Two-dimensional Yang-Mills Theories Are String Theories

We show that two-dimensional SO(N) and Sp(N) Yang-Mills theories without fermions can be interpreted as closed string theories. The terms in the 1/N expansion of the partition function on an orientable or nonorientable manifold M can be associated with maps from a string worldsheet onto M. These maps are unbranched and branched covers of M with an arbitrary number of infinitesimal worldsheet cross-caps mapped to points in M. These string theories differ from SU(N) Yang-Mills string theory in that they involve odd powers of 1/N and require both orientable and nonorientable worldsheets.Comment: (two references added; one old, one recent) 14pages, Latex, BRX-TH-346, JHU-TIPAC-93001

Interiors : works by Gregor Bell, Geoff Kleem, Ted Riggs, Derek Smith, Alex Wanders, Geoff Weary

Interiors : works by Gregor Bell, Geoff Kleem, Ted Riggs, Derek Smith, Alex Wanders, Geoff Wear

Frequency dependence of acoustic waves in marine sediments

In situ techniques provide the most reliable method of examining the geoacoustical properties of marine sediments. In the past, individual in situ surveys have only been able to examine compressional waves over a maximum frequency range of 100 Hz to 50 kHz. A new in situ acoustic device, the Sediment Probing Acoustic Detection Equipment, or SPADE, has been developed, which can emit a variety of pulses, e.g. tonal and swept-frequency, over a continuous frequency range of 10 - 100 kHz. Data from a recent field trial are analysed to obtain the in situ velocity and attenuation over frequency increments of 5 kHz between 10 - 75 kHz. Results imply that scattering is a dominant attenuation mechanism from 10-75 kHz and the media is dispersive for frequencies between 60 and 70 kHz and below 20 kHz. Biot theory cannot accurately model the observed velocity and attenuation

The low wind expansion velocity of metal-poor carbon stars in the Halo and the Sagittarius stream

We report the detection, from observations using the James Clerk Maxwell Telescope, of CO J $=$ 3$\to$ 2 transition lines in six carbon stars, selected as members of the Galactic Halo and having similar infrared colors. Just one Halo star had been detected in CO before this work. Infrared observations show that these stars are red (J-K $>$3), due to the presence of large dusty circumstellar envelopes. Radiative transfer models indicates that these stars are losing mass with rather large dust mass-loss rates in the range 1--3.3 $\times$$10^{-8}$M$_{\odot}$yr$^{-1}$, similar to what can be observed in the Galactic disc. We show that two of these stars are effectively in the Halo, one is likely linked to the stream of the Sagittarius Dwarf Spheroidal galaxy (Sgr dSph), and the other three stars certainly belong to the thick disc. The wind expansion velocities of the observed stars are low compared to carbon stars in the thin disc and are lower for the stars in the Halo and the Sgr dSph stream than in the thick disc. We discuss the possibility that the low expansion velocities result from the low metallicity of the Halo carbon stars. This implies that metal-poor carbon stars lose mass at a rate similar to metal-rich carbon stars, but with lower expansion velocities, as predicted by recent theoretical models. This result implies that the current estimates of mass-loss rates from carbon stars in Local Group galaxies will have to be reconsidered.Comment: 10 pages, 7 figures, accepted for publication in MNRA

The String Calculation of QCD Wilson Loops on Arbitrary Surfaces

Compact string expressions are found for non-intersecting Wilson loops in SU(N) Yang-Mills theory on any surface (orientable or nonorientable) as a weighted sum over covers of the surface. All terms from the coupled chiral sectors of the 1/N expansion of the Wilson loop expectation values are included.Comment: 10 pages, LaTeX, no figure

Directed mutagenesis as a technique to study protein function: application to β-lactamase

The function of a protein follows uniquely from its three-dimensional structure, which is unambiguously determined by the linear sequence of amino acids. Thus to undertake a systematic study of the relationship between protein structure and function, one would ideally like to be able to alter the structural gene in various ways to encode proteins with novel sequences, structures and functions. Various mutagenic strategies and methods have recently been developed that allow one to achieve these objectives

Moving the Needle on Justice Reform: A Report on the American Justice Summit 2014

Executive Summary: Taking place over 5 hours during the afternoon of November 10th, 2014, in John Jay College’s Gerald W. Lynch Theater, the American Justice Summit was an unprecedented public meeting of some of the most important individuals working in contemporary criminal justice reform. The event placed these individuals in front of an audience of six hundred-odd practitioners, activists, students, elected officials, and policy professionals, in conversation with leading journalists and each other, to describe the scope and contours of the problems posed by the country’s dysfunctional and interlocking systems of criminal justice – mass incarceration, police-community relations, the system’s disproportionate criminalization of young people, people of color, and the mentally ill, its contributions to urban poverty, violence, and alienation – and to grapple with potential solutions. This report synthesizes data gathered from the event itself and its publicly available video record with dozens of participant and audience interviews in order to describe points of consensus and divergence among the gathered experts, to detail the full range of their proposed solutions, to evaluate the event’s impact on the gathered participants and the audience bearing witness, and to consider potentially fruitful directions for future efforts on a similar template. Having established the mold for large-scale, high-profile public events addressing criminal justice policy and advocating reform, Tina Brown Live Media and John Jay College have provided a powerful model for moving this essential conversation forward. In addition to providing a snapshot of the event and its immediate impact, this report attempts to address the context of a fast-moving reform conversation and an ideologically inclusive movement, the shape and focus of which is in constant flux as it takes place across academic institutions, policy forums, and media platforms. More voices join this conversation every day; it is the job of events like the American Justice Summit to curate these voices, and amplify those with the most meaningful ideas to contribute. Please note: Featured quotations throughout the document (shaded text boxes) contain hyperlinks to clips of the video and audio interviews from which they were drawn