The social cost of methane: theory and applications.

Methane emissions contribute to global warming, damage public health and reduce the yield of agricultural and forest ecosystems. Quantifying these damages to the planetary commons by calculating the social cost of methane (SCM) facilitates more comprehensive cost-benefit analyses of methane emissions control measures and is the first step to potentially incorporating them into the marketplace. Use of a broad measure of social welfare is also an attractive alternative or supplement to emission metrics focused on a temperature target in a given year as it incentivizes action to provide benefits over a broader range of impacts and timescales. Calculating the SCM using consistent temporal treatment of physical and economic processes and incorporating climate- and air quality-related impacts, we find large SCM values, e.g. ∼$2400 per ton and ∼$3600 per ton with 5% and 3% discount rates respectively. These values are ∼100 and 50 times greater than corresponding social costs for carbon dioxide. Our results suggest that ∼110 of 140 Mt of identified methane abatement via scaling up existing technology and policy options provide societal benefits that outweigh implementation costs. Within the energy sector, renewables compare far better against use of natural gas in electricity generation when incorporating these social costs for methane. In the agricultural sector, changes in livestock management practices, promoting healthy diets including reduced beef and dairy consumption, and reductions in food waste have been promoted as ways to mitigate emissions, and these are shown here to indeed have the potential to provide large societal benefits (∼$50-150 billion per year). Examining recent trends in methane and carbon dioxide, we find that increases in methane emissions may have offset much of the societal benefits from a slowdown in the growth rate of carbon dioxide emissions. The results indicate that efforts to reduce methane emissions via policies spanning a wide range of technical, regulatory and behavioural options provide benefits at little or negative net cost. Recognition of the full SCM, which has typically been undervalued, may help catalyze actions to reduce emissions and thereby provide a broad set of societal benefits.

Indirect radiative forcing of climate change through ozone effects on the land-carbon sink.

The evolution of the Earth's climate over the twenty-first century depends on the rate at which anthropogenic carbon dioxide emissions are removed from the atmosphere by the ocean and land carbon cycles. Coupled climate-carbon cycle models suggest that global warming will act to limit the land-carbon sink, but these first generation models neglected the impacts of changing atmospheric chemistry. Emissions associated with fossil fuel and biomass burning have acted to approximately double the global mean tropospheric ozone concentration, and further increases are expected over the twenty-first century. Tropospheric ozone is known to damage plants, reducing plant primary productivity and crop yields, yet increasing atmospheric carbon dioxide concentrations are thought to stimulate plant primary productivity. Increased carbon dioxide and ozone levels can both lead to stomatal closure, which reduces the uptake of either gas, and in turn limits the damaging effect of ozone and the carbon dioxide fertilization of photosynthesis. Here we estimate the impact of projected changes in ozone levels on the land-carbon sink, using a global land carbon cycle model modified to include the effect of ozone deposition on photosynthesis and to account for interactions between ozone and carbon dioxide through stomatal closure. For a range of sensitivity parameters based on manipulative field experiments, we find a significant suppression of the global land-carbon sink as increases in ozone concentrations affect plant productivity. In consequence, more carbon dioxide accumulates in the atmosphere. We suggest that the resulting indirect radiative forcing by ozone effects on plants could contribute more to global warming than the direct radiative forcing due to tropospheric ozone increases.

Directed mutagenesis of the Rhodobacter capsulatus puhA gene and orf 214: pleiotropic effects on photosynthetic reaction center and light-harvesting 1 complexes.

Rhodobacter capsulatus puhA mutant strains containing either a nonpolar, translationally in-frame deletion or a polar insertion of an antibiotic resistance cartridge were constructed and evaluated for their photosynthetic growth properties, absorption spectroscopy profiles, and chromatophore protein compositions. Both types of mutants were found to be incapable of photosynthetic growth and deficient in the reaction center (RC) and light-harvesting 1 (LH1) complexes. The translationally in-frame puhA deletion strains were restored to the parental strain phenotypes by complementation with a plasmid containing the puhA gene, whereas the polar puhA mutants were not. Analogous nonpolar and polar disruptions of orf 214 (located immediately 3' of the puhA gene) were made, and the resultant mutant strains were evaluated as described above. The strain containing the nonpolar deletion of orf 214 exhibited severely impaired photosynthetic growth properties and had greatly reduced levels of the RC and LH1 complexes. Complementation of this strain with a plasmid that expressed orf 214 from the nifHDK promoter restored photosynthetic growth capability, as well as the RC and LH1 complexes. The polar disruption of orf 214 yielded cells that were incapable of photosynthetic growth and had even lower levels of the RC and LH1 complexes, and complementation in trans with orf 214 only marginally improved these deficiencies. These results indicate that orf 214 and at least one additional gene located 3' of orf 214 are required to obtain the RC and LH1 complexes, and transcription read-through from the puhA superoperon is necessary for optimal expression of these new photosynthesis genes.

