Quantum interferometric optical lithography:towards arbitrary two-dimensional patterns

As demonstrated by Boto et al. [Phys. Rev. Lett. 85, 2733 (2000)], quantum lithography offers an increase in resolution below the diffraction limit. Here, we generalize this procedure in order to create patterns in one and two dimensions. This renders quantum lithography a potentially useful tool in nanotechnology.Comment: 9 pages, 5 figures Revte

Archaeal Hel308 helicase targets replication forks in vivo and in vitro and unwinds lagging strands

Mutations in mammalian and Drosophila Hel308 and PolQ paralogues cause genome instability but their helicase functions are mysterious. By in vivo and in vitro analysis, we show that Hel308 from archaea (Hel308a) may act at stalled replication forks. Introducing hel308a into Escherichia coli dnaE strains that conditionally accumulate stalled forks caused synthetic lethality, an effect indistinguishable from E.coli RecQ. Further analysis in vivo indicated that the effect of hel308a is exerted independently of homologous recombination. The minimal biochemical properties of Hel308a protein were the same as human Hel308. We describe how helicase actions of Hel308a at fork structures lead specifically to displacement of lagging strands. The invading strand of D-loops is also targeted. Using archaeal Hel308, we propose models of action for the helicase domain of PolQ, promoting loading of the translesion polymerase domain. We speculate that removal of lagging strands at stalled forks by Hel308 promotes the formation of initiation zones, priming restart of lagging strand synthesis

Assessment of Waste for Use on Agricultural Land

The disposal of waste to agricultural land requires a systematic and transparent assessment procedure to ensure environmental and production sustainability. A hybrid model of risk assessment used in the general risk, environmental management and the mining industries was developed and tested using the waste from a yeast factory. The model is systematic and cybernetic and develops a succession of decisions that have the capacity to focus the environmental and agronomic considerations down to individual crops, land and management systems. The process directly links environmental risk assessment and development of management plans to agronomic development of the use waste products

Eigenfunction statistics for a point scatterer on a three-dimensional torus

In this paper we study eigenfunction statistics for a point scatterer (the Laplacian perturbed by a delta-potential) on a three-dimensional flat torus. The eigenfunctions of this operator are the eigenfunctions of the Laplacian which vanish at the scatterer, together with a set of new eigenfunctions (perturbed eigenfunctions). We first show that for a point scatterer on the standard torus all of the perturbed eigenfunctions are uniformly distributed in configuration space. Then we investigate the same problem for a point scatterer on a flat torus with some irrationality conditions, and show uniform distribution in configuration space for almost all of the perturbed eigenfunctions.Comment: Revised according to referee's comments. Accepted for publication in Annales Henri Poincar

²¹⁰Pb- ²²⁶Ra chronology reveals rapid growth rate of Madrepora oculata and Lophelia pertusa on world's largest cold-water coral reef

Here we show the use of the 210Pb- 226Ra excess method to determine the growth rate of two corals from the world's largest known cold-water coral reef, Røst Reef, north of the Arctic circle off Norway. Colonies of each of the two species that build the reef, Lophelia pertusa and Madrepora oculata, were collected alive at 350 m depth using a submersible. Pb and Ra isotopes were measured along the major growth axis of both specimens using low level alpha and gamma spectrometry and trace element compositions were studied. 210Pb and 226Ra differ in the way they are incorporated into coral skeletons. Hence, to assess growth rates, we considered the exponential decrease of initially incorporated 210Pb, as well as the increase in 210Pb from the decay of 226Ra and contamination with 210Pb associated with Mn-Fe coatings that we were unable to remove completely from the oldest parts of the skeletons. 226Ra activity was similar in both coral species, so, assuming constant uptake of 210Pb through time, we used the 210Pb- 226Ra chronology to calculate growth rates. The 45.5 cm long branch of M. oculata was 31 yr with an average linear growth rate of 14.4 ± 1.1 mm yr -1 (2.6 polyps per year). Despite cleaning, a correction for Mn-Fe oxide contamination was required for the oldest part of the colony; this correction corroborated our radiocarbon date of 40 yr and a mean growth rate of 2 polyps yr -1. This rate is similar to the one obtained in aquarium experiments under optimal growth conditions. For the 80 cm-long L. pertusa colony, metal-oxide contamination remained in both the middle and basal part of the coral skeleton despite cleaning, inhibiting similar age and growth rate estimates. The youngest part of the colony was free of metal oxides and this 15 cm section had an estimated a growth rate of 8 mm yr -1, with high uncertainty (∼1 polyp every two to three years). We are less certain of this 210Pb growth rate estimate which is within the lowermost ranges of previous growth rate estimates. We show that 210Pb- 226Ra dating can be successfully applied to determine the age and growth rate of framework-forming cold-water corals if Mn-Fe oxide deposits can be removed. Where metal oxides can be removed, large M. oculata and L. pertusa skeletons provide archives for studies of intermediate water masses with an up to annual time resolution and spanning over many decades. © 2012 Author(s)

Providing marketing information to smallholders in Zimbabwe: What can the state usefully do?

In recent decades, significant international assistance has been provided to assist the establishment of market information systems (MISs) in a range of developing countries, including many in Africa. However, experience with state-run MISs, looking to provide current price information to market participants, has not been encouraging. Volatile horticultural markets provide particular challenges for such MISs. Therefore, it is suggested that it might be more appropriate to provide other types of marketing information to inform the production and marketing decisions of smallholder producers. This paper reports on recent efforts by the national extension agency, Agritex, to provide such information to smallholder horticultural producers in two districts of north-eastern Zimbabwe. Drawing on an initial evaluation of this pilot programme, the paper suggests that: 1) in the Zimbabwe case, the extension service may provide a viable vehicle for dissemination of marketing information to smallholder (horticultural) producers; 2) information on new crops and market opportunities is valued more highly by farmers than information on current market prices; 3) such information should complement, not supplant, traditional production extension advice. The paper concludes by considering some of the issues pertaining to the continuation and expansion of the pilot programme.Marketing,

Chemical Evolution of Irregular and Blue Compact Galaxies

We discuss the chemical evolution of metal poor galaxies and conclude that their oxygen deficiency is not due to: the production of black holes by massive stars or a varying slope of the Initial Mass Function, IMF, at the high-mass end. A varying IMF at the low-mass end alone or in combination with: (a) an outflow of oxygen-rich material, (b) an outflow of well-mixed material, and (c) the presence of dark matter that does not participate in the chemical evolution process, is needed to explain their oxygen deficiency. Outflow of material rich in oxygen helps to account for the large helium to oxygen mass ratio values derived from these objects, but it works against explaining the carbon to oxygen mass ratio and the heavy elements minus carbon and oxygen to oxygen mass ratio values.Comment: 26 pages, plain Tex, a postscript version with the figures included is available at ftp://132.248.1.7/papers/chem_evolution/irr_bcg.tar ; ApJ accepte