Influence of Volatile Degassing on Initial Flow Structure and Entrainment During Undersea Volcanic Fire Fountaining Eruptions

Release of dissolved volatiles during submarine fire fountaining eruptions can profoundly influence the buoyancy flux at the vent. Theoretical considerations indicate that in some cases buoyant magma can be erupted prior to fragmentation (~75% vesicle volume threshold). Laboratory simulations using immiscible fluids of contrasting density indicate that the structure of the source flow at the vent depends critically on the relative magnitudes of buoyancy and momentum fluxes as reflected in the Richardson number (Ri). Analogue laboratory experiments of buoyant discharges demonstrate a variety of complex flow structures with the potential for greatly enhanced entrainment of surrounding seawater. Such conditions are likely to favor a positive feedback between phreatomagmatic explosions and volatile degassing that will contribute to explosive volcanism. The value of the Richardson number for any set of eruption parameters (magma discharge rate and volatile content) will depend on water depth as a result of the extent to which the exsolved volatile components can expand

Remote Analysis of Grain Size Characteristic in Submarine Pyroclastic Deposits from Kolumbo Volcano, Greece

Grain size characteristics of pyroclastic deposits provide valuable information about source eruption energetics and depositional processes. Maximum size and sorting are often used to discriminate between fallout and sediment gravity flow processes during explosive eruptions. In the submarine environment the collection of such data in thick pyroclastic sequences is extremely challenging and potentially time consuming. A method has been developed to extract grain size information from stereo images collected by a remotely operated vehicle (ROV). In the summer of 2010 the ROV Hercules collected a suite of stereo images from a thick pumice sequence in the caldera walls of Kolumbo submarine volcano located about seven kilometers off the coast of Santorini, Greece. The highly stratified, pumice-rich deposit was likely created by the last explosive eruption of the volcano that took place in 1650 AD. Each image was taken from a distance of only a few meters from the outcrop in order to capture the outlines of individual clasts with relatively high resolution. Mosaics of individual images taken as the ROV transected approximately 150 meters of vertical outcrop were used to create large-scale vertical stratigraphic columns that proved useful for overall documentation of the eruption sequence and intracaldera correlations of distinct tephra units. Initial image processing techniques, including morphological operations, edge detection, shape and size estimation were implemented in MatLab and applied to a subset of individual images of the mosiacs. A large variety of algorithms were tested in order to best discriminate the outlines of individual pumices. This proved to be challenging owing to the close packing and overlapping of individual pumices. Preliminary success was achieved in discriminating the outlines of the large particles and measurements were carried out on the largest clasts present at different stratigraphic levels. In addition, semi-quantitative analysis of the size distribution could also be determined for individual images. Although a complete size distribution is not possible with this technique, information about the relative distribution of large and medium size clasts is likely to provide a reasonable proxy for the overall sorting of submarine deposits. Our preliminary work represents the first attempt to carry out an in situ granulometric analysis of a thick submarine pyroclastic sequence. This general technique is likely to be valuable in future studies of submarine explosive volcanism given the recent discoveries of extensive pumiceous deposits in many submarine calderas associated with subduction zone environments. AGU session number OS13A-150

Reproductive Outcomes Following Maternal Exposure to the Events of September 11, 2001, at the World Trade Center, in New York City

Objectives: To estimate associations between exposure to the events of September 11, 2001, (9/11) and low birth weight (LBW), preterm delivery (PD), and small size for gestational age (SGA). Methods: We matched birth certificates filed in New York City for singleton births between 9/11 and the end of 2010 to 9/11-related exposure data provided by mothers who were World Trade Center Health Registry enrollees. Generalized estimating equations estimated associations between exposures and LBW, PD, and SGA. Results:Among 3360 births, 5.8% were LBW, 6.5% were PD, and 9% were SGA. Having incurred at least 2 of 4 exposures, having performed rescue or recovery work, and probable 9/11-related posttraumatic stress disorder 2 to 3 years after 9/11 were associated with PD and LBW during the early study period. Conclusions: Disasters on the magnitude of 9/11 may exert effects on reproductive outcomes for several years. Women who are pregnant during and after a disaster should be closely monitored for physical and psychological sequelae. Public Health Implications: In utero and maternal disaster exposure may affect birth outcomes. Researchers studying effects of individual disasters should identify commonalities that may inform postdisaster responses to minimize disaster-related adverse birth outcomes

Adolescent behavior and PTSD 6–7 years after the World Trade Center terrorist attacks of September 11, 2001

Behavioral problems and psychopathologies were reported in children exposed to the World Trade Center (WTC) attacks in New York City within 2–3 y post-disaster. Little is known of subsequent 9/11 related behavioral and emotional problems. We assessed risk factors for behavioral difficulties and probable posttraumatic stress disorder (PTSD) in 489 adolescent enrollees ages 11–18 y of age in the World Trade Center Health Registry cohort using the Strengths and Difficulties Questionnaire (SDQ) and DISC Predictive Scales (DPS), respectively, as reported by the adolescents. Associations between parental PTSD and adolescent PTSD and behavioral problems were studied in a subset of 166 adolescent-parent pairs in which the parent was also a Registry enrollee. Nearly one-fifth (17.4%) of the adolescents, all of whom were 5–12 y old at the time of the attacks, scored in the abnormal (5.7%) or borderline (11.7%) range of total SDQ. Problems were more frequent in minority, low-income, and single-parent adolescents. Abnormal and borderline SDQ scores were significantly associated with direct WTC exposures and with WTC-related injury or death of a family member. Adolescent PTSD was significantly associated with WTC exposure and with fear of one's own injury or death, and with PTSD in the parent (OR = 5.6; 95% CI 1.1–28.4). This adolescent population should be monitored for persistence or worsening of these problems. Co-occurrence of parent and child mental health symptoms following a disaster may have implications for healthcare practitioners and for disaster response planners

Heterosexual anal intercourse and HIV infection risks in the context of alcohol serving venues, Cape Town, South Africa

<p>Abstract</p> <p>Background</p> <p>The most efficient sexual behavior for HIV transmission is unprotected receptive anal intercourse. However, it is unclear what role heterosexual unprotected anal sex is playing in the world's worst HIV epidemics of southern Africa. The objective is to examine the prevalence of heterosexual unprotected anal intercourse among men and women who drink at informal alcohol serving establishments (shebeens) in South Africa.</p> <p>Methods</p> <p>Cross-sectional surveys were collected from a convenience sample of 5037 patrons of 10 shebeens in a peri-urban township of Cape Town, South Africa. Analyses concentrated on establishing the rates of unprotected anal intercourse practiced by men and women as well as the factors associated with practicing anal intercourse.</p> <p>Results</p> <p>We found that 15% of men and 11% of women reported anal intercourse in the previous month, with 8% of men and 7% of women practicing any unprotected anal intercourse. Multiple logistic regression showed that younger age, having primary and casual sex partners, and meeting sex partners at shebeens were independently associated with engaging in anal intercourse. Mathematical modeling showed that individual risks are significantly impacted by anal intercourse but probably not to the degree needed to drive a generalized HIV epidemic.</p> <p>Conclusions</p> <p>Anal intercourse likely plays a significant role in HIV infections among a small minority of South Africans who patronize alcohol serving establishments. Heterosexual anal intercourse, the most risky sexual behavior for HIV transmission, should not be ignored in HIV prevention for South African heterosexuals. However, this relatively infrequent behavior should not become the focus of prevention efforts.</p