196,166 research outputs found
Widening use of dexamethasone implant for the treatment of macular edema
No full textVincenza Bonfiglio, Michele Reibaldi, Matteo Fallico, Andrea Russo, Alessandra Pizzo, Stefano Fichera, Carlo Rapisarda, Iacopo Macchi, Teresio Avitabile, Antonio Longo Department of Ophthalmology, University of Catania, Catania, Italy Abstract: Sustained-release intravitreal 0.7 mg dexamethasone (DEX) implant is approved in Europe for the treatment of macular edema related to diabetic retinopathy, branch retinal vein occlusion, central retinal vein occlusion, and non-infectious uveitis. The implant is formulated in a biodegradable copolymer to release the active ingredient within the vitreous chamber for up to 6 months after an intravitreal injection, allowing a prolonged interval of efficacy between injections with a good safety profile. Various other ocular pathologies with inflammatory etiopathogeneses associated with macular edema have been treated by DEX implant, including neovascular age-related macular degeneration, Irvine–Gass syndrome, vasoproliferative retinal tumors, retinal telangiectasia, Coats’ disease, radiation maculopathy, retinitis pigmentosa, and macular edema secondary to scleral buckling and pars plana vitrectomy. We undertook a review to provide a comprehensive collection of all of the diseases that benefit from the use of the sustained-release DEX implant, alone or in combination with concomitant therapies. A MEDLINE search revealed lack of randomized controlled trials related to these indications. Therefore we included and analyzed all available studies (retrospective and prospective, comparative and non-comparative, randomized and nonrandomized, single center and multicenter, and case report). There are reports in the literature of the use of DEX implant across a range of macular edema-related pathologies, with their clinical experience supporting the use of DEX implant on a case-by-case basis with the aim of improving patient outcomes in many macular pathologies. As many of the reported macular pathologies are difficult to treat, a new treatment option that has a beneficial influence on the clinical course of the disease may be useful in clinical practice. Keywords: macular edema, dexamethasone, intravitreal, implant, corticosteroid
A note on the fractal behavior of hydraulic conductivity and effective porosity for experimental values in a confined aquifer
No full textHydraulic conductivity and effective porosity values for the confined sandy loam aquifer of the Montalto Uffugo (Italy) test field were obtained by laboratory and field measurements; the first ones were carried out on undisturbed soil samples and the others by slug and aquifer tests. A direct simple-scaling analysis was performed for the whole range of measurement and a comparison among the different types of fractal models describing the scale behavior was made. Some indications about the largest pore size to utilize in the fractal models were given. The results obtained for a sandy loam soil show that it is possible to obtain global indications on the behavior of the hydraulic conductivity versus the porosity utilizing a simple scaling relation and a fractal model in coupled manner. © 2013 Samuele De Bartolo et al
Scaling analysis of water retention curves for unsaturated sandy loam soils by using fractal geometry
No full textFractal geometry was deployed to analyse water retention curves (WRC). The three models used to estimate the curves were the general pore-solid fractal (PSF) model and two specific cases of the PSF model: the Tyler & Wheatcraft (TW) and the Rieu & Sposito (RS) models. The study was conducted on 30 undisturbed, sandy loam soil samples taken from a field and subjected to laboratory analysis. The fractal dimension, a non-variable scale factor characterizing each water retention model proposed, was estimated by direct scaling. The method for determining the fractal dimension proposed here entails limiting the analysis to the interval between an upper and lower pressure head cut-off on a log-log plot, and defining the dimension itself as the straight regression line that interpolates the points in the interval with the largest coefficient of determination, R2. The scale relative to the cut-off interval used to determine the fractal behaviour in each model used is presented. Furthermore, a second range of pressure head values was analysed to approximate the fractal dimension of the pore surface. The PSF model exhibited greater spatial variation than the TW or RS models for the parameter values typical of a sandy loam soil. An indication of the variability of the fractal dimension across the entire area studied is also provided. © 2010 The Authors. Journal compilation © 2010 British Society of Soil Science
Usage of infinitesimals in the Menger's Sponge model of porosity
No full textThe present work concerns the calculation of the infinitesimal porosity by using the Menger's Sponge model. This computation is based on the grossone theory considering the pore volume estimation for the Menger's Sponge and afterwards the classical definition of the porosity, given by the ratio between the volume of voids and the total volume (voids plus solid phase). The aim is to investigate the different solutions given by the standard characterization of the porosity and the grossone theory without the direct estimation of the fractal dimension. Once the utility of this procedure had been clarified, the focus moves to possible practical applications in which infinitesimal parts can play a fundamental role. The discussion on this matter still remains open. © 2011 Elsevier Inc. All rights reserved
Scaling effect of the hydraulic conductivity in a confined aquifer
