Adaptive Evolutionary Clustering

In many practical applications of clustering, the objects to be clustered evolve over time, and a clustering result is desired at each time step. In such applications, evolutionary clustering typically outperforms traditional static clustering by producing clustering results that reflect long-term trends while being robust to short-term variations. Several evolutionary clustering algorithms have recently been proposed, often by adding a temporal smoothness penalty to the cost function of a static clustering method. In this paper, we introduce a different approach to evolutionary clustering by accurately tracking the time-varying proximities between objects followed by static clustering. We present an evolutionary clustering framework that adaptively estimates the optimal smoothing parameter using shrinkage estimation, a statistical approach that improves a naive estimate using additional information. The proposed framework can be used to extend a variety of static clustering algorithms, including hierarchical, k-means, and spectral clustering, into evolutionary clustering algorithms. Experiments on synthetic and real data sets indicate that the proposed framework outperforms static clustering and existing evolutionary clustering algorithms in many scenarios.Comment: To appear in Data Mining and Knowledge Discovery, MATLAB toolbox available at http://tbayes.eecs.umich.edu/xukevin/affec

Photoelastic evaluation of fiber surface-treatments on the interfacial performance of a polyester fiber/epoxy model composite

The interfacial adhesion between a polyester fiber and an epoxy matrix was improved by chemical and topological modifications of the fiber surface. The maximum interfacial shear strength was measured using photoelasticity to assess the interfacial performance in pull-out single-fiber composite specimens. An increase of the interfacial shear strength was observed when plasma-treated or surface-modified fibers were used: also, as the applied load to the free fiber was increased, the fiber treatment caused a reduction of the debonded area at the fiber-matrix interface. (C) 2011 Elsevier Ltd. All rights reserved

A Regularized Graph Layout Framework for Dynamic Network Visualization

Many real-world networks, including social and information networks, are dynamic structures that evolve over time. Such dynamic networks are typically visualized using a sequence of static graph layouts. In addition to providing a visual representation of the network structure at each time step, the sequence should preserve the mental map between layouts of consecutive time steps to allow a human to interpret the temporal evolution of the network. In this paper, we propose a framework for dynamic network visualization in the on-line setting where only present and past graph snapshots are available to create the present layout. The proposed framework creates regularized graph layouts by augmenting the cost function of a static graph layout algorithm with a grouping penalty, which discourages nodes from deviating too far from other nodes belonging to the same group, and a temporal penalty, which discourages large node movements between consecutive time steps. The penalties increase the stability of the layout sequence, thus preserving the mental map. We introduce two dynamic layout algorithms within the proposed framework, namely dynamic multidimensional scaling (DMDS) and dynamic graph Laplacian layout (DGLL). We apply these algorithms on several data sets to illustrate the importance of both grouping and temporal regularization for producing interpretable visualizations of dynamic networks.Comment: To appear in Data Mining and Knowledge Discovery, supporting material (animations and MATLAB toolbox) available at http://tbayes.eecs.umich.edu/xukevin/visualization_dmkd_201

