Optical Stark Effect and Dressed Excitonic States in a Mn-doped Quantum Dot

We report on the observation of spin dependent optically dressed states and optical Stark effect on an individual Mn spin in a semiconductor quantum dot. The vacuum-to-exciton or the exciton-to-biexciton transitions in a Mn-doped quantum dot are optically dressed by a strong laser field and the resulting spectral signature is measured in photoluminescence. We demonstrate that the energy of any spin state of a Mn atom can be independently tuned using the optical Stark effect induced by a control laser. High resolution spectroscopy reveals a power, polarization and detuning dependent Autler-Townes splitting of each optical transition of the Mn-doped quantum dot. This experiment demonstrates a complete optical resonant control of the exciton-Mn system

A quantitative, pooled analysis and systematic review of controlled trials on the impact of electrical stimulation settings and placement on pressure ulcer healing rates in persons with spinal cord injuries

Pressure ulcers (PrUs) are among the most common secondary complications following spinal cord injury (SCI). External electrical current applied to a wound is believed to mimic the body's natural bioelectricity and to restart and stimulate endogenous electrical fields to promote wound healing. A systematic review was conducted to critically appraise and synthesize updated evidence on the impact of electrical stimulation (ES) versus standard wound care (comprising cleansing, dressing, nutrition, and debridement as necessary) and/or sham stimulation on PrU healing rates in persons with SCIs. Medline, Embase, the Cumulative Index for Nursing and Allied Health Literature (CINAHL), PsycINFO, and Cochrane Central were searched using the terms spinal cord injury, electrical stimulation, and pressure ulcer in free text and MESH terms. Publications were limited to peer-reviewed, randomized controlled trials (RCTs) and non-RCTs (CCTs) published in English from 1985 to 2014. The methodological quality of the RCTs was evaluated using the Jadad scale; CCTs were assessed using the Downs and Black tool. Pooled analyses were performed to calculate the mean difference (MD) for continuous data, odds ratio (OR) for dichotomous data, and 95% confidence intervals (CI). A total of 8 trials were reviewed - 6 RCTs and 2 CCTs included a total of 517 SCI participants who had at least 1 PrU. The number of patients per study ranged from 7 to 150 and the number of wounds from 7 to 192. Comparison models included ES irrespective of current type and placement of electrodes against sham/no ES (7 trials), ES delivered by electrodes overlaid on the ulcer versus sham/no ES (4 trials), ES delivered by electrodes placed on intact skin around the ulcer versus sham/no ES (4 trials), ES delivered by electrodes overlaid on the wound bed versus placed on intact skin around the ulcer (1 trial), ES with pulsed current versus sham/no ES (6 trials), ES with constant current versus sham/no ES (2 trials), pulsed current ES versus constant current ES (1 trial), number of PrUs closed (2 trials), and incidence of PrU worsened by ES versus sham/no ES (2 trials). The overall quality of studies was moderate; 2 trials were rated as good quality, 2 were poor quality, and 4 were moderate. Evidence showed ES increased the rate of PrU healing in patients with SCI (MD 4.97, 95% CI 1.97-7.98, P = 0.00; N = 7 studies and 559 ulcers), and a higher proportion of ulcers healed (OR 2.68, 95% CI 1.17-6.14, P = 0.02; N = 2 studies and 226 ulcers). The data suggest pulsed current ES increased the healing rate (MD 6.27, 95% CI 2.77-9.78, P = 0.0005; N = 6 studies and 509 ulcers) more than constant current (MD 4.50, 95% CI 1.19-10.18, P = 0.12; N = 2 studies and 200 ulcers). In addition, wounds with electrodes overlaying the wound bed seemed to heal ulcer faster than wounds with electrodes placed on intact skin around the ulcer. Future preclinical, in vivo models and clinical trials examining the impact of electrodes configuration for PrU healing are warranted

Do electrical stimulation enhance pressure ulcer healing in people living with spinal cord injuries: a meta-analysis and systematic review of randomised and non-randomised controlled trials

Aim: To quantitatively analyse the effect of ES on PrU healing compared with standard wound care (SWC) and/or sham stimulation. Method: Review was limited to peer-reviewed studies published in English from 1970 to May 2014. Studies included randomized controlled trials (RCTs) and non-RCTs. Methodological quality was assessed using established instruments. Pooled analyses were performed to calculate mean difference (MD) for continuous data, odds ratio (OR) for dichotomous data. Results / Discussion: Eight prospective controlled studies were reviewed, five studies were RCTs, and three studies were non-RCTs. Pooled analyses of eight trials showed ES significantly improved daily healing rate (MD 0.89, 95% CI 0.23-1.55, p=0.008) with significant heterogeneity. Pulsed current ES significantly improved daily healing rates compared with constant direct current (DC) or alternating current (AC) in two trials (MD 1.50, 95% CI 0.62, 2.39, p=0.0009, I2=81%). Pooled analysis of two trials showed significant higher numbers of ulcer healed (OR 2.95, 95% CI 1.69–5.17, p=0.0002, I2=0%) with ES treatment. There was a trend towards less number of ulcer worsened with ES treatment (OR 0.38, 95% CI 0.12–1.24, p=0.11, I2=18%).intervals (CI). Conclusion: ES can significantly enhance PrU healing in SCI according to limited level I evidence. Pulsed current ES may confer better benefit on PrU healing than DC or AC. Electrodes placed on wound bed maybe superior to those applied on the intact skin

Mechanism of fragmentation and atomization of molecular ions in gasdynamic transport cell

