bluuebunny/crossref_metadata_2025 huggingface dataset:
RESEARCH REPORT Psychiatric co‐morbidity among male heroin addicts: differences between hospital and incarcerated subjects in Taiwan
Authors: Chen Chiao‐Chicy , Tsai Shang‐Ying , Su Lien‐Wen , Yang Tien‐Wei , Tsai Chang‐Jer , Hwu Hai‐Gwo
Published: July 2002

Aims. To examine the differences in psychiatric co‐morbidity between hospital and incarcerated groups of heroin addicts in Taiwan. Design. Life‐time prevalence of DSM‐III‐R‐based coexisting psychiatric disorders, including personality disorders, were surveyed. Settings. A psychiatric hospital and two prisons. Participants. Two hundred and sixty heroin users who were incarcerated in prisons, and 47 heroin users who voluntarily sought help in a psychiatric hospital were interviewed by board‐certified psychiatrists. Measurements. Using two psychometric instruments, the Psychiatric Diagnostic Assessment (PDA) and the Structured Interview for DSM‐III‐R Personality Disorders (SIPD‐R), psychiatric co‐morbidity was assessed. Findings. Different life‐time rates of coexisting psychiatric disorders among heroin addicts in different settings were found: 83% of hospital subjects and 66% of incarcerated subjects were diagnosed as having at least one coexisting axis I or II disorder. The most prevalent coexisting DSM‐III‐R defined axis I disorders were additional substance use disorders (alcohol and methamphetamine), while the axis II disorder was antisocial personality disorder. The hospital group had a significantly higher prevalence rate of mood disorder (p<0.001), paranoid personality disorder (p<0.05) and antisocial personality disorder (p<0.001) than the incarcerated group. Conclusions. We suggest that heroin addicts with coexisting psychiatric disorders receive relevant psychiatric treatment. Those with personality disorders, especially the antisocial type, should be considered for specialized therapeutic community programmes instead of incarceration .
Patterns of alcohol consumption and social consequences. Results from an 8‐year follow‐up study in Switzerland
Authors: Rehm Jurgen , Gmel Gerhard
Published: July 2002

Aims. (1) To estimate the impact of drinking patterns on negative social (behaviour) consequences. (2) To test for the additional impact of overall volume of alcohol consumed on these social consequences. (3) To explore whether the impact on social consequences of drinking patterns is comparable for measures that do and do not explicitly mention alcohol consumption. Design and setting. An 8‐year follow‐up to a 1987 study of the Swiss general population carried out through face‐to‐face interviews; the follow‐up data presented in this article was collected in 1995 through a mailed questionnaire. Participants. Nine hundred and fifty‐three respondents from the 1987 survey who also completed the mailed questionnaire in 1995. Measurements. Variables used were as follows: volume of drinking, eight drinking patterns differentiated by volume and frequency, four social consequences without mention of alcohol and six with mention of alcohol. All multivariate analyses control for sex, age and linguistic region. Findings. High volumes of drinking per occasion predicted negative social consequences independently of overall drinking volume. This finding was independent of explicit mention of alcohol in item formulation. For unemployment and accidents, if assessed independently of alcohol consumption, no significant relationship with either overall volume of drinking or drinking pattern was observed. Conclusions. Patterns of alcohol consumption are an important determinant of social problems. Future research with better design is necessary to establish their exact risk relations with different social consequences.
Growth hormone but not insulin‐like growth factor‐I improves wound strength in pigs
Authors: Robertson J. Gray , Walton Paul E. , Dunshea Frank , Dunaiski Vera , Ballard F. John , Belford David A.
Published: July 2002

Systemic growth hormone and locally administered insulin‐like growth factor‐I have been shown in a number of studies to improve the breaking strength of incisional wounds, especially in compromised animals. The objective of the present study was to compare these two agents when administered subcutaneously distant from an incisional wound site in pigs, as well as to examine effects of a combination growth hormone/insulin‐like growth factor treatment. Growth hormone was shown to increase wound breaking strength in two experiments, whereas insulin‐like growth factor‐I or a more potent analog had no effect. Moreover, breaking strength was only minimally improved above the vehicle groups by the combination of growth hormone and insulin‐like growth factor‐I. These effects could not be explained by changes in plasma insulin‐like growth factor‐I concentrations which were highest in the combination groups, nor by plasma insulin‐like growth factor binding protein‐3 which was raised equally whenever growth hormone was administered. We conclude that systemic growth hormone but not insulin‐like growth factor‐I improves wound strength in normal pigs, whereas insulin‐like growth factor‐I reduces the magnitude of the growth hormone effect by an unknown mechanism.
The mast cell‐nerve axis in wound healing: a hypothesis
Authors: Gottwald Thomas , Coerper Stephan , Schäffer Michael , Köveker Gerhard , Stead Ronald H.
Published: July 2002

