bluuebunny/crossref_metadata_2025 huggingface dataset:
An analysis of 0+ barbel (Barbus barbus) response to discharge fluctuations in a flume
Authors: Vilizzi Lorenzo , Copp Gordon H.
Published: April 2005

We studied the response in velocity use and time in refuge of 0+ juvenile barbel (Barbus barbus) to an increase in discharge in a flume. Each of five treated and five control fish were observed individually in separate eight‐hour experiments. Observations (trials) were arranged into a hierarchically structured, semi‐randomized sampling schedule consisting of four time levels: phase (4 h) ⊃ period (2 h) ⊃ sub‐period (30 min) ⊃ trial (120 s). Increased discharge caused treated barbel to use higher velocities than control individuals, with individual differences in behaviour present at the various temporal tiers. Individual responses were modelled as either random‐walk or short‐memory processes, and those by treated fish were generally abrupt and permanent, with only one individual showing a gradual and permanent use of the higher velocities. Time in refuge was not affected by increased discharge, except for one fish that sought shelter after intervention. There was a significant relationship for most treated individuals between selection of lower velocities and time in refuge, and most barbel (both treated and control) showed significant deviations of used from mean flume velocities. The potential of the proposed approach to assess memory‐based individual fish responses to discharge and its consequences for (PHABSIM‐oriented) behavioural studies is discussed, and the mosaic of barbel behaviours observed is compared with available laboratory and field studies. Copyright © 2005 John Wiley & Sons, Ltd.
Assessing the effectiveness of enhancement activities in urban streams: I. Habitat responses
Authors: Suren Alastair M. , Riis Tenna , Biggs Barry J. F. , McMurtrie Shelley , Barker Rachel
Published: April 2005

Effects of stream enhancement on habitat conditions in five spring‐fed urban streams in Christchurch, New Zealand, were investigated. Stream enhancement consisted of riparian planting at three sites, and riparian planting and channel modifications at two sites, where a concrete dish channel and a timber‐lined channel were removed, and natural banks reinstated. Sites were surveyed prior to enhancement activities and 5 years after, and changes in riparian conditions (composition, horizontal and vertical cover), instream conditions (bank modifications, inorganic and organic material on the streambed), and hydraulic conditions (wetted perimeter, cross‐sectional area, depths and velocities) quantified. Enhanced sites generally had higher marginal vegetation cover, as well as increased overhanging riparian vegetation, reflecting planting of Carex sedges close to the water. Bed sediments changed at some sites, with the greatest change being replacement of a concrete channel with gravel and cobble substrate. Bryophyte cover declined at this site, reflecting loss of stable habitat where these plants grew. Bed sediments changed less at other sites, and cover of fine sediments increased in some enhanced sites, presumably from sediment runoff from nearby residential development. Filamentous algal cover decreased at one stream where shade increased, but increased in another stream where the removal of timber‐lined banks and creation of a large pond decreased shade. Stream enhancement increased variability in velocity at three of the five sites, but overall changes to stream hydraulics were small. Although enhancement activities altered the physical conditions of the streams, major changes occurred only to riparian vegetation and bank conditions. Lack of other major changes to instream physical conditions most likely reflected the limited range of channel morphology alterations undertaken. Moreover, the flat topography of Christchurch and naturally low stream discharge further constrained changes to instream physical conditions from enhancement activities. Sediment inputs from continuing urban development also negated the effects of adding coarse substrates. These over‐arching factors may constrain the success of future stream enhancement projects within Christchurch. Copyright © 2005 John Wiley & Sons, Ltd.
Assessing the effectiveness of enhancement activities in urban streams: II. Responses of invertebrate communities
Authors: Suren Alastair M. , McMurtrie Shelley
Published: April 2005

The effects of habitat enhancement on the invertebrate communities in five urban streams in Christchurch, New Zealand, were investigated. All streams underwent riparian planting, while extensive channel modifications were made at two streams, where a concrete dish channel and a wooden timber‐lined stream were removed and natural banks reinstated. Benthic invertebrates were collected before enhancement and 5 years after from the same locations. Invertebrates were also collected from control sites in each stream in 2001. Desired goals of enhancement activities included increasing the densities of mayflies and caddisflies, and decreasing densities of oligochaetes, snails and midges. Enhancement activities changed riparian vegetation and bank conditions, as well as substrate composition, instream organic matter and variability of instream velocities. Invertebrate communities prior to enhancement were typical of those in urban environments, and dominated by snails (Potamopyrgus, Physa), the amphipod Paracalliope, the hydroptilid caddisfly Oxyethira, oligochaetes and chironomids. Stream enhancement caused only small changes to the invertebrate community, with subtle shifts in overall abundance, species evenness, diversity, and ordination scores. Lack of a consistent strong response by invertebrates to enhancement activities, and continued absence of caddisflies and mayflies from enhanced sites may reflect lack of sufficient change to instream conditions as a result of stream enhancement, colonization bottlenecks for aerial stages of these animals, and the inability of individuals outside the urban watershed to perceive these enhanced ‘islands’ of good habitat. Alternatively, contamination of streambed sediments, excess sedimentation and reduced base flows may be limiting factors precluding successful invertebrate colonization in enhanced sites. These results highlight the importance of setting clear goals and objectives necessary to meet these goals. Enhancement of riparian zones in urban streams may not be adequate to improve benthic invertebrate communities. Identifying over‐arching factors that potentially limit invertebrate communities will enable the enhancement potential of streams to be better assessed, and allow managers to identify sites where recovery of biological communities is possible, and where such recovery is not. Copyright © 2005 John Wiley & Sons, Ltd.
Advances in fluid therapy and the early care of the burn patient
Authors: Pruitt Basil A.
Published: April 2005

