bluuebunny/crossref_metadata_2025 huggingface dataset:
Endogenous MHC Class II Processing of a Viral Nuclear Antigen After Autophagy
Authors: Paludan Casper , Schmid Dorothee , Landthaler Markus , Vockerodt Martina , Kube Dieter , Tuschl Thomas , Münz Christian
Published: December 2004

CD4
+
T cells classically recognize antigens that are endocytosed and processed in lysosomes for presentation on major histocompatibility complex (MHC) class II molecules. Here, endogenous Epstein-Barr virus nuclear antigen 1 (EBNA1) was found to gain access to this pathway by autophagy. On inhibition of lysosomal acidification, EBNA1, the dominant CD4
+
T cell antigen of latent Epstein-Barr virus infection, slowly accumulated in cytosolic autophagosomes. In addition, inhibition of autophagy decreased recognition by EBNA1-specific CD4
+
T cell clones. Thus, lysosomal processing after autophagy may contribute to MHC class II–restricted surveillance of long-lived endogenous antigens including nuclear proteins relevant to disease.
Surface-enhanced Raman scattering (SERS) from a silver electrode modified with oxazine 720
Authors: Brolo Alexandre G , Sanderson Aaron C
Published: December 2004

Electrochemical and spectroelectrochemical data was obtained for a silver electrode modified with oxazine 720 immersed in 0.2 mol L1 KCl solution. A quasi-reversible redox behaviour was observed for the modified electrode. The electrochemical charges, obtained during either the anodic or the cathodic processes, were higher than expected for a monolayer of flat-adsorbed oxazine 720. Surface-enhanced Raman scattering (SERS) was recorded in situ for different applied potentials. Although the tilt angle was not determined, the analysis of the most enhanced vibrational modes in the SERS data, in conjunction with results of a DFT calculation, suggest that the molecule is adsorbed with its ring perpendicular to the electrode surface. This adsorption mode allows a higher surface packing than for flat-adsorbed molecules, consistent with the electrochemically estimated surface coverage. The potential dependence of the SERS signal is consistent with the redox process observed from cyclic voltammetry. The SERS intensities remain relatively constant between 200 and 500 mV (vs. Ag | AgCl | Clsat), but decrease drastically as the applied potential is made more negative than the onset of oxazine 720 reduction at 500 mV. The spectroelectrochemical data indicate that the molecule remains adsorbed at the SERS active sites even in its reduced form.Key words: phenoxazine electrochemistry, oxazine 720, modified electrodes, surface-enhanced Raman scattering, SERS, molecular orientation.
In situ ATR-SEIRAS study of adsorption and phase formation of trimesic acid on Au(111-25 nm) film electrodes
Authors: Han B , Li Z , Pronkin S , Wandlowski Th.
Published: December 2004

The adsorption and phase formation of 3 mmol L1 trimesic acid (TMA) on Au(111-25 nm) film electrodes in contact with aq. 0.1 mol L1 HClO4 electrolyte have been investigated by in situ ATR-SEIRAS, cyclic voltammetry, chronoamperometry, and STM measurements. Depending on the applied electrode potential, TMA molecules assemble in three distinctly different 2D ordered adlayers. In the range 0.10 < E < 0.50 V, planar-oriented molecules form an open ring honeycomb pattern (phase I) stabilized by directional hydrogen bonds. Interfacial water molecules are being replaced. A close-packed, physisorbed adlayer II forms at higher potentials in the range 0.58 < E < 0.75 V. Further increase of the electrode potential causes an orientation change. An initially disordered phase transforms into an ordered, stripe-like chemisorbed adlayer III of perpendicularly oriented TMA molecules (0.90 < E < 1.20 V). One carboxylate group per molecule is bound to the electrode surface, while the two other protonated carboxyl groups are directed toward the electrolyte, and act as structure-determining components of a hydrogen-bonded molecular ladder network. Strongly hydrogen-bonded and isolated water species are co-adsorbed. The potential-induced formation of chemisorbed TMA proceeds in two steps: (i) orientation change from planar to a disordered tilted and (or) perpendicular phase IIIa (τ < 5 ms) according to a Langmuir-type kinetics; (ii) subsequently, the chemisorbed TMA molecules align into a highly ordered, stripe-like phase IIIb with co-adsorbed water species. Key words: ATR-SEIRAS, trimesic acid, Au(111), supramolecular assembly.
Distribution of oxides on iron materials used for remediation of organic groundwater contaminants  Implications for hydrogen evolution reactions
Authors: Odziemkowski M S , Simpraga R P
Published: December 2004

The distribution of oxides on commercial iron materials used for remediation of organic groundwater contaminants was studied using confocal Raman microspectroscopy. Raman microprobe mapping experiments revealed that commercial iron materials used for the construction of permeable reactive barriers are covered with an oxide film consisting of an inner film of magnetite Fe3O4 and an outer film of Fe2O3. The calculated probability of the charge transfer process (i.e., electron tunnelling probability) at commercial Fe | Fe2O3 (semiconductor) | solution interfaces approaches zero, indicating that "as received" commercial iron materials should not be reactive towards both organic contaminants and water. The combination of OCP (corrosion potential)  time measurements with in situ Raman spectroscopy demonstrated that the breakdown of the protective Fe2O3 oxide film followed by autoreduction of Fe2O3 is a requirement for the commercial materials to be chemically active towards both water and organic contaminants. Hydrogen evolution reactions on metals and oxide-covered iron were also investigated. In particular, spectroscopic evidence for adsorption of atomic hydrogen on polycrystalline Pt is presented. The possibility of adsorption of H on magnetite-covered iron was considered using thermodynamic calculations after Marcus and Protopopoff. The evolution of hydrogen on commercial iron materials is described. It is suggested that the separation of the anodic and cathodic sites because of opening of pores in the bulk metallic Fe and the involvement of spill-over hydrogen may play a crucial role in the catalytic hydrogenation of groundwater contaminants.Key words: Raman microprobe confocal spectroscopy, iron oxides, hydrogen evolution, remediation of organic groundwater contaminants.
Phase behaviour and dynamics in ethylammonium halide salts
Authors: Ratcliffe Christopher I
Published: December 2004

