Population structure and genetics of longevity in a colony of dog guides

The objectives of this study were the description of changes in genetic diversity in a colony of dog guides since its founding, and the investigation of the genetics of longevity in that population. Two breeds of dog, German Shepherds (GS) and Labrador Retrievers (LR), were evaluated. There were rapid increases in average pairwise relationship in both breeds, although the average was approximately one-third higher in the GS population than in the LR population. A similar trend was observed for average inbreeding. In the current generation, relationship and inbreeding for all animals averaged 25.3% and 26.2% in GS and 15.5% and 22.0% in LR, respectively. Effective founder numbers initially decreased in GS until generation 3, and then increased steadily. There was a constant increase in effective founder number in LR after founding. A similar pattern was seen for effective ancestor number as well. Founder genome equivalents were initially higher in the GS but decreased over time in both breeds. New breeding stock should be imported in order to reduce the levels of inbreeding and relationship in this colony. Data on longevity for 1,403 GS and 1,816 LR dogs who worked as guides were used to estimate genetic parameters for working life. Two measures of working life were considered: working life to 18 months post-graduation (EWL) and working life beyond 18 months post-graduation (LWL). Survival analysis was used to estiamte the sire component of variance and estimated breedinb values (EBVs). Linearized heritability estimates were small: 0.032 and 0.045 for EWL and 0.016 and 0.032 for LWL in GS and LR, respectively. Genetic trend was estimated by regression of EBVs on year. No trend was observed for either trait in either breed, suggesting that historical selection criteria were not effective in improving working life. An antagonistic relationship may exist between aptitude for guide work and risk of culling for temperament

ECONOMIC EVALUATION OF CROPSHARE AND CASH LEASE CONTRACTS IN SOUTH DAKOTA AND NEBRASKA

Factors influencing choice of share or cash rental leases for cropland are examined using a 1996 dataset containing 1071 lease contracts in Nebraska and in South Dakota. Logistic regression results indicate tenant's age, capital position, and relationship with landlord were more important than leased land use or crop management variables.Farm Management,

Was Old Jules Right?: Soil Stewardship on Leased Land

In a country where more than 40% of the agricultural land is farmed by tenant operators, the question of how that land base is farmed becomes paramount In this study we examined soil erosion levels in relation to land tenure and surveyed tenant farmer practices and attitudes in Nebraska and South Dakota, We found leased land was farmed and maintained by tenants in an environmentally sustainable manner, Furthermore, we found no evidence to suggest variation from this norm due to type of lease, size of farm, type of farm organization, or landowner classification, While educational level and years of experience (age) contributed to soil stewardship practices, to a great extent tenant farmers in these Great Plains states farmed leased land in a conscientious manner to maintain their integrity and reputation in the community as being a good farmer, Landowners, as well as society at large, benefit from this perspective

Extravehicular Mobility Unit (EMU) / International Space Station (ISS) Coolant Loop Failure and Recovery

Following the Colombia accident, the Extravehicular Mobility Units (EMU) onboard ISS were unused for several months. Upon startup, the units experienced a failure in the coolant system. This failure resulted in the loss of Extravehicular Activity (EVA) capability from the US segment of ISS. With limited on-orbit evidence, a team of chemists, engineers, metallurgists, and microbiologists were able to identify the cause of the failure and develop recovery hardware and procedures. As a result of this work, the ISS crew regained the capability to perform EVAs from the US segment of the ISS

Direct Kerr-frequency-comb atomic spectroscopy

Microresonator-based soliton frequency combs - microcombs - have recently emerged to offer low-noise, photonic-chip sources for optical measurements. Owing to nonlinear-optical physics, microcombs can be built with various materials and tuned or stabilized with a consistent framework. Some applications require phase stabilization, including optical-frequency synthesis and measurements, optical-frequency division, and optical clocks. Partially stabilized microcombs can also benefit applications, such as oscillators, ranging, dual-comb spectroscopy, wavelength calibration, and optical communications. Broad optical bandwidth, brightness, coherence, and frequency stability have made frequency-comb sources important for studying comb-matter interactions with atoms and molecules. Here, we explore direct microcomb atomic spectroscopy, utilizing a cascaded, two-photon 1529-nm atomic transition of rubidium. Both the microcomb and the atomic vapor are implemented with planar fabrication techniques to support integration. By fine and simultaneous control of the repetition rate and carrier-envelope-offset frequency of the soliton microcomb, we obtain direct sub-Doppler and hyperfine spectroscopy of the $4^2D_{5/2}$ manifold. Moreover, the entire set of microcomb modes are stabilized to this atomic transition, yielding absolute optical-frequency fluctuations of the microcomb at the kilohertz-level over a few seconds and < 1 MHz day-to-day accuracy. Our work demonstrates atomic spectroscopy with microcombs and provides a rubidium-stabilized microcomb laser source, operating across the 1550 nm band for sensing, dimensional metrology, and communication.Comment: 5 pages, 3 figure

The Star Formation History of the Large Magellanic Cloud

Using WFPC2 aboard the Hubble Space Telescope, we have created deep color-magnitude diagrams in the V and I passbands for approximately 100,000 stars in a field at the center of the LMC bar and another in the disk. The main--sequence luminosity functions (LFs) from 19 mag < V < 23.5 mag, the red clump and horizontal branch morphologies, and the differential Hess diagram of the two fields all strongly imply that the disk and bar have significantly different star-formation histories (SFHs). The disk's SFH has been relatively smooth and continuous over the last 15 Gyr while the bar's SFH was dominated by star formation episodes at intermediate ages. Comparison of the LF against predictions based on Padova theoretical stellar evolution models and an assumed age-metallicity relationship allows us to identify the dominant stellar populations in the bar with episodes of star formation that occurred from 4 to 6 and 1 to 2 Gyr ago. These events accounted, respectively, for approximately 25% and 15% of its stellar mass. The disk field may share a mild enhancement in SF for the younger episode, and thus we identify the 4 to 6 Gyr episode with the formation of the LMC bar.Comment: 14 pages, 5 figures, Latex, also available at http://www.ps.uci.edu/physics/smeckerhane.html. Accepted for publication in Ap

Resolving the Formation of Protogalaxies. I. Virialization

(Abridged) Galaxies form in hierarchically assembling dark matter halos. With cosmological three dimensional adaptive mesh refinement simulations, we explore in detail the virialization of baryons in the concordance cosmology, including optically thin primordial gas cooling. We focus on early protogalaxies with virial temperatures of 10^4 K and their progenitors. Without cooling, virial heating occurs in shocks close to the virial radius for material falling in from voids. Material in dense filaments penetrates deeper to about half that radius. With cooling the virial shock position shrinks and also the filaments reach scales as small as a third the virial radius. The temperatures in protogalaxies found in adiabatic simulations decrease by a factor of two from the center and show flat entropy cores. In cooling halos the gas reaches virial equilibrium with the dark matter potential through its turbulent velocities. We observe turbulent Mach numbers ranging from one to three in the cooling cases. This turbulence is driven by the large scale merging and interestingly remains supersonic in the centers of these early galaxies even in the absence of any feedback processes. The virial theorem is shown to approximately hold over 3 orders of magnitude in length scale with the turbulent pressure prevailing over the thermal energy. The turbulent velocity distributions are Maxwellian and by far dominate the small rotation velocities associated with the total angular momentum of the galaxies. Decomposing the velocity field using the Cauchy-Stokes theorem, we show that ample amounts of vorticity are present around shocks even at the very centers of these objects.Comment: 13 pages, 6 figures. Submitted to ApJ on 8 March 2007. Revised manuscript. Comments welcom