The resuscitation and early care of the burn patient has been placed on a more sound physiologic basis as a result of recent studies of the pathologic effects of thermal injury and the clinical application of technological advances. Whichever resuscitation formula is employed, its application should be guided by the patient's response to treatment. The surgeon must preserve vital organ function while taking advantage of compensatory mechanisms to minimize the deleterious effects of both the injury and the therapy. Resuscitation using only balanced salt solution in the first 24 hours, and reserving colloid‐containing fluids for the second 24 hours, is clinically effective in the vast majority of burn patients, but should be altered in terms of volume and composition to meet the particular needs of any given burn patient. Repeated planned monitoring of cardiopulmonary function and of the peripheral circulation is mandatory to achieve maximum survival of unburned tissue and to reduce mortality. Careful fluid management, including daily assessment of fluid balance, is required from the time of admission until the burn wound has healed or been grafted.
Functional assessment of myoblast transplantation for cardiac repair with magnetic resonance imaging
Authors: van den Bos Ewout J. , Thompson Richard B. , Wagner Anja , Mahrholdt Heiko , Morimoto Yoshihisa , Thomson Louise E.J. , Wang Lynn H. , Duncker Dirk J. , Judd Robert M. , Taylor Doris A.
Published: April 2005

Background:

Contraction of transplanted myoblasts and their effects on function and remodeling after myocardial infarction remain controversial.

Aim:

We used magnetic resonance imaging (MRI) to study wall thickening and left ventricular (LV) function and geometry after myoblast transplantation.

Methods and results:

Three weeks after cryo‐infarction rabbits were randomized to receive an injection of ∼2×108 myoblasts (n=8) or medium (n=9) into the scar. Cine MRI and contrast enhanced (ce) MRI images were acquired before injection (baseline) and 4 weeks later (endpoint). Regional wall thickening was measured at the site of transmural hyperenhancement. In the control group, regional wall thickening decreased to −15.3±8.6% at baseline, which further decreased to −18.3±5.7% at endpoint. Further, end‐diastolic volume increased from 3.96±0.27 to 5.00±0.46 ml and end‐systolic volume from 2.23±0.19 to 2.96±0.30 ml (both P<0.05 vs. baseline), which was accompanied by increased LV wall volumes (P<0.05 vs. baseline). In contrast, myoblast transplantation increased regional wall thickening from −11.9±15.9% at baseline to 26.9±17.0% (P<0.05 vs. control), which resulted in significantly improved two‐dimensional ejection fractions at the infarct level and prevented the increase in end‐diastolic and end‐systolic volumes and wall volume.

Conclusion:

Intracardiac myoblast transplantation after myocardial infarction improves regional wall thickening and prevents progressive left ventricular remodeling.
The B‐Lynch and other uterine compression suture techniques
Authors: Allam M.S. , B‐Lynch C.
Published: April 2005

Background

Postpartum hemorrhage (PPH) remains among the 5 main causes of maternal death in developing and developed countries, and uterine atony is the most common cause (75–90%) of primary PPH. Uterine compression sutures running through the full thickness of both uterine walls (posterior as well as anterior) have recently been described for surgical management of atonic PPH. Christopher B‐Lynch was the first to highlight this revolutionary principle, and other uterine compression suture techniques have since been described by Hayman and Cho.

Objectives

Step‐by‐step description of the B‐Lynch brace suture and discussion of the current compression suture techniques.

Conclusions

The different uterine suture techniques have proved to be valuable and safe alternatives to hysterectomy in the control of massive PPH, and the present review can make the surgeon better aware of their effective use and the risks they may entail.
Serum troponin I levels in hyperthyroid cats before and after treatment with radioactive iodine
Authors: Connolly David J. , Guitian Javier , Boswood Adrian , Neiger Reto
Published: April 2005

A raised concentration of serum cardiac troponin I (cTnI) is a sensitive marker of cardiac myocyte injury in the cat and assays developed for its measurement in human patients have been validated in the cat. Raised levels have been associated with a number of cardiac insults including hypertrophic cardiomyopathy and trauma. Hyperthyroidism is a common disease of older cats and excess thyroid hormone is known to produce significant cardiovascular effects in this species. This study evaluated the effect of treatment for hyperthyroidism with radioactive iodine on cTnI concentration, assessed the association between thyroxin levels and glomerular filtration rate (GFR) and cTnI concentration in cats treated for hyperthyroidism and described changes in echocardiographic parameters following treatment. Prior to the treatment serum cTnI was measured and echocardiography performed, thyroxin, cTnI, and echocardiography were then repeated at various time points following radioisotope therapy. The results show that higher thyroxin levels were significantly ( P=0.002) associated with a higher likelihood of the cat presenting with detectable levels of cTnI. No significant association was found between GFR and presence of detectable levels of cTnI. Furthermore the results indicate that the effects of hyperthyroidism on echocardiographic parameters appear considerably less in this study than in previous studies and that the main outcome of treatment on these parameters is a significant reduction in fractional shortening ( P=0.006). These results suggest that chronic exposure to excess thyroid hormone may induce myocyte damage of sufficient severity to raise serum cTnI concentration in a proportion of cats that resolves following establishment of a euthyroid state.
Histomorphology and microradiography of quadriceps tendon–patellar bone grafts in press‐fit anterior cruciate ligament reconstruction
Authors: Dargel Jens , Schmidt‐Wiethoff Rüdiger , Schmidt Joachim , Koebke Jürgen
Published: April 2005

