bluuebunny/crossref_metadata_2025 huggingface dataset:
Adaptive modulation and combining for bandwidth and power efficient communication over fading channels
Authors: Belhaj Nesrine , Hamdi Noureddine , Alouini Mohamed‐Slim , Bouallegue Ammar
Published: July 2006

Traditional fading mitigation techniques are designed relative to the worst‐case channel conditions, resulting in a poor utilization of the spectrum and the available power a good percentage of the time. In contrast, we introduce and investigate in this paper new adaptive modulation and diversity combining techniques that jointly select the most appropriate constellation size and the most suitable diversity branches in response to the channel variation and given a desired bit error rate (BER) requirement. Numerical results show that these newly proposed adaptive modulation and combining schemes can reduce considerably the average receiver channel estimation complexity as well as the power drain from the battery while offering high spectral efficiency and satisfying the desired outage probability and BER requirements. Copyright © 2006 John Wiley & Sons, Ltd.
Probability of error analysis of predetection generalized selection combining receivers with correlated unbalanced Nakagami branches
Authors: Al‐Hussien Abdel‐Hakim S. , Banat Mohammad M.
Published: July 2006

In this paper we determine the probability of error of a predetection generalized selection combining (GSC) receiver with correlated and unbalanced diversity branches in a Nakagami‐m multipath fading channel. We start by finding the joint probability density function (PDF) of the decision variables. This involves the derivation of the joint PDF of the L largest random variables (L maxima) of an input population of N > L correlated nonidentically distributed random variables, based on the statistics of the input population. The results obtained are then used in the derivation of the error probabilities of noncoherent FSK (NCFSK) and DPSK receivers. Copyright © 2006 John Wiley & Sons, Ltd.
Sartre, Schelling, and onto-theology
Authors: GARDNER SEBASTIAN
Published: July 2006

It is well known that Sartre describes his form of existentialism as atheistic, and much of the rhetoric of Sartrean existentialism draws off the image of God's absence from the world. There are nevertheless, I argue, deep grounds for thinking that the coherence and well-groundedness of Sartre's thought requires that his phenomenological ontology take finally the form of an onto-theology: Sartre's ontology runs into difficulties concerning the origin of the for-itself and the unity of being; an onto-theology like Schelling's, which avoids the ‘ontological optimism’ that Sartre objects to in Hegel, both releases Sartre's ontology from its difficulties and furthers Sartre's central philosophical purposes.
A problem with Alston's indirect analogy-argument from religious experience
Authors: ZACKARIASSON ULF
Published: July 2006

In this paper, William Alston's argument from religious experience in Perceiving God is characterized and assessed as an indirect analogy-argument. Such arguments, I propose, should establish two similarities between sense perception (SP) and religious experience (CMP): a structural and a functional. I argue that Alston neglects functional similarity, and that SP and CMP actually perform different functions within the practices they belong to. Alston's argument is therefore significantly weaker than generally assumed. Finally, I argue that regardless of whether an increased emphasis on fruits could strengthen indirect analogy-arguments or not, this is not a strategy available to Alston as long as he retains his commitments to religious exclusivism and a religious metaphysical realism.
Theism and the philosophy of nature
Authors: CORDRY BENJAMIN S.
Published: July 2006

In this paper I argue that traditional theism, in its theory, history, and practice has implications for the philosophy of nature. Namely, nature should be designed around aesthetic or meaningful principles and nature should be engineered in order to fulfil a fairly well defined set of purposes. If theism is true, we should be able to study nature objectively as a teleological system. After all, the teleological structure of nature is more important to us as spiritual beings than its mechanisms. Since a teleological philosophy of nature is no longer viable, traditional theism is untenable.
Hasidic mysticism as an activism
Authors: GELLMAN JEROME
Published: July 2006

In her important work, Hasidism as Mysticism: Quietistic Elements in Eighteenth Century Hasidic Thought, the late Rivkah Schatz-Uffenheimer depicted early eighteenth-century Hasidism as a movement with pronounced ‘quietist tendencies’. In this paper I raise several difficulties with this thesis. These follow from social-activist features of early Hasidism as well as from a selection from the writings of leading early Hasidic masters. I conclude that a major stream of thought in early Hasidim was not quietist in tendency. Finally, I compare the intentions of the masters I cite to some non-quietist themes in Eastern mystical thought.
English-medium teaching in European higher education
Authors: Coleman James A.
Published: July 2006

In the global debates on English as international lingua franca or as ‘killer language’, the adoption of English as medium of instruction in Higher Education is raising increasing concern. Plurilingualism and multilingualism are embedded in the official policies of the European Union and Council of Europe, and the Bologna Process for harmonizing Higher Education promises ‘proper provision for linguistic diversity’. But even enthusiasts acknowledge the problems of implementing such policies in the face of an inexorable increase in the use of English. This survey draws on the most recent and sometimes disparate sources in an attempt to paint a comprehensive and up-to-date picture of the spread of English-medium teaching in Europe's universities. The article sets the changes in the context of accelerating globalization and marketization, and analyses the forces which are driving the adoption of English, and some of the problems which accelerating ‘Englishization’ of European Higher Education might create.
Divergent leaf traits among congeneric tropical trees with contrasting habitat associations on Borneo
Authors: Paoli Gary David
Published: July 2006

