Simulations of thermally broadened HI Lya absorption arising in the warm-hot intergalactic medium

Recent far-ultraviolet (FUV) absorption line measurements of low-redshift quasars have unveiled a population of intervening broad HI Lya absorbers (BLAs) with large Doppler parameters (b> 40 km/s). If the large width of these lines is dominated by thermal line broadening, the BLAs may trace highly-ionized gas in the warm-hot intergalactic medium (WHIM) in the temperature range T ~ 10^5-10^6 K, a gas phase that is expected to contain a large fraction of the baryons at low redshift. In this paper we use a hydrodynamical simulation to study frequency, distribution, physical conditions, and baryon content of the BLAs at z=0. From our simulated spectra we derive a number of BLAs per unit redshift of (dN/dz)_BLA ~ 38 for HI absorbers with log (N(cm^-2)/b(km/s))>10.7, b>40 km/s, and log N(HII)<20.5. The baryon content of these systems is Omega_b(BLA)=0.0121/h_65, which represents ~25 percent of the total baryon budget in our simulation. Our results thus support the idea that BLAs represent a significant baryon reservoir at low redshift. BLAs predominantly trace shock-heated collisionally ionized WHIM gas at temperatures log T~4.4-6.2. About 27 percent of the BLAs in our simulation originate in the photoionized Lya forest (log T<4.3) and their large line widths are determined by non-thermal broadening effects such as unresolved velocity structure and macroscopic turbulence. Our simulation implies that for a large-enough sample of BLAs in FUV spectra it is possible to obtain a reasonable approximation of the baryon content of these systems solely from the measured HI column densities and b values.Comment: 11 pages, 8 figures; minor modifications; accepted for publication in A&

Biology of nesting sea turtles along the Florida panhandle

The purpose of this study was to determine how the dynamic system off Cape San Blas affects its unique group of nesting sea turtles. We assessed: 1. changes in beach topography, 2. changes in offshore topography, 3. current flows and direction, 4. tidal patterns, 5. sand composition and origin, 6. sea turtle nesting pattern, and 7. structure of the sea turtle group nesting along Cape San Blas. (9 page document

The Cape San Blas Ecological Study

Eglin AFB on Cape San Blas consists of approximately 250 acres located about 180 miles east of the main Eglin reservation. This area lies on the S1. Joseph peninsula, part of a dynamic barrier island chain that extends across the northern Gulf of Mexico. Due to the natural forces that formed Cape San Blas and those that maintain this area, St. Joseph Peninsula has experienced severe land form change over time (see GIS land form change maps). These changes allow for fluctuations in habitat types along Cape San Blas (see GIS land cover change maps)that influence the floral and faunal species using this area. The dynamic environment along Cape San Blasincludes flatwoods, interdunal swale, rosemary scrub, and beachfront. These habitats support a wide array of species, including several threatened and endangered species such as the loggerhead sea turtle (Caretta caretta), PipingPlover (Charadnus melodus), Least Tern (Sterna antillarum), and Bald Eagle (Haliaeetus leucocephalus). Proper management of these species and their habitats require knowledge of their abundance and distribution, and the effects disturbances have on their survival. In addition to threatened and endangered flora and fauna, Cape San Blas also supports tourists and recreationists. Although Gulf County is sparsely populated, with approximately 13,000 inhabitants throughout 578 square miles, summer tourism and heavy recreational use of beaches for fishing, crabbing, and shelling place continued and increasing pressure on the natural resources of these areas (Rupert 1991). Gulf County is also one of the few remaining counties in Florida that permits vehicular traffic on its beaches, including Cape San Blas. In addition to recreational use of these habitats;EAFB also uses the area for military missions. Air Force property on Cape San Blas is primarily used for radar tracking of flying missions over the Gulf of Mexico, although in recent years it has been used for missile launchings and other various military activities. To allow continued military and public use of Air Force property while also protecting the unique flora and fauna of the area,EAFB proposed a characterization of the resources found along Cape San Blas. A complete inventory of the physical features of the area included investigating topography, soil chemistry, hydrology, archeology, and the dynamics of land mass and land cover change over time. Various thematic layers within a geographic information system (GIS) were used to spatially portray georeferenced data. Large scale changes over time were assessed using stereo aerial photography. Vegetation transects, soil samples, elevation transects, an archeological survey, freshwater wells, and a tidal monitor were used to investigate the remaining features. (247 page document

