1,720,968 research outputs found
Manufacturing and characterization of hemp-reinforced epoxy composites
No full textThe adoption of natural-based fibers in place of inorganic reinforcements is an effective approach to reduce the environmental and economic impact of composite materials. In particular, hemp is an attractive solution due to its mechanical, physical, and growing properties. The present article deals with the manufacturing of thermoset hemp-reinforced composite materials. In particular, the investigation moves into the production by resin transfer molding and by resin powder molding with the use of epoxy polymeric material. To describe the effects of the technological cycle onto the characteristic of realized products, different manufacturing parameters have been combined during the braiding of reinforcement and the polymerization of the final composite. Computed tomography, microscopical analysis, and tensile tests have been used to observe the main effects of the manufacturing process and mechanical properties of the materials. Furthermore, elastic moduli of the materials have been estimated by means of modified rule of mixture and Halpin-Tsai models in order to verify their effectiveness in forecasting stiffness of the hemp-reinforced composites in the early design phase. The article extends the existing knowledge base on hemp-reinforced thermoset composites manufactured with different processes. Results also illustrate relations existing between error introduced by calculation models and the intrinsic variability in mechanical properties
Spontaneous resolution of a shallow detachment of the macula in a highly myopic eye
No full textPURPOSE: To report a case of pathologic myopia with shallow detachment of the macula and anatomic reattachment after spontaneous posterior vitreous separation. DESIGN: Observational case report. METHODS: A 66,year-old woman with pathologic myopia presented with decreased vision of 20/400 in her left eye. Biomicroscopy showed myopic chorioretinal changes, posterior staphyloma, and a shallow macular elevation. Optical coherence tomography was performed at the initial and follow-up examinations. RESULTS: Initial optical coherence tomography revealed a retinal detachment, retinoschisis, and incomplete poste, rior vitreous detachment. One and one half years after the initial visit the patient's best-corrected visual acuity improved to 20/200, and optical coherence tomography disclosed macular reattachment, release of vitreous adhesions, and restoration of normal retinal tomographic appearance. CONCLUSIONS: Spontaneous resolution of chronic shallow detachment of the macula in highly myopic eyes may occur and can be attributed to spontaneous posterior vitreous detachment. (C) 2003 by Elsevier Science Inc. All rights reserved
Anatomical and visual outcome of idiopathic macular hole surgery with infracyanine green-assisted peeling ofthe internal limiting membrane
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Contributo radiologico nel controllo precoce e a distanza delle esofagoplastiche per cancro esofageo
No full textRepeatability and reproducibility of fast macular thickness mapping with stratus optical coherence tomography
No full textObjective: To determine the repeatability and reproducibility of retinal thickness measurements with the fast macular thickness mapping protocol of Stratus optical coherence tomography.
Methods: Ten eyes of 10 healthy subjects and 15 eyes of 15 diabetic patients with clinically significant macular edema (CSME) underwent 2 scanning sessions before and after pupil dilation during the same visit by 2 experienced examiners. Healthy subjects also received a third scanning session during a second visit. Repeatability and reproducibility for the foveolar center and for each of 9 Early Treatment of Diabetic Retinopathy Study (ETDRS)-like regions were calculated by their repeatability and reproducibility coefficients and intraclass correlation coefficients.
Results: The coefficients of repeatability were less than 8% in healthy subjects and less than 9% in patients with diabetes and CSME. The reproducibility coefficients were less than 10% and 11% in healthy subjects and diabetic patients with CSME, respectively. There was no significant difference between scans acquired by different observers or during different visits. The intraclass correlation coefficients were always greater than 0.80 and 0.98 in healthy subjects and diabetic patients with CSME, respectively. Average +/- SD thickness was found to be 223 14 and 404 108 pm for the central ETDRS-like region in healthy subjects and diabetic patients with CSME, respectively.
