bluuebunny/crossref_metadata_2025 huggingface dataset:
Tectonic implications of Palaeoproterozoic anatexis and Late Miocene metamorphism in the Lesser Himalayan Sequence, Sutlej Valley, NW India
Authors: CHAMBERS J.A. , ARGLES T.W. , HORSTWOOD M.S.A. , HARRIS N.B.W. , PARRISH R.R. , AHMAD T.
Published: April 2008

Unravelling the kinematic evolution of orogenic belts requires that the defining tectonostratigraphic units, and structural elements that bound them, are properly identified and characterized. In the Sutlej Valley (western Himalaya), the Munsiari and Vaikrita thrusts have both been correlated with the Main Central Thrust. The sequence of amphibolite-grade rocks (the Jutogh Group) bounded by these faults has been variously assigned to the Lesser Himalayan Sequence (based on provenance ages) and to the Greater Himalayan Sequence (from its metamorphic grade). Trace-element and geochronological data from leucogranites in the Jutogh Group (1) indicate crustal melting at
c
. 1810 Ma, before the deposition of the Greater Himalayan Sequence, thus correlating the Jutogh Group with the Lesser Himalayan Sequence, and (2) record Proterozoic metamorphism overprinted at 10.5 ± 1.1 Ma (established from U–Pb analysis of uraninite) during the Himalayan orogeny. Pressure–temperature–time data indicate that the Jutogh Group and Greater Himalayan Sequence represent distinct tectonic units of the metamorphic core that were decoupled during their extrusion. This precludes extrusion along a single, widening channel, and requires a southward shift of the locus of movement during the Late Miocene, coincident with present-day precipitation patterns.
Mechanical Behavior of Metallic Glasses: Microscopic Understanding of Strength and Ductility
Authors: Chen Mingwei
Published: April 2008

The widespread enthusiasm for research on bulk metallic glasses is driven by both a fundamental interest in the structure and properties of disordered materials and their unique promise for structural and functional applications. Unlike the case for crystalline materials, the disordered and nonequilibrium nature of metallic glasses causes their underlying deformation mechanisms to be poorly known. A definite correlation between mechanical behavior and the atomic/electronic structures of metallic glasses has not been established. In this article, I focus on the micromechanisms of mechanical behavior of metallic glasses and present a brief overview of the current understanding of their strength, ductility, and plasticity at the microscopic and atomic scales. The important factors that control the mechanical behavior of metallic glasses are outlined on the basis of recent theoretical and experimental findings. The outstanding issues highlighted in this review are expected to be important for future research on the mechanical properties of metallic glasses.
Mathematical model of the neonatal mouse ventricular action potential
Authors: Wang Linda J. , Sobie Eric A.
Published: April 2008

Therapies for heart disease are based largely on our understanding of the adult myocardium. The dramatic differences in action potential (AP) shape between neonatal and adult cardiac myocytes, however, indicate that a different set of molecular interactions in neonatal myocytes necessitates different treatment for newborns. Computational modeling is useful for synthesizing data to determine how interactions between components lead to systems-level behavior, but this technique has not been used extensively to study neonatal heart cell function. We created a mathematical model of the neonatal ( day 1) mouse myocyte by modifying, on the basis of experimental data, the densities and/or formulations of ion transport mechanisms in an adult cell model. The new model reproduces the characteristic AP shape of neonatal cells, with a brief plateau phase and longer duration than the adult (action potential duration at 80% repolarization = 60.1 vs. 12.6 ms). The simulation results are consistent with experimental data, including 1) decreased density and altered inactivation of transient outward K+ currents, 2) increased delayed rectifier K+ currents, 3) Ca2+ entry through T-type as well as L-type Ca2+ channels, 4) increased Ca2+ influx through Na+/Ca2+ exchange, and 5) Ca2+ transients resulting from transmembrane Ca2+ entry rather than release from the sarcoplasmic reticulum (SR). Simulations performed with the model generated novel predictions, including increased SR Ca2+ leak and elevated intracellular Na+ concentration in neonatal compared with adult myocytes. This new model can therefore be used for testing hypotheses and obtaining a better quantitative understanding of differences between neonatal and adult physiology.
GABAAreceptors are expressed and facilitate relaxation in airway smooth muscle
Authors: Mizuta Kentaro , Xu Dingbang , Pan Yaping , Comas George , Sonett Joshua R. , Zhang Yi , Panettieri Reynold A. , Yang Jay , Emala Charles W.
Published: April 2008

