Search

This paper presents a one-dimensional model for the transient liquid flow (without cavitation) in constant diameter pipes. The system equations, which describe the macroscopic thermo-mechanical behavior of the pipe-flow system, are obtained within the framework of the continuum mechanics and classical thermodynamics. The flow problem is formulated as an inverse problem. Experimental data, concerning the propagation of pressure waves in liquid-filled pipes, are used to infer the parameters that characterize the fluid-pipe system. The numerical results show that the model is able to reproduce flow features including the attenuation and the phase shift of intense pressure waves which occurs in water hammer phenomena. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate fixation stability using two different fixation targets with the Nidek MP1 microperimeter. Twenty-nine healthy subjects with a mean age of 26.53 ± 7.35 years and visual acuity ≥0.0 logMAR were enrolled in this study. Fifty-eight eyes of 29 patients without ophthalmic and/or systemic disease underwent a fixation test with the MP1 microperimeter. Fixation stability related to a red cross (central) and/or a red circle (pericentral) target was quantified using either Fujii classification or by calculating the bivariate contour ellipse area (BCEA). For statistical analysis, BCEA values were converted into their logarithms (logBCEA) and all data obtained were analyzed using paired Student's t test. The inclination values of the axis of BCEA were analyzed with Chi squared test. The mean values of logBCEA and the mean values of the major and minor axis of the ellipses related to the cross and the circle fixation target were significantly different (68.2 %, p = 0.00; 95.4 %, p = 0.00; 99.6 %, p = 0.00, respectively) for each BCEA standard deviation. Fixation was significantly less stable for the pericentral fixation target in normal subjects, indicating an advantage for central fixation targets. These results are of particular interest when evaluation of changes in fixation is needed. [ABSTRACT FROM AUTHOR]

This paper deals with the theoretical derivation of the conservation equations for single phase flow in a porous medium. The derivation is obtained within the framework of the continuum mechanics and classical thermodynamics. The adopted procedure provides the conservation equations of mass, momentum, mechanical energy, total energy, internal energy, entropy, temperature, enthalpy, Gibbs free energy and Helmholtz free energy. The obtained results highlight the connection between the basic equations of fluid mechanics and of fluid flow in porous media, as well as the restrictions and the limitations of Darcy's law and Richards' equation. [ABSTRACT FROM AUTHOR]

Within the framework of one-dimensional unsteady compressible flow in deformable pipes, the present work proposes expressions able to represent the stress state of a 'fluid-pipe' continuous system. The coefficients needed to define the friction forces are calibrated against experimental results. The proposed expressions highlight the crucial role played by the fluid compressibility on the wave resistance. [ABSTRACT FROM AUTHOR]

PurposeTo obtain age-specific data on changes in the prevalence and management of optically correctable visual impairments (OCVIs) in Ponza, Italy.MethodsOphthalmologic examinations were carried out to 1000 Ponzans aged 40–87 years in 1988 and to 836 persons in 2000. Visual acuity (VA) was evaluated under uncorrected (VAUC), presenting (VAPR), and best-corrected (VABC) conditions. We calculated the prevalence of total OCVIs (subjects with VAUC>0.5 logMAR and VABC0.5 logMAR in the better eye), uncorrected OCVIs (VAPR>0.5 logMAR), and corrected OCVIs (VAPR0.5 logMAR) as well as the OCVI correction rate ((corrected OCVI/total OCVI) × 100). Subjects with uncorrected OCVIs were compared to those with corrected OCVIs to evaluate possible associations with some risk factors.ResultsAmong 52- to 63-year olds there were increases in the prevalence of total OCVI (from 15.7 to 22.7%, P=0.051), corrected OCVI (from 10.9 to 19.9%, P=0.005), and OCVI correction rate (from 69.2 to 87.8%, P=0.045). Among 64- to 75-year olds decreases were observed in the prevalence of total OCVI (from 28.5 to 20.0%, P=0.029) and uncorrected OCVI (from 12.6 to 4.8%, P=0.003) while the OCVI correction rate increased from 55.9 to 76.1% (P=0.033). The overall prevalence of uncorrected OCVIs dropped from 7.5 to 4.1%. In 2000, uncorrected OCVI was associated with limited education, very advanced age, retirement, and refractive error associated with eye diseases.ConclusionsRefractive error management has improved in Ponza since 1988, and these changes may be, in part, due to higher education levels, increased frequency of cataract surgery, and slower progression of cataract-related disability.Eye (2009) 23, 522–529; doi:10.1038/eye.2008.104; published online 18 April 2008 [ABSTRACT FROM AUTHOR]

