32,243 research outputs found
Measurements of inclusive jet and dijet cross sections at the Large Hadron Collider
This review discusses the measurements of the inclusive jet and dijet cross
section performed by the experimental collaborations at the LHC during what is
now being called LHC Run 1 (2009 - 2013). It summarises some of the
experimental challenges and the techniques used in the measurements of jets
cross sections during the LHC Run 1.Comment: Contribution to "Jet Measurements at the LHC", G. Dissertori ed. To
appear in International Journal of Modern Physics A (IJMPA
A temperate former West Antarctic ice sheet suggested by an extensive zone of bed channels
Several recent studies predict that the West Antarctic Ice Sheet will become increasingly unstable under warmer conditions. Insights on such change can be assisted through investigations of the subglacial landscape, which contains imprints of former ice-sheet behavior. Here, we present radio-echo sounding data and satellite imagery revealing a series of ancient large sub-parallel subglacial bed channels preserved in the region between the Möller and Foundation Ice Streams, West Antarctica. We suggest that these newly recognized channels were formed by significant meltwater routed along the icesheet bed. The volume of water required is likely substantial and can most easily be explained by water generated at the ice surface. The Greenland Ice Sheet today exemplifies how significant seasonal surface melt can be transferred to the bed via englacial routing. For West Antarctica, the Pliocene (2.6–5.3 Ma) represents the most recent sustained period when temperatures could have been high enough to generate surface melt comparable to that of present-day Greenland. We propose, therefore, that a temperate ice sheet covered this location during Pliocene warm periods
How are Forbush decreases related to interplanetary magnetic field enhancements ?
Aims. Forbush decrease (FD) is a transient decrease followed by a gradual
recovery in the observed galactic cosmic ray intensity. We seek to understand
the relationship between the FDs and near-Earth interplanetary magnetic field
(IMF) enhancements associated with solar coronal mass ejections (CMEs).
Methods. We use muon data at cutoff rigidities ranging from 14 to 24 GV from
the GRAPES-3 tracking muon telescope to identify FD events. We select those FD
events that have a reasonably clean profile, and magnitude > 0.25%. We use IMF
data from ACE/WIND spacecrafts. We look for correlations between the FD profile
and that of the one hour averaged IMF. We ask if the diffusion of high energy
protons into the large scale magnetic field is the cause of the lag observed
between the FD and the IMF. Results. The enhancement of the IMF associated with
FDs occurs mainly in the shock-sheath region, and the turbulence level in the
magnetic field is also enhanced in this region. The observed FD profiles look
remarkably similar to the IMF enhancement profiles. The FDs typically lag the
IMF enhancement by a few hours. The lag corresponds to the time taken by high
energy protons to diffuse into the magnetic field enhancement via cross-field
diffusion. Conclusions. Our findings show that high rigidity FDs associated
with CMEs are caused primarily by the cumulative diffusion of protons across
the magnetic field enhancement in the turbulent sheath region between the shock
and the CME.Comment: accepted in A&
Digital image correlation (DIC) analysis of the 3 December 2013 Montescaglioso landslide (Basilicata, Southern Italy). Results from a multi-dataset investigation
Image correlation remote sensing monitoring techniques are becoming key tools for
providing effective qualitative and quantitative information suitable for natural hazard assessments,
specifically for landslide investigation and monitoring. In recent years, these techniques have
been successfully integrated and shown to be complementary and competitive with more standard
remote sensing techniques, such as satellite or terrestrial Synthetic Aperture Radar interferometry.
The objective of this article is to apply the proposed in-depth calibration and validation analysis,
referred to as the Digital Image Correlation technique, to measure landslide displacement.
The availability of a multi-dataset for the 3 December 2013 Montescaglioso landslide, characterized
by different types of imagery, such as LANDSAT 8 OLI (Operational Land Imager) and TIRS
(Thermal Infrared Sensor), high-resolution airborne optical orthophotos, Digital Terrain Models
and COSMO-SkyMed Synthetic Aperture Radar, allows for the retrieval of the actual landslide
displacement field at values ranging from a few meters (2–3 m in the north-eastern sector of the
landslide) to 20–21 m (local peaks on the central body of the landslide). Furthermore, comprehensive
sensitivity analyses and statistics-based processing approaches are used to identify the role of the
background noise that affects the whole dataset. This noise has a directly proportional relationship to
the different geometric and temporal resolutions of the processed imagery. Moreover, the accuracy
of the environmental-instrumental background noise evaluation allowed the actual displacement
measurements to be correctly calibrated and validated, thereby leading to a better definition of
the threshold values of the maximum Digital Image Correlation sub-pixel accuracy and reliability
(ranging from 1/10 to 8/10 pixel) for each processed dataset
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