A State of the Salamander Address was printed in PNAS recently.1 An international group of scientists looked for evolutionary ancestry and “Global patterns of diversification in the history of modern amphibians.” It would seem Mr. Darwin has a bit of frog in his throat:The fossil record of modern amphibians (frogs, salamanders, and caecilians) provides no evidence for major extinction or radiation episodes throughout most of the Mesozoic and early Tertiary. However, long-term gradual diversification is difficult to reconcile with the sensitivity of present-day amphibian faunas to rapid ecological changes and the incidence of similar environmental perturbations in the past that have been associated with high turnover rates in other land vertebrates. To provide a comprehensive overview of the history of amphibian diversification, we constructed a phylogenetic timetree based on a multigene data set of 3.75 kb for 171 species. Our analyses reveal several episodes of accelerated amphibian diversification, which do not fit models of gradual lineage accumulation. Global turning points in the phylogenetic and ecological diversification occurred after the end-Permian mass extinction and in the late Cretaceous…. Approximately 86% of modern frog species and >81% of salamander species descended from only five ancestral lineages that produced major radiations in the late Cretaceous and early Tertiary. This proportionally late accumulation of extant lineage diversity contrasts with the long evolutionary history of amphibians but is in line with the Tertiary increase in fossil abundance toward the present.Note: “accelerated diversification” can be considered a synonym for “abrupt appearance” for all practical purposes. “Because of its incompleteness, the fossil record of amphibians sheds little light on the time and rate at which modern taxa attained their current diversity,” they said; “…the timing and intensity of important macroevolutionary trends are obscured by fossil scarcity.” Molecular evidence, however, failed to rescue Darwinian gradualism. Their charts show no clear upward trend in diversity over time, but peaks and valleys and a sudden burst of diversification in the most recent epoch. “Our results, inferred from extant taxa,” they said in conclusion, “provide evidence for substantial fluctuations in the history of amphibian net diversification and reject the hypothesis of gradual lineage accumulation.” See also the report on New Scientist and its discussion of “exploding frogs.”1Roelants et al, “Global patterns of diversification in the history of modern amphibians,” Proceedings of the National Academy of Sciences USA, 10.1073/pnas.0608378104c, published online before print January 9, 2007.OK, another research project has falsified Darwin’s prediction. Keep up the good work.(Visited 31 times, 1 visits today)FacebookTwitterPinterestSave分享0
2 May 2007The South African government is looking to increase its reliance on nuclear power generation as a means of ensuring energy security, diversifying the country’s current energy supply and reducing its greenhouse gas emissions.Addressing the Nuclear Energy and Uranium Renaissance Conference in Johannesburg in February, Minerals and Energy Minister Buyelwa Sonjica said there was a need to develop advanced, efficient, non-polluting, cost-effective energy technologies, especially for use in developing countries.“You are all aware that currently the South African electricity generation is dependent on coal. The over-reliance on coal will need to be reduced, particularly as investment is being made into new national electricity generation capacity,” Sonjica said.South Africa is to spend R97-billion to increase the capacity of its electricity grid over the next five years.In February, the government backed state-owned power utility Eskom in its plans to build a second nuclear power station in the southern part of the country, to contribute upwards of 1 000 megawatts of base-load power.The country is also busy experimenting with the Pebble Bed Modular Reactor concept, with a demonstration reactor set to be operational outside Cape Town by 2010.To prepare for an expanded nuclear programme, the Department of Minerals and Energy is putting together a strategy that will outline the future of nuclear energy in South Africa, while also ensuring investment in uranium beneficiation, given the presence of the mineral in the country.“[The] government is strongly encouraging the beneficiation of our minerals resources,” Sonjica said. “It goes without saying that beneficiation of uranium comes with its own responsibilities and sensitivities, and we should pursue this beneficiation within our national and international obligations.”