bluuebunny/crossref_metadata_2025 huggingface dataset:
Equivalence analysis and its application in improving the efficiency of program slicing
Authors: Liang Donglin , Harrold Mary Jean
Published: October 2002

Existing methods for handling pointer variables during dataflow analyses can make such analyses inefficient in both time and space because the data-flow analyses must store and propagate large sets of data facts that are introduced by dereferences of pointer variables. This article presents
equivalence analysis
, a general technique to improve the efficiency of data-flow analyses in the presence of pointer variables. The technique identifies equivalence relations among the memory locations accessed by a procedure, and ensures that two equivalent memory locations share the same set of data facts in a procedure and in the procedures that are called by that procedure. Thus, a data-flow analysis needs to compute the data-flow information for only a representative memory location in an equivalence class. The data-flow information for other memory locations in the equivalence class can be derived from that of the representative memory location. The article also shows the extension to an interprocedural slicing algorithm that uses equivalence analysis to improve the efficiency of the algorithm. Our empirical studies suggest that equivalence analysis may effectively improve the efficiency of many data-flow analyses.
Email winners and losers
Authors: Wilson E. Vance
Published: October 2002

It's more difficult than you think to predict when sending email will advance your personal interests, help you get ahead at work, or improve your social life.
An example of stepwise refinement of distributed programs: quiescence detection
Authors: Chandy Mani , Misra Jayadev
Published: October 2002

We propose a methodology for the development of concurrent programs and apply it to an important class of problems: quiescence detection. The methodology is based on a novel view of programs. A key feature of the methodology is the separation of concerns between the core problem to be solved and details of the forms of concurrency employed in the target architecture and programming language. We begin development of concurrent programs by ignoring issues dealing with concurrency and introduce such concerns in manageable doses. The class of problems solved includes termination and deadlock detection.
On iterative constructs
Authors: Parnas David Lorge
Published: October 2002

The wheel is repeatedly reinvented because it is a good idea. Perhaps Anson's
"A Generalized Iterative Construct and Its Semantics"
[1] confirms that “A Generalized Control Structure and Its Formal Definition” [2], and the earlier “An Alternative Control Structure and its Formal Definition” [3] presented good ideas. However, there are several misstatements in [1] that should be corrected.

The discussion of these issues is made a bit academic by the four-year delay between Anson's submission of his paper (which apparently coincided with the publication of [2]) and the publication of [1]. In that time a generalization of both schemes has been published as a Technical Report [6] and has been submitted for publication. In this generalization the decision about whether a command is iterating or terminating can be made during execution, and the semantics must be that of DO TERM. Further generalizations make the seman tics of the constructs more practical, since side-effects are accurately treated in all cases. A method for reducing the length of guards and avoiding duplicated subexpressions is also provided.
Search direction by goal failure in goal-oriented programming
Authors: Darlington Jared L.
Published: October 2002

A new approach to goal-oriented programming is described, whereby the search for values of variables to satisfy a goal is invariably directed by that goal or by information provided by its failure. This goal-directed approach is in contrast to that employed by logic programming systems, which attempt to satisfy a goal that has failed by resatisfying an already tested goal, and which furthermore do this in a way determined solely by the order of facts and rules in the database and without reference to the goal that has failed. Proposed changes in the control structure of logic programs designed to improve their execution serve more to reduce the search space than to add goal direction. A goal-directed language that embodies the new approach is presented. It is at the same time a functional programming language and a specification interpreter for the direct execution and testing of functional specifications, and permits the user to write executable program descriptions in which some of the constituent functions are fully defined while others are “merely” specified. The language has been successfully tested on examples drawn from such fields as deductive question answering and problem solving, where it compares favorably with the logic programming languages.
Soundness of Hoare's logic: an automated proof using LCF
Authors: Sokolowski Stefan
Published: October 2002

This paper presents a natural deduction proof of Hoare's logic carried out by the Edinburgh LCF theorem prover. The emphasis is on the way Hoare's theory is presented to the LCF, which looks very much like an exposition of syntax and semantics to human readers; and on the programmable heuristics (tactics). We also discuss some problems and possible improvements to the LCF.
Short- and Long-Term Neuroadrenergic Effects of Moderate Dietary Sodium Restriction in Essential Hypertension
Authors: Grassi Guido , Dell’Oro Raffaella , Seravalle Gino , Foglia Gerardo , Trevano Fosca Quarti , Mancia Giuseppe
Published: October 2002

Background—

In essential hypertension, marked restrictions in dietary sodium intake cause in the short-term period an increase in muscle sympathetic nerve traffic (MSNA) and a baroreflex impairment. The present study was set out to assess on a long-term basis the neuroadrenergic and reflex effects of moderate sodium restriction.

Methods and Results—

In 11 untreated mild to moderate essential hypertensive patients (age 42.0±2.6 years, mean±SEM), we measured beat-to-beat blood pressure (Finapres), heart rate (ECG), and MSNA (microneurography) at rest and during stepwise intravenous infusions of phenylephrine and nitroprusside. Measurements were performed at regular sodium intake, after 1 and 8 weeks of low-sodium diet (80 mmol NaCl/d), and repeated again at regular sodium intake. After 1 week, urinary sodium excretion was markedly reduced. This was accompanied by a slight blood pressure reduction, no heart rate change, and a significant increase in plasma renin activity, aldosterone, and MSNA (+23.0±4.6%
P
<0.05). Whereas baroreflex heart-rate control was unchanged, baroreflex modulation of MSNA was reduced by 46.8±5.1% (
P
<0.01). At the end of the 8-week low-sodium diet, the neurohumoral and baroreflex responses were similar to the ones observed after 1 week of the dietary intervention. All changes disappeared when regular sodium diet was restored.

