology (not luminosity) should be distinctly slower than that for sources with FR II morphology. The model also suggests the existence of a population of high-redshift, sub-mJy FR I and II radio sources associated with spiral or pre-spiral galaxies that flared once when their black holes were formed but were never again re-kindled by mergers.Comment: 14 pages, 2 figures, final version to appear in Sept Ap

Design and Performance of the CMS Pixel Detector Readout Chip

The readout chip for the CMS pixel detector has to deal with an enormous data rate. On-chip zero suppression is inevitable and hit data must be buffered locally during the latency of the first level trigger. Dead-time must be kept at a minimum. It is dominated by contributions coming from the readout. To keep it low an analog readout scheme has been adopted where pixel addresses are analog coded. We present the architecture of the final CMS pixel detector readout chip with special emphasis on the analog readout chain. Measurements of its performance are discussed.Comment: 8 pages, 11 figures. Contribution to the Proceedings of the Pixel2005 Workshop, Bonn, German

Unexpected Effect of Internal Degrees of Freedom on Transverse Phonons in Supercooled Liquids

We show experimentally that in a supercooled liquid composed of molecules with internal degrees of freedom the internal modes contribute to the frequency dependent shear viscosity and damping of transverse phonons, which results in an additional broadening of the transverse Brillouin lines. Earlier, only the effect of internal modes on the frequency dependent bulk viscosity and damping of longitudinal phonons was observed and explained theoretically in the limit of weak coupling of internal degrees of freedom to translational motion. A new theory is needed to describe this new effect. We also demonstrate, that the contributions of structural relaxation and internal processes to the width of the Brillouin lines can be separated by measurements under high pressure

Multi-Dimensional Astrophysical Structural and Dynamical Analysis I. Development of a Nonlinear Finite Element Approach

A new field of numerical astrophysics is introduced which addresses the solution of large, multidimensional structural or slowly-evolving problems (rotating stars, interacting binaries, thick advective accretion disks, four dimensional spacetimes, etc.). The technique employed is the Finite Element Method (FEM), commonly used to solve engineering structural problems. The approach developed herein has the following key features: 1. The computational mesh can extend into the time dimension, as well as space, perhaps only a few cells, or throughout spacetime. 2. Virtually all equations describing the astrophysics of continuous media, including the field equations, can be written in a compact form similar to that routinely solved by most engineering finite element codes. 3. The transformations that occur naturally in the four-dimensional FEM possess both coordinate and boost features, such that (a) although the computational mesh may have a complex, non-analytic, curvilinear structure, the physical equations still can be written in a simple coordinate system independent of the mesh geometry. (b) if the mesh has a complex flow velocity with respect to coordinate space, the transformations will form the proper arbitrary Lagrangian- Eulerian advective derivatives automatically. 4. The complex difference equations on the arbitrary curvilinear grid are generated automatically from encoded differential equations. This first paper concentrates on developing a robust and widely-applicable set of techniques using the nonlinear FEM and presents some examples.Comment: 28 pages, 9 figures; added integral boundary conditions, allowing very rapidly-rotating stars; accepted for publication in Ap.

Silicon dendritic web material

The development of a low cost and reliable contact system for solar cells and the fabrication of several solar cell modules using ultrasonic bonding for the interconnection of cells and ethylene vinyl acetate as the potting material for module encapsulation are examined. The cells in the modules were made from dendritic web silicon. To reduce cost, the electroplated layer of silver was replaced with an electroplated layer of copper. The modules that were fabricated used the evaporated Ti, Pd, Ag and electroplated Cu (TiPdAg/Cu) system. Adherence of Ni to Si is improved if a nickel silicide can be formed by heat treatment. The effectiveness of Ni as a diffusion barrier to Cu and the ease with which nickel silicide is formed is discussed. The fabrication of three modules using dendritic web silicon and employing ultrasonic bonding for interconnecting calls and ethylene vinyl acetate as the potting material is examined