The press‐fit fixation technique has become an alternative fixation method in anterior cruciate ligament (ACL) reconstruction. While the stability of press‐fit fixated grafts reported in the literature predominantly had been analysed by biomechanical testing, this study investigated the specific histomorphologic and microradiographic features important for graft stability, using human quadriceps tendon–patellar bone (QTPB) grafts. Six QTPB grafts with cylindrical bone plugs were obtained from frozen fresh human cadaver knees and fixed to porcine, bovine, or human femora in a press‐fit technique. The specimens were plastinated, dissected into 1.5 mm slices, studied microradiographically and stained for histologic evaluation. The specimens showed an osseous inclusion of the graft within the femoral tunnel, which was most evident on the cancellous side. Histologic analysis revealed a trabecular interdigitation with a penetration of patellar and femoral trabecular structures, contributing to primary stability of the press‐fit fixation. Graft inclusion was most obvious in bovine and least in human femora, assumably because of varying bone quality. The circular bone‐to‐bone contact in press‐fit fixation technique should contribute to both rapid and stable graft healing. © 2005 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.
A single systemic dose of pamidronate improves bone mineral content and accelerates restoration of strength in a rat model of fracture repair
Authors: Amanat Negin , Brown Richard , Bilston Lynne E. , Little David G.
Published: April 2005

Complications in fracture repair that lead to a delay in union remain clinically problematic. We believe that unwanted pre‐mature catabolism of the healing callus, for example, in stress shielded situations, diminishes the rate at which strength is restored in bone repair and possibly leads to delayed union. We hypothesized that a single systemic dose of a nitrogen‐containing bisphosphonate (N‐BP) would increase bone mineral content (BMC), volume, and mechanical strength of union in fracture repair. We also set out to investigate local delivery to assess whether systemic exposure could be eliminated, due to concerns of bisphosphonate dosing of non‐target organs. After an open osteotomy fixed with a K wire, 40 12‐week old Wistar male rats were divided into four groups of 10: saline control, bolus systemic subcutaneous injection of pamidronate (3 mg/kg), local low dose of pamidronate (0.1 mg), and a local high dose of pamidronate (1.0 mg). Rats were sacrificed 6 weeks post‐operatively. Operated and non‐operated femora underwent radiographic evaluation, quantitative computer tomography, and biomechanical testing in torsion. The growth plates and metaphyses of the tibia of the non‐operated side were assessed for evidence of systemic exposure in the local groups. Significant increases in callus BMC and volume of the bolus systemic dose group were found compared to the saline control (p ⩽ 0.05). Further, the strength of the systemic dose callus was increased by 60% from 0.35 Nm (±0.11) for the saline control callus to 0.56 Nm (±0.25) for the systemic group (p = 0.05). Local treatment did not result in increased strength. The contralateral tibial growth plates of the local groups showed evidence of systemic exposure by the presence of retained primary spongiosa. This study confirms that a single perioperative systemic dose of pamidronate leads to significant increases in the BMC, volume, and strength of healing fractures in rats, making single dose N‐BP therapy an appealing candidate for further examination in fracture repair. © 2005 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved.
Qualitative simulation and related approaches for the analysis of dynamic systems
Authors: DE JONG HIDDE
Published: April 2005

Methods for qualitative simulation allow predictions on the dynamics of a system to be made in the absence of quantitative information, by inferring the range of possible qualitative behaviors compatible with the structure of the system. This article reviews QSIM and other qualitative simulation methods. It discusses two problems that have seriously compromised the application of these methods to realistic problems in science and engineering: the occurrence of spurious behavior predictions and the combinatorial explosion of the number of behavior predictions. In response to these problems, related approaches for the qualitative analysis of dynamic systems have emerged: qualitative phase-space analysis and semi-quantitative simulation. The article argues for a synthesis of these approaches in order to obtain a computational framework for the qualitative analysis of dynamic systems. This should provide a solid basis for further upscaling and for the development of model-based reasoning applications of a wider scope.
A review of explanation methods for heuristic expert systems
Authors: LACAVE CARMEN , DIEZ FRANCISCO J.
Published: April 2005

Explanation of reasoning is one of the most important abilities an expert system should provide in order to be widely accepted. In fact, since MYCIN, many expert systems have tried to include some explanation capability. This paper reviews the methods developed to date for explanation in heuristic expert systems.
Subcellular localization of phosducin in rod photoreceptors
Authors: CHEN JING , YOSHIDA TATSURO , NAKANO KOICHI , BITENSKY MARK W.
Published: April 2005

