Graph Treewidth and Geometric Thickness Parameters

Consider a drawing of a graph $G$ in the plane such that crossing edges are coloured differently. The minimum number of colours, taken over all drawings of $G$, is the classical graph parameter "thickness". By restricting the edges to be straight, we obtain the "geometric thickness". By further restricting the vertices to be in convex position, we obtain the "book thickness". This paper studies the relationship between these parameters and treewidth. Our first main result states that for graphs of treewidth $k$, the maximum thickness and the maximum geometric thickness both equal $\lceil{k/2}\rceil$. This says that the lower bound for thickness can be matched by an upper bound, even in the more restrictive geometric setting. Our second main result states that for graphs of treewidth $k$, the maximum book thickness equals $k$ if $k \leq 2$ and equals $k+1$ if $k \geq 3$. This refutes a conjecture of Ganley and Heath [Discrete Appl. Math. 109(3):215-221, 2001]. Analogous results are proved for outerthickness, arboricity, and star-arboricity.Comment: A preliminary version of this paper appeared in the "Proceedings of the 13th International Symposium on Graph Drawing" (GD '05), Lecture Notes in Computer Science 3843:129-140, Springer, 2006. The full version was published in Discrete & Computational Geometry 37(4):641-670, 2007. That version contained a false conjecture, which is corrected on page 26 of this versio

Evaluation of a chest radiograph reading and recording system for tuberculosis in a HIV-positive cohort.

Aim To assess the impact of introducing a chest radiograph reading and recording system (CRRS) with a short training session, on the accuracy and inter-reader variability of tuberculosis (TB) interpretation of chest radiographs (CXRs) by a group of non-expert readers in a human immunodeficiency virus (HIV)-positive cohort. Materials and methods A set of 139 CXRs was reviewed by a group of eight physicians pre- and post-intervention at two clinics in Shan State, Myanmar, providing HIV/TB diagnosis and treatment services. The results were compared against the consensus of expert radiologists for accuracy. Results Overall accuracy was similar pre- and post-intervention for most physicians with an average area under the receiver operating characteristic curve difference of 0.02 (95% confidence interval: –0.03, 0.07). The overall agreement among physicians was poor pre- and post-intervention (Fleiss κ=0.35 and κ=0.29 respectively). The assessment of agreement for specific disease patterns associated with active TB in HIV-infected patients showed that for intrinsically subtle findings, the agreement was generally poor but better for the more intrinsically obvious disease patterns: pleural effusion (Cohen’s kappa range = 0.37–0.67) and milliary nodular pattern (Cohen’s kappa range = 0.25–0.52). Conclusion This study demonstrated limited impact of the introduction of a CRRS on CXR accuracy and agreement amongst non-expert readers. The role in which CXRs are used for TB diagnosis in a HIV-positive cohort in similar clinical contexts should be reviewed

On a Tree and a Path with no Geometric Simultaneous Embedding

Two graphs $G_1=(V,E_1)$ and $G_2=(V,E_2)$ admit a geometric simultaneous embedding if there exists a set of points P and a bijection M: P -> V that induce planar straight-line embeddings both for $G_1$ and for $G_2$. While it is known that two caterpillars always admit a geometric simultaneous embedding and that two trees not always admit one, the question about a tree and a path is still open and is often regarded as the most prominent open problem in this area. We answer this question in the negative by providing a counterexample. Additionally, since the counterexample uses disjoint edge sets for the two graphs, we also negatively answer another open question, that is, whether it is possible to simultaneously embed two edge-disjoint trees. As a final result, we study the same problem when some constraints on the tree are imposed. Namely, we show that a tree of depth 2 and a path always admit a geometric simultaneous embedding. In fact, such a strong constraint is not so far from closing the gap with the instances not admitting any solution, as the tree used in our counterexample has depth 4.Comment: 42 pages, 33 figure

An alternative procedure for selecting a good value for the parameter c in RBF-interpolation

The impact of the scaling parameter c on the accuracy of interpolation schemes using radial basis functions (RBFs) has been pointed out by several authors. Rippa (Adv Comput Math 11:193-210, 1999) proposes an algorithm based on the idea of cross validation for selecting a good such parameter value. In this paper we present an alternative procedure, that can be interpreted as a refinement of Rippa's algorithm for a cost function based on the euclidean norm. We point out how this method is related to the procedure of maximum likelihood estimation, which is used for identifying covariance parameters of stochastic processes in spatial statistics. Using the same test functions as Rippa we show that our algorithm compares favorably with cross validation in many cases and discuss its limitations. Finally we present some computational aspects of our algorithm

Dietary factors impact on the association between CTSS variants and obesity related traits.

