312 research outputs found

    Long-range potentials and (n1)d+ns(n-1)d+ns molecular resonances in an ultracold rydberg gas

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    We have calculated long-range molecular potentials of the 0g+0_g^{+}, 0u0_u^{-} and 1u1_u symmetries between highly-excited rubidium atoms. Strong np+npnp+np potentials characterized by these symmetries are important in describing interaction-induced phenomena in the excitation spectra of high npnp Rydberg states. Long-range molecular resonances are such phenomena and they were first reported in S.M. Farooqi {\it et al.}, Phys. Rev. Lett. {\bf 91} 183002. One class of these resonances occurs at energies corresponding to excited atom pairs (n1)d+ns(n-1)d+ns. Such resonances are attributed to \ell-mixing due to Rydberg-Rydberg interactions so that otherwise forbidden molecular transitions become allowed. We calculate molecular potentials in Hund's case (c), use them to find the resonance lineshape and compare to experimental results.Comment: 11 pages, 7 figure

    Reconstructive Procedures after Total Gastrectomy for Gastric Cancer

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    Till this day, there are more than 60 described surgical procedures of the intestinal reconstructions after a total gastrectomy. In 1897, Schlatter reconstructed the digestive tract by creating a termino-lateral esophagojejunostomies that was the first successful total gastrectomy. Many of the total gastrectomy pioneers did the reconstruction by esophagoduodenostomy or by forming a loop esophagojejunostomy. The main reconstruction modalities after a total gastrectomy are a restitution of the intestinal continuity, without a preservation of the duodenal food passage (esophagojejunostomy with a Roux-en-Y configuration) and a restitution of the intestinal continuity with a preservation of the duodenal passage (esophagojejunostomy with Roux-en-Y configuration and forming of the lateral-terminal jejunoduodenal anastomosis double tract and jejunal interposition by Longmire). The surgeries in these categories can be combined with forming of an enteral pouch or a stomach reservoir which would simulate a reservoir of a normal intact stomach. The ideal reconstruction procedure after total gastrectomy should replace all lost functions of the stomach. Preservation of duodenal transit with replacement of the jejunal segment, the so-called physiological route, is now believed to be preferential for postoperative nutritional condition, prevents persistent postgastrectomy syndrome, and improves the quality of life. Reconstructive procedures which allow duodenal passage should be regarded as a key to physiological reconstruction

    Unsupervised phenotypic clustering for determining clinical status in children with cystic fibrosis

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    BACKGROUND: Cystic Fibrosis (CF) is a multisystem disease in which assessing disease severity based on lung function alone may not be appropriate. The aim of the study was to develop a comprehensive machine-learning algorithm to assess clinical status independent of lung function in children. METHODS: A comprehensive prospectively collected clinical database (Toronto, Canada) was used to apply unsupervised cluster analysis. The defined clusters were then compared by current and future lung function, risk of future hospitalisation, and risk of future pulmonary exacerbation (PEx) treated with oral antibiotics. A K-Nearest Neighbours (KNN) algorithm was used to prospectively assign clusters. The methods were validated in a paediatric clinical CF dataset from Great Ormond Street Hospital (GOSH). RESULTS: The optimal cluster model identified four (A-D) phenotypic clusters based on 12 200 encounters from 530 individuals. Two clusters (A,B) consistent with mild disease were identified with high FEV1, and low risk of both hospitalisation and PEx treated with oral antibiotics. Two clusters (C,D) consistent with severe disease were also identified with low FEV1. Cluster D had the shortest time to both hospitalisation and PEx treated with oral antibiotics. The outcomes were consistent in 3124 encounters from 171 children at GOSH. The KNN cluster allocation error rate was low, at 2.5% (Toronto), and 3.5% (GOSH). CONCLUSION: Machine learning derived phenotypic clusters can predict disease severity independent of lung function and could be used in conjunction with functional measures to predict future disease trajectories in CF patients

    Spirometry reference equations for central European populations from school age to old age.

