165 research outputs found

    From spin-Peierls to superconductivity: (TMTTF)_2PF_6 under high pressure

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    The nature of the attractive electron-electron interaction, leading to the formation of Cooper-pairs in unconventional superconductors has still to be fully understood and is subject to intensive research. Here we show that the sequence spin-Peierls, antiferromagnetism, superconductivity observed in (TMTTF)_2PF_6 under pressure makes the (TM)_2X phase diagram universal. We argue that the suppression of the spin-Peierls transition under pressure, the close vicinity of antiferromagnetic and superconducting phases at high pressure as well as the existence of critical antiferromagnetic fluctuations above T_c strongly support the intriguing possibility that the interchain exchange of antiferromagnetic fluctuations provides the pairing mechanism required for bound charge carriers.Comment: 4 pages, revtex, 4 figures (jpeg,eps,png

    A Comparative Study of the Effectiveness of Adaptive Filter Algorithms, Spectral Kurtosis and Linear Prediction in Detection of a Naturally Degraded Bearing in a Gearbox

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    Diagnosing bearing faults at the earliest stages is critical in avoiding future catastrophic failures. Many techniques have been developed and applied in diagnosing bearings faults; however, these traditional diagnostic techniques are not always successful when the bearing fault occurs in gearboxes where the vibration response is complex; under such circumstances, it may be necessary to separate the bearing signal from the complex signal. In this paper, an adaptive filter has been applied for the purpose of bearing signal separation. Four algorithms were compared to assess their effectiveness in diagnosing a bearing defect in a gearbox, least mean square (LMS), linear prediction, spectral kurtosis and fast block LMS. These algorithms were applied to decompose the measured vibration signal into deterministic and random parts with the latter containing the bearing signal. These techniques were applied to identify a bearing fault in a gearbox employed for an aircraft control system for which endurance tests were performed. The results show that the LMS algorithm is capable of detecting the bearing fault earlier in comparison with the other algorithms

    Dielectric response of charge induced correlated state in the quasi-one-dimensional conductor (TMTTF)2PF6

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    Conductivity and permittivity of the quasi-one-dimensionsional organic transfer salt (TMTTF)2PF6 have been measured at low frequencies (10^3-10^7 Hz) between room temperature down to below the temperature of transition into the spin-Peierls state. We interpret the huge real part of the dielectric permittivity (up to 10^6) in the localized state as the realization in this compound of a charge ordered state of Wigner crystal type due to long range Coulomb interaction.Comment: 11 pages, 3 .eps figure

    On the effect of ultrasound-assisted atmospheric freeze-drying on the antioxidant properties of eggplant

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    [EN] The low operating temperatures employed in atmospheric freeze-drying permits an effective drying of heat sensitive products, without any impairment of their quality attributes. When using power ultrasound, the drying rate can be increased, thus reducing the process duration. However, ultrasound can also affect the product quality. The aim of this study was to evaluate the effect of various drying process variables, namely air temperature and velocity, ultrasound power and sample size, on the antioxidant properties of eggplant (Solanum Melongena L.) samples. For this reason, drying experiments were carried out at different drying temperatures (-5, -7.5, -10 °C), power ultrasound levels (0, 25, 50 W; 21.9 kHz) and air velocities (2, 5 m s-1) using different sample sizes (8.8 mm and 17.6 mm cube side). The ascorbic acid content (Jagota and Dani method), total phenolic content (Folin-Ciocalteau method), and the antioxidant capacity (FRAP method) of the dried products were considered as quality indicators of the dried samples. The increase in air velocity and temperature, as well as the sample size, significantly reduced the antioxidant potential of the dried samples (p-value < 0.05). For a given sample size, the application of ultrasound, at the acoustic power levels tested, did not produce significant effects on the antioxidant indicators considered. Temperature measurements inside the drying sample showed a non-negligible temperature rise when acoustic power was applied.The authors acknowledge the financial support from Generalitat Valenciana (PROMETEOII/2014/005) and INIA-ERDF (RTA2015-00060-C04-02).Colucci, D.; Fisore, D.; Rosselló, C.; Carcel Carrión, JA. (2018). On the effect of ultrasound-assisted atmospheric freeze-drying on the antioxidant properties of eggplant. Food Research International. 106:580-588. https://doi.org/10.1016/j.foodres.2018.01.022S58058810

