Simultaneous Representation of Proper and Unit Interval Graphs

In a confluence of combinatorics and geometry, simultaneous representations provide a way to realize combinatorial objects that share common structure. A standard case in the study of simultaneous representations is the sunflower case where all objects share the same common structure. While the recognition problem for general simultaneous interval graphs - the simultaneous version of arguably one of the most well-studied graph classes - is NP-complete, the complexity of the sunflower case for three or more simultaneous interval graphs is currently open. In this work we settle this question for proper interval graphs. We give an algorithm to recognize simultaneous proper interval graphs in linear time in the sunflower case where we allow any number of simultaneous graphs. Simultaneous unit interval graphs are much more "rigid" and therefore have less freedom in their representation. We show they can be recognized in time O(|V|*|E|) for any number of simultaneous graphs in the sunflower case where G=(V,E) is the union of the simultaneous graphs. We further show that both recognition problems are in general NP-complete if the number of simultaneous graphs is not fixed. The restriction to the sunflower case is in this sense necessary

Perspectives on Gene-Environment Interplay in Psychiatry

Sir Michael Rutter began the symposium with a broad overview of gene-environment interplay.
He described the goals of studying such interactions and pointed to the inherent challenges. He concluded by stressing the need for a variety of strategies for research. 

To watch Sir Rutter’s presentation, please see the Panel 1 "Google Video posting.":http://video.google.com/videoplay?docid=-3097337289947323438&hl=en Panel 1 also features welcoming remarks by Dr. Mildred Cho and Professor Hank Greely, both of Stanford University. 
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Many-to-One Boundary Labeling with Backbones

In this paper we study \emph{many-to-one boundary labeling with backbone leaders}. In this new many-to-one model, a horizontal backbone reaches out of each label into the feature-enclosing rectangle. Feature points that need to be connected to this label are linked via vertical line segments to the backbone. We present dynamic programming algorithms for label number and total leader length minimization of crossing-free backbone labelings. When crossings are allowed, we aim to obtain solutions with the minimum number of crossings. This can be achieved efficiently in the case of fixed label order, however, in the case of flexible label order we show that minimizing the number of leader crossings is NP-hard.Comment: 23 pages, 10 figures, this is the full version of a paper that is about to appear in GD'1

Experimental calibration of hornblende as a proposed emprical geobarometer

The recent Eos report by Anderson [1987] reviewed prospects for using dated granitoid plutons as crustal nails in the reconstruction of descent or ascent of deformed crust during orogenic processes, if suitable geobarometers could be established. Hammarstrom and Zen [1986] and Hollister et al [1987] have proposed an empirical geobarometer for calcalkaline plutonic rocks of tonalite and granodiorite composition based on the total Al content (Air) of calcic hornblendes. This proposition has generated considerable interest

Medullary thyroid cancer in a 9-week-old infant with familial MEN 2B: Implications for timing of prophylactic thyroidectomy

BACKGROUND: Patients with Multiple Endocrine Neoplasia type 2 (MEN 2) are at high risk of developing aggressive medullary thyroid carcinoma (MTC) in childhood, with the highest risk in those with MEN type 2B (of whom >95% have an M918T RET proto-oncogene mutation). Metastatic MTC has been reported as young as 3 months of age. Current guidelines recommend prophylactic thyroidectomy within the first year of life for MEN 2B. PATIENT FINDINGS: We report a 9-week-old infant with MTC due to familial MEN 2B. A full-term male infant, born to a mother with known MEN 2B and metastatic MTC, had an M918T RET proto-oncogene mutation confirmed at 4 weeks of age. He underwent prophylactic total thyroidectomy at 9 weeks of age. Pathology showed a focal calcitonin-positive nodule (2.5 mm), consistent with microscopic MTC. SUMMARY: This case highlights the importance of early prophylactic thyroidectomy in MEN 2B. Although current guidelines recommend surgery up to a year of life, MTC may occur in the first few weeks of life, raising the question of how early we should intervene. In this report, we discuss the risks, benefits and barriers to performing earlier thyroidectomy, soon after the first month of life, and make suggestions to facilitate timely intervention. Prenatal anticipatory surgical scheduling could be considered in familial MEN 2B. Multidisciplinary collaboration between adult and pediatric specialists is key to the optimal management of the infant at risk

Evaluation of Amino Acid Composition as a Geochronometer in Buried Soils on Mount Kenya, East Africa

