bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of dislocation scattering on the transport properties of InN grown on GaN substrates by molecular beam epitaxy
Authors: Wang Kejia (Albert) , Cao Yu , Simon John , Zhang Jing , Mintairov Alexander , Merz James , Hall Douglas , Kosel Thomas , Jena Debdeep
Published: October 2006

The authors report the structural, optical, and transport properties of high quality InN epitaxial films grown on GaN substrates by plasma-assisted molecular beam epitaxy. They have found a strong correlation between the structural quality and the measured carrier mobilities. Comparison of temperature-dependent Hall data with a theoretical transport model indicates that the electron mobility in state-of-art InN is limited by charged dislocation scattering. The model predicts that an order-of-magnitude increase in electron mobilities can be achieved by the reduction of dislocation densities in InN.
Experimental technique for characterizing arbitrary aspect ratio piezoelectric resonators
Authors: Kim Moojoon , Kim Jungsoon , Cao Wenwu
Published: October 2006

The electromechanical coupling coefficient k is the most important parameter for the characterization of a piezoelectric material and for the design of electromechanical devices. Standard resonance technique for measuring the k value is based on one-dimensional approximation, which needs to use samples having extreme geometries. For small size crystals and/or due to geometrical constraints in many devices, piezoelectric resonators may not be made into such extreme geometries. An averaging scheme has been developed to tackle this challenging experimental task, and the so obtained k values agree well with theoretical predictions of k values for arbitrary aspect ratio resonators.
Band gap and band parameters of InN and GaN from quasiparticle energy calculations based on exact-exchange density-functional theory
Authors: Rinke P. , Scheffler M. , Qteish A. , Winkelnkemper M. , Bimberg D. , Neugebauer J.
Published: October 2006

The authors have studied the electronic structure of InN and GaN employing G0W0 calculations based on exact-exchange density-functional theory. For InN their approach predicts a gap of 0.7eV. Taking the Burnstein-Moss effect into account, the increase of the apparent quasiparticle gap with increasing electron concentration is in good agreement with the observed blueshift of the experimental optical absorption edge. Moreover, the concentration dependence of the effective mass, which results from the nonparabolicity of the conduction band, agrees well with recent experimental findings. Based on the quasiparticle band structure the parameter set for a 4×4k∙p Hamiltonian has been derived.
Temperature dependence of Raman scattering in GaMnN
Authors: Guo L. L. , Zhang Y. H. , Shen W. Z.
Published: October 2006

A detailed investigation of temperature-dependent Raman scattering has been carried out on ion-implanted GaMnN with different Mn doses. The observed frequency downshift and linewidth broadening with increasing temperature can be well described by a model taking into account the contributions of the thermal expansion and decay of optical phonons into two and three phonons of lower energy. The authors have demonstrated clear dependence of the phonon frequency, linewidth, and decay process on the Mn concentration in GaMnN, which is found to be closely related to the crystal structure.
The Influence of the Residential Environment on Green-Space Travel: Testing the Compensation Hypothesis
Authors: Maat Kees , de Vries Paul
Published: October 2006

We investigated whether the use of parks and other green recreational facilities is influenced by the amount of green space around a dwelling and in the immediate neighbourhood. We paid particular attention to testing the compensation hypothesis, which states that people with less green space in their own residential environment are more likely to visit parks or nature reserves. The frequency of visits to green amenities was analyzed in relation to detailed spatial data based on sociodemographic variables. The findings indicated that, although people tend to make more use of green space if it is available in the vicinity, a brown (more urban) residential environment does not result in compensation behaviour. An explanation for this may be self-selection in the residential-choice process. It is conceivable, however, that some of the people who do not live in a green neighbourhood but would prefer to do so will move to a more suburban or rural environment.
Remaking Urban Environments: The Political Ecology of Air Pollution in Delhi
Authors: véron René
Published: October 2006

In the growing field of urban political ecology, so far not much attention has been paid to air-quality and related policies. In this paper I examine the recent far-reaching air-pollution policies in India's capital, as well as the role of environmental nongovernmental organizations and judicial activism, in view of their implications for different groups of the urban population. I analyze these policies in the wider context of Delhi's ongoing strive for ‘city beautification’ and for changing (environmental) governmentalities, and reveal a marked middle-class bias in the environmental and judicial activisms practised, which also contributes to the refining of the boundary between public and private environments. Furthermore, it is argued that air quality with its complex sociospatial patterns plays a significant part in the coproduction of urban ‘socioenvironments' that needs to be addressed in political-ecological studies.
Competition and Saturation in West European Grocery Retailing
Authors: Poole Rachel , Clarke Graham P , Clarke David B
Published: October 2006

The international (and, increasingly, global) nature of grocery retailing is promoting the need to consider developments across numerous markets in order to understand fully any given country's market characteristics. However, compared with the breadth of research on various aspects of UK grocery retailing, there is a relative paucity of work across the same range of topics and scales in European contexts (broad national-level comparisons excepted). The paper therefore extends work on UK retail change, assessing the extent of corresponding or diverging development trajectories elsewhere in Europe. Key indicators are used to map spatial variations in competition, saturation, and internationalization at a subnational scale. Inferences are made regarding likely patterns of future development through the identification of growth opportunities that may be exploited by organic expansion or merger-and-acquisition activity. Some speculative merger-and-acquisition scenarios are also considered, which suggest the validity of regulatory concerns over local competition and spatial monopoly.
Limitations in the use of electrical conductivity to monitor the behaviour of soil solution
Authors: Rose D. A. , Abbas F. , Adey M. A.
Published: October 2006

