Optimization of photon storage fidelity in ordered atomic arrays

A major application for atomic ensembles consists of a quantum memory for light, in which an optical state can be reversibly converted to a collective atomic excitation on demand. There exists a well-known fundamental bound on the storage error, when the ensemble is describable by a continuous medium governed by the Maxwell-Bloch equations. The validity of this model can break down, however, in systems such as dense, ordered atomic arrays, where strong interference in emission can give rise to phenomena such as subradiance and "selective" radiance. Here, we develop a general formalism that finds the maximum storage efficiency for a collection of atoms with discrete, known positions, and a given spatial mode in which an optical field is sent. As an example, we apply this technique to study a finite two-dimensional square array of atoms. We show that such a system enables a storage error that scales with atom number $N_\mathrm{a}$ like $\sim (\log N_\mathrm{a})^2/N_\mathrm{a}^2$, and that, remarkably, an array of just $4 \times 4$ atoms in principle allows for an efficiency comparable to a disordered ensemble with optical depth of around 600.Comment: paper is now identical to published versio

Relativistic Tunneling Through Two Successive Barriers

We study the relativistic quantum mechanical problem of a Dirac particle tunneling through two successive electrostatic barriers. Our aim is to study the emergence of the so-called \emph{Generalized Hartman Effect}, an effect observed in the context of nonrelativistic tunneling as well as in its electromagnetic counterparts, and which is often associated with the possibility of superluminal velocities in the tunneling process. We discuss the behavior of both the phase (or group) tunneling time and the dwell time, and show that in the limit of opaque barriers the relativistic theory also allows the emergence of the Generalized Hartman Effect. We compare our results with the nonrelativistic ones and discuss their interpretation.Comment: 7 pages, 3 figures. Revised version, with a new appendix added. Slightly changes in the styles and captions of Figures 1 and 2. To appear in Physical Review

Solid-phase synthesis of peptides containing reverse-turn mimetic bicyclic lactams

The solid-phase synthesis and characterization of a series of peptides (4-15) containing reverse-turn mimetic bicyclic lactams is reported. The bicyclic lactams (1a, 1b) possess high structural similarity to the two central residues of a Pturn. Amino acid conjugates of these bicyclic lactams were synthesized on solid supports following a g-fluorenylmethoxycarbonyl (FMOC) protection strategy on WangMerrifield resin. Coupling between amino acids was accomplished by means of diisopropylcarbodiimide (DIC)/ hydroxyazabenzotriazole (HOAt). Coupling between amino acids and the mimics was performed with the potent Carpino's reagent O-(7-azabenzotriazol-1-yl)-N,N,N',N'-tetramelhyluronium hexafluorophosphate (HATU). The final compounds were cleaved from the resin and obtained as N-acetylated methyl esters or benzyl amides

Multimodal treatment of gastric cancer in the west: Where are we going?

The incidence of gastric cancer (GC) is decreasing worldwide, especially for intestinal histotype of the distal third of the stomach. On the contrary, proximal location and diffuse Lauren histotype have been reported to be generally stable over time. In the west, no clear improvement in long-term results was observed in clinical and population-based studies. Results of treatment in these neoplasms are strictly dependent on tumor stage. Adequate surgery and extended lymphadenectomy are associated with good long-term outcome in early-stage cancer; however, results are still unsatisfactory for advanced stages (III and IV), for which additional treatments could provide a survival benefit. This implies a tailored approach to GC. The aim of this review was to summarize the main multimodal treatment options in advanced resectable GC. Perioperative or postoperative treatments, including chemotherapy, chemoradiotherapy, targeted therapies, and hyperthermic intraperitoneal chemotherapy have been reviewed, and the main ongoing and completed trials have been analyzed. An original tailored multimodal approach to non-cardia GC has been also proposed

Bioecologia e sugestões para o Manejo da traça-dos-cachos em uva de vinho no Submédio do Vale do São Francisco.

bitstream/item/31860/1/Circular-Tecnica-93.pd

Modulation of the postural effects of cognitive load by hypnotizability

Aim of the experiment was to study whether cognitive load aVects postural control more in low (Lows) than in highly hypnotizable (Highs) subjects due to the latter\u27s greater attentional abilities. Standing Highs and Lows underwent an experimental session (closed eyes) consisting of a basal condition and of mental computation in an easy (stable support) and a diYcult (unstable support) postural condition. Variability [standard deviation (SD)] and complexity [sample entropy (SampEn)] of the movement of the centre of pressure (CoP), its mean velocity (Velocity), the area swept by the CoP (Area) and the ratio between the CoP trajectory length and area [length for surface (LFS)] were measured. Few hypnotizability-related diVerences were detected (reduction in the Highs\u27 SD and increases in the Lows\u27 LFS in the diYcult postural condition). Thus, the hypnotizability-related postural diVerences observed in previous studies during sensory alteration could not be accounted mainly by attentional abilities

