bluuebunny/crossref_metadata_2025 huggingface dataset:
Disruption and basic phenotypic analysis of six novel genes from the right arm of chromosome XII of Saccharomyces cerevisiae
Authors: Watson Martin D.
Published: August 2002

Six open reading frames (ORFs) of unknown function from the right arm of Saccharomyces cerevisiae chromosome XII were deleted in two genetic backgrounds by disruption cassettes with regions of short flanking homology. This work was carried out within the framework of the EUROFAN consortium. The SFH disruption cassettes, obtained by PCR, were made by amplification of the kanMX marker module with oligonucleotides containing approximately 40 bp of homology to either the promoter or translation terminator regions of the relevant ORF. Transformants resistant to geneticin (G418) were selected. The SFH disruption cassettes were cloned into a bacterial vector. Each cognate gene was also cloned into a yeast centromeric plasmid. Sporulation and tetrad analysis of the disrupted heterozygous strains revealed that ORF YLR153c (now known as ACS2) is essential. Basic phenotypic analysis was performed on haploid deletants of both mating types of the five non‐essential ORFs, YLR082c (now known as SRL2), YLR149c, YLR151c, YLR152c and YLR154c. Plate growth tests on different media at 15°C, 30°C and 37°C did not reveal any significant differences between parental and mutant cells. Mating and sporulation efficiencies were not affected in any of the viable disruptants as compared to wild‐type cells. Copyright © 2001 John Wiley & Sons, Ltd.
At acidic pH, the GPA2–cAMP pathway is necessary to counteract the ORD1‐mediated repression of the hypoxic SRP1/TIR1 yeast gene
Authors: Bourdineaud J.‐P.
Published: August 2002

The hypoxic SRP1/TIR1 gene encodes a stress‐response cell wall mannoprotein and this gene is downregulated at acidic pH. The stress‐responsive HOG pathway is necessary to maintain hypoxic TIR1 expression, but only at acidic pH. However, unlike known HOG pathway‐dependent genes, TIR1 is under positive cAMP control and this effect is mediated by GPA2 but not by RAS2. Genetic analysis showed that ord1 mutation was epistatic to the gpa2 mutation, thereby indicating that Gpa2p is needed to counteract the Ord1 factor, which is involved in the repression of hypoxic TIR1 expression, while the HOG pathway appears to be independent from Ord1 repression. In addition, an increased ORD1 gene expression was observed in the Δgpa2 mutant cells, meaning that GPA2 maintains a low basal level of ORD1 transcripts. Thus, cAMP allows partial relief of the TIR1 repression exerted by Ord1p. However, this is contradicted at acidic pH by the HOG pathway requirement because Hog1p is activated under stress conditions when the cAMP cellular content is low. The opposite effects of the GPA2–cAMP and HOG pathways are likely to explain the diminished hypoxic expression of TIR1 at acidic pH. Copyright © 2001 John Wiley & Sons, Ltd.
Use of levonorgestrel as an effective means of contraception in the white‐faced saki (Pithecia pithecia)
Authors: Savage Anne , Zirofsky Dara S. , Shideler Susan E. , Smith Tessa E. , Lasley Bill L.
Published: August 2002

This study examines the use levonorgestrel (Norplant®‐2) as a means of contracepting white‐faced sakis (Pithecia pithecia). A 70‐mg silastic tubule of levonorgestrel was implanted subdermally between the scapulae in four multiparous and two nulliparous females. Implants remained in the females housed with males of proven fertility for 81 to 734 days. All females experienced low, acyclic levels of estrone conjugates (E1C, < 500 ng/mg Cr) and pregnanediol‐3‐glucuronide (PdG, < 1.5 μg/mg Cr) after insertion of the implant. In five females having nine contraceptive bouts, ovulation was completely blocked for the entire duration of Norplant insertion (range: 81–734 days) as evidenced by a lack of cyclic changes in excretory hormone levels. However, one female was observed to have cyclic ovarian hormonal levels 5.8 months after Norplant insertion. Thus, levonorgestrel can be an effective method for blocking cyclic ovarian hormonal changes for 1 year (n = 2) and possibly as long as 2 years (n = 3). Zoo Biol 21:49–57, 2002. © 2002 Wiley‐Liss, Inc.
Nest attendants in parakeet auklets
Authors: Grimes Julie , Logan Cheryl
Published: August 2002

Breeding behaviors in a captive population of parakeet auklets (Cyclorrhynchus psittacula) were observed to determine whether a third bird present at the entrances to nest tunnels was a helper or competitor. Comparisons were made between focal pairs of nesting birds, two with and two without attendants. Pairs with attendants spent more time feeding and more time bathing and had less time with intruders (other than the third bird) at their tunnels. Nest attendants also helped in nest defense and incubation (taking some of the burden off the focal pair). Relatedness is unknown; therefore, kin selection cannot be assessed. Because all nest tunnels were occupied, however, limited breeding resources in the captive environment may make helping an adaptive alternative for mature birds. Zoo Biol 20:271–277, 2001. © 2001 Wiley‐Liss, Inc.
Knaster-Tarski Revisited
Authors: Jonker Jan Eppo
Published: August 2002

