bluuebunny/crossref_metadata_2025 huggingface dataset:
Perturbation theory of the electron correlation cusp based on a partitioning of the electron–electron interaction into long- and short-range components
Authors: Sirbu Ioana , King Harry F.
Published: October 2002

We propose a method, using low order, Rayleigh Schrödinger perturbation theory (RSPT), for systematically increasing the accuracy of traditional, orbital-based, ab initio electronic structure computations. The method is designed to be equally applicable to closed- or open-shell systems. The interelectron interaction is partitioned into long- and short-range components using an expression containing an arbitrary smoothing parameter, γ. The smooth, nonsingular, long-range component of the interelectron interaction is retained in the reference Hamiltonian, and the exponentially-short-range component is included in the perturbation. Modified Fock operators are introduced to prevent spurious core shrinkage. Orbital-based methods are employed for the reference problem. Explicitly correlated Gaussian geminal basis functions are used for variational solution of the RSPT equations. The computational burden shifts from solution of the reference problem to that of the RSPT equations as the extent of smoothing is increased, i.e., as γ is decreased. It is shown that smoothing the interelectron interaction out to a distance of about one Bohr for the helium atom is a reasonable compromise yielding satisfactory rates of convergence of both CI and RSPT expansions. The accuracy of the computed energy increases by two decimal digits for each additional perturbation order in the wave function. Expanding the wave function through third order for γ=2 bohr−1 yields the helium atom energy in error by only 4 nanohartrees.
Field-independent grating formation rate in a photorefractive polymer composite sensitized by CdSe quantum dots
Authors: Binks David J. , West David P. , Norager Sebastian , O’Brien Paul
Published: October 2002

The rate of grating formation in a photorefractive polymer composite sensitized by CdSe quantum dots is found to be independent of applied field, in contrast to similar composites sensitized by other types of nanoparticles. The photorefractive polymer composite under study consists of poly(N-vinylcarbazole) as the nominal charge transporting matrix, an electro-optic dye, and CdSe quantum dots passivated by tri-n-octylphosphine oxide. Both the field-independent grating formation rate and the lower diffraction efficiency compared to other nanoparticle-sensitized composites are attributed to low initial trap density, i.e., a reduced stability of ionized quantum dots within the composite in the dark.
Electronic susceptibility in thin films and interfaces
Authors: Jameson John R. , Harrison Walter , Griffin P. B.
Published: October 2002

We use tight-binding theory to investigate the electronic contribution to dielectric susceptibility in thin films and interfaces of covalent materials. We begin by describing the effects of an electric field on the elemental unit of a covalent material, the bond. Then, we show how the responses of individual bonds can be added up to obtain an estimate of the susceptibility of a bulk material. In doing so, we see that the polarization of a material can be viewed as arising from the transfer of charge from one side of the system to the other, and that this viewpoint leads naturally to a local definition of susceptibility in semiconductors. Using this concept, we examine dielectric susceptibility in thin films and interfaces, with a Si/Ge/Si heterostructure serving as an example. The interesting feature of thin films and interfaces is that they exhibit spatial variations in susceptibility, which we attribute to: (i) elastic distortions; (ii) the creation of bonds at an interface which are of a type not found in either bulk material; and (iii) the coupling of a bond to neighboring antibonds different than those in the bulk material. We then ask what error is introduced by neglecting these local variations when calculating the capacitance of a multilayer dielectric. For the Si/Ge/Si heterostructure, we find that effect (iii) introduces only small errors, even for very thin Ge layers, because the decrease in susceptibility on the Ge side of an interface is offset by the increase in susceptibility on the Si side. Similarly, effect (ii) is small because the polarizability of the Si–Ge bonds at the interface is very nearly the average of that for Si and Ge. On the other hand, effect (i) does lead to noticeable errors, but these errors can be removed almost entirely by choosing the permittivity of the Ge layer to be that of bulk Ge under the same state of strain as the Ge layer in the heterostructure. We conclude by interpreting recent experiments on “high-k” dielectrics in term of what we have learned here. [C. M. Perkins et al., Appl. Phys. Lett. 78, 2357 (2001); M. Koyama et al., Tech. Dig. Int. Electron Devices Meet., 459 (2001); W.-J. Qi et al., ibid., 145 (1999)].
Structural properties of InAs nanocrystals formed by sequential implantation of In and As ions in the Si (100) matrix
Authors: Tchebotareva A. , Brebner J. L. , Roorda S. , Desjardins P. , White C. W.
Published: October 2002