Beyond their classic roles in allergic reactions and defence against parasites, mast cells can now be viewed as key players in regulating connective tissue homeostasis. There is good evidence that mast cells are in close morphological and functional contact with the peripheral nervous system. Although substantial differences exist between mast cells of different tissues and different species, they produce a wide range of agents, including cytokines, growth factors, and other regulatory molecules, and they respond to an equally wide range of substances, including neuropeptides. At our current level of understanding wound healing, inflammation plays a central role in this process, with macrophages being central protagonists at the cellular level. There is now increasing evidence that mast cells are also involved in wound healing, in health and disease. They produce and secrete histamine, heparin, and multifunctional cytokines and growth factors, which represent important agents in the wound‐healing process. Reviewing the recent literature supporting this hypothesis, we also outline the clinical importance of this work to help close the gap between basic research and clinical application.
Expression of inducible nitric oxide synthase in human burn wounds
Authors: Paulsen Stephen M. , Wurster Samuel H. , Nanney Lillian B.
Published: July 2002

Nitric oxide is produced by various cell types and can initiate either beneficial or deleterious effects. Because cultured human keratinocytes express an inducible isoform of nitric oxide synthase, it was postulated that keratinocytes within a burn wound would express increased levels of inducible nitric oxide synthase following the injury. Immunohistochemical staining identified the sites of cellular expression and temporal sequence of inducible nitric oxide synthase protein within partial‐ and full‐thickness burns excised from 29 patients. While migrating keratinocytes at the immediate edge of the wounds showed decreased or undetectable levels of inducible nitric oxide synthase, the immediately adjacent proliferative population and upwardly growing keratinocytes from surviving hair follicles showed increasingly greater cytoplasmic staining for inducible nitric oxide synthase at 4–21 days after injury. Noninjured skin showed minimal inducible nitric oxide synthase staining. Within the wound, detectable inducible nitric oxide synthase protein appeared to decrease as keratinocytes assumed a differentiated phenotype in the outer newly resurfaced epidermis, in inner root sheath layers of hair follicles, or in epithelium of eccrine sweat ducts. Within granulation tissue, immunoreactive inducible nitric oxide synthase was detected in capillary endothelium and in arterial smooth muscle layer. Focal increases in inducible nitric oxide synthase expression were noted in association with inflammatory infiltrates. In conclusion, the cellular and temporal distributions of immunoreactive inducible nitric oxide synthase suggest that nitric oxide may play a role in the regulation of wound repair processes beyond the acute burn injury.
Endogenous lateral electric fields around bovine corneal lesions are necessary for and can enhance normal rates of wound healing
Authors: Sta. Iglesia Drina D. , Vanable Joseph W.
Published: July 2002

The strength of the electric fields in the vicinity of 1.5 mm circular lesions in the bovine cornea has been found to influence the rate of re‐epithelization. A decrease in the field strength by submersion of the lesions or by treating the lesions with the Na+‐channel blocker, benzamil, significantly retarded healing. An increase in the field strength of lesions treated with Na+‐depleted Hanks' solution, by the addition of direct current, increased epithelization. Epithelization was fastest in wounds with field strengths raised to − 80 mV/mm, more than twice the normal field strength present in wounds maintained in Hanks' solution alone. Epithelization decreased, however, when the field strengths were increased to −120 mV/mm. A similar pattern was also observed when the field's polarity was reversed. By manipulating and monitoring the field strengths, we have been able to show for the first time that increased wound field strengths enhance corneal wound epithelization, and that field strengths with reversed polarity also enhance this epithelization.
Report on the Fourth International Granulocyte Immunology Workshop: progress toward quality assessment
Authors: Lucas Geoffrey , Rogers Susan , De Haas Masja , Porcelijn Leendert , Bux Juergen
Published: July 2002

BACKGROUND: A formal quality assurance (QA) scheme has been established to facilitate proficiency testing for granulocyte antibodies and antigens.

STUDY DESIGN AND METHODS: Fifteen laboratories participated in the Fourth International Granulocyte Immunology Workshop. The main objective of the workshop was to establish a formal QA scheme for granu‐ locyte serology and molecular typing methods. A secondary objective was to determine the relative sensitivities of the granulocyte immunofluorescence test, granulocyte agglutination test, and MoAb immobilization assays using defined antisera and protocols.

RESULTS: Laboratories scored between 16.7 and 100 percent (mean, 57.5%) of the maximum available in the serologic part of this QA exercise. There were particular problems in detecting granulocyte‐specific human neutrophil antigen‐1 (HNA‐1a) IgM antibodies and HNA‐2a antibodies in the presence of HNA‐1b antibodies. The granulocyte immunofluorescence test was more sensitive than the granulocyte agglutination test in titration studies, but the latter method more readily identified the presence of HNA‐3a antibodies. HNA genotyping was generally well performed, with nine laboratories obtaining 100‐percent correct results for HNA‐1a, HNA‐1b, and HNA‐1c.

CONCLUSIONS: There is a need to standardize the detection of granulocyte‐specific antibodies. Laboratories with good performance tended to use two methods for detecting granulocyte‐specific antibodies and an HNA‐typed panel of granulocytes. The use of a method for elucidating mixtures of granulocyte‐ and lymphocyte‐reactive antibodies (e.g., MoAb immobilization assay) and the use of methods for detecting both cytotoxic and noncytotoxic HLA class I antibodies were also associated with a higher than average performance.
FCGR3 variants and expression of human neutrophil antigen‐1a, ‐1b, and ‐1c in the populations of northern Germany and Uganda
Authors: Flesch Brigitte K. , Doose Sandra , Siebert Reiner , Ntambi Elisabeth , Neppert Juergen
Published: July 2002

BACKGROUND: Human neutrophil antigen‐1c (HNA‐1c) (SH) has been described as the third alloantigen of the Fc receptor type IIIb (FcγRIIIb) for IgG beside the known alloantigens HNA‐1a (NA1) and HNA‐1b (NA2). Controversy exists on the assignment of the HNA‐1c coding gene to the FCGR3B locus and on a possible linkage between the HNA‐1c and HNA‐1a coding genes.