A prediction of the hypothesis that niche processes control plant species distributions across edaphic gradients is that pairwise comparisons of related species on contrasting soils should show consistent patterns of trait divergence. This hypothesis was tested in lowland Bornean rain forest by combining measurements of leaf traits, soil nutrients and the distribution of tree species in the Dipterocarpaceae across a nutrient gradient. Nine species were studied, comprising four related pairs in Shorea (phylogenetic independent contrasts; PICs) and one habitat generalist (Dipterocarpus sublamellatus). Lamina area, specific leaf area (SLA), leaf nitrogen (N) and phosphorus (P) were measured for ∼10 saplings of each species; habitat associations were defined as a continuous function of soil nutrients and categorically in relation to substrate. Species distributions and traits varied significantly with soil nutrients. When all species were pooled, SLA and leaf P increased significantly with species' distribution across the nutrient gradient; leaf N showed the same trend. Trait shifts with habitat were stronger and more pervasive when habitat was defined categorically – in all four PICs, rich-soil specialists had larger leaves, higher SLA, leaf N and P, and lower N:P ratios. Trait shifts with habitat at least partly reflect intrinsic differences between species. Within Shorea, variation in lamina area and N:P ratio were more strongly related to phylogeny than habitat, whereas the reverse held for SLA and leaf P. Phylogeny also influenced the extent of trait divergence between related species on different soils, and patterns of trait correlation within lineages. Results support the hypothesis that niche processes influence the distribution of species and traits in lowland tropical tree communities, and highlight the value of phylogenetic information for increasing the power of comparative studies.
Seasonality in reproduction, age structure and density of the gracile mouse opossum Gracilinanus microtarsus (Marsupialia: Didelphidae) in a Brazilian cerrado
Authors: Martins Eduardo Guimarães , Bonato Vinícius , da-Silva Cibele Queiroz , dos Reis Sérgio Furtado
Published: July 2006

The temporal pattern of reproduction and its consequences for age structure and density were investigated in a population of the gracile mouse opossum Gracilinanus microtarsus in south-eastern Brazil. Individuals of G. microtarsus were monitored through capture–mark–recapture methods from August 2000 to February 2003 in a remnant of cerradão, a forest-like physiognomy of the highly seasonal cerrado biome. The temporal pattern of reproduction of the population studied was highly seasonal with rearing of the offspring occurring in the first half of the warm-wet season, when the abundance of food resources – primarily insects – in the cerrado is high. Shortly after reproduction, the density of adults decreased sharply, possibly because of high post-mating mortality, leading to a gradual replacement of adults by their offspring in the following months and little overlap of generations. Our data suggest that climatic and environmental factors affect the onset of reproduction and interact with endogenous factors that decrease post-mating survival to produce the observed pattern of seasonal variation in age structure and density. It is suggested that the dynamics of populations of G. microtarsus may be driven primarily by food limitation and that long-term studies are needed to understand its feedback structure.
Species–habitat associations in a Sri Lankan dipterocarp forest
Authors: Gunatilleke C. V. S. , Gunatilleke I. A. U. N. , Esufali S. , Harms K. E. , Ashton P. M. S. , Burslem D. F. R. P. , Ashton P. S.
Published: July 2006

Forest structure and species distribution patterns were examined among eight topographically defined habitats for the 205 species with stems ≥ 1 cm dbh inhabiting a 25-ha plot in the Sinharaja rain forest, Sri Lanka. The habitats were steep spurs, less-steep spurs, steep gullies and less-steep gullies, all at either lower or upper elevations. Mean stem density was significantly greater on the upper spurs than in the lower, less-steep gullies. Stem density was also higher on spurs than in gullies within each elevation category and in each upper-elevation habitat than in its corresponding lower-elevation habitat. Basal area varied less among habitats, but followed similar trends to stem density. Species richness and Fisher's alpha were lower in the upper-elevation habitats than in the lower-elevation habitats. These differences appeared to be related to the abundances of the dominant species. Of the 125 species subjected to torus-translation tests, 99 species (abundant and less abundant and those in different strata) showed at least one positive or negative association to one or more of the habitats. Species associations were relatively more frequent with the lower-elevation gullies. These and the previous findings on seedling ecophysiology, morphology and anatomy of some of the habitat specialists suggest that edaphic and hydrological variation related to topography, accompanied by canopy disturbances of varying intensity, type and extent along the catenal landscape, plays a major role in habitat partitioning in this forest.
Mortality and recruitment of hemi-epiphytic figs in the canopy of a Bornean rain forest
Authors: Harrison Rhett D.
Published: July 2006

