Simulation of charged particle trajectories in the neutron decay correlation experiment abBA

The proposed neutron decay correlation experiment, abBA, will directly detect the direction of emission of decay protons and electrons as well as providing spectroscopic information for both particles. In order to provide this information, the abBA experiment incorporates spatially varying electric and magnetic fields. We report on detailed simulations of the decay particle trajectories in order to assess the impact of various systematic effects on the experimental observables. These include among others; adiabaticity of particle orbits, tracking of orbits, reversal of low energy protons due to inhomogeneous electric field, and accuracy of proton time of flight measurements. Several simulation methods were used including commercial software (Simion), custom software, as well as analytical tools based on the use of adiabatic invariants. Our results indicate that the proposed field geometry of the abBA spectrometer will be substantially immune to most systematic effects and that transport calculations using adiabatic invariants agree well with solution of the full equations of motion

Spin-Dependent Electron Scattering from Polarized Protons and Deuterons with the BLAST Experiment at MIT-Bates

The Bates Large Acceptance Spectrometer Toroid (BLAST) experiment was operated at the MIT-Bates Linear Accelerator Center from 2003 until 2005. The experiment was designed to exploit the power of a polarized electron beam incident on polarized targets of hydrogen and deuterium to measure, in a systematic manner, the neutron, proton, and deuteron form factors as well as other aspects of the electromagnetic interaction on few-nucleon systems. We briefly describe the experiment, and present and discuss the numerous results obtained.United States. Dept. of EnergyNational Science Foundation (U.S.

The fables of pity: Rousseau, Mandeville and the animal-fable

Copyright @ 2012 Edinburgh University PressPrompted by Derrida’s work on the animal-fable in eighteenth-century debates about political power, this article examines the role played by the fiction of the animal in thinking of pity as either a natural virtue (in Rousseau’s Second Discourse) or as a natural passion (in Mandeville’s The Fable of the Bees). The war of fables between Rousseau and Mandeville – and their hostile reception by Samuel Johnson and Adam Smith – reinforce that the animal-fable illustrates not so much the proper of man as the possibilities and limitations of a moral philosophy that is unable to address the political realities of the state

Dynamics of BAF- Polycomb Complex Opposition on Heterochromatin in Normal and Oncogenic States

The opposition between polycomb repressive complexes (PRC) and BAF (mSWI/SNF) complexes plays critical roles in development and disease. Mutations in the genes encoding BAF subunits contribute to over 20% of human malignancy, yet the underlying mechanisms remain unclear owing largely to a lack of assays to assess BAF function in vivo. To address this, we have developed a widely applicable recruitment assay system and find that BAF opposes PRC by rapid, ATP-dependent eviction, leading to the formation of accessible chromatin. Reversing this process results in reassembly of facultative heterochromatin. Surprisingly, BAF-mediated PRC eviction occurs in the absence of PolII occupancy, transcription, and replication. Further, we find that tumor suppressor and oncogenic BAF complex mutations result in differential effects on PRC eviction. These studies define a mechanistic sequence underlying the resolution and formation of facultative heterochromatin and demonstrate that BAF opposes polycomb complexes on a minute-by-minute basis to provide epigenetic plasticity

General classification and analysis of neutron beta-decay experiments

A general analysis of the sensitivities of neutron beta-decay experiments to manifestations of possible interaction beyond the standard model is carried out. In a consistent fashion, we take into account all known radiative and recoil corrections arising in the standard model. This provides a description of angular correlations in neutron decay in terms of one parameter, which is accurate to the level of similar to 10(-5). Based on this general expression, we present an analysis of the sensitivities to new physics for selected neutron decay experiments. We emphasize that the usual parametrization of experiments in terms of the tree-level coefficients a,A, and B is inadequate when the experimental sensitivities are at the same or higher level relative to the size of the corrections to the tree-level description

The BLAST Cherenkov detectors

We report on the design, construction, and operation of a large array of diffusely reflective aerogel Cherenkov detectors. They are part of the detector instrumentation of the Bates Large Acceptance Spectrometer Toroid (BLAST) at the MIT-Bates Linear Accelerator Center. The Cherenkov detectors are used for particle identification. They are able to discriminate between pions and electrons with momenta up to 700 MeV/c. (c) 2005 Elsevier B.V. All rights reserved

A systematic characterization of Cwc21, the yeast ortholog of the human spliceosomal protein SRm300

Cwc21 (complexed with Cef1 protein 21) is a 135 amino acid yeast protein that shares homology with the N-terminal domain of human SRm300/SRRM2, a large serine/arginine-repeat protein shown previously to associate with the splicing coactivator and 3′-end processing stimulatory factor, SRm160. Proteomic analysis of spliceosomal complexes has suggested a role for Cwc21 and SRm300 at the core of the spliceosome. However, specific functions for these proteins have remained elusive. In this report, we employ quantitative genetic interaction mapping, mass spectrometry of tandem affinity-purified complexes, and microarray profiling to investigate genetic, physical, and functional interactions involving Cwc21. Combined data from these assays support multiple roles for Cwc21 in the formation and function of splicing complexes. Consistent with a role for Cwc21 at the core of the spliceosome, we observe strong genetic, physical, and functional interactions with Isy1, a protein previously implicated in the first catalytic step of splicing and splicing fidelity. Together, the results suggest multiple functions for Cwc21/SRm300 in the splicing process, including an important role in the activation of splicing in association with Isy1

Revisiting the local structure in Ge-Sb-Te based chalcogenide superlattices

\u3cp\u3eThe technological success of phase-change materials in the field of data storage and functional systems stems from their distinctive electronic and structural peculiarities on the nanoscale. Recently, superlattice structures have been demonstrated to dramatically improve the optical and electrical performances of these chalcogenide based phase-change materials. In this perspective, unravelling the atomistic structure that originates the improvements in switching time and switching energy is paramount in order to design nanoscale structures with even enhanced functional properties. This study reveals a high- resolution atomistic insight of the [GeTe/Sb\u3csub\u3e2\u3c/sub\u3eTe\u3csub\u3e3\u3c/sub\u3e] interfacial structure by means of Extended X-Ray Absorption Fine Structure spectroscopy and Transmission Electron Microscopy. Based on our results we propose a consistent novel structure for this kind of chalcogenide superlattices.\u3c/p\u3