The exact sample complexity of PAC-learning problems with unit VC dimension

The Vapnik-Chervonenkis (VC) dimension is a combinatorial measure of a certain class of machine learning problems, which may be used to obtain upper and lower bounds on the number of training examples needed to learn to prescribed levels of accuracy. Most of the known bounds apply to the Probably Approximately Correct (PAC) framework, which is the framework within which we work in this paper. For a learning problem with some known VC dimension, much is known about the order of growth of the sample-size requirement of the problem, as a function of the PAC parameters. The exact value of sample-size requirement is however less well-known, and depends heavily on the particular learning algorithm being used. This is a major obstacle to the practical application of the VC dimension. Hence it is important to know exactly how the sample-size requirement depends on VC dimension, and with that in mind, we describe a general algorithm for learning problems having VC dimension 1. Its sample-size requirement is minimal (as a function of the PAC parameters), and turns out to be the same for all non-trivial learning problems having VC dimension 1. While the method used cannot be naively generalised to higher VC dimension, it suggests that optimal algorithm-dependent bounds may improve substantially on current upper bounds.

Problems with formative and higher-order reflective variables

Cadogan and Lee (this issue) discuss the problems inherent in modeling formative latent variables as endogenous. In response to the commentaries by Rigdon (this issue) and Finn and Wang (this issue), the present article extends the discussion on formative measures. First, the article shows that regardless of whether statistical identification is achieved, researchers are unable to illuminate the nature of a formative latent variable. Second, the study clarifies issues regarding formative indicator weighting, highlighting that the weightings of formative components should be specified as part of the construct definition. Finally, the study shows that higher-order reflective constructs are invalid, highlights the damage their use can inflict on theory development and knowledge accumulation, and provides recommendations on a number of alternative models which should be used in their place (including the formative model). © 2012 Elsevier Inc.

Problems with mutual wills:a study of probate practice

Legislation: Law of Property (Miscellaneous Provisions) Act 1989 (c.34) s.2 Case: Healey v Brown [2002] W.T.L.R. 849 (Ch D) Paper looks at the use of mutual wills in practice. An empirical survey of probate solicitors is carried out and the results analysed. Significantly most solicitors seem, unaware of the controversial ruling as regards mutual wills in Healey v Brown and the impact of S.2 Law of Property Miscellaneous Provisions Act 1989 where land is concerned. Unsuprisingly the survey demonstrates that mutual wills are not commonly used and tend to be avoided by practising solicitors.

Design of a genetic algorithm for bi-objective flow shop scheduling problems with re-entrant jobs

This paper presents a simulated genetic algorithm (GA) model of scheduling the flow shop problem with re-entrant jobs. The objective of this research is to minimize the weighted tardiness and makespan. The proposed model considers that the jobs with non-identical due dates are processed on the machines in the same order. Furthermore, the re-entrant jobs are stochastic as only some jobs are required to reenter to the flow shop. The tardiness weight is adjusted once the jobs reenter to the shop. The performance of the proposed GA model is verified by a number of numerical experiments where the data come from the case company. The results show the proposed method has a higher order satisfaction rate than the current industrial practices.

Corporate governance and compliance with International Financial Reporting Standards (IFRSs):evidence from two MENA stock exchanges

