830 research outputs found
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A new control system for an old tandem
In an effort to maintain the most flexible environment for accelerator-based atomic physics research at ORNL EN Tandem facility, a recirculating terminal stripper project has been in development. In the early stages of planning for this upgrade, the necessity for monitoring and control of various parameters in the accelerator terminal was considered. To provide proper flexibility and accuracy, telemetry via computer seemed to be the obvious route. Since the development of a robust system not prone to upset from sparks was necessary, a phased development approach was taken. This involves first converting the accelerator`s ground potential systems, then ion source ({similar_to}100 kV) systems that can be easily accessed by merely running down high voltage supplies, and finally terminal potential systems operating in high pressure gas at potentials over 7 MV. Progress to date, including hardware arrangement and software development, is discussed
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Continuing scearch for a new type charging belt
The EN Tandem accelerator at Oak Ridge National Laboratory (ORNL) operates to support a varied program of atomic physics research. As such, the demands on the accelerator often require a range of operation from {approximately}0.38 to 7.0 MV on the terminal, with low ripple and long term steady state operation. The standard charging belts obtained from the manufacture have generally given acceptable performance, but it is reasonable that modem manufacturing techniques and materials could increase belt lifetimes and improve accelerator performance, particularly voltage ripple. A new belt of significantly different construction from that of the conventional belts was specified, purchased, and installed in 1993. After 2800 hours of use at voltages from 0.38 to 5.8 MV, it was removed from the accelerator in early August 1995
Biophysical characteristics of a morphologically-complex macrotidal tropical coastal system during a dry season
Four boat-based surveys and several moored measurements were conducted over the dry season in June,
July, August and September 2008 in the central Kimberley region of northwestern Australia; a macrotidal
tropical coastal region, characterised by numerous island archipelagos and shallow reefs. The objective
was to determine the influence of this complex morphology on the biophysical properties of the local
coastal water masses and the resultant impact on phytoplankton biomass. Despite negligible rainfall
during the dry-season, decreased salinity towards the coast suggested a persistent fresh water source.
The water column was weakly vertically-stratified throughout much of the study region, only becoming
well-mixed in topographically constricted regions. The vertical stratification resulted in a cross-shore
subsurface in situ chl-a fluorescence maxima (at ~30 m depth) in June, July and August. The presence
of a chain of islands and shallow reefs led to the partial isolation of the semi-enclosed embayment,
Collier Bay, creating distinct water masses across this relatively small area. The confluence of the two
most distinct water masses formed a front at latitude ~15.65e15.7 �S, in both June and August, indicating
it was a persistent feature during the dry season. In situ chl-a fluorescence was highest at the front
location. In Collier Bay, NOx concentrations were up to five times higher, with a 20% higher proportion of
larger extracted chl-a biomass (cells > 5 mm), a proxy for phytoplankton. In the more open waters of
Camden Sound, relatively high concentrations of picophytoplankton, bacteria and viruses were observed.
Such spatial shifts in nutrient concentrations, phytoplankton biomass and phytoplankton and microbial
community composition across the persistent density front are likely to have important consequences on
the region's planktonic food web function
Results of the First Coincident Observations by Two Laser-Interferometric Gravitational Wave Detectors
We report an upper bound on the strain amplitude of gravitational wave bursts
in a waveband from around 800Hz to 1.25kHz. In an effective coincident
observing period of 62 hours, the prototype laser interferometric gravitational
wave detectors of the University of Glasgow and Max Planck Institute for
Quantum Optics, have set a limit of 4.9E-16, averaging over wave polarizations
and incident directions. This is roughly a factor of 2 worse than the
theoretical best limit that the detectors could have set, the excess being due
to unmodelled non-Gaussian noise. The experiment has demonstrated the viability
of the kind of observations planned for the large-scale interferometers that
should be on-line in a few years time.Comment: 11 pages, 2 postscript figure
Single-Proton Removal Reaction Study of 16B
The low-lying level structure of the unbound system B has been
investigated via single-proton removal from a 35 MeV/nucleon C beam. The
coincident detection of the beam velocity B fragment and neutron allowed
the relative energy of the in-flight decay of B to be reconstructed. The
resulting spectrum exhibited a narrow peak some 85 keV above threshold. It is
argued that this feature corresponds to a very narrow (100 keV)
resonance, or an unresolved multiplet, with a dominant + configuration which decays by d-wave neutron
emission.Comment: 16 pages, 5 figures, 1 table, submitted to Phys. Lett.
