Influences of urban fabric on pyroclastic density currents at Pompeii (Italy): 1. Flow direction and deposition

To assess ways in which the products of explosive eruptions interact with human settlements, we performed volcanological and rock magnetic analyses on the deposits of the A.D. 79 eruption at the Pompeii excavations (Italy). During this eruption the Roman town of Pompeii was covered by 2.5 m of fallout pumice and then partially destroyed by pyroclastic density currents (PDCs). Anisotropy of magnetic susceptibility measurements performed on the fine matrix of the deposits allowed the quantification of the variations in flow direction and emplacement mechanisms of the parental PDCs that entered the town. These results, integrated with volcanological field investigations, revealed that the presence of buildings, still protruding through the fallout deposits, strongly affected the distribution and accumulation of the erupted products. All of the PDCs that entered the town, even the most dilute ones, were density stratified currents in which interaction with the urban fabric occurred in the lower part of the current. The degree of interaction varied mainly as a function of obstacle height and density stratification within the current. For examples, the lower part of the EU4pf current left deposits up to 3 m thick and was able to interact with 2- to 4-m-high obstacles. However, a decrease in thickness and grain size of the deposits across the town indicates that even though the upper portion of the current was able to decouple from the lower portion, enabling it to flow over the town, it was not able to fully restore the sediment supply to the lower portion in order to maintain the deposition observed upon entry into the town.PublishedB052134.3. TTC - Scenari di pericolosità vulcanica3.6. Fisica del vulcanismoJCR Journalreserve

Accretion onto the Companion of Eta Carinae During the Spectroscopic Event. IV. the Disappearance of Highly Ionized Lines

We show that the rapid and large decrease in the intensity of high-ionization emission lines from the Eta Carinae massive binary system can be explained by the accretion model. These emission lines are emitted by material in the nebula around the binary system that is being ionized by radiation from the hot secondary star. The emission lines suffer three months long deep fading every 5.54 year, assumed to be the orbital period of the binary system. In the accretion model, for ~70 day the less massive secondary star is accreting mass from the primary wind instead of blowing its fast wind. The accretion event has two effects that substantially reduce the high-energy ionizing radiation flux from the secondary star. (1) The accreted mass absorbs a larger fraction of the ionizing flux. (2) The accreted mass forms a temporarily blanked around the secondary star that increases its effective radius, hence lowering its effective temperature and the flux of high energy photons. This explanation is compatible with the fading of the emission lines at the same time the X-ray is declining to its minimum, and with the fading being less pronounced in the polar directions.Comment: ApJ, in pres

Accretion onto the Companion of Eta Carinae During the Spectroscopic Event: III. the He II 4686 Line

We continue to explore the accretion model of the massive binary system eta Carinae by studying the anomalously high He II 4686 line. The line appears just before periastron and disappears immediately thereafter. Based on the He II 4686 line emission from O-stars and their modeling in the literature, we postulate that the He II 4686 line comes from the acceleration zone of the secondary stellar wind. We attribute the large increase in the line intensity to a slight increase in the density of the secondary stellar wind in its acceleration zone. The increase in density could be due to the ionization and subsequent deceleration of the wind by the enhanced X-ray emission arising from the shocked secondary wind further downstream or to accretion of the primary stellar wind. Accretion around the secondary equatorial plane gives rise to collimation of the secondary wind, which increases its density, hence enhancing the He II 4686 emission line. In contrast with previous explanations, the presently proposed model does not require a prohibitively high X-ray flux to directly photoionize the He.Comment: ApJ, in pres

Copper deficiency anemia after bariatric surgery

Copper is a trace mineral essential to hematopoiesis and to the structure and function of the nervous system. Copper acts as a ligand to ferroxidase II, which oxidizes iron, allowing it to be mobilized and transported from the hepatic stores to the bone marrow to be used in erythropoiesis..Copper deficiency is a rare cause of anemia, leukopenia, and myeloneuropathy. In this report we describe a case of a 49 year-old overweight Caucasian woman who was referred June 2008 to the Obesity Outpatient Clinic at UNIFESP for evaluation of muscular pain and weakness in both legs, fatigue and chronic anemia. The past medical history included Scopinaro Surgery for severe obesity in November 2004 when her weight was approximately 180 Kg (BMI 68.6 kg/m2). She lost considerable weight after surgery, with her weight being stable around 80 kg (BMI 30). Because of clinical manifestations of sub nutrition, protein and vitamin deficiencies and severe anemia, which lead to several hospital admissions, in February 2008 she was submitted to another surgery from conversion of the gastrointestinal surgical Scopinaro procedure to that performed by Capella. She also had a history of hypothyroidism, hyperuricemia and panic syndrome, requiring specific medications, beyond parenteral iron and B12 vitamin therapies for anemia. Physical examination revealed a bilateral edema and no other abnormality. Laboratory tests revealed hypoalbuminemia and hypochromic megaloblastic anemia with normal serum levels of B12 vitamin, iron and ferritin. Due to the persistence of the neurologic symptoms and anemia in spite of adequate iron and B12 vitamin therapies, the hypothesis of copper deficiency was considered and a low serum level of 40μg/dl was found. An oral supplementation with high doses of copper resulted in evident clinical and laboratorial improvements after eight weeks of therapy. The diagnosis of copper deficiency has to be part of the differential diagnosis in patients with unexplained neurologic symptoms, anemia, and leukopenia, especially in those who underwent to previous gastrointestinal surgery

The Binarity of Eta Carinae and its Similarity to Related Astrophysical Objects

I examine some aspects of the interaction between the massive star Eta Carinae and its companion, in particular during the eclipse-like event, known as the spectroscopic event or the shell event. The spectroscopic event is thought to occur when near periastron passages the stellar companion induces much higher mass loss rate from the primary star, and/or enters into a much denser environment around the primary star. I find that enhanced mass loss rate during periastron passages, if it occurs, might explain the high eccentricity of the system. However, there is not yet a good model to explain the presumed enhanced mass loss rate during periastron passages. In the region where the winds from the two stars collide, a dense slow flow is formed, such that large dust grains may be formed. Unlike the case during the 19th century Great Eruption, the companion does not accrete mass during most of its orbital motion. However, near periastron passages short accretion episodes may occur, which may lead to pulsed ejection of two jets by the companion. The companion may ionize a non-negligible region in its surrounding, resembling the situation in symbiotic systems. I discuss the relation of some of these processes to other astrophysical objects, by that incorporating Eta Car to a large class of astrophysical bipolar nebulae.Comment: Updated version. ApJ, in pres