Hemi-epiphytic figs (Moraceae; Ficus subgenus Urostigma) are a distinctive component of the canopy of tropical rain forests. The hemi-epiphytic habit has risen independently several times, and is recorded in over 20 plant families today, but with approximately 350 species globally figs are by far the most important (Berg & Corner 2005, Putz & Holbrook 1986). They are ubiquitously diverse in tropical lowland rain forests and are represented by independent radiations in each region (Harrison 2005, Jousselin et al. 2003). Moreover, their abundant production of fruit at all times of the year makes them functionally important as food for wildlife, especially during periods of general fruit shortage (Shanahan et al. 2001a). However, hemi-epiphytic fig populations occur at very low densities and this, combined with the difficulties of access to the canopy, has meant that study of their biology lags behind that of other rain forest plants (Harrison et al. 2003). Here, I present the first estimates of mortality and recruitment for any community of hemi-epiphytic figs.
Assessing intraspecific phenological synchrony in zoochorous trees from the monsoon forests of northern Australia
Authors: Franklin Donald C. , Bach Christine S.
Published: July 2006

Intraspecific synchrony in the phenology of tropical forest trees has implications for satiation of browsers and seed predators, pollination, dispersal and interpreting plant responses to environmental cues and stresses. Community phenological studies have been constrained in their consideration of these issues by the lack of concise quantitative measures of intraspecific synchrony. We propose a novel application of Colwell's predictability indices to overcome this deficiency. Its application is demonstrated by evaluating the leaf and reproductive phenologies of 8–16 individuals of each of 20 monsoon forest tree species from northern Australia monthly for 30 mo. The indices yielded substantial additional information over that provided by summaries averaged amongst conspecifics. Marked intraspecific asynchronies in leaf flush or flowering occurred in five evergreen species and two deciduous fig species, and were associated with prolonged individual commitments to these states. Five partly deciduous species exhibited marked intraspecific variation in the seasonal extent of leaf loss. We interpret the observed variation in intraspecific synchrony in terms of contrasting water-use and pollination strategies. The synchronicity indices are concise and robust to small and variable sample sizes, and may thus enhance studies of species-rich assemblages.
Estimating species-specific wood density from the genus average in Indonesian trees
Authors: Slik J. W. F.
Published: July 2006

To be able to make accurate estimates of the carbon stocks present in the world's tropical forests, there is a growing need for accurate tree biomass estimations on large spatial scales (Chave et al. 2004, Cummings et al. 2002, Nascimento & Laurance 2004). Wood-specific gravity forms an important component of these biomass estimations (Baker et al. 2004, Magcale-Macandog 2004, Nogueira et al. 2005). Even though Chave et al. (2004) found that the most important source of error in above-ground biomass estimation (AGB) is currently related to the choice of allometric model, Baker et al. (2004) show that for two estimates of AGB in Amazonian forests derived using different allometric equations, stand-level specific wood gravity still explained 45.4% and 29.7% of the total variation in AGB.
Validität des BIP und des NEO-PI-R
Authors: Hülsheger Ute R. , Specht Elke , Spinath Frank M.
Published: July 2006

Zusammenfassung. Die vorliegende Studie untersuchte die konkurrente Validität eines explizit berufsbezogenen (BIP) und eines allgemeinen Persönlichkeitsverfahrens (NEO-PI-R) zur Erklärung objektiver und subjektiver Berufserfolgskriterien. Als objektive Kriterien wurden Bruttoeinkommen und Berufsstatus erhoben, stellen- sowie umfeldbezogene Arbeitszufriedenheit und der subjektiv eingeschätzte Berufserfolg dienten hingegen als subjektive Kriterien des beruflichen Erfolges. Anhand einer Stichprobe berufstätiger Erwachsener wurde einerseits die Validität der beiden Persönlichkeitstests separat untersucht, andererseits wurde der inkrementelle Anteil bestimmt, den BIP und NEO-PI-R zur Varianzaufklärung über den jeweils anderen Test hinaus lieferten. Unter Kontrolle verschiedener mit Berufserfolg in Beziehung stehender Variablen (Alter, Geschlecht, Ausbildungsniveau, Durchschnittsnote, Dauer der Tätigkeit) leisteten beide Verfahren bedeutsame Beiträge zur Erklärung der Varianz objektiver und subjektiver Berufserfolgskriterien. Darüber hinaus leisteten beide Inventare vergleichbare Beiträge zur Varianzaufklärung über das jeweils andere Verfahren hinaus. Auch in Bezug auf die von den Teilnehmern beurteilte Akzeptanz unterschieden sich die beiden Verfahren nicht substanziell voneinander. Implikationen dieser Befunde werden in Hinblick auf bisherige Ergebnisse zum Zusammenhang zwischen Persönlichkeitsvariablen und Berufserfolg diskutiert.
Assessing the Big-Five Personality Domains via Short Forms
Authors: Herzberg Philipp Yorck , Brähler Elmar
Published: July 2006

This research evaluated a German version of a recently introduced brief measure of the Big-Five domains (Ten Item Personality Inventory [TIPI]). Since we could not confirm the virtues of the TIPI in a representative, general population-based sample from Germany, we develop a revised short form, measuring the Big-Five personality domains with 16 adjectives. These new scales showed better reliability than the TIPI, fit the Big-Five factor structure, and were orthogonal. As preliminary evidence of construct validity, support was found for convergence correlations with the NEO-FFI and other criterion measures. Although somewhat inferior to standard Big-Five instruments, this brief adjective measure can stand as reasonable proxy for longer Big-Five measures when research conditions do not allow the use of longer instruments.
The Assessment of Psychological Strain in Work Contexts
Authors: Mohr Gisela , Müller Andreas , Rigotti Thomas , Aycan Zeynep , Tschan Franziska
Published: July 2006

