516 research outputs found
Recommended from our members
Surface-Plasmon-Assisted Photoelectrochemical Reduction of CO2 and NO3− on Nanostructured Silver Electrodes
Electrochemical reduction of carbon dioxide (CO2) typically suffers from low selectivity and poor reaction rates that necessitate high overpotentials, which impede its possible application for CO2 capture, sequestration, or carbon-based fuel production. New strategies to address these issues include the utilization of photoexcited charge carriers to overcome activation barriers for reactions that produce desirable products. This study demonstrates surface-plasmon-enhanced photoelectrochemical reduction of CO2 and nitrate (NO3−) on silver nanostructured electrodes. The observed photocurrent likely originates from a resonant charge transfer between the photogenerated plasmonic hot electrons and the lowest unoccupied molecular orbital (MO) acceptor energy levels of adsorbed CO2, NO3−, or their reductive intermediates. The observed differences in the resonant effects at the Ag electrode with respect to electrode potential and photon energy for CO2 versus NO3− reduction suggest that plasmonic hot-carriers interact selectively with specific MO acceptor energy levels of adsorbed surface species such as CO2, NO3−, or their reductive intermediates. This unique plasmon-assisted charge generation and transfer mechanism can be used to increase yield, efficiency, and selectivity of various photoelectrochemical processes
Assessing the Impact of Anger State on the Three Attentional Networks With the ANT-I
Anger is a negative and highly aroused emotion. Previous research has revealed that a high level of arousal can induce the participant in a physical preparation and self-awareness. The aim of this research was to study the influence of anger on the attentional network using the Attention Network Test-Interactions (ANT-I). This test has been developed in order to assess 3 attentional networks: alerting, orienting, and executive control. Here, participants were induced in anger using the autobiographic recall procedure or in a neutral mood before the realization of the ANT-I. As expected, the results showed a better alerting score for the angry group. The possible origin of this alerting gain related to the high level of arousal is discussed. The results obtained should enlighten the interaction between emotion and the functioning of the attentional system. They also may be relevant for applied fields related to anger. (PsycINFO Database Record (c) 2014 APA, all rights reserved)
From Poincare to affine invariance: How does the Dirac equation generalize?
A generalization of the Dirac equation to the case of affine symmetry, with
SL(4,R) replacing SO(1,3), is considered. A detailed analysis of a Dirac-type
Poincare-covariant equation for any spin j is carried out, and the related
general interlocking scheme fulfilling all physical requirements is
established. Embedding of the corresponding Lorentz fields into
infinite-component SL(4,R) fermionic fields, the constraints on the SL(4,R)
vector-operator generalizing Dirac's gamma matrices, as well as the minimal
coupling to (Metric-)Affine gravity are studied. Finally, a symmetry breaking
scenario for SA(4,R) is presented which preserves the Poincare symmetry.Comment: 34 pages, LaTeX2e, 8 figures, revised introduction, typos correcte
Intact Semantic Priming of Critical Lures in Alzheimer's Disease: Implications for False Memory
OBJECTIVES: The present study examines the question of the activation of the critical lure (CL) in Alzheimer\u27s patients with a Deese-Roediger-McDermott (DRM)-like task. More precisely, older adults and Alzheimer\u27s patients performed a lexical decision task in which they were asked to categorize strings of letters as words or nonwords. Contrary to the DRM paradigm in which the activation of the CL is inferred from its production at recall, such a lexical decision task does not require the joint use of intentional recovery strategies and source-monitoring processes that are known to be particularly impaired in Alzheimer\u27s patients. The performance at the lexical decision therefore reflects the activation of the CL without contamination from such strategic processes. METHOD: Twenty-nine older adults and 25 Alzheimer\u27s patients performed a lexical decision task with DRM lists intermixed with neutral words and nonwords. RESULTS: Analysis indicated that older adults as well as Alzheimer\u27s patients showed shorter lexical decision latencies for CLs than for other types of words. DISCUSSION: Contrary to the existing literature, our results suggest that the activation of the CL is preserved in Alzheimer\u27s patients at mild to moderate stages of the disease
