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Following an original idea of Palmas, Palomo and Romero, recently developed in , we study codimension two spacelike submanifolds contained in the light cone of the Lorentz-Minkowski spacetime through an approach which allows us to compute their extrinsic and intrinsic geometries in terms of a single function u. As the first application of our approach, we classify the totally umbilical ones. For codimension two compact spacelike submanifolds into the light cone, we show that they are conformally diffeomorphic to the round sphere and that they are given by an explicit embedding written in terms of u. In the last part of the paper, we consider the case where the submanifold is (marginally, weakly) trapped. In particular, we derive some non-existence results for weakly trapped submanifolds into the light cone.
We monitored egg clutch numbers of a population of the endemic Italian agile frog Rana latastei in a Site of Community Interest in northern Italy (SCI IT 209000) during 1997–2017 with the aim of assessing the long-term variation in its abundance. We walked along the banks of canals and small ponds (n = 22) 1–3 times per week between early February and mid-April each year to detect egg clutches. The relationships between the start of the breeding season, yearly egg mass counts, rate of yearly change in the number of recorded egg masses and 15 climatic and environmental variables were assessed by multiple regression. The first deposition of eggs occurred progressively later in the year throughout the study period and mean air temperature during the breeding season decreased over this period. Agile frogs showed high deposition site-fidelity. Despite large variations in the number of egg clutches detected from year to year, the population size remained stable in the long term. Peaks in the number of egg clutches occurred 2 years after the dredging of canals, carried out every 4–6 years to improve water availability, starting in 2004 as part of a LIFE Nature Project. This was the only predictor of the number of egg clutches deposited, suggesting that periodical management is needed to support the agile frog population. Our results reinforce the need for multi-year monitoring to determine both the long-term success of habitat restoration projects and the status of residual populations.
The Prado-Recoletos axis is the main historical boulevard in Madrid, which contains the most important concentration of art museums in all of Spain: the Museo Nacional Centro de Arte Reina Sofía, the Museo Nacional del Prado and the Museo Nacional Thyssen-Bornemisza. In the last years, they have undergone extensive renovation. The different renovation projects can be used to examine how museum libraries today juggle the needs of their users while addressing the challenge of providing the services of a modern research library. The new State Museum Libraries Network (BIMUS) has been an important factor in this development.
This study explores the hypothesis that the existence of a short sensitive period for lower-level speech perception/articulation skills, and a long one for higher-level language skills, may partly explain the language outcomes of children with cochlear implants (CIs). The participants were fourteen children fitted with a CI before their second birthday. Data about their language skills and the environmental conditions (e.g. Family Involvement in rehabilitation) were obtained over a period of three years. Age at implantation correlated exclusively with the ratio of errors of place of articulation, a phonological feature for which CIs provide insufficient information. The degree of Family Involvement was significantly correlated with the remaining language measures. We conclude that small plasticity reductions affecting lower-level skills may partly explain the difficulties of some CI users in developing language.
In this theoretical paper we propose three different kinds of cognitive structure that have not been differentiated in the psychological and cognitive linguistic literatures. They are spatial primitives, image schemas, and schematic integrations. Spatial primitives are the first conceptual building blocks formed in infancy, image schemas are simple spatial stories built from them, and schematic integrations use the first two types to build concepts that include non-spatial elements, such as force and emotion. These different kinds of structure have all come under the umbrella term of ‘image schemas’. However, they differ in their content, developmental origin, imageability, and role in meaning construction in language and in thought. The present paper indicates how preverbal conceptualization needs to be taken into account for a complete understanding of image schemas and their uses. It provides examples to illustrate this influence, the most important of these being the primacy of imageable spatial information.
