5,490 research outputs found
An overview of the Daya Bay Reactor Neutrino Experiment
The Daya Bay Reactor Neutrino Experiment discovered an unexpectedly large
neutrino oscillation related to the mixing angle in 2012. This
finding paved the way to the next generation of neutrino oscillation
experiments. In this article, we review the history, featured design, and
scientific results of Daya Bay. Prospects of the experiment are also described.Comment: 18 pages, 5 figures. An overview to appear in the Special Issue on
neutrino oscillations of Nuclear Physics
Asymmetric nuclear matter:the role of the isovector scalar channel
We try to single out some qualitative new effects of the coupling to the
-isovector-scalar meson introduced in a minimal way in a
phenomenological hadronic field theory. Results for the equation of state
() and the phase diagram of asymmetric nuclear matter () are
discussed. We stress the consistency of the -coupling introduction in a
relativistic approach. New contributions to the slope and curvature of the
symmetry energy and the neutron-proton effective mass splitting appear
particularly interesting. A more repulsive for neutron matter at high
baryon densities is expected. Effects on new critical properties of warm ,
mixing of mechanical and chemical instabilities and isospin distillation, are
also presented. The influence is mostly on the {\it isovectorlike}
collective response.
The results are largely analytical and this makes the physical meaning quite
transparent. Implications for nuclear structure properties of drip-line nuclei
and for reaction dynamics with Radioactive Beams are finally pointed out.Comment: 12 pages, 10 Postscript figure
ReaxFF Reactive Force-Field Modeling of the Triple-Phase Boundary in a Solid Oxide Fuel Cell
In our study, the Ni/YSZ ReaxFF reactive force field was developed by combining the YSZ and Ni/C/H descriptions. ReaxFF reactive molecular dynamics (RMD) were applied to model chemical reactions, diffusion, and other physicochemical processes at the fuel/Ni/YSZ interface. The ReaxFF RMD simulations were performed on the H_2/Ni/YSZ and C_4H_(10)/Ni/YSZ triple-phase boundary (TPB) systems at 1250 and 2000 K, respectively. The simulations indicate amorphization of the Ni surface, partial decohesion (delamination) at the interface, and coking, which have indeed all been observed experimentally. They also allowed us to derive the mechanism of the butane conversion at the Ni/YSZ interface. Many steps of this mechanism are similar to the pyrolysis of butane. The products obtained in our simulations are the same as those in experiment, which indicates that the developed ReaxFF potential properly describes complex physicochemical processes, such as the oxide-ion diffusion, fuel conversion, water formation reaction, coking, and delamination, occurring at the TPB and can be recommended for further computational studies of the fuel/electrode/electrolyte interfaces in a SOFC
BACE2 distribution in major brain cell types and identification of novel substrates
β-Site APP-cleaving enzyme 1 (BACE1) inhibition is considered one of the most promising therapeutic strategies for Alzheimer's disease, but current BACE1 inhibitors also block BACE2. As the localization and function of BACE2 in the brain remain unknown, it is difficult to predict whether relevant side effects can be caused by off-target inhibition of BACE2 and whether it is important to generate BACE1-specific inhibitors. Here, we show that BACE2 is expressed in discrete subsets of neurons and glia throughout the adult mouse brain. We uncover four new substrates processed by BACE2 in cultured glia: vascular cell adhesion molecule 1, delta and notch-like epidermal growth factor-related receptor, fibroblast growth factor receptor 1, and plexin domain containing 2. Although these substrates were not prominently cleaved by BACE2 in healthy adult mice, proinflammatory TNF induced a drastic increase in BACE2-mediated shedding of vascular cell adhesion molecule 1 in CSF. Thus, although under steady-state conditions the effect of BACE2 cross-inhibition by BACE1-directed inhibitors is rather subtle, it is important to consider that side effects might become apparent under physiopathological conditions that induce TNF expression
A Multi-Phase Transport model for nuclear collisions at RHIC
To study heavy ion collisions at energies available from the Relativistic
Heavy Ion Collider, we have developed a multi-phase transport model that
includes both initial partonic and final hadronic interactions. Specifically,
the parton cascade model ZPC, which uses as input the parton distribution from
the HIJING model, is extended to include the quark-gluon to hadronic matter
transition and also final-state hadronic interactions based on the ART model.
