7,559 research outputs found
Operative strategy for fistula-in-ano without division of the anal sphincter
We would like to thank Mr ER MacDonald for his contribution in data collection during the early years of the study. The material in this paper was presented as a poster at the annual meeting of the American Society of Colon and Rectal Surgeons held in Vancouver, Canada, May 2011.Peer reviewedPublisher PD
Simulated Quantum Computation of Global Minima
Finding the optimal solution to a complex optimization problem is of great
importance in practically all fields of science, technology, technical design
and econometrics. We demonstrate that a modified Grover's quantum algorithm can
be applied to real problems of finding a global minimum using modest numbers of
quantum bits. Calculations of the global minimum of simple test functions and
Lennard-Jones clusters have been carried out on a quantum computer simulator
using a modified Grover's algorithm. The number of function evaluations
reduced from O(N) in classical simulation to in quantum
simulation. We also show how the Grover's quantum algorithm can be combined
with the classical Pivot method for global optimization to treat larger
systems.Comment: 6 figures. Molecular Physics, in pres
Comprehensive Two-Point Analyses of Weak Gravitational Lensing Surveys
We present a framework for analyzing weak gravitational lensing survey data,
including lensing and source-density observables, plus spectroscopic redshift
calibration data. All two-point observables are predicted in terms of
parameters of a perturbed Robertson-Walker metric, making the framework
independent of the models for gravity, dark energy, or galaxy properties. For
Gaussian fluctuations the 2-point model determines the survey likelihood
function and allows Fisher-matrix forecasting. The framework includes nuisance
terms for the major systematic errors: shear measurement errors, magnification
bias and redshift calibration errors, intrinsic galaxy alignments, and
inaccurate theoretical predictions. We propose flexible parameterizations of
the many nuisance parameters related to galaxy bias and intrinsic alignment.
For the first time we can integrate many different observables and systematic
errors into a single analysis. As a first application of this framework, we
demonstrate that: uncertainties in power-spectrum theory cause very minor
degradation to cosmological information content; nearly all useful information
(excepting baryon oscillations) is extracted with ~3 bins per decade of angular
scale; and the rate at which galaxy bias varies with redshift substantially
influences the strength of cosmological inference. The framework will permit
careful study of the interplay between numerous observables, systematic errors,
and spectroscopic calibration data for large weak-lensing surveys.Comment: submitted to Ap
Group Leaders Optimization Algorithm
We present a new global optimization algorithm in which the influence of the
leaders in social groups is used as an inspiration for the evolutionary
technique which is designed into a group architecture. To demonstrate the
efficiency of the method, a standard suite of single and multidimensional
optimization functions along with the energies and the geometric structures of
Lennard-Jones clusters are given as well as the application of the algorithm on
quantum circuit design problems. We show that as an improvement over previous
methods, the algorithm scales as N^2.5 for the Lennard-Jones clusters of
N-particles. In addition, an efficient circuit design is shown for two qubit
Grover search algorithm which is a quantum algorithm providing quadratic
speed-up over the classical counterpart
Update Frequency and Background Corpus Selection in Dynamic TF-IDF Models for First Story Detection
First Story Detection (FSD) requires a system to detect the very first story that mentions an event from a stream of stories. Nearest neighbour-based models, using the traditional term vector document representations like TF-IDF, currently achieve the state of the art in FSD. Because of its online nature, a dynamic term vector model that is incrementally updated during the detection process is usually adopted for FSD instead of a static model. However, very little research has investigated the selection of hyper-parameters and the background corpora for a dynamic model. In this paper, we analyse how a dynamic term vector model works for FSD, and investigate the impact of different update frequencies and background corpora on FSD performance. Our results show that dynamic models with high update frequencies outperform static model and dynamic models with low update frequencies; and that the FSD performance of dynamic models does not always increase with higher update frequencies, but instead reaches steady state after some update frequency threshold is reached. In addition, we demonstrate that different background corpora have very limited influence on the dynamic models with high update frequencies in terms of FSD performance
Shortest paths in nearly conservative digraphs
We introduce the following notion: a digraph D = (V, A) with arc weights c: A → R is called nearly conservative if every negative cycle consists of two arcs. Computing shortest paths in nearly conservative digraphs is NP-hard, and even deciding whether a digraph is nearly conservative is coNP-complete. We show that the “All Pairs Shortest Path” problem is fixed parameter tractable with various parameters for nearly conservative digraphs. The results also apply for the special case of conservative mixed graphs
Confluent Orthogonal Drawings of Syntax Diagrams
We provide a pipeline for generating syntax diagrams (also called railroad
diagrams) from context free grammars. Syntax diagrams are a graphical
representation of a context free language, which we formalize abstractly as a
set of mutually recursive nondeterministic finite automata and draw by
combining elements from the confluent drawing, layered drawing, and smooth
orthogonal drawing styles. Within our pipeline we introduce several heuristics
that modify the grammar but preserve the language, improving the aesthetics of
the final drawing.Comment: GD 201
A quantum genetic algorithm with quantum crossover and mutation operations
In the context of evolutionary quantum computing in the literal meaning, a
quantum crossover operation has not been introduced so far. Here, we introduce
a novel quantum genetic algorithm which has a quantum crossover procedure
performing crossovers among all chromosomes in parallel for each generation. A
complexity analysis shows that a quadratic speedup is achieved over its
classical counterpart in the dominant factor of the run time to handle each
generation.Comment: 21 pages, 1 table, v2: typos corrected, minor modifications in
sections 3.5 and 4, v3: minor revision, title changed (original title:
Semiclassical genetic algorithm with quantum crossover and mutation
operations), v4: minor revision, v5: minor grammatical corrections, to appear
in QI
The UK register of HIV seroconverters: Methods and analytical issues
A Register of HIV-infected persons who have had a negative antibody test within 3 years of their first antibody positive test (seroconverters) is being set up in the UK to monitor the distribution of times from HIV seroconversion to AIDS (the incubation period) and to death. It will also provide a national resource for use by those designing studies in this group of individuals. Clinicians caring for HIV-positive persons in Genito-Urinary Medicine, Infectious Disease and other departments throughout the UK were asked to participate by providing information on eligible subjects. Most laboratories undertaking HIV antibody testing were also contacted and asked to provide the name of the attending clinician for all seroconverters identified through the HIV laboratory reporting systems of the PHLS Communicable Disease Surveillance Centre (CDSC) and the Scottish Centre for Infection and Environmental Health (SCIEH) and for any other seroconverters known to them but not identified by CDSC or SCIEH. Data items sought for the Register include: sex, ethnic group, probable route of HIV transmission, annual CD4 counts, details of therapy and prophylaxis prescribed, AIDS-defining events and vital status. Follow up information is collected annually. Wherever possible, all seroconverters known to a clinic have been identified, whether currently alive or dead, either from clinic records or laboratory reporting or both. The objective is to establish and update a complete register of seroconverters on a long-term basis to provide reliable estimates of the incubation period on which future projections of AIDS cases in the UK can be made
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