bluuebunny/crossref_metadata_2025 huggingface dataset:
Zielorientierungen: Zur Relevanz der Schulfächer
Authors: Sparfeldt Jörn R. , Buch Susanne R. , Wirthwein Linda , Rost Detlef H.
Published: November 2007

Zusammenfassung. Zielorientierungen gelten als wichtige Determinanten schulischen Lernens. Wie auch bei anderen motivationalen Konstrukten stellt sich die Frage, inwieweit Zielorientierungen eher schulfachübergreifend oder schulfachspezifisch sind. Schülerinnen und Schüler der 7.-10. Klassenstufe (N = 1210) bearbeiteten einen Fragebogen zur Erfassung von vier Zielorientierungen, jeweils auf sechs Schulfächer bezogen (Mathematik, Physik, Chemie, Deutsch, Englisch, Geschichte). Konfirmatorische Faktorenanalysen konnten die vier postulierten Zielorientierungen Lernziele, Annäherungs-Leistungsziele, Vermeidungs-Leistungsziele und Arbeitsvermeidung in jedem der sechs Schulfächer bestätigen. Zudem ließen sich die sechs Fächer innerhalb jeder der vier Zielorientierungen trennen. Anschließende Modellvergleiche dokumentierten die Bedeutung einer simultanen Beachtung beider Gliederungsaspekte. Differentielle Beziehungen der schulfachspezifischen Zielorientierungen zu Fachzensuren und fachspezifischen Selbstkonzepten wiesen auf deren konvergente/divergente Validität hin.
Evaluation der deutschen Version des Autismus-Spektrum-Quotienten (AQ) - die Kurzversion AQ-k
Authors: Freitag Christine M. , Retz-Junginger Petra , Retz Wolfgang , Seitz Christiane , Palmason Haukur , Meyer Jobst , Rösler Michael , von Gontard Alexander
Published: November 2007

Zusammenfassung. Theoretischer Hintergrund: Autistische Störungen zeichnen sich durch Einschränkungen in den Bereichen Soziale Interaktion, Kommunikation und stereotypes, restriktives Verhalten aus. Bisher existiert noch kein deutschsprachiges Selbstbeurteilungsinstrument, das zum Screening bei Verdacht auf autistische Störung eingesetzt werden kann. Fragestellung: Testtheoretische Analyse des Screening-Fragebogens Autismus-Spektrum-Quotient (AQ). Methode: Die psychometrischen Kennwerte des AQ wurden in zwei nicht-klinischen, einer klinisch-forensischen und einer Stichprobe mit High-functioning Autismus/Asperger Syndrom ermittelt. Ergebnisse: Auf Grund einer teilweise sehr niedriger Trennschärfe der Einzelitems wurde eine Kurzversion des Fragebogens (AQ-k) gebildet, bestehend aus Items mit ausreichender Trennschärfe. Die Hauptkomponentenanalyse des AQ-k resultierte in drei Faktoren (Soziale Interaktion und Spontaneität, Fantasie und Vorstellungsvermögen, Kommunikation und Reziprozität), deren innere Konsistenzen zwischen 0,65-0,87 lagen. Die Retest-Reliabilität war zufrieden stellend, ebenso die externe Validität. Die Sensitivitätsanalyse ergab einen cut-off-Wert von 17. Schlussfolgerung: Der AQ-k eignet sich als Selbstbeurteilungsinstrument zum Screening auf autistische Störung bei normal begabten Personen ab 16 Jahren. Eine Diagnose kann durch das Instrument nicht gestellt werden.
Data mining in space physics: MineTool algorithm
Authors: Karimabadi H. , Sipes T. B. , White H. , Marinucci M. , Dmitriev A. , Chao J. K. , Driscoll J. , Balac N.
Published: November 2007

A novel data mining method called MineTool is introduced which, by virtue of automating the modeling process and model evaluations, makes it more accessible to nonexperts. The technique aggregates the various stages of model building into a four‐step process consisting of (1) data segmentation and sampling, (2) variable preselection and transform generation, (3) predictive model estimation and validation, and (4) final model testing. Optimal strategies are chosen for each modeling step. However, the modular design of the MineTool enables the substitution of alternative strategies in any of the four modeling steps. A notable feature of the technique is that the final model is always in closed analytical form rather than “black box” form of most other techniques. MineTool can be used for analysis of data (e.g., time series) as well as images. The utility of the technique is illustrated through several examples based on synthetic data. Application of the technique to analysis of spacecraft data will be presented in subsequent papers.
Self‐similar scaling of kinetic energy density in the inertial range of solar wind turbulence
Authors: Podesta J. J.
Published: November 2007

Probability density functions (pdfs) for time‐delayed differences of the solar wind proton density np are shown to be approximately self‐similar over the range of timescales from ∼90 to 1100 s with an approximate scaling exponent γ = 0.274. The density pdfs are found not to be self‐similar over the expanded range of timescales from 90 to 104 s in the spacecraft frame. Pdfs for time‐delayed differences of the kinetic energy density ρV2 are found not to be self‐similar over either of these two time ranges. The observed self‐similar scaling of the proton density is important because it implies that the nonlinear evolution of this quantity in the inertial range of the turbulence is devoid of intermittency effects. These conclusions are based on the analysis of 10 years (a) of data from the Solar Wind Experiment on board the Wind spacecraft covering the time period from 1995 to 2004 and containing approximately 2.5 × 106 data points. Two types of analyses are performed. First, a graphical analysis is used to see whether the rescaled pdfs all lie on a common curve. Then, an analysis of low‐order structure functions is performed to see if the scaling properties of the structure functions are consistent with self‐similar scaling. Ideally, the results of the pdf scaling analysis and the structure function analysis should both produce the same value of the scaling exponent. Because structure functions are influenced by the presence of outliers in the data, special analysis techniques have to be used to extract the scaling behavior. The special techniques employed here are found to be of limited practical utility because of difficulties in obtaining demonstrable convergence of the scaling exponents.
THE ROLE OF THE LYMPHATIC SYSTEM AND LYMPHOID CELLS IN THE ESTABLISHMENT OF IMMUNOLOGICAL MEMORY
Authors: Smith JB , Cunningham AJ , Lafferty KJ , Morris Bede
Published: November 2007

