40 research outputs found
The three-nucleon bound state using realistic potential models
The bound states of H and He have been calculated using the Argonne
plus the Urbana three-nucleon potential. The isospin state
have been included in the calculations as well as the - mass difference.
The H-He mass difference has been evaluated through the charge
dependent terms explicitly included in the two-body potential. The calculations
have been performed using two different methods: the solution of the Faddeev
equations in momentum space and the expansion on the correlated hyperspherical
harmonic basis. The results are in agreement within 0.1% and can be used as
benchmark tests. Results for the CD-Bonn interaction are also presented. It is
shown that the H and He binding energy difference can be predicted
model independently.Comment: 5 pages REVTeX 4, 1 figures, 6 table
The Effect of Bound Dineutrons upon BBN
We have examined the effects of a bound dineutron, n2, upon big bang
nucleosynthesis (BBN) as a function of its binding energy B_n2. We find a
weakly bound dineutron has little impact but as B_n2 increases its presence
begins to alter the flow of free nucleons to helium-4. Due to this disruption,
and in the absence of changes to other binding energies or fundamental
constants, BBN sets a reliable upper limit of B_n2 <~ 2.5 MeV in order to
maintain the agreement with the observations of the primordial helium-4 mass
fraction and D/H abundance
Neuroprotective Effect of Combination Therapy of Glatiramer Acetate and Epigallocatechin-3-Gallate in Neuroinflammation
Multiple sclerosis (MS) is an inflammatory autoimmune disease of the central nervous system. However, studies of MS and the animal model, experimental autoimmune encephalomyelitis (EAE), indicate that neuronal pathology is the principle cause of clinical disability. Thus, there is need to develop new therapeutic strategies that not only address immunomodulation but also neuroprotection. Here we show that the combination therapy of Glatiramer acetate (GA), an immunomodulatory MS therapeutic, and the neuroprotectant epigallocatechin-3-gallate (EGCG), the main phenol in green tea, have synergistic protective effects in vitro and in the EAE model. EGCG and GA together led to increased protection from glutamate- and TRAIL-induced neuronal cell death in vitro. EGCG combined with GA induced regeneration of hippocampal axons in an outgrowth assay. The combined application of EGCG and GA did not result in unexpected adverse events in vivo. Neuroprotective and neuroregenerative effects could be translated in the in vivo model, where combination treatment with EGCG and GA significantly delayed disease onset, strongly reduced clinical severity, even after onset of symptoms and reduced inflammatory infiltrates. These results illustrate the promise of combining neuroprotective and anti-inflammatory treatments and strengthen the prospects of EGCG as an adjunct therapy for neuroinflammatory and neurodegenerative diseases
Delay of Squeezing and Entanglement using Electromagnetically Induced Transparency in a Vapour Cell
We demonstrate experimentally the delay of squeezed light and entanglement
using Electromagnetically Induced Transparency (EIT) in a rubidium vapour cell.
We perform quadrature amplitude measurements of the probe field and find no
appreciable excess noise from the EIT process. From an input squeezing of 3.1
dB at low sideband frequencies, we observed the survival of 2 dB of squeezing
at the EIT output. By splitting the squeezed light on a beam-splitter, we
generated biased entanglement between two beams. We transmit one of the
entangled beams through the EIT cell and correlate the quantum statistics of
this beam with its entangled counterpart. We experimentally observed a 2 s
delay of the biased entanglement and obtained a preserved degree of
wavefunction inseparability of 0.71, below the unity value for separable
states.Comment: 8 pages, 5 figure
The Spectrometer/Telescope for Imaging X-rays (STIX)
Aims. The Spectrometer Telescope for Imaging X-rays (STIX) on Solar Orbiter is a hard X-ray imaging spectrometer, which covers the energy range from 4 to 150 keV. STIX observes hard X-ray bremsstrahlung emissions from solar flares and therefore provides diagnostics of the hottest (⪆10 MK) flare plasma while quantifying the location, spectrum, and energy content of flare-accelerated nonthermal electrons.
