169,713 research outputs found
Structure of the c(2x2)-Br/Pt(110) surface
No full textWe present a detailed investigation of the c(2x2)-Br/Pt(110) adlayer structure supplemented by the analysis of the (1x2) missing-row (MR) structure of the clean Pt(110) surface. Quantitative low energy electron diffraction analyses and first-principles calculations are in impressive agreement in both cases. The clean surface reconstruction is determined with unprecedented accuracy. For the adsorbate, the analysis retrieves a simple Br-adlayer structure with the Br atoms residing in every second short bridge position on the close-packed Pt rows with the MR reconstruction lifted. The Br-Pt bond length L=2.47 Angstrom is almost equal to the sum of the atomic radii. The substrate below the adsorbate exhibits a contraction of the first layer spacing which amounts to half of that calculated for an unreconstructed clean surface
(3x1)-Br/Pt(110) structure and the charge-density-wave-assisted c(2x2) to (3x1) phase transition
No full textAfter our recent report on the formation of a (3x1) charge-density-wave phase in the quasi-one-dimensional system Br/Pt(110) we present a detailed investigation of the c(2x2)-->(3x1) transition in the Br/Pt(110) adsorption system. This includes the atomic structure of the (3x1) phase as determined by quantitative low-energy electron diffraction (LEED) and density functional theory calculations. While in the parent c(2x2) phase with coverage Theta=1/2 ML the Br atoms occupy every second short-bridge site on the unreconstructed (1x1)-Pt(110) surface, the adatoms in the (3x1) phase at coverage Theta=2/3 ML reside in every third short-bridge and long-bridge sites. Charge densities and vertical relaxations of the Pt atoms forming the short- and long-bridge sites are different, thus yielding a modulation of both, the charge and the position of the outermost Pt atoms with a period of three nearest-neighbor spacings. For 1/2 ML<Thetaless than or equal to0.58 ML LEED intensity and scanning tunneling microscope (STM) measurements reveal the nucleation of (3x1) islands surrounded by areas with a local coverage of 1/2 ML. Within the latter areas the STM measurements indicate dynamical fluctuations of the Br positions at room temperature. In the time average every short-bridge site is sampled by the mobile Br atoms, but in the neighborhood of (3x1) islands every third short-bridge site seems to be preferentially occupied
Halogen-Induced Corrosion of Platinum
No full textThe interaction of Cl with Pt(110) was studied in UHV by scanning tunneling microscopy, low-energy electron diffraction, temperature- programmed desorption, and DFT calculations. Up to half a monolayer (ML) of Cl forms an adsorbate structure. Compression to higher local coverages leads to erosion of Pt atoms from the top layer and formation of PtCl(4) pentamers. Anneating results in heating of the Pt defects and formation of a long- range-ordered PtCl(4)/Cl/Pt(110) adlayer that is remarkably simitar to the adtayer structure found after deposition of [PtCl(4)](2-) from an electrolyte onto Au(100). Coadsorption of 0.5 ML of Cl with CO initiates PtCl(4) formation, but no volatile compounds are formed under these conditions. In similar experiments with Br, the original Pt surface is left intact, even if Br is compressed to local coverages of 0.75 ML, in agreement with the expected tower corrosion activity of Br
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Mitomycin C in highly myopic eyes - Author reply
No full textOphthalmology. 2005 Feb;112(2):208-18; discussion 219.
Mitomycin C modulation of corneal wound healing after photorefractive keratectomy in highly myopic eyes.
Gambato C, Ghirlando A, Moretto E, Busato F, Midena E.
SourceRefractive Surgery Service and Antimetabolite Therapy Research Unit, Department of Ophthalmology, University of Padova, Padova, Italy.
Abstract
PURPOSE: To evaluate the role of topical mitomycin C in corneal wound healing (CWH) after photorefractive keratectomy (PRK) in highly myopic eyes.
DESIGN: Prospective, double-masked, randomized clinical trial.
