231 research outputs found

    Influencia del riego en precosecha sobre la calidad de manzanas Golden Supreme y Golden Smoothee.

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    El riego, práctica habitual y a la vez indispensable de nuestra fruticultura constituye, en su manejo, uno de los principales factores determinantes de la producción y calidad final del fruto, y sobre el cual el agricultor desempeña un papel indispensable como regulador. A este respecto hay varios estudios que entre si presentan conclusiones dispares. El hecho de aumentar la frecuencia y dosis de riego provoca, según varios autores, una disminución en la firmeza de las manzanas (Asaf et al., 1975), mientras que en otras investigaciones se observa el fenómeno contrario (Reichel y Schmidt, 1983). También hay estudios con resultados dispares en relación al efecto que el riego pueda tener en la acidez titulable y el contenido en sólidos solubles del fruto. No obstante, parece ser que una restricción de riego en precosecha se traduce en un aumento de los sólidos solubles de los frutos (Ramos et al., 1993) y en una disminución de su acidez (Recasens et al., 1988). La fecha de recolección también es un factor muy importante en vistas a una optimización tanto de rendimientos de la plantación como de la aptitud del fruto para su frigoconservación. Recolectar un mismo fruto una semana más tarde implica una pérdida de firmeza durante su frigoconservación de aproximadamente 1,5 N por mes, pasando de unas pérdidas mensuales de 3 N a 4,5 N según se haga la recolección en el momento optimo o después (Duran, 1990). Es este acumulo de discrepancias el que ha motivado el planteamiento de este ensayo para nuestras propias condiciones de cultivo. En él se pretende ver si diferentes fechas de recolección y condiciones de riego pueden influir en la firmeza de los frutos y por tanto en su sensibilidad a la manipulación, aspecto de gran interés en el momento de la cosecha. Asimismo es preciso comprobar que estas prácticas culturales no afecten a la calidad del fruto

    I.B.S. coatings on large substrates: Towards an improvement of the mechanical and optical performances

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    présenté par A. RemillieuxLarge mirrors (350 mm), having extremely low optical loss (absorption, scattering, wavefront) were coated for the VIRGO interferometer. The new mirror generation needs better wavefront and lower mechanical loss. The first results are discussed

    Original optical metrologies of large components

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    présentée par A. RemillieuxThe coating deposition on large optical components (diameter 350 mm) has required the development of new metrology tools at 1064 nm. To give realistic values of the optical performances, the whole surface of the component needs to be scanned. Our scatterometer (commercial system) has been upgraded to support large and heavy samples. The other metrology tools are prototypes we have developed. We can mention the absorption (photothermal effect) and birefringence bench, a control interferometer equipped with an original stitching option, the optical profilometer (RMS roughness and small defect measurements). A detailed description of these metrology benches will be exposed. Their sensitivity, accuracy and capability to map the optical properties of substrates or mirrors will be discussed. We will describe the recent developments: the stitching option adapted to the Micromap profilometer to measure the RMS roughness on larger area (exploration of a new spatial frequency domain), the accurate bulk absorption calibration

    Titania-doped tantala/silica coatings for gravitational-wave detection

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    Reducing thermal noise from optical coatings is crucial to reaching the required sensitivity in next generation interferometric gravitational-wave detectors. Here we show that adding TiO2 to Ta2O5 in Ta2O5/SiO2 coatings reduces the internal friction and in addition present data confirming it reduces thermal noise. We also show that TiO2-doped Ta2O5/SiO2 coatings are close to satisfying the optical absorption requirements of second generation gravitational-wave detectors

    GRANIT project: a trap for gravitational quantum states of UCN

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    Previous studies of gravitationally bound states of ultracold neutrons showed the quantization of energy levels, and confirmed quantum mechanical predictions for the average size of the two lowest energy states wave functions. Improvements in position-like measurements can increase the accuracy by an order of magnitude only. We therefore develop another approach, consisting in accurate measurements of the energy levels. The GRANIT experiment is devoted to the study of resonant transitions between quantum states induced by an oscillating perturbation. According to Heisenberg's uncertainty relations, the accuracy of measurement of the energy levels is limited by the time available to perform the transitions. Thus, trapping quantum states will be necessary, and each source of losses has to be controlled in order to maximize the lifetime of the states. We discuss the general principles of transitions between quantum states, and consider the main systematical losses of neutrons in a trap.Comment: presented in ISINN 15 seminar, Dubn

