A Galerkin boundary element method for high frequency scattering by convex polygons

In this paper we consider the problem of time-harmonic acoustic scattering in two dimensions by convex polygons. Standard boundary or finite element methods for acoustic scattering problems have a computational cost that grows at least linearly as a function of the frequency of the incident wave. Here we present a novel Galerkin boundary element method, which uses an approximation space consisting of the products of plane waves with piecewise polynomials supported on a graded mesh, with smaller elements closer to the corners of the polygon. We prove that the best approximation from the approximation space requires a number of degrees of freedom to achieve a prescribed level of accuracy that grows only logarithmically as a function of the frequency. Numerical results demonstrate the same logarithmic dependence on the frequency for the Galerkin method solution. Our boundary element method is a discretization of a well-known second kind combined-layer-potential integral equation. We provide a proof that this equation and its adjoint are well-posed and equivalent to the boundary value problem in a Sobolev space setting for general Lipschitz domains

Developing arts-based methods for exploring virtual reality technologies: A university–industry case study

Collaborations between human–computer interaction (HCI) researchers and arts practitioners frequently centre on the development of creative content using novel – often emergent – technologies. Concurrently, many of the techniques that HCI researchers use in evaluative participant-based research have their roots in the arts – such as sketching, writing, artefact prototyping and role play. In this reflective paper, we describe a recent collaboration between a group of HCI researchers and dramatists from the immersive theatre organization Kilter, who worked together to design a series of audience-based interventions to explore the ethics of virtual reality (VR) technology. Through a process of knowledge exchange, the collaboration provided the researchers with new techniques to explore, ideate and communicate their work, and provided the dramatists with a solid academic grounding in order to produce an accurate yet provocative piece of theatrically based design fiction. We describe the formation of this partnership between academia and creative industry, document our journey together, and share the lasting impact it has had upon both parties

Environmental controls on daytime net community calcification on a Red Sea reef flat

Coral growth and carbonate accumulation form the foundation of the coral reef ecosystem. Changes in environmental conditions due to coastal development, climate change, and ocean acidification may pose a threat to net carbonate production in the near future. Controlled laboratory studies demonstrate that calcification by corals and coralline algae is sensitive to changes in aragonite saturation state (Ωa), as well as temperature, light, and nutrition. Studies also show that the dissolution rate of carbonate substrates is impacted by changes in carbonate chemistry. The sensitivity of coral reefs to these parameters must be confirmed and quantified in the natural environment in order to predict how coral reefs will respond to local and global changes, particularly ocean acidification. We estimated the daytime hourly net community metabolic rates, both net community calcification (NCC) and net community productivity (NCP), at Sheltered Reef, an offshore platform reef in the central Red Sea. Average NCC was 8 ± 3 mmol m[superscript −2] h[superscript −1] in December 2010 and 11 ± 1 mmol m[superscript −2] h[superscript −1] in May 2011, and NCP was 21 ± 7 mmol m[superscript −2] h[superscript −1] in December 2010 and 44 ± 4 mmol m[superscript −2] h[superscript −1] in May 2011. We also monitored a suite of physical and chemical properties to help relate the rates at Sheltered Reef to published rates from other sites. While previous research shows that short-term field studies investigating the NCC–Ωa relationship have differing results due to confounding factors, it is important to continue estimating NCC in different places, seasons, and years, in order to monitor changes in NCC versus Ω in space and time, and to ultimately resolve a broader understanding of this relationship.National Science Foundation (U.S.) (Graduate Research Fellowship

Polytypic Genetic Programming

Program synthesis via heuristic search often requires a great deal of boilerplate code to adapt program APIs to the search mechanism. In addition, the majority of existing approaches are not type-safe: i.e. they can fail at runtime because the search mechanisms lack the strict type information often available to the compiler. In this article, we describe Polytope, a Scala framework that uses polytypic programming, a relatively recent advance in program abstraction. Polytope requires a minimum of boilerplate code and supports a form of strong-typing in which type rules are automatically enforced by the compiler, even for search operations such as mutation which are applied at run-time. By operating directly on language-native expressions, it provides an embeddable optimization procedure for existing code. We give a tutorial example of the specific polytypic approach we adopt and compare both runtime efficiency and required lines of code against the well-known EpochX GP framework, showing comparable performance in the former and the complete elimination of boilerplate for the latter

Pseudo-Random Streams for Distributed and Parallel Stochastic Simulations on GP-GPU