This study examines the influence of corporate governance structures on the levels of compliance with IFRSs disclosure requirements by companies listed on the stock exchanges of two leading MENA (Middle East and North Africa) countries, Egypt and Jordan. This study employs a cross-sectional analysis of a sample of non-financial companies listed on the two stock exchanges for the fiscal year 2007. Using an unweighted disclosure index, the study measures the levels of compliance by companies listed on the two stock exchanges investigated.Univariate and multivariate regression analyses are used to estimate the relationships proposed in the hypotheses. In addition, the study uses semi-structured interviews in order to supplement the interpretation of the findings of the quantitative analyses. An innovative theoretical foundation is deployed, in which compliance is interpretable through three lenses - institutional isomorphism theory, secrecy versus transparency (one of Gray’s accounting sub-cultural values), and financial economics theories. The study extends the financial reporting literature, cross-national comparative financial disclosure literature, and the emerging markets disclosure literature by carrying out one of the first comparative studies of the above mentioned stock exchanges. Results provide evidence of a lack of de facto compliance (i.e., actual compliance) with IFRSs disclosure requirements in the scrutinised MENA countries. The impact of corporate governance mechanisms for best practice on enhancing the extent of compliance with mandatory IFRSs is absent in the stock exchanges in question. The limited impact of corporate governance best practice is mainly attributed to the novelty of corporate governance in the region, a finding which lends support to the applicability of the proposed theoretical foundation to the MENA context. Finally, the study provides recommendations for improving de facto compliance with IFRSs disclosure requirements and corporate governance best practice in the MENA region and suggests areas for future research.

Visual function and subjective quality of life compared in subjects with acquired macular disease

PURPOSE: To determine the objective measures of visual function that are most relevant to subjective quality of vision and perceived reading ability in patients with acquired macular disease. METHODS: Twenty-eight patients with macular disease underwent a comprehensive assessment of visual function. The patients also completed a vision-related quality-of-life questionnaire that included a section of general questions about perceived visual performance and a section with specific questions on reading. RESULTS: Results of all tests of vision correlated highly with reported vision-related quality-of-life impairment. Low-contrast tests explained most of the variance in self-reported problems with reading. Text-reading speed correlated highly with overall concern about vision. CONCLUSIONS: Reading performance is strongly associated with vision-related quality of life. High-contrast distance acuity is not the only relevant measure of visual function in relation to the perceived visual performance of a patient with macular disease. The results suggest the importance of print contrast, even over print size, in reading performance in patients with acquired macular disease.

Correlates of spontaneous reporting of adverse drug reactions within primary care: the paradox of low prescribers who are high reporters

AIM(S) To examine Primary Care Trust (PCT) demographics influencing general practitioner (GP) involvement in pharmacovigilance. METHODS PCT adverse drug reaction (ADR) reports to the Yellow Card scheme between April 2004 and March 2006 were obtained for the UK West Midlands region. Reports were analysed by all drugs, and most commonly reported drugs (‘top drugs’). PCT data, adjusted for population size, were aggregated. Prescribing statistics and other characteristics were obtained for each PCT, and associations between these characteristics and ADR reporting rates were examined. RESULTS During 2004–06, 1175 reports were received from PCTs. Two hundred and eighty (24%) of these reports were for 14 ‘top drugs’. The mean rate of reporting for PCTs was 213 reports per million population. A total of 153 million items were prescribed during 2004–06, of which 33% were ‘top drugs’. Reports for all drugs and ‘top drugs’ were inversely correlated with the number of prescriptions issued per thousand population (rs = -0.413, 95% CI -0.673, -0.062, P < 0.05, and r = -0.420, 95% CI -0.678, -0.071, P < 0.05, respectively). Reporting was significantly negatively correlated with the percentages of male GPs within a PCT, GPs over 55 years of age, single-handed GPs within a PCT, the average list size of a GP within a PCT, the overall deprivation scores and average QOF total points. ADR reports did not correlate significantly with the proportion of the population over 65 years old. CONCLUSIONS Some PCT characteristics appear to be associated with low levels of ADR reporting. The association of low prescribing areas with high ADR reporting rates replicates previous findings.