γ-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the mammalian central nervous system and exerts its actions via both ionotropic (GABAA) channels and metabotropic (GABAB) receptors. GABAAchannels are ubiquitously expressed in neuronal tissues, and in mature neurons modulate an inward chloride current resulting in neuronal inhibition due to membrane hyperpolarization. In airway smooth muscle (ASM) cells, membrane hyperpolarization favors smooth muscle relaxation. Although GABAAchannels and GABABreceptors have been functionally identified on peripheral nerves in the lung, GABAAchannels have never been identified on ASM itself. We detected the mRNA encoding of the GABAAα4-, α5-, β3-, δ-, γ1–3-, π-, and θ-subunits in total RNA isolated from native human and guinea pig ASM and from cultured human ASM cells. Selected immunoblots identified the GABAAα4-, α5-, β3-, and γ2-subunit proteins in native human and guinea pig ASM and cultured human ASM cells. The GABAAβ3-subunit protein was immunohistochemically localized to ASM in guinea pig tracheal rings. While muscimol, a specific GABAAchannel agonist, did not affect the magnitude or the time to peak contractile effect of substance P, it directly concentration dependently relaxed a tachykinin-induced contraction in guinea pig tracheal rings, which was inhibited by the GABAA-selective antagonist gabazine. Muscimol also relaxed a contraction induced by an alternative contractile agonist histamine. These results demonstrate that functional GABAAchannels are expressed on ASM and suggest a novel therapeutic target for the relaxation of ASM in diseases such as asthma and chronic obstructive lung disease.
ABCB- and ABCC-type transporters confer multixenobiotic resistance and form an environment-tissue barrier in bivalve gills
Authors: Luckenbach Till , Epel David
Published: April 2008

Aquatic organisms and, in particular, filter feeders, such as mussels, are continuously exposed to toxicants dissolved in the water and, presumably, require adaptations to avoid the detrimental effects from such chemicals. Previous work indicates that activity of ATP-binding cassette (ABC) transporters protects mussels against toxicants, but the nature of these transporters and the structural basis of protection are not known. Here we meld studies on transporter function, gene expression, and localization of transporter protein in mussel gill tissue and show activity and expression of two xenobiotic transporter types in the gills, where they provide an effective structural barrier against chemicals. Activity of ABCB/MDR/P-glycoprotein and ABCC/MRP-type transporters was indicated by sensitivity of efflux of the test substrate calcein-AM to the ABCB inhibitor PSC-833 and the ABCC inhibitor MK-571. This activity profile is supported by our cloning of the complete sequence of two ABC transporter types from RNA in mussel tissue with a high degree of identity to transporters from the ABCB and ABCC subfamilies. Overall identity of the amino acid sequences with corresponding homologs from other organisms was 38–50% (ABCB) and 27–44% (ABCC). C219 antibody staining specific for ABCB revealed that this transporter was restricted to cells in the gill filaments with direct exposure to water flow. Taken together, our data demonstrate that ABC transporters form an active, physiological barrier at the tissue-environment interface in mussel gills, providing protection against environmental xenotoxicants.
The natriuretic and diuretic response to dopamine is maintained during rat pregnancy
Authors: Sasser Jennifer M. , Baylis Chris
Published: April 2008

During pregnancy, there is a marked plasma volume expansion due to renal sodium retention. Pregnant rats exhibit a blunted response to natriuretic stimuli that signal via cGMP, and expression and activity of the cGMP phosphodiesterase PDE-5 are upregulated in the inner medullary collecting duct during pregnancy. Here, we tested the hypothesis that the natriuretic response to a cAMP agonist, dopamine, is maintained during pregnancy. Anesthetized pregnant ( day 16) and age-matched virgin Sprague-Dawley rats were used to determine whether dopamine-cAMP-mediated natriuresis remains intact in pregnant rats. Blood pressure, renal clearances of inulin and p-aminohippuric acid, and excretion of sodium were measured during baseline and dopamine infusion periods. Pregnant rats had a lower blood pressure and hematocrit at baseline than their age-matched virgin counterparts. Dopamine infusion decreased blood pressure and increased glomerular filtration rate and renal plasma flow in virgin but not pregnant rats. Dopamine infusion also increased urine volume, sodium excretion, and the fractional excretion of sodium to a similar extent in virgin and pregnant rats. These results indicate that a cAMP-mediated natriuresis and diuresis (stimulated by dopamine) persists in pregnant rats.
Developmental Changes in the Fidelity and Short-Term Plasticity of GABAergic Synapses in the Neonatal Rat Dorsal Horn
Authors: Ingram Rachel A. , Fitzgerald Maria , Baccei Mark L.
Published: April 2008

The lower thresholds and increased excitability of dorsal horn neurons in the neonatal rat suggest that inhibitory processing is less efficient in the immature spinal cord. This is unlikely to be explained by an absence of functional GABAergic inhibition because antagonism of γ-aminobutyric acid (GABA) type A receptors augments neuronal firing in vivo from the first days of life. However, it is possible that more subtle deficits in GABAergic signaling exist in the neonate, such as decreased reliability of transmission or greater depression during repetitive stimulation, both of which could influence the relative excitability of the immature spinal cord. To address this issue we examined monosynaptic GABAergic inputs onto superficial dorsal horn neurons using whole cell patch-clamp recordings made in spinal cord slices at a range of postnatal ages (P3, P10, and P21). The amplitudes of evoked inhibitory postsynaptic currents (IPSCs) were significantly lower and showed greater variability in younger animals, suggesting a lower fidelity of GABAergic signaling at early postnatal ages. Paired-pulse ratios were similar throughout the postnatal period, whereas trains of stimuli (1, 5, 10, and 20 Hz) revealed frequency-dependent short-term depression (STD) of IPSCs at all ages. Although the magnitude of STD did not differ between ages, the recovery from depression was significantly slower at immature GABAergic synapses. These properties may affect the integration of synaptic inputs within developing superficial dorsal horn neurons and thus contribute to their larger receptive fields and enhanced afterdischarge.
An Analysis of Professional Judgments
Authors: Rose Heather , Sonstelie Jon
Published: April 2008

