bluuebunny/crossref_metadata_2025 huggingface dataset:
The Stereospecific Substitution of the Xenon Atom in cis‐Perfluoroalk‐1‐enylxenon(II) Salts by Hydrogen, Halogens, and the Phenyl Group
Authors: Frohn Hermann‐Josef , Bardin Vadim V.
Published: June 2004

The substitution of the xenon atom in reactions of [cis‐CnF2n+1CF=CFXe][Y] salts with benzene, iodide, and bromide anions in propionitrile solution by the phenyl group, or iodine, and bromine atoms, respectively, occurred stereospecifically. When a propionitrile solution of [cis‐C2F5CF=CFXe][AsF6] was kept at —40 °C without an additional reactant, the fluoroalkene cis‐C2F5CF=CFH was the only isomer obtained.
Pt2(HSO4)2(SO4)2, the First Binary Sulfate of Platinum
Authors: Pley Martin , Wickleder Mathias S.
Published: June 2004

Red single crystals of Pt2(HSO4)2(SO4)2 were obtained by the reaction of elemental platinum with conc. sulfuric acid at 350 °C in sealed glass ampoules. The crystal structure (monoclinic, P21/c, Z = 2, a = 868.6(2), b = 826.2(1), c = 921.8(2) pm, β=116.32(1)°, Rall = 0.0348) shows dumbbell shaped Pt26+ cations which are coordinated by four SO42— and two HSO4— ions. Each of the sulfate ions is attached to another Pt26+ ion yielding layers according to [Pt2(SO4)4/2(HSO4)2/1]. The layers are connected by hydrogen bonds with the OH group of the hydrogensulfate ion as donor and the non‐bonding oxygen atom of the sulfate ion as acceptor.
Über Münzmetall‐Quecksilber‐Chalkogenidhalogenide. V1) Solvothermalsynthese und Kristallstruktur der Hochtemperatur‐Modifikation von AgHgSI
Authors: Beck Johannes , Keller Hans‐Lothar , Rompel Matthias , Wimbert Lars , Ewald Bastian
Published: June 2004

α‐AgHgSI wird aus AgI und α‐HgS durch solvothermale Umsetzung bei 300 °C in verdünnter HI‐Lösung in Form von gelben Kristallen erhalten. Die Substanz kristallisiert in der Raumgruppe P212121 mit a = 707, 47(1), b = 773, 18(2), c = 847, 53(2) pm und Z = 4. Innerhalb der Kristallstruktur bilden Schwefel und Iod das Motiv einer verzerrt hexagonal dichtesten Packung, in der Silber ein Viertel der Tetraederlücken und Quecksilber die Hälfte der Oktaederlücken besetzt. Die Verzerrungen werden durch den sterischen Anspruch freier Elektronenpaare hervorgerufen, was durch Berechnungen der Elektronenlokalisierungsfunktion (ELF) bestätigt werden konnte. Die hier beschriebene Modifikation von AgHgSI kann bei 273 °C aus dem schon bekannten β‐AgHgSI gebildet werden und wird somit als α‐AgHgSI bezeichnet.
Synthese und Kristallstruktur von Vanadium(III)‐borophosphat, V2[B(PO4)3]
Authors: Meisel Manfred , Päch Michael , Wilde Lutz , Wulff‐Molder Dirk
Published: June 2004

Synthesis and Crystal Structure of Vanadium(III) Borophosphate, V2[B(PO4)3]

By reaction of boron phosphate, BPO4, and vanadium(IV)‐oxide, VO2, at 1050 °C a hitherto unknown vanadium(III)‐borophosphate is formed. Its composition was found to be V2BP3O12, its structure was elucidated by single crystal X‐ray diffraction, the cell parameters are: a = b = 13.9882Å; c = 7.4515Å; α = β = 90°, γ = 120°; Z = 6; space group: P6 3/m. Noteworthy features of the structure are V2O9 units (two VIIIO6 octahedra connected via their faces) and isolated trisphosphatoborate groups, B(PO4)3. By shared oxide ions, the aforementioned groups are interconnected, thus forming a three dimensional network. The structural relation between the title compound and an analogous chromium compound is discussed.
Calix[4]arene stabilized Transition Metal Imido Complexes
Authors: Radius U.
Published: June 2004

The usage of calix[n]arenes as ancillary poly(phenolate) ligands is a rapidly developing area in coordination chemistry. This article focuses on the synthesis, structure and reactivity of calix[4]arene‐ and calix[4]arene ether‐stabilized imido complexes of group 4 — 6 transition metals as well as on the comparison of calix[4]arene dialkyl ethers in particular with other widely employed related ligand systems such as salenes, porphyrins and tetraazaannulenes. Contrary to these nitrogen containing systems, it is much easier to control the charge of the ligand system through the degree of alkylation of the calixarene's lower rim without a major change in the geometry of the resulting metal complex. This could lead to isoelectronic and structurally closely related transition metal complex fragments for metals in neighboring groups of the periodic table or for metals in different oxidation states. The “intrinsic” reactivity of metal imido linkages might therefore be explored using calix[4]arenes and calix[4]arene ethers and first results are summarized in this research report.
The Changing Historiographies of Laos: A Focus on the Early Period
Authors: Pholsena Vatthana
Published: June 2004

