524 research outputs found
Neutrino Oscillations in Intermediate States.II -- Wave Packets
We analyze oscillations of intermediate neutrinos in terms of the scattering
of particles described by Gaussian wave packets. We study a scalar model as in
a previous paper (I) but in realistic situations, where the two particles of
the initial state and final state are wave packets and neutrinos are in the
intermediate state. The oscillation of the intermediate neutrino is found from
the time evolution of the total transition probability between the initial
state and final state. The effect of a finite lifetime and a finite relaxation
time are also studied. We find that the oscillation pattern depends on the
magnitude of wave packet sizes of particles in the initial state and final
state and the lifetime of the initial particle. For eV, the oscillation probability deviates from that of the standard
formula if the wave packet sizes are around m for 0.4 MeV neutrino.Comment: 29 pages, 11 figures. typos corrected, appendix adde
Printable Thermoelectric Device
We have fabricated a printed flexible thermoelectric generator using composite of Bi2Te3 and PEDOT:PSS. The nano-structured thermoelectric thin film was made by printing method and the paste for printing was prepared by mixing nano-particles of Bi2Te3, PEDOT:PSS and polyamic acid as a additives. The non-dimensional figure of merit was 0.2 for p-type composite thin film at room temperature due to the low thermal conductivity. The interfacial thermal resistance between Bi2Te3 and PEDOT:PSS was measured to understand the low effective thermal conductivity of the printed thermoelectric composite. The measured organic-inorganic interfacial thermal resistance is in the order of 10−7 (m2centerdotK)/W which is about 10 times higher than the inorganic-inorganic interfacial thermal resistance. The extremely low thermal conductivity of the printed thermoelectric materials can be explained by high interfacial resistance between inorganic-organic materials.18th International Conference on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerMEMS 2018), 4–7 December 2018, Daytona Beach, Florida, US
Measurement of black carbon at Syowa station, Antarctica: seasonal variation, transport processes and pathways
International audienceMeasurement of black carbon (BC) was carried out at Syowa station Antarctica (69° S, 39° E) from February 2004 until January 2007. The BC concentration at Syowa ranged from below detection to 176 ng m?3 during the measurements. Higher BC concentrations were observed mostly under strong wind (blizzard) conditions due to the approach of a cyclone and blocking event. The BC-rich air masses traveled from the lower troposphere of the Atlantic and Indian Oceans to Syowa (Antarctic coast). During the summer (November?February), the BC concentration showed a diurnal variation together with surface wind speed and increased in the katabatic wind from the Antarctic continent. Considering the low BC source strength in the Antarctic continent, the higher BC concentration in the continental air (katabatic wind) might be caused by long range transport of BC via the free troposphere from mid- and low- latitudes. The seasonal variation of BC at Syowa had a maximum in August, while at the other coastal stations (Halley, Neumayer, and Ferraz) and the continental station (Amundsen-Scott), the maximum occurred in October. This difference may result from different transport pathways and scavenging of BC by precipitation during the transport from the source regions. During the austral summer, long-range transport of BC via the free troposphere is likely to make an important contribution to the ambient BC concentration. The BC transport flux indicated that BC injection into the Antarctic region strongly depended on the frequency of storm (blizzard) conditions. The seasonal variation of BC transport flux increased by 290 mg m?2 month?1 in winter?spring when blizzards frequently occurred, whereas the flux decreased to lower than 50 mg m?2 month?1 in the summer with infrequent blizzards
Properties of aerosols and their wet deposition in the arctic spring during ASTAR2004 at Ny-Alesund, Svalbard
During the period of scientific campaign "Arctic Study of Tropospheric Aerosols, Clouds and Radiation 2004" (ASTAR2004), precipitation samples were collected in late spring at Ny-Alesund, Svalbard and their ionic components were analyzed in parallel with the measurement of properties of atmospheric aerosol particles at the same place. Backward trajectory analyses indicated that the air mass above the observatory initially dominated by air masses from the Arctic Ocean, then those from western Siberia and later those from Greenland and the Arctic Ocean. In the measurement period, six precipitation samples were obtained and five of them were analyzed their ionic components by ionchromatography. The concentrations of nss-sulphate in precipitations were between 1.8 and 24.6 ppm from which the scavenging ratio and scavenging coefficients were calculated using the data such as the concentrations of nss-sulphate in aerosol particles, amounts of precipitations, and the heights of precipitations obtained from radar echo data. The scavenging ratio ranged from 1.0&times;10<sup>6</sup> to 17&times;10<sup>6</sup> which are comparable values reported in other areas. A detailed comparison between precipitation events and the number concentration of aerosol particles obtained from optical particle counters suggests that the type of precipitations, i.e. rain or snow, significantly affects the number concentrations of aerosol particles
Remarks on flavor-neutrino propagators and oscillation formulae
We examine the general structure of the formulae of neutrino oscillations
proposed by Blasone and Vitiello(BV). Reconstructing their formulae with the
retarded propagators of the flavor neutrino fields for the case of many
flavors, we can get easily the formulae which satisfy the suitable boundary
conditions and are independent of arbitrary mass parameters ,
as is obtained by BV for the case of two flavors. In this two flavor case, our
formulae reduce to those obtained by BV under -invariance condition.
Furthermore, the reconstructed probabilities are shown to coincide with those
derived with recourse to the mass Hilbert space which is
unitarily inequivalent to the flavor Hilbert space . Such a
situation is not found in the corresponding construction a la BV. Then the new
factors in the BV's formulae, which modify the usual oscill ation formulae, are
not the trace of the flavor Hilbert space construction, but come from
Bogolyubov transformation among the operators of spin-1/2 ne utrino with
different masses.Comment: revtex, 16 page
Measurement of tau polarization in e+ e- annihilation at sqrt{s}=58 GeV
The polarization of tau leptons in the reaction e+ e- --> tau+ tau- has been
measured using a e+e- collider, TRISTAN, at the center-of-mass energy of 58
GeV. From the kinematical distributions of daughter particles in tau --> e nu
nu-bar, mu nu nu-bar, rho nu or pi(K) nu decays, the average polarization of
tau- and its forward-backward asymmetry have been evaluated to be 0.012 +-
0.058 and 0.029 +- 0.057, respectively.Comment: 18 pages, 5 figure
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