235 research outputs found
High-Frequency Nanofluidics: An Experimental Study using Nanomechanical Resonators
Here we apply nanomechanical resonators to the study of oscillatory fluid
dynamics. A high-resonance-frequency nanomechanical resonator generates a
rapidly oscillating flow in a surrounding gaseous environment; the nature of
the flow is studied through the flow-resonator interaction. Over the broad
frequency and pressure range explored, we observe signs of a transition from
Newtonian to non-Newtonian flow at , where is a
properly defined fluid relaxation time. The obtained experimental data appears
to be in close quantitative agreement with a theory that predicts purely
elastic fluid response as
Interactions between directly and parametrically driven vibration modes in a micromechanical resonator
The interactions between parametrically and directly driven vibration modes
of a clamped-clamped beam resonator are studied. An integrated piezoelectric
transducer is used for direct and parametric excitation. First, the parametric
amplification and oscillation of a single mode are analyzed by the power and
phase dependence below and above the threshold for parametric oscillation.
Then, the motion of a parametrically driven mode is detected by the induced
change in resonance frequency in another mode of the same resonator. The
resonance frequency shift is the result of the nonlinear coupling between the
modes by the displacement-induced tension in the beam. These nonlinear modal
interactions result in the quadratic relation between the resonance frequency
of one mode and the amplitude of another mode. The amplitude of a
parametrically oscillating mode depends on the square root of the pump
frequency. Combining these dependencies yields a linear relation between the
resonance frequency of the directly driven mode and the frequency of the
parametrically oscillating mode.Comment: 5 pages, 4 figure
A Universality in Oscillating Flows
We show that oscillating flow of a simple fluid in both the Newtonian and the
non-Newtonian regime can be described by a universal function of a single
dimensionless scaling parameter , where is the oscillation
(angular) frequency and is the fluid relaxation-time; geometry and
linear dimension bear no effect on the flow. Experimental energy dissipation
data of mechanical resonators in a rarefied gas follow this universality
closely in a broad linear dimension ( m m) and
frequency ( Hz Hz) range. Our results suggest a
deep connection between flows of simple and complex fluids.Comment: To be published in Physical Review Letter
Network Behavior in Thin Film Growth Dynamics
We present a new network modeling approach for various thin film growth
techniques that incorporates re-emitted particles due to the non-unity sticking
coefficients. We model re-emission of a particle from one surface site to
another one as a network link, and generate a network model corresponding to
the thin film growth. Monte Carlo simulations are used to grow films and
dynamically track the trajectories of re-emitted particles. We performed
simulations for normal incidence, oblique angle, and chemical vapor deposition
(CVD) techniques. Each deposition method leads to a different dynamic evolution
of surface morphology due to different sticking coefficients involved and
different strength of shadowing effect originating from the obliquely incident
particles. Traditional dynamic scaling analysis on surface morphology cannot
point to any universal behavior. On the other hand, our detailed network
analysis reveals that there exist universal behaviors in degree distributions,
weighted average degree versus degree, and distance distributions independent
of the sticking coefficient used and sometimes even independent of the growth
technique. We also observe that network traffic during high sticking
coefficient CVD and oblique angle deposition occurs mainly among edges of the
columnar structures formed, while it is more uniform and short-range among
hills and valleys of small sticking coefficient CVD and normal angle
depositions that produce smoother surfaces.Comment: 11 pages, 9 figures, revtex
The effect of modafinil on the rat dopamine transporter and dopamine receptors D1–D3 paralleling cognitive enhancement in the radial arm maze
