The Dilworth Number of Auto-Chordal-Bipartite Graphs

The mirror (or bipartite complement) mir(B) of a bipartite graph B=(X,Y,E) has the same color classes X and Y as B, and two vertices x in X and y in Y are adjacent in mir(B) if and only if xy is not in E. A bipartite graph is chordal bipartite if none of its induced subgraphs is a chordless cycle with at least six vertices. In this paper, we deal with chordal bipartite graphs whose mirror is chordal bipartite as well; we call these graphs auto-chordal bipartite graphs (ACB graphs for short). We describe the relationship to some known graph classes such as interval and strongly chordal graphs and we present several characterizations of ACB graphs. We show that ACB graphs have unbounded Dilworth number, and we characterize ACB graphs with Dilworth number k

Simulation of a multimaterial model for modified auxetic structures

Auxetic structures, which is a term used to describe materials with a negative Poisson’s ratio, show beneficial properties like a low density, a high energy absorption capacity and an increased indentation resistance. This enables applications in many fields, such as aerospace and sports industries. Given their potential, many studies have already been conducted. Previously, the geometry of a selected auxetic re-entrant structure was optimized to maximize its mass-specific energy absorption capacity for ideal usage in lightweight applications. Moreover, a homogeneous material was used, whereas the combination of multiple materials could drastically increase the performance of such structures. Hence, in this study the use of two different materials combined into a modified re-entrant structure is investigated via Finite Element simulation. The Poisson’s ratio could thus be improved, which leads toa more pronounced and longer lasting auxetic effect

Methoden der Statistik zur Analyse von Single Nucleotide Polymorphism (SNP) anhand der Auswertung von Genotypdaten aus einer neoadjuvanten Chemotherapiestudie

Background Over the last three decades, a rapid development of technologies for analyzing genetic marker has taken place. Simultaneously, a development of statistical methods to analyze the increasing data sets was going on. These developments made genome wide association studies (GWAS) possible, which genotypes a huge number of Single Nucleotide Polymorphism (SNPs) across the whole genome to analyze the associations of these variations with a disease. This study examines some methods for association of genetic factors with disease risk on the basis of a genome wide SNP data set from a neoadjuvant chemotherapy study. Two main questions are of interest: Can the occurrence of side effects during the first four cycles of neoadjuvant chemotherapy be explained by genetic differences between the patients? Furthermore: Is it possible to improve the informative value of the results by modifying the genetic data model? Methods Between November 2007 and July 2010, a total of 2.600 patients took part in the GeparQuinto study, a study for the combination of Bevacizumab, Everolimus or Lapatinib with neoadjuvant chemotherapy. Blood samples from 2.000 patients were genotyped and data sets with 693.543 SNPs were generated. After data cleaning in the sense of quality control 642.801 SNPs remained in the data sets. With a genome wide association study these SNPs were tested for an association between the occurrences of side effects during the first four treatment cycles. On the basis of these tests the top 20 SNPs with the smallest p-values were selected for a comparison of this univariate model with two multivariate models. By this means it shall be investigated if the results could be improved by extending the models to additional genetic variables. Results After correction for multiple testing no result of an association test remained significant. The comparison of the genetic models did not show any clear differences concerning the quality of the models. Conclusions In this study, the extension of the models by additional genetic variables showed no improvement of the informative value of these models. But this result cannot be generalized and is not readily transferable to other data sets. The exploration and development of methods for the analysis of genome wide data sets is still continuing. In the next few years, it will surely generate further interesting approaches.Hintergrund und Ziele In den letzten drei Jahrzehnten hat eine rasante Entwicklung der Technologien stattgefunden, mit denen genetische Merkmale untersucht werden können. Parallel dazu hat die Entwicklung statistischer Methoden, mit denen diese immer größer werdenden Datensätze analysiert werden können, ebenso stark zugenommen. Diese Entwicklungen haben auch genomweite Assoziationsstudien (GWAS) ermöglicht, die eine große Anzahl von Single Nucleotide Polymorphism (SNP) quer über das gesamte Genom genotypisieren, um die Variationen auf einen Zusammenhang mit einer Krankheit zu untersuchen. Diese Arbeit beschäftigt sich mit einigen Methoden zur Assoziation von genetischen Einflüssen auf ein Krankheitsrisiko am Beispiel eines genomweiten SNP-Datensatzes aus einer neoadjuvanten Chemotherapiestudie. Dabei stehen zwei Fragestellungen im Vordergrund: Lässt sich das Auftreten oder Ausbleiben von Nebenwirkungen während der ersten vier Zyklen neoadjuvanter Chemotherapie durch genetische Unterschiede zwischen den Patientinnen erklären? Und: Lässt sich durch bestimmte Veränderungen des genetischen Datenmodells die Aussagekraft der Ergebnisse verbessern? Material und Methoden An der GeparQuinto-Studie, einer Studie zur Kombination von Bevacizumab, Everolimus oder Lapatinib mit einer neoadjuvanten Chemotherapie, nahmen im Zeitraum von November 2007 bis Juli 2010 insgesamt 2.600 Patientinnen mit primärem Mammakarzinom teil. Blutproben von 2.000 Patientinnen wurden genotypisiert und Datensätze mit 693.543 SNPs generiert. Nach einer Datenbereinigung im Sinne von Qualitätskontrollen verblieben 642.801 SNPs im Datensatz, die im Rahmen einer genomweiten Assoziationsanalyse auf einen Zusammenhang mit dem Auftreten von Nebenwirkungen in den ersten Behandlungszyklen neoadjuvanter Chemotherapie untersucht wurden. Auf Grundlage dieser Tests wurden die 20 SNPs mit den kleinsten p-Werten ausgesucht um einen Vergleich des univariaten Modells mit zwei multivariaten Modellen anzustellen. Damit sollte untersucht werden, ob die Ergebnisse durch Erweiterung der Modelle um zusätzliche genetische Variablen verbessert werden können. Ergebnisse und Beobachtungen Nach einer Korrektur für multiples Testen ergab sich für keinen Assoziationstest ein signifikantes Ergebnis. Im Modellvergleich zeigten sich für keines der Modelle deutliche Unterschiede hinsichtlich der Güte des Modells. Praktische Schlussfolgerungen In dieser Analyse hat die Erweiterung der Modelle um zusätzliche genetische Variablen keine Verbesserung hinsichtlich der Aussagekraft bewirkt. Dieses Ergebnis lässt sich allerdings nicht so ohne weiteres verallgemeinern oder auf andere Datensätze übertragen. Die Erforschung und Entwicklung von Methoden zur Analyse von genomweiten Datensätzen geht nach wie vor weiter und wird in den nächsten Jahren sicherlich weitere interessante Ansätze hervorbringen

