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

An Alternative Method to Deduce Bubble Dynamics in Single Bubble Sonoluminescence Experiments

In this paper we present an experimental approach that allows to deduce the important dynamical parameters of single sonoluminescing bubbles (pressure amplitude, ambient radius, radius-time curve) The technique is based on a few previously confirmed theoretical assumptions and requires the knowledge of quantities such as the amplitude of the electric excitation and the phase of the flashes in the acoustic period. These quantities are easily measurable by a digital oscilloscope, avoiding the cost of expensive lasers, or ultrafast cameras of previous methods. We show the technique on a particular example and compare the results with conventional Mie scattering. We find that within the experimental uncertainties these two techniques provide similar results.Comment: 8 pages, 5 figures, submitted to Phys. Rev.

Fitting the integrated Spectral Energy Distributions of Galaxies

Fitting the spectral energy distributions (SEDs) of galaxies is an almost universally used technique that has matured significantly in the last decade. Model predictions and fitting procedures have improved significantly over this time, attempting to keep up with the vastly increased volume and quality of available data. We review here the field of SED fitting, describing the modelling of ultraviolet to infrared galaxy SEDs, the creation of multiwavelength data sets, and the methods used to fit model SEDs to observed galaxy data sets. We touch upon the achievements and challenges in the major ingredients of SED fitting, with a special emphasis on describing the interplay between the quality of the available data, the quality of the available models, and the best fitting technique to use in order to obtain a realistic measurement as well as realistic uncertainties. We conclude that SED fitting can be used effectively to derive a range of physical properties of galaxies, such as redshift, stellar masses, star formation rates, dust masses, and metallicities, with care taken not to over-interpret the available data. Yet there still exist many issues such as estimating the age of the oldest stars in a galaxy, finer details ofdust properties and dust-star geometry, and the influences of poorly understood, luminous stellar types and phases. The challenge for the coming years will be to improve both the models and the observational data sets to resolve these uncertainties. The present review will be made available on an interactive, moderated web page (sedfitting.org), where the community can access and change the text. The intention is to expand the text and keep it up to date over the coming years.Comment: 54 pages, 26 figures, Accepted for publication in Astrophysics & Space Scienc

Frost Growth in Laminar Channel Flows with Streamwise Vortices

An experimental study of frost growth under the influence of streamwise vortices in a laminar channel flow is presented. A new model of frost growth is developed to normalize the growth rate of frost with respect to the effects of environmental parameters and time. This normalization and a scale analysis show that the dimensionless frost thickness grows with the square root of environmental time, a single parameter capturing environmental and temporal effects. Experimental plain-channel data obey this relationship to within the uncertainty of the measurements. Also in agreement with the model, the data show no significant dependence on channel location or on Reynolds number (for 5OO<Re<2500 based on hydraulic diameter). Comparisons of model predictions to data from previous studies demonstrate good agreement with these independent data obtained under other conditions. The growth patterns of frost behind a delta-wing fixed to the surface of the channel are explained using flow visualization results. The appearance of frost on the surface occurs sooner, and the frost has an internal structure in regions where the vortices impose a flow toward the surface different from regions unaffected by vortices. Horseshoe vortices form at the junction of the channel and wing and the interaction of tip vortex and horseshoe vortex were qualitatively observed. The maximum frost height behind the delta wing in the spanwise direction is compared to the plain channel results: frost growth rate under the influence of the streamwise vortex was approximately 13% higher than for the plain-channel case.Air Conditioning and Refrigeration Project 5

Soluble Tin(II) Macroinitiator Adducts for the Controlled Ring-Opening Polymerization of Lactones and Cyclic Carbonates

Polyesters and poly(ester carbonates) were synthesized via ring-opening polymerization with new tin(II) macroinitiator adducts containing oligomeric (L)-lactide (LLA,), rac-lactide (rac-LA), and is an element of-caprolactone (CL). The novel initiating species were synthesized by the reaction of LLA, rac-LA, or CL with Sn(OEt)(2) (monomer concentration/initiator concentration less than or equal to20) and then were dissolved in methylene chloride or toluene and stored in a stoppered flask for the subsequent ring-opening polymerization of cyclic esters and carbonates. The soluble tin alkoxide macroinitiators yielded predictable and quantitative initiation of polymerization for up to 1 month of storage time at room temperature. The resulting polymers displayed low polydispersity (less than or equal to 1.5), and a high monomer conversion (greater than or equal to95%) was obtained within relatively short polymerization times (less than or equal to2 h). Adjusting the monomer/macroinitiator ratio effectively controlled the molecular weights of the polymers. NMR was used to characterize the initiating species and polymer microstructure, and size exclusion chromatography was used to determine the molecular weight properties of the polymers. (C) 2002 Wiley Periodicals, Inc