8,627 research outputs found
Air pollution from aircraft
A series of fundamental problems related to jet engine air pollution and combustion were examined. These include soot formation and oxidation, nitric oxide and carbon monoxide emissions mechanisms, pollutant dispension, flow and combustion characteristics of the NASA swirl can combustor, fuel atomization and fuel-air mixing processes, fuel spray drop velocity and size measurement, ignition and blowout. A summary of this work, and a bibliography of 41 theses and publications which describe this work, with abstracts, is included
Trees and the urban environment - weighing risks and benefits
The presence of mature, broad-leafed trees in urban areas is increasingly evidenced as being beneficial for public health, mental well-being and the environment. Consequently, any loss of such trees should be regarded as increasing risk, potentially with significant consequences. Currently, austerity measures and fragmented policies are tending to miss out on the opportunities presented by a greener environment, and some policies connected with, for example, road safety and highway engineering have the potential to reduce tree presence if disproportionately applied, as does fear of litigation
Temperature dependence of collisional deactivation of highly vibrationally excited biphenylene.
Molecular Phylogenetics of Cypripedium L. (Cypripedioideae: Orchidaceae) Based on Plastid and Nuclear DNA Sequences
Specific heat and thermal conductivity in the mixed state of MgB2
The specific heat C and the electronic and phononic thermal conductivities
kappa_e and kappa_{ph} are calculated in the mixed state for magnetic fields H
near H_{c2}. The effects of supercurrent flow and Andreev scattering of the
Abrikosov vortex lattice on the quasiparticles are taken into account. The
resulting function C(H) is nearly linear while kappa_e(H) exhibits an upward
curvature near H_{c2}. The slopes decrease with impurity scattering which
improves the agreement with the data on MgB_2. The ratio of phonon relaxation
times tau_n/tau_s = g(omega_0,H) for phonon energy omega_0, which is nearly a
step function at omega_0 = 2Delta for the BCS state, is smeared out and tends
to one for increasing H. This leads to a rapid reduction of kappa_{ph}(H) in
MgB_2 for relatively small fields due to the rapid suppression of the smaller
energy gap.Comment: 8 pages, 4 figures, accepted for publication in Phys. Rev. Letter
Normal metal to ferromagnetic superconductor tunneling
We study the point-contact tunneling between normal metal and ferromagnetic
superconductor. In the case of magnon-induced pairing the tunneling conductance
is continuous and smooth function of the applied voltage. For small values of
the applied voltage the Ohm law holds. We show that one can obtain the
magnetization and the superconducting order parameter from the tunneling
conduc- tance. In the case of paramagnon-induced superconductivity the
tunneling does not depend on the magnetization. We argue that tunneling
experiment can unambiguously determine the correct pairing mechanism in the
ferromagnetic superconductors.Comment: 6 pages, 4 figur
Pressure-temperature Phase Diagram of Polycrystalline UCoGe Studied by Resistivity Measurement
Recently, coexistence of ferromagnetism (T_Curie = 2.8K) and
superconductivity (T_sc = 0.8K) has been reported in UCoGe, a compound close to
a ferromagnetic instability at ambient pressure P. Here we present resistivity
measurements under pressure on a UCoGe polycrystal. The phase diagram obtained
from resistivity measurements on a polycrystalline sample is found to be
qualitatively different to those of all other ferromagnetic superconductors. By
applying high pressure, ferromagnetism is suppressed at a rate of 1.4 K/GPa. No
indication of ferromagnetic order has been observed above P ~ 1GPa. The
resistive superconducting transition is, however, quite stable in temperature
and persists up to the highest measured pressure of about 2.4GPa.
Superconductivity would therefore appear also in the paramagnetic phase.
However, the appearance of superconductivity seems to change at a
characteristic pressure P* ~ 0.8GPa. Close to a ferromagnetic instability, the
homogeneity of the sample can influence strongly the electronic and magnetic
properties and therefore bulk phase transitions may differ from the
determination by resistivity measurements.Comment: 4 pages, 4 figures, submitted to J. Phys. Soc. Jp
A note on the Gauss decomposition of the elliptic Cauchy matrix
Explicit formulas for the Gauss decomposition of elliptic Cauchy type
matrices are derived in a very simple way. The elliptic Cauchy identity is an
immediate corollary.Comment: 5 page
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