A Machine Learning Approach for Identification Thesis and Conclusion Statements in Student Essays

This study describes and evaluates twoessay-based discourse analysis systems thatidentify thesis and conclusion statements fromstudent essays written on six different essaytopics. Essays used to train and evaluate thesystems were annotated by two human judges,according to a discourse annotation protocol. Using a machine learning approach, a number ofdiscourse-related features were automaticallyextracted from a set of annotated trainingdata. Using these features, two discourseanalysis models were built using C5.0 withboosting: a topic-dependent and atopic-independent model. Both systemsoutperformed a positional algorithm. While thetopic-dependent system showed somewhat higherperformance, the topic-independent systemshowed similar results, indicating that asystem can generalize to unseen data – thatis, essay responses on topics that the systemhas not seen in training.     

The repassivation of nickel-copper alloys in sulphuric acid

The behaviour of freshly generated electrode surfaces of Ni, Ni-30Cu, Ni-50Cu and Ni-70Cu in 1.0 M H₂SO₄ has been investigated. At low potentials all metals grow a monolayer of film designated as MOH when M is Cu⁺ or Ni⁺. The kinetics of formation of this monolayer follows Tafel's equation. At higher potentials passivation of the metals occurs by film growth under high electric field, with two different sets of high field parameters for different film thicknesses. The rate of film growth for all metals is controlled largely by the nickel oxide component of the film.     

Surface-modified reusable gold electrode for detection of dissolved oxygen

The behavior of gold electrodes for the detection of dissolved oxygen was studied by the method of cyclic voltammetry in a phosphate-buffered solution with physiological pH. Surface modification with electropolymerized poly (o-phenylenediamine) film was performed to improve electrode antifouling properties. The voltammetric signature of oxygen was considered in terms of film electropolymerization conditions and post-deposition conditioning of the electrodes. The changes in the chemical structure of the poly (o-phenylenediamine) films as a result of these factors were confirmed by X-ray photoelectron spectroscopy analysis. Following long post-deposition conditioning in a phosphate-buffered solution, the modified electrodes exhibited stable voltammetric signatures in repeated tests and during storage as well as in the presence of a dense population of Escherichia coli (characterized by negligible metabolic activity) in the buffer. The results are indicative of the improved electrode antifouling properties.     

The temperature dependence of passivity breakdown on a titanium alloy determined by cyclic noise thermammetry

A new sensitive electrochemical technique is presented which is designed to measure the temperature dependence of the breakdown of passivity of metal surfaces. The method, termed “cyclic noise thermammetry”, consists of scanning the temperature of an electrochemical cell linearly and cyclically between two predefined limits, whilst simultaneously measuring the current flowing from a potentiostatically maintained microelectrode. An example of the new technique is presented, which describes the effect of temperature on the nucleation of corrosion pits on the titanium-based alloy, Ti-6Al-4V, in acidic chloride solution far below the pitting potential. Results are presented over the temperature range 20-50 °C. Events due to breakdown of passivity were detected throughout the entire temperature range. These events are the nucleation of corrosion pits, although they do not propagate into stable pits under the applied experimental conditions. Results show that passivity breaks down over the entire range of temperature, at a frequency that increases with increase in temperature.     

A semantic Web services architecture

The semantic Web services initiative architecture (SWSA) committee has created a set of architectural and protocol abstractions that serve as a foundation for semantic Web service technologies. This article summarizes the committee's findings, emphasizing its review of requirements gathered from several different environments. We also identify the scope and potential requirements for a semantic Web services architecture.     

Use of cardiopulmonary bypass to salvage patients with multiple-chamber heart wounds

BACKGROUND: The need for cardiopulmonary bypass in the treatment of penetrating heart injuries is debated. OBJECTIVES: To review our experience with penetrating heart injuries and determine the indications and outcome for cardiopulmonary bypass. DESIGN: Retrospective review. SETTING: A university-based, level I trauma center. PATIENTS: All victims of penetrating heart injury presenting between July 1, 1989, and December 31, 1995. METHODS: Medical records were reviewed for demographic and physiological data, operative findings, and outcome. RESULTS: Overall survival for 106 patients with penetrating heart injury was 55%. In an effort to resuscitate the heart, 4 patients with unresponsive cardiogenic shock were placed on cardiopulmonary bypass; none survived. Of 30 patients with multiple-chamber injuries, 11 presented with signs of life and 7 survived. Cardiopulmonary bypass was essential to repair complex injuries in 2 of the 7 survivors. CONCLUSION: Cardiopulmonary bypass was ineffective in salvaging patients with cardiogenic shock but was essential in some patients with complex multiple-chamber cardiac injuries that could not be exposed and repaired by other means.     