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    Spirometry reference values are important for the interpretation of spirometry results. Reference values should be updated regularly, derived from a population as similar to the population for which they are to be used and span across all ages. Such spirometry reference equations are currently lacking for central European populations. To develop spirometry reference equations for central European populations between 8 and 90 years of age. We used data collected between January 1993 and December 2010 from a central European population. The data was modelled using "Generalized Additive Models for Location, Scale and Shape" (GAMLSS). The spirometry reference equations were derived from 118'891 individuals consisting of 60'624 (51%) females and 58'267 (49%) males. Altogether, there were 18'211 (15.3%) children under the age of 18 years. We developed spirometry reference equations for a central European population between 8 and 90 years of age that can be implemented in a wide range of clinical settings

    ELECTRO-ACOUSTIC ANALOGIES BETWEEN THERMOELASTIC COMPONENT OF THE PHOTOACOUSTIC SIGNAL AND LOW-PASS RC FILTER

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    This paper presents a new approach to the thermal characterization of aluminum, based on the electro-acoustic analogy between the thermoelastic component of the photoacoustic signal and the passive RC low-pass filter. The analogies were used to calculate the characteristic thermoelastic cut-off frequencies of the photoacoustic component and obtain their relationship with the thickness of the aluminum samples. Detailed numerical analysis showed that the required relationship is linear in the log-log scale and can serve as a reference curve for the given material. The results of the numerical analysis were also confirmed experimentally

    Observation of coherent many-body Rabi oscillations

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    A two-level quantum system coherently driven by a resonant electromagnetic field oscillates sinusoidally between the two levels at frequency Ω\Omega which is proportional to the field amplitude [1]. This phenomenon, known as the Rabi oscillation, has been at the heart of atomic, molecular and optical physics since the seminal work of its namesake and coauthors [2]. Notably, Rabi oscillations in isolated single atoms or dilute gases form the basis for metrological applications such as atomic clocks and precision measurements of physical constants [3]. Both inhomogeneous distribution of coupling strength to the field and interactions between individual atoms reduce the visibility of the oscillation and may even suppress it completely. A remarkable transformation takes place in the limit where only a single excitation can be present in the sample due to either initial conditions or atomic interactions: there arises a collective, many-body Rabi oscillation at a frequency N0.5ΩN^0.5\Omega involving all N >> 1 atoms in the sample [4]. This is true even for inhomogeneous atom-field coupling distributions, where single-atom Rabi oscillations may be invisible. When one of the two levels is a strongly interacting Rydberg level, many-body Rabi oscillations emerge as a consequence of the Rydberg excitation blockade. Lukin and coauthors outlined an approach to quantum information processing based on this effect [5]. Here we report initial observations of coherent many-body Rabi oscillations between the ground level and a Rydberg level using several hundred cold rubidium atoms. The strongly pronounced oscillations indicate a nearly complete excitation blockade of the entire mesoscopic ensemble by a single excited atom. The results pave the way towards quantum computation and simulation using ensembles of atoms

    Response Factors to Pegylated Interferon-Alfa/Ribavirin Treatment in Chronic Hepatitis C Patients Genotype 1b

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    Hepatitis C virus infection is the most common chronic blood-borne infection and one of the most important causes of chronic liver disease. Knowing the predictors associated with pegylated interferon/ribavirin (PEG-IFN/RBV) combination therapy response is important for evidence-based treatment recommendations. The goal of this study was to identify host and viral factors of response to PEG-IFN/RBV treatment in chronic hepatitis C genotype 1b patients. We have examined the relationship between gender, age, level of alanine aminotransferase (ALT), viral load and liver fibrosis progression on therapy response. ALT level and viral load were evaluated before starting treatment with combination therapy. The elevated levels of ALT and route of HCV transmission were found to be significantly associated with the response to therapy in HCV-infected patients. Our findings may be useful for estimating a patients likelihood Of achieving sustained viral response
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