561 research outputs found

    Ordering phenomena in quasi one-dimensional organic conductors

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    Low-dimensional organic conductors could establish themselves as model systems for the investigation of the physics in reduced dimensions. In the metallic state of a one-dimensional solid, Fermi-liquid theory breaks down and spin and charge degrees of freedom become separated. But the metallic phase is not stable in one dimension: as the temperature is reduced, the electronic charge and spin tend to arrange themselves in an ordered fashion due to strong correlations. The competition of the different interactions is responsible for which broken-symmetry ground state is eventually realized in a specific compound and which drives the system towards an insulating state. Here we review the various ordering phenomena and how they can be identified by optic and magnetic measurements. While the final results might look very similar in the case of a charge density wave and a charge-ordered metal, for instance, the physical cause is completely different. When density waves form, a gap opens in the density of states at the Fermi energy due to nesting of the one-dimension Fermi surface sheets. When a one-dimensional metal becomes a charge-ordered Mott insulator, on the other hand, the short-range Coulomb repulsion localizes the charge on the lattice sites and even causes certain charge patterns. We try to point out the similarities and conceptional differences of these phenomena and give an example for each of them. Particular emphasis will be put on collective phenomena which are inherently present as soon as ordering breaks the symmetry of the system.Comment: Review article Naturwissenschaften 200

    State Transfer Between a Mechanical Oscillator and Microwave Fields in the Quantum Regime

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    Recently, macroscopic mechanical oscillators have been coaxed into a regime of quantum behavior, by direct refrigeration [1] or a combination of refrigeration and laser-like cooling [2, 3]. This exciting result has encouraged notions that mechanical oscillators may perform useful functions in the processing of quantum information with superconducting circuits [1, 4-7], either by serving as a quantum memory for the ephemeral state of a microwave field or by providing a quantum interface between otherwise incompatible systems [8, 9]. As yet, the transfer of an itinerant state or propagating mode of a microwave field to and from a mechanical oscillator has not been demonstrated owing to the inability to agilely turn on and off the interaction between microwave electricity and mechanical motion. Here we demonstrate that the state of an itinerant microwave field can be coherently transferred into, stored in, and retrieved from a mechanical oscillator with amplitudes at the single quanta level. Crucially, the time to capture and to retrieve the microwave state is shorter than the quantum state lifetime of the mechanical oscillator. In this quantum regime, the mechanical oscillator can both store and transduce quantum information

    Clinical-pathological study on β-APP, IL-1β, GFAP, NFL, Spectrin II, 8OHdG, TUNEL, miR-21, miR-16, miR-92 expressions to verify DAI-diagnosis, grade and prognosis

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    Traumatic brain injury (TBI) is one of the most important death and disability cause, involving substantial costs, also in economic terms, when considering the young age of the involved subject. Aim of this paper is to report a series of patients treated at our institutions, to verify neurological results at six months or survival; in fatal cases we searched for βAPP, GFAP, IL-1β, NFL, Spectrin II, TUNEL and miR-21, miR-16, and miR-92 expressions in brain samples, to verify DAI diagnosis and grade as strong predictor of survival and inflammatory response. Concentrations of 8OHdG as measurement of oxidative stress was performed. Immunoreaction of β-APP, IL-1β, GFAP, NFL, Spectrin II and 8OHdG were significantly increased in the TBI group with respect to control group subjects. Cell apoptosis, measured by TUNEL assay, were significantly higher in the study group than control cases. Results indicated that miR-21, miR-92 and miR-16 have a high predictive power in discriminating trauma brain cases from controls and could represent promising biomarkers as strong predictor of survival, and for the diagnosis of postmortem traumatic brain injury

    The impact of young age on cancer-specific and non-cancer-related survival after surgery for colorectal cancer: 10-year follow-up

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    <b>Background</b>: It has been reported that although young patients present with more advanced disease, when adjusted for stage, cancer-specific survival is not different after surgery for colorectal cancer. However, few studies have examined non-cancer survival in young patients and 10-year survival has rarely been reported. Moreover, the largest study included patients of old age as a comparator. The aim of this study was to compare cancer-specific and non-cancer-related survival at 10 years in a young age cohort and a middle age cohort in patients undergoing surgery for colorectal cancer. <b>Methods</b>: Two thousand and seventy seven patients who underwent surgery for colorectal cancer between 1991 and 1994 in 11 hospitals in Scotland were included in the study. Ten-year cancer-specific and non-cancer-related survival and the hazard ratios (HR) were calculated according to age groups (<45/45–54/55–64/65–74 years). <b>Results</b>: On follow-up, 1066 patients died of their cancer and 369 died of non-cancer-related causes. At 10 years, overall survival was 32%, cancer-specific was 45%, and non-cancer-related survival was 72%. On multivariate analysis of all factors, sex (HR 0.77, 95% CI 0.68–0.88, P<0.001), mode of presentation (HR 1.64, 95% CI 1.44–1.87, P<0.01), Dukes' stage (HR 2.69, 95% CI 2.49–2.90, P<0.001), and specialisation (HR 1.24, 95% CI 1.04–1.44, P<0.01) were independently associated with cancer-specific survival. On multivariate analysis of all factors, age (HR 2.46, 2.04–2.97, P<0.001), sex (HR 0.56, 0.45–0.70, P<0.001), and deprivation (HR 1.16, 1.10–1.24, P<0.001) were independently associated with non-cancer-related survival. <b>Conclusion</b>: The results of this study confirm that young age does not have a negative impact on cancer-specific survival. Moreover, they show that, with 10-year follow-up, young age does not have a negative impact on non-cancer-related survival

