60 research outputs found
Origin and Detection of Microstructural Clustering in Fluids with Spatial-Range Competitive Interactions
Fluids with competing short-range attractions and long-range repulsions mimic
dispersions of charge-stabilized colloids that can display equilibrium
structures with intermediate range order (IRO), including particle clusters.
Using simulations and analytical theory, we demonstrate how to detect cluster
formation in such systems from the static structure factor and elucidate links
to macrophase separation in purely attractive reference fluids. We find that
clusters emerge when the thermal correlation length encoded in the IRO peak of
the structure factor exceeds the characteristic lengthscale of interparticle
repulsions. We also identify qualitative differences between the dynamics of
systems that form amorphous versus micro-crystalline clusters.Comment: 6 pages, 5 figure
Characterization and validation of an intra-fraction motion management system for masked-based radiosurgery
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Monkeypox Virus Infection of Rhesus Macaques Induces Massive Expansion of Natural Killer Cells but Suppresses Natural Killer Cell Functions
Natural killer (NK) cells play critical roles in innate immunity and in bridging innate and adaptive immune responses against viral infection. However, the response of NK cells to monkeypox virus (MPXV) infection is not well characterized. In this intravenous challenge study of MPXV infection in rhesus macaques (Macaca mulatta), we analyzed blood and lymph node NK cell changes in absolute cell numbers, cell proliferation, chemokine receptor expression, and cellular functions. Our results showed that the absolute number of total NK cells in the blood increased in response to MPXV infection at a magnitude of 23-fold, manifested by increases in CD56+, CD16+, CD16-CD56- double negative, and CD16+CD56+ double positive NK cell subsets. Similarly, the frequency and NK cell numbers in the lymph nodes also largely increased with the total NK cell number increasing 46.1-fold. NK cells both in the blood and lymph nodes massively proliferated in response to MPXV infection as measured by Ki67 expression. Chemokine receptor analysis revealed reduced expression of CXCR3, CCR7, and CCR6 on NK cells at early time points (days 2 and 4 after virus inoculation), followed by an increased expression of CXCR3 and CCR5 at later time points (days 7-8) of infection. In addition, MPXV infection impaired NK cell degranulation and ablated secretion of interferon-γ and tumor necrosis factor-α. Our data suggest a dynamic model by which NK cells respond to MPXV infection of rhesus macaques. Upon virus infection, NK cells proliferated robustly, resulting in massive increases in NK cell numbers. However, the migrating capacity of NK cells to tissues at early time points might be reduced, and the functions of cytotoxicity and cytokine secretion were largely compromised. Collectively, the data may explain, at least partially, the pathogenesis of MPXV infection in rhesus macaques
Spectroscopy and Thermometry of Drumhead Modes in a Mesoscopic Trapped-Ion Crystal using Entanglement
We demonstrate spectroscopy and thermometry of individual motional modes in a
mesoscopic 2D ion array using entanglement-induced decoherence as a method of
transduction. Our system is a 400 m-diameter planar crystal of
several hundred Be ions exhibiting complex drumhead modes in the
confining potential of a Penning trap. Exploiting precise control over the
Be valence electron spins, we apply a homogeneous spin-dependent
optical dipole force to excite arbitrary transverse modes with an effective
wavelength approaching the interparticle spacing (20 \nolinebreakm).
Center-of-mass displacements below 1 nm are detected via entanglement of spin
and motional degrees of freedom.Comment: 12 pages, 7 figures (includes Supplementary Material
De Broglie Wavelength of a Nonlocal Four-Photon
Superposition is one of the most distinct features of quantum theory and has
been demonstrated in numerous realizations of Young's classical double-slit
interference experiment and its analogues. However, quantum entanglement - a
significant coherent superposition in multiparticle systems - yields phenomena
that are much richer and more interesting than anything that can be seen in a
one-particle system. Among them, one important type of multi-particle
experiments uses path-entangled number-states, which exhibit pure higher-order
interference and allow novel applications in metrology and imaging such as
quantum interferometry and spectroscopy with phase sensitivity at the
Heisenberg limit or quantum lithography beyond the classical diffraction limit.
Up to now, in optical implementations of such schemes lower-order interference
effects would always decrease the overall performance at higher particle
numbers. They have thus been limited to two photons. We overcome this
limitation and demonstrate a linear-optics-based four-photon interferometer.
Observation of a four-particle mode-entangled state is confirmed by
interference fringes with a periodicity of one quarter of the single-photon
wavelength. This scheme can readily be extended to arbitrary photon numbers and
thus represents an important step towards realizable applications with
entanglement-enhanced performance.Comment: 19 pages, 4 figures, submitted on November 18, 200
Engineered 2D Ising interactions on a trapped-ion quantum simulator with hundreds of spins
The presence of long-range quantum spin correlations underlies a variety of
physical phenomena in condensed matter systems, potentially including
high-temperature superconductivity. However, many properties of exotic strongly
correlated spin systems (e.g., spin liquids) have proved difficult to study, in
part because calculations involving N-body entanglement become intractable for
as few as N~30 particles. Feynman divined that a quantum simulator - a
special-purpose "analog" processor built using quantum particles (qubits) -
would be inherently adept at such problems. In the context of quantum
magnetism, a number of experiments have demonstrated the feasibility of this
approach. However, simulations of quantum magnetism allowing controlled,
tunable interactions between spins localized on 2D and 3D lattices of more than
a few 10's of qubits have yet to be demonstrated, owing in part to the
technical challenge of realizing large-scale qubit arrays. Here we demonstrate
a variable-range Ising-type spin-spin interaction J_ij on a naturally occurring
2D triangular crystal lattice of hundreds of spin-1/2 particles (9Be+ ions
stored in a Penning trap), a computationally relevant scale more than an order
of magnitude larger than existing experiments. We show that a spin-dependent
optical dipole force can produce an antiferromagnetic interaction J_ij ~
1/d_ij^a, where a is tunable over 0<a<3; d_ij is the distance between spin
pairs. These power-laws correspond physically to infinite-range (a=0),
Coulomb-like (a=1), monopole-dipole (a=2) and dipole-dipole (a=3) couplings.
Experimentally, we demonstrate excellent agreement with theory for 0.05<a<1.4.
This demonstration coupled with the high spin-count, excellent quantum control
and low technical complexity of the Penning trap brings within reach simulation
of interesting and otherwise computationally intractable problems in quantum
magnetism.Comment: 10 pages, 10 figures; article plus Supplementary Material
The intraurban spatial distribution of employment: which government interventions make a difference?
Efficiency Analysis and Comparative Study of Hard and Soft Switching DC-DC Converters in a Wind Farm
This paper focuses on efficiency analysis and comparative study of hard-and soft-switching dc-dc boost converters in wind farms. The efficiency of an ac or a dc-based wind farm is dependent on the efficiency of its key components such as dc-dc converters. The demand for dc-dc converters depends on how voltage fluctuations are adjusted. This paper analyzes the efficiency of the switching method used in dc-dc converters. The switching and conduction losses of all the components of the dc-dc converters are modeled and the efficiency is calculated accurately. The power rating vs. efficiency of the dc-dc converters is also considered. The efficiency of the converter in soft switching mode is greater than in hard switching mode. The efficient operation of the converter at a given power rating is shown graphically
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