4,457 research outputs found
A primary electron beam facility at CERN
This document describes the concept of a primary electron beam facility at
CERN, to be used for dark gauge force and light dark matter searches. The
electron beam is produced in three stages: A Linac accelerates electrons from a
photo-cathode up to 3.5 GeV. This beam is injected into the Super Proton
Synchrotron, SPS, and accelerated up to a maximum energy of 16 GeV. Finally,
the accelerated beam is slowly extracted to an experiment, possibly followed by
a fast dump of the remaining electrons to another beamline. The beam parameters
are optimized using the requirements of the Light Dark Matter eXperiment, LDMX,
as benchmark
A primary electron beam facility at CERN
This paper describes the concept of a primary electron beam facility at CERN,
to be used for dark gauge force and light dark matter searches. The electron
beam is produced in three stages: A Linac accelerates electrons from a
photo-cathode up to 3.5 GeV. This beam is injected into the Super Proton
Synchrotron, SPS, and accelerated up to a maximum energy of 16 GeV. Finally,
the accelerated beam is slowly extracted to an experiment, possibly followed by
a fast dump of the remaining electrons to another beamline. The beam parameters
are optimized using the requirements of the Light Dark Matter eXperiment (LDMX)
as benchmark.Comment: 3 pages, 3 figure
QCD-supression by Black Hole Production at the LHC
Possible consequences of the production of small black holes at the LHC for
different scenarios with large extra dimensions are investigated. The effects
from black hole production on some standard jet observables are examined,
concentrating on the reduction of the QCD cross section. It is found that black
hole production of partons interacting on a short enough distance indeed seem
to generate a drastic drop in the QCD cross section. However from an
experimental point of view this will in most cases be camouflaged by energetic
radiation from the black holes
Soft Photoproduction Physics
Several topics of interest in soft photoproduction physics are discussed.
These include jet universality issues (particle flavour composition), the
subdivision into event classes, the buildup of the total photoproduction cross
section and the effects of multiple interactions.Comment: 10 pages, LaTeX2e, no figures, to appear in the proceedings of the
Durham Workshop on HERA Physics, ``Proton, Photon and Pomeron Structure'',
17--23 September 1995, Durham, U.
The influence of wind direction on the capture of the wood warbler (Phylloscopus sibilatrix), an uncommon migratory species in the western Mediterranean
The wood warbler (Phylloscopus sibilatrix) is a migratory species in the western Mediterranean wintering in the Gulf of Guinea region, West Africa. In autumn and spring, this species, along with the populations breeding in Ireland and Britain, uses the Italian peninsula as its main axis of migration. From the data of captured birds at several ringing stations in the western Mediterranean (Balearic Islands and coastal Iberian Peninsula), we analyzed capture rates of the species during spring migration from 1993 to 2007. Based on the selection of days with a significant number of captures and those without captures, we analyzed the effect of wind direction over the western Mediterranean to determine a relationship between winds and the number of captures. From a total of 663 wood warblers captured between 1993 and 2007, a total of 31 days have been selected as significant days with a high number of captures, and 31 days have been selected as no-capture days. On days of maximum captures, winds coming from an easterly direction, i.e. Algeria and Tunisia, were dominant, indicating days with a clear eastern component. Contrary to expected results, captures were also made on days when the wind direction was predominantly from a northerly direction. Analysis of the origin of the winds in north eastern Spain (western Mediterranean) revealed that the majority of northerly winds originated from Africa and not from Europe as is usual for this region. Days or periods selected as no-capture days were characterized by winds coming from a northerly (European origin) or westerly direction
Self-organising human gonads generated by a Matrigel-based gradient system.