The narrative of the origins of the Lao people in contemporary Lao-language history books and textbooks is divided among divergent interpretations. The most popular reading is the ‘Ai-Lao’ version, an implicit response to Thai nationalist historiography. Marxist-Leninist-orientated historiography, by contrast, resembles the Vietnamese Communist narrative. As far as likely future trends are concerned, a journey back to the ‘roots’ seems ultimately to reveal the biography of a pre-modern spatial identity.
Esoteric Buddhism in Southeast Asia in the Light of Recent Scholarship
Authors: Woodward Hiram
Published: June 2004

Indian esoteric Buddhism: A social history of the Tantric movement. By Ronald M. Davidson. New York: Columbia University Press, 2002. Pp. 475. Maps, Illustrations, Glossary, Bibliographies, Index.
Connective tissue diseases in later life
Authors: Brockbank John E
Published: June 2004

The connective tissues diseases are a group of related disorders, which are primarily autoimmune and triggered by environmental factors in susceptible individuals. They usually affect multiple organs and most of them can result in a shortened lifespan. Fortunately they are also very uncommon, and even rarer in later life. They are usually diagnosed on a clinical basis and, to help this, most have strict diagnostic criteria. However, a lot of patients do not fit well into one particular category, but overlap with several. Indeed a single individual could have features of or fulfil the criteria for all the diseases discussed in this review. A further group of patients are ‘undifferentiated’, often having mild disease and initially failing to fulfil any set of criteria.
Polymyalgia rheumatica
Authors: Bird HA
Published: June 2004

Polymyalgia rheumatica and temporal arteritis represent opposite poles of a single disease spectrum. In the former, girdle stiffness predominates; in the latter, frank vasculitis is demonstrable. There is no diagnostic laboratory test for polymyalgia rheumatica, and earlier reviews in 1993 and 1998 in this journal both drew attention to the difficulty in diagnosing polymyalgia rheumatica, particularly in the elderly.
Dementia in people with an intellectual disability
Authors: Deb Shoumitro
Published: June 2004

Medical advances and improved living conditions mean that people who have an intellectual disability (ID), characterized by lifelong limited intellectual, social and vocational capabilities, are living longer. There has been a concomitant increase in the prevalence of age-associated diseases, including dementia.
Rehabilitation nursing: the role of the nurse and the development of the specialist role
Authors: Clark Mark , Wall Jenny
Published: June 2004

This article will first set rehabilitation nursing and the older person into an appropriate context and then address the nature of rehabilitation nursing, how definitions have developed over time and lastly, what it is that we now provide, in conjunction with others, to meet the rehabilitative needs of our older population. The boundaries defining ‘old’, and between seeing a person as experienced, a bit wrinkly, forgetful and perhaps eccentric, versus a person who is old and demented are by no means clear-cut.
ANTICIPATORY PROCESSING IN SOCIAL ANXIETY
Authors: Vassilopoulos Stephanos Ph.
Published: June 2004

A psychometric study was conducted with the aim of collecting basic information about anticipatory processing and its relationship to social anxiety. A self-report measure of anticipatory processing was developed and utilized in a large student sample. The results confirmed that such processing is very common before an anticipated feared social event and a significant correlation (r=0.49) between anticipatory processing scores and social anxiety was found, which remained when trait anxiety and depression were controlled. A factor analysis indicated that all items of the measure except for two loaded significantly on one factor and accounted for the 47.3% of the variance. Socially anxious individuals in the study reported that their thoughts about the event were recurrent, intrusive, interfered with their concentration and increased their state of anxiety. Also, they reported that they wished they could avoid the situation. The results are discussed in terms of the Clark and Wells cognitive model of social phobia.
FIRST EPISODE PSYCHOSIS: TWO CASES TO ILLUSTRATE THE ROLE OF COGNITIVE BEHAVIOUR THERAPY IN MAKING SENSE OF UNUSUAL EXPERIENCES
Authors: Grazebrook Katy A. , Siddle Ronald , Leadley Karen , Everitt Julie , Benn Andy , Haddock Gillian , Kinderman Peter K. , Tarrier Nick
Published: June 2004

This paper describes two cases involving the use of cognitive behavioural therapy (CBT) to treat the positive symptoms of schizophrenia. In both cases the individuals were experiencing acute psychotic symptoms during their first admission to hospital. Each case illustrates how CBT was used to tackle a particular issue pertinent to the delivery of treatment at this early stage in the development of an individual's experiences of psychotic symptoms. Case one describes therapy with a young person of 17 where developmental issues are pertinent; case two describes the use of therapy to engage a person whose symptoms have ostensibly remitted. In both cases the promotion of understanding of the origin of their experiences was vital to the conduct of therapy. The implications of these issues to conducting therapy with this client group and the methods used to overcome them are discussed with reference to the future developments of cognitive behavioural therapy for use with this client group.
PSYCHOLOGICAL FACTORS INFLUENCING THIRST AND DRINKING IN HAEMODIALYSIS PATIENTS ON A FLUID RESTRICTION
Authors: Fisher Linda
Published: June 2004

Models of panic and health anxiety are used to explore the possible psychological processes contributing to excessive fluid intake in kidney patients on a fluid restriction. Some simple figures concerning the role of attention in thirst intensity are presented.
CLINICAL PERFECTIONISM: A CASE REPORT
Authors: Shafran Roz , Lee Michelle , Fairburn Christopher G.
Published: June 2004