PARTICIPANTS: Seventy-two eyes of 36 patients affected by high (>7 diopters) myopia.
METHODS: In each patient, one eye was randomly assigned to PRK with intraoperative topical 0.02% mitomycin C application, and the fellow eye was treated with a placebo. Postoperatively, mitomycin C-treated eyes received artificial tears (3 times daily, tapered in 3 months), whereas the fellow eye was treated with fluorometholone sodium 2% and artificial tears (3 times daily, tapered in 3 months).
MAIN OUTCOME MEASURES: Uncorrected visual acuity (UCVA) and best-corrected visual acuity (BCVA), contrast sensitivity, manifest refraction, and biomicroscopy. Contrast sensitivity was determined using the Pelli-Robson chart. Corneal confocal microscopy documented CWH.
RESULTS: Mean follow-up was 18 months (range, 12-36). No side effects or toxic effects were documented. At 12-month follow-up examination, UCVAs (logarithm of the minimum angle of resolution) were 0.4+/-0.48 and 0.5+/-0.53 (P = .03) in mitomycin C-treated eyes and corticosteroid-treated eyes, respectively. At 1 year, corneal haze developed in 20% of corticosteroid-treated eyes, versus 0% of mitomycin C-treated eyes. At 12, 24, and 36 months, corneal confocal microscopy showed activated keratocytes and extracellular matrix significantly more evident in untreated eyes (Ps = 0.004, 0.024, and 0.046, respectively).
CONCLUSION: Topical intraoperative application of 0.02% mitomycin C can reduce haze formation in highly myopic eyes undergoing PRK.
Comment in
Ophthalmology. 2006 Feb;113(2):357; author reply 357-8
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
A Multi-Language Comparison of Influences on Author Verification using Character N-Grams
No full textWe create a new multi-language corpus for author verification based on Wikipedia talkpages, and evaluate the influence that differences in topic and time have on character n-gram author profiles. Topic alignment between two texts is found to increase author verification precision, and an authors writing style is found to change over time, but not more significantly after 3 years than after 1 year.Information ArchitectureWISElectrical Engineering, Mathematics and Computer Scienc
A 0.12mm<sup>2</sup> Wien-Bridge Temperature Sensor with 0.1°C (3σ) Inaccuracy from -40°C to 180°C
No full text Resistor-based temperature sensors can achieve much higher resolution and energy efficiency than conventional BJT-based sensors [1], but they typically occupy more area (> 0.25 mm 2 ) and have lower operating temperatures (le 125 {circ} {C}) [2]-[4]. This work describes a 0.12mm 2 resistor-based sensor that uses a Wien-bridge (WB) filter to achieve 0.1 {circ} {C} (3 sigma) inaccuracy from - 40 {circ} {C} to 180 {circ} {C}. Compared to a state-of-the-art WB sensor [4], it occupies 6 × less area and achieves comparable relative accuracy over a 76% wider operating range. Session 10.3 Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic InstrumentationMicroelectronic
A ±25A Versatile Shunt-Based Current Sensor with 10kHz Bandwidth and ±0.25% Gain Error from -40°C to 85°C Using 2-Current Calibration
No full textAccurate current sensing is critical in many industrial applications, such as battery management and motor control. Precise shunt-based current sensors have been reported with gain errors of less than 1% over the industrial temperature range (-40°C to 85°C) [1]–[4]. However, since they are intended for coulomb counting, their bandwidth is limited to a few tens of Hz, making them unsuitable for battery impedance or motor-current sensing. This paper presents a current sensor with a wide (10kHz) bandwidth and a tunable temperature compensation scheme (TCS), which allows it to be flexibly used with different types of shunts while maintaining high accuracy. A low-cost room-temperature calibration scheme is proposed to optimize gain flatness over temperature by exploiting the shunt's self-heating at large currents. Over the industrial temperature range and a ±25A current range, it achieves state-of-the-art gain error (±0.25%) with both low-cost PCB and stable metal-alloy shunts.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Electronic InstrumentationMicroelectronic
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