STUDY DESIGN AND METHODS: Two hundred sixty northern German blood donors and 43 individuals from Uganda were typed for FCGR3B*1 (NA1), FCGR3B*2 (NA2), and FCGR3B*3 (SH) by allele‐specific PCR. In a subset of FCGR3B*3‐positive probands, PCR‐amplified FCGR3 fragments were subcloned and sequenced. Transmission of FCGR3B*3 was analyzed in family studies. A possible correlation with the FcγRIIIb alloantigen expression was investigated by flow cytometry.

RESULTS: In the northern German population, FCGR3B*3 was found exclusively in individuals carrying FCGR3B*1 independent of the existence of FCGR3B*2 at a frequency of 5 percent. In the individuals from Uganda, each possible combination of FCGR3B*1, FCGR3B*2, and FCGR3B*3 was detected. FCGR3B*3 frequency was 34.9 percent. Within both populations, some individuals carried each of the three genotypes. DNA sequencing revealed new FCGR3 variants caused by single nucleotide exchanges at the typical polymorphic positions. In one individual, six different FCGR3 variants were detected.

CONCLUSION: The coincidence of the three known FCGR3B alleles varies within the population of Germany and Uganda. Three simultaneous FCGR3B forms may be explained by two gene loci, but the basis of the high number of different variants in some individuals still remains unclear. Possible explanations may be a hypermutation mechanism or a number of FCGR3 higher than expected hitherto.
Effects of Gabapentin and Carbamazepine on the EEG and Cognition in Healthy Volunteers
Authors: Salinsky Martin C. , Binder Lawrence M. , Oken Barry S. , Storzbach Daniel , Aron Carey R. , Dodrill Carl B.
Published: July 2002

Summary:  Purpose: Antiepileptic drug (AED) therapy can be associated with neurotoxic side effects including cognitive dysfunction. Objective methods for detection of neurotoxicity in individual patients would be useful. We studied the effects of gabapentin (GBP) and carbamazepine (CBZ) on neurophysiologic and cognitive/behavioral measures in healthy volunteers.

Methods: In a 12‐week, randomized, double‐blind, parallel‐group study of CBZ and GBP in healthy volunteers, 23 subjects completed the protocol. All achieved the target dose of 1,200 mg CBZ or 3,600 mg GBP. A structured EEG for quantitative analysis and a cognitive test battery were administered before AED therapy and again after 12 weeks of therapy. Test–retest differences were compared with those of 72 untreated control subjects.

Results: Both CBZ and GBP significantly decreased the peak frequency of the posterior (alpha) rhythm, with CBZ exerting a greater effect. Ten CBZ and six GBP subjects exceeded the 95% confidence interval (CI) for an individual. Cognitive tests revealed AED vs. control group effects for two of seven measures (Digit Symbol, Stroop) and all subjective measures. However, few subjects exceeded the 95% CI for any objective test. Differences between CBZ and GBP were not significant. Greater EEG slowing was associated with greater subjective neurotoxicity and poorer test–retest performance on a cognitive test summary measure.

Conclusions: Prolonged CBZ and GBP therapy induced EEG slowing that correlated with cognitive complaints and often exceeded the confidence interval for individual subjects. Quantitative EEG measures may be useful in the objective determination of AED‐related neurotoxicity.
Low‐frequency Electric Cortical Stimulation Has an Inhibitory Effect on Epileptic Focus in Mesial Temporal Lobe Epilepsy
Authors: Yamamoto Junichi , Ikeda Akio , Satow Takeshi , Takeshita Kazuhide , Takayama Motohiro , Matsuhashi Masao , Matsumoto Riki , Ohara Shinji , Mikuni Nobuhiro , Takahashi Jun , Miyamoto Susumu , Taki Waro , Hashimoto Nobuo , Rothwell John C. , Shibasaki Hiroshi
Published: July 2002

Summary:  Purpose: This study was conducted to investigate the effect of low‐frequency electric cortical stimulation on epileptic focus in humans.

Methods: We stimulated the epileptic focus in a patient with medically intractable mesial temporal lobe epilepsy (MTLE) by means of subdural electrodes and evaluated the change in the number of interictal epileptiform discharges. We used biphasic electric current of 0.3‐ms duration presented at 0.9‐Hz frequency for 250 s, comparing stimulus intensity of 7.5, 2, and 0.5 mA.

Results: Interictal epileptiform discharges at the ictal focus occurred less frequently after the stimulation with the intensity of 0.5 mA. With the intensity of 7.5 mA and 2.0 mA, however, habitual auras were elicited by the stimulation, and afterdischarges were seen on the cortical EEG.