The aim of this case report is to describe the impact of an intervention for clinical perfectionism, derived from a new cognitive-behavioural analysis, in a patient with binge-eating disorder. It was hypothesized that clinical perfectionism was contributing to the maintenance of the eating disorder, and on this basis it was predicted that reducing clinical perfectionism would improve her eating disorder psychopathology. Standardized independent assessments were found to be consistent with this hypothesis, in that clinical perfectionism and eating disorder psychopathology improved over an eight-session intervention and improvements were largely maintained at 5-month follow-up.
EFFECTIVE BEHAVIOR THERAPY IN A MEDICAL CRISIS: A CASE REPORT
Authors: Powell Douglas H. , Birk C. Lee , Powell Virginia S.
Published: June 2004

This is report of the successful use of behavioral treatment in a medical crisis. The intubation process inadvertently punctured a patient's throat during the application of general anesthesia while having a routine arthroscopy. This resulted in a rapidly spreading infection, spiking temperature and dehydration. To locate the puncture, a barium swallow x-ray was necessary, but the patient's weakened condition made standing impossible. A friend and experienced therapist accompanying the patient helped him stand for the several minutes necessary to complete the barium swallow by countering the hypotensive state with angry imagery to stimulate an adrenalin surge. Several principles of effective therapeutic practice were demonstrated by this case, including the importance of the alliance, of technical eclecticism, of engaging the patient in the treatment process, and therapist experience.
Near‐surface hydrocarbon anomalies in shelf sediments off Spitsbergen: Evidences for past seepages
Authors: Knies Jochen , Damm Ellen , Gutt Julian , Mann Ute , Pinturier Laurence
Published: June 2004

As global warming occurs, the dissociation of bound methane on Arctic shelves due to ocean current temperature changes may become a major contributor to the global methane budget, and thus contribute to strong positive climate feedback mechanisms. However, little is known about the magnitude and fate of methane emissions from shallow submarine sediments to the atmosphere in the peculiar area. In this paper, we present one of the first direct evidences for seepage on the northwestern Barents Sea shelf. By studying the molecular and isotopic signatures of low‐molecular‐weight hydrocarbons in seawater, near‐surface sediment pore space and the sediment matrix at 26 locations, we provide a detailed view on the partitioning of gaseous hydrocarbons in the sediment‐water interface off Spitsbergen. In the free gas phase, low concentration of methane (∼28 ng/g wet Sediment) paired with constantly high isotopic values (∼−65‰) is consistent with high impact of methane oxidation on the isotopic composition. In contrast, high concentrations of adsorbed CH4 (up to 5292 ng/g wet <63 μm) and C2+ (ethane through pentane) (up to 1724 ng/g wet <63 μm) in the sediment matrix suggest that the adsorbed gas is reasonably well protected against microbial degradation. Moreover, the isotopic and molecular signatures of adsorbed CH4 (−38–−60‰; ∼100–∼5300 ng/g wet <63 μm) and C2H6 (−20–−36‰; ∼30–∼1700 ng/g wet <63 μm) indicate an integrated, but strongly varying signal of historic thermally derived hydrocarbon plumes plus in situ adsorbed gas of biological origin. This suggests a minimal exchange and unlike histories of free and adsorbed gas. The majority of gaseous hydrocarbons in the adsorbed pool may be the result of past seepages. Past upward flow of thermogenic gas and impregnation with mature hydrocarbons was particularly strong along tectonic lineaments. Active petroleum source rocks along the continental margin and migration of gaseous hydrocarbons at re‐activated fault systems might explain the anomalies along these conduits.
On the increases in nitric oxide density at midlatitudes during ionospheric storms
Authors: Richards P. G.
Published: June 2004

This study examines the causes of changes in observed and modeled nitric oxide density at midlatitudes during magnetic storms in September 1974. Results are presented for two altitudes where the behavior of nitric oxide is different because of the different chemical lifetimes. At 110 km altitude, the lifetime is a day or more, while at 150 km altitude the lifetime is a few hours. In addition, vertical diffusion is a net sink of NO at 150 km but an important source at 110 km. The Atmosphere Explorer‐C (AE‐C) satellite data show that the midlatitude NO density increased by a factor of 3 above ∼150 km following a large increase in magnetic activity on 15 September 1974 and this increase is well modeled. In the model the storm time increase begins when the Sun illuminates the disturbed thermosphere about 6 hours after the onset of the storm. The model NO density increases above 150 km are the direct result of increased NO production through solar production on storm‐induced enhancements in O2 density and neutral temperature. At 150 km the storm‐enhanced NO density decreases within a day. Downward vertical diffusion of this enhanced NO then causes a large increase in model NO density at 110 km following the storm with a time delay of about 1 day and the enhancement lasts for more than a day. Model calculations indicate that at and above 150 km, any NO transported from high latitudes is likely to be swamped by local chemical processes once the Sun rises. At lower altitudes near 110 km, where the NO density peaks, the aurorally produced NO lasts long enough to be transported from high latitudes to midlatitudes. Thus for horizontal transport from high latitudes to be effective in producing midlatitude increases in NO density, it must take place at low altitudes. Additional calculations for a magnetic storm in the high solar activity period of April 2002 show similar NO behavior to the low solar activity period in September 1974. Since NO radiation is an important sink of thermospheric energy, the midlatitude source associated with enhanced O2 density and neutral temperature is likely to be important in speeding the recovery of the thermosphere and ionosphere following magnetic storms.
Continental crust under compression: A seismic refraction study of South Island Geophysical Transect I, South Island, New Zealand
Authors: Van Avendonk Harm J. A. , Holbrook W. Steven , Okaya David , Austin Jeffrey K. , Davey Fred , Stern Tim
Published: June 2004