The capacity of lymph nodes to show secondary reactivity has been investigated in sheep and in mice, using Swine Influenza virus and sheep red blood cells as antigens, respectively. Following a primary challenge to the political node of one leg, the node of the contralateral leg becomes primed and reacts with a secondary response to its first direct encounter of the antigen. This secondary reactivity is acquired in an indirect way and is not due to the transfer of antigen from the injection site in the opposite leg. The secondary response that occurs in “indirectly primed” nodes is not as vigorous or as prompt as mat occurring in “directly primed” nodes. This difference is thought to be due to the presence of both “residential” and “circulating” memory cells, the former class of cells being generated and remaining in lymph nodes where antigen becomes localized while the latter are free‐floating cells of lymph and blood. Circulating memory cells are recruited to a lymph node when an antigen is taken up there, but this recruitment does not appear to be a specific phenomenon.
A METHOD FOR THE ASSESSMENT OF THE CHRONIC HEPATOXICITY OF PYRROLIZIDINE ALKALOIDS
Authors: Jago Marjorie V
Published: November 2007

A method for the assessment of the relative chronic hepatotoxicity of pyrrolizidine alkaloids is described. Graded doses of the test‐compounds over the dose range 0·025–3·2 mmoles/kg. body weight were administered as single, intraperitoneal injections to two‐week‐old rats and the livers of the survivors examined four weeks later. The relative acute toxicity of the test‐compound was indicated by the dose‐levels which caused death within about a week and the chronic hepatotoxicity by those which produced hepatic megalocytosis within four weeks of the injection. It is suggested that the severity and extent of the megalocytosis produced is a measure of the persistent antimitotic action of the alkaloids. Detailed results of the screening of seven pyrrolizidine alkaloids are given.
Presynaptic nicotinic receptors: a dynamic and diverse cholinergic filter of striatal dopamine neurotransmission
Authors: Exley R , Cragg S J
Published: November 2007

The effects of nicotine on dopamine transmission from mesostriatal dopamine neurons are central to its reinforcing properties. Only recently however, has the influence of presynaptic nicotinic receptors (nAChRs) on dopaminergic axon terminals within striatum begun to be understood. Here, rather than simply enhancing (or inhibiting) dopamine release, nAChRs perform the role of a presynaptic filter, whose influence on dopamine release probability depends on presynaptic activity in dopaminergic as well as cholinergic neurons. Both mesostriatal dopaminergic neurons and striatal cholinergic interneurons play key roles in motivational and sensorimotor processing by the basal ganglia. Moreover, it appears that the striatal influence of dopamine and ACh cannot be fully appreciated without an understanding of their reciprocal interactions. We will review the powerful filtering by nAChRs of striatal dopamine release and discuss its dependence on activity in dopaminergic and cholinergic neurons. We will also review how nicotine, acting via nAChR desensitization, promotes the sensitivity of dopamine synapses to activity. This filtering action might provide a mechanism through which nicotine promotes how burst activity in dopamine neurons facilitates goal‐directed behaviour and reinforcement processing. More generally, it indicates that we should not restrict our view of presynaptic nAChRs to simply enhancing neurotransmitter release. We will also summarize current understanding of the forms and functions of the diverse nAChRs purported to exist on dopaminergic axons. A greater understanding of nAChR form and function is imperative to guide the design of ligands with subtype‐selective efficacy for improved therapeutic interventions in nicotine addiction as well as Parkinson's disease.

British Journal of Pharmacology(2008)153, S283–S297; doi:10.1038/sj.bjp.0707510; published online 26 November 2007
Cardiac capsaicin‐sensitive sensory nerves regulate myocardial relaxation viaS‐nitrosylation of SERCA: role of peroxynitrite
Authors: Bencsik P , Kupai K , Giricz Z , Görbe A , Huliák I , Fürst S , Dux L , Csont T , Jancsó G , Ferdinandy P
Published: November 2007

Background and purpose:

Sensory neuropathy develops in the presence of cardiovascular risk factors (e.g. diabetes, dyslipidemia), but its pathological consequences in the heart are unclear. We have previously shown that systemic sensory chemodenervation by capsaicin leads to impaired myocardial relaxation and diminished cardiac nitric oxide (NO) content. Here we examined the mechanism of diminished NO formation and if it may lead to a reduction of peroxynitrite (ONOO−)‐inducedS‐nitrosylation of sarcoendoplasmic reticulum Ca2+‐ATPase (SERCA2a).

Experimental approach:

Male Wistar rats were treated with capsaicin for 3 days to induce sensory chemodenervation. Seven days later, myocardial function and biochemical parameters were measured.

