2,784 research outputs found
Modelling interfacial coupling in thin film magnetic exchange springs at finite temperature
This is the final version of the article. Available from the American Institute of Physics via the DOI in this record.We report a numerical study that demonstrates the interface layer between a soft and hard magnetic phase, the exchange transition layer, is the dominant factor that influences the magnetization reversal process at room temperature and long measurement times. It is found that the exchange transition layer thickness affects the magnetization reversal and the coupling of a bi-layer system by lowering the switching field and changing the angle dependent magnetization reversal. We show that the change in angle dependence of reversal is due to an increased incoherency in the lateral spin behavior. Changing the value of exchange coupling in the exchange transition layer affects only the angle dependent behavior and does not lower the switching field. © 2013 AIP Publishing LLC.We would like to thank the EPSRC for financial support under Grant Nos. EP/G032440/1 and EP/G032300/1, the WWTF Project MA09-029 and the Royal Society UF080837
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Experimental evidence on promotion of electric and improved biomass cookstoves.
Improved cookstoves (ICS) can deliver "triple wins" by improving household health, local environments, and global climate. Yet their potential is in doubt because of low and slow diffusion, likely because of constraints imposed by differences in culture, geography, institutions, and missing markets. We offer insights about this challenge based on a multiyear, multiphase study with nearly 1,000 households in the Indian Himalayas. In phase I, we combined desk reviews, simulations, and focus groups to diagnose barriers to ICS adoption. In phase II, we implemented a set of pilots to simulate a mature market and designed an intervention that upgraded the supply chain (combining marketing and home delivery), provided rebates and financing to lower income and liquidity constraints, and allowed households a choice among ICS. In phase III, we used findings from these pilots to implement a field experiment to rigorously test whether this combination of upgraded supply and demand promotion stimulates adoption. The experiment showed that, compared with zero purchase in control villages, over half of intervention households bought an ICS, although demand was highly price-sensitive. Demand was at least twice as high for electric stoves relative to biomass ICS. Even among households that received a negligible price discount, the upgraded supply chain alone induced a 28 percentage-point increase in ICS ownership. Although the bundled intervention is resource-intensive, the full costs are lower than the social benefits of ICS promotion. Our findings suggest that market analysis, robust supply chains, and price discounts are critical for ICS diffusion
Grain boundaries in granular materials-A fundamental limit for thermal stability
This is the final version of the article. Available from the American Institute of Physics via the DOI in this record.We show that thermal-stability and the associated switching field in well segregated, nanoscale granular materials is explained by grain boundary and interface effects. Grain boundaries pose a fundamental limit on scaling rooted in their chemical and morphological structure, while exchange interactions across interfaces cause the switching to deviate from the expected coherent Stoner-Wohlfarth behaviour. Measurements and simulations of CoCrPt-systems show a clear shift in applied field angle behaviour, arising from exchange-coupling between magnetic-phases, while the quantitative switching field can only be explained by a transition layer surrounding the grains. These results are potentially significant for Heat-Assisted-Magnetic Recording and Bit-Patterned-Media Recording. © 2013 AIP Publishing LLC.We would like to thank the EPSRC for financial support under Grants No. EP/G032440/1, EP/G032300/1, the WWTF Project MA09-029 and the Royal Society
On Global Flipped SU(5) GUTs in F-theory
We construct an SU(4) spectral divisor and its factorization of types (3,1)
and (2,2) based on the construction proposed in [1]. We calculate the chiral
spectra of flipped SU(5) GUTs by using the spectral divisor construction. The
results agree with those from the analysis of semi-local spectral covers. Our
computations provide an example for the validity of the spectral divisor
construction and suggest that the standard heterotic formulae are applicable to
the case of F-theory on an elliptically fibered Calabi-Yau fourfold with no
heterotic dual.Comment: 45 pages, 12 tables, 1 figure; typos corrected, footnotes added, and
a reference adde
Flipped SU(5) GUTs from E_8 Singularities in F-theory
In this paper we construct supersymmetric flipped SU(5) GUTs from E_8
singularities in F-theory. We start from an SO(10) singularity unfolded from an
E_8 singularity by using an SU(4) spectral cover. To obtain realistic models,
we consider (3,1) and (2,2) factorizations of the SU(4) cover. After turning on
the massless U(1)_X gauge flux, we obtain the SU(5) X U(1)_X gauge group. Based
on the well-studied geometric backgrounds in the literature, we demonstrate
several models and discuss their phenomenology.Comment: 46 pages, 23 tables, 1 figure, typos corrected, references added, and
new examples presente
Behaviour change techniques to optimise participation in physical activity or exercise in adolescents and young adults with chronic cardiorespiratory conditions: a systematic review
Participation in regular physical activity decreases the risk of developing cardiometabolic disease. However, the proportion of people who participate in the recommended amount of physical activity is low, with common barriers including competing interests and inclement weather. In people with chronic cardiorespiratory conditions, participation in physical activity is reduced further by disease-specific barriers; time-burden of treatment and unpleasant symptoms during physical activity. Addressing these barriers during adolescence and early adulthood may promote greater physical activity participation into older age. The aim of this review was, in people aged 15 to 45 years with chronic cardiorespiratory conditions, to classify interventions aimed at optimising participation in physical activity as 'promising' or 'not promising', and categorise the behaviour change techniques (BCTs) within these interventions. Nine databases and registries were searched (October 2017) for studies that reported objective measures of physical activity before and after an intervention period. Interventions were classified as 'promising' if a between-group difference in physical activity was demonstrated. Michie et al.'s (2013) v1 Taxonomy was used to unpack the BCTs within interventions. Across the six included studies (n = 396 participants), 19 (20%) of 93 BCTs were described. The interventions of three studies were classified as 'promising'. The most commonly used BCTs comprised goal setting, action planning and social support. Five BCTs were solely used in 'promising' interventions. Our review demonstrated that only 20% of BCTs have been utilised and isolated those BCTs that were used only in 'promising' physical activity interventions in adolescents and adults with chronic cardiorespiratory conditions. This article is protected by copyright. All rights reserved
Population genetics of trypanosoma brucei rhodesiense: clonality and diversity within and between foci
African trypanosomes are unusual among pathogenic protozoa in that they can undergo their complete morphological life cycle in the tsetse fly vector with mating as a non-obligatory part of this development. Trypanosoma brucei rhodesiense, which infects humans and livestock in East and Southern Africa, has classically been described as a host-range variant of the non-human infective Trypanosoma brucei that occurs as stable clonal lineages. We have examined T. b. rhodesiense populations from East (Uganda) and Southern (Malawi) Africa using a panel of microsatellite markers, incorporating both spatial and temporal analyses. Our data demonstrate that Ugandan T. b. rhodesiense existed as clonal populations, with a small number of highly related genotypes and substantial linkage disequilibrium between pairs of loci. However, these populations were not stable as the dominant genotypes changed and the genetic diversity also reduced over time. Thus these populations do not conform to one of the criteria for strict clonality, namely stability of predominant genotypes over time, and our results show that, in a period in the mid 1990s, the previously predominant genotypes were not detected but were replaced by a novel clonal population with limited genetic relationship to the original population present between 1970 and 1990. In contrast, the Malawi T. b. rhodesiense population demonstrated significantly greater diversity and evidence for frequent genetic exchange. Therefore, the population genetics of T. b. rhodesiense is more complex than previously described. This has important implications for the spread of the single copy T. b. rhodesiense gene that allows human infectivity, and therefore the epidemiology of the human disease, as well as suggesting that these parasites represent an important organism to study the influence of optional recombination upon population genetic dynamics
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