6,220 research outputs found
Properties of a coupled two species atom-heteronuclear molecule condensate
We study the coherent association of a two-species atomic condensate into a
condensate of heteronuclear diatomic molecules, using both a semiclassical
treatment and a quantum mechanical approach. The differences and connections
between the two approaches are examined. We show that, in this coupled
nonlinear atom-molecule system, the population difference between the two
atomic species plays a significant role in the ground-state stability
properties as well as in coherent population oscillation dynamics.Comment: 7 pages, 4 figure
Creating stable molecular condensate using a generalized Raman adiabatic passage scheme
We study the Feshbach resonance assisted stimulated adiabatic passage of an
effective coupling field for creating stable molecules from atomic Bose
condensate. By exploring the properties of the coherent population trapping
state, we show that, contrary to the previous belief, mean-field shifts need
not to limit the conversion efficiency as long as one chooses an adiabatic
passage route that compensates the collision mean-field phase shifts and avoids
the dynamical unstable regime.Comment: 4+\epsilon pages, 3 figure
Measurement back-action on the quantum spin-mixing dynamics of a spin-1 Bose-Einstein condensate
We consider a small F=1 spinor condensate inside an optical cavity driven by
an optical probe field, and subject the output of the probe to a homodyne
detection, with the goal of investigating the effect of measurement back-action
on the spin dynamics of the condensate. Using the stochastic master equation
approach, we show that the effect of back-action is sensitive to not only the
measurement strength but also the quantum fluctuation of the spinor condensate.
The same method is also used to estimate the atom numbers below which the
effect of back-action becomes so prominent that extracting spin dynamics from
this cavity-based detection scheme is no longer practical
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Unsaturated Ligands Seed an Order to Disorder Transition in Mixed Ligand Shells of CdSe/CdS Quantum Dots.
A phase transition within the ligand shell of core/shell quantum dots is studied in the prototypical system of colloidal CdSe/CdS quantum dots with a ligand shell composed of bound oleate (OA) and octadecylphosphonate (ODPA). The ligand shell composition is tuned using a ligand exchange procedure and quantified through proton NMR spectroscopy. Temperature-dependent photoluminescence spectroscopy reveals a signature of a phase transition within the organic ligand shell. Surprisingly, the ligand order to disorder phase transition triggers an abrupt increase in the photoluminescence quantum yield (PLQY) and full-width at half-maximum (FWHM) with increasing temperature. The temperature and width of the phase transition show a clear dependence on ligand shell composition, such that QDs with higher ODPA fractions have sharper phase transitions that occur at higher temperatures. In order to gain a molecular understanding of the changes in ligand ordering, Fourier transform infrared and vibrational sum frequency generation spectroscopies are performed. These measurements confirm that an order/disorder transition in the ligand shell tracks with the photoluminescence changes that accompany the ligand phase transition. The phase transition is simulated through a lattice model that suggests that the ligand shell is well-mixed and does not have completely segregated domains of OA and ODPA. Furthermore, we show that the unsaturated chains of OA seed disorder within the ligand shell
Generalized Balanced Tournament Packings and Optimal Equitable Symbol Weight Codes for Power Line Communications
Generalized balance tournament packings (GBTPs) extend the concept of
generalized balanced tournament designs introduced by Lamken and Vanstone
(1989). In this paper, we establish the connection between GBTPs and a class of
codes called equitable symbol weight codes. The latter were recently
demonstrated to optimize the performance against narrowband noise in a general
coded modulation scheme for power line communications. By constructing classes
of GBTPs, we establish infinite families of optimal equitable symbol weight
codes with code lengths greater than alphabet size and whose narrowband noise
error-correcting capability to code length ratios do not diminish to zero as
the length grows
Thermal performance of an active-passive ventilation wall with phase change material in solar greenhouses
© 2018 Elsevier Ltd Using phase change material (PCM) in the north wall of solar greenhouses has been recommended as an efficient solution for promoting their indoor thermal environment. In this type of walls, however, there is always a thermal-stable layer, which would greatly decrease their heat storage capacity. To solve this problem, an active-passive ventilation wall with PCM has been developed in this study, and a comparative study was carried out using both experimental and numerical methods to justify its advantages over conventional walls. Several important parameters have been monitored or calculated to reflect the contribution of the newly proposed method to the performance of the middle layer of the wall, the indoor thermal environment and the plants’ growth. The obtained results confirmed the great effectiveness of the proposed wall in promoting the temperature of its middle layer and irradiated surface. In the newly proposed wall, there was no thermal-stable layer observed, resulting in a minimum temperature rise of 1.34 °C. The proposed solution also enhanced the wall's heat storage capacity by 35.27–47.89% and the heat release capacity by 49.93–60.21%, resulting in an average increase of indoor air temperature, daily effective accumulative temperature and soil temperature by 1.58–4.16 °C, 33.33–55.06% and 0.53–1.09 °C, respectively. The plant height, stem diameter and fruit yield have been increased by 30%, 25% and 28%, respectively
Matter-wave bistability in coupled atom-molecule quantum gases
We study the matter-wave bistability in coupled atom-molecule quantum gases,
in which heteronuclear molecules are created via an interspecies Feshbach
resonance involving either two-species Bose or two-species Fermi atoms at zero
temperature. We show that the resonant two-channel Bose model is equivalent to
the nondegenerate parametric down-conversion in quantum optics, while the
corresponding Fermi model can be mapped to a quantum optics model that
describes a single-mode laser field interacting with an ensemble of
inhomogeneously broadened two-level atoms. Using these analogy and the fact
that both models are subject to the Kerr nonlinearity due to the two-body
s-wave collisions, we show that under proper conditions, the population in the
molecular state in both models can be made to change with the Feshbach detuning
in a bistable fashion.Comment: 6 pages, 5 figure
Intravenous renal cell transplantation with SAA1-positive cells prevents the progression of chronic renal failure in rats with ischemic-diabetic nephropathy
Diabetic nephropathy, the most common cause of progressive chronic renal failure and end-stage renal disease, has now reached global proportions. The only means to rescue diabetic patients on dialysis is renal transplantation, a very effective therapy but severely limited by the availability of donor kidneys. Hence, we tested the role of intravenous renal cell transplantation (IRCT) on obese/diabetic Zucker/SHHF F1 hybrid (ZS) female rats with severe ischemic and diabetic nephropathy. Renal ischemia was produced by bilateral renal clamping of the renal arteries at 10 wk of age, and IRCT with genetically modified normal ZS male tubular cells was given intravenously at 15 and 20 wk of age. Rats were euthanized at 34 wk of age. IRCT with cells expressing serum amyloid A had strong and long-lasting beneficial effects on renal function and structure, including tubules and glomeruli. However, donor cells were found engrafted only in renal tubules 14 wk after the second infusion. The results indicate that IRCT with serum amyloid A-positive cells is effective in preventing the progression of chronic kidney disease in rats with diabetic and ischemic nephropathy
Cavity-Mediated Strong Matter Wave Bistability in a Spin-1 Condensate
We study matter wave bistability in a spin-1 Bose-Einstein condensate
dispersively coupled to a unidirectional ring cavity. A unique feature is that
the population exchange among different modes of matter fields are accomplished
via the spin-exchange collisions. We show that the interplay between the atomic
spin mixing and the cavity light field can lead to a strong matter wave
nonlinearity, making matter wave bistability in a cavity at the single-photon
level achievable.Comment: 4 pages, 4 figure
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