Diverse agroecosystems offer phytophagous insects a wide choice of host plants. Myzus persicae is a polyphagous aphid common in moderate climates. During its life cycle it alternates between primary and secondary hosts. A spatial genetic population structure may arise due to environmental factors and reproduction modes. The aim of this work was to determine the spatial and temporal genetic population structure of M. persicae in relation to host plants and climatic conditions. For this, 923 individuals of M. persicae collected from six plant families between 2005 and 2008 in south-eastern Spain were genotyped for eight microsatellite loci. The population structure was inferred by neighbour-joining, analysis of molecular variance (AMOVA) and Bayesian analyses. Moderate polymorphism was observed for the eight loci in almost all the samples. No differences in the number of alleles were observed between primary and secondary hosts or between geographical areas. The proportion of unique genotypes found in the primary host was similar in the north (0.961 ± 0.036) and the south (0.987 ± 0.013), while in the secondary host it was higher in the north (0.801 ± 0.159) than in the south (0.318 ± 0.063). Heterozygosity excess and linkage disequilibrium suggest a high representation of obligate parthenogens in areas with warmer climate and in the secondary hosts. The FST-values pointed to no genetic differentiation of M. persicae on the different plant families. FST-values, AMOVA and Bayesian model-based cluster analyses pointed to a significant population structure that was related to primary and secondary hosts. Differences between primary and secondary hosts could be due to the overrepresentation of parthenogens on herbaceous plants.
ZnO is a promising material for use in solar cell applications which require antireflective coatings and transparent conducting materials in front contacts. Its resistivity can be reduced by appropriate doping with different group III elements, which act as donors, without sacrificing optical transmission. Besides, it constitutes a non-toxic and cheap alternative to ITO (In2O3:SnO2), which is nowadays commonly used as transparent conducting oxide (TCO) in optoelectronic devices. Al(III) is one of the cheapest elements on nature, and has been therefore one of the first candidates to be used as a dopant. However recent studies demonstrate that for similar amounts of dopant the use of Ga largely improves both the optical and electrical properties of the films. The interface between Si (used as substrate) and the corresponding TCO is a critical part of Si-based solar cells, since the conversion efficiency may be profoundly altered by the presence of recombination centers formed at the interface. In this work we present a comparison of Si/ZnO, Si/ZnO:Ga and Si/ZnO:Al interfaces (with [dopant]/[Zn] = 2%) by using HRTEM and associated spectroscopies. Resistivity values of the films are: ρ(ZnO) = 4.4 × 10-2 Ω × cm; ρ(Ga:ZnO) = 6.3 × 10-4 Ω × cm; ρ(Al:ZnO) = 2.9 × 10-3 Ω × cm. and the films optical transmitance is larger than 80% along the visible spectrum.
SbVO4 series of compounds could be used as oxidation catalysts of industrial interest yielding 20% cheaper acrylonitrile by the ammoxidation of propane compared to current method producing 8×106 ton/year based on propylene as starting reactant.
δ-Bi2O3, a material with a fluorite-type structure, is one of the best solid-state oxygen-ion conductors. It is a high-temperature form that cannot be quenched to room temperature. However, doping with small amounts of transition metal oxides preserves the δ-Bi2O3 structure at low temperature and retains its anionic conduction properties. The Bi2O3–MoO3 materials are interesting because of their functional properties, chiefly as catalysts and as good ionic conductors. All the phases in this system are related to the fluorite structure except Bi2MoO6 which shows an Aurivillius-type structure.
Following ICNIRP Guidelines of 1998, European Parliament in 2004 has stated the reference levels for workers exposure to electromagnetic fields. In low frequency regime, due to the nature of the basic mechanism of short term interaction, the exposure limits are based on the values of induced eddy currents inside human body, thus electromagnetic simulation is an important tool for the assessment of electromagnetic field exposure. This paper presents a method for computing eddy currents inside human body and applies the method to the evaluation of eddy currents induced by a resistance spot welding system. A comparison between results obtained with two different models of human body and with different discretization levels is performed and results are discussed.