‘Shift in mindset’According to Sonjica, developing a nuclear industry of such magnitude requires a shift in mindset from all role players in the local industry. South Africa would have to invest in nuclear research and development – currently being undertaken by the Nuclear Energy Corporation of SA (Necsa), as well as in manufacturing capacity.She said, however, that current rates of skills development were not sufficient, and that the government had to look into other methods, such as twinning local talent with international experts, to accelerate skills development.The department has since introduced initiatives such as the South African Young Nuclear Professionals Society and Women in Nuclear South Africa to promote the industry among previously disadvantaged people.Necsa chief executive Rob Adam told Engineering News that the corporation had been given R10-million a year for the next three years to establish a National Nuclear Manufacturing Centre.The centre will incorporate Necsa’s existing facilities at the Pelindaba complex outside Pretoria, including Fabritek (the manufacturing component of the old Atomic Energy Corporation), an existing design centre, and Necsa’s current fuel manufacturing activities at the Safari-1 research reactor.“What we have discovered is that South African companies are finding it hard to manufacture to nuclear specifications, and we fear that, when the building of new nuclear power stations starts, local companies will find it difficult to respond and money that we had hoped would be spent in South Africa will have to be spent abroad,” Adam told Engineering News.“This centre would both do its own manufacturing and help other South African companies to meet the required standards and be able to manufacture for nuclear.”Sonjica also called on the National Nuclear Regulator to strengthen its capacity to evaluate different technologies, adding that the state would also have to improve its system for ensuring compliance with its non-proliferation obligations.“Nuclear safety is going to be paramount in the pursuit of our objectives,” she said.SouthAfrica.info reporter Want to use this article in your publication or on your website?See: Using SAinfo material
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Fewer dials improve flight operationsThe number of dials required for cockpit procedures reduced dramatically. For normal procedures, the number of dials/gauges reduced from 107 to 34; for engine fire, from 15 to 4; for fuel jettison, from 11 to 7; for decompression, from 20 to 3; and for cargo fire, from 16 to 2. The simplification doesn’t end there. Fourteen computers dedicated to flight control on the 747-300 were replaced by just three on the -400 model. Glass cockpitWhat is now termed “the glass cockpit” was introduced by Airbus with the A320 family in the mid-1980s, followed by the 747 and MD-11 in the early 1990s. The advances in cockpit automation have also led to a dramatic improvement in safety. This is best illustrated by the evolution of the Douglas DC-9 which first flew in 1965 into the latest model the Boeing 717. In 1965, the initial DC-9 had a crash record of 1.26 Per one Million Departures (PMD). In 1980, an updated model, the DC-9 Super 80, later renamed the MD-80, had a crash rate of 0.43 PMD. From 1996 to 2013, the ultimate version, the MD-95, renamed 717 after the merger with Boeing, has had a perfect record. Need for fewer flight crewThe navigator’s position disappeared in the early 1960s, together with the engineer’s role. While the three-engine 140-seat 727 of 1962 required an engineer, the twin-engine 100-seat DC-9 of 1965 was certified by the Federal Aviation Administration (FAA) with just two flight crew. In 1981 the FAA deemed that a flight engineer was no longer required on any aircraft and that a two-pilot crew was safe, due to the advances in cockpit automation and the dramatic improvement in engine reliability. Cockpit computerization advancesIn 1991 that dramatic increase in automation was underscored when Boeing moved from an analogue (conventional) cockpit with gauges and dials on the 747-300 to a computerized cockpit for the 747-400 with eight-inch Cathode Ray Tube (CRTs) displays. The result was the elimination of 600 dials and gauges. An illustration of the improvement in cockpit technology was the significant reduction in crew procedures from the 747-300 to the 747-400. Flying by the starsThe first aircraft cockpits were rudimentary affairs with just a handful of instruments to provide the pilot with very basic information. However, by 1939 cockpits had become very complex. On the Boeing 314 Clipper the cockpit required a crew of five. Even on the first jet powered commercial aircraft like the 707 in the 1950s, you would find a four-crew cockpit with two pilots, an engineer and a navigator. There was even an observation dome for star sightings to assist with navigation! According to Boeing’s 2018 Pilot & Technician Outlook, the industry will need 790,000 new civil aviation pilots and 754,000 new maintenance technicians to fly and maintain the world fleet over the next 20 years.