A series of drugs have been reported to increase memory performance modulating the dopaminergic system and herein modafinil was tested for its working memory (WM) enhancing properties. Reuptake inhibition of dopamine, serotonin (SERT) and norepinephrine (NET) by modafinil was tested. Sixty male Sprague–Dawley rats were divided into six groups (modafinil-treated 1–5–10 mg/kg body weight, trained and untrained and vehicle treated trained and untrained rats; daily injected intraperitoneally for a period of 10 days) and tested in a radial arm maze (RAM), a paradigm for testing spatial WM. Hippocampi were taken 6 h following the last day of training and complexes containing the unphosphorylated or phosphorylated dopamine transporter (DAT-CC and pDAT-CC) and complexes containing the D1–3 dopamine receptor subunits (D1–D3-CC) were determined. Modafinil was binding to the DAT but insignificantly to SERT or NET and dopamine reuptake was blocked specifically (IC50 = 11.11 μM; SERT 1547 μM; NET 182 μM). From day 8 (day 9 for 1 mg/kg body weight) modafinil was decreasing WM errors (WMEs) in the RAM significantly and remarkably at all doses tested as compared to the vehicle controls. WMEs were linked to the D2R-CC and the pDAT-CC. pDAT and D1–D3-CC levels were modulated significantly and modafinil was shown to enhance spatial WM in the rat in a well-documented paradigm at all the three doses and dopamine reuptake inhibition with subsequent modulation of D1–3-CC is proposed as a possible mechanism of action. © 2015 Karabacak, Sase, Aher, Sase, Saroja, Cicvaric, Höger, Berger, Bakulev, Sitte, Leban, Monje and Lubec
Analytical solution of second Stokes problem of behaviour of rarefied gas with Cercignani boundary accomodation conditions
Analytical solution of second Stokes problem of behaviour of rarefied gas
with Cercignani boundary accomodation conditions The second Stokes problem
about behaviour of rarefied gas filling half-space is analytically solved. A
plane, limiting half-space, makes harmonious fluctuations in the plane. The
kinetic BGK-equation (Bhatnagar, Gross, Krook) is used. The boundary
accomodation conditions of Cercignani of reflexion gaseous molecules from a
wall are considered. Distribution function of the gaseous molecules is
constructed. The velocity of gas in half-space is found, also its value direct
at a wall is found. The force resistance operating from gas on border is found.
Besides, the capacity of dissipation of the energy falling to unit of area of
the fluctuating plate limiting gas is obtained.Comment: 26 pages, 5 figure
Minimization of phonon-tunneling dissipation in mechanical resonators
Micro- and nanoscale mechanical resonators have recently emerged as
ubiquitous devices for use in advanced technological applications, for example
in mobile communications and inertial sensors, and as novel tools for
fundamental scientific endeavors. Their performance is in many cases limited by
the deleterious effects of mechanical damping. Here, we report a significant
advancement towards understanding and controlling support-induced losses in
generic mechanical resonators. We begin by introducing an efficient numerical
solver, based on the "phonon-tunneling" approach, capable of predicting the
design-limited damping of high-quality mechanical resonators. Further, through
careful device engineering, we isolate support-induced losses and perform the
first rigorous experimental test of the strong geometric dependence of this
loss mechanism. Our results are in excellent agreement with theory,
demonstrating the predictive power of our approach. In combination with recent
progress on complementary dissipation mechanisms, our phonon-tunneling solver
represents a major step towards accurate prediction of the mechanical quality
factor.Comment: 12 pages, 4 figure
Constraining Bosonic Supersymmetry from Higgs results and 8 TeV ATLAS multi-jets plus missing energy data
The collider phenomenology of models with Universal Extra Dimensions (UED) is
surprisingly similar to that of supersymmetric (SUSY) scenarios. For each
level-1 bosonic (fermionic) Kaluza-Klein (KK) state, there is a fermionic
(bosonic) analog in SUSY and thus UED scenarios are often known as bosonic
supersymmetry. The minimal version of UED (mUED) gives rise to a
quasi-degenerate particle spectrum at each KK-level and thus, can not explain
the enhanced Higgs to diphoton decay rate hinted by the ATLAS collaboration of
the Large Hadron Collider (LHC) experiment. However, in the non-minimal version
of the UED (nmUED) model, the enhanced Higgs to diphoton decay rate can be
easily explained via the suitable choice of boundary localized kinetic (BLK)
terms for higher dimensional fermions and gauge bosons. BLK terms remove the
degeneracy in the KK mass spectrum and thus, pair production of level-1 quarks
and gluons at the LHC gives rise to hard jets, leptons and large missing energy
in the final state. These final states are studied in details by the ATLAS and
CMS collaborations in the context of SUSY scenarios. We find that the absence
of any significant deviation of the data from the Standard Model (SM)
prediction puts a lower bound of about 2.1 TeV on equal mass excited quarks and
gluons.Comment: 19 page
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