bluuebunny/crossref_metadata_2025 huggingface dataset:
Vanadium(V) Oxoperoxo Complexes with Side Chain SubstitutedN‐Salicylidenehydrazides: Modeling Supramolecular Interactions inVanadium Haloperoxidases
Authors: Nica Simona , Pohlmann Axel , Plass Winfried
Published: May 2005

The Schiff‐base ligand derived from salicylaldehyde and γ‐hydroxybutanoic acid hydrazide (H2Salhyhb) reacts with potassium metavanadate and hydrogen peroxide in a water/methanol solution with a pH value of around two to yield the corresponding vanadium(V) oxoperoxo complex [VO(O2)HSalhyhb(H2O)] (1). Complex 1 crystallizes with one molecule of water as 1·H2O in the monoclinic space group P21/n. For the vanadium atom a pentagonal‐bipyramidal coordination geometry is observed, with a side‐on bonded peroxo ligand in the equatorial plane. The hydroxy side chain of the hydrazide ligand is involved in a hydrogen‐bond network with the peroxo ligand at the vanadium atom. This network shows some similarities with the hydrogen‐bonding scheme found for the peroxo form of vanadium haloperoxidases. The stoichiometric reaction of 1 with 1,3,5‐trimethoxybenzene (TMB) in the presence of tetrabutylammonium bromide leads to the formation of 1‐bromo‐2,4,6‐trimethoxybenzene (Br‐TMB), thus mimicking the oxidative halogenation function of the native enzyme. Complex 1 is also capable of oxidizing triphenylphosphane and methylphenylsulfane, yielding a cis‐dioxovanadium(V) complex and the corresponding phosphane or sulfane oxide, respectively. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Endoplasmic reticulum stress induces the phosphorylation of small heat shock protein, Hsp27
Authors: Ito Hidenori , Iwamoto Ikuko , Inaguma Yutaka , Takizawa Takenori , Nagata Koh‐ichi , Asano Tomiko , Kato Kanefusa
Published: May 2005

There are several reports describing participation of small heat shock proteins (sHsps) in cellular protein quality control. In this study, we estimated the endoplasmic reticulum (ER) stress‐induced response of Hsp27 and αB‐crystallin in mammalian cells. Treatment targeting the ER with tunicamycin or thapsigargin induced the phosphorylation of Hsp27 but not of αB‐crystallin in U373 MG cells, increase being observed after 2–10 h and decline at 24 h. Similar phosphorylation of Hsp27 by ER stress was also observed with U251 MG and HeLa but not in COS cells and could be blocked using SB203580, an inhibitor of p38 MAP kinase. Other protein kinase inhibitors, like Gö6983, PD98059, and SP600125, inhibitors of protein kinase C (PKC), p44/42 MAP kinase, and JNK, respectively, were without major influence. Prolonged treatment with tunicamycin but not thapsigargin for 48 h caused the second induction of the phosphorylation of Hsp27 in U251 MG cells. Under these conditions, the intense perinuclear staining of Hsp27, with some features of aggresomes, was observed in 10%–20% of the cells. © 2005 Wiley‐Liss, Inc.
Near-field mapping of surface refractive-index distributions
Authors: Radko I P , Volkov V S , Bozhevolnyi S I , Henningsen J , Pedersen J
Published: May 2005

Scanning near-field optical microscopy (SNOM) in
reflection is employed for high-resolution mapping of surface
refractive-index distributions. Two different single-mode optical
fibers with step-index profiles are characterized using a
reflection SNOM setup, in which cross-polarized detection is
employed to increase the contrast in optical images and, thereby,
the method sensitivity. The SNOM images exhibit a clear
ring-shaped structure associated with the fiber step-index
profile, indicating that surface refractive-index variations being
smaller than 10-2 can be detected. It is found that the
quantitative interpretation of SNOM images requires accurate
characterization of a fiber tip used, because the detected optical
signal is a result of interference between the optical fields
reflected by the sample surface and by the fiber tip itself. The
possibilities and limitations of this experimental technique are
discussed.
A Versatile Preparation Route for Thin Free‐Standing Liquid Single Crystal Elastomers
Authors: Komp Ansgar , Rühe Jürgen , Finkelmann Heino
Published: May 2005

Summary: Thin films of nematic and cholesteric side‐chain polymers containing reactive benzophenone units can be macroscopically oriented by electric/magnetic fields or surface interactions. After UV‐irradiation, liquid single crystal elastomers (LSCEs) are formed. With this simple, new pathway, macroscopically ordered free‐standing LSCE films are easily accessible having a thickness in the range of about 100 nm to 100 μm as outlined in Figure.

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Laser Single Pulse Initiated RAFT Polymerization for Assessing Chain‐Length Dependent Radical Termination Kinetics
Authors: Buback Michael , Junkers Tanja , Vana Philipp
Published: May 2005

Summary: A novel method combining RAFT polymerization with pulsed‐laser initiation for determining chain‐length dependent termination rate coefficients, kt, is presented. Degenerative chain‐transfer in RAFT enables single‐pulse pulsed‐laser polymerization (SP‐PLP) traces to be measured on systems with a narrow radical distribution that remains essentially unchanged during the experiment. SP‐PLP‐RAFT experiments at different polymerization times allow for determining kt as a function of chain length via classical kinetics assuming chain‐length independent kt.

Single‐pulse pulsed‐laser polymerization trace for BMPT‐mediated RAFT polymerization of butyl acrylate.