The 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) is the rate-limiting enzyme in the biosynthesis of cholesterol. We have studied the role of the HMGCR gene in pig lipid metabolism by means of expression and structural analysis. We describe here the complete coding region of this gene in pigs and report two synonymous single nucleotide polymorphisms in the coding region. We have, additionally, studied the association of one of these polymorphisms (HMGCR:c.807A>C) with several lipid deposition- and cholesterol-related traits in a half-sib population generated from a commercial Duroc line, showing in some families a positive relationship of HMGCR:c.807A allele with serum low-density lipoprotein (LDL)-bound cholesterol and triglyceride levels, and also with intramuscular fat (IMF) content of gluteus medius muscle. We have also assessed the expression levels in muscle and in liver from 68 Duroc individuals corresponding to the most extreme animals for the analysed traits. Liver HMGCR expression correlated negatively with the serum high-density lipoprotein (HDL) levels, carcass lean percentage and stearic acid content, while muscle expression correlated also negatively with the carcass lean percentage, stearic and linoleic acids content, but showed a positive correlation with the serum lipid cholesterol (HDL, LDL and total cholesterol), IMF and muscle oleic and palmitic fatty acid content. With this information, we have performed an association analysis of expression data with lipid metabolism phenotypic levels and the HMGCR genotype. The results indicate that HMGCR expression levels in muscle are different in the two groups of pigs with extreme values for fat deposition and total cholesterol levels, and also between animals with the different HMGCR genotypes.
We are concerned with the Lipschitz modulus of the optimal set mapping
associated with canonically perturbed convex semi-infinite optimization
problems. Specifically, the paper provides a lower and an upper bound for
this modulus, both of them given exclusively in terms of the problem's data.
Moreover, the upper bound is shown to be the exact modulus when the number
of constraints is finite. In the particular case of linear problems the
upper bound (or exact modulus) adopts a notably simplified expression. Our
approach is based on variational techniques applied to certain difference of
convex functions related to the model. Some results of [M.J. Cánovas et al., J. Optim. Theory Appl. (2008) Online First]
(which go back to [M.J. Cánovas, J. Global Optim.41 (2008) 1–13] and [Ioffe, Math. Surveys55 (2000) 501–558; Control Cybern.32 (2003) 543–554])
constitute the starting point of the present work.
This paper discusses several topics related to light management that improve our understanding of the performance and potential of the intermediate band solar cell (IBSC). These topics are photon recycling, photon selectivity and light confinement. It is found that neglecting photon recycling leads to underestimate the limiting efficiency of the IBSC in 7 points (56.1 % vs 63.2 %). Light trapping allows to effectively absorbing photons whose energy is associated to the weakest of the optical transitions in the IBSC, allowing also for higher efficiencies with lower device thickness. The impact of photon selectivity on the cell performance is also discussed.
In this paper, we describe the experimental validation of the technique of correction of wavefront aberration in the middle of the laser amplifying chain. This technique allows the correction of the aberrations from the first part of the laser system, and the pre-compensation of the aberrations built in the second part. This approach will allow an effective aberration management in the laser chain, to protect the optical surfaces and optimize performances, and is the only possible approach for multi-petawatt laser system from the technical and economical point of view. This approach is now possible after the introduction of new deformable mirrors with lower static aberrations and higher dynamic than the standard devices.
High hydrostatic pressure disruption of casein micelle isolates was studied by analytical ultracentrifugation and transmission electron microscopy. Casein micelles were isolated from skim milk and subjected to combinations of thermal treatment (85°C, 20 min) and high hydrostatic pressure (up to 676 MPa) with and without whey protein added. High hydrostatic pressure promoted extensive disruption of the casein micelles in the 250 to 310 MPa pressure range. At pressures greater than 310 MPa no further disruption was observed. The addition of whey protein to casein micelle isolates protected the micelles from high hydrostatic pressure induced disruption only when the mix was thermally processed before pressure treatment. The more whey protein was added (up to 5 g/l) the more the protection against high hydrostatic pressure induced micelle disruption was observed in thermally treated samples subjected to 310 MPa.