413 research outputs found
Deformation of the Fermi surface in the extended Hubbard model
The deformation of the Fermi surface induced by Coulomb interactions is
investigated in the t-t'-Hubbard model. The interplay of the local U and
extended V interactions is analyzed. It is found that exchange interactions V
enhance small anisotropies producing deformations of the Fermi surface which
break the point group symmetry of the square lattice at the Van Hove filling.
This Pomeranchuck instability competes with ferromagnetism and is suppressed at
a critical value of U(V). The interaction V renormalizes the t' parameter to
smaller values what favours nesting. It also induces changes on the topology of
the Fermi surface which can go from hole to electron-like what may explain
recent ARPES experiments.Comment: 5 pages, 4 ps figure
A Quantitative Metric to Identify Critical Elements within Seafood Supply Networks
A theoretical basis is required for comparing key features and critical elements in wild fisheries and aquaculture
supply chains under a changing climate. Here we develop a new quantitative metric that is analogous to indices used to
analyse food-webs and identify key species. The Supply Chain Index (SCI) identifies critical elements as those elements with
large throughput rates, as well as greater connectivity. The sum of the scores for a supply chain provides a single metric that
roughly captures both the resilience and connectedness of a supply chain. Standardised scores can facilitate crosscomparisons
both under current conditions as well as under a changing climate. Identification of key elements along the
supply chain may assist in informing adaptation strategies to reduce anticipated future risks posed by climate change. The
SCI also provides information on the relative stability of different supply chains based on whether there is a fairly even
spread in the individual scores of the top few key elements, compared with a more critical dependence on a few key
individual supply chain elements. We use as a case study the Australian southern rock lobster Jasus edwardsii fishery, which
is challenged by a number of climate change drivers such as impacts on recruitment and growth due to changes in largescale
and local oceanographic features. The SCI identifies airports, processors and Chinese consumers as the key elements in
the lobster supply chain that merit attention to enhance stability and potentially enable growth. We also apply the index to
an additional four real-world Australian commercial fishery and two aquaculture industry supply chains to highlight the
utility of a systematic method for describing supply chains. Overall, our simple methodological approach to empiricallybased
supply chain research provides an objective method for comparing the resilience of supply chains and highlighting
components that may be critical
Phase-field models for brittle and cohesive fracture
In this paper we first recapitulate some basic notions of brittle and cohesive fracture models, as well as the phase-field approximation to fracture. Next, a critical assessment is made of the sensitivity of the phase-field approach to brittle fracture, in particular the degradation function, and the use of monolithic versus partitioned solution schemes. The last part of the paper makes extensions to a recently developed phase-field model for cohesive fracture, in particular for propagating cracks. Using some simple examples the current state of the cohesive phase-field model is shown
Electrically pumped continuous-wave IIIâV quantum dot lasers on silicon
Reliable, efficient electrically pumped silicon-based lasers would enable full integration of photonic and electronic circuits, but have previously only been realized by wafer bonding. Here, we demonstrate continuous-wave InAs/GaAs quantum dot lasers directly grown on silicon substrates with a low threshold current density of 62.5â
Aâ
cmâ2, a room-temperature output power exceeding 105â
mW and operation up to 120â
°C. Over 3,100â
h of continuous-wave operating data have been collected, giving an extrapolated mean time to failure of over 100,158â
h. The realization of high-performance quantum dot lasers on silicon is due to the achievement of a low density of threading dislocations on the order of 105â
cmâ2 in the IIIâV epilayers by combining a nucleation layer and dislocation filter layers with in situ thermal annealing. These results are a major advance towards reliable and cost-effective silicon-based photonicâelectronic integration
Chromosomal-level assembly of the Asian Seabass genome using long sequence reads and multi-layered scaffolding
