bluuebunny/crossref_metadata_2025 huggingface dataset:
Abundance and size structure of Thalassoma pavo (Pisces: Labridae) in the western Mediterranean Sea: variability at different spatial scales
Authors: Guidetti Paolo , Bianchi Carlo Nike , La Mesa Gabriele , Modena Milena , Morri Carla , Sara Giampietro , Vacchi Marino
Published: October 2002

The present study was carried out during the summer of 1997 in three locations of the western Italian coast (La Spezia, Ligurian Sea; Ischia, central Tyrrhenian Sea; Ustica, southern Tyrrhenian Sea) to investigate variability in abundance and size structure of the labrid fish Thalassoma pavo along a latitudinal gradient and over different spatial scales. Fish abundance and size were estimated by visual census in shallow rocky reefs. Significant differences were detected in average abundances of T. pavo (with and without the contribution of juveniles) among locations (separated by a distance of hundreds of kilometres from each other) and over the smallest scale examined (i.e. among sites located tens of metres from each other). However, most variability was explained considering the largest spatial scale associated with the latitudinal gradient. Average abundances generally decreased from the southern Tyrrhenian to the Ligurian Sea. In terms of frequency, juveniles (<5 cm total length (TL)) increased from north to south, while the largest fish (16–20 cm) displayed an opposite trend. The intermediate size-classes (6–10 and 11–15 cm) did not show any distinct patterns. In terms of abundance, small T. pavo (0–5 cm) showed significantly higher densities at Ustica, followed by Ischia and La Spezia. Fish 6–10 and 11–15 cm long were significantly less abundant at La Spezia than at Ischia and Ustica, while those between 16 and 20 cm TL did not differ numerically among the three locations. The results of the present study provide suggestive evidence that factors acting on a geographical scale are likely to influence distribution patterns of the thermophilic fish T. pavo, although significant effects have been also observed at the smallest spatial scale examined. Climatic conditions (e.g. water temperature along the latitudinal gradient) and substrate features (e.g. macroalgal cover, physical complexity, slope) are thus likely to affect average abundances and size structures of T. pavo populations along the western Italian coast.
Magnetic domains and flux pinning properties of a nanostructured ferromagnet/superconductor bilayer
Authors: Van Bael M. J. , Raedts S. , Temst K. , Swerts J. , Moshchalkov V. V. , Bruynseraede Y.
Published: October 2002

We have investigated the magnetic and superconducting properties of a nanostructured ferromagnet/superconductor hybrid system, consisting of a Co layer with a square array of rectangular holes (antidots), covered with a thin continuous (nonperforated) superconducting Pb layer. The Co film with an antidot lattice shows a strong in-plane magnetic shape anisotropy determined by the array configuration and the rectangular shape of the antidots. Remanent domain structures in the uncovered Co antidot array are imaged at room temperature by magnetic force microscopy. The superconducting pinning properties of the hybrid ferromagnet/superconductor system are studied for different magnetic states of the Co antidot lattice. We demonstrate that the contribution to the superconducting pinning potential caused by the stray field from the domain walls is stronger than that arising from the periodic modulation due to the underlying antidot lattice.
A scanning Hall probe microscope for large area magnetic imaging down to cryogenic temperatures
Authors: Gregory J. K. , Bending S. J. , Sandhu A.
Published: October 2002

We describe the design, construction, and operation of a large area scanning Hall probe microscope that is built around a closed-cycle refrigerator capable of cooling samples down to 35 K. The system operates in a custom vacuum housing that utilizes a flexible vacuum bellows to link to external stepping motor positioning stages allowing x–y scans of 5 mm×5 mm under vacuum at 35 K, increasing to 25 mm×25 mm in atmospheric pressure at 300 K and in magnetic fields up to 0.06 T. The Hall probe can be viewed with a microscope through a window and lowered to the desired scanning height and tilted with micrometer screws. The system has an effective lateral spatial resolution of 1.25 μm and a minimum detectable field of ∼0.08 μT/√Hz. We describe the performance of the system and illustrate its potential with images of the local magnetic induction at the surface of various magnetic recording media at room temperature as well as an array of superconducting YBa2Cu3O7−δ squares at 40 K.
Frequency response analysis of a 1:1 transmission line based transformer
Authors: Homma Akira
Published: October 2002

A theoretical approach to study the frequency response characteristics of a 1:1 transmission line based transformer is described. The frequency and impulse response were calculated to take into account signals that inevitably appears in outside space around and between the transmission lines. Experimental confirmation of the deduced frequency response function was made for a prototype transmission line based transformer where semirigid coaxial cables were used as transmission lines. Good agreement was obtained between the theoretical and experimental results in the 50 MHz–3 GHz frequency range. A 3 dB bandwidth of the transformer was obtained from 20 MHz to 1 GHz. The theory described here would be useful in the design of actual high frequency transformers.
Fabrication of ruby sensor probe for the fiber-optic thermometer using fluorescence decay
Authors: Aizawa H. , Ohishi N. , Ogawa S. , Katsumata T. , Komuro S. , Morikawa T. , Toba E.
Published: October 2002

