bluuebunny/crossref_metadata_2025 huggingface dataset:
Hollow-fiber ultrafiltration ofCryptosporidium parvumoocysts from a wide variety of 10-L surface water samples
Authors: Kuhn Ryan C , Oshima Kevin H
Published: October 2002

An optimized hollow-fiber ultrafiltration system (50 000 MWCO) was developed to concentrate Cryptosporidium oocysts from 10-L samples of environmental water. Seeded experiments were conducted using a number of surface-water samples from the southwestern U.S.A. and source water from four water districts with histories of poor oocyst recovery. Ultrafiltration produced a mean recovery of 47.9% from 19 water samples (55.3% from 39 individual tests). We also compared oocyst recoveries using the hollow-fiber ultrafiltration system with those using the Envirochek filter. In limited comparison tests, the hollow-fiber ultrafiltration system produced recoveries similar to those of the Envirochek filter (hollow fiber, 74.1% (SD = 2.8); Envirochek, 71.9% (SD = 5.2)) in low-turbidity (3.9 NTU) samples and performed better than the Envirochek filter in high-turbidity (159.0 NTU) samples (hollow fiber, 27.5%; Envirochek, 0.4%). These results indicate that hollow-fiber ultrafiltration can efficiently recover oocysts from a wide variety of surface waters and may be a cost-effective alternative for concentrating Cryptosporidium from water, given the reusable nature of the filter.Key words: Cryptosporidium, ultrafiltration, oocyst.
Impact studies on Nordic forests: effects of elevated CO2 and fertilization on gas exchange
Authors: Sigurdsson Bjarni D , Roberntz Peter , Freeman Michael , Næss Marius , Saxe Henrik , Thorgeirsson Halldor , Linder Sune
Published: October 2002

The effects of rising atmospheric carbon dioxide concentration, [CO2], and fertilization on gas exchange of four field-grown tree species were examined using the branch bag technique (Picea abies (L.) Karst., Pinus sylvestris L., Fagus sylvatica L.) or whole tree chambers (Populus trichocarpa Torr. & Gray). Results are presented on changes in light-saturated rates of net photosynthesis (Asat), carboxylation efficiency (α), stomatal conductance (gs), and stomatal limitation of photosynthesis (Ls) after 24 years of CO2 exposure. Fertilization alone did not significantly change Asat, α, gs, or Ls for any of the species, but α and Asat were linearly related to foliage nitrogen content when compared across all treatments. No significant CO2 effects were detected for α, gs, or Asat when compared at the same intercellular [CO2], i.e., no downregulation of Asat was apparent. "Long-term" CO2 enrichment increased Asat significantly by 49, 53, 86, and 114% in Populus trichocarpa, Picea abies, F. sylvatica, and Pinus sylvestris, respectively. In all the species the relative CO2 effect on Asat increased linearly with temperature. Thus, application of a simple linear relationship could improve predictions of future tree growth responses to increasing CO2 and temperature in cool climates.
Effects of stand age on net primary productivity of boreal black spruce forests in Ontario, Canada
Authors: Chen Wenjun , Chen Jing M , Price David T , Cihlar Josef
Published: October 2002

Quantification of the effects of stand age on its net primary productivity (NPP) is critical for estimating forest NPP and carbon budget at regional to global scales. This paper reports a practical method for quantifying ageNPP relationships using existing normal yield tables, biomass equations, and measurements of fine-root turnover and litterfall. Applying this method, we developed mean ageNPP relationships for black spruce (Picea mariana (Mill.) BSP) stands in Ontario. We define "mean ageNPP relationship", as the changes in NPP that occur with age under long-term mean environmental conditions. These relationships indicate that NPP at more productive sites culminates to a higher value and at an earlier age and also declines more rapidly thereafter. A further component analysis indicates that the decrease in biomass growth of woody tissues is the main contributor to the decline with age. Finally, error assessment suggests that the uncertainty in NPP estimates can be substantially reduced with a better quantification of fine-root turnover and litterfall, which are the two dominant NPP components, particularly in the later stages of stand development. With new techniques now available, more accurate measurement of these components is possible, and thus strongly recommended.
Effects of mechanized careful logging on natural regeneration and vegetation competition in the southeastern Canadian boreal forest
Authors: Harvey Brian , Brais Suzanne
Published: October 2002

Careful logging regulations in Quebec restrict circulation of harvesting and forwarding or skidding machinery to evenly spaced, parallel trails, which creates a particular pattern of disturbed and relatively undisturbed zones in cutovers. A 7-year monitoring study was established to evaluate the effects of careful logging on vegetation development in the southern boreal forest of Quebec. A total of 255 sample plots (2 m2) were located in seven cutovers in predominantly black spruce (Picea mariana (Mill.) BSP) forests that were whole-tree "careful logged": 120 on fresh to moist silty clays or silty clay loams and 135 on dry to fresh loamy sands. Three microsites were sampled: skid trails and the edge and the centre of protection strips. A gradient of disturbance from the skid trail to centre of the protection strip was evident for finer textured sites. Careful logging resulted in high densities of black spruce and balsam fir (Abies balsamea (L.) Mill.) (> 20 000 stems/ha each) in the protection strip. Survival of other understory species was also favoured in protection strips. Higher disturbance levels in skid trails favoured establishment of larch (Larix laricina (Du Roi) K. Koch), raspberry (Rubus idaeus L.), and graminoids. Reduction of ericaceous cover occurred in skid trails on coarse-textured sites but was only temporary. Softwood stocking 7 years after harvest (based on 2-m2 plots), ranged from 69 to 74% on fine- to medium-textured sites and from 31 to 51% on coarse-textured sites. The pattern of vegetation development created by careful logging has important implications for silvicultural decisions and stand modelling.
Survival of artificially regenerated Scots pine on till soils with respect to varying dielectric properties
Authors: Sutinen R , Teirilä A , Pänttäjä M , Sutinen M -L
Published: October 2002