Using interior point algorithms for the solution of linear programs with special structural features

Linear Programming (LP) is a powerful decision making tool extensively used in various economic and engineering activities. In the early stages the success of LP was mainly due to the efficiency of the simplex method. After the appearance of Karmarkar's paper, the focus of most research was shifted to the field of interior point methods. The present work is concerned with investigating and efficiently implementing the latest techniques in this field taking sparsity into account. The performance of these implementations on different classes of LP problems is reported here. The preconditional conjugate gradient method is one of the most powerful tools for the solution of the least square problem, present in every iteration of all interior point methods. The effect of using different preconditioners on a range of problems with various condition numbers is presented. Decomposition algorithms has been one of the main fields of research in linear programming over the last few years. After reviewing the latest decomposition techniques, three promising methods were chosen the implemented. Sparsity is again a consideration and suggestions have been included to allow improvements when solving problems with these methods. Finally, experimental results on randomly generated data are reported and compared with an interior point method. The efficient implementation of the decomposition methods considered in this study requires the solution of quadratic subproblems. A review of recent work on algorithms for convex quadratic was performed. The most promising algorithms are discussed and implemented taking sparsity into account. The related performance of these algorithms on randomly generated separable and non-separable problems is also reported.

Can incident reporting improve safety? Healthcare practitioners' views of the effectiveness of incident reporting

OBJECTIVE: Recent critiques of incident reporting suggest that its role in managing safety has been over emphasized. The objective of this study was to examine the perceived effectiveness of incident reporting in improving safety in mental health and acute hospital settings by asking staff about their perceptions and experiences. DESIGN: /st>Qualitative research design using documentary analysis and semi-structured interviews. SETTING: /st>Two large teaching hospitals in London; one providing acute and the other mental healthcare. PARTICIPANTS: /st>Sixty-two healthcare practitioners with experience of reporting and analysing incidents. RESULTS: /st>Incident reporting was perceived as having a positive effect on safety, not only by leading to changes in care processes but also by changing staff attitudes and knowledge. Staff discussed examples of both instrumental and conceptual uses of the knowledge generated by incident reports. There are difficulties in using incident reports to improve safety in healthcare at all stages of the incident reporting process. Differences in the risks encountered and the organizational systems developed in the two hospitals to review reported incidents could be linked to the differences we found in attitudes to incident reporting between the two hospitals. CONCLUSION: /st>Incident reporting can be a powerful tool for developing and maintaining an awareness of risks in healthcare practice. Using incident reports to improve care is challenging and the study highlighted the complexities involved and the difficulties faced by staff in learning from incident data.

Colour image coding with wavelets and matching pursuit

This thesis considers sparse approximation of still images as the basis of a lossy compression system. The Matching Pursuit (MP) algorithm is presented as a method particularly suited for application in lossy scalable image coding. Its multichannel extension, capable of exploiting inter-channel correlations, is found to be an efficient way to represent colour data in RGB colour space. Known problems with MP, high computational complexity of encoding and dictionary design, are tackled by finding an appropriate partitioning of an image. The idea of performing MP in the spatio-frequency domain after transform such as Discrete Wavelet Transform (DWT) is explored. The main challenge, though, is to encode the image representation obtained after MP into a bit-stream. Novel approaches for encoding the atomic decomposition of a signal and colour amplitudes quantisation are proposed and evaluated. The image codec that has been built is capable of competing with scalable coders such as JPEG 2000 and SPIHT in terms of compression ratio.

General and multiplicative non-parametric corporate performance models with interval ratio data

The increasing intensity of global competition has led organizations to utilize various types of performance measurement tools for improving the quality of their products and services. Data envelopment analysis (DEA) is a methodology for evaluating and measuring the relative efficiencies of a set of decision making units (DMUs) that use multiple inputs to produce multiple outputs. All the data in the conventional DEA with input and/or output ratios assumes the form of crisp numbers. However, the observed values of data in real-world problems are sometimes expressed as interval ratios. In this paper, we propose two new models: general and multiplicative non-parametric ratio models for DEA problems with interval data. The contributions of this paper are fourfold: (1) we consider input and output data expressed as interval ratios in DEA; (2) we address the gap in DEA literature for problems not suitable or difficult to model with crisp values; (3) we propose two new DEA models for evaluating the relative efficiencies of DMUs with interval ratios, and (4) we present a case study involving 20 banks with three interval ratios to demonstrate the applicability and efficacy of the proposed models where the traditional indicators are mostly financial ratios. © 2011 Elsevier Inc.