Many states have used professional judgment panels to determine the resources schools need to meet certain performance targets. This study initiates a critical study of that method. Using budget simulations with hypothetical schools, we collected the judgments of forty-five principals about how school budgets should be allocated and how school resources affect student achievement. We found considerable variation among principals in both budget allocations and achievement predictions. We also found that principals were more optimistic about student achievement than is warranted by either achievement in comparable schools or recent research on the relationship between resources and achievement.
The Impact of Peer Effects on Student Outcomes in New York City Public Schools
Authors: Zabel Jeffrey E.
Published: April 2008

The impact of peers on student outcomes has important policy implications for how students are organized into classes and the overall impact of education interventions. But it is difficult to accurately measure peer effects because of the nonrandom sorting of students and teachers into classrooms and the endogeneity of peers' achievement. In this study, an education production function (EPF) is specified that includes student and peer characteristics as regressors. This model is estimated using student-level data from New York City public schools for 1995–2000. The richness of these data allows six sources of bias that arise in the EPF model to be addressed, including the above-mentioned nonrandom classroom assignment and the endogeneity of peers' achievement. This results in credible evidence of (small) peer group effects. Instrumenting for the mean of peers' achievement significantly reduces the associated peer effect. Nonlinear peer group effects are evident in the form of a small positive impact associated with the homogeneity of peers' achievement. Generally, peer characteristics do not appear to affect individual performance. Also included in this analysis is an application of a new methodology developed by Graham (2007) that identifies peer group effects through their impact on the variance in classroom mean test scores. The approach is less susceptible to the six biases that plague the EPF approach. The evidence from this exercise indicates that peer group effects are present and corroborates the results from the EPF approach.
Are Students Left Behind? The Distributional Effects of the No Child Left Behind Act
Authors: Krieg John M.
Published: April 2008

The No Child Left Behind Act imposes sanctions on schools if the fraction of students demonstrating proficiency on a high-stakes test falls below a statewide pass rate. While the motivation behind this system is improved public school performance, it also provides incentives for schools to focus educational resources on the marginal student rather than those on the tails of the ability distribution. Using statewide, student-level panel data, students on the tails of the ability distribution, especially high-ability students, are demonstrated to score below expectations if their school is in danger from No Child Left Behind sanctions.
Structure-Property Relationships in Isotactic Poly(propylene)/Ethylene Propylene Rubber/Montmorillonite Nanocomposites
Authors: Causin Valerio , Marega Carla , Marigo Antonio , Ferrara Giuseppe , Ferraro Angelo , Selleri Roberta
Published: April 2008

Nanocomposites based on isotactic polypropylene/ethylene propylene rubber (iPP/EPR) were prepared adding different amounts of montmorillonite and maleated polypropylene. The structure and morphology of the samples were characterized by small angle X-ray scattering, wide angle X-ray
diffraction, electronic and optical microscopy and differential scanning calorimetry. iPP showed a polymorphic behavior. Clay disrupted the ordered crystallization of iPP and had a key role in shaping the distribution of iPP and EPR phases: larger filler contents brought about smaller, less
coalesced and more homogeneous rubber domains. Clay distributed itself only in the continuous phase and not in the rubber domains. Tactoids persisted on the surface of the sample, while delamination proceeded to a greater degree in the bulk of the materials. Melt flow rate, impact strength,
flexural and tensile properties, were also measured and a structure-property correlation was sought. Clay produced its most significant effect on physical-mechanical properties by controlling the size of rubber domains in the heterophasic matrix. This allowed to obtain nanocomposites with
increased stiffness and impact strength, a remarkable achievement for polymer layered-silica nanocomposites that usually suffer the drawback of being stiffer than the unfilled matrix, but at the same time with a lower resistance to impact. A beneficial effect of clay on thermal stability was
also observed.
Towards Crossbar Nanoarray Structure via Microcontact Printing
Authors: Yadav Yamini , Padigi SudhaPrasanna Kumar , Prasad Shalini , Song Xiaoyu
Published: April 2008

The method for patterning arrays of multiwalled carbon nanotubes (MWCNT's) in symmetric patterns to form junctions has been demonstrated. This has been achieved by incorporating the technique of microcontact printing using poly-dimethylsiloxane (PDMS) molds. Relief structures in the
order of a few micrometers were fabricated that enabled the transfer of continuous horizontal arrays of MWCNT's in aqueous suspension in a controlled manner. The MWCNT's were patterned onto silicon microelectrode substrates with metallic gold electrodes. These were fabricated using standard
photolithography techniques. The silicon substrates served as a base platform with suitable measurement microelectrodes for electrically characterizing the crossbar junction arrays. Using a dual alignment and stamping process, PDMS molds were inked alternatively with p-type and n-type suspensions
of MWCNT's and transferred in a grid-like manner onto the base platform. Parallel alignment of the MWCNT's was achieved due to the geometry of the mold relief structures. This step-by-step assembly resulted in the formation of crossbar MWCNT array structures. Each of these crosspoints in the
individual junction can function as an addressable crossbar nanodevice. The functionality of this circuit was demonstrated through the current–voltage (I–V) characteristics. Using these high-density crossarray circuit patterns, addressable nanostructures that form the building
blocks of highly integrated device arrays can be built.
Interfacial Spin Polarization and Magnetic Structure of Co/MgO/Co Magnetic Tunnel Junction: Ab Initio Calculation
Authors: Kim Chiho , Chung Yong-Chae
Published: April 2008