The concept “complete partial order” is generalized to the concept “functionally complete partial order.” The correctness of a corresponding generalization of the Knaster-Tarski fixpoint theorem is proved. The theory is applied to yield a fixpoint mapping theorem.
The SH-Verification Tool — Abstraction-Based Verification of Co-operating Systems
Authors: Ochsenschläger P. , Repp J. , Rieke R. , Nitsche U.
Published: August 2002

The sh-verification tool comprises computing abstractions of finite-state behaviour representations as well as automata and temporal logic based verification approaches. To be suitable for the verification of so called co-operating systems, a modified type of satisfaction relation (approximate satisfaction) is considered. Regarding abstraction, alphabetic language homomorphisms are used to compute abstract behaviours. To avoid loss of important information when moving to the abstract level, abstracting homomorphisms have to satisfy a certain property called simplicity on the concrete (i.e. not abstracted) behaviour. The well known state space explosion problem is tackled by a compositional method combined with a partial order method.
Editorial
Authors: Groote Jan Friso , Luttik Bas , van Wamel Jos
Published: August 2002

Formal Aspects of Computing

is devoted to the best papers presented at the third ERCIM workshop on Formal Methods for Industrial Critical Systems (FMICS98), held at the CWI in Amsterdam.

The FMICS workshops are intended to bring together scientists who are active in the area of formal methods and who are interested in exchanging their experiences in industrial usage of these methods. They also aim at the promotion of research and development for the improvement of the theory and their tools for industrial applications.

We are satisfied to see that time and again, the application of these methods clarifies the structure and inner workings of many systems and exposes many mistakes and conceptual errors. We are particularly delighted, as the reader may see when browsing through this special issue, that throughout the years a steady improvement can be observed regarding the size and complexity of systems that are being investigated. We hope and expect that this trend will continue throughout the forthcoming FMICS workshops.

We want to thank all those that have helped in producing this special issue. Especially the program committee, assisted by numerous referees, as well as the authors of the contributions and the participants of the workshop.
Probabilistic Duration Calculus for Continuous Time
Authors: Van Hung Dang , Chaochen Zhou
Published: August 2002

This paper deals with dependability of imperfect implementations concerning given requirements. The requirements are assumed to be written as formulas in Duration Calculus. Implementations are modelled by continuous semi-Markov processes with finite state space, which are expressed in the paper as finite automata with stochastic delays of state transitions. A probabilistic model for Duration Calculus formulas is introduced, so that the satisfaction probabilities of Duration Calculus formulas with respect to semi-Markov processes can be defined, reasoned about and calculated through a set of axioms and rules of the model.
Computing Permutation Encodings
Authors: Leino K. Rustan M.
Published: August 2002

A permutation can be encoded in several different ways. This paper discusses some relations among some encodings and how one can be computed from others. The paper shows a short proof of an existing efficient algorithm for encoding a permutation and presents two new efficient algorithms. One of the new algorithms is constructed as the inverse of an existing algorithm for decoding, making it the first efficient permutation encoding algorithm obtained in that way.
A Minimal Graphical User Interface for the Jape Proof Calculator
Authors: Bornat Richard , Sufrin Bernard
Published: August 2002

GUI design isn't simply a matter of putting a nice front-end on a capable program. It requires thought about the way in which people might be expected to use a system, and investigation of the ways that they actually use it. Jape's GUI has been designed to be as simple as possible, so that it will not get in the way of the business of proof. It is designed to be minimal in the information that it displays and the gestures that it requires from the user. In this paper we introduce and give a rationale for the design of Jape's user interface, then note some of its drawbacks.
Are Patients with Multiple Endocrine Neoplasia Type I Prone to Premature Death?
Authors: Dean Patrick G. , van Heerden Jon A. , Farley David R. , Thompson Geoffrey B. , Grant Clive S. , Harmsen W. Scott , Ilstrup Duane M.
Published: August 2002

Multiple endocrine neoplasia type I (MEN‐I) is an autosomal dominant disorder characterized by endocrinopathies involving the anterior pituitary gland, parathyroid glands, and pancreas. The long‐term prognosis for patients affected with this disorder is uncertain. To better characterize this prognosis, we performed a retrospective review of all patients with MEN‐I treated at a single institution during the period 1951–1997. A group of 233 patients served as the study population. Their records were analyzed for confirmation of diagnosis, treatments received, long‐term survival, and cause of death. Altogether, 108 eight male patients (46%) and 125 female patients (54%) were identified. At the conclusion of the study, 164 (70%) were alive and 69 (30%) were deceased, with a median follow‐up for patients alive at last contact of 13.4 years (range < 1 month to 54.3 years). The cause of death was reliably obtained in 60 patients. Of these patients, 17 (28%) died of causes related to MEN‐I, most commonly metastatic islet cell tumors (10 patients). The remaining patients died of causes unrelated to MEN‐I, most commonly coronary artery disease and nonendocrine malignancies (14% each). The overall 20‐year survival of MEN‐I patients was 64% (95% CI was 56–72%), and that of an age‐ and gender‐matched upper Midwest population was 81% (p < 0.001). Patients with MEN‐I appear to be at increased risk of premature death. Earlier diagnosis and treatment of potentially malignant pancreatic islet cell neoplasms may result in a decrease of this premature mortality.
Effects of Polyglycolic Acid and Polypropylene Meshes on Postoperative Adhesion Formation in Mice
Authors: Baykal Atac , Onat Demirali , Rasa Kemal , Renda Nurten , Sayek Iskender
Published: August 2002

