Collapsing regions and black hole formation

Up to a conjecture in Riemannian geometry, we significantly strengthen a recent theorem of Eardley by proving that a compact region in an initial data surface that is collapsing sufficiently fast in comparison to its surface-to-volume ratio must contain a future trapped region. In addition to establishing this stronger result, the geometrical argument used does not require any asymptotic or energy conditions on the initial data. It follows that if such a region can be found in an asymptotically flat Cauchy surface of a spacetime satisfying the null-convergence condition, the spacetime must contain a black hole with the future trapped region therein. Further, up to another conjecture, we prove a strengthened version of our theorem by arguing that if a certain function (defined on the collection of compact subsets of the initial data surface that are themselves three-dimensional manifolds with boundary) is not strictly positive, then the initial data surface must contain a future trapped region. As a byproduct of this work, we offer a slightly generalized notion of a future trapped region as well as a new proof that future trapped regions lie within the black hole region.Comment: 11 pages, REVTeX 3.

Installation drag considerations as related to turboprop and turbofan engines

Some of the specific areas associated with straight jet and turboprop engine installations are outlined where drag reduction and, thus, improved aircraft system performance is obtained. Specific areas constitute air intake sizing for general aviation aircraft, exhaust duct geometries and cooling system arrangements for propeller powered aircraft

Two-way digital driver/receiver uses one set of lines

Two-way /bilateral/ digital driver/receiver system using MOS circuits was designed for a multiprocess computer having several subsystems at relatively close locations. The system requires only a single set of communication lines between subsystems, thus achieving lower cost with increased reliability

A preliminary investigation of trunk and wrist kinematics when using drivers with different shaft properties

It is unknown whether skilled golfers will modify their kinematics when using drivers of different shaft properties. This study aimed to firstly, determine if golf swing kinematics and swing parameters and related launch conditions differed when using modified drivers, then secondly, determine which kinematics were associated with clubhead speed. Twenty high level amateur male golfers (Mean ± SD: handicap = 1.9 ± 1.9 score) had their three-dimensional trunk and wrist kinematics collected for two driver trials. Swing parameters and related launch conditions were collected using a launch monitor. A one-way repeated measures ANOVA revealed significant (p ≤ 0.003) between-driver differences; specifically, faster trunk axial rotation velocity and an early wrist release for the low kick point driver. Launch angle was shown to be 2° lower for the high kick point driver. Regression models for both drivers explained a significant amount of variance (60 – 67%) in clubhead speed. Wrist kinematics were most associated with clubhead speed, indicating the importance of the wrists in producing clubhead speed regardless of driver shaft properties

Economic Impacts of E. Coqui frogs in Hawaii

Eleutherodactylus coqui, a small frog native to Puerto Rico, was introduced to Hawaii in the late 1980s, presumably as a hitchhiker on plant material from the Caribbean or Florida (Kraus et al. 1999). The severity of the frogs' songs on the island of Hawaii has lead to a hypothesis touted both in the scientific community and in the popular media that the presence of the frog on or near a property results in a decline in that property's value. The objective of this study is to explicitly test the extent to which this hypothesis is true, and if it is, what the level of localized damage incurred on a property's value is. The invasion began on either Hawaii or Maui, and has now expanded to Oahu and Kauai. Spread has occurred through the movement of nursery plants and through intentional introduction of the frogs to previously uninfested areas. The coqui frogs have attained some of the highest densities ever observed for terrestrial amphibian populations (up to 133,000 per ha on Hawaii). These extremely dense populations have lead to both economic and ecological concerns, especially on the island of Hawaii. The loud mating song of the male frogs is the most widely cited complaint in Hawaii. The frog's song has been measured to range in the 80-100 decibel level (Beard and Pitt 2005). Given that 45 decibels may be enough to prevent the average person from sleeping , the song of the coqui is considered a form of noise pollution in Hawaii. In this study we focus only on the direct damage costs of the coqui's loud mating songs through a hedonic pricing model. Because this only one component of the economic costs of noise pollution, it should be considered a lower bound estimate of the true cost of their noise and their presence. Since this lower bound is generated through measurable losses in property value, its use in invasive species policy should be welcomingly straightforward compared to survey methods or other efforts to quantify damages from ecosystem change. We find that coqui frogs do impose localized damages to real estate values, but by 800 meters distance from a complaint this damage is declining relative to the effect at 500m. The per-transaction reduction in value when frog complaints have been lodged within 500m appears to be about 0.16%, holding constant district, acreage, financial conditions, zoning, and neighborhood characteristics. This is just over 1/3 of the impact that an increase of 1% in mortgage rates is estimated to have on price.Land Economics/Use,

Environmental Policy Issues for Sustainable Economic Development in China

A central pillar of the sustainability movement is the call to include environmental accounting in standard measures of economic performance. This increased transparency would, in principle, mitigate the temptation of economic managers and policy makers to increase growth in material consumption at the expense of the environment. Moreover, as Repetto (1989) and others have argued, deducting depreciation of produced capital from NNP but not deducting depreciation of natural capital is inconsistent and debases NNP as a possible indicator of welfare. Based on the evidence available, it appears that while GNNP is substantially less than NNP, these adjustments do not adversely compromise existing estimates of economic growth for China.Environmental Economics and Policy,

Precision measurement with an optical Josephson junction

We study a new type of Josephson device, the so-called "optical Josephson junction" as proposed in Phys. Rev. Lett. {\bf 95}, 170402 (2005). Two condensates are optically coupled through a waveguide by a pair of Bragg beams. This optical Josephson junction is analogous to the usual Josephson junction of two condensates weakly coupled via tunneling. We discuss the use of this optical Josephson junction, for making precision measurements.Comment: 6 pages, 1 figur