The structural properties of InAs nanocrystals formed in Si by sequential implantation of In and As ions are studied in detail. We use a combination of x-ray diffraction, Rutherford backscattering spectroscopy, channeling, and transmission electron microscopy analyses to demonstrate that, regardless of the order in which ion species are implanted, InAs nanocrystals can be produced in Si (100) by means of sequential ion implantation complemented by subsequent thermal annealing. Whichever the order of implantation is, the nanocrystals are facetted and terminated by (111) planes, the epitaxial relationship being cube-on-cube, (100)InAs‖(100)Si with [001]InAs‖[001]Si, for most InAs nanocrystals. The size distribution of nanocrystals is much affected by the sequence of implantation. With As ions implanted first, nanocrystals of different sizes are concentrated within one and the same layer under the sample’s surface. In contrast, when In ions are implanted first, nanocrystals of different sizes are produced separately in space, forming a three-layer structure. As a consequence, inverting the order of implantation entails considerable changes in the morphology of the InAs nanocrystals obtained, affecting both their concentration profile and their size distribution. The result has a significant impact on the optical properties of the resulting samples.
Hydrogen transfer in photo-excited phenol/ammonia clusters by UV–IR–UV ion dip spectroscopy and ab initio molecular orbital calculations. II. Vibrational transitions
Authors: Ishiuchi Shun-ichi , Daigoku Kota , Saeki Morihisa , Sakai Makoto , Hashimoto Kenro , Fujii Masaaki
Published: October 2002

The vibrational spectra of phenol/ammonia clusters (1:2–5) in S0 and those of their photochemical reaction products, (NH3)n−1NH4 (n=2–5), which are generated by excited-state hydrogen transfer, have been measured by UV–IR–UV ion dip spectroscopy. The geometries, IR spectra and normal modes of phenol-(NH3)n (n=1–5) have been examined by ab initio molecular orbital calculations, at the second-order Møller–Plesset perturbation theory level with large basis sets. For the n=2 and 3 reaction products, similar vibrational analyses have been carried out. From the geometrical information of reactants and products, it has been suggested that the reaction products have memories of the reactant’s structure, which we call “memory effect.”
Cascaded Raman self-frequency shifted soliton generation in an Er/Yb-doped fiber amplifier
Authors: Kim Do-Hyun , Kang Jin U. , Khurgin Jacob B.
Published: October 2002

The polarization and power dependencies of cascaded Raman self-frequency shifted solitons generation in a polarization maintaining high power Er/Yb fiber amplifier have been experimentally investigated. The experimental results show the number and amount of cascaded Raman solitons generations and frequency shifts, respectively, dependent on the input polarization state and the gain of the all-PM fiber amplifier. The numerical modeling was also conducted based on the experimental parameters and the experimental results are shown to be in good agreement with the theory.
Thermodynamic equilibrium and metal-organic interface dipole
Authors: Yan Li , Watkins N. J. , Zorba S. , Gao Yongli , Tang C. W.
Published: October 2002

We determined the interface dipoles at a number of metal-organic interfaces using ultraviolet and x-ray photoelectron spectroscopy. A linear dependence of the dipole on the metal work function is observed. This is consistent with the theory based on the charge transfer and thermodynamic equilibrium across the interface. The agreement suggests that charge transfer is one major factor in the formation of interface dipole. In addition, we find that the pushing back of the electron cloud tail that extends out of the metal surface and the permanent dipole moment of the organic molecule affect the interface dipole.
Activation of oxide-ion conduction in KNbO3 by addition of Mg2+
Authors: Li Liping , Li Guangshe , Smith R. L. , Inomata H.
Published: October 2002

Niobate perovskite oxides of KNb1−xMgxO3−δ were synthesized directly at high temperature and pressure. X-ray diffraction confirmed the formation of single-phase orthorhombic structures. High-temperature Raman spectroscopy in combination with thermal analysis showed that phase transitions occurred from orthorhombic to tetragonal, to pseudo cubic, and finally to cubic, in sequence. Addition of Mg2+ at the Nb5+ sites of perovskite KNbO3 lattice led to a dramatic enhancement of oxide-ion conduction. This enhancement in oxide-ion conduction was through the suppression of the contribution from p-type holes, which shows that these high-temperature phases can be promising candidates as conductive materials.
Studies on the biological effects of ozone: 11. Release of factors from human endothelial cells
Authors: Valacchi Giuseppe , Bocci Velio
Published: October 2002

Background: Empirical observations have shown that ozonated autohemotherapy markedly improves the symptoms of chronic limb ischemia (muscular pain at rest, intermittent claudication, etc ) in atherosclerotic patients, but mechanisms of action remain unclear.

Aims: Human endothelial cells (HUVECs) are known to release nitrogen monoxide (NO) and we investigated the biological effects of human ozonated serum on HUVECs in culture.

Methods: We assessed the relevance of peroxidation, the release of NO as nitrite and of three classical cytokines.

Results: The treatment of HUVECs with ozonated serum yields a dose dependent increase of thiobarbituric acid reactive substances (TBARS) and of hydrogen peroxide (H2O2) and a decrease of protein thiol groups (PTG). Concomitantly, in comparison to either the control or the oxygenated sample, there is a significant and steady increase of nitric oxide (NO) production; this is markedly enhanced by the addition of L‐arginine (20 μM) and inhibited in the presence of the NO inhibitor, L‐NAME (20 mM). The main mediator of ozone action is H2O2 as it has been shown either after its direct measurement or by the addition of 20, 40 and 100 μM. Moreover, during 24 hours incubation we have investigated the production of endothelin 1 (ET‐1), E‐selectin and Interleukin 8 (IL‐8) and it appears that ozonation enhances IL‐8, inhibits E‐selectin and hardly modifies ET‐1 production.