Ruby single crystals have been grown successfully from the melt droplet on the sapphire crystal fibers as the sensor head directly coupled with optical fiber for the thermometer applications using fluorescence decay. In this fabrication process, droplets of slurry of ruby powders are formed on the end of the sapphire crystal fiber and are dried, sintered, and then melted and solidified in a floating-zone furnace. The photoluminescence (PL) lifetime of the ruby sensor head varies from τ=3.8 to 2.5 ms with the Cr3+ concentrations from 0.07 to 1.0 at. %. The ruby crystal with a Cr3+ concentration of 0.35 at. % is found to be the most suitable sensor head having the longest PL lifetime. The temperature coefficient of the fiber-optic thermometer equipment using the directly coupled ruby sensor head with a Cr3+ concentration of 0.35 at. % is −12.4 μs/K.
Characterization of ultrathin metal–oxide–semiconductor structures using coupled current and capacitance–voltage models based on quantum calculation
Authors: Simonetti O. , Maurel T. , Jourdain M.
Published: October 2002

We have developed a capacitance–voltage (C–V) and a current–voltage (I–V) quasistatic quantum model of ultrathin metal–oxide–semiconductor (MOS) structures based on the self-consistent solution of the Schrödinger and Poisson equations. The direct tunneling current takes into account the carrier distribution in energy subbands and uses the notions of corrected tunnel transparency and of impact frequency at the injecting electrode. These models are used to obtain the main physical parameters of n+-polysilicon/SiO2/〈100〉 p-Si MOS structures, with oxide thickness ranging from 1.2 to 3.5 nm. The extracted parameters are the oxide thickness (TOX), the substrate doping, both at the Si/SiO2 interface [NS(0)] and deep in the bulk [NS(∞)], and the polysilicon gate doping (NP) near the polysilicon/SiO2 interface. For this range of oxide thickness, the direct tunneling current strongly perturbs the C–V measurements, which must be corrected. Down to 1.5 nm oxide thickness, these parameters are obtained by C–V characterization. Below 1.5 nm oxide thickness, the C–V correction fails and TOX is obtained by a coupled C–V and I–V characterization procedure, based on the adjustment of the effective mass of the electrons in the oxide (mOX) with the oxide thickness. The whole characterization procedure provides TOX values with associated errors very close to the ellipsometric measurements. The information obtained on the substrate doping seems to correspond well with advanced MOS technologies. The C–V and I–V simulation results are in good agreement with measurements for all the samples and a good consistency is found between the C–V and I–V models. Finally, we show that the extracted TOX obtained with the variation of mOX with TOX provide a better agreement than those with a constant mOX value, compared to the ellipsometric measurements.
Enhanced stability of rocksalt-type AIN phase in AIN/TiN superlattices synthesized by room-temperature pulsed laser deposition
Authors: Pankov V. , Evstigneev M. , Prince R. H.
Published: October 2002

AlN/TiN superlattice coatings with bilayer thickness, Λ, of 1–20 nm were synthesized by pulsed laser deposition (PLD) at room temperature. Below a critical value of bilayer thickness, Λc≈3 nm, the coatings formed a single-phase NaCl-type structure due to pseudomorphic stabilization of the nonequilibrium rocksalt-type (B1) AlN phase. Exceeding Λc resulted in the loss of continuous coherent growth of alternating AlN and TiN layers that is usually attributed to a rocksalt→wurtzite AlN phase transformation occurring in AlN layers when their thickness exceeds a certain critical value. However, in contrast to previous reports, a substantial amount of crystalline B1–AlN has been detected within the volume of AlN layers in AlN/TiN superlattices with Λ>Λc. The observed enhanced pseudomorphic stability of B1–AlN in superlattices fabricated by room-temperature PLD is explained by kinetically limited conditions inherent to this deposition technique. The presence of the B1–AlN phase in AlN/TiN multilayers is assumed to be mainly responsible for their increased hardness in the range of Λ where the Koehler hardness enhancement mechanism is inoperative.
Effect of growth temperature on the structure and magnetic properties of sputtered biepitaxial (111) permalloy films
Authors: Loloee R. , Crimp M. A.
Published: October 2002

Electron backscatter diffraction (EBSD) patterns and coercivity values obtained from magnetization hysteresis loops of several sputtered biepitaxial (111)Py films grown at different temperatures on sputtered biepitaxial (111)Cu buffer layers have been collected. The results show that the coercive field of the Py films systematically increases as the growth temperature decreases, consistent with an increase in the degradation of the corresponding EBSD patterns due to enhancement of strain caused by misfit dislocations, threading defects, and point defects. The magnetization measurements also revealed no magnetocrystalline anisotropy for any of biepitaxial Py films studied. However, strain-induced uniaxial anisotropy was observed in all biepitaxial Py films.
Spectroscopic detection of the SiCCl free radical
Authors: Smith Tony C. , Evans Corey J. , Clouthier Dennis J.
Published: October 2002

