ABSTRACT
Atmospheric carbon dioxide concentration is expected to exceed 500 parts per million and global temperatures to rise by at least 2 degrees C by 2050 to 2100, values that significantly exceed those of at least the past 420,000 years during which most extant marine organisms evolved. Under conditions expected in the 21st century, global warming and ocean acidification will compromise carbonate accretion, with corals becoming increasingly rare on reef systems. The result will be less diverse reef communities and carbonate reef structures that fail to be maintained. Climate change also exacerbates local stresses from declining water quality and overexploitation of key species, driving reefs increasingly toward the tipping point for functional collapse. This review presents future scenarios for coral reefs that predict increasingly serious consequences for reef-associated fisheries, tourism, coastal protection, and people. As the International Year of the Reef 2008 begins, scaled-up management intervention and decisive action on global emissions are required if the loss of coral-dominated ecosystems is to be avoided.
Subject(s)
Anthozoa , Climate , Ecosystem , Greenhouse Effect , Seawater/chemistry , Animals , Anthozoa/growth & development , Anthozoa/physiology , Atmosphere , Carbon Dioxide , Dinoflagellida/physiology , Eukaryota/physiology , Fishes , Forecasting , Hydrogen-Ion Concentration , Oceans and Seas , TemperatureABSTRACT
Burlin's general cavity theory for intermediate sized cavities incorporated two weighting factors: d, the average reduction in the electron fluence from the medium inside the cavity, and 1 - d, the average fractional build-up to equilibrium of the cavity-generated electron spectrum--both calculated for an average path length g of electrons crossing the cavity. A new weighting factor d' has been introduced expressing the fact that average path length for medium- and cavity-generated electrons are not equal and this leads to a modified general cavity expression. The new expression is applied to 60Co thermoluminescence dosimetry experimental results of other workers. For LiF TLD in all the media agreement with experiment is improved. There is a significant dependence of the theoretical results on the effective mass attenuation coefficient, indicating the need for further studies.
Subject(s)
Cobalt Radioisotopes , Lithium Compounds , Radiation Dosage , Thermoluminescent Dosimetry , Fluorides , Gamma Rays , Lithium , Mathematics , Models, TheoreticalSubject(s)
Diuretics/therapeutic use , Hypertension/drug therapy , Metolazone/therapeutic use , Adult , Aged , Drug Evaluation , Female , Humans , Male , Middle AgedABSTRACT
The thermal neutron thermoluminescent response of CaF2 : Dy (TLD-200, 0-35% wt Dy) and CaF2 : mn (TLD-400, 2% wt Mn) has been measured by exposure to a monoenergetic, parallel beam of 81-0 meV neutrons from a Kandi-II diffractometer. The TL dosemeters were rectangular and of 0-165 X 0-165 X 0-83 cm dimensions. The measured integral TLD-200 response for a neutron fluence of 10(10) n cm-2 was 0-21 +/- 0-013 R of 60Co which translates to 0-33 +/- 0-021 R 60Co for a Maxwellian neutron energy distribution at T = 293-6 K. The measured integral TLD-400 response for a neutron fluence of 10(10) n cm-2 was 0-09 +/- 0-006 R 60Co which similarly translates to 0-14 +/- 0-010 R 60Co for a Maxwellian neutron energy distribution at T = 293-6 K. The thermoluminescent response of both materials is both theoretically and experimentally shown to be composed of a thermal neutron induced prompt gamma component (approximately 20%) as well as the major component due to the thermal neutron induced beta decay of 165Dy and 56Mn. It is pointed out that the thermal neutron thermoluminescent response of both materials is size and geometry dependent.