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Single‐pulse pulsed‐laser polymerization trace for BMPT‐mediated RAFT polymerization of butyl acrylate.
New Poly(propylene glycol)‐ and Poly(ethylene glycol)‐Based Polymer Gelators with L‐Lysine
Authors: Suzuki Masahiro , Owa Sanae , Shirai Hirofusa , Hanabusa Kenji
Published: May 2005

Summary: New polymer gelators consisting of poly(propylene glycol) or poly(ethylene glycol) and L‐lysine‐based low‐molecular‐weight gelators have been developed. These polymer gelators were synthesized according to a simple procedure with high reaction yield, and formed organogels in many organic solvents. The organogelation mechanism was proposed from the transmission electron microscopy and FTIR spectroscopy studies.

Structures of the polymer gelators synthesized here.

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Structures of the polymer gelators synthesized here.
Thermal conductivity of high strength polyethylene fiber in low temperature
Authors: Yamanaka Atsuhiko , Fujishiro Hiroyuki , Kashima Toshihiro , Kitagawa Tooru , Ema Kimiko , Izumi Yoshinobu , Ikebe Manabu , Nishijima Shigehiro
Published: May 2005

High strength polyethylene fiber (Toyobo, Dyneema® fiber, hereinafter abbreviated to DF) used as reinforcement of fiber‐reinforced plastics for cryogenic use has a high thermal conductivity. To understand the thermal conductivity of DF, the relation between fiber structure and thermal conductivity of several kinds of polyethylene fibers having different modulus from 15 to 134 GPa (hereinafter abbreviated to DFs) was investigated. The mechanical series‐parallel model composed of crystal and amorphous was applied to DFs for thermal conductivity. This mechanical model was obtained by crystallinity and crystal orientation angle measured by solid state NMR and X‐ray. Thermal conductivity of DF in fiber direction was dominated by that of the continuous crystal region. The thermal conductivity of the continuous crystal part estimated by the mechanical model increases from 16 to 900 mw/cmK by the increasing temperature from 10 to 150K, and thermal diffusivity of the continuous crystal part was estimated to about 100 mm2/s, which is almost temperature independent. The phonon mean free path of the continuous crystal region of DF obtained by thermal diffusivity is almost temperature independent and its value about 200 Å. With the aforementioned, the mechanical series‐parallel model composed of crystal and amorphous regions could be applied to DFs for thermal conductivity. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1495–1503, 2005
Proton conducting composite membranes from polysulfone and heteropolyacid for fuel cell applications
Authors: Smitha B. , Sridhar S. , Khan A. A.
Published: May 2005

The viability of using composite membranes of heteropolyacid (HPA)/polysulfone (PSF), HPA/sulfonated polysulfone (SPSF) for use in proton exchange membrane fuel cells (PEMFC) was investigated. PSF and its sulfonated polymer, SPSF was solution‐blended with phosphotungstic acid, a commercially available HPA. Fourier transform infrared (FTIR) spectroscopy of the HPA–40/SPSF composite exhibited band shifts showing a possibility of intermolecular hydrogen bonding interaction between the HPA additive and the sulfonated polymer. The composite membranes exhibited improved mechanical strength and low water uptake. The conductivity of the composite membrane, HPA–40/SPSF, consisting of 40 wt % HPA and 60 wt % SPSF [with a degree of Sulfonation (DS) of 40%] exhibited a conductivity 0.089 S/cm at room temperature that linearly increased upto 0.14 S/cm at 120 °C, whereas the widely used commercial membrane Nafion 117, exhibited a room temperature conductivity of 0.1 S/cm that increased to only 0.12 S/cm at 120 °C. In contrast, the composite of HPA–40/PSF exhibited a proton conductivity of 0.02 S/cm at room temperature that increased only to 0.07 S/cm at a temperature of 100 °C. The incorporation of HPA into SPSF not only rendered the membranes suitable for elevated temperature operation of PEMFC but also provides an inexpensive alternative compared to Nafion. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 1538–1547, 2005
Surface Analysis of Plasma‐Deposited Polymer Films, 4
Authors: Swaraj Sufal , Oran Umut , Lippitz Andreas , Schulze Rolf‐Dieter , Friedrich Joerg F. , Unger Wolfgang E. S.
Published: May 2005

Summary: XPS and NEXAFS spectroscopy were used for the chemical characterization of pulsed plasma‐deposited ethylene films before and after exposure to ambient air. The influence of external plasma parameters on the spectroscopic results was investigated. Information on the chemical character of the plasma‐polymerized films, such as the regularity of the primary structure, the amount of long‐living radicals, and branching or cross‐linking or both was derived from this data. “Irregularity” and radical concentration for post‐plasma reactions of the plasma‐deposited films increased with the duty cycle or power. A decreased level of monomer fragmentation and, consequently, an increase in regularity is partially concluded from the experimental data when the monomer pressure is increased. The concentration of surface radicals available for post‐plasma reactions also increased with monomer pressure. The correlation found between the degree of the post‐plasma oxygen incorporation and the variation of the various external parameters agreed with earlier ToF‐SSIMS findings.

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Controlled Surface Engineering and Device Fabrication of Optoelectronic Polymers and Carbon Nanotubes by Plasma Processes
Authors: Chen Wei , Dai Liming , Jiang Hao , Bunning Timothy J.
Published: May 2005

Summary:Owing to theirπ‐electron delocalization along the backbone, conjugated polymers possess unique optoelectonic properties attractive for a wide range of applications in various electronic and photonic devices. Having a conjugated all‐carbon structure with specific molecular symmetries, carbon nanotubes have also attracted a great deal of interest for optoelectronic applications. It is well known that surface and/or interfacial properties are of paramount importance for most optoelectronic applications. Recent developments in the field have clearly indicated the possibility of using radio‐frequency glow‐discharge plasma for introducing functional surfaces/interfaces with region‐specific characteristics necessary for advanced electronic and/or photonic devices. In this article, we summarize our work on the use of plasma processes (both plasma treatment and plasma polymerization) for the surface and interface control of optoelectronic polymers and carbon nanotubes for potential applications in electronic and photonic devices, and reference is also made to other complementary work as appropriate.