Phosducin (Pd) is a 28-kD phosphoprotein whose expression in retina appears limited to photoreceptor cells. Pd binds to the β,γ subunits of transducin (Gt). Their binding affinity is markedly diminished by Pd phosphorylation. While Pd has long been regarded as a candidate for the regulation of Gt, the molecular details of Pd function remain unclear. This gap in understanding is due in part to a lack of precise information concerning the total amount and subcellular localization of rod Pd. While earlier studies suggested that Pd was a rod outer segment (ROS) protein, recent findings have demonstrated that Pd is distributed throughout the rod. In this report, the subcellular distribution and amounts of rat Pd are quantified with immunogold electron microscopy. After light or dark adaptation, retinal tissues were fixedin situand prepared for ultrathin sectioning and immunogold labeling. Pd concentrations were analyzed over the entire length of the rod. The highest Pd labeling densities were found in the rod synapse. Less intense Pd staining was observed in the ellipsoid and myoid regions, while minimal labeling densities were found in the ROS and the rod nucleus. In contrast with rod Gt, no evidence was found for light-dependent movement of Pd between inner and outer segments. There is a relative paucity of Pd in the ROS as compared with the large amounts of Gtfound there. This does not support the earlier idea that Pd could modulate Gtactivity by controlling its concentration. On the other hand, the presence of Pd in the nucleus is consistent with its possible role as a regulator of transcription. The functions of Pd in the ellipsoid and myoid regions remain unclear. The highest concentration of Pd was found at the rod synapse, consistent with a suggested role for Pd in the regulation of synaptic function.
Estimates of Multiple Intelligences: A Study in Poland
Authors: Furnham Adrian , Wytykowska Agata , Petrides K.V.
Published: April 2005

Abstract. Participants from Poland (N = 258) provided estimates of their own, their parents', and their grandparents' general and multiple intelligences. Males gave higher self-estimates than females on general, spatial, and musical intelligence. There was evidence of perceived generational differences in estimates of general intelligence, with participants rating themselves slightly higher than their parents, and their parents slightly higher than their grandparents. Regression analyses showed that the most consistent predictors of estimated general intelligence were verbal, mathematical, and intrapersonal intelligence. A comparison between Polish and British (N = 185) data revealed interesting cultural effects, primarily concerning father and mother estimates. Overall, the results were broadly in line with those of other studies, although several cultural differences are noted and discussed.
Affective Concomitants of Information on Morality and Competence
Authors: Wojciszke Bogdan
Published: April 2005

Abstract. A research program on the affective concomitants of information on morality (M) and competence (C) is reviewed. The program originated from the assumption that M and C are the most important categories of behavior construal and that both categories can be, and are, used in interpretation of the same behavioral acts. Whereas in the observer perspective (when interpreting the behavior of others) M is more relevant than C, in the actor perspective (when interpreting one's own behavior) C is more relevant than M. Based on these theses it was predicted and found that: (1) M-related acts of others (moral acts and transgressions) instigated stronger affective responses than C-related acts (successes and failures), (2) the opposite was true for the participant's own acts, (3) attitudes toward other persons were more strongly influenced by the M than C-related information, and (4) attitudes toward the self (self-esteem) were more strongly influenced by the C than M-related information. The findings were discussed in terms of M and C being differently relevant for social inclusion-exclusion processes.
Surface circulation and fronts of the South Pacific Ocean, east of 120°W
Authors: Chaigneau Alexis , Pizarro Oscar
Published: April 2005

The South Pacific surface circulation east of 120°W is studied, using satellite tracked drifters from 1979–2004. The major currents of this region are described such as the Antarctic Circumpolar, the South Pacific, the Chile‐Peru and the Cape Horn Currents. We suggest the presence of a branch, exiting from the ACC between 100–120°W, and transporting subantarctic surface water toward lower latitudes. We also show the existence of an anticyclonic recirculation cell north of 35°S. Finally, based on hydrographic sections, we show that in the eastern South Pacific the core of the Subtropical front corresponds to the 14°C isotherm at 150 m depths and to the 2.7 m of dynamic height relative to 3000 m. The Subantarctic front is located by maximum temperature gradients in the range 3–8°C at 100–400 m depth.
Determining cloud forcing by cloud type from geostationary satellite data
Authors: Futyan J. M. , Russell J. E. , Harries J. E.
Published: April 2005

To fully attribute differences in cloud forcing between regions, or between models and observations, requires separation of the effects of different cloud types. This can only be achieved using data which resolve both day to day and diurnal variations. Here we propose a method which takes advantage of the high temporal resolution of geostationary data to estimate the contribution of individual cloud types to the monthly mean and monthly time‐step mean cloud forcing in each grid‐box. Details of the method are outlined, and data from the Meteosat‐8 satellite for June 2004 are used to demonstrate its benefits.
DOAS measurement of glyoxal as an indicator for fast VOC chemistry in urban air
Authors: Volkamer Rainer , Molina Luisa T. , Molina Mario J. , Shirley Terry , Brune William H.
Published: April 2005

