12,007 research outputs found
Transforming the European Economy
Europe grew rapidly for many years, but now, faced with greater challenges, several of the large economies in Europe have either failed to generate enough jobs or have failed to achieve the highest levels of productivity or both. This study explores why Europe's growth slowed, what contribution information technology makes to growth, and what policies could facilitate economic transformation. It emphasizes a system with strong work incentives and a high level of competitive intensity. Europe doesn't need to eliminate its protections for individuals, the authors conclude, but both social programs and policies toward business must be reoriented so that they encourage economic change.
Icequakes coupled with surface displacements for predicting glacier break-off
A hanging glacier at the east face of Weisshorn (Switzerland) broke off in
2005. We were able to monitor and measure surface motion and icequake activity
for 25 days up to three days prior to the break-off. The analysis of seismic
waves generated by the glacier during the rupture maturation process revealed
four types of precursory signals of the imminent catastrophic rupture: (i) an
increase in seismic activity within the glacier, (ii) a decrease in the waiting
time between two successive icequakes, (iii) a change in the size-frequency
distribution of icequake energy, and (iv) a modification in the structure of
the waiting time distributions between two successive icequakes. Morevover, it
was possible to demonstrate the existence of a correlation between the seismic
activity and the log-periodic oscillations of the surface velocities
superimposed on the global acceleration of the glacier during the rupture
maturation. Analysis of the seismic activity led us to the identification of
two regimes: a stable phase with diffuse damage, and an unstable and dangerous
phase characterized by a hierarchical cascade of rupture instabilities where
large icequakes are triggered.Comment: 16 pages, 7 figure
Moment tensor inversions of icequakes on Gornergletscher, Switzerland
We have determined seismic source mechanisms for shallow and intermediate-depth icequake clusters recorded on the glacier Gornergletscher, Switzerland, during the summers of 2004 and 2006. The selected seismic events are part of a large data set of over 80,000 seismic events acquired with a dense seismic network deployed in order to study the yearly rapid drainage of Gornersee lake, a nearby ice-marginal lake. Using simple frequency and distance scaling and Green’s functions for a homogeneous half-space, we calculated moment tensor solutions for icequakes with M_w-1.5 using a full-waveform inversion method usually applied to moderate seismic events (M_w>4) recorded at local to regional distances (≈50–700 km). Inversions from typical shallow events are shown to represent tensile crack openings. This explains well the dominating Rayleigh waves and compressive first motions observed at all recording seismograms. As these characteristics can be observed in most icequake signals, we believe that the vast majority of icequakes recorded in the 2 yr is due to tensile faulting, most likely caused by surface crevasse openings. We also identified a shallow cluster with somewhat atypical waveforms in that they show less dominant Rayleigh waves and quadrantal radiation patterns of first motions. Their moment tensors are dominated by a large double-couple component, which is strong evidence for shear faulting. Although less than a dozen such icequakes have been identified, this is a substantial result as it shows that shear faulting in glacier ice is generally possible even in the absence of extreme flow changes such as during glacier surges. A third source of icequakes was located at 100 m depth. These sources can be represented by tensile crack openings. Because of the high-hydrostatic pressure within the ice at these depths, these events are most likely related to the presence of water lenses that reduce the effective stress to allow for tensile faulting
Estimating the ice thickness of mountain glaciers with a shape optimization algorithm using surface topography and mass-balance
We present a shape optimization algorithm to estimate the ice thickness distribution within a two-dimensional, non-sliding mountain glacier, given a transient surface geometry and a mass-balance distribution. The approach is based on the minimization of the surface topography misfit at the end of the glacier's evolution in the shallow ice approximation of ice flow. Neither filtering of the surface topography where its gradient vanishes nor interpolation of the basal shear stress is involved. Novelty of the presented shape optimization algorithm is the use of surface topography and mass-balance only within a time-dependent Lagrangian approach for moving-boundary glaciers. On real-world inspired geometries, it is shown to produce estimations of even better quality in smaller time than the recently proposed steady and transient inverse methods. A sensitivity analysis completes the study and evinces the method's higher susceptibility to perturbations in the surface topography than in surface mass-balance or rate facto
Investigating calving front dynamics with a local seismic-infrasound network (Bowdoin glacier, Greenland)
第6回極域科学シンポジウム分野横断セッション:[IA] 急変する北極気候システム及びその全球的な影響の総合的解明―GRENE北極気候変動研究事業研究成果報告2015―11月19日(木) 国立極地研究所 2階 大会議
Physical and Biogeochemical Studies in the Subtropical and Tropical Atlantic
Maria S. Merian Cruise Report MSM18/L2
Cruise No. 18, Leg 2
May 11 – June 19, 2011
Mindelo (Cape Verde Islands) – Mindelo (Cape Verde Islands
Selection and counterselection of the rtI233V adefovir resistance mutation during antiviral therapy
Recently, we reported on three patients with chronic hepatitis B virus (HBV) infection for whom adefovir (ADF) therapy virologically failed, most likely due to a preexisting rtI233V HBV polymerase mutation. Here, we describe two further patients with chronic HBV infection who were found to develop the rtI233V mutation after initiation of ADF therapy. These patients represent the first cases known so far in which the rtI233V ADF resistance mutation evolved under persistent HBV replication during HBV therapy with ADF. Interestingly, one of the previously described patients, who was initially successfully switched from ADF to tenofovir (TDF) and became virologically suppressed subsequently, experienced a moderate but remarkable rebound of HBV viremia after switching from TDF to entecavir, due to the emergence of renal toxicity. Thus, we provide evidence for the selection and counterselection of the rtI233V ADF resistance mutation during antiviral therapy
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