Artificial regeneration to Scots pine (Pinus sylvestris L.) has faced substantial economical losses in Finnish Lapland on sites underlain by glacial tills and formerly covered by stands dominated by Norway spruce (Picea abies (L.) Karst.). We studied the survival of pine seedlings and saplings with respect to soil dielectric permittivity (ε), as dependent on soil water content (θv), of ploughed tills. The ε values (θv) were determined beneath 10 500 pines varying in age between 2 and 41 years and growing on 21 sites, 500 per site. Based on the logistic regression models, the survival rate of 2- to 7-year-old seedlings was independent of the soil ε (i.e., θv). In contrast, a significant correlation between the survival rate of 12- to 16-year-old saplings and soil ε was observed. In this age-class, a survival rate of 50% with ε50 = 15.1, with ε50 = 17.0 for planted saplings and ε50 = 12.7 for sowed saplings, were obtained. Of the 2000 pine trees aged between 20 and 41 years, 96.5% were observed to be growing on dry tills with ε < 15 with mean ε = 9.9. The results of this study suggest that artificial regeneration of Scots pine in Lapland is risky on moist and wet tills (ε > 15, θv > 0.27 cm3·cm3).
The effect of a north-facing forest edge on tree water use in a boreal Scots pine stand
Authors: Cienciala Emil , Mellander Per-Erik , Kučera Jiří , Oplutilová Magda , Ottosson-Löfvenius Mikaell , Bishop Kevin
Published: October 2002

Tree water use and growth increment were studied in a north-facing forest edge of a 70-year-old monospecific Scots pine (Pinus sylvestris L.) stand growing on poor sandy soils in the northern boreal zone of Sweden. The forest edge in this study bordered a 20-year-old clearcut. There were differences in water use and growth increment during the growing season between trees growing at the forest edge and trees growing in the forest interior. These differences were likely related to soil conditions, such as access to soil moisture, soil temperature, and soil frost conditions, whereas an effect of aboveground microclimate was not found. The estimated tree water use and growth increment over one growing season tended to be greater for trees at the edge zone relative to those from the interior. The variability of the measured tree water fluxes was high, especially for the edge-zone trees. There were also structural differences between the two groups of trees, most notably in the radial profile of conductive xylem, in tree height, and in green crown length, but these differences were on the limits of statistical significance. The estimated seasonal transpiration was low, about 70 mm when estimated exclusively for trees in the forest interior and 107 mm when estimated exclusively for trees at the forest edge. This illustrates the likely magnitude of water use enhancement resulting from the conditions specific to the forest edge.
Natural clonal variation of wood extractives in Populus tremuloides
Authors: Fernandez M P , Breuil C , Watson P A
Published: October 2002

Analysis of the potential genetic variation in quaking aspen (Populus tremuloides Michx.) wood extractives was performed by sampling nine natural clones at breast height. Significant clonal differences were found not only in the levels of total acetone extractives but also in the levels of sterolstriterpenes, steryl esterswaxes, and triglycerides, all of which are known to contribute to pitch formation in pulping and papermaking. In addition, extractive compounds known to elicit toxic effects in aquatic organisms showed statistically significant differences between natural aspen clones. In some cases (e.g., flavonoids), these compounds formed a part of the defense system in the living tree and, thus, were affected in part by the presence of decayed wood.
Use of multiobjective optimization models to examine behavioural trade-offs of white-tailed deer habitat use in forest harvesting experiments
Authors: Rothley Kristina D
Published: October 2002

I evaluated the habitat use of white-tailed deer (Odocoileus virginianus Zimmermann) in a boreal mixedwood forest managed for timber production in northern Saskatchewan, Canada, to determine which kinds of factors (e.g., forage abundance, canopy cover) influenced habitat use, if white-tailed deer considered these habitat factors in isolation or instead there was evidence of trade-offs, and whether the identification of the factors or the way in which they were traded off varied subsequent to the introduction of harvested patches or changes in hunting traffic. Habitat use was estimated through ground-based surveys before and after the elimination of hunting traffic in a partially harvested site and before and after harvesting in a formerly hunted but unharvested site. Forage abundance was always a significant, or marginally significant, predictor of habitat use. Canopy cover was only important in sites with limited water access. In the presence of hunting traffic, white-tailed deer balanced multiple habitat factors (e.g., food access vs. road avoidance); when hunting traffic was eliminated, the trade-off behaviour was abandoned. The variety in behaviour that the white-tailed deer exhibited in my study implies that to successfully protect habitat, it may not be sufficient to simply identify the factors that influence habitat use (and presumably value). We may also need to understand how the animals deal with these factors under different conditions.
Songbird abundance in clear-cut and burned stands: a comparison of natural disturbance and forest management
Authors: Simon N PP , Schwab F E , Otto R D
Published: October 2002

To evaluate the efficacy of forest management to emulate natural disturbance, we compared bird abundances among burned and clear-cut, former black spruce (Picea mariana (Mill.) BSP) sites, after 5, 14, and 27 years of succession. Total bird density was lower in clear-cut sites resulting from fewer hermit thrushes, yellow warblers, Swainson's thrushes, and fox sparrows. Hermit thrushes were positively correlated with snag density while yellow warblers and Swainson's thrushes were positively associated with deciduous tree cover and negatively correlated with conifer cover. Only yellow-rumped warblers had higher densities on clear-cut sites, likely due to greater conifer cover. Bird densities and species richness peaked in the 14-year-old burns and exceeded that of mature forests reported for Labrador. This demonstrates the importance of natural early successional forests for birds. Although logged areas support several species found in natural young burns, logging does not precisely mimic fire. This suggests that forest managers should allow some forests to burn naturally.
Distribution and diversity of tree species with respect to soil electrical characteristics in Finnish Lapland
Authors: Sutinen R , Teirilä A , Pänttäjä M , Sutinen M -L
Published: October 2002