Adherence to antiepileptic medicines in children:a multiple-methods assessment involving dried blood spot sampling

Purpose - To evaluate adherence to prescribed antiepileptic drugs (AEDs) in children with epilepsy using a combination of adherence-assessment methods. Methods - A total of 100 children with epilepsy (≤17 years old) were recruited. Medication adherence was determined via parental and child self-reporting (≥9 years old), medication refill data from general practitioner (GP) prescribing records, and via AED concentrations in dried blood spot (DBS) samples obtained from children at the clinic and via self- or parental-led sampling in children's own homes. The latter were assessed using population pharmacokinetic modeling. Patients were deemed nonadherent if any of these measures were indicative of nonadherence with the prescribed treatment. In addition, beliefs about medicines, parental confidence in seizure management, and the presence of depressed mood in parents were evaluated to examine their association with nonadherence in the participating children. Key Findings - The overall rate of nonadherence in children with epilepsy was 33%. Logistic regression analysis indicated that children with generalized epilepsy (vs. focal epilepsy) were more likely (odds ratio [OR] 4.7, 95% confidence interval [CI] 1.37–15.81) to be classified as nonadherent as were children whose parents have depressed mood (OR 3.6, 95% CI 1.16–11.41). Significance - This is the first study to apply the novel methodology of determining adherence via AED concentrations in clinic and home DBS samples. The present findings show that the latter, with further development, could be a useful approach to adherence assessment when combined with other measures including parent and child self-reporting. Seizure type and parental depressed mood were strongly predictive of nonadherence.

Body representation alterations in personal but not in extrapersonal neglect patients

There is still a matter of debate around the nature of personal neglect. Is it an attention disorder or a body representation disorder? Here we investigate the presence of body representation deficits (i.e., the visuo-spatial body map) in right and left brain-damaged patients and in particular in those affected by personal neglect. 23 unilateral brain-damaged patients (5 left-brain-damaged and 18 right-brain-damaged patients) and 15 healthy controls took part in the study. The visuo-spatial body map was assessed by means of the “Frontal body-evocation subtest (FBE),” in which participants have to put tiles representing body parts on a small wooden board where only the head is depicted as a reference point. In order to compare performance on the FBE with performance on an inanimate object that had well-defined right and left sides, participants also performed the “Car test.” Group statistical analysis shows that the performance of patients with personal neglect is significantly worse than that of the controls and patients without personal neglect in the FBE but not in the Car test. Single case analyses of the five patients with pure personal neglect confirm the results of group analysis. Our data supports the hypothesis that personal neglect is a pervasive body representation disorder.

The emergence of integrated private reporting

Purpose - This paper aims to provide evidence to suggest that private social and environmental reporting (i.e. one-on-one meetings between institutional investors and investees on social and environmental issues) is beginning to merge with private financial reporting and that, as a result, integrated private reporting is emerging. Design/methodology/approach - In this paper, 19 FTSE100 companies and 20 UK institutional investors were interviewed to discover trends in private integrated reporting and to gauge whether private reporting is genuinely becoming integrated. The emergence of integrated private reporting through the lens of institutional logics was interpreted. The emergence of integrated private reporting as a merging of two hitherto separate and possibly rival institutional logics was framed. Findings - It was found that specialist socially responsible investment managers are starting to attend private financial reporting meetings, while mainstream fund managers are starting to attend private meetings on environmental, social and governance (ESG) issues. Further, senior company directors are becoming increasingly conversant with ESG issues. Research limitations/implications - The findings were interpreted as two possible scenarios: there is a genuine hybridisation occurring in the UK institutional investment such that integrated private reporting is emerging or the financial logic is absorbing and effectively neutralising the responsible investment logic. Practical implications - These findings provide evidence of emergent integrated private reporting which are useful to both the corporate and institutional investment communities as they plan their engagement meetings. Originality/value - No study has hitherto examined private social and environmental reporting through interview research from the perspective of emergent integrated private reporting. This is the first paper to discuss integrated reporting in the private reporting context.