Lisa Blas: Meet Me at the Mason Dixon

The Schmucker Art Gallery at Gettysburg College is extremely pleased to mount the remarkable series of paintings, photographs, and mixed-media installation by contemporary artist Lisa Blas entitled Meet Me at the Mason Dixon. This exhibition is an official part of Gettysburg area’s 150th Commemoration of the American Civil War as well as Gettysburg College’s Kick-Off event for this significant anniversary. Gettysburg provides an especially appropriate backdrop for the exhibition, as the artist took the history of this “hallowed ground” and its current resonances as the subject of her work. Blas traveled the Gettysburg National Military Park, as well as to the Antietam National Battlefield, the Smithsonian Institution, the National Archives and the Museum of the Confederacy in Richmond, Virginia, among many other sites, to investigate how national identity and cultural myths are shaped in response to this momentous period of American history. The title of this exhibition, Meet Me at the Mason Dixon, invokes an encounter at a historical boundary line known for centuries of conflict. The Mason-Dixon Line originally was intended to solve a British colonial dispute. Later, it divided the northern from the southern United States based on the legality of slavery, and as such, symbolizes the massive fracturing of the country during the American Civil War. To contemporary artist Lisa Blas, however, the Mason-Dixon emblematizes the tensions implicit in the concept of historical memory. How are traumas witnessed and remembered? What becomes codified as history, and what other narratives are thereby repressed? What age-old divisions haunt us in the present? Blas comprehends such questions as open-ended, visualizing the past as fundamentally, and persistently, conflicted. [excerpt]https://cupola.gettysburg.edu/artcatalogs/1006/thumbnail.jp

Rectangular Full Packed Format for Cholesky's Algorithm: Factorization, Solution and Inversion

We describe a new data format for storing triangular, symmetric, and Hermitian matrices called RFPF (Rectangular Full Packed Format). The standard two dimensional arrays of Fortran and C (also known as full format) that are used to represent triangular and symmetric matrices waste nearly half of the storage space but provide high performance via the use of Level 3 BLAS. Standard packed format arrays fully utilize storage (array space) but provide low performance as there is no Level 3 packed BLAS. We combine the good features of packed and full storage using RFPF to obtain high performance via using Level 3 BLAS as RFPF is a standard full format representation. Also, RFPF requires exactly the same minimal storage as packed format. Each LAPACK full and/or packed triangular, symmetric, and Hermitian routine becomes a single new RFPF routine based on eight possible data layouts of RFPF. This new RFPF routine usually consists of two calls to the corresponding LAPACK full format routine and two calls to Level 3 BLAS routines. This means {\it no} new software is required. As examples, we present LAPACK routines for Cholesky factorization, Cholesky solution and Cholesky inverse computation in RFPF to illustrate this new work and to describe its performance on several commonly used computer platforms. Performance of LAPACK full routines using RFPF versus LAPACK full routines using standard format for both serial and SMP parallel processing is about the same while using half the storage. Performance gains are roughly one to a factor of 43 for serial and one to a factor of 97 for SMP parallel times faster using vendor LAPACK full routines with RFPF than with using vendor and/or reference packed routines

On the Performance Prediction of BLAS-based Tensor Contractions

Tensor operations are surging as the computational building blocks for a variety of scientific simulations and the development of high-performance kernels for such operations is known to be a challenging task. While for operations on one- and two-dimensional tensors there exist standardized interfaces and highly-optimized libraries (BLAS), for higher dimensional tensors neither standards nor highly-tuned implementations exist yet. In this paper, we consider contractions between two tensors of arbitrary dimensionality and take on the challenge of generating high-performance implementations by resorting to sequences of BLAS kernels. The approach consists in breaking the contraction down into operations that only involve matrices or vectors. Since in general there are many alternative ways of decomposing a contraction, we are able to methodically derive a large family of algorithms. The main contribution of this paper is a systematic methodology to accurately identify the fastest algorithms in the bunch, without executing them. The goal is instead accomplished with the help of a set of cache-aware micro-benchmarks for the underlying BLAS kernels. The predictions we construct from such benchmarks allow us to reliably single out the best-performing algorithms in a tiny fraction of the time taken by the direct execution of the algorithms.Comment: Submitted to PMBS1