Kostenanalyse der Langzeittherapie bei Patienten mit chronischer und aggressiver Parodontitis in der Klinik für Zahnerhaltung und Parodontologie des Universitätsklinikums Kiel

Ziel Eine aktive und unterstützende Parodontitistherapie (APT, UPT) erlaubt einen langfristigen Zahnerhalt bei Parodontitis. Die Langzeitkosten des Zahnerhalts sowie mögliche Einflussfaktoren auf diese Kosten sind aber unzureichend untersucht. Wir analysierten die Langzeitkosten des Zahnerhalts im Rahmen der Parodontitistherapie in einer norddeutschen Universitätszahnklinik. Methoden Es wurden 325 Patienten mit chronischer/aggressiver Parodontitis (CP/AgP), die eine APT sowie UPT > 9 Jahre erhalten hatten und bei denen vollständige klinische und röntgenologische Befunde vor/nach der APT (T0/T1) sowie dem Ende der UPT (T3) vorlagen, eingeschlossen. Die Kosten für den Zahnerhalt (parodontale, restaurative, prothetische, chirurgische Behandlungen) wurden mittels Gebührenpositionen (BEMA/GOZ) aus der Zahlerperspektive quantifiziert und mit 3%/Jahr diskontiert. Der Einfluss von Patienten- und Zahnlevelvariablen auf die jährlichen Kosten wurden mittels generalisierten gemischten linearen Modellen analysiert. Ergebnisse Patienten mit CP (n=273) wiesen initial (T0) 24.3±4.5 Zähne auf und konnten über 18.7±5.7 Jahre nachverfolgt werden. Die gesamten Behandlungskosten für diesen Zeitraum beliefen sich auf 6146±2236€ je Patient (222±98€ je Zahn). Die jährlichen Behandlungskosten betrugen 348±159€ je Patient (12.4±5.7€ je Zahn). Patienten mit AgP (n=52) wiesen initial 26.5±4.0 Zähne auf und wurden über 16.9±5.4 Jahren nachverfolgt. Die gesamten Behandlungskosten betrugen 6998±3807€ je Patient (267±148€ je Zahn) beziehungsweise 536±209€ je Patient (20.1±65.0€ je Zahn) jährlich. In beiden Kohorten verursachte die Durchführung der UPT den Großteil der Kosten (CP/AgP: 92%/87%). Unabhängig der parodontalen Diagnose waren ein höheres Patientenalter und eine geringere Zahnanzahl bei T0 mit höheren Kosten assoziiert. Schlussfolgerung Die jährlichen Kosten zum Erhalt von Zähnen bei Patienten mit chronischer Parodontitis waren deutlich niedriger als mit aggressiver Verlaufsform. Insgesamt waren die Kosten aber in beiden Kohorten begrenzt