We present the first direct measurements of glyoxal (CHOCHO) in the atmosphere, and demonstrate that glyoxal measurements are possible by differential optical absorption spectroscopy (DOAS). Glyoxal was routinely detected during the daytime in Mexico City, where mixing ratios ranged from <0.15 ppbv (detection limit) to 1.82 ppbv. These time‐resolved measurements resolve the rapid diurnal variation of glyoxal, and indicate the onset of volatile organic compound (VOC) oxidation about 1hr after sunrise. The atmospheric lifetime of glyoxal is determined to be 1.3 hr for overhead sun conditions. Then elevated glyoxal levels indicate a persistently active VOC chemistry during most of the day. Glyoxal forms from the oxidation of numerous VOCs, which foster the formation of ‘photochemical smog’ including ozone and aerosol particles; atmospheric levels are essentially unaffected by direct vehicle emissions in Mexico City. Satellite measurements of glyoxal seem feasible, making possible the better identification of photochemical hot spots in the Earth's atmosphere.
SOD1 Overexpression and Female Sex Exhibit Region-Specific Neuroprotection after Global Cerebral Ischemia Due to Cardiac Arrest
Authors: Kofler Julia , Hurn Patricia D , Traystman Richard J
Published: April 2005

Cardiac arrest is often associated with poor neurologic outcome since therapeutic options are limited. We tested the hypothesis that overexpression of CuZn superoxide dismutase (SOD+/–) is neuroprotective in a new murine model of cardiac arrest and cardiopulmonary resuscitation (CPR). Second, we investigated if female and male mice sustain similar injury and if sex-specific outcomes are altered by SOD overexpression. Neuronal injury was quantified 3 days after 8 mins of KCl-induced cardiac arrest by calculating the percentage of ischemic neurons for caudoputamen and hippocampal CA1 region. In rostral caudoputamen, less neuronal cell loss was found for SOD+/– mice (31%+22%) when compared with wild-type (WT) mice (47%+31%, P<0.05). Superoxide dismutase overexpression did not reduce injury in the caudal caudoputamen. No sex-linked protection was evident in either genotype in the caudoputamen. Female WT mice had less CA1 injury than male WT mice (26%+31% versus 54%+30%, P<0.05), whereas no sex difference was found in SOD+/– mice (female: 42%+29%; male: 37%+37%). Comparison of hippocampal injury between genotypes revealed no differences for either males or females. In conclusion, SOD1 overexpression and female sex were associated with significant neuroprotection in this murine cardiac arrest model. However, no additive neuroprotection was observed, and these beneficial effects were restricted to specific brain regions.
Density functional approach to thermodynamics of self-assembly
Authors: Saksena Radhika S. , Woodcock Leslie V.
Published: April 2005

A local density functional approximation for predicting the surface crystallization of a thermodynamically small system under gravity is described and tested. Using the model of the classical soft-sphere fluid, the state parameters for such systems are identified. A generalized phase diagram based upon the scaling variables is obtained; systems with the same reduced-state parameters exhibit identical profiles of thermodynamic properties such as density, pressure, and intrinsic chemical potential, measured in the direction of the applied field. The point-thermodynamic approximation of Rowlinson and the local density approximation of the density functional formalism are found to be remarkably accurate. A configurational temperature is defined and shown to agree with the corresponding kinetic temperature for inhomogeneous systems at equilibrium. The structural profiles at the crystal-fluid interface are indicative of a mesolayer of lower density crystal, not seen in the field-free isobaric crystal-liquid interface.
An investigation into the magnetic properties of Co–Cu nanoparticles at different temperatures
Authors: Sun Shih-Jye , Ju Shin-Pon , Lo Yu-Chieh , Lin Jenn-Sen
Published: April 2005

This study employs molecular-dynamics simulations to predict the distribution function of diluted magnetic Co atoms in a Cu host and then uses the Weise mean-field theory and the Ruderman–Kittel–Kasuya–Yosida theory to calculate the magnetic properties of the Co–Cu alloys. Specifically, this study investigates the dependency of the nanoparticle magnetization on the Curie temperature for Co–Cu alloys with five different Co concentrations. The proposed method successfully overcomes the limitations of molecular-dynamics simulation in magnetic studies, for diluted systems at least.
InGaAs
∕
InP
quantum well intermixing studied by high-resolution x-ray diffraction and grazing incidence x-ray analysis
Authors: Piva P. G. , Mitchell I. V. , Chen Huajie , Feenstra R. M. , Aers G. C. , Poole P. J. , Charbonneau S.
Published: April 2005

Following a study of implantation enhanced interdiffusion of InGaAs∕InP multiple quantum well (MQW) structures by cross-sectional scanning tunneling microscopy (XSTM), the techniques of low temperature photoluminescence spectroscopy, high-resolution x-ray diffraction (HRXRD), and grazing incidence x-ray analysis (GIXA) are used to independently investigate the suitability of a square well model for the interdiffused MQW profiles, and the observed dependence of strain development as a function of the implanted ion range relative to the MQW stacks. In agreement with previous XSTM findings, when ions are implanted through the MQWs, HRXRD measurements indicate equivalent extents of interdiffusion occurring on both sublattices, while GIXA measurements further indicate the compositional profiles to be non-Fickian and compatible with uniformly broadened square well distributions. Following shallow ion implants (where ions are deposited between the MQWs and the sample surface), (004) HRXRD measurements indicate preferential group V interdiffusion. Dynamical simulations of the superlattice envelope in the (004) HRXRD rocking curves show the compositional profiles to be non-Fickian and compatible with a square well model for the broadened compositional profiles. Additional analysis of the (001) bilayer spacing from previously published XSTM linescan data for this structure is also consistent with this finding. Results of a preliminary photoluminescence and HRXRD investigation of disordering induced by indium implants and the effects of extended annealing on a series of MQW samples (with and without implantation) are presented. Implications for the implantation enhancement of interdiffusion in the InGaAs∕InP material system are discussed. The interpretation of quantum well interdiffusion experiments in this material system in terms of Fickian diffusion models warrants revision in light of the present findings.
Grain boundary grooving and cathode voiding in bamboo-like metallic interconnects by surface drift diffusion under the capillary and electromigration forces
Authors: Ogurtani Tarik Omer , Akyildiz Oncu
Published: April 2005