Solutions of KBr and K2SO4 of various concentrations were separately displaced by deionised water through 2 contrasting saturated materials, inert solid particles (glass ballotini), and a reactive but non-swelling aggregated clay mineral (sepiolite) over a wide range of flow rates. The concentration of the individual ions in the effluent was analysed (Br– and K+ with ion-specific electrodes, SO42+ by ion chromatography) and that of bulk solution was measured by electrical conductivity (EC). For each displacement, the individual breakthrough curves (BTCs) for the anion, the cation, and the bulk solution were optimised by CXTFIT 2.0.
In ballotini, the BTCs of the anion, cation, and solution were always congruent, the retardation factors did not differ significantly from unity, and the coefficients of hydrodynamic dispersion were identical. For sepiolite, the ions were separated; the bulk solution eluted faster than the cation, slower than the anions. Retardation factors were always less than unity for the anions, greater than unity for the cation, and close to but less than unity for the bulk solution, and became more extreme as the concentration of solute decreased. Dispersion coefficients were, however, unaffected by type of solute, concentration range, or particular ion/EC.
The separation of ions means that the composition as well as the concentration of a solution changes continuously during flow through a reactive soil. Estimates of solution concentration from measurements of EC may thus fail to characterise adequately the movement of the individual components of the solution in such materials. This has implications for the interpretation of any leachate monitoring in reactive soils by methods based on the measurement of EC, such as time-domain reflectometry.
Sampling considerations for surveying copper concentrations in Australian vineyard soils
Authors: Wightwick Adam , Mollah Mahabubur , Smith Jennifer , MacGregor Alison
Published: October 2006

The Australian wine industry has funded a study to determine the concentrations of copper in vineyard soils and to assess whether the continued use of copper-based fungicides is likely to be detrimental to the long-term agricultural sustainability of vineyard soils. Prior to the conduct of regional surveys to determine copper concentrations in vineyard soils, a preliminary study was conducted in 6 vineyards near Mildura (34°S, 142°E) (north-western Vic., Australia) to determine sampling considerations. The study investigated the distribution of copper in the soils of vineyards with 3 different histories of copper-based fungicide use: <5 years old; at least 30 years old during which time the vineyard had been ploughed and replanted; and at least 60 years old. At 3 locations in each vineyard, soil samples were collected from 2 depths (0–0.15 and 0.15–0.30 m) at 0.30-m intervals along two 1.50-m-long transects running at right angles in opposite directions from the vine trunk towards the inter-row areas. The results showed that copper concentrations were higher in the top 0.15 m of soil (P < 0.001) and declined with distance from the vine (P = 0.002). The variation in copper concentrations between vineyards was found to be much greater than the variation within vineyards (variance component of 0.7746 and 0.0893, respectively). Balancing an acceptable level of error with the resources required to collect samples, we recommend obtaining 1 composite soil sample from each vineyard in regional surveys to determine copper concentrations in vineyard soils. Sampling depth and distance from the vine should also be taken into consideration in future soil sampling depending on the objective of the study.
Improved measurement of conductivity on swelling clay soils using a modified disc permeameter method
Authors: Foley J. L. , Tolmie P. E. , Silburn D. M.
Published: October 2006

Disc permeameters are the preferred method for measuring unsaturated hydraulic conductivity (Kψ) in situ. However, in swelling clays, Kψ measured using 3-D measurement and analysis methods are often several orders of magnitude too high and are of no value for modelling internal drainage. During a series of experiments, the causes of inflated Kψ values were identified and a modified method developed to accurately measure Kψ.
On a Black Vertosol, Kψ was strongly correlated with water content and measurement period, with higher flow rates occurring until the soil profile had fully wet up. Near-saturated Kψ measured under permeameters was up to 2 orders of magnitude higher than field-saturated conductivity (KFS) measured in ponded rings. This discrepancy was caused by residual capillarity and unrestricted swelling at the wetting front in unsaturated soils. In addition, lateral flow was common and surface depressions around permeameters filled with water, erroneously contributing to measured infiltration and invalidating assumptions in the 3-D analysis. To prevent this, permeameters were confined within rings to restrict flow to 1D, and measured Kψ (confined) was then compared with Kψ (unconfined) and KFS (ponded rings). Confining flow to 1D reduced Kψ by up to 2 orders of magnitude for a Black Vertosol and by a factor of 3 for a Red Ferrosol. Near-saturated Kψ from confined permeameters agreed well with KFS after similar short measurement durations (e.g. 0.5 h), but Kψ was still overestimated until steady-state flow was established. Therefore, to derive estimates of Kψ that reflect natural flow during internal drainage, we recommend (i) pre-wetting the soil and extending measurement time to attain steady-state flow, and (ii) confining permeameters within rings to restrict flow to 1 dimension.
This method was used to compare lucerne ley and annual cropping treatments on 2 Black Vertosols (Bongeen and Waco). Kψ was similar between cropping treatments, suggesting that initial differences in structure and porosity were transient and related to soil moisture content. The Bongeen soil had a significantly lower Kψ (K–1 cm of 0.8 mm/h) than the Waco soil (2.0 mm/h).
Effluent flux prediction in variably saturated soil zones within a septic tank—soil absorption trench
Authors: Beal Cara D. , Gardner Ted , Rassam David W. , Vieritz Alison M. , Menzies Neal W.
Published: October 2006

