Acceptance dependence of fluctuation measures near the QCD critical point

We argue that a crucial determinant of the acceptance dependence of fluctuation measures in heavy-ion collisions is the range of correlations in the momentum space, e.g., in rapidity, $\Delta y_{\rm corr}$. The value of $\Delta y_{\rm corr}\sim1$ for critical thermal fluctuations is determined by the thermal rapidity spread of the particles at freezeout, and has little to do with position space correlations, even near the critical point where the spatial correlation length $\xi$ becomes as large as $2-3$ fm (this is in contrast to the magnitudes of the cumulants, which are sensitive to $\xi$). When the acceptance window is large, $\Delta y\gg\Delta y_{\rm corr}$, the cumulants of a given particle multiplicity, $\kappa_k$, scale linearly with $\Delta y$, or mean multiplicity in acceptance, $\langle N\rangle$, and cumulant ratios are acceptance independent. While in the opposite regime, $\Delta y\ll\Delta y_{\rm corr}$, the factorial cumulants, $\hat\kappa_k$, scale as $(\Delta y)^k$, or $\langle N\rangle^k$. We demonstrate this general behavior quantitatively in a model for critical point fluctuations, which also shows that the dependence on transverse momentum acceptance is very significant. We conclude that extension of rapidity coverage proposed by STAR should significantly increase the magnitude of the critical point fluctuation signatures.Comment: 9 pages, 4 figures, references adde

Gamma-Ray Spectral Characteristics of Thermal and Non-Thermal Emission from Three Black Holes

Cygnus X-1 and the gamma-ray transients GROJ0422+32 and GROJ1719-24 displayed similar spectral properties when they underwent transitions between the high and low gamma-ray (30 keV to few MeV) intensity states. When these sources were in the high gamma-ray intensity state (gamma-2, for Cygnus X-1), their spectra featured two components: a Comptonized shape below 200-300 keV with a soft power-law tail (photon index >3) that extended to ~1 MeV or beyond. When the sources were in the low-intensity state (gamma-0, for Cygnus X-1), the Comptonized spectral shape below 200 keV typically vanished and the entire spectrum from 30 keV to ~1 MeV can be characterized by a single power law with a relatively harder photon index ~2-2.7. Consequently the high- and low-intensity gamma-ray spectra intersect, generally in the ~400 keV - 1 MeV range, in contrast to the spectral pivoting seen previously at lower (~10 keV) energies. The presence of the power-law component in both the high- and low-intensity gamma-ray spectra strongly suggests that the non-thermal process is likely to be at work in both the high and the low-intensity situations. We have suggested a possible scenario (Ling & Wheaton, 2003), by combining the ADAF model of Esin et al. (1998) with a separate jet region that produces the non-thermal gamma-ray emission, and which explains the state transitions. Such a scenario will be discussed in the context of the observational evidence, summarized above, from the database produced by EBOP, JPL's BATSE earth occultation analysis system.Comment: 6 pages, 3 figures, accepted for publication in Proceedings of 2004 Microquasar Conference, Beijing, China, Chinese Journal of Astronomy and Astrophysics, minor corrections per refere

Fire extinguishant materials

Fire extinguishant composition comprising a mixture of a finely divided aluminum compound and alkali metal, stannous or plumbous halide is provided. Aluminum compound may be aluminum hydroxide, alumina or boehmite but preferably it is an alkali metal dawsonite. The metal halide may be an alkali metal, e.g. potassium iodide, bromide or chloride or stannous or plumbous iodide, bromide or chloride. Potassium iodide is preferred

Binary matrices of optimal autocorrelations as alignment marks

We define a new class of binary matrices by maximizing the peak-sidelobe distances in the aperiodic autocorrelations. These matrices can be used as robust position marks for in-plane spatial alignment. The optimal square matrices of dimensions up to 7 by 7 and optimal diagonally-symmetric matrices of 8 by 8 and 9 by 9 were found by exhaustive searches.Comment: 8 pages, 6 figures and 1 tabl