    Professionalism and Evolving Concepts of Quality

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    For much of the twentieth century, quality of care was defined specifically in terms of physician characteristics and behaviors. High-quality physicians were well trained, knowledgeable, skillful, and compassionate. More recently, quality of care has been defined in terms of systems of care. High-quality organizations develop and adopt practices to reduce adverse events and optimize outcomes. This essay discusses this transformation from physician-based to organization-based concepts of quality and the consequences for patient care and medical professionalism

    Multimode circuit optomechanics near the quantum limit

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    The coupling of distinct systems underlies nearly all physical phenomena and their applications. A basic instance is that of interacting harmonic oscillators, which gives rise to, for example, the phonon eigenmodes in a crystal lattice. Particularly important are the interactions in hybrid quantum systems consisting of different kinds of degrees of freedom. These assemblies can combine the benefits of each in future quantum technologies. Here, we investigate a hybrid optomechanical system having three degrees of freedom, consisting of a microwave cavity and two micromechanical beams with closely spaced frequencies around 32 MHz and no direct interaction. We record the first evidence of tripartite optomechanical mixing, implying that the eigenmodes are combinations of one photonic and two phononic modes. We identify an asymmetric dark mode having a long lifetime. Simultaneously, we operate the nearly macroscopic mechanical modes close to the motional quantum ground state, down to 1.8 thermal quanta, achieved by back-action cooling. These results constitute an important advance towards engineering entangled motional states.Comment: 6+7 page

    A Multilevel Analysis of the Impact of Socio-Structural and Environmental Influences on Condom Use Among Female Sex Workers

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    This study uses multilevel analysis to examine individual, organizational and community levels of influence on condom use among female commercial sex workers (FSW) in the Philippines. A randomized controlled study involving 1,382 female commercial sex workers assigned to three intervention groups consisting of peer education, managerial training, combined peer and managerial intervention and a usual care control group was conducted. The results of the multilevel analysis show that FSWs who work in establishments with condom use rules tend to have a higher level of condom use (β = .70, P < 0.01). Among the different intervention groups, the combined peer and managerial intervention had the largest effect on condom use (β = 1.30, P < 0.01) compared with the usual care group. Using a three-level hierarchical model, we found that 62% of the variation lies within individuals, whereas 24% and 14% of the variation lies between establishments, and communities, respectively. Standard errors were underestimated when clustering of the FSWs in the different establishments and communities were not taken into consideration. The results demonstrate the importance of using multilevel analysis for community-based HIV/AIDS intervention programs to examine individual, establishment and community effects

    Optimality regions and fluctuations for Bernoulli last passage models

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    We study the sequence alignment problem and its independent version,the discrete Hammersley process with an exploration penalty. We obtain rigorous upper bounds for the number of optimality regions in both models near the soft edge.At zero penalty the independent model becomes an exactly solvable model and we identify cases for which the law of the last passage time converges to a Tracy-Widom law

    Cutoff value determines the performance of a semi-quantitative immunochemical faecal occult blood test in a colorectal cancer screening programme

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    BACKGROUND: The cutoff of semi-quantitative immunochemical faecal occult blood tests (iFOBTs) influences colonoscopy referrals and detection rates. We studied the performance of an iFOBT (OC-Sensor) in colorectal cancer (CRC) screening at different cutoffs. METHODS: Dutch screening participants, 50-75 years of age, with average CRC risk and an iFOBT value >or=50 ng ml(-1) were offered colonoscopy. The detection rate was the percentage of participants with CRC or advanced adenomas (>or=10 mm, >or=20% villous, high-grade dysplasia). The number needed to scope (NNTScope) was the number of colonoscopies to be carried out to find one person with CRC or advanced adenomas. RESULTS: iFOBT values >or=50 ng ml(-1) were detected in 526 of 6157 participants (8.5%) and 428 (81%) underwent colonoscopy. The detection rate for advanced lesions (28 CRC and 161 with advanced adenomas) was 3.1% (95% confidence interval: 2.6-3.5%) and the NNTScope was 2.3. At 75 ng ml(-1), the detection rate was 2.7%, the NNTScope was 2.0 and the CRC miss rate compared with 50 ng ml(-1) was <5% (N=1). At 100 ng ml(-1), the detection rate was 2.4% and the NNTScope was <2. Compared with 50 ng ml(-1), up to 200 ng ml(-1) CRC miss rates remained at 16% (N=4). CONCLUSIONS: Cutoffs below the standard 100 ng ml(-1) resulted in not only higher detection rates of advanced lesions but also more colonoscopies. With sufficient capacity, 75 ng ml(-1) might be advised; if not, up to 200 ng ml(-1) CRC miss rates are acceptable compared with the decrease in performed colonoscopies
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