Conclusions: Low‐frequency, low‐intensity electric cortical stimulation could produce inhibitory effects on epileptic activity. At the same time, however, a caution for possible induction of EEG seizures is needed, even when applying low‐frequency electric stimulation.
Carbonic Anhydrase Inhibitor Sulthiame Reduces Intracellular pH and Epileptiform Activity of Hippocampal CA3 Neurons
Authors: Leniger Tobias , Wiemann Martin , Bingmann Dieter , Widman Guido , Hufnagel Andreas , Bonnet Udo
Published: July 2002

Summary:  Purpose: Sulthiame is a carbonic anhydrase (CA) inhibitor with an anticonvulsant effect in the treatment of benign and symptomatic focal epilepsy in children. The aim of the study was to elucidate the mode of action of sulthiame with respect to possible changes of intracellular pH (pHi) that might develop along with sulthiame's anticonvulsant properties.

Methods: The effects of sulthiame (a) on pHi of 2′,7‐bis(2‐carboxyethyl)‐5(6)‐carboxyfluorescein‐acetoxymetyl ester (BCECF‐AM) loaded CA3 neurones as well as (b) on epileptiform activity (induced by 50 μM 4‐aminopyridine) were compared with those of the CA inhibitors acetazolamide and benzolamide.

Results: In the majority of neurons, sulthiame (1.0–1.5 mM; n = 8) as well as the membrane permeant acetazolamide (0.5–1.0 mM; n = 6) reversibly decreased pHi by 0.18 ± 0.05 (SD) and 0.17 ± 0.10 (SD) pH units, respectively, within 10 min. The poor membrane permeant benzolamide (1.0–2.0 mM) had no influence on pHi (n = 8). Sulthiame (1.0–2.5 mM) and acetazolamide (1.0–2.0 mM) reversibly reduced the frequency of action potentials and epileptiform bursts after 10–15 min (n = 9, n = 7), whereas benzolamide (1.0–2.0 mM) had no effect (n = 6).

Conclusions: The results suggest that sulthiame acts as a membrane‐permeant CA inhibitor whose beneficial effect on epileptiform activity results at least in part from a modest intracellular acidosis of central neurons.
Electrochemical potentials during radiofrequency energy delivery: a new method to control catheter ablation of arrhythmias
Authors: Erdogan Ali , Carlsson Joerg , Grumbrecht Stephan , Kostin Sawa , Schulte Britta , Schlapp Michael , Neuzner Joerg , Pitschner Heinz F.
Published: July 2002

Aims

Thermal injury of subendocardial tissue leads to a release of electrolytes and free radicals from the intracellular site creating a change in electrochemical potential (eP) between the distal and the proximal catheter tip electrodes. The aim of the study was to verify the detection of ablation-induced release of electrolytes and free radicals and to assess the suitability of control-line energy delivery at ablation by measuringeP .

Methods and Results

In vitro tests under constant flow conditions were performed in a 10 l bath of physiological saline solution or bovine blood. Endomyocardial preparations of fresh bovine hearts were used. Closed-loop temperature-controlled, irrigated and closed-loop eP -controlled ablations were performed.In vivo animal investigations were performed in six anaesthetized and ventilated pigs. The existence of the eP was established in the tank model and was confirmed in animal investigations. High correlations were found between eP and catheter tip temperature (r=0·87) and between maximum eP and induced lesion size (r=0·85). Also a high correlation (r=0·85, P< 0·001) was found between eP and lesion volume.

Conclusions

Control of energy delivery during RF ablation by the measurement ofeP is feasible. In comparison with temperature controlled RF ablation, ablation guided by eP -measurement revealed a superior correlation with induced lesion size. Especially during cooled radiofrequency catheter ablation eP is the only parameter for control of energy delivery.
Pollination of Angelonia cornigera Hook. (Scrophulariaceae) by Long‐Legged, Oil‐Collecting Bees in NE Brazil
Authors: Machado I. C. , Vogel S. , Lopes A. V.
Published: July 2002

Abstract: The pollination of Angelonia cornigera Hook. (Scrophulariaceae) was studied in Caatinga vegetation, in the municipality of Buíque, Pernambuco state, northeastern Brazil. The plant is a perennial of open areas. Up to 60 flowers are produced in terminal, leafy racemes. The flowers are violet, strongly zygomorphic, of gullet type, with a pair of posterior pockets. Each pocket contains a patch of oil‐producing glandular hairs (elaiophore). The flowers were only visited, and pollinated, by oil‐collecting female bees of the Apidae‐Apinae: Centris hyptidis and Tapinotaspis spec. nov. 1. These two bees differ considerably in size but they share the peculiarity of possessing one pair of disproportionately elongate legs suitable to gain access to the concealed elaiophores. In C. hyptidis, it is the front pair, whereas in T. spec. nov. 1 the mid pair of legs is elongated. T. spec. nov. 1 exhibited two modes of visiting behaviour. Angelonia cornigera is self‐incompatible; it does not set fruits from spontaneous or manual self‐pollination. This is the fifth observed species of the genus Angelonia whose flowers are adapted to oil‐collecting bees in the Caatinga formation. Its flowers deviate in several aspects from the other studied Angelonia spp. regarding pollination relationships. New data on A. hirta and A. tomentosa are appended.
Gene Stability in Transgenic Aspen‐Populus ‐ III. T‐DNA Repeats Influence Transgene Expression Differentially among Different Transgenic Lines
Authors: Fladung M. , Kumar S.
Published: July 2002