A low magnification SEM micrograph of multicomponent, interposed, carbon nanotube micropatterns with non‐aligned carbon nanotubes region‐specifically adsorbed between aligned carbon nanotube patterns.

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A low magnification SEM micrograph of multicomponent, interposed, carbon nanotube micropatterns with non‐aligned carbon nanotubes region‐specifically adsorbed between aligned carbon nanotube patterns.
Photoluminescence studies of Eu‐implanted GaN epilayers
Authors: Katchkanov V. , O'Donnell K. P. , Dalmasso S. , Martin R. W. , Braud A. , Nakanishi Y. , Wakahara A. , Yoshida A.
Published: May 2005

Photoluminescence (PL) of Eu‐implanted GaN epilayers grown by Metalorganic Vapour Phase Epitaxy (MOVPE) was studied as a function of temperature. The implantation was done at ion energies of 75 keV, 200 keV and 350 keV with doses of 1014cm–2and 1015cm–2. PL spectra of all samples show the emission line assigned to the5D0–7F2transition of Eu3+in GaN to be split into three spectral components at 620.7 nm, 621.6 nm and 622.5 nm. The split lines are seen to have very different temperature dependences of integrated intensity. Such splitting might be explained by Eu3+ion site multiplicity. The variation of the temperature quenching factor of the PL integrated intensity from sample to sample and from line to line suggests that optically active Eu3+ions are coupled to defects and impurities, thus forming complexes with different energy position of the carrier trapping level in the bandgap of GaN. The appearance and quenching of an additional PL line at 617.3 nm with increasing temperature is observed in the range of 13–295 K. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Structure, stability and electronic properties of TiO2 nanostructures
Authors: Enyashin Andrey N. , Seifert Gotthard
Published: May 2005

The structural properties, the stability and the electronic properties of various nanostructures based on the titania layer modifications (anatase and lepidocrocite) are studied using the density‐functional‐based tight‐binding method (DFTB). The anatase nanotubes were found as the most stable nanostructure of TiO2. Based on the results of the calculations of the anatase nanostructures a model of their stability was developed. All anatase nanoforms are semiconductors with a direct band gap (∼4.2 eV). The lepidocrocite nanotubes are semiconductors with an indirect band gap (∼4.5 eV). (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evolutionary Preference/Utility Functions: A Dynamic Perspective
Authors: DeSarbo Wayne S. , Fong Duncan K. H. , Liechty John , Coupland Jennifer Chang
Published: May 2005

The collection of repeated measures in psychological research is one of the most common data collection formats employed in survey and experimental research. The behavioral decision theory literature documents the existence of the dynamic evolution of preferences that occur over time and experience due to learning, exposure to additional information, fatigue, cognitive storage limitations, etc. We introduce a Bayesian dynamic linear methodology employing an empirical Bayes estimation framework that permits the detection and modeling of such potential changes to the underlying preference utility structure of the respondent. An illustration of revealed stated preference analysis (i.e., conjoint analysis) is given involving students’ preferences for apartments and their underlying attributes and features. We also present the results of several simulations demonstrating the ability of the proposed procedure to recover a variety of different sources of dynamics that may surface with preference elicitation over repeated sequential measurement. Finally, directions for future research are discussed.
The European Forum for Clinical Management: prophylaxis against the respiratory syncytial virus in infants and young children with congenital cardiac disease
Authors: Tulloh Robert M. R. , Feltes Timothy F.
Published: May 2005

A recent, randomised, double-blind, placebo-controlled trial has demonstrated the effectiveness of palivizumab (Synagis®) for prophylaxis against infection by the respiratory syncytial virus in 1,287 young children with congenital cardiac disease. Guidelines for the use of palivizumab in these children considered to be at high risk were published by the American Academy of Pediatrics, followed by similar guidelines from the British Paediatric Cardiac Association, and recommendations from a number of other individual countries, including Canada, Germany, Spain, and France.

In May, 2004, further discussion was held between a group of 15 paediatric cardiologists at a European forum for clinical management held in Munich, Germany. The objective of this forum was to define optimal recommendations on prevention of infection by the respiratory syncytial virus in infants and young children with congenital cardiac disease, appropriate to the clinical needs and style of those practising in paediatrics in individual countries. Participants were invited because of their knowledge of the therapeutic area, and for their experience of using palivizumab for prophylaxis against the respiratory syncytial virus in children with congenitally malformed hearts. Measures to educate the carers of children with such congenital malformations on precautions against infection by the respiratory syncytial virus were discussed, along with the many different aspects of best practice for therapeutic prophylaxis with palivizumab. The most appropriate timing of prophylaxis, recommendations for which children are most likely to benefit from prophylaxis, and suggested protocols were among the issues covered. The recommendations resulting from the discussions are presented in this paper, as a step towards reaching consensus.
The efficacy and safety of the Amplatzer ductal occluder in young children and infants
Authors: Al-Ata Jameel , Arfi Amin M. , Hussain Arif , Kouatli Amjad A. , Jalal M. Omar
Published: May 2005