Soil dielectric permittivity (ε), which is dependent on soil water content (θv), and electrical conductivity (σ), which is dependent on soil solute concentration, were measured in the immediate vicinity of 7596 mature trees naturally established on glacial deposits across granitoid and greenstone assemblages in Finnish Lapland (67°30' N-68°40' N). The proportions of the main timber species Scots pine (Pinus sylvestris L.), Norway spruce (Picea abies (L.) Karst.), and downy birch (Betula pubescens Ehrh.) or the diversity of tree species were not affected by the temperature sum (between 750 and 600 degree-days), but the occurrences were strongly influenced by the soil's electrical characteristics. Scots pine and silver birch (Betula pendula Roth) were found to only occupy dry soils (fixed effect estimates ε(p) = 8.5 and ε(sb) = 8.3) with low solute concentration (σ(p) = 0.64 mS·m-1 and σ(sb) = 0.56 mS·m-1), while Norway spruce, downy birch, aspen (Populus tremula L.) and sallow (Salix caprea L.) occupied sites with higher soil moisture (ε(s) = 17.0, ε(db) = 14.7, ε(a) = 16.7, and ε(sa) = 16.7) and solute concentration (σ(s) = 0.96 mS·m-1, σ(db) = 0.90 mS·m-1, σ(a) = 1.07 mS·m-1, and σ(sa) = 0.93 mS·m-1). Species diversity was found to be at its highest with the following soil parameters: 12 < ε < 15 and 0.8 < σ < 1.2 mS·m-1. Scots pine was concentrated on tills derived from granitoid rocks. Norway spruce dominated sites on tills particularly derived from the mafic metavolcanic rocks of the Greenstone Belt but did not occur on tills derived from granulite. The edaphic constraint for pine appeared to be θv > 0.27 cm3·cm-3 (ε > 15) and for spruce σ < 0.5 mS·m-1, respectively.
REPRESENTATION AND CONSTRUCTION OF ONTOLOGIES FOR WEB INTELLIGENCE
Authors: ZHONG NING
Published: October 2002

Ontologies and agent technology can play a crucial role in enabling Web-based knowledge processing, sharing, and reuse between applications. The paper investigates representation and construction of ontologies for Web intelligence. Three ontology categories are suggested, some of the research and development with respect to the three categories is presented, the major ontology languages are surveyed, and a multi-phase process of automatic construction of the domain-specific ontologies is discussed.
HIERARCHIES OF GENERALIZED KOLMOGOROV COMPLEXITIES AND NONENUMERABLE UNIVERSAL MEASURES COMPUTABLE IN THE LIMIT
Authors: SCHMIDHUBER JÜRGEN
Published: October 2002

The traditional theory of Kolmogorov complexity and algorithmic probability focuses on monotone Turing machines with one-way write-only output tape. This naturally leads to the universal enumerable Solomonoff-Levin measure. Here we introduce more general, nonenumerable but cumulatively enumerable measures (CEMs) derived from Turing machines with lexicographically nondecreasing output and random input, and even more general approximable measures and distributions computable in the limit. We obtain a natural hierarchy of generalizations of algorithmic probability and Kolmogorov complexity, suggesting that the "true" information content of some (possibly infinite) bitstring x is the size of the shortest nonhalting program that converges to x and nothing but x on a Turing machine that can edit its previous outputs. Among other things we show that there are objects computable in the limit yet more random than Chaitin's "number of wisdom" Omega, that any approximable measure of x is small for any x lacking a short description, that there is no universal approximable distribution, that there is a universal CEM, and that any nonenumerable CEM of x is small for any x lacking a short enumerating program. We briefly mention consequences for universes sampled from such priors.
TRANSITIVE BEHAVIOR IN REVERSIBLE ONE-DIMENSIONAL CELLULAR AUTOMATA WITH A WELCH INDEX 1
Authors: MORA JUAN CARLOS SECK TUOH
Published: October 2002

The problem of knowing and characterizing the transitive behavior of a given cellular automaton is a very interesting topic. This paper provides a matrix representation of the global dynamics in reversible one-dimensional cellular automata with a Welch index 1, i.e., those where the ancestors differ just at one end. We prove that the transitive closure of this matrix shows diverse types of transitive behaviors in these systems. Part of the theorems in this paper are reductions of well-known results in symbolic dynamics. This matrix and its transitive closure were computationally implemented, and some examples are presented.
PROBING LEPTON FLAVOUR VIOLATION IN νμ + N → τ + ⋯ SCATTERING AND μ → τ CONVERSION ON NUCLEONS
Authors: GNINENKO S. N. , KIRSANOV M. M. , KRASNIKOV N. V. , MATVEEV V. A.
Published: October 2002

We study lepton flavour-violating interactions which could result in the τ-lepton production in the νμN scattering or in μ → τ conversion on nucleons at high energies. Phenomenological bounds on the strength of [Formula: see text] interactions are extracted from the combined result of the NOMAD and CHORUS experiments on searching for νμ - ντ oscillations. Some of these bounds supersede limits from rare decays.

