1,189 research outputs found
State-dependent Jastrow correlation functions for 4He nuclei
We calculate the ground-state energy for the nucleus 4He with V4 nucleon
interactions, making use of a Jastrow description of the corresponding
wavefunction with state-dependent correlation factors. The effect related to
the state dependence of the correlation is quite important, lowering the upper
bound for the ground-state energy by some 2 MeV.Comment: 10 pages, REVTeX, to be published in J. Phys. G: Nucl. Part. Phy
Improvement in clinical markers in CF patients using a reduced glutathione regimen: An uncontrolled, observational study
AbstractCFTR mutation, which causes cystic fibrosis (CF), has also recently been identified as causing glutathione system dysfunction and systemic deficiency of reduced glutathione (GSH). Such dysfunction and deficiency regarding GSH may contribute to the pathophysiology of CF. We followed 13 patients (age range 1–27 years) with cystic fibrosis who were using a regimen of reduced glutathione (GSH), including oral glutathione and inhaled buffered glutathione in an uncontrolled, observational study. Dosage ranged from 66–148 mg/kg/day in divided doses, and the term examined was the initial 5.5 months of GSH use (45 days of incrementally adjusted dose, plus 4 months of use at full dosage). Baseline and post-measurements of FEV1 percent predicted, BMI percentile, and weight percentile were noted, in addition to bacterial status and pulmonary exacerbations. Significant improvement in the following clinical parameters was observed: average improvement in FEV1 percent predicted (N=10) was 5.8 percentage points (p<0.0001), average weight percentile (N=13) increased 8.6 points (p<0.001), BMI percentile (N=11) improved on average 1.22 points (p<0.001). All patients improved in FEV1 and BMI, if measured in their case; 12 of 13 patients improved in weight percentile. Positive sputum cultures of bacteria in 11 patients declined from 13 to 5 (p<0.03) with sputum cultures of Pseudomonas aeruginosa becoming negative in 4 of 5 patients previously culturing PA, including two of three patients chronically infected with PA as determined by antibody status. Use of a daily GSH regimen appears to be associated in CF patients with significant improvement in lung function and weight, and a significant decline in bacteria cultured in this uncontrolled study. These findings bear further clinical investigation in larger, randomized, controlled studies
Hemigrapsus takanoi Asakura and Watanabe, 2005 (Crustacea: Decapoda: Brachyura: Grapsoidea): first records of the brush-clawed shore crab from Great Britain
The brush-clawed shore crab is reported from the River Medway, Kent and the River Colne, Essex, England. These represent the first records of Hemigrapsus takanoi Asakura and Watanabe, 2005 from Great Britain. If H. takanoi becomes established in GB, it may pose a threat to populations of the native shore crab Carcinus maenas
Tracking Target Signal Strengths on a Grid using Sparsity
Multi-target tracking is mainly challenged by the nonlinearity present in the
measurement equation, and the difficulty in fast and accurate data association.
To overcome these challenges, the present paper introduces a grid-based model
in which the state captures target signal strengths on a known spatial grid
(TSSG). This model leads to \emph{linear} state and measurement equations,
which bypass data association and can afford state estimation via
sparsity-aware Kalman filtering (KF). Leveraging the grid-induced sparsity of
the novel model, two types of sparsity-cognizant TSSG-KF trackers are
developed: one effects sparsity through -norm regularization, and the
other invokes sparsity as an extra measurement. Iterative extended KF and
Gauss-Newton algorithms are developed for reduced-complexity tracking, along
with accurate error covariance updates for assessing performance of the
resultant sparsity-aware state estimators. Based on TSSG state estimates, more
informative target position and track estimates can be obtained in a follow-up
step, ensuring that track association and position estimation errors do not
propagate back into TSSG state estimates. The novel TSSG trackers do not
require knowing the number of targets or their signal strengths, and exhibit
considerably lower complexity than the benchmark hidden Markov model filter,
especially for a large number of targets. Numerical simulations demonstrate
that sparsity-cognizant trackers enjoy improved root mean-square error
performance at reduced complexity when compared to their sparsity-agnostic
counterparts.Comment: Submitted to IEEE Trans. on Signal Processin
An Alternative Interpretation of Statistical Mechanics
In this paper I propose an interpretation of classical statistical mechanics that centers on taking seriously the idea that probability measures represent complete states of statistical mechanical systems. I show how this leads naturally to the idea that the stochasticity of statistical mechanics is associated directly with the observables of the theory rather than with the microstates (as traditional accounts would have it). The usual assumption that microstates are representationally significant in the theory is therefore dispensable, a consequence which suggests interesting possibilities for developing non-equilibrium statistical mechanics and investigating inter-theoretic answers to the foundational questions of statistical mechanics
Solid 4He and the Supersolid Phase: from Theoretical Speculation to the Discovery of a New State of Matter? A Review of the Past and Present Status of Research
The possibility of a supersolid state of matter, i.e., a crystalline solid
exhibiting superfluid properties, first appeared in theoretical studies about
