Tight focal spots using azimuthally polarised light from a Fresnel cone

When focusing a light beam at high numerical aperture, the resulting electric field profile in the focal plane depends on the transverse polarisation profile, as interference between different parts of the beam needs to be taken into account. It is well known that radial polarised light produces a longitudinal polarisation component and can be focused below the conventional diffraction limit for homogeneously polarised light, and azimuthally polarised light that carries one unit of angular momentum can achieve even tighter focal spots. This is of interest for example for enhancing resolution in scanning microscopy. There are numerous ways to generate such polarisation structures, however, setups can be expensive and usually rely on birefringent components, hence prohibiting broadband operation. We have recently demonstrated a passive, low-cost technique using a simple glass cone (Fresnel cone) to generate beams with structured polarisation. We show here that the polarisation structure generated by Fresnel cones focuses better than radial polarised light at all numerical apertures. Furthermore, we investigate in detail the application of polarised light structures for two-photon microscopy. Specifically we demonstrate a method that allows us to generate the desired polarisation structure at the back aperture of the microscope by pre-compensating any detrimental phase shifts using a combination of waveplates

Investigation of double beta decay with the NEMO-3 detector

The double beta decay experiment NEMO~3 has been taking data since February 2003. The aim of this experiment is to search for neutrinoless ($0\nu\beta\beta$) decay and investigate two neutrino double beta decay in seven different isotopically enriched samples ($^{100}$Mo, $^{82}$Se, $^{48}$Ca, $^{96}$Zr, $^{116}$Cd, $^{130}$Te and $^{150}$Nd). After analysis of the data corresponding to 3.75 y, no evidence for $0\nu\beta\beta$ decay in the $^{100}$Mo and $^{82}$Se samples was found. The half-life limits at the 90% C.L. are $1.1\cdot 10^{24}$ y and $3.6\cdot 10^{23}$ y, respectively. Additionally for $0\nu\beta\beta$ decay the following limits at the 90% C.L. were obtained, $> 1.3 \cdot 10^{22}$ y for $^{48}$Ca, $> 9.2 \cdot 10^{21}$ y for $^{96}$Zr and $> 1.8 \cdot 10^{22}$ y for $^{150}$Nd. The $2\nu\beta\beta$ decay half-life values were precisely measured for all investigated isotopes.Comment: 12 pages, 4 figures, 5 tables; talk at conference on "Fundamental Interactions Physics" (ITEP, Moscow, November 23-27, 2009

Viscosity of High Energy Nuclear Fluids

Relativistic high energy heavy ion collision cross sections have been interpreted in terms of almost ideal liquid droplets of nuclear matter. The experimental low viscosity of these nuclear fluids have been of considerable recent quantum chromodynamic interest. The viscosity is here discussed in terms of the string fragmentation models wherein the temperature dependence of the nuclear fluid viscosity obeys the Vogel-Fulcher-Tammann law.Comment: 6 pages, ReVTeX 4 format, two figures, *.eps forma

Global action-angle coordinates for completely integrable systems with noncompact invariant submanifolds

The obstruction to the existence of global action-angle coordinates of Abelian and noncommutative (non-Abelian) completely integrable systems with compact invariant submanifolds has been studied. We extend this analysis to the case of noncompact invariant submanifolds.Comment: 13 pages, to be published in J. Math. Phys. (2007

A method to construct refracting profiles

We propose an original method for determining suitable refracting profiles between two media to solve two related problems: to produce a given wave front from a single point source after refraction at the refracting profile, and to focus a given wave front in a fixed point. These profiles are obtained as envelopes of specific families of Cartesian ovals. We study the singularities of these profiles and give a method to construct them from the data of the associated caustic.Comment: 12 pages, 5 figure

High-field vortices in Josephson junctions with alternating critical current density

We study long Josephson junctions with the critical current density alternating along the junction. New equilibrium states, which we call the field synchronized or FS states, are shown to exist if the applied field is from narrow intervals centered around equidistant series of resonant fields, $H_m$. The values of $H_m$ are much higher than the flux penetration field, $H_s$. The flux per period of the alternating critical current density, $\phi_i$, is fixed for each of the FS states. In the $m$-th FS state the value of $\phi_i$ is equal to an integer amount of flux quanta, $\phi_i =m\phi_0$. Two types of single Josephson vortices carrying fluxes $\phi_0$ or/and $\phi_0/2$ can exist in the FS states. Specific stepwise resonances in the current-voltage characteristics are caused by periodic motion of these vortices between the edges of the junction.Comment: 4 pages, 5 figure

Calcutta Botanic Garden and the colonial re-ordering of the Indian environment

This article examines three hand-painted colour maps that accompanied the annual report of the Calcutta Botanic Garden for 1846 to illustrate how the Garden’s layout, uses and functions had changed over the previous 30 years. The evolution of the Calcutta Botanic Garden in the first half of the nineteenth-century reflects a wider shift in attitudes regarding the relationship between science, empire and the natural world. On a more human level the maps result from, and illustrate, the development of a vicious personal feud between the two eminent colonial botanists charged with superintending the garden in the 1840s

A preliminary design study of a microparticle accelerator final report, 30 jan. - 13 apr. 1964

Design study for 2MV microparticle accelerato

Evidence for Recent Wet-Based Crater Glaciation in Tempe Terra, Mars.

[Introduction] Mars’ mid-latitudes host abundant putative debris-covered water-ice glaciers (viscous flow features; VFF). Eskers emerging from 110-150 Myr-old VFF in Phlegra Montes and Tempe Terra provide evidence for rare occurences of past, localized basal melting of their parent VFF, despite the cold climates of the late Amazonian (see this conf.). Eskers are sinuous ridges comprising glaciofluvial sediment deposited by meltwater flowing through tunnels within glacial ice. Here, we describe a population of sinuous ridges emerging from VFF in an unnamed ~45 km-diameter crater (38.47 N, 72.43 W) in Tempe Terra, ~600 km from the VFF-linked esker identified by Butcher et al. We consider two working hypotheses for the formation of the sinuous ridges; that they are either (1) eskers formed by melting of the glaciers from which they emerge, or (2) topographically inverted fluvial channels which formed prior to glaciation of the crater. We present observations from preliminary geomorphic mapping of the crater to start to test those hypotheses