435 research outputs found

    Strong coupling theory for driven tunneling and vibrational relaxation

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    We investigate on a unified basis tunneling and vibrational relaxation in driven dissipative multistable systems described by their N lowest lying unperturbed levels. By use of the discrete variable representation we derive a set of coupled non-Markovian master equations. We present analytical treatments that describe the dynamics in the regime of strong system-bath coupling. Our findings are corroborated by ``ab-initio'' real-time path integral calculations.Comment: 4 LaTeX pages including 3 figure

    Differential performance of two forage species, Medicago truncatula and Sulla carnosa, under water-deficit stress and recovery

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    The response patterns during water deficit stress and subsequent recovery of two forage species, Medicago truncatula and Sulla carnosa, were studied. After germination and pre-treatment, seedlings were individually cultivated for two months under two irrigation modes: 100% and 33% of field capacity. Measured parameters were plant growth, water relations, leaf osmotic potential, lipid peroxidation, and leaf inorganic (Na+ and K+) and organic (proline and soluble sugars) solute contents, as well as delta-1-pyrroline-5-carboxylate synthase (P5CS) and proline dehydrogenase (PDH) activities. Our results showed that under control conditions, and in contrast to roots, no significant differences were observed in shoot biomass production between the two species. However, when subjected to water-deficit stress, M. truncatula appeared to be more tolerant than S. carnosa (reduction by 50 and 70%, respectively). In the two studied species, water-deficit stress led to an increase in root/shoot ratio and leaf proline and soluble sugar contents, and a decrease in leaf osmotic potential. Enzymatic assay revealed that in the two species, P5CS activity was stimulated whereas that of PDH was inhibited under stress conditions. Despite greater accumulation of proline, sugar, and potassium in leaves of S. carnosa, M. truncatula was more tolerant to water deficit. This was essentially due to its capacity to control tissue hydration and water-use efficiency, in addition to its greater ability to protect membrane integrity. Following stress relief, M. truncatula and S. carnosa showed partial re-establishment of growth capacity

    Cirurgia de revascularização do miocårdio: complicaçÔes pleuro-pulmonares agudas caracterizadas por tomografia computadorizada de tórax