Background: We have used the Amplatzer ductal occluder for transcatheter closure of large persistently patent arterial ducts, and used our experience to assess the safety and efficacy of the device in young children and infants. Methods and patients: We used the Amplatzer ductal occluder prospectively in 43 patients with large patent arterial ducts, reviewing our experience to identify any problems or complications. Results: The procedure proved successful in 42 of the patients. We achieved complete occlusion of the duct in 33 (78.5 per cent) of the patients on the day of insertion. In 6 additional patients, complete occlusion occurred 1 week to 6 months after the procedure. Trivial leaks persisted in 2 patients, while one had a significant residual leak. Problems were encountered in 7 patients. The procedure failed in one, a device was wasted in 2, pulled through in 3, while we experienced kinking of the long Mullins sheath, being unable to retrieve the device, in one patient. Minor complications occurred in 6 patients, finding flow at a peak velocity of 2.2 metres per second in the descending aorta in 2 patients, and at 2.5 metres per second in 2 further patients, and flow at 2.5 metres per second in the pulmonary arteries of two patients. One patient experienced a major complication due to excessive bleeding. Out of the 14 patients suffering adverse events, 13 weighed less than 10 kilograms. This rate of problems and complication in these patients weighing less than 10 kilograms was significantly higher than in the patients weighing more than 10 kilograms. Conclusion: Transcatheter occlusion of moderate to large patent arterial ducts with the Amplatzer ductal occluder device is safe and effective, with a high rate of complete occlusion. Problems and minor complications may be encountered in children weighing less than 10 kilograms. If the device is to be deployed completely in the ductal ampulla, and to avoid descending aortic obstruction, the size of the retention flanges of the occluder should not exceed the largest diameter of the patent arterial duct.
Congenital cardiac disease in children with Down's syndrome in Guatemala
Authors: Vida Vladimiro L. , Barnoya Joaquín , Larrazabal Luis A. , Gaitan Guillermo , Garcia Flor de Maria , Castañeda Aldo R.
Published: May 2005

Background:Congenital cardiac disease is the greatest cause of death in patients with Down's syndrome during the first two years of life, with from two-fifths to two-thirds of those with Down's syndrome also having congenital cardiac malformations. The lesions within the heart can be single or multiple. Our objective was to evaluate the frequency and type of such congenital cardiac malformations in patients born with Down's in Guatemala, and to provide baseline information for further research.Methods:We reviewed all patients with Down's syndrome who underwent a cardiologic screening examination between January, 1997, and December, 2003, in the only department dealing with Paediatric Cardiology in Guatemala.Results:Of the 349 patients reviewed, 189 (54.1 per cent) also had an associated congenital cardiac malformation. The median age at diagnosis was 6 months, with a range from 2 to 13 months. In 152 patients (80.4 per cent), the cardiac lesion was isolated, while 37 patients (19.6 per cent) had multiple defects. The most common single defect was patency of the arterial duct, found in 54 of the 189 patients (28.6 per cent), followed by ventricular septal defect in 27.5 per cent, atrial septal defect in 12.7 per cent, and atrioventricular septal defect with common atrioventricular junction in 9.5 per cent. The most frequent concomitant malformation found co-existing with other congenital cardiac lesions was patency of the arterial duct, found in 17.5 per cent.Conclusions:As far as we are aware, ours is the first epidemiologic study concerning the frequency and type of congenital cardiac disease found in Guatemalan children with Down's syndrome. The high frequency of patency of the arterial duct, and the differential distribution of the cardiac malformations associated with Down's syndrome among Guatemalan children, differ from what has been reported in the United States of America, Europe, and Asia. This difference warrants further research.
Ventricular tachycardia secondary to prolongation of the QT interval in a fetus with autoimmune mediated congenital complete heart block
Authors: Duke Christopher , Stuart Graham , Simpson John M.
Published: May 2005

We report a case where fetal echocardiography identified both complete heart block and ventricular tachycardia. The mother tested positive for anti-Ro antibodies. Prenatal detection of this unusual combination of arrhythmias prompted early postnatal evaluation, which revealed prolongation of the QT interval. Autoimmune mediated congenitally complete heart block associated with such prolongation of the QT interval has a poor prognosis. The child was successfully treated with beta blockers and implantation of a pacemaker.
Planen und prospektives Erinnern von Absichten bei Kindern mit einer hyperkinetischen Störung
Authors: Kliegel Matthias , Kerber Ulrike
Published: May 2005

Zusammenfassung. Die vorliegende Studie verfolgte das Ziel, mögliche Defizite beim Planen und prospektiven Erinnern von Absichten bei Kindern mit einer hyperkinetischen Störung (HKS) zu identifizieren und phasenbezogen zu spezifizieren. Insgesamt 40 Kinder wurden hierfür mit dem Heidelberger Exekutivdiagnostikum ( Martin & Kliegel, 2003 ) dahingehend untersucht, inwieweit sie verschiedene Aufgaben planen und nach zeitlicher Verzögerung und unter Beachtung bestimmter Regeln selbstständig initiieren und ausführen können. Die Ergebnisse zeigen differenzielle Unterschiede in verschiedenen Aufgabenaspekten der komplexen prospektiven Gedächtnisaufgabe zwischen den Gruppen. Kinder mit HKS zeigen qualitativ schlechtere Leistungen vor allem in der Handlungsplanung und der Güte der ausgeführten Handlung. Die vorliegenden Daten stützen die Befunde zu defizitären exekutiven Funktionsleistungen in HKS-Patienten und liefern erste spezifische Hinweise hinsichtlich konkreter eingeschränkter Komponenten in einer komplexen prospektiven Gedächtnisaufgabe bei Kindern mit HKS.
Lebensqualität in Familien mit einem herzkranken Kind
Authors: Goldbeck Lutz , Melches Juliane , Franz Axel , Voßbeck Sabine , Lang Dieter , Mihatsch Walter
Published: May 2005