Repeatability and reproducibility estimates from collaborative studies based on total concentration of trace analytes

In the process of validating a given analytical method for the total concentration of a trace analyte, the precision indicators, repeatability and reproducibility, are obtained from a collaborative study of the method based on a standard one-way completely randomized model. This report discusses the shortcomings of the statistical models used in such studies, defines the component makeup for estimates of the repeatability and reproducibility variances based on these models, and considers suggestions offered as new policy regarding method performance based on total concentration.     

Regulation of beta-adrenoceptors in the guinea-pig sinoatrial node

This study examined the changes of beta-adrenoceptors in the guinea-pig sinoatrial nodal region following 7 day (-)-isoprenaline (400 micrograms/kg/h s.c.) infusion and the relationship between beta-adrenoceptor desensitization and receptor down-regulation. Changes in beta 1- and beta 2-adrenoceptor density were measured using quantitative autoradiography and function in organ bath studies. (-)-Isoprenaline treatment produced a marked decrease in total (from 57.5 to 33.9 fmol/mg protein), beta 1- (from 49.4 to 32.8 fmol/mg protein), and beta 2-adrenoceptor density (from 8.1 to 1.05 fmol/mg protein) in the sinoatrial node. In adjacent right atrium, treatment produced no change in total (39.5 and 36.7 fmol/mg protein) or beta 1-adrenoceptors (35.9 and 36.4 fmol/mg protein) but did decrease beta 2-adrenoceptors (from 3.7 to 0.3 fmol/mg protein). Chronotropic effects were measured in spontaneously beating right atrium. Procaterol, a selective beta 2-adrenoceptor agonist, caused a biphasic chronotropic response in control right atria, the first part of which was abolished in the tissue from treated animals. The maximum increase in right atrial rate to RO363, a beta 1-adrenoceptor selective partial agonist, was reduced from 114 bpm in control to 43 bpm in treated animals. In electrically driven right atrium with the sinoatrial node removed procaterol failed to produce a positive inotropic response via beta 2-adrenoceptors, but the maximum response to RO363 was reduced from 0.75 g in the control tissue to 0.12 g in the treated tissue. This study showed that changes in beta 2-adrenoceptor density following 7 day (-)-isoprenaline infusion are compatible with reduced functional responsiveness in the SA node. The reduction of beta 1-adrenoceptor number in the SA node was also compatible with the reduced chronotropic response in this tissue. However the lack of effect on beta 1-adrenoceptor density in the right atrium was not consistent with the decrease in beta 1-adrenoceptor mediated inotropic response in this tissue. This suggests that beta-adrenoceptor desensitization is not always associated with receptor down-regulation but depends also on the changes in the cell signalling system beyond the level of the receptor which differ according to the cardiac location.     

The effect of an infusion of low molecular weight dextran on peripheral resistance in patients with arteriosclerosis

Low molecular weight dextran is frequently given to improve the flow of blood to the periphery, but its mode of action is uncertain. We measured the effect of an infusion of 500 ml of Dextran 40 on the peripheral resistance in 12 patients undergoing reconstructive surgery for atherosclerotic occlusion of the superficial femoral artery. After the infusion, values of packed cell volume and blood viscosity indicated haemodilution. There was a consistent increase in mean flow and a fall in peripheral resistance. There was no correlation between change in viscosity and change in peripheral resistance, but there was a good correlation between the percentage change in resistance and the initial resistance. This suggests that the increase in flow of blood was due to reflex vasodilatation rather than to any reduction in viscosity.     

Extensive restriction site polymorphism at the human phenylalanine hydroxylase locus and application in prenatal diagnosis of phenylketonuria

A total of 10 restriction site polymorphisms have been identified at the human phenylalanine hydroxylase locus using a full-length human phenylalanine hydroxylase cDNA clone as a hybridization probe to analyze human genomic DNA. These polymorphic patterns segregate in a Mendelian fashion and concordantly with the disease state in various PKU kindreds. The frequencies of the restriction site polymorphisms at the human phenylalanine hydroxylase locus among Caucasians are such that the observed heterozygosity in the population is 87.5%. Thus, most families with a history of classical phenylketonuria can take advantage of the genetic analysis for prenatal diagnosis and carrier detection of the hereditary disorder.