The treatment and hydraulic mechanisms in a septic tank–soil absorption system (SAS) are highly influenced by the clogging layer or biomat zone which develops on bottom and lower sidewall surfaces within the trench. Flow rates through the biomat and sub-biomat zones are governed largely by the biomat hydraulic properties (resistance and hydraulic conductivity) and the unsaturated hydraulic conductivity of the underlying soil. One- and 2-dimensional models were used to investigate the relative importance of sidewall and vertical flow rates and pathways in SAS. Results of 1-dimensional modelling show that several orders of magnitude variation in saturated hydraulic conductivity (Ks) reduce to a 1 order of magnitude variation in long-term flow rates.
To increase the reliability of prediction of septic trench hydrology, HYDRUS-2D was used to model 2-dimensional flow. In the permeable soils, under high trench loading, effluent preferentially flowed in the upper region of the trench where no resistant biomat was present (the exfiltration zone). By comparison, flow was more evenly partitioned between the biomat zones and the exfiltration zones of the low permeability soil. An increase in effluent infiltration corresponded with a greater availability of exfiltration zone, rather than a lower resistance of biomat. Results of modelling simulations demonstrated the important role that a permeable A horizon may play in limiting surface surcharge of effluent under high trench hydraulic loading.
Survival of pathogenic and indicator bacteria in biosolids applied to agricultural land
Authors: Eamens G. J. , Waldron A. M. , Nicholls P. J.
Published: October 2006

Concentrations of surviving Escherichia coli, Clostridium perfringens, and Salmonella spp. were determined temporally in mechanically dewatered biosolids derived from anaerobic–mesophilic digestion and applied to agricultural land. Following applications in different seasons, repeated assessments of bacterial concentrations in biosolid clumps, using most-probable-number (MPN) techniques, found sustained high levels of these bacteria. Bacterial concentrations were often well above soil background levels at 6 months, and in some cases 11–12 months, after land application. Survival in surface-applied biosolids was similar to that for biosolids incorporated into the soil, and between application rates of 10 or 30 dry t/ha. Salmonella concentrations in applied biosolids were not predicted from, and could exceed those of, the indicator organism E. coli. Multiple plot analyses indicated regrowth of E. coli and Salmonella can occur within biosolids, up to several months after application. However, Salmonella serovars likely to pose a significant risk to animal health were not detected among isolates from the dewatered biosolids. Reduced accessibility for grazing livestock by soil incorporation, together with the time taken for normal pasture establishment practices, and the limited pathogenicity of the vast majority of salmonellae present in biosolids may significantly reduce the risk of spread of these organisms to the human food chain.
The indirect estimation of saturated hydraulic conductivity of soils, using measurements of gas permeability. I. Laboratory testing with dry granular soils
Authors: Wells Tony , Fityus Stephen , Smith David W. , Moe Hlwan
Published: October 2006

A comprehensive knowledge of soil hydraulic conductivity is essential when modelling the distribution of soil moisture within soil profiles and across catchments. The high spatial variability of soil hydraulic conductivity, however, necessitates the taking of many in situ measurements, which are costly, time-consuming, and labour-intensive. This paper presents an improved method for indirectly determining the saturated hydraulic conductivity of granular materials via an in situ gas flow technique. The apparatus employed consists of a cylindrical tube which is embedded in the soil to a prescribed depth. Nitrogen at a range of pressures was supplied to the tube and allowed to escape by permeating through the soil. A 3-dimensional, axisymmetric, steady-state, finite element flow model was then used to determine the value of the soil intrinsic gas permeability which produces the best fit to the pressure–air flow data. Saturated hydraulic conductivities estimated from the application of the gas flow technique to 5 granular soils covering a wide range of permeabilities were in close agreement with values determined using a conventional permeameter. The results of this preliminary study demonstrate the potential of this approach to the indirect determination of saturated hydraulic conductivity based on measurement of gas flow rates in granular and structured soils.
Short-term tillage practices on soil organic matter pools in a tropical Ultisol
Authors: Sotomayor-Ramírez David , Espinoza Yusmary , Rámos-Santana Rafael
Published: October 2006

