169,933 research outputs found
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
Genetic simulations of population interactions during past human expansions in Europe
No full textTwo prehistoric demographic events profoundly affected human species in Europe. The first one is the replacement of Neanderthals by early modern humans from around 45,000 to 30,000 years ago and the second one corresponds to the Neolithic transition around 10,000 years ago. Both events entail to the arrival of new individuals coming from the East and the successive disappearance of pre-existing local people. In both cases the main question is how large was the contribution of pre-existing populations to the genetic pool of contemporary Europeans. In order to answer this question, we developed a new approach allowing the simulation of interactions between two populations (competition, admixture and assimilation) during a colonization phase and the resulting genetic structure of the remaining population. We applied this methodology to both the Neanderthal disappearance and the Neolithic transition by testing many different demographic scenarios. Our results showed that there were probably no genetic exchanges between Neanderthals and modern humans and that they therefore may have constituted two different species. We also showed no genetic evidence for a large replacement of European pre-existing hunter-gatherer populations during the Neolithic transition. Finally we point out the importance of taking in consideration the type of genetic markers used for the analysis as they can reveal very different patterns
Incorporating environmental heterogeneity in spatially-explicit simulations of human genetic diversity
No full textWe recently developed a simulation framework (SPLATCHE) to model the past demography of human population and the resulting genetic diversity at neutral markers. Additional to range expansions and population subdivisions, we increase here the realism of our simulations by incorporating spatial and temporal heterogeneity of the environment. This heterogeneity can be translated into maps of carrying capacities (maximum density of individuals) and frictions (difficulty of moving) that will in turn influence the size of local populations and the direction and the intensity of migrations. We have considered the influence of several environmental variables: the type of vegetation directly affects the available resource and therefore the carrying capacities; streams and coastlines act as migration corridors with higher carrying capacities than the surrounding environment; a rough topography may also drastically influence migrations. We discuss in this paper each of these environmental variables and how one can estimate carrying capacities and friction values for each of them. We also present an innovative way of considering dynamic changes of vegetation through temporal vegetation heterogeneity. Finally, we examine how environmental heterogeneity might affect genetic differentiation of human populations, and discuss the limitations and perspectives of our approach
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
Where was Paradise? A simulation study of the spread of early modern humans in heterogeneous environments
No full textSeveral lines of evidence argue in favour of a recent and unique origin of modern humans in sub-Saharan Africa, but no attempt has really been made at quantifying the likelihood of this model, relative to alternative hypotheses of human evolution. In this paper, we investigate the possibility of using multi-locus genetic data to correctly infer the geographic origin of modern humans, and to distinguish between a unique origin (UO) and a multiregional evolution (ME) model. We use an approach based on realistic simulations of the genetic diversity expected after an expansion process of modern humans into the Old World from different possible areas, and with different environmental scenarios, under both UO and ME models. We find that UO and ME models should produce distinctive patterns of genetic diversity in observed data. Moreover, the geographic origin of an expansion is recoverable under the UO model provided that a large number of independent markers are used, and that precise information on past demography and potential places of origin(s) are available. We also find that the successful recovery of past scenarios is related to the degree with which environmental heterogeneity impacts on past demography and migration, suggesting that use of a realistic representation of past environment is important to make correct inferences. Finally, the application of our simulation framework to the problem of the origin of mankind clearly rejects multiregional evolution scenarios, and points toward a unique and African origin of modern humans
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