1,724 research outputs found
Ab Initio No Core Shell Model - Recent Results and Further Prospects
There has been significant recent progress in solving the long-standing
problems of how nuclear shell structure and collective motion emerge from
underlying microscopic inter-nucleon interactions. We review a selection of
recent significant results within the ab initio No Core Shell Model (NCSM)
closely tied to three major factors enabling this progress: (1) improved
nuclear interactions that accurately describe the experimental two-nucleon and
three-nucleon interaction data; (2) advances in algorithms to simulate the
quantum many-body problem with strong interactions; and (3) continued rapid
development of high-performance computers now capable of performing floating point operations per second. We also comment on prospects for
further developments.Comment: Invited paper presented at NTSE-2014 and published online in the
proceedings (see footnote on p.1
Localization dynamics in a centrally coupled system
In systems where interactions couple a central degree of freedom and a bath,
one would expect signatures of the bath's phase to be reflected in the dynamics
of the central degree of freedom. This has been recently explored in connection
with many-body localized baths coupled with a central qubit or a single cavity
mode -- systems with growing experimental relevance in various platforms. Such
models also have an interesting connection with Floquet many-body localization
via quantizing the external drive, although this has been relatively
unexplored. Here we adapt the multilayer multiconfigurational time-dependent
Hartree (ML-MCTDH) method, a well-known tree tensor network algorithm, to
numerically simulate the dynamics of a central degree of freedom, represented
by a -level system (qudit), coupled to a disordered interacting 1D spin
bath. ML-MCTDH allows us to reach lattice sites, a far larger
system size than what is feasible with exact diagonalization or kernel
polynomial methods. From the intermediate time dynamics, we find a well-defined
thermodynamic limit for the qudit dynamics upon appropriate rescaling of the
system-bath coupling. The spin system shows similar scaling collapse in the
Edward-Anderson spin glass order parameter or entanglement entropy at
relatively short times. At longer time scales, we see slow growth of the
entanglement, which may arise from dephasing mechanisms in the localized system
or long-range interactions mediated by the central degree of freedom. Similar
signs of localization are shown to appear as well with unscaled system-bath
coupling
Enhancing the dynamic range of deformable mirrors with compression bias
We report the design and testing of a compression-biased thermally-actuated deformable mirror that has a dynamic range larger than the limit imposed by pure-bending stress, negligible higher-order-mode scattering, and a linear defocus response and that is vacuum compatible. The optimum design principles for this class of actuator are described and a mirror with 370 mD dynamic range is demonstrated
Design and analysis of a microplate assay in the presence of multiple restrictions on the randomization
Experiments using multi-step protocols often involve several restrictions on
the randomization. For a specific application to in vitro testing on
microplates, a design was required with both a split-plot and a strip-plot
structure. On top of two-level treatment factors and the factors that define
the randomization restrictions, a multi-level fixed blocking factor not
involving further restrictions on the randomization had to be added. We develop
a step-by-step approach to construct a design for the microplate experiment and
analyze a response. To consolidate the approach, we study various alternative
scenarios for the experiment.Comment: 31 pages, 13 tables, 4 figure
Mid-IR laser for wavefront correction in gravitational wave detectors
The next-generation gravitational wave detectors aim to enhance our understanding of extreme phenomena in the Universe. The high-frequency sensitivity of these detectors will be maximized by injecting squeezed vacuum states into the detector. However, the performance advantages offered by squeezed state injection can be easily degraded by losses in the system. A significant source of loss is the mode mismatch between optical cavities within the interferometer. To overcome this issue, new actuators are required that can produce a highly spherical wavefront change, with minimal higher order aberrations, whist adding low phase noise to the incident beam
Viscous Brane Cosmology with a Brane-Bulk Energy Interchange Term
We assume a flat brane located at y=0, surrounded by an AdS space, and
consider the 5D Einstein equations when the energy flux component of the
energy-momentum tensor is related to the Hubble parameter through a constant Q.
We calculate the metric tensor, as well as the Hubble parameter on the brane,
when Q is small. As a special case, if the brane is tensionless, the influence
from Q on the Hubble parameter is absent. We also consider the emission of
gravitons from the brane, by means of the Boltzmann equation. Comparing the
energy conservation equation derived herefrom with the energy conservation
equation for a viscous fluid on the brane, we find that the entropy change for
the fluid in the emission process has to be negative. This peculiar effect is
related to the fluid on the brane being a non-closed thermodynamic system. The
negative entropy property for non-closed systems is encountered in other areas
in physics also, in particular, in connection with the Casimir effect at finite
temperature.Comment: 12 pages, latex, no figure
Exploring the utility of human DNA methylation arrays for profiling mouse genomic DNA
AbstractIllumina Infinium Human Methylation (HM) BeadChips are widely used for measuring genome-scale DNA methylation, particularly in relation to epigenome-wide association studies (EWAS) studies. The methylation profile of human samples can be assessed accurately and reproducibly using the HM27 BeadChip (27,578 CpG sites) or its successor, the HM450 BeadChip (482,421 CpG sites). To date no mouse equivalent has been developed, greatly hindering the application of this methodology to the wide range of valuable murine models of disease and development currently in existence. We found 1308 and 13,715 probes from HM27 and HM450 BeadChip respectively, uniquely matched the bisulfite converted reference mouse genome (mm9). We demonstrate reproducible measurements of DNA methylation at these probes in a range of mouse tissue samples and in a murine cell line model of acute myeloid leukaemia. In the absence of a mouse counterpart, the Infinium Human Methylation BeadChip arrays have utility for methylation profiling in non-human species
Circulating Markers of Neutrophil Extracellular Traps Are of Prognostic Value in Patients With COVID-19
OBJECTIVE: The full spectrum of coronavirus disease 2019 (COVID-19) infection ranges from asymptomatic to acute respiratory distress syndrome, characterized by hyperinflammation and thrombotic microangiopathy. The pathogenic mechanisms are poorly understood, but emerging evidence suggest that excessive neutrophil extracellular trap (NET) formation plays a key role in COVID-19 disease progression. Here, we evaluate if circulating markers of NETs are associated with COVID-19 disease severity and clinical outcome, as well as to markers of inflammation and in vivo coagulation and fibrinolysis. Approach and Results: One hundred six patients with COVID-19 with moderate to severe disease were enrolled shortly after hospital admission and followed for 4 months. Acute and convalescent plasma samples as well as plasma samples from 30 healthy individuals were assessed for markers of NET formation: citrullinated histone H3, cell-free DNA, NE (neutrophil elastase). We found that plasma levels of NET markers were all elevated in patients with COVID-19 relative to healthy controls, were associated with respiratory support requirement and short-term mortality, and declined to those found in healthy individuals 4 months post-infection. Levels of the NET markers also correlated with white blood cells, neutrophils, inflammatory cytokines, and C-reactive protein, as well as to markers of in vivo coagulation, fibrinolysis, and endothelial damage. CONCLUSIONS: Our findings suggest a role of NETs in COVID-19 disease progression, implicating their contribution to an immunothrombotic state. Further, we observed an association between circulating markers of NET formation and clinical outcome, demonstrating a potential role of NET markers in clinical decision-making, as well as for NETs as targets for novel therapeutic interventions in COVID-19. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT04402944, NCT04541979, NCT04445285, NCT04432987, NCT04402970
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