6,892 research outputs found
Recursive Program Optimization Through Inductive Synthesis Proof Transformation
The research described in this paper involved developing transformation techniques which increase the efficiency of the noriginal program, the source, by transforming its synthesis proof into one, the target, which yields a computationally more efficient algorithm. We describe a working proof transformation system which, by exploiting the duality between mathematical induction and recursion, employs the novel strategy of optimizing recursive programs by transforming inductive proofs. We compare and contrast this approach with the more traditional approaches to program transformation, and highlight the benefits of proof transformation with regards to search, correctness, automatability and generality
The impact of water on free-falling bodies
Report discussed measures to cushion impact on body falling into water. Heavy loads are generated by impact and by pressures of water cavity collapsing onto the body
The construction of a reliable potential for GeO2 from first-principles
The construction of a reliable potential for GeO2, from first-principles, is
described. The obtained potential, which includes dipole polarization effects,
is able to reproduce all the studied properties (structural, dynamical and
vibrational) to a high degree of precision with a single set of parameters. In
particular, the infrared spectrum was obtained with the expression proposed for
the dielectric function of polarizable ionic solutions by Weis et al. [J.M.
Caillol, D. Levesque and J.J. Weis, J. Chem. Phys. 91, 5544 (1989)]. The
agreement with the experimental spectrum is very good, with three main bands
that are associated to tetrahedral modes of the GeO2 network. Finally, we give
a comparison with a simpler pair-additive potential.Comment: 9 pages, 8 figure
Characterizing heterogeneous dynamics at hydrated electrode surfaces
In models of Pt 111 and Pt 100 surfaces in water, motions of molecules in the
first hydration layer are spatially and temporally correlated. To interpret
these collective motions, we apply quantitative measures of dynamic
heterogeneity that are standard tools for considering glassy systems.
Specifically, we carry out an analysis in terms of mobility fields and
distributions of persistence times and exchange times. In so doing, we show
that dynamics in these systems is facilitated by transient disorder in
frustrated two-dimensional hydrogen bonding networks. The frustration is the
result of unfavorable geometry imposed by strong metal-water bonding. The
geometry depends upon the structure of the underlying metal surface. Dynamic
heterogeneity of water on the Pt 111 surface is therefore qualitatively
different than that for water on the Pt 100 surface. In both cases, statistics
of this adlayer dynamic heterogeneity responds asymmetrically to applied
voltage.Comment: 6 page, 4 figure
Integrated analysis of environmental and genetic influences on cord blood DNA methylation in new-borns
Variations of the Mid-IR Aromatic Features Inside and Among Galaxies
We present the results of a systematic study of mid-IR spectra of Galactic
regions, Magellanic HII regions, and galaxies of various types (dwarf, spiral,
starburst), observed by the satellites ISO and Spitzer. We study the relative
variations of the 6.2, 7.7, 8.6 and 11.3 micron features inside spatially
resolved objects (such as M82, M51, 30 Doradus, M17 and the Orion Bar), as well
as among 90 integrated spectra of 50 objects. Our main results are that the
6.2, 7.7 and 8.6 micron bands are essentially tied together, while the ratios
between these bands and the 11.3 micron band varies by one order of magnitude.
This implies that the properties of the PAHs are remarkably universal
throughout our sample, and that the relative variations of the band ratios are
mainly controled by the fraction of ionized PAHs. In particular, we show that
we can rule out both the modification of the PAH size distribution, and the
mid-infrared extinction, as an explanation of these variations. Using a few
well-studied Galactic regions (including the spectral image of the Orion Bar),
we give an empirical relation between the I(6.2)/I(11.3) ratio and the
ionization/recombination ratio G0/ne.Tgas^0.5, therefore providing a useful
quantitative diagnostic tool of the physical conditions in the regions where
the PAH emission originates. Finally, we discuss the physical interpretation of
the I(6.2)/I(11.3) ratio, on galactic size scales.Comment: Accepted by the ApJ, 67 pages, 70 figure
The Nature of the Low-Metallicity ISM in the Dwarf Galaxy NGC 1569
We are modeling the spectra of dwarf galaxies from infrared to submillimeter
wavelengths to understand the nature of the various dust components in
low-metallicity environments, which may be comparable to the ISM of galaxies in
their early evolutionary state. The overall nature of the dust in these
environments appears to differ from those of higher metallicity starbursting
systems. Here, we present a study of one of our sample of dwarf galaxies, NGC
1569, which is a nearby, well-studied starbursting dwarf. Using ISOCAM, IRAS,
ISOPHOT and SCUBA data with the Desert et al. (1990) model, we find consistency
with little contribution from PAHs and Very Small Grains and a relative
abundance of bigger colder grains, which dominate the FIR and submillimeter
wavelengths. We are compelled to use 4 dust components, adding a very cold dust
component, to reproduce the submillimetre excess of our observations.Comment: 4 pages, 4 postscript figures. Proceedings of "Infrared and
Submillimeter Astronomy. An International Colloquium to Honor the Memory of
Guy Serra" (2002
Intermediate range chemical ordering of cations in simple molten alkali halides
The presence of first sharp diffraction peaks in the partial structure
factors is investigated in computer simulations of molten mixtures of alkali
halides. An intermediate range ordering appears for the Li+ ions only, which is
associated with clustering of this species and is not reflected in the
arrangement of other ions. This ordering is surprising in view of the
simplicity of the interionic interactions in alkali halides. The clustering
reflects an incomplete mixing of the various species on a local length scale,
which can be demonstrated by studying the complementary sub-space of cations in
the corresponding pure alkali halides by means of a void analysis.Comment: 5 pages, 5 figure
Cephalic Papillae of Giant Kidney Nematode \u3ci\u3eDioctophyma renale\u3c/i\u3e (Goeze, 1782) and Comparison with \u3ci\u3eEustrongylides\u3c/i\u3e spp.
Cephalic papillae of third- and fifth-stage Dioctophyma renale and fourth- and fifth-stage Eustrongylides spp. were found to be of three kinds in addition to the amphids. In all the stages of both genera studied, six papillae were in an internal circle, six in an external circle, and eight to 10 in two lateral fields of four or five each between the internal and external circles. Amphids were closely associated with the externolateral papillae. Another porelike papilla was found between the ventroventral papillae in all but fifth-stage D. renale. In third-stage D. renale, lateral rows of somatic papillae were spatially separated from the cephalic papillae, but in fifth-stage D. renale and fourthand fifth-stage Eustrongylides, the somatic papillae were adjacent to the cephalic papillae
- …