We also propose a "missing energy" type experiment searching for μ → τ conversion on nucleons. The experiment can be performed at a present accelerator or at a future neutrino factory.
GRAVITATIONAL-WAVE INSTABILITIES IN ROTATING STARS
Authors: ANDERSSON NILS
Published: October 2002

This article provides a brief overview of recent research into the gravitational-wave driven instability of the r-modes in rotating neutron stars.
ON BOOST-ROTATION SYMMETRIC SPACE–TIMES WITH (NON)SPINNING SOURCES
Authors: PRAVDA V. , PRAVDOVÁ A.
Published: October 2002

Boost-rotation symmetric spacetimes are the only axially symmetric vacuum spacetimes with an additional symmetry that are radiative and admit global null infinity1,2. They are the only radiative asymptotically flat exact solutions representing the gravitational field of moving objects – uniformly accelerated "particles" of various kinds3. The general theory of boost-rotation symmetric spacetimes was first developed for nonspinning sources4 (i.e. for hypersurface orthogonal Killing vectors) and later partially generalized for spinning sources5.

The C-metric3 and the spinning C-metric6,7,8 belonging to this class were analyzed. With appropriately chosen parameters they represent the gravitational field of uniformly accelerated Schwarzschild and Kerr black or white holes. Stability of geodesics describing co-accelerated particles was also studied using an effective potential9 and a Lyapunov function8.
NLO Quarkonium Production in Hadronic Collisions
Authors: Mangano Michelangelo , Petrell Andrea
Published: October 2002

We present some preliminary results on the next-to-leading order calculation in QCD of quarkonium production cross sections in hadronic collisions. We will show that the NLO total cross sections for P-wave states produced at high energy are not reliable, due to the appearance of very large and negative contributions. We also discuss some issues related to the structure of final states in colour-octet production and to high-pt fragmentation.
Color-Singlet and Color-Octet Contributions to J/ψ Photoproduction
Authors: Krämer Michael
Published: October 2002

I discuss the impact of color-octet contributions and higher-order QCD corrections on the cross section for inelastic J/ψ photoproduction. The theoretical predictions are compared with recent experimental data obtained at HERA.
Lattice Calculation of Quarkonium Decay Matrix Elements
Authors: Bodwin G. T. , Sinclair D. K. , Kim S.
Published: October 2002

We calculate the NRQCD matrix elements for the decays of the lowest-lying S- and P-wave states of charmonium and bottomonium in quenched lattice QCD. We also compute the one-loop relations between the lattice and continuum matrix elements.
COMPUTER SIMULATION STUDY OF A NEMATOGENIC LATTICE-GAS MODEL WITH FOURTH-RANK INTERACTIONS
Authors: ROMANO S.
Published: October 2002

We have considered a classical lattice-gas model, consisting of a three-dimensional simple-cubic lattice, whose sites host three-component unit vectors; pairs of nearestneighboring sites interact via the nematogenic potential [Formula: see text] here P4(τ) denotes the fourth Legendre polynomial, nuj=0,1 are occupation numbers, uj are unit vectors (classical spins), and ∊ is a positive quantity setting the energy and temperature scales (i.e. T* =k B T / ∊). The total Hamiltonian is given by [Formula: see text] where ∑{j < k} denotes sum over all distinct nearest-neighboring pairs of lattice sites. The saturated-lattice version of this model defines a nematogenic lattice model, already studied in the literature, and found to possess a transition to an orientationally ordered phase at low temperature; moreover, according to available rigorous results, there exists a μ0<0, such that, for all μ>μ0, the system supports an ordering transition at a finite, μ-dependent, temperature. We present here a detailed study of the case μ=0, and characterize it by means of Monte Carlo simulation, Mean Field and Two Site Cluster treatments; the latter significantly improves the agreement with simulation results.
INTRINSIC PHASE-DECOHERENCE OF ELECTRONS BY TWO-LEVEL SYSTEMS
Authors: SRIVASTAVA VIPIN , KRISHNAN RAISHMA
Published: October 2002

The fundamental problem of the phase saturation of electrons in a disordered mesoscopic system at very low temperatures is addressed. The disorder in the medium has both static and dynamic components, the latter being in the form of two-level systems (TLSs) which become just about the only source of inelastic scattering in the limit T → 0. We propose that besides the inelastic nature of scattering from the TLSs, the phase shift of the electrons is also affected by the nature of tunneling in the TLSs. The tunneling becomes incoherent as T decreases due to increasing long-range interactions among the TLSs which affects the phase coherence of electrons scattering from them. The competition between this effect, which increases as ~ T-1, and that of the scattering rate [Formula: see text] behaving as ~ T apparently govern the phase shift of the electrons.
ADAPTIVE FEEDBACK LINEARIZING CONTROL OF CHUA'S CIRCUIT
Authors: BARONE KEVIN , SINGH SAHJENDRA N.
Published: October 2002

In this Letter a feedback linearizing adaptive control system for the control of Chua's circuits is presented. It is assumed that all the parameters of the system are unknown. Using a backstepping design procedure, an adaptive control system is designed which accomplishes trajectory control of the chosen node voltage by an independent voltage source. Simulation results are presented which show precise trajectory tracking and regulation of the state vector to the desired terminal state.
COMPUTING ROUNDNESS IS EASY IF THE SET IS ALMOST ROUND
Authors: DEVILLERS OLIVIER , RAMOS PEDRO A.
Published: October 2002