The global response of relativistic radiation belt electrons to the January 1997 magnetic cloud

In January 1997 a large fleet of NASA and US military satellites provided the most complete observations to date of the changes in \u3e2 MeV electrons during a geomagnetic storm. Observations at geosynchronous orbit revealed a somewhat unusual two-peaked enhancement in relativistic electron fluxes [ Reeves et al., 1998]. In the heart of the radiation belts at L ≈ 4, however, there was a single enhancement followed by a gradual decay. Radial profiles from the POLAR and GPS satellites revealed three distinct phases. (1) In the acceleration phase electron fluxes increased simultaneously at L ≈ 4–6. (2) During the passage of the cloud the radiation belts were shifted radially outward and then relaxed earthward. (3) For several days after the passage of the cloud the radial gradient of the fluxes flattened, increasing the fluxes at higher L-shells. These observations provide evidence that the acceleration of relativistic electrons takes place within the radiation belts and is rapid. Both magnetospheric compression and radial diffusion can cause a redistribution of electron fluxes within the magnetosphere that make the event profiles appear quite different when viewed at different L-shells

Unraveling the alcohol harm paradox: a population-based study of social gradients across very heavy drinking thresholds

BACKGROUND: There is consistent evidence that individuals in higher socioeconomic status groups are more likely to report exceeding recommended drinking limits, but those in lower socioeconomic status groups experience more alcohol-related harm. This has been called the ‘alcohol harm paradox’. Such studies typically use standard cut-offs to define heavy drinking, which are exceeded by a large proportion of adults. Our study pools data from six years (2008–2013) of the population-based Health Survey for England to test whether the socioeconomic distribution of more extreme levels of drinking could help explain the paradox. METHODS: The study included 51,498 adults from a representative sample of the adult population of England for a cross-sectional analysis of associations between socioeconomic status and self-reported drinking. Heavy weekly drinking was measured at four thresholds, ranging from 112 g+/168 g + (alcohol for women/men, or 14/21 UK standard units) to 680 g+/880 g + (or 85/110 UK standard units) per week. Heavy episodic drinking was also measured at four thresholds, from 48 g+/64 g + (or 6/8 UK standard units) to 192 g+/256 g + (or 24/32 UK standard units) in one day. Socioeconomic status indicators were equivalised household income, education, occupation and neighbourhood deprivation. RESULTS: Lower socioeconomic status was associated with lower likelihoods of exceeding recommended limits for weekly and episodic drinking, and higher likelihoods of exceeding more extreme thresholds. For example, participants in routine or manual occupations had 0.65 (95 % CI 0.57–0.74) times the odds of exceeding the recommended weekly limit compared to those in ‘higher managerial’ occupations, and 2.15 (95 % CI 1.06–4.36) times the odds of exceeding the highest threshold. Similarly, participants in the lowest income quintile had 0.60 (95 % CI 0.52–0.69) times the odds of exceeding the recommended weekly limit when compared to the highest quintile, and 2.30 (95 % CI 1.28–4.13) times the odds of exceeding the highest threshold. CONCLUSIONS: Low socioeconomic status groups are more likely to drink at extreme levels, which may partially explain the alcohol harm paradox. Policies that address alcohol-related health inequalities need to consider extreme drinking levels in some sub-groups that may be associated with multiple markers of deprivation. This will require a more disaggregated understanding of drinking practices

Elementary solution to the time-independent quantum navigation problem

A quantum navigation problem concerns the identification of a time-optimal Hamiltonian that realizes a required quantum process or task, under the influence of a prevailing ‘background’ Hamiltonian that cannot be manipulated. When the task is to transform one quantum state into another, finding the solution in closed form to the problem is nontrivial even in the case of timeindependent Hamiltonians. An elementary solution, based on trigonometric analysis, is found here when the Hilbert space dimension is two. Difficulties arising from generalizations to higher-dimensional systems are discussed