7,818 research outputs found
Strongly coupled modes in a weakly driven micromechanical resonator
We demonstrate strong coupling between the flexural vibration modes of a
clamped-clamped micromechanical resonator vibrating at low amplitudes. This
coupling enables the direct measurement of the frequency response via
amplitude- and phase modulation schemes using the fundamental mode as a
mechanical detector. In the linear regime, a frequency shift of
is observed for a mode with a line width of
in vacuum. The measured response is well-described by the
analytical model based on the Euler-Bernoulli beam including tension.
Calculations predict an upper limit for the room-temperature Q-factor of
for our top-down fabricated micromechanical beam
resonators.Comment: 9 pages, 2 figure
Recommended from our members
Measuring the impact of observations on the predictability of the Kuroshio Extension in a shallow-water model
In this paper sequential importance sampling is used to assess the impact of observations on a ensemble prediction for the decadal path transitions of the Kuroshio Extension (KE). This particle filtering approach gives access to the probability density of the state vector, which allows us to determine the predictive power — an entropy based measure — of the ensemble prediction. The proposed set-up makes use of an ensemble that, at each time, samples the climatological probability distribution. Then, in a post-processing step, the impact of different sets of observations is measured by the increase in predictive power of the ensemble over the climatological signal during one-year. The method is applied in an identical-twin
experiment for the Kuroshio Extension using a reduced-gravity shallow water model. We investigate the impact of assimilating velocity observations from different locations during the elongated and the contracted meandering state of the KE. Optimal observations location correspond to regions with strong potential vorticity gradients. For the elongated state the optimal location is in the first meander of the KE. During the contracted state of the KE it is located south of Japan, where the Kuroshio separates from the coast
Somatisation and functional impairment in adolescents: longitudinal link with mothers' reactions
Adolescents' somatisation (i.e., the psychological tendency to experience and report multiple physical complaints for which no definite medical cause can be found; SOM) and functional impairment (i.e., all bothersome aftermath of somatisation; FI) were studied in relation to mothers' protection, encouraging/monitoring, and minimisation of physical functional complaints. Besides main effects, interaction effects with other child and parenting characteristics were examined. A total of 990 adolescents and their mothers filled out questionnaires when the adolescents were respectively 12-13 (T1) and 13-14 (T2) years old. At T1, there was a significant relation between mothers' higher amounts of minimisation and adolescents' higher levels of SOM. Further, the link between mothers' higher levels of T1 minimisation and adolescents' higher amounts of T1 FI was significant, but not for adolescents with high levels of depressive mood. Longitudinal analyses revealed that mothers' reactions did not significantly predict adolescents' SOM/FI, nor did adolescents' SOM/FI significantly predict mothers' reactions. Practical implications are discussed
Numerical simulations on the motion of atoms travelling through a standing-wave light field
The motion of metastable helium atoms travelling through a standing light
wave is investigated with a semi-classical numerical model. The results of a
calculation including the velocity dependence of the dipole force are compared
with those of the commonly used approach, which assumes a conservative dipole
force. The comparison is made for two atom guiding regimes that can be used for
the production of nanostructure arrays; a low power regime, where the atoms are
focused in a standing wave by the dipole force, and a higher power regime, in
which the atoms channel along the potential minima of the light field. In the
low power regime the differences between the two models are negligible and both
models show that, for lithography purposes, pattern widths of 150 nm can be
achieved. In the high power channelling regime the conservative force model,
predicting 100 nm features, is shown to break down. The model that incorporates
velocity dependence, resulting in a structure size of 40 nm, remains valid, as
demonstrated by a comparison with quantum Monte-Carlo wavefunction
calculations.Comment: 9 pages, 4 figure
Initialization by measurement of a two-qubit superconducting circuit
We demonstrate initialization by joint measurement of two transmon qubits in
3D circuit quantum electrodynamics. Homodyne detection of cavity transmission
is enhanced by Josephson parametric amplification to discriminate the two-qubit
ground state from single-qubit excitations non-destructively and with 98.1%
fidelity. Measurement and postselection of a steady-state mixture with 4.7%
residual excitation per qubit achieve 98.8% fidelity to the ground state, thus
outperforming passive initialization.Comment: 5 pages, 4 figures, and Supplementary Information (7 figures, 1