No full textPrevious studies showed that the values of the representative parameters of an aquifer, such as the hydraulic conductivity (k), increase with the scale, that is, with the aquifer volume involved in the measurement. The main cause of this behavior is commonly ascribed to the heterogeneity of the porous media. Heterogeneity influences the scaling behavior differently for laboratory or field measurement, but the scale dependence of hydraulic conductivity is not dependent on the specific measurement method. In the present study, the scaling law of this parameter was determined on a real confined aquifer, using measurements obtained, both in the laboratory (flow cells) and the field (slug tests and aquifer tests). The corresponding data were statistically analyzed. A scaling law was proposed for both the laboratory and field scale, using the data obtained from flow cells, slug tests, and aquifer tests. Afterward, the scaling law was estimated at just the field scale, first using the slug tests and aquifer tests and then using only the aquifer test data.The scale dependence of the storativity was also investigated for all field measurements and then using only the aquifer test data. In conclusion, for both hydraulic conductivity and storativity, the trend to reach an upper bound increasing the scale parameter was investigated in the scale ranges of 67 and 99 m, respectively, examining only the data set relative to aquifer test measurements. Copyright © 2012 by Lippincott Williams & Wilkins
Simple scaling analysis of active channel patterns in Fiumara environment
No full textA simple scaling analysis was performed on experimental data relative to a riverbed reach of the Allaro Fiumara, a fluvial environment typical of Southern Italy. For this purpose, a simplified geometrical approach was followed to determine the spatial distribution of the number of active channels for the river stretch considered. In particular, the section lines crossing the braided network skeleton with distance ranging from 5 to 200. m were considered. Firstly, a probabilistic analysis of the experimental data was carried out by using a truncated Poisson distribution to characterize the examined river morphologically. Afterward, a scaling analysis was performed to investigate the existence of a possible multimodal behaviour of the number of active channels and to identify the corresponding cutoff values. For this second approach by the so-called standard coarse graining analysis, we defined a power law usable to give the probability distribution of the active channels number with varying spatial partition (distance between consecutive sections). In this way, verifying the existence of a bimodal scaling behaviour was possible. Moreover, the cutoff limits that characterize the bimodal behaviour of the active channels were found for all the partition distances from 5 to 100. m, while the corresponding shape and scale parameters were also determined. A comparison of the results obtained by the statistical approach and the scaling analysis was carried out. The variability of the characteristic parameters of the Poisson and power type laws with scale was also investigated
Spatial dependence of the hydraulic conductivity in a well-type configuration at the mesoscale
No full textThe spatial distribution of the hydraulic conductivity is modelled by a power law, and we present a methodological approach to quantify the exponent (crowding index) of such a law as detected within a well-type flow configuration. Based upon the outcome of several pumping tests con- ducted into a caisson (mesoscale), we identify the crowding index as function of the volumetric flow rate. Hence, we develop a simple (although approximated) procedure to assess whether the spatial distribution of can be characterized by a power law. We demonstrate that, even at the mesoscale, the conductivity can not be regarded as a formation's property (nonlocality), in agreement with the recent developments on the theory of flows into radial configurations
On the dependence of the saturated hydraulic conductivity upon the effective porosity through a power law model at different scales
No full textWe study the scale dependence of the saturated hydraulic conductivity Ks through the effective porosity ne by means of a newly
developed power-law model (PLM) which allows to use simultaneously measurements at different scales. The model is
expressed as product between a single PLM (capturing the impact of the dominating scale) and a characteristic function κ⋆
accounting for the correction because of the other scale(s). The simple (closed form) expression of the κ⋆-function enables one to
easily identify the scales which are relevant for Ks.
The proposed model is then applied to a set of real data taken at the experimental site of Montalto Uffugo (Italy), and we show
that in this case two (i.e. laboratory and field) scales appear to be the main ones. The implications toward an important
application (solute transport) in Hydrology are finally discussed
Scaling analysis of hydraulic conductivity and porosity on a sandy medium of an unconfined aquifer reproduced in the laboratory
No full textMany studies have shown that the characteristic parameters of an aquifer, specifically the hydraulic conductivity, increase with an increase in the portion of the aquifer tested. The main cause of this behavior is the heterogeneity within the aquifer. Sets of measurements performed on an artificial aquifer by different methods are utilized here, because it was verified that the scale dependence of hydraulic conductivity does not depend on the specific method of measurement. The unconfined aquifer in question was created in the laboratory utilizing sandy porous medium with a well-known grain-size distribution. An experimental scaling law of the power type was obtained for the hydraulic conductivity, utilizing values measured at different scales by different methods (on undisturbed soil samples by flux cells, on the artificial aquifer by slug tests and aquifer tests). Similarly, porosity measurements of a direct and indirect type were carried out: the former performed in the laboratory and the latter utilizing a relation between k and Φ based on the particle size analysis of the porous media considered. Successively, a new empirical relationship is proposed here, to derive Φ, since the k values and vice versa, are well-known, the validity of which is limited to the sands with effective grain size between 0.059 mm and 0.82 mm and for volumes of aquifer not higher than those investigated here. © 2010 Elsevier B.V
Evidence-Based Evaluation Technique to Assess Augmentation Mammaplasty Results: A Simple Method to Objectively Analyze Mammary Symmetry and Position.
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