Conclusions—

Thus, a moderate dietary sodium restriction triggers a sympathetic activation and a baroreflex impairment. Maintenance of low-sodium diet for several weeks does not attenuate these adverse adrenergic and reflex effects.
Digits, Discourse, and Documentation: Performance Research and Hypermedia
Authors: Dixon Steve
Published: October 2002

Is digital multimedia the new interface between performance theory and practice? An exploration of hypermedia discourse and documentation supported by the interactive CD-ROM Chameleons 2: Theatre in a Movie Screen.
SUFFERING FOR THE REIGN OF GOD. THE PERSECUTION OF DISCIPLES IN Q
Authors: Jervis L. Ann
Published: October 2002

The standard understanding of Q's presentation of the suffering entailed in discipleship is Deuteronomistic; just as the Deuteronomistic history describes prophets being persecuted and even killed when they preached repentance, so does Q present Jesus' followers. The Deuteronomistic explanation, however, fails to reckon adequately with the fact that Q does not portray Jesus' disciples as prophets preaching repentance, and that the cause of their suffering is not Israel's refusal to repent. Rather, Q's understanding of discipleship suffering is that it is the means by which the reign of God is extended.
CELL FRACTIONATION ANALYSIS OF HUMAN CD8 GLYCOPROTEIN TRANSPORT BETWEEN ENDOPLASMIC RETICULUM, INTERMEDIATE COMPARTMENT AND GOLGI COMPLEX IN TISSUE CULTURED CELLS
Authors: Erra Maria Carmen , Iodice Luisa , Lotti Lavinia Vittoria , Bonatti Stefano
Published: October 2002

We have set up an analytical cell fractionation procedure to dissect, by a non‐morphological method, the anterograde transport of proteins from endoplasmic reticulum, intermediate compartment and Golgi complex in tissue cultured cells. Using this procedure after pulse‐chase labelling of cells expressing human CD8 glycoprotein, we obtained results that: (1) support the view that the intermediate compartment is a distinct station in the export from the endoplasmic reticulum to the Golgi complex; and (2) strongly suggests that the O ‐glycosylation process starts after the intermediate compartment, presumably in thecis ‐Golgi complex.
New species of Xanthoparmelia (lichenized Ascomycotina, Parmeliaceae) from Africa
Authors: Elix John A.
Published: October 2002

The following new species of Parmeliaceae are described from Africa: Xanthoparmelia bainskloofensis Elix & T. H. Nash, X. boyeri Elix, X. dubitella Elix, X. kleinswartbergensis Elix, X. lobuliferella Elix, X. malawiensis Elix, X. micromaculata Elix and X. waboomsbergensis Elix. The new combination Xanthoparmelia patula (Brusse) Elix is made and X. hypoleiella Elix, X. neoconspersa (Gyeln.) Hale, X. neocumberlandia T. H. Nash & Elix and X. sipmanii T. H. Nash & Elix are reported from Africa for the first time.
The lichen genus Sclerophyton in India
Authors: Makhija Urmila , Adawadkar Bharati
Published: October 2002

Sclerophyton is reported for the first time from India and two species ofthis genus, namely S. elegans Eschw. and a new species S. indicum U. V. Makhija & B. A. Adawadkar are recorded.
Elevational Shifts of Coleogyne ramossissima in the Mojave Desert during the Little Ice Age
Authors: Hunter Kimberly L. , McAuliffe Joseph R.
Published: October 2002

Plant macrofossils from woodrat (Neotoma) middens collected in the Mojave Desert of southern Nevada were used to reconstruct the timing and magnitude of vegetation change during the past 1000 yr. Although vegetation at the site now is dominated by the shrubColeogyne ramossissima, this species does not occur in fossil middens prior to 600 ± 50 yr B.P. The appearance and persistence ofC. ramosissimain middens was coincident with the Little Ice Age (ca. 1250 to 1850 A.D.) and was probably related to an increase in precipitation.
Precipitation Source Inferred from Stable Isotopic Composition of Pleistocene Groundwater and Carbonate Deposits in the Western Desert of Egypt
Authors: Sultan Mohamed , Sturchio Neil , Hassan Fekri A. , Hamdan Mohamed Abdel Rahman , Mahmood Abdel Moneim , Alfy Zeinhom El , Stein Tom
Published: October 2002

An Atlantic source of precipitation can be inferred from stable isotopic data (H and O) for fossil groundwaters and uranium-series-dated carbonate spring deposits from oases in the Western Desert of Egypt. In the context of available stable isotopic data for fossil groundwaters throughout North Africa, the observed isotopic depletions (δD −72 to −81‰; δ18O −10.6 to −11.5‰) of fossil (≥32,000 yr B.P.) groundwaters from the Nubian aquifer are best explained by progressive condensation of water vapor from paleowesterly wet oceanic air masses that traveled across North Africa and operated at least as far back as 450,000 yr before the present. The values of δ18O (17.1 to 25.9‰) for 45,000- to >450,000-yr-old tufas and vein-filling calcite deposits from the Kharga and Farafra Oases are consistent with deposition from groundwaters having oxygen isotopic compositions similar to those of fossil groundwaters sampled recently at these locations.
Mid-Holocene Climate and Culture Change in the Atacama Desert, Northern Chile
Authors: Grosjean Martin , Núñez Lautaro , Cartajena Isabel , Messerli Bruno
Published: October 2002

