We compute the general expression of the one-loop vertex correction in an arbitrary plane-wave background field for the case of two on-shell external electrons and an off-shell external photon. The ...properties of the vertex corrections under gauge transformations of the plane-wave background field and of the radiation field are studied. Concerning the divergences of the vertex correction, the infrared one is cured by assigning a finite mass to the photon, whereas the ultraviolet one is shown to be renormalized exactly as in vacuum. Finally, the corresponding expression of the vertex correction within the locally constant crossed field approximation is also derived and the high-field asymptotic is shown to scale according to the Ritus-Narozhny conjecture, although the terms featuring the leading-order dependence on the field are found not to contribute to physical transition amplitudes.
New information and communication technologies (ICTs) provide educators and learners with an innovative learning environment to stimulate and enhance the teaching and learning process. In this ...context, novel educational concepts such as blended learning are being developed. In the present paper, we present the results obtained from a blended learning experience carried out at the University of Granada. A total of 17 groups took part, with 1431 students registered for the 2009–2010 academic year. In this study, we use objective outcomes and the students’ perceptions regarding the blended learning activities performed. The study shows that the use of blended learning has a positive effect in reducing dropout rates and in improving exam marks. Moreover, the students’ perceptions on blended learning are interrelated, with their final marks depending on the blended learning activities, and on the students’ age, background and class attendance rate.
Hosts and their symbionts are involved in intimate physiological and ecological interactions. The impact of these interactions on the evolution of each partner depends on the time-scale considered. ...Short-term dynamics – ‘coevolution’ in the narrow sense – has been reviewed elsewhere. We focus here on the long-term evolutionary dynamics of cospeciation and speciation following host shifts. Whether hosts and their symbionts speciate in parallel, by cospeciation, or through host shifts, is a key issue in host–symbiont evolution. In this review, we first outline approaches to compare divergence between pairwise associated groups of species, their advantages and pitfalls. We then consider recent insights into the long-term evolution of host–parasite and host–mutualist associations by critically reviewing the literature. We show that convincing cases of cospeciation are rare (7%) and that cophylogenetic methods overestimate the occurrence of such events. Finally, we examine the relationships between short-term coevolutionary dynamics and long-term patterns of diversification in host–symbiont associations. We review theoretical and experimental studies showing that short-term dynamics can foster parasite specialization, but that these events can occur following host shifts and do not necessarily involve cospeciation. Overall, there is now substantial evidence to suggest that coevolutionary dynamics of hosts and parasites do not favor long-term cospeciation.
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► The dynamic behavior of bimodal magnetorheological fluids is studied. ► Their settling rate is highly modified by the addition of small amounts of nanomagnetite. ► A standard ...penetration needle is used for the prediction of redispersibility. ► A hard sediment is absent if magnetite is added. ► Magnetorheology experiments confirm that the mixed fluids have excellent performance.
In this work, we investigate the stability and redispersibility of magnetorheological fluids (MRFs). These are disperse systems where the solid is constituted by ferro- or ferri-magnetic microparticles. Upon the application of external magnetic field, they experience rapid and reversible increases in yield stress and viscosity. The problem considered here is first of all the determination of their stability against sedimentation, an essential issue in their practical application. Although this problem is typically faced through the addition of thixotropic agents to the liquid medium, in this work, we propose the investigation of the effect of magnetic nanoparticles addition, so that the dispersion medium is in reality a ferrofluid. It is found that a volume fraction of nanoparticles not higher than 3% is enough to provide a long-lasting stabilization to MRFs containing above 30% iron microparticles. In the, in fact unavoidable, event of settling, the important point is the ease of redispersion of the sediment. This is indirectly evaluated in the present investigation by measuring the penetration force in the suspension, using a standard hardness needle. Again, it is found that the nanoparticles addition produces soft sediments by avoiding short-range attractions between the large iron particles. Finally, the performance of the designed MRFs is evaluated by obtaining their steady-state rheograms for different volume fractions of magnetite and different magnetic field strengths. The yield stress is found to be strongly field-dependent, and it can achieve the high values expected in standard magnetorheological fluids but with improved stability and redispersibility.