Sexually transmitted infections, including HIV, in the Netherlands in 2013

Het aantal mensen dat zich bij een Centrum Seksuele Gezondheid heeft laten testen op een seksueel overdraagbare aandoening (soa) is verder gestegen in 2013. Het percentage mensen met een soa is voor het eerst licht gedaald (met 0,4 procent) sinds 2007. Desondanks blijft dit percentage hoog (14,7 procent). Een goed functionerende soa-monitoring blijft daarom essentieel om zicht te houden op relevante trends, opkomende soa binnen groepen die een grotere kans hebben er een op te lopen, en de effectiviteit van preventieprogramma's. De Centra Seksuele Gezondheid (CSG), voorheen soa-poli's, bieden hoogrisicogroepen de mogelijkheid om zich gratis te laten testen op soa en verstrekken medicatie als er een wordt vastgesteld. Het totaal aantal consulten in 2013 bedroeg 133.585 en is met 10 procent toegenomen ten opzichte van 2012. Van alle bezoekers werden de meeste soa gediagnosticeerd bij mensen die ervoor gewaarschuwd waren dat ze mogelijk een soa hadden opgelopen, mensen jonger dan 25 jaar, migranten uit gebieden waar soa en hiv veel voorkomen (bijvoorbeeld Afrika, Zuid-Amerika of Oost-Europa), of mannen die seks hebben met mannen (MSM). Chlamydia Net als in voorgaande jaren was chlamydia de meest gediagnosticeerde soa bij de CSG in 2013 (15.767 diagnoses). Het percentage mensen dat chlamydia had, daalde licht ten opzichte van 2012 (van 12,2 naar 11,8 procent). Chlamydia werd het meest vastgesteld bij heteroseksuelen, zowel mannen als vrouwen, onder de 25 jaar. Na de uitschieter in 2012 van het aantal en percentage mensen met een agressieve variant van chlamydia, lymphogranuloma venereum, zijn deze cijfers weer afgenomen naar het niveau van de jaren daarvoor (7 procent in 2013). Gonorroe Het percentage personen met een gonorroe-infectie bij de CSG bleef in 2013 stabiel ten opzichte van 2012 (3,6 procent in 2012 en 3,4 procent in 2013), nadat het in de voorgaande jaren licht was gestegen. Deze soa werd het meest gediagnosticeerd bij MSM. Het blijft belangrijk om te volgen of de gonorroe-bacterie resistent raakt tegen de antibiotica die in Nederland voorgeschreven worden, de zogenoemde derde generatie cefalosporines. In diverse Europese landen is deze resistentie waargenomen. Hiv Het aantal personen met een hiv-infectie, gediagnosticeerd bij een van de CSG, is in 2013 gelijk gebleven ten opzichte van 2012 (358 versus 356 in 2012). Het percentage positieve testen daalt sinds 2008: van 3,0 procent naar 1,4 procent bij MSM in 2013. Het percentage mensen dat in een laat stadium van een hiv-infectie bij een hiv-behandelcentrum komt, is de afgelopen jaren gedaald. Het is van belang om tijdig de hiv-diagnose te stellen en zo snel mogelijk de behandeling te starten, omdat hierdoor de gezondheidsschade bij de patiënt verkleind kan worden. Ook neemt door behandeling de besmettelijkheid af, waardoor de kans kleiner is dat hiv wordt overgedragen.In 2013, more people were tested for sexually transmitted infections (STI) at Dutch STI clinics than in previous years. Although the percentage of people with an STI showed a slight decrease (0.4 per cent) for the first time since 2007, it remained high at 14.7 per cent. Effective STI monitoring remains essential for the identification of relevant trends, emerging STIs in high-risk groups, and the effectiveness of prevention programmes. STI clinics offer high-risk groups access to free testing for STI and provide care and treatment if an STI is diagnosed. The total number of consultations in 2013 was 133,585, an increase of 10% compared with 2012. In 2013, STI clinic attendees with an STI were mainly people who reported having been notified of their possible exposure to STI, people aged 20-24, people originating from areas in which STI/HIV is common (e.g. Africa, South America or Eastern Europe), and men who have sex with men (MSM). Chlamydia With 15,767 cases, chlamydia remains the most commonly diagnosed STI in 2013. The percentage of people diagnosed with chlamydia was slightly lower in 2013 than in 2012 (11.8 versus 12.2 respectively). Chlamydia was primarily diagnosed in heterosexuals younger than 25 years old and in both men and women. Following the increase in the number and percentage of lymphogranuloma venereum (LGV; an aggressive variant of chlamydia) infections in 2012, these numbers declined to a level comparable to previous years in 2013. Gonorrhoea Whereas the percentage of people with a gonorrhoea infection slightly had increased in previous years, the percentage remained stable in 2013 (3.4 per cent) compared with 2012 (3.6 per cent). Gonorrhoea was mostly diagnosed in MSM. It remains important to monitor the resistance of the gonorrhoea bacteria against the antibiotic currently recommended in the Netherlands, a third-generation cephalosporin. A rising rate of resistance to this antibiotic has been observed in several European countries. HIVThe number of people diagnosed with HIV at STI clinics in 2013 was similar to that of 2012 (358 versus 356 respectively). Among MSM, the percentage of positive HIV tests decreased from 3.0 per cent in 2008 to 1.4 per cent in 2013. The percentage of HIV-positive people who were diagnosed at a late stage of the infection has decreased in previous years. Early diagnosis and treatment of an HIV infection is important because of individual health benefits and the potential reduction of HIV transmission

The dimensional structure of the functional abilities in cases of long-term sickness absence

<p>Abstract</p> <p>Background</p> <p>The health problems that working people suffer can affect their functional abilities and, consequently, can cause a mismatch between those abilities and the demands of the work, leading to sickness absence. A lasting decrease in functional abilities can lead to long-term sickness absence and work disability, with negative consequences for both the worker and the larger society. The objective of this study was to identify common disability characteristics among large groups of long-term sick-listed and disabled employees.</p> <p>Methods</p> <p>As part of the disability benefit entitlement procedure in the Netherlands, an insurance physician assesses the functional abilities of the claimant in a standardised form, known as the List of Functional Abilities (LFA), which consists of six sections containing a total of 106 items. For the purposes of this study, we compiled data from 50,931 assessments. These data were used in an exploratory factor analyses, and the results were then used to construct scales. The stability of dimensional structure of the LFA and of the internal consistency of the scales was studied using data from 80,968 assessments carried out earlier, under a slightly different legislation.</p> <p>Results</p> <p>Three separate factor analyses carried out on the functional abilities of five sections of the LFA resulted in 14 scale variables, and one extra scale variable was based on the items from the sixth section. The resulting scale variables showed Cronbach's Alphas ranging from 0.59 to 0.97, with the exception of one of 0.54. The dimensional structure of the LFA in the verification population differed in some aspects. The Cronbach's Alphas of the verification population ranged from 0.58 to 0.97, again with the exception of the same scale: Alpha = 0.49.</p> <p>Conclusion</p> <p>The differences between the dimensional structures of the primary data and the earlier data we found in this study restrict the possibilities to generalise the results. The scales we constructed can be utilised to produce a compact description of the functional abilities of groups of claimants in the Netherlands. Moreover, the matching work demands can be used to identify jobs low on those demands as being the most accessible for the specific type of disabled employees, particularly severely disabled individuals.</p