Abstract: Transgene silencing mechanisms have been confirmed in many crop plants, however, few reports are currently available for long‐lived tree species. Three transgenic aspen lines carrying the rolC gene of Agrobacterium rhizogenes, under control of the 35S promoter of the cauliflower mosaic virus, but showing very different types of reversion from rolC‐phenotype to wild type are investigated in detail. A complete suppression of rolC phenotype was observed after one year of in vitro culturing in one transgenic line, whereas the second transgenic line showed gradual decrease in rolC expression, and the plants were comparable to control plants after three to four years in the greenhouse. In the third transgenic line, however, transgene inactivation was observed only in some shoots of the greenhouse‐grown plants which reverted to the rolC phenotype in subsequent years. Southern blotting experiments using a rolC probe revealed the integration of one or two tandem copies of the foreign genes into the host genome. All three transgenic lines contain in/complete T‐DNA repeats, as indicated by reverse primer (rp) PCR. In the reverted tissues of two transgenic lines loss of rolC protein was observed despite the presence of the rolC transcript. The third transgenic line, showing a completely suppressed rolC phenotype, was found positive for the rolC transcript and protein. On the basis of the molecular data presented for the three unstable lines, including Southern, Northern and Western blotting experiments, as well as a survey of transgenic methylation patterns, new insights were obtained with respect to structure and inactivation of transgenes following their transfer in a host tree species.
Performance and Photosynthetic Ecophysiology of Three Photo‐Types of Dioscorea zingiberensis under Differing Light Intensities
Authors: Li H. M. , He P. , Veste M. , Neudorf K.
Published: July 2002

Abstract: The performance and photosynthetic ecophysiology of three photo‐types of Dioscorea zingiberensis were studied. The three types are designated DzTL, DzTM and DzTH, according to their adaptation to low (LL), medium (ML) and high (HL) light intensities, respectively. Under LL (23 ‐ 55 μmol m‐2 s‐1) and simulated natural light (SNL), DzTM grows well with increased longevity, and green leaves which are unspotted; while its leaves became small, light yellow and short‐lived under HL (550 ‐ 850 μmol m‐2 s‐1). In contrast, under LL the leaves of DzTH were very large, spotted, light yellow and short‐lived; while they were small, green and long‐lived under HL. Under HL, DzTH had a much higher chlorophyll content than DzTM. Under LL, DzTM and DzTL had a higher Chl content than DzTH. Among the three types, DzTM had the highest peroxidase activity. DzTL had a higher electron transport rate (ETR), maximal quantum yield (MQY) and effective quantum yield (EQY) than DzTH and DzTL under LL, while DzTH had higher ETR, MQY and EQY than the other two types under ML and HL. Therefore, three different photo‐types can be characterized according to their adaptation to LL, ML and HL: DzTL, DzTM and DzTH, respectively.
Control of the viscous sublayer for drag reduction
Authors: Lee Changhoon , Kim John
Published: July 2002

We investigate the possibility of manipulating turbulence structures in the viscous sublayer for the purpose of drag reduction using a direct numerical simulation of a turbulent channel flow. Recognizing that a great portion of production of vorticity occurs in the viscous sublayer, a body force is used to suppress spanwise velocity in the sublayer, and a significant amount of drag reduction is obtained. A more realistic body force or wall movement in the spanwise direction using instantaneous wall-shear stress in a closed-loop control is shown to reduce drag as much as 35%. Implementation of such a body force using an electromagnetic force is also discussed.
Eulerian and Lagrangian Langmuir circulation patterns
Authors: Bhaskaran Rajesh , Leibovich Sidney
Published: July 2002

An idealized Langmuir circulation pattern in the oceanic surface layer consists of parallel rolls with a fixed spatial periodicity. Observed surface manifestations of the circulation patterns, formed as collections of floating material and known as windrows, are roughly parallel to the surface wind direction, but form a network of intersecting lines. Field observations of the windrow intersections, referred to as “Y-junctions,” indicate a preferred orientation in which the two forks of the “Y” coalesce when viewed from upwind (the Y-junctions are said to point downwind). Weakly nonlinear theory yields patterns in the instantaneous Eulerian fields, for example contours of surface convergence, that show joinings and bifurcations at locations that may be termed pattern defects. These take the form of downwind-pointing Y-junctions occurring at negative defects and their obverse at positive defects with no preference for either type. We show that the preferential orientation of the Y-junctions can be explained as a Lagrangian effect. A simplified model for studying Y-junction formation was developed and shows that downwind-pointing Y-junctions are created by negative defects when the basic state surface velocity component transverse to the rolls is less than or equal to the perturbation velocity. Positive defects do not create any windrow intersections. Surface tracer simulations using the weakly nonlinear theory confirm predictions of the simplified model.
Proper orthogonal decomposition of an axisymmetric turbulent wake behind a disk
Authors: Johansson Peter B. V. , George William K. , Woodward Scott H.
Published: July 2002

