474 research outputs found
Thermal and Cold Neutron Computed Tomography at the Los Alamos Neutron Scattering Center Using an Amorphous Silicon Detector Array
The use of the EG&G-Heimann RTM 128 [1] or dpiX FS20 [2] amorphous silicon (a-Si) detector array for thermal neutron radiography/computed tomography has proven to be a quick and efficient means of producing high quality digital radiographic images. The resolution, although not as good as film, is about 750 μm with the RTM and 127 μm with the dpiX array with a dynamic range in excess of 2800. In many respects using an amorphous silicon detector is an improvement over other techniques such as imaging with a CCD camera, using a storage phosphor plate or film radiography. Unlike a CCD camera, which is highly susceptible to radiation damage, a-Si detectors can be placed in the beam directly behind the object under examination and do not require any special optics or turning mirrors. The amorphous silicon detector also allows enough data to be acquired to construct a digital image in just a few seconds (minimum gate time 40 ms) whereas film or storage plate exposures can take many minutes and need to be digitized with a scanner. The flat panel can, therefore, acquire a complete 3D computed tomography data set in just a few tens of minutes. While a-Si detectors have been proposed for use in imaging neutron beams [3], this is the first reported implementation of such a detector for neutron imaging [4]
Crucial Physical Dependencies of the Core-Collapse Supernova Mechanism
We explore with self-consistent 2D F{\sc{ornax}} simulations the dependence
of the outcome of collapse on many-body corrections to neutrino-nucleon cross
sections, the nucleon-nucleon bremsstrahlung rate, electron capture on heavy
nuclei, pre-collapse seed perturbations, and inelastic neutrino-electron and
neutrino-nucleon scattering. Importantly, proximity to criticality amplifies
the role of even small changes in the neutrino-matter couplings, and such
changes can together add to produce outsized effects. When close to the
critical condition the cumulative result of a few small effects (including
seeds) that individually have only modest consequence can convert an anemic
into a robust explosion, or even a dud into a blast. Such sensitivity is not
seen in one dimension and may explain the apparent heterogeneity in the
outcomes of detailed simulations performed internationally. A natural
conclusion is that the different groups collectively are closer to a realistic
understanding of the mechanism of core-collapse supernovae than might have
seemed apparent.Comment: 25 pages; 10 figure
Spectrally resolved observations of atmospheric emitted radiance in the H2O rotation band
This paper presents the project Earth Cooling by Water
Vapor Radiation, an observational programme, which aims at
developing a database of spectrally resolved far infrared
observations, in atmospheric dry conditions, in order to
validate radiative transfer models and test the quality of water
vapor continuum and line parameters. The project provides
the very first set of far-infrared spectral downwelling
radiance measurements, in dry atmospheric conditions,
which are complemented with Raman Lidar-derived
temperature and water vapor profiles
Quantitative Gait and Balance Outcomes for Ataxia Trials: Consensus Recommendations by the Ataxia Global Initiative Working Group on Digital-Motor Biomarkers
\ua9 2023, The Author(s).With disease-modifying drugs on the horizon for degenerative ataxias, ecologically valid, finely granulated, digital health measures are highly warranted to augment clinical and patient-reported outcome measures. Gait and balance disturbances most often present as the first signs of degenerative cerebellar ataxia and are the most reported disabling features in disease progression. Thus, digital gait and balance measures constitute promising and relevant performance outcomes for clinical trials. This narrative review with embedded consensus will describe evidence for the sensitivity of digital gait and balance measures for evaluating ataxia severity and progression, propose a consensus protocol for establishing gait and balance metrics in natural history studies and clinical trials, and discuss relevant issues for their use as performance outcomes
The integrated action framework of Rete Natura 2000 Basilicata
Basilicata Natura 2000 network consists of 50 Sites of Community Importance (SCI) and 17 Special Protection Zones (SPZs), covering alltogether more than 17% of the regional area. This network, partially overlapping other forms of land protection, represents a valuable environmental, agricultural and cultural heritage, in which the safeguard of natural resources and landscapes has to be coupled with the needs of the local population; especially in relation to development and social welfare.
