Noncommutative open strings from Dirac quantization

We study Dirac commutators of canonical variables on D-branes with a constant Neveu-Schwarz 2-form field by using the Dirac constraint quantization method, and point out some subtleties appearing in previous works in analyzing constraint structure of the brane system. Overcoming some ad hoc procedures, we obtain desirable noncommutative coordinates exactly compatible with the result of the conformal field theory in recent literatures. Furthermore, we find interesting commutator relations of other canonical variables.Comment: 13 pages, revtex, Expressions are change

A REEXAMINATION OF FRACTIONAL INTEGRATING DYNAMICS IN FOREIGN CURRENCY MARKETS

This paper reexamines foreign currency markets for evidence of fractional integration, and extends the extant literature in several important dimensions. First, we utilize a new semiparametric wavelet-based estimator, which is far superior to the more prevalent GPH estimator on the basis of mean squared error. Second, we utilize a broader and longer sample, which better facilitates the detection of long memory dynamics. Our analysis yields interesting empirical results that contrast with other recent studies. In particular, we find new evidence that a large proportion (fourteen out of nineteen) of exchange rate series display evidence of long memory, with little variation over alternative sample periods.Financial Economics,

Thermal expansion of liquid Ti–6Al–4V measured by electrostatic levitation

The liquid density of Ti–6Al–4V was measured over a temperature range from 1661 to 1997 K that included undercooling by as much as 280 K. The sample was levitated in an electrostatic levitator and video imaging technique was used to capture the volume changes as a function of temperature. Over the temperature range the liquid density can be expressed by rholiq(T)=4123–0.254 (T–Tm) kg/m^3, where the melting temperature Tm is 1943 K. The corresponding volume expansion coefficient is alphaliq=6.05×10^–5 K^–1 near Tm

Massless vs. Massive Hawking Radiation in AdS2_2 Spacetime

We study massless and massive Hawking radiations on a two-dimensional AdS spacetime. For the massless case, the quantum stress-energy tensor of a massless scalar field on the AdS background is calculated, and the expected null radiation is obtained. However, for the massive case, the scattering analysis is performed in order to calculate the absorption and reflection coefficients which are related to statistical Hawking temperature. On the contrary to the massless case, we obtain a nonvanishing massive radiation.Comment: 13 pages, revtex, to appear in Phys. Lett.

Effect of Time on Gypsum-Impression Material Compatibility

The purpose of this study was to evaluate the compatibility of dental gypsum with three recently introduced irreversible hydrocolloid (alginate) alternatives. The test materials were Alginot® (Kerr™), Position Penta Quick® (3M ESPE™) and Silgimix® (Sultan Dental™). The irreversible hydrocolloid impression material, Jeltrate Plus antimicrobial® (Dentsply Caulk™) served as the control. Materials and Methods: Testing of materials was conducted in accordance with ANSI/ADA Specification No. 18 for Alginate Impression Materials. Statistical Analysis: The 3-Way ANOVA test was used to analyze measurements between different time points at a significance level of (p \u3c 0.05) Outcome: It was found that there was greater compatibility between gypsum and the alternative materials over time than the traditional irreversible hydrocolloid material that was tested. A statistically significant amount of surface change/incompatibility was found over time with the combination of the dental gypsum products and the control impression material (Jeltrate Plus antimicrobial®)

Decay Rate and Low-Energy Near-Horizon Dynamics of Acoustic Black Holes

We study the low-energy dynamics of an acoustic black hole near the sonic horizon. For the experimental test of black hole evaporation in the laboratory, the decay rate (greybody factor) of the acoustic black hole (sonic hole) can be calculated by the usual low-energy perturbation method. As a consequence, we obtain the decay rate of the sonic horizon from the absorption and the reflection coefficients. Moreover, we show that the thermal emission from the sonic horizon is only proportional to a control parameter which describes the velocity of the fluid.Comment: 13pages, 3figures, RevTeX3, some minors corrected. version to appear in PL

Use of NH3 fuel to achieve deep greenhouse gas reductions from US transportation

AbstractThe transportation sector is one of the largest sources of greenhouse gases (GHGs) emissions in the United States. This study identifies scenarios for dramatically reducing future GHG emissions from the US transportation sector, specifically from light-duty vehicles (LDVs), by phasing in ammonia (NH3)-fueled vehicles in place of vehicles using petroleum-based fuels.Projected US LDV carbon dioxide (CO2) emissions from the Annual Energy Outlook (AEO) 2013 reference case projections prepared by the United States Department of Energy serve as the reference case for this study. Two scenarios, in addition to the AEO reference case, have been developed in this study to illustrate the GHG emissions mitigation potential of implementing NH3-fueled vehicles in the US LDV transportation sector through 2040. This study uses the software tool LEAP (the Long range Energy Alternatives Planning System), with which alternative scenarios can be created and evaluated by comparing their energy requirements and environmental impacts.Aggressive implementation of NH3-fueled vehicles replacing gasoline vehicles to account for 100% in 2040 achieves reduction of about 30% of the cumulative LDV CO2 emissions from 2010 through 2040 produced in the reference case. It eliminates most of the annual LDV CO2 emissions projected in the reference case in the year 2040, with a 96% reduction from reference case levels, equivalent to a reduction of approximately 718 million metric tons CO2 equivalent in that year’s emissions.The current study demonstrates that NH3-fueled vehicles could be a promising near-term alternative for LDV because of its significant contribution in reducing CO2 emissions compared with vehicles of carbon based fuels