Key results:

Capsaicin pretreatment significantly increased left ventricular end‐diastolic pressure (LVEDP) decreased cardiac NO level, Ca2+‐dependent NO synthase (NOS) activity, and NOS‐3 mRNA. Myocardial superoxide content, xanthine oxidoreductase and NADPH oxidase activities did not change, although superoxide dismutase (SOD) activity increased. Myocardial and serum ONOO−concentration andS‐nitrosylation of SERCA2a were significantly decreased.

Conclusions and implications:

Our results show that sensory chemodenervation decreases cardiac NO via decreased expression and activity of Ca2+‐dependent NOS and increases SOD activity, thereby leading to decreased basal ONOO−formation and reduction ofS‐nitrosylation of SERCA2a, which causes impaired myocardial relaxation characterized by increased left ventricular end‐diastolic pressure (LVEDP). This suggests that capsaicin sensitive sensory neurons regulate myocardial relaxation via maintaining basal ONOO−formation and SERCAS‐nitrosylation.

British Journal of Pharmacology(2008)153, 488–496; doi:10.1038/sj.bjp.0707599; published online 26 November 2007
Role of cGMP‐dependent protein kinase in development of tolerance to nitroglycerine in porcine coronary arteries
Authors: Dou D , Zheng X , Qin X , Qi H , Liu L , Raj J U , Gao Y
Published: November 2007

Background and purpose:

The cGMP‐dependent protein kinase (PKG) is a key enzyme for nitrovasodilator‐induced vasodilation. The present study was to determine its role in nitrate tolerance.

Experimental approach:

isolated porcine coronary arteries were incubated for 24 h with nitroglycerin (NTG) and their relaxant responses were determined. PKG activity was assayed by measuring the incorporation of 32P into BPDEtide. PKG protein was determined by Western blotting and PKG mRNA by real‐time PCR.

Key results:

A 24 h incubation with NTG attenuated relaxation of coronary arteries to NTG, which was associated with decreased PKG activity. The nitrate tolerance induced with NTG at 10−7 M was affected by a scavenger of reactive oxygen species and the tolerance induced with NTG at 10−6 and 10−5 M showed cross‐tolerance to DETA NONOate and 8‐Br‐cGMP (a cell permeable cGMP analogue). PKG protein and mRNA were down‐regulated by a 24 h incubation with NTG at 10−5 M but not at 10−7 M. Acute exposure to exogenous superoxide inhibited PKG activity stimulated by NTG at 10−7 M but not at 10−5 M. Superoxide had no effect on PKG activity stimulated with exogenous cGMP.

Conclusions and implications:

Nitrate tolerance induced by NTG at low concentrations may result from an increased production of reactive oxygen species acting on sites upstream of PKG. The tolerance induced by NTG at higher concentrations may be in part due to suppression of PKG expression resulting from sustained activation of the enzyme. These distinct mechanisms of nitrate tolerance may be of clinical significance.

British Journal of Pharmacology (2008) 153, 497–507; doi:10.1038/sj.bjp.0707600; published online 26 November 2007
Optimal amplification of the Crow instability
Authors: Brion Vincent , Sipp Denis , Jacquin Laurent
Published: November 2007

A mechanism for promoting the Crow instability in a counter-rotating vortex pair is presented within the framework of linear dynamics. It consists of (i) the creation of a periodic array of vortex rings along the length of the vortices by stretching of vorticity at the leading hyperbolic point of the dipole, and (ii) the deformation of the vortices by the vortex rings leading to the Crow instability. A reduction of the characteristic time of the Crow instability by a factor of roughly 2 can be obtained by this mechanism.
Equivalence of nonequilibrium algorithms for simulations of planar Couette flow in confined fluids
Authors: Petravic Janka
Published: November 2007

Shear flow in fluids confined between planar solid walls is conventionally simulated by moving the walls past each other at constant relative velocity. In infinite fluids (in periodic boundary conditions), it is simulated using one of the “synthetic” nonequilibrium algorithms (the so-called Sllod and Dolls algorithms). Here I formulate the boundary conditions for the motion of confining walls that make these three algorithms equivalent in the weak-field limit.
Charge state of the fast gate in chloride channels: Insights from electrostatic calculations in a schematic model
Authors: Wijesinghe Rajiv , Coorey Nathan , Kuyucak Serdar
Published: November 2007

Fast gating is a unique property of chloride channels, where a permeating Cl− ion acts as its own ligand in opening the channel. The glutamate residue implicated in fast gating normally carries a unit negative charge. Whether this charge needs to be protonated to enable permeation of a Cl− ion is an important question that will affect how models of chloride channels are constructed. We investigate the energetic consequences of the charge state of this glutamate residue from continuum electrostatics using a schematic cylindrical channel model. Both analytical solutions of the Poisson equation for an infinite cylinder and numerical ones for a finite cylinder are employed in the calculations.
Enhanced forward emission from ZnO via surface plasmons
Authors: Lei D. Y. , Ong H. C.
Published: November 2007

By using metal-insulator-metal (MIM) as the cap layer, we have enhanced the photoluminescent emission from ZnO in the forward direction via coupling of surface plasmons. The basic principle behind the enhancement involves two steps. First, the overall light emission efficiency of ZnO is increased significantly due to the coupling and scattering of nonradiative surface plasmons at the metal/ZnO interface. The forward emission is then increased by enhanced transmission due to the excitation of radiative surface plasmons in the MIM structure. As a result, the forward emission from MIM/ZnO is found to be 7 and 3.5 times stronger than that from uncapped ZnO and M/ZnO. We expect that the MIM structure could evolve as an effective means in fabricating high brightness light emitting diodes from semiconductors.
Observation of electric-field induced Ni filament channels in polycrystalline NiOx film
Authors: Park Gyeong-Su , Li Xiang-Shu , Kim Dong-Chirl , Jung Ran-Ju , Lee Myoung-Jae , Seo Sunae
Published: November 2007