The process of grain boundary (GB) grooving and cathode voiding in sandwich type thin film bamboo lines are simulated by introducing a mathematical model, which flows from the fundamental postulates of irreversible thermodynamics. In the absence of the electric field, the computer studies on the triple junction kinetics show that it obeys the first order reaction kinetics at early transient stage, which is followed by the familiar time law as t¯1∕4, at the steady state regime. The applied electric field (EF) in constant current experiments modifies this time law drastically above the well-defined electron wind intensity (EWI) threshold, and puts an upper limit for the groove depth, which decreases monotonically with EWI. Below the threshold level, the capillary regime predominates, and EF has little effect on the general kinetics of GB grooving, other than the linear increase in total elapsed time with EWI. An analytical formula for the cathode failure time in constant voltage test is obtained in terms of the system parameters, which are closely associated with the cathode voiding or grain thinning by surface drift diffusion.
Hybrid-phase growth in microcrystalline silicon thin films deposited by plasma enhanced chemical vapor deposition at low temperatures
Authors: Sugano T. , Kitagawa T. , Sobajima Y. , Toyama T. , Okamoto H.
Published: April 2005

Crystallographic studies on microcrystalline silicon (μc-Si) films, which were prepared by very-high-frequency plasma-enhanced chemical vapor deposition at a low temperature of 180°C, have been performed employing thickness evolutions of x-ray and electron diffraction measurements. The experimental results revealed that amorphous phase in μc-Si is transited to crystalline phase in solid phase in whole region from the top to the bottom, and the transition to the (220) orientation is dominantly found. These growth phenomena are interpreted in terms of a proposed model, i.e., the hybrid-phase growth model consisting of conventional vapor-phase growth at the surface plus the solid-phase crystallization occurring in the film. Moreover, the hybrid-phase growth, particularly solid-phase crystallization at low temperatures, is discussed in conjunction with the further results on the thickness evolutions associated with μc-Si films deposited on various underlayers or at substrate temperatures of 160–350°C, or at SiH4 concentrations of 3%–5%.
Characteristics of InGaAs quantum dots grown on tensile-strained GaAs1−xPx
Authors: Kim N. H. , Ramamurthy P. , Mawst L. J. , Kuech T. F. , Modak P. , Goodnough T. J. , Forbes D. V. , Kanskar M.
Published: April 2005

InGaAs quantum dots (QDs) embedded in tensile-strained GaAs1−xPx (x=0.0–0.45) barrier layers are grown using low-pressure metal-organic chemical-vapor deposition. Variable-temperature photoluminescence (PL) measurement demonstrates that the lowest-energy QD transition can be blueshifted up to 90nm compared with similar structures utilizing GaAs barriers. Temperature-dependent PL measurements and atomic force microscopy surface imaging show that the InGaAs QDs grown on GaAsP exhibit reduced height, which is consistent with shorter-wavelength emission. Preliminary results from broad stripe (100μm wide) diode lasers utilizing two stacks of InGaAs QDs embedded in GaAs0.82P0.18 barriers exhibit a 30% reduction in threshold current density compared with similar laser structures which have GaAs barriers.
Nonequilibrium Monte Carlo simulation of lattice block copolymer chains subject to oscillatory shear flow
Authors: Ji Shichen , Ding Jiandong
Published: April 2005

This paper has extended nonequilibrium Monte Carlo (MC) approach to simulate oscillatory shear flow in a lattice block copolymer system. Phase transition and associated rheological behaviors of multiple self-avoiding chains have been investigated. Stress tensor has been obtained based upon sampled configuration distribution functions. At low temperatures, micellar structures have been observed and the underlying frequency-dependent rheological properties exhibit different initial slopes. The simulation outputs are consistent with the experimental observations in literature. Chain deformation during oscillatory shear flow has also been revealed. Although MC simulation cannot account for hydrodynamic interaction, the highlight of our simulation approach is that it can, at small computing cost, investigate polymer chains simultaneously at different spatial scales, i.e., macroscopic rheological behaviors, mesoscopic self-assembled structures, and microscopic chain configurations.
Red light-emitting diodes based on InP∕GaP quantum dots
Authors: Hatami F. , Lordi V. , Harris J. S. , Kostial H. , Masselink W. T.
Published: April 2005

The growth, fabrication, and device characterization of InP quantum-dot light-emitting diodes based on GaP are described and discussed. The diode structures are grown on gallium phosphide substrates using gas-source molecular-beam epitaxy and the active region of the diode consists of self-assembled InP quantum dots embedded in a GaP matrix. Red electroluminescence originating from direct band-gap emission from the InP quantum dots is observed at low temperatures.With increasing temperature, however, the emission line shifts to the longer wavelength. The emission light is measured to above room temperature.
Polarizabilities and effective parameters for collections of spherical nanoparticles formed by pairs of concentric double-negative, single-negative, and∕or double-positive metamaterial layers
Authors: Alù Andrea , Engheta Nader
Published: April 2005

