1,874 research outputs found
All you need is spin: SU(2) equivariant variational quantum circuits based on spin networks
Variational algorithms require architectures that naturally constrain the
optimisation space to run efficiently. In geometric quantum machine learning,
one achieves this by encoding group structure into parameterised quantum
circuits to include the symmetries of a problem as an inductive bias. However,
constructing such circuits is challenging as a concrete guiding principle has
yet to emerge. In this paper, we propose the use of spin networks, a form of
directed tensor network invariant under a group transformation, to devise SU(2)
equivariant quantum circuit ans\"atze -- circuits possessing spin rotation
symmetry. By changing to the basis that block diagonalises SU(2) group action,
these networks provide a natural building block for constructing parameterised
equivariant quantum circuits. We prove that our construction is mathematically
equivalent to other known constructions, such as those based on twirling and
generalised permutations, but more direct to implement on quantum hardware. The
efficacy of our constructed circuits is tested by solving the ground state
problem of SU(2) symmetric Heisenberg models on the one-dimensional triangular
lattice and on the Kagome lattice. Our results highlight that our equivariant
circuits boost the performance of quantum variational algorithms, indicating
broader applicability to other real-world problems.Comment: 36+14 page
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Astrocyte alignment in 3D collagen gels increases neurite outgrowth; implications for improving spinal cord repair
A major impediment to tissue engineered repair of CNS damage is the glial scar that forms around implanted graft devices and creates an inhibitory environment for axon growth out of the repair site 1. The glial scar is composed of a 3-dimensional (3D) meshwork of astrocytes which become reactive in response to damage stimuli. Previous studies have shown that longitudinal alignment of astrocytes growing in monolayer is sufficient to direct and enhance the growth of neurites over their surface 2,3. The aim of this work therefore was to develop a 3D culture system in which the effect of astrocyte alignment on neurite growth could be modelled in a spatially relevant environment
Interacting effects of temperature, habitat and phenotype on predator avoidance behaviour in <i>Diadema antillarum</i>: implications for restorative conservation
Caribbean long-spined sea urchin Diadema antillarum populations crashed following a mass mortality event in 1983-1984 with cascading effects on reef health. Population restoration efforts may be hampered by unknown effects of short- and long-term elevated sea surface temperature (SST). We investigated how a key behavioural trait, predator avoidance behaviour (PAB; percentage of long defensive spines that moved in response to shadow stimuli), was affected by elevated SST in 180 individuals from 2 contrasting Honduran reefs: Utila (flattened reef structure, dearth of predation refugia) and Banco Capiro (complex reef structure, abundant refugia). Initiation of PAB is mediated by melanin, which breaks down at elevated water temperatures; thus, as SST rises, D. antillarum may become vulnerable to predation. We compared local current SST (CSST; 29.7°C) with 2 IPCC predicted long-term climate change scenarios under laboratory conditions. PAB decreased by 13.98-15.37% at CSST +1.4°C and 31.67-42.44% at CSST +3.1°C. Trial temperatures were similar to maxima recorded in the Caribbean during the 2016 El Niño, so our results also represent likely responses to worst-case short-term acute temperature anomalies. Juveniles maintained higher PAB than adults, indicating increased reliance on anti-predation behaviours. White-spined phenotypes from Utila’s flattened reef maintained higher PAB than black-spined counterparts, likely due to increased conspicuousness to visual predators. Habitat complexity may mitigate temperature-driven losses in natural behavioural defences. D. antillarum may be resilient to near-term (D. antillarum populations must be coupled to augmented reef complexity to improve future resilience
The DLV System for Knowledge Representation and Reasoning
This paper presents the DLV system, which is widely considered the
state-of-the-art implementation of disjunctive logic programming, and addresses
several aspects. As for problem solving, we provide a formal definition of its
kernel language, function-free disjunctive logic programs (also known as
disjunctive datalog), extended by weak constraints, which are a powerful tool
to express optimization problems. We then illustrate the usage of DLV as a tool
for knowledge representation and reasoning, describing a new declarative
programming methodology which allows one to encode complex problems (up to
-complete problems) in a declarative fashion. On the foundational
side, we provide a detailed analysis of the computational complexity of the
language of DLV, and by deriving new complexity results we chart a complete
picture of the complexity of this language and important fragments thereof.
