716 research outputs found

    A titanium-nitride near-infrared kinetic inductance photon-counting detector and its anomalous electrodynamics

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    We demonstrate single-photon counting at 1550 nm with titanium-nitride (TiN) microwave kinetic inductance detectors. Energy resolution of 0.4 eV and arrival-time resolution of 1.2 microseconds are achieved. 0-, 1-, 2-photon events are resolved and shown to follow Poisson statistics. We find that the temperature-dependent frequency shift deviates from the Mattis-Bardeen theory, and the dissipation response shows a shorter decay time than the frequency response at low temperatures. We suggest that the observed anomalous electrodynamics may be related to quasiparticle traps or subgap states in the disordered TiN films. Finally, the electron density-of-states is derived from the pulse response.Comment: 4 pages, 3 figure

    Fate of Allochthonous Dissolved Organic Carbon in Lakes: A Quantitative Approach

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    Inputs of dissolved organic carbon (DOC) to lakes derived from the surrounding landscape can be stored, mineralized or passed to downstream ecosystems. The balance among these OC fates depends on a suite of physical, chemical, and biological processes within the lake, as well as the degree of recalcintrance of the allochthonous DOC load. The relative importance of these processes has not been well quantified due to the complex nature of lakes, as well as challenges in scaling DOC degradation experiments under controlled conditions to the whole lake scale. We used a coupled hydrodynamic-water quality model to simulate broad ranges in lake area and DOC, two characteristics important to processing allochthonous carbon through their influences on lake temperature, mixing depth and hydrology. We calibrated the model to four lakes from the North Temperate Lakes Long Term Ecological Research site, and simulated an additional 12 ‘hypothetical’ lakes to fill the gradients in lake size and DOC concentration. For each lake, we tested several mineralization rates (range: 0.001 d−1 to 0.010 d−1) representative of the range found in the literature. We found that mineralization rates at the ecosystem scale were roughly half the values from laboratory experiments, due to relatively cool water temperatures and other lake-specific factors that influence water temperature and hydrologic residence time. Results from simulations indicated that the fate of allochthonous DOC was controlled primarily by the mineralization rate and the hydrologic residence time. Lakes with residence times <1 year exported approximately 60% of the DOC, whereas lakes with residence times >6 years mineralized approximately 60% of the DOC. DOC fate in lakes can be determined with a few relatively easily measured factors, such as lake morphometry, residence time, and temperature, assuming we know the recalcitrance of the DOC

    Oestrogen inactivation in the colon: analysis of the expression and regulation of 17 β -hydroxysteroidehydrogenase isozymes in normal colon and colonic cancer

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    Epidemiological data suggest that oestrogen contributes to the aetiology of colonic cancer. Furthermore, recent studies have suggested that local hormone metabolism may play a key role in determining colonic responsiveness to oestrogen. To further clarify this mechanism we have characterized the expression and regulation of isozymes of 17β-hydroxysteroid dehydrogenase (17β-HSD) in vitro and in situ. Immunohistochemistry was used to confirm expression of the type 2 and 4 isozymes of 17β-HSD (17β-HSD2 and 4) in normal colonic epithelial cells. Parallel studies suggested that both isozymes were abnormally expressed in colonic tumours and this was confirmed by Western blot analyses. Abnormal expression of 17β-HSD2 and 4 proteins was also observed in Caco-2, HT-29 and SW620 colonic cancer cell lines, although the overall pattern of oestrogen metabolism in these cells was similar to that seen in primary colonic mucosal tissue. The predominant activity (conversion of oestradiol to oestrone) was highest in Caco-2>SW620>HT-29, which correlated inversely with the rate of proliferation of the cell lines. Regulatory studies using SW620 cells indicated that the most potent stimulator of oestradiol to oestrone inactivation was the antiproliferative agent 1,25-dihydroxyvitamin D 3(1,25D 3), whilst oestradiol itself inhibited 17β-HSD activity. Both oestradiol and 1,25D 3 decreased mRNA for 17β-HSD2 and 4. Data indicate that the high capacity for inactivation of oestrogens in the colon is associated with the presence of 17β-HSD2 and 4 in epithelial cells. Abnormal expression of both isozymes in colonic cancer cells and the stimulation of oestrogen inactivation by the antiproliferative agent 1,25D 3 highlights a possible role for 17β-HSD isozymes as modulators of colonic cell proliferation. © 2000 Cancer Research Campaig

    Monopoles and Knots in Skyrme Theory

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    We show that the Skyrme theory actually is a theory of monopoles which allows a new type of solitons, the topological knots made of monopole-anti-monopole pair,which is different from the well-known skyrmions. Furthermore, we derive a generalized Skyrme action from the Yang-Mills action of QCD, which we propose to be an effective action of QCD in the infra-red limit. We discuss the physical implications of our results.Comment: 4 pages. Phys. Rev. Lett. in pres

