122 research outputs found
Mathematical Model of the Stick-Slip Effect for Describing the "Drumbeat" Seismic Regime During the Eruption of the Kizimen Volcano in Kamchatka
During the eruption of the Kizimen volcano in 2010-2013. There was a uniform
squeezing of the viscous lava flow. Simultaneously with its movement,
earthquakes with an unusual quasi-periodicity were recorded, the "drumbeats"
mode. In this work, we show that these earthquakes were generated by the
movement of the flow front, which was observed for the first time in the
practice of volcanological research. We represent the movement of the flow as
an intermittent slip with the inclusion of the "stick-slip" mechanism with the
initiation of a self-oscillating process. The plausibility of the
phenomenological model at the qualitative level is confirmed by the
mathematical model of a fractional nonlinear oscillator
The nexus of soil radon and hydrogen dynamics and seismicity of the northern flank of the Kuril-Kamchatka subduction zone
The comparison of kinematics and dynamic parameters of radon and molecular hydrogen concentration in subsoil
air on the stations network at the Petropavlovsk-Kamchatsky geodynamic proving ground with seismicity
of the northern flank of the Kuril-Kamchatka subduction zone was fulfilled in the period from July till August
2004. On the basis of correlation analysis of the regional seismicity and variations of radon flux density calculated
using the data of gas-discharge counters of STS-6 type and SSNTDs it was shown that the radon mass
transfer abnormal variations are conditioned by both regional seismicity in total and the subduction zone of proving
ground. The azimuths of «geodeformation waves» coming to the registration points are calculated during
clearly expressed anomaly beginnings, which coincide with directions to earthquake epicenters taking place at
the same time. The geochemical anomalies recorded are presumptively deformative by nature and can be conditioned
by processes of «quasi-viscous» flow of the lithosphere during rearrangement of tectonic stress fields of
the subduction zone. The short-term (predicted time Τ <14 days) precursor of the earthquakes swarm was revealed
in hydrogen dynamics on August, 4-5 (four earthquakes had M≥5.3 and epicentral distance about 130 km
from the Paratunka base station)
Non-Equilibrium Evolution Thermodynamics Theory
Alternative approach for description of the non-equilibrium phenomena arising
in solids at a severe external loading is analyzed. The approach is based on
the new form of kinetic equations in terms of the internal and modified free
energy. It is illustrated by a model example of a solid with vacancies, for
which there is a complete statistical ground. The approach is applied to the
description of important practical problem - the formation of fine-grained
structure of metals during their treatment by methods of severe plastic
deformation. In the framework of two-level two-mode effective internal energy
potential model the strengthening curves unified for the whole of deformation
range and containing the Hall-Petch and linear strengthening sections are
calculated.Comment: 7 pages, 1 figur
Flux measurements of explosive degassing using a yearlong hydroacoustic record at an erupting submarine volcano
Author Posting. © American Geophysical Union, 2012. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 13 (2012): Q0AF07, doi:10.1029/2012GC004211.The output of gas and tephra from volcanoes is an inherently disorganized process that makes reliable flux estimates challenging to obtain. Continuous monitoring of gas flux has been achieved in only a few instances at subaerial volcanoes, but never for submarine volcanoes. Here we use the first sustained (yearlong) hydroacoustic monitoring of an erupting submarine volcano (NW Rota-1, Mariana arc) to make calculations of explosive gas flux from a volcano into the ocean. Bursts of Strombolian explosive degassing at the volcano summit (520 m deep) occurred at 1–2 min intervals during the entire 12-month hydrophone record and commonly exhibited cyclic step-function changes between high and low intensity. Total gas flux calculated from the hydroacoustic record is 5.4 ± 0.6 Tg a−1, where the magmatic gases driving eruptions at NW Rota-1 are primarily H2O, SO2, and CO2. Instantaneous fluxes varied by a factor of ∼100 over the deployment. Using melt inclusion information to estimate the concentration of CO2 in the explosive gases as 6.9 ± 0.7 wt %, we calculate an annual CO2 eruption flux of 0.4 ± 0.1 Tg a−1. This result is within the range of measured CO2 fluxes at continuously erupting subaerial volcanoes, and represents ∼0.2–0.6% of the annual estimated output of CO2from all subaerial arc volcanoes, and ∼0.4–0.6% of the mid-ocean ridge flux. The multiyear eruptive history of NW Rota-1 demonstrates that submarine volcanoes can be significant and sustained sources of CO2 to the shallow ocean.The National Oceanic
and Atmospheric Administration Office of Ocean Exploration
and Research, the NOAA Vents Program, and the National
Science Foundation (OCE-0751776) for support.2013-05-2
Dislocation of the Cervical Anastomosis toward the Mediastinum after McKeown Esophagectomy: A Single-Center Retrospective Study
Background: This study aimed to assess the frequency of cervical anastomosis dislocation toward the mediastinum after McKeown esophagectomy and the significance of this phenomenon for postoperative complications.