Furthermore, we illustrate the general architecture of the DLV system which
has been influenced by these results. As for applications, we overview
application front-ends which have been developed on top of DLV to solve
specific knowledge representation tasks, and we briefly describe the main
international projects investigating the potential of the system for industrial
exploitation. Finally, we report about thorough experimentation and
benchmarking, which has been carried out to assess the efficiency of the
system. The experimental results confirm the solidity of DLV and highlight its
potential for emerging application areas like knowledge management and
information integration.Comment: 56 pages, 9 figures, 6 table
The Investigation of Space Charge Dominated Beams in a Synchrotron
This research was sponsored by the National Science Foundation Grant NSF PHY-931478
Troubling the exclusive privileges of citizenship: mobile solidarities, asylum seekers, and the right to work
This article discusses asylum seekers and the right to work in the UK. Differential access to the labour market is one of the ways in which the state maintains a distinction between British citizens, who ‘belong’, and non-citizens who do not. While such a policy approach garners widespread support amongst the general public of citizens, it does not go uncontested. This article discusses a UK-based campaign, ‘Let Them Work’, which has sought to influence the government in extending the right to work to asylum seekers. In doing so, it demonstrates the ways in which the stratified regime of citizenship rights is contested politically, and explores how such contestation troubles the exclusive privileges of citizenship by enacting mobile solidarities from marginalised spaces
Variation in pigmentation gene expression is associated with distinct aposematic color morphs in the poison frog Dendrobates auratus
Background:
Color and pattern phenotypes have clear implications for survival and reproduction in many species. However, the mechanisms that produce this coloration are still poorly characterized, especially at the genomic level. Here we have taken a transcriptomics-based approach to elucidate the underlying genetic mechanisms affecting color and pattern in a highly polytypic poison frog. We sequenced RNA from the skin from four different color morphs during the final stage of metamorphosis and assembled a de novo transcriptome. We then investigated differential gene expression, with an emphasis on examining candidate color genes from other taxa.
Results:
Overall, we found differential expression of a suite of genes that control melanogenesis, melanocyte differentiation, and melanocyte proliferation (e.g., tyrp1, lef1, leo1, and mitf) as well as several differentially expressed genes involved in purine synthesis and iridophore development (e.g., arfgap1, arfgap2, airc, and gart).
Conclusions:
Our results provide evidence that several gene networks known to affect color and pattern in vertebrates play a role in color and pattern variation in this species of poison frog
RAS oncogenic activity predicts response to chemotherapy and outcome in lung adenocarcinoma.
Activating mutations in KRAS occur in 32% of lung adenocarcinomas (LUAD). Despite leading to aggressive disease and resistance to therapy in preclinical studies, the KRAS mutation does not predict patient outcome or response to treatment, presumably due to additional events modulating RAS pathways. To obtain a broader measure of RAS pathway activation, we developed RAS84, a transcriptional signature optimised to capture RAS oncogenic activity in LUAD. We report evidence of RAS pathway oncogenic activation in 84% of LUAD, including 65% KRAS wild-type tumours, falling into four groups characterised by coincident alteration of STK11/LKB1, TP53 or CDKN2A, suggesting that the classifications developed when considering only KRAS mutant tumours have significance in a broader cohort of patients. Critically, high RAS activity patient groups show adverse clinical outcome and reduced response to chemotherapy. Patient stratification using oncogenic RAS transcriptional activity instead of genetic alterations could ultimately assist in clinical decision-making
Effect of left ventricular hypertrophy on long-term survival of patients with coronary artery disease following percutaneous coronary intervention
The impact of left ventricular hypertrophy (LVH) on survival among patients with established coronary artery disease (CAD) is not well understood. We sought to evaluate the effect of LVH on the survival of patients with CAD following percutaneous coronary intervention (PCI). Three hospitals in New York City contributed prospectively defined data on 4284 consecutive patients undergoing PCI. Allcause mortality at a mean follow-up of three years was the primary endpoint. LVH was present in 383 patients (8.9%). LVH patients had a greater prevalence of hypertension (88% vs. 68%, p<0.001), vascular disease (21% vs. 6.6%, p=0.001), and prior heart failure (10% vs. 5.5%, p<0.001). LVH patients presented less often with one-vessel disease (38% vs. 50%, p=0.040) and more often with two- (34% vs. 29%, p=0.014) or three-vessel (22% vs. 18%, p=0.044) disease. Ejection fractions and angiographic success were similar in both groups. In-hospital mortality did not differ between groups. At three-year follow-up, the survival rate for patients with LVH was 86% vs. 91% in patients without LVH (log-rank p=0.001). However, after adjustment for differences in baseline characteristics using Cox proportional hazards analysis, LVH was found not to be an independent predictor of mortality (hazard ratio, 0.93; 95% confidence interval, 0.68–1.28; p=0.67). We conclude that LVH at the time of PCI is not independently associated with an increase in the hazard of death at three years
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