    The Self Model and the Conception of Biological Identity in Immunology

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    The self/non-self model, first proposed by F.M. Burnet, has dominated immunology for sixty years now. According to this model, any foreign element will trigger an immune reaction in an organism, whereas endogenous elements will not, in normal circumstances, induce an immune reaction. In this paper we show that the self/non-self model is no longer an appropriate explanation of experimental data in immunology, and that this inadequacy may be rooted in an excessively strong metaphysical conception of biological identity. We suggest that another hypothesis, one based on the notion of continuity, gives a better account of immune phenomena. Finally, we underscore the mapping between this metaphysical deflation from self to continuity in immunology and the philosophical debate between substantialism and empiricism about identity

    Producción de vaquillonas pesadas en condiciones de pastoreo y su impacto en la terneza de la carne

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    Históricamente, en el mercado argentino la vaquillona de más de 320 kg de peso vivo (PV) ha sido incluida en la categoría de “vacas”, lo cual disminuye sensiblemente el precio que el productor obtenía por ese animal. Dado que dentro de un amplio rango de edades la terneza se encuentra negativamente asociada con la edad del animal, esta modalidad de comercialización se habría implementado para evitar comercializar vacas como vaquillonas. Sin embargo, Shackelford et al. (1995) concluyen que la magnitud de la diferencias de terneza en el músculo longissimus encontradas entre vaquillonas (15-18 meses de edad) y vacas de dos años de edad difí- cilmente justifiquen un menor valor de mercado de las últimas respecto a las vaquillonas. En Argentina, a partir de diciembre de 2005 entró en vigencia la disposición de la Oficina de Nacional de Control Comercial Agropecuario (ONCCA) 5701/2005, a través de la cual se crearon distintas categorías de peso vivo de vaquillonas especiales y buenas (300 a 340, 341 a 380, y 381 a 420 kg PV), y una categoría de vaquillonas regulares. Esta nueva categorización permitiría diferenciar las vaquillonas de las vacas. Sin embargo, las vaquillonas de más de 320 kg PV siguieron siendo penalizadas en el mercado con un menor precio. Según la base de datos del Mercado de Liniers S.A. (http://www.mercado deliniers.com.ar/), el precio medio durante el año 2006 en ese Mercado para las vaquillonas de 300 a 340 kg PV fue de 2.50porkgPVyparalasde381a420kgPVde2.50 por kg PV y para las de 381 a 420 kg PV de 2,17. Esta reducción en el precio de vaquillonas por aumento de peso fue 80% mayor que en los novillitos por similar cambio de peso (2,60a2,60 a 2,46 por kg). Esto se reflejó en que durante el 2006, sólo el 6% del total de vaquillonas comercializadas correspondió a vaquillonas pesadas, mientras que los novillitos pesados representaron el 27% del total de novillitos. En la literatura hay evidencias que indican que las diferencias en terneza generadas por variaciones en la edad o por el sexo no justificarían tales desviaciones en los precios. En un sistema de producción pastoril con una ganancia diaria de peso vivo media de 500 g, producir una vaquillona pesada en vez de una liviana demandaría aproximadamente 5 meses más. Si bien Wulf et al. (1996) observaron que lag fuerza de corte (dureza) de distintos cortes de carne de novillos en el rango de 15 a 18 meses de edad terminados en dietas a base de concentrados se correlacionaba positivamente con la edad, el coeficiente de correlación fue relativamente bajo (r=0.18). Sin embargo, dado que en este trabajo los animales fueron faenados a medida que alcanzaban los 400 kg de peso vivo o 1 cm de espesor de grasa dorsal, habría un efecto confundido de la edad y la tasa de ganancia de peso sobre la terneza (Perry and Thompson, 2005). Por otra parte, Field et al. (1996) no observaron diferencias en la terneza del músculo longissimus dorsi de vaquillonas faenadas a 31, 33 y 35 meses de edad luego de 100 d de alimentación con concentrados. Lawrence et al. (2001) al evaluar el efecto de la edad (determinada por el número de incisivos permanentes: 0, 2, 4, 6, y 8), el sexo (vaquillonas vs. novillos) y su interacción sobre la terneza del músculo longissimus dorsi tampoco encontraron diferencias significativas. Si bien en el trabajo de Zinn et al., (1970) el sexo (vaquillonas vs. novillos) no afectó la terneza de tres músculos (Triceps brachii, longissimus dorsi y Semimenbranosus) de animales terminados con dietas concentradas, Choat et al. (2006) reportan que, con 7 d de maduración, la terneza del músculo longissimus dorsi fue menor en vaquillonas que en novillos. Sin embargo, dicha diferencia desapareció al incrementar el tiempo de maduración de la carne. El presente trabajo busca definir elementos biológicos que ayuden a establecer el valor de la carne producida de forma más objetiva. Así el primer objetivo del presente trabajo fue el de comparar la fuerza de corte (terneza) de los músculos longissimus y gluteus medius de vaquillonas pesadas con la de los mismos músculos de vaquillonas livianas, novillitos pesados, o vacas de refugo. El segundo objetivo fue el de determinar si posibles diferencias en la fuerza de corte del producto obtenido con las distintas categorías o con distintos músculos pueden ser eliminadas con un mayor tiempo de maduración.Fil: Lucero Borja, J. Universidad Nacional de Mar del Plata; ArgentinaFil: Pouzo, Laura Beatriz. Universidad Nacional de Mar del Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Langman, L.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación de Agroindustria. Instituto de Tecnología de Alimentos; ArgentinaFil: Carduza, F.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación de Agroindustria. Instituto de Tecnología de Alimentos; ArgentinaFil: Corva, P.. Universidad Nacional de Mar del Plata; ArgentinaFil: Santini, Francisco Jose. Universidad Nacional de Mar del Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Pavan, E.. Universidad Nacional de Mar del Plata; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