Twenty archaeological campsites intercalated between more than 30 debris flows caused by heavy rainfall events between 6200 and 3100 14C yr B.P. have recently been discovered at Quebrada Puripica in the Atacama Desert of northern Chile. This record provides detailed information about extreme, short-lived climatic events during the hyperarid mid-Holocene period. For the first time, we found evidence of continuous human occupation in this area, filling the regional hiatus in the Atacama basin (“Silencio Arqueologico”) between 8000 and 4800 14C yr B.P. The transformation of Early Archaic hunters into the complex Late Archaic cultural tradition was an adaptive process. During this time, the site was a local ecological refuge with abundant resources in a generally hostile environment.
The influence of foliar diseases, and their control by fungicides, on the protein concentration in wheat grain: a review
Authors: DIMMOCK J. P. R. E. , GOODING M. J.
Published: October 2002

Experiments investigating effects of foliar disease control on wheat grain protein concentration (GPC) are reviewed. Fungicidal control of rusts (Puccinia spp.) and powdery mildew (Erysiphe graminis) increased or had no significant effect on GPC in almost all cases, whilst control of the Septoria spp. often resulted in reduced GPC, but with exceptions. Reasons for these differences are discussed with reference to host pathogen interactions. Irrespective of infection strategy (biotrophic or necrotrophic), controlling severe infection increased nitrogen yield and the proportion of above-ground crop nitrogen that was partitioned to the grain. Similar effects are recorded for above-ground biomass and dry matter harvest index. The relationships between fungicide effects on green flag leaf area duration (GFLAD) and GPC were examined and shown to be unaffected by mode of action of the fungicide. Interactions between fungicide use and cultivar, nitrogen and growing season are related to the amount and type of pathogen present, and environment. An economic analysis demonstrated that fungicide effects on GPC should not affect the choice of fungicide or application programme, but that applications of foliar urea at the start of grain filling can deliver a cost-effective method of eliminating GPC reductions that may occasionally result from fungicide use.
Population biology of Hirondellea sp. nov. (Amphipoda: Gammaridea: Lysianassoidea) from the Atacama Trench (south-east Pacific Ocean)
Authors: Perrone F.M. , Dell'Anno A. , Danovaro R. , Croce N. Della , Thurston M.H.
Published: October 2002

A new species of Hirondellea was trapped in large numbers (N=441) in the Atacama Trench (Pacific Ocean) at 7800 m depth. The species accounted for 47% of the total number of amphipods collected and was the second most abundant amphipod after Eurythenes gryllus. Adult males and females reached maximum lengths of 13·5 and 14·1 mm. Length–frequency histograms showed no clear evidence of growth classes, but instars could be determined by using a combination of morphological criteria and size–frequency data. Growth factors based on mean lengths of successive instars ranged from 1·09 to 1·24 except at moults immediately prior to maturity when factors were in the range 1·02–1·04. Females moult from the pre-adult to the adult instar, without body growth. Moulting modalities of immature males are unclear. Equations obtained from regression analysis between wet weight and total body length indicate an allometric growth. Females grow at a rate of 10% higher than males, and both females and males display growth rates lower than those observed for juveniles, but growth increments at each instar of females are not significantly higher than those of males. The relationship between total body length (L) and wet weight (W) of all instars of Hirondellea sp. nov. is expressed by the power curve W=0·012 L3·279 (W in mg and L in mm).
Effects of discharging nematocysts when an eolid nudibranch feeds on a hydroid
Authors: Martin Rainer , Walther Paul
Published: October 2002

The exposure to discharging nematocysts of the eolid nudibranch Cratena peregrina feeding on polyps of the hydroid Eudendrium racemosum was examined. The smaller size-class of microbasic eurytele mastigophor nematocysts is located on the tentacles of the hydroid polyps, while the larger size-class of holotrichous isorhiza nematocysts is located on long cnidophores and basal rings of some polyps. Discharging nematocysts of the tentacles do not appear to have damaging effects on the dorsal appendages of the snail, the cerata. In contrast, contact of a cnidophore with a ceras elicits massive discharge of nematocysts, which results in adherence, membranolysis and local destruction of the epidermis within seconds. The differential locations and effects indicate that the small tentacle nematocysts serve for capturing prey, while the large cnidophore nematocysts serve for the hydroid's defence. Both small and large, discharged and intact nematocysts were found in the pharynx and stomach of the snail after feeding. Thus, the alimentary tract appears to be efficiently protected against discharging nematocysts. Small and large intact nematocysts, which were capable of discharge, were also found in the cnidosacs.
Regularity of induced representations and a theorem
of Quigg and Spielberg
Authors: AN HUEF ASTRID , RAEBURN IAIN
Published: October 2002

