661 research outputs found

    The 250AH/90A active lithium-thionyl chloride cell for Centaur-G application

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    A high rate active Li/SOCl2 cell was designed for use in a 28 volt, 250 amp-hour space battery system. The lithium battery is being considered as a replacement of its heavier silver-zinc counterpart on board the Centaur-G booster rocket which is used to launch payloads from the Space Shuttle cargo bay into deep-space. Basically a feasibility study, this development effort is demonstrating the ability of the lithium cell to deliver up to 90 amps safely at power densities of approximately 25 watts per pound. Test data on 4 prototype units is showing an energy density of 85 watt-hours per pound and 9.0 watt-hours/cu in. The cells tested typically delivered 280 to 300 amp-hours under ambient temperature test conditions using alternating continuous loads of 90, 55, and 20 amperes throughout life. Data from four cells tested are presented to demonstrate the capability of Li/SOCl2 technology for a C/3 discharge rate in active and hermetic cell units

    Entangled symmetric states of N qubits with all positive partial transpositions

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    From both theoretical and experimental points of view symmetric states constitute an important class of multipartite states. Still, entanglement properties of these states, in particular those with positive partial transposition (PPT), lack a systematic study. Aiming at filling in this gap, we have recently affirmatively answered the open question of existence of four-qubit entangled symmetric states with positive partial transposition and thoroughly characterized entanglement properties of such states [J. Tura et al., Phys. Rev. A 85, 060302(R) (2012)] With the present contribution we continue on characterizing PPT entangled symmetric states. On the one hand, we present all the results of our previous work in a detailed way. On the other hand, we generalize them to systems consisting of arbitrary number of qubits. In particular, we provide criteria for separability of such states formulated in terms of their ranks. Interestingly, for most of the cases, the symmetric states are either separable or typically separable. Then, edge states in these systems are studied, showing in particular that to characterize generic PPT entangled states with four and five qubits, it is enough to study only those that assume few (respectively, two and three) specific configurations of ranks. Finally, we numerically search for extremal PPT entangled states in such systems consisting of up to 23 qubits. One can clearly notice regularity behind the ranks of such extremal states, and, in particular, for systems composed of odd number of qubits we find a single configuration of ranks for which there are extremal states.Comment: 16 pages, typos corrected, some other improvements, extension of arXiv:1203.371

    Studio dell'influenza genotipo-ambiente sulle caratteristiche qualitative dell'olio vergine di oliva (Olea europea L.)

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    The quality of virgin olive oil depends on cultivar, environment, orchard management, oil extraction and storage technology. The aim of this PhD project was to investigate the cultivar and environmental influences on virgin olive oil quality during 4 years (1998-2001). The first goal (cultivar influence) was divided in three aspects: chemiometric (61 oils from 18 cultivars), enzymatic (22 olive samples from 3 cultivars at different ripening stages) and aromatic (40 commercial oils). The second goal (environmental influence) was divided in two parts: mesoclimate effect (77 oils of 4 cultivars from 17 orchards in western cost of lake Garda, northern Italy) and macroclimate effect (33 oils of 3 cultivars at three ripening stages from different Italian regions). The analytical determinations on oils were: fatty acids, triglycerides, aliphatic and triterpenic alcohols, sterols, polyphenols, tocopherols, pigments, volatile compounds, oxidative stability and sensory analysis. The cultivar resulted the most important factor influencing the oil quality, while the environment was less important in influencing the oil orchard origin in Garda area, whereas it was more significant in separating the cultivar and the origin from different region. Some cultivars were similar according to chemical profile, whereas others resulted well distinct and characterized. In addition, the oxidative stability was correlated to total polyphenols, saturated on polyunsaturated fatty acids ratio and total tocopherols

    Four-qubit entangled symmetric states with positive partial transpositions

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    We solve the open question of the existence of four-qubit entangled symmetric states with positive partial transpositions (PPT states). We reach this goal with two different approaches. First, we propose a half-analytical-half-numerical method that allows to construct multipartite PPT entangled symmetric states (PPTESS) from the qubit-qudit PPT entangled states. Second, we adapt the algorithm allowing to search for extremal elements in the convex set of bipartite PPT states [J. M. Leinaas, J. Myrheim, and E. Ovrum, Phys. Rev. A 76, 034304 (2007)] to the multipartite scenario. With its aid we search for extremal four-qubit PPTESS and show that generically they have ranks (5,7,8). Finally, we provide an exhaustive characterization of these states with respect to their separability properties.Comment: 5+4 pages, improved version, title slightly modifie

    Genotype-environment-year interaction on oil antioxidants in an olive district of Northern Italy

