Restoring sight: how cataract surgery improves the lives of older adults.

The fundamental aim of most ophthalmic interventions in later life is to improve the quality of patients' lives, whether through sight-restoring cataract surgery or the provision of visual aids. Amidst the pressures of targets, outputs, and backlogs, this may be all too easily forgotten. It is therefore important to step back and remember just how important good vision is in the lives of older adults.Vision loss has a major negative impact on the quality of older people's lives. Sight remains as valued and important in later life as at any other age and its loss is one of the things older people fear most. Improving access to eye care services for this age group, as well as older people's uptake of such services, is therefore very important.This article takes a closer look at some of the ways in which vision loss and blindness can affect the lives of older adults; it also highlights the positive impact sight-restoring cataract surgery has on older people's lives

Using formal metamodels to check consistency of functional views in information systems specification

UML notations require adaptation for applications such as Information Systems (IS). Thus we have defined IS-UML. The purpose of this article is twofold. First, we propose an extension to this language to deal with functional aspects of IS. We use two views to specify IS transactions: the first one is defined as a combination of behavioural UML diagrams (collaboration and state diagrams), and the second one is based on the definition of specific classes of an extended class diagram. The final objective of the article is to consider consistency issues between the various diagrams of an IS-UML specification. In common with other UML languages, we use a metamodel to define IS-UML. We use class diagrams to summarize the metamodel structure and a formal language, B, for the full metamodel. This allows us to formally express consistency checks and mapping rules between specific metamodel concepts. (C) 2007 Elsevier B.V. All rights reserved

A study of flight control requirements for advanced, winged, earth-to-orbit vehicles with far-aft center-of-gravity locations

Control requirements of Controlled Configured Design Approach vehicles with far-aft center of gravity locations are studied. The baseline system investigated is a fully reusable vertical takeoff/horizontal landing single stage-to-orbit vehicle with mission requirements similar to that of the space shuttle vehicle. Evaluations were made to determine dynamic stability boundaries, time responses, trim control, operational center-of-gravity limits, and flight control subsystem design requirements. Study tasks included a baseline vehicle analysis, an aft center of gravity study, a payload size study, and a technology assessment

The cost-utility of telemedicine to screen for diabetic retinopathy in India.

PURPOSE: To assess the cost-effectiveness of a telemedicine diabetic retinopathy (DR) screening program in rural Southern India that conducts 1-off screening camps (i.e., screening offered once) in villages and to assess the incremental cost-effectiveness ratios of different screening intervals. DESIGN: A cost-utility analysis using a Markov model. PARTICIPANTS: A hypothetical cohort of 1000 rural diabetic patients aged 40 years who had not been previously screened for DR and who were followed over a 25-year period in Chennai, India. METHODS: We interviewed 249 people with diabetes using the time trade-off method to estimate utility values associated with DR. Patient and provider costs of telemedicine screening and hospital-based DR treatment were estimated through interviews with 100 diabetic patients, sampled when attending screening in rural camps (n = 50) or treatment at the base hospital in Chennai (n = 50), and with program and hospital managers. The sensitivity and specificity of the DR screening test were assessed in comparison with diagnosis using a gold standard method for 346 diabetic patients. Other model parameters were derived from the literature. A Markov model was developed in TreeAge Pro 2009 (TreeAge Software Inc, Williamstown, MA) using these data. MAIN OUTCOME MEASURES: Cost per quality-adjusted life-year (QALY) gained from the current teleophthalmology program of 1-off screening in comparison with no screening program and the cost-utility of this program at different screening intervals. RESULTS: By using the World Health Organization threshold of cost-effectiveness, the current rural teleophthalmology program was cost-effective ($1320 per QALY) compared with no screening from a health provider perspective. Screening intervals of up to a frequency of screening every 2 years also were cost-effective, but annual screening was not (>$3183 per QALY). From a societal perspective, telescreening up to a frequency of once every 5 years was cost-effective, but not more frequently. CONCLUSIONS: From a health provider perspective, a 1-off DR telescreening program is cost-effective compared with no screening in this rural Indian setting. Increasing the frequency of screening up to 2 years also is cost-effective. The results are dependent on the administrative costs of establishing and maintaining screening at regular intervals and on achieving sufficient coverage

The Fermi edge singularity of spin polarized electrons

We study the absorption spectrum of a two-dimensional electron gas (2DEG) in a magnetic field. We find that that at low temperatures, when the 2DEG is spin polarized, the absorption spectra, which correspond to the creation of spin up or spin down electron, differ in magnitude, linewidth and filling factor dependence. We show that these differences can be explained as resulting from creation of a Mahan exciton in one case, and of a power law Fermi edge singularity in the other.Comment: 4 pages, 4 figures, published in Phys. Rev. Let

Inversion of hematocrit partition at microfluidic bifurcations

Partitioning of red blood cells (RBCs) at the level of bifurcations in the microcirculatory system affects many physiological functions yet it remains poorly understood. We address this problem by using T-shaped microfluidic bifurcations as a model. Our computer simulations and in vitro experiments reveal that the hematocrit ($\phi_0$) partition depends strongly on RBC deformability, as long as $\phi_0 <20$% (within the normal range in microcirculation), and can even lead to complete deprivation of RBCs in a child branch. Furthermore, we discover a deviation from the Zweifach-Fung effect which states that the child branch with lower flow rate recruits less RBCs than the higher flow rate child branch. At small enough $\phi_0$, we get the inverse scenario, and the hematocrit in the lower flow rate child branch is even higher than in the parent vessel. We explain this result by an intricate up-stream RBC organization and we highlight the extreme dependence of RBC transport on geometrical and cell mechanical properties. These parameters can lead to unexpected behaviors with consequences on the microcirculatory function and oxygen delivery in healthy and pathological conditions.Comment: 16 page