Conclusions: It appears that reinfusion of ozonated blood, by enhancing release of NO, may induce vasodilation in ischemic areas and reduce hypoxia.
Two-Generation Oral (Diet) Reproductive Toxicity Study of Resorcinol Bis-Diphenylphosphate (Fyrolflex RDP) in Rats
Authors: Henrich R. , Ryan B. M. , Selby R. , Garthwaite S. , Morrissey R. , Freudenthal R. I.
Published: October 2002

Fyrolflex resorcinol bis-diphenylphosphate (RDP) was evaluated in a two-generation reproductive study as part of a program to assess the overall toxicology of this flame retardant. RDP was administered to male and female Sprague-Dawley rats in the diet at concentrations of 1000, 10,000 or 20,000 ppm. The control group was given diet alone. Parental (P1) animals were treated for 10 weeks prior to mating, during the 2-week mating period, throughout gestation, and through lactation until sacrifice. The F1 generation (P1 offspring) was treated following a regimen similar to P1. The F2 generation was not treated. No significant difference in Utter survival was observed between the control and treated groups. Body weights were significantly decreased in P1 rats during the 1st week due to an initial flavor aversion of the test substance in the diet. Body weight, weight gains, and food consumption were decreased in the test substance-treated pups (F1) during lactationand after weaning. These changes were also attributed to a flavor aversion. Anogenital distance was similar in the control and high-dose groups, whereas vaginal opening and preputial separation were delayed in the 10,000 and 20,000 ppm groups, and were considered to be secondary to the reduction in F1 body weight. Neither parents nor offspring exhibited any test substance-related clinical signs of toxicity. Vaginal cytology and cyclicity and male reproductive functions (sperm count, motility, and morphology) were unaffected by treatment. Mating performance was similar in the treated groups relative to the control. No treatment-related lesions were noted in the reproductive organs. Increased liver weight and associated hepatic periportal hypertrophy were observed in the RDP-treated animals (P1 and F1). In conclusion, there were no adverse effects on reproductive performance or fertility parameters associated with RDP administration in the diet. Fyrolflex RDP administered for greater than 13 weeks and up to the entire life span (i.e., F1, from conception to euthanasia) resulted in increased liver weights with associated periportal hypertrophy. This change was considered an adaptive process associated with RDP metabolism in the liver.
Immunotoxicity Evaluation of Resorcinol Bis-Diphenylphosphate (Fyrolflex RDP) in B6C3F1 Mice
Authors: Sherwood R. L. , House R. V. , Ratajczak H. V. , Freudenthal R. I. , Henrich R. T.
Published: October 2002

RDP was administered daily to groups of female B6C3F1 mice by oral gavage for 28 days at dose levels of 500, 1500, or 5000 mg/kg/day body weight (BW). Control animals were sham dosed. Animals were euthanized 1 day following final exposure or following a 60-day recovery period. End point observations included necropsy and histopathology, spleen and thymus weights and cellularity, peritoneal cell numbers and differential cell analysis, splenic natural killer (NK) cell activity, lymphocyte blastogenesis, antibody-forming cell (AFC) response, peritoneal macrophage phagocytic activity, and host susceptibility to Listeria monocytogenes infection. In-life observations included weekly clinical examinations and body weights. No adverse clinical signs were noted and the only significant finding was an increase in body weight in high dose mice on week 4 as compared to sham controls. Small changes in body weight gain were seen in all dose groups as compared to sham controls after completion of dosing on weeks 5 and 6 and in mid-dose mice on weeks 7 and 12. No significant differences were found in spleen and thymus weights or in cellularity. No changes were found in peritoneal cell numbers or cell types, peritoneal macrophage phagocytic activity, or host susceptibility to infection. Likewise, splenic NK cell activity, lymphocyte blastogenesis, and AFC function were also unaffected. No histopathologic changes were observed. All animals that received positive-control substances demonstrated a significant effect in the respective tests. In conclusion, a standardized and validated battery of immune function tests demonstrated no immunotoxicity following daily oral exposure to up to 5000 mg/kg BW of RDP for 28 days.
In Vitro Inhibition of Mammalian Glutathione Transferases by Selected Nitrobenzenes
Authors: Sajan Mini , Reddy Gunda , Kulkarni Arun P.
Published: October 2002

