38,475 research outputs found
Lung cancer in Hong Kong Chinese: mortality and histological types, 1960-1972.
Age-adjusted mortality from lung cancer rose rapidly in both males and females in Hong Kong from 1960-1972. The relative frequency of epidermoid carcinoma increased in male bronchial biopsies but not in lung biopsies, resections, or autopsies; there was a decline in small-cell anaplastic carcinoma. In both males and females the ratio of Kreyberg Group I (epidermoid and small-cell anaplastic) to Group II (adenocarcinoma and carcinoid) tumours did not increase, despite an 80% rise in mortality from lung cancer. Adenocarcinoma was the most common type in females, despite the high mortality from lung cancer. It is speculated that cigarette smoking might produce a different pattern of histological types among Hong Kong Chinese, or that additional aetiological factors may be operating there
Development of a CCD for ultraviolet imaging using a CCD photocathode combination
CCD in the electron-in mode, coupled with a bi-alkali photocathode to produce UV photon conversion, provides the following desirable features: (1) high UV response of the bi-alkali photocathode; (2) excellent imaging quality of a CCD area array; and (3) high signal-to-noise ratio due to the EBS (electron bombarded silicon) gain of the CCD operating in a tube configuration. This paper describes the rationale and progress made in developing a CCD for use as an UV imager
Radiating Shear-Free Gravitational Collapse with Charge
We present a new shear free model for the gravitational collapse of a
spherically symmetric charged body. We propose a dissipative contraction with
radiation emitted outwards. The Einstein field equations, using the junction
conditions and an ansatz, are integrated numerically. A check of the energy
conditions is also performed. We obtain that the charge delays the black hole
formation and it can even halt the collapse.Comment: 22 pages, 9 figures. It has been corrected several typos and included
several references. Accepted for publication in GR
Surface counterterms and boundary stress-energy tensors for asymptotically non-anti-de Sitter spaces
For spaces which are not asymptotically anti-de Sitter where the asymptotic
behavior is deformed by replacing the cosmological constant by a dilaton scalar
potential, we show that it is possible to have well-defined boundary
stress-energy tensors and finite Euclidean actions by adding appropriate
surface counterterms. We illustrate the method by the examples of domain-wall
black holes in gauged supergravities, three-dimensional dilaton black holes and
topological dilaton black holes in four dimensions. We calculate the boundary
stress-energy tensor and Euclidean action of these black configurations and
discuss their thermodynamics. We find new features of topological black hole
thermodynamics.Comment: 27 pages, Late
Secondary organic aerosol formation from m-xylene, toluene, and benzene
Secondary organic aerosol (SOA) formation from the photooxidation of m-xylene, toluene, and benzene is investigated in the Caltech environmental chambers. Experiments are performed under two limiting NOx conditions; under high-NOx conditions the peroxy radicals (RO2) react only with NO, while under low-NOx conditions they react only with HO2. For all three aromatics studied (m-xylene, toluene, and benzene), the SOA yields (defined as the ratio of the mass of organic aerosol formed to the mass of parent hydrocarbon reacted) under low-NOx conditions substantially exceed those under high-NOx conditions, suggesting the importance of peroxy radical chemistry in SOA formation. Under low-NOx conditions, the SOA yields for m-xylene, toluene, and benzene are constant (36%, 30%, and 37%, respectively), indicating that the SOA formed is effectively nonvolatile under the range of Mo(>10 μg m−3) studied. Under high-NOx conditions, aerosol growth occurs essentially immediately, even when NO concentration is high. The SOA yield curves exhibit behavior similar to that observed by Odum et al. (1996, 1997a, b), although the values are somewhat higher than in the earlier study. The yields measured under high-NOx conditions are higher than previous measurements, suggesting a "rate effect" in SOA formation, in which SOA yields are higher when the oxidation rate is faster. Experiments carried out in the presence of acidic seed aerosol reveal no change of SOA yields from the aromatics as compared with those using neutral seed aerosol
The Casimir force on a surface with shallow nanoscale corrugations: Geometry and finite conductivity effects
We measure the Casimir force between a gold sphere and a silicon plate with
nanoscale, rectangular corrugations with depth comparable to the separation
between the surfaces. In the proximity force approximation (PFA), both the top
and bottom surfaces of the corrugations contribute to the force, leading to a
distance dependence that is distinct from a flat surface. The measured Casimir
force is found to deviate from the PFA by up to 15%, in good agreement with
calculations based on scattering theory that includes both geometry effects and
the optical properties of the material
Black plane solutions in four dimensional spacetimes
The static, plane symmetric solutions and cylindrically symmetric solutions
of Einstein-Maxwell equations with a negative cosmological constant are
investigated. These black configurations are asymptotically anti-de Sitter not
only in the transverse directions, but also in the membrane or string
directions. Their causal structure is similar to that of Reissner-Nordstr\"{o}m
black holes, but their Hawking temperature goes with , where is
the ADM mass density. We also discuss the static plane solutions in
Einstein-Maxwell-dilaton gravity with a Liouville-type dilaton potential. The
presence of the dilaton field changes drastically the structure of solutions.