The purpose of this study was to investigate the effects of polyglycolic acid (PGA), an absorbable (ABS) mesh, and polypropylene (PP), a nonabsorbable (NA) mesh, on intestinal adhesion formation. Altogether 72 mice were divided into a control group of 24, an ABS mesh group of 23, and an NA mesh group of 25. All three groups were divided into two subgroups for evaluation of adhesion severity at postoperative (po) days 5 and 90. Adhesion severity was measured with adhesion grading and tissue hydroxyproline (OHP) levels. Adhesion degree was minimal (1) in all subjects on day 5. Also there was no difference in tissue OHP levels between three groups on day 5
(
p > 0.05). Adhesion degree and tissue OHP levels as determinants of adhesion severity were higher in the PGA mesh group than the control group and the PP mesh group on day 90
(p < 0.001). There was no difference between the control group and the PP mesh groups (p > 0.05). Adhesion degree was higher on day 90 than on day 5 in the control group and the PGA mesh group (p < 0.05), whereas tissue OHP level was higher on day 90 than on day 5 in all three groups
(p < 0.001). Also there was linear correlation between adhesion degree and tissue OHP levels (r=
0.86, p < 0.001). The study demonstrates that ABS PGA mesh has higher potential for adhesion formation than the NA PP mesh, probably related to the increased foreign body and inflammatory reactions during the absorption process of the mesh.
Surgical Treatment of Complicated Duodenal Ulcers: Controlled Trials
Authors: Millat Bertrand , Fingerhut Abe , Borie Fredéric
Published: August 2002

Indications for surgery of duodenal ulcer (DU) have changed radically because of the efficacy of H2‐antagonists, endoscopic procedures, and eradication of Helicobacter pylorus. The aim of this study was to analyze the current literature to determine if definitive surgery is still relevant for complicated DU (bleeding, perforation, gastric outlet obstruction). Two studies have compared early to late surgery in terms of bleeding. One recommended early surgery (significant reduction in mortality) in the elderly, but no statistically significant difference was found when analyzed with “intention to treat.” In the other, mortality with early surgery was five times higher than with expectant therapy (when it was possible). Two studies comparing different surgical techniques for bleeding favored the radical procedure. Of at least 15 studies comparing endoscopic treatments, however, none has compared endoscopic therapy to surgical intervention for bleeding DU. One trial, comparing nonoperative to surgical treatment for perforation, found similar rates of morbidity, intraabdominal abscess, and mortality; but the hospital stay was longer (p < 0.001). Nonoperative treatment failed more often (p < 0.05) in patients over age 70. In three trials, postoperative morbidity (excepting wound sepsis in one) was not significantly increased by definitive surgery, with less ulcer recurrence (p < 0.05) compared with simple closure. Laparoscopy (versus laparotomy) was shown to take longer (p < 0.001) but required less postoperative analgesics (p < 0.03); there were no statistically significant differences as concerns the duration of nasogastric aspiration, intravenous drips, hospital stay, time to resume normal diet, Visual Analogous Scale pain scores for the first 24 hours after surgery, morbidity, reoperation rate, or mortality. Of 48 laparoscopic patients, 11 (23%) underwent conversion to open surgery. Three surgical techniques [highly selective vagotomy (HSU) + gastrojejunostomy (group 1), HSV + Jaboulay gastroduodenostomy (group 2), or selective vagotomy (group 3) + antrectomy) for gastric outlet obstruction (GOO)] showed that although postoperative results were similar (except wound sepsis in one trial), long‐term Visick scores were significantly (p < 0.01) better in group 1 than in group 2, but not in group 3. Further studies are needed to determine the exact prevalence of Helicobacter pylori in complicated DU and to compare (1) definitive to minimal surgery (stop the bleeding or close the perforation) combined with antisecretory drugs and eradication of H. pylori; (2) surgery to endoscopic treatment combined with eradication of H. pylori; and (3) for GOO, surgery to balloon dilatation combined with eradication of H. pylori.
A dynamic system interpretation of irreducible complexity
Authors: Boyarsky Abraham , Góra Pawel
Published: August 2002

Behe recently defined the idea of irreducible complexity for biological systems. Using the language of mathematics, we reinterpret his definition from a dynamical systems perspective. Our basic premise is that living organisms behave dynamically in a chaotic way while predictable periodic behavior reflects cessation of function. We consider the dynamics of a functioning system and altered versions of it to draw conclusions about the irreducible complexity of the original system. The dynamics of an organism is described by means of a discrete time transformation τ on the phase space of the system. The statistical behavior of τ is studied by means of its Frobenius–Perron operator which, in special cases, can be represented by a matrix. Using these matrices we rewrite our definition of irreducible complexity:M is irreducibly complex if it is primitive but no principal submatrix of M is primitive. The primitivity property implies chaotic behavior, while failure to have the primitivity property reflects periodic behavior. Examples of irreducibly complex dynamical systems are presented. We show that certain dynamical systems which are irreducibly complex have an additional property, namely that other systems arbitrarily close to it behave in a dramatically different way. Such behavior suggests that selective evolution by means of small perturbations may not be a general mechanism for achieving the dynamical behavior of a complex system.
Design Procedure Based on VHDL Language Transformations
Authors: Varga László , Hosszú Gábor , Kovács Ferenc
Published: August 2002