Unusual scattering effects from tiny spherical particles may be obtained when concentric shells are designed by pairing together “complementary” double-negative, single-negative, and∕or standard double-positive materials. By embedding these highly polarizable scatterers in a host medium one can achieve a bulk medium with interesting effective parameters. Some physical insights and justifications for the anomalous polarizability of these concentric spherical nanoparticles and the effective parameters of the bulk composite medium are discussed.
van der Waals interaction of simple, parallel polymers
Authors: Kleis Jesper , Schröder Elsebeth
Published: April 2005

We study the mutual interactions of simple parallel polymers within the framework of density-functional theory (DFT). As the conventional implementations of DFT do not treat the long-range dispersion [van der Waals (vdW)] interactions, we develop a systematic correction scheme for the nonlocal energy contribution of the polymer interaction at the intermediate to the asymptotic separations. We primarily focus on the three polymers, polyethylene, isotactic polypropylene, and isotactic polyvinylchloride, but the scheme presented applies also more generally to other simple polymers. From first-principle calculations we extract the geometrical and electronic structures of the polymers and the local part of their interaction energy, as well as the static electric response. The dynamic electrodynamic response is modeled on the basis of these static calculations, from which the nonlocal vdW interaction of the polymers is extracted.
Ferroelectric and piezoelectric properties of lanthanoid-substituted Bi4Ti3O12 thin films grown on (111)Pt and (100)IrO2 electrodes
Authors: Adachi Yutaka , Su Dong , Muralt Paul , Setter Nava
Published: April 2005

We investigated the effect of film orientation on piezoelectric and ferroelectric properties of (Bi3.25Ln0.75)Ti3O12 (Ln=La, Nd, and Sm). c-axis-oriented films were grown on (111)Pt electrodes with nondoped Bi4Ti3O12 buffer layers. The films grown on (100)IrO2 electrodes showed predominantly (111) and (110) orientation. The piezoelectric coefficient d33,f and the remanent polarization Pr were larger for (111)- and (110)-oriented films than for c-axis-oriented films. This relation was independent of the type of lanthanide species used as Bi substituting ion. This strongly indicates that the direction of the spontaneous polarization vector does not turn toward the c axis due to such substitutions, as was recently proposed in the literature.
Green electroluminescence from an ionic iridium complex
Authors: Slinker Jason D. , Koh Cheong Y. , Malliaras George G. , Lowry Michael S. , Bernhard Stefan
Published: April 2005

We report green emission from a single-layer device based on the ionic transition metal complex [Ir(F-mppy)2(dtb-bpy)]+(PF6−), where F-mppy is 2-(4′-fluorophenyl)-5-methylpyridine and dtb-bpy is 4,4′-di-tert-butyl-2,2′bipyridine. External quantum efficiencies of up to 1.1% are achieved with air-stable contacts, and up to 1.8% with a CsF∕Al top contact. Addition of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate was found to improve the device response time and cause a bias-dependent shift in the emission spectrum. As a result, electroluminescence was observed at 531 nm (CIE coordinates: 0.3230 and 0.5886), the lowest wavelength reported to date for a device based on ionic transition metal complexes.
Magnetic nanobelts of iron-doped zinc oxide
Authors: Xu C. X. , Sun X. W. , Dong Z. L. , Yu M. B. , Xiong Yong Zhong , Chen J. S.
Published: April 2005

Magnetic nanobelts of iron-doped zinc oxide were fabricated by vapor–phase transport using zinc oxide, iron oxide, and graphite as source materials. The nanobelts grew mainly along [101¯0] orientation and enclosed by ±(0001) and ±(1¯21¯0) surfaces. The measurements of x-ray diffraction, energy-dispersive x-ray spectroscopy, and high-resolution transmission electron microscopy demonstrated that iron was doped into the nanobelts. As a result, the nanobelts were magnetic.
Noise properties of the Bloch oscillating transistor
Authors: Lindell René , Hakonen Pertti
Published: April 2005

We have measured the current noise spectral density of the Bloch oscillating transistor as a function of current gain. We find, as expected from theory and simulations, that the equivalent input noise that shows up in the output is less than the shot noise of the normal-insulating-superconductor tunnel junction (base junction). At the optimal operating point we find a reduced input current noise of 1.0fA∕Hz and a corresponding noise temperature of 0.4 K. The differential current gain at the same point is as large as 30 and the power gain amounts to 35.
Formation of ZnS/SiO2 nanocables
Authors: Fan Xia , Meng Xiang-Min , Zhang Xiao-Hong , Wu Shi-Kang , Lee Shuit-Tong
Published: April 2005

Nanometer-sized coaxial cables with a single-crystal ZnS core and a thin amorphous SiO2 shell were synthesized by simple thermal evaporation in vacuum. As-fabricated ZnS/SiO2 nanocables were studied using scanning electron microscopy, x-ray diffraction and transmission electron microscopy. The ZnS/SiO2 nanocables have diameters of ∼50nm, lengths of several tens of micrometers, and shell thickness of ∼4nm. The core of the nanocable has a wurtzite structure with a growth direction along [001]. The nanocables show strong photoluminescence with two peaks related to band gap and defect-related emission.
Rescaled temperature dependence of dielectric behavior of ferroelectric polymer composites
Authors: Dang Zhi-Min , Wang Lan , Wang Hai-Yan , Nan Ce-Wen , Xie Dan , Yin Yi , Tjong S. C.
Published: April 2005

