539 research outputs found
Formation of capillary bridges in AFM-like geometry
We discuss the phase diagram of fluid confined in AFM-like geometry. It
combines the properties of capillary condensation and complete filling of a
wedge.Comment: 9 pages, 7 figure
The influence of line tension on the formation of liquid bridges
The formation of liquid bridges between a planar and conical substrates is
analyzed macroscopically taking into account the line tension. Depending on the
value of the line tension coefficient \tau and geometric parameters of the
system one observes two different scenarios of liquid bridge formation upon
changing the fluid state along the bulk liquid-vapor coexistence. For \tau >
\tau * (\tau * < 0) there is a first-order transition to a state with
infinitely thick liquid bridge. For \tau < \tau * the scenario consists of two
steps: first there is a first-order transition to a state with liquid bridge of
finite thickness which upon further increase of temperature is followed by
continuous growth of the thickness of the bridge to infinity. In addition to
constructing the relevant phase diagram we examine the dependence of the width
of the bridge on thermodynamic and geometric parameters of the system.Comment: 4 pages, 5 figure
The evolution of a Ku-Band satellite network
The purpose of this study was to undertake the management and development of CTS terminals and time on appropriate Ku-Band satellites was procured. A community of public service users who have readily addressable needs and resources to pay for services on an ad hoc Ku-Band network was developed and a test network for selected users was managed
A novel approach to structural load control using intelligent actuators
The recent trend towards large multi-MW wind turbines resulted in the role of the control system becoming increasingly important. The extension of the role of the controller to alleviate structural loads has motivated the exploration of novel control strategies, which seek to maximise load reduction by exploiting the blade pitch system. The reduction of blade fatigue loads through individual blade pitch control is one of the examples. A novel approach to reduction of the unbalanced rotor loads by pitch control is presented in this paper. Each blade is equipped with its own actuator,sensors and controller. These local blade control loops operate in isolation without a need of communication with each other. The single blade control approach to regulation of unbalanced rotor loads presented in this paper has an important advantage of being relatively easy to design and tune. Furthermore, it does not affect the operation of the central controller and the latter need not be re-designed when used in conjunction with the single blade controllers. Their performance is assessed using BLADED simulations
Mesoscopic analysis of Gibbs' criterion for sessile nanodroplets on trapezoidal substrates
By taking into account precursor films accompanying nanodroplets on
trapezoidal substrates we show that on a mesoscopic level of description one
does not observe the phenomenon of liquid-gas-substrate contact line pinning at
substrate edges. This phenomenon is present in a macroscopic description and
leads to non-unique contact angles which can take values within a range
determined by the so-called Gibbs' criterion. Upon increasing the volume of the
nanodroplet the apparent contact angle evaluated within the mesoscopic approach
changes continuously between two limiting values fulfilling Gibbs' criterion
while the contact line moves smoothly across the edge of the trapezoidal
substrate. The spatial extent of the range of positions of the contact line,
corresponding to the variations of the contact angle between the values given
by Gibbs' criterion, is of the order of ten fluid particle diameters.Comment: 23 pages, 27 figure
Left Atrial Function Is Associated with Earlier Need for Cardiac Surgery in Moderate to Severe Mitral Regurgitation: Usefulness in Targeting for Early Surgery
BACKGROUND: The aim of this study was to determine whether assessment of left atrial (LA) function helps identify patients at risk for early deterioration during follow-up with mitral valve prolapse and mitral regurgitation. METHODS: Patients with moderate to severe mitral regurgitation but no guideline-based indications for surgery were retrospectively identified from a dedicated clinical database. Maximal and minimal LA volumes were used to derive total LA emptying fraction ([maximal LA volume - minimal LA volume]/maximal L volume × 100%). Average values of peak contractile, conduit, and reservoir strain were obtained using two-dimensional speckle-tracking imaging. The study outcome was time to mitral surgery. RESULTS: One hundred seventeen patients were included; median follow-up was 18 months. Sixty-eight patients underwent surgery. Receiver operating characteristic curves were used to derive optimal cutoffs for TLAEF (>50.7%) and strain (reservoir, >28.5%; contractile, >12.5%). Using Cox analysis, TLAEF and contractile, reservoir, and conduit strain were univariate predictors of time to event. After multivariate analysis, TLAEF (hazard ratio, 2.59; P = .001), reservoir strain (hazard ratio, 3.06; P < .001), and contractile strain (hazard ratio, 2.01; P = .022) remained independently associated with events, but conduit strain did not. Using Kaplan-Meier curves, event-free survival was considerably improved in patients with values above the derived thresholds (TLAEF: 1-year survival, 78 ± 5% vs 28 ± 8%; 3-year survival, 68 ± 6% vs 13 ± 5%; P < .001 for both; reservoir strain: 1-year survival, 79 ± 5% vs 29 ± 7%; 3-year survival, 67 ± 6% vs 15 ± 6%; P < .001 for both; contractile strain: 1-year survival, 80 ± 5% vs 41 ± 7%; 3-year survival, 69 ± 6% vs 24 ± 6%; P < .001 for both). CONCLUSION: LA function is independently associated with surgery-free survival in patients with mitral valve prolapse and moderate to severe mitral regurgitation. Quantitative assessment of LA function may have clinical utility in guiding early surgical intervention in these patients