The laser-induced fluorescence spectrum of the jet-cooled silicon chloromethylidyne (SiCCl) free radical has been identified in the 600–665 nm region. The excitation energy, rotational band contours, vibrational frequencies, and chlorine isotope effects are all consistent with our previous ab initio predictions of the spectroscopic parameters of this radical [J. Chem. Phys. 117, 6439 (2002)]. Single vibronic level emission spectra show an extensive pattern of ground-state vibrational levels which can be assigned to activity in ν1″=1275 cm−1, ν2″=214.2 cm−1, and ν3″=528.2 cm−1. An analysis of the emission spectra yielded the Renner–Teller parameter ε=0.136(14) and the spin–orbit coupling constant A=−159.4 cm−1. The ab initio predictions of the manifold of ground-state vibrational and spin–orbit energy levels were found to be clearly diagnostic, allowing assignments to be made with little ambiguity.
Delayed fluorescence of a poly (p-phenylenevinylene) derivative: Triplet–triplet annihilation versus geminate pair recombination
Authors: Gerhard A. , Bässler H.
Published: October 2002

The question of the origin of delayed fluorescence from a phenyl-substituted poly(p-phenylenevinylene)-type copolymer (Ph-PPV) is addressed. Two origins have to be considered, i.e., triplet–triplet annihilation and recombination of geminate electron–hole pairs. Ph-PPV is investigated in the form of two different samples, namely diluted in 2-methyltetrahydrofuran (MTHF) glass at 80 K and as a thin film of optical density of 0.6. It will be shown that in the diluted solution, delayed fluorescence is due to triplet–triplet annihilation and in the thin film, it is due to geminate pair recombination. The assignment of delayed fluorescence to geminate pair recombination in the thin film could be made due to delayed fluorescence experiments under applying an electric field of 2×106 V/cm. The delayed fluorescence is strongly influenced by the electric field which is a sign that charged species, i.e., geminate electron–hole pairs, are involved in the process of delayed fluorescence.
Pattern formation arising from interactions between Turing and wave instabilities
Authors: Yang Lingfa , Dolnik Milos , Zhabotinsky Anatol M. , Epstein Irving R.
Published: October 2002

We study pattern formation arising from the interaction of the stationary Turing and wave (oscillatory Turing) instabilities. Interaction and competition between these symmetry-breaking modes lead to the emergence of a large variety of spatiotemporal patterns, including modulated Turing structures, modulated standing waves, and combinations of Turing structures and spiral waves. Spatial resonances are obtained near codimension-two Turing-wave bifurcations. Far from bifurcation lines, we obtain inwardly propagating spiral waves with Turing spots at their tips. We demonstrate that the coexistence of Turing spots and traveling waves is a result of interaction between Turing and oscillatory modes, while the inwardly propagating waves (antispirals) do not require this interaction; they can arise from the wave instability combined with a negative group velocity.
Optimal methods for calculation of the amount of intermolecular electron transfer
Authors: Szefczyk Borys , Sokalski W. Andrzej , Leszczynski Jerzy
Published: October 2002

In order to determine the optimal methodology for evaluation of the magnitude of intermolecular charge transfer, several methods have been examined: Mulliken population, natural population analysis, atoms in molecules (AIM) as well as charges from electrostatic potentials using a grid-based method (Chelp and Chelpg) procedures using a series of correlation consistent cc-pVXZ (X=D, T, Q) basis sets within LCAO MO SCF, MP2, DFT, and coupled cluster theory levels. In contrast to previous nonconclusive comparative studies, the present calculations reveal close matching of the recently available experimental data for six Lewis acid-base adducts with theoretical values derived from the Chelpg approach, whereas for the remaining methods relative errors are almost doubled. On the other hand, AIM and Chelpg results display the best linear correlation coefficients with the experimental data. Since reasonably accurate Chelpg results could be already obtained with SCF or DFT B3LYP methods using cc-pVDZ, such an approach opens the way to study intermolecular charge transfer in larger molecular systems. Preliminary results obtained within cc-pVDZ basis set and B3LYP functional for pyridine-SO3 complex do not exceed relative error limits observed for other smaller complexes. Analysis of corresponding interaction energy components calculated consistently in the dimer basis set indicates significant role of electrostatic, exchange and delocalization contributions, with rather negligible correlation term. In contrast to previous findings, the experimentally observed amount of transferred charge seems not to correlate with any interaction energy term.
Morphological and structural analyses of plasma-induced damage to n-type GaN
Authors: Choi H. W. , Chua S. J. , Tripathy S.
Published: October 2002

Plasma-induced damage to n-type GaN has been studied by atomic force microscopy and Raman spectroscopy. It was found that the extent of surface roughening is largely dependent on the surface defect density, since preferential sputtering at these sites takes place. Several Raman defect modes have emerged from the plasma-damaged samples, and have been compared to the defect modes observed from ion-implanted GaN. The defect peaks centered at 300 and 360 cm−1 have been assigned to disorder-activated Raman scattering modes, while the 453 and 639 cm−1 peaks have been attributed to vacancy scattering. It has also been demonstrated that structural damage can be annealed out at 900 °C for 60 s in flowing N2.
Investigation of interlayer coupling in [Fe/Cr]n magnetic multilayer structures by the ferromagnetic resonance method (Review)
Authors: Kreines N. M.
Published: October 2002

