Ground ice and slope sediments archiving Late Quaternary paleoenvironment and paleoclimate signals at the margins of Elgygytgyn Crater, NE Siberia

An accumulation terrace close to the El'gygytgyn Impact Crater in northeastern Siberia contains stratigraphic and periglacial evidence of the paleoenvironmental and paleoclimatic history and permafrost dynamics during late Quaternary time. A succession of paleo active-layer depositsthat mirror environmental changes records periods favorable for the establishment and growth of ice-wedge polygonal networks and sediment variations. These two elements of the periglacial landscape serve as complementary paleoenvironmental archives that can be traced back to 14,000 cal yr BP. The slope sediments and the ground ice contained therein have prominent relative maxima and minima in properties (grain size, total organic content, oxygen isotopes). They document a regional early Holocene thermal maximum at about 9000 cal yr BP, followed by a transition to slightly cooler conditions, and a subsequent transition to slightly warmer conditions after about 4000 cal yr BP. Results from sedimentary analysis resemble morphological and geochemical (oxygen and hydrogen isotopes) results from ice wedge studies, in which successive generations of ice-wedge polygonal networks record warmer winters in late Holocene time. Moreover, peaks of light soluble cation contents and quartz-grain surface textures reveal distinct traces of cryogenic weathering. We propose a conclusive sedimentation model illustrating terrace formation in a permafrost terrain

Echocardiography in pediatric pulmonary arterial hypertension:early study on assessing disease severity and predicting outcome

BACKGROUND: The value of echocardiography in assessing disease severity and predicting outcome in pediatric pulmonary arterial hypertension (PAH) is insufficiently defined. The aim of this study was to describe correlations between echocardiography and disease severity and outcome in pediatric PAH. METHODS AND RESULTS: Forty-three consecutive children (median age, 8.0 years; range, 0.4-21.5) with idiopathic/hereditary PAH (n=25) or PAH associated with congenital heart disease (n=18) were enrolled in a prospective single-center observational study. Anatomic and right ventricular-functional variables were obtained by two-dimensional echocardiography and Doppler-echocardiography at presentation and at standardized follow-up and were correlated with measures of disease severity (World Health Organization functional class [WHO-FC], N-terminal-pro-B-type natriuretic peptide, hemodynamics) and lung-transplantation-free survival. Right atrial and right ventricular dimensions correlated with WHO-FC and hemodynamics (P<0.05), whereas left ventricular dimensions correlated with hemodynamics and survival (P<0.05). Right-to-left ventricular dimension ratiocorrelated with WHO-FC, hemodynamics and survival (P<0.05). Right ventricular ejection time correlated with hemodynamics and survival (P<0.05) and tended to correlate with WHO-FC (P=0.071). Tricuspid annular plane systolic excursion correlated with WHO-FC, mean right atrial pressure and survival (P<0.05). CONCLUSIONS: This early descriptive study shows that echocardiographic chararacteristics of both the right and the left heart correlate with disease severity and outcome in pediatric PAH, both at presentation and during the course of the disease. The preliminary data from this study support the potential value of echocardiography as a tool in guiding management in children with PAH