    Results of the BiPo-1 prototype for radiopurity measurements for the SuperNEMO double beta decay source foils

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    The development of BiPo detectors is dedicated to the measurement of extremely high radiopurity in 208^{208}Tl and 214^{214}Bi for the SuperNEMO double beta decay source foils. A modular prototype, called BiPo-1, with 0.8 m2m^2 of sensitive surface area, has been running in the Modane Underground Laboratory since February, 2008. The goal of BiPo-1 is to measure the different components of the background and in particular the surface radiopurity of the plastic scintillators that make up the detector. The first phase of data collection has been dedicated to the measurement of the radiopurity in 208^{208}Tl. After more than one year of background measurement, a surface activity of the scintillators of A\mathcal{A}(208^{208}Tl) == 1.5 μ\muBq/m2^2 is reported here. Given this level of background, a larger BiPo detector having 12 m2^2 of active surface area, is able to qualify the radiopurity of the SuperNEMO selenium double beta decay foils with the required sensitivity of A\mathcal{A}(208^{208}Tl) << 2 μ\muBq/kg (90% C.L.) with a six month measurement.Comment: 24 pages, submitted to N.I.M.

    Influence of temperature and ultrasound on drying kinetics and antioxidant properties of red pepper

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    This is an Author's Accepted Manuscript of J. A. Cárcel, D. Castillo, S. Simal & A. Mulet (2019) Influence of temperature and ultrasound on drying kinetics and antioxidant properties of red pepper, Drying Technology, 37:4, 486-493, DOI: 10.1080/07373937.2018.1473417 [copyright Taylor & Francis], available online at: http://www.tandfonline.com/10.1080/07373937.2018.1473417[EN] Red pepper samples (1 m/s) were dried at different temperatures (30, 50, 70 degrees C) without and with (20.5 kW/m(3); 21.7 kHz) ultrasound application. The antioxidant capacity (AC), the total phenolic content (TPC), and the ascorbic acid (AA) content of fresh and dried red pepper samples were used as indicators of the quality of the dried products. Ultrasound application significantly improved the kinetics in every case, influencing not only the effective diffusivity but also the mass transport coefficient thus implying a reduction in energy needs. Drying significantly reduced AC, TPC, and AA, this reduction being significantly smaller at 70 degrees C due to the shorter drying time. Compared with conventional drying, ultrasound application reduced the loss of antioxidant properties at 50 degrees C but produced greater degradation at 70 degrees C, which points toward an optimal drying temperature when using ultrasound.The authors acknowledge the financial support from Generalitat Valenciana [PROMETEOII/2014/005] and INIA [RTA2015-00060-C04-02 and RTA2015-00060-C04-03].Carcel, JA.; Castillo, D.; Simal, S.; Mulet Pons, A. (2019). Influence of temperature and ultrasound on drying kinetics and antioxidant properties of red pepper. Drying Technology. 37(4):486-493. https://doi.org/10.1080/07373937.2018.1473417S486493374Di Scala, K., & Crapiste, G. (2008). Drying kinetics and quality changes during drying of red pepper. LWT - Food Science and Technology, 41(5), 789-795. doi:10.1016/j.lwt.2007.06.007Doymaz, İ., & Pala, M. (2002). Hot-air drying characteristics of red pepper. Journal of Food Engineering, 55(4), 331-335. doi:10.1016/s0260-8774(02)00110-3Cárcel, J. A., García-Pérez, J. V., Riera, E., Rosselló, C., & Mulet, A. (2017). Ultrasonically Assisted Drying. Ultrasound in Food Processing, 371-391. doi:10.1002/9781118964156.ch14Kowalski, S. J., & Pawłowski, A. (2015). Intensification of apple drying due to ultrasound enhancement. Journal of Food Engineering, 156, 1-9. doi:10.1016/j.jfoodeng.2015.01.023Soria, A. C., & Villamiel, M. (2010). Effect of ultrasound on the technological properties and bioactivity of food: a review. Trends in Food Science & Technology, 21(7), 323-331. doi:10.1016/j.tifs.2010.04.003Do Nascimento, E. M. G. C., Mulet, A., Ascheri, J. L. R., de Carvalho, C. W. P., & Cárcel, J. A. (2016). Effects of high-intensity ultrasound on drying kinetics and antioxidant properties of passion fruit peel. 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Effect of drying in antioxidant activity and changes of ascorbic acid and colour by different drying and storage in Korean red pepper (Capsicum annuum, L.). International Journal of Food Science and Technology, 41(s1), 90-95. doi:10.1111/j.1365-2621.2006.01349.xCarrillo Montes, J. P., Cruz y Victoria, M. T., Anaya Sosa, I., & Santiago Pineda, T. (2010). Quality assessment of dehydrated red bell pepper using tempering drying cycles. International Journal of Food Science & Technology, 45(6), 1270-1276. doi:10.1111/j.1365-2621.2010.02273.xMoreno, C., Brines, C., Mulet, A., Rosselló, C., & Cárcel, J. A. (2017). Antioxidant potential of atmospheric freeze-dried apples as affected by ultrasound application and sample surface. Drying Technology, 35(8), 957-968. doi:10.1080/07373937.2016.1256890Wang, J., Fang, X.-M., Mujumdar, A. S., Qian, J.-Y., Zhang, Q., Yang, X.-H., … Xiao, H.-W. (2017). Effect of high-humidity hot air impingement blanching (HHAIB) on drying and quality of red pepper (Capsicum annuum L.). Food Chemistry, 220, 145-152. doi:10.1016/j.foodchem.2016.09.200Garau, M. C., Simal, S., Rosselló, C., & Femenia, A. (2007). Effect of air-drying temperature on physico-chemical properties of dietary fibre and antioxidant capacity of orange (Citrus aurantium v. Canoneta) by-products. Food Chemistry, 104(3), 1014-1024. doi:10.1016/j.foodchem.2007.01.009Ahmad-Qasem, M. H., Barrajón-Catalán, E., Micol, V., Mulet, A., & García-Pérez, J. V. (2013). Influence of freezing and dehydration of olive leaves (var. Serrana) on extract composition and antioxidant potential. Food Research International, 50(1), 189-196. doi:10.1016/j.foodres.2012.10.028López, J., Uribe, E., Vega-Gálvez, A., Miranda, M., Vergara, J., Gonzalez, E., & Di Scala, K. (2010). 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    Neurodegeneration and Epilepsy in a Zebrafish Model of CLN3 Disease (Batten Disease)

