bluuebunny/crossref_metadata_2025 huggingface dataset:
Solar wind density control of energy transfer to the magnetosphere
Authors: Lopez R. E. , Wiltberger M. , Hernandez S. , Lyon J. G.
Published: April 2004

It is generally believed that the coupling of energy between the solar wind and the magnetosphere depends almost exclusively on the solar wind speed and magnetic field, with density and temperature playing little or no role. However, recent studies have indicated that under certain conditions, such as the main phase of a storm, density can have a significant role in modulating the transfer of energy to the magnetosphere. In this paper we demonstrate the effect using global MHD simulations of the solar wind‐magnetosphere interaction. We also identify the physical mechanism that leads to the density control, namely the modification of the compression ratio of the bow shock, and explain why it is only apparent during periods of strong, southward IMF.
Fractional Laplace model for hydraulic conductivity
Authors: Meerschaert Mark M. , Kozubowski Tomasz J. , Molz Fred J. , Lu Silong
Published: April 2004

Based on an examination of K data from four different sites, a new stochastic fractal model, fractional Laplace motion, is proposed. This model is based on the assumption of spatially stationary ln(K) increments governed by the Laplace PDF, with the increments named fractional Laplace noise. Similar behavior has been reported for other increment processes (often called fluctuations) in the fields of finance and turbulence. The Laplace PDF serves as the basis for a stochastic fractal as a result of the geometric central limit theorem. All Laplace processes reduce to their Gaussian analogs for sufficiently large lags, which may explain the apparent contradiction between large‐scale models based on fractional Brownian motion and non‐Gaussian behavior on smaller scales.
On the decay of stratospheric pollutants: Diagnosing the longest‐lived eigenmode
Authors: Ehhalt D. H. , Rohrer F. , Schauffler S. , Prather M.
Published: April 2004

On the basis of a one‐dimensional (1‐D) analysis the decay time of the lowest eigenmode, τ1, for the stratospheric distribution of a conserved tracer is derived from measured vertical profiles of the mean age of stratospheric air. Two case studies (a and b) give τ1,a = 3.8 ± 0.8 years and τ1,b = 5.3 ± 1.1 years. These semiobservational times are considerably longer than most of the τ1 derived from 2‐D and 3‐D models. At the same time they are shorter than the observational eigentime, τ1,HTO = 7.7 ± 2 years, determined from the decay of the tritium (T) content in stratospheric water vapor, following the thermonuclear test explosions in the early 1960s. Part of the differences among the observational eigentimes can be explained by the assumptions that had to be made to extract τ1,HTO from the trend in the T content of stratospheric water vapor (namely, the cosmogenic background of tritiated water vapor and the trend in stratospheric water vapor). This leads to a revised value τ1,HTO = 6.3 ± 0.9 years for the time period 1975–1983. Allowing for a possible temporal trend in Γ and hence τ1, the value for the current τ1 decreases to 5.3 ± 1 years.
A modeling study of the export pathways of pollution from Europe: Seasonal and interannual variations (1987–1997)
Authors: Duncan B. N. , Bey I.
Published: April 2004

We present a study of the export pathways of pollution from Europe from 1987 to 1997, using a three‐dimensional model of chemistry and transport. The dominant export pathways in winter are advection to the (1) middle/high latitudes of the North Atlantic Ocean, (2) Russia and the Russian Arctic, and (3) middle/low latitudes of the North Atlantic Ocean from western Europe and from northern Africa via the Mediterranean Basin. In summer, export occurs by both advection and convection; advective transport occurs predominantly to Russia and the Mediterranean Basin/northern Africa. There are two major regions of convection in summer that loft European pollution into the free troposphere, one centered over Germany and the other over the Ural Mountains in Russia. Another region of lofting, not associated with moist convection, occurs in northwestern Africa by the Western Saharan Low. Summertime ozone in our model is enhanced by European pollution (∼5 ppbv on average) in the middle troposphere near these three regions of lofting. European pollution causes summertime surface ozone levels in northern Africa and the Near East to exceed regularly the European Council's human health standard. The two dominant causes of interannual variation in European pollution export are variations in transport, especially associated with the North Atlantic Oscillation (NAO), and changes in anthropogenic emissions. The tropospheric burden of carbon monoxide (CO) from European sources varies by as much as ±20% over both western Europe and the North Atlantic and ±15% over the Arctic in winter because of interannual variations in transport. When the NAO is in the positive (negative) phase, the CO burden from European sources tends to be lower (higher) over the North Atlantic and higher (lower) over the Arctic. European emissions of CO and nitrogen oxides decrease by 36% and 20% over the study period, respectively, with a nearly linear concomitant decrease in the CO burden associated with European emissions. We find that it is necessary to consider both of these factors when interpreting trends in observed trace gas concentrations over Europe.
Observed covariance between ecosystem carbon exchange and atmospheric boundary layer dynamics at a site in northern Wisconsin
Authors: Yi C. , Davis K. J. , Bakwin P. S. , Denning A. S. , Zhang N. , Desai A. , Lin J. C. , Gerbig C.
Published: April 2004