1H and 2H NMR spin-lattice relaxation times (T1) have been studied as a function of temperature to obtain activation energies for the threefold reorientations of CH3 groups (Ea = 22.83, 18.95, and 18.39 kJ mol1) and NH3 groups (Ea = 47.64, 45.31, and 28.74 kJ mol1) in the β-phases of ethylammonium chloride, -bromide, and -iodide, respectively, for comparison with barriers determined from Raman torsional frequencies. T1, 2H NMR lineshapes, and DSC studies have been used to clarify the existence of a β → α phase transition above room temperature in all three salts, and the absence of a transition at low temperature. 2H NMR lineshape analysis indicates a rapid n-fold (probably fourfold) reorientation of the whole molecule in the α-phase. This motion occurs about an axis in the molecular CCN mirror plane in the bromide and iodide. In the chloride, the axis is in the plane perpendicular to the bisector of the DCD bond angle.Key words: ethylammonium halides, solid state 1H and 2H NMR, molecular dynamics, rotational barriers, phase behaviour.
The reductive deposition of quaternary pyridinium corrosion inhibitor multilayers on glassy carbon electrodes
Authors: Wong Rick PC , Wong Jennifer E , Birss Viola I
Published: December 2004

The redox behaviour of several quaternary pyridinium corrosion inhibitors ("Quats") at glassy carbon (GC) electrodes has been investigated in neutral aqueous solutions. The primary emphasis is on n-butyl-3-(N-octyl carbamyl)pyridinium bromide, one of the Quats determined to have very good corrosion inhibition properties based on parallel weight loss experiments. It is demonstrated that the reduction of the Quats, which occurs in a two-electron reaction at potentials negative of 1.0 V vs. SSCE, results in the formation of a neutral product. This forms a porous film on the electrode surface, with clusters that expand and thicken as more Quat deposits, as confirmed by atomic force microscopy. The film charge density reaches a maximum of ~4 mC/cm2, equivalent to more than 100 monolayers of Quat, after which no further Quat can be deposited, suggesting full surface coverage by a nonconducting product. The Quat multilayer can then be redissolved at potentials positive of ~ 0.2 V, during its oxidation back to its original solution-soluble form. Key words: quaternarized pyridinium compounds, reductive film deposition, glassy carbon, multilayer, corrosion inhibitors, cyclic voltammetry, AFM.
Western white pine growth relative to forest openings
Authors: Jain Theresa B , Graham Russell T , Morgan Penelope
Published: December 2004

In northern Rocky Mountains moist forests, timber harvesting, fire exclusion, and an introduced stem disease have contributed to the decline in western white pine (Pinus monticola Dougl. ex D. Don) abundance (from 90% to 10% of the area). Relations between canopy openings (0.1–15 ha) and western white pine growth within different physical settings are identified. Objectives include relating western white pine seedling and sapling growth to canopy opening attributes (defined by fisheye photography), identifying western white pine competitive thresholds (occupancy, competitive advantage, free-to-grow status) in relation to opening size, and relating canopy opening attributes to overstory density descriptors. We sampled 620 western white pine plus competing trees, canopy opening characteristics, landscape position, and overstory density descriptors. Analysis included log-linear and polynomial regression. Visible sky (canopy opening) and tree age were significantly related to growth of selected pines. Radiation explained less variation in growth than canopy opening. Thresholds for western white pine to occupy a site (>23% canopy opening), gain a competitive advantage (>50% canopy opening), and achieve free-to-grow status (>92% canopy opening) over western hemlock were developed. There was a significant although weak (R2 < 0.12) relation between canopy opening and overstory density descriptors.
A model of fragmentation in the Canadian boreal forest
Authors: Tchir T L , Johnson E A , Miyanishi K
Published: December 2004

Ecological studies have generally examined forest fragmentation in terms of descriptive metrics or simulation using Monte Carlo or percolation processes that assume fragmentation is a random process. However, most fragmentation results from human decisions on agricultural settlement. This study used a previously tested rule-based agricultural settlement process model (GEOMOD2) to describe which parts of a boreal forest landscape are selectively cleared for agriculture. Nearness to neighbors, amount of stoniness, soil type, and soil texture best explained the fragmentation process. To compare settler's decisions on the productivity of the landscape with moisturenutrient gradients, we used a hydrological topographic index to capture the variability of wetness according to hillslope position. Results showed that settlers were selecting higher hillslope positions irrespective of substrate (glaciolacustrine or glacial till); i.e., they appear to have used observable attributes such as stoniness, soil texture, and hillslope position rather than soil productivity in making settlement decisions. Thus, the species richer upper hillslopes of aspen parkland (glaciolacustrine) and aspen and white spruce forest (glacial till) were settled first, while the species poorer lower hillslopes of aspen forest (glaciolacustrine) and white spruce and balsam fir forest (glacial till) were settled later.
Commercial tree regeneration 6 years after high-intensity burns in a seasonally dry forest in Bolivia
Authors: Kennard Deborah
Published: December 2004

