Metastable Cosmic Strings in Realistic Models

We investigate the stability of the electroweak Z-string at high temperatures. Our results show that while finite temperature corrections can improve the stability of the Z-string, their effect is not strong enough to stabilize the Z-string in the standard electroweak model. Consequently, the Z-string will be unstable even under the conditions present during the electroweak phase transition. We then consider phenomenologically viable models based on the gauge group $SU(2)_L \times SU(2)_R \times U(1)_{B-L}$ and show that metastable strings exist and are stable to small perturbations for a large region of the parameter space for these models. We also show that these strings are superconducting with bosonic charge carriers. The string superconductivity may be able to stabilize segments and loops against dynamical contraction. Possible implications of these strings for cosmology are discussed.Comment: 24 pages, 2 figures (available on request); HUTP-92/A032, Fermilab-Pub-92/228-

Ka-band Ga-As FET noise receiver/device development

The development of technology for a 30 GHz low noise receiver utilizing GaAs FET devices exclusively is discussed. This program required single and dual-gate FET devices, low noise FET amplifiers, dual-gate FET mixers, and FET oscillators operating at Ka-band frequencies. A 0.25 micrometer gate FET device, developed with a minimum noise figure of 3.3 dB at 29 GHz and an associated gain of 7.4 dB, was used to fabricate a 3-stage amplifier with a minimum noise figure and associated gain of 4.4 dB and 17 dB, respectively. The 1-dB gain bandwidth of this amplifier extended from below 26.5 GHz to 30.5 GHz. A dual-gate mixer with a 2 dB conversion loss and a minimum noise figure of 10 dB at 29 GHz as well as a dielectric resonator stabilized FET oscillator at 25 GHz for the receiver L0. From these components, a hybrid microwave integrated circuit receiver was constructed which demonstrates a minimum single-side band noise figure of 4.6 dB at 29 GHz with a conversion gain of 17 dB. The output power at the 1-dB gain compression point was -5 dBm

Minor degree of hypohydration adversely influences cognition: a mediator analysis

Background: The assumption that small changes in hydration statusare readily compensated by homeostatic mechanisms has been littlestudied. In this study, the influence of hypohydration on cognition wasexamined.Objectives: We assessed whether a loss of ,1% of body mass dueto hypohydration adversely influenced cognition, and examined thepossible underlying mechanisms.Design: A total of 101 individuals were subjected to a temperature of308C for 4 h and randomly either did or did not consume 300 mLH2O during that period. Changes in body mass, urine osmolality,body temperature, and thirst were monitored. Episodic memory, focusedattention, mood, and the perceived difficulty of tasks weremeasured on 3 occasions. The data were analyzed with the use ofa regression-based approach whereby we looked for variables that mediatedthe influence of hypohydration on psychological functioning.Results: Drinking water improved memory and focused attention.In the short-term, thirst was associated with poorer memory. Later,a greater loss of body mass was associated with poorer memory andattention (mean loss: 0.72%). At 90 min, an increase in thirst wasassociated with a decline in subjective energy and increased anxietyand depression, effects that were reduced by drinking water. At180 min, subjects found the tests easier if they had consumed water.Conclusions: Drinking water was shown, for the first time to ourknowledge, to benefit cognitive functioning when there was a lossof ,1% body mass at levels that may occur during everydayliving. Establishing the variables that generate optimal fluid consumptionwill help to tailor individual advice, particularly in clinicalsituations

Si3AlP: A new promising material for solar cell absorber

First-principles calculations are performed to study the structural and optoelectronic properties of the newly synthesized nonisovalent and lattice-matched (Si2)0.6(AlP)0.4 alloy [T. Watkins et al., J. Am. Chem. Soc. 2011, 133, 16212.] We find that the ordered CC-Si3AlP with a basic unit of one P atom surrounded by three Si atoms and one Al atom is the most stable one within the experimentally observed unit cell.1 Si3AlP has a larger fundamental band gap and a smaller direct band gap than Si, thus it has much higher absorption in the visible light region. The calculated properties of Si3AlP suggest that it is a promising candidate for improving the performance of the existing Si-based solar cells. The understanding on the stability and band structure engineering obtained in this study is general and can be applied for future study of other nonisovalent and lattice-matched semiconductor alloys

Brief of Natural Resources in Opposition to Plaintiff\u27s Opening Briefs, Appendix A

Findings of Fact before the Indian Claims Commissio

Brief of Natural Resources in Opposition to Plaintiff\u27s Opening Briefs, Appendix A

Findings of Fact before the Indian Claims Commissio

Macroscopic control parameter for avalanche models for bursty transport

Similarity analysis is used to identify the control parameter RA for the subset of avalanching systems that can exhibit self-organized criticality (SOC). This parameter expresses the ratio of driving to dissipation. The transition to SOC, when the number of excited degrees of freedom is maximal, is found to occur when RA-->0. This is in the opposite sense to (Kolmogorov) turbulence, thus identifying a deep distinction between turbulence and SOC and suggesting an observable property that could distinguish them. A corollary of this similarity analysis is that SOC phenomenology, that is, power law scaling of avalanches, can persist for finite RA with the same RA-->0 exponent if the system supports a sufficiently large range of lengthscales, necessary for SOC to be a candidate for physical (RA finite) systems

The Birth of High Mass Stars: Accretion and/or Mergers?

The observational consequences of the merger scenario for massive star formation are explored and contrasted with the gradual accumulation of mass by accretion. Protostellar mergers may produce high luminosity infrared flares lasting years to centuries followed by a luminosity decline on the Kelvin-Helmholtz time-scale of the merger product. Mergers may be surrounded by thick tori of expanding debris, impulsive wide-angle outflows, and shock induced maser and radio continuum emission. Collision products are expected to have fast stellar rotation and a large multiplicity fraction. Close encounters or mergers will produce circumstellar debris disks with an orientation that differs form that of a pre-existing disk. The extremely rare merger of two stars close to the upper-mass end of the IMF may be a possible pathway to hypernova generated gamma-ray bursters. While accretional growth can lead to the formation of massive stars in isolation or in loose clusters, mergers can only occur in high-density cluster environments. It is proposed that the outflow emerging from the OMC1 core in the Orion molecular cloud was produced by a protostellar merger that released between $10^{48}$ to $10^{49}$ ergs less than a thousand years ago