1,074 research outputs found
Entangled Wavefunctions from Classical Oscillator Amplitudes
In the first days of quantum mechanics Dirac pointed out an analogy between
the time-dependent coefficients of an expansion of the Schr\"odinger equation
and the classical position and momentum variables solving Hamilton's equations.
Here it is shown that the analogy can be made an equivalence in that, in
principle, systems of classical oscillators can be constructed whose position
and momenta variables form time-dependent amplitudes which are identical to the
complex quantum amplitudes of the coupled wavefunction of an N-level quantum
system with real coupling matrix elements. Hence classical motion can reproduce
quantum coherence.Comment: extended versio
Box traps on an atom chip for one-dimensional quantum gases
We present the implementation of tailored trapping potentials for ultracold
gases on an atom chip. We realize highly elongated traps with box-like
confinement along the long, axial direction combined with conventional harmonic
confinement along the two radial directions. The design, fabrication and
characterization of the atom chip and the box traps is described. We load
ultracold (K) clouds of Rb in a box trap, and demonstrate
Bose-gas focusing as a means to characterize these atomic clouds in arbitrarily
shaped potentials. Our results show that box-like axial potentials on atom
chips are very promising for studies of one-dimensional quantum gases.Comment: 9 pages 4 figure
Three-dimensional character of atom-chip-based rf-dressed potentials
We experimentally investigate the properties of radio-frequency-dressed
potentials for Bose-Einstein condensates on atom chips. The three-dimensional
potential forms a connected pair of parallel waveguides. We show that
rf-dressed potentials are robust against the effect of small magnetic-field
variations on the trap potential. Long-lived dipole oscillations of condensates
induced in the rf-dressed potentials can be tuned to a remarkably low damping
rate. We study a beam-splitter for Bose-Einstein condensates and show that a
propagating condensate can be dynamically split in two vertically separated
parts and guided along two paths. The effect of gravity on the potential can be
tuned and compensated for using a rf-field gradient.Comment: 9 pages, 7 figure
Yang-Yang thermodynamics on an atom chip
We investigate the behavior of a weakly interacting nearly one-dimensional
(1D) trapped Bose gas at finite temperature. We perform in situ measurements of
spatial density profiles and show that they are very well described by a model
based on exact solutions obtained using the Yang-Yang thermodynamic formalism,
in a regime where other, approximate theoretical approaches fail. We use
Bose-gas focusing [Shvarchuck etal., Phys. Rev. Lett. 89, 270404 (2002)] to
probe the axial momentum distribution of the gas, and find good agreement with
the in situ results.Comment: extended introduction and conclusions, and minor changes throughout;
accepted for publication in Phys. Rev. Let
Efficient estimation of energy transfer efficiency in light-harvesting complexes
The fundamental physical mechanisms of energy transfer in photosynthetic
complexes is not yet fully understood. In particular, the degree of efficiency
or sensitivity of these systems for energy transfer is not known given their
non-perturbative and non-Markovian interactions with proteins backbone and
surrounding photonic and phononic environments. One major problem in studying
light-harvesting complexes has been the lack of an efficient method for
simulation of their dynamics in biological environments. To this end, here we
revisit the second-order time-convolution (TC2) master equation and examine its
reliability beyond extreme Markovian and perturbative limits. In particular, we
present a derivation of TC2 without making the usual weak system-bath coupling
assumption. Using this equation, we explore the long time behaviour of exciton
dynamics of Fenna-Matthews-Olson (FMO) protein complex. Moreover, we introduce
a constructive error analysis to estimate the accuracy of TC2 equation in
calculating energy transfer efficiency, exhibiting reliable performance for
environments with weak and intermediate memory and strength. Furthermore, we
numerically show that energy transfer efficiency is optimal and robust for the
FMO protein complex of green sulphur bacteria with respect to variations in
reorganization energy and bath correlation time-scales.Comment: 16 pages, 9 figures, modified version, updated appendices and
reference lis
Influence of Complex Exciton-Phonon Coupling on Optical Absorption and Energy Transfer of Quantum Aggregates
We present a theory that efficiently describes the quantum dynamics of an
electronic excitation that is coupled to a continuous, highly structured phonon
environment. Based on a stochastic approach to non-Markovian open quantum
systems, we develop a dynamical framework that allows us to handle realistic
systems where a fully quantum treatment is desired yet the usual approximation
schemes fail. The capability of the method is demonstrated by calculating
spectra and energy transfer dynamics of mesoscopic molecular aggregates,
elucidating the transition from fully coherent to incoherent transfer
Tunable exciton interactions in optical lattices with polar molecules
Rotational excitation of polar molecules trapped in an optical lattice gives
rise to rotational excitons. Here we show that non-linear interactions of such
excitons can be controlled by an electric field. The exciton--exciton
interactions can be tuned to induce exciton pairing, leading to the formation
of biexcitons. Tunable non-linear interactions between excitons can be used for
many applications ranging from the controlled preparation of entangled
quasiparticles to the study of polaron interactions and the effects of
non-linear interactions on quantum energy transport in molecular aggregates.Comment: Some typos have been corrected in this versio
