1,322 research outputs found
Proof Relevant Corecursive Resolution
Resolution lies at the foundation of both logic programming and type class
context reduction in functional languages. Terminating derivations by
resolution have well-defined inductive meaning, whereas some non-terminating
derivations can be understood coinductively. Cycle detection is a popular
method to capture a small subset of such derivations. We show that in fact
cycle detection is a restricted form of coinductive proof, in which the atomic
formula forming the cycle plays the role of coinductive hypothesis.
This paper introduces a heuristic method for obtaining richer coinductive
hypotheses in the form of Horn formulas. Our approach subsumes cycle detection
and gives coinductive meaning to a larger class of derivations. For this
purpose we extend resolution with Horn formula resolvents and corecursive
evidence generation. We illustrate our method on non-terminating type class
resolution problems.Comment: 23 pages, with appendices in FLOPS 201
An output-sensitive algorithm for the minimization of 2-dimensional String Covers
String covers are a powerful tool for analyzing the quasi-periodicity of
1-dimensional data and find applications in automata theory, computational
biology, coding and the analysis of transactional data. A \emph{cover} of a
string is a string for which every letter of lies within some
occurrence of . String covers have been generalized in many ways, leading to
\emph{k-covers}, \emph{-covers}, \emph{approximate covers} and were
studied in different contexts such as \emph{indeterminate strings}.
In this paper we generalize string covers to the context of 2-dimensional
data, such as images. We show how they can be used for the extraction of
textures from images and identification of primitive cells in lattice data.
This has interesting applications in image compression, procedural terrain
generation and crystallography
Automatic Optimization of Python Skeletal Parallel Programs
International audienceSkeletal parallelism is a model of parallelism where parallel constructs are provided to the programmer as usual patterns of parallel algorithms. High-level skeleton libraries often offer a global view of programs instead of the common Single Program Multiple Data view in parallel programming. A program is written as a sequential program but operates on parallel data structures. Most of the time, skeletons on a parallel data structure have counterparts on a sequential data structure. For example, the map function that applies a given function to all the elements of a sequential collection (e.g., a list) has a map skeleton counterpart that applies a sequential function to all the elements of a distributed collection. Two of the challenges a programmer faces when using a skeleton library that provides a wide variety of skeletons are: which are the skeletons to use, and how to compose them? These design decisions may have a large impact on the performance of the parallel programs. However, skeletons, especially when they do not mutate the data structure they operate on, but are rather implemented as pure functions , possess algebraic properties that allow to transform compositions of skeletons into more efficient compositions of skeletons. In this paper, we present such an automatic transformation framework for the Python skeleton library PySke and evaluate it on several example applications
Current undergraduate dental implantology teaching in UK
Dental Implants are a popular treatment option for tooth replacement, with documented long-term success and survival rates of more than 95% over a period of 10 years. However, incorporating dental implantology into an undergraduate dental curriculum has issues associated. Therefore, the aim of this research was to examine and evaluate current undergraduate dental implantology education in the UK, investigate the amount of time allocated to this subject and analyse the barriers that are currently impeding the development of the programmes. An online questionnaire hosted by Online Surveys was designed, piloted, and sent to 16 dental schools providing undergraduate education in the UK. Ethical approval was gained from The University of Salford to conduct the study. Out of the 16 dental schools contacted, eight questionnaire responses were received, hence a response rate of 50% was achieved. The hours dedicated to the implant teaching programme varied from 3 h to 25 h, with a mean average of 11 h. It was identified from the results that no teaching of dental implantology was conducted in year 2; 12% of the schools responded that the subject was taught in year 1, 37% in year 3, 75% in year 4 and 50% in year 5. The methods used to deliver the programme were mainly lecture-based teaching, with only one dental school allowing students to place implants on patients. The main barriers to progression of the programme were financial (75%), followed by time limitations imposed by the curriculum (37%) and liability insurance (37%). However, there appears to be a consensus that further training beyond bachelor's degree level is required to teach implantology effectively.</b