The 1996 South Island Geophysical Transect (SIGHT) active source seismic survey was designed to show the style of lithospheric thickening due to late Cenozoic oblique convergence across the Australian‐Pacific plate boundary in New Zealand. As part of this study, two seismic refraction lines were shot across central South Island and offshore extensions of the continental crust in the Tasman Sea and Pacific Ocean. We present the data and a 603 km long seismic velocity profile of the crust and uppermost mantle along one of these seismic transects. A tomographic inversion of 62,563 travel times from crustal and upper mantle refractions and wide‐angle reflections resulted in a model with a two‐layer crust. Upper crustal velocities were between 5.9 and 6.3 km/s, and lower crustal velocities were between 6.5 and 7.0 km/s. Continental compression has locally reduced the seismic velocities in the Pacific plate crust by 0.2–0.3 km/s, a possible effect of high strain and fluids in the crust. The thickening of the crust from 28 km at the east coast of South Island to 37 km beneath the Southern Alps can account for about 25% of the 80–110 km shortening of Pacific plate crust, while the rest must be accounted for by rapid erosion of Mesozoic sedimentary rocks on the west side of the orogen. In our model the lower crust forms a continuous 2–6 km thick layer beneath central South Island. The asymmetric topography of the Southern Alps is reflected in the crustal root which has a steeper flank at the west coast. This observation is consistent with westward underthrusting of Pacific lower lithosphere beneath South Island that has been suggested in earlier studies.
Spaceborne ClO observations by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) before and during the Antarctic major warming in September/October 2002
Authors: Glatthor N. , von Clarmann T. , Fischer H. , Grabowski U. , Höpfner M. , Kellmann S. , Kiefer M. , Linden A. , Milz M. , Steck T. , Stiller G. P. , Mengistu Tsidu G. , Wang D.‐Y. , Funke B.
Published: June 2004

The first ClO profiles retrieved from limb emission spectra recorded by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) Fourier transform spectrometer on board the European research satellite ENVISAT (Environmental Satellite) are presented. These measurements were taken between 8 September and 13 October 2002. They cover the Antarctic major warming around 25 September, an event which had never been observed before. Since ClO has only weak signatures in the midinfrared, more than a dozen of the strongest lines, all situated in the central P branch and Q branch region of the 1‐0 band, were used for profile retrievals, which were based on constrained nonlinear least squares fitting. During the period of investigation, MIPAS measured typical ClO volume mixing ratios (vmrs) between 1 ± 0.4 and 2 ± 0.6 ppbv from 8 September until 23 September in contiguous parts of the dayside lower Antarctic stratosphere (400–625 K levels of potential temperature, Θ), i.e., before and at the beginning of the major warming. After 23 September no significant amounts of ClO were detected anymore, apart from some remains on 26 September. Daily averages of inside vortex daytime ClO showed a slight increase until about 17 September and a subsequent rapid ClO decrease. Further, a positive response of inside vortex nighttime ClO to increasing temperatures due to enhanced Cl2O2 dissociation was detected. Comparison with measurements of the Microwave Limb Sounder (MLS) on the Upper Atmospheric Research Satellite (UARS) from the years 1992–1997 generally showed a similar temporal development. Thus the warming event obviously happened too late to lead to a premature chlorine deactivation significantly different from previous Antarctic winters.
Denmark Strait overflow for Last Glacial Maximum to Holocene conditions
Authors: Kösters Frank , Käse Rolf , Fleming Kevin , Wolf Detlef
Published: June 2004

The Denmark Strait plays an important role as a dense water gateway between the Arctic and the subpolar North Atlantic. Previous studies have shown that the volume transport over the sill is limited by hydraulic constraints. A regional ocean‐circulation model (ROMS) with a horizontal resolution of ≈1/20° degree and 30 sigma layers in the vertical is applied to study the through flow characteristics for Last Glacial Maximum to Holocene conditions. The bathymetry of the gateway region is obtained from a geodynamic model that takes into account the differential ice loading of the adjacent continents. First, the upstream reservoir conditions are systematically changed to test hydraulic limitations for altered bathymetry. Generally, the through flow is less than the predicted maximal value from hydraulic theory by almost 50%. The results indicate that the reduction in gateway depth and aperture owing to glacial‐isostatic processes alone lead to a considerable further reduction of the overflow, by approximately 33%, compared to the present day. Second, the through flow is modeled using average density profiles and wind stress from global model data. The reduction in the density‐driven part of the overflow is partly compensated by an enhanced wind stress but is still reduced by a factor of 5. Owing to the narrowing of the strait during the glacial and the increased northerly wind, the North Icelandic Irminger Current was strongly reduced but still existent.
A focused radar antenna for use in seismic mine detection systems
Authors: Lee Seung H. , Scott Waymond R.
Published: June 2004