One of the major problems within the VHDL based behavioral synthesis is to start the design on higher abstraction level than the register transfer level (RTL). VHDL semantics was designed strictly for simulation, therefore it was not considered as high‐level synthesis language. A novel synthesis procedure was developed, which uses the methodology of high level synthesis. It starts from an abstract VHDL model and produces an RTL VHDL description through successive language transformations while preserving the VHDL standard simulation semantics. The steps of the synthesis do not use graph representation or other meta‐language, but apply the standard VHDL only. This VHDL representation is simulatable and accessible, functional verification can be performed by simulation at any time, and the simulation results can be used to guide the synthesis process. The output VHDL format is suitable to continue the design flow with RTL based synthesis tools.
The Bohm criterion and sheath formation
Authors: K -U Riemann
Published: August 2002

In the limit of a small Debye length ( lambdaDto 0) the analysis of the plasma boundary layer leads to a two-scale problem of a collision free sheath and of a quasi-neutral presheath. Bohm's criterion expresses a necessary condition for the formation of a stationary sheath in front of a negative absorbing wall. The basic features of the plasma-sheath transition and their relation to the Bohm criterion are discussed and illustrated from a simple cold-ion fluid model. A rigorous kinetic analysis of the vicinity of the sheath edge allows one to generalize Bohm's criterion accounting not only for arbitrary ion and electron distributions, but also for general boundary conditions at the wall. It is shown that the generalized sheath condition is (apart from special exceptions) marginally fulfilled and related to a sheath edge field singularity. Due to this singularity, smooth matching of the presheath and sheath solutions requires an additional transition layer. Previous investigations concerning particular problems of the plasma-sheath transition are reviewed in the light of the general relations.
Consistent analysis of a weakly ionized plasma and its boundary layer
Authors: K -U Riemann
Published: August 2002

The boundary layer problem of a weakly ionized collision-dominated plasma in front of a negative absorbing wall is considered. The electrons are assumed to be Boltzmann distributed; the ions are governed by symmetric charge exchange. The Debye length is small compared with the mean free path. A former kinetic analysis of the Knudsen layer is matched with an adapted macroscopic theory of the plasma body accounting for ionization, nonplanar geometry and filed-dependent ion mobility. The consistent analysis of plasma and boundary layer is illustrated with the examples of a cylindrical plasma column, a spherical probe in an infinitely extended plasma without ion generation, and a semi-infinite plasma with Saha ionization equilibrium distorted by wall losses.
Mechanism of oils and lubricants action under transient conditions of bearing operation
Authors: N F Dmitrichenko  , R G Mnatsakanov  , M V Raiko  , V G Grabchak
Published: August 2002

The lubricating effect of oils and lubricants has been investigated in local contact of bearing systems using models and real units under different types of non-stationary conditions taking into account their dynamic, kinematic and temperature characteristics. The results obtained show that the antiwear and antiscuff resistance of bearing systems under non-stationary conditions is explained by the discovered mechanism of lubrication by oils and lubricants through complicated physico-chemical processes of transformations of friction surfaces.
Rapid precipitation of biochemicals
Authors: A J Mahajan  , D J Kirwan
Published: August 2002

The production of uniform fine crystalline particles is highly desirable for pharmaceutical products in order to enhance stability and dissolution rates and, thereby, to favour high bioavailability. Precipitation under high-supersaturation conditions favours nucleation over growth processes and will result in smaller particles. Little fundamental information is available on the kinetics of nucleation and growth of organic compounds when precipitated under high-supersaturation conditions by the addition of a non-solvent. In order to accurately measure such rapid kinetics a technique for rapid mixing prior to any nucleation events is required. The authors report the use of a grid mixing device with a mixing time of less than 3 ms to measure the nucleation and growth rates of L-asparagine and lovastatin when precipitated by non-solvents at high supersaturation ratios. Nucleation induction times as small as 60 ms are observed, and the growth of asparagine at high supersaturation is found to be described by the same rate law as previously determined at low supersaturations.
Scattering of non-relativistic electrons in tip structures
Authors: M Weber
Published: August 2002

Fine tip structures are required for many applications in different technologies, for example in scanning probe microscopy or vacuum microelectronic devices. Tips can be produced with nanometre precision by the electron-beam-induced deposition technique. The deposition process, however, is still not really understood. This paper describes the results of a Monte Carlo simulation of electron scattering in tip structures, which reveal some fundamental differences from flat and tilted bulk substrates. An analytical expression is found for the total energy loss of electrons in tips consisting of various materials deposited at 8-30 keV beam energy.
On the chromatic variational function of a combined focusing-deflection system
Authors: Yu Li
Published: August 2002

