Heralded quantum memory for single-photon polarization qubits

We propose a scheme to implement a heralded quantum memory for single-photon polarization qubits with a single atom trapped in an optical cavity. In this scheme, an injected photon only exchanges quantum state with the atom, so that the heralded storage can be achieved by detecting the output photon. We also demonstrate that the scheme can be used for realizing the heralded quantum state transfer, exchange and entanglement distribution between distant nodes. The ability to detect whether the operation has succeeded or not is crucial for practical application.Comment: 5 pages, 6 figure

Characterization of electrostatic shock in laser-produced optically-thin plasma flows using optical diagnostics

We present a method for evaluating the properties of electrostatic shock in laser-produced plasmas by using optical diagnostics. A shock is formed by a collimated jet in counter-streaming plasmas in nearly collisionless condition, showing the steepening of the transition width in time. In the present experiment, a streaked optical pyrometry was applied to evaluate the electron density and temperatures in the upstream and downstream regions of the shock so that the shock conditions are satisfied, by assuming thermal bremsstrahlung emission in optically thin plasmas. The derived electron densities are nearly consistent with those estimated from interferometry

Acute renal failure in an AIDS patient on tenofovir: a case report

This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

Effects of ecstasy/polydrug use on memory for associative information

Rationale Associative learning underpins behaviours that are fundamental to the everyday functioning of the individual. Evidence pointing to learning deficits in recreational drug users merits further examination. Objectives A word pair learning task was administered to examine associative learning processes in ecstasy/polydrug users. Methods After assignment to either single or divided attention conditions, 44 ecstasy/polydrug users and 48 non-users were presented with 80 word pairs at encoding. Following this, four types of stimuli were presented at the recognition phase: the words as originally paired (old pairs), previously presented words in different pairings (conjunction pairs), old words paired with new words, and pairs of new words (not presented previously). The task was to identify which of the stimuli were intact old pairs. Results Ecstasy/ploydrug users produced significantly more false-positive responses overall compared to non-users. Increased long-term frequency of ecstasy use was positively associated with the propensity to produce false-positive responses. It was also associated with a more liberal signal detection theory decision criterion value. Measures of long term and recent cannabis use were also associated with these same word pair learning outcome measures. Conjunction word pairs, irrespective of drug use, generated the highest level of false-positive responses and significantly more false-positive responses were made in the divided attention condition compared to the single attention condition. Conclusions Overall, the results suggest that long-term ecstasy exposure may induce a deficit in associative learning and this may be in part a consequence of users adopting a more liberal decision criterion value

TIME EVOLUTION of KELVIN-HELMHOLTZ VORTICES ASSOCIATED with COLLISIONLESS SHOCKS in LASER-PRODUCED PLASMAS

We report experimental results on Kelvin-Helmholtz (KH) instability and resultant vortices in laser-produced plasmas. By irradiating a double plane target with a laser beam, asymmetric counterstreaming plasmas are created. The interaction of the plasmas with different velocities and densities results in the formation of asymmetric shocks, where the shear flow exists along the contact surface and the KH instability is excited. We observe the spatial and temporal evolution of plasmas and shocks with time-resolved diagnostics over several shots. Our results clearly show the evolution of transverse fluctuations, wavelike structures, and circular features, which are interpreted as the KH instability and resultant vortices. The relevant numerical simulations demonstrate the time evolution of KH vortices and show qualitative agreement with experimental results. Shocks, and thus the contact surfaces, are ubiquitous in the universe; our experimental results show general consequences where two plasmas interact

Cooperative coupling of ultracold atoms and surface plasmons

Cooperative coupling between optical emitters and light fields is one of the outstanding goals in quantum technology. It is both fundamentally interesting for the extraordinary radiation properties of the participating emitters and has many potential applications in photonics. While this goal has been achieved using high-finesse optical cavities, cavity-free approaches that are broadband and easy to build have attracted much attention recently. Here we demonstrate cooperative coupling of ultracold atoms with surface plasmons propagating on a plane gold surface. While the atoms are moving towards the surface they are excited by an external laser pulse. Excited surface plasmons are detected via leakage radiation into the substrate of the gold layer. A maximum Purcell factor of $\eta_\mathrm{P}=4.9$ is reached at an optimum distance of $z=250~\mathrm{nm}$ from the surface. The coupling leads to the observation of a Fano-like resonance in the spectrum.Comment: 9 pages, 4 figure

