Pair creation in boost-invariantly expanding electric fields and two-particle correlations

Pair creation of scalar particles in a boost-invariant electric field which is confined in the forward light cone is studied. We present the proper-time evolution of momentum distributions of created particles, which preserve the boost invariance of the background field. The two-particle correlation of the created particles is also calculated. We find that long-range rapidity correlations may arise from the Schwinger mechanism in the boost-invariant electric field.Comment: 21 pages, 10 figures; v2: minor changes, to appear in Phys. Rev.

All-Optical Switch and Transistor Gated by One Stored Photon

The realization of an all-optical transistor where one 'gate' photon controls a 'source' light beam, is a long-standing goal in optics. By stopping a light pulse in an atomic ensemble contained inside an optical resonator, we realize a device in which one stored gate photon controls the resonator transmission of subsequently applied source photons. A weak gate pulse induces bimodal transmission distribution, corresponding to zero and one gate photons. One stored gate photon produces fivefold source attenuation, and can be retrieved from the atomic ensemble after switching more than one source photon. Without retrieval, one stored gate photon can switch several hundred source photons. With improved storage and retrieval efficiency, our work may enable various new applications, including photonic quantum gates, and deterministic multiphoton entanglement.Comment: 20 pages, 5 figures. Published in Science. Includes supplemental informatio

Multi-focal Metabolic Disturbances in Human Brain at a Chronic Stage of Stroke Studied with 18FDG and Positron Emission Tomography

開始ページ、終了ページ: 冊子体のページ付

A Study of Sum Peak Method in Biological Substances by Using 111In

開始ページ、終了ページ: 冊子体のページ付

A Study of Dopamine Metabolism in a Patient with Juvenile Parkinsonism by Positron Emission Tomography

開始ページ、終了ページ: 冊子体のページ付

Sustainable Irrigation Management of Ornamental Cordyline Fruticosa “Red Edge” Plants with Saline Water

The aim of this work was to analyze the influence of the salinity of the nutrient solution on the transpiration and growth of Cordyline fruticosa var. “Red Edge” plants. A specific irrigation management model was calibrated with the experimental data. An experiment was performed with four treatments. These treatments consisted of the application of four nutrient solutions with different electrical conductivity (ECw) levels ranging from 1.5 dS m−1 (control treatment) to 4.5 dS m−1. The results showed that day-time transpiration decreases when salt concentration in the nutrient solution increases. The transpiration of the plant in the control treatment was modelled by applying a combination method while the effect of the salinity of the nutrient solution was modelled by deriving a saline stress coefficient from the experimental data. The results showed that significant reductions in plant transpiration were observed for increasing values of ECw. The crop development and yield were also affected by the increasing salinity of the nutrient solution. A relationship between the ECw and the relative crop yield was derived

Calibration of low-level laser therapy equipment

CONTEXTUALIZAÇÃO: A laserterapia de baixa intensidade (LBI) vem sendo cada vez mais utilizada, porém ainda não há consenso na literatura quanto ao tempo em que os equipamentos devem ser submetidos à aferição ou calibragem. OBJETIVO: Analisar a potência média real (PmR) dos equipamentos de LBI na região da Grande São Paulo. MÉTODOS: Para análise dos equipamentos, utilizou-se um potenciômetro (Lasercheck), próprio para aferição de equipamentos contínuos, o qual foi programado com dados referentes ao comprimento de onda do laser a ser avaliado, obtendo-se assim a PmR emitida. Os equipamentos foram analisados de duas formas: uma, com o LBI desaquecido, e outra, após 10 minutos de uso (aquecido), sendo que três análises foram feitas para cada condição. A caneta emissora foi acoplada ao potenciômetro, o qual fornecia a PmR emitida pelo LBI. Todos os dados e informações referentes à aplicação do laser foram coletados por um questionário respondido pelos responsáveis. RESULTADOS: Os 60 equipamentos avaliados mostraram déficit na PmR com os equipamentos desaquecidos e aquecidos. A análise estatística (ANOVA) mostrou diminuição significativa (P<0,05) da PmR aferida em relação à potência média do fabricante (PmF). Em média, a dose mais empregada nas clínicas foi de 4 J/cm², tendo os efeitos de cicatrização e anti-inflamatório como os mais desejados. Segundo a World Association for Laser Therapy (WALT), para atingir esse efeito, necessita-se de 1 a 4 J de energia final, sendo que apenas um dos 60 aparelhos conseguiria atingir a janela terapêutica preconizada. CONCLUSÃO: Os equipamentos de LBI apresentam um déficit acentuado na PmR, o que mostra uma desordem na utilização desse recurso. Neste estudo, observou-se a necessidade de aferição periódica dos aparelhos de LBI bem como melhor conhecimento técnico dos profissionais envolvidos.BACKGROUND: Despite the increase in the use of low-level laser therapy (LLLT), there is still a lack of consensus in the literature regarding how often the equipment must be calibrated. OBJECTIVE: To evaluate the real average power of LLLT devices in the Greater São Paulo area. METHODS: For the evaluation, a LaserCheck power meter designed to calibrate continuous equipment was used. The power meter was programmed with data related to the laser's wavelength to gauge the real average power being emitted. The LLLT devices were evaluated in two ways: first with the device cooled down and then with the device warmed up for 10 minutes. For each condition, three tests were performed. The laser probe was aligned with the power meter, which provided the real average power being emitted by the LLLT device. All of the data and information related to the laser application were collected with the use of a questionnaire filled in by the supervising therapists. RESULTS: The 60 devices evaluated showed deficit in real average power in the cooled-down and warmed-up condition. The statistical analysis (ANOVA) showed a significant decrease (p<0.05) in the real average power measured in relation to the manufacturer's average power. On average, the most common dose in the clinics was 4 J/cm², and the most desired effects were healing and anti-inflammatory effects. According to the World Association for Laser Therapy (WALT), 1 to 4 J of final energy are necessary to achieve these effects, however only one device was able to reach the recommended therapeutic window. CONCLUSION: The LLLT devices showed a deficit in real average power that emphasized a lack of order in the application of this tool. The present study also showed the need for periodical calibration of LLLT equipment and a better technical knowledge of the therapists involved

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