In this paper, the second-order and fourth-order relativistic chromatic variational functions for all kinds of relativistic chromatic aberrations of a combined electrostatic-magnetostatic focusing-deflection system have been derived in detail. Here, the relativistic chromatic aberrations produced by the variations of accelerating voltage, currents of magnetostatic round lenses, voltages of electrostatic round lenses and excitations of deflector multipoles are considered.
Kinetic effects in protein crystals. I. The role of hydration in protein aggregation
Authors: D A Noever
Published: August 2002

Crystallizing proteins presents long-standing problems with sluggish kinetics and competing growth-limiting factors in solution. This work examines potential limiting factors arising from protein-water interactions and protein-protein aggregation. Since a hydrated shell shields bare protein contacts, multiple layers of highly viscous water impose restrictions on protein addition. If proteins attach to the crystal as aggregates, they are found to be particularly sensitive to misalignments and denaturation. The modelling extends to include the protein's shape as a fractal, the number of its binding sites and possible effects of flow-induced shear. It concludes that: (i) when protein-water interactions are taken into account convective shear approaches velocities of the order of magnitude that alter protein kinetics; (ii) protein aggregation puts narrow tolerances on correct molecular alignments; and (iii) a protein's characteristic 'stringy' shape as a fractal can favour aggregates compared with the monomer as a growth unit. A model for protein addition as an extensible, tethered molecule is proposed and examined against flow strengths and random thermal vibrations. Comparison of the protein model with experimental lysozyme results suggests that forced fluid flows as small as 100 mu m s-1can disrupt protein attachment and thus detrimentally limit crystal growth on a microscopic scale.
The symmetry group and harmonic potentials of a generalized multipole
Authors: Yu Li
Published: August 2002

The concept of an electrostatic (a magnetostatic) ordinary multipole has been extended to that of an electrostatic (a magnetostatic) generalized multipole which consists of a closely placed electrostatic ordinary multipole and electrostatic round lens (or closely placed magnetostatic ordinary multipole and magnetostatic round lens). The definition of the M function for an ordinary multipole has been extended to that of the M function for its corresponding generalized multipole. The relation between the symmetry group of an ordinary multipole and that of its corresponding generalized multipole and the relation between their constraint relations among their mth partial harmonic potentials have been derived. The following conclusion is derived: if an electrostatic deflector-multipole and an electrostatic round lens are placed in close proximity, one cannot assert that this combined system can always be treated by the aberration theory of a combined focusing - deflection system.
Characteristics of a laser plasma induced by irradiation of a normal-oscillation YAG laser at low pressures
Authors: H Kurniawan  , W Setia Budi  , M M Suliyanti  , A M Marpaung  , K Kagawa
Published: August 2002

The generation of a laser-induced shock wave plasma in air at reduced pressure was achieved by focusing a normal-oscillation Nd:YAG laser on a brass sheet. The characteristics of the plasma were analysed under three different conditions: free expansion of the plasma, confinement of the plasma by limiting the plasma region using two parallel glass plates and interruption of the plasma by placement of a wedge in front of the plasma, in order to interrupt the expansion of the plasma. Spatially and temporally integrated methods were also developed in order to develop a more detailed understanding of the excitation mechanism of the plasma. Furthermore, a new technique of shadow graphing which involves the use of a He - Ne laser as a probe light was also developed as well as a measurement of the time profile of the temperature. By using this new method the relationship between the density jump and the starting point of atomic emission was detected simultaneously. The results show that the plasma was also generated by the shock wave as for the case of the short-pulse laser (Q switched). The extremely low ion and background emission, as low as compared with neutral emission, makes this plasma potentially useful for spectrochemical analysis.
Spatially resolved relaxometry and pore size distribution by single-point MRI methods: porous media calorimetry
Authors: Pablo J Prado  , Bruce J Balcom  , Steven D Beyea  , Theodore W Bremner  , Robin L Armstrong  , Rashmi Pishe  , Patrick E Gratten-Bellew
Published: August 2002

A single-point magnetic resonance imaging study of water freezing in saturated and non-saturated porous materials is presented. Relevant considerations about relaxation time mapping in short relaxation time systems (of tens to hundreds of microseconds) are discussed and results in concrete and mortar samples under cooling conditions are shown. A spatially resolved estimation of the occupied pore size distribution is achieved in specimens presenting short relaxation times. To the best of our knowledge, this is the first report on the effective determination of spatially resolved pore size distribution of intact concrete materials. Evolution of one-dimensional images as a function of temperature is qualitatively compared with a series of differential scanning calorimetry experiments for cement pastes conditioned under controlled humidity. No supercooling effect is observed in a water saturated concrete single-point imaging experiment.
On the multi-harmonic scattering from a boundary of a nonlinear medium
Authors: Ioseph Gurwich
Published: August 2002

The multi-harmonic reflection from a plane boundary with a nonlinear medium is discussed. The main attention is focused on two special effects, namely nonlinear suppression of the reflection on the fundamental frequency and the total reflection which can occur at several critical angles in a nonlinear case.
An alternative to the Maugis model of adhesion between elastic spheres
Authors: J A Greenwood  , K L Johnson
Published: August 2002