The properties and nature of the interlayer coupling and the possible types of magnetic ordering in magnetic superlattices and sandwiches remain topical questions in the physics of magnetic phenomena. The existing models describing the interaction between ferromagnetic layers via the nonferromagnetic spacer layer and the predicted temperature dependence of the coupling constants in those models are briefly reviewed. The effectiveness of the ferromagnetic resonance method for investigating the interlayer coupling is discussed. A review of recent experimental studies of the interlayer coupling in superlattices and sandwiches of the Fe/Cr system by this method over a wide range of temperatures is presented (including original papers by the author and co-workers). The experimental data are analyzed on the basis of the existing theories. The regions of applicability of these model for describing the properties of such systems.
On the conditions for the existence of 1D magnetic solitons with frequency characteristics falling in the continuous spectrum
Authors: Kosevich A. M. , Grishaev V. I.
Published: October 2002

Solutions of a modified (with higher-order dispersion taken into account) sine-Gordon equation in the form of a double soliton (4π kink) and a pair of spatially separated bound kinks are investigated. An analytical condition for the absence of radiation from the soliton at large distances is formulated. The previous finding of the existence of a discrete set of nonradiative composite solitons is confirmed. The physical meaning of this result is that at certain distances between kinks the radiation generated by one of the kinks completely quenches the field of the other kink outside the soliton as a result of ordinary interference of waves in antiphase.
Possibility of formation and reversible rearrangement of equilibrium domain structure in antiferromagnets
Authors: Gomonay E. V. , Loktev V. M.
Published: October 2002

It is shown that the magnetoelastic interaction can play a substantial role in the formation of the equilibrium domain structure in antiferromagnets having two or more equivalent easy directions of the axis of magnetic anisotropy. It is demonstrated with the use of the methods of nonlinear theory of elasticity in the framework of a phenomenological model that the surface of the crystal can and does serve as a source of fictitious “elastic charges” of incompatibility, which have consequences analogous to those of the magnetostatic charges that arise on the surface of ferromagnetic crystals and lead to the formation of domains. Here the surface of the crystal is treated as a special phase with its own magnetic, elastic, and magnetoelastic properties. The field of the “elastic charges” is long-ranged, and, accordingly, its contribution to the stray (“detwinning”) energy, which plays the main role in the formation of the equilibrium domain structure, is proportional to the volume of the sample rather than its surface area. The formation of the domain structure is nothing more than the restoration of the initial global symmetry of the crystal in those cases when the phase transformation that breaks this symmetry is described by an order parameter which is conjugate to the shear strain. The conditions for the absence of “elastic charges” inside the sample impose certain restrictions on the morphology of the magnetoelastic domain structure in antiferromagnets. It is shown how the character of the equilibrium state of the crystal is influenced by disclinations arising at places where three or more domains come together.
Noncollinear magnetic structures in an Fe/Si/Fe film with a ferromagnetic interlayer exchange interaction
Authors: Chizhik A. B. , Gnatchenko S. L. , Baran M. , Fronc K. , Szymczak R. , Zuberek R.
Published: October 2002

Results are presented from magnetic and magnetooptical studies of the magnetic configurations in a three-layer film Fe(30 Å)/Si(14 Å)/Fe(30 Å) in which ferromagnetic and biquadratic exchange between iron layers is observed and which also possesses cubic and uniaxial anisotropy. These studies were done at temperatures of 300 and 10 K. It was found that in the absence of magnetic field a noncollinear magnetic structure, the form of which changes with temperature, is observed in this system. A calculation of the stable noncollinear configurations is done on the basis of a model in which it is assumed that both the exchange interaction constant and the cubic and uniaxial anisotropy constants in the iron layer change with temperature. The values of the angles characterizing the magnetization direction in the iron layers in the stable noncollinear configurations are determined on the basis of a comparative analysis of the experimental data and the results of the calculation. It is shown that both the angle between the magnetization directions in the two iron layers and the direction of the easy axis of the system as a whole change with temperature.
Z-contrast imaging of dislocation cores at the GaAs/Si interface
Authors: Lopatin S. , Pennycook S. J. , Narayan J. , Duscher G.
Published: October 2002

The interface between silicon and epitaxial GaAs thin film grown by metalorganic chemical vapor deposition was studied using atomic-resolution Z-contrast imaging. Z-contrast imaging provides chemical composition information and allows direct interpretation of micrographs without simulation. Three different types of dislocations were identified. As expected, a dangling bond was found in the atomic structure of the 60° dislocation. One of the observed 90° dislocations had the reconstructed atomic core structure (with no dangling bonds). The core structure of the other 90° dislocation exhibited a dangling bond.
Negative refraction of modulated electromagnetic waves
Authors: Smith D. R. , Schurig D. , Pendry J. B.
Published: October 2002

We show that a modulated Gaussian beam undergoes negative refraction at the interface between a positive and negative refractive index material. While the refraction of the beam is clearly negative, the modulation interference fronts are not normal to the group velocity, and thus exhibit a sideways motion relative to the beam—an effect due to the inherent frequency dispersion associated with the negative index medium. In particular, the interference fronts appear to bend in a manner suggesting positive refraction, such that for a plane wave, the true direction of the energy flow associated with the refracted beam is not obvious.
Nuclear magnetic resonance molecular photography
Authors: Khitrin Anatoly K. , Ermakov Vladimir L. , Fung B. M.
Published: October 2002