In tropical regions, pasture establishment involves tillage operations. Adoption of conservation tillage practices could result in lower costs and in improved soil quality by decreasing soil organic carbon (SOC) losses. This study investigated the effects of 3 tillage practices on the establishment of Brachiaria decumbens and on the total SOC and soil organic nitrogen (SON) content and its fractions in an Ultisol from the humid mountain zone of Puerto Rico that was previously under pasture. The treatments evaluated were no-tillage, minimum tillage, and conventional tillage (CT). At 120 days after planting (DAP), plant cover and density was improved in the CT treatment compared with the other treatments. At 180 DAP, there were no significant differences in the SOC, SON, aggregate size distribution, distribution of C within aggregate size classes, and labile C physical fractions among tillage treatments. Approximately 60% of the total SOC associated with aggregates was found within macroaggregates. About an equal proportion of the particulate organic matter (POM) was associated within aggregates and nonaggregate-protected free light fraction, and these were not affected by tillage management. Lower amounts of C mineralised after disruption of macroaggregates containing POM with high C/N ratio was probably due to immobilisation of the more labile protected C (iPOM). Labile forms of C were greater in macroaggregates than in microaggregates, yet comprised a lower proportion of total SOC, suggesting that macroaggregates have a greater proportion of C physically protected from microbial attack. The results indicate that there are no short-term changes in the tendency of the soil to lose C and N as a result of tillage practices for the establishment of pastures in this soil.
Regulation of the SUMO pathway sensitizes differentiating human endometrial stromal cells to progesterone
Authors: Jones Marius C. , Fusi Luca , Higham Jenny H. , Abdel-Hafiz Hany , Horwitz Kathryn B. , Lam Eric W.-F. , Brosens Jan J.
Published: October 2006

cAMP is required for differentiation of human endometrial stromal cells (HESCs) into decidual cells in response to progesterone, although the underlying mechanism is not well understood. We now demonstrate that cAMP signaling attenuates ligand-dependent sumoylation of the progesterone receptor (PR) in HESCs. In fact, decidualization is associated with global hyposumoylation and redistribution of small ubiquitin-like modifier (SUMO)-1 conjugates into distinct nuclear foci. This altered pattern of global sumoylation was not attributable to impaired maturation of SUMO-1 precursor or altered expression of E1 (SAE1/SEA2) or E2 (Ubc9) enzymes but coincided with profound changes in the expression of E3 ligases and SUMO-specific proteases. Down-regulation of several members of the protein inhibitors of activated STAT (PIAS) family upon decidualization pointed toward a role of these E3 ligases in PR sumoylation. We demonstrate that PIAS1 interacts with the PR and serves as its E3 SUMO ligase upon activation of the receptor. Furthermore, we show that silencing of PIAS1 not only enhances PR-dependent transcription but also induces expression of prolactin, a decidual marker gene, in progestin-treated HESCs without the need of simultaneous activation of the cAMP pathway. Our findings demonstrate how dynamic changes in the SUMO pathway mediated by cAMP signaling determine the endometrial response to progesterone.
Evolutionary trade-off between weapons and testes
Authors: Simmons Leigh W. , Emlen Douglas J.
Published: October 2006

It has long been recognized that male mating competition is responsible for the evolution of weaponry for mate acquisition. However, when females mate with more than one male, competition between males can continue after mating in the form of sperm competition. Theory predicts that males should increase their investment in sperm production as sperm competition is increased, but it assumes that males face a trade-off between sperm production and other life-history traits such as mate acquisition. Here, we use a genus of horned beetle,Onthophagus, to examine the trade-off between investment in testes required for fertilizations and investment in weapons used to obtain matings. In a within-species study, we prevented males from developing horns and found that these males grew larger and invested relatively more in testes growth than did males allowed to grow horns. Among species, there was no general relationship between the relative sizes of horns and testes. However, the allometric slope of horn size on body size was negatively associated with the allometric slope of testes size on body size. We suggest that this reflects meaningful evolutionary changes in the developmental mechanisms regulating trait growth, specifically in the degree of nutrition-dependent phenotypic plasticity versus canalization of traits. Finally, we show how this resource allocation trade-off has influenced the evolutionary diversification of weapons, revealing a rich interplay between developmental trade-offs and both pre- and postmating mechanisms of sexual competition.
Mammalian reovirus, a nonfusogenic nonenveloped virus, forms size-selective pores in a model membrane
Authors: Agosto Melina A. , Ivanovic Tijana , Nibert Max L.
Published: October 2006

During cell entry, reovirus particles with a diameter of 70–80 nm must penetrate the cellular membrane to access the cytoplasm. The mechanism of penetration, without benefit of membrane fusion, is not well characterized for any such nonenveloped animal virus. Lysis of RBCs is an
in vitro
assay for the membrane perforation activity of reovirus; however, the mechanism of lysis has been unknown. In this report, osmotic-protection experiments using PEGs of different sizes revealed that reovirus-induced lysis of RBCs occurs osmotically, after formation of small size-selective lesions or “pores.” Consistent results were obtained by monitoring leakage of fluorophore-tagged dextrans from the interior of resealed RBC ghosts. Gradient fractionations showed that whole virus particles, as well as the myristoylated fragment μ1N that is released from particles, are recruited to RBC membranes in association with pore formation. We propose that formation of small pores is a discrete, intermediate step in the reovirus membrane-penetration pathway, which may be shared by other nonenveloped animal viruses.
Structural and dynamical changes in an α-subunit of a heterotrimeric G protein along the activation pathway
Authors: Van Eps Ned , Oldham William M. , Hamm Heidi E. , Hubbell Wayne L.
Published: October 2006