Rescaled temperature dependence of dielectric behavior of ferroelectric polyvinylidene fluoride (PVDF) filled with electroactive ceramic particles of rocksalt-type Li and Ti codoped NiO (LTNO) was studied at wide frequency ranges. Dielectric behavior of the flexible PVDF-LTNO composites with LTNO filler at the volumetric function of 0.3 exhibits a dielectric constant value, ε≈50 at broad temperature range (290–360 K), and the value is frequency independent from 103 to 106Hz. The dielectric response of the composite is almost in accordance to that of pure PVDF matrix polymer. It was found that though the dielectric constant value of the composites is high due to an introduction of the rock salt-type LTNO ceramic particles with high dielectric constant, the glass transition of the polymer and dielectric relaxation related to the wide-angle oscillation of polar groups attached to the main polymer chain determine the dielectric behavior of the composite.
Collective behavior and disorder-induced resonator of random lasers
Authors: Li Sheng , Wang Zi-Jun , Chen Liang-Shan , Sun Xin , George Thomas F.
Published: April 2005

The localization caused by multiple scattering of lightwaves provides a mode for random laser action. It is shown that once the gain surpasses a certain threshold, photons are driven to localized modes, which greatly suppresses the energy loss and leads to laser emission. Concurrent with the localization of the random laser, unique collective behaviors of the localized modes appear, as distinguished from the other modes, which reveals the “invisible” microcavities of random lasers.
Strain-compensated AlInGaAs–GaAsP superlattices for highly polarized electron emission
Authors: Subashiev A. V. , Gerchikov L. G. , Mamaev Y. A. , Yashin Y. P. , Roberts J. S. , Luh D.-A. , Maruyama T. , Clendenin J. E.
Published: April 2005

Spin-polarized electron emission from superlattice photocathodes developed with strain compensation is investigated. An opposite strain in the quantum well and barrier layers is accomplished using an InAlGaAs∕GaAsP superlattice structure. The measured values of maximum polarization and quantum yield for the structure with a 0.18μm thick working layer are excellent results for a strained superlattice photocathode structure, demonstrating the high potential of strain compensation for future photocathode applications. An analysis of the photoemission spectra is used to estimate the parameters responsible for the polarization losses.
Thermal and electrical conductivity of a suspended platinum nanofilm
Authors: Zhang Xing , Xie Huaqing , Fujii Motoo , Ago Hiroki , Takahashi Koji , Ikuta Tatsuya , Abe Hidekazu , Shimizu Tetsuo
Published: April 2005

This letter reports on the measurements of the in-plane thermal conductivity and the electrical conductivity of a microfabricated, suspended, nanosized platinum thin film with the width of 260nm, the thickness of 28nm, and the length of 5.3μm. The experimental results show that the electrical conductivity, the resistance-temperature coefficient and the in-plane thermal conductivity of the nanofilm are greatly lower than the corresponding bulk values from 77to330K. The comparison results indicate that the relation between the thermal conductivity and the electrical conductivity of this nanofilm might not follow the Wiedemann–Franz law that describes the relation between the thermal conductivity and the electrical conductivity of a bulk metallic material.
Large open-circuit voltage improvement by rapid thermal annealing of evaporated solid-phase-crystallized thin-film silicon solar cells on glass
Authors: Terry Mason L. , Straub Axel , Inns Daniel , Song Dengyuan , Aberle Armin G.
Published: April 2005

In this letter, we investigate the impact of rapid thermal annealing (RTA) on thin-film polycrystalline silicon (pc-Si) solar cells on glass made by evaporation of amorphous silicon (a-Si) and subsequent solid-phase crystallization (SPC). These devices have the potential to deliver low-cost photovoltaic electricity and are named EVA cells (SPC of EVAporated a-Si). The RTA is used to perform a high-temperature (>700°C) process for point defect annealing and dopant activation. RTA processes have predominantly been developed for wafer-based devices yet also have great potential for low-temperature devices such as thin-film pc-Si on glass solar cells. Parameter variations are performed on EVA solar cells to determine optimum values for point defect removal and dopant activation while minimizing dopant diffusion causing junction smearing. The 1-Sun open-circuit voltage, Voc, of the as-crystallized pc-Si devices is rather modest (135mV). However, after RTA and subsequent hydrogen passivation in a rf PECVD plasma, a Voc of 454mV is realized, representing a large improvement by a factor of 3.4. With an optimized passivation and dopant profile, a Voc greater than 500mV is well within the reach of the EVA technology.
How restriction enzymes became the workhorses of molecular biology
Authors: Roberts Richard J.
Published: April 2005

Restriction enzymes have proved to be invaluable for the physical mapping of DNA. They offer unparalleled opportunities for diagnosing DNA sequence content and are used in fields as disparate as criminal forensics and basic research. In fact, without restriction enzymes, the biotechnology industry would certainly not have flourished as it has. The first experiments demonstrating the utility of restriction enzymes were carried out by Danna and Nathans and reported in 1971. This pioneering study set the stage for the modern practice of molecular biology in which restriction enzymes are ubiquitous tools, although they are often taken for granted.