Using ab initio method based on the density functional theory, the equilibrium bcc-Co(001)/rocksalt-MgO(001)/bcc-Co(001) magnetic tunnel junction structure was investigated. Spin polarization and magnetic moment were calculated for each atomic slab in the equilibrium structure
by spin dependent density of states analysis. Interfacial Co atoms showed significantly larger spin polarization of –88.3%, compared to the value of inner Co slabs, –82.3%, and bulk bcc Co, –82.1%. Interestingly, Mg and O atoms also showed induced spin polarizability ranged
from –45.0% to –66.0%, except for O atoms in the centered slab of barrier layer, which showed relatively small polarization, –14.9%. Magnetic moments for the electrode Co atoms were calculated to be ∼1.74 μB with no significant variation across the
electrode.
Chain-Like Structure Created by Assembly of Cobalt Nanoparticles Using PVP as Soft Template
Authors: Zhang YaHui , Liang Fang , Wang Ning , Guo Lin , He Lin , Chen Chinping , Zhang Qi , Zhong Qunpeng
Published: April 2008

Using a wet chemical method, we have synthesized chain-like structure with diameters of 200–250 nm and lengths of ∼10 μm formed by assembly of small cobalt nanoparticles. The chain-like structures were realized via reaction of CoCl2˙6H2O
and N2H4 in the presence of PVP in an ethylene glycol solution. Magnetic measurements show a coercivity of about 122 Oe at 300 K. We also propose a possible mechanism for the formation of the chain-like structures.
Hybrid Permeable Metal-Base Transistor with Large Common-Emitter Current Gain and Low Operational Voltage
Authors: Feng Chengang , Yi Mingdong , Yu Shunyang , Hümmelgen Ivo A. , Zhang Tong , Ma Dongge
Published: April 2008

We demonstrate the suitability of N,N′-diphenyl-N,N′-bis(1-naphthylphenyl)-1,1′-biphenyl-4,4′-diamine (NPB), an organic semiconductor widely used in organic light-emitting diodes (OLEDs), for high-gain, low operational voltage nanostructured
vertical-architecture transistors, which operate as permeable-base transistors. By introducing vanadium oxide (V2O5) between the injecting metal and NPB layer at the transistor emitter, we reduced the emitter operational voltage. The addition of two Ca layers, leading
to a Ca/Ag/Ca base, allowed to obtain a large value of common-emitter current gain, but still retaining the permeable-base transistor character. This kind of vertical devices produced by simple technologies offer attractive new possibilities due to the large variety of available molecular
semiconductors, opening the possibility of incorporating new functionalities in silicon-based devices.
Electrodeposition and Characterization of CdSe Semiconducting Nanowires
Authors: Yu-Zhang K. , Guo D. Z. , Mallet J. , Molinari M. , Loualiche A. , Troyon M.
Published: April 2008

In this paper, we present our work on the electrodeposited CdSe semiconducting nanowires. Using a low cost and low temperature approach by electrochemistry, CdSe nanowires were successfully grown using polycarbonate template. Depending on the host pore dimension of the substrate, wire
diameter can be varied from 400 nm down to 30 nm and wire length from a few microns to tens microns. The as-deposited nanowires exhibit predominantly metastable zinc blende (ZB) structure but after the heat treatment they become wurtzite (W) structure. A combination of different characterization
techniques, such as X-ray diffraction, SEM, TEM-HRTEM and EDXS, was used to investigate the growth morphology, crystalline structure and defects in the nanowires. The luminescent properties of CdSe nanowires have also been studied by means of photoluminescence.
Fluorescence and Structure of Methyl Red-Clay Nanocomposites
Authors: Simha Martynková Gražyna , Kulhánková Lenka , Malý Petr , Čapková Pavla
Published: April 2008

Two types of clay minerals—montmorillonite and vermiculite have been chosen as a host matrix for the intercalation of methyl red (MR) in order to investigate a possible fluorescence tuning via dye-clay interactions. The effect of silicate layer charge on the structure and fluorescence
of dye-clay intercalated hybrid nanostructures was investigated using combination of molecular modeling with experiment. Structure of both intercalates MR-vermiculite (MR-VER) and MR-montmorillonite (MR-MMT) exhibits high degree of structural disorder resulting in broaden emission band. The
fluorescence wavelength range of MR intercalated in clays is shifted to lower wavelengths compared with the pristine MR polycrystalline sample (800 nm). Results showed the strong dependence of fluorescence band maximum on the silicate layer charge, λmax = 565 nm for MR-MMT,
645 nm for MR-VER and 800 nm for the methyl red fine crystalline powder, whereas the structural disorder in the arrangement of dye molecules affects the emission band broadening.
Small-Angle Neutron Scattering Investigations on Sintering Behavior of Combustion Synthesized La0.8Sr0.2CrO3
Authors: Patra A. K. , Bahadur J. , Mazumder S. , Nair Sathi , Purohit R. D. , Tyagi A. K.
Published: April 2008