Ecosystem CO2 exchange and atmosphere boundary layer (ABL) mixing are correlated diurnally and seasonally as they are both driven by solar insulation. Tracer transport models predict that these covariance signals produce a meridional gradient of annual mean CO2 concentration in the marine boundary layer that is half as strong as the signal produced by fossil fuel emissions. This rectifier effect is simulated by most global tracer transport models. However, observations to constrain the strength of these covariance signals in nature are lacking. We investigate the covariance between ecosystem carbon dioxide exchange and ABL dynamics by comparing one widely cited transport model with observations in the middle of the North American continent. We measured CO2 flux and mixing ratio using an eddy‐covariance system from a 447‐m tower in northern Wisconsin, mixed layer depths using a 915‐MHz boundary layer profiling radar near the tower, and vertical CO2 profiles from aircraft in the vicinity of the tower. We find (1) that simulated and observed net daily CO2 fluxes are similar; (2) the simulated maximum ABL depths were too shallow throughout year; (3) the simulated seasonal variability of the CO2 mixing ratio in the lowest layer of the free troposphere is 3 ppm smaller than that inferred from a mixed layer jump model and boundary layer observations; and (4) the simulated diurnal and seasonal covariance between CO2 flux and mixing ratio are weaker than the observed covariance. The comparison between model and observations is limited by the questionable representativeness of a single observing site and a bias towards fair weather observing conditions.
Airborne measurements of areal spectral surface albedo over different sea and land surfaces
Authors: Wendisch Manfred , Pilewskie Peter , Jäkel Evelyn , Schmidt Sebastian , Pommier John , Howard Steve , Jonsson Haflidi H. , Guan Hong , Schröder Marc , Mayer Bernhard
Published: April 2004

Airborne measurements of the ratio of spectral upward and downward irradiances (so‐called spectral albedo) are used to derive the areal spectral surface albedo in the wavelength range from 330 to 1670 nm. The data were collected over different sea and land surfaces in cloudless atmospheric conditions during three field campaigns. Measurements from the Albedometer (developed at IfT) and the NASA Solar Spectral Flux Radiometer (SSFR) are employed. Spectral radiative transfer calculations show that atmospheric scattering and absorption within the layer beneath the flight level considerably contribute to the airborne albedo measurements reported here, even for low flight altitudes (0.2–0.5 km). To remove this atmospheric masking, a nonlinear extrapolation of the airborne albedo measurements to the ground is performed. The nonlinearity is due to the vertically inhomogeneous distribution of the particle microphysical properties. This fact underlines the importance of aerosol profile measurements for the proper correction of atmospheric masking. Examples of the extrapolated areal spectral surface albedos are discussed in terms of their solar zenith angle dependence, their small‐scale, and general variability. Finally, typical areal spectral surface albedos for different sea and land surfaces, as derived from the three measurement campaigns, are supplied in parameterized form for use in radiative transfer applications.
High dielectric insulation coating for time domain reflectometry soil moisture sensor
Authors: Fujiyasu Y. , Pierce C. E. , Fan L. , Wong C. P.
Published: April 2004

Insulation coating is often applied to time domain reflectometry (TDR) soil moisture sensors to reduce the conduction loss of energy. However, because of low dielectric constants of common plastic insulation materials, sensitivity is reduced, and the measurements are strongly dependent on coating thickness. Analytical studies clearly showed that these unwanted features could be mitigated if a high dielectric material is used for coating. An epoxy‐ceramic nanocomposite was selected as a high dielectric insulation material because of its high dielectric constant and high adhesion. Experimental work using this composite indicated that the material has the potential to be used as a high dielectric coating for TDR soil moisture probes. On the basis of the results of these analytical and experimental studies a framework for designing an improved epoxy‐ceramic composite for coating TDR soil moisture sensors is suggested.
Experimental evidence for ice particle interaction with metal atoms at the high latitude summer mesopause region
Authors: Lübken Franz‐Josef , Höffner Josef
Published: April 2004

Potassium number densities were measured in 2001–2003 with a resonance lidar in Spitzbergen (78°N). Typical number densities in the 85–100 km height range are 5–70 atoms/cm3 with a maximum around 92 km in summer. Comparison of the seasonal and height variation of K number densities with similar measurements at mid latitudes (54°N) shows a remarkable reduction in the lower part of the layer during the summer months. This reduction strongly correlates with the appearance of ice particles detected as noctilucent clouds (NLC) and polar mesosphere summer echoes (PMSE) by the same lidar and by a VHF radar, respectively. In a total of 226 hours of simultaneous K and NLC observations, the upper edge of the NLC layer was always detected below the lower edge of the K layer (i.e., no overlap), even when both edges vary substantially with height and time. The ice particle effect on potassium seems to correlate with the ice particle size: ‘large’ particles (>10–20 nm, detectable as NLC) completely remove all available K atoms, whereas smaller particles (but still large enough to create PMSE) gradually reduce the number of K atoms. Our observations suggest that the loss of K atoms on ice is just in the right order of magnitude to compete with the major production and loss terms.
Structure of Spa15, a type III secretion chaperone from Shigella flexneri with broad specificity
Authors: van Eerde André , Hamiaux Cyril , Pérez Javier , Parsot Claude , Dijkstra Bauke W
Published: April 2004