Attenuation of Renovascular Damage in Zucker Diabetic Fatty Rat by NWT-03, an Egg Protein Hydrolysate with ACE- and DPP4-Inhibitory Activity
Background Dipeptidyl peptidase 4 (DPP4) and angiotensin-converting enzyme (ACE) are important target enzymes in glycemic control and renovascular protection. Here, we studied the effect of NWT-03, an egg protein hydrolysate with DPP4- and ACE-inhibitory activity, on renovascular damage in Zucker diabetic fatty (ZDF) rats. Comparisons were made to rats treated with vildagliptin (VIL), included as a positive control for the effect of DPP4 inhibition. Methods ZDF rats received NWT-03 (1 g/kg/day) or VIL (3 mg/kg/day) from 10 to 25 weeks of age. Metabolic and renal functions were assessed; the kidney was removed for histological analysis of glomerulosclerosis and expression of pro-inflammatory/fibrotic markers (RT-PCR and Western blotting); and the aorta was removed for studies of endothelium-dependent relaxation (EDR). Findings Hyperinsulinemic ZDF rats typically developed signs of type-2 diabetes and renovascular damage, as evidenced by albuminuria, glomerulosclerosis, and impaired EDR. Neither NWT-03 nor VIL improved metabolic parameters; for VIL, this was despite a 5-fold increase in glucagon-like peptide (GLP)-1 levels. NWT-03 and VIL both reduced renal interleukin (Il)-1Ăź/Il-13 mRNA expression and glomerulosclerosis. However, only NWT-03 additionally decreased renal tumor necrosis factor (TNF)-a mRNA and P22phox protein expression, reduced albuminuria, and restored aortic EDR. Indomethacin added to the organ bath instantly improved aortic EDR, indicating a role for cyclooxygenase (COX)-derived contractile prostanoids in opposing relaxation in ZDF rats. This indomethacin effect was reduced by NWT-03, but not by VIL, and coincided with decreased renal COX-1/2 protein expression. Conclusion and Interpretation Long-term supplementation with the egg protein hydrolysate NWT-03 attenuated renovascular damage in this preclinical rat model of type 2 diabetes. A comparison to the DPP4-inhibitor VIL suggests that the effects of NWT-03 were related to both ACE- and DPP4-inhibitory properties. The development of protein hydrolysates with a multiple-targeting strategy may be of benefit to functional food formulations
A species-independent lateral flow microarray immunoassay to detect WNV and USUV NS1-specific antibodies in serum
Arboviruses such as West Nile Virus (WNV) and Usutu Virus (USUV) are emerging pathogens that circulate between mosquitoes and birds, occasionally spilling over into humans and horses. Current serological screening methods require access to a well-equipped laboratory and are not currently available for on-site analysis. As a proof of concept, we propose here a species-independent lateral flow microarray immunoassay (LMIA) able to quickly detect and distinguish between WNV Non-Structural 1 (NS1) and USUV NS1-specific antibodies. A double antigen approach was used to test sera collected from humans, horses, European jackdaws (Corvus monedula), and common blackbirds (Turdus merula). Optimization of the concentration of capture antigen spotted on the LMIA membrane and the amount of detection antigen conjugated to detector particles indicated that maximizing both parameters increased assay sensitivity. Upon screening of a larger serum panel, the optimized LMIA showed significantly higher spot intensity for a homologous binding event. Using a Receiver Operating Characteristics (ROC) curve, WNV NS1 LMIA results in humans, horses, and C. monedula showed good correlation when compared to “gold standard” WNV FRNT90. The most optimal derived sensitivity and specificity of the WNV NS1 LMIA relative to corresponding WNV FRNT90-confirmed sera were determined to be 96% and 86%, respectively. While further optimization is required, this study demonstrates the feasibility of developing a species-independent LMIA for on-site analysis of WNV, USUV, and other arboviruses. Such a tool would be useful for the on-site screening and monitoring of relevant species in more remote or low-income regions.</p
A species-independent lateral flow microarray immunoassay to detect WNV and USUV NS1-specific antibodies in serum
Arboviruses such as West Nile Virus (WNV) and Usutu Virus (USUV) are emerging pathogens that circulate between mosquitoes and birds, occasionally spilling over into humans and horses. Current serological screening methods require access to a well-equipped laboratory and are not currently available for on-site analysis. As a proof of concept, we propose here a species-independent lateral flow microarray immunoassay (LMIA) able to quickly detect and distinguish between WNV Non-Structural 1 (NS1) and USUV NS1-specific antibodies. A double antigen approach was used to test sera collected from humans, horses, European jackdaws (Corvus monedula), and common blackbirds (Turdus merula). Optimization of the concentration of capture antigen spotted on the LMIA membrane and the amount of detection antigen conjugated to detector particles indicated that maximizing both parameters increased assay sensitivity. Upon screening of a larger serum panel, the optimized LMIA showed significantly higher spot intensity for a homologous binding event. Using a Receiver Operating Characteristics (ROC) curve, WNV NS1 LMIA results in humans, horses, and C. monedula showed good correlation when compared to “gold standard” WNV FRNT90. The most optimal derived sensitivity and specificity of the WNV NS1 LMIA relative to corresponding WNV FRNT90-confirmed sera were determined to be 96% and 86%, respectively. While further optimization is required, this study demonstrates the feasibility of developing a species-independent LMIA for on-site analysis of WNV, USUV, and other arboviruses. Such a tool would be useful for the on-site screening and monitoring of relevant species in more remote or low-income regions.</p
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