Transferring avalanches between paths

Estimates of exceedance probabilities of runout lengths of avalanches for a specific path can rarely be based on measured avalanches in that slope alone, if they are to become statistically reliable. Thus one has, directly or indirectly, to include information of known runout lengths in other paths, i.e. to transfer runout lengths between paths. An attempt is made to classify such transfer methods, including both topographical methods that only make use of information on the shape of the path, such as methods based on runout ratios and a/ß-models, as well as physical methods which also make use of physical models, simulating the avalanche as it runs down the path. By introducing a specific standard slope all avalanches in a given dataset can be transferred to that slope. The length of the transferred avalanche in the standard slope then becomes a slope-independent measure of its length. Using an Icelandic dataset of 196 avalanches we demonstrate how estimates of exceedance probabilities of run out lengths may vary with the choice of transfer method and how the order of the slope-independent lengths of the avalanches in the dataset will vary. The implication for avalanche risk assessment is briefly discussed

Appendicitis and appendectomy in children in Reykjavik Hospitals in 1996 and 2006

Neðst á síðunni er hægt að nálgast greinina í heild sinni með því að smella á hlekkinn View/OpenINTRODUCTION: Appendicitis is a common disease and can be life-threatening if not adequately treated. Studies have shown that if less than 20% of appendices removed are normal it indicates missing or delaying the diagnosis of appendicitis, resulting in an increased incidence of perforation. The purpose of this study was to analyze appendicitis in children during two separate time periods in the pediatric wards of the hospitals in Reykjavík and to increase our knowledge of appendicitis in children in the country. MATERIALS AND METHODS: Patients entering this study are two groups of 100 children (< or =16 years) consecutively undergoing appendectomy in the Reykjavik hospitals, one group in 1996 and the other in 2006. Data on sex, age, clinical symptoms and treatment was obtained from patients records. The impression of the surgeon at time of operation on the inflammation of the removed appendix was compared with results of histopathology analysis. All histopathology slides from appendices from 2006 were re-evaluated. The parameters in open appendectomies were compared to those in laparoscopic appendectomies. The two study periods were compared. RESULTS: The proportion of normal appendices was similar in both periods of the study, 18% in 2006 and 20% in 1996. The appendices were more often normal in female patients (p<0.05) and the large majority of those were removed by laparoscopic surgery. Perforation was present in 17% of inflamed appendices in both study groups. The time from patients arrival to hospital until surgery surpassed 10 hours in only one case in each study group. A discrepancy between the surgeon's assessment and the pathology result was noted only once in 2006 and in one additional case was the histopathological diagnosis altered following re-evaluation of the pathology slides. DISCUSSION: The proportion of non-inflamed appendices in appendectomies in children in Reykjavik is in accordance with that reported elsewhere and perforation is not common. There is a good concordance between surgical and pathological assessment with regard to inflammation of the appendices.Inngangur: Botnlangabólga er algengur sjúkdómur og lífshættulegur ef ekki er brugðist rétt við. Rannsóknir hafa sýnt að ef minna en fimmti hver fjarlægður botnlangi reynist óbólginn er fylgni við hækkun á hlutfalli rofinna botnlanga. Meginmarkmið rannsóknarinnar var að kanna hlutfall óbólginna fjarlægðra botnlanga á Barnaspítala Hringsins og barnadeild Sjúkrahúss Reykjavíkur á tveimur árum með 10 ára millibili og auka þekkingu á botnlangabólgu barna á Íslandi. Efniviður og aðferðir: Alls 100 börn (?16 ára) sem fóru í botnlangatöku á árinu 2006 og 100 börn frá árinu 1996 komu inn í rannsóknina, en hópurinn var samfelldur og því ekki valinn. Upplýsingum um kyn, aldur, klínísk einkenni og meðferð var safnað úr sjúkraskýrslum. Klínísk greining og mat skurðlækna á ástandi botnlanga í aðgerð var borin saman við vefjagreiningarniðurstöður. Öll vefjasýni ársins 2006 voru endurskoðuð af rannsakendum og matið borið saman við fyrri vefjagreiningar. Niðurstöður frá árunum tveimur voru bornar saman. Niðurstöður: Hlutfall óbólginna botnlanga var svipað bæði rannsóknarárin, eða 18% árið 2006 og 20% árið 1996. Botnlangi í stúlkum reyndist marktækt oftar eðlilegur (p<0,05) og nær eingöngu stúlkur fóru í aðgerð með kviðsjá. Bólgnu botnlangarnir reyndust rofnir í 17% tilvika bæði árin. Biðtími sjúklinga frá komu á sjúkrahús að aðgerð var aðeins í eitt skipti hvort árið lengri en 10 klst. Í einu tilviki 2006 kom fram misræmi milli mats skurðlæknis og niðurstöðu vefjagreiningar og meinafræðiáliti var breytt í eitt skipti eftir endurmat vefjasneiða. Ályktanir: Hlutfall óbólginna botnlanga í þessari rannsókn er í samræmi við það sem hingað til hefur verið viðurkennt að erfitt sé að komast hjá og rof á botnlanga reyndist ekki algengt. Gott samræmi er milli mats skurðlækna á botnlanga í aðgerð og meinafræðiniðurstöðu