Mackey's imprimitivity theorem characterizes the unitary representations of a
locally compact group G which have been induced from representations of a closed
subgroup K; Rieffel's influential reformulation says that the group C*-algebra C*(K)
is Morita equivalent to the crossed product C0(G/K)×G [14]. There have since been
many important generalizations of this theorem, especially by Rieffel [15, 16] and
by Green [3, 4]. These are all special cases of the symmetric imprimitivity theorem
of [11], which gives a Morita equivalence between two crossed products of induced
C*-algebras.
Bilateral Elbow Flexion Reconstruction with Functioning Free Muscle Transfer for Obstetric Brachial Plexus Palsy
Authors: BALIARSING A. S. , DOI K. , HATTORI Y.
Published: October 2002

A child suffered a bilateral obstetric brachial plexus palsy involving the C5 and C6 nerve roots. Abduction of the shoulder joints had recovered by 1 year, but elbow flexion did not recover on either side. Free gracilis muscle transfers were performed on both sides, at an interval of 6 months, to achieve elbow flexion. The spinal accessory nerve was used as the donor nerve.
Topical Anaesthesia to Reduce Pain Associated with Carpal Tunnel Surgery
Authors: LAWRENCE T. M. , DESAI V. V.
Published: October 2002

This randomized, double-blinded study assessed the effectiveness of a topical anaesthetic, eutectic mixture of local anaesthetics (EMLA), in reducing pain associated with carpal tunnel release performed under local anaesthetic. Fifty-six patients undergoing carpal tunnel release under local anaesthetic were randomized into either EMLA ( n=29) or placebo ( n=27) groups. Visual analogue pain scores were obtained for needle insertion, injection of anaesthetic and surgery itself. Pain scores were significantly less for needle insertion ( P=0.001) and injection of anaesthetic ( P=0.0005). Scores related to surgery were also lower in the EMLA group, but this did not reach statistical significance.
Swanson versus Apl Arthroplasty in the Treatment of Osteoarthritis of the Trapeziometacarpal Joint: a Prospective and Randomized Study in 26 Patients
Authors: TÄGIL M. , KOPYLOV P.
Published: October 2002

Twenty-six patients were operated because of osteo-arthritis of the trapeziometacarpal joint. After excision of the trapezium, they were randomized to receive either a Swanson silicone trapezium implant or a tendon interposition arthroplasty using a strip of the abductor pollicis longus tendon (APL). No infection or clinical silicone synovitis occurred and no major radiographic cyst formation was found. Two endoprostheses dislocated early. All 13 patients in the Swanson group and 11 of the 13 in the APL group were subjectively satisfied at 2–5 year (mean, 43 months) follow-up. All patients were free of pain at rest and at light work, but half of the patients in each group still experienced pain with heavy work. Thumb pinch strength and range of motion were not significantly different in the two groups. The trapezial space decreased both with load and length of follow-up in both groups. Five endoprostheses subluxed during stressed pinch.

In conclusion, both methods gave good, but not complete, pain relief and neither produced better results than the other in the short term.
Hot photoluminescence in GaN: Carrier energy relaxation and hot phonon effects
Authors: Duboz Jean Yves
Published: October 2002

A theoretical study of carrier energy relaxation in wurzite GaN is presented. The analysis is focused on describing phenomena which occur when very energetic electrons and holes are optically injected into the material, as is the case during a hot photoluminescence experiment. Due to the wurtzite symmetry, transverse optical-like phonon modes become active for carrier scattering. Their contribution is analyzed and quantitatively compared to the longitudinal optical (LO) phonon contribution. A pseudoisotropic model of optical phonons in GaN is proposed and is shown to give similar results as the more rigorous anisotropic model. The electron and hole energy relaxation rates are calculated. It is predicted that very energetic carriers should form a discrete distribution, only slightly broadened by carrier–carrier scattering. The conditions for having the electron and hole gases thermalized at the bottom or top of their band are given. Their actual temperature is calculated with or without taking into account hot phonon effects. The LO phonon temperature is calculated and found to be significantly higher than the lattice temperature. Hot phonon effects are important and contribute to equalizing the electron and hole temperatures. The resulting photoluminescence temperature is calculated and compared with experimental data. The agreement with experimental results is improved if hot phonons are included in the calculation.
Frequency stabilization of an extended cavity semiconductor diode laser for chirp cooling
Authors: Morzinski J. , Bhatia P. S. , Shahriar M. S.
Published: October 2002

We present a technique to stabilize in an atomic transition the chirping frequency of a narrow-band semiconductor diode laser. The technique is demonstrated to chirp-cool Rb85 atoms used for loading a magneto-optical trap. The stabilization process eliminates long-term fluctuations and drifts in the number of atoms caught in the trap. This is a simple, easy-to-implement, and robust method for wide range of laser cooling experiments employing frequency chirping.
Stoichiometry control during deposition by ion beam sputtering
Authors: Nair Jaya P. , Zon Ilya , Oron Matti , Popovitz-Biro Ronit , Feldman Yishay , Lubomirsky Igor
Published: October 2002

Ion beam sputtering of chemical compounds is in general nonstoichiometric. The problem is especially severe for inorganic insulators because target charging and ionic emission render sputtering rates unstable. This study reports on the influence of target charging on ion beam sputtering of Al2O3 and LiNbO3 films on Si and Al2O3/Si substrates. It was found that undesirable ionic emission could be minimized by eliminating target charging, controlled via electron to ion neutralization ratio of the incident beam. Experimental data suggest that the stoichiometric sputtering corresponds to zero target charging and thus can be used as an effective feedback parameter during deposition. When the target charging was minimal, high quality stoichiometric Al2O3 films were obtained without the need for oxygen supplied to the deposition chamber. The dependence of refractive index, residual stress, and specific resistance on neutralization ratio showed abrupt change in the vicinity of zero target charging. In a separate experiment, minimization of the target charging helped to maintain stoichiometry during ion beam sputtering of LiNbO3, suggesting that this method is also beneficial for sputtering of ternary compounds.
Experimental and numerical investigations on microstereolithography of ceramics
Authors: Sun C. , Zhang X.
Published: October 2002