For high density of resistive random access memory applications using NiOx films, understanding of the filament formation mechanism that occurred during the application of electric fields is required. We show the structural changes of polycrystalline NiOx (x=1–1.5) film in the set (low resistance), reset (high resistance), and switching failed (irreversible low resistance) states investigated by simultaneous high-resolution transmission electron microscopy and electron energy-loss spectroscopy. We have found that the irreversible low resistance state facilitates further increases of Ni filament channels and Ni filament density that resulted from the grain structure changes in the NiOx film.
Highly efficient and compact photonic wire splitters on GaAs
Authors: Schuller Ch. , Höfling S. , Forchel A. , Etrich C. , Pertsch T. , Iliew R. , Lederer F. , Reithmaier J. P.
Published: November 2007

Symmetrical optical power T-splitters were fabricated using miniaturized 90° bends with a curvature radius of 2μm and a high transmittance of almost 99% per bend. A constant excess loss of only 1.4dB was achieved at a photonic wire width of 450nm over the wide wavelength range from 1.50to1.58μm. The dependence of the transmittance on the width of the photonic wires of the T-splitter was investigated experimentally and theoretically, and good agreement between experiments and three-dimensional finite-difference time-domain simulations was obtained.
Effect of molecular weight on the dielectric breakdown strength of ferroelectric poly(vinylidene fluoride-chlorotrifluoroethylene)s
Authors: Claude Jason , Lu Yingying , Wang Qing
Published: November 2007

The dielectric strengths of poly(vinylidene fluoride-chlorotrifluoroethylene) copolymers have been investigated as a function of molecular weights (MW) at different temperatures. We have shown that the electrical breakdown strength increases with increasing MW and decreasing temperature. Experimental measurements of the electrical breakdown field at 25°C agree fairly well with an electromechanical breakdown model. The dielectric breakdown at lower temperatures near and below the glass transition is attributed to the existence of thermal breakdown process, which is supported by numerical calculations and experimental measurements.
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2
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dual-layer gate dielectric for InGaAs enhancement mode metal-oxide-semiconductor field-effect transistor with channel inversion
Authors: Zheng J. F. , Tsai W. , Lin T. D. , Lee Y. J. , Chen C. P. , Hong M. , Kwo J. , Cui S. , Ma T. P.
Published: November 2007

A dual-layer gate dielectric approach for application in III-V metal-oxide-semiconductor field-effect transistor (MOSFET) was studied by using ultrahigh vacuum deposited 7–8nm thick Ga2O3(Gd2O3) as the initial dielectric to unpin the surface Fermi level of In0.18Ga0.82As and then molecular-atomic deposition of ∼2–3nm thick Si3N4 as a second dielectric protecting Ga2O3(Gd2O3). The total equivalent oxide thickness achieved in this study is 5nm. We have demonstrated an enhancement mode In0.18Ga0.82As∕GaAs MOSFET with surface inverted n channel with drain current (Id) of 0.1mA for a gate length of 10μm and a gate width of 880μm at Vds=1V and Vg=4.5V.
The effect of spatial structure on adaptation inEscherichia coli
Authors: Perfeito Lilia , Pereira M. Inês , Campos Paulo R.A , Gordo Isabel
Published: November 2007

Populations of organisms are generally organized in a given spatial structure. However, the vast majority of population genetic studies are based on populations in which every individual competes globally. Here we use experimental evolution inEscherichia colito directly test a recently made prediction that spatial structure slows down adaptation and that this cost increases with the mutation rate. This was studied by comparing populations of different mutation rates adapting to a liquid (unstructured) medium with populations that evolved in a Petri dish on solid (structured) medium. We find that mutators adapt faster to both environments and that adaptation is slower if there is spatial structure. We observed no significant difference in the cost of structure between mutator and wild-type populations, which suggests that clonal interference is intense in both genetic backgrounds.
Characteristics of patients who are violent to staff and towards other people from a community mental health service in South East England
Authors: RAO H. , LUTY J. , TRATHEN B.
Published: November 2007

Professionals working in the public sector in the UK report widespread violence towards staff working in areas such as health care, social services and education. This study compares the characteristics of patients with and without a history of violence in a large sample of patients attending a community mental health service in South East England. The data were taken from a study of comorbidity and cannabis use in a mental health trust covering a semi‐rural population of 250 000 people in Harlow and the surrounding area of South East England. Key workers were interviewed using semi‐structured questionnaires from the Comorbidity of Substance Misuse and Mental illness in Community Mental Health and Substance Misuse Services study. Rates of violence against health workers were more than 20 times higher among those patients with a history of violence (23.6% vs. 1%, P < 0.001). Alcohol and drug use was more frequent in those who were violent. Prevalence of comorbidity, schizophrenia and personality disorders was high. Key workers' estimates suggested that there was no difference in aggression, engagement or adherence to care plan among those with a history of violence.
Seasonality of forest soil microfungi in southern Quebec
Authors: Widden Paul
Published: November 2007

