Canonical general relativity: Matter fields in a general linear frame

Building on the results of previous work, we demonstrate how matter fields are incorporated into the general linear frame approach to general relativity. When considering the Maxwell one-form field, we find that the system that leads naturally to canonical vierbein general relativity has the extrinsic curvature of the Cauchy surface represented by gravitational as well as non-gravitational degrees of freedom. Nevertheless the metric compatibility conditions are undisturbed, and this apparent derivative-coupling is seen to be an effect of working with (possibly orthonormal) linear frames. The formalism is adapted to consider a Dirac Fermion, where we find that a milder form of this apparent derivative-coupling appears.Comment: 13 pages; uses AMS-latex style file

Simulation of Laser Ablation in Aluminum: The Effectivity of Double Pulses

Lasers are becoming a more and more important tool in cutting and shaping materials. Improving precision and effectivity is an ongoing demand in science and industry. One possibility are double pulses. Here we study laser ablation of aluminum by the two-temperature model. There the laser is modeled as a source in a continuum heat conduction equation for the electrons, whose temperature then is transferred to a molecular dynamics particle model by an electron-phonon coupling term. The melting and ablation effectivity is investigated depending on the relative intensity and the time delay between two Gaussian shaped laser pulses. It turns out that at least for aluminum the optimal pulse shapes are standard Gaussian pulses. For double pulses with delay times up to 200 ps we find a behavior as observed in experiment: the ablation depth decreases beyond a delay of 10 ps even if one does not account for the weakening at the second pulse due to laser-plasma interaction.Comment: 18 pages, 6 figure

Shark Declines in the Mediterranean Sea

Summarizes a study of population and biomass trends of large sharks in the Mediterranean, and highlights the risk of some species becoming extinct as a result of unintended capture in fishing gear, targeted shark fishing, and human population pressure

A Spatial Mathematical Model Analysis of the Linkage between Agricultural Trade and Deforestation

Like agricultural trade, deforestation has increased tremendously throughout the past five decades. We analyse the linkage between both factors by applying trade and forest policy scenarios to the global land-use model MAgPIE ("Model of Agricultural Production and its Impact on the Environment"). The model predicts global landuse patterns in a spatially explicit way and uses endogenously derived technological change and land expansion rates. Our study is the first which combines global trade analysis with a spatially explicit mapping of deforestation. By implementing self-sufficiency rates in the regional demand and supply equations, we are able to simulate different trade settings. Our baseline scenario fixes current trade patterns until the year 2045. The three liberalisation scenarios assume a path of increasing trade liberalisation which ends with no trade barriers in 2045 and they differ by applying different forest protection policies. Regions with comparative advantages like Latin America for oilcrops and China for cereals will export more. Whereas, Latin America will buy this competitiveness by converting large parts of its Amazonian rainforest into cropland, China will benefit most due to its decreasing food demand after 2025. In contrast, regions like the Middle East, North Africa and South Asia face the highest increases of imports. Forest protection policies lead to higher technological change rates. In absence of such policies, investments in agricultural Research & Development are the most effective way for protecting the forest.International Relations/Trade, Resource /Energy Economics and Policy,

Electronic structure of an iron porphyrin derivative on Au(1 1 1)

Surface-bound porphyrins are promising candidates for molecular switches, electronics and spintronics. Here, we studied the structural and the electronic properties of Fe-tetra-pyridil-porphyrin adsorbed on Au(1 1 1) in the monolayer regime. We combined scanning tunneling microscopy/spectroscopy, ultraviolet photoemission, and two-photon photoemission to determine the energy levels of the frontier molecular orbitals. We also resolved an excitonic state with a binding energy of 420 meV, which allowed us to compare the electronic transport gap with the optical gap

Visualizing intramolecular distortions as the origin of transverse magnetic anisotropy

The magnetic properties of metal–organic complexes are strongly influenced by conformational changes in the ligand. The flexibility of Fe-tetra-pyridyl-porphyrin molecules leads to different adsorption configurations on a Au(111) surface. By combining low-temperature scanning tunneling spectroscopy and atomic force microscopy, we resolve a correlation of the molecular configuration with different spin states and magnitudes of magnetic anisotropy. When the macrocycle exhibits a laterally undistorted saddle shape, the molecules lie in a S = 1 state with axial anisotropy arising from a square-planar ligand field. If the symmetry in the molecular ligand field is reduced by a lateral distortion of the molecule, we find a finite contribution of transverse anisotropy. Some of the distorted molecules lie in a S = 2 state, again exhibiting substantial transverse anisotropy