Type III secretion (TTS) systems are used by many Gram‐negative pathogens to inject virulence proteins into the cells of their hosts. Several of these virulence effectors require TTS chaperones that maintain them in a secretion‐competent state. Whereas most chaperones bind only one effector, Spa15 from the human pathogen Shigella flexneri and homologous chaperones bind several seemingly unrelated effectors, and were proposed to form a special subgroup. Its 1.8 Å crystal structure confirms this specific classification, showing that Spa15 has the same fold as other TTS effector chaperones, but forms a different dimer. The presence of hydrophobic sites on the Spa15 surface suggests that the different Spa15 effectors all possess similar structural elements that can bind these sites. Furthermore, the Spa15 structure reveals larger structural differences between class I chaperones than previously anticipated, which does not support the hypothesis that chaperone–effector complexes are structurally conserved and function as three‐dimensional secretion signals.
On the exterior structure of graphs
Authors: Kastler Daniel
Published: April 2004

After a detailed ab initio description of the exterior structure of graphs as handled by Connes and Kreimer in their work on renormalization (illustrated by the example of the φ3 model in six dimensions) we spell out in detail their study of the Lie algebra of infinitesimal characters and of the group of characters of the Hopf algebra of Feynman graphs.
Double product integrals and Enriquez quantization of Lie bialgebras I: The quasitriangular identities
Authors: Hudson R. L. , Pulmannová S.
Published: April 2004

Let 𝒯(ℒ) be the space of all tensors over a Lie algebra ℒ in which the Lie bracket is obtained by taking commutators in an associative algebra. We show that 𝒯(ℒ) becomes a Hopf algebra when equipped with a noncommutative modification of the shuffle product together with the standard coproduct. A definition is given of directed double product integrals as iterated single product integrals driven by formal power series with coefficients in the tensor product of ℒ with an appropriate associative algebra. For the Hopf algebra T(L)[[h]] of formal power series we show that elements R[h] of (T(L)⊗T(L))[[h]] satisfying (Δ⊗id)R[h]=R[h]13R[h]23,  (id⊗Δ)R[h]=R[h]13R[h]12,and which are unitalized by the counit in either copy of 𝒯(ℒ), can be characterized as such directed double product integrals ∏∏(1+d⃗⊗d↙r[h]) where r[h] is a formal power series with coefficients in L⊗L and vanishing constant term.
Supersymmetric exact sequence, heat kernel and super Korteweg–de Vries hierarchy
Authors: Andrea S. , Restuccia A. , Sotomayor A.
Published: April 2004

We introduce the free N=1 supersymmetric derivation ring and prove the existence of an exact sequence of supersymmetric rings and linear transformations. We apply necessary and sufficient conditions arising from this exact supersymmetric sequence to obtain the essential relations between conserved quantities, gradients and the N=1 super Korteweg–de Vries (KdV) hierarchy. We combine this algebraic approach with an analytic analysis of the super heat operator. We obtain the explicit expression for the Green’s function of the super heat operator in terms of a series expansion and discuss its properties. The expansion is convergent under the assumption of bounded bosonic and fermionic potentials. We show that the asymptotic expansion when t→0+ of the Green’s function for the superheat operator evaluated over its diagonal generates all the members of the N=1 super KdV hierarchy.
Adiabatic approximation of the Schrödinger–Poisson system with a partial confinement: The stationary case
Authors: Pinaud Olivier
Published: April 2004

Asymptotic quantum transport models of a two-dimensional gas are presented. The models are the stationary versions of those introduced in a previous paper by Ben Abdallah, Méhats, Pinaud. The starting point is a singular perturbation of the three-dimensional stationary Schrödinger–Poisson system posed on bounded domain. The electron injection in the device is modeled thanks to open boundary conditions. Under a small density assumption, the asymptotics lead to a full two-dimensional first-order approximation of the initial model. An intermediate model, called the “2.5D adiabatic model” in Ben Abdallah, Méhats, Pinaud is then introduced. It shares the same structure as the limit but is shown to be a second-order approximation of the three-dimensional model.
Anisotropic scattering kernel: Generalized and modified Maxwell boundary conditions
Authors: Dadzie S. Kokou , Méolans J. Gilbert
Published: April 2004