Zusammenfassung. Die Studie untersucht die Lebensqualität ambulanter kinderkardiologischer Patienten aus ihrer eigenen Sicht und aus Elternsicht sowie die Lebensqualität ihrer Eltern. Der Zusammenhang zwischen Krankheitsschwere und Lebensqualität wird analysiert. Im Rahmen eines computergestützten Screening-Verfahrens wurden 75 Patientenfamilien aus einer kinderkardiologischen Klinikambulanz mit den Lebensqualitätsfragebögen LQ-KID, LQ-KID-E und ULQIE befragt. Die Ausprägung der Herzerkrankung wurde durch die behandelnden Ärzte eingeschätzt. Selbst- und Elterneinschätzung der Lebensqualität der Patienten korrelieren nur mäßig. Signifikante Effekte der Krankheitsschwere auf die Lebensqualität fanden sich hinsichtlich der familiären Beziehungen aus Sicht der Kinder und der emotionalen Belastung der Eltern.
Mobile Diabetesschulung Schleswig-Holstein (MDSH)
Authors: von Sengbusch Simone , Wagner Verena , Müller-Godeffroy Esther , Hiort Olaf , Thyen Ute
Published: May 2005

Zusammenfassung. Kinder und Jugendliche mit Diabetes mellitus Typ 1 sowie ihre Eltern benötigen regelmäßig Schulungen, um die komplexe Diabetestherapie angemessen im Alltag umsetzen zu können. Seit 1999 bietet ein mobiles Diabetesschulungs- und Behandlungsteam der Universitätskinderklinik Lübeck in acht Kinderkliniken des Bundeslandes strukturierte, stationäre Diabetesschulungen für Kinder, Jugendliche und Eltern an. Das Schulungskonzept wird beschrieben und die Auswirkungen auf die Belastung der Eltern untersucht. Es fand sich eine verminderte Belastung der Eltern in Bezug auf die praktische Umsetzung der Diabetestherapie im Alltag. Persönliche und familiäre Probleme der Eltern wurden durch die Schulung nicht beeinflusst. Es ist anhand unserer Ergebnisse zu überlegen, ob Zeitrahmen und Setting des Schulungsmodells stärker auf die Belange von Eltern fokussieren sollten. Das Studienergebnis unterstreicht die Notwendigkeit der psychosozialen Unterstützung von Eltern diabeteserkrankter Kinder als ein wesentlicher Bestandteil der Langzeitbetreuung.
Observational and modeling analysis of a severe air pollution episode in western Hong Kong
Authors: Fung J. C. H. , Lau A. K. H. , Lam J. S. L. , Yuan Z.
Published: May 2005

A severe air pollution episode occurred over much of the western part of Hong Kong (HK) between 28 and 30 December 1999. In this study, multiple analyses were made to understand the cause of this episode; first, the main emission source of the pollution episode was identified using remote sensing techniques from satellite pictures and was located about 100 km to the northeast of HK. Second, analyses were made on PM10 chemical species characterization in four air quality monitor stations (AQMSs), and a high concentration of potassium ions (K+) on the episode days indicates the significant impact of biomass burning. The ratio of elemental carbon and organic carbon values in two western AQMSs indicated that regional transport, rather than the local vehicle emission and power plant, played an important role in this episode. This result is in contrast with the early finding by H. Liu and J. C. L. Chan that this pollution episode is solely due to local sources. Third, to study the transport, diffusion, and trapping of pollutants during this air pollution episode, two numerical models were coupled in this study: a three‐dimensional mesoscale meteorological model MM5 and a three‐dimensional Lagrangian particle dispersion model. With the help of the Lagrangian dispersion model we show that this severe air pollution event was associated with transport of pollutants over HK within the boundary layer. These pollutants were subsequently brought down to the surface by the local land‐sea breeze circulation and trapped over the western part of HK during the day by the same land‐sea breeze.
Nitrogen cycling on the Namibian shelf and slope over the last two climatic cycles: Local and global forcings
Authors: Pichevin Laetitia , Martinez Philippe , Bertrand Philippe , Schneider Ralph , Giraudeau Jacques , Emeis Kay
Published: May 2005

In the light of new surface sediment δ15N data collected over the Namibian shelf and slope, we examined glacial‐interglacial variations of N inventory in the area of Lüderitz (25°6S) by deciphering δ15N signals of three cores distributed from the upper to the lower continental slope. The lower slope cores display low δ15N during cold periods and high δ15N during climatic optima, akin to many other records from the world ocean, whereas the upper slope core displays a high‐frequency low‐amplitude δ15N signal without obvious glacial‐interglacial variability. This dissimilarity results from the segregation of the upwelling structure in two cells, decoupling nutrient dynamics of the shelf from those beyond the shelf‐edge. The δ15N signal of the coastal cell is relatively constant irrespective of wind strength variations and shows that nitrate was never depleted in the surface water. For the deeper cores, comparisons between N isotopic signals and indicators of paleoproductivity (total organic carbon) and upwelling intensity (sea surface temperature and dust grain size) reveal that, over Milankovitch cycles, nitrate delivery to the photic zone was driven by the nutrient richness of the South Atlantic Central Water (depending, in turn, on Aghulas water inflow and denitrification at a global scale) rather than by atmospheric forcing. We propose that the δ15N signals of the deeper cores do not only mirror changes in relative nitrate utilization, as it seems the case over annual timescales, but are arguably influenced by global ocean changes in middepth nitrate δ15N.
Fluvial processes and streamflow variability: Interplay in the scale‐frequency continuum and implications for scaling
Authors: Dodov Boyko , Foufoula‐Georgiou Efi
Published: May 2005