Plasma REST: a novel candidate biomarker of Alzheimer’s disease is modified by psychological intervention in an at-risk population
The repressor element 1-silencing transcription (REST) factor is a key regulator of the aging brain’s stress response. It is reduced in conditions of stress and Alzheimer’s disease (AD), which suggests that increasing REST may be neuroprotective. REST can be measured peripherally in blood plasma. Our study aimed to (1) examine plasma REST levels in relation to clinical and biological markers of neurodegeneration and (2) alter plasma REST levels through a stress-reduction intervention—mindfulness training. In study 1, REST levels were compared across the following four well-characterized groups: healthy elderly (n=65), mild cognitive impairment who remained stable (stable MCI, n=36), MCI who later converted to dementia (converter MCI, n=29) and AD (n=65) from the AddNeuroMed cohort. REST levels declined with increasing severity of risk and impairment (healthy elderly>stable MCI>converter MCI>AD, F=6.35, P<0.001). REST levels were also positively associated with magnetic resonance imaging-based hippocampal and entorhinal atrophy and other putative blood-based biomarkers of AD (Ps<0.05). In study 2, REST was measured in 81 older adults with psychiatric risk factors for AD before and after a mindfulness-based stress reduction intervention or an education-based placebo intervention. Mindfulness-based training caused an increase in REST compared with the placebo intervention (F=8.57, P=0.006), and increased REST was associated with a reduction in psychiatric symptoms associated with stress and AD risk (Ps<0.02). Our data confirm plasma REST associations with clinical severity and neurodegeneration, and originally, that REST is modifiable by a psychological intervention with clinical benefit
Stigma and GPs’ perceptions of dementia
YesObjectives: General practitioners (GPs) are crucial to improving timely diagnosis, but little is reported about how they
perceive dementia, and whether their perceptions display any elements of stigma. The aim of this study was to explore how
GPs’ perceptions of dementia map onto current conceptualizations of stigma and whether GPs feel that stigma affects
timely diagnosis.
Methods: Twenty-three GPs from England were interviewed by telephone. Data were analyzed by means of content
analysis. This involved open coding followed by the application of a coding framework derived from the literature to
explore how and to what extent their perceptions relate to stigma as well as the unique nature of their perceptions.
Results: Three themes emerged from the analysis: (1) ‘making sense of dementia’, (2) ‘relating perceptions of dementia to
oneself’ and (3) ‘considering the consequences of dementia’. GPs’ perceptions of dementia mapped onto current
conceptualizations of stigma. Perceptions about dementia that were linked to their own existential anxiety and to a
perceived similarity between people with dementia and themselves were particularly salient. GPs perceived dementia as a
stigma which was gradually being overcome but that stigma still hindered timely diagnosis. They provided examples of
structural discrimination within the health service, including lack of time for patients and shortcomings in training that
were to the detriment of people with dementia.
Conclusion: Measures to involve GPs in tackling stigma should include training and opportunities to explore how they
perceive dementia, as well as support to address structural discrimination.The study was funded by Alzheimer Europe (Luxembourg) in the form of tuition fees for Dianne Gove for her PhD study
Anthropogenic alteration of nutrient supply increases the global freshwater carbon sink
Lakes have a disproportionate effect on the global carbon (C) cycle relative to their area, mediating C transfer from land to atmosphere, and burying organic-C in their sediments. The magnitude and temporal variability of C burial is, however, poorly constrained, and the degree to which humans have influenced lake C cycling through landscape alteration has not been systematically assessed. Here, we report global and biome specific trajectories of lake C sequestration based on 516 lakes and show that some lake C burial rates (i.e., those in tropical forest and grassland biomes) have quadrupled over the last 100 years. Global lake C-sequestration (~0.12 Pg year-1) has increased by ~72 Tg year-1 since 1900, offsetting 20% of annual CO2 freshwater emissions rising to ~30% if reservoirs are included and contributing to the residual continental C sink. Nutrient availability explains ~70% of the observed increase, while rising temperatures have a minimal effect
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