Data on microfungi isolated from the soils of four forests in southern Quebec were analysed, to detect seasonal changes in the community. Two-way analysis of variance showed that significant changes occurred for individual species, both between sites and sample times, and that significant season–site interactions occurred. Discriminant analysis showed that at all sites, there was a tendency for the community to shift towards a characteristic winter community during the colder periods of the year. Geomyces pannorus, Paecilomyces fumosoroseus, Pae. marquandii, Penicillium purpurogenum, Trichoderma koningii, T. polysporum, Botryotrichum piluliferum, Chrysosporum verrucosum, and Exophiala sp. LP111 were associated with samples from the colder months, in one or more of the sites. Sterile fungi, Fusarium solani, T. harzianum, T. hamatum, Pen. thomii, and Staphyotrichum coccosporum tended to be associated with the warmer months. There was also a tendency for samples from the seasonal "extremes" (warm dry summer samples and cold winter samples) to show some similarities. It is suggested that this trend may exist because fungi abundant during relatively unfavorable times of the year are not good competitors and therefore should be considered as "survivors." In this study, Exophiala sp. LP111, Gliomastix murorum, Paecilomyces carneus, T. viride, and Trichoderma sp. LP58 may fall into this category.
Plains cottonwood recruitment and survival on a prairie meandering river floodplain, Milk River, southern Alberta and northern Montana
Authors: Bradley Cheryl E. , Smith Derald G.
Published: November 2007

Age, distribution, and density of two populations of plains cottonwood (Populus deltoides var. occidentalis Rydb.) on the floodplain of the Milk River, southern Alberta and northern Montana, were studied in relation to historical river hydrology and sedimentation regimes. In Alberta, cottonwood recruitment leading to long-term survival on river meander lobes (point bars) correlates with years when daily maximum flows during the period of seed dispersal (June 1 to July 10) attain a stage equal to or greater than the 2-year return flood, based on the annual flood series. Such flood events during the seed dispersal period recur an average of once in 5 years. In Montana, on the floodplain for 25 km downstream of Fresno Dam, built in 1939, the densities of cottonwoods recruited since 1939 are significantly lower than on floodplain sites upstream, in Alberta. Results suggest that this is due to a marked reduction in flood magnitude and frequency, rates of sedimentation and meander migration. Based on this study, the prospects for cottonwood survival on floodplains downriver from dams in this and other prairie river valleys are not encouraging unless management measures are taken to reverse the trend.
Contribution de l'étude du polymorphisme enzymatique à la systématique des Pleurotes des Ombellifères
Authors: Boisselier-Dubayle Marie-Catherine , Baudoin Raymond
Published: November 2007

This study presents a contribution to the systematics of Pleurotus species growing on Umbellifers, which are classically divided into three types. Studies of enzyme polymorphism by electrophoresis performed on synthetized dikaryotic mycelia and their haploid components (homokaryons) allowed a genotypic determination of "wild" dikaryons, and a statistical treatment of homokaryotic genotypes. These results show a distinction between P. nebrodensis on one hand, and P. eryngii and P. ferulae on the other hand, and support the hypothesis of a division of P. nebrodensis into two types at least as distinct from each other as P. eryngii from P. ferulae. Different hypotheses related to internal dynamics and evolution of this group of Basidiomycetes are discussed.
Irrigation protects black walnut from frost damage
Authors: Beineke Walter F.
Published: November 2007

Late spring frost damage to black walnut (Juglansnigra L.) in a research clone bank was prevented by over-tree irrigation. Even though temperatures fell as low as −4.4 °C one night and 0 °C or lower on nine other occasions after leafing out began, irrigation provided adequate leaf, flower, and shoot protection. Highly significant differences were found in degree of frost damage between protected and unprotected areas. Flowering and seed production of protected grafts were increased 15- and 30-fold respectively over unprotected ramets of the same clones.
Cone size and seed yield in young Piceamariana trees
Authors: Caron G. E. , Powell G. R.
Published: November 2007

Black spruce (Piceamariana (Mill.) B.S.P.) cones were collected in 1980, l981, and 1982 from young trees in four plantations of different ages. Nine measures of cone size, seed yield per cone, and seed weight were determined by cone analysis, and the variation among plantations and years was assessed by analysis of variance. Relationships among the nine measures were assessed by correlation. Cone length, cone weight, total scales per cone, potential filled seeds per cone, total seeds per cone, total filled seeds per cone, and seed efficiency were all depressed in 1981, the year of poorest cone production. Potential filled-seed yield and actual filled-seed yield were highly correlated with most cone-size measures but poorly correlated with each other. Pollen availability in 1982 was assessed by trapping and by counting pollen cones. The catch of pollen grains was positively correlated with the numbers of pollen cones per tree. Total filled seeds per cone in 1982 was strongly related to pollen availability. Seed efficiencies of less than 35%, which occurred in the younger plantations and in the year of poorest pollen-cone and seed-cone production (1981), indicated excessive loss of potential seed.
Nothofagus regeneration in treefall gaps in northern Patagonia
Authors: Veblen Thomas T.
Published: November 2007

In the rain shadow of the Andes in northern Patagonia, the evergreen beech Nothofagusdombeyi occurs in mixed stands with the xeric trees Austrocedruschilensis and (or) Nothofagusantarctica. In two old-growth stands (>150 years old), size and age structures, treefall patterns, and regeneration responses to treefalls were examined. In the stand codominated by N. dombeyi and Austrocedrus, recruitment of both species occurs in small treefall gaps. The relative proportions of treefalls and potential successors in gaps imply that gap-phase regeneration is maintaining this stand in compositional equilibrium. In the second stand, N. antarctica was formerly a common canopy tree, but currently is not regenerating in treefall gaps; gaps are occupied instead by N. dombeyi. The successful regeneration of N. dombeyi in small treefall gaps in Patagonian forests contrasts with the dependence of this species on large-scale exogenous disturbance for its regeneration in lowland and montane Chilean rain forests. Small-scale gap-phase regeneration of N. dombeyi in Patagonian forests is successful because of (i) the lack of competing shade-tolerant tree species and (ii) the inability of understory bamboos to form dence understories in these relatively xeric habitats.
QUANTUM SIZE EFFECTS ON THE ENERGY LEVELS AND FAR-INFRARED SPECTRA: CHANGES FROM QUANTUM DOTS TO QUANTUM RINGS
Authors: PAN HUI
Published: November 2007

