Spectral signatures of photosynthesis I: Review of Earth organisms

Why do plants reflect in the green and have a 'red edge' in the red, and should extrasolar photosynthesis be the same? We provide: 1) a brief review of how photosynthesis works; 2) an overview of the diversity of photosynthetic organisms, their light harvesting systems, and environmental ranges; 3) a synthesis of photosynthetic surface spectral signatures; 4) evolutionary rationales for photosynthetic surface reflectance spectra with regard to utilization of photon energy and the planetary light environment. Given the surface incident photon flux density spectrum and resonance transfer in light harvesting, we propose some rules with regard to where photosynthetic pigments will peak in absorbance: a) the wavelength of peak incident photon flux; b) the longest available wavelength for core antenna or reaction center pigments; and c) the shortest wavelengths within an atmospheric window for accessory pigments. That plants absorb less green light may not be an inefficient legacy of evolutionary history, but may actually satisfy the above criteria.Comment: 69 pages, 7 figures, forthcoming in Astrobiology March 200

Disposition kinetics and urinary excretion of ciprofloxacin in goats following single intravenous administration

We evaluated the pharmacokinetics of ciprofloxacin in serum (n = 6) and urine (n = 4) in goats following a single intravenous administration of 4 mg/kg body weight. The serum concentration-time curves of ciprofloxacin were best fitted by a two-compartment open model. The drug was detected in goat serum up to 12 h. The elimination rate constant (β) and elimination half-life (t1/2β) were 0.446 ± 0.04 h-1 and 1.630 ± 0.17 h, respectively. The apparent volume of distribution at steady state (Vdss) was 2.012 ± 0.37 l/kg and the total body clearance (ClB) was 16.27 ± 1.87 ml/min/kg. Urinary recovery of ciprofloxacin was 29.70% ± 10.34% of the administered dose within 36 h post administration. In vitro serum protein binding was 41% ± 13.10%. Thus, a single daily intravenous dose of 4 mg/kg is sufficient to maintain effective levels in serum and for 36 h in urine, allowing treatment of systemic, Gram-negative bacterial infections and urinary tract infections by most pathogens

Household food insufficiency and mental health in South Africa

Background: Both mental illness and food insufficiency are common in low and middle income countries. However, there are limited data on the relation between food insufficiency and mental disorders, despite the potential relevance of such data for the development of policy-level interventions. The relationship between food insufficiency and mental disorders within a nationally representative sample of South African adults was examined. Methods: A national survey of 4185 South African adults was conducted using the WHO Composite International Diagnostic Interview to generate psychiatric diagnoses. The survey included a widely used single-item measure of household food insufficiency. The independent effects of food insufficiency and demographic characteristics on 12-month and lifetime DSM-IV diagnosis were assessed using logistic regression. Results: 29% of respondents reported that their household 'sometimes' did not have enough to eat while 9% reported that they 'often' did not have enough to eat. After controlling for conventional socioeconomic and sociodemographic variables, food insufficiency was associated with having any 12-month (OR 1.44, 95% CI 1.1 to 1.9) and lifetime (OR 1.35, 95% CI 1.1 to 1.7) DSM-IV disorder. Conclusions: In South Africa the prevalence of household food insufficiency is very high compared with studies conducted in the developed world, and is independently associated with having a 12-month and lifetime DSM-IV diagnosis. The relationship between food insufficiency and mental health has implications for reducing the burden of common mental disorders in South Africa since, unlike a number of major risk factors for mental illness, food insufficiency may be relatively amenable to intervention.Articl

Endemism, speciation and adaptive radiation in great lakes.

Evolution in great lakes has often been both quantitative (many endemic species of distantly related taxa often being present) and qualitative (outstanding levels of adaptive radiation having sometimes been achieved). These situations pose many questions, such as why there are so many endemics and so many superspecialists (and at the same time often many sibling species), as well as presenting problems relating to such matters as convergent evolution in different lakes, the possible role of key innovations, the nature of isolating mechanisms, competition and co-existence in complex communities, the roles of diverse mutualistic associations, and many others. These rich faunas also provide particularly favourable opportunities for studying patterns of speciation, while attempts to elucidate phylogenies in groups such as African cichlid fishes, that have radiated in several lakes, can be pursued on both a broad scale and at the intralacustrine level using both recently developed techniques and time-honoured methods. Rates of evolution, which differ widely between ecologically equivalent taxa in different lakes, have sometimes been extremely rapid, as attested by both molecular data and evidence from field studies. Notwithstanding their evolutionary exuberance, these rich faunas are fragile as demonstrated dramatically by the appalling tragedy that has befallen the haplochromine cichlid flock of Lake Victoria