The Micro-Arcsecond Scintillation-Induced Variability (MASIV) Survey II: The First Four Epochs
We report on the variability of 443 flat spectrum, compact radio sources
monitored using the VLA for 3 days in 4 epochs at ~ 4 month intervals at 5 GHz
as part of the Micro-Arcsecond Scintillation-Induced Variability (MASIV)
survey. Over half of these sources exhibited 2-10% rms variations on timescales
over 2 days. We analyzed the variations by two independent methods, and find
that the rms variability amplitudes of the sources correlate with the emission
measure in the ionized Interstellar Medium along their respective lines of
sight. We thus link the variations with interstellar scintillation of
components of these sources, with some (unknown) fraction of the total flux
density contained within a compact region of angular diameter in the range
10-50 micro-arcseconds. We also find that the variations decrease for high mean
flux density sources and, most importantly, for high redshift sources. The
decrease in variability is probably due either to an increase in the apparent
diameter of the source, or a decrease in the flux density of the compact
fraction beyond z ~ 2. Here we present a statistical analysis of these results,
and a future paper will the discuss the cosmological implications in detail.Comment: 62 pages, 13 figures. Accepted for publication in the Astrophysical
Journa
Unusual Flaring Activity in the Blazar PKS 1424-418 during 2008-2011
Context. Blazars are a subset of active galactic nuclei (AGN) with jets that
are oriented along our line of sight. Variability and spectral energy
distribution (SED) studies are crucial tools for understanding the physical
processes responsible for observed AGN emission.
Aims. We report peculiar behaviour in the bright gamma-ray blazar PKS
1424-418 and use its strong variability to reveal information about the
particle acceleration and interactions in the jet. Methods. Correlation
analysis of the extensive optical coverage by the ATOM telescope and nearly
continuous gamma-ray coverage by the Fermi Large Area Telescope is combined
with broadband, time-dependent modeling of the SED incorporating supplemental
information from radio and X-ray observations of this blazar.
Results. We analyse in detail four bright phases at optical-GeV energies.
These flares of PKS 1424-418 show high correlation between these energy ranges,
with the exception of one large optical flare that coincides with relatively
low gamma-ray activity. Although the optical/gamma-ray behaviour of PKS
1424-418 shows variety, the multiwavelength modeling indicates that these
differences can largely be explained by changes in the flux and energy spectrum
of the electrons in the jet that are radiating. We find that for all flares the
SED is adequately represented by a leptonic model that includes inverse Compton
emission from external radiation fields with similar parameters.
Conclusions. Detailed studies of individual blazars like PKS 1424-418 during
periods of enhanced activity in different wavebands are helping us identify
underlying patterns in the physical parameters in this class of AGN.Comment: accepted for publication in A&
Heasim and Skyback Simulation Tools and Their Application to the Hitomi Mission
We present an introduction to the heasim multimission observation and skyback background, high-energy pseudo Monte Carlo astrophysical simulation tools. Heasim may be used to accurately and efficiently construct flexible image transport system (FITS) event files for simple or composite sources with a wide range of standard and user-defined spatial, spectral, and temporal characteristics. Skyback is designed to enable users to assess the impact of background discrete and diffuse emission on prospective observations, and skyback output may be directly input into heasim. We present a brief overview of heasim and skyback input, algorithms, usage, and output. We also introduce the sxsbranch tool that computes Hitomi soft X-ray spectrometer resolution grade branching ratios, emphasizing its application to simulations. We include several examples of particular relevance to the Hitomi mission
Defect ferromagnetism induced by lower valence cation doping:Li-doped SnO(2)nanoparticles
To explore the role of Li in establishing room-temperature ferromagnetism in SnO2, the structural, electronic and magnetic properties of Li-doped SnO(2)compounds were studied for different size regimes, from nanoparticles to bulk crystals. Li-doped nanoparticles show ferromagnetic ordering plus a paramagnetic contribution for particle sizes in the range of 16-51 nm, while pure SnO(2)and Li-doped compounds below and above this particular size range are diamagnetic. The magnetic moment is larger for compositions where the Li substitutes for Sn than for compositions where Li prevalently occupies interstitial sites. The observed ferromagnetic ordering in Li-doped SnO(2)nanoparticles is mainly due to the holes created when Li substitutes at a Sn site. Conversely, Li acts as an electron donor and electrons from Li may combine with holes to decrease ferromagnetism when lithium mainly occupies interstitial sites in the SnO(2)lattice
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