•Solar tracking is a crucial task in efficiently harvesting solar power in a PV plant.•Horizontal Single-axis tracking systems require a precise estimation of its axis’ orientation.•This methodology ...uses available data to accurately estimate the tracker’s orientation.•This methodology estimates height differences in adjacent trackers.•The improve tracking and backtracking strategies increase production by 1%.
Photovoltaic (PV) energy production is becoming a more significant part of the energy mix world-wide due to its clean origin, supportive and cost reductions. Therefore, it is increasingly important to develop methodologies to improve efficiency and reduce energy losses. Solar tracking is a way of increasing the irradiance over the PV field and, subsequently, boosting energy production. Both single-axis and double-axis tracking systems (SATS & DATS) are well known methods but both require not only a proper estimation of the sun’s position but also precise knowledge of the tracker’s position and orientation. Several factors (construction, design, configuration) can cause the values used to calculate the optimal tracking to be inaccurate, thus increasing production losses. This paper proposes a methodology to calculate the actual orientation of the trackers’ axis based on the energy production of its associated strings. Additionally, it provides the height differences between adjacent trackers by detecting shading patterns. This information is key to defining more efficient tracking and backtracking strategies the avoid row-to-row shading and, overall increasing energy production. The proposed method is applied to a real 5 MW facility, identifying misalignments of several degrees in most trackers that were causing annual losses (1 %), not only due to inaccurate tracking but also row-to-row shading.
The recent advancements in high-throughput sequencing have resulted in the availability of annotated genomes, as well as of multi-omics data for many living organisms. This has increased the need for ...graphic tools that allow the concurrent visualization of genomes and feature-associated multi-omics data on single publication-ready plots.
We present chromoMap, an R package, developed for the construction of interactive visualizations of chromosomes/chromosomal regions, mapping of any chromosomal feature with known coordinates (i.e., protein coding genes, transposable elements, non-coding RNAs, microsatellites, etc.), and chromosomal regional characteristics (i.e. genomic feature density, gene expression, DNA methylation, chromatin modifications, etc.) of organisms with a genome assembly. ChromoMap can also integrate multi-omics data (genomics, transcriptomics and epigenomics) in relation to their occurrence across chromosomes. ChromoMap takes tab-delimited files (BED like) or alternatively R objects to specify the genomic co-ordinates of the chromosomes and elements to annotate. Rendered chromosomes are composed of continuous windows of a given range, which, on hover, display detailed information about the elements annotated within that range. By adjusting parameters of a single function, users can generate a variety of plots that can either be saved as static image or as HTML documents.
ChromoMap's flexibility allows for concurrent visualization of genomic data in each strand of a given chromosome, or of more than one homologous chromosome; allowing the comparison of multi-omic data between genotypes (e.g. species, varieties, etc.) or between homologous chromosomes of phased diploid/polyploid genomes. chromoMap is an extensive tool that can be potentially used in various bioinformatics analysis pipelines for genomic visualization of multi-omics data.
Summary
The aetiopathogenesis of hidradenitis suppurativa (HS) is not fully understood; however, increasing evidence suggests that it may be an immune‐mediated disorder. Autoimmune thyroid disease ...(AITD) has classically been considered as the ‘paradigm’ of autoimmunity, and it has been linked to a variety of skin disorders. To our knowledge, the prevalence of AITD has not been investigated in patients with HS. The aim of the present study was to assess and compare, for the first time, the prevalence of thyroid autoimmunity in 70 patients with HS and in 70 age‐ and sex‐matched controls. In all participants, thyroid autoantibodies and thyroid function tests were analysed. No statistically significant difference was detected between patients with HS and controls, either for the prevalence of thyroid antibodies or for thyroid function parameters. This lack of an association between HS and thyroid autoimmunity suggests that conventional autoimmune mechanisms may not be implicated in the pathogenesis of HS.
