13,958 research outputs found
A proposal to detect vortices above the superconducting transition temperature
We propose a simple experiment to determine whether vortices persist above
the superconducting transition temperature Tc in the pseudogap phase of high
temperature cuprate superconductors. This involves using a magnetic dot to
stabilize a vortex in a thin cuprate film beneath the dot. We calculate the
magnetic field profile as a function of distance from the dot if a vortex is
present, and discuss possible measurements that could be done to detect this.
Finally, we comment on the temperature range where a stable vortex should be
observable.Comment: 3 pages, 2 figure
Study of a Proposed Infrared Horizon Scanner for Use in Space-Orientation Control Systems
An attitude-sensing device for space vehicles which detects the thermal radiation discontinuity at opposite horizons of a planetary body to produce an attitude error signal is described. The planetary body may be the Earth, its Moon, Mars, or Venus. The sensor is expected to have an accuracy of 0.25 degrees for the Earth, a long continuous operating lifetime, a wide altitude range, a wide capture capability, and an inherent ability to produce signals indicating vehicle altitude. An experimental model incorporating many of the features of the proposed sensor indicates that the proposed sensor will be low in weight, volume, and power consumption. The sensor's altitude range, accuracy, lifetime, and sensitivity to radiation from the Moon and planets are discussed
Renormalization of spectral lineshape and dispersion below Tc in Bi2Sr2CaCu2O8+d
Angle-resolved photoemission (ARPES) data in the superconducting state of
Bi2Sr2CaCu2O8+d show a kink in the dispersion along the zone diagonal, which is
related via a Kramers-Kronig analysis to a drop in the low-energy scattering
rate. As one moves towards (pi,0), this kink evolves into a spectral dip. The
occurrence of these anomalies in the dispersion and lineshape throughout the
zone indicate the presence of a new energy scale in the superconducting state.Comment: New Figure 3 with expanded discussio
The X-ray emission of z>2.5 active galactic nuclei can be obscured by their host galaxies
We present a multi-wavelength study of seven AGN at spectroscopic redshift
>2.5 in the 7 Ms Chandra Deep Field South, selected to have good FIR/sub-mm
detections. Our aim is to investigate the possibility that the obscuration
observed in the X-rays can be produced by the interstellar medium (ISM) of the
host galaxy. Based on the 7 Ms Chandra spectra, we measured obscuring column
densities N in excess of 7x10 cm and intrinsic X-ray
luminosities L>10 erg s for our targets, as well as
equivalent widths for the Fe K emission line EW>0.5-1 keV. We built the
UV-to-FIR spectral energy distributions by using broad-band photometry from
CANDELS and Herschel catalogs. By means of an SED decomposition technique, we
derived stellar masses (M~10 Msun), IR luminosities
(L>10 Lsun), star formation rates (SFR~190-1680 Msun yr)
and AGN bolometric luminosities (L~10 erg s) for our
sample. We used an empirically-calibrated relation between gas masses and
FIR/sub-mm luminosities and derived M~0.8-5.4x10 Msun.
High-resolution (0.3-0.7'') ALMA data (when available, CANDELS data otherwise)
were used to estimate the galaxy size and hence the volume enclosing most of
the ISM under simple geometrical assumptions. These measurements were then
combined to derive the column density associated with the ISM of the host, on
the order of N~10 cm. The comparison between the
ISM column densities and those measured from the X-ray spectral analysis shows
that they are similar. This suggests that, at least at high redshift,
significant absorption on kpc scales by the dense ISM in the host likely adds
to or substitutes that produced by circumnuclear gas on pc scales (i.e., the
torus of unified models). The lack of unobscured AGN among our ISM-rich targets
supports this scenario.Comment: 15 pages, 3 figures. Accepted for publication in A&
Cargo/Logistics Airlift System Study (CLASS), Volume 2
Air containerization is discussed in terms of lower freight rates, size and pallet limitations, refrigeration, backhaul of empties, and ownership. It is concluded that there is a need for an advance air cargo system as indicated by the industry/transportation case studies, and a stimulation of the air cargo would result in freight rate reductions
Cargo/Logistics Airlift System Study (CLASS), Volume 1
Current and advanced air cargo systems are evaluated using industrial and consumer statistics. Market and commodity characteristics that influence the use of the air mode are discussed along with a comparison of air and surface mode on typical routes. Results of on-site surveys of cargo processing facilities at airports are presented, and institutional controls and influences on air cargo operations are considered
Cargo/Logistics Airlift System Study (CLASS), Executive Summary
The current air cargo system is analyzed along with advanced air cargo systems studies. A forecast of advanced air cargo system demand is presented with cost estimates. It is concluded that there is a need for a dedicated advance air cargo system, and with application of advanced technology, reductions of 45% in air freight rates may be achieved
Magnetic resonance at 41 meV and charge dynamics in YBa_2Cu_3O_6.95
We report an Eliashberg analysis of the electron dynamics in YBa_2Cu_3O_6.95.
The magnetic resonance at 41 meV couples to charge carriers and defines the
characteristic shape in energy of the scattering rate \tau^{-1}(T,\omega) which
allows us to construct the charge-spin spectral density I^2\chi(\omega,T) at
temperature T. The T dependence of the weight under the resonance peak in
I^2\chi(\omega,T) agrees with experiment as does that of the London penetration
depth and of the microwave conductivity. Als, at T=0 condensation energy, the
fractional oscillator strength in the condensate, and the ratio of gap to
critical temperature agree well with the data.Comment: 7 Pages, 3 Figures, accepted for publication in Europhysics Letter
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