The energy levels and far-infrared spectra of two electrons confined in quantum dots and quantum rings under a magnetic field have been investigated. The size and shape effects of quantum rings on the levels and the spectra are clearly revealed. It is found that the spin oscillation of two electrons in a quantum ring with a magnetic field is caused by the Coulomb interaction. The transitions of two-electron far-infrared spectra are clearly shown from quantum dots to quantum rings. The influence of electron–electron interaction on the energy levels and far-infrared spectra has been discussed. The quantum size effects predict a possibility to observe phenomena related to electron-electron interaction in quantum rings.
ACOUSTIC EMISSION FROM PZT-5A AND PZT-8 CERAMICS DURING THE APPLICATION OF AC FIELD AT DIFFERENT FREQUENCIES
Authors: PRABAKAR K.
Published: November 2007

Acoustic Emission (AE) and hysteresis parameters were studied from PZT-5A (soft) and PZT-8 (hard) ceramics during the application of ac fields in the frequency range of 0.2 Hz to 5 Hz. AE was found to occur mainly due to domain switching in these ceramics during the application of ac fields. In PZT-5A, a threshold field was observed for the AE activity to begin in both the direction of the applied field and in general, it was found to decrease with increasing frequency. Apart from this, AE activity was found to decrease with increasing number of applied ac cycles, and is attributed to domain pinning. In the case of PZT-8, AE was found to occur even at zero field at higher frequencies and AE activity was found to increase with increasing number of field cycles. These are explained on the basis of the defect dipole — domain interaction in these ceramics.
Formation of n and p Regions in (114) and (5 5 12)-Silicon Substrates
Authors: De la Hidalga-W F. Javier , Rosales-Q Pedro , Torres-J Alfonso , Calleja-A Wilfrido , Gutierrez-D Edmundo , Kendall Don L.
Published: November 2007

In this work, the diffusion mechanisms of both boron and phosphorus dopants are analyzed when they are ion-implanted and thermally activated in high-index silicon substrates. Si(1 1 4) and Si(5 5 12) wafers are reported as highly promising substrates for the development of novel quantum structures specially for MOS devices. In order to obtain the final dopant distribution an electrochemical profiler was utilized. Because it is well known the lack of reported experimental data regarding the doping mechanism in these high-index silicon substrates, Si(1 0 0) and Si(1 1 1) substrates were utilized as reference. The experimental work was conducted varying the following ion implantation parameters: dose, energy, tilt angle, and silicon oxide masking film thickness; the thermal activation of the impurities was specially evaluated because their influence in the final distribution of dopants.
EIS and Microstructural Studies of TiN Coatings Deposited by PVD d.c. Magnetron Sputtering
Authors: Hidalgo Joaquin A. , Ocampo Cecilia M.
Published: November 2007

This work reports the electrochemical and microstructural behavior of TiN thin films prepared modifying the nitrogen fraction XN2 and the target power WB in a PVD d.c. magnetron sputtering system. EIS tests along with structural analysis by AFM and SEM shows that the coating thickness by itself is unable to explain the properties of the TiN coatings, also the microstructure plays an important role on the definition of corrosion behavior of the films. The thicker, denser and flatter coatings reveal the best corrosion resistance in long immersion time, showing low capacitance Cd (between 19-86 μF cm- 2) and high resistance Rct values.
Effect of Relative Humidity on Membrane Degradation Rate and Mechanism in PEM Fuel Cells
Authors: Xu Hui , Boroup Rodney , Brosha Eric , Gazon Fernando , Pivovar B. S.
Published: November 2007

The degradation rates and mechanisms of catalyst coated Nafion 212 membranes were investigated at a series of relative humidifies (RH). Degradation studies at open circuit voltage (OCV) showed that membrane degradation rates were faster at 60% RH than at 20% or 100% RH. Degradation studies performed under load (0.6V) showed that membrane degradation rates significantly increased after switching from high RH (100%) to low RH (25%) after 500 hours. This accelerated degradation was likely due to the dual effects of mechanical and chemical degradation. Gas chromatography performed on fuel cell exhaust gases has shown increased gas permeability at increased RH, but cannot fully explain the change of degradation rates with RH. A model is proposed to explain the effect of RH on membrane degradation rate. RH impacts the formation of oxygen radicals via both reactant concentration and reaction rate. Increased RH leads to higher gas permeability of hy drogen and oxygen thus higher reactant concentrations for oxygen radical formation. Conversely, the platinum surface tends to be more highly oxidized at high RH, lowering the reaction rates for oxygen radical formation. The tradeoffs between these phenomenon result in a higher membrane degradation rate at 60% RH than at either 20% or 100% RH for the conditions presented.
Modeling of Direct Methanol Fuel Cell Using a Resistive-Capacitive-Inductive Transmission-Line Equivalent Circuit
Authors: Wang Yang , Au George , Plichta Edward J. , Zheng Jim P.
Published: November 2007

