Anisotropic evolution of D-dimensional FRW spacetime

We examine the time evolution of the D=d+4 dimensional Einstein field equations subjected to a flat Robertson-Walker metric where the 3D and higher-dimensional scale factors are allowed to evolve at different rates. We find the exact solution to these equations for a single fluid component, which yields two limiting regimes offering the 3D scale factor as a function of the time. The fluid regime solution closely mimics that described by 4D FRW cosmology, offering a late-time behavior for the 3D scale factor after becoming valid in the early universe, and can give rise to a late-time accelerated expansion driven by vacuum energy. This is shown to be preceded by an earlier volume regime solution, which offers a very early-time epoch of accelerated expansion for a radiation-dominated universe for d=1. The time scales describing these phenomena, including the transition from volume to fluid regime, are shown to fall within a small fraction of the first second when the fundamental constants of the theory are aligned with the Planck time. This model potentially offers a higher-dimensional alternative to scalar-field inflationary theory and a consistent cosmological theory, yielding a unified description of early- and late-time accelerated expansions via a 5D spacetime scenario.Comment: Title changed from "A possible higher-dimensional alternative to scalar-field inflationary theory". Several new results have been added including a predicted lower- and upper-bound on the time scales marking the end of an early-time inflationary epoch and the beginning of an FRW epoch for d=

Diversity-induced resonance in a system of globally coupled linear oscillators

The purpose of this paper to analyze in some detail the arguably simplest case of diversity-induced reseonance: that of a system of globally-coupled linear oscillators subjected to a periodic forcing. Diversity appears as the parameters characterizing each oscillator, namely its mass, internal frequency and damping coefficient are drawn from a probability distribution. The main ingredients for the diversity-induced-resonance phenomenon are present in this system as the oscillators display a variability in the individual responses but are induced, by the coupling, to synchronize their responses. A steady state solution for this model is obtained. We also determine the conditions under which it is possible to find a resonance effect.Comment: Reported at the XI International Workshop "Instabilities and Nonequilibrium Structures" Vina del Mar (Chile

The promise of fuel cell-based automobiles

Fuel cell-based automobiles have gained attention in the last few years due to growing public concern about urban air pollution and consequent environmental problems. From an analysis of the power and energy requirements of a modern car, it is estimated that a base sustainable power of ca. 50 kW supplemented with short bursts up to 80 kW will suffice in most driving requirements. The energy demand depends greatly on driving characteristics but under normal usage is expected to be 200 Wh/km. The advantages and disadvantages of candidate fuel-cell systems and various fuels are considered together with the issue of whether the fuel should be converted directly in the fuel cell or should be reformed to hydrogen onboard the vehicle. For fuel cell vehicles to compete successfully with conventional internal-combustion engine vehicles, it appears that direct conversion fuel cells using probably hydrogen, but possibly methanol, are the only realistic contenders for road transportation applications. Among the available fuel cell technologies, polymer-electrolyte fuel cells directly fueled with hydrogen appear to be the best option for powering fuel cell vehicles as there is every prospect that these will exceed the performance of the internal-combustion engine vehicles but for their first cost. A target cost of $ 50/kW would be mandatory to make polymer-electrolyte fuel cells competitive with the internal combustion engines and can only be achieved with design changes that would substantially reduce the quantity of materials used. At present, prominent car manufacturers are deploying important research and development efforts to develop fuel cell vehicles and are projecting to start production by 2005

1998 PRICING PERFORMANCE OF MARKET ADVISORY SERVICES FOR CORN AND SOYBEANS

The purpose of this research report is to present an evaluation of advisory service pricing performance in 1998 for corn and soybeans. Specifically, the average price received by a subscriber to an advisory service is calculated for corn and soybean crops harvested in 1998. The average net advisory price across all 23 corn programs is $2.17 per bushel - seven cents below the market benchmark price. The net advisory prices for corn range from a minimum of$1.93 per bushel to a maximum of $2.51 per bushel. The average net advisory price across all 22 soybean programs is$5.82 per bushel - four cents less than the market benchmark. The net advisory prices for soybeans range from a minimum of $5.11 per bushel to a maximum of$6.58 per bushel.Marketing,