    Risk factors for squamous cell carcinoma of the oesophagus in women: a case–control study

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    Oesophageal cancer rates in women in the UK are more than 3 times higher than in most other European populations. A population-based matched case–control study of histologically confirmed squamous cell carcinoma of the oesophagus in women was carried out in 4 regions in England and Scotland. Interviews were carried out in hospital or at home and topics included: smoking; alcohol; tea and coffee consumption; medical and obstetric history; and diet. Response rates were 62% for cases and 65% for first-chosen controls. There were 159 case–control pairs. Significant results were found for: eating salads (odds ratio (OR) 0.42, 95% CI 0.20–0.92 in the highest quartile of consumption) and a light (as distinct from no) breakfast (OR 0.18, 95% CI 0.07 – 0.48) were protective; quantity of tea was a risk factor and there was a significant positive trend with temperature at which hot drinks were consumed (P = 0.03). Alcohol consumption was unrelated to risk, but there was a significant trend with years of smoking (P = 0.015). A protective effect of aspirin consumption was confined to the English centres (OR 0.08, 95% CI 0.01–0.56). Comparison with a parallel study of adenocarcinoma indicated a common protective effect of a healthy diet but otherwise distinct risk factors. © 2001 Cancer Research Campaign http://www.bjcancer.co

    The antecedents of biliary cancer: a primary care case–control study in the United Kingdom

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    In a case–control study using a large UK primary care database, we found that non-steroidal anti-inflammatory drugs had no protective effect against biliary carcinomas (cholangiocarcinoma and gall bladder cancer). Increased risks were observed for cigarette smoking, diabetes, gallstone disease and obesity

    Rizatriptan versus rizatriptan plus rofecoxib versus rizatriptan plus tolfenamic acid in the acute treatment of migraine

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    BACKGROUND: Rizatriptan is an effective and fast acting drug for the acute treatment of migraine. Some nonsteroidal anti-inflammatory drugs (NSAID) have also demonstrated efficacy in treating migraine attacks. There is evidence that the combination of a triptan and a NSAID decreases migraine recurrence in clinical practice. The primary aim of this randomized open label study was to assess the recurrence rates in migraine sufferers acutely treated with rizatriptan (RI) alone vs. rizatriptan plus a COX-2 enzyme inhibitor (rofecoxib, RO) vs. rizatriptan plus a traditional NSAID (tolfenamic acid, TO). We were also interested in comparing the efficacy rates within these three groups. METHODS: We assessed 45 patients from a headache clinic in Rio de Janeiro (35 women and 10 men, ages 18 to 65 years, mean 37 years). Patients with IHS migraine were randomized to one out of 3 groups, where they had to treat 6 consecutive moderate or severe attacks in counterbalanced order. In group 1, patients treated the first two attacks with 10 mg RI, the third and fourth attacks with RI + 50 mg RO and the last attacks with RI + 200 mg of TA. In group 2, we began with RI + TA, followed by RI, and RI + RO. Group 3 treated in the following order: RI + RO, RI + TA, RI alone. The presence of headache, nausea and photophobia at 1, 2 and 4 hours, as well as recurrence and side effects were compared. RESULTS: A total of 33 patients finished the study, treating 184 attacks. The pain-free rates at 1 hour were: RI: 15.5%; RI + RO: 22.6%; RI + TA: 20.3%(NS). Pain-free rates at 2 h were: RI: 37.9%; RI + RO: 62.9%, and RI + TA: 40.6% (p = 0.008 for RI vs. RI + RO; p = 0.007 for RI + RO vs. RI + TA, NS for RI vs RI + TA). At 4 h, pain-free rates were: RI: 69%; RI + RO: 82.3%; RI + TA: 78.1% (NS for all comparisons). The combination of RI + RO was superior to RI and to RI + TA in regard of the absense of nausea and photophobia at 4 hours. Recurrence (after being pain-free at 2 h) was observed in 50% of patients treated with RI, in 15,4% of those treated with RI + RO, and in 7,7% of those treated with RI + TA. CONCLUSIONS: Despite the methodological limitations of this study, the combination of RI and RO revealed a higher response rate at 2 hours. Recurrence was also clearly decreased with both combinations in relation to the use of RI alone. Controlled studies are necessary to provide additional evidence
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