Pilot clinical study of a fluoride resin and conditioning paste for desensitising dentine.

The clinical trial was carried out on 34 'hypersensitive' teeth in 10 subjects. Dentine sensitivity was measured as the pain perception thresholds to controlled air and probe stimuli. In each subject, pairs of teeth of comparable initial sensitivity were randomly assigned to a test (T) or control (C) treatment. All teeth were cleaned and a conditioning paste applied. Group T was treated with a topically-applied light-cured resin; Group C received a placebo, sham light-cured. Air sensitivity was remeasured after treatment, and the procedures were repeated after 1, 2, and 3 weeks. When comparing air thresholds before and after treatment at each visit, the test agent caused significantly greater reduction in sensitivity than the control. The median increase in air threshold in the test group was 2.5 s at visit no. 1, 1.3 s at visit no. 2 and 0.8 s at visit no. 3. Comparisons of the initial thresholds at each visit showed no significant long-term changes in sensitivity in either group.

Thresholds of hypersensitive teeth to 2 forms of controlled stimulation.

2 new methods are described for measuring the sensitivity of dentine to mechanical (probe) and cold-air stimulation. The methods are suitable for clinical use and could be used in the evaluation of desensitising treatments. In addition to qualitative differences in the pattern of sensitivity of teeth to these stimuli, considerable variation was observed in the distribution of pain thresholds to probe and air stimulation. Thresholds were not significantly affected by the age or sex of the subjects, but mean thresholds of teeth sensitive to only one stimulus were significantly greater than thresholds of teeth sensitive to both stimuli; these differences were most marked in female subjects. Factors such as the qualitative differences in sensitivity to various stimuli and quantitative differences in the degree of sensitivity to the stimuli require to be considered in clinical evaluation of desensitizing treatments.

Spontaneous pneumothorax: report of a case in podiatric surgery.

The authors have reviewed the literature concerning the subject of spontaneous pneumothoraces. Included in the review are the types of spontaneous pneumothoraces, such as: primary, secondary, tension, and catamenial. The symptomatology, diagnosis, and treatments were discussed. A case report of a catamenial spontaneous pneumothorax in a preoperative podiatric patient was presented.

Instrumentation for measurement of dental plaque thickness in situ.

A commercial digital micrometer has been modified mechanically and electronically to allow the measurement, in situ, of the thickness of dental plaque. The device detects initial contact between a moving probe and the plaque, and measures subsequent probe displacement through to the tooth surface. Instrument accuracy is +/- 5 micron over a displacement range of 0-5 mm, with 1 micron resolution. In practice, after a short 'learning' phase, reliable clinical results can be obtained.

Diels-Alder adducts of fulvenes and halogenated dienes. Synthesis and insecticidal activity.

A series of eight adducts (1--8) of substituted fulvenes and polychlorinated cyclodienes was synthesized by Diels-Alder cyclization. The products isolated were the endo bicyclo adducts as determined by detailed 1H and 13C NMR spectral analysis. Steric hindrance of end-product bridge substituents coupled with bulky substituents at C6 of the fulvenes led to one isomeric product in most cases. Compounds 1--8 demonstrated weak insecticidal action in Musca domestica as determined by topical LD50 and oral LC50 assays.

Pulmonary vasculitis complicating childhood ulcerative colitis.

A case of pulmonary vasculitis complicating ulcerative colitis is presented, and the literature is reviewed. Unexplained pulmonary problems complicating severe ulcerative colitis should prompt a review of rare etiologies to include pulmonary vasculitis, apical pulmonary fibrosis, and salicylazosulfapyridine-induced lung disease. Lung biopsy will establish a diagnosis of pulmonary vasculitis.