Validation of magnetophonon spectroscopy as a tool for analyzing hot-electron effects in devices

It is shown that very high precision hot-electron magnetophonon experiments made on n+n−n+-GaAs sandwich device structures which are customized for magnetoresistance measurements can be very accurately modeled by a new Monte Carlo technique. The latter takes account of the Landau quantization and device architecture as well as material parameters. It is proposed that this combination of experiment and modeling yields a quantitative tool for the direct analysis of spatially localized very nonequilibrium electron distributions in small devices and low dimensional structures

Star Formation in Bright Rimmed Clouds. I. Millimeter and Submillimeter Molecular Line Surveys

We present the results of the first detailed millimeter and submillimeter molecular line survey of bright rimmed clouds, observed at FCRAO in the CO (J=1-0), C18O (J=1-0), HCO+ (J=1-0), H13CO+ (J=1-0), and N2H+ (J=1-0) transitions, and at the HHT in the CO (J=2-1), HCO+ (J=3-2), HCO+ (J=4-3), H13CO+ (J=3-2), and H13CO+ (J=4-3) molecular line transitions. The source list is composed of a selection of bright rimmed clouds from the catalog of such objects compiled by Sugitani et al. (1991). We also present observations of three Bok globules done for comparison with the bright rimmed clouds. We find that the appearance of the millimeter CO and HCO+ emission is dominated by the morphology of the shock front in the bright rimmed clouds. The HCO+ (J=1-0) emission tends to trace the swept up gas ridge and overdense regions which may be triggered to collapse as a result of sequential star formation. Five of the seven bright rimmed clouds we observe seem to have an outflow, however only one shows the spectral line blue-asymmetric signature that is indicative of infall, in the optically thick HCO+ emission. We also present evidence that in bright rimmed clouds the nearby shock front may heat the core from outside-in thereby washing out the normally observed line infall signatures seen in isolated star forming regions. We find that the derived core masses of these bright rimmed clouds are similar to other low and intermediate mass star forming regions.Comment: 67 pages, including 35 figures and 6 tables. Accepted for publication in ApJ. Version with embedded full-resolution figures available at http://www.astro.umass.edu/~devries/brc1

Multiple fragmented habitat-patch use in an urban breeding passerine, the Short-toed Treecreeper

Individual responses of wild birds to fragmented habitat have rarely been studied, despite large-scale habitat fragmentation and biodiversity loss resulting from widespread urbanisation. We investigated the spatial ecology of the Short-toed Treecreeper Certhia brachydactyla, a tiny, resident, woodland passerine that has recently colonised city parks at the northern extent of its range. High resolution spatiotemporal movements of this obligate tree-living species were determined using radio telemetry within the urbanized matrix of city parks in Copenhagen, Denmark. We identified regular edge crossing behaviour, novel in woodland birds. While low numbers of individuals precluded a comprehensive characterisation of home range for this population, we were able to describe a consistent behaviour which has consequences for our understanding of animal movement in urban ecosystems. We report that treecreepers move freely, and apparently do so regularly, between isolated habitat patches. This behaviour is a possible driver of the range expansion in this species and may contribute to rapid dispersal capabilities in certain avian species, including Short-toed Treecreepers, into northern Europe. Alternatively, these behaviours might be common and/or provide an adaptive advantage for birds utilising matrix habitats, for example within urban ecosystems

First Passage Properties of the Erdos-Renyi Random Graph

We study the mean time for a random walk to traverse between two arbitrary sites of the Erdos-Renyi random graph. We develop an effective medium approximation that predicts that the mean first-passage time between pairs of nodes, as well as all moments of this first-passage time, are insensitive to the fraction p of occupied links. This prediction qualitatively agrees with numerical simulations away from the percolation threshold. Near the percolation threshold, the statistically meaningful quantity is the mean transit rate, namely, the inverse of the first-passage time. This rate varies non-monotonically with p near the percolation transition. Much of this behavior can be understood by simple heuristic arguments.Comment: 10 pages, 9 figures, 2-column revtex4 forma

The Distribution of Water Emission in M17SW

We present a 17-point map of the M17SW cloud core in the 1_{10}-1_{01} transition of ortho-water at 557 GHz obtained with the Submillimeter Wave Astronomy Satellite. Water emission was detected in 11 of the 17 observed positions. The line widths of the water emission vary between 4 and 9 km s^{-1}, and are similar to other emission lines that arise in the M17SW core. A direct comparison is made between the spatial extent of the water emission and the ^{13}CO J = 5\to4 emission; the good agreement suggests that the water emission arises in the same warm, dense gas as the ^{13}CO emission. A spectrum of the H_2^{18}O line was also obtained at the center position of the cloud core, but no emission was detected. We estimate that the average abundance of ortho-water relative to H_2 within the M17 dense core is approximately 1x10^{-9}, 30 times smaller than the average for the Orion core. Toward the H II region/molecular cloud interface in M17SW the ortho-water abundance may be about 5 times larger than in the dense core.Comment: 4 pages, 3 Postscript figures, uses aastex.cls, emulateapj5.sty (included), and apjfonts.sty (included