Five structurally related nitrobenzenes (1,2-dinitrobenzene, 1,3-dinitrobenzene, 1,4-dinitrobenzene, 1,3,5-trinitrobenzene, and picric acid) and Meisenheimer complex [1-(S-glutathionyl)-2,4,6-trinitrocyclohexadienate] were evaluated as possible inhibitors of affinity purified mammalian glutathione transferases (GSTs) isolated from human liver or human term placenta and rat fiver. The results suggest that the degree of GST inhibition depends upon both the chemical in question and the enzyme source. Among the nitrobenzenes tested, 1,3,5-trinitrobenzene (TNB) was found to be the most potent inhibitor of GST activity toward 1-chloro-2,4-dinitrobenzene (CDNB) from all the sources, whereas 1,3-dinitrobenzene (1,3-DNB) was the least effective. TNB-caused inhibition of GST activity toward CDNB appeared to be isozyme specific in that compared to the enzyme from human term placenta (GSTP1–1), the degree of inhibition of the mixture of GST isozymes present in the fivers of adult rats and humans was low. The enzyme assays conducted with 3,4-dichloro-1-nitrobenzene (DCNB), ethacrynic acid (EA), and 4-nitropyridinei N-oxide also suggested the isozymespecific inhibition of rat fiver GST activity by TNB. The nature of TNB-caused inhibition of GSTP1–1 was competitive with respect to CDNB and yielded a Ki value of 12.5 θ M. With EA, a specific substrate for GSTP1–1, an IC50 value of ∼ 16 θ M was estimated for the GSTP1–1 inhibition by TNB. The Meisenheimer complex, the product of nonenzymatic GSH conjugation with TNB by different GSTs, was found to be the most potent inhibitor of mammalian GSTs, and IC50 values ranged between 1 and 4 θ M when the enzyme activity was assayedusing CDNB. The nature of GSTP1–1 inhibition was noncompetitive with respect to CDNB, with a Ki value of 1 θ M for Meisenheimer complex. Although a precise mechanism was not identified, it is postulated that GSH depletion and/or GST inhibition may contribute, at least partly, to the target organ toxicity caused by exposures of animals to different nitrobenzenes reported in the literature.
Prescribing to drug misusers in practice—often effective, but rarely straightforward
Authors: Seivewright Nicholas , Iqbal Muhammad Z.
Published: October 2002

Many reviews describe the effectiveness of methadone treatment in reducing illicit drug use and associated behaviours among opiate misusers. The strongest evidence includes social outcomes such as reduced debt and crime, and relates overwhelmingly to maintenance rather than detoxification treatment. Drug clinics are often dominated by individuals unable to withdraw fully from methadone, while the “harm reduction” model accepts some ongoing drug use, with attendant risks. Security measures are necessary to avoid abuse of treatments, but these may be undermined by the agenda of “partnerships with patients” in decision‐making. Buprenorphine appears both safer and less addictive than methadone, and lofexidine is effective as a non‐substitute detoxification method. Naltrexone can clearly reduce relapse rates, provided consumption is assured, while for individuals unable to detoxify or avoid euphoriant opiates, morphine and diamorphine are sometimes used. In non‐opiate misuse, clinical studies of a wide range of medications have produced relatively few positive findings.
Leiomyosarcoma of the Oropharynx and Neurogenic Tumors in a Young Patient With Turner′s Syndrome
Authors: De Chiara Annarosaria , Apice Gaetano , Silvestro Giustino , Losito Simona , Botti Gerardo , Ionna Francesco , De Rosa Vincenzo , Borghese Annamaria , Ninfo Vito
Published: October 2002

Patient: A case of Turner′s syndrome developing a leiomyosarcoma of the oropharynx and metachronous neurogenic
tumors (mediastinal ‘ganglioneuroblastoma intermixed’, subcutaneous neurilemoma) is described.

Discussion: To our knowledge, this case is the second reported leiomyosarcoma in a patient with Turner′s syndrome. Also
the site of involvement (palate and oropharynx) is particularly unusual for the already rare leiomyosarcomas in the young age.
Leiomyosarcoma of the Penis
Authors: Katsikas Vasilios S. , Kalyvas Konstantinos D. , Ioannidis Spiros S. , Papathanasiou Michalis V. , Panagiotopoulou Konstantina P. , Hitiroglou Panagiotis M. , Yannakoyorgos Konstantinos
Published: October 2002

We report a case of a 78‐year‐old patient with penile leiomyosarcoma, treated by radical penectomy. Two years after the
operation the patient is without evidence of local recurrence or metastatic disease.We also discuss the treatment options
and attempt a review of the literature.
Serine phosphorylation of RUNX2 with novel potential functions as negative regulatory mechanisms
Authors: Wee Hee‐Jun , Huang Gang , Shigesada Katsuya , Ito Yoshiaki
Published: October 2002

The RUNX family represents a small group of heterodimeric transcription factors that master‐regulate osteogenesis and hematopoiesis in mammals. Their genetic defects cause human diseases such as cleidocranial dysplasia (CCD) and acute myelogenous leukemia. However, the mechanism(s) regulating their functions are still poorly understood. Here, we report a novel observation that suggests that the osteogenesis‐associated homologue RUNX2 is negatively regulated by the phosphorylation of two conserved serines (S104 and S451) in two distinct functional aspects. The phosphorylation of S104 could abolish the heterodimerization of RUNX2 with the partner subunit, PEBP2β, which enhances the metabolic stability of RUNX2. On the other hand, the phosphorylation of S451 resides within the C‐terminal transcription inhibition domain of RUNX2 and hence is implicated in its functional mobilization. One CCD mutation, S104R of RUNX2, appears to mimic the phosphorylation‐dependent inhibition of heterodimerization, thereby rendering RUNX2 metabolically unstable.
ABC transporters: one, two or four extracytoplasmic substrate‐binding sites?
Authors: van der Heide Tiemen , Poolman Bert
Published: October 2002