The Gα subunits of heterotrimeric G proteins (Gαβγ) mediate signal transduction via activation by receptors and subsequent interaction with downstream effectors. Crystal structures indicate that conformational changes in “switch” sequences of Gα, controlled by the identity of the bound nucleotide (GDP and GTP), modulate binding affinities to the Gβγ subunits, receptor, and effector proteins. To investigate the solution structure and dynamics of Gαi1 through the G protein cycle, nitroxide side chains (R1) were introduced at sites in switch II and at a site in helix α4, a putative effector binding region. In the inactive Gαi1(GDP) state, the EPR spectra are compatible with conformational polymorphism in switch II. Upon complex formation with Gβγ, motions of R1 are highly constrained, reflecting direct contact interactions at the Gαi1–Gβ interface; remarkably, the presence of R1 at the sites investigated does not substantially affect the binding affinity. Complex formation between the heterotrimer and activated rhodopsin leads to a dramatic change in R1 motion at residue 217 in the receptor-binding α2/β4 loop and smaller allosteric changes at the Gαi1–Gβγ interface distant from the receptor binding surface. Upon addition of GTPγS, the activated Gαi1(GTP) subunit dissociates from the complex, and switch II is transformed to a unique conformation similar to that in crystal structures but with a flexible backbone. A previously unreported activation-dependent change in α4, distant from the interaction surface, supports a role for this helix in effector binding.
Isoelectric focusing technology quantifies protein signaling in 25 cells
Authors: O'Neill Roger A. , Bhamidipati Arunashree , Bi Xiahui , Deb-Basu Debabrita , Cahill Linda , Ferrante Jason , Gentalen Erik , Glazer Marc , Gossett John , Hacker Kevin , Kirby Celeste , Knittle James , Loder Robert , Mastroieni Catherine , MacLaren Michael , Mills Thomas , Nguyen Uyen , Parker Nineveh , Rice Audie , Roach David , Suich Daniel , Voehringer David , Voss Karl , Yang Jade , Yang Tom , Vander Horn Peter B.
Published: October 2006

A previously undescribed isoelectric focusing technology allows cell signaling to be quantitatively assessed in <25 cells. High-resolution capillary isoelectric focusing allows isoforms and individual phosphorylation forms to be resolved, often to baseline, in a 400-nl capillary. Key to the method is photochemical capture of the resolved protein forms. Once immobilized, the proteins can be probed with specific antibodies flowed through the capillary. Antibodies bound to their targets are detected by chemiluminescence. Because chemiluminescent substrates are flowed through the capillary during detection, localized substrate depletion is overcome, giving excellent linearity of response across several orders of magnitude. By analyzing pan-specific antibody signals from individual resolved forms of a protein, each of these can be quantified, without the problems associated with using multiple antibodies with different binding avidities to detect individual protein forms.
Cosmological parameters from combining the Lyman-α forest with CMB, galaxy clustering and SN constraints
Authors: Seljak Uroš , Slosar Anže , McDonald Patrick
Published: October 2006

We combine the Ly-α forest power spectrum (LYA) from the Sloan Digital Sky Survey (SDSS) and high resolution spectra with cosmic microwave background (CMB) including three-year WMAP, and supernovae (SN) and galaxy clustering constraints to derive new constraints on cosmological parameters. The existing LYA power spectrum analysis is supplemented by constraints on the mean flux decrement derived using a principle component analysis for quasar continua, which improves the LYA constraints on the linear power. We find some tension between the WMAP3 and LYA power spectrum amplitudes, at the ∼2σ level, which is partially alleviated by the inclusion of other observations: we find σ8= 0.85 ± 0.02 compared to σ8= 0.80 ± 0.03 without LYA. For the slope, we findns= 0.965 ± 0.012. We find no evidence for the running of the spectral index in the combined analysis, dn/dlnk= −(1.5 ± 1.2) × 10−2, in agreement with inflation. The limits on the sum of neutrino masses are significantly improved:at 95% (<0.32 eV at 99.9%). This result, when combined with atmospheric and solar neutrino mixing constraints, requires that the neutrino masses cannot be degenerate,m3/m1>1.3 (95% c.l.). Assuming a thermalized fourth neutrino, we findms<0.26 eV at 95% c.l. and such a neutrino cannot be an explanation for the LSND results. In the limits of massless neutrinos, we obtain the effective number of neutrinosNνeff= 5.3−0.6+0.4−1.7+2.1−2.5+3.8andNνeff= 3.04 is allowed only at 2.4 sigma. The constraint on the dark energy equation of state isw= −1.04 ± 0.06. The constraint on curvature is Ωk= −0.003 ± 0.006. Cosmic strings limits areGμ<2.3 × 10−7at 95% c.l. and correlated isocurvature models are also tightly constrained.
Psychological symptoms and physical health and health behaviours in adolescents: a prospective 2‐year study in East London
Authors: Clark Charlotte , Haines Mary M. , Head Jenny , Klineberg Emily , Arephin Muna , Viner Russell , Taylor Stephanie J. C. , Booy Robert , Bhui Kam , Stansfeld Stephen A.
Published: October 2006

Aims  To examine whether physical health and health‐risk behaviours in young people are risk factors for psychological distress and depressive symptoms over a 2‐year period.

