24 research outputs found
Does the quality of fish muscle tissue with respect to lipids decrease during and post spawning season?
Increased sensitivity and discrimination in screening through an immobilized-resin microbiological assay method
Problems with present bioactive microbial product screening techniques include low sensitivity and insufficient discrimination capabilities. These problems are addressed by our new immobilized-resin microbiological assay. This technique concentrates bioactive samples on macroporous polymeric resins that are immobilized in hydrogel beads. These beads are then subjected to elution in the wells of an agar diffusion microbiological assay medium. With a strong base anion exchanger, the sensitivity to ampicillin of the β-lactam-supersensitive Escherichia coli mutant ESS-22-31 was increased 10-fold. Similar increases in sensitivity were obtained in the detection of streptomycin using a weak acid cation exchanger with Bacillus subtilis and for cycloheximide by a neutral resin and Saccharomyces cerevisiae NRRL-Y-139. A judicious choice of resin type and eluent permitted a selective sensitivity increase based on the charge or hydrophobic nature of the desired product. This selectivity imparts a discrimination capability to the technique.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47948/1/10295_2005_Article_BF01569546.pd
A Precise Measurement of the Muon Neutrino-Nucleon Inclusive Charged Current Cross-Section off an Isoscalar Target in the Energy Range 2.5 < E_\nu < 40 GeV by NOMAD
We present a measurement of the muon neutrino-nucleon inclusive charged
current cross-section, off an isoscalar target, in the neutrino energy range
GeV. The significance of this measurement is its
precision, % in GeV, and % in GeV regions, where significant uncertainties in previous
experiments still exist, and its importance to the current and proposed long
baseline neutrino oscillation experiments.Comment: 14 pages, 3 figures, submitted to Phys.Lett.
A Measurement of Coherent Neutral Pion Production in Neutrino Neutral Current Interactions in NOMAD
We present a study of exclusive neutral pion production in neutrino-nucleus
Neutral Current interactions using data from the NOMAD experiment at the CERN
SPS. The data correspond to muon-neutrino Charged Current
interactions in the energy range GeV. Neutrino
events with only one visible in the final state are expected to result
from two Neutral Current processes: coherent production, {\boldmath
} and single production in
neutrino-nucleon scattering. The signature of coherent production is an
emergent almost collinear with the incident neutrino while 's
produced in neutrino-nucleon deep inelastic scattering have larger transverse
momenta. In this analysis all relevant backgrounds to the coherent
production signal are measured using data themselves. Having determined the
backgrounds, and using the Rein-Sehgal model for the coherent
production to compute the detection efficiency, we obtain {\boldmath } corrected coherent- events with GeV. We measure {\boldmath }.
This is the most precise measurement of the coherent production to
date.Comment: 23 pages, 9 figures, accepted for publication in Phys. Lett.
The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets
This review addresses our current understanding of comets that venture close to the Sun, and are hence exposed to much more extreme conditions than comets that are typically studied from Earth. The extreme solar heating and plasma environments that these objects encounter change many aspects of their behaviour, thus yielding valuable information on both the comets themselves that complements other data we have on primitive solar system bodies, as well as on the near-solar environment which they traverse. We propose clear definitions for these comets: We use the term near-Sun comets to encompass all objects that pass sunward of the perihelion distance of planet Mercury (0.307 AU). Sunskirters are defined as objects that pass within 33 solar radii of the Sun’s centre, equal to half of Mercury’s perihelion distance, and the commonly-used phrase sungrazers to be objects that reach perihelion within 3.45 solar radii, i.e. the fluid Roche limit. Finally, comets with orbits that intersect the solar photosphere are termed sundivers. We summarize past studies of these objects, as well as the instruments and facilities used to study them, including space-based platforms that have led to a recent revolution in the quantity and quality of relevant observations. Relevant comet populations are described, including the Kreutz, Marsden, Kracht, and Meyer groups, near-Sun asteroids, and a brief discussion of their origins. The importance of light curves and the clues they provide on cometary composition are emphasized, together with what information has been gleaned about nucleus parameters, including the sizes and masses of objects and their families, and their tensile strengths. The physical processes occurring at these objects are considered in some detail, including the disruption of nuclei, sublimation, and ionisation, and we consider the mass, momentum, and energy loss of comets in the corona and those that venture to lower altitudes. The different components of comae and tails are described, including dust, neutral and ionised gases, their chemical reactions, and their contributions to the near-Sun environment. Comet-solar wind interactions are discussed, including the use of comets as probes of solar wind and coronal conditions in their vicinities. We address the relevance of work on comets near the Sun to similar objects orbiting other stars, and conclude with a discussion of future directions for the field and the planned ground- and space-based facilities that will allow us to address those science topics
A Search for Single Photon Events in Neutrino Interactions
We present a search for neutrino-induced events containing a single,
exclusive photon using data from the NOMAD experiment at the CERN SPS where the
average energy of the neutrino flux is GeV. The search is motivated
by an excess of electron-like events in the 200--475 MeV energy region as
reported by the MiniBOONE experiment. In NOMAD, photons are identified via
their conversion to in an active target embedded in a magnetic field.
