Searching for Ground Truth: a stepping stone in automating genre classification

This paper examines genre classification of documents and its role in enabling the effective automated management of digital documents by digital libraries and other repositories. We have previously presented genre classification as a valuable step toward achieving automated extraction of descriptive metadata for digital material. Here, we present results from experiments using human labellers, conducted to assist in genre characterisation and the prediction of obstacles which need to be overcome by an automated system, and to contribute to the process of creating a solid testbed corpus for extending automated genre classification and testing metadata extraction tools across genres. We also describe the performance of two classifiers based on image and stylistic modeling features in labelling the data resulting from the agreement of three human labellers across fifteen genre classes.

Effect of transient pinning on stability of drops sitting on an inclined plane

We report on new instabilities of the quasi-static equilibrium of water drops pinned by a hydrophobic inclined substrate. The contact line of a statically pinned drop exhibits three transitions of partial depinning: depinning of the advancing and receding parts of the contact line and depinning of the entire contact line leading to the drop's translational motion. We find a region of parameters where the classical Macdougall-Ockrent-Frenkel approach fails to estimate the critical volume of the statically pinned inclined drop

On recurrence and ergodicity for geodesic flows on noncompact periodic polygonal surfaces

We study the recurrence and ergodicity for the billiard on noncompact polygonal surfaces with a free, cocompact action of $\Z$ or $\Z^2$. In the $\Z$-periodic case, we establish criteria for recurrence. In the more difficult $\Z^2$-periodic case, we establish some general results. For a particular family of $\Z^2$-periodic polygonal surfaces, known in the physics literature as the wind-tree model, assuming certain restrictions of geometric nature, we obtain the ergodic decomposition of directional billiard dynamics for a dense, countable set of directions. This is a consequence of our results on the ergodicity of \ZZ-valued cocycles over irrational rotations.Comment: 48 pages, 12 figure

The Emergence of a Twisted Flux Tube into the Solar Atmosphere: Sunspot Rotations and the Formation of a Coronal Flux Rope

We present a 3D simulation of the dynamic emergence of a twisted magnetic flux tube from the top layer of the solar convection zone into the solar atmosphere and corona. It is found that after a brief initial stage of flux emergence during which the two polarities of the bipolar region become separated and the tubes intersecting the photosphere become vertical, significant rotational motion sets in within each polarity. The rotational motions of the two polarities are found to twist up the inner field lines of the emerged fields such that they change their orientation into an inverse configuration (i.e. pointing from the negative polarity to the positive polarity over the neutral line). As a result, a flux rope with sigmoid-shaped, dipped core fields form in the corona, and the center of the flux rope rises in the corona with increasing velocity as the twisting of the flux rope footpoints continues. The rotational motion in the two polarities is a result of propagation of non-linear torsional Alfv\'en waves along the flux tube, which transports significant twist from the tube's interior portion towards its expanded coronal portion. This is a basic process whereby twisted flux ropes are developed in the corona with increasing twist and magnetic energy, leading up to solar eruptions.Comment: 33 pages, 14 figures, Submitted to Ap

Detection of left ventricular hypertrophy by Tc-99 tetrofosmin gated-SPECT.

Introduction. Left ventricular hypertrophy (LVH) is a strong cardiovascular risk factor and an independent major cardiac risk factor for sudden cardiac death, myocardial infarction and stroke. The objective of this study was to determine the specificity, sensitivity, positive predictive value (PPV) Negative Predictive Value (NPV) and accuracy of a Tc-99 gated-SPECT method for detecting LVH. Methods: Patients referred for evaluation of known or suspected CAD, who underwent myocardial perfusion SPECT imaging with Tc-99 Tetrofosmin and who had also an echocardiogram performed within the previous 2 months were prospectively enrolled in the study. The group consisted of 52 patients, 25 men and 27 women, the mean age was 64.5 ± 12 yrs. Results: When the echocardiographic LVH was defined as a mean wall thickness VSTd + PWTd/2 ≥ 11mm, the SPECT method had aspecificity and sensitivity of 91% and 33% respectively, a PPV of 94%, a NPV of 48% and an accuracy of 58%. When the LVH was defined as a thickness to radius ratio (h/r) >0.45, the SPECT Method showed a specificity of 95%, sensitivity of 37% and a PPV of 97% and NPV of 54% with an accuracy of 62% . In Men, when the LVH criteria was a LV Mass >111 g/m2, the specificity and sensitivity for the SPECT method criteria was 100% and 20% respectively with a PPV, NPV and Accuracy of 100%, 45% and 48%. In Women, when LVH was defined as a LV Mass >106 g/m2, the SPECT method had a specificity of 91% and sensitivity of 44%, a PPV of 94%, and NPV and Accuracy of 42% and 63%. If the criteria was a LV Mass >125 g/m2, SPECT showed a specificity and sensitivity of 86% and 30% respectively and a PPV of 85% and a NPV of 64% with an Accuracy of 62 %

