169,925 research outputs found
Reactions of 7,7,8,8-tetracyanoquinodimethane (TCNQ) with alkynyl-iron- and -ruthenium complexes: synthesis of Ru{C=CC(CN)=C(6)H(4)=C(CN)(2)}(PPh(3))(2)Cp, a new donor-acceptor molecular array
No full textReactions of 7,7,8,8-tetracyanoquinodimethane (TCNQ) with the alkynyl-iron and ruthenium complexes [M](C=CR) {[M] = Fe(dppe)Cp*, Ru(PPh3)2Cp; R = H, Ph} are described. The iron complex Fe(C=CPh)(dppe)Cp* (2a) is oxidized by TCNQ to give the kinetically stable salt [2a•+][TCNQ]•– . Displacement of [TCNQ]•– is achieved by ionic metathesis upon addition of KPF6 to produce [2a•+]PF6. In contrast, Fe(C=CH)(dppe)Cp* (2b) reacted with TCNQ to give a mixture of compounds containing Fe(=C=CH2)(dppe)Cp* (3a), {Fe(dppe)Cp*}2(µ-C=CHCH=C) (3b), and the zwitterionic complex Fe+{=C=CHC(CN)2C6H4C–(CN)2}(dppe)Cp* (3c). In contrast, the reaction of TCNQ with Ru(C=CR)(PPh3)2Cp (4a, R = Ph; 4b, R = H) gave selectively the zwitterionic vinylidenes Ru+{=C=CRC(CN)2C6H4C–(CN)2}(PPh3)2Cp (5a, R = Ph; 5b, R = H), in which the Ru centres are positively charged and the counter-anion is located on the further C(CN)2 group. On heating 5b, elimination of HCN affords Ru{C=CC(CN)=C6H4=C(CN)2}(PPh3)2Cp (1), while similar treatment of 5a gives Ru{?3-C(CN)2CPh=C6H4=C(CN)2}(PPh3)Cp (6) with loss of PPh3. X-ray structures of 1, 5a, and 6, cyclic voltammetry, and UV-vis spectroscopy of 1 provided evidence for the electronic structures of the new complexes.Michael I. Bruce, Alexandre Burgun, Guillaume Grelaud, Claude Lapinte, Brian W. Skelton, and Natasha N. Zaitsev
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
Iron and ruthenium sigma-Polyynyls of the general formula [{M(dppe)Cp*}-(C triple bar C)n-R](0)/(+) (M = Fe, Ru): an experimental and theoretical investigation
No full textTwo series of metal-polyynyl complexes of iron and ruthenium of general formula [{M(dppe)Cp*}-(C≡C) n-R] 0/+ (M = Fe, Ru; R = H, Ph, SiMe 3, Au(PPh 3); n = 1-3), have been synthesized, characterized, and theoretically analyzed. The results provide a comprehensive description of the effect of the length of the conjugated carbon chain and the role of the nature of the metal atom and the terminal substituent on their neutral and oxidized states. For the latter, the spin density found on the carbon chain is a source of instability; e.g., for R = Au(PPh 3), the oxidized compounds are much more accessible electrochemically than the rest of the series but are susceptible to radical attack. Of particular interest is the use of joint experimental and theoretical EPR studies, which allow elucidation of the differences of behavior within the two series. It reveals that the atomic spin density on the metal is not a sufficient criterion to evaluate EPR anisotropy but that the specific nodal properties of the frontier spin-orbitals highly influence the EPR components. The localization of the spin density on specific carbon atoms of the conjugated chain (even numbered) opens up the possibility of building extended systems by targeted radical reactions. © 2012 American Chemical Society.Frédéric Gendron, Alexandre Burgun, Brian W. Skelton, Allan H. White, Thierry Roisnel, Michael I. Bruce, Jean-François Halet, Claude Lapinte, and Karine Costua
Syntheses and structural studies of several group 8 metal complexes derived from 1,3-butadiyne
No full textAs part of an extensive investigation into the chemistry of complexes containing metal-ligand centers linked by chains of C(sp) atoms, the preparation, characterization, and single-crystal X-ray diffraction molecular structure determinations of four complexes {MLn}-C≡CC≡C-{M′L′m} [MLn = Ru(dppe)Cp*, M′L′m = Fe(dppp)Cp* (1), Ru(dppe)Cp* (2), MLn = M′L′m = Os(PPh3)2Cp (3)], and {Cp*(dppe)Ru}C≡CC≡C{trans-RuCl(dppe)2} (4), in which the alternating C(sp)–C(sp) bonds have values between 1.375 and 1.40 Å (single) and between 1.20 and 1.259 Å (triple), respectively, are described. In addition, a structure determination of Ru3(μ-H){μ3-C2C≡C[Ru(PPh3)2Cp]}(CO)9 (5) shows that the C2 fragment attached to the HRu3 cluster shows the expected lengthening [to 1.311(7) Å] and bending at the two carbon atoms [to 152.6(6) and 157.6(5)°] (resulting from back-bonding from the Ru3 cluster into the C≡C π* orbitals) compared with the essentially linear Ru–CC– moiety [C≡C 1.222(6) Å, angles at C of 178.0(5), 172.3(6)°],Michael I. Bruce, Marcus L. Cole, Karine Costuas, Benjamin G. Ellis, Kathy A. Kramarczuk, Claude Lapinte, Brian K. Nicholson, Gary J. Perkins, Brian W. Skelton, Allan H. White and Natasha N. Zaitsev
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
Synthesis, structures and some reactions of Ru(CXiCCXiCFc)(PP)Cp (PP = dppm, dppe) and related compounds
No full textThe compounds Ru(C≡CC≡CFc)(PP)Cp [PP=dppe (1), dppm (2)], have been obtained from reactions between RuCl(PP)Cp and FcC≡CC≡CSiMe3 in the presence of KF (1) or HC≡CC≡CFc and K[PF6] (2), both with added dbu. The dppe complex reacts with Co2(CO)6 (L2)[L2=(CO)2, dppm] to give 3, 4 in which the Co2(CO)4 (L2) group is attached to the outer C≡C triple bond. The PPh 3 analogue of 3 (5) has also been characterised. In contrast, tetracyanoethene reacts to give two isomeric complexes 6 and 7, in which the cyano-olefin has added to either C≡C triple bond. The reaction of RuCl(dppe)Cp with HC≡CC≡CFc, carried out in a thf/NEt3 mixture in the presence of Na[BPh4], gave [Ru{C≡CC(NEt3)- CHFc}(dppe)Cp]BPh4 (8), probably formed by addition of the amine to an (unobserved) intermediate butatrienylidene [Ru(-C-C-C-CHFc)(dppe)Cp]+. The reaction of I2 with 8 proceeds via an unusual migration of the alkynyl group to the Cp ring to give [RuI(dppe) {η-C5H4 C≡CC(NEt3)-CHFc}]I3 (9). Single-crystal X-ray structural determinations of 1, 2 and 4-9 are reported. © Published by Elsevier B.V.Michael I. Brucea, Frédéric de Montigny, Martyn Jevric, Claude Lapinte, Brian W. Skelton, Mark E. Smith, and Allan H. Whitehttp://www.elsevier.com/wps/find/journaldescription.cws_home/504090/description#descriptio
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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