We report here the ~670 Mb genome assembly of the Asian seabass (Lates calcarifer), a tropical marine teleost. We used long-read sequencing augmented by transcriptomics, optical and genetic mapping along with shared synteny from closely related fish species to derive a chromosome-level assembly with a contig N50 size over 1 Mb and scaffold N50 size over 25 Mb that span ~90% of the genome. The population structure of L. calcarifer species complex was analyzed by re-sequencing 61 individuals representing various regions across the species' native range. SNP analyses identified high levels of genetic diversity and confirmed earlier indications of a population stratification comprising three clades with signs of admixture apparent in the South-East Asian population. The quality of the Asian seabass genome assembly far exceeds that of any other fish species, and will serve as a new standard for fish genomics
Observation of associated near-side and away-side long-range correlations in âsNN=5.02ââTeV proton-lead collisions with the ATLAS detector
Two-particle correlations in relative azimuthal angle (ÎÏ) and pseudorapidity (Îη) are measured in âsNN=5.02ââTeV p+Pb collisions using the ATLAS detector at the LHC. The measurements are performed using approximately 1ââÎŒb-1 of data as a function of transverse momentum (pT) and the transverse energy (ÎŁETPb) summed over 3.1<η<4.9 in the direction of the Pb beam. The correlation function, constructed from charged particles, exhibits a long-range (2<|Îη|<5) ânear-sideâ (ÎÏâŒ0) correlation that grows rapidly with increasing ÎŁETPb. A long-range âaway-sideâ (ÎÏâŒÏ) correlation, obtained by subtracting the expected contributions from recoiling dijets and other sources estimated using events with small ÎŁETPb, is found to match the near-side correlation in magnitude, shape (in Îη and ÎÏ) and ÎŁETPb dependence. The resultant ÎÏ correlation is approximately symmetric about Ï/2, and is consistent with a dominant cosâĄ2ÎÏ modulation for all ÎŁETPb ranges and particle pT
Comparison between eletrosurgery and cold blade in tongues of rats: a preliminary experimental study
Molecular targets for anticancer redox chemotherapy and cisplatin-induced ototoxicity: the role of curcumin on pSTAT3 and Nrf-2 signalling
In oncology, an emerging paradigm emphasises molecularly targeted approaches for cancer prevention and therapy and the use of adjuvant chemotherapeutics to overcome cisplatin limitations. Owing to their safe use, some polyphenols, such as curcumin, modulate important pathways or molecular targets in cancers. This paper focuses on curcumin as an adjuvant molecule to cisplatin by analysing its potential implications on the molecular targets, signal transducer and activator of transcription 3 (STAT3) and NF-E2 p45-related factor 2 (Nrf-2), in tumour progression and cisplatin resistance in vitro and the adverse effect ototoxicity in vivo
Multi-model seascape genomics identifies distinct environmental drivers of selection among sympatric marine species
Background
As global change and anthropogenic pressures continue to increase, conservation and management increasingly needs to consider speciesâ potential to adapt to novel environmental conditions. Therefore, it is imperative to characterise the main selective forces acting on ecosystems, and how these may influence the evolutionary potential of populations and species. Using a multi-model seascape genomics approach, we compare putative environmental drivers of selection in three sympatric southern African marine invertebrates with contrasting ecology and life histories: Cape urchin (Parechinus angulosus), Common shore crab (Cyclograpsus punctatus), and Granular limpet (Scutellastra granularis).
Results
Using pooled (Pool-seq), restriction-site associated DNA sequencing (RAD-seq), and seven outlier detection methods, we characterise genomic variation between populations along a strong biogeographical gradient. Of the three species, only S. granularis showed significant isolation-by-distance, and isolation-by-environment driven by sea surface temperatures (SST). In contrast, sea surface salinity (SSS) and range in air temperature correlated more strongly with genomic variation in C. punctatus and P. angulosus. Differences were also found in genomic structuring between the three species, with outlier loci contributing to two clusters in the East and West Coasts for S. granularis and P. angulosus, but not for C. punctatus.
Conclusion
The findings illustrate distinct evolutionary potential across species, suggesting that species-specific habitat requirements and responses to environmental stresses may be better predictors of evolutionary patterns than the strong environmental gradients within the region. We also found large discrepancies between outlier detection methodologies, and thus offer a novel multi-model approach to identifying the principal environmental selection forces acting on species. Overall, this work highlights how adding a comparative approach to seascape genomics (both with multiple models and species) can elucidate the intricate evolutionary responses of ecosystems to global change
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