Pulping characteristics of Pinus caribaea var. hondurensis and Pinus oocarpa grown in Zimbabwe (ODNRI Bulletin No. 7)

Three samples of Pinus caribaea var. hondurensis and four of Pinus oocarpa grown in Zimbabwe over an altitudinal range of 700 m to 1 300 m were examined to determine their suitability for the production of papermaking pulps. Details of growing conditions, climate and rate of growth are reported. The wood density of P. caribaea decreased with increased altitude of the growing site: altitude had no effect on the wood density of the samples of P. oocarpa. Both species were pulped by the sulphate process, P. caribaea yielding 45% and P. oocarpa 46% of pulp with a kappa number of 40. There was little difference in tensile and bursting strengths of pulps from any of the samples. P. caribaea grown at low altitudes had the highest tearing strength and with this species tearing strength decreased with increasing altitude of the growing site. P. oocarpa yielded pulp with a tearing strength similar to that of P. caribaea from the middle altitude and altitude had no influence on pulp quality of this species. All samples were pulped by the Refiner Mechanical and Thermal Refiner Mechanical processes and yielded pulps suitable for use in newsprint

Pulping characteristics of Eucalyptus species grown in Malawi (ODNRI Bulletin No. 33)

Eight species of Eucalyptus, E. camaldulensis, E. citriodora, E. cloeziana, E. grandis, E. maculata, E. maidenii, E. saligna and F. tereticornis grown in the Viphya plateau, Malawi, were examined to determine their suitability for the production of papermaking pulp. The size of 9-year-old trees, wood density, chemical characteristics and fibre dimensions are reported. All species were pulped by sulphate, soda and soda-anthraquinone processes. By the sulphate process all species yielded over 45% (two over 50%) of bleachable pulp with good strength characteristics. The soda-anthraquinone process yielded similar quantities of pulp, with the same kappa number and marginally lower strength characteristics. The soda process needed a more severe chemical dose to yield less pulp, with the same kappa number and much lower strength characteristics. All species were pulped, also, by the neutral sulphite semi-chemical process to yield about 70% of pulp suitable for use in packaging grades of board. One digestion by the chemi-refiner mechanical process on E. grandis indicated that, if conditions were optimized, pulps produced by this process should be suitable for the production of newsprint

Pulping characteristics of reafforestation species grown in Solomon Islands (ODNRI Bulletin No. 32)

Samples of Pinus caribaea, Pinus oocarpa, Campnosperma brevipetiolata, Eucalyptus deglupta, Terminalia brassii and Terminalia calamansanai, all of which have shown potential for growing in plantations in Solomon Islands, were examined to determine their potential value for the production of pulpwood chips for export. Details are given of growing conditions, size of trees, wood characteristics, fibre dimensions and pulping by sulphate, soda and soda/anthraquinone processes. P. caribaea, P. oocarpa, C. brevipetiolata and F. deglupta were all considered promising for the production of pulpwood. T. brassii and T. calamansanai, both of which required very severe chemical conditions to pulp, were not considered promising

Field-Driven Transitions in the Dipolar Pyrochlore Antiferromagnet Gd2_2Ti2_2O7_7

We present a mean-field theory for magnetic field driven transitions in dipolar coupled gadolinium titanate Gd$_2$Ti$_2$O$_7$ pyrochlore system. Low temperature neutron scattering yields a phase that can be regarded as a 8 sublattice antiferromagnet, in which long-ranged ordered moments and fluctuating moments coexist. Our theory gives parameter regions where such a phase is realized, and predicts several other phases, with transitions amongst them driven by magnetic field as well as temperature. We find several instances of {\em local} disorder parameters describing the transitions.Comment: 4 pages, 5 figures. v2: longer version with 2 add.fig., to appear in PR

Order induced by dipolar interactions in a geometrically frustrated antiferromagnet

We study the classical Heisenberg model for spins on a pyrochlore lattice interacting via long range dipole-dipole forces and nearest neighbor exchange. Antiferromagnetic exchange alone is known not to induce ordering in this system. We analyze low temperature order resulting from the combined interactions, both by using a mean-field approach and by examining the energy cost of fluctuations about an ordered state. We discuss behavior as a function of the ratio of the dipolar and exchange interaction strengths and find two types of ordered phase. We relate our results to the recent experimental work and reproduce and extend the theoretical calculations on the pyrochlore compound, Gd$_2$Ti$_2$O$_7$, by Raju \textit{et al.}, Phys. Rev. B {\bf 59}, 14489 (1999).Comment: 5 pages, 5 figures, AMSLaTe

Miniaturizing the laparoscope: Current applications of micro‐ and minilaparoscopy

Technological advancements have enabled miniaturization of the endoscope without significant compromise to either diagnostic or operative abilities. With a complement of instruments < 5 mm in diameter, newer minimally invasive techniques have been developed to decrease the pain and trauma associated with surgical procedures. These advancements involve additional options for peritoneal access as well as facilitating diagnostic evaluation of the pelvis. Although the robustness and durability of the smaller instruments is an area of concern, a thorough understanding of the clinical advantages and disadvantages has the potential to improve patient outcomes.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135513/1/ijgo94.pd

