Even Orientations and Pfaffian graphs

We give a characterization of Pfaffian graphs in terms of even orientations, extending the characterization of near bipartite non--pfaffian graphs by Fischer and Little \cite{FL}. Our graph theoretical characterization is equivalent to the one proved by Little in \cite{L73} (cf. \cite{LR}) using linear algebra arguments

An Explanation of the Very Low Radio Flux of Young Planet-mass Companions

We report Atacama Large Millimeter/submillimeter Array (ALMA) 1.3 mm continuum upper limits for 5 planetary-mass companions DH Tau B, CT Cha B, GSC 6214-210 B, 1RXS 1609 B, and GQ Lup B. Our survey, together with other ALMA studies, have yielded null results for disks around young planet-mass companions and placed stringent dust mass upper limits, typically less than 0.1 M_earth, when assuming dust continuum is optically thin. Such low-mass gas/dust content can lead to a disk lifetime estimate (from accretion rates) much shorter than the age of the system. To alleviate this timescale discrepancy, we suggest that disks around wide companions might be very compact and optically thick, in order to sustain a few Myr of accretion yet have very weak (sub)millimeter flux so as to still be elusive to ALMA. Our order-of-magnitude estimate shows that compact optically-thick disks might be smaller than 1000 R_jup and only emit ~micro-Jy of flux in the (sub)millimeter, but their average temperature can be higher than that of circumstellar disks. The high disk temperature could impede satellite formation, but it also suggests that mid- to far-infrared might be more favorable than radio wavelengths to characterize disk properties. Finally, the compact disk size might imply that dynamical encounters between the companion and the star, or any other scatterers in the system, play a role in the formation of planetary-mass companions.Comment: Accepted for publication in A

Even Orientations of Graphs: Part I

A graph G is 1-extendable if every edge belongs to at least one 1-factor. Let G be a graph with a 1-factor F. Then an even F-orientation of G is an orientation in which each F-alternating cycle has exactly an even number of edges directed in the same fixed direction around the cycle. In this paper, we examine the structure of 1-extendible graphs G which have no even F-orientation where F is a fixed 1-factor of G. In the case of cubic graphs we give a characterization. In a companion paper [M. Abreu, D. Labbate and J. Sheehan. Even orientations of graphs: Part II], we complete this characterization in the case of regular graphs, graphs of connectivity at least four and k--regular graphs for $k\ge3$. Moreover, we will point out a relationship between our results on even orientations and Pfaffian graphs developed in [M. Abreu, D. Labbate and J. Sheehan. Even orientations and Pfaffian graphs].Comment: 40 pages, 2 figure

A descriptive study of the burden of animal-related trauma at Cork University Hospital

Farming is the most dangerous occupation in Ireland1 and the incidence of farm accidents is rising. This study examines major farm animal-related trauma treated at Cork University Hospital over a 5 year period. There were 54 patients admitted to Cork University Hospital (C.U.H.) with major farm animal-related trauma. The median age was 56 years, 85% were male and the median hospital length of stay was four days. Older patients had longer lengths of stay; 5.5 vs 4 days (p=0.026). Tibia/fibula fractures were the most common injuries (N=13, 24%); head injury occurred in six patients (11%). There were 32 (59%) patients who required surgery, the majority for orthopaedic injuries. There were nine patients (16.7%) admitted to the intensive care unit; their median ICU stay was four days. Injury prevention and treatment strategies require that the age profile, mechanism of injury and injury patterns of farmers sustaining animal-related trauma is recognised

Initial infant feeding decisions and duration of breastfeeding in women from English, Arabic and Chinese-speaking backgrounds in Australia.

Anecdotally, concerns are often expressed about the varying infant feeding decisions among women from different cultural groups. This paper reports the early infant feeding decisions and duration of breastfeeding in 986 women from English, Chinese and Arabic-speaking backgrounds in Sydney during 1997 and 1998. Data were collectedfrom an audit of medical records and through a questionnaire at eight weeks postpartum. Chinese-speaking women were less likely to express an intention to breastfeed and fewer initiated breastfeeding compared with other women. Arabic-speaking women had significantly longer duration rates compared with other women. A greater proportion of the Chinese-speaking women who initiated breastfeeding were still breastfeeding at eight weeks compared with English-speaking women. This study suggests that there are differences in the infant feeding decisions between English, Arabic and Chinese-speaking women. Clinicians need to further understand cultural differences when providing care, education and support in a multicultural context

J D Bernal: philosophy, politics and the science of science

This paper is an examination of the philosophical and political legacy of John Desmond Bernal. It addresses the evidence of an emerging consensus on Bernal based on the recent biography of Bernal by Andrew Brown and the reviews it has received. It takes issue with this view of Bernal, which tends to be admiring of his scientific contribution, bemused by his sexuality, condescending to his philosophy and hostile to his politics. This article is a critical defence of his philosophical and political position