9,970 research outputs found
MEVTV study: Early tectonic evolution of Mars: Crustal dichotomy to Valles Marineris
Several fundamental problems were addressed in the early impact, tectonic, and volcanic evolution of the martian lithosphere: (1) origin and evolution of the fundamental crustal dichotomy, including development of the highland/lowland transition zone; (2) growth and evolution of the Valles Marineris; and (3) nature and role of major resurfacing events in early martian history. The results in these areas are briefly summarized
Observation of nonlinear dispersion relation and spatial statistics of wave turbulence on the surface of a fluid
We report experiments on gravity-capillary wave turbulence on the surface of
a fluid. The wave amplitudes are measured simultaneously in time and space
using an optical method. The full space-time power spectrum shows that the wave
energy is localized on several branches in the wave-vector-frequency space. The
number of branches depend on the power injected within the waves. The
measurement of the nonlinear dispersion relation is found to be well described
by a law suggesting that the energy transfer mechanisms involved in wave
turbulence are not only restricted to purely resonant interaction between
nonlinear waves. The power-law scaling of the spatial spectrum and the
probability distribution of the wave amplitudes at a given wave number are also
measured and compared to the theoretical predictions.Comment: accepted to Phys. Rev. Lett
Independent AND-parallel implementation of narrowing
We present a parallel graph narrowing machine, which is
used to implement a functional logic language on a shared memory multiprocessor. It is an extensión of an abstract machine for a purely functional language. The result is a programmed graph reduction machine which integrates the mechanisms of unification, backtracking, and independent
and-parallelism. In the machine, the subexpressions of an expression can run in parallel. In the case of backtracking, the structure of an expression is used to avoid the reevaluation of subexpressions as far as possible. Deterministic computations are detected. Their results are maintained and need not be reevaluated after backtracking
Depression in small-vessel disease relates to white matter ultrastructural damage, not disability.
OBJECTIVE: To determine whether cerebral small-vessel disease (SVD) is a specific risk factor for depression, whether any association is mediated via white matter damage, and to study the role of depressive symptoms and disability on quality of life (QoL) in this patient group.
METHODS: Using path analyses in cross-sectional data, we modeled the relationships among depression, disability, and QoL in patients with SVD presenting with radiologically confirmed lacunar stroke (n = 100), and replicated results in a second SVD cohort (n = 100). We then compared the same model in a non-SVD stroke cohort (n = 50) and healthy older adults (n = 203). In a further study, to determine the role of white matter damage in mediating the association with depression, a subgroup of patients with SVD (n = 101) underwent diffusion tensor imaging (DTI).
RESULTS: Reduced QoL was associated with depression in patients with SVD, but this association was not mediated by disability or cognition; very similar results were found in the replication SVD cohort. In contrast, the non-SVD stroke group and the healthy older adult group showed a direct relationship between disability and depression. The DTI study showed that fractional anisotropy, a marker of white matter damage, was related to depressive symptoms in patients with SVD.
CONCLUSION: These results suggest that in stroke patients without SVD, disability is an important causal factor for depression, whereas in SVD stroke, other factors specific to this stroke subtype have a causal role. White matter damage detected on DTI is one factor that mediates the association between SVD and depression
Elusiveness of bishomoaromaticity in anionic systems: the bicyclo[3.2.1]octa-3,6-dien-2-yl anion
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