Irritation as defined in this paper is the subjectively perceived emotional and cognitive strain in occupational contexts. The structural equivalence of the Arabic, Dutch, English, French, Italian, Russian, Spanish, Turkish, and Polish adaptations of the German Irritation Scale is examined. The Irritation Scale is recommended for application particularly in occupational contexts. In this field it can be used for evaluating interventions, for research on stress at work, and for individual counseling. Exploratory factor analyses, as well as single group and different multiple-group confirmatory factor analyses, were performed. Structural equivalency in terms of equal factor loadings as well as equal factor covariances across all adaptations can be claimed. However, the single group analyses suggest that the hypothesized factor model should be rejected in the English, Russian, Spanish, and Turkish versions, mainly because of borderline values in the RMSEA index.
The WHO Quality of Life Assessment Instrument (WHOQOL-100)
Authors: Trompenaars Fons J. , Masthoff Erik D. , Van Heck Guus L. , Hodiamont Paul P. , De Vries Jolanda
Published: July 2006

This study scrutinizes the ability of the WHO quality of life assessment instrument (WHOQOL-100) to discriminate (1) between psychiatric outpatients and the general population, and (2) between subgroups of psychiatric outpatients. A sample of Dutch adult psychiatric outpatients (N = 410) completed the WHOQOL-100. In addition, DSM-IV Axis-I and Axis-II diagnoses were obtained. Compared with the general population, psychiatric outpatients scored significantly lower on all aspects of self-reported quality of life (QOL). Within the group of outpatients, participants with DSM-IV diagnoses had lower scores than those without. Participants with diagnoses on both Axis-I and Axis-II of DSM-IV (comorbidity) had the lowest self-reported QOL. It is concluded that in psychiatric outpatients, outcome scores of self-reported QOL were negatively related to presence and degree of psychopathology. The WHOQOL-100 has good discriminant ability for psychiatric outpatients.
Acceleration of antiearthward electron fluxes in the auroral region
Authors: Andersson L. , Ergun R. E.
Published: July 2006

This study presents a statistical analysis of antiearthward electron fluxes associated with the downward current region of the aurora based on 600 events from the FAST mission. A comparison between the observed particle energies and the electrostatic potentials inferred from the perpendicular electric field measurement suggests that the acceleration process can be separated into two types. One type fits a model with quasi‐static parallel electric fields which can account roughly one half of the events. A second type consists of events in which the antiearthward electrons appear to be accelerated by a dynamic process such as Alfvén waves or evolving parallel electric fields. We also point out that a nonaccelerated class of antiearthward electron fluxes produced by secondary electron production in the ionosphere also exists.
Rates of continental breakup magmatism and seafloor spreading in the Norway Basin–Iceland plume interaction
Authors: Breivik Asbjørn Johan , Mjelde Rolf , Faleide Jan Inge , Murai Yoshio
Published: July 2006

In year 2000, an ocean bottom seismometer (OBS) profile was acquired across the Møre margin to the Aegir Ridge, an extinct seafloor spreading axis. The margin is an early Eocene volcanic passive margin, located between the Faeroe‐Iceland Ridge (FIR) and the East Jan Mayen Fracture Zone (EJMFZ). The P wave data were modeled by ray tracing to give a crustal transect showing a 10–11 km thick igneous crust created by breakup magmatism, tapering off to magma‐starved seafloor spreading by C23 time (51.4 Ma). The location of the EJMFZ was reinterpreted from a satellite derived gravity map, and spreading direction in the Norway Basin reevaluated. No other fracture zones were confirmed, and both thin oceanic crust (4–5 km) and lack of fracture zones resemble ultraslow spreading on the Arctic Gakkel Ridge. Magnetic seafloor spreading anomalies were identified from the magnetic track recorded with the OBS profile, and half spreading rates were derived. Early seafloor spreading was slow (15–32 mm yr−1), approaching ultraslow (6–8 mm yr−1) by C20 time (42.7 Ma). A V‐shaped pattern seen in the gravity field located only around the northern part of the Aegir Ridge corresponds to increased crustal thickness in the seismic model, recording northeast transport (3–6 mm yr−1) of more melt‐fertile asthenosphere zones. The magma‐starved character of the Norwegian Basin seen also during slow seafloor spreading may be the result of depletion of the asthenosphere when the Iceland plume constructed the FIR to the south, as the asthenosphere is subsequently transported into the Norway Basin.
Optical determinations of suspended sediment dynamics in western Long Island Sound and the Connecticut River plume
Authors: Ackleson Steven G.
Published: July 2006