The fragmentation of molecular ions formed upon the electrospraying of a sample and transported through the gasdynamic system of a mass spectrometer equipped with an IESAP (Ion Extraction from Solution at Atmospheric Pressure) source has been experimentally studied. It is established that ion fragmentation in a Kantorowicz-Gray type cell takes place in the immediate vicinity of a skimmer port, apparently, as a result of collisions between ions (accelerated in an electric field) and stagnant gas. Molecular mechanisms of fragmentation are considered and it is concluded that this process can take place in a single ion-molecule collision even

Electron-nuclei spin dynamics in II-VI semiconductor quantum dots

We report on the dynamics of optically induced nuclear spin polarization in individual CdTe/ZnTe quantum dots loaded with one electron by modulation doping. The fine structure of the hot trion (charged exciton $X^-$ with an electron in the $P$-shell) is identified in photoluminescence excitation spectra. A negative polarisation rate of the photoluminescence, optical pumping of the resident electron and the built-up of dynamic nuclear spin polarisation (DNSP) are observed in time-resolved optical pumping experiments when the quantum dot is excited at higher energy than the hot trion triplet state. The time and magnetic field dependence of the polarisation rate of the $X^-$ emission allows to probe the dynamics of formation of the DNSP in the optical pumping regime. We demonstrate using time-resolved measurements that the creation of a DNSP at B=0T efficiently prevents longitudinal spin relaxation of the electron caused by fluctuations of the nuclear spin bath. The DNSP is built in the microsecond range at high excitation intensity. A relaxation time of the DNSP in about 10 microseconds is observed at $B=0T$ and significantly increases under a magnetic field of a few milli-Tesla. We discuss mechanisms responsible for the fast initialisation and relaxation of the diluted nuclear spins in this system

Quantum and approximation algorithms for maximum witnesses of Boolean matrix products

The problem of finding maximum (or minimum) witnesses of the Boolean product of two Boolean matrices (MW for short) has a number of important applications, in particular the all-pairs lowest common ancestor (LCA) problem in directed acyclic graphs (dags). The best known upper time-bound on the MW problem for n\times n Boolean matrices of the form O(n^{2.575}) has not been substantially improved since 2006. In order to obtain faster algorithms for this problem, we study quantum algorithms for MW and approximation algorithms for MW (in the standard computational model). Some of our quantum algorithms are input or output sensitive. Our fastest quantum algorithm for the MW problem, and consequently for the related problems, runs in time \tilde{O}(n^{2+\lambda/2})=\tilde{O}(n^{2.434}), where \lambda satisfies the equation \omega(1, \lambda, 1) = 1 + 1.5 \, \lambda and \omega(1, \lambda, 1) is the exponent of the multiplication of an n \times n^{\lambda}$ matrix by an n^{\lambda} \times n matrix. Next, we consider a relaxed version of the MW problem (in the standard model) asking for reporting a witness of bounded rank (the maximum witness has rank 1) for each non-zero entry of the matrix product. First, by adapting the fastest known algorithm for maximum witnesses, we obtain an algorithm for the relaxed problem that reports for each non-zero entry of the product matrix a witness of rank at most \ell in time \tilde{O}((n/\ell)n^{\omega(1,\log_n \ell,1)}). Then, by reducing the relaxed problem to the so called k-witness problem, we provide an algorithm that reports for each non-zero entry C[i,j] of the product matrix C a witness of rank O(\lceil W_C(i,j)/k\rceil ), where W_C(i,j) is the number of witnesses for C[i,j], with high probability. The algorithm runs in \tilde{O}(n^{\omega}k^{0.4653} +n^2k) time, where \omega=\omega(1,1,1).Comment: 14 pages, 3 figure

A four-season prospective study of muscle strain reoccurrences in a professional football club

The aim of this investigation was to characterise muscle strain reinjuries and examine their impact on playing resources in a professional football club. Muscle strains and reoccurrences were prospectively diagnosed over four seasons in first-team players (n = 46). Altogether, 188 muscle strains were diagnosed with 44 (23.4%) of these classed as reinjuries, leading to an incidence of 1.32 strain reoccurrences per 1,000 hours exposure (95% Confidence Interval [CI], 0.93–1.71). The incidence of recurrent strains was higher in match-play compared with training (4.51, 95% CI, 2.30–6.72 vs 0.94, 95% CI, 0.59–1.29). Altogether, 50.0% of players sustained at least 1 reoccurrence of a muscle strain, leading to approximately 3 days lost and 0.4 matches missed per player per season. The incidence of recurrent strains was highest in centre-forwards (2.15, 95% CI, 1.06–3.24), peaked in May (3.78, 95% CI, 0.47–7.09), and mostly affected the hamstrings (38.6% of all reoccurrences). Mean layoff for nonreoccurrences and recurrences was similar: ∼7.5 days. These results provide greater insight into the extent of the problem of recurrent muscle strains in professional football

Maximum likelihood drift estimation for a threshold diffusion

We study the maximum likelihood estimator of the drift parameters of a stochastic differential equation, with both drift and diffusion coefficients constant on the positive and negative axis, yet discontinuous at zero. This threshold diffusion is called drifted Oscillating Brownian motion.For this continuously observed diffusion, the maximum likelihood estimator coincide with a quasi-likelihood estimator with constant diffusion term. We show that this estimator is the limit, as observations become dense in time, of the (quasi)-maximum likelihood estimator based on discrete observations. In long time, the asymptotic behaviors of the positive and negative occupation times rule the ones of the estimators. Differently from most known results in the literature, we do not restrict ourselves to the ergodic framework: indeed, depending on the signs of the drift, the process may be ergodic, transient or null recurrent. For each regime, we establish whether or not the estimators are consistent; if they are, we prove the convergence in long time of the properly rescaled difference of the estimators towards a normal or mixed normal distribution. These theoretical results are backed by numerical simulations