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    INTRODUCTION: Pleuropulmonary changes are common following coronary artery bypass grafting surgery performed with a saphenous vein graft, with or without an internal mammary artery. The presence of atelectasis or pleural effusions reflects the thoracic trauma. PURPOSE: To define the postoperative incidence of changes in the lung and in the pleural space and to evaluate the influence of the trauma. METHODS: Thirty patients underwent elective coronary artery bypass grafting surgery (8 saphenous vein grafts and 22 saphenous vein grafts and internal mammary artery grafts with pleurotomy). Chest tubes in the left pleural space were used in all internal mammary artery patients. On the second (day 2) and seventh (day 7) postoperative day, patients underwent a computed tomography, and pleural effusions were rated as follows: grade 0 = no fluid to grade 4 = fluid in more than 75% of the hemithorax. Atelectasis was rated as follows: laminar = 1, segmental = 3, and lobar = 10 points. RESULTS: All patients had pleural effusion or atelectasis. Between day 2 and day 7, the number of patients with effusions or atelectasis on the right side decreased (P < 0.05). The incidence of effusions on day 2 in the saphenous vein graft group (87.5%) was higher (P < 0.05) than in the internal mammary artery group (52.3%). The incidence of atelectasis in the lower right lobe decreased (P < 0.05) from 86.7% (day 2) to 26.7% (day 7). The degree of atelectasis in both sides did not differ on day 2 (P = 0.42) but did on day 7 (P < 0.0001). There was a decrease in the atelectasis from day 2 to day 7 on the right side (P < 0.001), but not on the left (P = 0.21). On day 2 there was a relationship between atelectasis and effusion on the right (P = 0.04), but not on the left (P = 0.113). CONCLUSION: The present series demonstrates that there is a high incidence of both minimal pleural effusion and atelectasis after coronary artery bypass grafting surgery, which drops on the right side from day 2 to day 7 post surgery. Factors that contribute to the persistence of changes on the left side include the thoracic trauma and the presence of chest tubes and pericardial effusion.INTRODUÇÃO: O comprometimento pleuro-pulmonar Ă© freqĂŒente apĂłs cirurgia de revascularização do miocĂĄrdio independente do uso de veia safena ou de artĂ©ria mamĂĄria interna. A presença de atelectasias e derrame pleural tem sido atribuĂ­da ao trauma torĂĄcico. OBJETIVOS: Definir a incidĂȘncia do comprometimento pleuro-pulmonar observado atravĂ©s de tomografia computadorizada, analisando a influĂȘncia do trauma no desenvolvimento destas complicaçÔes. MÉTODOS: Trinta pacientes foram submetidos a cirurgia eletiva de revascularização do miocĂĄrdio (8 safena e 22 tambĂ©m mamĂĄria com pleurotomia). Foi drenada a cavidade pleural esquerda de todos os pacientes do grupo mamĂĄria. Realizada Tomografia Computadorizada do tĂłrax no 2Âș e 7Âș dias pĂłs-op, avaliando-se o derrame pleural (0: sem lĂ­quido e 4: derrame em mais de 75% do hemitĂłrax) e atelectasias (laminar: 1, segmentar: 3 e lobar: 10 pontos). RESULTADOS: Todos os pacientes apresentaram derrame pleural ou atelectasia. Entre o 2Âș e o 7Âș dia, o nĂșmero de pacientes com derrame ou com atelectasia, no lado direito, diminuiu (p < 0.05). A prevalĂȘncia de derrames, no 2Âș dia, no grupo safena, (87.5%) foi maior (p < 0.05) do que no grupo mamĂĄria (52.3%). A prevalĂȘncia de atelectasias no lobo inferior direito diminuiu (p < 0.05) de 86.7% (2Âș dia) para 26.7% (7Âș dia). O grau de atelectasias, em ambos os lados, nĂŁo diferiu no dia 2 (p = 0,42) mas sim no dia 7 (p < 0.0001). Houve diminuição das atelectasias do dia 2 para o 7, Ă  direita (p < 0.001), mas nĂŁo Ă  esquerda (p = 0.21). Houve correlação (dia 2) entre as atelectasias e os derrames Ă  direita (p = 0.04), mas nĂŁo Ă  esquerda (p = 0.113). CONCLUSÃO: Este estudo evidencia alta prevalĂȘncia de derrame pleural e atelectasias apĂłs cirurgia de revascularização do miocĂĄrdio, que se reduz Ă  direita no 7Âș dia de pĂłs-operatĂłrio. Os fatores envolvidos na persis-tĂȘncia das alteraçÔes Ă  esquerda incluem o maior trauma torĂĄcico, ressaltando-se a drenagem e a presença de derrame pericĂĄrdico

    Increasing confidence and changing behaviors in primary care providers engaged in genetic counselling.

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    BackgroundScreening and counseling for genetic conditions is an increasingly important part of primary care practice, particularly given the paucity of genetic counselors in the United States. However, primary care physicians (PCPs) often have an inadequate understanding of evidence-based screening; communication approaches that encourage shared decision-making; ethical, legal, and social implication (ELSI) issues related to screening for genetic mutations; and the basics of clinical genetics. This study explored whether an interactive, web-based genetics curriculum directed at PCPs in non-academic primary care settings was superior at changing practice knowledge, attitudes, and behaviors when compared to a traditional educational approach, particularly when discussing common genetic conditions.MethodsOne hundred twenty one PCPs in California and Pennsylvania physician practices were randomized to either an Intervention Group (IG) or Control Group (CG). IG physicians completed a 6 h interactive web-based curriculum covering communication skills, basics of genetic testing, risk assessment, ELSI issues and practice behaviors. CG physicians were provided with a traditional approach to Continuing Medical Education (CME) (clinical review articles) offering equivalent information.ResultsPCPs in the Intervention Group showed greater increases in knowledge compared to the Control Group. Intervention PCPs were also more satisfied with the educational materials, and more confident in their genetics knowledge and skills compared to those receiving traditional CME materials. Intervention PCPs felt that the web-based curriculum covered medical management, genetics, and ELSI issues significantly better than did the Control Group, and in comparison with traditional curricula. The Intervention Group felt the online tools offered several advantages, and engaged in better shared decision making with standardized patients, however, there was no difference in behavior change between groups with regard to increases in ELSI discussions between PCPs and patients.ConclusionWhile our intervention was deemed more enjoyable, demonstrated significant factual learning and retention, and increased shared decision making practices, there were few differences in behavior changes around ELSI discussions. Unfortunately, barriers to implementing behavior change in clinical genetics is not unique to our intervention. Perhaps the missing element is that busy physicians need systems-level support to engage in meaningful discussions around genetics issues. The next step in promoting active engagement between doctors and patients may be to put into place the tools needed for PCPs to easily access the materials they need at the point-of-care to engage in joint discussions around clinical genetics