Many-body Theory vs Simulations for the pseudogap in the Hubbard model
The opening of a critical-fluctuation induced pseudogap (or precursor
pseudogap) in the one-particle spectral weight of the half-filled
two-dimensional Hubbard model is discussed. This pseudogap, appearing in our
Monte Carlo simulations, may be obtained from many-body techniques that use
Green functions and vertex corrections that are at the same level of
approximation. Self-consistent theories of the Eliashberg type (such as the
Fluctuation Exchange Approximation) use renormalized Green functions and bare
vertices in a context where there is no Migdal theorem. They do not find the
pseudogap, in quantitative and qualitative disagreement with simulations,
suggesting these methods are inadequate for this problem. Differences between
precursor pseudogaps and strong-coupling pseudogaps are also discussed.Comment: Accepted, Phys. Rev. B15 15Mar00. Expanded version of original
submission, Latex, 8 pages, epsfig, 5 eps figures (Last one new). Discussion
on fluctuation and strong coupling induced pseudogaps expande
Phase-fluctuation induced reduction of the kinetic energy at the superconducting transition
Recent reflectivity measurements provide evidence for a "violation" of the
in-plane optical integral in the underdoped high-T_c compound
Bi_2Sr_2CaCu_2O_{8+\delta} up to frequencies much higher than expected by
standard BCS theory. The sum rule violation may be related to a loss of
in-plane kinetic energy at the superconducting transition. Here, we show that a
model based on phase fluctuations of the superconducting order parameter can
account for this change of in-plane kinetic energy at T_c. The change is due to
a transition from a phase-incoherent Cooper-pair motion in the pseudogap regime
above T_c to a phase-coherent motion at T_c.Comment: 5 pages, 3 eps-figure
Quantifying loopy network architectures
Biology presents many examples of planar distribution and structural networks
having dense sets of closed loops. An archetype of this form of network
organization is the vasculature of dicotyledonous leaves, which showcases a
hierarchically-nested architecture containing closed loops at many different
levels. Although a number of methods have been proposed to measure aspects of
the structure of such networks, a robust metric to quantify their hierarchical
organization is still lacking. We present an algorithmic framework, the
hierarchical loop decomposition, that allows mapping loopy networks to binary
trees, preserving in the connectivity of the trees the architecture of the
original graph. We apply this framework to investigate computer generated
graphs, such as artificial models and optimal distribution networks, as well as
natural graphs extracted from digitized images of dicotyledonous leaves and
vasculature of rat cerebral neocortex. We calculate various metrics based on
the Asymmetry, the cumulative size distribution and the Strahler bifurcation
ratios of the corresponding trees and discuss the relationship of these
quantities to the architectural organization of the original graphs. This
algorithmic framework decouples the geometric information (exact location of
edges and nodes) from the metric topology (connectivity and edge weight) and it
ultimately allows us to perform a quantitative statistical comparison between
predictions of theoretical models and naturally occurring loopy graphs.Comment: 17 pages, 8 figures. During preparation of this manuscript the
authors became aware of the work of Mileyko at al., concurrently submitted
for publicatio
Induced local spin-singlet amplitude and pseudogap in high cuprates
In this paper we show that local spin-singlet amplitude with d-wave symmetry,
, can be induced by short-range spin correlations even
in the absence of pairing interactions. Fluctuation theory is formulated to
make connection between pseudogap temperature $T^{*}$, pseudogap size
$\Delta_{pg}$ and . In the present scenario for the
pseudogap, the normal state pseudogap is caused by the induced local
spin-singlet amplitude due to short-range spin correlations, which compete in
the low energy sector with superconducting correlations to make go to
zero near half-filling. Calculated falls from a high value onto the
line and closely follows mean-field N\'{e}el temperature .
The calculated is in good agreement with experimental results. We
propose an experiment in which the present scenario can be critically tested.Comment: 5 pages, 3 figure
- …