A combinatorial approach to knot recognition

This is a report on our ongoing research on a combinatorial approach to knot recognition, using coloring of knots by certain algebraic objects called quandles. The aim of the paper is to summarize the mathematical theory of knot coloring in a compact, accessible manner, and to show how to use it for computational purposes. In particular, we address how to determine colorability of a knot, and propose to use SAT solving to search for colorings. The computational complexity of the problem, both in theory and in our implementation, is discussed. In the last part, we explain how coloring can be utilized in knot recognition

The STAR MAPS-based PiXeL detector

The PiXeL detector (PXL) for the Heavy Flavor Tracker (HFT) of the STAR experiment at RHIC is the first application of the state-of-the-art thin Monolithic Active Pixel Sensors (MAPS) technology in a collider environment. Custom built pixel sensors, their readout electronics and the detector mechanical structure are described in detail. Selected detector design aspects and production steps are presented. The detector operations during the three years of data taking (2014-2016) and the overall performance exceeding the design specifications are discussed in the conclusive sections of this paper

Effect of Tuned Parameters on a LSA MCQ Answering Model

This paper presents the current state of a work in progress, whose objective is to better understand the effects of factors that significantly influence the performance of Latent Semantic Analysis (LSA). A difficult task, which consists in answering (French) biology Multiple Choice Questions, is used to test the semantic properties of the truncated singular space and to study the relative influence of main parameters. A dedicated software has been designed to fine tune the LSA semantic space for the Multiple Choice Questions task. With optimal parameters, the performances of our simple model are quite surprisingly equal or superior to those of 7th and 8th grades students. This indicates that semantic spaces were quite good despite their low dimensions and the small sizes of training data sets. Besides, we present an original entropy global weighting of answers' terms of each question of the Multiple Choice Questions which was necessary to achieve the model's success.Comment: 9 page

Squirrelpox virus: assessing prevalence, transmission and environmental degradation

Red squirrels (Sciurus vulgaris) declined in Great Britain and Ireland during the last century, due to habitat loss and the introduction of grey squirrels (Sciurus carolinensis), which competitively exclude the red squirrel and act as a reservoir for squirrelpox virus (SQPV). The disease is generally fatal to red squirrels and their ecological replacement by grey squirrels is up to 25 times faster where the virus is present. We aimed to determine: (1) the seropositivity and prevalence of SQPV DNA in the invasive and native species at a regional scale; (2) possible SQPV transmission routes; and, (3) virus degradation rates under differing environmental conditions. Grey (n = 208) and red (n = 40) squirrel blood and tissues were sampled. Enzyme-linked immunosorbent assay (ELISA) and quantitative real-time polymerase chain reaction (qPCR) techniques established seropositivity and viral DNA presence, respectively. Overall 8% of squirrels sampled (both species combined) had evidence of SQPV DNA in their tissues and 22% were in possession of antibodies. SQPV prevalence in sampled red squirrels was 2.5%. Viral loads were typically low in grey squirrels by comparison to red squirrels. There was a trend for a greater number of positive samples in spring and summer than in winter. Possible transmission routes were identified through the presence of viral DNA in faeces (red squirrels only), urine and ectoparasites (both species). Virus degradation analyses suggested that, after 30 days of exposure to six combinations of environments, there were more intact virus particles in scabs kept in warm (25°C) and dry conditions than in cooler (5 and 15°C) or wet conditions. We conclude that SQPV is present at low prevalence in invasive grey squirrel populations with a lower prevalence in native red squirrels. Virus transmission could occur through urine especially during warm dry summer conditions but, more notably, via ectoparasites, which are shared by both species

Solving order constraints in logarithmic space.

We combine methods of order theory, finite model theory, and universal algebra to study, within the constraint satisfaction framework, the complexity of some well-known combinatorial problems connected with a finite poset. We identify some conditions on a poset which guarantee solvability of the problems in (deterministic, symmetric, or non-deterministic) logarithmic space. On the example of order constraints we study how a certain algebraic invariance property is related to solvability of a constraint satisfaction problem in non-deterministic logarithmic space

Signature of a Pre-Human Population Decline in the Critically Endangered Reunion Island Endemic Forest Bird Coracina newtoni

