The ability of a field population of diatoms to discriminate between phosphate and arsenate

Dissolved inorganic arsenic and phosphate levels present in an enclosed experimental ecosystem have been studied during the course of a natural spring diatom bloom. Whilst phosphate levels dropped rapidly to almost zero as the bloom developed, arsenic levels remained constant even when arsenate levels exceeded the dissolved phosphate. Certain diatom species (Thalassiosira spp., Chaetoceras spp. and Skeletonema costatum) therefore appear to be capable of discriminating, either by uptake or excretion, between phosphate and arsenate. The implications of such findings are discussed.     

Consistency tests of cosmogonic theories from models of Uranus and Neptune

The planetary ratios of ice to rock $\text{(}\text{I}\text{R}\text{)}$ abundances expected in Uranus and Neptune are derived on the basis of several cosmogonic theories. For both Uranus and Neptune the value of $\text{I}\text{R}$ lies between about 1.0 and 3.6. This value is difficult to reconcile with a scenario in which N and C are accreted primarily in the form of N₂ and CO. It is consistent with some versions of both giant protoplanet theories and equilibrium accretion theories.     

Spatial modeling of annual minimum and maximum temperatures in Iceland

Bayesian hierarchical modeling is applied to the analysis of annual minimum and maximum temperatures. In both cases the generalized extreme value distribution is selected as the marginal distribution at each site due to its flexibility and theoretical basis. This distribution has three unknown parameters, a location parameter, a scale parameter and a shape parameter. The location and scale parameters are assumed to vary across sites while the shape parameter is assumed to be the same for all sites. The location and the scale parameters are modeled as two independent Gaussian spatial processes which are governed by the Matérn correlation function. These spatial processes play a central role in spatial predictions at unobserved sites. The location parameter is also modeled with a common time effect which includes a linear trend and a linear site effect with altitude, distance to open sea, latitude and longitude as covariates. This model allows for spatial predictions for any set of unobserved sites, the scale of the grid can be as fine as possible as long as the covariates are observed at each of the unobserved sites. Data on the annual minimum and maximum temperatures in Iceland from 1961 to 2009?at 72 sites are analyzed and used to predict the 2nd percentile of the minimum temperature for the 12-month period from July 2011 to June 2012 and the 98th percentile of maximum temperature for the year 2011 for a large set of unobserved sites across Iceland at which the covariates are available. The spatial predictions reveal that the 2nd percentile of minimum temperature for 2011 to 2012 reaches ?35°C in the central part of Iceland and ranges from ?12 to ?22°C around the coast of Iceland with the lowest coastal temperatures in the Northern part and the Northeastern part. The 98th percentile of maximum temperature in 2011 ranges from 10 to 30°C where the warmest areas are found in the Eastern part, the North-Eastern part and the Southern part of the country. The estimated increase in minimum and maximum temperatures over the years 1961 to 2009 is 0.71 and 0.47°C per decade, respectively, while the average annual temperature increased 0.24°C per decade over the same period.     

Genetic techniques for livestock breeding: Restructuring institutional relationships in agriculture

This paper explores some of the key institutional transformations in livestock breeding associated with the increasing significance of genetic techniques, situating this within an assessment of an emerging agricultural bioeconomy. Focusing on beef cattle and sheep breeding in the United Kingdom, the paper examines how a move towards the involvement of international and corporate interests in livestock breeding is restructuring the network of institutional interests affecting the knowledge and decision making of individual breeders. The paper suggests that the structural transformation of beef cattle and sheep breeding is complicated by the need for negotiation between breeders’ ‘traditional’ knowledge-practices and the ‘geneticised’ techniques being made available to them. We are thus seeing the emergence of new and complex interactions between the major actors which are reconfiguring power relationships in the UK livestock breeding sector.     

Possible formation of meteoritic chondrules and inclusions in the precollapse Jovian protoplanetary atmosphere

Most meteoritic chondrules and inclusions appear to have been liquid droplets at one time, or at least to have been close to the melting point so that they are easily deformed. The simplest mode of formation of such objects would be to have the liquid phases of the chondrules in thermodynamic equilibrium with gas in the primitive solar nebula, as suggested some years ago by Wood, but unfortunately pressures in the primitive solar nebula are orders of magnitude too small at temperatures in the range of the liquid mineral phases. This difficulty has led to an abandonment of this basic idea, but we suggest that the idea should be reexamined in view of the presence of higher pressures at moderate temperatures, together with water vapor enrichments, in the protoplanetary atmosphere of Jupiter prior to the collapse stage, which was recently studied by Perri and Cameron. A number of advantages arise from the complexities of such a model, and we discuss these together with a number of constraints.