A proper orthogonal decomposition (POD) study of the axisymmetric turbulent wake behind a disk has been performed using multipoint hot-wire data. The Reynolds number based on the free stream velocity and disk diameter was kept constant at 28 000. The investigated region spanned from 10 to 50 disk diameters downstream. The hot-wire data were obtained using two rakes: a seven wire fixed array and a six wire array azimuthally traversable to span the cross section of the flow in increments of 15°. The instantaneous streamwise velocity component data were Fourier transformed in time and decomposed in Fourier series in the azimuthal direction to form the kernel for the POD. For all downstream positions, two distinct peaks were found in the first eigenspectrum: one at azimuthal mode 2 at near zero frequency, and another at azimuthal mode 1 at a fixed Strouhal number (fd/U∞) of 0.126. Both peaks decrease in magnitude as the flow evolves downstream, but the peak at the Strouhal number 0.126 decreases more rapidly than the one at near-zero frequency, leaving the latter to eventually dominate. Because of this evolution, the eigenvalues integrated over frequency show an azimuthal mode-1 dominance at x/D=10 and a mode-2 dominance by x/D=50. The results are compared to those recently obtained in the axisymmetric far jet, and the results of previous wake investigations.
Mechanical imperfections effect on the minimum volume stability limit of liquid bridges
Authors: Gómez M. , Parra I. E. , Perales J. M.
Published: July 2002

The bifurcation to unstable equilibrium shapes in the neighborhood of the minimum volume stability limit of liquid bridges has been described by using the Lyapunov–Schmidt technique. Prior to the bifurcation analysis, the stability limits of axisymmetric liquid bridges (both that of maximum and that of minimum volume) have been analytically calculated when the liquid bridge supports are two circular, coaxial disks. The interface shapes have been parametrically described and the parameters corresponding to the marginally stable shapes have been determined in terms of elliptic variables. Bifurcation equations have been obtained analytically describing the behavior near the critical points previously calculated and the effect of small axisymmetric imperfections has been considered. The considered imperfections are inequality in the diameter of the supporting disks, small body forces due to an axial gravity, and liquid bridge rotation as a solid body.
Near-wall structure of turbulent boundary layer with spanwise-wall oscillation
Authors: Choi Kwing-So
Published: July 2002

An investigation was carried out with an aim to better understand the mechanism of turbulent drag reduction with spanwise-wall oscillation, by carefully analyzing the experimental data of the near-wall structure of the boundary layer modified by the wall motion. It was found that the mean velocity gradient of the turbulent boundary layer was reduced close to the wall, and the logarithmic velocity profile shifted upwards by the wall oscillation. We argue that these changes in the mean velocity profile are mainly due to a negative spanwise vorticity created in the near-wall region of the boundary layer over the oscillating wall. The resultant near-wall velocity reduction seems to have weakened the near-wall turbulence activity by hampering the stretching of the quasistreamwise longitudinal vortices, leading to a reduction in skin-friction drag. Indeed, the signatures of the sweep events over the oscillating wall indicated that the duration and the strength were reduced by 78% and 64%, respectively. The reductions obtained by a 2D numerical model, incorporating the streamwise flow and associated stretching of the longitudinal vortical structure, were 47% for the sweep duration and 23% for the sweep strength, although these reductions were observed within the first cycle of wall oscillation. By phase averaging the conditionally sampled velocity data, we were able to show that the frequency of sweep events was reduced with a reduction in streamwise velocity when the negative spanwise vorticity is created by the wall oscillation in the near-wall region. It was also shown that the turbulent skin-friction reduction with spanwise-wall oscillation can be optimized with a nondimensional, spanwise wall velocity, and nearly 45% drag reduction can be obtained in the turbulent boundary layer at an optimum value of w+=15.
Redefining spinors in Lorentz-violating quantum electrodynamics
Authors: Colladay Don , McDonald Patrick
Published: July 2002

An analysis of spinor redefinitions in the context of the Lorentz-violating quantum electrodynamics (QED) extension is performed. Certain parameters that apparently violate Lorentz invariance are found to be physically irrelevant as they can be removed from the Lagrangian using an appropriate redefinition of the spinor field components. It is shown that conserved currents may be defined using a modified action of the complex extension of the Lorentz group on the redefined spinors. This implies a natural correspondence between the apparently Lorentz-violating theory and conventional QED. Redefinitions involving derivatives are shown to relate certain terms in the QED extension to Lagrangians involving nonlocal interactions or skewed coordinate systems. The redundant parameters in the QED extension are identified and the Lagrangian is rewritten in terms of physically relevant coupling constants. The resulting Lagrangian contains only physically relevant parameters and transforms conventionally under Lorentz transformations.
Coagulation-induced particle-concentration fluctuations in homogeneous, isotropic turbulence
Authors: Koch Donald L. , Pope Stephen B.
Published: July 2002

The turbulent coagulation of micron-sized colloidal particles in a liquid is controlled by the shearing motion produced by Kolmogorov scale eddies. The rate of energy dissipation has fluctuations which vary over the integral length and time scale in a homogeneous, isotropic turbulent flow. We present a model of the particle concentrations and coagulation rates in a set of fluid packets that are large compared with the Kolmogorov scale and small compared with the integral scale. Particle coagulation occurs rapidly in regions of the flow with large dissipation rates, leading to a depletion of singlet particles. Thus, the singlet number density is negatively correlated with the shear rate. Turbulent mixing mitigates these concentration variations and the particle concentration field becomes nearly uncorrelated with dissipation rate in very dilute suspensions with φRλ≪1. Here, φ is the particle volume fraction and Rλ is the Reynolds number based on the Taylor microscale. A simulation of a suspension of coalescing drops shows that the imperfect mixing at finite φRλ broadens the drop size distribution.
Materials issues for layered tunnel barrier structures
Authors: Casperson Julie D. , Bell L. Douglas , Atwater Harry A.
Published: July 2002

