Heisenberg exchange in magnetic monoxides

The superexchange intertacion in transition-metal oxides, proposed initially by Anderson in 1950, is treated using contemporary tight-binding theory and existing parameters. We find also a direct exchange for nearest-neighbor metal ions, larger by a factor of order five than the superexchange. This direct exchange arises from Vddm coupling, rather than overlap of atomic charge densities, a small overlap exchange contribution which we also estimate. For FeO and CoO there is also an important negative contribution, related to Stoner ferromagnetism, from the partially filled minority-spin band which broadens when ionic spins are aligned. The corresponding J1 and J2 parameters are calculated for MnO, FeO, CoO, and NiO. They give good accounts of the Neel and the Curie-Weiss temperatures, show appropriate trends, and give a reasonable account of their volume dependences. For MnO the predicted value for the magnetic susceptibility at the Neel temperature and the crystal distortion arising from the antiferromagnetic transition were reasonably well given. Application to CuO2 planes in the cuprates gives J=1220oK, compared to an experimental 1500oK, and for LiCrO2 gives J1=4 50oK compared to an experimental 230oK.Comment: 21 pages, 1 figure, submitted to Phys. Rev. B 1/19/07. Realized J=4V^2/U applies generally, as opposed to J=2V^2/U from one-electron theory (1/28 revision

Deficiency of G1 regulators P53, P21Cip1 and/or pRb decreases hepatocyte sensitivity to TGFbeta cell cycle arrest

TGFbeta is critical to control hepatocyte proliferation by inducing G1-growth arrest through multiple pathways leading to inhibition of E2F transcription activity. The retinoblastoma protein pRb is a key controller of E2F activity and G1/S transition which can be inhibited in viral hepatitis. It is not known whether the impairment of pRb would alter the growth inhibitory potential of TGFbeta in disease. We asked how Rb-deficiency would affect responses to TGFbeta-induced cell cycle arrest.Publisher PDFPeer reviewe

Polaron Induced Deformations in Carbon Nanotubes

We compute for the first time full elastic deformations, as well as length, of self-trapped electronic states in carbon nanotubes of general radius and chirality, within the unifying framework of a recently introduced two field model for electromechanics of carbon nano-structures. We find that deformations are highly non monotonic in the chiral angle, whereas the length of the polaron is not. Applications include nano-mechanical devices as electrically or optically driven nano-actuators.Comment: 4 Pages, 1 Figure Phys Rev B Brief Repor

Tree Planting Progress at Four Community Forestry Sites In Leyte: Some Observations and Lessons Learned

This paper critically reviews tree farming and community forestry in four municipalities in Leyte. It examines problems and issues experienced by the local people in communities with respect to forestry, and makes observations about the progress of tree planting in both community and farm forestry. Field visits and discussions with local people, Local Government Unit (LGU) officials and Department of Environmental and Natural Resources (DENR) personnel were undertaken in each of the four sites. Some lessons are drawn and problems identified with respect to the development of community and farm forestry. Planting progress has been relatively slow at the four sites, and a number of difficulties have been apparent in relation to physical stand performance and property rights of growers. The importance of organizational assistance, livelihood support and availability of seedlings of suitable species is apparent. Regardless of the difficulties, a high level of enthusiasm exists for forestry projects, and the potential community benefits are considerable

Cluster magnetic fields from large-scale-structure and galaxy-cluster shocks

The origin of the micro-Gauss magnetic fields in galaxy clusters is one of the outstanding problem of modern cosmology. We have performed three-dimensional particle-in-cell simulations of the nonrelativistic Weibel instability in an electron-proton plasma, in conditions typical of cosmological shocks. These simulations indicate that cluster fields could have been produced by shocks propagating through the intergalactic medium during the formation of large-scale structure or by shocks within the cluster. The strengths of the shock-generated fields range from tens of nano-Gauss in the intercluster medium to a few micro-Gauss inside galaxy clusters.Comment: 4 pages, 2 color figure

Clyde tributaries : report of urban stream sediment and surface water geochemistry for Glasgow

This report presents the results of an urban drainage geochemical survey carried out jointly by the British Geological Survey (BGS) and Glasgow City Council (GCC) during June 2003. 118 stream sediment and 122 surface water samples were collected at a sample density of 1 per 1 km2 from all tributaries draining into the River Clyde within the GCC administrative area. The study was carried out as part of the BGS systematic Geochemical Surveys of Urban Environments (GSUE) programme. Stream sediment and surface water samples underwent analysis for approximately 46 chemical elements including contaminants such as As, Al, Cd, Cu, Cr, Ni, Pb, Se, V and Zn according to standard GSUE procedures. In addition, parameters such as ammonium, asbestos and Hg as well as organic contaminants such as total petroleum hydrocarbons (TPH), polycyclic aromatic hydrocarbons (PAH), poly-chlorinated biphenyls (PCB) and organo-tin compounds were assessed. The aim of the project was to provide an overview of urban drainage geochemistry in Glasgow to link to an on-going sister project, which is investigating the geochemistry of the Clyde estuary. This report presents the initial findings of the Clyde tributaries survey but it is envisaged that the data will be interpreted in more detail as part of a wider Clyde basin study once the Clyde estuary survey is completed

Creating a Market for Smallholder Timber in Leyte Province: A Mechanism for Bringing Timber Buyers and Sellers Together

Difficulty in smallholder timber marketing is widely observed in developing countries. As noted by Scherr (2004, p. 357-358), ‘most forest-product markets, and market institutions and policy, are structured to serve large-scale natural forest and plantation producers ... small-farm participation in commercial wood markets could potentially make a major contribution to rural economic development, poverty reduction and eco-system objectives’. Activity 2.3 of Project ASEM/2003/052 aims to develop a pilot scheme which will bring timber buyers and sellers together, through either establishment of a local timber auction system or creation of a market information system, with either a People’s Organisation or NGO acting as a middleman or timber broker. It is tentatively proposed that the initiative be implemented through the LSU College of Forestry and possibly incorporated into a radio segment developed as part of Activity 1.2. This paper examines options for developing a pilot scheme, and the strengths and limitations of alternative market and information system approaches. This assessment is made on the basis of experiences from research undertaken as part of Project ASEM/2000/088 and observations elsewhere in the Philippines and South East Asia, as well as with information on market information systems and computer-aided marketing of other commodities in other countries

Experiences Gained and Lessons Learnt from the Training Workshop

This review module attempts to draw together some of the experiences gained and lessons learned from conducting the training workshop on socio-economic research methods in forestry research. A workshop of this nature had been an ambition of The University of Queensland forestry research group for more than two years, so it was gratifying to see this ambition fulfilled. As a first run by the research group at such a training workshop, this was something of an experiment, and impressions gained here may be of assistance should the 'training package' be employed in other situations. This paper reflects on the workshop experience and on the feedback obtained from delegates and presenters. No formal survey was undertaken to gain impressions of participants, but considerable informal feedback was obtained