171,877 research outputs found
A study on the diffuse attenuation coefficient of down-welling irradiance around the yellow sea
No full textThe diffuse attenuation coefficient for down-welling irradiance (Kd) is an important parameter for ocean studies including remote sensing applications. For the vast ocean, ocean color remote sensing is the only possible means to get the fine-scale measurements of Kd. To develop a technique of estimating Kd from remotely sensed data, the following underwater optical parameters (absorption coefficient (a), attenuation coefficient (c), scattering coefficient (b), diffuse attenuation coefficient (Kd), etc.) have been studied. For this research we conducted the field campaign around the Yellow Sea at 8~9 June, 2006. We obtained a set of underwater optical parameter data: down-welling irradiance (Ed), up-welling irradiance (Eu) and up-welling radiance (Lu) using TriOS optical sensors and a, c coefficient using Spectral Absorption and Attenuation Meter (AC-S). We then derived Kd values from Ed for each depth.1
A geometric characterization of c-optimal designs for heteroscedastic regression
No full textWe consider the common nonlinear regression model where the variance as well as the mean is a parametric function of the explanatory variables. The c-optimal design problem is investigated in the case when the parameters of both the mean and the variance function are of interest. A geometric characterization of c-optimal designs in this context is presented, which generalizes the classical result of Elfving (1952) for c-optimal designs. As in Elfving's famous characterization c-optimal designs can be described as representations of boundary points of a convex set. However, in the case where there appear parameters of interest in the variance, the structure of the Elfving set is different. Roughly speaking the Elfving set corresponding to a heteroscedastic regression model is the convex hull of a set of ellipsoids induced by the underlying model and indexed by the design space. The c-optimal designs are characterized as representations of the points where the line in direction of the vector c intersects the boundary of the new Elfving set. The theory is illustrated in several examples including pharmacokinetic models with random effects. --c-optimal design,heteroscedastic regression,Elfving's theorem,pharmacokinetic models,random effects,locally optimal design,geometric characterization
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
Detergent extraction of herpes simplex virus type 1 glycoprotein D by zwitterionic and non-ionic detergents and purification by ion-exchange high-performance liquid chromatography
No full textDetergents (surfactants) are the key reagents in the extraction and purification of integral membrane proteins. Zwitterionic and non-ionic detergents were used for the extraction of recombinant glycoprotein D (gD-1) of herpes simplex virus type 1 (HSV-1) from insect cells infected with recombinant baculovirus. The highest yield was obtained with the two alkyl carboxybetaine detergents (N-dodecyl-N,N-dimethylammonio)undecanoate [DDMAU, critical micelle concentration (CMC)=0.13 mM] and (N-dodecyl-N,N-dimethylammonio)butyrate (DDMAB, CMC=4.3 mM). Therefore these zwitterionic detergents were used as additives to the elution buffers in ion-exchange high-performance liquid chromatography (HPIEC) to purify gD-1 of HSV-1 from the extracts. The non-ionic detergent pentaethyleneglycol monodecyl ether (C(10)E(5)) that was used in earlier studies [R.A. Damhof, M. Feijlbrief, S. Welling-Wester: G,W Welling, J. Chromatogr. A, 676 (1994) 43] was used for comparison. Two columns were used, Mono Q and Resource Q, at 1 and 5 ml/min flow-rates, respectively. The results show that the detergents DDMAU and C(10)E(5) are superior to DDMAB, when the detergents were used as additives to the elution buffers at 0.2% (w/v). With 0.2% DDMAB in the eluent, purification of HSV gD-1 was not possible. Detergents with a high CMC may be less suitable as additives in elution buffers. HPIEC at flow-rates of 1 and at 5 ml/min showed satisfactory results. At 5 ml/min HSV gD-1 was mainly concentrated in two eluent fractions. The highest recovery of gD-1 was obtained either by chromatography of a C(10)E(5) extract using a Mono Q column at a flow-rate of 1 ml/min or by chromatography of a DDMAU extract using a Resource Q column at a flow-rate of 5 ml/min. (C) 1998 Elsevier Science B.V. All rights reserved.</p
Detergent extraction of herpes simplex virus type 1 glycoprotein D by zwitterionic and non-ionic detergents and purification by ion-exchange high-performance liquid chromatography