The magnitude of beam attenuation attributed to suspended sediments, cp, and the slope of the log‐transformed attenuation spectrum, γ, were used to investigate the properties and dynamic nature of matter suspended in the waters of western Long Island Sound (LIS) and the adjacent Connecticut River plume (CRP). Within the LIS, cp and γ indicate a robust relationship between sediment concentration and particle size distribution (PSD). As concentration increased, the PSD shifted to larger particles. The highest concentrations and particle sizes were found in a nepheloid layer adjacent to the sound floor. Within the adjacent CRP, sediments were observed to shift towards smaller particles at the lateral plume boundary, where current shear stress may have disrupted large particle aggregates, relative to sediments in the more quiescent plume interior. A strong linear correlation between γ and salinity was also found, indicating that mixing between the two water masses may also have altered the PSD of the plume sediments. A suspended sediment attenuation model based on Mie theory, a power law form of the PSD, and a single sediment source indicates that the observed changes in LIS cp and γ are consistent with sediment removal as particles settle with size‐dependent rates. In contrast, within the CRP, the model supports the hypothesis that turbulence‐induced aggregate disruption at the lateral plume boundary is responsible for the observed variability in cp and γ. However, mixing between the LIS and CRP particle populations would violate the single source requirement of the model and necessitate a more complicated set of particle dynamics in order to correctly interpret the observed variability in particulate attenuation.
Light field around a point light source in the ocean
Authors: Kirk John T. O.
Published: July 2006

Bioluminescence in the ocean can, to a reasonable approximation, be regarded as originating in point sources of light. In addition, submerged artificial point sources can be used to measure the absorption coefficients of seawater. To arrive at a better quantitative understanding of these phenomena, a theoretical and computer modeling study has been carried out of the nature of the light field around an underwater point source as determined by the inherent optical properties of the seawater. It has been shown that the radial attenuation coefficient for net outward plane irradiance due solely to absorption and scattering (i.e., setting aside inverse square law attenuation) can satisfactorily be expressed as a function of the IOP by KEab(av) = [a2 + 1.5(1 − s)ab]. In addition to providing a predictive tool for the light field around bioluminescent events, this relationship makes possible more accurate determination of absorption coefficients using submerged point sources of light.
Comparison of different global information sources used in surface radiative flux calculation: Radiative properties of the near‐surface atmosphere
Authors: Zhang Yuanchong , Rossow William B. , Stackhouse Paul W.
Published: July 2006

Direct estimates of surface radiative fluxes that resolve regional and weather‐scale variability over the whole globe with reasonable accuracy have only become possible with the advent of extensive global, mostly satellite, data sets within the past couple of decades. The accuracy of these fluxes, estimated to be about 10–15 W/m2, is largely limited by the uncertainties of the input data sets. This study presents a fuller, more quantitative evaluation of these uncertainties, mainly for the near‐surface air temperature and humidity, by comparing the main available global data sets from the European Centre for Medium‐Range Weather Forecasts, NASA, the National Centers for Environmental Prediction, the International Satellite Cloud Climatology Project (ISCCP) and the Laboratoire de Météorologie Dynamique that are treated as ensemble realizations of actual climate such that their differences represent an estimate of the uncertainty in their measurements (because we do not know the absolute truth). The results are globally representative and may be taken as a generalization of our previous ISCCP‐based uncertainty estimates for the input data sets. Near‐surface atmospheric properties have the primary role in determining the surface downward longwave (LW) flux. From this study, the most important quantity, the surface air temperature, has a uncertainty of about 2–4 K (3 K on average), which would easily induce about 15 W/m2 uncertainty for surface downward LW flux. The humidity profile comparison suggests an uncertainty of 20–25% for the atmospheric column precipitable water below the 300 hPa level, which would cause ≲10 W/m2 uncertainty for surface downward LW flux, making it the second largest source of uncertainty. The comparison for the difference between surface skin and air temperature shows its uncertainty is about 2–3 K, which translates into 10–15 W/m2 uncertainty for surface net LW flux. The used atmospheric data set from ISCCP represents the diurnal variations better than the other available sources (as it was designed to do) and the synoptic variations only slightly better than the other sources, but it still has notable clear‐cloudy sky biases and interannual variations that are dominated by spurious changes introduced by methodology changes in the original TOVS product. In a companion paper, the work is extended to evaluate the uncertainties of surface radiative properties.
Climate change scenarios for seasonal precipitation in South America from IPCC‐AR4 models
Authors: Vera Carolina , Silvestri Gabriel , Liebmann Brant , González Paula
Published: July 2006

A subset of climate simulations of the 20th century from the IPCC‐AR4 is analyzed to assess the ability of these models to reproduce the observed climatological seasonal precipitation in South America during the period 1970–1999. Changes of the model climatology in a climate change scenario (SRESA1b) for the period 2070–2099 are also discussed. Results show that models are able to reproduce the main features of the precipitation seasonal cycle over South America, although the precipitation in the SACZ region and the precipitation maximum over southeastern South America observed during the cold season are not well‐ represented. There is a general consensus among models that the precipitation changes projected are mainly: i) an increase of summer precipitation over southeastern subtropical South America; ii) a reduction of winter precipitation over most of the continent; and iii) reduction of precipitation in all seasons along the southern Andes.
Are decadal anthropogenic emission reductions in Europe consistent with surface ozone observations?
Authors: Vautard Robert , Szopa Sophie , Beekmann Matthias , Menut Laurent , Hauglustaine Didier A. , Rouil Laurence , Roemer Michiel
Published: July 2006

