Structure and stability of non-symmetric Burgers vortices

We investigate, numerically and analytically, the structure and stability of steady and quasi-steady solutions of the Navier–Stokes equations corresponding to stretched vortices embedded in a uniform non-symmetric straining field, ([alpha]x, [beta]y, [gamma]z), [alpha]+[beta]+[gamma]=0, one principal axis of extensional strain of which is aligned with the vorticity. These are known as non-symmetric Burgers vortices (Robinson & Saffman 1984). We consider vortex Reynolds numbers R=[Gamma]/(2[pi]v) where [Gamma] is the vortex circulation and v the kinematic viscosity, in the range R=1[minus sign]104, and a broad range of strain ratios [lambda]=([beta][minus sign][alpha])/([beta]+[alpha]) including [lambda]>1, and in some cases [lambda][dbl greater-than sign]1. A pseudo-spectral method is used to obtain numerical solutions corresponding to steady and quasi-steady vortex states over our whole (R, [lambda]) parameter space including [lambda] where arguments proposed by Moffatt, Kida & Ohkitani (1994) demonstrate the non-existence of strictly steady solutions. When [lambda][dbl greater-than sign]1, R[dbl greater-than sign]1 and [epsilon][identical with][lambda]/R[double less-than sign]1, we find an accurate asymptotic form for the vorticity in a region 11. An iterative technique based on the power method is used to estimate the largest eigenvalues for the non-symmetric case [lambda]>0. Stability is found for 0[less-than-or-eq, slant][lambda][less-than-or-eq, slant]1, and a neutrally convective mode of instability is found and analysed for [lambda]>1. Our general conclusion is that the generalized non-symmetric Burgers vortex is unconditionally stable to two-dimensional disturbances for all R, 0[less-than-or-eq, slant][lambda][less-than-or-eq, slant]1, and that when [lambda]>1, the vortex will decay only through exponentially slow leakage of vorticity, indicating extreme robustness in this case

Conservation and Management of the High Elevation Subspecies of the Gunnison’s Prairie Dog, Cynomys Gunnisoni Gunnisoni

Species of conservation concern often exist in fragmented habitats and experience low population numbers. Habitat fragmentation can separate groups of individuals into small demographically independent populations, which are susceptible to evolutionary processes like genetic drift, which can erode genetic diversity and reduce the adaptive potential of a population. Maintaining large population numbers, conserving genetic variation, and preserving population connectivity is important for the long-term persistence of populations and for the exchange of individuals and genetic diversity between populations. The focus of my research is on Cynomys gunnisoni gunnisoni, a subspecies of Gunnison&rsquo;s prairie dog that inhabits the montane regions of south-central Colorado and north-central New Mexico. Today, C.g. gunnisoni exists in a patchwork of colonies among large mountain valleys and basins separated by impassable mountain ranges. In my dissertation research, I evaluated how populations of C.g. gunnisoni are connected across the landscape, used genetic information to evaluate population structure, and characterized genetic diversity among colonies and populations. In Chapter 1 I address how conservation actions are needed to stem the loss of biodiversity. Some species, such as prairie dogs in the genus Cynomys, are keystone species and ecological engineers whose presence and actions have disproportionately large impacts on ecosystems. The large reduction in prairie dog population numbers has negatively impacted species and ecosystems in the Great Plains and Rocky Mountains. Conservation actions that benefit prairie dogs could have cascading effects that benefit habitats and the species that interact with prairie dogs such as the burrowing owl, mountain plover, and black-footed ferrets. C.g. gunnisoni is of conservation concern due to low population sizes and because it inhabits a fragmented landscape of the southern Rocky Mountains. Better understanding the population dynamics and conservation concerns of C.g. gunnisoni can inform on conservation management actions for the subspecies. In Chapter 2, I use landscape genetics methods with a circuit theory modeling approach to investigate how the landscape influences dispersal patterns and population distributions of the subspecies. I found that distance, extreme elevations, sloping terrain, and forest, aquatic, and urban habitats are expected to resist population connectivity. The conversion of habitat for agriculture and food production may be important in altering dispersal paths away from areas which would otherwise promote prairie dog dispersal. Large mountain ranges act to separate the subspecies&rsquo; range into multiple population areas while drainage systems may provide habitat corridors that allow prairie dogs to colonize marginal habitat space in mountainous terrain. In Chapter 3, I used multiple methods of genetic clustering and phylogenetic networks to investigate the genetic structure of C.g. gunnisoni and inform on the establishment of management units for the subspecies. I identified at least three genetic groups within the subspecies. Colonies within major watersheds generally cluster together more than do colonies from different watersheds. I observe there is high genetic differentiation between most colonies that are not geographically near (within a few kilometers of each other) and little gene flow occurs across large distances. I also found that genetic diversity is overall low within colonies, though unique allelic variation may be harbored in colonies that are isolated or at the edges of occupied habitats. The conservation of C.g. gunnisoni may benefit from management actions that focus on elevating the genetic connectivity of prairie dog populations to prohibit reduction of population fitness by genetic deterioration and other processes, perhaps using assisted migration strategies. In my last Chapter, I presented a remote learning lesson in population and conservation biology with the Northern Spotted Owl. In this lesson I present a lab that utilizes Google Earth Web to create a virtual simulation where students can perform a &ldquo;mark-recapture&rsquo; exercise and collect data to conduct a demographic analysis of how a population of Northern Spotted Owls is doing. This lesson introduces students to population biology, conservation management, the use of demographic data and only requires internet access to be conducted remotely or independently.</p

