78 research outputs found
A Compact Beam Stop for a Rare Kaon Decay Experiment
We describe the development and testing of a novel beam stop for use in a
rare kaon decay experiment at the Brookhaven AGS. The beam stop is located
inside a dipole spectrometer magnet in close proximity to straw drift chambers
and intercepts a high-intensity neutral hadron beam. The design process,
involving both Monte Carlo simulations and beam tests of alternative beam-stop
shielding arrangements, had the goal of minimizing the leakage of particles
from the beam stop and the resulting hit rates in detectors, while preserving
maximum acceptance for events of interest. The beam tests consisted of
measurements of rates in drift chambers, scintilation counter hodoscopes, a gas
threshold Cherenkov counter, and a lead glass array. Measurements were also
made with a set of specialized detectors which were sensitive to low-energy
neutrons, photons, and charged particles. Comparisons are made between these
measurements and a detailed Monte Carlo simulation.Comment: 39 pages, 14 figures, submitted to Nuclear Instruments and Method
Properties of the BFKL equation and structure function predictions for HERA
The general properties of the Lipatov or BFKL equation are reviewed.
Modifications to the infrared region are proposed. Numerical predictions for
the deep-inelastic electron-proton structure functions at small are
presented and confronted with recent HERA measurements.Comment: 21 pages, 11 figures, Latex file, Durham preprint DTP 92/2
Characteristics of the nuclear (18S, 5.8S, 28S and 5S) and mitochondrial (12S and 16S) rRNA genes of Apis mellifera (Insecta: Hymenoptera): structure, organization, and retrotransposable elements
As an accompanying manuscript to the release of the honey bee genome, we report the entire sequence of the nuclear (18S, 5.8S, 28S and 5S) and mitochondrial (12S and 16S) ribosomal RNA (rRNA)-encoding gene sequences (rDNA) and related internally and externally transcribed spacer regions of Apis mellifera (Insecta: Hymenoptera: Apocrita). Additionally, we predict secondary structures for the mature rRNA molecules based on comparative sequence analyses with other arthropod taxa and reference to recently published crystal structures of the ribosome. In general, the structures of honey bee rRNAs are in agreement with previously predicted rRNA models from other arthropods in core regions of the rRNA, with little additional expansion in non-conserved regions. Our multiple sequence alignments are made available on several public databases and provide a preliminary establishment of a global structural model of all rRNAs from the insects. Additionally, we provide conserved stretches of sequences flanking the rDNA cistrons that comprise the externally transcribed spacer regions (ETS) and part of the intergenic spacer region (IGS), including several repetitive motifs. Finally, we report the occurrence of retrotransposition in the nuclear large subunit rDNA, as R2 elements are present in the usual insertion points found in other arthropods. Interestingly, functional R1 elements usually present in the genomes of insects were not detected in the honey bee rRNA genes. The reverse transcriptase products of the R2 elements are deduced from their putative open reading frames and structurally aligned with those from another hymenopteran insect, the jewel wasp Nasonia (Pteromalidae). Stretches of conserved amino acids shared between Apis and Nasonia are illustrated and serve as potential sites for primer design, as target amplicons within these R2 elements may serve as novel phylogenetic markers for Hymenoptera. Given the impending completion of the sequencing of the Nasonia genome, we expect our report eventually to shed light on the evolution of the hymenopteran genome within higher insects, particularly regarding the relative maintenance of conserved rDNA genes, related variable spacer regions and retrotransposable elements
Tensor Polarization of the phi meson Photoproduced at High t
As part of a measurement of the cross section of meson photoproduction
to high momentum transfer, we measured the polar angular decay distribution of
the outgoing in the channel in the
center-of-mass frame (the helicity frame). We find that s-channel helicity
conservation (SCHC) holds in the kinematical range where -channel exchange
dominates (up to GeV for =3.6 GeV). Above this
momentum, -channel production of a meson dominates and induces a
violation of SCHC. The deduced value of the coupling constant lies in
the upper range of previously reported values.Comment: 6 pages; 5 figure
The first two centuries of colonial agriculture in the cape colony: A historiographical reviewâ
Marine connections in North America during the late Maastrichtian: Palaeogeographic and palaeobiogeographic significance of Jeletzkytes nebrascensis Zone cephalopod fauna from the Elk Butte Member of the Pierre Shale, SE South Dacota and NE Nebrasca.
Assessment of ozone and UV pre-oxidation processes for mitigating microbiologically accelerated monochloramine decay
This paper reports the effects of pre-oxidation processes including ozone and ultraviolet (UV) irradiation prior to chloramination on microbiologically assisted monochloramine decay. Water samples with varying water qualities were pre-oxidated by ozone and UV irradiation, followed by determination of chemical and microbiological monochloramine decay (Fm). Both ozone and UV could effectively improve the reduction of microbial-like compounds responsible for monochloramine decay in treated water samples. Reductions in Fm values were observed for ozone contact times (Ct) greater than 5 mg min/L and UV doses greater than 30 mJ/cm2. However, UV was less effective than ozone in reducing Fm values in raw water samples. Complete removal of the microbiological component of the decay for raw water samples was not found either with ozone (even with Ct of 50 mg min/L) or UV (even with UV dose of 120 mJ/cm2). The effects of pre-oxidation processes on chemical (kc) and microbial (km) decay coefficients were assessed. Increasing both ozone Ct and UV dose ahead of chloramine did not affect the chemical decay component, but they changed the microbiological component of decay. Changes in organic matter after ozonation were also characterized using three-dimensional fluorescence excitationâemission matrix (3D-FEEM) spectroscopy, and correlations between 3D-FEEM spectroscopy results and Fm values were found. Intensities of humic-like, fulvic-like, microbial protein-like and aromatic protein-like substances were reduced by pre-ozonation. Based on the 3D-FEEM results, we can confirm that the slowdown of monochloramine decay rate is due to the reduction of marine humic-like substances and soluble microbial protein-like compounds by pre-ozonation
Being a Good Senior Manager in Indigenous Community Governance: Working with Public Purpose and Private Benefit
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