550 research outputs found

    Alpine Space Prospective Study. Sustainable territorial development in the Alpine Space: Towards long term transnational cooperation

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    This "Prospective Study" argues that a long term transnational cooperation will be able to pursue the sustainable territorial development in the Alpine Space only at the condition of a substantial improvement of the current experience. This regards an increased awareness of the complexity of issues and challenges currently at stake in the Alpine area but especially, in this light, the capacity of involving all relevant institutional and socioeconomic stakeholders in the building of shared transnational strategie

    Alpine Space Prospective Study. Sustainable territorial development in the Alpine Space: Towards long term transnational cooperation

    Get PDF
    This "Prospective Study" argues that a long term transnational cooperation will be able to pursue the sustainable territorial development in the Alpine Space only at the condition of a substantial improvement of the current experience. This regards an increased awareness of the complexity of issues and challenges currently at stake in the Alpine area but especially, in this light, the capacity of involving all relevant institutional and socioeconomic stakeholders in the building of shared transnational strategies

    Modulation induced frequency shifts in a CPT-based atomic clock

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    We investigate systematic errors associated with a common modulation technique used for phase sensitive detection of a coherent population trapping (CPT) resonance. In particular, we show that modification of the CPT resonance lineshape due to the presence of off-resonant fields leads to frequency shifts which may limit the stability of CPT-based atomic clocks. We also demonstrate that an alternative demodulation technique greatly reduces these effects.Comment: 14 pages, 7 figure

    Pulsed beams as field probes for precision measurement

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    We describe a technique for mapping the spatial variation of static electric, static magnetic, and rf magnetic fields using a pulsed atomic or molecular beam. The method is demonstrated using a beam designed to measure the electric dipole moment of the electron. We present maps of the interaction region, showing sensitivity to (i) electric field variation of 1.5 V/cm at 3.3 kV/cm with a spatial resolution of 15 mm; (ii) magnetic field variation of 5 nT with 25 mm resolution; (iii) radio-frequency magnetic field amplitude with 15 mm resolution. This new diagnostic technique is very powerful in the context of high-precision atomic and molecular physics experiments, where pulsed beams have not hitherto found widespread application.Comment: 6 pages, 12 figures. Figures heavily compressed to comply with arxiv's antediluvian file-size polic

    Metrological characterization of the pulsed Rb clock with optical detection

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    We report on the implementation and the metrological characterization of a vapor-cell Rb frequency standard working in pulsed regime. The three main parts that compose the clock, physics package, optics and electronics, are described in detail in the paper. The prototype is designed and optimized to detect the clock transition in the optical domain. Specifically, the reference atomic transition, excited with a Ramsey scheme, is detected by observing the interference pattern on a laser absorption signal. \ The metrological analysis includes the observation and characterization of the clock signal and the measurement of frequency stability and drift. In terms of Allan deviation, the measured frequency stability results as low as 1.7×1013 τ1/21.7\times 10^{-13} \ \tau^{-1/2}, τ\tau being the averaging time, and reaches the value of few units of 101510^{-15} for τ=104\tau=10^{4} s, an unprecedent achievement for a vapor cell clock. We discuss in the paper the physical effects leading to this result with particular care to laser and microwave noises transferred to the clock signal. The frequency drift, probably related to the temperature, stays below 101410^{-14} per day, and no evidence of flicker floor is observed. \ We also mention some possible improvements that in principle would lead to a clock stability below the 101310^{-13} level at 1 s and to a drift of few units of 101510^{-15} per day

    Investigation of microwave transitions and nonlinear magneto-optical rotation in anti-relaxation-coated cells

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    Using laser optical pumping, widths and frequency shifts are determined for microwave transitions between ground-state hyperfine components of 85^{85}Rb and 87^{87}Rb atoms contained in vapor cells with alkane anti-relaxation coatings. The results are compared with data on Zeeman relaxation obtained in nonlinear magneto-optical rotation (NMOR) experiments, a comparison important for quantitative understanding of spin-relaxation mechanisms in coated cells. By comparing cells manufactured over a forty-year period we demonstrate the long-term stability of coated cells, an important property for atomic clocks and magnetometers

    Mean field ground state of a spin-1 condensate in a magnetic field

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    We revisit the topic of the mean field ground state of a spin-1 atomic condensate inside a uniform magnetic field (BB) under the constraints that both the total number of atoms (NN) and the magnetization (M\cal M) are conserved. In the presence of an internal state (spin component) independent trap, we also investigate the dependence of the so-called single spatial mode approximation (SMA) on the magnitude of the magnetic field and M{\cal M}. Our result indicate that the quadratic Zeeman effect is an important factor in balancing the mean field energy from elastic atom-atom collisions that are known to conserve both NN and M\cal M.Comment: 13 pages, 9 figures, to be published in New J. Phys. (http://www.njp.org/

    Parity nonconservation in Atomic Zeeman Transitions

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    We discuss the possibility of measuring nuclear anapole moments in atomic Zeeman transitions and perform the necessary calculations. Advantages of using Zeeman transitions include variable transition frequencies and the possibility of enhancement of parity nonconservation effects

    Glucosylceramidase Mass and Subcellular Localization Are Modulated by Cholesterol in Niemann-Pick Disease Type C

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    Niemann-Pick disease type C (NPC) is characterized by the accumulation of cholesterol and sphingolipids in the late endosomal/lysosomal compartment. The mechanism by which the concentration of sphingolipids such as glucosylceramide is increased in this disease is poorly understood. We have found that, in NPC fibroblasts, the cholesterol storage affects the stability of glucosylceramidase (GCase), decreasing its mass and activity; a reduction of cholesterol raises the level of GCase to nearly normal values. GCase is activated and stabilized by saposin C (Sap C) and anionic phospholipids. Here we show by immunofluorescence microscopy that in normal fibroblasts, GCase, Sap C, and lysobisphosphatidic acid (LBPA), the most abundant anionic phospholipid in the endolysosomal system, reside in the same intracellular vesicular structures. In contrast, the colocalization of GCase, Sap C, and LBPA is markedly impaired in NPC fibroblasts but can be re-established by cholesterol depletion. These data show for the first time that the level of cholesterol modulates the interaction of GCase with its protein and lipid activators, namely Sap C and LBPA, regulating the GCase activity and stability

    Compostos fenólicos e atividade antioxidante de grãos de arroz de pericarpo vermelho e de pericarpo preto.

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    Objetivou-se, com o presente estudo, avaliar o teor de compostos fenólicos livres e complexados e a atividade antioxidante pelo método ABTS, tanto da fração de fenólicos livres como de fenólicos complexados, de grãos de duas cultivares de arroz de pericarpo preto (IAC 600 e SCS 120) e de duas cultivares de arroz de pericarpo vermelho (BRS 902 e SCS 119).Os grãos de arroz foram colhidos no campo experimental da Embrapa Arroz e Feijão, em Santo Antônio de Goiás, Goiás, Brasil
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