An array of radars is developed as a standoff sensor for use in seismic/elastic mine detection systems. The array consists of N radar sensors which operate independently to sense the displacement of the surface of Earth due to elastic waves propagating in Earth. Each of the sensors consists of a lens‐focused, conical, corrugated, horn antenna and a homodyne radar. The focused antenna allows the sensor to have greater standoff than with the previous unfocused antenna while maintaining the spatial resolution required for a mine detection system. By using an array of N sensors instead of a single sensor, the scan rate of the array is improved by a factor of N. A theoretical model for the focused antenna is developed, and an array of two radars is developed and used to validate the theoretical model. The array is tested in the experimental model for the seismic mine detection system. Results from the experimental model are presented.
A 3D partial‐equilibrium model to simulate coupled hydrogeological, microbiological, and geochemical processes in subsurface systems
Authors: Phanikumar M. S. , McGuire Jennifer T.
Published: June 2004

This paper reports the development and application of a three‐dimensional multi‐component reactive transport model (BGTK) to simulate a wide range of biogeochemical processes in subsurface environments. The model can handle both equilibrium and kinetically controlled reactions and is based on the well tested modular models RT3D [Clement et al., 1998] and PHREEQC‐2 [Parkhurst and Appelo, 1999]. Here we describe the details of the new coupled model and demonstrate its capabilities using test problems involving microbial transport in a laboratory column and redox zonation in a contaminated aquifer.
Considerations when using pre‐1979 NCEP/NCAR reanalyses in the southern hemisphere
Authors: Tennant Warren
Published: June 2004

NCEP/NCAR reanalysis data is used widely in the atmospheric sciences. Although these data are generated using homogenous techniques, the effect of changes in the atmospheric observing system is unavoidable. One prominent impact is the introduction of satellite data in 1978, particularly over the southern hemisphere where conventional observations are sparse. This paper attempts to quantify the extent to which the introduction of satellite data impacts both daily and inter‐annual scales of variability, using a Self‐Organizing Map (SOM) analysis technique. It is clear that daily circulation statistics are quite different before and after 1979, and are generally more typical of model climatology before 1979. Inter‐annual variability also appears to be reduced before 1979 in the mid‐latitudes of the southern hemisphere. These caveats need to be borne in mind when performing studies over the southern hemisphere pre‐1979.
Cirrus clouds in the tropical tropopause layer: Role of heterogeneous ice nuclei
Authors: Kärcher B.
Published: June 2004

The role of heterogeneous ice nuclei in controlling the occurrence and properties of cirrus clouds in the tropical tropopause layer is examined with the help of a Lagrangian microphysical cirrus model that includes competition between insoluble and volatile aerosol particles during ice nucleation and small‐scale temperature perturbations. The potential of ice nuclei to influence the moisture budget of air at entry to the stratosphere appears to be limited. Additional dehydration of up to 0.3 ppmv may occur, relative to 1.3 ppmv caused by pure homogeneous freeze‐drying. In contrast, ice nuclei significantly enhance the frequency of occurrence of subvisible cirrus clouds, even when present at concentrations as low as 0.01 L−1. This is likely to be the largest effect of ice nuclei on cirrus near the tropical tropopause. Ice nuclei may also alter cloud radiative forcing by changing the ice water content, increasing the effective crystal radius, and decreasing the cloud lifetime.
Western Pacific coral δ18O records of anomalous Holocene variability in the El Niño–Southern Oscillation
Authors: McGregor Helen V. , Gagan Michael K.
Published: June 2004

Skeletal oxygen isotope ratios in Holocene Porites corals from northern Papua New Guinea record decreases in sea surface temperature (SST) and rainfall during El Niño events. Threshold analysis of seven fossil coral δ18O records spanning the period 7.6–5.4 ka (thousand years ago) shows 8–12 El Niño events/century, significantly less than the 23 events/century recorded by the NINO3.4 Index. The coral reconstructions also show a 15% reduction in El Niño event amplitude for 7.6–5.4 ka, compared to today, which is greater than the suppression given by model studies. In contrast, large and protracted El Niño events are identified for 2.5–1.7 ka. Taken together, the results indicate a non‐linear atmospheric response to Holocene changes in El Niño SST anomalies. We propose that small changes in tropical SST gradients, the positioning of the Intertropical Convergence Zone, and the Pacific tradewind climatology modify the impact of El Niño events on western Pacific rainfall.
Comparison of local precipitation–SST relationship between the observation and a reanalysis dataset
Authors: Arakawa Osamu , Kitoh Akio
Published: June 2004

We defined a grid–scale time–phase relationship between precipitation (PR) and underlying sea surface temperature (SST) as the local PR–SST relationship, and compared the spatial distribution of the relationship in the observation with that in a reanalysis dataset. An analysis using observed pentad mean data shows precipitation lagging SST for two pentads over large areas of tropical oceans. A reanalysis dataset, on the other hand, has a shorter time–phase difference between precipitation and SST than that in the observation and does not match the spatial distribution of the observed local PR–SST relationship over the tropical Indian Ocean and the tropical western Pacific. A reanalysis dataset may not capture the observed local PR–SST relationship in terms of either time–phase difference or spatial distribution because a numerical model in a data assimilation system uses SST as a lower boundary condition as well as the inhomogeneity of observations the system used.
Interplanetary coronal mass ejections observed by Voyager 2 between 1 and 30 AU
Authors: Wang C. , Richardson J. D.
Published: June 2004