Myocardial perfusion in patients with ST depression during the recovery phase of treadmill stress tests

Objectives: To determine the incidence and characteristics of myocardial perfusion abnormalities in patients with ST depression in recovery only, using Tc-99m gated-SPECT. Background: The significance of ST depression in recovery only after exercise treadmill testing (ETT) remains controversial. Such finding has been classified as a false positive, false negative and inconclusive sign of CAD. Methods: Fifty patients who underwent ETT and Tc-99m gated-SPECT and demonstrated ST depression only in recovery were analyzed. The group consisted of 28 men and 22 females, mean age of 61 ± 9 years. Perfusion abnormalities, reverse redistribution, heart/lung ratio, changes in LV cavity size and global function were assessed. Results: The mean peak heart rate (PHR) was 139 ± 18 bpm (88% ± 14 of the predicted maximal heart rate). Sixty % of the patients had evidence of CAD in form of either fixed or reversible perfusion abnormalities. Fixed only perfusion abnormalities were found in 3 patients (6%), seven (14%) had fixed and reversible perfusion defects and 20 (40%) showed ischemia only. Ischemia was observed in the anterior wall in 10 patients, inferior wall in 12, lateral wall in 5, apex in 8 and septum in 1 patient. Mean extent of the perfusion abnormalities were 3.7 segments (out of 20) ± 2. Conclusions: Evidence of CAD was found in 60% of the patients with ST depression in recovery only. The most common finding was ischemia in 54% of the patients, and the anterior and inferior walls were most frequently involved. The mean extent of myocardial involvement was moderate, which implies prognostic significance

From fields to a super-cluster: the role of the environment at z=0.84 with HiZELS

At z=0, clusters are primarily populated by red, elliptical and massive galaxies, while blue, spiral and lower-mass galaxies are common in low-density environments. Understanding how and when these differences were established is of absolute importance for our understanding of galaxy formation and evolution, but results at high-z remain contradictory. By taking advantage of the widest and deepest H-alpha narrow-band survey at z=0.84 over the COSMOS and UKIDSS UDS fields, probing a wide range of densities (from poor fields to rich groups and clusters, including a confirmed super-cluster with a striking filamentary structure), we show that the fraction of star-forming galaxies falls continuously from ~40% in fields to approaching 0% in rich groups/clusters. We also find that the median SFR increases with environmental density, at least up to group densities - but only for low and medium mass galaxies, and thus such enhancement is mass-dependent at z~1. The environment also plays a role in setting the faint-end slope (alpha) of the H-alpha luminosity function. Our findings provide a sharper view on galaxy formation and evolution and reconcile previously contradictory results at z~1: stellar mass is the primary predictor of star formation activity, but the environment also plays a major role.Comment: 5 pages, 4 figures, to appear in the proceedings of JENAM 2010 S2: `Environment and the Formation of Galaxies: 30 years later', ASSP, Springe

Lateral Pile Response from Model Tests in a Large Centrifuge

Lateral loading tests on instrumented model piles in saturated sand in a centrifuge are described. Piles were tested in isolation and in groups of two, three and six piles. Data were obtained on deflections and bending moments in single piles and on interaction factors between piles. Response of single piles compared favourably with data from Mustang Island field tests. Experimental interaction factors generally differed from those commonly used which are derived from elastic theory. The difference depends on pile spacing