A novel resistive-capacitive-inductive transmission-line equivalent circuit was used to model direct methanol fuel cell (DMFC). This fuel cell model inherited and improved existing impedance fuel cell model and transmission-line fuel cell model in many aspects. The transmission line model can properly describe the inductive and capacitive behaviors of DMFC operating in both low and high frequency regions. The advantages of this transmission line fuel cell model have been discussed based on well-known experimental impedance spectrum of DMFC. Finally, the model has been used to simulate the capacitance efficiency of DMFC. The numerical simulation proved that increasing double-layer capacitance of DMFC can provide good dynamic performance similar to a DMFC and supercapacitor hybrid power component.
Effects of Electrode Potential, SiCl4 Concentration, and Electrolysis Duration Period on Si Electrodeposition in a Hydrophobic Room-Temperature Molten Salt
Authors: Nishimura Yusaku , Fukunaka Yasuhiro
Published: November 2007

Effects of electrode potential and SiCl4 concentration on electrodeposition of Si were examined in trimethyl-n- hexylammonium bis(trifluoromethylsulfonyl)imide (TMHATFSI) containing various concentrations of SiCl4. A rougher and thicker film was electrodeposited in TMHATFSI containing higher concentration of SiCl4 or at more negative electrode potential. Current efficiency estimated from EDX spectra is highest at −2.0 V vs. Pt quasi-reference electrode (Q.R.E.). Time evolution of Si electrodeposition at −2.0 V vs. Pt Q.R.E. was also studied in TMHATFSI containing 0.1 M SiCl4. As the electrolysis progressed, the thickness of electrodeposited Si film increased, while current efficiency decreased, with approaching constant values.
Superconformal Electrodeposition of Silver from a Cyanide-free Bath for on-chip Metallization
Authors: Sun Jian-Jun , Chen Xiao-Bo , Xie Bu-Gao , Xiang Tong-Ling , Chen Jin-Huai , Chen Guo-Nan
Published: November 2007

A cyanide-free plating bath was used for the superconformal deposition of silver into fine trenches. It shows that in thiosulfate silver plating bath, cysteine as an additives adsorbed on silver electrode surface could enhance the polarization of silver deposition and suppress silver deposition rate. Trenches with 300 nm in width were void- freely filled in this bath.
Ineffectiveness of Electrolyte Additives for Overcharge Protection in Li-Ion Battery
Authors: Belov Dmitry , Yang Mo-Hua
Published: November 2007

A series of well-known overcharge protecting electrolyte additives for Li-ion batteries (diphenyl ether (PE), biphenyl (BP), cyclohexyl benzene (CHB) and N, N-dimethylacetamide (DMAC) were tested at equal conditions. A high energy density prismatic cell with LiCoO2 as a cathode was used. Overcharge additives in various concentrations in electrolyte (EC/PC/EMC, 1.1M LiPF6) were overcharged at 1C/12V conditions. The additives' influences on electrochemical cell performance were tested as well. None of the tested additives showed any notable improvements on battery safety during overcharge. Possible mechanisms of Li ion battery failure at overcharge will be discussed.
Synthesis and Characterization of a New Class of Monolithium Salts for PEO-Based Solid Polymer Electrolyte Systems
Authors: Chakrabarti Amartya , Filler Robert , Mandal Braja K.
Published: November 2007

Lithium ion conducting polymer electrolytes have significant potential in the field of secondary lithium batteries, including display and sensor devices. We report here a new class of lithium sulfonimide salts for use in lithium-ion battery electrolytes. These salts, prepared by a two- to three- step synthetic strategy from inexpensive and readily available starting materials, were characterized by 1H-NMR, FTIR and elemental analysis. The thermal properties of the salts were determined by thermogravimetric analysis and showed stabilities up to 300ºC. Earlier studies demonstrated that the ionic conductivity of solid polymer electrolytes could be improved by use of a borate ester plasticizer. In order to optimize conductivity, solid polymer electrolyte films were prepared by incorporating this plasticizer with each of the new salts in a PEO matrix. We observed that the Li:O ratio of 1:20 exhibits maximum ionic conductivity (2.05x10-6 S/cm at 30ºC for the salt ALT01). A trend of decreasing conductivity with increasing size of the anionic moiety was also noted. It was found that 1 g of plasticizer can be loaded in a film containing 1 g of PEO without deterioration of mechanical properties. An improved ionic conductivity of 3.82x10-5 S/cm at 30ºC was observed. The films also exhibited good thermal and electrochemical stabilities. Glass transition temperature of the films were determined using differential scanning calorimetry.
Redox Chemistry and Electrochemistry of DNA-wrapped Carbon Nanotubes
Authors: Zheng Ming
Published: November 2007

This manuscript is based on a presentation I gave at the 211th ECS Meeting (Chicago) in May 2007. It is a brief summary of our effort in the study of transition metal complexes with DNA/RNA-wrapped carbon nanotubes. I provide two examples to illustrate the rich chemistry between the two classes of molecules that is yet to be fully explored. These types of chemistry are of both fundamental scientific interest and technological importance.
Carbon Nano Sheet Powder
Authors: Yang Wubao , Zhao Zhen , Wang Yong
Published: November 2007

