"Soft X-ray transient" outbursts which aren't soft

We have accumulated multiwavelength (X-ray, optical, radio) lightcurves for the eight black hole X-ray binaries which have been observed to enter a supposed `soft X-ray transient' outburst, but remained in the low/hard state throughout the outburst. Comparison of the lightcurve morphologies, spectral behaviour, properties of the quasi-periodic oscillations and the radio jet provides the first study of such objects as a sub-class of X-ray transients. However rather than assuming that these hard state X-ray transients are different from the `canonical' soft X-ray transient, we prefer to consider the possibility that new analysis of both soft and hard state X-ray transients in a spectral context will provide a model capable of explaining the outburst mechanisms of (almost) all black hole X-ray binaries.Comment: Accepted for publication in New Astronom

The Hard Truth about Some "Soft" X-ray Transients

We have accumulated multiwavelength lightcurves for eight black hole X-ray binaries which have been observed to enter a supposed ``soft X-ray transient'' outburst, but which in fact remained in the low/hard state throughout the outburst. Comparison of the lightcurve morphologies, spectral behaviour, properties of the QPOs and the radio jet provides the first study of such objects as a subclass of X-ray transients (XRTs). However, rather than assuming that these hard state XRTs are different from ``canonical'' soft XRTs, we prefer to consider the possibility that a new analysis of both soft and hard state XRTs in a spectral context will provide a model capable of explaining the outburst mechanisms for the majority of black hole X-ray binaries.Comment: 3 pages, 2 figures; to appear in the Proceedings of the 4th Microquasar Workshop, 2002, eds. Durouchoux, Fuchs & Rodriguez, published by the Center for Space Physics: Kolkat

Optimal quantum state reconstruction for cold trapped ions

We study the physical implementation of an optimal tomographic reconstruction scheme for the case of determining the state of a multi-qubit system, where trapped ions are used for defining qubits. The protocol is based on the use of mutually unbiased measurements and on the physical information described in H. H\"{a}ffner \emph{et. al} [Nature \textbf{438}, 643-646 (2005)]. We introduce the concept of physical complexity for different types of unbiased measurements and analyze their generation in terms of one and two qubit gates for trapped ions.Comment: Accepted for publication in Phys. Rev. A as Rap. Com

Trade and child labor: a general equilibrium analysis

This paper augments the existing literature on trade and child labor by exploring the effects of terms of trade changes in the context of a three good general equilibrium model, where one of the goods is a non-traded good. We find that under quasi-linear preferences the effect of the terms of trade on child labor depends critically on the pattern of substitutability (or complimentarity) in the excess demand functions between the export good and the non-traded good. We extend the analysis to the case where factors move freely between the three goods as in a Heckscher-Ohlin type framework. Finally, we show that a balanced budget policy of taxing the education of skilled families and subsidizing the education of unskilled families must reduce child labor without any impact on aggregate welfare.Child labor ; Balance of payments

Ethnic networks and U.S. exports

This paper provides new estimates of the effects of ethnic networks on U.S. exports. In line with recent research, our dataset is a panel of exports from U.S. states to 29 foreign countries. Our analysis departs from the literature in two ways, both of which show that previous estimates of the ethnic-network elasticity of trade are sensitive to the restrictions imposed on the estimated models. Our first departure is to control for unobserved heterogeneity with properly specified fixed effects, which we can do because our dataset contains a time dimension absent from previous studies. Our second departure is to remove the restriction that the network effect is the same for all ethnicities. We find that ethnic-network effects are much larger than has been estimated previously, although they are important only for a subset of countries.Exports ; Regional economics

Kinetic study of adsorption and photo-decolorization of Reactive Red 198 on TiO2 surface

