We have observed x-ray speckle at grazing incidence from gold-coated films of symmetric diblock copolymers of polystyrene (PS) and polymethylmethacrylate (PMMA). The polymer films consisted of ...micron-sized islands on a uniform surface. Coherent 6-keV photons were selected by monochromatizing and collimating the x-ray beam from a bending magnet synchrotron source. The visibility of the speckle patterns was enhanced with increasing degrees of spatial coherence of the photons. Speckles due to coherent scattering from islands with length scales up to 100 mum were clearly identified.
Recoil momentum spectroscopy has been used to distinguish experimentally between contributions to the ionization of hydrogenlike O and F projectiles from interactions with the electrons and with the ...nucleus of a target He atom. The electron-electron contribution is separated from the nuclear one in the final momentum space of the recoil He ion, and is found to produce much smaller recoil momenta, both transverse and longitudinal, than the nuclear process. The relative contributions of the two mechanisms are consistent with theoretical expectations.
Daily dietary-boron intake and on-the-job inspired boron were compared with blood- and urine-boron concentrations in workers engaged in packaging and shipping borax. Fourteen workers handling borax ...at jobs of low, medium, and high dust exposures were sampled throughout full shifts for 5 consecutive days each. Airborne borax concentrations ranged from means of 3.3 mg/ m3to 18 mg/ m3, measured gravimetrically. End-of-shift mean blood-boron concentrations ranged from 0.11 to 0.26 μg/g; end-of-shift mean urine concentrations ranged from 3.16 to 10.72 μ/mg creatinine. Creatinine measures were used to adjust for differences in urine-specific gravity such that 1 ml of urine contains approximately 1 mg creatinine. There was no progressive increase in end-of-shift blood- or urine-boron concentrations across the days of the week. Urine testing done at the end of the work shift gave a somewhat better estimate of borate exposure than did blood testing, was sampled more easily, and was analytically less difficult to perform. Personal air samplers of two types were used: one, the 37-mm closed-face, two-piece cassette to estimate total dust and the other, the Institute of Occupational Medicine (IOM) sampler to estimate inspirable particulate mass. Under the conditions of this study, the IOM air sampler more nearly estimated human exposure as measured by blood- and urine-boron levels than did the sampler that measured total dust. The highest mean blood- and urine-boron levels in the workers were approximately an order of magnitude lower than blood and urine values found by others in dogs during feeding studies conducted as part of reproductive toxicity studies at the no-observed-adverse-effect level (NOAEL). The mean dietary intake of the workers was 1.35 mg boron/day, close to the 1.521 mg boron/day reported recently for the standard U.S. diet. Total estimated boron intake, which is diet plus environmental exposure, had for the high-borax dust exposure group a mean daily boron intake of 27.90 mg/day or, based on the body weights of the subjects, 0.38 mg boron/kg/day. These subjects had a mean blood-boron level of 0.26 μg boron/g blood, a factor of 10 lower than found in the dog or rat at NOAEL exposure levels.
We present the three-loop contribution (order ital esup 4) to the pressure of massless quantum electrodynamics at nonzero temperature. The calculation is performed within the imaginary time ...formalism. Dimensional regularization is used to handle the usual, intermediate stage, ultraviolet and infrared singularities, and also to prevent overcounting of diagrams during resummation.
The cold dark matter scenario for structure formation in the Universe has many successes; however, when its spectrum of density perturbations is normalized to the Cosmic Background Explorer ...anisotropy measurement the level of inhomogeneity predicted on small scales is too large. This can be remedied by a tau neutrino of mass 1--10 MeV and lifetime 0.1--100 sec whose decay products include electron neutrinos because it allows the total energy density in relativistic particles to be doubled without interfering with nucleosynthesis.
Convergence of Productivity Baumol, William J; Nelson, Richard R; Wolff, Edward N
1994, 19940630, 1994-08-25, 19940101
eBook, Book
This comprehensive study is a collection of original articles that view the current state of knowledge of the convergence hypothesis. The hypothesis asserts that at least since the Second World War, ...and perhaps for a considerable period before that, the group of industrial countries was growing increasingly homogeneous in terms of levels of productivity, technology and per capita incomes. In addition, there was general catch up toward the leader, with gradual erosion of the gap between the leader country, the U.S., throughout most of the pertinent period, and that of the countries lagging most closely behind it. The book examines patterns displayed by individual industries within countries as well as the aggregate economies, various influences that underlie the process of convergence that seems to have occurred, and the role that convergence has played and promises to play in the future of the newly industrialized nations and the less developed countries. Much of the analysis is set in a historical perspective, with particular attention paid to the record following World War II. The prestigious editors conclude that increasing productivity is the key to rising living standards in a globalized marketplace. Contributors include: Moses Abramovitz, Alice M. Amsden, Magnus Blomstrom, David Dollar, Takashi Hikino, Gregory Ingram, William Lazonick, Frank Lichtenberg, Robert E. Lipsey, Angus Maddison, Gavin Wright, and Mario Zejan.
We present a generalized circle theorem which includes the Lee-Yang theorem for symmetric transitions as a special case. It is found that zeros of the partition function can be written in terms of ...discontinuities in the derivatives of the free energy. For asymmetric transitions, the locus of the zeros in tangent to the unit circle if the partition functions of the two phases are added up with unequal prefactors. This conclusion is substantiated by explicit calculation of zeroes of the partition function for the Blume-Capel model near and at the triple line at low temperatures.
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