The background to the single photon signal is dominated by the asymmetric decay
of neutral pions produced either in a coherent neutrino-nucleus interaction, or
in a neutrino-nucleon neutral current deep inelastic scattering, or in an
interaction occurring outside the fiducial volume. All three backgrounds are
determined {\it in situ} using control data samples prior to opening the
`signal-box'. In the signal region, we observe {\bf 155} events with a
predicted background of {\bf 129.2 8.5 3.3}. We interpret this as
null evidence for excess of single photon events, and set a limit. Assuming
that the hypothetical single photon has a momentum distribution similar to that
of a photon from the coherent decay, the measurement yields an upper
limit on single photon events, {\boldmath } per \nm\
charged current event. Narrowing the search to events where the photon is
approximately collinear with the incident neutrino, we observe {\bf 78} events
with a predicted background of {\bf 76.6 4.9 1.9} yielding a more
stringent upper limit, {\boldmath } per \nm\ charged
current event
The Origin, Early Evolution and Predictability of Solar Eruptions
Coronal mass ejections (CMEs) were discovered in the early 1970s when space-borne coronagraphs revealed that eruptions of plasma are ejected from the Sun. Today, it is known that the Sun produces eruptive flares, filament eruptions, coronal mass ejections and failed eruptions; all thought to be due to a release of energy stored in the coronal magnetic field during its drastic reconfiguration. This review discusses the observations and physical mechanisms behind this eruptive activity, with a view to making an assessment of the current capability of forecasting these events for space weather risk and impact mitigation. Whilst a wealth of observations exist, and detailed models have been developed, there still exists a need to draw these approaches together. In particular more realistic models are encouraged in order to asses the full range of complexity of the solar atmosphere and the criteria for which an eruption is formed. From the observational side, a more detailed understanding of the role of photospheric flows and reconnection is needed in order to identify the evolutionary path that ultimately means a magnetic structure will erupt
Multi-faceted roles for CXC-chemokines in prostate cancer progression
CXC-chemokines play an essential role in coordinating the function of the immune system. Increasingly, these small signaling molecules are recognized in facilitating communication between multiple cell types within the tumor microenvironment. This review will summarize the role of two members of this family, CXCL12 (stromal cell derived factor-1) and CXCL8 (interleukin-8) in promoting the disease progression of prostate cancer, the most prevalent non-cutaneous cancer in men in western society and the second leading cause of death from cancer in men. Evidence for a role of these chemokines in underpinning the development and progression of this disease is supported by examination of prostate tissue and serum samples from prostate cancer patients, from biochemical and molecular investigations conducted on cell-based models of this disease and from observation of CXC-chemokine promoted growth and systemic dissemination of human prostate tumors in in vivo models. The future potential of employing strategies to attenuate chemokine expression or alternatively to selectively block chemokine receptor signaling in order to effect greater long-term control or enhanced therapeutic response in this disease is also discussed.</p