Layered dielectric tunnel barriers are expected to greatly increase the program/erase speeds of nonvolatile floating gate memory devices and could allow both nanosecond program/erase times as well as archival data storage. We have correlated dielectric constants and band offsets with respect to silicon in order to help identify possible materials from which to construct these devices. A numerical model has been developed to assess potential layered tunnel barrier materials and structures suitable for integration into silicon electronics. With this model, we explore the relative dominance of Fowler–Nordheim tunneling and thermionic emission and we present simulated I–V curves for some candidate materials.
Energy considerations for linear instabilities of parallel magnetohydrodynamic flows
Authors: Andries J. , Goossens M.
Published: July 2002

A formulation with the flow as the prime source of instability and dissipation as a triggering mechanism is presented as an alternative to the “negative energy” formulation of instabilities of parallel flows. The formulation is based on the linear wave energy equation. The apparent opposition between the “negative energy” wave formulation and the linear wave energy formulation, where the wave energy is always positive, is resolved.
A boundary layer flow with multiple equilibria
Authors: Whitehead J. A.
Published: July 2002

Convection is driven by both a solute and heat imposed at one side of a vertical slot. Density distribution is calculated using boundary layer theory and flow is determined using a simple viscous flow law. More than one steady flow exists for some ranges of the governing parameters. The solution relates double diffusion and multiple equilibrium circulation concepts.
Statistical mechanical models with effective potentials: Definitions, applications, and thermodynamic consequences
Authors: Stillinger Frank H. , Sakai Hajime , Torquato Salvatore
Published: July 2002

Realistic interactions that operate in condensed matter systems can exhibit complicated many-particle characteristics. However, it is often useful to seek a more economical description using at most singlet and pair effective interactions that are density dependent, to take advantage of the theoretical and computational simplifications that result. This paper analyzes the statistical mechanical formalism required to describe thermal equilibrium in that kind of approach. Two distinct interpretations are available for the role of density dependence. Either one can be treated with internal consistency, but generally they lead to differing thermodynamic predictions. One regards the density dependence of effective interactions as merely a passive index for the state at which the optimal choice of those effective interactions was determined (Case I). The other treats the density as an active variable on the same footing as particle coordinates (Case II). Virial pressure and isothermal compressibility expressions in terms of particle distribution functions are displayed for both cases. Under special circumstances it is possible for the two interpretations to yield the same pressure isotherms; the conditions producing this coincidental concordancy have been explored by means of density expansions.
High-spin electronic interaction of small lithium and sodium cluster formation in the excited states
Authors: Hotta Shigeru , Doi Kentaro , Nakamura Koichi , Tachibana Akitomo
Published: July 2002

We have carried out the MRCI ab initio calculations for small lithium and sodium clusters, and elucidate the interaction between atoms in various high-spin electronic states, in terms of the quantum mechanical energy densities based on the regional density functional theory [Tachibana, J. Chem. Phys. 115, 3497 (2001)]. When the separated two electronic drop regions, where the electronic kinetic-energy density is positive, connect to each other, it is observed that ratios of occupation on configurations change rapidly in the Li2 molecule. These results are considered as one of the evidences that valence electrons can move around both two Li atoms freely in the meaning of classical mechanics. The shape of electronic drop region depends strongly on the electronic state and represents the characteristics of interaction clearly, and the electronic tension density also gives new images of microscopic electronic stresses. Furthermore, we have clarified the most stable structures of Li3 and Li4 for the high-spin electronic state, which are respectively different from the most stable structures for the low-spin electronic state. The stabilization energy due to taking in a Li atom is raised gradually as the number of atoms in Lin cluster increases in the initial stage of cluster propagation. The formation energies of Na2, Na3, and Na4 clusters are much smaller than that of the corresponding lithium clusters.
Stability of wall modes in fluid flow past a flexible surface
Authors: Shankar V. , Kumaran V.
Published: July 2002

The stability of wall modes in fluid flow past a flexible surface is analyzed using asymptotic and numerical methods. The fluid is Newtonian, while two different models are used to represent the flexible wall. In the first model, the flexible wall is modeled as a spring-backed, plate-membrane-type wall, while in the second model the flexible wall is considered to be an incompressible viscoelastic solid of finite thickness. In the limit of high Reynolds number (Re), the vorticity of the wall modes is confined to a region of thickness O(Re−1/3) in the fluid near the wall of the channel. An asymptotic analysis is carried out in the limit of high Reynolds number for Couette flow past a flexible surface, and the results show that wall modes are always stable in this limit if the plate-membrane wall executes motion purely normal to the surface. However, the flow is shown to be unstable in the limit of high Reynolds number when the wall can deform in the tangential direction. The asymptotic results for this case are in good agreement with the numerical solution of the complete governing stability equations. It is further shown using a scaling analysis that the high Reynolds number wall mode instability is independent of the details of the base flow velocity profile within the channel, and is dependent only on the velocity gradient of the base flow at the wall. A similar asymptotic analysis for flow past a viscoelastic medium of finite thickness indicates that the wall modes are unstable in the limit of high Reynolds number, thus showing that the wall mode instability is independent of the wall model used to represent the flexible wall. The asymptotic results for this case are in excellent agreement with a previous numerical study of Srivatsan and Kumaran.
Above-room-temperature ferromagnetism in GaSb/Mn digital alloys
Authors: Chen X. , Na M. , Cheon M. , Wang S. , Luo H. , McCombe B. D. , Liu X. , Sasaki Y. , Wojtowicz T. , Furdyna J. K. , Potashnik S. J. , Schiffer P.
Published: July 2002