Conclusion: With the fast macular thickness mapping protocol of Stratus ocular coherance tomography, our results indicate that retinal thickness measurements in dilated and undilated eyes of healthy subjects and diabetic patients with CSME are repeatable and reproducible
Diurnal variation in clinically significant diabetic macular edema measured by the stratus OCT
No full textPurpose: To investigate diurnal variation in clinically significant macular edema (CSME) using the Stratus OCT (Carl Zeiss Meditec). Methods: Fifteen eyes of 15 diabetic patients with CSME and 10 healthy subjects (controls) underwent four optical coherence tomography (OCT) measurements of macular thickness with the fast macular thickness mapping protocol of the Stratus OCT at 9 AM, 12 Pm, 3 Pm, and 6 Pm. Early Treatment Diabetic Retinopathy Study visual acuity and refraction data were also collected at each time. Retinal thickness measurements from each of the nine macular Early Treatment Diabetic Retinopathy Study areas of the retina map, visual acuity, and refraction were plotted over time. Results: Mean retinal thickness remained unchanged in all retinal sectors over the course of the day for the controls and the 6 diabetic patients with a baseline foveal thickness of = 300 mu m (ANOVA model for repeated measures). In these patients, the mean initial foveal thickening +/- SD of 211 +/- 104 mu m was reduced by an average of 6.1%, 15.2%, and 21.2% at 12 PM, 3 PM, and 6 PM, respectively. Two of these nine patients also had an increase in visual acuity without change in refraction. There were no changes in refractive errors over the course of the study in the two groups. A positive correlation between initial central thickening and decrease in thickness was found (r = 0.732; P = 0.002). Conclusion: This study suggests that macular thickening, as measured by the Stratus OCT, may spontaneously decrease in some patients with more severe CSME over the course of the day, and it confirms previous findings. However, in our study, the entity of this decline was relatively small and not relevant from a clinical standpoint
Light versus "classic" laser treatment for clinically significant diabetic macular oedema
No full textAim: To compare the effectiveness of "light" versus "classic" laser photocoagulation in diabetic patients with clinically significant macular oedema (CSMO). Methods: A prospective randomised pilot clinical trial in which 29 eyes of 24 diabetic patients with mild to moderate non-proliferative diabetic retinopathy (NPDR) and CSMO were randomised to either "classic" or "light" Nd:YAG 532 nm (frequency doubled) green laser. "Light" laser treatment differed from conventional ("classic") photocoagulation in that the energy employed was the lowest capable to produce barely visible burns at the level of the retinal pigment epithelium. Primary outcome measure was the change in foveal retinal thickness as measured by optical coherence tomography (OCT); secondary outcomes were the reduction/elimination of macular oedema on contact lens biomicroscopy and fluorescein angiography, change in visual acuity, contrast sensitivity, and mean deviation in the central 10° visual field. Examiners were masked to patients' treatment. Results: 14 eyes were assigned to "classic" and 15 were assigned to "light" laser treatment. At 12 months, seven (50%) of 14 eyes treated with "classic" and six (43%) of 14 eyes treated with "light" laser had a decrease of foveal retinal thickness on OCT (p = 0.79). A comparison of reduction/elimination of oedema, visual improvement, visual loss, change in contrast sensitivity, and mean deviation in the central 10° showed no statistical difference between the groups at 12 months (p>0.05 for all groups). Conclusions: This study suggests that "light" photocoagulation for CSMO may be as effective as "classic" laser treatment, thus supporting the rationale for a larger equivalence trial
Multidetector computed tomography and 2- and 3-dimensional postprocessing in the evaluation of congenital thoracic vascular anomalies.
No full text.Objective: We report examples of congenital anomalies of the thoracic vessels studied with multidetector computed tomography (MDCT), with special respect to bidimensional (2D) and 3-dimensional (3D) postprocessing. Methods: Nonselected patients with vascular and nonvascular disorders underwent chest MDCT with the use of a 16-row scanner. Postprocessing was done to obtain 2D and 3D postprocessing images. Conclusion: MDCT with 2D and 3D postprocessing is helpful in evaluating complex vascular congenital anomalies of the chest. © 2008 Society of Cardiovascular Computed Tomography
Idiopathic macular hole surgery with low-concentration infracyanine green-assisted peeling of the internal limiting membrane
No full textPURPOSE: To evaluate the efficacy of pars plana vitrectomy with infracyanine green (IFCG)-assisted internal limiting membrane peeling for the treatment of idiopathic macular hole.
DESIGN: Prospective, noncomparative interventional case series.
METHODS: Thirty-eight consecutive eyes of 35 patients with idiopathic macular hole were included in the study. Patients underwent early treatment diabetic retinopathy (ETDRS) visual acuity examination, dilated ophthalmoscopy, and optical coherence tomography before treatment and during follow,up. Fluorescein angiography was done in selected cases. Patients underwent a three-port pars plana vitrectomy with complete posterior hyaloid and epiretinal membrane removal. The internal limiting membrane (ILM) was stained with 0.5 cc of IFCG (0.5 mg/ml, 308 mOsm) and peeled up to the vascular arcades. Perfluoropropane gas (Us) 10% was used as tamponade.
RESULTS: Mean follow-up duration was 10 5 months (range, 3 to 24 months). Six eyes had stage 2 macular hole, 15 eyes stage 3, and 16 eyes stage 4. Overall, 37 of 38 macular holes closed after a single surgery. Median visual acuity was 20/100 (range, 20/400 to 20/50) before surgery and 20/50 (range, 20/640 to 20/25) after surgery. Visual acuity after surgery was 20/50 or better in 24 of 38 (63.1%) eyes. Twenty,five (65.8%) eyes improved by 2 or more lines, nine (23.7%) eyes were stable, and four (10.5%) eyes worsened by 2 or more lines.
CONCLUSIONS: This study suggests that IFCG (0.05%) effectively stains the ILM with apparent safety, and that IFCG-assisted peeling of the ILM may be useful in the treatment of idiopathic macular hole
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