The effects of three site-preparation treatments (high-intensity burn, low-intensity burn, and mechanical cleaning with machetes and chainsaws) on the regeneration of commercial tree species, composition and structure of competing vegetation, and soil chemical and structural properties were evaluated in a seasonally dry forest in southeast Bolivia. Six years after controlled burns, the high-intensity burn treatment had the both the highest density and the tallest individuals of shade-intolerant commercial tree species. Competing vegetation was also less dominant in the high-intensity burn treatment relative to other treatments. However, high-intensity burns were not beneficial for commercial tree species with shade-tolerant or intermediate regeneration. Soil analyses revealed that certain changes in soil texture and soil chemistry (e.g., Ca and Mg concentrations and cation exchange capacity) caused by high-intensity burns persisted 6 years after the fires. These findings confirm that this suite of shade-intolerant commercial species requires very intense disturbances for their regeneration. However, several ecological, economic, and social barriers currently preclude the management-scale application of prescribed fire in Bolivia. More research is needed on cost-effective treatments to improve regeneration.
Conservation priorities for peripheral species: the example of British Columbia
Authors: Bunnell Fred L , Campbell R Wayne , Squires Kelly A
Published: December 2004

Most jurisdictions must assign conservation priorities to peripheral species. British Columbia hosts more than 1300 peripheral taxa, about 900 of which appear on the Red and Blue Lists prepared by the province to guide conservation actions. Conversely, fewer than half of the endemic taxa, or taxa for which the province has major global stewardship responsibility, appear on provincial Red and Blue Lists. We examine why we conserve and list species, concluding that the primary scientific or practical reason is to sustain genetic variability. We consider two broad kinds of peripheral species: disjunct (geographically marginal) populations and continuous peripheral populations that straggle irregularly across provincial boundaries. Populations of both groups may be ecologically marginal, with λ < 1. We document the degree to which each group enters provincial Red and Blue Lists. Factors used to modify rankings of risk are correlated in a fashion that artificially biases continuous peripheral populations toward rankings of higher risk. Federal initiatives in recovery plans for most continuous peripheral species appear doomed to failure for sound biological reasons. We note alternative approaches to ranking species for conservation action and recommend that conservation efforts for peripheral species be focused on disjunct peripheral populations, rather than continuous peripheral populations.
Fire disturbance during climate change: failure of postfire forest recovery on a boreal floodplain
Authors: Bouchon Élodie , Arseneault Dominique
Published: December 2004

We used tree remains to document the failure of postfire forest recovery following a 1941 fire on a boreal floodplain along a third-order stream in northern Quebec. Two sites, one with postfire shrubs and the other an unburned forest, were studied. Tree remains on the floodplain and within the stream channel at the shrub site suggest the former presence of a forest stand similar to present-day vegetation at the forest site. At both sites, black spruce (Picea mariana (Mill.) BSP) has been the dominant tree species, whereas eastern larch (Larix laricina (Du Roi) K. Koch) and balsam fir (Abies balsamea (L.) Mill.) have made up only a small proportion of all living and dead stems. Sustained tree recruitment before the mid-19th century was followed by much reduced recruitment, in synchrony with the well-documented increasing trend of winter precipitation in northern Quebec. In combination with more frequent spring floods during the 20th century, the 1941 fire at the shrub site probably reduced the density of conifer stems, increased the abundance of shrubs, and excluded the fire-sensitive balsam fir and eastern larch. The fire also abruptly increased inputs of tree remains into the stream channel. Because of low establishment rate and slow growth of postfire conifers, forest recovery towards prefire tree density is unlikely under present-day conditions. Frequent fires in boreal landscapes, along with the anticipated increase of precipitation, suggest that some floodplains and associated streams may respond similarly to future climate change.
Fire-related landform associations of remnant old-growth trees in the southern Washington Cascade Range
Authors: Keeton William S , Franklin Jerry F
Published: December 2004

The spatial distribution of biological legacies left by natural disturbances is an important source of variability in forest development. We investigated one type of biological legacy: remnant old-growth trees persisting in mature Douglas-fir forests. We hypothesized that persistence varies with topographic heterogeneity influencing fire behavior. Our two study areas are located in the southern Washington Cascade Range, USA. They have an unfragmented, mature forest cover that regenerated following wildfire. We mapped all remnant old-growth trees (live and dead) within 4.26.4 km long belt transects. Digital elevation models were used to generate convergent and divergent landform classes. Frequency analysis was used to test for landform associations. Live remnant western hemlock and western redcedar were strongly associated with convergent landforms and aspects that had greater availability of soil moisture. Live remnant Douglas-fir were most abundant, but were not correlated with convergence or divergence, although certain landforms had higher concentrations. Remnant snags were abundant across convergent and divergent landforms. We conclude that species with low fire resistance survive most frequently on landforms that have a dampening effect on fire intensity. Topographic variability may indirectly influence ecological functions associated with biological legacies by affecting the spatial distributions of remnant old-growth trees.
Effects of surrounding forest and site conditions on growth reduction of balsam fir and spruce caused by spruce budworm defoliation
Authors: MacKinnon Wayne E , MacLean David A
Published: December 2004