Pore morphology of La0.8Sr0.2CrO3 (LSC) powder compacts, sintered between 1200 °C and 1450 °C for a fixed time, has been characterized by small-angle neutron scattering (SANS) in the scattering wave vector 'q' range, 0.003–0.17 nm–1
of a double crystal based instrument. Scattering profile of green compact exhibits fractal scaling at two regions of 'q' with magnitudes of fractal dimensionality 1.8 and 2.36. Scattering profiles of sintered pellets have been modeled assuming a random distribution of near spherical
pores in the solid matrix. Estimated pore size distributions of sintered pellets indicate decrease in pore volume has taken place by progressive elimination of smallest pores and growth of relatively larger pores with increasing sintering temperature. SANS results are supplemented by light
scattering measurement and TEM image of powder and SEM image of the fracture surface of sintered pellet.
Size-Controlled Synthesis and NMR Characterization of Mesitylene-Vinylsiloxanes Stabilized Pt Nanoparticles in Solution
Authors: Evangelisti Claudio , Raffa Patrizio , Balzano Federica , Uccello Barretta Gloria , Vitulli Giovanni , Salvadori Piero
Published: April 2008

Pt nanoclusters have been generated by reaction of Pt vapour and mesitylene vapour and the role of the mesitylene/platinum ratio and the Pt particle size has been evaluated, quenching the resulting mesitylene solvated Pt atoms with 1,3-divinyltetramethyldisiloxane (DVS) as additional
ligand. The Pt particle sizes have been estimated on the basis of DOSY (Diffusion-Ordered SpectroscopY) analysis and information on their structure features have been obtained by combined use of 2D NMR techniques.
Magnetic Properties of γ-Fe2O3/Poly(Ether-Ester) Nanocomposites
Authors: Guskos N. , Likodimos V. , Glenis S. , Maryniak M. , Baran M. , Szymczak R. , Roslaniec Z. , Kwiatkowska M. , Petridis D.
Published: April 2008

The magnetic properties of γ-Fe2O3 nanoparticles embedded in a thermoplastic elastomer poly(ether-ester) copolymer by the in situ polycondensation reaction process have been investigated by means of magnetization and ferromagnetic resonance
(FMR) measurements at low filler concentrations of 0.1 and 0.3 wt% with the magnetic additive introduced in the polymer matrix in powder and solution form. The magnetic behavior of the magnetopolymeric nanocomposites indicates significant interparticle interaction effects that depend mainly
on the dispersion state of the magnetic nanoparticles as well as their concentration, consistent with the variation of the particle microstructure characterized by magnetic aggregates in the nanometer and micron scale for the solution and powder dispersions, respectively. The magnetization
and FMR results at different filler concentrations and dispersions showa close correspondence to the relaxation processes of the copolymer, implying the coupling of polymeric and magnetic properties.
Poly(vinylpyrrolidone) Coated Iron Nanoparticles in Polar Aprotic Solvent
Authors: Ban Zhihui , Cushing Brian L. , O'Connor Charles J.
Published: April 2008

Poly(vinylpyrrolidone) (PVP) coated iron nanoparticles which show well-defined core–shell structures have been successfully synthesized in a polar aprotic solvent. In this approach, PVP was employed not as capping agent, but as coating polymer directly applied to the metallic
(iron) core nanoparticles. The morphologies, structures, compositions and magnetic properties of the products were investigated by transmission electron microscopy (TEM), X-ray powder diffraction (XRD), energy dispersive X-ray spectroscopy (EDXS), SQUID magnetometry and FTIR spectroscopy.
Nanotexturized Polytetrafluoroethylene Substrates Formed by Large Crystalline Nanofibrils in Amorphous Matrices
Authors: de Souza E. F. , Torriani I. C. L. , Teschke O.
Published: April 2008

Plastic deformation has proved to be an attractive tool for obtaining ultrafine grained and nanocrystalline metallic materials. A description of plastic deformation as a technique to create nanotexturized polytetrafluoroethylene substrates free of defects, such as pores or impurities,
which has potential applications as templates for the oriented growth of organic and inorganic compounds, is presented here. The obtained morphology characterized by nanosized fibrils arrangements was revealed by atomic force microscopy. Nanofibrils with a width from 330 to 980 nm and lengths
from 1.85 to 11 μm were observed on polytetrafluoroethylene substrates annealed at 330 °C and 390 °C, respectively. Wide angle X-ray scattering spectra for untreated and annealed samples show that there is a slight decrease in the amorphous component for samples annealed
at 380 °C but not for samples annealed at 330 °C showing that the amorphous substrate matrix in little altered by the annealing. The pattern formation is associated with superficial polymeric domains that become large crystalline nanofibrils in an amorphous matrix.
Luminescence of Nanostructured SnO2-SiO2 Glass-Ceramics Prepared Sol–Gel Method
Authors: del-Castillo J. , Yanes A. C. , Méndez-Ramos J. , Rodríguez V. D.
Published: April 2008