This article presents a model of a scattering kernel of boundary conditions for the Boltzmann equation. The proposed scattering kernel is based on an anisotropic accommodation argument. Three parameters equal to the momentum accommodation coefficients are shown as characterizing the influence of each direction. First the new scattering kernel is derived from a phenomenological criticism of the first form of the scattering kernel proposed by Maxwell; then the same result is established from an analytic approach based on the spectral nature of the linear integral operator associated to the scattering kernel problem. As a result, the model provides a correct form of scattering kernel to handle the influence of each direction in particle collisions with the wall. Finally independent accommodation of each internal mode is added to extend the model to the case of polyatomic gases.
On the discrete spectrum of non-self-adjoint Schrödinger differential equation with an operator coefficient
Authors: Bayramoglu Mehmet , Taşçi Fatih , Zeynalov Djafar
Published: April 2004

We study the discrete part of spectrum of a singular non-self-adjoint second-order differential equation on a semiaxis with an operator coefficient. Its boundedness is proved. The result is applied to the Schrödinger boundary value problem −Δu+q(x)u=λ2u, u|∂D=0, with a complex potential q(x) in an angular domain.
On the extra phase correction to the semiclassical spin coherent-state propagator
Authors: Pletyukhov Mikhail
Published: April 2004

The problem of an origin of the Solari–Kochetov extra-phase contribution to the naive semiclassical form of a generalized phase-space propagator is addressed with the special reference to the su(2) spin case which is the most important in applications. While the extra-phase correction to a flat phase-space propagator can straightforwardly be shown to appear as a difference between the principal and the Weyl symbols of a Hamiltonian in the next-to-leading order expansion in the semiclassical parameter, the same statement for the semiclassical spin coherent-state propagator holds provided the Holstein–Primakoff representation of the su(2) algebra generators is employed.
Curvature singularity of the distributional Bañados, Teitelboim, and Zanelli black hole geometry
Authors: Pantoja N. R. , Rago H. , Rodrı́guez R. O.
Published: April 2004

For the nonrotating Bañados, Teitelboim, and Zanelli black hole, the distributional curvature tensor field is found. It is shown to have singular parts proportional to a δ-distribution with support at the origin. This singularity is related, through Einstein field equations, to a point source. Coordinate invariance and independence on the choice of differentiable structure of the results are addressed.
Green functions of the Dirac equation with magnetic-solenoid field
Authors: Gavrilov S. P. , Gitman D. M. , Smirnov A. A.
Published: April 2004

Various Green functions of the Dirac equation with a magnetic-solenoid field (the superposition of the Aharonov–Bohm field and a collinear uniform magnetic field) are constructed and studied. The problem is considered in 2+1 and 3+1 dimensions for the natural extension of the Dirac operator (the extension obtained from the solenoid regularization). Representations of the Green functions as proper time integrals are derived. The nonrelativistic limit is considered. For the sake of completeness the Green functions of the Klein–Gordon particles are constructed as well.
Applications and generalizations of Fisher–Hartwig asymptotics
Authors: Forrester P. J. , Frankel N. E.
Published: April 2004

Fisher–Hartwig asymptotics refers to the large n form of a class of Toeplitz determinants with singular generating functions. This class of Toeplitz determinants occurs in the study of the spin–spin correlations for the two-dimensional Ising model, and the ground state density matrix of the impenetrable Bose gas, amongst other problems in mathematical physics. We give a new application of the original Fisher–Hartwig formula to the asymptotic decay of the Ising correlations above Tc, while the study of the Bose gas density matrix leads us to generalize the Fisher–Hartwig formula to the asymptotic form of random matrix averages over the classical groups and the Gaussian and Laguerre unitary matrix ensembles. Another viewpoint of our generalizations is that they extend to Hankel determinants the Fisher–Hartwig asymptotic form known for Toeplitz determinants.
Semisynthesis of a segmental isotopically labeled protein splicing precursor: NMR evidence for an unusual peptide bond at the N-extein–intein junction
Authors: Romanelli Alessandra , Shekhtman Alexander , Cowburn David , Muir Tom W.
Published: April 2004

Protein splicing is a posttranslational autocatalytic process in which an intervening sequence, termed an intein, is removed from a host protein, the extein. Although we have a reasonable picture of the basic chemical steps in protein splicing, our knowledge of how these are catalyzed and regulated is less well developed. In the current study, a combination of NMR spectroscopy and segmental isotopic labeling has been used to study the structure of an active protein splicing precursor, corresponding to an N-extein fusion of the
Mxe
GyrA intein. The
1
J
NC′
coupling constant for the (-1) scissile peptide bond at the N-extein–intein junction was found to be ≈12 Hz, which indicates that this amide is highly polarized, perhaps because of nonplanarity. Additional mutagenesis and NMR studies indicate that conserved box B histidine residue is essential for catalysis of the first step of splicing and for maintaining the (-1) scissile bond in its unusual conformation. Overall, these studies support the “ground-state destabilization” model as part of the mechanism of catalysis.
Protein ranking: From local to global structure in the protein similarity network
Authors: Weston Jason , Elisseeff Andre , Zhou Dengyong , Leslie Christina S. , Noble William Stafford
Published: April 2004