Microstereolithography (μSL) uses laser light to solidify UV-curable resin mixed with concentrated ceramic powders. During the μSL process, the light scattering from the particle suspension is found to significantly influence the fabrication resolution in both lateral and depth dimensions which are critical for the complex three-dimensional (3D) microfabrication. In this work, we performed Monte Carlo simulations and experimental studies to understand the detailed microscale optical scattering, chemical reaction (polymerization), and their influence on critical fabrication parameters. As a result, it was found that due to the scattering, the fabricated line is wider in width and smaller in depth compared with polymeric fabrication at the same condition. The doping technique that we used substantially reduced the light scattering, which in turn enhanced the fabrication precision and control. In addition, the experimental values of curing depth and radius agreed reasonably well with the theoretical modeling. When a laser beam was focused to the diffraction limit, an ultimate linewidth resolution with ceramic μSL was found at about 2.6 μm.
Quantum optimal control of unbounded molecular dynamics: Application to NaI predissociation
Authors: Nakagami Kazuyuki , Ohtsuki Yukiyoshi , Fujimura Yuichi
Published: October 2002

In order to achieve optimal control of unbounded molecular dynamics, we develop an algorithm to deal with a spatially delocalized final condition of homogeneous pulse design equations that are derived from a typical optimal control procedure. We introduce a quasiprojector to specify a spatially delocalized physical objective, while we store wave packet components that spread beyond the grid region in memory. The quasiprojector, which can explicitly identify target products in photodissociation and bimolecular reactions, is a weighted sum of projectors, whose weight function is constant outside the grid region. This algorithm, combined with an efficient iteration method, is applied to the control of NaI predissociation with the aim of obtaining a high dissociation probability within one cycle of nuclear vibration. We discuss how the control mechanisms are changed depending on the potential coupling strengths and restriction imposed on the optical interaction region. The effects of molecular orientation on a control pathway are also examined using a two-orientation model with the assumption of a frozen rotational wave packet.
Intermolecular potentials and second virial coefficients of the water–neon and water–argon complexes
Authors: Hodges Matthew P. , Wheatley Richard J. , Harvey Allan H.
Published: October 2002

We construct potential-energy surfaces for the water–neon and water–argon complexes from scaled perturbation theory, and calibrate them using accurate supermolecule data. Our best estimates of the binding energies for these two systems are 66.9 and 142.7 cm−1, respectively, where the latter value is in good agreement with the spectroscopically determined AW2 potential. We calculate second virial coefficients, B12(T), and the related property φ12=B12−T(dB12/dT), and compare our results with experimental data for water–argon. The perturbation theory and AW2 B12(T) results are consistent, and demonstrate that current theoretical approaches yield more precise second virial coefficient data than any in the literature. Our φ12 calculations are in good agreement with experimental results derived from enthalpy-of-mixing data, though our estimated uncertainties are significantly smaller.
Polymer nanodroplets adsorbed on nanocylinders: A Monte Carlo study
Authors: Milchev Andrey , Binder Kurt
Published: October 2002

The structure and the shape of polymer droplets of nanoscopic size on ultrathin cylindrical fibers (with diameters in the range of nanometers) is investigated by Monte Carlo simulation of a coarse-grained bead-spring type model. The interaction between atoms in the solid nanocylinder and the effective monomers is assumed to be of Lennard-Jones-type, but the detailed atomistic structure of the nanofiber is ignored, using a homogeneous cylinder with a perfectly smooth surface. Depending on the size of the droplet, the fiber radius, and the strength of the adsorption potential, droplets have either the (axially symmetric) “barrel shape,” or the asymmetric “clamshell shape,” or are unstable against spreading out along the fiber. For the barrel-shaped droplets, the dependence of the contact angle on the parameters mentioned above is estimated. For comparison, using the same model also the case of droplets on a flat horizontal surface and in a wedge with opening angle of 90° has been studied. When appropriate, the simulation results are interpreted in terms of current theoretical predictions.
Perturbed hard-body fluid analysis of the global effects of solvation on conformational thermodynamics
Authors: McClain Brian L. , Ben-Amotz Dor
Published: October 2002

The molecular perturbed hard-body fluid (PHF) model is used to extract repulsive (cavity formation) and attractive (cohesive) solvent excess perturbations to the conformational equilibria of 1,2-dichloroethane (DCE) and trans-1,2-dichlorocyclohexane (T12D) dissolved in diethyl ether. This represents the first combined theoretical/experimental global analysis of the complete set of solvent excess thermodynamic functions (ΔGx, ΔSx, ΔVx, ΔHx, ΔUx, and ΔAx) for any chemical process. Cavity formation is modeled by treating molecules either as hard spheres or anisotropic hard bodies while cohesive interactions are treated using the van der Waals mean field approximation. The results are used to test PHF approximations and elucidate solvent contributions to each thermodynamic function. Cohesive interactions are invariably found to favor the more polar isomer while cavity formation favors the more polar isomer of DCE but the less polar isomer of T12D. This difference is shown to be consistent with independent excluded volume calculations and to explain the stronger pressure dependence of the excess isomerization volume of DCE than T12D.
Reliable method for determination of the velocity of a sinker in a high-pressure falling body type viscometer
Authors: Dindar Cigdem , Kiran Erdogan
Published: October 2002