Predictions of the model for central Au on Au collisions at RHIC are reported.Comment: 7 pages, 4 figure
Deteriorated regional calf microcirculation measured by contrast-free MRI in patients with diabetes mellitus and relation with physical activity
OBJECTIVE: To evaluate regional calf muscle microcirculation in people with diabetes mellitus (DM) with and without foot ulcers, compared to healthy control people without DM, using contrast-free magnetic resonance imaging methods.
METHODS: Three groups of subjects were recruited: non-DM controls, DM, and DM with foot ulcers (DM + ulcer), all with ankle brachial index (ABI) \u3e 0.9. Skeletal muscle blood flow (SMBF) and oxygen extraction fraction (SMOEF) in calf muscle were measured at rest and during a 5-min isometric ankle plantarflexion exercise. Subjects completed the Yale physical activity survey.
RESULTS: The exercise SMBF (ml/min/100 g) of the medial gastrocnemius muscle were progressively impaired: 63.7 ± 18.9 for controls, 42.9 ± 6.7 for DM, and 36.2 ± 6.2 for DM + ulcer,
CONCLUSIONS: Contrast-free MR imaging identified progressively impaired regional microcirculation in medial gastrocnemius muscles of people with DM with and without foot ulcers. Exercise SMBF in the medial gastrocnemius muscle was the most sensitive index and was associated with HbA1c. Lower exercise SMBF in the soleus muscle was associated with lower Yale score
Probing Mechanical and Chemical Instabilities in Neutron-Rich Matter
The isospin-dependence of mechanical and chemical instabilities is
investigated within a thermal and nuclear transport model using a Skyrme-type
phenomenological equation of state for neutron-rich matter. Respective roles of
the nuclear mean field and the 2-body stochastic scattering on the evolution of
density and isospin fluctuations in either mechanically or chemically unstable
regions of neutron-rich matter are investigated. It is found that the mean
field dominates overwhelmingly the fast growth of both fluctuations, while the
2-body scattering influences significantly the later growth of the isospin
fluctuation only. The magnitude of both fluctuations decreases with the
increasing isospin asymmetry because of the larger reduction of the attractive
isoscalar mean field by the stronger repuslive neutron symmetry potential in
the more neutron-rich matter. Moreover, it is shown that the isospin
fractionation happens later, but grows faster in the more neutron-rich matter.
Implications of these results to current experiments exploring properties of
neutron-rich matter are discussed.Comment: 18 pages & 15 figures, Nuclear Physics A (2001) in pres
Theoretical Review of B-physics
Weak decays and mixing of B-hadrons play a special role in our understanding
of the physics of the Standard Model and beyond. The measured amplitudes,
however, result from a complicated interplay of weak and strong interaction
effects. Understanding strong interaction dynamics, which becomes simpler for
heavy quarks, is thus a fundamental part of the game. In this review, several
theoretical aspects of B dynamics which are relevant for current and future
experimental measurements are discussed.Comment: LaTeX, 27 pages, 5 figures. Summary talk given at BEAUTY 96, June
17-21 1996, Rome (Italy), to appear in the Proceeding
Facile purification of milligram to gram quantities of condensed tannins according to mean degree of polymerization and flavan-3-ol subunit composition
Unambiguous investigation of condensed tannin (CT) structure-activity relationships in biological systems requires well-characterized, high-purity CTs. Sephadex LH-20 and Toyopearl HW-50F resins were compared for separating CTs from acetone/water extracts and column fractions analyzed for flavan-3-ol subunits, mean degree of polymerization (mDP) and purity. Toyopearl HW-50F generated fractions with higher mDP values and better separation of procyanidins (PC) and prodelphinidins (PD) but required a pre-purification step, more time for large scale purifications and gave poorer recoveries. Therefore, two gradient elution schemes were developed for CT purification on Sephadex LH-20 providing 146 - 2000 mg/fraction. Fractions were analyzed by thiolysis and NMR spectroscopy. In general, PC/PD ratios decreased and mDP increased during elution. 1H NMR spectroscopy served as a rapid screening tool to qualitatively determine CT enrichment and carbohydrate impurities present, guiding fractionation towards re-purification or 1H-13C HSQC NMR spectroscopy and thiolysis. These protocols provide options for preparing highly pure CT samples
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