A procedure is described for storing a two-dimensional (2D) pattern consisting of 32×32=1024 bits in a spin state of a molecular system and then retrieving the stored information as a stack of nuclear magnetic resonance spectra. The system used is a nematic liquid crystal, the protons of which act as spin clusters with strong intramolecular interactions. The technique used is a programmable multifrequency irradiation with low amplitude. When it is applied to the liquid crystal, a large number of coherent long-lived H1 response signals can be excited, resulting in a spectrum showing many sharp peaks with controllable frequencies and amplitudes. The spectral resolution is enhanced by using a second weak pulse with a 90° phase shift, so that the 1024 bits of information can be retrieved as a set of well-resolved pseudo-2D spectra reproducing the input pattern.
Safety Pharmacology Screening: Practical Problems in Drug Development
Authors: Mortin Lawrence I. , Horvath Christopher J. , Wyand Michael S.
Published: October 2002

Undesired pharmacologic activities of novel drugs or biologies may limit development of a therapeutic prior to the characterization of any toxicologic effects. In rodent species, general pharmacology assays have traditionally been used to screen new agents for pharmacologic effects on the central and peripheral nervous systems, the autonomic nervous system and smooth muscles, the respiratory and cardiovascular systems, the digestive system, and the physiologic mechanisms of water and electrolyte balance. In large animal species, such as dogs and nonhuman primates, smaller numbers of animals per study limit their use for screening assays, but these species may play an important role in more detailed mechanistic studies. For drugs and biologies that must be tested in nonhuman primates because of species-specific action of the test agent, functional pharmacologic data are often collected during acute or subacute toxicity studies. This requires careful experimental design to minimize any impact pharmacologic effects or instrumentation may have on the assessment of toxicity. In addition, with many new therapies targeted at immunologic diseases, the pharmacologic effect of therapeutics on the immune system presents new challenges for pharmacologic profiling. The application of pharmacology assays by organ system in both rodent and large animal species are discussed, as well as practical issues in assessing pharmacology endpoints in the context of toxicity studies.
A No-Observed-Adverse-Effect Level of 1000 Mg/Kg in A 28-Day Repeated-Dose Study as a Limit Value for Acute Toxicity Testing
Authors: Pieters Moniek N. , Kramer Hester J. , Slob Wout
Published: October 2002

Following the guidelines of the European Community (EC), chemicals are not classified according to acute toxicity if the estimated LD50 exceeds 2000 mg kg-1. Instead of an LD50 test, a limit test is often performed for relatively nontoxic chemicals. Since a short-term repeated-dose study is required in addition to an acute toxicity test, our investigation was aimed at finding out if acute toxicity testing could be omitted under certain circumstances. The latter would contribute to the reduction of (unnecessary) animal use. Data on LD50 and the no-observed-adverse-effect level values of 28-day repeated-dose studies (NO AEL 28-d) were retrieved from EC notifications for new substances. We statistically evaluated the LD50 and the NOAEL28-d values of 766 compounds (rat data only). At a NO AEL28-d of 1000 mg kg-1 there was a 4% probability of the associated LD50 being lower than 2000 mg kg-1. The probability of the LD50 being lower than 200 mg kg-1 was estimated at 0.04%. If such small probabilities of misclassification are considered acceptable, acute toxicity testing could be omitted at a NOAEL28-d of 1000 mg kg-1 or higher. A NOAEL28-d of 1000 mg kg-1 could thus function as a limit value for the acute toxicity testing requirement. Application of this limit value would have made acute toxicity testing redundant for 286 out of 766 compounds reviewed. The use of the limit value may thus form an important contribution to the reduction of animal use.
Ulceration of the Small and Large Bowel Mucosain Resection Specimens of Cystic Fibrosis Patients with Fibrosing Colonopathy
Authors: Lannon C. L. , Hinchliffe S. A. , Pope J. D. , Ball L. M. , Van Velzen D.
Published: October 2002

Fibrosing colonopathy (FC), observed in cystic fibrosis patients taking high-strength pancreatic enzyme preparations, is characterized by progressive obstruction of the ascending colon, with long-segment fusiform stenosis due to the deposition of submucosal fibrous tissue. The pathogenesis is uncertain, although direct toxic damage to the colonic mucosa by a constituent of such preparations has been proposed as an explanation. Mucosal defects and rectal bleeding have been observed by colonoscopy in cystic fibrosis patients at risk for and with evident FC. In a quantitative, observational study, mucosal defects were studied in six ileo-cecal resection specimens with FC confirmed by three independent pathologists' review. Representative areas (2.5-cm-long segments) were taken of terminal ileum, cecal colon, and ascending colon both at the site of most severe stenosis and at the most distal ascending colon site available; after processing with paraffin, the areas were serially sectioned at 500-μm intervals for the preparation of 5-μm sections for microscopical assessment. Marking in each section the area affected by (repairing) ulceration, and using three-dimensional reconstructions of the bowel lining, individual mucosal lesions were reconstructed. Using the reconstructed bowels, point scoring analysis of the area fraction affected by ulceration as well as the area of individual lesions was carried out. Lesions of variable age were found in the terminal
Intravenous flumazenil versus oxazepam tapering in the treatment of benzodiazepine withdrawal: a randomized, placebo‐controlled study
Authors: Gerra G. , Zaimovic A. , Giusti F. , Moi G. , Brewer C.
Published: October 2002