Cathepsin S, a protein coded by the CTSS gene, is implicated in adipose tissue biology--this protein enhances adipose tissue development. Our hypothesis is that common variants in CTSS play a role in body weight regulation and in the development of obesity and that these effects are influenced by dietary factors--increased by high protein, glycemic index and energy diets

Reducing Calorie Intake May Not Help You Lose Body Weight

Background Previously a meta-analysis found that multi-vitamin/mineral supplementation reduced mild psychiatric symptoms. To establish mechanisms, and to pin-point the individuals most likely to benefit, the role of various polymorphisms were examined. Supplementation was found to influence mild-psychiatric symptoms depending on the form of particular genes: genes that are risk factors for psychiatric disease and influence mechanisms by which drugs act. Methods In a double-blind trial young healthy males rated psychiatric symptoms, before and after taking vitamin/mineral supplements for three months, and the response was related to single nucleotide polymorphisms associated with catecholamines and serotonin. Outcomes With rs1800497 (Taq1A; dopamine D2 receptor), those with the CT allele benefitted from a vitamin/mineral supplement. Similarly with rs1800955 (DRD4 – dopamine D4 receptor), the mood of those with the CC allele benefitted selectively. With rs6296 (HTR1B) only those with the GC alleles responded, and with rs6311 (HTR2A) supplementation produced a beneficial response in those with the GG allele. With rs1050565 (5HTT gene - Human Serotonin Transporter gene) supplementation increased the mental health of those with the AA allele. Interpretation In a situation where a substantial proportion of patients do not benefit from drug therapy, and there is an element of trial and error when prescribing, it was proposed that future work should consider distinguishing patients depending on various polymorphisms and micro-nutrient status. In those with particular alleles, we should consider if drug administration and vitamin / mineral status interact synergistically to influence the therapeutic outcom

Assessment of scattered and leakage radiation from ultra-portable digital chest X-ray systems: An independent study

Ultraportable X-ray devices are ideal for TB screening in resource-limited settings. Unfortunately, guidelines on the radiation safety of these devices are lacking. The aim of the study was to determine the radiation dose by scattered and leakage radiation of ultraportable X-ray devices to provide a basis for these guidelines. Radiation dose measurements were performed with four ultraportable X-ray devices that meet the WHO-IAEA criteria. An anthropomorphic thorax phantom was positioned in posterior-anterior orientation in a clinically representative X-ray setup. X-ray exams were acquired with the following scan parameters: 90kV, 2.5mAs and maximum mAs, 1m and 1.8m source-to-skin distance. The entrance skin dose was measured at the center of the phantom. The scattered radiation dose was measured at 1m from the phantom as a function of scatter angle. Leakage radiation was measured at 0.5m from the X-ray tube with collimators closed and covered with additional lead. From the scatter measurements, the 'safe distance bunny' was determined, which was the minimum distance to the phantom to stay below the international dose limit to the public (1mSv per year) at a given workload. The longest distance (related to highest scatter dose) was observed behind the edges of the detector and back towards the X-ray tube, whereas the shortest distance (related to lowest scatter dose) was observed to the sides of the phantom. For the radiographer position, the total radiation dose by scattered and leakage radiation was determined in various scenarios. In most cases, the total radiation dose of ultraportable X-ray devices can be kept below 1mSv per year by employing basic radiation safety rules:1. Reduce time in the field, 2. Increase distance to the X-ray source, and 3. Use shielding measures (lead apron). Ultraportable X-ray devices can be safely used for TB screening when using adequate precautions

The relationship between conditions governing rupture and flow

RESP-201

Jahresbericht des Kunstgewerbe-Vereins zu Braunschweig: Jahrgang 1896/97

RESP-200

“It just makes me feel a little less alone” a qualitative exploration of the podcast “menopause unmuted” on women's perceptions of menopause

Objective: Menopause can negatively impact women's quality of life, with many women reporting inadequate information and support. Podcasts have grown in popularity in recent years and have been found to be accessible methods for increasing knowledge and challenging perceptions of stigmatized topics. The current research aimed to understand the impact of the podcast “menopause: unmuted” on women's menopause-related knowledge, understanding, and communication practices. Methods: A diverse sample of 30 women aged 40 to 60 years listened to the podcast series, which focused on menopause stories, before taking part in semistructured interviews to discuss the impact of the podcast on how they understood and communicated about menopause. The interviews were analyzed thematically. Results: Two overarching themes were identified in the data. A “journey of knowledge gain” explores participants’ understanding of menopause before listening to the podcast and describes how this is deepened by hearing and connecting with women's stories. “Reframing menopause” describes the impact of the podcast, where women reflect on the value of communication amongst women, challenge and re-evaluate the stigmatization of menopause, and discuss ways to make positive behavioral changes in their lives. Conclusions: The podcast “menopause: unmuted” helped women to learn about the menopause experience, have a greater sense of belonging to a community of women, and feel empowered to make changes in their own lives. Sharing stories via podcasts has potential as an accessible and impactful medium to educate women and reduce the widespread stigma associated with menopause