A feasibility assessment of installation, operation and disposal options for nuclear reactor power system concepts for a NASA growth space station

A preliminary feasibility assessment of the integration of reactor power system concepts with a projected growth space station architecture was conducted to address a variety of installation, operational disposition, and safety issues. A previous NASA sponsored study, which showed the advantages of space station - attached concepts, served as the basis for this study. A study methodology was defined and implemented to assess compatible combinations of reactor power installation concepts, disposal destinations, and propulsion methods. Three installation concepts that met a set of integration criteria were characterized from a configuration and operational viewpoint, with end-of-life disposal mass identified. Disposal destinations that met current aerospace nuclear safety criteria were identified and characterized from an operational and energy requirements viewpoint, with delta-V energy requirement as a key parameter. Chemical propulsion methods that met current and near-term application criteria were identified and payload mass and delta-V capabilities were characterized. These capabilities were matched against concept disposal mass and destination delta-V requirements to provide the feasibility of each combination

Cosmological baryon and lepton number in the presence of electroweak fermion-number violation

In the presence of rapid fermion-number violation due to nonperturbative electroweak effects certain relations between the baryon number of the Universe and the lepton numbers of the Universe are predicted. In some cases the electron-neutrino asymmetry is exactly specified in terms of the baryon asymmetry. Without introducing new particles, beyond the usual quarks and leptons, it is necessary that the Universe possess a nonzero value of B - L prior to the epoch of fermion-number violation if baryon and lepton asymmetries are to survive. Contrary to intuition, even though electroweak processes violate B + L, a nonzero value of B + L persists after the epoch of rapid fermion-number violation. If the standard model is extended to include lepton-number violation, for example through Majorana neutrino masses, then electroweak processes will reduce the baryon number to zero even in the presence of an initial B - L unless 20 M(sub L) approximately greater than the square root of (T(sub B - L) m(sub P1)) where M(sub L) sets the scale of lepton number violation and T(sub B - L) is the temperature at which a B - L asymmetry is produced. In many models this implies that neutrinos must be so light that they cannot contribute appreciably to the mass density of the Universe

Applied Welfare Economics with Discrete Choice Models

Economists have been paying increasing attention to the study of situations in which consumers face a discrete rather than a continuous set of choices. Such models are potentially very important in evaluating the impact of government programs upon consumer welfare. But very little has been said in general regarding the tools of applied welfare economics indiscrete choice situations. This paper shows how the conventional methods of applied welfare economics can be modified to handle such cases. It focuses on the computation of the excess burden of taxation, and the evaluation of quality change. The results are applied to stochastic utility models, including the popular cases of probit and logit analysis. Throughout, the emphasis is on providing rigorous guidelines for carrying out applied work.

Perturbations of near-horizon geometries and instabilities of Myers-Perry black holes

It is shown that the equations governing linearized gravitational (or electromagnetic) perturbations of the near-horizon geometry of any known extreme vacuum black hole (allowing for a cosmological constant) can be Kaluza-Klein reduced to give the equation of motion of a charged scalar field in AdS_2 with an electric field. One can define an effective Breitenlohner-Freedman bound for such a field. We conjecture that if a perturbation preserves certain symmetries then a violation of this bound should imply an instability of the full black hole solution. Evidence in favour of this conjecture is provided by the extreme Kerr solution and extreme cohomogeneity-1 Myers-Perry solution. In the latter case, we predict an instability in seven or more dimensions and, in 5d, we present results for operator conformal weights assuming the existence of a CFT dual. We sketch a proof of our conjecture for scalar field perturbations.Comment: 24 pages (+ 16 pages appendices), 2 figures. v2: Corrected error in CFT operator dimensions (they are all integers). v3: Various improvements and corrections, in particular for electromagnetic perturbations. Accepted by Physical Review

Trust in Biotechnology Risk Managers: Insights from the United Kingdom, 1996-2002

The mid to late 1990s saw a series of negative media events in the United Kingdom (UK) related to biotechnology. According to the trust asymmetry hypothesis, such events ought to cause public trust in risk managers of biotechnology to fall quickly but rise slowly. We present evidence from the Eurobarometer surveys that from 1996 to 1999 public trust in the UK declined, but it increased sharply between 1999 and 2002. We seek to explain this apparent contradiction to the asymmetry hypothesis. We use canonical discriminant analysis of public trust to show that whether people trust or distrust risk managers of biotechnology depends significantly on the amount of knowledge people have about science. We speculate that knowledge of science moderates the trust asymmetry effect.Research and Development/Tech Change/Emerging Technologies,

Trust in Biotechnology Risk Managers: Insights from the United Kingdom, 1996-2002

During the late 1990s a series of negative events occurred in the United Kingdom (UK) related to biotechnology. These events signaled potential risks associated with biotech foods and crops and were highly reported. According to the trust asymmetry hypothesis, such events ought to cause public trust in risk managers of biotechnology to decline rapidly and rebound more slowly. We find, based on data taken from the Eurobarometer surveys conducted in 1996, 1999 and 2002, that public trust in risk managers did decline from 1996 to 1999. However, the level of trust rebounded sharply between 1999 and 2002. Canonical discriminant analysis of public trust is used to reveal possible explanatory factors in this response. We find that whether people trust or distrust risk managers depends significantly on the amount of objective knowledge they have. We argue that knowledge of science might moderate the trust asymmetry effect.Research and Development/Tech Change/Emerging Technologies, Risk and Uncertainty,

Tension is Dimension

We propose a simple universal formula for the tension of a D-brane in terms of a regularized dimension of the associated conformal field theory statespace.Comment: 18 pages, harvmac (b), one ref added, one typo fixe

On-board processing satellite network architecture and control study

The market for telecommunications services needs to be segmented into user classes having similar transmission requirements and hence similar network architectures. Use of the following transmission architecture was considered: satellite switched TDMA; TDMA up, TDM down; scanning (hopping) beam TDMA; FDMA up, TDM down; satellite switched MF/TDMA; and switching Hub earth stations with double hop transmission. A candidate network architecture will be selected that: comprises multiple access subnetworks optimized for each user; interconnects the subnetworks by means of a baseband processor; and optimizes the marriage of interconnection and access techniques. An overall network control architecture will be provided that will serve the needs of the baseband and satellite switched RF interconnected subnetworks. The results of the studies shall be used to identify elements of network architecture and control that require the greatest degree of technology development to realize an operational system. This will be specified in terms of: requirements of the enabling technology; difference from the current available technology; and estimate of the development requirements needed to achieve an operational system. The results obtained for each of these tasks are presented