Susceptibility and dilution effects of the kagome bi-layer geometrically frustrated network. A Ga-NMR study of SrCr_(9p)Ga_(12-9p)O_(19)

We present an extensive gallium NMR study of the geometrically frustrated kagome bi-layer compound SrCr_(9p)Ga_(12-9p)O_(19) (Cr^3+, S=3/2) over a broad Cr-concentration range (.72<p<.95). This allows us to probe locally the kagome bi-layer susceptibility and separate the intrinsic properties due to the geometric frustration from those related to the site dilution. Our major findings are: 1) The intrinsic kagome bi-layer susceptibility exhibits a maximum in temperature at 40-50 K and is robust to a dilution as high as ~20%. The maximum reveals the development of short range antiferromagnetic correlations; 2) At low-T, a highly dynamical state induces a strong wipe-out of the NMR intensity, regardless of dilution; 3) The low-T upturn observed in the macroscopic susceptibility is associated to paramagnetic defects which stem from the dilution of the kagome bi-layer. The low-T analysis of the NMR lineshape suggests that the defect can be associated with a staggered spin-response to the vacancies on the kagome bi-layer. This, altogether with the maximum in the kagome bi-layer susceptibility, is very similar to what is observed in most low-dimensional antiferromagnetic correlated systems; 4) The spin glass-like freezing observed at T_g=2-4 K is not driven by the dilution-induced defects.Comment: 19 pages, 19 figures, revised version resubmitted to PRB Minor modifications: Fig.11 and discussion in Sec.V on the NMR shif

Herd-level risk factors of bovine tuberculosis in England and Wales after the 2001 foot-and-mouth disease epidemic

We present the results of a 2005 case–control study of bovine tuberculosis (bTB) breakdowns in English and Welsh herds. The herd management, farming practices, and environmental factors of 401matched pairs of case and control herds were investigated to provide a picture of herd-level risk factors in areas of varying bTB incidence. A global conditional logistic regression model, with region-specific variants, was used to compare case herds that had experienced a confirmed bTB breakdown to contemporaneous control herds matched on region, herd type, herd size, and parish testing interval. Contacts with cattle from contiguous herds and sourcing cattle from herds with a recent history of bTB were associated with an increased risk in both the global and regional analyses. Operating a farm over several premises, providing cattle feed inside the housing, and the presence of badgers were also identified as significantly associated with an increased bTB risk. Steps taken to minimize cattle contacts with neighboring herds and altering trading practices could have the potential to reduce the size of the bTB epidemic. In principle, limiting the interactions between cattle and wildlife may also be useful; however this study did not highlight any specific measures to implement

A multi‐proxy record of abrupt cooling events during the Windermere Interstadial at Crudale Meadow, Orkney, UK

Three clearly defined abrupt cooling events (ACEs) can be observed within Greenland Interstadial (GI)‐1 in the Greenland ice‐core records. However, the spatial variation in amplitude and timing of these ACEs is poorly understood due to the paucity of well‐dated records with quantified temperature reconstructions. This study presents high‐resolution chironomid‐inferred July air temperature (TJul) and oxygen isotope (δ18O) records from Crudale Meadow (Orkney Isles, UK). Three centennial‐scale ACEs punctuate the Windermere Interstadial at Crudale Meadow. The largest ACE shows an amplitude of 5.4 °C and a 1% isotopic decline and is centred on ~14.0 ka BP, consistent with the timing of the GI‐1d event in the Greenland stratigraphy. The two other observed ACEs are of smaller magnitude and are centred on ~13.6 ka BP and ~13.2 ka BP, with these smaller magnitude events tentatively correlated with the GI‐1cii and GI‐1b events, respectively, but lack sufficient chronological constraint to fully assess their timing. When comparing the Crudale Meadow record with other locations in the British Isles a strong relationship can be observed between the magnitude of TJul cooling and latitude, with a reduced signal in more southerly locations, indicating that oceanic forcing may be a key driver of the ACEs

Quantum disorder in the two-dimensional pyrochlore Heisenberg antiferromagnet

We present the results of an exact diagonalization study of the spin-1/2 Heisenberg antiferromagnet on a two-dimensional version of the pyrochlore lattice, also known as the square lattice with crossings or the checkerboard lattice. Examining the low energy spectra for systems of up to 24 spins, we find that all clusters studied have non-degenerate ground states with total spin zero, and big energy gaps to states with higher total spin. We also find a large number of non-magnetic excitations at energies within this spin gap. Spin-spin and spin-Peierls correlation functions appear to be short-ranged, and we suggest that the ground state is a spin liquid.Comment: 7 pages, 11 figures, RevTeX minor changes made, Figure 6 correcte