Online and offline heuristics for inferring hierarchies of repetitions in sequences

Hierarchical dictionary-based compression schemes form a grammar for a text by replacing each repeated string with a production rule. While such schemes usually operate online, making a replacement as soon as repetition is detected, offline operation permits greater freedom in choosing the order of replacement. In this paper, we compare the online method with three offline heuristics for selecting the next substring to replace: longest string first, most common string first, and the string that minimized the size of the grammar locally. Surprisingly, two of the offline techniques, like the online method, run in time linear in the size of the input. We evaluate each technique on artificial and natural sequences. In general, the locally-most-compressive heuristic performs best, followed by most frequent, the online technique, and, lagging by some distance, the longest-first technique

Detecting sequential structure

Programming by demonstration requires detection and analysis of sequential patterns in a user’s input, and the synthesis of an appropriate structural model that can be used for prediction. This paper describes SEQUITUR, a scheme for inducing a structural description of a sequence from a single example. SEQUITUR integrates several different inference techniques: identification of lexical subsequences or vocabulary elements, hierarchical structuring of such subsequences, identification of elements that have equivalent usage patterns, inference of programming constructs such as looping and branching, generalisation by unifying grammar rules, and the detection of procedural substructure., Although SEQUITUR operates with abstract sequences, a number of concrete illustrations are provided

Steady-state, effective-temperature dynamics in a glassy material

We present an STZ-based analysis of numerical simulations by Haxton and Liu (HL). The extensive HL data sharply test the basic assumptions of the STZ theory, especially the central role played by the effective disorder temperature as a dynamical state variable. We find that the theory survives these tests, and that the HL data provide important and interesting constraints on some of its specific ingredients. Our most surprising conclusion is that, when driven at various constant shear rates in the low-temperature glassy state, the HL system exhibits a classic glass transition, including super-Arrhenius behavior, as a function of the effective temperature.Comment: 9 pages, 6 figure

Increased human pathogenic potential of Escherichia coli from polymicrobial urinary tract infections in comparison to isolates from monomicrobial culture samples

The current diagnostic standard procedure outlined by the Health Protection Agency for urinary tract infections (UTIs) in clinical laboratories does not report bacteria isolated from samples containing three or more different bacterial species. As a result many UTIs go unreported and untreated, particularly in elderly patients, where polymicrobial UTI samples are especially prevalent. This study reports the presence of the major uropathogenic species in mixed culture urine samples from elderly patients, and of resistance to front-line antibiotics, with potentially increased levels of resistance to ciprofloxacin and trimethoprim. Most importantly, the study highlights that Escherichia coli present in polymicrobial UTI samples are statistically more invasive (P<0.001) in in vitro epithelial cell infection assays than those isolated from monomicrobial culture samples. In summary, the results of this study suggest that the current diagnostic standard procedure for polymicrobial UTI samples needs to be reassessed, and that E. coli present in polymicrobial UTI samples may pose an increased risk to human health

Generalized Modeling Approaches to Risk Adjustment of Skewed Outcomes Data

There are two broad classes of models used to address the econometric problems caused by skewness in data commonly encountered in health care applications: (1) transformation to deal with skewness (e.g., OLS on ln(y)); and (2) alternative weighting approaches based on exponential conditional models (ECM) and generalized linear model (GLM) approaches. In this paper, we encompass these two classes of models using the three parameter generalized gamma (GGM) distribution, which includes several of the standard alternatives as special cases OLS with a normal error, OLS for the log normal, the standard gamma and exponential with a log link, and the Weibull. Using simulation methods, we find the tests of identifying distributions to be robust. The GGM also provides a potentially more robust alternative estimator to the standard alternatives. An example using inpatient expenditures is also analyzed.

Extracting text from PostScript

We show how to extract plain text from PostScript files. A textual scan is inadequate because PostScript interpreters can generate characters on the page that do not appear in the source file. Furthermore, word and line breaks are implicit in the graphical rendition, and must be inferred from the positioning of word fragments. We present a robust technique for extracting text and recognizing words and paragraphs. The method uses a standard PostScript interpreter but redefines several PostScript operators, and simple heuristics are employed to locate word and line breaks. The scheme has been used to create a full-text index, and plain-text versions, of 40,000 technical reports (34 Gbyte of PostScript). Other text-extraction systems are reviewed: none offer the same combination of robustness and simplicity

Prognostic significance of short-term blood pressure variability in acute stroke

Background and Purpose— Blood pressure variability (BPV) may be an important prognostic factor acutely after stroke. This review investigated the existing evidence for the effect of BPV on outcome after stroke, also considering BPV measurement techniques and definitions. Methods— A literature search was performed according to a prespecified study protocol. Two reviewers independently assessed study eligibility and quality. Where appropriate, meta-analyses were performed to assess the effect of BPV on poor functional outcome. Results— Eighteen studies from 1359 identified citations were included. Seven studies were included in a meta-analysis for the effect of BPV on functional outcome (death or disability). Systolic BPV was significantly associated with poor functional outcome: pooled odds ratio per 10-mm Hg increment, 1.2; confidence interval (1.1–1.3). A descriptive review of included studies also supports these findings, and in addition, it suggests that systolic BPV may be associated with increased risk of intracranial hemorrhage in those treated with thrombolytic therapy. Conclusions— This systematic review and meta-analysis suggest that greater systolic BPV, measured early from ischemic stroke or intracerebral hemorrhage onset, is associated with poor longer-term functional outcome. Future prospective studies should investigate how best to measure and define BPV in acute stroke, as well as to determine its prognostic significance. </jats:sec

Transposon mutagenesis in a hyper-invasive clinical isolate of Campylobacter jejuni reveals a number of genes with potential roles in invasion

Transposon mutagenesis has been applied to a hyper-invasive clinical isolate of Campylobacter jejuni, 01/51. A random transposon mutant library was screened in an in vitro assay of invasion and 26 mutants with a significant reduction in invasion were identified. Given that the invasion potential of C. jejuni is relatively poor compared to other enteric pathogens, the use of a hyper-invasive strain was advantageous as it greatly facilitated the identification of mutants with reduced invasion. The location of the transposon insertion in 23 of these mutants has been determined; all but three of the insertions are in genes also present in the genome-sequenced strain NCTC 11168. Eight of the mutants contain transposon insertions in one region of the genome (∼14 kb), which when compared with the genome of NCTC 11168 overlaps with one of the previously reported plasticity regions and is likely to be involved in genomic variation between strains. Further characterization of one of the mutants within this region has identified a gene that might be involved in adhesion to host cells

Development and validation of a measure of disengagement, The

Includes bibliographical references.2015 Summer.Even though no measure of disengagement exists, researchers and practitioners have claimed to identify employees who are disengaged using measures that assess satisfaction, engagement, or burnout. This study outlines the development and initial validation of a theoretically-based measure of employee disengagement. Consistent with theory, the measure is composed of affective, physical, and cognitive factors. Data from 709 participants collected through Amazon‟s crowdsourcing tool, Mechanical Turk (MTurk), show that disengagement is distinct from, but moderately related to engagement, burnout, and withdrawal. Consistent with theory, low levels of the psychological conditions of psychological meaningfulness, safety, and availability predicted higher level of disengagement. Additionally, high levels of psychological meaningfulness and psychological availability predicted high levels of engagement. The new measure of disengagement developed in this study may help researchers develop a more accurate understanding of disengaged employees