BACKGROUND: Advances in three-dimensional culture technologies have led to progression in systems used to model the gonadal microenvironment in vitro. Despite demonstrating basic functionality, tissue organisation is often limited. We have previously detailed a three-dimensional culture model termed the three-layer gradient system to generate rat testicular organoids in vitro. Here we extend the model to human first-trimester embryonic gonadal tissue. RESULTS: Testicular cell suspensions reorganised into testis-like organoids with distinct seminiferous-like cords situated within an interstitial environment after 7 days. In contrast, tissue reorganisation failed to occur when mesonephros, which promotes testicular development in vivo, was included in the tissue digest. Organoids generated from dissociated female gonad cell suspensions formed loosely organised cords after 7 days. In addition to displaying testis-specific architecture, testis-like organoids demonstrated evidence of somatic cell differentiation. Within the 3-LGS, we observed the onset of AMH expression in the cytoplasm of SOX9-positive Sertoli cells within reorganised testicular cords. Leydig cell differentiation and onset of steroidogenic capacity was also revealed in the 3-LGS through the expression of key steroidogenic enzymes StAR and CYP17A1 within the interstitial compartment. While the 3-LGS generates a somatic cell environment capable of supporting germ cell survival in ovarian organoids germ cell loss was observed in testicular organoids. CONCLUSION: The 3-LGS can be used to generate organised whole gonadal organoids within 7 days. The 3-LGS brings a new opportunity to explore gonadal organogenesis and contributes to the development of more complex in vitro models in the field of developmental and regenerative medicine
Cadmium-Induced Effects on Bone in a Population-Based Study of Women
High cadmium exposure is known to cause bone damage, but the association between low-level cadmium exposure and osteoporosis remains to be clarified. Using a population-based women’s health survey in southern Sweden [Women’s Health in the Lund Area (WHILA)] with no known historical cadmium contamination, we investigated cadmium-related effects on bone in 820 women (53–64 years of age). We measured cadmium in blood and urine and lead in blood, an array of markers of bone metabolism, and forearm bone mineral density (BMD). Associations were evaluated in multiple linear regression analysis including information on the possible confounders or effect modifiers: weight, menopausal status, use of hormone replacement therapy, age at menarche, alcohol consumption, smoking history, and physical activity. Median urinary cadmium was 0.52 μg/L adjusted to density (0.67 μg/g creatinine). After multivariate adjustment, BMD, parathyroid hormone, and urinary deoxypyridinoline (U-DPD) were adversely associated with concentrations of urinary cadmium (p < 0.05) in all subjects. These associations persisted in the group of never-smokers, which had the lowest cadmium exposure (mainly dietary). For U-DPD, there was a significant interaction between cadmium and menopause (p = 0.022). Our results suggest negative effects of low-level cadmium exposure on bone, possibly exerted via increased bone resorption, which seemed to be intensified after menopause. Based on the prevalence of osteoporosis and the low level of exposure, the observed effects, although slight, should be considered as early signals of potentially more adverse health effects
Consistency of data on soft photon production in hadronic interactions
The glob model of Lichard and Van Hove and the modified soft annihilation
model (MSAM) of Lichard and Thompson are used as a phenomenological tool for
relating results from various experiments on soft photon production in high
energy collisions. The total phenomenological expectation is composed of
contributions from classical bremsstrahlung, the soft annihilation model and
the glob model. The empirical excess above the background from hadronic decays
at very small longitudinal momenta of photons is well reproduced, as well as
that for transverse momenta pT >~ 10 MeV/c. Some data do not require the glob
model and MSAM components in the phenomenological mixture, but do not exclude
them. On the basis of consistency of all data with the total theoretical
expectation we argue that the results of all experiments are mutually
consistent. The models are unable to describe the excess of ultrasoft photons
(pT <~ 10 MeV/c), seen by some, but not all, experiments. This may indicate an
as yet unknown projectile-mass-dependent production mechanism. Possible
relations of soft photon production to other phenomena are discussed. A
simple-to-use, but physically equivalent version of the glob model is
developed, which enables an easy check of presented results.Comment: 25 pages, RevTeX, epsf.sty, 12 embedded figure
Multi-boson effects and the normalization of the two-pion correlation function
The two-pion correlation function can be defined as a ratio of either the
measured momentum distributions or the normalized momentum space probabilities.
We show that the first alternative avoids certain ambiguities since then the
normalization of the two-pion correlator contains important information on the
multiplicity distribution of the event ensemble which is lost in the second
alternative. We illustrate this explicitly for specific classes of event
ensembles.Comment: 6 pages, three figures,submit to PR
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