Possible mechanism for achieving glass-like thermal conductivities in crystals with off-center atoms

In the filled Ga/Ge clathrate, Eu and Sr are off-center in site 2 but Ba is on-center. All three filler atoms (Ba,Eu,Sr) have low temperature Einstein modes; yet only for the Eu and Sr systems is there a large dip in the thermal conductivity, attributed to the Einstein modes. No dip is observed for Ba. Here we argue that it is the off-center displacement that is crucial for understanding this unexplained difference in behavior. It enhances the coupling between the "rattler" motion and the lattice phonons for the Eu and Sr systems, and turns on/off another scattering mechanism (for 1K < T < 20K) produced by the presence/absence of off-center sites. The random occupation of different off-center sites produces a high density of symmetry-breaking defects which scatters phonons. It may also be important for improving our understanding of other glassy systems.Comment: 4 pages, 1 figure (2 parts) -- v2: intro broadened; strengthened arguments regarding need for additional phonon scattering mechanis

High-power CW ultraviolet ion lasers

Over 1 watt of continuous ultraviolet output has been obtained from an argon ion laser in the 3500-3700Å range. This paper describes the discharge tube structure used and the operating characteristics of high-power ultraviolet laser transitions in argon and other noble gas ions. Operation at new wavelengths as well as CW operation of transitions previously observed only in pulsed operation are reported. Measurements of the dependence of spontaneous emission intensity from different ionization states on current and pressure are related to the excitation mechanisms for visible and uv ion lasers. The technique of population modulation by intracavity interruption has been used to study processes in the throat and uniform bore regions of ion laser discharges. The results of these studies are described. Problems encountered in the CW operation of ion laser discharge tubes at current densities above 1000Å/cm^2 are described

MiRo: Social Interaction and Cognition in an Animal-like Companion Robot

Future companion and assistive robots will interact directly with end-users in their own homes over extended periods of time. To be useful, and remain engaging over the long-term, these technologies need to pass a new threshold in social robotics-to be aware of people, their identities, emotions and intentions and to adapt their behavior to different individuals. Our immediate goal is to match the social cognition ability of companion animals who recognize people and their intentions without linguistic communication. The MiRo robot is a pet-sized mobile platform, with a brain-based control system and an emotionally-engaging appearance, which is being developed for research on companion robotics, and for applications in education, assistive living and robot-assisted therapy. This paper describes new MiRo capabilities for animal-like perception and social cognition that support the adaptation of behavior towards people and other robots

Nutritional Management Post-AI to Enhance Pregnancy Outcomes

Effective replacement heifer development is a critical segment of the integrated management program in an efficient beef cow production system. The most critical factor determining the success of any heifer development program is nutrition. Most efforts are concentrated in providing the right amount and quality of feed to achieve gains from 1.5 to 2.0 lb/day, so heifers can reach 65% of their mature BW by the day of breeding. Approximately 80% of the U.S. cow-herds are spring calving, which means that producers utilizing estrous synchronization and AI are keeping their heifers in a feedlot environment until heifers are inseminated. Immediately following AI, heifers are typically moved to pasture. It is known that maternal recognition of pregnancy takes place around d 15 - 17 post-insemination and that transporting animals near this time compromises conception rates. However, moving heifers within the first 5 days post-insemination does not cause this reduction. Although, research suggests that conception rates are compromised when heifers are placed on early growth pasture forages. We hypothesized that feeding this high moisture pasture forage at turnout is limiting DMI which in turn causes a temporary energy deficiency that results in temporary heifer weight loss during the critical stages of early embryonic development and maternal recognition of pregnancy. Therefore, it is beneficial to ensure heifers maintain the same plane of nutrition after breeding, at least until day 25 when the embryo should be completely attached to the uterus. If this is true, maintaining a positive plane of nutrition on heifers after breeding will increase 1st service conception rates, improving herd fertility and longevity

The structure and evolution of confined tori near a Hamiltonian Hopf Bifurcation

We study the orbital behavior at the neighborhood of complex unstable periodic orbits in a 3D autonomous Hamiltonian system of galactic type. At a transition of a family of periodic orbits from stability to complex instability (also known as Hamiltonian Hopf Bifurcation) the four eigenvalues of the stable periodic orbits move out of the unit circle. Then the periodic orbits become complex unstable. In this paper we first integrate initial conditions close to the ones of a complex unstable periodic orbit, which is close to the transition point. Then, we plot the consequents of the corresponding orbit in a 4D surface of section. To visualize this surface of section we use the method of color and rotation [Patsis and Zachilas 1994]. We find that the consequents are contained in 2D "confined tori". Then, we investigate the structure of the phase space in the neighborhood of complex unstable periodic orbits, which are further away from the transition point. In these cases we observe clouds of points in the 4D surfaces of section. The transition between the two types of orbital behavior is abrupt.Comment: 10 pages, 14 figures, accepted for publication in the International Journal of Bifurcation and Chao

Phased Array Noise Source Localization Measurements of an F404 Nozzle Plume at Both Full and Model Scale

A 48-microphone planar phased array system was used to acquire jet noise source localization data on both a full-scale F404-GE-F400 engine and on a 1/4th scale model of a F400 series nozzle. The full-scale engine test data show the location of the dominant noise sources in the jet plume as a function of frequency for the engine in both baseline (no chevron) and chevron configurations. Data are presented for the engine operating both with and without afterburners. Based on lessons learned during this test, a set of recommendations are provided regarding how the phased array measurement system could be modified in order to obtain more useful acoustic source localization data on high-performance military engines in the future. The data obtained on the 1/4th scale F400 series nozzle provide useful insights regarding the full-scale engine jet noise source mechanisms, and document some of the differences associated with testing at model-scale versus fullscale

Assessing the Benefits of Misting–Cooling Systems for Growing/Finishing Swine as Affected by Environment and Pig Placement Date

The NCPIG swine growth model was used to evaluate swine growth performance for Wilmington, North Carolina; Bardstown and Mayfield, Kentucky; and Oklahoma City, Oklahoma as influenced by the use of a misting–cooling system. Five pig placement dates (Julian days 106, 126, 146, 166, and 186) were evaluated for each location using 22 years of weather data (1978–1999). The use of a misting system, while quite variable, was found to be generally profitable, reducing the length of the time to reach market weight. As the placement date increased, the average return to misting ($/pig/year) decreased from$8.12 to $1.98 for Oklahoma City, from$6.00 to $1.16 for Wilmington, from$4.14 to $0.99 for Mayfield, and from$3.07 to $0.87 for Bardstown. Based on the prorated value of$1.39 per pig/per year for the cost of a misting system, probabilities for recovering the initial investment amount were determined for each pig placement date and location. These probabilities decreased as the pig placement date increased, except for Oklahoma City, which remained above 98% regardless of the date. For the locations other than Oklahoma City, the probabilities indicated that the earlier placement dates were more favorable for recovering the initial investment

Assessing the Benefits of Misting-Cooling Systems for Growing-Finishing Swine in Kentucky as Affected by Environment and Pig Placement Date

The growth performance of animals is often affected by extreme environmental conditions. In the case of swine, generally a cold environment will increase feed intake as the pig strives to maintain body temperature, while warmer environments may reduce growth, increase body maintenance demands, and subject the animal to environmental stress. Confinement houses are widely used as a primary means of modifying the environment to improve conditions for the growth of swine. Environment in these structures is usually controlled by natural or mechanical ventilation and by insulation for cold climates and limited use of evaporative cooling for summertime conditions