By peeling off the carbon film from substrate, carbon nano sheet powders (CNSP) were prepared. The carbon film was fabricated by high energy plasma enhanced chemical vapor deposition method. AFM showed that, its grain size is less than 100 nm, surface roughness Ra is 17.95 nm in a range of 5× 5μm of this film. Raman spectra discovered that there is strong and broadened dispersion peak only about 1580 cm-1 in this film. The shapes of CNSP are various irregular sheets, the smallest sheet is less than 10μm, the largest sheet is larger than 500μm in length, and the sheet is frizzy in width when it is long enough. The BET surface area is 6.66 m2/g and there are no any pore tested by N2 adsorption-desorption isotherms. Isotherm adsorption testing showed that even, when the relative pressure P/P0 larger than 0.3, the adsorption volume is decreased instead. After active elements of Mo and W were carried, the CNSP based catal ysts showed super desulfurizing performance of 459.9 ppm/g or 69.01 ppm/m2 from diesel oil hydrogenation.
Pentaheptite Allotropes of Carbon Nanotubes
Authors: Milosevic Ivanka , Volonakis George , Logothetidis Stergios , Popovic Zoran , Damnjanovic Milan
Published: November 2007

Stone-Wales bond rotation converts 4 adjacent graphene hexagons into 2 pentagon-heptagone pairs. If such an algorithm is applied on all primitive cells of hexagons, graphene is transformed into a sheet of interlinked pentagones and heptagones. Under condition that pentagons occur only as isolated pairs 2D hexagonal and rectangular pentaheptite (57) lattices are obtained. We determine the symmetry of nanotubes (NTs) rolled up from these lattices and perform symmetry preserving relaxation in order to assess stability and conducting properties of 57NTs . Density functional tight binding calculations are carried out by full-symmetry implemented POLSym code. Vast majority of 57NT is found to be metallic having considerably higher electronic density of states at Fermi level than their metallic conventional counterparts. Pathway for synthesis of certain types of 57NTs directly from the conventional CNTs by putting them under uniaxial tension is p roposed. Release of the strain goes through formation of double pentagon-heptagone pairs.
Landau Damping Effects on SO Limited Mobility
Authors: Shah Raheel , De Souza M. M.
Published: November 2007

Surface optical phonons scattering is essential in determning the channel mobility of high-k gate dielectric MOSFETs. Metal gates are believed to modulate the effects of high-k phonons to some extent in comparison to poly-Si gates. In this work nonideal metal gate model is used to study the impact of SO scattering on the nMOSFET channel mobility. Landau damping effects, which are found to be important in the coupled plasmon-phonon scattering, are studied from the perspective of different criteria in selecting the Landau limits.
One-Step Synthetic Procedures and Electrochemical Properties of Monodisperse 1-2 nm Metallic Nanoparticles
Authors: Freemantle Ruel G. , Guo Wen , Liu Minghong , Obare Sherine O.
Published: November 2007

We report the electrochemical properties and charge storage ability of thioether stabilized Pd nanoparticles. A new synthetic strategy was used to prepare monodisperse Pd nanoparticles less than 2 nm in diameter. Pd nanoparticles brought in contact with a charged semiconductor were found to accept and store the charge. By employing an iron (III) porphyrin complex as a redox couple [Fe(III/II)], we observed transfer of electrons from the Pd nanoparticles. The data supports the notion that Pd nanoparticles in the 1-2 nm size range are capable of behaving as small capacitors and are thus able to store charge and transfer them as needed.
On Natures of Sub-Gap Photoelectric and Optical Spectra in Nitrogen-Contaminated Nanocrystalline Diamond
Authors: Ligatchev Valeri , Ong Khuong Phuong , Wu Ping , Ostrikov Ken
Published: November 2007

Experimentally observed optical and photoelectrical spectra of nitrogen-contaminated (unintentionally doped) nano-crystalline CVD diamond films are simulated using semi-empirical adiabatic General Skettrup Model (GSM), which presumes dominant contributions of defect states from sp3-coordinated intra- granular carbon atoms to intra-band single electron spectrum N(E) of the material. This picture disagrees with a common viewpoint that the N(E) spectrum of the gap states in diamond powders and polycrystalline CVD films mainly originates from p and p* bonds of sp2-coordinated carbon atoms, which are distributed nearly uniformly over outer surfaces and/or interfaces of the diamond grains. The GSM predicts as well strong effect of granular morphology on the density of intra- band defect states in polycrystalline diamonds.
Properties of Sol Gel Dip Coated ZnO Films
Authors: Murali K. R. , Manjunathan U. , Kathiravan J. , Senthil P. , Krishna J.
Published: November 2007

Zinc oxide films were deposited on glass substrates by the sol gel dip coating method using Acrylamide route. The films were characterized by x-ray diffraction studies which indicated wurtzite structure. Optical absorption measurements indicated band gap in the range of 3.17 - 3.32 eV. XPS studies indicated the formation of ZnO. The resistivity of the films were in the range of 1000 - 10000 ohm cm.
Functional Changes of the Heart During Hypothermia
Authors: Cardi Luigi
Published: November 2007

The increasing use of hypothermia by surgeons has awakened the interest of physiologists and cardiologists in the effects of lowering body temperature upon the heart. In spite of a numerous literature on the subject, it was considered that a new experimental study, by means of electro- and phonocardiography, would be of interest.
Wasserburger : The Normal and Abnormal Unipolar Electrodiagramin Infants and Children
Authors: Wasserburger Richard H.
Published: November 2007

Only with a thorough knowledge of the normal EKG of infants and children can the abnormal be placed in its proper clinical perspective. Dr. WASSERBURGER has for the first time provided this knowledge with an analysis of 259,915 measurements on 1150 normal infants. With this data in hand, he is then able to discuss the various abnormalities which are to be met in clinical practice. This is of special value to the cardiologist and pediatrician, who are dealing with an entirely different physiology than that of the adult patient. A glance at the contents listed below will reveal some of the particular abnormalities considered.