The species composition of surrounding forest and site characteristics have been postulated to influence growth loss caused by eastern spruce budworm (Choristoneura fumiferana Clem.) defoliation. Forty spruce (Picea spp.) and balsam fir (Abies balsamea (L.) Mill.) stands located in north-central New Brunswick, Canada, were measured for defoliation and tree growth and used to determine the effects of surrounding forest (softwood, mixedwood), site (wet soil  nutrient poor; moist soil  nutrient rich), and species group (balsam fir, spruce) on growth reduction caused by spruce budworm. Stem analysis of six trees per stand (total 240 trees) determined mean specific volume increment (SVI) per year in 19731993. There was relatively little defoliation during the 19891993 measurement period, and regression analyses showed that SVI was significantly (p = 0.0299) related to mean defoliation for only one of eight treatment classes: balsam fir on moistrich sites in mixedwood forests. However, two periods of earlier growth reduction were evident, and analysis of variance showed that balsam fir on wetpoor sites sustained 12% greater (p = 0.0071) reduction in SVI from 1987 to 1990 than balsam fir on moistrich sites. White spruce (Picea glauca (Moench) Voss) sustained 13% greater (p = 0.0198) reduction in SVI from 1973 to 1978 than red spruce (Picea rubens Sarg.)  black spruce (Picea mariana (Mill.) BSP). Surrounding forest type did not significantly affect SVI reduction from 1973 to 1978 or from 1987 to 1990, but from 1973 to 1978 stands in softwood forest sustained 5%8% more growth reduction than those in mixedwood forest.
High-resolution analysis of stem increment and sap flow for loblolly pine trees attacked by southern pine beetle
Authors: Wullschleger Stan D , McLaughlin Samuel B , Ayres Matthew P
Published: December 2004

Manual and automated dendrometers, and thermal dissipation probes were used to measure stem increment and sap flow for loblolly pine (Pinus taeda L.) trees attacked by southern pine beetle (Dendroctonus frontalis Zimm.) in east Tennessee, USA. Seasonal-long measurements with manual dendrometers indicated linear increases in stem circumference from April through June. Changes in stem circumference slowed after this time, and further increases were either modest or not observed. These effects coincided with a massive midsummer infestation of trees with southern pine beetles. High-resolution measurements with automated dendrometers confirmed that, while early-season increases in radial increment were positive, daily rates of radial increment for slow- and fast-growing trees were largely negative in early to late July. Sap velocity also declined despite favorable weather conditions, but these reductions were not observed until mid-August. Thus, effects on radial increment and stem circumference preceded those on sap velocity by several weeks. The timing of these events, combined with the known developmental rate of southern pine beetles, suggest that disruption of whole-tree water balance is not a prerequisite for the success of attacking beetles or for oviposition by colonizing females and larval development, all of which were completed by early August. Additional field experiments that use high-resolution techniques to measure stem increment and sap flow are needed to more rigorously characterize temporal changes in host physiology during initial invasion and colonization of trees by southern pine beetle.
GROWTH OF SiC NANOSTRUCTURES ON Si (100) USING LOW ENERGY CARBON ION IMPLANTATION AND ELECTRON BEAM RAPID THERMAL ANNEALING
Authors: MARKWITZ A. , JOHNSON S. , RUDOLPHI M. , BAUMANN H.
Published: December 2004

A combination of 10 keV 13 C low energy ion implantation and electron beam rapid thermal annealing (EB-RTA) is used to fabricate silicon carbide nanostructures on (100) silicon surfaces. These large ellipsoidal features appear after EB-RTA at 1000°C for 15 s. Prior to annealing, the silicon surfaces are virgin-like flat. Atomic force microscopy was used to study the morphology of these structures and it was found that the diameter and number of nanoboulders are linearly dependent on the implantation fluence. Further, a linear relationship between nanoboulder diameter and spacing suggests crystal coarsening is a fundamental element in the growth mechanism.
SUPPRESSION OF SILICON NANOSTRUCTURE GROWTH BY MEDIUM ENERGY NITROGEN ION IMPLANTATION
Authors: KENNEDY V. J. , JOHNSON S. , MARKWITZ A. , RUDOLPHI M. , BAUMANN H. , MAGUDAPATHY P. , NAIR K. G. M.
Published: December 2004

A novel nanofabrication technology to produce dense arrays of silicon nanowhiskers up to 20 nm high has been developed. This rapid and simple technology employs electron beam rapid thermal annealing (EB-RTA) of untreated silicon. Pre-implantation of the silicon substrate with nitrogen at low energy (5 keV) has been shown to suppress the formation of these nanostructures. In this paper we demonstrate identical silicon nanostructure growth suppression when produced following nitrogen ion implantation at 50 keV and 100 keV. Specimens were implanted at room temperature and subsequently annealed at 1000°C for 15 s (temperature gradient 5° Cs -1). Specific results obtained from AFM and NRA analysis are discussed highlighting the possibility of silicon nanowhisker growth control using nitrogen ion implantation.
AB-INITIO CALCULATIONS OF THE OPTICAL BAND GAP OF TiO2 THIN FILMS
Authors: WUNDERLICH WILFRIED , MIAO LEI , TANEMURA MASAKI , TANEMURA SAKAE , JIN PING , KANEKO KENJI , TERAI ASUKA , NABATOVA-GABIN NATALIYA , BELKADA RACHID
Published: December 2004

