Ionized Gas in the Galactic Center: New Observations and Interpretation

We present new observations of the [Ne II] emission from the ionized gas in Sgr A West with improved resolution and sensitivity. About half of the emission comes from gas with kinematics indicating it is orbiting in a plane tipped about 25\degree\ from the Galactic plane. This plane is consistent with that derived previously for the circumnuclear molecular disk and the northern arm and western arc ionized features. However, unlike most previous studies, we conclude that the ionized gas is not moving along the ionized features, but on more nearly circular paths. The observed speeds are close to, but probably somewhat less than expected for orbital motions in the potential of the central black hole and stars and have a small inward component. The spatial distribution of the emission is well fitted by a spiral pattern. We discuss possible physical explanations for the spatial distribution and kinematics of the ionized gas, and conclude that both may be best explained by a one-armed spiral density wave, which also accounts for both the observed low velocities and the inward velocity component. We suggest that a density wave may result from the precession of elliptical orbits in the potential of the black hole and stellar mass distribution.Comment: 28 pages, 13 figures, ApJ in pres

Sunderland Software City: The Impact of a Collaborative Project to Develop the Software Industry within the North East of England

This paper uses a case study approach to evaluate the impact of a collaborative initiative within the North East of England which sets out to grow and sustain a software industry, based on the strengths of regional players. The project Sunderland Software City has the ambitious aim of developing the people, the infrastructure and the business and enterprise culture to create and sustain a software industry. This paper focuses upon the impact of the project, and presents some lessons learned to date

Latitudinal gradients in leaf litter decomposition in streams: Effects of leaf chemistry and temperature

Thesis (Ph.D.) University of Alaska Fairbanks, 1993Autumnal leaf litter that falls into streams of forested regions forms a major source of energy for stream food webs. The processing of this litter has been studied for many years, and two generalizations have come from this research: (1) nitrogen concentration is positively correlated with breakdown rate, and (2) temperature is negatively correlated with breakdown rate. Along with investigators in Michigan and Costa Rica, I examined these generalizations by estimating breakdown rates of litter of ten tree species with widely varying nutritional quality along the latitudinal gradient of Costa Rica to Michigan to Alaska. At each site, litter processing experiments were done using leaves of the same ten tree species and the same methods in streams with similar character. We found that (1) condensed tannin, a plant defense against herbivory, was more highly correlated (negatively) with breakdown rates than was nitrogen (positively correlated with breakdown), and (2) breakdown rate showed a complex response to water temperature (i.e., latitude). I propose a model of leaf litter breakdown in which the microbial contribution to litter breakdown is negatively correlated with latitude (i.e., temperature) and the invertebrate contribution to litter breakdown is positively correlated with latitude. In addition, I suggest that secondary compounds of low solubility, especially condensed tannin, should be considered along with nitrogen when evaluating a tree species for leaf litter quality

An Overview of the Landsat Data Continuity Mission

The advent of the Landsat Data Continuity Mission (LDCM), currently with a launch readiness date of December, 2012, will see evolutionary changes in the Landsat data products available from the U.S. Geological Survey (USGS) Earth Resources Observation and Science (EROS) Center. The USGS initiated a revolution in 2009 when EROS began distributing Landsat data products at no cost to requestors in contrast to the past practice of charging the cost of fulfilling a request; that is, charging $600 per Landsat scene. To implement this drastic change, EROS terminated data processing options for requestors and began to produce all data products using a consistent processing recipe. EROS plans to continue this practice for the LDCM and will required new algorithms to process data from the LDCM sensors. All previous Landsat satellites flew multispectral scanners to collect image data of the global land surface. Additionally, Landsats 4, 5, and 7 flew sensors that acquired imagery for both reflective spectral bands and a single thermal band. In contrast, the LDCM will carry two pushbroom sensors; the Operational Land Imager (OLI) for reflective spectral bands and the Thermal InfraRed Sensor (TIRS) for two thermal bands. EROS is developing the ground data processing system that will both calibrate and correct the data from the thousands of detectors employed by the pushbroom sensors and that will also combine the data from the two sensors to create a single data product with registered data for all of the OLI and TIRS bands

Sunderland Software City: The Impact of a Collaborative Project to Develop the Software Industry Within the North East of England

This paper uses a case study approach to evaluate theimpact of a collaborative initiative within the North East ofEngland which sets out to grow and sustain a software industry,based on the strengths of regional players. The projectSunderland Software City has the ambitious aim of developingthe people, the infrastructure and the business and enterpriseculture to create and sustain a software industry. This paperfocuses upon the impact of the project, and presents some lessonslearned to date

Life histories and community structure of the caddisflies (Trichoptera) of two Alaskan subarctic streams