The floating photovoltaic (FPV) market has been expanding at an impressive rate over the last decade, doubling its global installed capacity year after year. This growth was possible due to the ...numerous advantages FPV plants pose over ground-mounted plants, which are mainly related to land occupation and energy efficiency. However, this expansion has been limited to freshwater applications, despite the vast potential that the offshore environment entails. The lack of maturity of the sector and the harsher environmental conditions have hindered the transition of this technology to the marine environment. Furthermore, a lack of publications regarding the structural analysis of this technology was found, as well as no specific designs standards for marine FPV. On these grounds, this article reviews the design aspects of this technology with a focus on marine applications, highlighting relevant aspects to be tackled. First, the main components of the FPV technology are described and their compatibility with the marine environment is assessed. Then, a structural classification of the current plants is proposed. This allows the individual suitability analysis of each typology for the marine environment. Existing marine FPV projects are described and classified. Afterwards, synergies between marine FPV plants and other sectors are gathered and discussed. Finally, general design guidelines are provided, with a focus on the structural response of FPV structures subjected to marine environmental actions. Insight on the nature of these actions (wind, waves, currents, and tides) as well as how they interact with FPV plants is provided.
•Relevant design adaptations are required to transit to marine FPV applications.•Standards and publications for the design of marine FPV structures are scarce.•The methods to estimate environmental loads on marine FPV structures were reviewed.•Insight on the response models for marine FPV structures is provided.•Potential synergies with MRE, aquaculture and desalination and others are found.
Hybrid ternary blends comprising two polymers and one mineral (nano)filler are increasingly studied because they are starting to be widely used to respond to industrial issues. The objective of this ...review is to gather information on these particular systems. Concerning first thermodynamic effects of fillers on the phase separation of an immiscible polymer blend, Flory–Huggins theory demonstrate stabilization. This theory was particularly taken up and developed for the case of two polymers and one filler by Lipatov and Nesterov in the 90s. More recently, Ginzburg generalized this theory to the case of unfavorable enthalpic interactions between a particle and the two polymers. They showed that the amount of particles had to attain a certain threshold to stabilize the system and the lower the particle radius, the higher the stable zone area. Generally speaking, all the phenomena regarding the morphology of polymer blends are governed by thermodynamics and/or kinetic effects, as well as the localization of nanoparticles. The main discussed thermodynamically controlling parameter of the localization is the wetting parameter ωAB. However, because of the viscosity of the system, the equilibrium dictated by ωAB may never be reached. Hence, concerning the kinetic effects, the final localization of fillers in a polymer pair is guided by the sequence of mixing of the components, the viscosity ratio, the composition, the temperature, the shear rate and the time of mixing. When the particles are placed at the interface between two polymers, coalescence can be suppressed or/and interfacial tension can be reduced. In that case, particles are known to play the role of a compatibilizer. In a ternary system, (i) the shape of the particle (spheres, rods or “onions-shape”), (ii) the particle radius (Rp) versus the radius of gyration of the polymers (Rg) and (iii) the surface chemistry of the particles affect the final localization of the particles (thus, the compatibilizing effect) and the final properties of the material, such as mechanical, conductive, magnetic and thermal properties. This review details recent works for which those four above mentioned properties are improved by incorporating different kind of fillers in polymer blends.
An intensive isolation program carried out in three replicated composting piles allowed the identification of the resident and transient components of the composting microbiome. More than 4000 ...bacterial strains were isolated, enzymatically characterized and identified by partial sequencing of their 16S rRNA gene. While microorganisms isolated under mesophilic conditions were prominent throughout the process, thermophilic stages gathered the highest total counts and spore-forming bacteria prevailed at the bio-oxidative phase of composting. Enzymatic capabilities related to the degradation of polymeric materials were exhibited by most of the isolates and as a result of these activities, more soluble compounds could be made available to the entire composting microbiota. A high proportion of isolates showed to be thermotolerant as they were detected at mesophilic and thermophilic phases. Isolated strains belonged to 187 bacterial species. Biodiversity was greater at the central stages of composting and mesophilic, thermophilic and cooling phases shared 50% of species.
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