We present a new sensor configuration and data reduction process to improve the accuracy and reliability of determining the terminal velocity of a falling sinker in falling body type viscometers. This procedure is based on the use of multiple linear variable differential transformer sensors and precise mapping of the sensor signal and position along with the time of fall which is then converted to distance versus fall time along the complete fall path. The method and its use in determination of high-pressure viscosity of n-pentane and carbon dioxide are described.
Development of a fast valve for mitigating disruptions in tokamaks
Authors: Savtchkov A. , Finken K. H. , Mank G.
Published: October 2002

In support of our disruption mitigation profram, a fast gas valve has been constructed and tested on TEXTOR at FZJ Juelich. Its main features have been shown to be: (1) rapid response time: 0.5 ms; (2) amount of injected gas: variable, 2–1000 mbar×l; (3) linear dependence of the number of injected particles on the gas pressure; (4) capability of working in a strong magnetic field; (5) sort of gas: any. The valve has the standard CF 35 flange, commonly used in vacuum engineering. All the components that have contact with vacuum were made of stainless steel, except for the closing aluminum piston. To prevent gas leaking directly from the bottles to the experimental vessel there are also two safety valves, closing the bottles before the shot. The required control equipment includes a high power supply and the combined controller for the safety valves and baratrons, both being able to work with TTL control signals. During tests and experiments on TEXTOR and ASDEX-Upgrade, the valve showed successful operation with three gas types: He, Ne, Ar.
The uncertainty tree: Reducing the uncertainty of uncertainty analysis
Authors: Longtin Jon P.
Published: October 2002

Uncertainty analysis is an integral aspect of experimental measurements, though accurately assessing the flow of uncertainty in a measurement system—particularly for complicated systems with more than a few variables—can become a challenging, error-prone task, while being less enjoyable than it should be. This note proposes the uncertainty tree, a graphical, hierarchal structure to quickly and accurately assess the flow of uncertainty in experimental measurements. A few basic rules for tree construction are set forth that provide the essential building blocks to construct the tree. An example is provided that illustrates the use of the uncertainty tree concept in a real-world problem.
Effects of quenched impurities on surface diffusion, spreading, and ordering of O/W(110)
Authors: Nikunen P. , Vattulainen I. , Ala-Nissila T.
Published: October 2002

We study how quenched impurities affect the surface diffusion and ordering of strongly interacting adsorbate atoms on surfaces. To this end, we carry out Monte Carlo simulations for a lattice-gas model of O/W(110), including small concentrations of immobile impurities which block their adsorption sites. We examine the behavior of the diffusion coefficients and order parameters as a function of coverage corresponding to various ordered phases at low temperatures. The effects of impurities are examined under both equilibrium and nonequilibrium conditions, and the results are compared to recent studies on a completely clean surface. We find that even minute impurity concentrations affect the diffusion behavior considerably in equilibrium. The effects are strongest in ordered phases and close to phase boundaries, where quenched impurities lead to a reduction of order, which in turn leads to significant changes in the collective diffusion and phase behavior. As the impurity concentration is increased to a level of a few percent of the total surface area, the reduction in order becomes particularly prominent at high coverages. Further studies under nonequilibrium conditions reveal that nonequilibrium effects are strong in the absence of impurities, while for surfaces covered by impurities the nonequilibrium effects are relatively weaker.
Electrical properties of Li2B4O7 single crystals in the [001] direction: Comparison between crystals grown from Li2CO3 and B2O3 mixed powder and from Li2B4O7 powder
Authors: Kim Chung-Sik , Kim Dong Jin , Hwang Yoon-Hwae , Kim Hyung Kook , Kim Jung Nam
Published: October 2002

The two different Li2B4O7 single crystals prepared from Li2CO3 and B2O3 mixed powder (LTBm) and Li2B4O7 powder (LTBp) were compared in the ac impedance study for the [001] direction in the frequency range from 100 Hz to 10 MHz at temperatures up to 350 °C. The thickness dependence of the complex resistivities exhibits that LTBm has distinct grain boundary-like effect while LTBp does not. This boundary effect may be due to the charge-depleted region constructed temporarily by the ion blocking of the microcracks in the applied ac electric field. The activation energies of volume conductivities are almost the same in LTBm and LTBp, but the absolute value of volume conductivity in LTBm is about 3 to 4 times larger than that in LTBp. The conductions in the electrode interface and boundary region are ascribed to the identical charge carriers activated by the applied electric field and result in the same activation energies. A relatively large blocking factor in LTBm below 100 °C is observed. It may be due to a one-dimensional channel of ion conduction path in the [001] direction of Li2B4O7 crystal.
Anomalous inverse absorption features in the far-infrared RAIRS spectra of SnCl4 on thin-film SnO2 surfaces
Authors: Pilling M. J. , Le Vent S. , Gardner P. , Awaluddin A. , Wincott P. L. , Pemble M. E. , Surman M.
Published: October 2002

