Three-dimensional MHD Simulations of Jets from Accretion Disks

We report the results of 3-dimensional magnetohydrodynamic (MHD) simulations of a jet formation by the interaction between an accretion disk and a large scale magnetic field. The disk is not treated as a boundary condition but is solved self-consistently. To investigate the stability of MHD jet, the accretion disk is perturbed with a non-axisymmetric sinusoidal or random fluctuation of the rotational velocity. The dependences of the jet velocity $(v_z)$, mass outflow rate $(\dot{M}_w)$, and mass accretion rate $(\dot{M}_a)$ on the initial magnetic field strength in both non-axisymmetric cases are similar to those in the axisymmetric case. That is, $v_z \propto B_0^{1/3}$, $\dot{M}_w \propto B_0$ and $\dot{M}_a \propto B_0^{1.4}$ where $B_0$ is the initial magnetic field strength. The former two relations are consistent with the Michel's steady solution, $v_z \propto (B_0^2/\dot{M}_w)^{1/3}$, although the jet and accretion do not reach the steady state. In both perturbation cases, a non-axisymmetric structure with $m=2$ appears in the jet, where $m$ means the azimuthal wave number. This structure can not be explained by Kelvin-Helmholtz instability and seems to originate in the accretion disk. Non-axisymmetric modes in the jet reach almost constant levels after about 1.5 orbital periods of the accretion disk, while all modes in the accretion disk grow with oscillation. As for the angular momentum transport by Maxwell stress, the vertical component, $$, is comparable to the radial component,$$, in the wide range of initial magnetic field strength.Comment: Accepted for publication in ApJ. The pdf file with high resolution figures can be downloaded at http://www.kusastro.kyoto-u.ac.jp/~hiromitu/3j050806.pd

Oxide phosphors for light upconversion; Yb3+ and Tm3+ co-doped Y2BaZnO5

Copyright 2011 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. This article appeared in Journal of Applied Physics 109, 063104 (2011) and may be found at

Oesophageal atresia is correctable and survivable in infants less than 1 kg

INTRODUCTION: Management of oesophageal atresia (OA) and trachea-oesophageal fistula (TOF) in babies of low birth weight is challenging especially when associated with other anomalies. Birth weight of <1500 g has previously formed part of a classification system designed to predict outcome, alongside the cardiac status of the patient. Improvements in neonatal care have led to increasing numbers of premature low birth weight infants surviving. The aim of this study was to look at the experience of our institution in the extremely low birth weight (ELBW) patients. METHODS: A retrospective review of our institutions OA database was performed from 1993 to June 2015. Patients of birth weight less than 1000 g were included. A review of our OA/TOF clinical database and notes review established the following; gestation, birth weight, associated anomalies, operative procedures, morbidity and mortality. RESULTS: Of 349 patients with OA across the 22-year period, 9 ELBW patients were identified (<1000 g). Six males and three females. Gestational age ranged from 23 to 34 weeks and median birth weight was 815 g ranging from 630 to 950 g. Overall survival was 56 % (5/9). There were double the numbers of ELBW OA/TOF patients seen in the second half of the study period presumably the result of improving neonatal care. Seven patients had type C OA with TOF and underwent emergency TOF ligation, two had concomitant oesophageal repair. One of these patients died from NEC; the other survived. Of the five who had isolated TOF ligation three died-two from cardiac disease and one from prematurity. Both type A patients survived and after initial gastrostomy placement one had a primary delayed repair, the other a gastric transposition. All three babies under 800 g died-one from cardiac disease the others from conditions indicative of their prematurity-necrotising enterocolitis and intraventricular haemorrhage. CONCLUSIONS: 50 % survival is achievable in OA/TOF under 1 kg and the Spitz classification is still applicable in this group as a whole. However, none of the current classification systems are applicable in infants <800 g who in our study all had poor outcomes. We suggest these should be considered as separate group when predicting outcomes

Supersoft X-ray Sources in M31: I. A Chandra Survey and an Extension to Quasisoft Sources

We report on very soft X-ray sources (VSSs) in M31. In a survey which was most sensitive to soft sources in four 8'x8' regions covered by Chandra's ACIS-S S3 CCD, we find 33 VSSs that appear to belong to M31. Fifteen VSSs have spectral characteristics mirroring the supersoft X-ray sources studied in the Magellanic Cloud and Milky Way ($k T_{eff} \leq 100$ eV); we therefore call these ``classical'' supersoft sources, or simply supersoft sources (SSSs). Eighteen VSSs may either have small (< 10%) hard components, or slightly higher effective temperatures (but still < 350 eV). We refer to these VSSs as quasisoft sources (QSSs). While hot white dwarf models may apply to SSSs, the effective temperatures of QSSs are too high, unless, e.g., the radiation emanates from only a small portion of surface. Two of the SSSs were first detected and identified as such through ROSAT observations. One SSS and one QSS may be identified with symbiotics, and 2 SSSs with supernova remnants. Both SSSs and QSSs in the disk are found near star-forming regions, possibly indicating that they are young. VSSs in the outer disk and halo are likely to be old systems; in these regions, there are more QSSs than SSSs, which is opposite to what is found in fields closer to the galaxy center. The largest density of bright VSSs is in the bulge; some of the bulge sources are close enough to the nucleus to be remnants of the tidal disruption of a giant by the massive central black hole. By using Chandra data in combination with ROSAT and XMM observations, we find most VSSs to be highly variable, fading from or brightening toward detectability on time scales of months. There is evidence for VSSs with low luminosities ($\sim 10^{36}$ erg s$^{-1}$).Comment: 14 pages, 4 figures. Accepted for publication in ApJ. Classification of supersoft and quasisoft sources is clarifie