No full textDetergents (surfactants) are the key reagents in the extraction and purification of integral membrane proteins. Zwitterionic and non-ionic detergents were used for the extraction of recombinant glycoprotein D (gD-1) of herpes simplex virus type 1 (HSV-1) from insect cells infected with recombinant baculovirus. The highest yield was obtained with the two alkyl carboxybetaine detergents (N-dodecyl-N,N-dimethylammonio)undecanoate [DDMAU, critical micelle concentration (CMC)=0.13 mM] and (N-dodecyl-N,N-dimethylammonio)butyrate (DDMAB, CMC=4.3 mM). Therefore these zwitterionic detergents were used as additives to the elution buffers in ion-exchange high-performance liquid chromatography (HPIEC) to purify gD-1 of HSV-1 from the extracts. The non-ionic detergent pentaethyleneglycol monodecyl ether (C(10)E(5)) that was used in earlier studies [R.A. Damhof, M. Feijlbrief, S. Welling-Wester: G,W Welling, J. Chromatogr. A, 676 (1994) 43] was used for comparison. Two columns were used, Mono Q and Resource Q, at 1 and 5 ml/min flow-rates, respectively. The results show that the detergents DDMAU and C(10)E(5) are superior to DDMAB, when the detergents were used as additives to the elution buffers at 0.2% (w/v). With 0.2% DDMAB in the eluent, purification of HSV gD-1 was not possible. Detergents with a high CMC may be less suitable as additives in elution buffers. HPIEC at flow-rates of 1 and at 5 ml/min showed satisfactory results. At 5 ml/min HSV gD-1 was mainly concentrated in two eluent fractions. The highest recovery of gD-1 was obtained either by chromatography of a C(10)E(5) extract using a Mono Q column at a flow-rate of 1 ml/min or by chromatography of a DDMAU extract using a Resource Q column at a flow-rate of 5 ml/min. (C) 1998 Elsevier Science B.V. All rights reserved
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
e-Galform 1 year research masters
No full textAdvancing internet technologies and increasing computer processing and data transfer rates have allowed computers separated by large distances to communicate with each other and transfer large amounts of data that were previously impractical. This has opened new opportunities allowing university departments to share research and information via web servers and web browsers. In this thesis, I describe the development of e-Galform, an internet based database application that seeks to allow scientists both within the University of Durham and from other universities across the globe to take advantage of Galform, a galaxy formation model developed by theoretical galaxy formation research staff at Durham. e-Galform features a web based interface allowing users to understand the capabilities of Galform without the necessity to understand the finer underlying technical and scientific complexities, whilst offering documentation that would support further understanding. A user can extract tailored predictions from a library of pre-existing Galform runs using the e-Galform web interface. A further primary feature is the production of Galform data in a new and more verbose data format, VOTable, which may be used in other database applications and is expected to become a standardised data format for use in astronomical software globally. The VOTable format is under development primarily by the United States Virtual Observatory (US-VO). Rather than run the Galform simulation directly, e-Galform extracts requested galaxy properties by running an intermediate binary program (samplegals.exe) on a pre-generated Galform dataset. e-Galform is also configurable and extendible via the use of ๒-built administrative facilities. The aim of the administrative facilities is to allow users to extend the facility to extract newly added galaxy properties as the underlying Galform model is extended, without the necessity of requiring new code
Maximum Likelihood Estimation for the Offset-Normal Shape Distributions Using EM
No full textThe offset-normal shape distribution is defined as the induced shape distribution of a Gaussian distributed random configuration in the plane. Such distributions were introduced by Dryden and Mardia (1991) and represent an important parameterized family of shape distributions for shape analysis. This article reports a method for performing maximum likelihood estimation of parameters involved. The method consists of an EM algorithm with simple update rules and is shown to be easily applicable in many practical examples. We also show the necessary adjustments needed for using this algorithm for shape regression, missing landmark data, and mixtures of offset-normal shape distributions
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