Optical Surface Vortices and Their Use in Nanoscale Manipulation

Following a brief overview of the physics underlying the interaction of twisted light with atoms at near-resonance frequencies, the essential ingredients of the interaction of atoms with surface optical vortices are described. It is shown that surface optical vortices can offer an unprecedented potential for the nanoscale manipulation of absorbed atoms congregating at regions of extremum light intensity on the surface

Tax Distortions and Global Climate Policy

We consider the efficiency implications of policies to reduce global carbon emissions in a world with pre-existing tax distortions. We first note that the weak double-dividend, the proposition that the welfare improvement from a tax reform where environmental taxes are used to lower distorting taxes must be greater than the welfare improvement from a reform where the environmental taxes are returned in a lump sum fashion, need not hold in a world with multiple distortions. We then present a large-scale computable general equilibrium model of the world economy with distortionary taxation. We use this model to evaluate a number of policies to reduce carbon emissions. We find that the weak double dividend is not obtained in a number of European countries. Results also demonstrate the point that the interplay between carbon policies and pre-existing taxes can differ markedly across countries. Thus one must be cautious in extrapolating the results from a country specific analysis to other countries.

Tax Distortions and Global Climate Policy

We consider the efficiency implications of policies to reduce global carbon emissions in a world with pre-existing tax distortions. We first note that the weak double-dividend, the proposition that the welfare improvement from a tax reform where environmental taxes are used to lower distorting taxes must be greater than the welfare improvement from a reform where the environmental taxes are returned in a lump sum fashion, need not hold in a world with multiple distortions. We then present a large-scale computable general equilibrium model of the world economy with distortionary taxation. We use this model to evaluate a number of policies to reduce carbon emissions. We find that the weak double dividend is not obtained in a number of European countries. Results also demonstrate the point that the interplay between carbon policies and pre-existing taxes can differ markedly across countries. Thus one must be cautious in extrapolating the results from a country specific analysis to other countries.

Pulmonary thrombo embolism in pregnancy.

Pulmonary thrombo embolism in pregnancy

Utility of Lymph Node Aspiration in the Diagnosis of Visceral Leishmaniasis in Sudan.

We evaluated lymph node aspiration (LNA) as a simple diagnostic procedure for visceral leishmaniasis (VL). Lymph node aspiration was compared with the direct agglutination test (DAT) using a diagnostic titer > or = 1:6,400 in 7,880 suspected VL patients in eastern Sudan. Compared with DAT, LNA had a sensitivity of 65.1% (95% confidence interval = 63.5-66.6%). Parasite density in LNA correlated strongly with DAT titers (P < 0.0001), and low parasite density accounted for 78.1% of positive LNA results with DAT titers < 1:6,400 (n = 782). Risk factors predictive of a positive LNA result were an age of 1-29 years, male sex, a hemoglobin level < 10.0 g/dL, a DAT titer > or = 1:800, and a location with a higher prevalence of VL. Lymph node and splenic aspirations were similarly accurate as tests of cure after treatment of 50 VL patients in southern Sudan. Pre-treatment LNA results were negative in 20 cases of severe post kala-azar dermal leishmaniasis

Surface optical vortices

It is shown how the total internal reflection of orbital-angular-momentum-endowed light can lead to the generation of evanescent light possessing rotational properties in which the intensity distribution is firmly localized in the vicinity of the surface. The characteristics of these surface optical vortices depend on the form of the incident light and on the dielectric mismatch of the two media. The interference of surface optical vortices is shown to give rise to interesting phenomena, including pattern rotation akin to a surface optical Ferris wheel. Applications are envisaged to be in atom lithography, optical surface tweezers, and spanners

Graphene-like optical light field and its interaction with two-level atoms

The theoretical basis leading to the creation of a light field with a hexagonal honeycomb structure resembling graphene is considered along with its experimental realization and its interaction with atoms. It is argued that associated with such a light field is an optical dipole potential which leads to the diffraction of the atoms, but the details depend on whether the transverse spread of the atomic wave packet is larger than the transverse dimensions of the optical lattice (resonant Kapitza-Dirac effect) or smaller (optical Stern-Gerlach effect). Another effect in this context involves the creation of gauge fields due to the Berry phase acquired by the atom moving in the light field. The experimental realization of the light field with a honeycomb hexagonal structure is described using holographic methods and we proceed to explore the atom diffraction in the Kapitza-Dirac regime as well as the optical Stern-Gerlach regime, leading to momentum distributions with characteristic but different hexagonal structures. The artificial gauge fields too are shown to have the same hexagonal spatial structure and their magnitude can be significantly large. The effects are discussed with reference to typical parameters for the atoms and the fields