The problem of how contact between elastic spheres is modified by the surface forces which act between them is becoming of great interest with the possibility of studying such contacts experimentally in the atomic force microscope and in the surface force apparatus. Experiments are frequently interpreted with the help of the JKR adhesion theory, in which the action of the surface forces is represented by the change in surface energy involved in uniting or separating the two surfaces. This has two drawbacks: it is strictly valid only when the Tabor parameteris large, though in fact it appears that the conditionis sufficient, and it gives no help with the attractive forcesbeforecontact takes place, which may cause `jumping on'. However, it has one enormous virtue: the results are described by simple algebraic equations, which all can manipulate as required. In contrast, full numerical analyses, such as the pioneering solution by Muller, Derjaguin and Toporov and a more recent solution by Greenwood, give only the results the authors choose to pass on. These establish when the JKR solution is valid and indicate the ways in which it is incomplete; but stop there. For this reason, an analytical solution by Maugis using a simplified force-separation law, that the adhesive stress has a fixed value whenever the separation is less than a critical distance, has proved most valuable. However, it too has a drawback, though a minor one: the shape of the gap involves elliptical integrals, which is inconvenient when the extension to visco-elastic spheres is considered. Here we present an alternative to the Maugis theory, based on the combination of two Hertzian pressure distributions. The results are very close to those of the Maugis model, but the gap shape now involves only elementary functions.
On the symmetry group and harmonic potentials of a generalized multipole
Authors: Yu Li
Published: August 2002

The relation between theMfunction for a generalized multipole and the pure mathematicalMfunction is discussed. The concept of rotation sense has been replaced by the clearer and more general concept of screw sense. The influence of the infinitesimal orders of harmonic potentials on aberrations in connection with the constraints of the symmetry group of a GM are discussed. A simple, unified and powerful method to determine the constraint relations among the harmonic potentials of a generalized multipole or ordinary multipole is given and rigorously proved.
Electroluminescence in organics
Authors: Jan Kalinowski
Published: August 2002

There is growing interest in organic electroluminescence (EL). A great deal of progress has been made recently in improving the performance of various classes of organic EL devices. Some of these are now adequate for many applications. However, specialists focusing on selected aspects of organic EL devices have often lost contact with the general subject of EL. Therefore, a review covering all aspects of EL mechanisms and their experimental manifestation seemed necessary. This article is concerned with the new EL device physics that can be realized using crystals, or films made of organic materials, as electrically and optically active components, in devices ranging from simple single-component light emitting diodes (LEDs), through double- and multi-layer LEDs to light emitting electrochemical cells (LECs) and organic LED-based light transducers. The investigation of the properties of these devices has provided in turn a very effective method for studying the basic EL phenomena in these materials. Since the subject of the present review has generated a huge amount of literature, and it is impossible to mention here all that has been done, we have attempted to provide an outline of the background of the field of organic EL, and discussed in some detail those aspects most relevant to the EL device physics. Because of the diversity of the types of material and EL structure, there is no single, simple description of EL in organics. Therefore, the initial sections of the article are devoted to a discussion of the types of EL and related phenomena, such as carrier injection and recombination or nature of emitting states. Then, the fundamentals of the fabrication of various types of EL devices are discussed along with the most representative examples. In general, the reader will find in the article a brief historical review of the subject as well as a description of the latest trends in organic EL research covering all the new concepts and most important data which have become available before the time of publication.
A simulation study of the cloud propagation model
Authors: S S Seker  , O Çerezci
Published: August 2002

Propagation through a sparse distribution of lossy particles in a cloud is investigated. Using a discrete modelling technique, a mathematical model to aid in the interpretation of the interaction data obtained by electromagnetic probing of mixed ice crystals and waterdrop clouds is developed. Such clouds can contain many possible crystal forms, most notably thin long cylinders and flat plate crystals. The present work is a simulation of the theoretical aspects of this problem. The attenuation, phase, bistatic scattering patterns and emissivity are computed for waves of selected polarizations passing through clouds with specified sizes, shape and distributions. The results are compared with the literature and good agreement is obtained.
Hybrid model of a plane-parallel hollow-cathode discharge
Authors: Kinga Kutasi  , Zoltán Donkó
Published: August 2002

The development of the hollow-cathode effect in a plane-parallel hollow cathode dc argon glow discharge was investigated experimentally and by means of a two-dimensional self-consistent hybrid model, combining the fluid description of positive ions and slow electrons with a particle simulation of fast electrons. In the experiments the discharge was formed between two flat disc copper electrodes (of 3.14 cm diameter and separated by aL= 2 cm gap) serving as cathodes and a metal tube surrounding these electrodes which served as the anode. The electrical characteristics of the discharge and the spatial intensity distribution of selected spectral lines (Ar I 750.3 nm, 811.5 nm and Ar II 476.5 nm) were recorded at current densities 0.1 mA cm-2j0.5 mA cm-2and for gas pressures 0.2 mbarp1 mbar. While at pressures of ~1 mbar the cathode regions are developed separately for both cathodes, the light intensity distribution measurements demonstrated the gradual merging of the negative glows with decreasing pressure. AtpL0.8 mbar cm, a common negative glow is formed in the discharge. Complementing the experimental observations, the simulations made it possible to determine various discharge characteristics (e.g. spatial distribution of electric potential, ionization source, and ion density). At lowpLvalues the simulations also indicated the existence of oscillating electrons. The spatial distribution of light intensity calculated for different pressures shows good qualitative agreement with the experimentally observed distributions.
A modified pseudo-equilibrium model competing with kinetic models to determine the composition of a two-temperature SF6atmosphere plasma
Authors: V Rat  , P André  , J Aubreton  , M F Elchinger  , P Fauchais  , A Lefort
Published: August 2002