Optimal cut-off criteria for duplex ultrasound for the diagnosis of restenosis in stented carotid arteries: Review and protocol for a diagnostic study

Background: Carotid angioplasty with stenting is a relatively new, increasingly used, less-invasive treatment for the treatment of symptomatic carotid artery stenosis. It is being evaluated in ongoing and nearly finished randomized trials. An important factor in the evaluation of stents is the occurrence of in-stent restenosis. An un-stented carotid artery is likely to have a more elastic vessel wall than a stented one, even if stenosis is present. Therefore, duplex ultrasound cut-off criteria for the degrees of an in-stent stenosis, based on blood velocity parameters, are probably different from the established cut-offs used for un-stented arteries. Routine criteria can not be applied to stented arteries but new criteria need to be established for this particular purpose. Methods/Design: Current literature was systematically reviewed. From the selected studies, the following data were extracted: publication year, population size, whether the study was prospective, which reference test was used, and if there was an indication for selection bias and for verification bias in particular. Previous studies often were retrospective, or the reference test (DSA or CTA) was carried out only when a patient was suspected of having restenosis at DUS, which may result in verification bias. Results: In general, the cut-off values are higher than those reported for unstented arteries. Previous studies often were retrospective, or the reference test (DSA or CTA) was carried out only when a patient was suspected of having restenosis at DUS, which may result in verification bias. Discussion: To address the deficiencies of the existing studies, we propose a prospective cohort study nested within the International Carotid Stenting Study (ICSS), an international multi-centre trial in which over 1,700 patients have been randomised between stenting and CEA. In this cohort we will enrol a minimum of 300 patients treated with a stent. All patients undergo regular DUS examination at the yearly follow-up visit according to the ICSS protocol. To avoid verification bias, an additional computed tomography angiography (CTA) will be performed as a reference test in all consecutive patients, regardless of the degree of stenosis on the initial DUS test

Workplace-based assessment: effects of rater expertise

Traditional psychometric approaches towards assessment tend to focus exclusively on quantitative properties of assessment outcomes. This may limit more meaningful educational approaches towards workplace-based assessment (WBA). Cognition-based models of WBA argue that assessment outcomes are determined by cognitive processes by raters which are very similar to reasoning, judgment and decision making in professional domains such as medicine. The present study explores cognitive processes that underlie judgment and decision making by raters when observing performance in the clinical workplace. It specifically focuses on how differences in rating experience influence information processing by raters. Verbal protocol analysis was used to investigate how experienced and non-experienced raters select and use observational data to arrive at judgments and decisions about trainees’ performance in the clinical workplace. Differences between experienced and non-experienced raters were assessed with respect to time spent on information analysis and representation of trainee performance; performance scores; and information processing––using qualitative-based quantitative analysis of verbal data. Results showed expert-novice differences in time needed for representation of trainee performance, depending on complexity of the rating task. Experts paid more attention to situation-specific cues in the assessment context and they generated (significantly) more interpretations and fewer literal descriptions of observed behaviors. There were no significant differences in rating scores. Overall, our findings seemed to be consistent with other findings on expertise research, supporting theories underlying cognition-based models of assessment in the clinical workplace. Implications for WBA are discussed

Global institutions and local filtering: Introducing independent directors to Taiwanese corporate boards

Drawing on the idea of selective interaction between organizations and environments, the authors examine how organizations change their traditional practices when they are exposed to new institutional environments. In the context of corporate governance change in response to financial market globalization, they argue that global institutional influence is moderated by local corporate control contexts that function as filtering mechanisms. The authors empirically analyse the adoption of a new corporate governance practice, i.e., the initial introduction of independent directors, in Taiwanese public firms, where family governance has been a dominant governance model. The findings suggest that while firms exposed to US capital markets are more likely to adopt independent directors, this facilitating effect weakens when the firms are under strong family control and is amplified when they are unbound from local frameworks through the key leader???s education or their geographic context