221 research outputs found
Dealloying of Platinum-Aluminum Thin Films Part II. Electrode Performance
Highly porous Pt/Al thin film electrodes on yttria stabilized zirconia
electrolytes were prepared by dealloying of co-sputtered Pt/Al films. The
oxygen reduction capability of the resulting electrodes was analyzed in a solid
oxide fuel cell setup at elevated temperatures. During initial heating to 523 K
exceptionally high performances compared to conventional Pt thin film
electrodes were measured. This results from the high internal surface area and
large three phase boundary length obtained by the dealloying process. Exposure
to elevated temperatures of 673 K or 873 K gave rise to degradation of the
electrode performance, which was primarily attributed to the oxidation of
remaining Al in the thin films.Comment: 5 pages, 4 figure
Dealloying of Platinum-Aluminum Thin Films Part I. Dynamics of Pattern Formation
Applying focused ion beam (FIB) nanotomography and Rutherford backscattering
spectroscopy (RBS) to dealloyed platinum-aluminum thin films an in-depth
analysis of the dominating physical mechanisms of porosity formation during the
dealloying process is performed. The dynamical porosity formation due to the
dissolution of the less noble aluminum in the alloy is treated as result of a
reaction-diffusion system. The RBS analysis yields that the porosity formation
is mainly caused by a linearly propagating diffusion front, i.e. the
liquid/solid interface, with a uniform speed of 42(3) nm/s when using a 4M
aqueous NaOH solution at room temperature. The experimentally observed front
evolution is captured by the normal diffusive
Fisher-Kolmogorov-Petrovskii-Piskounov (FKPP) equation and can be interpreted
as a branching random walk phenomenon. The etching front produces a gradual
porosity with an enhanced porosity in the surface-near regions of the thin film
due to prolonged exposure of the alloy to the alkaline solution.Comment: 4 pages, 5 figure
Anatomical variation of bony pelvis from the viewpoint of transobturator sling placement for stress urinary incontinence
Efficient template attacks
This is the accepted manuscript version. The final published version is available from http://link.springer.com/chapter/10.1007/978-3-319-08302-5_17.Template attacks remain a powerful side-channel technique to eavesdrop on tamper-resistant hardware. They model the probability distribution of leaking signals and noise to guide a search for secret data values. In practice, several numerical obstacles can arise when implementing such attacks with multivariate normal distributions. We propose efficient methods to avoid these. We also demonstrate how to achieve significant performance improvements, both in terms of information extracted and computational cost, by pooling covariance estimates across all data values. We provide a detailed and systematic overview of many different options for implementing such attacks. Our experimental evaluation of all these methods based on measuring the supply current of a byte-load instruction executed in an unprotected 8-bit microcontroller leads to practical guidance for choosing an attack algorithm.Omar Choudary is a recipient of the Google Europe Fellowship in
Mobile Security, and this research is supported in part by this Google Fellowship
Second-harmonic generation from coupled plasmon modes in a single dimer of gold nanospheres
We show that a dimer made of two gold nanospheres exhibits a remarkable
efficiency for second-harmonic generation under femtosecond optical excitation.
The detectable nonlinear emission for the given particle size and excitation
wavelength arises when the two nanoparticles are as close as possible to
contact, as in situ controlled and measured using the tip of an atomic force
microscope. The excitation wavelength dependence of the second-harmonic signal
supports a coupled plasmon resonance origin with radiation from the dimer gap.
This nanometer-size light source might be used for high-resolution near-field
optical microscopy.Comment: 6 pages, 5 figure
Trocar-guided total tension-free vaginal mesh repair of post-hysterectomy vaginal vault prolapse
Contains fulltext :
81076.pdf (publisher's version ) (Closed access)INTRODUCTION AND HYPOTHESIS: The objective of this study was to report 1 year anatomical and functional outcomes of trocar-guided total tension-free vaginal mesh (Prolift) repair for post-hysterectomy vaginal vault prolapse with one continuous piece of polypropylene mesh. METHODS: We conducted a prospective observational cohort study of 46 patients. A minimum sample size of 35 patients was needed to detect a recurrence rate of less than 20% at 12 months. Instruments of measurement used were pelvic organ prolapse quantification and validated questionnaires. RESULTS: Overall anatomical success was 91% (95% confidence interval 83-99), with significant improvement in experienced bother and quality of life. Mesh exposure occurred in seven patients (15%). No adverse effects on sexual function could be detected. CONCLUSIONS: Trocar-guided total tension-free vaginal mesh (Prolift) repair with one continuous piece of mesh for post-hysterectomy vaginal vault prolapse is well tolerated and anatomically and functionally highly effective. Results of controlled trials will determine its position in the operative armamentarium
Mode imaging and selection in strongly coupled nanoantennas
The number of eigenmodes in plasmonic nanostructures increases with
complexity due to mode hybridization, raising the need for efficient mode
characterization and selection. Here we experimentally demonstrate direct
imaging and selective excitation of the bonding and antibonding plasmon mode in
symmetric dipole nanoantennas using confocal two-photon photoluminescence
mapping. Excitation of a high-quality-factor antibonding resonance manifests
itself as a two-lobed pattern instead of the single spot observed for the broad
bonding resonance, in accordance with numerical simulations. The two-lobed
pattern is observed due to the fact that excitation of the antibonding mode is
forbidden for symmetric excitation at the feedgap, while concomitantly the mode
energy splitting is large enough to suppress excitation of the bonding mode.
The controlled excitation of modes in strongly coupled plasmonic nanostructures
is mandatory for efficient sensors, in coherent control as well as for
implementing well-defined functionalities in complex plasmonic devices.Comment: 11 pages, 5 figures, 1 supplementary informatio
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