Methods. To accomplish this, STIX applies an indirect bigrid Fourier imaging technique using a set of tungsten grids (at pitches from 0.038 to 1 mm) in front of 32 coarsely pixelated CdTe detectors to provide information on angular scales from 7 to 180 arcsec with 1 keV energy resolution (at 6 keV). The imaging concept of STIX has intrinsically low telemetry and it is therefore well-suited to the limited resources available to the Solar Orbiter payload. To further reduce the downlinked data volume, STIX data are binned on board into 32 selectable energy bins and dynamically-adjusted time bins with a typical duration of 1 s during flares.
Results. Through hard X-ray diagnostics, STIX provides critical information for understanding the acceleration of electrons at the Sun and their transport into interplanetary space and for determining the magnetic connection of Solar Orbiter back to the Sun. In this way, STIX serves to link Solar Orbiter’s remote and in-situ measurements
Quantum entanglement and disentanglement of multi-atom systems
We present a review of recent research on quantum entanglement, with special
emphasis on entanglement between single atoms, processing of an encoded
entanglement and its temporary evolution. Analysis based on the density matrix
formalism are described. We give a simple description of the entangling
procedure and explore the role of the environment in creation of entanglement
and in disentanglement of atomic systems. A particular process we will focus on
is spontaneous emission, usually recognized as an irreversible loss of
information and entanglement encoded in the internal states of the system. We
illustrate some certain circumstances where this irreversible process can in
fact induce entanglement between separated systems. We also show how
spontaneous emission reveals a competition between the Bell states of a two
qubit system that leads to the recently discovered "sudden" features in the
temporal evolution of entanglement. An another problem illustrated in details
is a deterministic preparation of atoms and atomic ensembles in long-lived
stationary squeezed states and entangled cluster states. We then determine how
to trigger the evolution of the stable entanglement and also address the issue
of a steered evolution of entanglement between desired pairs of qubits that can
be achieved simply by varying the parameters of a given system.Comment: Review articl
An accurate nucleon-nucleon potential with charge-independence breaking
We present a new high-quality nucleon-nucleon potential with explicit charge
dependence and charge asymmetry, which we designate Argonne . The model
has a charge-independent part with fourteen operator components that is an
updated version of the Argonne potential. Three additional
charge-dependent and one charge-asymmetric operators are added, along with a
complete electromagnetic interaction. The potential has been fit directly to
the Nijmegen and scattering data base, low-energy scattering
parameters, and deuteron binding energy. With 40 adjustable parameters it gives
a per datum of 1.09 for 4301 and data in the range 0--350
MeV.Comment: 36 pages, PHY-7742-TH-9
Hif1a inactivation rescues photoreceptor degeneration induced by a chronic hypoxia-like stress
Reduced choroidal blood flow and tissue changes in the ageing human eye impair oxygen delivery to photoreceptors and the retinal pigment epithelium. As a consequence, mild but chronic hypoxia may develop and disturb cell metabolism, function and ultimately survival, potentially contributing to retinal pathologies such as age-related macular degeneration (AMD). Here, we show that several hypoxia-inducible genes were expressed at higher levels in the aged human retina suggesting increased activity of hypoxia-inducible transcription factors (HIFs) during the physiological ageing process. To model chronically elevated HIF activity and investigate ensuing consequences for photoreceptors, we generated mice lacking von Hippel Lindau (VHL) protein in rods. This activated HIF transcription factors and led to a slowly progressing retinal degeneration in the ageing mouse retina. Importantly, this process depended mainly on HIF1 with only a minor contribution of HIF2. A gene therapy approach using AAV-mediated RNA interference through an anti-Hif1a shRNA significantly mitigated the degeneration suggesting a potential intervention strategy that may be applicable to human patients