Pathogenic role of delta 2 tubulin in bortezomib-induced peripheral neuropathy

The pathogenesis of chemotherapy-induced peripheral neuropathy (CIPN) is poorly understood. Here, we report that the CIPN-causing drug bortezomib (Bort) promotes delta 2 tubulin (D2) accumulation while affecting microtubule stability and dynamics in sensory neurons in vitro and in vivo and that the accumulation of D2 is predominant in unmyelinated fibers and a hallmark of bortezomib-induced peripheral neuropathy (BIPN) in humans. Furthermore, while D2 overexpression was sufficient to cause axonopathy and inhibit mitochondria motility, reduction of D2 levels alleviated both axonal degeneration and the loss of mitochondria motility induced by Bort. Together, our data demonstrate that Bort, a compound structurally unrelated to tubulin poisons, affects the tubulin cytoskeleton in sensory neurons in vitro, in vivo, and in human tissue, indicating that the pathogenic mechanisms of seemingly unrelated CIPN drugs may converge on tubulin damage. The results reveal a previously unrecognized pathogenic role for D2 in BIPN that may occur through altered regulation of mitochondria motility

Representational Switching by Dynamical Reorganization of Attractor Structure in a Network Model of the Prefrontal Cortex

The prefrontal cortex (PFC) plays a crucial role in flexible cognitive behavior by representing task relevant information with its working memory. The working memory with sustained neural activity is described as a neural dynamical system composed of multiple attractors, each attractor of which corresponds to an active state of a cell assembly, representing a fragment of information. Recent studies have revealed that the PFC not only represents multiple sets of information but also switches multiple representations and transforms a set of information to another set depending on a given task context. This representational switching between different sets of information is possibly generated endogenously by flexible network dynamics but details of underlying mechanisms are unclear. Here we propose a dynamically reorganizable attractor network model based on certain internal changes in synaptic connectivity, or short-term plasticity. We construct a network model based on a spiking neuron model with dynamical synapses, which can qualitatively reproduce experimentally demonstrated representational switching in the PFC when a monkey was performing a goal-oriented action-planning task. The model holds multiple sets of information that are required for action planning before and after representational switching by reconfiguration of functional cell assemblies. Furthermore, we analyzed population dynamics of this model with a mean field model and show that the changes in cell assemblies' configuration correspond to those in attractor structure that can be viewed as a bifurcation process of the dynamical system. This dynamical reorganization of a neural network could be a key to uncovering the mechanism of flexible information processing in the PFC

Confronto de critérios de avaliação da aprendizagem diante das apreciações dos estudantes de enfermagem

The objective of this study is not only to research the students’ perceptions of this new assessment format but also its impact in their learning. The study took place in a University in Rio de Janeiro, Brazil; the participants were 26 students from the third part of Nursing studies. Data collection was made through an instrument with open questions carried out from April to May of 2008. Results were analyzed and described in a thematic unit. Three thematic units elaborated are: the evaluation process facilitates a reliable assessment of knowledge, the students’ learning; the evaluation process facilitates a critical reflection of the questions; the assessment form requires more student effort. The students’ perceptions regarding the evaluation process follow the new perspectives of the curriculum guidelines of nursing studies, mainly in regards to educating critical and reflexive professionals.Este estudio tiene como objetivo investigar sobre las percepciones de los estudiantes acerca de esta nueva forma de evaluación así como el impacto en su aprendizaje. El escenario del estudio fue un centro Universitario del Estado de Río de Janeiro, los sujetos fueron 26 estudiantes del tercer período en el curso de Graduación de Enfermería. La recogida de datos se realizó por medio de un instrumento con preguntas abiertas, desarrollado en el período comprendido entre abril y mayo de 2008. Los resultados fueron analizados y descritos en la unidad temática. Las tres unidades temáticas elaboradas son: el proceso de evaluación permite una evaluación fiable del conocimiento - aprendizaje de los estudiantes; el proceso de evaluación permite una reflexión crítica sobre las cuestiones; la forma de evaluación requiere un mayor compromiso de los estudiantes. La percepción de los estudiantes sobre el proceso de evaluación sale al encuentro con las nuevas perspectivas de las directrices curriculares para la graduación en enfermería, especialmente en lo que se refiere a formar profesionales críticos y reflexivos.O presente estudo tem por objetivo a investigar sobre as percepções dos estudantes acerca desta nova forma avaliativa como também o impacto em seu aprender. O cenário do estudo foi um centro Universitário do Estado do Rio de Janeiro, os sujeitos foram 26 estudantes do terceiro período do curso de Graduação em Enfermagem. A coleta de dados foi realizada através de um instrumento com perguntas abertas, desenvolvido no período de abril a maio de 2008. Os resultados foram analisados e descritos em unidade temática. As três unidades temáticas elaboradas são: o processo avaliativo possibilita uma avaliação fidedigna do conhecimento - aprendizagem dos estudantes; o processo avaliativo possibilita uma reflexão crítica sobre as questões; a forma de avaliação exige mais empenho dos estudantes. As percepções dos estudantes acerca do processo avaliativo, vão de encontro com as novas perspectivas das diretrizes curriculares do curso de graduação em enfermagem, principalmente no que refere a formar profissionais críticos e reflexivos