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    A two-year survey in 18 representative groves of a north Italian olive district sampled cvs. 'Caltivar' and 'Leccino' for single-site oils. Polyphenols had a major role in determining oil autoxidation stability with respect to tocopherols, even if the higher autoxidation stability of 'Leccino' over 'Casaliva' was probably due to the more than double content in tocopherols, which was significantly affected by years. In spite of the large variations both in oil and in environmental parameters, no statistically significant model emerged for relations between antioxidants oil content and site parameters

    Evaluation of Hemp Seed Oils Stability under Accelerated Storage Test

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    The interest in hemp seed oil has recently increased, due to the latest regulations which allow its use as food. Hemp seed oil is characterized by a high content of polyunsaturated fatty acids, which are highly prone to oxidation. Accelerated thermal oxidation (60 °C, 18 days) has been applied to nine types of cold-pressed hemp seed oils to monitor the evolution of the samples during oxidative deterioration. The results showed that the only determinations of primary (peroxide value) and secondary (TBARs) oxidation products did not allow a sufficient or correct evaluation of the oxidative changes of hemp seed oils during storage. In fact, samples at the end of the test were primarily characterized by a high presence of oxidation volatile compounds and a significant decrease of antioxidants. Several volatiles identified before the accelerated storage, such as the predominant α-pinene and β-pinene, gradually decreased during the accelerated storage period. On the other hand, aldehydes (hexanal, (E)-2-hexenal, heptanal, (E,E)-2,4-hexadienal, (E)-2-heptenal, (E,E)-2,4-heptadienal, (E,Z)-2,4-heptadienal, 2-octenal, nonanal, nonenal, 2,4-nonadienal, (E,E)-2,4-decadienal and 2,4-decadienal), ketones (1-octen-3-one, 3-octen-2-one, (E,E)-3,5-octadien-2-one and 3,5-octadien-2-one), acids (propionic acid, pentanoic acid, hexanoic acid and heptanoic acid) and 2pentyl-furan increased during the accelerated storage, as principal markers of oxidation

    A Plant-Based Dietary Intervention Improves Beta-Cell Function and Insulin Resistance in Overweight Adults: A 16-Week Randomized Clinical Trial.

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    The aim of this study was to test the effect of a plant-based dietary intervention on beta-cell function in overweight adults with no history of diabetes. Participants (n = 75) were randomized to follow a low-fat plant-based diet (n = 38) or to make no diet changes (n = 37) for 16 weeks. At baseline and 16 weeks, beta-cell function was quantified with a mathematical model. Using a standard meal test, insulin secretory rate was calculated by C-peptide deconvolution. The Homeostasis Model Assessment (HOMA-IR) index was used to assess insulin resistance while fasting. A marked increase in meal-stimulated insulin secretion was observed in the intervention group compared with controls (interaction between group and time, Gxt, p \u3c 0.001). HOMA-IR index fell significantly (p \u3c 0.001) in the intervention group (treatment effect −1.0 (95% CI, −1.2 to −0.8); Gxt, p = 0.004). Changes in HOMA-IR correlated positively with changes in body mass index (BMI) and visceral fat volume (r = 0.34; p = 0.009 and r = 0.42; p = 0.001, respectively). The latter remained significant after adjustment for changes in BMI (r = 0.41; p = 0.002). Changes in glucose-induced insulin secretion correlated negatively with BMI changes (r = −0.25; p = 0.04), but not with changes in visceral fat. Beta-cell function and insulin sensitivity were significantly improved through a low-fat plant-based diet in overweight adult

    Sensory and chemical analyses of monovarietal olive oils from lake Garda (Northern Italy)

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    The qualitative description of an olive oil should be based not only on chemical and physical analyses but also on sensory evaluation. The present study was designed to evaluate by sensory analysis the monovarietal oils from olive accessions in a germplasm collection in northern Italy\u2019s Lake Garda area. Relationships of chemical and sensory evaluation were studied by correlation and multiple regression analysis. Olive accessions were successfully classified by oil sensory profile. A rather good agreement among sensory traits and chemical analysis of volatile compounds and polyphenols was found

    Solid-phase microextraction in the analysis of the volatile fraction of extra-virgin olive oil from fourteen cultivars grown in the lake Garda region (Italy)

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    Forty-one volatile compounds were identified in virgin olive oils from fourteen cultivars grown near Lake Garda, Italy, using headspace solid-phase microextraction cupled with gas chromatography/mass spectrometry. Analyses of oils from olives with comparable ripeness indices showed that C6 volatile compounds, enzymatically produced through the lipoxygenase pathway, accounted for 77.4% - 94.3% of the total volatile fraction. The C5 volatile compounds, which are not derived from the lipoxygenase pathway, accounted for 1.6% \u2013 8.4% of the total volatile fraction
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