They are asymptotically ``anti-de Sitter'' or ``de Sitter'' depending on the
parameters in the theory.Comment: 8 pages, RevTex, to appear in Phys. Rev.
Black hole as an Information Eraser
We discuss the identity of black hole entropy and show that the first law of
black hole thermodynamics, in the case of a Schwarzschild black hole, can be
derived from Landauer's principle by assuming that the black hole is one of the
most efficient information erasers in systems of a given temperature. The term
"most efficient" implies that minimal energy is required to erase a given
amount of information. We calculate the discrete mass spectra and the entropy
of a Schwarzschild black hole assuming that the black hole processes
information in unit of bits. The black hole entropy acquires a sub-leading
contribution proportional to the logarithm of its mass-squared in addition to
the usual mass-squared term without an artificial cutoff. We also argue that
the minimum of the black hole mass is .Comment: 12 pages, 4 figures, minor change
Role of aldehyde chemistry and NO_x concentrations in secondary organic aerosol formation
Aldehydes are an important class of products from atmospheric oxidation of hydrocarbons. Isoprene (2-methyl-1,3-butadiene), the most abundantly emitted atmospheric non-methane hydrocarbon, produces a significant amount of secondary organic aerosol (SOA) via methacrolein (a C_4-unsaturated aldehyde) under urban high-NO_x conditions. Previously, we have identified peroxy methacryloyl nitrate (MPAN) as the important intermediate to isoprene and methacrolein SOA in this NO_x regime. Here we show that as a result of this chemistry, NO_2 enhances SOA formation from methacrolein and two other α, β-unsaturated aldehydes, specifically acrolein and crotonaldehyde, a NO_x effect on SOA formation previously unrecognized. Oligoesters of dihydroxycarboxylic acids and hydroxynitrooxycarboxylic acids are observed to increase with increasing NO_2/NO ratio, and previous characterizations are confirmed by both online and offline high-resolution mass spectrometry techniques. Molecular structure also determines the amount of SOA formation, as the SOA mass yields are the highest for aldehydes that are α, β-unsaturated and contain an additional methyl group on the α-carbon. Aerosol formation from 2-methyl-3-buten-2-ol (MBO232) is insignificant, even under high-NO_2 conditions, as PAN (peroxy acyl nitrate, RC(O)OONO_2) formation is structurally unfavorable. At atmospherically relevant NO_2/NO ratios (3–8), the SOA yields from isoprene high-NO_x photooxidation are 3 times greater than previously measured at lower NO_2/NO ratios. At sufficiently high NO_2 concentrations, in systems of α, β-unsaturated aldehydes, SOA formation from subsequent oxidation of products from acyl peroxyl radicals+NO_2 can exceed that from RO_2+HO_2 reactions under the same inorganic seed conditions, making RO_2+NO_2 an important channel for SOA formation
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