Biologists regularly search databases of DNA or protein sequences for evolutionary or functional relationships to a given query sequence. We describe a ranking algorithm that exploits the entire network structure of similarity relationships among proteins in a sequence database by performing a diffusion operation on a precomputed, weighted network. The resulting ranking algorithm, evaluated by using a human-curated database of protein structures, is efficient and provides significantly better rankings than a local network search algorithm such as
psi-blast
.
The estrogen-related receptor α (ERRα) functions in PPARγ coactivator 1α (PGC-1α)-induced mitochondrial biogenesis
Authors: Schreiber Sylvia N. , Emter Roger , Hock M. Benjamin , Knutti Darko , Cardenas Jessica , Podvinec Michael , Oakeley Edward J. , Kralli Anastasia
Published: April 2004

Estrogen-related receptor α (ERRα) is one of the first orphan nuclear receptors to be identified, yet its physiological functions are still unclear. We show here that ERRα is an effector of the transcriptional coactivator PGC-1α [peroxisome proliferator-activated receptor γ (PPARγ) coactivator 1α], and that it regulates the expression of genes involved in oxidative phosphorylation and mitochondrial biogenesis. Inhibition of ERRα compromises the ability of PGC-1α to induce the expression of genes encoding mitochondrial proteins and to increase mitochondrial DNA content. A constitutively active form of ERRα is sufficient to elicit both responses. ERRα binding sites are present in the transcriptional control regions of ERRα/PGC-1α-induced genes and contribute to the transcriptional response to PGC-1α. The ERRα-regulated genes described here have been reported to be expressed at reduced levels in humans that are insulin-resistant. Thus, changes in ERRα activity could be linked to pathological changes in metabolic disease, such as diabetes.
Two types of inhibitory control: Predictive relations to social functioning
Authors: Thorell Lisa B. , Bohlin Gunilla , Rydell Ann-Margret
Published: April 2004

The aim was to investigate two inhibitory concepts—executive inhibition and inhibition to the unfamiliar. The relation between these two phenomena was studied as well as how they, alone or in combination, are related to the development of hyperactivity, social anxiety, and social competence. The results showed that there was a low, positive relation between these two inhibitory phenomena at age 5 ( n 1/4 151). Further, both types of inhibition were negatively related to nonclinical levels of hyperactivity in school 3 years later. Inhibition to the unfamiliar was also negatively related to social initiative, and positively related to social anxiety. Using nonlinear analyses, only the combination of high levels of both types of inhibition showed significant predictions to social anxiety. The results also indicated that high inhibition to the unfamiliar might have a protective role in the development of hyperactivity as low executive inhibition was related to hyperactivity, except when in combination with high inhibition to the unfamiliar. Regarding predictions to social competence, the results showed that the combination of high levels of both types of inhibition was associated with low social initiative, although this effect was only significant at the level of tendency.
Imaginary companions and peer acceptance
Authors: Gleason Tracy R.
Published: April 2004

Early research on imaginary companions suggests that children who create them do so to compensate for poor social relationships. Consequently, the peer acceptance of children with imaginary companions was compared to that of their peers. Sociometrics were conducted on 88 preschool-aged children; 11 had invisible companions, 16 had personified objects (e.g., stuffed animals animated by the child) and 65 had no imaginary companion. The three groups were compared on positive and negative nominations, social preference, social impact, and total number of reciprocal friends. Given the positive correlation between pretend play and social competence, fantasy predisposition was used as a covariate. The groups did not differ on number of positive nominations by peers, total number of reciprocal friends, or social preference scores. However, compared to their peers, children with personified objects had higher social impact scores, largely as a result of negative nominations. Attention is thus called to the differences between personified object and invisible imaginary companions, and to the underlying social cognition that may be involved in their creation.
A longitudinal study of the utility of the resilient, overcontrolled, and undercontrolled personality types as predictors of children’s and adolescents’ problem behaviour
Authors: van Leeuwen Karla , de Fruyt Filip , Mervielde Ivan
Published: April 2004

This study addresses the utility of the resilient, overcontrolled, and undercontrolled personality prototypes for predicting children’s and adolescents’ problem behaviour in a longitudinal general population sample ( N 1/4 491). Both parents and one child participated in the study at two measurement occasions separated by a 3-year interval. The major objective was to examine whether the prototypes predict different clinical patterns, as reflected by mean-level differences on the internalising and the externalising dimensions of the CBCL and the YSR. Prototype membership was derived from cluster analysing parental ratings of personality and adolescent self-rated personality. All three types could only be recovered from the adolescent self-ratings of personality. Although the prototypes showed clear differential relationships with measures of internalising and externalising problem behaviour, hierarchical multiple regression analyses showed that personality types do not predict adolescent problem behaviour beyond what is predicted by personality dimensions.
Evaluations and orientations in mother–child narratives as a function of attachment security: A longitudinal investigation
Authors: Newcombe Rhiannon , Reese Elaine
Published: April 2004