Two families of ATP‐binding cassette (ABC) transporters in which one or two extracytoplasmic substrate‐binding domains are fused to either the N‐ or C‐terminus of the translocator protein have been detected. This suggests that two, or even four, substrate‐binding sites may function in the ABC transporter complex. This domain organization in ABC transporters, widely represented among microorganisms, raises new possibilities for how the substrate‐binding protein(s) (SBPs) might interact with the translocator. One appealing hypothesis is that multiple substrate‐binding sites in proximity to the entry site of the translocation pore enhance the transport capacity. We also discuss the implications of multiple substrate‐binding sites in close proximity to the translocator in terms of broadened substrate specificity and possible cooperative interactions between SBPs and the translocator.
Molecular Characterization of a Chromosomal Rearrangement Involved in the Adaptive Evolution of Yeast Strains
Authors: Pérez-Ortı́n José E. , Querol Amparo , Puig Sergi , Barrio Eladio
Published: October 2002

Wine yeast strains show a high level of chromosome length polymorphism. This polymorphism is mainly generated by illegitimate recombination mediated by Ty transposons or subtelomeric repeated sequences. We have found, however, that the SSU1-R allele, which confers sulfite resistance to yeast cells, is the product of a reciprocal translocation between chromosomes VIII and XVI due to unequal crossing-over mediated by microhomology between very short sequences on the 5′ upstream regions of the SSU1 andECM34 genes. We also show that this translocation is only present in wine yeast strains, suggesting that the use for millennia of sulfite as a preservative in wine production could have favored its selection. This is the first time that a gross chromosomal rearrangement is shown to be involved in the adaptive evolution ofSaccharomyces cerevisiae.

[The sequence data from this study have been submitted to EMBL under accession nos. AF239757,AF239758, and AJ458340–AJ458367. The following individual kindly provided reagents, samples, or unpublished information as indicated in the paper: N. Goto-Yamamoto.]
Experimental Method for Residual Stress Evaluation Through the Thickness of a Plate
Authors: Andersen Lars Fuglsang
Published: October 2002

In the present work an experimental method is developed for residual stress evaluation in medium thick plates. On the basis of the incremental hole-drilling technique, a method to resolve the in-plane residual stresses through the plate thickness is given. An analysis of the hole-drilling configuration is carried out, resulting in a configuration which optimizes the stress calculation accuracy. Moreover, it is estimated that conventional milling can be applied without affecting the accuracy of the method. Finally, the results of a comprehensive stress calculation error analysis are presented.
Mechanism of Incomplete Mitral Leaflet Coaptation—Interaction of Chordal Restraint and Changes in Mitral Leaflet Coaptation Geometry
Authors: Nielsen Sten Lyager , Nygaard Hans , Mandrup Lars , Fontaine Arnold A. , Hasenkam J. Michael , He Shengqui , Yoganathan Ajit P.
Published: October 2002

Clinically observed incomplete mitral leaflet coaptation was reproduced in vitro by altering the balance of the chordal tethering and chordal coapting force components. Mitral leaflet coaptation geometry was distorted by changes of the spatial relations between the papillary muscles and the mitral valve as well as hemodynamics. Mitral leaflet malalignment was accentuated by a redistribution of the chordal tethering and coapting force components. For the overall assessment of systolic mitral leaflet configuration in functional mitral regurgitation it is important to consider the interaction between chordal restraint and an altered mitral leaflet coaptation geometry.
Deformation of Angle Profiles in Forward Kinematics for Nullifying End-Point Offset While Preserving Movement Properties
Authors: Zhang Xudong
Published: October 2002

This work describes a new approach that allows an angle-domain human movement model to generate, via forward kinematics, Cartesian-space human movement representation with otherwise inevitable end-point offset nullified but much of the kinematic authenticity retained. The approach incorporates a rectification procedure that determines the minimum postural angle change at the final frame to correct the end-point offset, and a deformation procedure that deforms the angle profile accordingly to preserve maximum original kinematic authenticity. Two alternative deformation schemes, named amplitude-proportional (AP) and time-proportional (TP) schemes, are proposed and formulated. As an illustration and empirical evaluation, the proposed approach, along with two deformation schemes, was applied to a set of target-directed right-hand reaching movements that had been previously measured and modeled. The evaluation showed that both deformation schemes nullified the final frame end-point offset and significantly reduced time-averaged position errors for the end-point as well as the most distal intermediate joint while causing essentially no change in the remaining joints. A comparison between the two schemes based on time-averaged joint and end-point position errors indicated that overall the TP scheme outperformed the AP scheme. In addition, no statistically significant difference in time-averaged angle error was identified between the raw prediction and either of the deformation schemes, nor between the two schemes themselves, suggesting minimal angle-domain distortion incurred by the deformation.
Field induced in inhomogeneous spheres by external sources. I. The scalar case
Authors: Kokkorakis Gerassimos C. , Fikioris John G. , Fikioris George
Published: October 2002

The evaluation of acoustic or electromagnetic fields induced in the interior of inhomogeneous penetrable bodies by external sources is based on well-known volume integral equations; this is particularly true for bodies of arbitrary shape and/or composition, for which separation of variables fails. In this paper the investigation focuses on acoustic (scalar fields) in inhomogeneous spheres of arbitrary composition, i.e., with r-, θ- or even φ-dependent medium parameters. The volume integral equation is solved by a hybrid (analytical–numerical) method, which takes advantage of the orthogonal properties of spherical harmonics, and, in particular, of the so-called Dini’s expansions of the radial functions, whose convergence is optimized. The numerical part comes at the end; it involves the evaluation of certain definite integrals and the matrix inversion for the expansion coefficients of the solution. The scalar case treated here serves as a steppingstone for the solution of the more difficult electromagnetic problem.
Dynamics of two-dimensional composites of elastic and viscoelastic layers
Authors: El-Raheb Michael
Published: October 2002

