Two-level atom in a squeezed vacuum with finite bandwidth

Abstract

The resonance fluorescence of a two-level atom driven by a coherent laser field and damped by a finite bandwidth squeezed vacuum is analysed. We extend the Yeoman and Barnett technique to a non-zero detuning of the driving field from the atomic resonance and discuss the role of squeezing bandwidth and the detuning in the level shifts, widths and intensities of the spectral lines. The approach is valid for arbitrary values of the Rabi frequency and detuning but for the squeezing bandwidths larger than the natural line-width in order to satisfy the Markoff approximation. The narrowing of the spectral lines is interpreted in terms of the quadrature-noise spectrum. We find that, depending on the Rabi frequency, detuning and the squeezing phase, different factors contribute to the line narrowing. For a strong resonant driving field there is no squeezing in the emitted field and the fluorescence spectrum exactly reveals the noise spectrum. In this case the narrowing of the spectral lines arises from the noise reduction in the input squeezed vacuum. For a weak or detuned driving field the fluorescence exhibits a large squeezing and, as a consequence, the spectral lines have narrowed linewidths. Moreover, the fluorescence spectrum can be asymmetric about the central frequency despite the symmetrical distribution of the noise. The asymmetry arises from the absorption of photons by the squeezed vacuum which reduces the spontaneous emission. For an appropriate choice of the detuning some of the spectral lines can vanish despite that there is no population trapping. Again this process can be interpreted as arising from the absorption of photons by the squeezed vacuum. When the absorption is large it may compensate the spontaneous emission resulting in the vanishing of the fluorescence lines.     

红透山铜矿尾矿库表层尾矿的酸化潜力及其变化特征

试验测定红透山铜矿尾矿样品的全硫含量和酸中和潜力(ANC),计算得到净产酸潜力NAPP和净产酸量NAG,据此分析预测酸化潜力。结果表明:红透山铜矿尾矿的NAPP和NAG分别为H2SO448.85 kg/t和22.86 kg/t,NAPP和NAG试验结果都说明该尾矿有较高的产酸潜力,产酸的主要原因是尾矿中硫含量较高。NAPP在0～135 cm的平均值为48.85 kg/t,其中0～45 cm的NAPP平均为20.71 kg/t,45～135 cm的平均值为62.92 kg/t,表明酸化主要发生在0～45 cm的风化表层。尾矿45～135 cm各层的NAPP明显大于NAG,这是由于NAPP是通过对含S量和ANC的测定,再计算尾矿的产酸量,所代表的是理论值,其值往往因为SO24-的存在而大于实际产酸量,这可能是由于表层风化层的S氧化形成SO24-在下层累积所导致的。     

Morphology-dependent redox and catalytic properties of CeO2 nanostructures: Nanowires, nanorods and nanoparticles

The redox features and the catalytic activities of ceria nanowires, nanorods and nanoparticles were comparatively studied. The morphology-dependent phenomenon is closely related to the nature of the exposed crystal planes. The CeO₂ nanoparticles mainly expose the stable {1 1 1} plane on the surface, whereas the rod-shaped nanostructures preferentially expose the reactive {1 1 0} and {1 0 0} planes, giving higher oxygen storage capacity and catalytic activity for CO oxidation. Although both the CeO₂ nanorods and the CeO₂ nanowires predominantly expose the reactive {1 1 0} and {1 0 0} planes, the CeO₂ nanowires favor to expose a large proportion of active planes on the surface, resulting in a much higher activity for CO oxidation than the nanorods.     

Application of positron annihilation spectroscopy to study recovery and recrystallization of commercial pure Al and Al-1 wt% Mn alloys

Isochronal annealing of cold worked commercial pure aluminum (99.5%) and Al-1wt% Mn alloys was demonstrated between room temperature and 823 K. The stages of recovery and recrystallization were studied using microhardness and positron annihilation lifetime measurements. Apositive correlation was established between the variation of the intensity of long lived component and Vickers microhardness with annealing temperature during the two stages of recovery, which were identified in both aluminum and Al(Mn). The retardation of the recovery stages and recrystallization in Al(Mn) alloys is interpreted in terms of precipitation of aluminum-manganese particles as well as manganese-vacancy interaction.     