Titanium dioxide has been extensively studied in recent decades for its important photocatalytic application in environmental purification. The search for a method to narrow the optical band gap of TiO 2 plays a key role for enhancing its photocatalytic application. The optical band gap of epitaxial rutile and anatase TiO 2 thin films deposited by helicon magnetron sputtering on sapphire and on SrTiO 3 substrates was correlated to the lattice constants. The optical band gap of 3.03 eV for bulk-rutile increased for the thin films to 3.37 on sapphire. The band gap of 3.20 eV for bulk-anatase increases to 3.51 on SrTiO 3. In order to interpret this expansion, ab-initio calculations were performed using the Vienna ab-initio software. The calculations for rutile as well anatase show an almost linear increase of the band gap width with decreasing volume or increasing lattice constant a. The calculated band gap fits well with the experimental values. The conclusion from these calculations is, in order to achieve a smaller band gap for both, rutile or anatase, the lattice constant c has to be compressed, and a has to be expanded.
MAGNETIC PROPERTIES OF Co-FERRITE AND SiO2-DOPED Co-FERRITE THIN FILMS AND POWDERS BY SOL–GEL
Authors: WANG Y. C. , DING J. , LIU B. H. , SHI Y.
Published: December 2004

Thin films and powders of Co -ferrite and SiO 2-doped Co -ferrite were fabricated via the sol–gel method. The structural and magnetic properties of the films and powders were investigated with X-Ray Diffractometer (XRD), Vibrating Sample Magnetometer (VSM), Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). VSM measurements showed an enhancement of coercivity by SiO 2-doping for Co -ferrite powders and thin films (coercivity of 3.5 kOe in SiO 2-doped thin films). XRD and SEM investigations revealed a nanostructure of the thin films. Low surface roughness was observed in our AFM study.
EFFECT OF NANO-Y-ZrO2 ADDITION ON THE MICROSTRUCTURE AND CRITICAL CURRENT DENSITY OF MgB2 SUPERCONDUCTORS
Authors: YAO Q. W. , WANG X. L. , LI A. H. , DOU S. X. , MUNROE P. R.
Published: December 2004

Polycrystalline MgB 2 samples with 0, 5, 10, and 20 wt% nano- Y - ZrO 2 (YSZ) powder addition were prepared by short time, as little as several minutes, or long time in-situ reaction process. The phases, microstructures and flux pinning behaviors were characterized using X-ray diffractometry (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscope (TEM) and Magnetic Measurements. Results indicated that nano-YSZ particles included in MgB 2 grains. Samples doped with 10wt% YSZ powders showed new record of critical current density Jc as high as 1×106 and 4×106 A/cm 2 in low magnetic fields at 30 and 20K, respectively. However, the Jc drops faster compared to that made by long time sintering samples. It is proposed that the improved Jc in low fields was due to the enhanced density of the sample, which was caused by the YSZ nano-particle inclusion.
DEVELOPMENT OF CARBON-BASED COATING OF EXTREMELY HIGH TOUGHNESS WITH GOOD HARDNESS
Authors: ZHANG S. , BUI X. L. , FU Y. , DU H.
Published: December 2004

Metallic Al was doped into amorphous carbon (a-C) to form a matrix of a-C(Al) of very low residual stress and high toughness at the expense of some hardness. Nanocrystallites of TiC (nc-TiC) of a few nanometers in size were embedded in this matrix to bring back the hardness. The nanocomposite coating of nc-TiC/a-C(Al) was deposited via co-sputtering of graphite, Ti , and Al targets. Although the nanocomposite coating exhibited a moderately high hardness (about 20 GPa), it possessed extremely high toughness (about 55% of plasticity during indentation deformation) and low residual stress (less than 0.4 GPa), smooth (Ra=5.5 nm ), and hydrophobic surface (contact angle with water reaches 100°).
SYNTHESIS OF Fe NANOPARTICLES BY REDOX REACTION USING AN ELECTRON BEAM DEPOSITION TECHNIQUE
Authors: JAIN S. , CHAN S. Y. , ADEYEYE A. O. , BOOTHROYD C. B.
Published: December 2004

A new technique for synthesizing Fe nanoparticles based on an electron beam deposition technique from a Fe 2 O 3 source has been developed. We deposited Fe 2 O 3 films directly on Si (001) substrates, Al and Cu buffer layer, and observed the formation of Fe nanoparticles at the Si (001) and Al interfaces respectively. The Al at the interface is oxidized to Al 2 O 3 and Si is oxidized to SiO 2. For films deposited on Cu buffer layer, however, no Fe nanoparticles were formed. We explain our results in terms of the enthalpy of formation of the oxides. The enthalpy of formation of SiO 2 and Al 2 O 3 is much lower than that of Fe 2 O 3, thus promoting the formation of Fe nanoparticles. The enthalpy of formation of CuO is however, greater than that of Fe 2 O 3 thus forbidding the formation of Fe nanoparticles. This is in agreement with both X-ray Photoelectron Spectroscopy (XPS) depth profile analysis and Transmission Electron Microscopy (TEM).
SIMULATION OF HIGH CURRENT FIELD EMISSION FROM VERTICALLY WELL-ALIGNED METALLIC CARBON NANOTUBES
Authors: KOH W. S. , ANG L. K.
Published: December 2004

We have studied the intense electron beams emitted from multiple metallic, vertical and well-aligned Carbon Nanotube (CNT) field emitters. A two-dimensional (2D) particle-in-cell simulation code MAGIC2D is used to obtain the I–V characteristics near to the apex of the emitters' surface for a given applied electric field and field enhancement factor over a wide range of parameters. The effects of electron space charge and electric field shielding from neighboring emitters are compared in low current and high current regimes. It is found that the electron space charge is dominant in high current regime, where the Fowler–Nordheim (FN) law becomes the 2D Child–Langmuir (CL) law. The emitter spacing, number of emitters, and emitter's uniformity are also particularly studied, and they are more critical in low current regime. Smooth transition from the FN law to CL law is demonstrated.
Role of endothelin in α-adrenoceptor coronary vasoconstriction
Authors: Gorman Mark W. , Farias Martin , Richmond Keith N. , Tune Johnathan D. , Feigl Eric O.
Published: December 2004