    Gender specific profiles of white coat and masked hypertension impacts on arterial structure and function in the SardiNIA study

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    Background: There is no definite consensus on the CV burden associated to Masked hypertension (MH) or White Coat Hypertension (WCH)-conditions that can be detected by out-of-office blood pressure measurements (24 hour Ambulatory Blood Pressure Monitoring, 24 h ABPM). Methods: We investigated the association of WCH and MH with arterial aging, indexed by a range of parameters of large artery structure and function in 2962 subjects, taking no antihypertensive medications, who are participating in a large community-based population of both men and women over a broad age range (14-102 years). Results: The overall prevalence of WCH was 9.5% and was 5.0% for MH, with 54.9% of subjects classified as true normotensive and 30.6% as true hypertensive. Both WCH and MH were associated with a stiffer aorta, a less distensible and thicker common carotid artery, and greater central BP than true normotensive subjects. Notably, the profile of arterial alterations in WCH and MH did not significantly differ from what was observed in true hypertensive subjects. The arterial changes accompanying WCH and MH differed in men and women, with women showing a greater tendency towards concentric remodeling, greater parietal wall stress, and PWV than men. Conclusion: Both WCH, and MH are associatedwith early arterial aging, and therefore, neither can be regarded as innocent conditions. Future studies are required to establish whether measurement of arterial aging parameters in subjects with WCH or MHwill identify subjects at higher risk of CV events and cognitive impairment, who may require more clinical attention and pharmacological intervention

    Left ventricular geometric patterns and adaptations to hemodynamics are similar in elderly men and women

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    <p>Abstract</p> <p>Background</p> <p>Common conditions such as obesity and hypertension result in hemodynamic alterations that will induce remodeling of the left ventricle (LV). However, differences between the genders in the relationship of hemodynamics to LV geometry are not well known.</p> <p>The present study aims to investigate differences between the genders in this respect, in a sample of elderly persons.</p> <p>Methods</p> <p>Echocardiography and Doppler was performed in a population-based sample aged 70 - The Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study (n = 922).</p> <p>Hemodynamic patterns obtained by echocardiography and Doppler were evaluated in relation to four LV geometric groups (normal, concentric remodeling, eccentric hypertrophy and concentric hypertrophy).</p> <p>Results</p> <p>No significant difference between the genders was observed regarding the prevalence of the LV geometric groups.</p> <p>Mean values of most evaluated echocardiography and Doppler variables differed between men and women, such as LA, IVS, LVEDD and IVRT, but the relationship of hemodynamic variables to LV geometric groups did not differ between the genders.</p> <p>Conclusions</p> <p>Although mean values of many echocardiographic variables differed between men and women, the LV geometric adaptations to a given hemodynamic load appear similar in both genders.</p

    Assessment of Left Ventricular Geometrical Patterns and Function among Hypertensive Patients at a Tertiary Hospital, Northern Tanzania.

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    With hypertension, the cardiovascular system changes to adapt to the varying neuro-humoral and hemodynamic changes and this may lead to the development of different left ventricular geometric patterns, each carrying a different risk profile for major adverse cardiovascular events. Using a consecutive sampling technique, a cross-sectional, prospective, hospital based study was done and two hundred and twenty seven (227) hypertensive patients were studied. The distribution of different abnormal LV geometrical patterns was 19.8%, 28.2%, 22% for concentric remodelling, concentric hypertrophy and eccentric hypertrophy respectively. With echocardiographic criteria, the proportion of patients with left ventricular hypertrophy (LVH) was higher when left ventricular mass (LVM) was indexed to height(2.7) than to body surface area (70.0% vs. 52.9%). Duration of hypertension markedly influenced the type of LV geometry with normal LV geometry predominating in early hypertension and abnormal geometrical patterns predominating in late hypertension. The left ventricular fractional shortening decreased with duration of hypertension and was common in patients with eccentric hypertrophy. Age of the patient, systolic blood pressure, duration of hypertension and body mass index were found to be independent predictors left ventricular hypertrophy. About 70% of hypertensive patients had abnormal geometry existing in different patterns. Eccentric hypertrophy had more of clinical and echocardiographic features suggestive of reduced left ventricular systolic function. Hypertensive patients should be recognized as a heterogeneous population and therefore stratifying them into their respective LV geometrical patterns is useful as way of assessing their risk profile as well as instituting appropriate management
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