Flumazenil (FLU), a benzodiazepine (BZD) partial agonist with a weak intrinsic activity, was previously found unable to precipitate withdrawal in tolerant subjects submitted to long‐lasting BZD treatment. The potential use of FLU to treat BZD withdrawal symptoms has also been evaluated tentatively in clinical studies. In the present experiment, FLU (treatment A) was compared with oxazepam tapering (treatment B) and placebo (treatment C) in the control of BZD withdrawal symptoms in three groups of BZD dependent patients. Group A patients (20) received FLU 1 mg twice a day for 8 days, and oxazepam 30 mg in two divided doses (15 mg + 15 mg) during the first night, oxazepam 15 mg during the second night and oxazepam 7.5 mg during the third night. FLU was injected i.v. in saline for 4 hours in the morning and 4 hours in the afternoon, in association with placebo tablets. Group B patients (20) were treated by tapering of oxazepam dosage (from 120 mg) and with saline solution (as placebo) instead of FLU for 8 days. Group C patients (10) received saline instead of FLU and placebo tablets instead of oxazepam for 8 days. FLU immediately reversed BZD effects on balance task and significantly reduced withdrawal symptoms in comparison with oxazepam and placebo on both self‐reported and observer‐rated withdrawal scales. The partial agonist also reduced craving scores during the detoxification procedure. In addition, during oxazepam tapering, group B patients experienced paradoxical symptoms that were not apparent in FLU patients. Patients treated with FLU showed a significantly lower relapse rates on days 15, 23 and 30 after the detoxification week. Our data provide further evidence of FLUs ability to counteract BZD effects, control BZD withdrawal and normalize BZD receptor function. The effectiveness of FLU may reflect its capacity to upregulate BZD receptors and to reverse the uncoupling between the recognition sites of BZD and GABA, on the GABA A macromolecular complex, that has been reported in tolerant subjects.
Depletion of MOM1 in non‐dividing cells of Arabidopsis plants releases transcriptional gene silencing
Authors: Tariq Muhammad , Habu Yoshiki , Paszkowski Jerzy
Published: October 2002

Mitotic and meiotic inheritance of epigenetic information is coupled to the reproduction of chromatin conformation and DNA methylation patterns. This implies that the S phase of the cell cycle provides a window of opportunity for changes in epigenetic determination. Recent studies, however, have suggested that chromatin structure is also rather dynamic in quiescent cells of multicellular eukaryotes and that silent heterochromatic regions can become accessible to transcription. Such epigenetic flexibility in differentiated tissues could be of physiological importance. The mechanisms and molecular components involved are of great interest but as yet unknown. We examined MOM1 (Morpheus' Molecule 1), a regulator of transcriptional gene silencing (TGS) that acts independently of DNA methylation, for its role in the maintenance of TGS in non‐dividing, differentiated cells. The results provide evidence that TGS maintenance mediated by MOM1 is a dynamic process that can be modified in non‐dividing cells of mature plant organs by depletion of MOM1.
The complex phase gradient method applied to leaky Lamb waves
Authors: Lenoir O. , Conoir J. M. , Izbicki J. L.
Published: October 2002

The classical phase gradient method applied to the characterization of the angular resonances of an immersed elastic plate, i.e., the angular poles of its reflection coefficient R_, was proved to be efficient when their real parts are close to the real zeros of R_ and their imaginary parts are not too large compared to their real parts. This method consists of plotting the partial reflection coefficient phase derivative with respect to the sine of the incidence angle, considered as real, versus incidence angle. In the vicinity of a resonance, this curve exhibits a Breit–Wigner shape, whose minimum is located at the pole real part and whose amplitude is the inverse of its imaginary part. However, when the imaginary part is large, this method is not sufficiently accurate compared to the exact calculation of the complex angular root. An improvement of this method consists of plotting, in 3D, in the complex angle plane and at a given frequency, the angular phase derivative with respect to the real part of the sine of the incidence angle, considered as complex. When the angular pole is reached, the 3D curve shows a clear-cut transition whose position is easily obtained.
A nonlinear model of thermoacoustic devices
Authors: Karpov Sergey , Prosperetti Andrea
Published: October 2002

This paper presents a nonlinear, time-domain model of thermoacoustic devices based on cross-sectional averaged equations. Heat transfer perpendicular to the device axis—which lies at the core of thermoacoustic effects—is modeled in a novel and more realistic way. Heat conduction in the solid surfaces surrounding the fluid medium is included. Contrary to the previous versions of this model [Watanabe et al., J. Acoust. Soc. Am. 102, 3484–3496 (1997)], the present version does not require artificial damping and is numerically robust. The model performance is illustrated on several examples: a prime mover, an externally driven thermoacoustic refrigerator, and a combined prime mover/refrigerator system.
Diffuse wavefields in cylindrical coordinates
Authors: Langley R. S. , Shorter P. J.
Published: October 2002