Simulation of a multimaterial model for modified auxetic structures

Auxetic structures, which is a term used to describe materials with a negative Poisson’s ratio, show beneficial properties like a low density, a high energy absorption capacity and an increased indentation resistance. This enables applications in many fields, such as aerospace and sports industries. Given their potential, many studies have already been conducted. Previously, the geometry of a selected auxetic re-entrant structure was optimized to maximize its mass-specific energy absorption capacity for ideal usage in lightweight applications. Moreover, a homogeneous material was used, whereas the combination of multiple materials could drastically increase the performance of such structures. Hence, in this study the use of two different materials combined into a modified re-entrant structure is investigated via Finite Element simulation. The Poisson’s ratio could thus be improved, which leads to a more pronounced and longer lasting auxetic effect

Changes in prognostic and therapeutic parameters in prostate cancer from an epidemiological view over 20 years

&lt;b&gt;&lt;i&gt;Background:&lt;/i&gt;&lt;/b&gt; The study objective was to examine changes in prognosis and treatment of prostate cancer patients over 20 years and to evaluate their impact on survival. &lt;b&gt;&lt;i&gt;Patients and Methods:&lt;/i&gt;&lt;/b&gt; 38,861 prostate cancer patients diagnosed between 1990 and 2010 and living in the catchment area of the Munich Cancer Registry were analysed. &lt;b&gt;&lt;i&gt;Results:&lt;/i&gt;&lt;/b&gt; Pre-therapeutic prostate-specific antigen (PSA) testing increased substantially in the early 1990s. A shift from capsule-exceeding tumours to capsule-limited tumours also took place especially in the 1990s. The proportion of radical prostatectomy increased continuously over the last 20 years from 20% to almost 50% whereas hormone therapy decreased from 55% to 18%. Radiation therapy and transurethral resection of the prostate increased slightly from about 5% to 10%. The 5- and 10-year relative survival rates increased from 92% to 97% and from 86% to 92%, respectively. &lt;b&gt;&lt;i&gt;Conclusions:&lt;/i&gt;&lt;/b&gt; 2 reasons may account for the rise in survival rates over 20 years: First, the establishment of widely used PSA testing resulted in a shift towards more favourable T categories due to the detection of many additional small tumours as well as the noticeable change in initial treatment strategy towards more radical prostatectomies. The second factor that likely increased survival was improvements in the therapies themselves.</jats:p

Pitfall trap sampling bias depends on body mass, temperature, and trap number: insights from an individual-based model

The diversity and community composition of ground arthropods is routinely analyzed by pitfall trap sampling, which is a cost- and time-effective method to gather large numbers of replicates but also known to generate data that are biased by species-specific differences in locomotory activity. Previous studies have looked at factors that influence the sampling bias. These studies, however, were limited to one or few species and did rarely quantify how the species-specific sampling bias shapes community-level diversity metrics. In this study, we systematically quantify the species-specific and community-level sampling bias with an allometric individual-based model that simulates movement and pitfall sampling of 10 generic ground arthropod species differing in body mass. We perform multiple simulation experiments covering different scenarios of pitfall trap number, spatial trap arrangement, temperature, and population density. We show that the sampling bias decreased strongly with increasing body mass, temperature, and pitfall trap number, while population density had no effect and trap arrangement only had little effect. The average movement speed of a species in the field integrates body mass and temperature effects and could be used to derive reliable estimates of absolute species abundance. We demonstrate how unbiased relative species abundance can be derived using correction factors that need only information on species body mass. We find that community-level diversity metrics are sensitive to the particular community structure, namely the relation between body mass and relative abundance across species. Generally, pitfall trap sampling flattens the rank-abundance distribution and leads to overestimations of ground arthropod Shannon diversity. We conclude that the correction of the species-specific pitfall trap sampling bias is necessary for the reliability of conclusions drawn from ground arthropod field studies. We propose bias correction is a manageable task using either body mass to derive unbiased relative abundance or the average speed to derive reliable estimates of absolute abundance from pitfall trap sampling