This paper explores the links between channel/floodplain morphometry, streamflow variability, and sediment transport across a wide range of scales and frequencies of discharge. On the basis of extensive analysis of observations from a climatologically and geologically homogeneous region in the midwestern United States, we provide evidence that streamflow statistics are significantly affected by the scale‐dependent channel/floodplain interactions, which in turn are controlled by (and at the same time actively participate in defining) the dominant fluvial processes at a given scale. More specifically, we document that (1) the channel cross‐sectional geometry exerts a strong control on the frequency distributions of both daily and maximum annual discharges; (2) the frequency of exceedance of bank‐full discharge is scale dependent (particularly, channels draining large areas flood less often but stay overbank longer than channels draining small areas); (3) the critical area at which the variability of floods with scale changes from increasing to decreasing associates with the scale at which the fluvial regime changes from net‐erosional to net‐depositional and the floodplain gets well established due to its increased frequency of occupation by the flow; and (4) scaling in suspended sediment load reflects the scaling in channel and floodplain morphometry and depicts the signature of the aforementioned fluvial regime transition. The observation is made that maximum annual floods are composed of two distinct populations, one from below and one from above bank‐full flows, and that the quantile at which this transition occurs depends on scale. On the basis of this observation, the notion of statistical multiscaling of floods is reexamined.
Extraction of roughness parameters from specular x-ray resonant scattering
Authors: Negusse Ezana , Idzerda Yves U.
Published: May 2005

We expand on a different approach for extracting a roughness parameter (perpendicular component) from standard specular θ−2θ x-ray resonant scattering scans. Modulated in the scattering patterns are the chemical and magnetic characteristics of the thin film and interface. Continuous media-based modeling of these spectra gives sharp Bragg features unlike the broadened features of the measured spectra due to interfacial roughness. Here we examine the effect of roughness due to the incoherent contribution to the scattered light from islands with varying thicknesses. The summed spectrum is computed from the calculated spectra at different thicknesses, which are used as a basis set, added incoherently according to a thickness distribution. The mean and rms thickness values of the distribution control the periodicity and depth of the interference patterns in the spectra, respectively.
Effect of Ga+ irradiation on magnetic and magnetotransport properties in (Ga,Mn)As epilayers
Authors: Kato H. , Hamaya K. , Kitamoto Y. , Taniyama T. , Munekata H.
Published: May 2005

We report on the magnetic and magnetotransport properties of ferromagnetic semiconductor (Ga,Mn)As modified by Ga+ ion irradiation using focused ion beam. A marked reduction in the conductivity and the Curie temperature is induced after the irradiation. Furthermore, an enhanced negative magnetoresistance and a change in the magnetization reversal process are also demonstrated at 4 K. Raman-scattering spectra indicate a decrease in the concentration of hole carriers after the irradiation, and a possible origin of the change in the magnetic properties is discussed.
Sample preparation and annealing effects on the ferromagnetism in Mn-doped ZnO
Authors: Zhang Jun , Skomski R. , Sellmyer D. J.
Published: May 2005

Magnetic properties of Mn-doped ZnO strongly depend on sample preparation and annealing. While the samples sintered in air at 500°C show ferromagnetism at room temperature, those sintered at 900°C are paramagnetic. The samples sintered in vacuum show a ferromagnetic transition at 45K, which is attributed to ferrimagnetic Mn3O4. With an increase of annealing temperature, the ferromagnetism observed at room temperature in the low-temperature-sintered samples is gradually suppressed and finally completely removed. These results can be understood by considering a metastable ferromagnetic phase and its stability under varying temperatures and atmospheres.
Low resistance tunnel junctions with remote plasma underoxidized thick barriers
Authors: Ferreira R. , Freitas P. P. , MacKenzie M. , Chapman J. N.
Published: May 2005

Low resistance tunnel junctions suitable for >200Gb∕inch2 read heads require R×A<1Ωμm2 and TMR>10%, usually achieved by natural oxidation with tAl<0.7nm barriers. This paper shows that as-deposited junctions with competitive electrical and magnetic properties can be produced starting from 0.9nm Al barriers and remote plasma oxidation in ion beam-deposited stacks using Co73.8Fe16.2B10 electrodes. TMR∼20% for R×A∼2–15Ωμm2 is obtained, while in the R×A∼40–140Ωμm2 range TMR can reach 40%–45%, in as-deposited samples. A limited number of junctions exhibits considerably lower R×A values with respect to the average while keeping similar MR (down to 0.44Ωμm2 with 20% and down to 2.2Ωμm2 with 51%).
Exchange biasing of the ferromagnetic semiconductor (Ga,Mn)As by MnO (invited)
Authors: Eid K. F. , Stone M. B. , Maksimov O. , Shih T. C. , Ku K. C. , Fadgen W. , Palmstrøm C. J. , Schiffer P. , Samarth N.
Published: May 2005

