Propagation of high-energy cosmic rays in extragalactic turbulent magnetic fields: resulting energy spectrum and composition

We extend previous studies of mixed-composition extragalactic cosmic-ray source models, by investigating the influence of a non-negligible extragalactic magnetic field on the propagated cosmic-ray spectrum and composition. We study the transport of charged particles in turbulent fields and the transition from a ballistic to a diffusive propagation regime. We introduce a method allowing a fast integration of the particle trajectories, which allows us to calculate extragalactic cosmic-ray spectra in the general case, without using either the diffusive or the rectilinear approximation. We find that the main features of the mixed-composition models -- regarding the interpretation of the ankle and the non-monotonous evolution of the average cosmic-ray mass -- remain essentially unchanged as long as the magnetic field intensity does not exceed a few nG.Comment: 15 pages, 20 figure

Study of coupled states for the (4s^{2})^{1}S + (4s4p)^{3}P asymptote of Ca_{2}

The coupled states A^{1}\Sigma_{u}^{+} (^{1}D +}1}S), c^{3}\Pi_{u} (^{3}P + ^{1}S) and a^{3}\Sigma_{u}^{+} (^{3}P +}1}S) of the calcium dimer are investigated in a laser induced fluorescence experiment combined with high-resolution Fourier-transform spectroscopy. A global deperturbation analysis of the observed levels, considering a model, which is complete within the subspace of relevant neighboring states, is performed using the Fourier Grid Hamiltonian method. We determine the potential energy curve of the A^{1}\Sigma_{u}^{+} and c^{3}\Pi_{u} states and the strengths of the couplings between them. The c^{3}\Pi_{u} and \as states are of particular importance for the description of collisional processes between calcium atoms in the ground state ^{1}S_{0} and excited state ^{3}P_{1} applied in studies for establishing an optical frequency standard with Ca.Comment: 15 pages, 12 figure

Focal plane transport assembly for the HEAO-B X-ray telescope

The High Energy Astronomy Observatory - Mission B (HEAO-B), an earth orbiting X-ray telescope facility capable of locating and imaging celestial X-ray sources within one second of arc in the celestial sphere, is considered. The Focal Plane Transport Assembly (FPTA) is one of the basic structural elements of the three thousand pound HEAO-B experiment payload. The FPTA is a multifunctional assembly which supports seven imaging X-ray detectors circumferentially about a central shaft and accurately positions any particular one into the focus of a high resolution mirror assembly. A drive system, position sensor, rotary coupler, and detent alignment system, all an integral part of the rotatable portion which in turn is supported by main bearings to the stationary focal plane housing are described

Bostonia. Volume 1

Founded in 1900, Bostonia magazine is Boston University's main alumni publication, which covers alumni and student life, as well as university activities, events, and programs

Experimental study of the Ca2 1S+1S asymptote

The filtered laser excitation technique was applied for measuring transition frequencies of the Ca$_2$ B-X system from asymptotic levels of the X$^1\Sigma_{\mathrm g}^{+}$ ground state reaching $v''=38$. That level has an outer classical turning point of about 20~\AA which is only 0.2 \rcm below the molecular $^1$S$+^1$S asymptote. Extensive analysis of the spectroscopic data, involving Monte Carlo simulation, allowed for a purely experimental determination of the long range parameters of the potential energy curve. The possible values of the s-wave scattering length could be limited to be between 250$a_0$ and 1000$a_0$.Comment: 10 pages, 7 figure

Between Europe and North Africa: Reflections on Spain and Morocco in the War Novels of Carmen de Burgos (1909) and Ernesto Giménez Caballero (1923)

This paper explores the notion of cultural and racial bonds and boundaries between Spain and North Africa in two literary works written during the Spanish colonial campaigns in Northern Morocco in the early twentieth century: Carmen de Burgos’ En la Guerra (1909), and Ernesto Giménez Caballero’s Notas Marruecas de un soldado (1923). My analysis centres on the opposing concepts of degeneration and regeneration. I argue that Carmen de Burgos’ novel establishes hierarchical moral and racial boundaries between Spain and Morocco, and that these boundaries reflect her underlying anxieties concerning cultural differences between Spain and North Africa and the possibility of degeneration through contact with an ‘uncivilized’ environment. Giménez Caballero’s vision of Morocco in Notas Marruecas is also informed by a set of binary oppositions; however, unlike Burgos’ positioning of Spain as culturally superior to Morocco, Giménez Caballero locates Spanish culture somewhere between Europe and North Africa and sees contact with Morocco as a potential source for national regeneration. Ultimately the analysis sheds light on some of the complexities and underlying anxieties of Spanish cultural discourse on North Africa in the first decades of the twentieth century

Parallel Implementation of the PHOENIX Generalized Stellar Atmosphere Program

We describe the parallel implementation of our generalized stellar atmosphere and NLTE radiative transfer computer program PHOENIX. We discuss the parallel algorithms we have developed for radiative transfer, spectral line opacity, and NLTE opacity and rate calculations. Our implementation uses a MIMD design based on a relatively small number of MPI library calls. We report the results of test calculations on a number of different parallel computers and discuss the results of scalability tests.Comment: To appear in ApJ, 1997, vol 483. LaTeX, 34 pages, 3 Figures, uses AASTeX macros and styles natbib.sty, and psfig.st

Characterizationn of Polumer-Based MEMS Pyroelectic Infrared Detector

AFRL/MLPJE had developed a novel thermal sensing material termed protein-impregnated-polymer (PIP). Thus far, a proof-of-concept has been demonstrated using a macro-sized pixel (0.64 mm2) as a bolometric detector. In an effort to better characterize this novel thermal sensing material, experimental data was used to determine figures of merit (FOMs) comparative to off-the-shelf thermal detectors. Microelectromechanical (MEMS) pixels were designed and used as the support structure for an inkjet-deposited droplet of the PIP. During the material characterization, two observations were made: PIP is a pyroelectric material, and the polymer (polyvinyl alcohol (PVA)) without the protein was found to be more suited for measurements taken on the micro-scaled pixels. Both PVA and PVA doped with carbon black (PVA-CB) were the materials focused on in this research, with the latter being the material used for FOM characterization. Pyroelectric coefficients for PVA and PVA-CB were found to be 755.11 nC/(cm2 K), and 108.32 nC/(cm2 K), respectively, which are both two orders of magnitude higher than values for current pyroelectric polymers. A responsivity of 1.66 x 104 V/W, thermal time constant of 3.59 sec, noise equivalent power of 21.3 nW, and a detectivity of 1.93 x 105 cm √Hz/W were the FOMs found in this thesis. Although the calculated FOMs are not stellar in comparison to current thermal detector technology, this material shows much promise. The shortfalls in FOMs could potentially be attributed to a poor pixel design. This thesis plants the scientific seed in cultivating a thermal imaging focal plane array (FPA) using a newly found pyroelectric polymer

Alien Registration- Allard, Paul E. (Brunswick, Cumberland County)

https://digitalmaine.com/alien_docs/31942/thumbnail.jp