It has been proposed that α-adrenoceptor vasoconstriction in coronary resistance vessels results not from α-adrenoceptors on coronary smooth muscle but from α-adrenoceptors on cardiac myocytes that stimulate endothelin (ET) release. The present experiments tested the hypothesis that the α-adrenoceptor-mediated coronary vasoconstriction that normally occurs during exercise is due to endothelin. In conscious dogs ( n = 10), the endothelin ETA/ETBreceptor antagonist tezosentan (1 mg/kg iv) increased coronary venous oxygen tension at rest but not during treadmill exercise. This result indicates that basal endothelin levels produce a coronary vasoconstriction at rest that is not observed during the coronary vasodilation during exercise. In contrast, the α-adrenoceptor antagonist phentolamine increased coronary venous oxygen tension during exercise but not at rest. The difference between the endothelin blockade and α-adrenoceptor blockade results indicates that α-adrenoceptor coronary vasoconstriction during exercise is not due to endothelin. However, in anesthetized dogs, bolus intracoronary injections of the α-adrenoceptor agonist phenylephrine produced reductions in coronary blood flow that were partially antagonized by endothelin receptor blockade with tezosentan. These results are best explained if α-adrenoceptor-induced endothelin release requires high pharmacological concentrations of catecholamines that are not reached during exercise.
Arginase inhibition restores arteriolar endothelial function in Dahl rats with salt-induced hypertension
Authors: Johnson Fruzsina K. , Johnson Robert A. , Peyton Kelly J. , Durante William
Published: December 2004

Vascular tissues express arginase that metabolizes l-arginine to l-ornithine and urea and thus reduces substrate availability for nitric oxide formation. Dahl salt-sensitive (Dahl-S) rats with salt-induced hypertension show endothelial dysfunction, including decreased vascular nitric oxide formation. This study tests the hypothesis that increased vascular arginase activity contributes to endothelial dysfunction in hypertensive Dahl-S rats. Male Dahl-S rats (5–6 wk) were placed on high (8%) or low (0.3%) NaCl diets for 4 wk. With respect to the low-salt group, mean arterial blood pressure was increased in the high-salt animals. Immunohistochemical stainings for arginase I and II were enhanced in arterioles isolated from high-salt Dahl-S rats. Experiments used isolated Krebs buffer-superfused first-order gracilis muscle arterioles with constant pressure (80 mmHg) and no luminal flow or constant midpoint but altered endpoint pressures to establish graded levels of luminal flow (0–50 μl/min). In high-salt arterioles, responses to an endothelium-dependent vasodilator acetylcholine (1 nmol/l to 3 μmol/l) and flow-induced dilation were decreased. Acute in vitro treatment with an inhibitor of arginase, 100 μmol/l ( S)-(2-boronoethyl)-l-cystine, or the nitric oxide precursor, 1 mmol/l l-arginine, similarly enhanced acetylcholine and flow-induced maximal dilations and abolished the differences between high- and low-salt arterioles. These data show that arteriolar arginase expression is increased and that endothelium-dependent vasodilation is decreased in high-salt Dahl-S rats. Acute pretreatment with an arginase inhibitor or with l-arginine restores endothelium-dependent vasodilation and abolishes the differences between high- and low-salt groups. These results suggest that enhanced vascular arginase activity contributes to endothelial dysfunction in Dahl-S rats with salt-induced hypertension and identifies arginase as a potential therapeutic target to prevent endothelial dysfunction.
Continued Lamivudine Therapy in Patients with Chronic Hepatitis B
Authors: Kumada Hiromitsu
Published: December 2004

From September 1995 through April 2002, 286 patients with chronic hepatitis B were started on lamivudine at the Toranomon Hospital in Tokyo, Japan, and most of them continued with it. At present, 16 patients received lamivudine for 5 years, 7 of whom for 7 years or longer. YMDD mutants increased gradually and developed in 69% of them during the 7 years on lamivudine. Biochemical and virological responses were achieved in 9 of the 16 patients (56%) at 5 years, and in 4 of the 7 patients (57%) at 7 years. Histological assessments were performed at 3 years in the 16 patients and further at 4 and 7 years in the 7 patients. Necroinflammatory changes improved remarkably with a decrease in the total histological activity score from 11.3 ± 3.0 to 4.1 ± 1.7 (p < 0.0001) at 3 years in the 16 patients. Histological improvements continued in 4 of the 7 patients (57%) at 7 years on lamivudine, while the pathology was unchanged in 2 patients (29%) and aggravated in the remaining 1 patient (14%). Severe acute exacerbation of hepatitis developed in 1 patient, who received additional interferon-α therapy to cope with it. Based on my experience, the continuation of lamivudine in patients with chronic hepatitis B benefits approximately two thirds of them with persistent virological and biochemical responses accompanied by histological improvements. Breakthrough hepatitis induced by YMDD mutants along the way in a small number of patients needs to be diagnosed promptly by regular monitoring for transaminases and, if it develops, it can be treated with interferon or other antiviral agents.
Peripheral Venous Thrombosis in Children and Adolescents with Adipsic Hypernatremia Secondary to Hypothalamic Tumors
Authors: Bergadá Ignacio , Aversa Luis , Heinrich Juan J.
Published: December 2004