We identify and characterize interplanetary coronal mass ejections (ICMEs) observed by Voyager 2 in the heliosphere between 1 and 30 AU. We use abnormally low proton temperatures as the primary identification signature of ICMEs and use other plasma and magnetic field data to verify these identifications. The ICME rate is solar cycle dependent; during the solar minimum of 1986–1987 only a few ICMEs were identified each year, compared with tens per year during solar maxima. The average radial width of ICMEs increases with distance from 1 to ∼15 AU; outside ∼15 AU the average radial width is roughly constant. The radial expansion speed of ICMEs is of the order of the Alfvén speed. Comparison of the radial profiles of the ICME and background solar wind shows that the magnetic field decreases faster in ICMEs than in the solar wind but that the density and temperature decrease more slowly than in the solar wind. Many ICMEs identified at Voyager 2 do not have obvious counterparts at Earth. A one‐dimensional MHD model is employed to associate ICMEs observed at Earth with those observed at Voyager 2.
Substorm dependence of plasmaspheric hiss
Authors: Meredith Nigel P. , Horne Richard B. , Thorne Richard M. , Summers Danny , Anderson Roger R.
Published: June 2004

We analyze wave and particle data from the CRRES satellite to determine the variability of plasmaspheric hiss (0.1 < f < 2 kHz) with respect to substorm activity as measured by AE*, defined as the maximum value of the AE index in the previous 3 hours. The study is relevant to modeling the acceleration and loss of relativistic electrons during storms and understanding the origin of the waves. The plasmaspheric hiss amplitudes depend on spatial location and susbtorm activity, with the largest waves being observed during high levels of substorm activity. Our survey of the global distribution of hiss indicates a strong day‐night asymmetry with two distinct latitudinal zones of peak wave activity primarily on the dayside. Equatorial hiss (∣λm∣ < 15°) is strongest during active conditions (AE* > 500 nT), with an average amplitude of 40 ± 1 pT observed in the region 2 < L < 4 from 0600 to 2100 MLT. Midlatitude (∣λm∣ > 15°) hiss is strongest during active conditions with an average amplitude of 47 ± 2 pT in the region 2 < L < 4 from 0800 to 1800 MLT but extending out beyond L = 6 from 1200 to 1500 MLT. Equatorial hiss at 600 Hz has minimum cyclotron resonant energies ranging from ∼20 keV at L = 6 to ∼1 MeV at L = 2, whereas midlatitude hiss at 600 Hz has minimum resonant energies ranging from ∼50 keV at L = 6 to ∼2 MeV at L = 2. The enhanced equatorial and midlatitude hiss emissions are associated with electron flux enhancements in the energy range of tens to hundreds of keV, suggesting that these electrons are the most likely source of plasmaspheric hiss. The enhanced levels of plasmaspheric hiss during substorm activity will lead to increased pitch‐angle scattering of energetic electrons and may play an important role in relativistic electron dynamics during storms.
Alfvén‐cyclotron fluctuations: Linear Vlasov theory
Authors: Gary S. Peter , Borovsky Joseph E.
Published: June 2004

Linear Vlasov dispersion theory for a homogeneous, collisionless electron‐proton plasma with Maxwellian velocity distributions is used to examine the damping of Alfvén‐cyclotron fluctuations. Fluctuations of sufficiently long wavelength are essentially undamped, but as k∥, the wave vector component parallel to the background magnetic field Bo, reaches a characteristic dissipation value kd, the protons become cyclotron resonant and damping begins abruptly. For proton cyclotron damping, kdc/ωp ∼ 1 for 10−3 ≲ βp ≲ 10−1, where βp ≡ 8πnpkBTp/Bo2 and ωp/c is the proton inertial length. At k∥ < kd, me/mp < βe, and βp ≲ 0.10 the electron Landau resonance becomes the primary contributor to fluctuation dissipation, yielding a damping rate that scales as ωr (k⊥c/ωp)2, where ωr is the real frequency and k⊥ is the wave vector component perpendicular to Bo. As βp increases from 0.10 to 10, the proton Landau resonance makes an increasing contribution to damping of these waves at k∥ < kd and 0° < θ < 30°, where θ = arccos( · o). The maximum damping rate due to the proton Landau resonance scales approximately as βp(kc/ωp)2 over 0.50 ≤ βp ≤ 10. Both magnetic transit time damping and electric Landau damping may contribute to Landau resonant dissipation; in the electron Landau resonance regime the former is important only at propagation almost parallel to Bo, whereas proton transit time damping can be relatively important at both quasi‐parallel and quasi‐perpendicular propagation of Alfvén‐cyclotron fluctuations.
Elastic, piezoelectric, and dielectric properties of 0.58Pb(Mg1/3Nb2/3)O3-0.42PbTiO3 single crystal
Authors: Cao Hu , Schmidt V. Hugo , Zhang Rui , Cao Wenwu , Luo Haosu
Published: June 2004