A diffuse wavefield is normally defined in terms of plane waves—to quote one textbook definition “plane waves are incident from all directions with equal probability and random phase.” In some vibro-acoustic problems the response of a two-dimensional component such as a plate is more conveniently expressed in terms of cylindrical waves, and it is not immediately obvious what properties should be assigned to the cylindrical waves to constitute a diffuse field. It is shown here that a diffuse wavefield can be modeled as a summation of statistically independent cylindrical waves, apart from the fact that each outgoing wave of a particular order is fully correlated to an incoming wave of the same order. A simple relationship is derived between the energy flow P in each wave component and the energy density e of the wavefield: P=ecg/k, where cg is the group velocity and k is the wavenumber. This result is shown to hold true for both bending waves and in-plane waves (longitudinal and shear) in a plate. The work has application to the calculation of coupling loss factors in statistical energy analysis.
An adaptive procedure for categorical loudness scaling
Authors: Brand Thomas , Hohmann Volker
Published: October 2002

In this study, an adaptive procedure for categorical loudness scaling is introduced and evaluated. The procedure adjusts the presentation levels to the subject’s individual auditory dynamic range without employing any premeasurement and presents levels in randomized order. The procedure has been named “Oldenburg—ACALOS” (Oldenburg—Adaptive CAtegorical LOudness Scaling). It was evaluated using repeated measurements with ten subjects with normal hearing and ten subjects with sensorineural hearing impairment. The results of this investigation revealed that the adaptive procedure provides greater reliability, while being more time efficient than a reference procedure that uses constant stimuli.
Discrimination of amplitude-modulated synthetic echo trains by an echolocating bottlenose dolphin
Authors: Dankiewicz Lois A. , Helweg David A. , Moore Patrick W. , Zafran Justine M.
Published: October 2002

Bottlenose dolphins (Tursiops truncatus) have an acute ability to use target echoes to judge attributes such as size, shape, and material composition. Most target recognition studies have focused on features associated with individual echoes as opposed to information conveyed across echo sequences (feature envelope of the multi-echo train). One feature of aspect-dependent targets is an amplitude modulation (AM) across the return echoes in the echo train created by relative movement of the target and dolphin. The current study examined whether dolphins could discriminate targets with different AM envelopes. “Electronic echoes” triggered by a dolphin’s outgoing echolocation clicks were manipulated to create sinusoidal envelopes with varying AM rate and depth. Echo trains were equated for energy, requiring the dolphin to extract and retain information from multiple echoes in order to detect and report the presence of AM. The dolphin discriminated amplitude-modulated echo trains from those that were not modulated. AM depth thresholds were approximately 0.8 dB, similar to other published amplitude limens. Decreasing the rate of modulation from approximately 16 to 2 cycles per second did not affect the dolphin’s AM depth sensitivity. The results support multiple-echo processing in bottlenose dolphin echolocation. This capability provides additional theoretical justification for exploring synthetic aperture sonar concepts in models of animal echolocation that potentially support theories postulating formation of images as an ultimate means for target identification.
Theory of inert gas-condensing vapor thermoacoustics: Propagation equation
Authors: Raspet Richard , Slaton William V. , Hickey Craig J. , Hiller Robert A.
Published: October 2002

The theory of acoustic propagation in an inert gas-condensing vapor mixture contained in a cylindrical pore with wet walls and an imposed temperature gradient is developed. It is shown that the vapor diffusion effects in the mixture are analogous to the heat diffusion effects in the thermoacoustics of inert gases, and that these effects occur in parallel with the heat diffusion effects in the wet system. The vapor diffusion effects can be expressed in terms of the thermoviscous function F(λ) used in the theory of sound propagation of constant cross-section tubes. As such, these results can be extended to any shape parallel-walled tube. The propagation equations predict that the temperature gradient required for onset of sound amplification in a wet-walled prime mover is much lower than the corresponding temperature gradient for an inert gas prime mover. The results of a measurement of the onset temperature of a simple demonstration prime mover in air with a dry stack and with a stack wetted with water provide a qualitative verification of the theory.
Use of complex frequency to analyze thermoacoustic engines
Authors: Parker James E. , Hamilton Mark F. , Ilinskii Yurii A. , Zabolotskaya Evgenia A.
Published: October 2002