The present study examined the socialisation of children’s narrative ability across the preschool period, exploring the association between children’s and mothers’ narrative style and children’s attachment security. Fifty-six children and their mothers engaged in past event memory conversations about everyday shared past experiences when the children were aged 19, 25, 32, 40, and 51 months. At 19 months, mothers completed the Attachment Q-Set (Version 3.0) as a measure of children’s attachment security. Importantly, the results showed different patterns of narrative use and socialisation as a function of children’s attachment security. Specifically, securely attached children and their mothers used more evaluations over time, had a more consistent narrative style, and had more bidirectional influences. We clarify the narrative socialisation process and discuss the link between attachment and narrative.
Connections between attitudes, group norms, and behaviour in bullying situations
Authors: Salmivalli Christina , Voeten Marinus
Published: April 2004

We examined the connections between attitudes, group norms, and students’ behaviour in bullying situations (bullying others, assisting the bully, reinforcing the bully, defending the victim, or staying outside bullying situations). The participants were 1220 elementary school children (600 girls and 620 boys) from 48 school classes from Grades four, five, and six, i.e., 9–10, 10–11, and 11–12 years of age. Whereas attitudes did predict behaviour at the student level in most cases (although the effects were moderate after controlling for gender), the group norms could be used in explaining variance at the classroom level, especially in the upper grades. The class context (even if not classroom norms specifically) had more effect on girls’ than on boys’ bullying-related behaviours.
French Field Experience with Buprenorphine
Authors: Auriacombe Marc , Fatséas Mélina , Dubernet Jacques , Daulouède Jean‐Pierre , Tignol Jean
Published: April 2004

In most European countries, methadone treatment is provided to only 20– 30% of opiate abusers who need treatment due to regulations and concerns about safety. To address this need in France, all registered medical doctors since 1995 have been allowed to prescribe buprenorphine (BUP) without any special education or licensing. This led to treating approximately 65,000 patients per year with BUP, about ten times more than with more restrictive methadone policies. French physician compensation mechanisms, pharmacy services, and medical insurance funding all minimized barriers to BUP treatment. About 20% of all physicians in France are using BUP to treat about half of the estimated 150,000 problem heroin users. Daily supervised dosing by a phamacist for the first six months resulted in significantly better treatment retention (80% vs 46%) and lower heroin use. Intravenous diversion of BUP may occur in up to 20% of BUP patients and has led to various infections and relatively rare overdoses in combination with sedatives. Opiate overdose deaths have declined substantially (by 79%) since BUP was introduced in 1995. Newborn opiate withdrawal in mothers treated with buprenorphine compared to methadone was reported to be less frequent, less severe, and of shorter duration. Although some of the public health benefits seen during the time of buprenorphine expansion in France might be contingent upon characteristics of the French health and social services system, the French model raises questions about the value of tight regulations on prescribing BUP imposed by many countries throughout the world.
Implementing Buprenorphine Treatment in Community Settings in Australia: Experiences from the Buprenorphine Implementation Trial
Authors: Lintzeris Nicholas , Ritter Alison , Panjari Mary , Clark Nicolas , Kutin Jozica , Bammer Gabriele
Published: April 2004

Buprenorphine was registered in Australia as a maintenance and detoxification agent for the management of opioid dependence in November, 2000, and became widely available in August, 2001. This paper provides an overview of key developments in the introduction of buprenorphine treatment in Australia, with an emphasis upon the delivery of services in community‐based (primary care) settings. A central study in this work was the Buprenorphine Implementation Trial (BIT), a randomized, controlled trial comparing buprenorphine and methadone maintenance treatment delivered under naturalistic conditions by specialist and community‐based service providers (general practitioners and community pharmacists) in 139 subjects across nineteen treatment sites. In addition to conventional patient outcome measures (treatment retention, drug use, psychosocial functioning, and cost effectiveness), the BIT study also involved the development and evaluation of clinical guidelines, training programs for clinicians, and client literature, which are described here. Integration of treatment systems (methadone with buprenorphine, specialist and primary care programs) and factors thought to be important in the uptake of buprenorphine treatment in Australia since registration are discussed.
Processes of Care During a Randomized Trial of Office‐based Treatment of Opioid Dependence in Primary Care
Authors: Fiellin David A. , O'Connor Patrick G. , Chawarski Marek , Schottenfeld Richard S.
Published: April 2004