Postsurgical policy in stage I testicular seminoma: cost and benefit of prophylactic irradiation in a long-term experience

The definitive cure rate for clinical stage 1 testicular seminoma is very close to 100%, and prophylactic irradiation of the regional lymph nodes is associated with a low morbidity. Nevertheless, in recent years a "wait-and-see" policy has been proposed by some researchers. We analysed the cost/benefit ratio of radiotherapy (RT) by review of the case histories of 299 patients treated at the Department of Radiotherapy of the Istituto Nazionale per lo Studio e la Cura dei Tumori in Milan from January 1968 to December 1989. The 5-year overall survival was 99% (97.5% at 10 years), while the 10-year disease-free survival was 96%. The recurrence rate was 2.3%, but no patient relapsed in the irradiated areas. Acute toxicity was very moderate with only 4 (1.3%) serious radiation sequelae occurring 6 to 27 years after treatment. However, 9 second malignancies (3%) were observed. Lastly, we have calculated the costs for our National Health Service comparing surveillance policy and prophylactic irradiation.     

A model for ethical management of faculty—Student dual relationships.

The article discusses the nature of faculty-student dual relationships and provides guidelines for their ethical management. Three general guidelines for faculty in maintaining ethical relationships with students are (a) acknowledging the power and responsibility of the faculty role, (b) developing a frame for evaluating faculty-student relationships, and (c) fostering and maintaining a climate that supports ethical relationships with students. As a profession, psychologists should be discussing this issue more openly, and research on problematic faculty-student relationships and their management is warranted. Awareness of dilemmas concerning dual-role relationships and experience in addressing these dilemmas may provide valuable lessons for the student's future professional interactions with clients, students, and other professionals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

基于电容放电特征的柔性直流配电网线路保护方案

针对换流设备直接接入直流母线的双端柔性直流配电网的保护配置问题,提出一种基于单端电气量的线路保护方案。首先分析了双端柔性直流配电网的直流线路故障特征,其次重点分析了处于不同母线处的换流器并联电容之间的放电特征差异。结合该差异设计出能够有效识别故障区域、在5 ms内隔离故障的主保护。同时为解决主保护可能存在检测失败的问题,设置了利用过电流判据以及动作延时的后备保护方案。最后通过PSCAD/EMTDC搭建仿真模型验证了所提方案的有效性。     

Lithium therapy and drinking water

ain causes of failure and giving up in psychotropic lithiotherapics because of instable lithiemy to the same patient or functional acute renal insufficiency, are principaly mistaken diets, those mistaken concerning the amount, the quality and the way of taking drinking water and other beverages. Lithium salt, taken either in two times, morning and evening, or in one, must be absorbed at the end of a solid meal with at least 25 cl. of water. The patient must absorb at least 1.5 l. of water per day, and up to 3 l. in case of physical efforts or heat. The pH of this water and it ionic compound should be stable, as close as possible to the plasma's, without additives that could change its taste. This includes cooking water and infusions. Physicopharmacological explanations.     

In vivo neutron dosimetry during high-energy Bremsstrahlung radiotherapy

PURPOSE: A new technique is presented for in vivo measurements of the dose equivalent from photoneutrons produced by high-energy radiotherapy accelerators. METHODS AND MATERIALS: The dosimeters used for this purpose are vials of superheated halocarbon droplets suspended in a tissue-equivalent gel. Neutron interactions nucleate the formation of bubbles, which can be recorded through the volume of gel they displace from the detector vials into graduated pipettes. These detectors offer inherent photon discrimination, dose-equivalent response to neutrons, passive operation, and small sensitive size. An in vivo vaginal probe was fabricated containing one of these neutron detector vials and a photon-sensitive diode. Measurements were carried out in patients undergoing high-energy x-ray radiotherapy and were also repeated in-phantom, under similar irradiation geometries. RESULTS AND CONCLUSION: Neutron doses of 0.02 Sv were measured in correspondence to the cervix, 50 cm from the photon beam axis, following a complete treatment course of 46.5 Gy with an upper mantle field of 18-MV x-rays. This fraction of dose from neutrons is measured reliably within an intense photon background, making the technique a valid solution to challenging dosimetry problems such as the determination of fetal exposure in radiotherapy. These measurements can be easily carried out with tissue-equivalent phantoms, as our results indicate an excellent correlation between in vivo and in-phantom dosimetry.     

阴离子交换树脂分离双波长分光光度法测定铅

在 p H7.5～ 9.0的缓冲介质中 ,铅与 5 - Br- PADAP形成稳定的红色三元胶束络合物 ,以 440 nm为参比波长 ,5 70 nm为测定波长 ,可用双波长法测定微量铅 ,表观摩尔吸光系数为ε=1 .0× 1 0 5L· mol- 1· cm- 1,铅的浓度在 0～ 1 .6mg· L- 1范围内符合比尔定律。本法用于矿样中微量铅的测定 ,结果较满意