Variant of the anastigmatic telescope with three mirrors for back focal length

In this paper, an optical design is presented for an anastigmatic telescope with back focal length corrected with exact ray tracing to eliminate spherical, coma, and astigmatism aberrations. The telescope is formed of three conical mirrors, two of them polished on the same substratum. The optical design is divided into three stages: we began the design obtaining the Gaussian parameters in a first-order solution; posteriorly, were obtained analytically the three mirrors' asphericity in a third-order design. The final design stage consists of the implementation of the Fermat's principle, the Abbe sine condition, and the Coddington equations for the exact correction for the three aforementioned aberrations.     

Athlete''s heart in elite disabled athletes

Nineteen children with congenital upper alimentary tract malformation were studied prospectively at the Department of Paediatrics, University College Hospital (UCH), Ibadan, over a period of 12 months. There were 20 cases, grouped into six types comprising congenital hypertrophic pyloric stenosis, seven; cleft lip and/or cleft palate, five; oesophagal atresia with or without tracheo-oesophageal fistula, four; jejunal atresia two and a case each of achalasia and annular pancreas. One patient had oesophageal atresia and congenital hypertrophic pyloric stenosis. The mortality rate was 31.51% (six out of nineteen). Low mortality was recorded in cases of cleft lip and/or palate, while mortalities of over 70% were recorded among cases of jejunal atresia, and oesophageal atresia with or without tracheo-oesophageal fistul. The common causes of death were milk feed aspiration (28.6%-two cases), purulent peritonitis (14.3%-one case), and probable septicaemia (14.3%-one case). The cause of death in two cases could not be determined.     

Improving TCP performance over wireless networks at the link layer

We present the transport unaware link improvement protocol (TULIP), which dramatically improves the performance of TCP over lossy wireless links, without competing with or modifying the transport- or network-layer protocols. TULIP is tailored for the half-duplex radio links available with today's commercial radios and provides a MAC acceleration feature applicable to collision-avoidance MAC protocols (e.g., IEEE 802.11) to improve throughput. TULIP's timers rely on a maximum propagation delay over the link, rather than performing a round-trip time estimate of the channel delay. The protocol does not require a base station and keeps no TCP state. TULIP is exceptionally robust when bit error rates are high; it maintains high goodput, i.e., only those packets which are in fact dropped on the wireless link are retransmitted and then only when necessary. The performance of TULIP is compared against the performance of the Snoop protocol (a TCP-aware approach) and TCP without link-level retransmission support. The results of simulation experiments using the actual code of the Snoop protocol show that TULIP achieves higher throughput, lower packet delay, and smaller delay variance. This revised version was published online in June 2006 with corrections to the Cover Date.     

Influence of the acid–base/redox properties of TiOx-sepiolite supported vanadium oxide catalysts in the gas-phase selective oxidation of toluene

Catalytic behaviour in the selective oxidation of toluene of a series of vanadium systems supported on TiO_x-coated sepiolite (6, 12 and 25 wt.% TiO₂) with a vanadia loading around the theoretical monolayer (10 wt.%) has been investigated. The surface acid–base/redox properties of the solids were also evaluated by using 2-propanol conversion and pyridine chemisorption. The reducibility of surface vanadia species was studied by H₂-TPR. Surface properties of vanadia species and, consequently, their catalytic behaviour were influenced by titania loading on sepiolite. Thus, the vanadium systems with the highest titania loading were the most active and selective in toluene oxidation. Furthermore, this behaviour seems to be mainly related to the density of the active sites capable of being reduced and producing propanone in the vanadium systems.     

Methimazole-induced aplastic anemia in third exposure: successful treatment with recombinant human granulocyte colony-stimulating factor

Treatments for diabetes in Ethiopia are at present only available in hospitals so many patients must travel great distances to obtain insulin, tablets, and diabetes education. We reviewed all 496 people with diabetes attending the diabetic clinic at Gondar Hospital (281 with Type 1 (insulin-dependent) diabetes mellitus (DM) and 215 with Type 2 (non-insulin-dependent) DM. Half of the patients came from rural areas, all but 3 of them travelling more than 20 km, one-quarter of them more than 100 km and 33 patients (13%) more than 180 km. It is likely that many patients who fail to attend from the more distant areas have died. We are developing a scheme which would enable diabetic patients to be treated at rural health centres by nurses trained in the principles of diabetes care which could greatly improve the outlook for diabetic patients in Ethiopia.     

Multi-Objective Optimization using Grid Computing

This paper analyzes some technical and practical issues concerning the use of parallel systems to solve multi-objective optimization problems using enumerative search. This technique constitutes a conceptually simple search strategy, and it is based on evaluating each possible solution from a given finite search space. The results obtained by enumeration are impractical for most computer platforms and researchers, but they exhibit a great interest because they can be used to be compared against the values obtained by stochastic techniques. We analyze here the use of a grid computing system to cope with the limits of enumerative search. After evaluating the performance of the sequential algorithm, we present, first, a parallel algorithm targeted to multiprocessor systems. Then, we design a distributed version prepared to be executed on a federation of geographically distributed computers known as a computational grid. Our conclusion is that this kind of systems can provide to the community with a large and precise set of Pareto fronts that would be otherwise unknown.     

Numerical Simulation of Rain Scavenging on Large Release of Water-Soluble Gases

A depth-integrated numerical model GP_Rain was developed to calculate the behavior of neutrally buoyant, highly soluble gases subjected to scavenging by rain. A neutrally buoyant release of hydrogen fluoride is used to illustrate the use of the model. The GP_Rain model was developed in two steps. The part without rain scavenging is based on AFTOX, a Gaussian puff/plume model. Then a first-order decay term for rain scavenging, which was developed by assuming a homogeneous rain field, was added to the concentration calculation for the puff. The model can predict the maximum release distance for a certain concentration limitation and a two-dimensional plume with or without rain.     

Mutant K-ras oncogenes in colon cancers Do not predict Patient's chemotherapy response or survival

One half of human colon cancers bear mutant c-K-ras oncogenes. Mutant K-ras oncogenes are associated with shortened survival in non-small cell lung cancers, and, in cell line models, with resistance to cis-platinum and to ionizing radiation. This study examines whether mutant K-ras alleles in colon cancer alter patients' response to chemotherapy or survival. We studied 37 patients who received chemotherapy with 5-fluorouracil and leucovorin, Exon 1 of the c-K-ras gene was PCR amplified from DNA extracted from paraffin-embedded tumor blocks. The presence of mutant or wild-type c-K-ras alleles was determined by dideoxy sequencing of the PCR-amplified c-K-ras DNA. c-K-ras mutations at codons 12 or 13 were present in 19 and absent in 18 cases. Responses to chemotherapy were equally likely in patients with either wild-type or mutant c-K-ras, occurring in 28% of patients with wild-type ras and 32% of patients with mutant ras (P = 0.8). Survival was also indistinguishable among both groups. Median survival from diagnosis was 35 months for ras wild-type patients and 31 months for ras mutant patients (P = 0.96). Median survival from starting chemotherapy was 14 months for ras wild-type patients and 17 months for ras mutant patients (P = 0.26). Patients with colon cancers bearing either wild-type or mutant c-K-ras alleles are indistinguishable in overall survival and are equally likely to respond to 5-fluorouracil-based chemotherapy.     

Prolonged bradyarrhythmias after coronary revascularization surgery

The authors report four cases of prolonged bradyarrhythmias after isolated coronary artery bypass graft surgery. All the four patients required permanent pacemaker implantation. Etiologic factors of conduction disturbances after coronary artery bypass and long term follow-up are discussed.