Attention deficit hyperactivity disorder and depressive symptoms in childhood

This research investigated the presentation and impact of depressive symptoms in children with attention deficit hyperactivity disorder across a three year period. It found that depressive symptoms occur in children with ADHD as young as six years of age. Those with ADHD experienced significantly more depressive symptoms than those without but the presentation of depressive symptoms across those with and without ADHD was found to be similar. Finally, this research demonstrated the significant impact depressive symptoms has on the outcomes of those with ADHD three years later

Chlorine isotope ratios record magmatic brine assimilation during rhyolite genesis

Publisher Copyright: © 2021 The Authors.Magmatic volatile phases within crustal silicic magma domains influence key volcanic processes such as the build up to eruptions and formation of magmatic-hydrothermal ore deposits. However, the extent and nature of fluid-melt interaction in such environments is poorly understood, as geochemical signals in volcanic rocks originating from pre-eruptive volatile processes are commonly overprinted by syn-eruptive degassing. Here, we use δ37Cl as a conservative tracer of brine-melt interaction on a broad suite of silicic volcanic rocks from Iceland. We find that the δ37Cl values of silicic rocks are systematically shifted to more negative values compared to associated basalts and intermediate rocks by up to 2.9 . These large shifts cannot be explained by well known processes inherent to silicic magma genesis, including crustal assimilation, mineral-melt fractionation and syn-eruptive degassing. Instead, we show that low δ37Cl values in silicic rocks can be attributed to assimilation of magmatic brines that are formed and stored in long lived crustal magma mushes. Our results indicate that magmatic brine assimilation is a fundamental, but previously unrecognised part of rhyolite genesis.Peer reviewe

The oldest marine vertebrate fossil from the volcanic island of Iceland:a partial right whale skull from the high latitude Pliocene Tjörnes Formation

Extant baleen whales (Cetacea, Mysticeti) are a disparate and species-rich group, but little is known about their fossil record in the northernmost Atlantic Ocean, a region that supports considerable extant cetacean diversity. Iceland's geographical setting, dividing North Atlantic and Arctic waters, renders it ideally situated to shed light on cetacean evolution in this region. However, as a volcanic island, Iceland exhibits very little marine sedimentary exposure, and fossil whales from Iceland older than the late Pleistocene are virtually unknown. Here, we present the first fossil whale found in situ from the Pliocene Tjörnes Formation (c. 4.5 Ma), Iceland's only substantial marine sedimentary outcrop. The specimen is diagnosed as a partial skull from a large right whale (Mysticeti, Balaenidae). This discovery highlights the Tjörnes Formation as a potentially productive fossil vertebrate locality. Additionally, this find indicates that right whales (Eubalaena) and bowhead whales (Balaena) were sympatric, with broadly overlapping latitudinal ranges in the Pliocene, in contrast to the modern latitudinal separation of their living counterparts.<br/