Nanostructured silica based glass-ceramics samples of composition (100 – x)SiO2-xSnO2, with x from 1 to 10, have been synthesized by thermal treatment of precursor sol–gel glasses. The average size of the obtained SnO2
nanocrystals, calculated by using the X-ray diffraction, can be predetermined by using well-controlled concentration of tin precursor. The mean radius ranging from 1.6 to 5.5 nm, is comparable to the exciton Bohr radius, corresponding to wide band-gap semiconductor quantum-dots in an insulator
SiO2 glass. A spectroscopy study in terms of optical absorption and photoluminescence spectra has been carried out as a function of SnO2 concentration. Size-dependent red-shifts of excitation and emission bands, with increasing of tin precursor concentration, point to
the quantum confinement effect. The nanocrystal sizes have been obtained and compared by using the Brus and Scherrer equations. The band gap increase is in agreement with results, based on the effective mass model. The recombination of conduction band electron with oxygen vacancies is proposed
to explain the luminescence red-shift.
Secondary Nanotube Growth on Aligned Carbon Nanofibre Arrays for Superior Field Emission
Authors: Watts Paul C. P. , Lyth Stephen M. , Henley Simon J. , Ravi S. , Silva P.
Published: April 2008

We report substantial improvement of the field emission properties from aligned carbon nanotubes grown on aligned carbon nanofibres by a two-stage plasma enhanced chemical vapour deposition (PECVD) process. The threshold field decreased from 15.0 to 3.6 V/μm after the secondary
growth. The field enhancement factor increased from 240 to 1480. This technique allows for superior emission of electrons for carbon nanotube/nanofibre arrays grown directly on highly doped silicon for direct integration in large area displays.
Wavelet Analysis of Cirrus Multiscale Structures from Lidar Backscattering: A Cirrus Uncinus Complex Case Study
Authors: Wang Likun , Sassen Kenneth
Published: April 2008

Although cirrus cloud structures play an important role in dynamics issues, cloud radiative calculations, and cloud parameter retrievals from satellite measurements, fully understanding cirrus cloud structures still remains a challenge. A case study of a cirrus containing mesoscale uncinus complexes (MUC) with a two-layer structure observed by a high-resolution lidar is presented using the method based on wavelet transform. The results indicate that dynamical processes play a leading role in determining cloud multiscale structures. The uncinus cells with a length scale on the order of ∼1 km, embedded in both the top and lower layers, have similar spectral features and are probably produced by a similar mechanism—thermal perturbation generated by heating and cooling effects associated with phase changes of water (i.e., adiabatic heating) and radiative processes. However, the mesoscale cloud patches are probably involved in different dynamics processes, suggesting that understanding of the interaction of cloud-scale convective activities with 2D turbulence and propagating gravity waves in cirrus cloud systems should receive more attention in future model simulations. The study also demonstrates the utility of the continuous and discrete wavelet transform to objectively and quantitatively analyze the properties of cirrus cloud structures, which is a useful supplement to the traditional Fourier transform method.
Tropical SST Preconditioning of the SH Polar Vortex during Winter 2002
Authors: Grassi Barbara , Redaelli Gianluca , Visconti Guido
Published: April 2008

The response of the Southern Hemisphere (SH) polar atmosphere to the tropical sea surface temperature (SST) during the 2002 winter–spring season is investigated by using a general circulation model (GCM). The SH stratospheric winter of 2002 was particularly unusual, characterized by a weaker-than-normal polar vortex during the whole season. It also registered, at the end of September, the first major warming yet observed in the SH. This event is unexpected in the SH, and it is supposed to be induced by a “preconditioning” of the polar vortex starting at the beginning of the winter. Atmospheric GCM experiments with prescribed SST boundary conditions are performed. The sensitivity of the Antarctic dynamics to the tropical SST of 2002 (a year characterized by an El Niño event of moderate intensity) is studied, and the uniqueness of the 2002 tropical oceanic condition is investigated through the comparison of the simulated response of the climatic system to 2002 and 1997 tropical SST (1997 being a year with a strong El Niño event). Model results highlight a primary role played by the tropical SST of 2002 in the development of the peculiar characteristics of the Antarctic dynamics during the winter months that appears to be a necessary condition for the generation of the anomalous destabilization of the polar vortex during the following spring. Results for June 2002 show a strong generation of vertically propagating waves resulting from the tropical SST that, through the perturbation of the westerly jet at middle latitudes, produces a preconditioning of the polar vortex by affecting the wave refraction index. The particular structure of the tropical SST anomalies during the winter of 2002 is thought to have influenced the subsequent preconditioning of the stratospheric vortex.
China's Changing Political Economy with Malaysia and Southeast Asia
Authors: Ku Samuel C.Y.
Published: April 2008

Malaysia was the first major Southeast Asian country to exchange diplomatic recognition with China. Since 1980, China began to change its relations with the world, including Malaysia and Southeast Asia. This article argues that China's increasing political economy with Malaysia and Southeast Asia is being pushed forward by three policy initiatives that started in the early 1980s. It examines China's three policy initiatives and the programs of China's relations with Malaysia and Southeast Asia. The article concludes that China's increasing political economy with Malaysia and with Southeast Asia will sustain as China continues its `going global' policy.
The Role of Ambivalence in College Nonsmokers' Information Seeking and Information Processing
Authors: Xiaoquan Zhao  , Xiaomei Cai
Published: April 2008

