Optical calibration hardware for the Sudbury Neutrino Observatory

The optical properties of the Sudbury Neutrino Observatory (SNO) heavy water Cherenkov neutrino detector are measured in situ using a light diffusing sphere ("laserball"). This diffuser is connected to a pulsed nitrogen/dye laser via specially developed underwater optical fibre umbilical cables. The umbilical cables are designed to have a small bending radius, and can be easily adapted for a variety of calibration sources in SNO. The laserball is remotely manipulated to many positions in the D2O and H2O volumes, where data at six different wavelengths are acquired. These data are analysed to determine the absorption and scattering of light in the heavy water and light water, and the angular dependence of the response of the detector's photomultiplier tubes. This paper gives details of the physical properties, construction, and optical characteristics of the laserball and its associated hardware.Comment: 17 pages, 8 figures, submitted to Nucl. Inst. Meth.

Low-threshold organic laser based on an oligofluorene truxene with low optical losses

A blue-emitting distributed feedback laser based on a star-shaped oligofluorene truxene molecule is presented. The gain, loss, refractive index, and (lack of) anisotropy are measured by amplified spontaneous emission and variable-angle ellipsometry. The waveguide losses are very low for an organic semiconductor gain medium, particularly for a neat film. The results suggest that truxenes are promising for reducing loss, a key parameter in the operation of organic semiconductor lasers. Distributed feedback lasers fabricated from solution by spin-coating show a low lasing threshold of 270 W/cm(2) and broad tunability across 25 nm in the blue part of the spectrum

New approaches to object classification in synoptic sky surveys

Digital synoptic sky surveys pose several new object classification challenges. In surveys where real-time detection and classification of transient events is a science driver, there is a need for an effective elimination of instrument-related artifacts which can masquerade as transient sources in the detection pipeline, e.g., unremoved large cosmic rays, saturation trails, reflections, crosstalk artifacts, etc. We have implemented such an Artifact Filter, using a supervised neural network, for the real-time processing pipeline in the Palomar-Quest (PQ) survey. After the training phase, for each object it takes as input a set of measured morphological parameters and returns the probability of it being a real object. Despite the relatively low number of training cases for many kinds of artifacts, the overall artifact classification rate is around 90%, with no genuine transients misclassified during our real-time scans. Another question is how to assign an optimal star-galaxy classification in a multi-pass survey, where seeing and other conditions change between different epochs, potentially producing inconsistent classifications for the same object. We have implemented a star/galaxy multipass classifier that makes use of external and a priori knowledge to find the optimal classification from the individually derived ones. Both these techniques can be applied to other, similar surveys and data sets

Laboratory capture, isolation and analysis of microparticles in aerogel: Preparation for the return of Stardust

We present observations from the laboratory capture of particles in aerogel. The paper focuses on a possible extraction technique and the bulk mineral characterization of the captured material using non-destructive analytical techniques

Towards real-time classification of astronomical transients

Exploration of time domain is now a vibrant area of research in astronomy, driven by the advent of digital synoptic sky surveys. While panoramic surveys can detect variable or transient events, typically some follow-up observations are needed; for short-lived phenomena, a rapid response is essential. Ability to automatically classify and prioritize transient events for follow-up studies becomes critical as the data rates increase. We have been developing such methods using the data streams from the Palomar-Quest survey, the Catalina Sky Survey and others, using the VOEventNet framework. The goal is to automatically classify transient events, using the new measurements, combined with archival data (previous and multi-wavelength measurements), and contextual information (e.g., Galactic or ecliptic latitude, presence of a possible host galaxy nearby, etc.); and to iterate them dynamically as the follow-up data come in (e.g., light curves or colors). We have been investigating Bayesian methodologies for classification, as well as discriminated follow-up to optimize the use of available resources, including Naive Bayesian approach, and the non-parametric Gaussian process regression. We will also be deploying variants of the traditional machine learning techniques such as Neural Nets and Support Vector Machines on datasets of reliably classified transients as they build up

Condensate fluctuations in finite Bose-Einstein condensates at finite temperature

A Langevin equation for the complex amplitude of a single-mode Bose-Einstein condensate is derived. The equation is first formulated phenomenologically, defining three transport parameters. It is then also derived microscopically. Expressions for the transport parameters in the form of Green-Kubo formulas are thereby derived and evaluated for simple trap geometries, a cubic box with cyclic boundary conditions and an isotropic parabolic trap. The number fluctuations in the condensate, their correlation time, and the temperature-dependent collapse-time of the order parameter as well as its phase-diffusion coefficient are calculated.Comment: 29 pages, Revtex, to appear in Phys.Rev.

Quantum Kinetic Theory V: Quantum kinetic master equation for mutual interaction of condensate and noncondensate

A detailed quantum kinetic master equation is developed which couples the kinetics of a trapped condensate to the vapor of non-condensed particles. This generalizes previous work which treated the vapor as being undepleted.Comment: RevTeX, 26 pages and 5 eps figure

A missense mutation (c.184C>T) in ovine CLN6 causes neuronal ceroid lipofuscinosis in Merino sheep whereas affected South Hampshire sheep have reduced levels of CLN6 mRNA

AbstractThe neuronal ceroid lipofuscinoses (NCLs, Batten disease) are a group of fatal recessively inherited neurodegenerative diseases of humans and animals characterised by common clinical signs and pathology. These include blindness, ataxia, dementia, behavioural changes, seizures, brain and retinal atrophy and accumulation of fluorescent lysosome derived organelles in most cells. A number of different variants have been suggested and seven different causative genes identified in humans (CLN1, CLN2, CLN3, CLN5, CLN6, CLN8 and CTSD). Animal models have played a central role in the investigation of this group of diseases and are extremely valuable for developing a better understanding of the disease mechanisms and possible therapeutic approaches. Ovine models include flocks of affected New Zealand South Hampshires and Borderdales and Australian Merinos. The ovine CLN6 gene has been sequenced in a representative selection of these sheep. These investigations unveiled the mutation responsible for the disease in Merino sheep (c.184C>T; p.Arg62Cys) and three common ovine allelic variants (c.56A>G, c.822G>A and c.933_934insCT). Linkage analysis established that CLN6 is the gene most likely to cause NCL in affected South Hampshire sheep, which do not have the c.184C>T mutation but show reduced expression of CLN6 mRNA in a range of tissues as determined by real-time PCR. Lack of linkage precludes CLN6 as a candidate for NCL in Borderdale sheep

Symmetric-Asymmetric transition in mixtures of Bose-Einstein condensates

We propose a new kind of quantum phase transition in phase separated mixtures of Bose-Einstein condensates. In this transition, the distribution of the two components changes from a symmetric to an asymmetric shape. We discuss the nature of the phase transition, the role of interface tension and the phase diagram. The symmetric to asymmetric transition is the simplest quantum phase transition that one can imagine. Careful study of this problem should provide us new insight into this burgeoning field of discovery.Comment: 6 pages, 3 eps figure