The exceptional biodiversity of Reunion Island is threatened by anthropogenic landscape changes that took place during the 350 years of human colonization. During this period the human population size increased dramatically from 250 to 800,000. The arrival of humans together with the development of agriculture, invasive species such as rats and cats, and deforestation has lead to the extinction of more than half of the original vertebrate species of the island. For the remaining species, significant work is being carried out to identify threats and conservation status, but little genetic work has been carried on some of the most endangered species. In the last decade theoretical studies have shown the ability of neutral genetic markers to infer the demographic history of endangered species and identify and date past population size changes (expansions or bottlenecks). In this study we provide the first genetic data on the critically endangered species the Reunion cuckoo-shrike Coracina newtoni. The Reunion cuckoo-shrike is a rare endemic forest bird surviving in a restricted 12-km2 area of forested uplands and mountains. The total known population consists of less than one hundred individuals out of which 45 were genotyped using seventeen polymorphic microsatellite loci. We found a limited level of genetic variability and weak population structure, probably due to the limited geographic distribution. Using Bayesian methods, we identified a strong decline in population size during the Holocene, most likely caused by an ancient climatic or volcanic event around 5000 years ago. This result was surprising as it appeared in apparent contradiction with the accepted theory of recent population collapse due to deforestation and predator introduction. These results suggest that new methods allowing for more complex demographic models are necessary to reconstruct the demographic history of populations

Mitiq: A software package for error mitigation on noisy quantum computers

We introduce Mitiq, a Python package for error mitigation on noisy quantum computers. Error mitigation techniques can reduce the impact of noise on near-term quantum computers with minimal overhead in quantum resources by relying on a mixture of quantum sampling and classical post-processing techniques. Mitiq is an extensible toolkit of different error mitigation methods, including zero-noise extrapolation, probabilistic error cancellation, and Clifford data regression. The library is designed to be compatible with generic backends and interfaces with different quantum software frameworks. We describe Mitiq using code snippets to demonstrate usage and discuss features and contribution guidelines. We present several examples demonstrating error mitigation on IBM and Rigetti superconducting quantum processors as well as on noisy simulators

Psychometric instruments for problematic pornography use: a systematic review

Despite a lack of consensus in the field about how best to conceptualize problematic pornography use, psychometric instruments have nonetheless been developed to assess the construct. The present systematic review aimed to: (i) identify psychometric tools that have been developed to assess problematic pornography use; (ii) summarize key characteristics, psychometric properties and strengths and limitations of instruments for problematic pornography use; (iii) compare the instruments’ theoretical conceptualizations of problematic pornography use; and (iv) evaluate each instrument on their ability to assess various core components of addiction. Twenty-two instruments assessing problematic pornography use were reviewed. Results indicated that while the instruments had different conceptualizations of problematic pornography use, addiction still emerged as the most common theoretical framework used by the instruments. Five of the most commonly assessed addiction components across the different instruments were (1) impaired control; (2) salience; (3) mood modification; (4) interpersonal conflict, and (5) general life conflict. Contextual factors that may potentially affect the assessment of problematic pornography use and recommendations for researchers and clinicians are discussed

Role of calcium channel blocking agents in the prevention of atherosclerosis

Calcium channel blocking agents, although effective and widely used in the symptomatic therapy of hypertension and ischemic heart disease, have an uncertain effect on the development of coronary atherosclerosis, plaque rupture, and postrupture thrombosis. Both nifedipine and nicardipine have been shown to prevent the development of new coronary lesions but not the progression of existing lesions in prospective randomized angiographic studies. Verapamil, in contrast, failed to prevent the development of new coronary lesions and had no significant effect on the progression of existing lesions. Diltiazem, although not studied in patients with coronary atheroscleroses, has been shown to prevent the development of post-transplant coronary vascular disease. Despite the beneficial effects of nifedipine and nicardipine on new coronary lesion development, they have not been shown to reduce the incidence of recurrent ischemic events or mortality in the prospective randomized studies that demonstrated their effect on new coronary lesion development. A relatively new dihydropyridine calcium channel blocking agent, amlodipine, is hypothesized to prevent atherosclerosis due to its calcium channel blocking properties as well as by mechanisms independent of its calcium channel blocking properties. This agent has been selected for evaluation in the Prospective Randomized Evaluation of the Vascular Effects of Norvasc Trial (PREVENT) to explore whether the use of amlodipine over 3 years will reduce the incidence of early atherosclerotic lesions and, possibly, the progression of existing lesions in both the coronary and carotid arterial beds. Amlodipine could play an important future role in the secondary prevention of ischemic heart disease, but further study and a demonstration of a beneficial effect on recurrent ischemic events is required before any final conclusions concerning its effectiveness are reached.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44649/1/10557_2004_Article_BF00878569.pd