Design/setting  A 2‐year, prospective epidemiological cohort study in East London.

Participants  A total of 1615 adolescents from the Research with East London Adolescents: Community Health Survey (RELACHS)—a representative cohort of young people aged 11–12 and 13–14 years at baseline, followed‐up after 2 years.

Measurements  Psychological distress and depressive symptoms identified by the self‐report Strengths and Difficulties Questionnaire and the Short Moods and Feelings Questionnaire at baseline and follow‐up. Data on overweight/obesity, general health, long‐standing illness, physical activity, smoking, alcohol use and drug use were collected from questionnaires completed by the adolescents at baseline and follow‐up.

Findings  At follow‐up, 10.1% of males and 12.9% of females reported psychological distress; 20% of males and 33.7% of females reported depressive symptoms. Having tried drugs or engaged in two or more health‐risk behaviours (smoking, alcohol use or drug use) at baseline predicted psychological distress and depressive symptoms at follow‐up. Smoking on its own, long‐standing illness, obesity/overweight and activity levels were not associated with later psychological health. Risk of poor psychological health at follow‐up was associated strongly with psychological health at baseline.

Conclusions  Psychological health at baseline was the strongest predictor of psychological health at follow‐up. Engaging in two or more health‐risk behaviours moderately increased the risk of poor psychological health, suggesting that prevention strategies targeting co‐occuring substance use may reduce burden of disease.
A latent class analysis of illicit drug abuse/dependence: results from the National Epidemiological Survey on Alcohol and Related Conditions
Authors: Agrawal Arpana , Lynskey Michael T. , Madden Pamela A. F. , Bucholz Kathleen K. , Heath Andrew C.
Published: October 2006

Aims  We examine the co‐occurrence of abuse/dependence across different illicit drugs and test associations between these classes and major psychiatric disorders.

Method  Latent class analyses were used to characterize polysubstance abuse/dependence (AB/D) in 43 093 individuals who participated in the National Epidemiological Survey on Alcohol and Related Conditions. Multinomial logistic regression was performed to examine the association between the classes of life‐time illicit drug AB/D and gender, age and race, as well as life‐time Diagnostic and Statistical Manual version IV (DSM‐IV) alcohol abuse/dependence, nicotine dependence, major depressive disorder, generalized anxiety disorder, panic disorder, social phobia and antisocial personality disorder.

Results  Five latent classes were identified: no AB/D (class 1: 92.5%), cannabis AB/D only (class 2: 5.8%), stimulants + hallucinogen AB/D (class 3: 0.6%), prescription drug AB/D (class 4: 0.6%) and polysubstance AB/D (class 5: 0.5%). Major depressive disorder and nicotine dependence were associated most strongly with class 5. Anxiety disorders were associated strongly with the prescription drug AB/D class while alcohol AB/D and ASPD were associated with classes 2, 3, 4 and 5 when compared to the reference class (class 1).

Conclusions  Significant heterogeneity exists in this US population for polysubstance AB/D patterns with evidence for a subgroup with high rates of sedative, tranquilizer and opiate AB/D and a history of anxiety disorders, a stimulant/hallucinogens group, a high‐risk group with elevated rates of all psychiatric disorders and a milder cannabis AB/D only group. Replication of such classes across other samples has significant implications, such as characterizing risk groups that may be etiologically diverse.
Bayesian selection of predictors of conception probabilities across the menstrual cycle
Authors: Scarpa Bruno , Dunson David B.
Published: October 2006

There is increasing interest in identifying predictors of human fertility, including environmental exposures, behavioural factors, and biomarkers, such as mucus or reproductive hormones. Epidemiological studies typically measure fecundability, the per menstrual cycle probability of conception, using time to pregnancy data. A critical predictor, which is often ignored in the design or analysis, is the timing of non‐contracepting intercourse in the menstrual cycle. In order to limit confounding by behavioural differences between exposure groups, it may be preferable to base inferences on day‐specific conception probabilities in relation to intercourse timing. This article proposes Bayesian methods for selection of predictors of day‐specific conception probabilities. A particular focus is the case in which data on ovulation timing are not available. We focus on the selection of fertile days in the cycle during which conception probabilities are non‐negligible and predictors may play a role. Data from recent European and Italian prospective studies of daily fecundability are presented, and the proposed approach is used to estimate cervical mucus effects within a mid‐cycle potentially fertile window using data from the Italian study.
Measuring fecundity with standardised estimates of expected pregnancies
Authors: Mikolajczyk Rafael T. , Stanford Joseph B.
Published: October 2006