The perseverance of Pacioli's goods inventory accounting system

This paper details sources of the 'undoubtedly strange' (Yamey, 1994a, p.119) system of goods inventory records described in Pacioli’s 1494 bookkeeping treatise and traces the longevity and widespread use of this early perpetual inventory recording (EPIR) system in English language texts. By doing so and contrasting this system with the bookkeeping treatment of modern texts, it is shown that the EPIR system persisted as the dominant form of goods inventory accounting for between 400 and 500 years and that the reasons for its demise are worthy of further consideration and research

Beneficios en la microbiota intestinal después de la suplementación con inulina y la goma guar parcialmente hidrolizada: un ensayo clínico aleatorizado en mujeres con estreñimiento

Introduction: Prebiotics positively affect gut microbiota composition, thus improving gut function. These properties may be useful for the treatment of constipation.Objectives: This study assessed the tolerance and effectiveness of a prebiotic inulin/partially hydrolyzed guar gum mixture (I-PHGG) for the treatment of constipation in females, as well as its influence on the composition of intestinal microbiota and production of short chain fatty acids.Methods: Our study enrolled 60 constipated female health worker volunteers. Participants reported less than 3 bowel movements per week. Volunteers were randomized to treatment with prebiotic or placebo. Treatment consisted of 3 weeks supplementation with 15 g/d I-PHGG (fiber group) or maltodextrin (placebo group). Abdominal discomfort, flatulence, stool consistency, and bowel movements were evaluated by a recorded daily questionnaire and a weekly interview. Changes in fecal bacterial population and short chain fatty acids were assessed by real-time PCR and gas chromatography, respectively.Results: There was an increased frequency of weekly bowel movements and patient satisfaction in both the fiber and placebo groups with no significant differences. Total Clostridium sp significantly decreased in the fiber group (p = 0.046) and increased in the placebo group (p = 0.047). There were no changes in fecal short chain fatty acid profile.Conclusions: Consumption of I-PHGG produced clinical results comparable to placebo in constipated females, but had additional protective effects on gut rnicrobiota by decreasing the amount of pathological bacteria of the Clostridium genera.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Univ São Paulo, Fac Med, Sch Med, Dept Gastroenterol,Surg Gastroenterol Discipline, BR-01246903 São Paulo, BrazilUniversidade Federal de São Paulo, Dept Biociences, Santos, BrazilGANEP Nutr Humana, São Paulo, BrazilUniversidade Federal de São Paulo, Dept Biociences, Santos, BrazilFAPESP: 07/58600-2Web of Scienc

Coherent pulse synthesis: Towards sub-cycle optical waveforms

The generation of sub-optical-cycle, carrier–envelope phase-stable light pulses is one of the frontiers of ultrafast optics. The two key ingredients for sub-cycle pulse generation are bandwidths substantially exceeding one octave and accurate control of the spectral phase. These requirements arevery challenging to satisfy with a single laser beam, and thus intense research activity is currently devoted to the coherent synthesis of pulses generated by separate sources. In this review we discuss the conceptual schemes and experimental tools that can be employed for the generation, amplification, control, and combination of separate light pulses. The main techniques for the spectrotemporal characterization of the synthesized fields are also described. We discuss recent implementations of coherent waveform synthesis: from the first demonstration of a single-cycle opticalpulse by the addition of two pulse trains derived from a fiber laser, to the coherent combination of the outputs from optical parametric chirped-pulse amplifiers

Preliminary definitions for the sonographic features of synovitis in children

Objectives Musculoskeletal ultrasonography (US) has the potential to be an important tool in the assessment of disease activity in childhood arthritides. To assess pathology, clear definitions for synovitis need to be developed first. The aim of this study was to develop and validate these definitions through an international consensus process. Methods The decision on which US techniques to use, the components to be included in the definitions as well as the final wording were developed by 31 ultrasound experts in a consensus process. A Likert scale of 1-5 with 1 indicating complete disagreement and 5 complete agreement was used. A minimum of 80% of the experts scoring 4 or 5 was required for final approval. The definitions were then validated on 120 standardized US images of the wrist, MCP and tibiotalar joints displaying various degrees of synovitis at various ages. Results B-Mode and Doppler should be used for assessing synovitis in children. A US definition of the various components (i.e. synovial hypertrophy, effusion and Doppler signal within the synovium) was developed. The definition was validated on still images with a median of 89% (range 80-100) of participants scoring it as 4 or 5 on a Likert scale. Conclusions US definitions of synovitis and its elementary components covering the entire pediatric age range were successfully developed through a Delphi process and validated in a web-based still images exercise. These results provide the basis for the standardized US assessment of synovitis in clinical practice and research