Methods and Results: The study included 82 patients with stage I-III esophageal cancer who underwent surgical intervention using McKeown esophagectomy in a completely open version (thoracotomy, laparotomy, cervicotomy) or hybrid esophagectomy (thoracoscopy on the right, laparotomy, cervicotomy).
After McKeown esophagectomy, dislocation of the cervical anastomosis (DCA) toward the posterior mediastinum was noted in 26.8% of cases. The overall incidence of anastomotic leakage was 18.3%. The groups of patients with and without DCA did not differ statistically in the incidence of anastomotic leakage (P=0.205). Mediastinal complications (mediastinitis, pleural empyema) were observed in 100% (6/6) of cases in the group with DCA and 33.3% (3/9) of cases in the group without DCA (P=0.013). Pulmonary complications (pneumonia, atelectasis) occurred in 5(22.7%) and 8(13.3%) of cases in groups with DCA and without DCA, respectively (P = 0.304).
Conclusion: After McKeown esophagectomy, DCA toward the posterior mediastinum was noted in 26.8% of cases. Dislocation of the cervical anastomosis toward the posterior mediastinum does not significantly impact the anastomotic leakage. Mediastinal complications are more common in patients with DCA, but the incidence of pulmonary complications is not associated with this phenomenon
Sarilumab in patients admitted to hospital with severe or critical COVID-19: a randomised, double-blind, placebo-controlled, phase 3 trial
Background: Elevated proinflammatory cytokines are associated with greater COVID-19 severity. We aimed to assess safety and efficacy of sarilumab, an interleukin-6 receptor inhibitor, in patients with severe (requiring supplemental oxygen by nasal cannula or face mask) or critical (requiring greater supplemental oxygen, mechanical ventilation, or extracorporeal support) COVID-19. Methods: We did a 60-day, randomised, double-blind, placebo-controlled, multinational phase 3 trial at 45 hospitals in Argentina, Brazil, Canada, Chile, France, Germany, Israel, Italy, Japan, Russia, and Spain. We included adults (≥18 years) admitted to hospital with laboratory-confirmed SARS-CoV-2 infection and pneumonia, who required oxygen supplementation or intensive care. Patients were randomly assigned (2:2:1 with permuted blocks of five) to receive intravenous sarilumab 400 mg, sarilumab 200 mg, or placebo. Patients, care providers, outcome assessors, and investigators remained masked to assigned intervention throughout the course of the study. The primary endpoint was time to clinical improvement of two or more points (seven point scale ranging from 1 [death] to 7 [discharged from hospital]) in the modified intention-to-treat population. The key secondary endpoint was proportion of patients alive at day 29. Safety outcomes included adverse events and laboratory assessments. This study is registered with ClinicalTrials.gov, NCT04327388; EudraCT, 2020-001162-12; and WHO, U1111-1249-6021. Findings: Between March 28 and July 3, 2020, of 431 patients who were screened, 420 patients were randomly assigned and 416 received placebo (n=84 [20%]), sarilumab 200 mg (n=159 [38%]), or sarilumab 400 mg (n=173 [42%]). At day 29, no significant differences were seen in median time to an improvement of two or more points between placebo (12·0 days [95% CI 9·0 to 15·0]) and sarilumab 200 mg (10·0 days [9·0 to 12·0]; hazard ratio [HR] 1·03 [95% CI 0·75 to 1·40]; log-rank p=0·96) or sarilumab 400 mg (10·0 days [9·0 to 13·0]; HR 1·14 [95% CI 0·84 to 1·54]; log-rank p=0·34), or in proportions of patients alive (77 [92%] of 84 patients in the placebo group; 143 [90%] of 159 patients in the sarilumab 200 mg group; difference −1·7 [−9·3 to 5·8]; p=0·63 vs placebo; and 159 [92%] of 173 patients in the sarilumab 400 mg group; difference 0·2 [−6·9 to 7·4]; p=0·85 vs placebo). At day 29, there were numerical, non-significant survival differences between sarilumab 400 mg (88%) and placebo (79%; difference +8·9% [95% CI −7·7 to 25·5]; p=0·25) for patients who had critical disease. No unexpected safety signals were seen. The rates of treatment-emergent adverse events were 65% (55 of 84) in the placebo group, 65% (103 of 159) in the sarilumab 200 mg group, and 70% (121 of 173) in the sarilumab 400 mg group, and of those leading to death 11% (nine of 84) were in the placebo group, 11% (17 of 159) were in the sarilumab 200 mg group, and 10% (18 of 173) were in the sarilumab 400 mg group. Interpretation: This trial did not show efficacy of sarilumab in patients admitted to hospital with COVID-19 and receiving supplemental oxygen. Adequately powered trials of targeted immunomodulatory therapies assessing survival as a primary endpoint are suggested in patients with critical COVID-19. Funding: Sanofi and Regeneron Pharmaceuticals
- …