Models of frequency response, acoustic transmission, and transient wave propagation are presented for a two-dimensional composite of elastic and viscoelastic layers, simply supported at the two boundaries. The three models adopt transfer matrices to relate state variables over the two faces of a layer. In the frequency domain, a viscoelastic constitutive law is derived by nonlinear fitting a Padé series to measured data of complex shear modulus. For an elastic material, the eigenproblem admits positive real eigenvalues and their negatives. For a viscoelastic material, it admits positive complex eigenvalues and their negative conjugates. The imaginary part of the eigenvalue acts as a velocity-dependent viscous damper. Modal analysis solving transient response utilizes the complex eigenquantities and the static-dynamic superposition method.
Meridional ray backscattering enhancements for empty truncated tilted cylindrical shells: Measurements, ray model, and effects of a mode threshold
Authors: Morse Scot F. , Marston Philip L.
Published: October 2002

Narrow-band backscattering experiments are used to characterize a meridional ray enhancement on a tilted, finite empty cylindrical shell having a blunt truncation. The meridional ray of the lowest order flexural leaky Lamb wave is examined, which has previously been shown to lead to large backscattering enhancements for excitation frequencies near and above the shell’s coincidence frequency. The measurements are used to validate a convolution formulation ray theory describing the far-field backscattered amplitudes. Comparisons are also made with an approximate partial wave series solution for the finite cylindrical shell. The amplitude of the meridional ray enhancement is dependent on the nature of the reflection of the leaky wave from the shell truncation. While the peak measured amplitude agrees with predictions at low frequencies, experiments indicate the enhancement is degraded at high frequencies and exhibits an abrupt drop near the frequency of the mode threshold (cutoff) for the next-highest flexural mode. The nature of the leaky wave end reflection is examined using an approximate calculation of the energy reflection coefficient for leaky waves on a semi-infinite free plate. Results suggest the observed degradation is the result of mode conversion effects.
Acoustical analysis and model-based sound synthesis of the kantele
Authors: Erkut Cumhur , Karjalainen Matti , Huang Patty , Välimäki Vesa
Published: October 2002

The five-string Finnish kantele is a traditional folk music instrument that has unique structural features, resulting in a sound of bright and reverberant timbre. This article presents an analysis of the sound generation principles in the kantele, based on measurements and analytical formulation. The most characteristic features of the unique timbre are caused by the bridgeless string termination around a tuning pin at one end and the knotted termination around a supporting bar at the other end. These result in prominent second-order nonlinearity and strong beating of harmonics, respectively. A computational model of the instrument is also formulated and the algorithm is made efficient for real-time synthesis to simulate these features of the instrument timbre.
Lateralization and detection of pulse trains with alternating interaural time delays
Authors: Balakrishnan Uma , Freyman Richard L.
Published: October 2002

The effect of onset interaural time differences (ITDs) on lateralization and detection was investigated for broadband pulse trains 250 ms long with a binaural fundamental frequency of 250 Hz. Within each train, ITDs of successive binaural pulse pairs alternated between two of three values (0 μs, 500 μs left-leading, and 500 μs right-leading) or were invariant. For the alternating conditions, the experimental manipulation was the choice of which of two ITDs was presented first (i.e., at stimulus onset). Lateralization, which was estimated using a broadband noise pointer with a listener adjustable interaural delay, was determined largely by the onset ITD. However, detection thresholds for the signals in left-leading or diotic continuous broadband noise were not affected by where the signals were lateralized. A quantitative analysis suggested that binaural masked thresholds for the pulse trains were well accounted for by the level and phase of harmonic components at 500 and 750 Hz. Detection thresholds obtained for brief stimuli (two binaural pulse or noise burst pairs) were also independent of which of two ITDs was presented first. The control of lateralization by onset cues appears to be based on mechanisms not essential for binaural detection.
Rising incidence of breast cancer after completion of the first prevalent round of the breast cancer screening programme
Authors: Schouten L.J. , de Rijke J.M. , Huveneers J.A.M. , Verbeek A.L.M.
Published: October 2002