Recycling and reuse of wastewater after purification will reduce the environmental pollution as well as fulfill the increasing demand of water. Adsorption-based water treatment process is very popular for dye-house wastewater treatment. The present study deals with treatment of wastewater contaminated by reactive dye. TiO2 is used as adsorbent and the spent adsorbent has been regenerated by Advanced Oxidation Process (AOP), without using any other chemicals. TiO2 adsorbs dye molecules and then those dye molecules have been oxidized via a photocatalytic reaction in presence of UV irradiation. Kinetics of dye adsorption and photocatalytic oxidation reaction has been developed in this study. Photocatalyst adsorbent (TiO2) has been reused several times after regeneration. The activity of catalyst decreases after each cycle; due to poisoning cause by intermediate by-products. Kinetic of this catalyst deactivation has been incorporated with L–H model to develop the photocatalytic reaction kinetic model

Hyperon bulk viscosity in strong magnetic fields

We study the bulk viscosity of neutron star matter including $\Lambda$ hyperons in the presence of quantizing magnetic fields. Relaxation time and bulk viscosity due to both the non-leptonic weak process involving $\Lambda$ hyperons and direct Urca processes are calculated here. In the presence of a strong magnetic field of $10^{17}$ G, the hyperon bulk viscosity coefficient is reduced whereas bulk viscosity coefficients due to direct Urca processes are enhanced compared with their field free cases when many Landau levels are populated by protons, electrons and muons.Comment: LaTex, 28 pages including 9 figures; new results are discussed in section I

GRO J1744-28, search for the counterpart: infrared photometry and spectroscopy

Using VLT/ISAAC, we detected 2 candidate counterparts to the bursting pulsar GRO J1744-28, one bright and one faint, within the X-ray error circles of XMM-Newton and Chandra. In determining the spectral types of the counterparts we applied 3 different extinction corrections; one for an all-sky value, one for a Galactic Bulge value and one for a local value. We find the local value, with an extinction law of alpha = 3.23 +- 0.01 is the only correction that results in colours and magnitudes for both bright and faint counterparts consistent with a small range of spectral types, and for the bright counterpart, consistent with the spectroscopic identification. Photometry of the faint candidate indicates it is a K7/M0 V star at a distance of 3.75 +- 1 kpc. This star would require a very low inclination angle (i < 9deg) to satisfy the mass function constraints; however it cannot be excluded as the counterpart without follow-up spectroscopy to detect emission signatures of accretion. Photometry and spectroscopy of the bright candidate indicate it is most likely a G/K III star. The spectrum does not show Br-gamma emission, a known indicator of accretion. The bright star's magnitudes are in agreement with the constraints placed on a probable counterpart by the calculations of Rappaport & Joss (1997) for an evolved star that has had its envelope stripped. The mass function indicates the counterpart should have M < 0.3 Msol for an inclination of i >= 15deg; a stripped giant, or a main sequence M3+ V star are consistent with this mass-function constraint. In both cases mass-transfer, if present, will be by wind-accretion as the counterpart will not fill its Roche lobe given the observed orbital period. The derived magnetic field of 2.4 x 10^{11} G will inhibit accretion by the propeller effect, hence its quiescent state.Comment: 12 pages, 6 figures, 4 table, MNRAS accepted Changes to the content and an increased analysis of the Galactic centre extinctio

What can the SNO Neutral Current Rate teach us about the Solar Neutrino Anomaly

We investigate how the anticipated neutral current rate from $SNO$ will sharpen our understanding of the solar neutrino anomaly. Quantitative analyses are performed with representative values of this rate in the expected range of $0.8 - 1.2$. This would provide a $5 - 10 \sigma$ signal for $\nu_e$ transition into a state containing an active neutrino component. Assuming this state to be purely active one can estimate both the $^8B$ neutrino flux and the $\nu_e$ survival probability to a much higher precision than currently possible. Finally the measured value of the $NC$ rate will have profound implications for the mass and mixing parameters of the solar neutrino oscillation solution.Comment: Brief discussion on the first NC result from SNO added; final version to be published in the MPL