The consistency between pollutant emission reductions in Europe during the 1990–2002 period and ozone observations is quantitatively verified by 13‐year long simulations over the whole period using the regional chemistry‐transport model and the EMEP emission inventory. A statistically significant decadal tendency of 0.65 ppb/year is found in the difference between simulated and observed summer 90th percentiles of ozone daily maxima when model emissions are kept constant from year to year. By contrast the use of yearly dependent emissions does not yield a statistically significant percentile difference tendency. The regional structure of the 90th percentile differences shows that emissions may have decreased with a higher rate than assumed in the U.K. and at a lower rate in central Europe. The observed 10th percentiles are also compatible with the assumed emission reductions in Europe during 1990–2002, but are of lesser agreement with simulations using a uniform trend in the baseline ozone.
Meteoric smoke fallout revealed by superparamagnetism in Greenland ice
Authors: Lanci L. , Kent D. V.
Published: July 2006

Meteoric material reaching Earth contains an appreciable percentage of iron, much of which can be oxidized into nanometric‐size particles produced by ablation and subsequent condensation in the atmosphere. New measurements of isothermal remanent magnetization (IRM) show that magnetic particles of extraterrestrial origin can be distinguished from terrigenous particles based on their smaller superparamagnetic (SP) size as inferred from magnetic relaxation and by the poor correlation of the SP fraction with dust contents. The magnetic relaxation data suggest that extraterrestrial magnetic particles are in the size range of about 7–17 nm, which is compatible with the expected size of condensed particles. The concentration of extraterrestrial material in Greenland ice was estimated from the magnetic relaxation data. Assuming an iron content typical of average chondritic composition, the results correspond to a particles concentration of 0.78 ± 0.22 ppb for Greenland, good agreement with results based on iridium concentrations in NGRIP ice samples.
Perturbation of ground surface temperature reconstructions by groundwater flow?
Authors: Ferguson Grant , Beltrami Hugo , Woodbury Allan D.
Published: July 2006

Subsurface temperatures have been shown to be a robust source of information on past climates. Most analyses neglect groundwater flow (GWF) and assume purely conductive heat flow. However, in many situations GWF has not been fully considered and to date there are no general GWF criteria for either accepting or rejecting a temperature profile for paleoclimate analysis. Here we examine the transition from conduction dominated environments to environments where advection has a significant effect on the subsurface temperature regime and thus ground surface temperature (GST) histories. We provide guidelines indicating when advection is important and conclude that it is unlikely that groundwater flow is a significant source of error in the global data set maintained by the International Heat Flow Commission.
Role of fluctuations in a snug-fit mechanism of KcsA channel selectivity
Authors: Asthagiri D. , Pratt Lawrence R. , Paulaitis Michael E.
Published: July 2006

The thermodynamic exclusion of Na+ relative to K+ in potassium channels is examined by calculating the distribution of binding energies for Na+ and K+ in a model of the selectivity filter of the KcsA potassium channel. These distributions are observed to take a surprisingly simple form: Gaussian with a slight positive skewness that is insignificant in the present context. Complications that might be anticipated from these distributions are not problematic here. Na+ occupies the filter with a mean binding energy substantially lower than that of K+. The difference is comparable to the difference in hydration free energies of Na+ and K+ in bulk aqueous solution. Thus, the average energies of binding to the filter do not discriminate Na+ from K+ when measured from a baseline of the difference in bulk hydration free energies. The strong binding of Na+ constricts the filter, consistent with a negative partial molar volume of Na+ in water in contrast with a positive partial molar volume of K+ in water. Discrimination in favor of K+ can be attributed to the scarcity of favorable binding configurations for Na+ compared to K+. That relative scarcity is quantified as enhanced binding energy fluctuations, which reflects both the energetically stronger binding of Na+ and the constriction of the filter induced by Na+ binding.
Proof of the existence of the axial-to-planar channeling transition in a simple crystal model
Authors: Sáenz A. W.
Published: July 2006

Consider a fast nonrelativistic, positively charged particle (ion) traversing a crystal, assumed to be simple cubic and monatomic for simplicity. Let the Cartesian coordinates X1,X2,X3 be parallel to the crystal axes, and ηi be the initial value of the component of the particle’s momentum vector along Xi. If ∣η3∣ is sufficiently large compared to ∣η1∣,∣η2∣, then (under mild technical assumptions) the ion’s motion is well approximated for a long time by a solution of the equations of motion (EOM) of the axial-continuum Hamiltonian H¯, obtained from the ion’s nonrelativistic Hamiltonian H by replacing the potential V(X1,X2,X3), describing its interaction with the atoms of the crystal, by its average V¯(X1,X2) over X3. Furthermore, if ∣η2∣,∣η3∣ are sufficiently large compared with ∣η1∣,∣η2∣, respectively, then to a good approximation its motion is given, again for a long time, by a solution of the EOM of the planar continuum Hamiltonian H̿, obtained from H¯ by replacing V¯(X1,X2) by its average V̿(X1) over X2. We define motions of the first (respectively, second) type as axial (respectively, planar) channeling. In this paper, the transition from the first to the second kind of motion, occurring when the crystal is suitably rotated, is discussed in a mathematically rigorous way by using an improved version of first-order single-phase averaging theory.
The Bargmann transform and regularization of the 2, 3, 5-dimensional Kepler problem
Authors: Villegas-Blas Carlos
Published: July 2006

