4,632 research outputs found
Photoionization Rates of Cs Rydberg Atoms in a 1064 nm Far Off-Resonance Trap
Experimental measurements of photoionization rates of Rydberg
states of Cs () in a 1064 nm far off-resonance dipole trap
are presented. The photoionization rates are obtained by measuring the
lifetimes of Rydberg atoms produced inside of a 1064 nm far off-resonance trap
and comparing the lifetimes to corresponding control experiments in a
magneto-optical trap. Experimental results for the control experiments agree
with recent theoretical predictions for Rydberg state lifetimes and measured
photoionization rates are in agreement with transition rates calculated from a
model potential.Comment: 12 pages, 4 figure
Feasibility study of full-reactor gas core demonstration test
Separate studies of nuclear criticality, flow patterns, and thermodynamics for the gas core reactor concept have all given positive indications of its feasibility. However, before serious design for a full scale gas core application can be made, feasibility must be shown for operation with full interaction of the nuclear, thermal, and hydraulic effects. A minimum sized, and hence minimum expense, test arrangement is considered for a full gas core configuration. It is shown that the hydrogen coolant scattering effects dominate the nuclear considerations at elevated temperatures. A cavity diameter of somewhat larger than 4 ft (122 cm) will be needed if temperatures high enough to vaporize uranium are to be achieved
Observation of blue-shifted ultralong-range Cs Rydberg molecules
We observe ultralong-range blue-shifted Cs molecular states near
Rydberg states in an optical dipole trap, where .
The accidental near degeneracy of and Rydberg states for in
Cs, due to the small fractional quantum defect, leads to non-adiabatic
coupling among these states, producing potential wells above the
thresholds. Two important consequences of admixing high angular momentum states
with states are the formation of large permanent dipole moments, Debye, and accessibility of these states via two-photon association.
The observed states are in excellent agreement with theory. Both projections of
the total angular momentum on the internuclear axis are visible in the
experiment
Weak-Coupling Theory of Pair Density-Wave Instabilities in Transition Metal Dichalcogenides
The possibility of realizing pair density wave (PDW) phases, in which Cooper
pairs have a finite momentum, presents an interesting challenge that has been
studied in a wide variety of systems. In conventional superconductors, this is
only possible when external fields lift the spin degeneracy of the Fermi
surface, leading to pair formation at an incommensurate momentum. Here, we
study a second possibility, potentially relevant to transition metal
dichalcogenides, in which the Fermi surface consists of a pair of pockets
centered at the points of the Brillouin zone as well as a central
pocket at the point. In the limit where these three pockets are
identical, the pairing susceptibility has a logarithmic divergence at the
non-zero wave-vectors , allowing for a weak-coupling analysis
of the PDW instability. We find that repulsive electronic interactions combine
to yield effective attractive interactions in the singlet and triplet PDW
channels, as long as the pocket is present. Because these PDW channels
decouple from the uniform superconducting channel, they can become the leading
unconventional pairing instability of the system. Upon solving the linearized
gap equations, we find that the PDW instability is robust against small
trigonal warping of the pockets and small detuning between the
and pockets, which affect the PDW transition in a similar way as the
Zeeman magnetic field affects the uniform superconducting transition. We also
derive the Ginzburg-Landau free energy for the PDW gaps with momenta , analyzing the conditions for and consequences of the emergence of
FF-type and LO-type PDW ground states. Our classification of the induced orders
in each ground state reveals unusual phases, including an odd-frequency
charge- superconductor in the LO-type PDW.Comment: 24 pages, 11 figure
Tapered-amplified AR-coated laser diodes for Potassium and Rubidium atomic-physics experiments
We present a system of room-temperature extended-cavity grating-diode lasers
(ECDL) for production of light in the range 760-790nm. The extension of the
tuning range towards the blue is permitted by the weak feedback in the cavity:
the diodes are anti-reflection coated, and the grating has just 10%
reflectance. The light is then amplified using semiconductor tapered amplifiers
to give more than 400mW of power. The outputs are shown to be suitable for
atomic physics experiments with potassium (767nm), rubidium (780nm) or both, of
particular relevance to doubly-degenerate boson-fermion mixtures
Assessing decision quality in patient-centred care requires a preference-sensitive measure.
A theory-based instrument for measuring the quality of decisions made using any form of decision technology, including both decision-aided and unaided clinical consultations is required to enable person- and patient-centred care and to respond positively to individual heterogeneity in the value aspects of decision making. Current instruments using the term 'decision quality' have adopted a decision- and thus condition-specific approach. We argue that patient-centred care requires decision quality to be regarded as both preference-sensitive across multiple relevant criteria and generic across all conditions and decisions. MyDecisionQuality is grounded in prescriptive multi criteria decision analysis and employs a simple expected value algorithm to calculate a score for the quality of a decision that combines, in the clinical case, the patient's individual preferences for eight quality criteria (expressed as importance weights) and their ratings of the decision just taken on each of these criteria (expressed as performance rates). It thus provides an index of decision quality that encompasses both these aspects. It also provides patients with help in prioritizing quality criteria for future decision making by calculating, for each criterion, the Incremental Value of Perfect Rating, that is, the increase in their decision quality score that would result if their performance rating on the criterion had been 100%, weightings unchanged. MyDecisionQuality, which is a web-based generic and preference-sensitive instrument, can constitute a key patient-reported measure of the quality of the decision-making process. It can provide the basis for future decision improvement, especially when the clinician (or other stakeholders) completes the equivalent instrument and the extent and nature of concordance and discordance can be established. Apart from its role in decision preparation and evaluation, it can also provide real time and relevant documentation for the patient's record
Calcium ionophore (A-23187) induced peritoneal eicosanoid biosynthesis: a rapid method to evaluate inhibitors of arachidonic acid metabolism in vivo
The present investigation characterizes calcium ionophore (A-23187) induced peritoneal eicosanoid biosynthesis in the rat. Intraperitoneal injection of A-23187 (20 μg/rat) stimulated marked biosynthesis of 6-keto-PGF1α (6-KPA), TxB2, LTC4 and LTB4, with no detectable changes on levels of PGE2. Levels of all eicosanoids decreased rapidly after a peak which was seen as early as 5 min. Enzyme markers of cellular contents of neutrophils and mononuclear cells, MPO and NAG respectively, decreased rapidly after ionophore injection; this was followed by increases after 60 min. Indomethacin, a selective cyclooxygenase inhibitor, and zileuton and ICI D-2138, two selective 5-lipoxygenase inhibitors attenuated prostaglandin and leukotriene pathways respectively. Oral administration of zileuton (20 mg/kg, p.o.) inhibited LTB4 biosynthesis for up to 6 h suggesting a long duration of pharmacological activity in the rats consistent with its longer half-life. The rapid onset and the magnitude of increases in levels of eicosanoids render the ionophore induced peritoneal eicosanoid biosynthesis a useful model to evaluate pharmacological profiles of inhibitors of eicosanoid pathways in vivo
High-precision calculations of van der Waals coefficients for heteronuclear alkali-metal dimers
Van der Waals coefficients for the heteronuclear alkali-metal dimers of Li,
Na, K, Rb, Cs, and Fr are calculated using relativistic ab initio methods
augmented by high-precision experimental data. We argue that the uncertainties
in the coefficients are unlikely to exceed about 1%.Comment: 11 pages, 2 figs, graphicx.st
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