Aggregation of metallochlorophylls - Examination by spectroscopy

Nuclear magnetic resonance measurements determine which metallochlorophylls, besides magnesium-containing chlorophylls, possess coordination aggregation properties. Infrared spectroscopy reveals that only zinc pheophytin and zinc methyl pheophorbide showed significant coordination aggregation, whereas divalent nickel and copper did not

Long and Short GRB

We report evidence from the 3B Catalogue that short (T_90 < 10 s) and long (T_90 > 10 s) GRB represent different populations and processes: Their spectral behavior is qualitatively different, with short bursts harder in the BATSE range, but chiefly long bursts detected at higher photon energies; \langle V/V_max \rangle = 0.385 \pm 0.019 for short GRB but \langle V/V_max \rangle = 0.282 \pm 0.014 for long GRB, differing by 0.103 \pm 0.024. Long GRB may be the consequence of accretion-induced collapse, but this mechanism fails for short GRB, for which we suggest colliding neutron stars.Comment: 5 pp., latex, no figures, revised to work around bug in latex compile

Application of advanced on-board processing concepts to future satellite communications systems: Bibliography

Abstracts are presented of a literature survey of reports concerning the application of signal processing concepts. Approximately 300 references are included

Application of CFD techniques toward the validation of nonlinear aerodynamic models

Applications of Computational fluid dynamics (CFD) methods to determine the regimes of applicability of nonlinear models describing the unsteady aerodynamic responses to aircraft flight motions are described. The potential advantages of computational methods over experimental methods are discussed and the concepts underlying mathematical modeling are reviewed. The economic and conceptual advantages of the modeling procedure over coupled, simultaneous solutions of the gasdynamic equations and the vehicle's kinematic equations of motion are discussed. The modeling approach, when valid, eliminates the need for costly repetitive computation of flow field solutions. For the test cases considered, the aerodynamic modeling approach is shown to be valid

Gravitational energy

Observers at rest in a stationary spacetime flat at infinity can measure small amounts of rest-mass+internal energies+kinetic energies+pressure energy in a small volume of fluid attached to a local inertial frame. The sum of these small amounts is the total "matter energy" for those observers. The total mass-energy minus the matter energy is the binding gravitational energy. Misner, Thorne and Wheeler evaluated the gravitational energy of a spherically symmetric static spacetime. Here we show how to calculate gravitational energy in any static and stationary spacetime for isolated sources with a set of observers at rest. The result of MTW is recovered and we find that electromagnetic and gravitational 3-covariant energy densities in conformastatic spacetimes are of opposite signs. Various examples suggest that gravitational energy is negative in spacetimes with special symmetries or when the energy-momentum tensor satisfies usual energy conditions.Comment: 12 pages. Accepted for publication in Class. Quantum Gra

The use of x-ray scattering to study the anomalous elastic properties of fe-ni alloys

X-ray scattering technique for study of elastic properties of nickel-iron allo

An Economist's Guide to U.S. v. Microsoft

We analyze the central economic issues raised by U.S. v Microsoft. Network effects and economies of scale in applications programs created a barrier to entry for new operating system competitors, which the combination of Netscape Navigator and the Java programming language potentially could have lowered. Microsoft took actions to eliminate this threat to its operating system monopoly, and some of Microsoft's conduct very likely harmed consumers. While we recognize the risks of the government's proposed structural remedy of splitting Microsoft in two, we are pessimistic that a limited conduct remedy would be effective in this case.

Qualitative and quantitative analysis of mixtures of compounds containing both hydrogen and deuterium

Method allows qualitative and quantitative analysis of mixtures of partially deuterated compounds. Nuclear magnetic resonance spectroscopy determines location and amount of deuterium in organic compounds but not fully deuterated compounds. Mass spectroscopy can detect fully deuterated species but not the location

Integral Constraints On cosmological Perturbations and their Energy

We show the relation between Traschen's integral equations and the energy, and ``position of the centre of mass'', of the matter perturbations in a Robertson-Walker spacetime. When the perturbations are ``localised'' we get a set of integral constraints that includes hers. We illustrate them on a simple example.Comment: 19 pages, Tex file, submitted to Classical and Quantum Gravit