This paper is devoted to calculation of the non-equilibrium composition in a SF6thermal plasma at atmospheric pressure. Non-equilibrium thermal plasmas are characterized by heavy species temperaturesThbelow 9000 K with electron temperatures at the maximum three times higher thanThwhen the latter is below 4000 K. Different theories have been used based on either multi-temperature plasmas, Saha-Potapov modified by Andréet al, van de Sandenet al, Cliteuret al, or kinetic calculations or the pseudo-equilibrium model, recently developed. This model gives results similar to those of kinetic calculations for N2and H2plasmas but with calculation times two orders magnitude faster. Pseudo-equilibrium calculation takes into account the reactions with low activation energies instead of ionization reactions, while keeping all the species present in the kinetic calculation. First, the theories are compared in a case already studied in the literature by Cliteur: a heavy species temperatureThat 6000 K, with the electron temperatureTevarying between 6000 and 15 000 K. Comparison of the results shows that the multi-temperature calculations, except those of Cliteur, are far from kinetic especially forneandnF-. In addition, the pseudo-equilibrium model fits rather well with the kinetic calculations as long as molecular species are present in the plasma. Second, to calculate the composition of non-equilibrium thermal plasmas the ratioTe/This assumed to vary as the logarithm of the electron densities ratione/ncmax,nemaxbeing the electron density over which equilibrium prevails, i.e. 1023 m-3. For kinetic reactions where electrons are involved (in the direct reaction while heavy species intervene in the reverse reaction), a temperatureT* betweenTeandThis defined.T* is calculated as a function of the electron flux to that of heavy species. The variation ofT* withThis smoother than that ofTe. In such conditions again, there is an excellent agreement between kinetic and pseudo-equilibrium calculations performed atT*, which is not the case for multi-temperature calculations. These results demonstrate that the pseudo-equilibrium calculation developed for thermal plasma simple forming gases such as N2and H2can also be applied to more complex gases such as SF6.
A Langmuir multi-probe system for the characterization of atmospheric pressure arc plasmas
Authors: C Fanara  , I M Richardson
Published: August 2002

It is well known that the use of Langmuir probes in `high' pressure plasmas (atmospheric and above) is extremely difficult due to the high degree of collisionality. In addition, electric arcs used in industry are highly non-homogeneous. In particular the degree of ionization varies from zero at the arc edges to values close to full ionization near the axis. Existing probe theories are therefore inappropriate. The `traditional' use of the characteristic curve for arc temperature and particle density mapping is time consuming and also leads to errors due to the collisional nature of the discharge. Existing probe theories are examined with respect to the application at high pressure and in this, the first of a series of papers, an interpretation based on different assumptions is presented.

A simple apparatus for the study of tungsten inert gas (TIG) welding arcs is described permitting data collection over short time periods (~0.1 s) for operating currents in the range 50-150 A. Difficulties encountered with probe applications are discussed highlighting the need for further theoretical developments.

The axial electric field is given by the derivative of the measured potential with respect to the axial position and shown to be in agreement with previous estimations. Results are discussed with reference to the sparse previous publications concerned with high pressure arc plasmas.
Quantum potential approach to a class of quantum cosmological models
Authors: Arkadiusz Blaut  , Jerzy Kowalski Glikman
Published: August 2002

In this paper we discuss the quantum potential approach of Bohm in the context of a quantum cosmological model. This approach makes it possible to convert the wavefunction of the universe into a set of equations describing the time evolution of the universe. Following Ashtekar et al we make use of a quantum canonical transformation to cast a class of a quantum cosmological models into a simple form in which they can be solved explicitly, and then we use the solutions to recover the time evolution.
The influence of plasma-edge properties on high confinement discharges with a radiating plasma mantle at the tokamak TEXTOR-94
Authors: B Unterberg  , A M Messiaen  , J Ongena  , M Brix  , G Bertschinger  , J Boedo  , G Bonheure  , M Ciotti  , Th Denner  , F Durodie  , P Dumortier  , K H Finken  , G Fuchs  , R Jaspers  , Y M Kim  , R Koch  , L Könen  , H R Koslowski  , A Krämer-Flecken  , A Lyssoivan  , G Mank  , G Van Oost  , A Pospieszczyk  , V Philipps  , J Rapp  , U Samm  , B Schweer  , G Telesca  , M Z Tokar'  , R Uhlemann  , P E Vandenplas  , M Vervier  , G Waidmann  , G Van Wassenhove  , F Weschenfelder  , R R Weynants  , G H Wolf
Published: August 2002