Objective: To determine the clinical presentation and laboratory follow-up in patients with the syndrome of adipsic hypernatremia complicated with a peripheral thrombosis event. Methods: Report of 3 patients (6–19 years old) with chronic hypernatremia with sustained difficulties to normalize their serum osmolality levels. Results: During post-surgical management the 3 patients developed a peripheral venous thrombotic event as a complication of their chronic hyperosmolality. Conclusions: Chronic hypernatremia in patients with prolonged immobilization is associated with an increased risk for development of deep venous thrombosis.
New-Onset Seizures after Liver Transplantation: Clinical Implications and Prognosis in Survivors
Authors: Choi Eun Jung , Kang Joong Koo , Lee Sang Ahm , Kim Ki Hun , Lee Sung Gyu , Andermann Frederick
Published: December 2004

Purpose: To identify the probable etiologies and characteristics of new-onset seizures after orthotopic liver transplantation (OLT) and to assess their clinical implications and prognosis. Methods: We retrospectively analyzed the clinical, electrophysiologic and laboratory data of 17 patients with new-onset seizures after OLT among 367 adult and pediatric patients who underwent OLT between 1999 and 2001. Results: A suspected etiology of seizures was identified in most patients, including 6 (35.2%) with neurotoxicity due to immunosuppressive therapy, 4 (23.5%) with cerebrovascular disease, 3 (17.6%) with severe metabolic derangement by sepsis or rejection, and 1 each (5.8%) with hyperglycemia and brain edema due to fulminant hepatic failure. Causative factors could not be identified in 2 patients (11.8%). Seizures recurred in 15 patients (88.2%), with 9 occurring on the same day as the original seizure. Attacks caused by neurotoxicity tended to have an earlier onset, within 1 week in 4 of 6 patients, than those caused by cerebrovascular disease and sepsis/rejection, but this was not statistically significant. A total of 21 EEGs were performed in 13 patients. Eleven patients had abnormal EEG findings, of whom 4 (30.7%) showed epileptiform discharges, but the outcome of patients with epileptiform activity did not differ statistically from that of patients without such discharges (p > 0.6). The incidence of poor outcome (death or persistent vegetative state) in the group with seizures was almost 10 times higher than in the group without seizures (52.9 vs. 5.7%, p < 0.001). The prognosis of patients with seizures due to cerebrovascular disease and severe metabolic derangement by sepsis/rejection was poorer than that of patients with seizures caused by the neurotoxicity of immunosuppressive drugs (p < 0.02), suggesting that the underlying cause of seizures is important in determining prognosis. Of 8 patients who survived, 1 was lost to follow-up. The long-term outcome of seizures in surviving patients was excellent, with all survivors available for follow-up being seizure-free for a mean follow-up of 42.5 months (range, 16–58 months). Conclusion: New-onset seizures after OLT may herald fatal outcome, especially in patients with cerebrovascular disease or sepsis. The prognosis of seizures in survivors is excellent, and long-term antiepileptic drugs are not required in most cases.
Interaction Between a Rat Model of Cerebral Ischemia and β-Amyloid Toxicity
Authors: Whitehead Shawn N. , Hachinski Vladimir C. , Cechetto David F.
Published: December 2004

Background and Purpose—

Clinical data suggest that Alzheimer disease (AD) and stroke together potentiate cognitive impairment. Inflammatory mechanisms are involved in AD pathology and stroke and may be the mediator between AD and stroke toxicity.

Methods—

AD was modeled by cerebroventricular injections of β-amyloid (Aβ[25–35]) and subcortical lacunar infarcts by striatal endothelin injections. Inflammatory mechanisms were examined using immunohistochemical analysis. Memory and motor tasks were assessed using the Montoya staircase test.

Results—

Aβ injections elicited increases in pathological and inflammatory correlates of AD in multiple forebrain sites. Increases in astrocytosis and reactive microglia in the hippocampus were enhanced with the combination of endothelin and Aβ(25–35). Aβ(25–35) treatment decreased performance in the Montoya staircase behavioral test.

Conclusions—

The enhanced inflammatory response with Aβ toxicity and ischemia may mediate the inability to improve behavioral performance caused by the stroke. Anti-inflammatory treatment may ameliorate the pathological and behavioral deficits associated with the combination of AD and stroke.
Prediction of August Atlantic Basin Hurricane Activity
Authors: Blake Eric S. , Gray William M.
Published: December 2004

Although skillful seasonal hurricane forecasts for the Atlantic basin are now a reality, large gaps remain in our understanding of observed variations in the distribution of activity within the hurricane season. The month of August roughly spans the first third of the climatologically most active part of the season, but activity during the month is quite variable. This paper reports on an initial investigation into forecasting year-to-year variability of August tropical cyclone (TC) activity using the National Centers for Environmental Prediction–National Center for Atmospheric Research reanalysis dataset. It is shown that 55%–75% of the variance of August TC activity can be hindcast using a combination of 4–5 global predictors chosen from a 12-predictor pool with each of the predictors showing precursor associations with TC activity. The most prominent predictive signal is the equatorial July 200-mb wind off the west coast of South America. When this wind is anomalously strong from the northeast during July, Atlantic TC activity in August is almost always enhanced. Other July conditions associated with active Augusts include a weak subtropical high in the North Atlantic, an enhanced subtropical high in the northwest Pacific, and low pressure in the Bering Sea region.