The Economics of Consumer Protection in Developing Countries' Food Economy: The Case of Diarrhea Prevention and Treatment in Rwanda

Food Consumption/Nutrition/Food Safety, Health Economics and Policy,

Early prediction of ripening and storage quality of pear fruit in South Africa

The original publication is available at http://www.actahort.org/books/671/671_11.htmMaturity index records for the principal pear cultivars in the two most important pear producing areas in South Africa were compiled to study the fluctuation in total soluble solids (TSS), fruit firmness and starch breakdown during consecutive seasons. Temperatures (heat units, hu), sunlight hours (ssh), fruit size (diameter), days after bloom (dafb) and soil type were used to calculate the rate of change in TSS levels, firmness and starch breakdown during the last five to six weeks before the picking date. These variables were shown to have an effect on the internal fruit quality. High temperatures were found to result in a faster drop in firmness levels and increased sunlight hours improved the TSS levels. Orchards on sandy soils showed consistently lower TSS levels and firmness when different orchards were compared during consecutive seasons. Equations were fitted to the data for each cultivar and area to develop models for the prediction of the different indices. The predicted rates of change of the different indices were compared with the actual values to test the accuracy and proved to explain more than 80% of the variation during consecutive seasons. The results also showed that the rate of change for these indices could be estimated as early as the middle of December. These models are considered important tools to assist growers, pack houses and marketers in identifying seasons when fruit will have a short shelf life. Picking dates, cold storage and marketing can be adapted to ensure the best possible fruit quality

Correlation of Kondo effect and molecular conformation of the acceptor molecule in the TTF-TCNE charge transfer complex

A Kondo resonance has been observed on purely organic molecules in several combinations of charge transfer complexes on a metal surface. It has been regarded as a fingerprint of the transfer of one electron from the donor to the extended π orbital of the acceptor's LUMO. Here, we investigate the stoichiometric checkerboard structure of tetrathiafulvalene (TTF) and tetracyanoethylene (TCNE) on a Au(1 1 1) surface using scanning tunneling and atomic force microscopy at 4.8 K. We find a bistable state of the TCNE molecules with distinct structural and electronic properties. The two states represent different conformations of the TCNE within the structure. One of them exhibits a Kondo resonance, whereas the other one does not, despite of both TCNE types being singly charged

The Impacts of Water Management Policies on Agricultural Production in Australia - An Economic Analysis

In the Australian Murray-Darling Basin (MDB) the combination of severe and prolonged droughts and historic water management decisions to divert water for cultivation stressed water resources in such an intensive manner that wetlands went dry and rivers are now far from a natural flow. More appropriate water management policies must be implemented to restore ecological function. However, with 39 % of Australia’s total value of agricultural production, transitions in use need to be managed to minimise economic and social impacts on basin communities while they adjust. Recent studies estimate that industries with high water usage but lower or more volatile value products will be impacted more than higher value products. Therefore, this study’s focus is to analyse different water management policies and their impacts on agricultural production, particularly changes in production of water low value and water high value crops and agricultural water consumption. By applying the Water Integrated Market (WatIM)-Model, benefits and costs of water management policies can be evaluated by identifying changes in quantities, prices and economic welfare, such as consumer and producer surplus. The WatIM-Model is a multi-market model combining water low and water high value crop markets and the water market with its supply and demand. Since the MDB is a complex system with different types of agriculture and water sharing rules in each catchment, economic variables are aggregated in the WatIMModel to examine overall trends and changes in the MDB. By the assumption that policy decisions on one market cause reactions on prices, supply and demand on other markets, market interdependencies can be derived. With these results, the merit of shifting production from water low value crops to water high value crops is examined and advantages and disadvantages of water management policies can be determined. This enables refinement of water management policies to optimise social, economic and environmental outcomes.Water market, water management policy, agriculture, sustainable water allocation, Resource /Energy Economics and Policy,