943 research outputs found
From quantum trajectories to classical orbits
Recently it has been shown that the evolution of open quantum systems may be
``unraveled'' into individual ``trajectories,'' providing powerful numerical
and conceptual tools. In this letter we use quantum trajectories to study
mesoscopic systems and their classical limit. We show that in this limit,
Quantum Jump (QJ) trajectories approach a diffusive limit very similar to the
Quantum State Diffusion (QSD) unraveling. The latter follows classical
trajectories in the classical limit. Hence, both unravelings show the rise of
classical orbits. This is true for both regular and chaotic systems (which
exhibit strange attractors).Comment: 7 pages RevTeX 3.0 + 2 figures (postscript). Submitted to Physical
Review Letter
Continuous stochastic Schrodinger equations and localization
The set of continuous norm-preserving stochastic Schrodinger equations
associated with the Lindblad master equation is introduced. This set is used to
describe the localization properties of the state vector toward eigenstates of
the environment operator. Particular focus is placed on determining the
stochastic equation which exhibits the highest rate of localization for wide
open systems. An equation having such a property is proposed in the case of a
single non-hermitian environment operator. This result is relevant to numerical
simulations of quantum trajectories where localization properties are used to
reduce the number of basis states needed to represent the system state, and
thereby increase the speed of calculation.Comment: 18 pages in LaTeX + 6 figures (postscript), uses ioplppt.sty. To
appear in J. Phys.
Emergence of pointer states in a non-perturbative environment
We show that the pointer basis distinguished by collisional decoherence
consists of exponentially localized, solitonic wave packets. Based on the
orthogonal unraveling of the quantum master equation, we characterize their
formation and dynamics, and we demonstrate that the statistical weights arising
from an initial superposition state are given by the required projection. Since
the spatial width of the pointer states can be obtained by accounting for the
gas environment in a microscopically realistic fashion, one may thus calculate
the coherence length of a strongly interacting gas.Comment: 8 pages, 1 figure; corresponds to published versio
Concatenated batch and continuous flow procedures for the upgrading of glycerol-derived aminodiols via N-acetylation and acetalization reactions
An unprecedented two-step sequence was designed by combining batch and continuous flow (CF) protocols for the upgrading of two aminodiol regioisomers derived from glycerol, i.e., 3-amino-1,2-propanediol and 2-amino-1,3-propanediol (serinol). Under batch conditions, at 80-90 °C, both substrates were quantitatively converted into the corresponding amides through a catalystfree N-acetylation reaction mediated by an innocuous enol ester as isopropenyl acetate (iPAc). Thereafter, at 30-100 °C and 1-10 atm, the amide derivatives underwent a selective CF-acetalisation in the presence of acetone and a solid acid catalyst, to afford the double-functionalized (amideacetal) products
Concatenated batch and continuous flow procedures for the upgrading of glycerol-derived aminodiols via N-acetylation and acetalization reactions
An unprecedented two-step sequence was designed by combining batch and continuous flow (CF) protocols for the upgrading of two aminodiol regioisomers derived from glycerol, i.e., 3-amino-1,2-propanediol and 2-amino-1,3-propanediol (serinol). Under batch conditions, at 80-90 \ub0C, both substrates were quantitatively converted into the corresponding amides through a catalystfree N-acetylation reaction mediated by an innocuous enol ester as isopropenyl acetate (iPAc). Thereafter, at 30-100 \ub0C and 1-10 atm, the amide derivatives underwent a selective CF-acetalisation in the presence of acetone and a solid acid catalyst, to afford the double-functionalized (amideacetal) products
Farm-wide virtual load monitoring for offshore wind structures via Bayesian neural networks
Offshore wind structures are subject to deterioration mechanisms throughout
their operational lifetime. Even if the deterioration evolution of structural
elements can be estimated through physics-based deterioration models, the
uncertainties involved in the process hurdle the selection of lifecycle
management decisions. In this scenario, the collection of relevant information
through an efficient monitoring system enables the reduction of uncertainties,
ultimately driving more optimal lifecycle decisions. However, a full monitoring
instrumentation implemented on all wind turbines in a farm might become
unfeasible due to practical and economical constraints. Besides, certain load
monitoring systems often become defective after a few years of marine
environment exposure. Addressing the aforementioned concerns, a farm-wide
virtual load monitoring scheme directed by a fleet-leader wind turbine offers
an attractive solution. Fetched with data retrieved from a fully-instrumented
wind turbine, a model can be trained and then deployed, thus yielding load
predictions of non-fully monitored wind turbines, from which only standard data
remains available. In this paper, we propose a virtual load monitoring
framework formulated via Bayesian neural networks (BNNs) and we provide
relevant implementation details needed for the construction, training, and
deployment of BNN data-based virtual monitoring models. As opposed to their
deterministic counterparts, BNNs intrinsically announce the uncertainties
associated with generated load predictions and allow to detect inaccurate load
estimations generated for non-fully monitored wind turbines. The proposed
virtual load monitoring is thoroughly tested through an experimental campaign
in an operational offshore wind farm and the results demonstrate the
effectiveness of BNN models for fleet-leader-based farm-wide virtual
monitoring
Effect of Recreational Intervention on the Approach of Pediatric Patients in Dental Treatment: Analysis of Salivary Cortisol
Objective: To verify whether recreational interaction with pediatric patient before dental care influences cortisol levels and anxiety. Material and Methods: Twelve children were selected and divided into two groups: 6 children who had not previously received recreational intervention (Group I) and 6 children who received recreational intervention before dental care (Group II). Saliva was collected with Salivettes™ kits before and soon after dental care for the measurement of cortisol. Wilcoxon test was applied to verify the difference in salivary cortisol levels before and after the dental visit in the whole sample, and the Mann- Whitney U test was used to analyze the difference between groups I and II. A significance level of 0.05 was considered. Results: Among patients from Group I, 3 had their cortisol levels increased after dental care, 2 had their cortisol levels decreased, and the other 1 patient remained constant. All participants from Group II had no significant difference in cortisol levels pre- and post-procedure. Mean salivary cortisol level was higher in Group I, pre- and post-procedure, compared to Group II. Conclusion: Pediatric patients who participated in an interactive activity prior to dental care have a lower level of anxiety according to the salivary cortisol levels obtained, compared to patients who did not participate in recreation. The techniques for the dentist to approach the child control the anxiety of the patient and make the procedure calmer and less stressful for both of them
Coronary flow reserve in stress-echo lab. From pathophysiologic toy to diagnostic tool
The assessment of coronary flow reserve by transthoracic echocardiography has recently been introduced into clinical practice with gratifying results for the diagnosis of left anterior descending artery disease simultaneously reported by several independent laboratories. This technological novelty is changing the practice of stress echo for 3 main reasons. First, adding coronary flow reserve to regional wall motion allows us to have – in the same sitting – high specificity (regional wall motion) and a high sensitivity (coronary flow reserve) diagnostic marker, with an obvious improvement in overall diagnostic accuracy. Second, the technicalities of coronary flow reserve shift the balance of stress choice in favour of vasodilators, which are a more robust hyperemic stress and are substantially easier to perform with dual imaging than dobutamine or exercise. Third, the coronary flow reserve adds a quantitative support to the exquisitely qualitative assessment of wall motion analysis, thereby facilitating the communication of stress echo results to the cardiological world outside the echo lab. The next challenges involve the need to expand the exploration of coronary flow reserve to the right and circumflex coronary artery and to prove the additional prognostic value – if any – of coronary flow reserve over regional wall motion analysis, which remains the cornerstone of clinically-driven diagnosis in the stress echo lab
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