Digital alloys of GaSb/Mn have been fabricated by molecular-beam epitaxy. Transmission electron micrographs showed good crystal quality with individual Mn-containing layers well resolved, no evidence of three-dimensional MnSb precipitates was seen in as-grown samples. All samples studied exhibited ferromagnetism with temperature-dependent hysteresis loops in the magnetization accompanied by metallic p-type conductivity with a strong anomalous Hall effect (AHE) up to 400 K (limited by the experimental setup). The anomalous Hall effect shows hysteresis loops at low temperatures and above room temperature very similar to those seen in the magnetization. The strong AHE with hysteresis indicates that the holes interact with the Mn spins above room temperature. All samples are metallic, which is important for spintronics applications.
Electrostatic potential of mean force between charged bovine serum albumin molecules in aqueous NaCl solutions by hypernetted-chain integral equation
Authors: Lin Yang-Zheng , Li Yi-Gui , Lu Jiu-Fang
Published: July 2002

The electrostatic potentials of mean force between charged bovine serum albumin (BSA) molecules at different NaCl and BSA concentrations are obtained by solving the hypernetted-chain integral equations. From the results, a short-range attractive force between the same charged BSA molecules is found at low BSA valences or high NaCl concentrations. Comparisons have been made with the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory and the Sogami–Ise (SI) theory. In aqueous BSA–NaCl solution, the DLVO theory is much more accurate than SI theory at low concentration as 0.15 mol/L, but they both failed in high salt concentrations such as 1.0 and 3.0 mol/L. The electrostatic interaction range shortens with the increase of salt concentration. The electrostatic repulsion between colloidal particles may be weakened by the increase of charges on macro-ions in certain charge range in high salt concentration. The influence of charged BSA concentrations on the electrostatic potential of mean force is also given. The electrostatic potentials of mean force between charged BSA molecules oscillate with the increase of its concentrations.
Right and wrong near critical endpoints
Authors: Fisher Michael E. , Kim Young C.
Published: July 2002

The implications of convexity (or thermodynamic stability) for isothermal density (or composition) phase diagrams near critical endpoints are investigated. In particular, Schreinemakers’ rules for the geometry of three coexisting phases in a space of densities are refined and extended physically to apply at and in the vicinity of a critical endpoint. Seemingly plausible phase diagrams are presented which violate the extended rules (and, in most cases, the Second Law of Thermodynamics). The requirements of convexity, supplemented for Ising-related systems by the Griffiths–Kelly–Sherman inequalities, also restrict the signs of important expansion coefficients of thermodynamic scaling functions for criticality and provide bounds on universal critical amplitude ratios.
Theoretical and experimental studies of the structures of 12-, 13-, and 14-atom bimetallic nickel/aluminum clusters
Authors: Rexer E. F. , Jellinek J. , Krissinel E. B. , Parks E. K. , Riley S. J.
Published: July 2002

The structures of NinAlp clusters of all compositions with n+p=12, 13, and 14 are studied both experimentally and theoretically. Experimental reactions of the clusters with N2 are used to determine the number of Ni atoms residing in the cluster surfaces. In agreement with the theoretical predictions, the N2 saturation levels are consistent with clusters having icosahedral and icosahedral-based structures. The various N2 adsorption channels seen in the experiment are explained in terms of the computed composition-dependent patterns of the configurational energies of the different structural forms.
An Airy discrete variable representation basis
Authors: Littlejohn Robert G. , Cargo Matthew
Published: July 2002

A new discrete variable representation (DVR) basis is presented, one that is based on Airy functions. That is, the functions of the “finite basis representation” (actually infinite in this case) are energy eigenfunctions in a constant force field. The exact matrix elements of the kinetic energy are computed. The use of the Airy DVR functions in diagonalizing a one-dimensional Hamiltonian is illustrated.
On the phase velocity effect of nonlinear interactions between surface gravity waves
Authors: Tanaka Mitsuhiro , Phan Van Catherine , Oldrini Olivier
Published: July 2002

The change of phase velocity of a train of surface gravity waves due to nonlinear interaction with another train of surface gravity waves is investigated. Three different expressions for the change of phase velocity have been derived from Zakharov-type equations, and it is confirmed that all these expressions are equivalent with each other, as well as with the classical result of Longuet-Higgins and Phillips. The theory for the interaction between two wave trains is also extended naively to that among component waves in a continuous energy spectrum, and the validity of this extension is assessed by comparing with direct numerical simulations based on the primitive equations.