How functional programming mattered
In 1989 when functional programming was still considered a niche topic, Hughes wrote a visionary paper arguing convincingly ‘why functional programming matters’. More than two decades have passed. Has functional programming really mattered? Our answer is a resounding ‘Yes!’. Functional programming is now at the forefront of a new generation of programming technologies, and enjoying increasing popularity and influence. In this paper, we review the impact of functional programming, focusing on how it has changed the way we may construct programs, the way we may verify programs, and fundamentally the way we may think about programs
Dynamic and approximate pattern matching in 2D
International audienc
On secondary loops in LAOS via self-intersection of Lissajous–Bowditch curves
When the shear stress measured in large amplitude oscillatory shear (LAOS) deformation is represented as a 2-D Lissajous–Bowditch curve, the corresponding trajectory can appear to self-intersect and form secondary loops. This self-intersection is a general consequence of a strongly nonlinear material response to the imposed oscillatory forcing and can be observed for various material systems and constitutive models. We derive the mathematical criteria for the formation of secondary loops, quantify the location of the apparent intersection, and furthermore suggest a qualitative physical understanding for the associated nonlinear material behavior. We show that when secondary loops appear in the viscous projection of the stress response (the 2-D plot of stress vs. strain rate), they are best interpreted by understanding the corresponding elastic response (the 2-D projection of stress vs. strain). The analysis shows clearly that sufficiently strong elastic nonlinearity is required to observe secondary loops on the conjugate viscous projection. Such a strong elastic nonlinearity physically corresponds to a nonlinear viscoelastic shear stress overshoot in which existing stress is unloaded more quickly than new deformation is accumulated. This general understanding of secondary loops in LAOS flows can be applied to various molecular configurations and microstructures such as polymer solutions, polymer melts, soft glassy materials, and other structured fluids
Zinc-Regulated DNA Binding of the Yeast Zap1 Zinc-Responsive Activator
The Zap1 transcription factor of Saccharomyces cerevisiae plays a central role in zinc homeostasis by controlling the expression of genes involved in zinc metabolism. Zap1 is active in zinc-limited cells and repressed in replete cells. At the transcriptional level, Zap1 controls its own expression via positive autoregulation. In addition, Zap1's two activation domains are regulated independently of each other by zinc binding directly to those regions and repressing activation function. In this report, we show that Zap1 DNA binding is also inhibited by zinc. DMS footprinting showed that Zap1 target gene promoter occupancy is regulated with or without transcriptional autoregulation. These results were confirmed using chromatin immunoprecipitation. Zinc regulation of DNA binding activity mapped to the DNA binding domain indicating other parts of Zap1 are unnecessary for this control. Overexpression of Zap1 overrode DNA binding regulation and resulted in constitutive promoter occupancy. Under these conditions of constitutive binding, both the zinc dose response of Zap1 activity and cellular zinc accumulation were altered suggesting the importance of DNA binding control to zinc homeostasis. Thus, our results indicated that zinc regulates Zap1 activity post-translationally via three independent mechanisms, all of which contribute to the overall zinc responsiveness of Zap1
Effects of vessel traffic on relative abundance and behaviour of cetaceans : the case of the bottlenose dolphins in the Archipelago de La Maddalena, north-western Mediterranean sea
Acknowledgements This study was part of the Tursiops Project of the Dolphin Research Centre of Caprera, La Maddalena. Financial and logistical support was provided by the Centro Turistico Studentesco (CTS) and by the National Park of the Archipelago de La Maddalena. We thank the Natural Reserve of Bocche di Bonifacio for the support provided during data collection. The authors thank the numerous volunteers of the Caprera Dolphin Research Centre and especially Marco Ferraro, Mirko Ugo, Angela Pira and Maurizio Piras whose assistance during field observation and skills as a boat driver were invaluable.Peer reviewedPostprin
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