The abundant prosmoking influences in college can cultivate a sense of ambivalence about smoking among many nonsmoking students. In this study, the authors investigated the role of ambivalence in college nonsmokers' seeking and processing of smoking-related information. Three hundred ninety-six nonsmoking college students participated in an online study. Hypotheses were built into a predictive model and tested using structural equation modeling. Higher ambivalence was found to be associated with greater information seeking in the past 30 days. Past information seeking, in turn, was associated with deeper processing and greater acceptance of new antismoking information. Implications of the results for smoking prevention on college campuses are discussed.
Political Ads and Citizen Communication
Authors: Cho Jaeho
Published: April 2008

This study explores the role that political advertising plays in the democratic process by examining whether and how political ads encourage citizens to engage in communication activities in the campaign process. To examine this question, political ad tracking data were combined with a national daily survey collected during the 2000 election campaign cycle. The resulting ad volume data and individual communication behavior by geographic location and date allowed examination of how political advertising contexts influenced citizen communication. Results show that, in response to an influx of local political advertising, people sought more political information through television news programs, the Internet, and social networks. Theoretical and methodological implications of these findings are discussed.
Collaborative Information Seeking in Intercultural Computer-Mediated Communication Groups
Authors: Cho Hichang , Lee Jae-Shin
Published: April 2008

This article examines the process of collaborative information seeking in intercultural computer-mediated communication (CMC) groups. The authors conducted a field experiment in which 86 students from three distant universities (one in the United States, two in Singapore) participated. The students participated in a collaborative learning practice in which they socially recommended information using a CMC system. The results demonstrate that the social context—that is, preexisting social networks, groups, and intergroup boundaries—significantly constrained the flow of information across intercultural CMC groups. The authors also found that the influence of the social context on CMC collaboration could be moderated by other contingent factors such as national culture and individuals' outcome expectancies of Internet use. The authors present the results from testing their hypotheses using multivariate p* and Quadratic Assignment Procedure network regression analyses and conclude with a discussion of the findings and implications for future research.
The Roles of Stress and Coping in Explaining Gender Differences in Risk for Psychopathology Among African American Urban Adolescents
Authors: Carlson Ginger Apling , Grant Kathryn E.
Published: April 2008

This study used self-report symptom inventories administered in school classrooms to examine relations among gender, psychological symptoms, stress, and coping in 1,200 low-income African American urban early adolescents. Girls reported more symptoms than boys, accounted for by higher internalizing symptoms. Boys reported more stress than girls, particularly major events, controllable events, exposure to violence, and sexual stressors. Boys in gangs reported greater exposure to sexual stressors than non-gang members. Expressing feelings coping, used more by girls, was related to more symptoms and is posited to be a type of co-rumination. Rumination coping, used as a primary strategy by both boys and girls, was related to higher symptom levels. Risk to low-income African American boys from high violence exposure and sexual stressors, the problematic effect of maladaptive coping strategies for youth exposed to high stress, and how culture and experience are relevant to understanding gender differences in psychological symptoms are discussed.
Contextual Variations in Negative Mood and State Self-Esteem
Authors: Reynolds Bridget M. , Repetti Rena L.
Published: April 2008

This study explores the link between peer problems in school and contextual variations in negative mood and state self-esteem over a 5-day period. Fifth-grade children completed measures of mood and state self-esteem while they were at home in the morning and while they were at school each day, allowing for an examination of whether psychological states change from context to context and whether these changes are influenced by types of peer events that children report experiencing at school. Results indicated that children who experienced more peer problems at school showed, on average, a shift toward more negative mood and lowered state self-esteem from mornings at home to afternoons at school during the week of data collection. Peer problems were also associated with higher levels of negative mood at school after controlling for academic problems but no longer predicted state self-esteem in school when academic problems were controlled.
Environmental impacts and costs of solid waste: a comparison of landfill and incineration
Authors: Rabl Ari , Spadaro Joseph V. , Zoughaib Assaad
Published: April 2008

The methodology for evaluating the impacts and damage costs (`external costs') due to pollution from waste treatment is described and the results are presented, based on the ExternE project series of the European Commission. The damage costs of landfill and incineration of municipal solid waste are compared, with due account for energy and materials recovery, as well as possible differences in transport distance. We have not been able to quantify the total damage costs of leachates because of the complexity of the environmental pathways and of the long time horizon of some persistent pollutants, but we consider an extreme scenario to show that they are not worth worrying about in the sense that reducing the pollutants in leachates beyond current regulations would bring negligible benefit in comparison with the abatement of other sources of the same pollutants. The damage costs due to the construction of the waste treatment facility are negligible. The damage costs of waste transport, which are illustrated by an arbitrary choice of a 100 km round trip by a 16 tonne truck, are also negligible. The benefits of materials recovery make a small contribution to the total damage cost. The only significant contributions come from direct emissions (of the landfill or incinerator) and from avoided emissions due to energy recovery (from an incinerator). Damage costs for incineration range from about 4 to 21 tonnewaste—1, and they are extremely dependent on the assumed scenario for energy recovery. For landfill the cost ranges from about 10 to 13 tonnewaste—1 ; it is dominated by greenhouse gas emissions because only a fraction of the CH4 can be captured (here assumed to be 70%). Amenity costs (odour, visual impact, noise) are highly site-specific and we only cite results from a literature survey which indicates that such costs could make a significant contribution, very roughly on the order of 1 tonnewaste —1.
Promoting Positive Youth Development
Authors: Kurtines William M. , Ferrer-Wreder Laura , Berman Steven L. , Lorente Carolyn Cass , Briones Ervin , Montgomery Marilyn J. , Albrecht Richard , Garcia Arlen J. , Arrufat Ondina
Published: April 2008

