Comparison of DCOM and CORBA distributed computing

The movement of distributed applications from 2-tier to n-tier architectures have enabled systems to be scaled to meet the demands of an ever increasing population of users. Two middleware architectures have come to the forefront: Microsoft\u27s DCOM and the OMG\u27s CORBA. These are not the only possible architectures for n-tier distributed applications, but they are currently the only two which offer a degree of platform independence and the flexibility of using different programming languages for development. CORBA provides platform independence because it provides a middle layer between the client and the server and services client requests using its internal naming service to identify server objects and then expose methods to the client through it\u27s object adapter (POA). CORBA is a self contained middleware that operates independent of the underlying operating system. CORBA offers the potential of ease of maintainability since server objects can be changed and the new methods can be discovered at runtime by the client using CORBAs Dynamic Invocation Interface. Client code would therefore not have be recompiled as it would using static IDL mappings and client and server stubs. DCOM, in contrast is a platform dependent solution that can only be used on Windows machines, although ports for other platforms are in the works. It relies on the Windows registry to identify objects and the operating system to assist in runtime control of objects. Because DCOM is nothing more of a remote extension to the already established Common Object Model which all contemporary Windows operating systems and applications are built upon, it may provide the easiest path to distributed applications for Windows developers that are already familiar with the Common Object Model

Systematic design of single-mode coupled-resonator optical waveguides in photonic crystals

By establishing a direct relation between the dispersion and the field profile of a coupled-resonator optical waveguide (CROW) and those of its constituent cavities, we present a systematic method for the design of a single-mode CROW and for control of its dispersion. The procedure includes the design of a single-mode cavity and control of its frequency by engineering its structure. Then, by chaining these cavities in the proper direction and at an appropriate distance, we achieve the desired dispersion for the CROW

Age-based disparities in end-of-life decisions in Belgium: a population-based death certificate survey

<p>Abstract</p> <p>Background</p> <p>A growing body of scientific research is suggesting that end-of-life care and decision making may differ between age groups and that elderly patients may be the most vulnerable to exclusion of due care at the end of life. This study investigates age-related disparities in the rate of end-of-life decisions with a possible or certain life shortening effect (ELDs) and in the preceding decision making process in Flanders, Belgium in 2007, where euthanasia was legalised in 2002. Comparing with data from an identical survey in 1998 we also study the plausibility of the ‘slippery slope’ hypothesis which predicts a rise in the rate of administration of life ending drugs without patient request, especially among elderly patients, in countries where euthanasia is legal.</p> <p>Method</p> <p>We performed a post-mortem survey among physicians certifying a large representative sample (n = 6927) of death certificates in 2007, identical to a 1998 survey. Response rate was 58.4%.</p> <p>Results</p> <p>While the rates of non-treatment decisions (NTD) and administration of life ending drugs without explicit request (LAWER) did not differ between age groups, the use of intensified alleviation of pain and symptoms (APS) and euthanasia/assisted suicide (EAS), as well as the proportion of euthanasia requests granted, was bivariately and negatively associated with patient age. Multivariate analysis showed no significant effects of age on ELD rates. Older patients were less often included in decision making for APS and more often deemed lacking in capacity than were younger patients. Comparison with 1998 showed a decrease in the rate of LAWER in all age groups except in the 80+ age group where the rate was stagnant.</p> <p>Conclusion</p> <p>Age is not a determining factor in the rate of end-of-life decisions, but is in decision making as patient inclusion rates decrease with old age. Our results suggest there is a need to focus advance care planning initiatives on elderly patients. The slippery slope hypothesis cannot be confirmed either in general or among older people, as since the euthanasia law fewer LAWER cases were found.</p

Understanding preventive behaviors among mid-Western African-American men: a pilot qualitative study of prostate screening

http://dx.doi.org/10.1016/j.jomh.2011.03.00

The James Webb Space Telescope Mission

Twenty-six years ago a small committee report, building on earlier studies, expounded a compelling and poetic vision for the future of astronomy, calling for an infrared-optimized space telescope with an aperture of at least $4m$. With the support of their governments in the US, Europe, and Canada, 20,000 people realized that vision as the $6.5m$ James Webb Space Telescope. A generation of astronomers will celebrate their accomplishments for the life of the mission, potentially as long as 20 years, and beyond. This report and the scientific discoveries that follow are extended thank-you notes to the 20,000 team members. The telescope is working perfectly, with much better image quality than expected. In this and accompanying papers, we give a brief history, describe the observatory, outline its objectives and current observing program, and discuss the inventions and people who made it possible. We cite detailed reports on the design and the measured performance on orbit.Comment: Accepted by PASP for the special issue on The James Webb Space Telescope Overview, 29 pages, 4 figure

British pamphleteers. Edited by George Orwell & Regina Reynolds.

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