forty years ago. After a long period of little interest due to the lack of
experimental evidence, it has attracted strong experimental and theoretical
attention in the last few years since Kim and Chan (Penn State, USA) reported
evidence for nonclassical rotational inertia effects, a typical signature of
superfluidity, in samples of solid 4He. Since this "first observation", other
experimental groups have observed such effects in the response to the rotation
of samples of crystalline helium, and it has become clear that the response of
the solid is extremely sensitive to growth conditions, annealing processes, and
3He impurities. A peak in the specific heat in the same range of temperatures
has been reported as well as anomalies in the elastic behaviour of solid 4He
with a strong resemblance to the phenomena revealed by torsional oscillator
experiments. Very recently, the observation of unusual mass transport in hcp
solid 4He has also been reported, suggesting superflow. From the theoretical
point of view, powerful simulation methods have been used to study solid 4He,
but the interpretation of the data is still rather difficult; dealing with the
question of supersolidity means that one has to face not only the problem of
the coexistence of quantum coherence phenomena and crystalline order, exploring
the realm of spontaneous symmetry breaking and quantum field theory, but also
the problem of the role of disorder, i.e., how defects, such as vacancies,
impurities, dislocations, and grain boundaries, participate in the phase
transition mechanism.Comment: Published on J. Phys. Soc. Jpn., Vol.77, No.11, p.11101
A Theory of Cheap Control in Embodied Systems
We present a framework for designing cheap control architectures for embodied
agents. Our derivation is guided by the classical problem of universal
approximation, whereby we explore the possibility of exploiting the agent's
embodiment for a new and more efficient universal approximation of behaviors
generated by sensorimotor control. This embodied universal approximation is
compared with the classical non-embodied universal approximation. To exemplify
our approach, we present a detailed quantitative case study for policy models
defined in terms of conditional restricted Boltzmann machines. In contrast to
non-embodied universal approximation, which requires an exponential number of
parameters, in the embodied setting we are able to generate all possible
behaviors with a drastically smaller model, thus obtaining cheap universal
approximation. We test and corroborate the theory experimentally with a
six-legged walking machine. The experiments show that the sufficient controller
complexity predicted by our theory is tight, which means that the theory has
direct practical implications. Keywords: cheap design, embodiment, sensorimotor
loop, universal approximation, conditional restricted Boltzmann machineComment: 27 pages, 10 figure
Characterization of halogen-bridged binuclear metal complexes as hybridized two-band materials
We study the electronic structure of halogen-bridged binuclear metal (MMX)
complexes with a two-band Peierls-Hubbard model. Based on a symmetry argument,
various density-wave states are derived and characterized. The ground-state
phase diagram is drawn within the Hartree-Fock approximation, while the thermal
behavior is investigated using a quantum Monte Carlo method. All the
calculations conclude that a typical MMX compound Pt_2(CH_3CS_2)_4I should
indeed be regarded as a d-p-hybridized two-band material, where the oxidation
of the halogen ions must be observed even in the ground state, whereas another
MMX family (NH_4)_4[Pt_2(P_2O_5H_2)_4X] may be treated as single-band
materials.Comment: 16 pages, 11 figures embedded, to be published in Phys. Rev.
Combinatorial Roles of Heparan Sulfate Proteoglycans and Heparan Sulfates in Caenorhabditis elegans Neural Development
Heparan sulfate proteoglycans (HSPGs) play critical roles in the development and adult physiology of all metazoan organisms. Most of the known molecular interactions of HSPGs are attributed to the structurally highly complex heparan sulfate (HS) glycans. However, whether a specific HSPG (such as syndecan) contains HS modifications that differ from another HSPG (such as glypican) has remained largely unresolved. Here, a neural model in C. elegans is used to demonstrate for the first time the relationship between specific HSPGs and HS modifications in a defined biological process in vivo. HSPGs are critical for the migration of hermaphrodite specific neurons (HSNs) as genetic elimination of multiple HSPGs leads to 80% defect of HSN migration. The effects of genetic elimination of HSPGs are additive, suggesting that multiple HSPGs, present in the migrating neuron and in the matrix, act in parallel to support neuron migration. Genetic analyses suggest that syndecan/sdn-1 and HS 6-O-sulfotransferase, hst-6, function in a linear signaling pathway and glypican/lon-2 and HS 2-O-sulfotransferase, hst-2, function together in a pathway that is parallel to sdn-1 and hst-6. These results suggest core protein specific HS modifications that are critical for HSN migration. In C. elegans, the core protein specificity of distinct HS modifications may be in part regulated at the level of tissue specific expression of genes encoding for HSPGs and HS modifying enzymes. Genetic analysis reveals that there is a delicate balance of HS modifications and eliminating one HS modifying enzyme in a compromised genetic background leads to significant changes in the overall phenotype. These findings are of importance with the view of HS as a critical regulator of cell signaling in normal development and disease
- …