The radiative improved mode obtained on the limiter tokamak TEXTOR-94 combines the possibility of power exhaust by a radiating plasma boundary (with a fractionof the radiated power with respect to the total input power up to 90% with neon or argon cooling) with improved energy confinement (as good as in the ELM-free H-mode in divertor tokamaks) at high plasma densities (line-averaged central-electron density equal to or even above the Greenwald density limit) in quasi-stationary discharges. An overview is given of the substantial changes in plasma-edge properties occurring at high radiated power levels. These changes are characterized by a reduction of the plasma-edge density and temperature, a reduction of particle transport out of the confined plasma volume and an increase of the penetration depth of deuterium and impurity atoms. As a consequence, the particle confinement time increases and the electron-density profiles steepen. The transition to improved confinement takes place as soon as the density peaking reaches a critical threshold. An internal transport barrier is observed in the bulk of RI-mode plasmas (at) characterized by an increase of the pressure gradient and of the shear of the toroidal velocity compared to discharges without additional impurity seeding. The dilution at the plasma boundary is strongly increased by the seeded impurities whereas the central dilution is only weakly affected.
New low-energy measurements and calculation of ionization in H+–H collisions
Authors: M B Shah  , J Geddes  , B M McLaughlin  , H B Gilbody
Published: August 2002

In response to the strong current theoretical interest in models of low-energy ionization in H+–H collisions, a crossed-beam coincidence counting technique previously used in this laboratory to obtain cross sections in the range 9–1500 keV amu−1has been successfully adapted to extend the measurements downwards in energy from 9 to 1.25 keV amu−1. In addition, we have extended the triple-centre calculations of McLaughlin B M, Winter T G and McCann J F 1997J. Phys. B: At. Mol. Opt. Phys.301043, down to 0.5 keV amu−1where agreement with experiment is found to be satisfactory. Our new measurements and calculation are at variance with relative cross sections measured by Pieksma M, Ovchinnikov S Y, van Eck J, Westerveld W B and Niehaus A 1994Phys. Rev. Lett.7346 in the range 1–6 keV amu−1, but are in good accord with their calculations based on the hidden-crossings model including only S and T promotion. However, our measurements and calculation do not support the more recent calculations by Pieksma M, Ovchinnikov S Y and Macek J H 1998J. Phys. B: At. Mol. Opt. Phys.311267 in which a contribution from a radial decoupling mechanism is also included in the model.
Auger anisotropy parameters α2for Xe M4–N4,5N4,5transitions induced by 3.6 MeV proton impact
Authors: A Hiltunen  , H Aksela  , S Aksela  , Gy Víkor  , S Ricz  , B Sulik
Published: August 2002

Angular distribution of the Xe M4–N4,5N4,5Auger transitions has been determined from an experiment which was carried out by 3.6 MeV proton impact. In a comparison with existing relativistic calculations for theα2parameters a good agreement was found which confirms the validity of relativistic theory in describing the core–core Auger transitions.
Mapping out the QCD phase transition in multiparticle production
Authors: Kabana Sonja , Minkowski Peter
Published: August 2002

We analyse multiparticle production in a thermal framework for seven central nucleus + nucleus collisions, e++ e-annihilation into hadrons on the Z resonance and four hadronic reactions p + p and p +; with partial centrality selection), with centre of mass energies ranging from= 2.6 GeV (per nucleon pair) to 1.8 TeV. Thermodynamic parameters at chemical freeze-out (temperature and baryon and strangeness fugacities) are obtained from appropriate fits, generally improving in quality for reactions subjected to centrality cuts. All systems with non-vanishing fugacities are extrapolated along trajectories of equal energy density, density and entropy density to zero fugacities. The so-obtained temperatures extrapolated to zero fugacities as a function of initial energy density εinuniversally show a strong rise followed by a saturating limit ofTlim= 155 ± 6 ± 20 MeV. We interpret this behaviour as mapping out the boundary between quark gluon plasma and hadronic phases. The ratio of strange antiquarks to light ones as a function of the initial energy density εinshows the same behaviour as the temperature, saturating at a value of 0.365 ± 0.033 ± 0.07. No distinctive feature of `strangeness enhancement' is seen for heavy ion collisions relative to hadronic and leptonic reactions, when compared at the same initial energy density.
Hot action at work: A different understanding of “understanding”
Authors: Beckett David
Published: August 2002

This chapter offers a new approach to “understanding.” Instead of asking how the learning, through training, is represented to the learner—Has there been a change in the state of the learner?—we need to ask a more profound question: What inferences can now be articulated by the learner?
Transfer effects in implicit memory and consumer choice
Authors: Butler Laurie T. , Berry Dianne C.
Published: August 2002

Two experiments investigated transfer effects in implicit memory and consumer choice, using a preference judgement task. Experiment 1 examined whether it is possible to obtain priming for unfamiliar food labels. Additionally, it investigated whether the experience of seeing a brand name with a particular product type would benefit subsequent processing of the brand name when linked with a different product type. Experiment 2 examined whether changes in modality between study and test would affect priming for unfamiliar brand names. Both questions are theoretically important, as well as pertaining to practical concerns in the consumer choice literature. Experiment 1 demonstrated significant priming for unfamiliar food labels, and established that priming was unaffected by changing the product type with which the brand name was associated. In Experiment 2, priming on both auditory and visual versions of the preference judgement task was reduced by changes in modality. The results and implications are discussed in relation to consumer choice and current theories of implicit memory. Copyright © 2001 John Wiley & Sons, Ltd.