DO AGRICULTURAL MARKET ADVISORY SERVICES BEAT THE MARKET? EVIDENCE FROM THE WHEAT MARKET OVER 1995-1998

The purpose of this report is to address two basic performance questions for market advisory services in wheat: 1) Do market advisory services, on average, outperform an appropriate market benchmark? and 2) Do market advisory services exhibit persistence in their performance from year-to-year? Data on wheat net price received for advisory services, as reported by the AgMAS Project, are available for the 1995, 1996, 1997 and 1998 crop years. Not only do market advisory programs in wheat consistently fail to "beat the market," their performance is significantly worse than the market. On average, market advisory service performance is about $14 per acre below benchmark revenue, an economically non-trivial amount by any reasonable standard. The predictability results provide little evidence that future advisory service pricing performance can be predicted from past performance.Marketing,

THE 1995 THROUGH 1998 PRICING PERFORMANCE OF MARKET ADVISORY SERVICES FOR WHEAT

The purpose of this research report is to present an evaluation of advisory service pricing performance from 1995 through 1998 for wheat. The average net advisory price across all 24 wheat programs in 1995 is $3.79 per bushel,$0.18 above the market benchmark price. The range in 1995 is $3.01 to$4.71 per bushel. The average net advisory service price for 23 wheat programs in 1996 is $3.82 per bushel,$0.13 below the market benchmark. The range in 1996 is $2.74 to$4.94 per bushel. The average net advisory price for all 20 wheat programs in 1997 is $2.64 per bushel,$0.58 below the market benchmark. The range in 1997 is $1.34 to$3.90 per bushel. Finally, the average net advisory price across all 21 services in 1998 is $2.36 per bushel,$0.54 below the market benchmark. The range in 1998 is $1.34 to$3.33 per bushel.Marketing,

Cold Positrons from Decaying Dark Matter

Many models of dark matter contain more than one new particle beyond those in the Standard Model. Often heavier particles decay into the lightest dark matter particle as the Universe evolves. Here we explore the possibilities that arise if one of the products in a (Heavy Particle) $\rightarrow$ (Dark Matter) decay is a positron, and the lifetime is shorter than the age of the Universe. The positrons cool down by scattering off the cosmic microwave background and eventually annihilate when they fall into Galactic potential wells. The resulting 511 keV flux not only places constraints on this class of models but might even be consistent with that observed by the INTEGRAL satellite.Comment: 20 pages, 7 figure

Lieb Mode in a Quasi One-Dimensional Bose-Einstein Condensate of Atoms

We calculate the dispersion relation associated with a solitary wave in a quasi-one-dimensional Bose-Einstein condensate of atoms confined in a harmonic, cylindrical trap in the limit of weak and strong interactions. In both cases, the dispersion relation is linear for long wavelength excitations and terminates at the point where the group velocity vanishes. We also calculate the dispersion relation of sound waves in both limits of weak and strong coupling.Comment: 4 pages, 2 ps figures, RevTe

Tissue Glycogen and Extracellular Buffering Limit the Survival of Red-Eared Slider Turtles during Anoxic Submergence at 3°C

The goal of this study was to identify the factors that limit the survival of the red-eared slider turtle Trachemys scripta during long-term anoxic submergence at 3°C. We measured blood acid-base status and tissue lactate and glycogen contents after 13, 29, and 44 d of submergence from ventricle, liver, carapace (lactate only), and four skeletal muscles. We also measured plasma Ca2+, Mg2+, Na+, K+, Cl-, inorganic phosphate (Pi), lactate, and glucose. After 44 d, one of the six remaining turtles died, while the other turtles were in poor condition and suffered from a severe acidemia (blood pH = 7.09 from 7.77) caused by lactic acidosis (plasma lactate 91.5 mmol L-1). An initial respiratory acidosis attenuated after 28 d. Lactate rose to similar concentrations in ventricle and skeletal muscle (39.3–46.1 μmol g-1). Liver accumulated the least lactate (21.8 μmol g-1), and carapace accumulated the most lactate (68.9 μmol g-1). Plasma Ca2+ and Mg2+ increased significantly throughout submergence to levels comparable to painted turtles at a similar estimated lactate load. Glycogen depletion was extensive in all tissues tested: by 83% in liver, by 90% in ventricle, and by 62%–88% in muscle. We estimate that the shell buffered 69.1% of the total lactate load, which is comparable to painted turtles. Compared with painted turtles, predive tissue glycogen contents and plasma HCO3- concentrations were low.We believe these differences contribute to the poorer tolerance to long-term anoxic submergence in red-eared slider turtles compared with painted turtles