The elastic, piezoelectric, and dielectric constants of 0.58Pb(Mg1/3Nb2/3)O3-0.42PbTiO3 (PMN-42%PT) were determined experimentally using combined resonance and ultrasonic methods. At room temperature the PMN-42%PT single crystal has tetragonal symmetry. The measured piezoelectric constant d33 is ∼260×10−12 C/N. The electromechanical coefficients k15, k31, k33, and kt are 0.80, 0.39, 0.78, and 0.62, respectively. From the measured material constants the orientational dependence of phase velocities and electromechanical coupling coefficients was calculated. The results showed the tetragonal crystal exhibits isotropy in the X-Y plane and k15, k33, and kt reach their maxima in [001].
Finite-size effect on magnetic properties in Prussian blue nanowire arrays
Authors: Zhou P. H. , Xue D. S.
Published: June 2004

We report the size effect on the magnetic properties in Prussian blue nanowire arrays. Samples with diameters in the range of 50–200 nm have been prepared by an electrodeposition technology with two-step anodizing anodic aluminum oxide films. The Mössbauer measurement results show that the composition of the continuous and highly crystalline Prussian blue nanowires with a fcc cubic structure remains the same as the diameters of nanowires decreasing with respect of Prussian blue bulk. The magnetic properties of the nanowires were investigated with the magnetic property measurement system. The Curie temperature is found to been reduced with respect to Prussian blue bulk, resulting from the diminution of the average number of nearest magnetic interaction neighbors and magnetic exchange interaction constants as the diameters of nanowires decrease. The low temperature hysteresis loops is also discussed.
Time-dependent density-functional calculations of S–S1 transition energies of poly(p-phenylene vinylene)
Authors: Han Young-Kyu , Lee Sang Uck
Published: June 2004

We used time-dependent density-functional-theory (TDDFT) approaches to calculate absorption (S0→S1) and emission (S1→S0) transition energies of poly(p-phenylene vinylene) (PPV). The absorption and emission energies were estimated to be 2.44 and 2.16 eV, respectively, from the extrapolation of calculated results for oligomers. Comparisons with available experimental data demonstrated that TDDFT is a very reliable tool for investigating the electronic transitions of PPV.
Practical and theoretical modal analysis of photonic crystal waveguides
Authors: Märki Iwan , Salt Martin , Herzig Hans Peter
Published: June 2004

We present practical and theoretical, stage-by-stage analysis of light propagation around a 90° corner in a two-dimensional photonic crystal waveguide. Using a series of different samples we quantify the coupling efficiency between the conventional ridge waveguide and the photonic crystal waveguide as well as the bending efficiency around the 90° corner. From this, the transmission spectra indicate nearly 90% bending efficiency. We compare the experimental results to the three-dimensional simulated band diagram and field distribution. The propagating defect modes are identified in detail and we show that efficient transmission around sharp bends in photonic crystal waveguides can be achieved for leaky modes above the light line with short photonic crystal sections.
Electronic stopping cross sections in silicon carbide for low-velocity ions with 1⩽Z1⩽15
Authors: Janson M. S. , Linnarsson M. K. , Hallén A. , Svensson B. G.
Published: June 2004

The mean projected range Rp for a large number of H1, H2, Li7, B11, N14, O16, Al27, and P31 implantations into SiC with ion energies ranging from 0.5 keV to 4 MeV are investigated. From the Rp data the electronic stopping cross sections Se are extracted. A plot of the extracted Se at a fixed velocity—below the Fermi velocity of the target valence electrons—versus the ion atomic number Z1 reveals a local maximum around Z1=7. Furthermore, in this velocity regime a slower than velocity-proportional energy dependence, Se∝E0.30–E0.45, is found for ions with 1⩽Z1⩽8, while Al27 and P31 exhibit an energy dependence just above velocity-proportionality: Se∝E0.52, for both ions. These finding are in good qualitative agreement with the low-velocity electronic stopping behavior previously reported for carbon targets.
Two-coefficient Cauchy model for low birefringence liquid crystals
Authors: Li Jun , Wu Shin-Tson
Published: June 2004

The three- and two-coefficient Cauchy equations are derived based on the three-band model for the wavelength- and temperature-dependent refractive indices of anisotropic liquid crystals. For high birefringence (Δn⩾0.2) liquid crystals, the three-coefficient Cauchy model fits experimental results more accurately than the two-coefficient model. For low birefringence (Δn⩽0.12) liquid crystal mixtures the two-coefficient Cauchy model works equally well as the three-coefficient model in the off-resonance spectral region.
Oxidation of nitrogen-implanted silicon: Comparison of nitrogen distribution and electrical properties of oxides formed by very low and medium energy N2+ implantation
Authors: Skarlatos D. , Kapetanakis E. , Normand P. , Tsamis C. , Perego M. , Ferrari S. , Fanciulli M. , Tsoukalas D.
Published: June 2004

In a previous work [Skarlatos et al., J. Appl. Phys. 93, 1832 (2003)] we investigated the influence of implantation energy on oxide growth and defect formation in nitrogen-implanted silicon substrates. It was shown that as the implantation energy decreases from medium to very low values the oxide reduction decreases. This was attributed to nitrogen out-diffusion, which is more effective when nitrogen is placed closer to the silicon surface. On the other hand very low implantation energy avoids the formation of dislocation loops in the silicon substrate, a key point for modern devices performance. In this second part we compare the nitrogen distribution and electrical properties of ultrathin (25–30 Å) oxides grown under the same oxidation conditions on very low (3 keV) and medium (25 keV) energy nitrogen-implantated silicon. Nitrogen distribution measurements show that a lower content of nitrogen remains within the oxides formed using 3 keV energy as compared to the 25 keV case supporting the results of the first part of this work. So at very low implantation energy the same oxide thickness is obtained increasing the implantation dose. On the other hand oxides formed through very low energy implants show superior electrical properties in terms of surface states and leakage currents due to the lower damage induced in the silicon substrate.
Slow positrons elastically scattered by solid targets
Authors: Chaoui Zine-El-Abidine , Bouarissa Nadir
Published: June 2004

