919 resultados para 54301-016


Relevância:

10.00% 10.00%

Publicador:

Resumo:

The spatial variability of soil nitrogen (N) mineralisation has not been extensively studied, which limits our capacity to make N fertiliser recommendations. Even less attention has been paid to the scale-dependence of the variation. The objective of this research was to investigate the scale-dependence of variation of mineral N (MinN, N–NO3− plus N–NH4+) at within-field scales. The study was based on the spatial dependence of the labile fractions of SOM, the key fractions for N mineralisation. Soils were sampled in an unbalanced nested design in a 4-ha arable field to examine the distribution of the variation of SOM at 30, 10, 1, and 0.12 m. Organic matter in free and intra-aggregate light fractions (FLF and IALF) was extracted by physical fractionation. The variation occurred entirely within 0.12 m for FLF and at 10 m for IALF. A subsequent sampling on a 5-m grid was undertaken to link the status of the SOM fractions to MinN, which showed uncorrelated spatial dependence. A uniform application of N fertiliser would be suitable in this case. The failure of SOM fractions to identify any spatial dependence of MinN suggests that other soil variables, or crop indicators, should be tested to see if they can identify different N supply areas within the field for a more efficient and environmentally friendly N management.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Cationic heterobimetallic complexes 5–7 [(PPh3)2Pt(μ-edt)MClCp′)]BF4 (edt=−S(CH2)2S−; 5: M=Rh and Cp′=η5-C5H5; 6: M=Rh and Cp′=η5-C5Me5 and 7: M=Ir and Cp′=η5-C5Me5) were prepared by reaction of [Pt(edt)(PPh3)2] with [Cp′ClM(μ-Cl)2MClCp′] in THF in the presence of two equivalents of AgBF4. The crystalline structure of 5 was determined by X-ray diffraction methods. Cationic heterobimetallic complexes [(PPh3)2Pt(μ-S(CH2)2S)MClCp′)]BF4 (M=Rh, Ir) were prepared. The crystalline structure of [(PPh3)2Pt(μ-edt)RhClCp)]BF4 was determined by X-ray diffraction methods.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

In this paper a new system identification algorithm is introduced for Hammerstein systems based on observational input/output data. The nonlinear static function in the Hammerstein system is modelled using a non-uniform rational B-spline (NURB) neural network. The proposed system identification algorithm for this NURB network based Hammerstein system consists of two successive stages. First the shaping parameters in NURB network are estimated using a particle swarm optimization (PSO) procedure. Then the remaining parameters are estimated by the method of the singular value decomposition (SVD). Numerical examples including a model based controller are utilized to demonstrate the efficacy of the proposed approach. The controller consists of computing the inverse of the nonlinear static function approximated by NURB network, followed by a linear pole assignment controller.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Seasonal sea-surface temperaturevariability for the Neoglacial (3300–2500 BP) and Roman WarmPeriod (RWP; 2500–1600 BP), which correspond to the Bronze and Iron Ages, respectively, was estimated using oxygen isotope ratios obtained from high-resolution samples micromilled from radiocarbon-dated, archaeological limpet (Patella vulgata) shells. The coldest winter months recorded in Neoglacial shells averaged 6.6 ± 0.3 °C, and the warmest summer months averaged 14.7 ± 0.4 °C. One Neoglacial shell captured a year without a summer, which may have resulted from a dust veil from a volcanic eruption in the Katla volcanic system in Iceland. RWP shells record average winter and summer monthly temperatures of 6.3 ± 0.1 °C and 13.3 ± 0.3 °C, respectively. These results capture a cooling transition from the Neoglacial to RWP, which is further supported by earlier studies of pine history in Scotland, pollen type analyses in northeast Scotland, and European glacial events. The cooling transition observed at the boundary between the Neoglacial and RWP in our study also agrees with the abrupt climate deterioration at 2800–2700 BP (also referred to as the Subboreal/Subatlantic transition) and therefore may have been driven by decreased solar radiation and weakened North Atlantic Oscillation conditions.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Semi-structured interviews with university students in the UK and Japan, undertaken in 2009 and 2010, are analysed with respect to the revealed attitudes to privacy, self-revelation and revelation by/of others on SNS.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

