171,946 research outputs found
Two-dimensional convection with a self-lubricating, simple-damage rheology
No full textWe present 2-D simulations of convection in the Earth's mantle with temperature and damage-dependent viscosity in a basally heated system. The equation governing the temporal evolution of damage includes a source term for damage, a healing term and an advection term. A systematic study of the influence of the different damage terms on the convection pattern shows that: (1) at least four different convective regimes can be distinguished depending on the size of the damage source term and (2) self-lubricating behaviour is possible only if the advection term in the damage equation is small enough compared with the other terms. We also demonstrate, that good plate-like behaviour in terms of (a) focused low-viscosity bands (LVB), (b) homogeneous surface velocities within the plates and abrupt velocity jumps across the plate boundaries and (c) asymmetric subduction, can be obtained with this kind of rheology, although an increase in subduction asymmetry tends to make convection highly time-dependent
Experimental and theoretical evidences of hysteresis in passive mode-locked quantum dots lasers
No full textWe report experimental evidence of coexistence between passive mode-locking (ML) solutions and laser off state in a monolithic two sections InAs/InGaAs Quantum Dot (QD) semiconductor laser. The considered device has a 0.4 mm long straight absorber and a 2.380 mm long active region characterized by a 2° full taper angle. The active side facet is as cleaved, while the absorber side facet is high reflection coated
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
The effect of oxidation on the stability of G-quadruplex DNA : implications for oncogene expression
No full textG-quadruplexes (G4-DNA) are a class of secondary structures formed from Guanine rich sequences. In recent years these structures have been implicated in both telomere maintenance and oncogene expression, and have been shown to be abundant in upstream promoter regions and at telomeric ends.
The mutagenic properties of oxidative stress on DNA have been widely studied, as has the association with carcinogenesis. The oxidation of deoxyguanosine to 8-oxo-2’deoxyguanosine (8-oxo-dG) is the most common result when DNA is under oxidative stress and as such, the G-rich sequences that form G-quadruplexes can be viewed as potential “hot-spots” for DNA oxidation. We propose that oxidation may destabilise the G-quadruplex structure, leading to its unfolding into the duplex structure, affecting gene expression. This would imply a possible mechanism by which oxidation may impact on oncogene expression.
This project used both in silico and in vitro methods to observe the effect of oxidation on the G-quadruplex structure and the consequences in oncogene expression, using two biologically relevant G-quadruplex structures, those found in the promoter regions of the proto-oncogenes c-Myc and c-Kit as proof of concept.
Molecular dynamics (MD) simulations were performed (isothermic, isobaric 500ns unrestrained simulation in explicit solvent and counterions) on the c-Kit and c-Myc G-quadruplex structures with and without 8-oxo-dG incorporated into the central tetrad. FRET experiments were performed on these same structures, observing the conformation of sequences known to form G-quadruplexes under near physiological conditions and subjected to oxidative stress, through Fenton chemistry. Gene expression data analyses were also performed to evaluate the prevalence of different G-quadruplex forming motifs (GQMs) in genes affected by oxidation.Although no relevant information was gained from the FRET experiments, the MD results constitute the longest simulations of this type performed on the c-Myc and c-Kit G-quadruplex structures published to date and predict the high stability of these structures under normal physiological conditions. They also clearly demonstrate a destabilising effect of oxidation on G-quadruplex structures, with the extent of the effect dependent on the structure oxidised.
Furthermore, gene expression data analysis showed that genes whose expression is significantly altered when subjected to oxidative stress are statisticallymore likely to contain a GQM than the remainder of the genome, through the use of significance testing.
These findings demonstrate a differential effect of oxidation on G-quadruplexes, likely dependent on other known characteristics affecting G4 stability such as loop length and sequence. Results also point towards this mechanism affecting gene expression. This is suggestive of a novel route for oxidation mediated carcinogenesis, through upregulation of oncogene expression or possibly downregulation of tumour suppression genes
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
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