Sickle Cell Retinopathy: a Review

Sickle cell disease is one of the most prevalent hemoglobinopathies in the world. In Iran, sickle cell disease is more common in southern parts of the country such as Khuzestan province. Retinopathy is the most representative ocular complication of sickle cell disease. Sickle cell retinopathy is characterized by the vaso-occlusion of capillary beds and is classified in two types of proliferative and non-proliferative according to presence or absence of vascular proliferation in fundus. In non-proliferative sickle cell retinopathy, the retinal changes do not involve neovascularization as they do in proliferative sickle cell retinopathy. The two most severe complication of proliferative sickle cell retinopathy are vitreous hemorrhage and retinal detachment, which may lead to visual loss. Identification and prompt referral of these patients has a critical role in prevention of irreversible visual loss.Newer imaging modalities such as ultra–wide field fluorescein angiography, spectral domain optical coherence tomography and optical coherence tomography angiography are now available. These techniques can detect the sickle cell retinopathy in its early stages. In this review, we briefly discuss the manifestations, diagnosis and management of sickle cell retinopathy.keywords: Anemia; Sickle Cell; Retinopathy; Diagnosis; Management; Iran.

Instrumentation for Flexible Pavements

DTFH61-88-R00052This report documents the findings of the literature search on instrumentation used in flexible pavements. The search covered areas such as strain, stress, deflection, temperature, moisture, load location, load magnitude, performance models, and backcalculation techniques. Each group of instrumentation was evaluated in terms of the design feasibility, cost, availability, and field performance

Pavement Testing Facility -- Pavement Performance of the Initial Two Test Sections

DTFH61-85-C-00149This report documents the pavement performance of two test sections at FHWA's Pavement Testing Facility. The traffic loading of the test asphalt concrete pavements was achieved by using the Accelerated Loading Facility (ALF). Field performance data consisting of longitudinal profile, rutting, cracking, and deflection were collected at the facility. Pavement temperature, moisture content, and environmental data were also collected. Various performance indicators were compared with regard to the number of wheel passes and 18-kip-equivalent single axle loads. In situ strain measurements were compared with calculated strain values. At the conclusion of each field test, the pavement section was opened, and a postmortem analysis was conducted. This analysis included a profile of each pavement layer and material sampling. The results of the postmortem analysis were compared with the performance indicators to explain the pavement failure. For these two initial tests, there was no general failure in any of the materials used in the tested pavement sections. The air voids in the asphalt concrete layers after construction were smaller than might be expected. This, coupled with the dense grading of both the wearing and binder layer and the tendency for rutting to be accentuated in accelerated testing, was expected to cause atypical rutting during trafficking. However, this was not the case. The rutting that was observed is typical of normally loaded highway pavements

Instrumentation for Flexible Pavements \u2013 Field Performance of Selected Sensors: Volume I: Final Report

DTFH61-88-R-00052This report presents the results of a research study on methods for measuring strain and stress in bituminous pavements subjected to dynamic vehicle loading. The research program was divided into two phases. In the first phase, an extensive literature\ub7 search was conducted to identify the existing pavement instrumentation and to select the most promising types of gauges for a field testing program. Two sections of bituminous pavement 6 and 10 in (152 and 254 mm) thick were constructed and instrumented with the selected gauges. The response of the gauges to dynamic loading applied by a tractor-semitrailer at different levels of axle loading, tire pressure, and speed was investigated. In the second phase, new concepts in pavement instrumentation were investigated. Prototype gauges were built and evaluated, first in the laboratory and then in a field testing program similar to the one conducted in the first phase. Two new gauges, an inductive sensor and the Hall effect sensor, performed very well in the tests. The pavement response data, collected in the field testing program, were used to evaluate methods for back-calculating pavement material properties. It was demonstrated that the back-calculated moduli are much more accurate if data from multiple sensors placed throughout the pavement structure, rather than a single sensor measurements, are used in the analysis

Correction: Decomposing socioeconomic inequality in dental caries in Iran: cross-sectional results from the PERSIAN cohort study

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