A sequence of surface and buried paleosols from the slopes of Mount Kenya, East Africa, has been identified and dated by radiocarbon and amino acid dating techniques in order to elucidate the Quaternary history of the area. Buried paleosols vary in radiocarbon age from 900 to > 40,000 yrs BP. They have developed in glacial and periglacial deposits of variable texture, consisting of a high percentage of clasts of phonolite, basalt and syenite. All but two paleosols are located in the Afroalpine zone (above 3200 m). D/L ratios of amino acids in Ab horizons were determined in order to establish their reliability for relative age dating. Alanine, aspartic acid, glutamic acid, leucine, valine, and phenylalanine were routinely analyzed. Aspartic acid, as in other cases, proved reliable yielding remarkably consistent results, with higher ratios corresponding to increasing age. Other acids analyzed showed distinct trends, although not as convincing as aspartic acid. In most cases, the aspartic acid ratio/ age relationships were supported by radiocarbon dates. D/L ratios of aspartic acid varied from approximately 0.07 for modern samples, to approximately 0.45 in samples > 40,000 years old.On a identifié et daté, au radiocarbone et à l'aide de techniques de datations à l'acide aminé, des paléosols enfouis et de surface afin de comprendre l'évolution quaternaire de la région. Les datations au radiocarbone des paléosols enfouis varient de 900 à plus de 40 000 BP. Les sols se sont développés dans des dépôts glaciaires et périglaciaires de différentes textures, constitués de fragments de roches détritiques, de phonolite, de basalte et de syénite. Tous les paléosols, sauf deux, sont situés dans la zone afroalpine (au-dessus de 3200 m). On a déterminé par racémisation les rapports D/L des acides aminés dans les horizons Ab en vue d'évaluer leur fiabilité pour la datation des âges relatifs. On a fait l'analyse de l'alaline, de l'acide aspartique, de l'acide glutamique, de la leucine, de la valine et du phénylalaline. L'acide aspartique, comme dans d'autres cas, a donné des résultats particulièrement satisfaisants, les quotients plus élevés correspondant aux âges les plus anciens. D'autres acides montraient des tendances bien distinctes, mais moins convaincantes que dans le cas de l'acide aspartique. Ainsi, dans la plupart des cas, les relations quotients/âges de l'acide aspartique étaient corroborées par les datations au radiocarbone. Les rapports D/L de l'acide aspartique variaient d'environ 0,07 pour les échantillons modernes à environ 0,45 pour les échantillons de plus de 40 000 ans.Eine Série von an der Oberflâche Negenden und begrabenen Palàobôden von den Hàngen des Mount Kenya, Ost-Afrika, wurde mittels Radiokarbon- und Aminosâuredatierungs-techniken identifiziert und datiert, um die Geschichte dieses Gebiets im Quaternàr zu erhellen. Das durch Radiokarbon bestimmte Alter der begrabenen Palàobôden variiert von 900 bis > 40,000 Jahren v.u.Z. Dièse Bôden haben sich in glazialen und periglazialen Ablagerungen verschiedener Beschaffenheit entwickelt, welche zu einem hohen Prozentsatz aus Trùmmern von Phonolith, Basait und Syenit bestehen. AuBer zweien befinden sich aile Palàobôden in der afroalpinen Zone (oberhalb 3200 m). Die D/L Anteile der Aminosâuren in den Ab-Horizonten wurden bestimmt, um ihre Verlâpiichkeit bei der relativen Altersbestimmung festzustellen. Alamin, aspartische Sàure, Glutamin-Sàure, Leuzin, Valin und Phenylalanin wurden laufend analysiert. Wie in anderen Fallen erwies sich die aspartische Sàure als verlàpiich, indem sie bemerkenswert bestàndige Ergebnisse ergab, bei denen die hôheren Quotienten dem hôheren Alter entsprachen. Andere analysierte Sàuren zeigten ausgepràgte Trends, wenn auch nicht so ùberzeugend wie die aspartische Sàure. In den meisten Fallen wurden die Beziehungen Quotient/Alter der aspartischen Sàure durch Radiokarbondatierungen gestùtzt. Die D/L Anteile der aspartischen Sàure variierten von ungefâhr 0.07 fur moderne Proben bis ungefâhr 0.45 in Proben, die > 40,000 Jahre ait sind

Heritability of autism spectrum disorders:A meta-analysis of twin studies

BACKGROUND: The etiology of Autism Spectrum Disorder (ASD) has been recently debated due to emerging findings on the importance of shared environmental influences. However, two recent twin studies do not support this and instead re‐affirm strong genetic effects on the liability to ASD, a finding consistent with previous reports. This study conducts a systematic review and meta‐analysis of all twin studies of ASD published to date and explores the etiology along the continuum of a quantitative measure of ASD. METHODS: A PubMed Central, Science Direct, Google Scholar, Web of Knowledge structured search conducted online, to identify all twin studies on ASD published to date. Thirteen primary twin studies were identified, seven were included in the meta‐analysis by meeting Systematic Recruitment criterion; correction for selection and ascertainment strategies, and applied prevalences were assessed for these studies. In addition, a quantile DF extremes analysis was carried out on Childhood Autism Spectrum Test scores measured in a population sample of 6,413 twin pairs including affected twins. RESULTS: The meta‐analysis correlations for monozygotic twins (MZ) were almost perfect at .98 (95% Confidence Interval, .96–.99). The dizygotic (DZ) correlation, however, was .53 (95% CI .44–.60) when ASD prevalence rate was set at 5% (in line with the Broad Phenotype of ASD) and increased to .67 (95% CI .61–.72) when applying a prevalence rate of 1%. The meta‐analytic heritability estimates were substantial: 64–91%. Shared environmental effects became significant as the prevalence rate decreased from 5–1%: 07–35%. The DF analyses show that for the most part, there is no departure from linearity in heritability. CONCLUSIONS: We demonstrate that: (a) ASD is due to strong genetic effects; (b) shared environmental effects become significant as a function of lower prevalence rate; (c) previously reported significant shared environmental influences are likely a statistical artefact of overinclusion of concordant DZ twins