Rotts equations of thermoacoustics are expressed in the frequency domain, and as such they describe steady-state conditions. In numerical algorithms such as deltae the frequency is considered real, and the solutions correspond to the equilibrium states associated with the critical temperature gradient in the stack. An alternative approach, and the one described here, is to allow frequency to be complex and to determine its value for a specified temperature gradient. A nonzero imaginary part of the frequency indicates a nonequilibrium state, and depending on its sign it determines the rate at which the amplitude of the sound field either increases or decreases initially with time toward equilibrium at the critical temperature gradient. For solutions corresponding to thermoacoustic instability the imaginary part may be interpreted as a negative loss coefficient, which provides an estimate of the nonlinear loss required to offset the instability. This in turn determines the acoustic pressure at saturation. Graphs of the imaginary part versus the position and length of the stack for various resonators provide insight into favorable operating configurations. Consideration is also given to nonconstant temperature gradients along the length of the stack. [Work supported by ONR.]
Experimental evaluation of a generic abstract interpretation algorithm for PROLOG
Authors: Le Charlier Baudouin , Van Hentenryck Pascal
Published: October 2002

Abstract interpretation of PROLOG programs has attracted many researchers in recent years, partly because of the potential for optimization in PROLOG compilers and partly because of the declarative nature of logic programming languages that make them more amenable to optimization than procedural languages. Most of the work, however, has remained at the theoretical level, focusing on the developments of frameworks and the definition of abstract domains.

This paper reports our effort to verify experimentally the practical value of this area of research. It describes the design and implementation of the generic abstract interpretation algorithm GAIA that we originally proposed in Le Charlier et al. [1991], its instantiation to a sophisticated abstract domain (derived from Bruynooghe and Janssens [1988]) containing modes, types, sharing, and aliasing, and its evaluation both in terms of performance and accuracy. The overall implementation (over 5000 lines of Pascal) has been systematically analyzed on a variety of programs and compared with the complexity analysis of Le Charlie et al. [1991] and the specific analysis systems of Hickey and Mudambi [1989], Taylor [1989; 1990], Van Roy and Despain [1990], and Warren et al. [1988].
Compositional specification and verification of distributed systems
Authors: Jonsson Bengt
Published: October 2002

We present a method for specification and verification of distributed systems that communicate via asynchronous message passing. The method handles both safety and liveness properties. It is compositional, i.e., a specification of a composite system can be obtained from specifications of its components. Specifications are given as labeled transition systems with fairness properties, using a program-like notation with guarded multiple assignments. Compositionality is attained by partitioning the labels of a transition system into input events, which intuitively denote message receptions, and output events, which intuitively denote message transmissions. A specification denotes a set of allowed sequences of message transmissions and receptions, in analogy with the way finite automata are used as acceptors of finite strings. A lower-level specification implements a higher-level one. We present a verification technique which reduces the problem of verifying the correctness of an implementation to classical verification conditions. Safety properties are verified by establishing a simulation relation between transition systems. Liveness properties are verified using methods for proving termination under fairness assumptions. Since specifications can be given at various levels of abstraction, the method is suitable in a development process where a detailed implementation is developed from an abstract specification through a sequence of refinement steps. As an application of the method, an algorithm by Thomas for updating a distributed database is specified and verified.
Improvements to graph coloring register allocation
Authors: Briggs Preston , Cooper Keith D. , Torczon Linda
Published: October 2002

We describe two improvements to Chaitin-style graph coloring register allocators. The first,
optimistic coloring
, uses a stronger heuristic to find a
k
-coloring for the interference graph. The second extends Chaitin's treatment of
rematerialization
to handle a larger class of values. These techniques are complementary. Optimistic coloring decreases the number of procedures that require spill code and reduces the amount of spill code when spilling is unavoidable. Rematerialization lowers the cost of spilling some values. This paper describes both of the techniques and our experience building and using register allocators that incorporate them. It provides a detailed description of optimistic coloring and rematerialization. It presents experimental data to show the performance of several versions of the register allocator on a suite of FORTRAN programs. It discusses several insights that we discovered only after repeated implementation of these allocators.
Optimal incremental parsing
Authors: Larchevêque J.-M.
Published: October 2002

This communication sets the problem of incremental parsing in the context of a complete incremental compiling system. It turns out that, according to the incrementally paradigm of the attribute evaluator and data-flow analyzer to be used, two definitions of optimal incrementality in a parser are possible. Algorithms for achieving both forms of optimality are given, both of them based on ordinary LALR(1) parse tables. Optimality and correctness proofs, which are merely outlined in this communication, are made intuitive thanks to the concept of awell-formed list of threaded trees, a natural extension of the concept ofthreaded treefound in earlier works on incremental parsing.
Reconciling responsiveness with performance in pure object-oriented languages
Authors: Hölzle Urs , Ungar David
Published: October 2002

Dynamically dispatched calls often limit the performance of object-oriented programs, since opject-oriented programming encourages factoring code into small, reusable units, thereby increasing the frequency of these expensive operations. Frequent calls not only slow down execution with the dispatch overhead per se, but more importantly they hinder optimization by limiting the range and effectiveness of standard global optimizations. In particular, dynamically dispatched calles prevent standard interprocedual optimizations that depend on the availability of a static call graph. The SELF implementation described here offers tow novel approaches to optimization.
Type feedback
speculatively inlines dynamically dispatched calls based on profile information that predicts likely receiver classes.
Adaptive optimization
reconciles optimizing compilation with interactive performance by incrementally optimizing only the frequently executed parts of a program. When combined, these two techniques result in a system that can execute programs significantly faster than previous systems while retaining much of the interactiveness of an interpreted system.