We provide an overview of progress on the exchange biasing of a ferromagnetic semiconductor (Ga1−xMnxAs) by proximity to an antiferromagnetic oxide layer (MnO). We present a detailed characterization study of the antiferromagnetic layer using Rutherford backscattering spectrometry, x-ray photoelectron spectroscopy, transmission electron microscopy, and x-ray reflection. In addition, we describe the variation of the exchange and coercive fields with temperature and cooling field for multiple samples.
Switching field distribution in magnetic tunnel junctions with a synthetic antiferromagnetic free layer
Authors: Jeong W. C. , Park J. H. , Koh G. H. , Jeong G. T. , Jeong H. S. , Kim Kinam
Published: May 2005

By replacing the traditional single magnetic free layer in magnetic random access memory (MRAM) with a synthetic antiferromagnetic (SAF) layer composed of two antiferromagnetically coupled layers, the possibility of the kink generation has been suppressed to a minimum level and the normalized free-layer shift has been reduced from 15% to less than 5%. These phenomena are thought to be from the reduction of the effective thickness and magnetic moment by introducing a SAF free layer. Since the SAF free layer decreases the magnetostatic interaction with the pinned layer, free-layer shift is also decreased. A SAF free layer forms a closed magnetic loop between two antiferromagnetically coupled layers. Therefore, it increases a tendency to become a single domain and its switching field distribution is enhanced. With the optimized SAF free layer, array quality factor [AQF, σ(Hc)∕Hc] is increased to more than 10 and switching window could be obtained which is the area to be selectively switched in the memory cell array. When adopted in a 64-kb MRAM, it is confirmed that cells can be selectively switched without the disturbance to the other cells.
Tunnel magnetoresistance effect in Cr1−δTe∕AlAs∕Ga1−xMnxAs magnetic tunnel junctions
Authors: Saito H. , Yuasa S. , Ando K.
Published: May 2005

Magnetic tunnel junctions (MTJs) consisting of ferromagnetic metal (Cr1−δTe) and semiconductor (Ga1−xMnxAs) electrodes with an AlAs tunnel barrier have been fabricated. A nonlinear behavior was clearly observed in the current versus bias-voltage characteristics, suggesting that the electric transport between the two ferromagnetic electrodes is tunneling. The MTJs exhibited the tunnel magnetoresistance (TMR) effect up to 14.5% at 5K. The TMR ratio was observed to rapidly decrease with increasing temperature and bias voltage. These experimental results imply that Cr1−δTe is applicable to the spintronic devices based on III-V semiconductors.
Magnetic properties of transition-metal nitrides
Authors: Lambrecht Walter R. L. , Miao M. S. , Lukashev Pavel
Published: May 2005

The structural stability of transition-metal nitrides (TMN’s) and their magnetic properties in different phases are investigated using first-principles calculations. The early TMN, ScN–CrN, are found to have rocksalt as equilibrium structure at ambient pressure while the later ones (MnN, FeN, and CoN) prefer zincblende. However, the early ones can also adopt the zincblende structure under tensile strain. The tendency towards magnetism is stronger in the rocksalt phase than in the zincblende phase. Antiferromagnetic versus ferromagnetic ordering in the different phases and the relevance of the results to TM-doped GaN are discussed.
Room temperature ferromagnetic and ultraviolet optical properties of Co-doped ZnO nanocluster films
Authors: Antony J. , Pendyala S. , Sharma A. , Chen X. B. , Morrison J. , Bergman L. , Qiang Y.
Published: May 2005

We prepared 2% and 5% Co-doped ZnO nanocluster films at room temperature (RT) using doped ZnO nanoclusters as building blocks. The nanoclusters are produced by a third-generation magnetron-sputtering-aggregation source. Superconducting quantum interference device (SQUID), photoluminescence (PL), x-ray diffraction (XRD), x-ray photoelectron spectrometer (XPS), and atomic force microscopy (AFM) measurements were done on the samples. The average nanocrystallite size of the nanoclusters was ∼7.5nm. The 2% Co-doped ZnO nanocluster films exhibit significant ferromagnetism and ultraviolet (UV) photoluminescence (PL) at RT. The coercivity (Hc) doubled in the 2% Co-doped samples when compared to the 5% Co-doped samples. A strong UV-PL of ∼3.33eV was observed for the 2% Co-doped ZnO nanocluster film at RT. The 5% Co-doped ZnO nanocluster film showed a ferromagnetic behavior at RT but no UV luminescence.
CPP transport properties of polycrystalline Fe3O4 thin films sputtered on Cu underlayers
Authors: Qin F. , Nozaki Y. , Matsuyama K.
Published: May 2005

Transport properties of sputtered Fe3O4 thin films have been studied with the current perpendicular to plane (CPP) configuration. Fabricated polycrystalline Fe3O4 films exhibit superior CPP conductivity of 12kΩ−1∙m−1. In addition to the Verwey transition (VT), observed at 114 K, another type of drastic conductivity change [field induced transition (FT)] was observed at lower temperature (T<70K) and higher bias voltage (Vb>0.18V) regime. The conductivity change at FT is discontinuous and several orders in magnitude. The transition temperature for FT presents considerable Vb dependence, contrarily no distinguished dependence for VT.
First-principles study of the structural and magnetic properties of iron indium nitride
Authors: Lukashev Pavel , Lambrecht Walter R. L.
Published: May 2005

A full-potential linear muffin-tin orbital method is used to study the magnetic and electronic properties of Fe1−xInxN alloys in zino-blende-derived structures. The lattice constant is found to vary linearly with concentration and to become matched to GaN near x=0.25. The materials are found to exhibit a magnetic moment beyond a critical lattice constant.
Magnetostriction effect of amorphous CoFeB thin films and application in spin-dependent tunnel junctions
Authors: Wang Dexin , Nordman Cathy , Qian Zhenghong , Daughton James M. , Myers John
Published: May 2005