In this paper we address the problem of computing the thinnest annulus containing a set of points S ⊂ Rd. For d = 2, we show that the problem can be solved in O(n) expected time for a fairly general family of almost round sets, by using a slight modification of Sharir and Welzl's algorithm for solving LP-type problems. We also show that, for points in convex position, the problem can be solved in (O(n) deterministic time using linear programming. For d = 2 and d = 3, we propose a discrete local optimization approach. Despite the extreme simplicity and worst case O(nd+1) complexity of the algorithm, we give empirical evidence that the algorithm performs very well (close to linear time) if the input is almost round. We also present some theoretical results that give a partial explanation of this behavior: although the number of local minima may be quadratic (already for d = 2), almost round configurations of points having more than one local minimum are very unlikely to be encountered in practice.
MATHEMATICAL ANALYSIS FOR THE RATIONAL LARGE EDDY SIMULATION MODEL
Authors: BERSELLI LUIGI C. , GALDI GIOVANNI P. , ILIESCU TRAIAN , LAYTON WILLIAM J.
Published: October 2002

In this paper we consider the Rational Large Eddy Simulation model recently introduced by Galdi and Layton. We briefly present this model, which (in principle) is similar to others commonly used, and we prove the existence and uniqueness of a class of strong solutions. Contrary to the gradient model, the main feature of this model is that it allows a better control of the kinetic energy. Consequently, to prove existence of strong solutions, we do not need subgrid-scale regularization operators, as proposed by Smagorinsky. We also introduce some breakdown criteria that are related to the Euler and Navier–Stokes equations.
SENSITIVITY ANALYSIS FOR AN INCOMPRESSIBLE AEROELASTIC SYSTEM
Authors: FERNÁNDEZ MIGUEL A. , MOUBACHIR MARWAN
Published: October 2002

This paper deals with problems arising in the sensitivity analysis for fluid-structure interaction systems. Our model consists of a fluid described by the incompressible Navier–Stokes equations interacting with a solid under large deformations. We obtain a linearized problem which allow us to compute the derivative of the state variable with respect to a given boundary parameter. We use a particular definition of the first-order correction for the perturbed state and consider a weak arbitrary Euler–Lagrange formulation for the coupled system.
GENERALLY COVARIANT FRESNEL EQUATION AND THE EMERGENCE OF THE LIGHT CONE STRUCTURE IN LINEAR PRE-METRIC ELECTRODYNAMICS
Authors: RUBILAR GUILLERMO F. , OBUKHOV YURI N. , HEHL FRIEDRICH W.
Published: October 2002

We study the propagation of electromagnetic waves in a spacetime devoid of a metric but equipped with a linear electromagnetic spacetime relation H ~ χ · F. Here H is the electromagnetic excitation [Formula: see text] and F the field strength (E,B), whereas χ (having 36 independent components) characterizes the electromagnetic permittivity/permeability of spacetime. We derive analytically the corresponding Fresnel equation and show that it is always quartic in the wave covectors. We study the "Fresnel tensor density" [Formula: see text] as (cubic) function of χ and identify the leading part of χ (20 components) as indispensable for light propagation. Upon requiring electric-magnetic reciprocity of the spacetime relation, the leading part of χ induces the light cone structure of spacetime (9 components), i.e., the spacetime metric up to a function. The possible existence of an Abelian axion field (1 component of χ) and/or of a skewon field (15 components) and their effect on light propagation is discussed in detail. The newly introduced skewon field is expected to be T-odd and related to dissipation.
LRS BIANCHI TYPE-I COSMOLOGICAL MODELS IN BARBER'S SECOND SELF CREATION THEORY
Authors: PRADHAN ANIRUDH , VISHWAKARMA ANIL KUMAR
Published: October 2002

Barber's second self creation theory with perfect fluid source for an LRS Bianchi type-I metric is considered using deceleration parameter to be constant where the metric potentials are taken as functions of x and t. In particular, some exact solutions have also been obtained for the vacuum universe, Zel'dovich universe and radiation universe. Some physical properties of the models are also discussed.
ZONE-PLATE-BASED SCANNING PHOTOELECTRON MICROSCOPY AT SRRC: PERFORMANCE AND APPLICATIONS
Authors: KLAUSER RUTH , HONG I.-H. , LEE T.-H. , YIN G.-C. , WEI D.-H. , TSANG K.-L. , CHUANG T. J. , WANG S.-C. , GWO S. , ZHARNIKOV MICHAEL , LIAO J.-D.
Published: October 2002

Adapting classical spectroscopic methods to the new challenge of studying nanomaterials, imaging techniques are the trendsetter in recent years. Among them is scanning photoelectron microscopy (SPEM) with submicron spatial resolution, where the sample surface is raster-scanned by a focused soft X-ray beam, and the emitted photoelectrons are collected at each point by the input optics of an electron energy analyzer. We have constructed such a station at SRRC in Taiwan, which is now fully in operation. In this paper, we introduce the specific features of the instrument and discuss application examples on the characterization of scanning-probe-induced Si 3 N 4 to SiO x conversion and electron- and plasma-induced chemical changes in alkanethiols self-assembled monolayers. In combining two-dimensional imaging and micro-photoemission, SPEM can reveal valuable information on the chemical and electronic properties of structured and multiphase materials.
CORE-EXCITATION-INDUCED BOND BREAKING OF CHEMISORBED MOLECULES PROBED BY EMISSION OF IONS, NEUTRALS, AND ELECTRONS
Authors: FEULNER P. , ECKER M. , ROMBERG R. , WEIMAR R. , FÖHLISCH A.
Published: October 2002

For selected examples of diatomic molecules chemisorbed on transition and noble metals [ N 2 on Ru(001) and Ni(111), CO on Ru(001) and Cu(111)], we survey core-induced bond breaking by N1s and O1s excitation. We demonstrate that supplementary information on the primarily excited electronic states and on the mechanism of bond dissociation is supplied by ions, neutral molecules and atoms, and decay electrons emitted upon electronic evolution. By comparing yields of neutrals and ions, and their translational energies as a function of excitation energy for the different systems, we discriminate between molecular and surface-induced aspects of bond dissociation. In particular we analyze the potential of the substrate–adsorbate interaction to enhance atom selectivity in core-excitation-induced bond breaking.
SPECTRAL PROPERTIES OF CONFINED ATOMS
Authors: DOLMATOV V. K. , CONNERADE J. P. , LAKSHMI A. P. , MANSON S. T.
Published: October 2002