OBJECTIVES: After completion of the prevalent screening round of the breast cancer screening programme in Limburg, The Netherlands, incidences started rising once again. This increase was contrary to expectations, which had predicted a slightly higher, but stable, incidence after the first screening round. The trends in incidence were studied to find explanations for the observed rise in incidence. SETTING: Breast cancer screening programme in mid-Limburg and southern Limburg, the Netherlands. METHODS: The data files of the breast cancer screening programme and the Maastricht cancer registry were linked to evaluate the effect of breast cancer screening. Only the first primary breast tumour was included in the evaluation. RESULTS: The second peak of incidence after the prevalent screening round was 45% higher than the incidences before the start of the screening. Also, the decrease in incidence of large and node positive tumours was interrupted. Compared with national detection rates, the number of screen detected cancers was lower before 1995 and higher after that year. After 1997, incidence decreased again of all breast cancers, but also of large and node positive tumours. The incidence of node positive tumours showed large fluctuations, probably due to the introduction of the sentinel node procedure and immunohistochemistry. In 1999, incidence of large tumours and node positive tumours was 18% and 28%, respectively, lower than before the start of the screening. CONCLUSIONS: An increase in the background incidences and improved detection in the screening programme most likely explain this trend. The improved detection after 1995, and the lower than desirable decrease in large tumours, indicate that the screening performance was not optimal before 1996. The incidence of node positive tumours cannot be used any more as an indicator of the success of the screening programme because of detection bias.
Accuracy of serial screening for abdominal aortic aneurysms by ultrasound
Authors: Wilmink A.B.M. , Forshaw M. , Quick C.R.G. , Hubbard C.S. , Day N.E.
Published: October 2002

OBJECTIVES: To assess the accuracy of screening for abdominal aortic aneurysms (AAAs) by ultrasound (US). SETTING: An aneurysm screening programme in Huntingdon. METHODS: False negative tests were identified by tracing all patients with a ruptured aneurysm who were screened and then finding the number classified as normal on US. False positive tests were identified by calculating the number of aneurysmal aortas on US that were classified as normal on CT. Measurement variability of the infrarenal aortic diameter between US and CT was estimated. RESULTS: 14 out of 93 patients with a ruptured AAA since 1991 had been screened. No ruptured aneurysm had been classified as normal on US. All 64 patients with an AAA larger than 4.5 cm on US had their aneurysm confirmed on CT. The mean difference between CT and US measurements was 4 mm. The limit of variability between CT and US was 12 mm. CONCLUSION: No false negative scans were found using a cut off point of 3 cm as abnormal. No false positives were found if subjects with an AAA exceeding 4.5 cm were referred for further procedures. A serial US screening policy has excellent screening performance, justifying its use as a screening tool.
A randomised trial of skin photography as an aid to screening skin lesions in older males
Authors: Hanrahan P.F. , D’Este C.A. , Menzies S.W. , Plummer T. , Hersey P.
Published: October 2002

OBJECTIVES: We have previously shown that photographs assist in detection of change in skin lesions and designed the present randomised population based trial to assess the feasibility of photographs as an aid to management of skin cancers in older men. SETTING: 1899 men over fifty, identified from the electoral roll in two regions in New South Wales (NSW), Australia, were invited by mail to participate. METHODS: A total of 973 of 1037 respondents were photographed and randomised into intervention (participants given their photographs) or control groups (photographs withheld by investigators). At one and two years from the time of photography, all participants were advised to see their primary care practitioner for a skin examination. Those in the intervention group were examined with their photographs and those in the control group without their photographs. RESULTS: The results indicated that the practitioners were more likely to leave suspicious lesions in place for follow up observation (37% v 29%) (p=0.006) and less likely to excise benign non pigmented lesions (20 v 32%). There was little difference in excision rates for benign pigmented lesions (21% v 23%). Lesions excised were more likely to be non-melanoma skin cancer (58% v 42%) from patients who had photographs compared to those without photographs (p=0.005). The use of skin photography resulted in a substantial savings due to the reduced excision of benign lesions. CONCLUSIONS: These results suggest that it would be feasible to conduct a large scale randomised trial to evaluate the value of photography in early detection of melanoma and that such a trial could be cost effective due to the reduced excision of benign skin lesions.
A model parametric real-time logic
Authors: Morzenti Angelo , Mandrioli Dino , Ghezzi Carlo
Published: October 2002

TRIO is a formal notation for the logic-based specification of real-time systems. In this paper the language and its straightforward model-theoretic semantics are briefly summarized. Then the need for assigning a consistent meaning to TRIO specifications is discussed, with reference to a variety of underlying time structures such as infinite-time structures (both dense and discrete) and finite-time structures. The main motivation is the ability to validate formal specifications. A solution to this problem is presented, which gives a new, model-parametric semantics to the language. An algorithm for constructively verifying the satisfiability of formulas in the decidable cases is defined, and several important temporal properties of specifications are characterized.
Subsequence references
Authors: Hansen Wilfred J.
Published: October 2002

Arrays of characters are a basic data type in many programming languages, but strings and substrings are seldom accorded first-class status as parameters and return values. Such status would enable a routine that calls a search function to readily access context on both sides of a return value. To enfranchise substrings, this paper describes a new data type for substrings as a special case of one for general subsequences. The key idea is that values are not sequences or references to positions in sequences, but rather references to subsequences. Primitive operations on the data type are constants, concatenation, and four new functions—
base
,
start
,
next
, and
extent
—which map subsequence references to subsequence references.