Water Abundance in Molecular Cloud Cores

We present Submillimeter Wave Astronomy Satellite (SWAS) observations of the 1_{10}-1_{01} transition of ortho-water at 557 GHz toward 12 molecular cloud cores. The water emission was detected in NGC 7538, Rho Oph A, NGC 2024, CRL 2591, W3, W3(OH), Mon R2, and W33, and was not detected in TMC-1, L134N, and B335. We also present a small map of the water emission in S140. Observations of the H_2^{18}O line were obtained toward S140 and NGC 7538, but no emission was detected. The abundance of ortho-water relative to H_2 in the giant molecular cloud cores was found to vary between 6x10^{-10} and 1x10^{-8}. Five of the cloud cores in our sample have previous water detections; however, in all cases the emission is thought to arise from hot cores with small angular extents. The water abundance estimated for the hot core gas is at least 100 times larger than in the gas probed by SWAS. The most stringent upper limit on the ortho-water abundance in dark clouds is provided in TMC-1, where the 3-sigma upper limit on the ortho-water fractional abundance is 7x10^{-8}.Comment: 5 pages, 3 Postscript figures, uses aastex.cls, emulateapj5.sty (included), and apjfonts.sty (included

Human Resources and the Resource Based View of the Firm

The resource-based view (RBV) of the firm has influenced the field of strategic human resource management (SHRM) in a number of ways. This paper explores the impact of the RBV on the theoretical and empirical development of SHRM. It explores how the fields of strategy and SHRM are beginning to converge around a number of issues, and proposes a number of implications of this convergence

Submillimeter Wave Astronomy Satellite observations of comet 9P/Tempel 1 and Deep Impact

On 4 July 2005 at 5:52 UT the Deep Impact mission successfully completed its goal to hit the nucleus of 9P/Tempel 1 with an impactor, forming a crater on the nucleus and ejecting material into the coma of the comet. NASA's Submillimeter Wave Astronomy Satellite (SWAS) observed the 1(10)-1(01) ortho-water ground-state rotational transition in comet 9P/Tempel 1 before, during, and after the impact. No excess emission from the impact was detected by SWAS and we derive an upper limit of 1.8e7 kg on the water ice evaporated by the impact. However, the water production rate of the comet showed large natural variations of more than a factor of three during the weeks before and after the impact. Episodes of increased activity with Q(H2O)~1e28 molecule/s alternated with periods with low outgassing (Q(H2O)<~5e27 molecule/s). We estimate that 9P/Tempel 1 vaporized a total of N~4.5e34 water molecules (~1.3e9 kg) during June-September 2005. Our observations indicate that only a small fraction of the nucleus of Tempel 1 appears to be covered with active areas. Water vapor is expected to emanate predominantly from topographic features periodically facing the Sun as the comet rotates. We calculate that appreciable asymmetries of these features could lead to a spin-down or spin-up of the nucleus at observable rates.Comment: 38 pages, 2 tables, 7 figures; Icarus, in pres

Far infrared mapping of three Galactic star forming regions : W3(OH), S 209 & S 187

Three Galactic star forming regions associated with W3(OH), S209 and S187 have been simultaneously mapped in two trans-IRAS far infrared (FIR) bands centered at ~ 140 and 200 micron using the TIFR 100 cm balloon borne FIR telescope. These maps show extended FIR emission with structures. The HIRES processed IRAS maps of these regions at 12, 25, 60 & 100 micron have also been presented for comparison. Point-like sources have been extracted from the longest waveband TIFR maps and searched for associations in the other five bands. The diffuse emission from these regions have been quantified, which turns out to be a significant fraction of the total emission. The spatial distribution of cold dust (T < 30 K) for two of these sources (W3(OH) & S209), has been determined reliably from the maps in TIFR bands. The dust temperature and optical depth maps show complex morphology. In general the dust around S209 has been found to be warmer than that in W3(OH) region.Comment: Accepted for publication in Journal of Astrophysics and Astronomy (20 pages including 8 figures & 3 tables

Topological Orthoalgebras

We define topological orthoalgebras (TOAs) and study their properties. While every topological orthomodular lattice is a TOA, the lattice of projections of a Hilbert space is an example of a lattice-ordered TOA that is not a toplogical lattice. On the other hand, we show that every compact Boolean TOA is a topological Boolean algebra. We also show that a compact TOA in which 0 is an isolated point is atomic and of finite height. We identify and study a particularly tractable class of TOAs, which we call {\em stably ordered}: those in which the upper-set generated by an open set is open. This includes all topological OMLs, and also the projection lattices of Hilbert spaces. Finally, we obtain a topological version of the Foulis-Randall representation theory for stably ordered TOAsComment: 16 pp, LaTex. Minor changes and corrections in sections 1; more substantial corrections in section