The Wind Energy Potential of Iceland

AbstractDownscaling simulations performed with the Weather Research and Forecasting (WRF) model were used to determine the large-scale wind energy potential of Iceland. Local wind speed distributions are represented by Weibull statistics. The shape parameter across Iceland varies between 1.2 and 3.6, with the lowest values indicative of near-exponential distributions at sheltered locations, and the highest values indicative of normal distributions at exposed locations in winter. Compared with summer, average power density in winter is increased throughout Iceland by a factor of 2.0–5.5. In any season, there are also considerable spatial differences in average wind power density. Relative to the average value within 10 km of the coast, power density across Iceland varies between 50 and 250%, excluding glaciers, or between 300 and 1500 W m−2 at 50 m above ground level in winter. At intermediate elevations of 500–1000 m above mean sea level, power density is independent of the distance to the coast. In addition to seasonal and spatial variability, differences in average wind speed and power density also exist for different wind directions. Along the coast in winter, power density of onshore winds is higher by 100–700 W m−2 than that of offshore winds. Based on these results, 14 test sites were selected for more detailed analyses using the Wind Atlas Analysis and Application Program (WAsP)

SUSTAIN drilling at Surtsey volcano, Iceland, tracks hydrothermal and microbiological interactions in basalt 50 years after eruption

The 2017 Surtsey Underwater volcanic System for Thermophiles, Alteration processes and INnovative concretes (SUSTAIN) drilling project at Surtsey volcano, sponsored in part by the International Continental Scientific Drilling Program (ICDP), provides precise observations of the hydrothermal, geochemical, geomagnetic, and microbiological changes that have occurred in basaltic tephra and minor intrusions since explosive and effusive eruptions produced the oceanic island in 1963–1967. Two vertically cored boreholes, to 152 and 192 m below the surface, were drilled using filtered, UV-sterilized seawater circulating fluid to minimize microbial contamination. These cores parallel a 181 m core drilled in 1979. Introductory investigations indicate changes in material properties and whole-rock compositions over the past 38 years. A Surtsey subsurface observatory installed to 181 m in one vertical borehole holds incubation experiments that monitor in situ mineralogical and microbial alteration processes at 25–124 ∘C. A third cored borehole, inclined 55∘ in a 264∘ azimuthal direction to 354 m measured depth, provides further insights into eruption processes, including the presence of a diatreme that extends at least 100 m into the seafloor beneath the Surtur crater. The SUSTAIN project provides the first time-lapse drilling record into a very young oceanic basaltic volcano over a range of temperatures, 25–141 ∘C from 1979 to 2017, and subaerial and submarine hydrothermal fluid compositions. Rigorous procedures undertaken during the drilling operation protected the sensitive environment of the Surtsey Natural Preserve

Gradual caldera collapse at Bárdarbunga volcano, Iceland, regulated by lateral magma outflow

Large volcanic eruptions on Earth commonly occur with a collapse of the roof of a crustal magma reservoir, forming a caldera. Only a few such collapses occur per century, and the lack of detailed observations has obscured insight into the mechanical interplay between collapse and eruption.We usemultiparameter geophysical and geochemical data to show that the 110-squarekilometer and 65-meter-deep collapse of Bárdarbunga caldera in 2014-2015 was initiated through withdrawal of magma, and lateral migration through a 48-kilometers-long dike, from a 12-kilometers deep reservoir. Interaction between the pressure exerted by the subsiding reservoir roof and the physical properties of the subsurface flow path explain the gradual, nearexponential decline of both collapse rate and the intensity of the 180-day-long eruption.</p