Thesis (M.S.) University of Alaska Fairbanks, 1985The ecology of Trichoptera was studied in two streams in interior Alaska. Monument Creek and West Fork are characterized by cold water temperatures, low allochthonous input and periphyton biomass, and lengthy ice cover. Nine species were found, Rhyacophila vofixa ? (Rhyacophilidae), Glossosoma verdona, G. alascense (Glossosomatidae), Brachycentrus americanus (Brachycentridae), Hydatophylax variabilis, Ecclisomyia conspersa, Onocosmoecus unicolor, Chyranda centralis and Apatania crymophila (Limnephilidae). There were four shredders, three scrapers, one omnivore, and one predator. Within shredders and scrapers, species had sequentially overlapping life histories, perhaps allowing functionally similar species to use the same food resources. Latitudinal gradients in the North American Trichoptera fauna were investigated using approximately 90 studies from the literature and unpublished Alaskan data. Taxonomic richness showed a weak negative correlation with latitude in light trap studies. Hydropsychoidea showed an inverse correlation, while Limnephiloidea and Limnephilidae showed positive correlations with latitude. Density and biomass were also negatively correlated to latitude.Alaska Cooperative Fisheries Research Uni

Effect of manufacturing method of a centrifugal fan hub on its heat dissipation characteristics.

As the process temperature of a fan system increases, the amount of heat that gets transmitted to the bearings and/or motor increases. If this is not accounted for, it can lead to catastrophic failure. The main heat conduction path is through the shaft, and certain mechanisms must be considered when looking for new solutions. These include; how heat is transmitted through the shaft or increasing the thermal resistance of the shaft, and dissipating heat as it is conducted through the shaft. These aspects must always be considered in addition to the impact of the manufacturing complexity. In the present study, an existing heat dissipation arrangement is reviewed and replaced by a new design which reduces the time taken to machine the part, and ultimately the overall cost of the product. Computation Fluid Dynamics (CFD) based techniques have been used to numerically simulate the designs under operating conditions, and the resulting heat transfer through the shaft compared with respect to the heat dissipation properties. The results demonstrate that although the new design is less effective at dissipating heat, it provides a substantial cost reduction compared to the existing design, while substantially reducing the impact of the design on various aspects of production

The benefits of expediting government gold sales

Additional gold can be made available either by mining at high cost (approximately $250 per ounce in 1997 dollars) or by mobilizing government stocks at zero cost. Governments own massive above‐ground stocks but loan out only a small percentage of these stocks. Making all government gold available for private uses immediately through some combination of sales and loans maximizes total welfare from private uses, a consequence of the first welfare theorem. We simulate a calibrated version of our model to quantify the effects of liquidating government stocks on alternative dates. If governments sell immediately rather than never, total welfare increases by$340 billion; if they make an unanticipated sale in 20 years, $105 billion of that amount is lost. By depressing prices, such sales benefit depletion and service users but injure private owners of stocks above and below‐ground. However, the injury to above‐ground stock owners is more than offset by the benefits to service users—often the same individuals. Mine owners would be the principal losers; however, they could be compensated (twice over) from government sales revenue without any need for tax increases.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142282/1/rfe235.pd

Effect of Manufacturing Method of a Centrifugal Fan Hub on its Heat Dissipation Characteristics

As the process temperature of a fan system increases, the amount of heat that gets transmitted to the bearings and/or motor increases. If this is not accounted for, it can lead to catastrophic failure. The main heat conduction path is through the shaft, and certain mechanisms must be considered when looking for new solutions. These include; how heat is transmitted through the shaft or increasing the thermal resistance of the shaft, and dissipating heat as it is conducted through the shaft. These aspects must always be considered in addition to the impact of the manufacturing complexity. In the present study, an existing heat dissipation arrangement is reviewed and replaced by a new design which reduces the time taken to machine the part, and ultimately the overall cost of the product. Computation Fluid Dynamics (CFD) based techniques have been used to numerically simulate the designs under operating conditions, and the resulting heat transfer through the shaft compared with respect to the heat dissipation properties. The results demonstrate that although the new design is less effective at dissipating heat, it provides a substantial cost reduction compared to the existing design, while substantially reducing the impact of the design on various aspects of production

Landsat Data Continuity Mission - Launch Fever

The year 2013 will be an exciting period for those that study the Earth land surface from space, particularly those that observe and characterize land cover, land use, and the change of cover and use over time. Two new satellite observatories will be launched next year that will enhance capabilities for observing the global land surface. The United States plans to launch the Landsat Data Continuity Mission (LDCM) in January. That event will be followed later in the year by the European Space Agency (ESA) launch of the first Sentinel 2 satellite. Considered together, the two satellites will increase the frequency of opportunities for viewing the land surface at a scale where human impact and influence can be differentiated from natural change. Data from the two satellites will provide images for similar spectral bands and for comparable spatial resolutions with rigorous attention to calibration that will facilitate cross comparisons. This presentation will provide an overview of the LDCM satellite system and report its readiness for the January launch