As part of a study of the chemistry of tin oxide chemical vapor deposition precursors at oxide surfaces, we have utilized the so-called buried metal layer approach to obtain far-IR reflection absorption infrared spectroscopy (RAIRS) spectra for SnCl4 adsorbed at a tin oxide surface supported on a polycrystalline tungsten foil. Two types of surface preparation—namely, sputtering with Ar or O2—have been used to clean the tin oxide surfaces prior to experiment. On O2-sputtered surfaces at 300 K, the spectra are dominated by an inverse-absorption feature in the form of a positive-going band in the spectrum, obtained via the ratio of the sample spectrum to that of the clean surface background. At low temperature, the spectra display both the positive-going inverse-absorption feature and the normal negative-going absorption features common to many RAIRS studies from metallic surfaces. On an Ar-sputtered surface, the inverse absorption band is not observed, but is replaced, at least at 300 K, by an absorption band at the same wave number. Simple models are employed to demonstrate how these features may arise from an analysis of the Fresnel equations for the system, and the data are discussed in terms of the possible models for inverse-absorption features that appear in the literature. It is concluded that the features observed are induced by the presence of the adsorbate, but are characteristic of the underlying oxide substrate.
Symmetry analysis of internal rotation
Authors: Szalay Viktor , Császár Attila G. , Senent Maria L.
Published: October 2002

Research papers and textbooks addressing the problem of internal rotation in a molecule explain symmetry properties of the torsional potential by local geometrical symmetries of the molecule. It is shown here that symmetry properties of a torsional potential derive from permutation inversion symmetry and a peculiar nature of torsional dynamics but have no relation to actual geometrical symmetries. To confirm the validity of our symmetry analysis a minimum energy torsional potential curve has been determined ab initio for acetaldehyde, resulting in exact 2π/3 periodicity that no previous ab initio calculations achieved.
Femtosecond time-resolved excited state dynamics of cyanine encapsulated by β-cyclodextrin
Authors: Huang Wentao , Wang Shufeng , Yang Hong , Gong Qihuang , Xu Guangzhi , Xiang Junfeng , Chen Ciping , Yan Wenpeng
Published: October 2002

Fluorescence dynamics of a cyanine dye, 3,3′-di(3-sulfopropyl)-thiacyanine triethylaminium salt, encapsulated by β-cyclodextrin was investigated by femtosecond fluorescence time-resolved up-conversion technique. The quickening up of the fluorescence decay was found in comparison with the fluorescence dynamics of the dye in water. This phenomenon may be a good experimental support for the expanded BFO theory with two-dimensional excited potential surface.
Fluctuations and bistability in a “hybrid” atomistic model for CO oxidation on nanofacets: An effective potential analysis
Authors: Liu Da-Jiang , Evans J. W.
Published: October 2002

We analyze fluctuations in a “hybrid” atomistic model mimicking CO oxidation on nanoscale facets of metal(100) catalyst surfaces. The model incorporates a mean-field-like treatment of infinitely mobile CO, and a lattice-gas treatment of the superlattice ordering of immobile O. For an infinite system, it exhibits an Ising-type order–disorder transition for O, together with mean-field-like bistability disappearing at a cusp bifurcation. For finite systems, we use kinetic Monte Carlo simulation to study the probability distribution for the population of adsorbed species, from which bistability can be observed, together with fluctuation-induced transitions between the two stable states. An effective potential picture emerges from our analyses that can be used to quantify both the system size dependence of fluctuations and the transition rates. Thus, our hybrid atomistic model displays fluctuation behavior analogous to traditional mean-field models. This qualitative behavior can be understood by approximate treatments of population dynamics using master equations and Fokker–Planck equations. A generalized model with finite mobility of CO is also analyzed for comparison with the hybrid model. In contrast, it exhibits fluctuation behavior akin to equilibrium systems with Ising-type first-order transitions.
Catalytic oxidation of hydrogen on free platinum clusters
Authors: Andersson Mats , Rosén Arne
Published: October 2002

The adsorption of hydrogen (deuterium) and oxygen on neutral platinum clusters has been investigated in a cluster beam experiment. The beam passes through two low-pressure reaction cells and the clusters, with and without adsorbed molecules, are detected by laser ionization and mass spectrometry. Both H2 and O2 adsorb efficiently on the platinum clusters with only moderate variations with cluster size in the investigated range, i.e., between 7 and 30 atoms. The coadsorption of H2 and O2 results in the formation and desorption of H2O, detected as a decreasing number of adsorbed oxygen atoms with an increasing number of collisions with H2 molecules. The water-formation reaction proceeds efficiently on all investigated clusters with more than seven atoms.
Multidimensional, closed-form analytic expressions for mobilities in Ga1−xAlxAs heterostructures
Authors: Bennett Herbert S.
Published: October 2002

A significant, practical challenge, which arises in developing computationally efficient physical models for use in computer simulations of microelectronic and optoelectronic devices (for example, transistors in digital cellular phones and in laser modulators, respectively), is to represent vast amounts of numerical data for transport properties in two or more dimensions in terms of closed- form analytic expressions. In this article, we use a methodology, which was presented in more detail previously, to achieve the above goal for a class of numerical data in a bounded two-dimensional space. We present here closed-form analytic expressions for the electron and hole mobilities at 300 K in p-type and n-type Ga1−xAlxAs as functions of dopant densities between 1016 and 1020 cm−3 and mole fractions of AlAs with x between 0.0 and 0.3. This methodology and its associated principles, strategies, regression analyses, and graphics are expected to be applicable to other problems beyond the specific case of mobilities addressed in this article.
Photoreflectance spectroscopy of strained (In)GaAsN/GaAs multiple quantum wells
Authors: Héroux J. B. , Yang X. , Wang W. I.
Published: October 2002