The Natura 2000 project involved a panel of experts belonging to 15 different institutions, to form a steering committee with the following professional and scientific skills: vegetation, landscape, fauna, geology, agriculture, forestry, sea, architecture and planning, territorial analysis and representation. Along the 4 years project, the steering committee designed and coordinated the activities of over 150 professionals, mostly from Basilicata, who carried out field surveys and data analysis aimed at assessing the environmental conditions in the SCI and SPZs, proposing measures and plans, implementing thematic databases.
SCI/SPZ management plans, by themselves, may not be sufficient to fulfill the requirements of an effective environmental policy, which has to go along with the awareness of people, citizens and local administrators about the instances of a sustainable policy. For this reason, the activities of surveying and management have been coupled with a communication project that involves all the experts and a relevant part of professionals who participated to the Natura 2000 project. The communication activity implies the use and the creation of several tools (publishing, video, websites, meetings, photo contests, social networks ...) targeted to different groups: policy makers (local, regional, national, European ), organizations, citizens, schools, farmers, small and medium enterprises (www.natura2000basilicata.it).
A further goal is to feature the environmental highlights of Basilicata which are linked to a specific and often surprising integration of an ancient human presence with the natural elements, and the role performed by the traditional farming activities in the maintenance of ecosystem dynamics and services (in particular with agriculture). In fact, a good number of Natura 2000 sites can be considered High Nature Value Farmlands (HNVF, sensu E. Andersen, 2003), in which a virtuous relationship was established a long time ago between traditional practices and the environment itself. In this context, it combines the convergence between the activities carried on the Natura 2000 network and the project Agrival (http://utagri.enea.it/projects/agrival), a research project led by ENEA in Val d'Agri, in order to experimentally contribute to the methodology for the identification of the High Nature Value Farmlands and make them cohabit with the other economic activities in the local context.
The process started with the project Basilicata Natura 2000 Network is therefore an interesting methodological model that, in coherence with the financial planning of the European Community for the period 2014-2020 (Brussels, 12.12.2011, COMM. 874) puts together projects on environmental issues to boost the meeting of agricultural, environmental, cultural and productive policies, fostered by the EC, and enhancing the implementation of the "Prioritized Actions Frameworks" (PAF), pointed out by the European Commission as the optimal tools for the management of Natura 2000 networks
Elliptic flow of electrons from heavy-flavor hadron decays in Au+Au collisions at 200, 62.4, and 39 GeV
We present measurements of elliptic flow () of electrons from the decays
of heavy-flavor hadrons () by the STAR experiment. For Au+Au collisions
at 200 GeV we report , for transverse momentum
() between 0.2 and 7 GeV/c using three methods: the event plane method
({EP}), two-particle correlations ({2}), and four-particle
correlations ({4}). For Au+Au collisions at = 62.4 and
39 GeV we report {2} for GeV/c. {2} and {4} are
non-zero at low and intermediate at 200 GeV, and {2} is consistent
with zero at low at other energies. The {2} at the two lower beam
energies is systematically lower than at 200 GeV for
GeV/c. This difference may suggest that charm quarks interact less
strongly with the surrounding nuclear matter at those two lower energies
compared to GeV.Comment: Version accepted by PR
Measurement of the mass difference and the binding energy of the hypertriton and antihypertriton
According to the CPT theorem, which states that the combined operation of
charge conjugation, parity transformation and time reversal must be conserved,
particles and their antiparticles should have the same mass and lifetime but
opposite charge and magnetic moment. Here, we test CPT symmetry in a nucleus
containing a strange quark, more specifically in the hypertriton. This
hypernucleus is the lightest one yet discovered and consists of a proton, a
neutron, and a hyperon. With data recorded by the STAR
detector{\cite{TPC,HFT,TOF}} at the Relativistic Heavy Ion Collider, we measure
the hyperon binding energy for the hypertriton, and
find that it differs from the widely used value{\cite{B_1973}} and from
predictions{\cite{2019_weak, 1995_weak, 2002_weak, 2014_weak}}, where the
hypertriton is treated as a weakly bound system. Our results place stringent
constraints on the hyperon-nucleon interaction{\cite{Hammer2002,
STAR-antiH3L}}, and have implications for understanding neutron star interiors,
where strange matter may be present{\cite{Chatterjee2016}}. A precise
comparison of the masses of the hypertriton and the antihypertriton allows us
to test CPT symmetry in a nucleus with strangeness for the first time, and we
observe no deviation from the expected exact symmetry
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