The changes in energy and photoionization spectra of atoms upon confinement by a spherical environment are explored theoretically. Two kinds of confinement are considered: an endohedral confinement, such as inside the bucky-ball C 60, and an impenetrable spherical confinement of adjustable radius. We demonstrate modifications in the energy spectrum and electron correlation effects in confined atoms, the appearance, nature and origin of "confinement" resonances in photoionization spectra of such atoms, as well as new regularities in the periodic table for "compressed" atoms. These findings are of importance for basic and applied physics and chemistry of atoms, molecules, surfaces, etc.
ELECTRONIC STRUCTURE AND REACTIVITY OF TM-DOPED La1-xSrxCoO3 (TM = Ni, Fe) CATALYSTS
Authors: GRICE S. C. , FLAVELL W. R. , THOMAS A. G. , WARREN S. , MARR P. G. , JEWITT D. E. , KHAN N. , DUNWOODY P. M. , JONES S. A.
Published: October 2002

The catalytic properties of LaCoO 3 in the oxidation of organic molecules in aqueous solution are explored as a function of doping with both Sr substitution for La and Fe and Ni substitution for Co. VUV photoemission is used to explore the surface reactivity of the ceramic catalysts in aqueous solution, using H 2 O as a probe molecule. These measurements are complemented by EXAFS and XANES measurements designed to probe the local defect structure and by GC measurements of catalytic activity in the aqueous epoxidation of crotyl alcohol. We relate the observed catalytic activity to the defect structure of the doped materials. In Ni-doped materials, oxygen vacancies appear to be the predominant defect, whereas in Fe-doped samples, electron holes are stabilised on Fe, leading to very different behaviour in oxidation. The surface reactivity to water is also influenced by the TM d electron count, with water binding more strongly to Fe-doped materials than to those containing Ni. The influence of these factors on the rate of the unwanted hydrogen peroxide decomposition reaction and hence on activity in epoxidation is discussed.
PHOTOEMISSION AND PHOTOABSORPTION INVESTIGATION OF THE ELECTRONIC STRUCTURE OF YTTERBIUM-DOPED STRONTIUM FLUOROAPATITE
Authors: NELSON A. J. , VAN BUUREN T. , BOSTEDT C. , SCHAFFERS K. I. , TERMINELLO LOU
Published: October 2002

X-ray photoemission and X-ray photoabsorption were used to study the composition and the electronic structure of ytterbium-doped strontium fluoroapatite (Yb:S-FAP). High resolution photoemission measurements on the valence band electronic structure were used to evaluate the density of occupied states of this fluoroapatite. Element-specific density of unoccupied electronic states in Yb:S-FAP was probed by X-ray absorption spectroscopy (XAS) at the Yb 4d ( N 4,5-edge), Sr 3d ( M 4,5-edge), P 2p ( L 2,3-edge), F 1s and O 1s (K-edges) absorption edges. These results provide the first measurements of the electronic structure and surface chemistry of this material.
ANGLE-SCANNED PHOTOELECTRON DIFFRACTION: FROM CLEAN SURFACES TO COMPLEX ADSORPTION SYSTEMS
Authors: BONDINO F. , COMELLI G. , BARALDI A. , ROSEI R. , LIZZIT S. , LOCATELLI A. , ESCH F. , GOLDONI A. , LARCIPRETE R. , PAOLUCCI G.
Published: October 2002

We exploit the capabilities of photoelectron diffraction (PED) to provide quantitative information on the local structure of the first layers of clean and adsorbate-covered surface systems. Selected studies of low-energy PED are presented, highlighting the advantages of the angle-scanning approach. In the first experiment, we evaluate the clean Rh(110) surface layer relaxation by employing the PED of the Rh 3d5/2 surface component. The resulting relaxation is in good accord with previous low energy electron diffraction data. In the second experiment, a system lacking long-range order is examined, namely the saturation layer formed by nitrogen monoxide on Rh(100) at 123 K. Preliminary results confirm the bridge adsorption geometry model. The last example is a chemical shift PED study of the c(4 × 2) phase of carbon monoxide on Pt(111). In this system, CO molecules are coadsorbed at two different adsorption sites, the energy separation of the respective C 1s components being 0.7 eV. Structural determination has been achieved by an independent analysis of the diffraction yield originated by the two chemically shifted C 1s components. The structure of Pt (111) + c(4 × 2)-2CO has been refined with an automated search of the best parameters using a modified version of MSCD (multiple scattering calculation of diffraction) code.
VARIATIONS IN THE LIFETIME OF 3d HOLE STATES IN ULTRATHIN Fe FILMS GROWN ON Cu(100) DEDUCED FROM THE LMM AUGER SPECTRA OF Fe
Authors: D'ADDATO S. , LUCHES P. , GOTTER R. , FLOREANO L. , CVETKO D. , MORGANTE A. , NEWTON A. , MARTIN D. , UNSWORTH P. , WEIGHTMAN P.
Published: October 2002