This paper is motivated to investigate the often neglected payoff to investments in the health of girls and women in terms of next generation outcomes. This paper investigates the intergenerational persistence of health across time and region as well as across the distribution of maternal health. It uses comparable microdata on as many as 2.24 million children born of about 0.6 million mothers in 38 developing countries in the 31 year period, 1970–2000. Mother's health is indicated by her height, BMI and anemia status. Child health is indicated by mortality risk and anthropometric failure. We find a positive relationship between maternal and child health across indicators and highlight non-linearities in these relationships. The results suggest that both contemporary and childhood health of the mother matter and that the benefits to the next generation are likely to be persistent. Averaging across the sample, persistence shows a considerable decline over time. Disaggregation shows that the decline is only significant in Latin America. Persistence has remained largely constant in Asia and has risen in Africa. The paper provides the first cross-country estimates of the intergenerational persistence in health and the first estimates of trends.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Parabens (alkyl esters of p-hydroxybenzoic acid) are used extensively as preservatives in consumer products, and intact esters have been measured in several human tissues. Concerns of a potential link between parabens and breast cancer have been raised, but mechanistic studies have centred on their oestrogenic activity and little attention has been paid to any carcinogenic properties. In the present study, we report that parabens can induce anchorage-independent growth of MCF-10A immortalized but non-transformed human breast epithelial cells, a property closely related to transformation and a predictor of tumour growth in vivo. In semi-solid methocel suspension culture, MCF-10A cells produced very few colonies and only of a small size but the addition of 5 × 10-4 M methylparaben, 10–5 M n-propylparaben or 10–5 M n-butylparaben resulted in a greater number of colonies per dish (P < 0.05 in each case) and an increased average colony size (P < 0.001 in each case). Dose-responses showed that concentrations as low as 10–6 M methylparaben, 10–7 M n-propylparaben and 10–7 M n-butylparaben could increase colony numbers (P = 0.016, P = 0.010, P = 0.008, respectively): comparison with a recent measurement of paraben concentrations in human breast tissue samples from 40 mastectomies (Barr et al., 2012) showed that 22/40 of the patients had at least one of the parabens at the site of the primary tumour at or above these concentrations. To our knowledge, this is the first study to report that parabens can induce a transformed phenotype in human breast epithelial cells in vitro, and further investigation is now justified into a potential link between parabens and breast carcinogenesis.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

This paper presents findings of our study on peer-reviewed papers published in the International Conference on Persuasive Technology from 2006 to 2010. The study indicated that out of 44 systems reviewed, 23 were reported to be successful, 2 to be unsuccessful and 19 did not specify whether or not it was successful. 56 different techniques were mentioned and it was observed that most designers use ad hoc definitions for techniques or methods used in design. Hence we propose the need for research to establish unambiguous definitions of techniques and methods in the field.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

The intake fraction (iF) of nonreactive constituents of exhaust from mobile vehicles in the urban area of HongKong is investigated using available monitoring data for carbon monoxide (CO) as a tracer of opportunity. Correcting for regional transport of carbon monoxide into HongKong, the annual-average iF for nonreactive motor vehicle emissions within the city is estimated to be around 270 per million. This estimated iF is much higher than values previously reported for vehicle emissions in US urban areas, Helsinki and Beijing, and somewhat lower than those reported for a densely populated street canyon in downtown Manhattan, New York City, or for emissions into indoor environments. The reported differences in intakefractions in various cities mainly result from the differences in local population densities. Our analysis highlights the importance of accounting for the influence of upwind transport of pollutants when using ambient data to estimate iF for an urban area. For vehicleexhaust in HongKong, it is found that the in/near vehicle microenvironment contributes similarly to the indoor home environment when accounting for the overall iF for children and adults. Keywords Intakefraction; Vehicle emission; Regional pollutant transport; Carbon monoxide; Exposure

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Unlike corporate and business levels, there is little research examining corporate responsibility (CR) at the functional level of the firm including supply chain strategy. The results of a firm-level survey show that CR internal awareness, and monitoring CR performance are positively related to the supply chain partnership approach, however sharing CR best practices is negatively associated. Furthermore, the impact of CR on firm performance is mediated by the functional behaviour of supply chain partnership formation. Our study provides support for including CR awareness building and monitoring in the development of partnerships but cautions against imposing CR best practices on suppliers.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Many virulence organelles of Gram-negative bacterial pathogens are assembled via the chaperone/ usher pathway. The chaperone transports organelle subunits across the periplasm to the outer membrane usher, where they are released and incorporated into growing fibers. Here, we elucidate the mechanism of the usher-targeting step in assembly of the Yersinia pestis F1 capsule at the atomic level. The usher interacts almost exclusively with the chaperone in the chaperone:subunit complex. In free chaperone, a pair of conserved proline residues at the beginning of the subunit-binding loop form a ‘‘proline lock’’ that occludes the usher-binding surface and blocks usher binding. Binding of the subunit to the chaperone rotates the proline lock away from the usher-binding surface, allowing the chaperone-subunit complex to bind to the usher. We show that the proline lock exists in other chaperone/usher systems and represents a general allosteric mechanism for selective targeting of chaperone:subunit complexes to the usher and for release and recycling of the free chaperone.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Although tactile representations of the two body sides are initially segregated into opposite hemispheres of the brain, behavioural interactions between body sides exist and can be revealed under conditions of tactile double simultaneous stimulation (DSS) at the hands. Here we examined to what extent vision can affect body side segregation in touch. To this aim, we changed hand-related visual input while participants performed a go/no-go task to detect a tactile stimulus delivered to one target finger (e.g., right index), stimulated alone or with a concurrent non-target finger either on the same hand (e.g., right middle finger) or on the other hand (e.g., left index finger = homologous; left middle finger = non-homologous). Across experiments, the two hands were visible or occluded from view (Experiment 1), images of the two hands were either merged using a morphing technique (Experiment 2), or were shown in a compatible vs incompatible position with respect to the actual posture (Experiment 3). Overall, the results showed reliable interference effects of DSS, as compared to target-only stimulation. This interference varied as a function of which non-target finger was stimulated, and emerged both within and between hands. These results imply that the competition between tactile events is not clearly segregated across body sides. Crucially, non-informative vision of the hand affected overall tactile performance only when a visual/proprioceptive conflict was present, while neither congruent nor morphed hand vision affected tactile DSS interference. This suggests that DSS operates at a tactile processing stage in which interactions between body sides can occur regardless of the available visual input from the body.