CoFeB thin films and magnetic tunnel junctions using them are studied for magnetostriction effect. The single-layer films were sputter deposited with excellent soft magnetic properties including a high saturation magnetization of 1.5T, a near-zero hard axis coercivity, a low easy axis coercivity of 2.0Oe, and an induced magnetic anisotropy field of 32Oe. The saturation magnetostriction constant is measured to be 31ppm. Magnetic tunnel junctions (MTJs) were fabricated and tested for potential strain gauge applications. The gauge factor for the magnetostrictive MTJs, a measure of strain sensitivity, is many times of the best piezoresistive devices.
Magnetization instability driven by spin torques
Authors: Li Z. , He J. , Zhang S.
Published: May 2005

Electric currents in a ferromagnet film produce adiabatic and nonadiabatic torques on magnetization. When the current density is sufficiently large, these torques drive the uniform magnetization into spatially and temporally chaotic motion of magnetization. We predict several key characteristics of the magnetization instability by calculating the current-induced domain wall creation, annihilation and dynamics.
Evidence for positive spin polarization in Co with SrTiO3 barriers
Authors: Thomas Andy , Moodera Jagadeesh S. , Satpati Biswarup
Published: May 2005

Recent negative tunneling magnetoresistance results with epitaxial SrTiO3 and TiO2 tunnel barriers were attributed to tunneling that favor d-like states from Co, resulting in negatively polarized electron tunneling. In order to confirm this, we carried out direct measurements of spin polarization of Co with SrTiO3 barriers using a superconductor as a spin detector. The polarization was observed to be positive (+31%), in contrast to published results. Furthermore, studies conducted on magnetic tunnel junctionswith SrTiO3 and TiO2 tunnel barriers are consistent with the direct measurements. The implications of our results, for the case of amorphous barriers, in comparison to crystalline barriers is discussed.
Fokker–Planck calculation of spin-torque resistance hysteresis and switching currents
Authors: Visscher P. B. , Apalkov D. M.
Published: May 2005

In this article we apply a recently developed Fokker–Planck theory of spin-torque switching rates to the prediction of current hysteresis curves and switching currents. A field dependence of the switching current, which is not predicted by nonthermal theories, is found and compared to experiment. We obtain useful analytic approximations to the exact hysteresis curves and the switching currents, which depend logarithmically on current sweep rate. In addition to switching between the parallel and antiparallel metastable states, we also take into account fluctuations in each of these potential wells, which cause rounding of the hysteresis curves.
Role of interface bonding in spin-dependent tunneling (invited)
Authors: Tsymbal E. Y. , Belashchenko K. D.
Published: May 2005

Measured positive values of the spin polarization of the tunneling current from 3d ferromagnetic metals are commonly explained by the dominant s-electron contribution based on symmetry considerations for bulk materials, ignoring the influence of the interfaces. In this work, three different models are considered which suggest that the spin polarization is primarily determined by the electronic and atomic structures of the ferromagnet/insulator interfaces rather than by the bulk properties. A simple tight-binding model demonstrates that the existence of interface states and their contribution to the tunneling current depend on the degree of hybridization between the orbitals on metal and insulator atoms. The decisive role of the interface bonding is further supported by considering spin-dependent tunneling from oxidized Co surfaces through vacuum and in Co∕Al2O3∕Co tunnel junctions within the first-principles Green’s-function approach. For the oxidized Co surface it is found that the Co–O bonding at the surface removes the conducting orbitals forming the bulk Bloch states from the Fermi level, creating an additional tunneling barrier for minority-spin electrons. For the Co∕Al2O3∕Co junctions, two types of the interface O atoms are distinguished: those which saturate Al bonds and those which are adsorbed by Co. The latter bind strongly to Co creating interface states which enhance the tunneling current in the majority-spin channel. In both cases, the spin polarization changes sign and becomes positive, evidencing the crucial role of the interface structure and bonding.
Spin-current-induced magnetization reversal in magnetic nanowires with constrictions
Authors: Florez S. H. , Krafft C. , Gomez R. D.
Published: May 2005

We have performed experiments on current-induced domain-wall motion (CIDWM) in the case of the domain walls (DW) trapped within the nanoscale constrictions in patterned NiFe structures. Direct observation of current-induced magnetization reversal was achieved and critical current densities jc were measured in the presence of easy-axis magnetic fields. The direction of CIDWM was found to be along the direction of the electron motion in absence of an applied magnetic field and in the direction of the field when in the presence of even relatively weak fields. Data for the field dependence of jc for both uniform and fast rising pulses suggest that the current, regardless of polarity, assists in the depinning of the DW. Only for the dc case does the data strongly reveal the influence of the electron pressure in promoting or hindering DW motion.
Current-induced magnetization switching in permalloy-based nanopillars with Cu, Ag, and Au
Authors: Kurt H. , Loloee R. , Pratt W. P. , Bass J.
Published: May 2005

We compare magnetoresistances (MR) and switching currents (Is) at room temperature (295K) and 4.2K for Permalloy∕N∕Permalloy nanopillars undergoing current-induced magnetization switching (CIMS), with nonmagnetic metals N=Cu, Ag, and Au. The N-metal thickness is held fixed at 10nm. Any systematic differences in MR and Is for the different N-metals are modest, suggesting that Ag and Au represent potentially viable alternatives for CIMS studies and devices to the more widely used Cu.