A probabilistic approach to hybrid role mining

Role mining algorithms address an important access con-trol problem: configuring a role-based access control sys-tem. Given a direct assignment of users to permissions, role mining discovers a set of roles together with an assignment of users to roles. The results should closely agree with the direct assignment. Moreover, the roles should be under-standable from the business perspective in that they reflect functional roles within the enterprise. This requires hybrid role mining methods that work with both direct assignments and business information from the enterprise. In this paper, we provide statistical measures to analyze the relevance of different kinds of business information for defining roles. We then present an approach that incor-porates relevant business information into a probabilistic model with an associated algorithm for hybrid role mining. Experiments on actual enterprise data show that our algo-rithm yields roles that both explain the given user-permission assignments and are meaningful from the business perspec-tive

Melody Transcription From Music Audio: Approaches and Evaluation

Although the process of analyzing an audio recording of a music performance is complex and difficult even for a human listener, there are limited forms of information that may be tractably extracted and yet still enable interesting applications. We discuss melody--roughly, the part a listener might whistle or hum--as one such reduced descriptor of music audio, and consider how to define it, and what use it might be. We go on to describe the results of full-scale evaluations of melody transcription systems conducted in 2004 and 2005, including an overview of the systems submitted, details of how the evaluations were conducted, and a discussion of the results. For our definition of melody, current systems can achieve around 70% correct transcription at the frame level, including distinguishing between the presence or absence of the melody. Melodies transcribed at this level are readily recognizable, and show promise for practical applications

Comparative investigations on digestion in grazing (Ceratotherium simum) and browsing (Diceros bicornis) rhinoceroses

Rhinoceroses represent the largest extant herbivores with extensive dietary specialization for plant groups like browse (black rhino Diceros bicornis) or grass (white rhino Ceratotherium simum). However, it is not clear to what extent such diet selection patterns are reflected in adaptations of digestive physiology of the respective feeding types. In this study, feeding trials with four black and five white rhinos were conducted in four zoos. The animals had ad libitum access to the same batch of grass hay (second cut; neutral detergent fiber (NDF) 63% dry matter (DM), crude protein 10.2% DM). Total intake, fecal N content, in vitro digestibility of NDF residues of feces, fecal particle size and mean retention time (MRT) of particles (Cr-mordanted fiber; 1–2 mm) and fluid (Co-EDTA) were quantified. The average daily DM intake was 70±12 g/kg BW0.75 for white and 73±10 g/kg BW0.75 for black rhinos. In the in vitro fermentation test fecal NDF residues of black rhinos resulted in higher gas productions at fermentation times of 12 to 24 h, indicating that white rhinos have a superior capacity to digest NDF. Average MRT for fluids and particles was 28±4 h and 43±5 h in white and 34±4 h and 39±4 h in black rhinos. The selectivity factor (SF=MRTparticle /MRTfluid) was higher for white (1.5±0.2) than for black rhinos (1.2±0.1) (p=0.016). In a comparison of 12 ruminant and 3 rhino species, SF was correlated to percentage of grass in diet (R=0.75). Mean fecal particle size was higher in white (9.1±1.94 mm) than in black rhinos (6.1±0.79 mm) (p=0.016). The results demonstrate differences between white and black rhinos in terms of retention times and fiber digestibility. The more selective retention of particles by the white rhino corresponds with the higher digestion of fiber measured indirectly. Furthermore there is indication for a general pattern of high SF in grazing ruminants and rhinos. The difference in fecal particle size between both rhino species might be due to the considerable difference in body weight

Global diversity of the Brachypodium species complex as a resource for genome-wide association studies demonstrated for agronomic traits in response to climate

The development of model systems requires a detailed assessment of standing genetic variation across natural populations. The Brachypodium species complex has been promoted as a plant model for grass genomics with translation to small grain and biomass crops. To capture the genetic diversity within this species complex, thousands of Brachypodium accessions from around the globe were collected and genotyped by sequencing. Overall, 1897 samples were classified into two diploid or allopolyploid species, and then further grouped into distinct inbred genotypes. A core set of diverse B. distachyon diploid lines was selected for whole genome sequencing and high resolution phenotyping. Genome-wide association studies across simulated seasonal environments was used to identify candidate genes and pathways tied to key life history and agronomic traits under current and future climatic conditions. A total of 8, 22, and 47 QTL were identified for flowering time, early vigor, and energy traits, respectively. The results highlight the genomic structure of the Brachypodium species complex, and the diploid lines provided a resource that allows complex trait dissection within this grass model species.We are grateful for funding and support from the Australian Research Council Centre of Excellence in Plant Energy Biology (CE140100008). Australian Plant Phenomics Facility is supported under the National Collaborative Research Infrastructure Strategy of the Australian Government. The research was undertaken with the assistance of resources from the National Computational Infrastructure (NCI), which is supported by the Australian Government

Ursinus College Alumni Journal, March 1965

Contributors • From the President • Chemathphy: The integrated science course • The changing face of history • Kirkridge • Candidates • Bargains in life income contracts and annuities with Ursinus College • Mid-year report of 1965 Loyalty Fund campaign • Alumni are nearing capital funds goal • Seeds of hope in Latin America • Campus clippings: Financial support; Soph at age 49; Women\u27s Club; On the air; TW3 was there; Devotions booklet; On treasurer\u27s staff; New reserve book room; The international tone; Bus link; ACLU board member; Farewell & welcome • Track prospects for 1965 • Indoor track • Cross country • Soccer success • New coaches • Wrestling • Alumnae hockey stars • Undefeated in hockey • Football finale • Husband and wife lead small-town church to union • Advertising executive sets fast pace in Baltimore • Class notebook • Weddings • Births • In memoriam • Regionals • At your service • End quotes: The alumnus as patron of learninghttps://digitalcommons.ursinus.edu/alumnijournal/1082/thumbnail.jp