The most important application of the August-only forecast is that predicted net tropical cyclone (NTC) activity in August has a significant relationship with the incidence of U.S. August TC landfall events. Better understanding of August-only TC variability will allow for a more complete perspective of total seasonal variability and, as such, assist in making better seasonal forecasts.
Finescale Surface Observations of the Dryline: A Mobile Mesonet Perspective
Authors: Pietrycha Albert E. , Rasmussen Erik N.
Published: December 2004

Mobile mesonet line normal, time-to-space converted data analysis on three meridional drylines that occurred in west Texas on 10 June 1999 and 5 May 2000 are presented herein; two occurred in a quiescent environment on 5 May 2000. Based on the data, the mixing zone across the dryline was composed of a series of large horizontal moisture differentials that were highly variable in width, ranging from 5 km down to several hundred meters. The largest dewpoint differential sampled was 10.0°C over 185 m.

Concurrent with a deceleration of dryline movement to nearly stationary, and while moisture differentials strengthened, surface-based mesoscale vertical circulations with horizontal diameters of 2 km down to less than 300 m were resolved in the data, and visual observations were made of numerous, strongly rotating dust devils. The estimated diameters of the largest dust devils were ∼80–100 m and ∼1 km deep, and these persisted for tens of minutes. All vortices were found to move along or adjacent to the zones of moisture differential. Additionally, when the circulations were observed, spatially isolated cumulus clouds located along the dryline exhibited rapid vertical development. It is plausible that the vortices protect an ascending air parcel by inhibiting mixing, thus allowing the parcel to reach its local lifting condensation level and level of free convection with relatively greater buoyancy than parcels not contained in vortices.
Analysis of Damage to Steel Gas Pipelines Caused by Ground Shaking Effects during the Chi-Chi, Taiwan, Earthquake
Authors: Hwang Howard , Chiu Yi-Huei , Chen Wei-Yao , Shih Ban-Jwu
Published: December 2004

This paper presents an investigation on damage to natural gas pipelines in Taichung City from the Chi-Chi Taiwan earthquake. This paper addresses damage due to ground shaking effects and does not address damage due to large ground deformations. Four parameters, that is, peak ground acceleration, peak ground velocity, Arias intensity, and spectral intensity, are used to represent ground shaking. Based on pipe repair data and recorded strong motion data, regression analyses of pipe repair rates were carried out to develop seismic vulnerability functions. From the regression analysis results, Arias intensity is considered as the best parameter for the derivation of seismic vulnerability function. The seismic vulnerability functions derived in this study are for steel gas pipelines with mechanical joints and the pipelines are located in firm soils and in the footwall area subject to ground shaking from an earthquake caused by a thrust fault.
Evaluation of Generalized Site Response Functions for Typical Soil Classes (B, C, and D) in Taiwan
Authors: Sokolov Vladimir Yu , Loh C-H. , Wen K-L.
Published: December 2004

Empirical amplification functions for site classes B, C, and D in Taiwan were evaluated as the ratio between Fourier amplitude spectra of recorded accelerograms and spectra modeled for a hypothetical very hard rock (VHR) site. The approach allowed testing applicability of various spectral models in the studied region. More than 1,000 acceleration records obtained during 21 intermediate-sized and large earthquakes (ML>5.5), including the ML 7.3 (MW 7.6) Chi-Chi earthquake (21 September 1999) and the large aftershocks (ML 6.8), were used. The evaluated amplification functions were compared with independent data, which were obtained recently for Taiwan, the western United States, and Greece. The prominent influence of geologic and geomorphologic factors on site amplification functions for the considered cases of rock (Class B), soft rock or very dense soil (Class C), and stiff soil (Class D) sites has been observed for the Taiwan region.
Is Agency Skin Deep? Surface Attributes Influence Infants' Sensitivity to Goal‐Directed Action
Authors: Guajardo Jose J. , Woodward Amanda L.
Published: December 2004

Three studies investigated the role of surface attributes in infants' identification of agents, using a habituation paradigm designed to tap infants' interpretation of grasping as goal directed (Woodward, 1998). When they viewed a bare human hand grasping objects, 7‐ and 12‐month‐old infants focused on the relation between the hand and its goal. When the surface properties of the hand were obscured by a glove, however, neither 7‐ nor 12‐month‐old infants represented its actions as goal directed (Study 1). Next, infants were shown that the gloved hands were part of a person either prior to (Study 2) or during (Study 3) the habituation procedure. Infants who actively monitored the gloved person in Study 2 and older infants in Study 3 interpreted the gloved reaches as goal directed. Thus, varying the extent to which an entity is identifiable as a person impacts infants' interpretation of the entity as an agent.
The Generality—Specificity Issue in Infants' Emotion Responses: A Comment on Bennett, Bendersky, and Lewis (2002)
Authors: Izard Carroll E.
Published: December 2004

Bennett, Bendersky, and Lewis (2002) highlighted a need for revision, or at least clarification, of aspects of differential emotions theory (DET) that relate to the development of facial expressions of discrete emotions. Their article reveals a need for a better theoretical integration of propositions about the emergence of discrete emotions, the generality and flexibility of emotion responding, and issue of specificity in event‐emotion relations. Bennett et al. tested and partly disconfirmed a hard version of an event‐emotion hypothesis that predicts a specific discrete emotion expression for a specific stimulus at a particular age (4 months). They noted that some statements of DET supported their hypothesis, whereas others did not. I clarify the relevant theoretical issues and formulate a soft hypothesis of event‐emotion relations. I suggest methodological changes that may prove necessary to verify or disconfirm hypotheses relating to infants' capacity to encode a specific discrete emotion expression at a given age.