Improving office‐based treatment of opioid dependence requires an evaluation of processes of care. We evaluated the care provided by physicians to opioid dependent patients during a trial of office‐based methadone maintenance. We conducted chart audits and a focus group. Audits identified lapses in monitoring of urine toxicology results and paperwork completion. The focus group identified the logistics of dispensing, the receipt of urine toxicology results, difficulties arranging psychiatric services, communications with the opioid treatment program, and non‐adherence to medication as problematic. Strategies to support logistical aspects of office‐based care should be developed. Chart audits and mentoring should be considered as a mechanism to foster quality care. These processes of care are likely to require attention for treatment using methadone or buprenorphine.
Direct and indirect effects of online learning on distance education
Authors: Shin Namin , Chan Jason K.Y.
Published: April 2004

This paper presents an exploratory study that investigates the effects of online learning on distance education students in an open university context. Two hypotheses are posited: (1) a direct relationship exists between students’ involvement in online learning and distance learning outcomes, and (2) an indirect relationship exists between these two domains via the mediating variable of an institutional Transactional Presence (TP), that is, a student's sense of the availability of and connectedness with an educational institution. Student learning achievement, satisfaction and intent‐to‐persist are used as indicators of outcomes of distance learning. The analysis of data garnered from 285 distance students reveals multifaceted relationships between students’ engagement in online learning, their perceptions of institutional TP and the three learning outcome variables. Besides the findings, the paper will discuss factors affecting students’ engagement in online learning in relation to different requirements, that is, optional or compulsory online use as well as the level of the course (undergraduate or postgraduate).
Improving the quality and effectiveness of computer‐mediated instruction through usability evaluations
Authors: Crowther Michael S. , Keller Chris C. , Waddoups Gregory L.
Published: April 2004

Brigham Young University's Center for Instructional Design (CID) creates online courses and multimedia instructional applications for university faculty. This paper asserts that including usability testing as a part of evaluation improves the quality and effectiveness of computer‐mediated instruction. The paper describes the fundamental purpose and functions of usability testing, and also distinguishes between different forms of evaluation: accessibility, quality assurance (QA), usability and implementation. Through a detailed case study, we describe how usability testing improved the quality of a computer‐based chemistry course and facilitated a clearer analysis of the learning effectiveness of this course.
The failure of a virtual social space (VSS) designed to create a learning community: lessons learned
Authors: McPherson Maggie , Nunes Miguel Baptista
Published: April 2004

The disappearance of physical social spaces from today's society is seen by some to be a modern phenomenon, resulting in isolation and lack of socialisation. In fact, this is always the case in distance education, due to geographical dispersion and disparate time schedules of learners. Very often, peer‐to‐peer socialisation in distance education only occurs as part of formal learning activities, or is just left to the student's own initiative. This situation is compounded by the modularity of Virtual Learning Environments (VLEs), forcing students to jump from one module space to another as they progress through a course. All discussion threads, conversations or record of previous dialogues are then lost. This paper reports on the design, development and extensive evaluation of a Virtual Social Space (VSS) conceived to address these problems and to support the creation of a learning community for a Continuing Professional Distance Education (CPDE) Masters in IT Management. An action research approach was adopted to establish student needs, design and develop the site and to explore it with students. Initially received with enthusiasm and perceived as a good idea by the students, the VSS was not entirely successful. This paper discusses how characteristics of this cohort had an impact on students’ perception and usage of this social space to create a learning community.
Mental constructions and constructions of web sites: learner and teacher points of view
Authors: Hazzan Orit
Published: April 2004

This research focuses on knowledge and ways in which knowledge may be constructed in the learner's mind. Specifically, it addresses the Web as a cognitive supporter for learning, organising and constructing a new domain of knowledge. In particular, the research analyses student reflection on constructing web sites. The analysis is based on an ongoing reflection of 40 prospective and in‐service teachers who took a course on educational computational environments. The students were asked to choose a complex topic and to document the process of constructing a web site that would present their chosen topic. They were to reflect upon the process with regard to their decision making, difficulties encountered, ways of thinking, considerations and insights. Student reflection is analysed from two perspectives: the first perspective examines how the task of constructing a web site contributes to student learning of complex topics, the second perspective views the students as teachers who explore how constructing a web site contributes to their understanding of learning processes.
Waves in consumption with interdependence among consumers
Authors: Cowan Robin , Cowan William , Peter Swann G.M.
Published: April 2004

Abstract.  In this paper we model the development of consumption when there are interactions between consumers. The consumer recognizes three reference groups: peer, distinction, and aspiration. The interplay of aspiration and distinction can lead to ‘waves’ in consumption; for example, the avant‐garde consumption of up‐market pioneers is copied by other types of consumer. As the latter aspire to emulate the former, the former seek distinction by varying their consumption. A consumption activity may start up market, then gradually descend the social spectrum. More complex patterns with continuing cycles in consumption can also be found. JEL classification D11,D62
Monopoly extraction of an exhaustible resource with two markets
Authors: Fischer Carolyn , Laxminarayan Ramanan
Published: April 2004

