651 research outputs found

    Device for producing and enclosing a hot plasma

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    1391103 High-frequency discharge tubes EUROPEAN ATOMIC ENERGY COM- MUNITY 24 July 1972 [23 July 1971] 34566/72 Heading H1D A device for producing and enclosing a hot plasma comprises a toroidal vessel 1 having means 2 for generating a magnetic field along the azimuthal axis 3 of the torus to induce annular electric currents along said axis, and means 6, 7 for generating an oscillating electric field in the vessel having a component parallel to the magnetic field and a frequency at or near the bounce frequency (i.e. about ten times the collison frequency of ions.) A second toroidal vessel or liner 4 is disposed in the first vessel 1, and the diameter of the plasma is limited by annular discs 5. The electric field is generated by annular electrodes 6 and 7 disposed above and below the axis 3 and connected through insulated ducts 8 to a generator producing oscillations having a fre- quency between 10 and 100 KHz. The electric field may alternatively be produced by an aerial disposed in an aperture in the vessel wall and fed with a signal having a fundamental frequency corresponding to the plasma frequency which is amplitude modulated at the bounce frequency

    An estimate of attributable cases of alzheimer disease and vascular dementia due to modifiable risk factors. the impact of primary prevention in europe and in italy

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    Background: Up to 53.7% of all cases of dementia are assumed to be due to Alzheimer disease (AD), while 15.8% are considered to be due to vascular dementia (VaD). In Europe, about 3 million cases of AD could be due to 7 potentially modifiable risk factors: diabetes, midlife hypertension and/or obesity, physical inactivity, depression, smoking, and low educational level. Aims: To estimate the number of VaD cases in Europe and the number of AD and VaD cases in Italy attributable to these 7 potentially modifiable risk factors. Methods: Assuming the nonindependence of the 7 risk factors, the adjusted combined population attributable risk (PAR) was estimated for AD and VaD. Results: In Europe, adjusted combined PAR was 31.4% for AD and 37.8% for VaD. The total number of attributable cases was 3,033,000 for AD and 873,000 for VaD. In Italy, assuming a 20% reduction of the prevalence of each risk factor, adjusted combined PAR decreased from 45.2 to 38.9% for AD and from 53.1 to 46.6% for VaD, implying a 6.4 and 6.5% reduction in the prevalence of AD and VaD, respectively. Conclusion: A relevant reduction of AD and VaD cases in Europe and Italy could be obtained through primary prevention

    PM2.5 Size Distribution and Characterization by Carbon Isotope in Tuscany (Italy)

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    This study is focused on the numerical distribution and isotopic description of PM2.5 developed within the PATOS II (Particolato Atmosferico TOScana) regional project about the characterization and source apportionment of atmospheric aerosol (PM2.5) in Tuscany. PM isotopic analysis can play an important role in the individuation of primary and secondary sources and also in the determination of the natural/biogenic or anthropogenic/combustion contribution to the measured concentration. In addition, the PM2.5 particle number concentrations and the relative contribution of ultrafine particles are interpreted to identify the emission sources, the main atmospheric processes and the factors related with the dispersion of atmospheric pollutants. The analytical results in term of δ13C parameter show a greater variability in the urban and suburban background sites than in the urban traffic site, where the δ13C parameter does not vary significantly: this could be strictly correlated with traffic emissions and independently from the total particles number. On the contrary, urban and suburban background sites are affected by the meteorology and atmospheric processes. For this reason we can observe a wider variability in the δ13C values due to the contribution of different emissions sources. Despite all, in urban background we can observe lower δ13C values related with high number of total particles; this effect could be related with a traffic emission transport, because the δ13C parameter is similar to the δ13C value of urban traffic site

    General quasi-non-spreading linear three-dimensional wave-packets

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    We introduce a general approach for generation of sets of three-dimensional quasi-non-spreading wavepackets propagating in linear media, also referred to as linear light bullets. The spectrum of rigorously non-spreading wavepackets in media with anomalous group velocity dispersion is localized on the surface of a sphere, thus drastically restricting the possible wavepacket shapes. However, broadening slightly the spectrum affords the generation of a large variety of quasi-non-spreading distributions featuring complex topologies and shapes in space and time that are of interest in different areas, such as biophysics or nanosurgery. Here we discuss the method and show several illustrative examples of its potential.Comment: 3 pages, 4 figures, to appear in Optics Letter

    Efficient magneto-optical trapping of a metastable helium gas

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    This article presents a new experiment aiming at BEC of metastable helium atoms. It describes the design of a high flux discharge source of atoms and a robust laser system using a DBR diode coupled with a high power Yb doped fiber amplifier for manipulating the beam of metastable atoms. The atoms are trapped in a small quartz cell in an extreme high vacuum. The trapping design uses an additional laser (repumper) and allows the capture of a large number of metastable helium atoms (approximately 10910^9) in a geometry favorable for loading a tight magnetostatic trap.Comment: 12 pages, 7 figures, Late

    Expansion of a coherent array of Bose-Einstein condensates

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    We investigate the properties of a coherent array containing about 200 Bose-Einstein condensates produced in a far detuned 1D optical lattice. The density profile of the gas, imaged after releasing the trap, provides information about the coherence of the ground-state wavefunction. The measured atomic distribution is characterized by interference peaks. The time evolution of the peaks, their relative population as well as the radial size of the expanding cloud are in good agreement with the predictions of theory. The 2D nature of the trapped condensates and the conditions required to observe the effects of coherence are also discussed.Comment: 4 pages, 3 figure

    Plasmas and Controlled Nuclear Fusion

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    Contains reports on three research projects.U. S. Atomic Energy Commission (Contract AT(11-1)-3070
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