The Fe LMM Auger and Auger vacancy satellite spectra of ultrathin Fe films grown on Cu(100) have been measured using photon excitation energies above and below the L 2 ionisation edge, and in coincidence with the Fe 2p 3/2 and Fe 2p 1/2 photoelectrons. A comparison of the relative intensities of the satellites and main Auger transitions indicates that the M 4,5 holes of L 3 M 4,5 double hole states are localised for longer than the L 3 lifetime for the 0.3 and 10 ML coverages but have a lifetime comparable to that of L 3 holes for the 1 ML coverage. The results for the 1 ML coverage are supported by the results of the coincidence experiments. The reasons for the variation in the lifetime of M 4,5 holes are discussed in terms of changes in the number of Fe–Fe neighbours and the density of states at the Fermi energy in these systems.
RESONANT SCATTERING OF POLARIZED X-RAYS AT THE 4d EDGE OF GADOLINIUM
Authors: MARIOT J.-M. , JOURNEL L. , DELAUNAY R. , HAGUE C. F. , SACCHI M. , SIROTTI F. , PANACCIONE G. , MIRONE A. , TURCHINI S. , PROSPERI T.
Published: October 2002

The impact of resonant scattering of polarized X-rays is illustrated taking the gadolinium 4d edge energy range as an example. It is shown that: (i) the study of the reflection of linearly polarized light by a magnetized Gd sample gives information on the electronic states of the system, similar to that given by magnetic circular dichroism in absorption; (ii) the energy-loss peaks corresponding to spin-flip transitions in the 4d → 4f excitation exhibit a strong circular dichroism.
MULTICENTERED THEORY OF MOLECULAR PHOTOIONIZATION
Authors: BALTENKOV A. S. , DOLMATOV V. K. , MANSON S. T.
Published: October 2002

A new theory for near-threshold photoionization of inner electrons of atoms confined in multicentered atomic formations, e.g. molecules or clusters, is developed. The formulas for fixed-in-space molecules have been derived. The interaction of the photoelectron in the continuum with atoms that surround the atom being ionized, is replaced by the suitable boundary conditions imposed on the photoelectron wave function at the location of nuclei of these atoms in the molecule. The general formulas derived are used to calculate photoelectron angular distributions of diatomic molecules. The calculated data are in qualitative agreement with experimental data and results of other calculations.
ORBITAL ORDERING IN LaMnO3: CLUSTER MODEL CALCULATION OF RESONANT X-RAY SCATTERING AND X-RAY ABSORPTION AT THE MnL2,3 EDGE
Authors: TAGUCHI M. , ALTARELLLI M.
Published: October 2002

We report theoretical results for resonant X-ray scattering (RXS) and linear dichroism (LD) in X-ray absorption spectra at the Mn L 2,3 edge in LaMnO 3, with special attention to the observation of orbital ordering. Calculations were performed on a ( MnO 6)10- cluster with D 4h symmetry, including the effect of intra-atomic multiplet coupling in the Mn ion. Anisotropy effects are also included, through the anisotropic Mn 3d– O 2p hybridization and crystal field parameters for Mn 3d states. The agreement between theory and experiment is good. Moreover, we show that the intensity of the peaks at the L 3 edge are strongly dependent on the Jahn–Teller distortion, while the peaks at the L 2 edge are mostly related to the orbital ordering.
A NEGATIVE SPIN-POLARIZATION STRUCTURE OF Ni(110): PROBED BY SPIN- AND ANGLE-RESOLVED PHOTOELECTRON SPECTROSCOPY
Authors: QIAO S. , KIMURA A. , NARITA H. , YAJI K. , KOTANI E. , SHIMADA K. , NAMATAME H. , TANIGUCHI M. , HARASAWA A. , KINOSHITA T. , KAKIZAKI A.
Published: October 2002

We already reported the spin- and angle-resolved photoelectron measurements of Ni(110), Ni (110)- p (2 × 1) O and Ni (110)- c (2 × 2) S along the [Formula: see text] line of the Ni(110) surface Brillouin zone using He I radiation. We found that the structure at about 1.3 eV binding energy showed unusual character near the [Formula: see text] point. The spin polarization of this structure was observed to be negative. After the adsorption of oxygen and sulfur on the Ni(110) surface, the degree of negative spin polarization was found to decrease. To study the property of this state, that it is a bulk or surface-related, and to clarify the origin of the negative polarization, we performed spin- and angle-resolved photoemission measurements for Ni(110) along the LW line of its bulk Brillouin zone. The results show that this negative polarization structure can be attributed to a surface state near the [Formula: see text] point.
ANGLE-RESOLVED SOFT X-RAY PHOTOEMISSION FOR THE VALENCE BAND OF GRAPHITE
Authors: MATSUSHITA TOMOHIRO , MURO TAKAYUKI , SAITOH YUJI , NAKATANI TAKESHI , SEKIYAMA AKIRA , SUGA SHIGEMASA
Published: October 2002

Angle-resolved photoemission in the soft X-ray region has so far been used to study crystal (surface) structure by using photoelectron diffraction phenomena. In this energy region, the observation of the band structure was considered to be difficult, because the momentum of the incident photon cannot be negligible, the emitted electron is strongly influenced by the electron diffraction effects, and the cross section of the valence band is very small. We have performed the angle-resolved photoemission from the valence bands of highly oriented pyrolytic graphite by using the soft X-ray (hν=980 eV ) and successfully observed the band structure. The appearance of the structures of the band density of state is also discussed. Since the escape depth for the electrons with high kinetic energies is longer than ARUPS, this experimental method is better than the usual ARUPS in order to study the bulk band structures in solids.
TUMOR NECROSIS FACTOR-α CONVERTING ENZYME EXPRESSION IN THE JOINTS OF RHEUMATOID ARTHRITIS PATIENTS
Authors: Takahi Koichiro , Tomita Tetsuya , Nakase Takanobu , Kaneko Motoharu , Takano Hiroshi , Myoui Akira , Hashimoto Jun , Ochi Takahiro , Yoshikawa Hideki
Published: October 2002

The purpose of this study is to investigate the expression of tumor necrosis factor-α converting enzyme (TACE) in the synovium and subchondral bone region of patients with rheumatoid arthritis (RA) and to determine the contribution of the enzyme to the pathogenesis of RA.