    Electron energy loss and induced photon emission in photonic crystals

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    The interaction of a fast electron with a photonic crystal is investigated by solving the Maxwell equations exactly for the external field provided by the electron in the presence of the crystal. The energy loss is obtained from the retarding force exerted on the electron by the induced electric field. The features of the energy loss spectra are shown to be related to the photonic band structure of the crystal. Two different regimes are discussed: for small lattice constants aa relative to the wavelength of the associated electron excitations λ\lambda, an effective medium theory can be used to describe the material; however, for a∌λa\sim\lambda the photonic band structure plays an important role. Special attention is paid to the frequency gap regions in the latter case.Comment: 12 pages, 7 figure

    Chaos or Noise - Difficulties of a Distinction

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    In experiments, the dynamical behavior of systems is reflected in time series. Due to the finiteness of the observational data set it is not possible to reconstruct the invariant measure up to arbitrary fine resolution and arbitrary high embedding dimension. These restrictions limit our ability to distinguish between signals generated by different systems, such as regular, chaotic or stochastic ones, when analyzed from a time series point of view. We propose to classify the signal behavior, without referring to any specific model, as stochastic or deterministic on a certain scale of the resolution Ï”\epsilon, according to the dependence of the (Ï”,τ)(\epsilon,\tau)-entropy, h(Ï”,τ)h(\epsilon, \tau), and of the finite size Lyapunov exponent, λ(Ï”)\lambda(\epsilon), on Ï”\epsilon.Comment: 24 pages RevTeX, 9 eps figures included, two references added, minor corrections, one section has been split in two (submitted to PRE

    Phase diffusion as a model for coherent suppression of tunneling in the presence of noise

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    We study the stabilization of coherent suppression of tunneling in a driven double-well system subject to random periodic ή−\delta-function ``kicks''. We model dissipation due to this stochastic process as a phase diffusion process for an effective two-level system and derive a corresponding set of Bloch equations with phase damping terms that agree with the periodically kicked system at discrete times. We demonstrate that the ability of noise to localize the system on either side of the double-well potenital arises from overdamping of the phase of oscillation and not from any cooperative effect between the noise and the driving field. The model is investigated with a square wave drive, which has qualitatively similar features to the widely studied cosinusoidal drive, but has the additional advantage of allowing one to derive exact analytic expressions.Comment: 17 pages, 4 figures, submitted to Phys. Rev.

    Perturbations of Noise: The origins of Isothermal Flows

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    We make a detailed analysis of both phenomenological and analytic background for the "Brownian recoil principle" hypothesis (Phys. Rev. A 46, (1992), 4634). A corresponding theory of the isothermal Brownian motion of particle ensembles (Smoluchowski diffusion process approximation), gives account of the environmental recoil effects due to locally induced tiny heat flows. By means of local expectation values we elevate the individually negligible phenomena to a non-negligible (accumulated) recoil effect on the ensemble average. The main technical input is a consequent exploitation of the Hamilton-Jacobi equation as a natural substitute for the local momentum conservation law. Together with the continuity equation (alternatively, Fokker-Planck), it forms a closed system of partial differential equations which uniquely determines an associated Markovian diffusion process. The third Newton law in the mean is utilised to generate diffusion-type processes which are either anomalous (enhanced), or generically non-dispersive.Comment: Latex fil
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