We introduce a Bargmann transform for the space L2(Sn) of square integrable functions on the n=2,3,5 dimensional unit sphere Sn inmersed in Rn+1. This is done on base of the Hopf fibration for the spheres Sk↦Sd with (k,d)=(1,1),(3,2),(7,4) and a suitable canonical transformation relating two different ways to regularize the n=2,3,5 dimensional Kepler problem (with fixed negative energy) involving the null complex quadric Qn inmersed in Cn+1. We prove the unitarity of the Bargmann transform onto a suitable space of analytical functions. We give reproducing kernels for these spaces of analytical functions which, for the cases n=3,5, are defined as the kernel of quantizations of restrictions for regularizations of the classical Kepler problem. We give an inversion formula for our Bargmann transform. We also give a set of coherent states for L2(Sn), n=2,3,5 and their semiclassical asymptotics (ℏ→0). Our Bargmann transform is actually a coherent states transform. Additionally, we use the moment map technique in order to construct a map with values in Qn that gives the base to define our canonical transformation.
Uniqueness of solutions to the helically reduced wave equation with Sommerfeld boundary conditions
Authors: Torre C. G.
Published: July 2006

We consider the helical reduction of the wave equation with an arbitrary source on (n+1)-dimensional Minkowski space, n⩾2. The reduced equation is of mixed elliptic-hyperbolic type on Rn. We obtain a uniqueness theorem for solutions on a domain consisting of an n-dimensional ball B centered on the reduction of the axis of helical symmetry and satisfying ingoing or outgoing Sommerfeld conditions on ∂B≈Sn−1. Nonlinear generalizations of such boundary value problems (with n=3) arise in the intermediate phase of binary inspiral in general relativity.
Misfit strain relaxation in (Ba0.60Sr0.40)TiO3 epitaxial thin films on orthorhombic NdGaO3 substrates
Authors: Simon W. K. , Akdogan E. K. , Safari A.
Published: July 2006

Strain relaxation in (Ba0.60Sr0.40)TiO3 (BST) thin films on ⟨110⟩ orthorhombic NdGaO3 substrates is investigated by x-ray diffractometry. Pole figure analysis indicates a [010]BST∥[1¯10]NGO and [001]BST∥[001]NGO in-plane and [100]BST∥[100]NGO out-of-plane epitaxial relationship. The residual strains are relaxed at h∼200nm, and for h>600nm, films are essentially strain free. Two independent dislocations mechanisms operate to relieve the anisotropic misfit strains along the principal directions. The critical thickness for misfit dislocation formation along [001] and [010] are 11 and 15nm, respectively. Stress analysis indicates deviation from linear elasticity for h<200. The films with 10<h<25nm are of monoclinic symmetry due to a finite principal shear stress along [110] of the initial orthorhombic cell.
Interface electronic structure in MnAs on GaAs (001) studied by in situ photoemission spectroscopy
Authors: Okabayashi J. , Kanai K. , Kubo K. , Toyoda S. , Oshima M. , Ono K. , Yoshino J.
Published: July 2006

We have investigated the relationship between surface morphology and electronic structure of MnAs on GaAs (001) depending on the MnAs layer thickness using in situ photoemission spectroscopy. For less than 4 ML (monolayer) growth of MnAs, metallic and ferromagnetic properties were not observed due to the island growth. Valence-band photoemission spectra revealed that the localized Mn 3d states for less than 4 ML growth gradually change to the itinerant characteristics with increasing MnAs layer thickness. Core-level photoemission spectra have revealed that the Ga atoms are not segregated onto the surface and an abrupt interface is identified.
Low-temperature solid-phase crystallization of amorphous silicon thin films deposited by rf magnetron sputtering with substrate bias
Authors: Jun Seung-Ik , Rack Philip D. , McKnight Timothy E. , Melechko Anatoli V. , Simpson Michael L.
Published: July 2006

The crystallization properties of amorphous silicon (a-Si) thin film deposited by rf magnetron sputter deposition with substrate bias have been thoroughly characterized. The crystallization kinetics for films deposited with substrate bias is enhanced relative to unbiased a-Si by films. The enhanced crystallization for substrate biased a-Si films are attributed to ion enhanced nucleation of crystallites during sputter deposition which subsequently grow during the postdeposition anneal. Conversely films sputter deposited without substrate bias have more intrinsic defects and residual oxygen which enhance nucleation and retard growth, respectively, and lead to a large number of small crystallites.
Local electron beam induced reduction and crystallization of amorphous titania films
Authors: Kern Philippe , Jäggi Christian , Utke Ivo , Friedli Vinzenz , Michler Johann
Published: July 2006

We report local electron beam induced reduction and crystallization of electrolytic amorphous TiO2 films on steel at 20keV, varying beam currents from 10nAto24μA. In situ substrate temperature measurements and beam heating calculations demonstrate the formation of anatase (Raman) below 270°C, clearly beneath the crystallization temperature of nonirradiated films (≈440°C). The evolution of the sample current was correlated to oxide reduction via electron stimulated desorption. Atomic force microscopy revealed well defined cavities with Gaussian shape. The e-beam sensitivity of amorphous TiO2 allows for patterning of macroscopic films, inducing local changes in oxidation state and phase.
Influence of insulation coating on thermal conductivity measurement by transient hot-wire method
Authors: Yu Wenhua , Choi Stephen U.-S.
Published: July 2006