Discrete gravity and and its continuum limit

Recently Gambini and Pullin proposed a new consistent discrete approach to quantum gravity and applied it to cosmological models. One remarkable result of this approach is that the cosmological singularity can be avoided in a general fashion. However, whether the continuum limit of such discretized theories exists is model dependent. In the case of massless scalar field coupled to gravity with $\Lambda=0$, the continuum limit can only be achieved by fine tuning the recurrence constant. We regard this failure as the implication that cosmological constant should vary with time. For this reason we replace the massless scalar field by Chaplygin gas which may contribute an effective cosmological constant term with the evolution of the universe. It turns out that the continuum limit can be reached in this case indeed.Comment: 16 pages,revised version published in MPL

Dynamics of shape fluctuations of quasi-spherical vesicles revisited

In this paper, the dynamics of spontaneous shape fluctuations of a single, giant quasi-spherical vesicle formed of a single lipid species is revisited theoretically. A coherent physical theory for the dynamics is developed based on a number of fundamental principles and considerations and a systematic formulation of the theory is also established. From the systematic theoretical formulation, an analytical description of the dynamics of shape fluctuations of quasi-spherical vesicles is derived. In particular, in developing the theory we have made a new interpretation of some of the phenomenological constants in a canonical continuum description of fluid lipid-bilayer membranes and shown the consequences of this new interpretation in terms of the characteristics of the dynamics of vesicle shape fluctuations. Moreover, we have used the systematic formulation of our theory as a framework against which we have discussed the previously existing theories and their discrepancies. Finally, we have made a systematic prediction about the system-dependent characteristics of the relaxation dynamics of shape fluctuations of quasi-spherical vesicles with a view of experimental studies of the phenomenon and also discussed, based on our theory, a recently published experimental work on the topic.Comment: 18 pages, 4 figure

Threshold Regression for Survival Analysis: Modeling Event Times by a Stochastic Process Reaching a Boundary

Many researchers have investigated first hitting times as models for survival data. First hitting times arise naturally in many types of stochastic processes, ranging from Wiener processes to Markov chains. In a survival context, the state of the underlying process represents the strength of an item or the health of an individual. The item fails or the individual experiences a clinical endpoint when the process reaches an adverse threshold state for the first time. The time scale can be calendar time or some other operational measure of degradation or disease progression. In many applications, the process is latent (i.e., unobservable). Threshold regression refers to first-hitting-time models with regression structures that accommodate covariate data. The parameters of the process, threshold state and time scale may depend on the covariates. This paper reviews aspects of this topic and discusses fruitful avenues for future research.Comment: Published at http://dx.doi.org/10.1214/088342306000000330 in the Statistical Science (http://www.imstat.org/sts/) by the Institute of Mathematical Statistics (http://www.imstat.org

P-wave diffusion in fluid-saturated medium

This paper considers the propagating P-waves in the fluid-saturated mediums that are categorized to fall into two distinct groups: insoluble and soluble mediums. P-waves are introduced with slowness in accordance to Snell Law and are shown to relate to the medium displacement and wave diffusion. Consequently, the results bear out that the propagating P-waves in the soluble medium share similar diffusive characteristic as of insoluble medium. Nonetheless, our study on fluid density in the mediums show that high density fluid promotes diffusive characteristic whiles low density fluid endorses non-diffusive P-wav

Analysis of the transient calibration of heat flux sensors: One dimensional case

The effect of transient heat flux on heat flux sensor response and calibration is analyzed. A one dimensional case was studied in order to elucidate the key parameters and trends for the problem. It has the added advantage that the solutions to the governing equations can be obtained by analytic means. The analytical results obtained to date indicate that the transient response of a heat flux sensor depends on the thermal boundary conditions, the geometry and the thermal properties of the sensor. In particular it was shown that if the thermal diffusivity of the sensor is small, then the transient behavior must be taken into account