The effect of a variation of the indium and nitrogen concentrations in InxGa1−xAs1−yNy/GaAs multiquantum wells grown by molecular beam epitaxy is studied systematically by room temperature photoreflectance spectroscopy. The band gap redshift caused by a nitrogen fraction of 1.5% decreases by as much as 30% as the indium fraction increases from 0% to 20%. A moderate increase of electron effective mass (Δme∼0.03 m0) is found in all samples containing nitrogen (y≳1%). In compressively strained quantum wells, the energy separation between the first confined heavy and light hole energy levels decreases in a regular manner as the nitrogen fraction increases from 0% to 1.7%, suggesting that the modification of the valence bands due to nitrogen incorporation can be explained by the strain variation.
Energy band bowing parameter in AlxGa1−xN alloys
Authors: Yun Feng , Reshchikov Michael A. , He Lei , King Thomas , Morkoç Hadis , Novak Steve W. , Wei Luncun
Published: October 2002

Molecular-beam epitaxy grown AlxGa1−xN alloys covering the entire range of alloy compositions, 0⩽x⩽1, have been used to determine the alloy band gap dependence on its composition. The Al chemical composition was deduced from secondary ion mass spectroscopy and Rutherford backscattering. The composition was also inferred from x-ray diffraction. The band gap of the alloy was extracted from low temperature optical reflectance measurements which are relatively more accurate than photoluminescence. Fitting of the band gap data resulted in a bowing parameter of b=1.0 eV over the entire composition range. The improved accuracy of the composition and band gap determination and the largest range of the Al composition over which our study has been conducted increase our confidence in this bowing parameter.
Bifunctional photovoltaic and electroluminescent devices using a starburst amine as an electron donor and hole-transporting material
Authors: Hong Z. R. , Lee C. S. , Lee S. T. , Li W. L. , Shirota Y.
Published: October 2002

Photovoltaic (PV) devices, using 4,4′,4″-tris(2-methylphenylphenylamino)triphenylamine (m-MTDATA) as an electron donor and tris-(8-hydroxyquinoline) aluminum (Alq) as an electron acceptor, were fabricated. The relationship between photocurrent generation, exciplex formation, and device structure was explored. PV performance was significantly enhanced by inserting a thin mixed layer (5 nm) of m-MTDATA and Alq between the two organic layers of the original m-MTDATA/Alq bilayer device. Both the bilayer and trilayer devices showed PV and electroluminescent (EL) properties, suggesting their potential use as multifunction devices. It was also shown that strong EL emission from exciplex might be used as an indicator of efficient exciton dissociation during the reverse PV process.
Energy band structure of Ru/(Ba,Sr)TiO3/Si capacitor deposited by inductively-coupled plasma-assisted radio-frequency-magnetron plasma sputtering
Authors: Kikkawa Takamaro , Fujiwara Naonori , Yamada Hiroshi , Miyazaki Seiichi , Nishiyama Fumitaka , Hirose Masataka
Published: October 2002

Properties of barium strontium titanate (Ba,Sr)TiO3 (BST) thin films, deposited by inductively-coupled-plasma (ICP)-assisted rf magnetron-plasma sputtering, were investigated. It is found that the ICP-assisted rf-magnetron plasma improved the stoichiometry of the BST film. The energy band structure of the Ru/BST/Si system was investigated. It is found that the bandgaps of BST and interface SiO2 were 4.30 and 8.95 eV, respectively, and the work function of Ru was 4.97 eV. The valence band offsets for BST/Si and interface SiO2/Si are 3.55 and 4.48 eV, respectively. As a result, the conduction band barrier height of Ru against BST was found to be 1.40 eV.
Optical diffraction gratings produced by laser interference structuring of amorphous germanium–nitrogen alloys
Authors: Mulato M. , Zanatta A. R. , Toet D. , Chambouleyron I. E.
Published: October 2002

We use the interference of two pulsed laser beams (wavelength=355 nm) to produce an optical diffraction grating in amorphous germanium–nitrogen alloy (a-GeN). At the constructive maxima of the interference pattern, the absorption of light leads to crystallization. The crystallized region results of pure microcrystalline germanium (μc-Ge). An indication that Ge–N bonds have broken and nitrogen outdiffused of the film is obtained from infrared spectroscopy and confirmed by Raman spectra. A pattern of alternating a-GeN and μc-Ge lines with a period of about 4 μm acts as an optical diffraction grating due to the difference in optical properties between the two materials, and the three dimensional surface profile, caused by N2 effusion, that is formed on the sample.
Second-harmonic generation tuning curves with narrow, high-intensity beams for quasiphase-matched potassium titanyl phosphate
Authors: Kim Hongki , Jankovic Ladislav , Stegeman George , Katz Mordechai , Carrasco Silvia , Torner Lluis
Published: October 2002

The tuning curves with temperature and incidence angle for second-harmonic generation were asymmetrically distorted and broadened with increasing intensity for narrow input fundamental beams in periodically poled KTiOPO4. Multiple phenomena including mutual self-focusing of the fundamental and harmonic, cascading, quadratic soliton generation, and artificially induced walk-off (for light incidence away from the poling axis) contribute, in good agreement with theory.