419,788 research outputs found
O. A. C. Review Volume IV Issue 1, October 1892
No full textStarting the new school year this issue contains articles on the use of wind power, the O. A. C. athletics association, and the type of soil to cultivate grapes. Alumni and student articles extol the virtues of farming.EditorialChat with our readersAgriculture as an occupationWind as a source of powerFootballO. A. C. athletic associationSecond year man`s dreamPersonalResignation of Mr. HuntWeddingLocalsY. M. C. A. notesGrape cultureExchangesadvertisin
O. A. C. Review Volume IV Issue 3, December 1892
No full textThis issue contains news of agriculture in Poland and Jamaica. Other articles pertain to campus activities of the local militia, Y. M. C. A. and Literary Society.EditorialMistakes we are makingPete a retrospectFew facts about PolandB batteryY. M. C. A. notesJamaicaO. A. C. Literary SocietyPersonalsExchangesLocalsChaffMens sana in corpore sanoadvertisin
Routing and power control in frequency-hop random-access ad hoc networks
No full textFrequency hopping provides some protection against multiple access interference in random-access ad hoc networks. Power control and the use of short routing hops can further reduce interference by promoting spatial reuse. If the network is fully connected, frequency hopping and power control alone may be sufficient to allow good throughput without the use of routing. This approach is particularly desirable as avoiding routing can simplify network setup and reduce packet delay. However, if the network is heavily loaded, frequency hopping may no longer sufficiently protect against interference, so including routing may be beneficial. In this paper, we consider application of least interference routing (LIR) to frequency hop random-access networks. The performance of a family of LIR metrics is considered for a variety of networks to determine which cases multi-hop routing should be used, and it is shown that the choice of the optimal metric is sensitive to several network characteristics.United States. Dept. of the Air Force (Contract FA8721-05-C-0002
Adaptive-rate techniques for frequency-hop multiple-access packet-radio networks
No full textThe effects of adaptive-rate transmissions and routing on the total throughput of a slow-frequency-hop packet-radio network are considered. Adaptive rates are achieved through the use of error-control coding with perfect side information. Both fixed-length codes and variable-length codes are considered. Performance results are obtained for direct transmission (i.e., no routing), two-hop limited routing, and full routing. Each link metric is a function of the amount of interference caused by using the link. We compare the total network throughput for each of these schemes with both fixed-rate and adaptive-rate coding.United States. Dept. of the Air Force (FA8721-05-C-0002
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
Nickel‐Catalyzed Electrooxidative C−H Amination: Support for Nickel(IV)
No full textAbstract Nickel‐catalyzed electrochemical C−H aminations were accomplished by chemo‐ and position‐selective C−H activation with ample scope. Detailed mechanistic studies highlighted a facile C−H cleavage with unique chemo‐selectivity, while cyclovoltammetric analysis provided support for a nickel(II/III/IV) manifold.Distinguished International Students Scholarship https://doi.org/10.13039/501100010893Deutsche Forschungsgemeinschaft https://doi.org/10.13039/501100001659Alexander von Humboldt-Stiftung https://doi.org/10.13039/10000515
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(IV) Alkyl Hydrazido Complexes: Electronic Structure, Fe–C Bond Homolysis, and N–C Bond Forming Migration Reactions
No full textHigh-valent iron-alkyl complexes are rare, as they are typically prone to Fe–C bond homolysis. We show here an unusual way to access formally iron(IV) alkyl complexes through double silylation of iron(I) alkyl dinitrogen complexes to form an NNSi2 group. When the alkyl group is trimethylsilylmethyl, the formally iron(IV) compound is stable at room temperature. Spectroscopically validated computations show that the disilylhydrazido(2–) ligand stabilizes the formal iron(IV) oxidation state through a strongly covalent Fe–N -interaction, in which one -bond fits an "inverted field" description. This means that the two bonding electrons are localized on the metal and not the ligand, and an iron(II) resonance structure is a significant contributor as with the phenyl analogue. However, in contrast to the phenyl analogue which has an S = 1 ground state, the ground state of the alkyl complex is S = 2, and this places one electron in the * orbital and weakens the Fe–N bonding, leading to longer Fe–N bonds. The reactivity of these hydrazido(2–) complexes has an interesting dependence on the specific alkyl group. When the alkyl group is methyl, the formally iron(IV) species undergoes migration of the carbon-based ligand to the NNSi2 group to form a new N–C bond, followed by an intriguing isomerization of the hydrazido ligand. This reactivity is not observed with the bulkier trimethylsilylmethyl complex. When the alkyl group is benzyl, yet another reactivity pathway is evident: the Fe–C bond homolyzes to give a three-coordinate iron(III) complex with a hydrazido(2–) ligand. DFT calculations are used to explain the differences between the behavior with the different alkyl groups. Overall, these formally iron(IV) compounds display a diverse set of reaction pathways associated with the specific alkyl groups
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
C iv emission-line properties and systematic trends in quasar black hole mass estimates
No full textBlack hole masses are crucial to understanding the physics of the connection between quasars and their host galaxies and measuring cosmic black hole-growth. At high redshift, z ≳ 2.1, black hole masses are normally derived using the velocity width of the C iv1548, 1550 broad emission line, based on the assumption that the observed velocity widths arise from virial-induced motions. In many quasars, the C iv emission line exhibits significant blue asymmetries (‘blueshifts’) with the line centroid displaced by up to thousands of km s−1 to the blue. These blueshifts almost certainly signal the presence of strong outflows, most likely originating in a disc wind. We have obtained near-infrared spectra, including the Hα 6565 emission line, for 19 luminous (LBol = 46.5–47.5 erg s−1) Sloan Digital Sky Survey quasars, at redshifts 2 2000 km s−1, the velocity widths appear to be dominated by non-virial motions. Black hole masses, based on the full width at half-maximum of the C iv emission line, can be overestimated by a factor of 5 at large blueshifts. A larger sample of quasar spectra with both C iv and H β, or Hα, emission lines will allow quantitative corrections to C iv-based black hole masses as a function of blueshift to be derived. We find that quasars with large C iv blueshifts possess high Eddington luminosity ratios and that the fraction of high-blueshift quasars in a flux-limited sample is enhanced by a factor of approximately 4 relative to a sample limited by black hole mass
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