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    The neuronal ceroid lipofuscinoses are a group of lysosomal storage disorders that comprise the most common, genetically heterogeneous, fatal neurodegenerative disorders of children. They are characterised by childhood onset, visual failure, epileptic seizures, psychomotor retardation and dementia. CLN3 disease, also known as Batten disease, is caused by autosomal recessive mutations in the CLN3 gene, 80–85% of which are a ~1 kb deletion. Currently no treatments exist, and after much suffering, the disease inevitably results in premature death. The aim of this study was to generate a zebrafish model of CLN3 disease using antisense morpholino injection, and characterise the pathological and functional consequences of Cln3 deficiency, thereby providing a tool for future drug discovery. The model was shown to faithfully recapitulate the pathological signs of CLN3 disease, including reduced survival, neuronal loss, retinopathy, axonopathy, loss of motor function, lysosomal storage of subunit c of mitochondrial ATP synthase, and epileptic seizures, albeit with an earlier onset and faster progression than the human disease. Our study provides proof of principle that the advantages of the zebrafish over other model systems can be utilised to further our understanding of the pathogenesis of CLN3 disease and accelerate drug discovery

    Canonical Variate Analysis for Performance Degradation under Faulty Conditions

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    Condition monitoring of industrial processes can minimize maintenance and operating costs while increasing the process safety and enhancing the quality of the product. In order to achieve these goals it is necessary not only to detect and diagnose process faults, but also to react to them by scheduling the maintenance and production according to the condition of the process. The objective of this investigation is to test the capabilities of canonical variate analysis (CVA) to estimate performance degradation and predict the behaviour of a system affected by faults. Process data was acquired from a large-scale experimental multiphase flow facility operated under changing operational conditions where process faults were seeded. The results suggest that CVA can be used effectively to evaluate how faults affect the process variables in comparison to normal operation. The method also predicted future process behaviour after the appearance of faults, modelling the system using data collected during the early stages of degradation
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