Approaches to measuring fecundity include the assessment of time to pregnancy and day‐specific probabilities of conception (daily fecundities) indexed to a day of ovulation. In this paper, we develop an additional approach of calculating expected pregnancies based on daily fecundities indexed to the last day of the menstrual cycle. Expected pregnancies can thus be calculated while controlling for frequency and timing of coitus. Comparing observed pregnancies with expected pregnancies allows for a standardised comparison of fecundity between studies or groups within studies, and can be used to assess the effects of categorical covariates on the woman or couple level, and also on the cycle level. This can be accomplished in a minimal data set that does not necessarily require hormonal measurement or the explicit identification of ovulation. We demonstrate this approach by examining the effects of age and parity on fecundity in a data set from women monitoring their fertility cycles with the Creighton Model FertilityCare System.
Expression of the recombinant protein disulphide isomerase of Teladorsagia circumcincta
Authors: MARTÍNEZ‐VALLADARES M. , GODIO‐FERNÁNDEZ R. , VARA‐DEL RÍO M. P. , MARTÍN J. F. , ROJO‐VÁZQUEZ F. A.
Published: October 2006

The aim of this experiment was to find an antigen from Teladorsagia circumcincta to measure the level of IgA in ovine serum samples. Previous experiments used the titre of IgA to select sheep resistant to infection with T. circumcincta. By Western blotting 22 experimentally infected ewes recognized many proteins, but not all of them were recognized by all animals. Sheep were divided into two groups of animals: those that recognized a protein in Western blotting and those that did not. Among all proteins, three showed significant associations between protein recognition and the titre of IgA in the serum.
Resistance to CO2 diffusion in cuticular membranes of amphibious plants and the implication for CO2 acquisition
Authors: FROST‐CHRISTENSEN HENNING , FLOTO FRANZ
Published: October 2006

Cuticular membranes (CMs) were isolated from leaves of amphibious and submerged plants and their CO2 resistances were determined as a contribution to establish quantitatively the series of resistances met by CO2 diffusing from bulk water to the chloroplasts of submerged leaves. The isolation was performed enzymatically; permeabilities were determined and converted to resistances. The range of permeance values was 3 to 43 × 10−6 m s−1 corresponding to resistance values of 23 to 295 × 103 s m−1, i.e. of the same order of magnitude as boundary layer resistances. The sum of boundary layer, CM, leaf cell and carboxylation resistances could be contained within the total diffusion resistance as determined from the photosynthetic CO2 affinity of the leaf. From the same species, the aerial leaf CM resistance was always higher than the aquatic leaf CM resistance. In a terrestrial plant, the CM resistance to CO2 diffusion was found lower in leaves developed submerged.
A randomised, double‐blind, placebo‐controlled trial of atovaquone–proguanil vs. sulphadoxine–pyrimethamine in the treatment of malarial anaemia in Zambian children
Authors: Mulenga Modest , Malunga Fidelis , Bennett Steve , Thuma Philip E , Shulman Caroline , Fielding Katherine , Alloueche Ali , Greenwood Brian M.
Published: October 2006

Objective  To compare the efficacy of atovaquone–proguanil (AP) and sulphadoxine–pyrimethamine (SP) in the treatment of malarial anaemia in Zambian children.

Methods  An individually randomised, double‐blind, controlled trial was undertaken in Zambian children with moderately severe anaemia and Plasmodium falciparum parasitaemia. The main trial endpoint was treatment failure defined as a need for blood transfusion or treatment with quinine, persistent anaemia or death within 14 days from the start of treatment. Secondary endpoints were parasitological and haematological findings 14 or 28 days after the start of treatment.

Results  A total of 128 children with a packed cell volume of <21% and >9% and P. falciparum parasitaemia received treatment with AP and 127 treatment with SP. Treatment failure occurred in 28 children (22%) who received SP and in 10 (8%) who received AP (OR: 3.34, 95% CI: 1.54, 7.21). Ten children required blood transfusion, all of whom were in the SP treatment group. Six children died, five of whom were in the AP group; none of the deaths were considered to be related directly to treatment.

Conclusions  Atovaquone–proguanil proved more effective than SP in the treatment of malarial anaemia in an area with a modest level of SP resistance. AP is no longer available through the Malarone Donation Programme and is too expensive for routine use in Africa. However, this study has shown that in an area with a modest level of resistance to SP, use of a more effective antimalaria reduces the need for blood transfusion in children with malarial anaemia.
Does Seed‐Caching Experience Affect Spatial Memory Performance by Pinyon Jays?
Authors: Stafford B. Lucas , Balda Russell P. , Kamil Alan C.
Published: October 2006

Food‐storing birds use spatial memory to find previously cached food items. Throughout winter, pinyon jays (Gymnorhinus cyanocephalus) rely heavily on cached pinyon pine (Pinus edulis) seeds. Because of a recent severe drought, pinyon pine trees had not produced a significant seed crop for several years. Therefore, 1‐ and 2‐yr‐old birds never had the opportunity to cache and recover seeds and birds 4 or more years of age had not recovered seeds in 3 yr. This study examined whether natural but extreme variability in experience might result in differences in abstract spatial memory ability during a non‐cache recovery test of spatial memory. Three groups of jays were tested for spatial memory ability in an open room analog of the radial arm maze. Two of the groups were 8 mo old: young/minimally experienced birds which had 2 mo of experience in the wild, while young/experienced birds had 5 mo of experience in their natural habitat. The third group, adult, consisted of birds more than 3 yr old, with at least 3 yr of experience in their natural habitat. This was the only group with experience caching pine seeds. All three groups performed equally and well above chance. This suggests that spatial memory is fully developed by 8 mo of age and is not affected by extensive experience in the wild.
First‐Year Common Nightingales (Luscinia megarhynchos) Have Smaller Song‐Type Repertoire Sizes Than Older Males
Authors: Kiefer Sarah , Spiess Anne , Kipper Silke , Mundry Roger , Sommer Christina , Hultsch Henrike , Todt Dietmar
Published: October 2006