Abstract.  Although much has been written about monopoly extraction of natural resources, the case of a resource being sold in two separate markets has escaped notice. We find that a monopolist facing two different iso‐elastic demand schedules extracts more rapidly than the social planner, whether or not arbitrage prevents price discrimination between markets. JEL classification: D42, Q3
A longitudinal analysis of earnings change in Canada
Authors: Beach Charles M. , Finnie Ross
Published: April 2004

Abstract.  We use tax‐based longitudinal microdata for 1982–99 to (i) examine how earnings distributions have shifted, (ii) identify changes in earnings mobility patterns, and (iii) replicate and update Beaudry and Green's cohort analysis of age‐earnings profiles. We find: (i) increased polarization of men's earnings and marked decline in real earnings of workers aged 20–4; (ii) general decline in men's earnings mobility, while women's mobility has increased for young and prime‐age workers; and (iii) upward drift in earnings profiles of 1960s–1970s entry cohorts and downward shifts for 1980s–1990s cohorts (largely confirming Beaudry and Green's findings), but suggestive of steepening profiles for the 1990s cohorts. JEL classification code : J31,O33
The impact of environmental noise on song amplitude in a territorial bird
Authors: Brumm Henrik
Published: April 2004

The impact of environmental background noise on the performance of territorial songs was examined in free‐ranging nightingales (Luscinia megarhynchos Brehm). An analysis of sound pressure levels revealed that males at noisier locations sang with higher sound levels than birds in territories less affected by background sounds.

This is the first evidence of a noise‐dependent vocal amplitude regulation in the natural environment of an animal.

The results yielded demonstrate that the birds tried to mitigate the impairments on their communication caused by masking noise. This behaviour may help to maintain a given transmission distance of songs, which are used in territory defence and mate attraction. At the same time, birds forced to sing with higher amplitudes have to bear the increased costs of singing.

This suggests that in songbirds the level of environmental noise in a territory will contribute to its quality and thus considerably affect the behavioural ecology of singing males.
A trade‐off between two resource‐demanding functions: post‐nuptial moult and immunity during reproduction in male pied flycatchers
Authors: Sanz Juan José , Moreno Juan , Merino Santiago , Tomás Gustavo
Published: April 2004

Costs of reproduction might be mediated by a resource‐allocation trade‐off between immunity and reproductive effort. Recent studies have suggested that the moult–breeding overlap observed mainly in males may affect this trade‐off. In order to test whether increased investment in immunity may affect the onset of moult or reproductive output in a species with moult–breeding overlap, we immunized breeding male pied flycatchers Ficedula hypoleuca (Pallas) with a non‐pathogenic antigen (sheep red blood cells) in the first week post‐hatching and compared their moult score, parental effort and reproductive success shortly before fledging with that of control males injected with sterile phosphate‐buffered saline.

Immunized males provisioning nestlings delayed the onset of post‐nuptial primary moult compared to control males. The experimental activation of the immune defence of males affected their stress levels (heterophile/lymphocyte ratio, heat‐shock proteins) on day 13 after chicks hatched. An activated immune response tended to depress reproductive output, although the experimental design was not efficient enough to find a significant effect because the manipulation was not performed early enough in the nestling period.

The results suggest that experimental activation of the males’ immune system decreased the resources necessary for initiating post‐nuptial moult. The trade‐off between immunity and moult onset may imply costs of delayed moult in cases of infection and may interact with reproductive immunosuppression in cases of moult–breeding overlap. Moult, immunity and reproduction are locked in a three‐way interaction which may markedly affect avian life histories.
Dietary self‐selection behaviour by the adults of the aphidophagous ladybeetle Harmonia axyridis (Coleoptera: Coccinellidae)
Authors: Soares António Onofre , Coderre Daniel , Schanderl Henrique
Published: April 2004

Harmonia axyridis is a generalist predator with a high range of accepted prey. Prey differ in nutritive contents, energetic values and cost associated with their capture and ingestion. As a result of selection pressures, animals will tend to hunt for their prey efficiently. In this paper we evaluated the suitability of Myzus persicae and Aphis fabae to the adults of the aulica phenotype of H. axyridis, their feeding preferences and the impact of mixed diets on their fitness. Feeding preference of predators was evaluated through their response to different relative abundance of prey.

Under a single diet regime, the adults of the aulica phenotype fed on more individuals M. persicae than A. fabae but consumed less biomass from the former. None of those prey affect relative growth rate and reproductive capacity of the ladybeetles.

Males and females present different types of response to three levels of different relative abundance of prey. While males show a constant feeding preference for M. persicae, females did not show a feeding preference (i.e. null switching response). Under a mixed diet regime, adults’ voracity gradually increased as the proportion of M. persicae increased, but biomass consumed and relative growth rate was not affected. On the other hand, fecundity and fertility increased.

Our results suggest that H. axyridis present self‐selection behaviour because they agree with the basic criteria of Waldbauer and Friedman's self‐selection, i.e. (i) the animal's choice of food or nutrients is non‐random, and (ii) the coccinellid benefits from self‐selecting.