Influence of motivation and a new digitized training program on undergraduate dental students during preclinical scaling training

Background The current study evaluated whether a new digitized scaling training program (DTP: n = 30; supervisor-student-ratio 1:10) improves the performance of undergraduate dental student during a preclinical course in regard to two different instruments [sonic scalers (AIR) and Gracey curettes (GRA)] compared to a conventional training program (CTP: n = 19; supervisor-student-ratio 1:4). Methods All the participants received a two-hour lecture on both instruments, followed by a 12-week period with a weekly training program lasting 45 min (10 sessions); one group was supported by DTP. At the end of the training phase, all the participants performed the subgingival scaling of six equivalent test teeth using GRA and AIR. Treatment time, proportion of removed simulated biofilm (relative cleaning efficacy, RCE-b) and hard deposits (RCE-d) were recorded. By using a pseudonymized questionnaire with a 5-point Likert scale, self-assessment of scaling effort, handling, root surface roughness/destruction and effectiveness were evaluated. In addition, personal data such as age, gender, handedness, regularity of playing computer games/consoles and previous dental/technical or medical education were elevated and correlated with cleaning efficacy. Results The DTP participants showed higher effectiveness in RCE-b compared to those who used the CTP with GRA (71.54% vs. 67.23%, p = 0.004) and AIR (71.75% vs. 62.63%, p ≤ 0.001), and the DTP students were faster with both instruments (p ≤ 0.001). For RCE-d, there was no significant difference between the DTP and CTP groups (GRA p = 0.471; AIR p = 0.158), whereas DTP showed better RCE-d results with GRA versus AIR (84.68% vs. 77.85%, p < 0.001). According to the questionnaire, no significant differences were detected between the training groups in terms of self-assessment, handling, treatment time, root surface roughness/destruction or effectiveness of the instruments. The CTP group favored AIR compared to GRA regarding the fatigue effect. The CTP and playing computer games/consoles regularly was correlated with lower RCE-b, whereas previous education in medicine/dentistry was correlated with higher RCE-b values. Conclusions Within the limitations of the study, the DTP with a reduced supervision effort compared to the CTP resulted in higher effectiveness and lower instrumentation time for removing simulated biofilms

Measuring carer outcomes in an economic evaluation: A content comparison of the Adult Social Care Outcomes Toolkit for Carers, Carer Experience Scale and Care-related Quality of Life using exploratory factor analysis

Background. To incorporate the spillover effects experienced by carers providing informal care in health policy decisions, new carer-related preference-based measures have been developed for use in economic evaluation, which include the Adult Social Care Outcomes Toolkit for Carers (ASCOT-Carer), Carer Experience Scale (CES), and Care-Related Quality of Life (CarerQoL). The aim of this study was to investigate the extent to which these 3 instruments measure complementary or overlapping constructs. Methods. Data were derived from an online survey undertaken with carers residing in Australia. An exploratory factor analysis was conducted to ascertain the underlying latent constructs of the 3 measures. Results. Data from 351 informal carers yielded a 5-factor model describing general quality of life outside caring, problems due to caring, fulfilment from caring, social support with caring, and relationship with the care recipient. Most of the ASCOT-Carer and the CarerQol items loaded onto the first and second factors, respectively. The greatest overlap was observed between CarerQol and CES items loading onto the other 3 shared common factors. Limitations. Online data collection resulted in inconsistent responses, which had to be removed to yield logical data. A convenience sampling approach may have compromised the generalizability of study findings. Conclusion. Although some overlap was observed, the 3 carer-related preference-based measures seem to tap into different constructs of carer-related quality of life and caring experiences and cannot be used interchangeably