table
The association between parenting behavior and somatization in adolescents explained by physiological responses in adolescents
Introduction: This study adds to the knowledge on somatization in adolescents by exploring its relation with parenting behavior and the mediating/moderating role of physiological responses in adolescents to parenting behavior. Method: Eighteen adolescents with high and 18 adolescents with low somatization scores and their mothers completed a discussion task, from which observed parenting behavior scores were derived. Skin conductance in adolescents was measured before and during the discussion. Results: For adolescents with high levels of physiological responses, unadaptive parenting was related to a higher chance of high somatization scores. For low physiologically responsive adolescents, the relation between parenting behavior and somatization was not significant. Conclusion: Parenting behavior is not univocally related to somatization in adolescents, but the association depends on physiological responses in adolescents. (C) 2014 Elsevier B.V. All rights reserved
Time correlations in a confined magnetized free-electron gas
The time-dependent pair correlation functions for a degenerate ideal quantum
gas of charged particles in a uniform magnetic field are studied on the basis
of equilibrium statistics. In particular, the influence of a flat hard wall on
the correlations is investigated, both for a perpendicular and a parallel
orientation of the wall with respect to the field. The coherent and incoherent
parts of the time-dependent structure function in position space are determined
from an expansion in terms of the eigenfunctions of the one-particle
Hamiltonian. For the bulk of the system, the intermediate scattering function
and the dynamical structure factor are derived by taking successive Fourier
transforms. In the vicinity of the wall the time-dependent coherent structure
function is found to decay faster than in the bulk. For coinciding positions
near the wall the form of the structure function turns out to be independent of
the orientation of the wall. Numerical results are shown to corroborate these
findings.Comment: 25 pages, 14 figures, to be published in Journal of Physics
Long-Ranged Orientational Order in Dipolar Fluids
Recently Groh and Dietrich claimed the thermodynamic state of a dipolar fluid
depends on the shape of the fluid's container. For example, a homogeneous fluid
in a short fat container would phase separate when transferred to a tall skinny
container of identical volume and temperature. Their calculation thus lacks a
thermodynamic limit. We show that removal of demagnetizing fields restores the
true, shape independent, thermodynamic limit. As a consequence, spontaneously
magnetized liquids display inhomogeneous magnetization textures.Comment: 3 pages, LaTex, no figures. Submitted as comment to PRL, May 199
Spin Stiffness in the Hubbard model
The spin stiffness of the repulsive Hubbard model that occurs
in the hydrodynamic theory of antiferromagnetic spin waves is shown to be the
same as the thermodynamically defined stiffness involved in twisting the order
parameter. New expressions for are derived, which enable easier
interpretation, and connections with superconducting weight and gauge
invariance are discussed.Comment: 21 Pages LaTeX2e, to be published in Journal of Physics
The relation between parenting stress and adolescents' somatisation trajectories: a growth mixture analysis
Objective: The impact of somatisation in adolescence is substantial. Knowledge on (predictors of) individual-level development of somatisation is necessary to develop tailored treatment. The current study assessed individual-level development of somatisation by means of latent mixed modelling. Parenting stress was included as a predictor of somatisation trajectory membership and within-trajectory variation. Methods: A total of 1499 adolescents and one of their parents (mostly the mother) agreed to participate. Questionnaires were administered when the adolescents were respectively 12-13 (T1), 13-14 (T2), and 14-15 (T3) years old. Adolescents reported on their somatisation, parents on their parenting stress. Results: Four individual somatisation trajectories were found: increased, long-term low, long-term high, and decreased. Higher early parenting stress (T1) significantly predicted less favourable trajectory membership (increased and long-term high). The relation between later parenting stress (T2 and T3) and somatisation depended on trajectory membership. For adolescents in the long-term high and decreased somatisation trajectories, lower T2 and T3 parenting stress was related to higher somatisation, while for adolescents in the long-term low and increased trajectories, higher T2 and T3 parenting stress was related to higher somatisation. Conclusions: The results support a general recommendation to prevent the onset of high levels of parenting stress. In addition, for families in which high levels of parenting stress already exist, clinicians should be aware of natural fluctuations in parenting stress, its associated features (e.g., aspects of overall care, like looking for professional help) and of the consequences this might have for the adolescent
- …