This paper informally presents the data type, demonstrates its convenience for defining search functions, and shows how it can be concisely implemented. Examples are given in Ness, a language incorporating the new data type, which is implemented as part of the Andrew User Interface System.
M-LISP: a representation-independent dialect of LISP with reduction semantics
Authors: Muller Robert
Published: October 2002

In this paper we introduce M-LISP, a dialect of LISP designed with an eye toward reconciling LISP's metalinguistic power with the
structural
style of operational semantics advocated by Plotkin [28]. We begin by reviewing the original definition of LISP [20] in an attempt to clarify the source of its metalinguistic power. We find that it arises from a problematic clause in this definition. We then define the abstract syntax and operational semantics of M-LISP, essentially a hybrid of M-expression LISP and Scheme. Next, we tie the operational semantics to the corresponding equational logic. As usual, provable equality in the logic implies operational equality.

Having established this framework we then extend M-LISP with the metalinguistic
eval
and
reify
operators (the latter is a nonstrict operator that converts its argument to its metalanguage representation). These operators encapsulate the matalinguistic representation conversions that occur globally in S-expression LISP. We show that the naive versions of these operators render LISP's equational logic inconsistent. On the positive side, we show that a naturally restricted form of the
eval
operator is confluent and therefore a conservative extension of M-LISP. Unfortunately, we must weaken the logic considerably to obtain a consistent theory of reification.
A general framework for semantics-based bottom-up abstract interpretation of logic programs
Authors: Barbuti Roberto , Giacobazzi Roberto , Levi Giorgio
Published: October 2002

The theory of abstract interpretation provides a formal framework to develop advanced dataflow analysis tools. The idea is to define a nonstandard semantics which is able to compute, in finite time, an approximated model of the program. In this paper, we define an abstract interpretation framework based on a fixpoint approach to the semantics. This leads to the definition, by means of a suitable set of operators, of an abstract fixpoint characterization of a model associated with the program. Thus, we obtain a specializable abstract framework for bottom-up abstract interpretations of definite logic programs. The specialization of the framework is shown on two examples, namely, gound-dependence analysis and depth-kanalysis.
Mathematical foundations for time warp systems
Authors: Leivent Jonathan I. , Watro Ronald J.
Published: October 2002

We develop a simple formal model of the Time Warp approach to distributed computation, prove several important properties of the model, and devise some extensions to Time Warp that provide improved termination behavior. Our model consists of processes that communicate solely via message passing. One of the basic process steps is a rollback operation that includes message retraction via transmission of antimessages. In the model, we consider three problems: safety, progress, and termination. By safety, we mean that for a given system of processes, if a run of the system terminates, then the final system state of the run is identical to the final system state of a rollback-free run. We give premises that imply safety, and a counterexample that shows how safety can fail. By progress, we mean that, as a run of a system proceeds, the minimum timestamp of an unprocessed message always eventually increases. We state three axioms that imply the progress property. By termination, we mean that, if all rollback-free runs of a system terminate, then all runs terminate. The termination property is generally false in existing implementations of Time Warp systems due to the possibility of Time Warp vortices. We define additional mechanisms that can guarantee the termination property for most Time Warp applications.
Program optimization and parallelization using idioms
Authors: Pinter Shlomit S. , Pinter Ron Y.
Published: October 2002

Programs in languages such as Fortran, Pascal, and C were designed and written for a sequential machine model. During the last decade, several methods to vectorize such programs and recover other forms of parallelism that apply to more advanced machine architectures have been developed (particularly for Fortran, due to its pointer-free semantics). We propose and demonstrate a more powerful translation technique for making such programs run efficiently on parallel machines which support facilities such as parallel prefix operations as well as parallel and vector capabilities. This technique, which is global in nature and involves a modification of the traditional definition of the program dependence graph (PDG), is based on the extraction of parallelizable program structures (“idioms”) from the given (sequential) program. The benefits of our technique extend beyond the above-mentioned architectures and can be viewed as a general program optimization method, applicable in many other situations. We show a few examples in which our method indeed outperforms existing analysis techniques.
Metalevel building blocks for modular systems
Authors: Jagannathan Suresh
Published: October 2002

The formal definition of any namespace device found in a programming language can be given in terms of transformations on a semantic environment. It is worthwhile, therefore, to consider the implications of incorporating environments as bona fide data objects in a programming system.

In this article, we propose a treatment of environments and the mechanism by which they are reified and manipulated, that addresses these concerns. The language described below (Rascal) permits environments to be reified into data structures, and data structures to be reflected into environments, but gives users great flexibility to constrain the extent and scope of these processes. We argue that the techniques and operators developed define a cohesive basis for building large-scale modular systems using reflective programming techniques.
Some comments on “a denotational semantics for Prolog”
Authors: Arbab Bijan , Berry Daniel M.
Published: October 2002

Two independently derived denotational semantics for Prolog are contrasted, Arbab and Berry's for the full language and Nicholson and Foo's for a databaseless language. Using the ideas suggested by the former, the latter can be easily extended to include the database operations.
A bounded first-in, first-enabled solution to the
l
-exclusion problem
Authors: Afek Yehuda , Dolev Danny , Gafni Eli , Merritt Michael , Shavit Nir
Published: October 2002

This article presents a solution to the
first-come, first-enabled
ℓ-exclusion problem of Fischer et al. [1979]. Unlike their solution, this solution does not use powerful read-modify-write synchronization primitives and requires only bounded shared memory. Use of the
concurrent timestamp system
of Dolev and Shavir [1989] is key in solving the problem within bounded shared memory.