Joint tissues were obtained during total knee arthroplasty from patients with RA and osteoarthritis (OA). The expression of TACE and TNF-α mRNA was detected by in situ hybridization. Characterization of TACE expressing cells was performed by immunohistochemistry using serial sections.

We found that TACE mRNA was expressed in both synovium and subchondral bone region and co-localized with TNF-α mRNA in RA. On the other hand, TACE mRNA expression was scarcely detectable in OA samples. TACE was expressed in mononuclear cells, such as CD3 and CD14 positive cells in RA samples.

In conclusion, the expression of TACE is up-regulated in the rheumatoid synovium and subchondral bone region, and the results in this study demonstrate that TACE may be involved and play a role in the pathogenesis of RA.
ONE-SELLER/TWO-BUYER MARKETS WITH BUYER EXTERNALITIES AND (IM)PERFECT COMPETITION
Authors: VAN DER LAAN GERARD , HOUBA HAROLD
Published: October 2002

In this paper the one-seller/two-buyer problem with buyer externalities is investigated under the assumption that the two buyers have legal opportunities to cooperate. It is shown that the Competitive equilibrium and the Core are robust with respect to negligible externalities and that the range of market prices in the Core belongs to range of Competitive equilibrium prices. However, these concepts yield no prediction for relatively severe externalities. Therefore, in order to provide a prediction the Bargaining set and the Multilateral Nash (MN) solution are also investigated. Surprisingly, in case of an empty Core the Bargaining set predicts a unique tuple of payoffs which are independent of the externalities and each pair of participants is equally likely. Markets with market imperfections are captured by the MN solution concept. The MN solution yields the paradox that the seller's price can be higher under imperfect competition than under perfect competition.
RELIABILITY OF AN ADVANCED METHOD FOR ISOMETRIC NECK MUSCLE STRENGTH MEASUREMENT
Authors: SENG KOK-YONG , LAM PIN-MIN
Published: October 2002

This paper is a descriptive study involving repeated within and between studies of maximal isometric strength measurements to determine the reproducibility of an advanced mechanical device in assessing maximal isometric strength of the cervical musculature.

Measurements of neck muscular strength and endurance present unique challenges, due to the complexity of neck motion and absence of appropriate reference bony landmarks. Assessment of cervical musculature characteristics is further complicated by a lack of affordable and reliable measurement equipment. Previous methods commonly employed strain gauge measurement and customized helmet dynamometry, but no device, engaging a computer-controled dynamometer, has been presented so far.

A new device incorporating anthropometry measurements of the local population was constructed for neck strength evaluation on the Biodex isokinetic dynamometer (Biodex, Corp., Shirley, NY). Intratester repeatability testing of the device was conducted in four principal directions: flexion, extension and left and right lateral bending. The result for intraday and day-to-day studies was good for all measured parameters.

This new device can be used to measure isometric flexion, extension and lateral bending torque. By permitting the neck's 'natural' motions, it may also quantify maximal isokinetic strength and endurance ratios. Hence, the device can serve as a useful and practical tool for neck strength measurement, training and rehabilitation purposes.
A FINITE ELEMENT STRESS ANALYSIS OF THE INTERFACE STRESS GENERATED DURING THE PUSH-OUT TEST
Authors: WILLIAMS K. R. , DRAUGHN R. A.
Published: October 2002

Within the dental sphere it is advantageous to be able to bond the restoration to dentine in order to avoid clinical problems such as marginal leakage with subsequent caries. Dentine bonding agents are normally employed to create an effective interface between the restoration and hard tissue with the formation of chemical links. The measurement of the bond strength between dental restorations or implants and surrounding hard tissue is generally achieved through the use of an experimental push-out test. However, these bond strengths have been found to be quite variable between laboratories even when similar chemical bonding agents have been used. This variability may be due to a number of factors including experimental differences such as, material moduli effects, specimen loading and changes in the thickness and properties of the interdiffusional zone (IDZ) that forms following polymerization of the bonding agent.

In this work, these variables have been explored using the finite element method initially through a 2-D description of the geometrical set up and subsequently a 3-D discretization. The results indicate that the loading and specimen support during testing have a significant effect on the measured push-out values. Furthermore the effects of a gradually changing modulus in the uppermost rings of the IDZ can have a significant influence on the support bearing property of the bonding agent. These changes in modulus of the IDZ may be the result of fluoride leaching to bring about increases in properties and modulus. A mixed moduli IDZ where the uppermost layer is approximately double the value of the remaining material can lead to increases in push-out values of 10% or more.
A STRUCTURE OF ROLES WITHIN VIRTUAL ORGANIZATIONS
Authors: BOSCH-SIJTSEMA PETRA
Published: October 2002

Virtual organizations (VO) are often characterized by their loose structure, lack of hierarchy and their empowered geographically dispersed members. However, in this paper it is claimed that there is a certain structure present in a VO. This structure can be found in specific roles identified in two VO case studies. The roles are within knowledge teams around a specific knowledge field, who cooperate with other knowledge teams. A second role can be recognized in a management part of the VO. Management is seen as an architect role, where the content of the work is integrated into an overall picture, and a broker role, who mediates between the different parties involved. The last role contains the autonomic partners who are the sponsors of the VO. Furthermore, the power of the VO is not equally distributed among its members, but divided over groups that are part of the architect management role.