The transient hot-wire method is widely used to determine the thermal conductivity of various media. It has been improved through the addition of an insulation coating to the wire. However, this coating could affect the accuracy of the thermal conductivity measurement. The temperature rise for the insulation-coated wire was calculated as a function of time by a Laplace transformation along with the expansion method outlined by Carslaw and Jaeger [Conduction of Heat in Solids (Oxford University Press, Oxford, 1959)]. The results of numerical simulations and experimental tests show that, for most engineering applications, the relative measurement errors of the thermal conductivity caused by the insulation coating are very small if the slopes of the temperature rise-logarithmic time diagrams are calculated for large time values. No correction to the insulation coating is necessary even for the conditions that the insulation coating thickness is comparable to the wire radius, and that the thermal conductivity of the insulation coating is lower than that of the measured medium.
Near ultraviolet-wavelength photonic-crystal biosensor with enhanced surface-to-bulk sensitivity ratio
Authors: Ganesh Nikhil , Block Ian D. , Cunningham Brian T.
Published: July 2006

We report the design and characterization of biosensors based on one-dimensional photonic-crystal reflectance filters operating at near-ultraviolet wavelengths. Rigorous coupled-wave analysis simulations predict an increased confinement of the resonant electric field at the surface of this biosensor as compared to previously fabricated near-infrared photonic-crystal biosensors. This change in the resonant electric field provides an improvement of over 4.5 times in the surface-sensitivity to bulk-sensitivity ratio, and therefore enables enhanced detection resolution for biomolecules adsorbed on the biosensor surface. These biosensors will be especially important for applications requiring the detection of small molecules or ultralow analyte concentrations.
Laser impulse generation and interferometer detection of zero group velocity Lamb mode resonance
Authors: Clorennec Dominique , Prada Claire , Royer Daniel , Murray Todd W.
Published: July 2006

In this letter, we describe experiments on the generation of the first order symmetric (S1) Lamb mode by a pulsed yttrium aluminum garnet laser. The vibration of the plate is detected at the same point by a heterodyne interferometer. The acoustic signal is dominated by the resonance at the point of the dispersion curve where the group velocity vanishes. The time decay of the signal leads to the local attenuation coefficient of the material. The spectrum exhibits a very sharp peak, the frequency of which is sensitive to the plate thickness. For a 0.49-mm-thick Duralumin plate, thickness variations as small as 0.1μm have been detected. Moving the detection point away from the source allows us to record the standing wave pattern resulting from the interference between the S1 and S2b Lamb waves having opposite wave vectors at the zero group velocity point.
Enhanced tunability of magnetron sputtered Ba0.5Sr0.5TiO3 thin films on c-plane sapphire substrates
Authors: Fardin E. A. , Holland A. S. , Ghorbani K. , Reichart P.
Published: July 2006

Thin films of Ba0.5Sr0.5TiO3 (BST) were deposited on c-plane (0001) sapphire by rf magnetron sputtering and investigated by complementary materials analysis methods. Microwave properties of the films, including tunability and Q factor were measured from 1to20GHz by patterning interdigital capacitors (IDCs) on the film surface. The tunability is correlated with texture, strain, and grain size in the deposited films. An enhanced capacitance tunability of 56% at a bias field of 200kV∕cm and total device Q of more than 15 (up to 20GHz) were achieved following postdeposition annealing at 900°C.
Hysteresis phenomena in reverse biased InAsSbP∕InAs heterostructure
Authors: Rathgeb Stéphane , Moeglin Jean-Pierre , Boffy Alain , Pasquinelli Marcel , Palais Olivier
Published: July 2006

We present experimental and theoretical results on InAsSbP∕InAs photodetectors for infrared detection. An unexpected hysteresis has been shown during the current-voltage I(V) investigations (300K). Drastic changes in the hysteresis cycle are observed depending on the temperature of the heterostructure. Additionally, the time step of the measurements has an influence on the hysteresis form. The appearance of such hysteresis can be explained by a tunneling effect and by considering the temperature of the structure. Experimental I(V) characteristics are in good agreement with the tunnel current coupled to a thermal approach.
Dynamical slowing down of polar nanoregion in relaxor-based ferroelctric 0.89Pb(Zn2∕3Nb1∕3)O3–0.11PbTiO3
Authors: Nakata Yohei , Tsujimi Yuhji , Katsuraya Kohei , Iwata Makoto , Yagi Toshirou
Published: July 2006

Light scattering experiment has been performed in a single crystal of 0.89Pb(Zn1∕3Nb2∕3)O3–0.11PbTiO3. The central peak (CP) spectra have been well detected with high resolution over the wide frequency region up to 150GHz. The distribution is discovered in the relaxation time associated with the CP. Moreover, it is found that the maximum relaxation time indicates the dynamical slowing down near the temperature Tm at which the low-frequency dielectric constant has a maximum. This finding strongly suggests that the physical origin of the CP is “polar nanoregions.”