Total and transport elastic scattering cross sections for positrons impinging on solid targets have been computed for energies in the range 10–10 000 eV. The phase shifts have been calculated by numerically solving the Schrödinger equation. The results have been discussed and compared where possible with other tabulations. Special attention has been given to the effect of the correlation potential. The latter was found to have much effect on the total elastic scattering cross sections while its effect on transport elastic scattering cross sections is more important when the positron energy is lowered.
Microfluidic transport based on direct electrowetting
Authors: Satoh Wataru , Loughran Michael , Suzuki Hiroaki
Published: June 2004

An integrated microfluidic system was fabricated which functions by deliberately manipulating interfacial tension. A distinctive characteristic of our system is the use of an array of adjacent, elongated, working electrodes and protruding polydimethylsiloxane open-flow channels. Microfluidic transport was realized directly on the bare gold electrode surface in the absence of an additional dielectric layer. By changing the potential of the working electrode to a negative potential, a liquid column could be transported from one end of an elongated working electrode to the other end. Transport of the liquid column could be altered without any valves by switching on the adjacent electrode in a given direction. The flow velocity depended on the applied potential, i.e., the velocity could be altered by deliberate manipulation of the electrode potential. In addition, the flow velocity increased as the dimensions of the flow channel decreased. The applied voltage was less than 2 V, and the power consumption was in the order of tens of μW.
Behavior of the contacts of quantum Hall effect devices at high currents
Authors: Meziani Y. M. , Chaubet C. , Bonifacie S. , Raymond A. , Poirier W. , Piquemal F.
Published: June 2004

We have analyzed the behavior of contacts of quantum Hall effect devices while increasing the current through the sample. Experiments have been performed in the i=2 plateau, which is used in all metrological measurements of the von Klitzing constant RK, before the onset of dissipation. Using only electrical measurements, we show that a high electric field zone appears in the vicinity of the current contact which injects the electrons in the two-dimensional electron gas, when the current is increased. This heating phenomenon develops in the region close to the source, increases the electronic temperature in the sample, and limits the precision in the measurement of RK. We have studied several samples of different width, using a well-defined configuration for the measurements. It is observed that the threshold current for the onset of the voltage drop across the contact increases with the width of the Hall bar. Consequences for high precision measurements are discussed in terms of experimental protocol and of contact’s geometry.
Nano-transistors in the Landauer–Büttiker formalism
Authors: Nemnes G. A. , Wulf U. , Racec P. N.
Published: June 2004

We investigate transport in nanotransistors in the Landauer–Büttiker formalism. A systematic linearization of the general expression for the current response yields the quantum version of the small signal equivalent circuit. This equivalent circuit can be compared with classical schemes so that explicit quantum mechanical expressions for the circuit elements can be extracted. Reducing our analysis to an effective Y-parameter description of the equivalent circuit we find the multi-terminal Büttiker formula except for one extra term. We show that this extra term is essential for the operation of transistors. An application of our theory to a simple transistor model yields a description of mismatch oscillations in the source-drain current experimentally observed in nano-transistors.
Strain-free bulk-like GaN grown by hydride-vapor-phase-epitaxy on two-step epitaxial lateral overgrown GaN template
Authors: Gogova D. , Kasic A. , Larsson H. , Hemmingsson C. , Monemar B. , Tuomisto F. , Saarinen K. , Dobos L. , Pécz B. , Gibart P. , Beaumont B.
Published: June 2004

Crack-free bulk-like GaN with high crystalline quality has been obtained by hydride-vapor-phase-epitaxy (HVPE) growth on a two-step epitaxial lateral overgrown GaN template on sapphire. During the cooling down stage, the as-grown 270-μm-thick GaN layer was self-separated from the sapphire substrate. Plan-view transmission electron microscopy images show the dislocation density of the free-standing HVPE-GaN to be ∼2.5×107 cm−2 on the Ga-polar face. A low Ga vacancy related defect concentration of about 8×1015 cm−3 is extracted from positron annihilation spectroscopy data. The residual stress and the crystalline quality of the material are studied by two complementary techniques. Low-temperature photoluminescence spectra show the main neutral donor bound exciton line to be composed of a doublet structure at 3.4715 (3.4712) eV and 3.4721 (3.4718) eV for the Ga- (N-) polar face with the higher-energy component dominating. These line positions suggest virtually strain-free material on both surfaces with high crystalline quality as indicated by the small full width at half maximum values of the donor bound exciton lines. The E1(TO) phonon mode position measured at 558.52 cm−1 (Ga face) by infrared spectroscopic ellipsometry confirms the small residual stress in the material, which is hence well suited to act as a lattice-constant and thermal-expansion-coefficient matched substrate for further homoepitaxy, as needed for high-quality III-nitride device applications.