6,671 research outputs found
Scanning Tunneling Spectroscopy of Suspended Single-Wall Carbon Nanotubes
We have performed low-temperature STM measurements on single-wall carbon
nanotubes that are freely suspended over a trench. The nanotubes were grown by
CVD on a Pt substrate with predefined trenches etched into it. Atomic
resolution was obtained on the freestanding portions of the nanotubes.
Spatially resolved spectroscopy on the suspended portion of both metallic and
semiconducting nanotubes was also achieved, showing a Coulomb-staircase
behavior superimposed on the local density of states. The spacing of the
Coulomb blockade peaks changed with tip position reflecting a changing tip-tube
capacitance
The physical environment and plant communities of the Messina Experimental Farm
A description of the climate, geology and plant communities of the study area is presented. The result of a TWINSPAN classification of 149 relevés was refined by Braun-Blanquet procedures. Eight plant communities of which one is divided into three variations, were distinguished. A hierarchical classification, ecological interpretation and vegetation map delineating the extent of the plant communities, are presented. An agro-ecological quantification of the woody vegetation was done in each plant community
Landauer-type transport theory for interacting quantum wires: Application to carbon nanotube Y junctions
We propose a Landauer-like theory for nonlinear transport in networks of
one-dimensional interacting quantum wires (Luttinger liquids). A concrete
example of current experimental focus is given by carbon nanotube Y junctions.
Our theory has three basic ingredients that allow to explicitly solve this
transport problem: (i) radiative boundary conditions to describe the coupling
to external leads, (ii) the Kirchhoff node rule describing charge conservation,
and (iii) density matching conditions at every node.Comment: final version, to be published in PR
Association of malalignment, muscular dysfunction, proprioception, laxity and abnormal joint loading with tibiofemoral knee osteoarthritis - a systematic review and meta-analysis
Background: To investigate (1) the association of specific biomechanical factors with knee osteoarthritis and knee osteoarthritis development, and (2) the impact of other relevant risk factors on this association.Methods: MEDLINE, EMBASE, CINAHL and SPORTDiscus were searched up until April 2017. Studies were included if they fulfilled the following criteria: the study 1) assessed the association of a biomechanical factor with knee osteoarthritis, or knee osteoarthritis development; 2) reported on skeletal malalignment, muscular dysfunction, impaired proprioception, laxity and abnormal loading during gait; 3) was a cohort study with participants developing knee osteoarthritis and participants not developing knee osteoarthritis, or a case-control or cross-sectional study with participants with knee osteoarthritis and without knee osteoarthritis. Risk of bias was assessed with the QUIPS tool and meta-analyses were performed using random effects models.Results: Of 6413 unique studies identified, 59 cross-sectional studies were eligible for meta-analyses (9825 participants, 5328 with knee osteoarthritis). No cohort studies fulfilled the inclusion criteria. Compared with healthy controls, patients with knee osteoarthritis have higher odds of having lower muscle strength, proprioception deficits, more medial varus-valgus laxity and less lateral varus-valgus laxity. Patients with medial knee osteoarthritis have higher odds of having a higher knee adduction moment than healthy controls. Level of evidence was graded as 'very low' to 'moderate' quality. Due to large between study differences moderation of other risk factors on biomechanical risk factors could not be evaluated.Conclusions: Patients with knee osteoarthritis are more likely to display a number of biomechanical characteristics. The causal relationship between specific biomechanical factors and the development of knee osteoarthritis could not be determined as no longitudinal studies were included. There is an urgent need for high quality, longitudinal studies to evaluate the impact of specific biomechanical factors on the development of knee osteoarthritis.Trial Registration: (PROSPERO ID: CRD42015025092)
"Bayesian anchoring" and the fourfold pattern of risk attitudes
Experiments on decision making under uncertainty are known to display a
classical pattern of risk aversion and risk seeking referred to as "fourfold
pattern" (or "reflection effect") , but recent experiments varying the speed
and order of mental processing have brought to light a more nuanced
phenomenology. We model experiments though a Bayesian formalization of the
anchor-and-adjust heuristic observed in empirical studies on cognitive bias.
Using only elementary assumptions on constrained information processing, we are
able to infer three separate effects found in recent observations: (1) the
reported enhancement of the fourfold pattern for quicker decision processes;
(2) the observed decrease of fluctuations for slower decision-making trials;
(3) the reported dependence of the outcome on the order in which options are
processed. The application of Bayesian modeling offers a solution to recent
empirical riddles by bridging two heretofore separate domains of experimental
inquiry on bounded rationality.Comment: 26 pages, 7 figure
Density waves in the shearing sheet IV. Interaction with a live dark halo
It is shown that if the self-gravitating shearing sheet, a model of a patch
of a galactic disk, is embedded in a live dark halo, this has a strong effect
on the dynamics of density waves in the sheet. I describe how the density waves
and the halo interact via halo particles either on orbits in resonance with the
wave or on non-resonant orbits. Contrary to expectation the presence of the
halo leads to a very considerable enhancement of the amplitudes of the density
waves in the shearing sheet. This effect appears to be the equivalent of the
recently reported enhanced growth of bars in numerically simulated stellar
disks embedded in live dark halos. Finally I discuss the transfer of linear
momentum from a density wave in the sheet to the halo and show that it is
mediated only by halo particles on resonant orbits.Comment: 8 pages, 4 figures, accepted by Astron. Astrophy
Piezoelectrically Actuated Linear Resonators on Ring-shaped Suspensions for Applications in MEMS Phase-sensitive Gyroscope
AbstractExcitation of linear resonators by means of thin aluminium nitride piezoelectric films processed on annular (ring-shaped) flexures was investigated. The in-plane resonance modes at 8-45kHz frequencies with quality factors >104 were measured for both single (uni-directional) and double (bi-directional) in-plane degree of freedom devices in vacuum. Annular springs have different spring constants for different directions of deformation allowing efficient decoupling of orthogonal modes in bi-directional symmetric devices. The primary application of the bi-directional resonators is in orbiting-motion MEMS gyroscopes that rely on phase-shift detection induced by external angular rates. To investigate the feasibility of differential piezoactuation for generation of motion in uni- and bi-directional devices by means of thin piezoelectric films processed on supporting annular springs, MEMS resonators were modelled, designed, fabricated and electrically characterized
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