International audienceRandom number generation is a key element of stochastic simulations. It has been widely studied for sequential applications purposes, enabling us to reliably use pseudo-random numbers in this case. Unfortunately, we cannot be so enthusiastic when dealing with parallel stochastic simulations. Many applications still neglect random stream parallelization, leading to potentially biased results. In particular parallel execution platforms, such as Graphics Processing Units (GPUs), add their constraints to those of Pseudo-Random Number Generators (PRNGs) used in parallel. This results in a situation where potential biases can be combined with performance drops when parallelization of random streams has not been carried out rigorously. Here, we propose criteria guiding the design of good GPU-enabled PRNGs. We enhance our comments with a study of the techniques aiming to parallelize random streams correctly, in the context of GPU-enabled stochastic simulations

Evolving text classification rules with genetic programming

We describe a novel method for using genetic programming to create compact classification rules using combinations of N-grams (character strings). Genetic programs acquire fitness by producing rules that are effective classifiers in terms of precision and recall when evaluated against a set of training documents. We describe a set of functions and terminals and provide results from a classification task using the Reuters 21578 dataset. We also suggest that the rules may have a number of other uses beyond classification and provide a basis for text mining applications

Comparing Genetic Programming Approaches for Non-functional Genetic Improvement

Genetic improvement (GI) uses automated search to find improved versions of existing software. While most GI work use genetic programming (GP) as the underlying search process, focus is usually given to the target software only. As a result, specifics of GP algorithms for GI are not well understood and rarely compared to one another. In this work, we propose a robust experimental protocol to compare different GI search processes and investigate several variants of GP- and random-based approaches. Through repeated experiments, we report a comparative analysis of these approaches, using one of the previously used GI scenarios: improvement of runtime of the MiniSAT satisfiability solver. We conclude that the test suites used have the most significant impact on the GI results. Both random and GP-based approaches are able to find improved software, even though the percentage of viable software variants is significantly smaller in the random case ( 14.5% vs. 80.1%). We also report that GI produces MiniSAT variants up to twice as fast as the original on sets of previously unseen instances from the same application domain

FANCD2 expression affects platinum response and further characteristics of high grade serous ovarian cancer in cells with different genetic backgrounds

High-grade serous ovarian cancer (HGSOC) is the most prevalent subtype of ovarian cancer and demonstrates 5-year survival of just 40%. One of the major causes of mortality is the development of tumour resistance to platinum-based chemotherapy, which can be modulated by dysregulation of DNA damage repair pathways. We therefore investigated the contribution of the DNA interstrand crosslink repair protein FANCD2 to chemosensitivity in HGSOC. Increased FANCD2 protein expression was observed in some cell line models of platinum resistant HGSOC compared with paired platinum sensitive models. Knockdown of FANCD2 in some cell lines, including the platinum resistant PEO4, led to increased carboplatin sensitivity. Investigation into mechanisms of FANCD2 regulation showed that increased FANCD2 expression in platinum resistant cells coincides with increased expression of mTOR. Treatment with mTOR inhibitors resulted in FANCD2 depletion, suggesting that mTOR can mediate platinum sensitivity via regulation of FANCD2. Tumours from a cohort of HGSOC patients showed varied nuclear and cytoplasmic FANCD2 expression, however this was not significantly associated with clinical characteristics. Knockout of FANCD2 was associated with increased cell migration, which may represent a non-canonical function of cytoplasmic FANCD2. We conclude that upregulation of FANCD2, possibly mediated by mTOR, is a potential mechanism of chemoresistance in HGSOC and modulation of FANCD2 expression can influence platinum sensitivity and other tumour cell characteristics

RFWD3 modulates response to platinum chemotherapy and promotes cancer associated phenotypes in high grade serous ovarian cancer

Background: DNA damage repair is frequently dysregulated in high grade serous ovarian cancer (HGSOC), which can lead to changes in chemosensitivity and other phenotypic differences in tumours. RFWD3, a key component of multiple DNA repair and maintenance pathways, was investigated to characterise its impact in HGSOC.Methods: RFWD3 expression and association with clinical features was assessed using in silico analysis in the TCGA HGSOC dataset, and in a further cohort of HGSOC tumours stained for RFWD3 using immunohistochemistry. RFWD3 expression was modulated in cell lines using siRNA and CRISPR/cas9 gene editing, and cells were characterised using cytotoxicity and proliferation assays, flow cytometry, and live cell microscopy. Results: Expression of RFWD3 RNA and protein varied in HGSOCs. In cell lines, reduction of RFWD3 expression led to increased sensitivity to interstrand crosslinking (ICL) inducing agents mitomycin C and carboplatin. RFWD3 also demonstrated further functionality outside its role in DNA damage repair, with RFWD3 deficient cells displaying cell cycle dysregulation, reduced cellular proliferation and reduced migration. In tumours, low RFWD3 expression was associated with increased tumour mutational burden, and complete response to platinum chemotherapy. Conclusions: RFWD3 expression varies in HGSOCs, which can lead to functional effects at both the cellular and tumour levels.<br/