The Miami Youth Development Project (YDP) had its beginnings in the early 1990s as a grassroots response to the needs of troubled (multiproblem) young people in the community (Arnett, Kurtines, & Montgomery, 2008, this issue). YDP is an important outcome of efforts to create positive youth development interventions that draw on the strengths of developmental intervention science outreach research in the development of community-supported positive development programs (i.e., an approach that focuses on meeting community needs as well as youth needs by generating innovative knowledge of evidence-based change intervention strategies that are feasible, affordable, and sustainable in “real world” settings, (Kurtines, Ferrer-Wreder, Cass Lorente, Silverman, Montgomery, 2008, this issue). Now completing its second decade, YDP represents an effort to bring together a more empowering model of knowledge development for research involvement in the community, a nuanced and contextualized notion of youth and their development, and methodologies that richly reflect rather than reduce the experiences of the young people whose development the authors seek to promote.
A Multi-Stage Longitudinal Comparative Design Stage II Evaluation of the Changing Lives Program
Authors: Arango Lisa Lewis , Kurtines William M. , Montgomery Marilyn J. , Ritchie Rachel
Published: April 2008

The study reported in this article, a Multi-Stage Longitudinal Comparative Design Stage II evaluation conducted as a planned preliminary efficacy evaluation (psychometric evaluation of measures, short-term controlled outcome studies, etc.) of the Changing Lives Program (CLP), provided evidence for the reliability and validity of the qualitative measures under development as well as the utility of unifying qualitative (e.g., open coding, theoretical sampling/ saturation, etc.) and quantitative (e.g., quasi-experimental designs, advanced statistical analysis, psychometric analysis, etc.) research methods and procedures for evaluating intervention programs. Specifically, when analyzed using Relational Data Analysis, response data from the Life Course Interview yielded theoretically meaningful categories with robust levels of reliability and concurrent (external) validity. Additionally, the pattern of qualitative change for participants in the intervention condition, the CLP, were found to be positive, significant, and in the hypothesized direction relative to the comparison group, providing support for the feasibility of creating evidence-based youth development programs for promoting positive development in self and identity in troubled youth.
A Multistage Longitudinal Comparative (MLC) Design Stage II
Authors: Kortsch Gabrielle , Kurtines William M. , Montgomery Marilyn J.
Published: April 2008

The study reported in this paper, a Multistage Longitudinal Comparative (MLC) Design Stage II evaluation conducted as a planned preliminary efficacy evaluation (psychometric evaluation of measures, short-term controlled outcome studies, etc.) of the Changing Lives Program (CLP), provided evidence for the reliability and validity of qualitative measures under development as well as the utility of unifying qualitative (e.g., open coding, theoretical sampling/saturation, etc.) and quantitative (e.g., quasi-experimental designs, advanced statistical analysis, psychometric analysis, etc.) research methods and procedures for evaluating intervention programs. Specifically, when analyzed using Relational Data Analysis, response data from the Future Possible Selves Questionnaire yielded theoretically meaningful categories with robust levels of reliability and construct and concurrent (external) validity. Additionally, the pattern of qualitative change for participants in the intervention condition, the CLP, were found to be positive, significant, and in the hypothesized direction relative to the comparison group, providing support for the feasibility of creating evidence-based youth development programs for promoting positive development in self and identity in troubled youth.
Benign Rolandic Epilepsy—Perhaps Not So Benign: Use of Magnetic Source Imaging as a Predictor of Outcome
Authors: Perkins F. Frederick , Breier Joshua , McManis Mark H. , Castillo Eduardo , Wheless James , McGregor Amy L. , Chacon Monica , Clarke Dave F.
Published: April 2008

The purpose of this study was to evaluate children with benign rolandic epilepsy, a childhood epilepsy characterized by centrotemporal/rolandic spike-wave discharges with infrequent partial seizures that may secondarily generalize. Recently, some investigators have questioned whether benign rolandic epilepsy is indeed “benign” or whether long-term cognitive outcome may be adversely affected. We initiated an ongoing study to identify children with benign rolandic epilepsy. The children were evaluated in the Texas Comprehensive Epilepsy Program using outpatient or continuous video-electroencephalographic monitoring, brain magnetic resonance imaging, magnetoencephalography, and neuropsychological testing. Neuropsychological testing revealed fine motor dysfunction, visuomotor integration deficits, dyscalculia, and/or expressive language deficits in all of the 9 patients evaluated, reaffirming that benign rolandic epilepsy is not necessarily a benign disorder. Our study shows a high concordance of motor and cognitive deficits in benign rolandic epilepsy, as others have previously suggested. Furthermore, magnetic source imaging shows a higher resolution of dipole localization compared with conventional electroencephalography, which may ultimately improve prediction of deficits. This reaffirms that magnetoencephalography is a valuable diagnostic tool in the evaluation of children with benign rolandic epilepsy.