A 500-kiloton airburst over Chelyabinsk and an enhanced hazard from small impactors.

Most large (over a kilometre in diameter) near-Earth asteroids are now known, but recognition that airbursts (or fireballs resulting from nuclear-weapon-sized detonations of meteoroids in the atmosphere) have the potential to do greater damage than previously thought has shifted an increasing portion of the residual impact risk (the risk of impact from an unknown object) to smaller objects. Above the threshold size of impactor at which the atmosphere absorbs sufficient energy to prevent a ground impact, most of the damage is thought to be caused by the airburst shock wave, but owing to lack of observations this is uncertain. Here we report an analysis of the damage from the airburst of an asteroid about 19 metres (17 to 20 metres) in diameter southeast of Chelyabinsk, Russia, on 15 February 2013, estimated to have an energy equivalent of approximately 500 (±100) kilotons of trinitrotoluene (TNT, where 1 kiloton of TNT = 4.

Mantle shear-wave velocity structure beneath the Hawaiian hot spot.

Defining the mantle structure that lies beneath hot spots is important for revealing their depth of origin. Three-dimensional images of shear-wave velocity beneath the Hawaiian Islands, obtained from a network of sea-floor and land seismometers, show an upper-mantle low-velocity anomaly that is elongated in the direction of the island chain and surrounded by a parabola-shaped high-velocity anomaly. Low velocities continue downward to the mantle transition zone between 410 and 660 kilometers depth, a result that is in agreement with prior observations of transition-zone thinning.

Quality of care of VLBW neonates: relationship between unit volume and outcome is different between metropolitan and rural regions.

Background: Recent studies from predominantly rural areas in Germany show that neonatal outcome of very low birth weight (VLBW) neonates is (on average) inferior with lower NICU (neonatal intensive care unit) volume. However, there are no data available which show that study results of one specific region can be transferred to other areas with possibly different medical infrastructure and needs.

Aim: It was investigated whether a systematic difference of treatment quality between smaller (1000-2000 births/year; < or =20 neonatal beds) vs.

Earth's free oscillations excited by the 26 December 2004 Sumatra-Andaman earthquake.

At periods greater than 1000 seconds, Earth's seismic free oscillations have anomalously large amplitude when referenced to the Harvard Centroid Moment Tensor fault mechanism, which is estimated from 300- to 500-second surface waves. By using more realistic rupture models on a steeper fault derived from seismic body and surface waves, we approximated free oscillation amplitudes with a seismic moment (6.5 x 10(22) Newton.

Evaluation of a rapid whole blood test to detect Helicobacter pylori infection in children.

Background: Rapid, patient near tests for detecting antibodies against Helicobacter pylori are offered for clinical use. We evaluated the BM-Test (Boehringer Mannheim, Germany; identical to the Helisal Rapid Blood Test) in children with recurrent abdominal pain.

Methods: The BM-Test and 13C-urea breath test (UBT) were performed in 195 children (4-18 years).