Multi-chord fiber-coupled interferometer with a long coherence length laser

This paper describes a 561 nm laser heterodyne interferometer that provides time-resolved measurements of line-integrated plasma electron density within the range of 10^15-10^18 cm^(-2). Such plasmas are produced by railguns on the Plasma Liner Experiment (PLX), which aims to produce \mu s-, cm-, and Mbar-scale plasmas through the merging of thirty plasma jets in a spherically convergent geometry. A long coherence length, 320 mW laser allows for a strong, sub-fringe phase-shift signal without the need for closely-matched probe and reference path lengths. Thus only one reference path is required for all eight probe paths, and an individual probe chord can be altered without altering the reference or other probe path lengths. Fiber-optic decoupling of the probe chord optics on the vacuum chamber from the rest of the system allows the probe paths to be easily altered to focus on different spatial regions of the plasma. We demonstrate that sub-fringe resolution capability allows the interferometer to operate down to line-integrated densities of order 10^15 cm^(-2).Comment: submitted to Rev. Sci. Instrum. (2011

Graded Hecke algebras for disconnected reductive groups

We introduce graded Hecke algebras H based on a (possibly disconnected) complex reductive group G and a cuspidal local system L on a unipotent orbit of a Levi subgroup M of G. These generalize the graded Hecke algebras defined and investigated by Lusztig for connected G. We develop the representation theory of the algebras H. obtaining complete and canonical parametrizations of the irreducible, the irreducible tempered and the discrete series representations. All the modules are constructed in terms of perverse sheaves and equivariant homology, relying on work of Lusztig. The parameters come directly from the data (G,M,L) and they are closely related to Langlands parameters. Our main motivation for considering these graded Hecke algebras is that the space of irreducible H-representations is canonically in bijection with a certain set of "logarithms" of enhanced L-parameters. Therefore we expect these algebras to play a role in the local Langlands program. We will make their relation with the local Langlands correspondence, which goes via affine Hecke algebras, precise in a sequel to this paper.Comment: Theorem 3.4 and Proposition 3.22 in version 1 were not entirely correct as stated. This is repaired in a new appendi

Dcse Estimation and Prediction of Radiation Effects on Aquatic Biota Resulting from Radioactive Releases .from the Nuclear Fuel Cycle*

ABSTRACT -NOTICE vepott was rnir . prepared as an accou.T of work S'Cut efponsibuity for the accuracy, completeness « uJulnas of any information, apparatus, product o process disclosed, or represents that its use would not d iht process disclo, p infringe privately owned lights. Aquatic organisms are exposed to radionuclides released to the environment during various steps of the nuclear fuel cycle. Routine releases from these processes are limited in compliance with technical specifications, requirements of federal regulations. These regulations reflect I.C.R.P. recommendations which are designed to provide an environment considered safe for man. It is generally accepted that aquatic organisms will not receive damaging external radiation doses in such environments; however, because of possible bioaccunulation of radionuclides there is concern that aquatic organisms might be adversely affected 'ay internal doses. The objectives of this paper are: (1) to estimate the radiation dose received by aquatic biota from the different processes and determine the major dose-contributing radionuclides, and (2) to assess the impact of estimated doses on aquatic biota. Dose estimates are made by using radionuclide concentration measured in the liquid effiuents of representative facilities. Where measurements of concentrations are rot available, predicted radioactive releases to the aquatic environment are used for dose calculations. Although radioactive releases from reactors used to generate electrical energy have received the most attention, and are the best documented, this evaluation indicates the potential for a greater radiation dose to aquatic biota from the nuclear fuel supply facilities (i.e., mining and milling).. The effects of chronic low-level radiation on aquatic organisms are discussed from somatic and genetic viewpoints. Based on the body of radiobiological evidence accumulated up to the present time, no significant deleterious effects are predicted for populations of aquatic organisms exposed to the estimated dose rates resulting from routine releases from conversion, enrichment, fabrication, reactors and reporcessing facilities. At the doses estimated for milling and mining operations it would be difficult to detect radiation effects on aquatic populations; however, the significance of such radiation exposures to aquatic populations cannot be fully evaluated without further research on effects of chronic low-level radiation

Sexual Hookups via Dating Apps: A Qualitative Study Exploring the Experiences of Black Men Who Have Sex with Men in Florida

Background: Sexual hookups via social media dating apps have been understudied among Black men who have sex with men (BMSM). Purpose: The objective of this qualitative study was to explore the role of dating apps on hookup culture and to describe the sexual experiences among BMSM in Florida. Specifically, this research delves into various sexual hookup themes. Methods: Seventeen semi-structured interviews were conducted with BMSM participants aged 18 to 25 in Florida who self-identified as frequent dating app users. A grounded theory approach was applied to thematically analyze the hookup encounters and the factors that drive these perceptions and experiences among BMSM. QSR NVIVO 12 was used to code, categorize, and collect emergent themes. Results: Three major themes emerged depicting the complexities of hookup culture using social media dating applications among BMSM. 1. Positive hookup experiences were linked to feelings of “no strings attached” to some participants, while others associated this positive experience to the use of alcohol and drugs; 2. Negative hookup experiences revolved around miscommunication on sexual roles, catfishing, and disclosure of HIV status; 3. Psychological aspects of hookups were centered on feelings of regret, disbelief, and disgust after a sexual hookup encounter. Discussion: Understanding BMSM hookup culture could aid in the development of prioritized evidence-based interventions for behavioral change to improve safer sexual health encounters among this vulnerable populatio