AimThe scientific literature contains recent data on the prevalence of blindness and low vision for a few European countries, but most of these studies have been focused exclusively on the elderly sector of the populations. The purpose of the present study was to provide age-specific estimates of the prevalence and causes of visual loss in an Italian population aged 40 years and over.MethodsIn total, 847 of the 1200 citizens >40 years of age (70.6%) in the island community of Ponza underwent complete standardized ophthalmological examinations. Visual acuity (VA) was measured using a standard logarithmic chart. World health organization (WHO) definitions of blindness and low vision were adopted (respectively, VA>1.3 logMAR or a visual field <10° around central fixation, and VA >0.5 to 1.3 logMAR or a visual field <20° around central fixation). Prevalence rates based on presenting VAs were also calculated.ResultsThe overall best-corrected prevalence rates were 0.6% (presenting, 0.8%) for better eye blindness, 2.1% (presenting, 6.7%) for better eye low vision, 1.8% (presenting, 2.6%) for monocular blindness, 5.0% (presenting, 11.2%) for monocular low vision. Cataract, glaucoma, degenerative myopia, and AMD were the main causes of better eye visual loss.ConclusionAge-specific prevalence rates in Ponza are fairly consistent with those for other European countries with similar socio-economic conditions and public healthcare systems. A substantial percentage of visual losses remains uncorrected despite the availability of potentially curative therapy. Greater emphasis needs to be placed on educating the public regarding the importance of good vision.Eye (2006) 20, 661–667. doi:10.1038/sj.eye.6701934; published online 27 May 2005 [ABSTRACT FROM AUTHOR]

AIM:To study the incidence of visual loss over a 12-year period in the survivors of an original cohort aged 40 years or older at baseline. METHODS:Visual acuity (VA) was measured by means of a standardized logMAR chart. World Health Organization definition of blindness and low vision was adopted (respectively, best-corrected VA>1.3?logMAR or a visual field<10°around central fixation, and best-corrected VA>0.5-1.3?logMAR or a visual field<20°around central fixation). Moreover, binocular visual loss incidence (VA>0.5?logMAR) was calculated in a‘healthy’group who had uncorrected VA of 0.0?logMAR or better in both eyes at baseline and absence of eye diseases. RESULTS:Of the 584 eligible survivors, 411 (70.7%) had a 12-year follow-up visit. The overall incidence figures were as follows: best-corrected binocular blindness (0.7%), binocular low vision (3.9%), monocular blindness (2.7%), and monocular low vision (5.0%), respectively. The results for presenting VAs were 1.2, 9.5, 4.2, and 15.3%. Figures for uncorrected, best-corrected, and presenting binocular visual loss incidence in the‘healthy’group were respectively 12.7, 0.9, and 3.7%. CONCLUSION:The discrepancy between the ideal and real situations that emerges from this study has important implications for health-care planning. Over a period of 12 years, a substantial percentage of‘healthy’subjects will have to seek medical care. Incident visual loss was caused mainly by untreated cataract, glaucoma, myopia, and age-related macular degeneration.Eye (2005) 19, 175-182. doi:10.1038/sj.eye.6701444 Published online 25 June 2004 [ABSTRACT FROM AUTHOR]

Background: There are many different strategies for the treatment of the main bile duct lithiasis. When lithiasis of the biliary tract is suspected at a preoperative stage, we can treat patients with sequential treatment: endoscopic netrograde cholangiopancreatography followed by laparoscopic cholecystectomy. If common bile duct-lithiasis is recognized at an intraoperative stage, many options for treatment exist, one of which is intraoperative retrograde endoscopic sphincterotomy (ES) (laparoendorendezvous).Methods: We report our experience using the aforementioned technique with 58 patients affected by cholelithiasis and complex Common bile duct disease who underwent laparoscopic cholecystectomy and intraoperative ES consecutively from March 1996 to May 2000. Of the 58 patients, 43 were affected by cholecystocholedocolithiasis: 12 by previously described lithiasis plus stenosant papillitis, 2 also by a pancreas head cancer, and 1 by cancer of the papilla.Results: The combined technique was performed in 86% of the cases. Six patients required conversion to open surgery. In two other patients, laparoscopic choledocotomy was performed with positioning of a Kehr-tube for an ampulla-impacted lithiasis.Conclusions: Intraoperative ES offers a valid approach to the treatment of cholecystocholedocolithiasis in one session. Furthermore, it represents a valid alternative to transcholedocical laparoscopic treatment of cholelithiasis and complex common bite duct pathology. [ABSTRACT FROM AUTHOR]