Geographical information retrieval with ontologies of place

Geographical context is required of many information retrieval tasks in which the target of the search may be documents, images or records which are referenced to geographical space only by means of place names. Often there may be an imprecise match between the query name and the names associated with candidate sources of information. There is a need therefore for geographical information retrieval facilities that can rank the relevance of candidate information with respect to geographical closeness of place as well as semantic closeness with respect to the information of interest. Here we present an ontology of place that combines limited coordinate data with semantic and qualitative spatial relationships between places. This parsimonious model of geographical place supports maintenance of knowledge of place names that relate to extensive regions of the Earth at multiple levels of granularity. The ontology has been implemented with a semantic modelling system linking non-spatial conceptual hierarchies with the place ontology. An hierarchical spatial distance measure is combined with Euclidean distance between place centroids to create a hybrid spatial distance measure. This is integrated with thematic distance, based on classification semantics, to create an integrated semantic closeness measure that can be used for a relevance ranking of retrieved objects

Loop colostomies are safe in anorectal malformations

Aim of the study: Divided colostomy (DC) has been recommended in anorectal malformations (ARMs) with previously reported advantages of decreasing overflow into the distal limb and urinary tract infections (UTIs). Skin bridge loop colostomy (LC) is a technically easier alternative without an increase in these complications. We report our institutional experience of LC in ARM. Methods: Retrospective study (Institution-approved Clinical Audit) reviewing the clinical records of all patients with ARM undergoing stoma formation in a single UK tertiary pediatric surgical center (2000–2015). Data collected included type of ARM, associated anomalies, type and level of colostomy, time to stoma closure, complications and UTIs. Results: One hundred and eighty-two (95 female) patients underwent colostomy formation for ARM. The vast majority (171/ 94%) underwent LC; 9 (5%) had a divided colostomy (DC) and 2 (1%) had no available data. The spectrum of defects in girls included rectovestibular (62/65%), rectovaginal (4/4%) and cloaca (29/31%). In boys, 71 (82%) had a fistula to the urinary tract and 16 (18%) presented with a perineal fistula. Urological abnormalities coexisted in 87 (47.8%) patients. Thirty five (21%) patients developed UTIs. Among the 19 girls who developed UTI, 8 had rectovestibular fistula and 11 had cloaca. Of the 16 boys who developed UTI, 14 had a fistula to the urinary tract and 11 had an independent urological abnormality. The mean time from stoma formation to stoma closure was 10 (3–52) months. Complications were reported in 22 (12%) LCs. Fifteen patients (9%) developed a stoma prolapse following LC with 10 (6%) requiring surgical revision. Conclusions: This is the largest reported series of outcomes following LC for ARM. LC is easier to perform and to close, requiring minimal surgical access, with comparable complications and outcomes to those published for DC. Type of study: Retrospective comparative study. Level of evidence: III

A comparative cohort study of Duhamel and Endorectal Pullthrough for Hirschsprung's Disease

Background: There are limited data available to compare outcomes between surgical approaches for Hirschsprung’s disease. Duhamel and endorectal pull-through (ERPT) are two of the most common procedures performed worldwide. // Methods: Objective outcomes were compared between contemporary cohorts (aged 4–32 years) after Duhamel or ERPT using case–control methodology. Data were collected using prospectively administered standardized questionnaires on bowel and bladder function and quality of life (Pediatric Quality of Life Inventory, Short form 36 and Gastrointestinal Quality of Life Index). Patients were compared in two age groups (18 years and younger and older than 18 years) and reference made to normative control data. Multivariable analysis explored factors associated with poor outcomes. // Results: Cohorts were well matched by demographics, disease characteristics and incidence of postoperative complications (120 patients who underwent Duhamel versus 57 patients who had ERPT). Bowel function scores were similar between groups. Patients who underwent Duhamel demonstrated worse constipation and inferior faecal awareness scores (P < 0.01 for both age groups). Recurrent postoperative enterocolitis was significantly more common after ERPT (34 versus 6 per cent; odds ratio 15.56 (95 per cent c.i. 6.19 to 39.24; P < 0.0001)). On multivariable analysis, poor bowel outcome was the only factor significantly associated with poor urinary outcome (adjusted odds ratio 6.66 (95 per cent c.i. 1.74 to 25.50; P = 0.006)) and was significantly associated with markedly reduced quality of life (QoL) in all instruments used (P < 0.001 for all). There were no associations between QoL measures and pull-through technique. // Conclusion: Outcomes from Duhamel and ERPT are good in the majority of cases, with comparable bowel function scores. Constipation and impaired faecal awareness were more prevalent after Duhamel, with differences sustained in adulthood. Recurrent enterocolitis was significantly more prevalent after ERPT. Clustering of poor QoL and poor functional outcomes were observed in both cohorts, with seemingly little effect by choice of surgical procedure in terms of QoL