Based on the assumptions that birdsong indicates male quality and that quality is related to age, one might expect older birds to signal their age. That is, in addition to actual body condition, at least some song features should vary with age, presumably towards more complexity. We investigated this issue by comparing repertoire sizes of free‐ranging common nightingale males in their first breeding season with those of older males. Nightingales are a good model species as they are open‐ended learners, where song acquisition is not confined to an early sensitive period of learning. Moreover, nightingales develop an extraordinarily large song‐type repertoire (approx. 180 different song types per male), and differences in repertoire size among males are pronounced. We analysed repertoire characteristics of the nocturnal song of nine nightingales in their first breeding season and compared them with the songs of nine older males. The repertoire size of older males was on average 53% larger than that of yearlings. When analysing two song categories of nightingales, whistle and non‐whistle songs separately, we found similar results. Our findings show marked differences in repertoire size between age categories, suggesting that this song feature may reflect a male's age. We discuss those mechanisms that may constrain the development of larger repertoires in first‐year males. Whether repertoire sizes are crucial for female mate choice or in vocal interactions among conspecific males remains open to further investigations.
Biodiversity loss under existing land use and climate change: an illustration using northern South America
Authors: Higgins Paul A. T.
Published: October 2006

Aim  Species richness depends on climate and land use. Maintaining locations with favourable climate and land‐use patterns is critical for protecting biodiversity because the loss of either can reduce the species richness that an area supports. Currently, the Guiana Shield (GS) receives abundant precipitation and has relatively light land use. For species richness this constitutes a good–good combination of climate and land use, respectively. In contrast, much of eastern Brazil receives low levels of precipitation and has heavy land use, which is a bad–bad combination for species richness. Thus, the current distribution of precipitation and land use in northern South America is relatively favourable for biodiversity. Palaeoclimate and model studies suggest, however, that the precipitation patterns for the two regions have switched before and could switch in response to greenhouse gas emissions. This paper examines the potential consequences of reconfiguring climate with respect to existing land‐use patterns using South America as an example.

Location  South America north of 20° S and east of the Andes.

Methods  Ecosystem structure and function are modelled under (1) historical climate and (2) altered precipitation following a shift in the location of the Inter‐Tropical Convergence Zone (ITCZ). The distribution of precipitation, biomes, net primary productivity (NPP) and land use are then used to predict levels of species richness under the two climate scenarios.

Results  Climate changes could shift the distribution of vegetation and NPP such that conditions favourable for species richness in the GS region disappear. If land‐use patterns were not prohibitive in eastern Brazil, the improved climate conditions there could compensate for the GS loss (assuming migratory barriers are overcome). Instead, existing land‐use patterns cause the combined species richness projected for the two regions to plummet.

Main conclusions  Human activities will alter current configurations of land use and climate throughout the world. For species richness, new configurations are likely to include both positive and negative combinations of climate and land use. However, the irreversibility of past extinctions due to land‐use patterns loads the dice against species richness.
Management Going‐concern Disclosures: Impact of Corporate Governance and Auditor Reputation
Authors: Uang Jinn‐Yang , Citron David B. , Sudarsanam Sudi , Taffler Richard J.
Published: October 2006

The UK regulatory requirements relating to going‐concern disclosures require directors to report on the going‐concern status of their firms. Such directors have incentives not to report fairly in the case of financially‐distressed firms. We expect effective corporate governance mechanisms will encourage directors to report more truthfully in such situations. This paper tests this proposition explicitly using a large sample of going‐concern cases over the period 1994–2000. We find that whereas auditors' going‐concern opinions predict the subsequent resolution of going‐concern uncertainties directors' going‐concern statements convey arbitrary and unhelpful messages to users. However, robust corporate governance structures and high auditor reputation constrain directors to be more truthful in their going‐concern disclosures, bringing these more into line with the more credible auditor opinions.
Shopping behaviour among gay men: issues of internalized homophobia and self‐esteem
Authors: Reilly Andrew , Rudd Nancy A.
Published: October 2006

Connections among internalized homophobia, self‐esteem and various shopping behaviours are investigated. Internalized homophobia, which affects nearly all gay men to some degree, and self‐esteem may affect shopping behaviours such as credit card debt, venue of shopping, enjoyment from shopping, amount of time spent shopping and frequency of shopping. Data from 213 gay men were collected using an Internet‐survey design. Results demonstrate that internalized homophobia has weak to moderate effects on thrift store shopping, discount store shopping and credit card debt. Although self‐esteem did not predict shopping behaviour, it was correlated with shopping enjoyment. Implications, limitations and future research are discussed.