bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of the magnetic field in a spherical torus plasma via electron Bernstein wave emission harmonic overlap
Authors: Jones B. , Taylor G. , Efthimion P. C. , Munsat T.
Published: February 2004

Measurement of the magnetic field in a spherical torus by observation of harmonic overlap frequencies in the electron Bernstein wave (EBW) spectrum has been previously suggested [V. F. Shevchenko, Plasma Phys. Rep. 26, 1000 (2000)]. EBW mode conversion to X-mode radiation has been studied in the Current Drive Experiment-Upgrade spherical torus (T. Jones, Ph.D. thesis, Princeton University, 1995) with emission measured at blackbody levels [B. Jones et al., Phys. Rev. Lett. 90, 165001 (2003)]. Sharp transitions in the thermally emitted EBW spectrum have been observed for the first two harmonic overlaps. These transition frequencies are determined by the magnetic field and electron density at the mode conversion layer in accordance with hot-plasma wave theory. Prospects of extending this measurement to higher harmonics, necessary in order to determine the magnetic field profile, and high-β equilibria are discussed for this proposed magnetic field diagnostic.
Measurements of ion and neutral atom flows and temperatures in the inner and outer midplane scrape-off layers of the Alcator C-Mod Tokamak
Authors: Ghosh J. , Griem H. R. , Elton R. C. , Terry J. L. , Marmar E. , Lipschultz B. , LaBombard B. , Rice J. E. , Weaver J. L.
Published: February 2004

Measurements of toroidal flow velocities in the midplane of the inner and outer scrape-off layers (SOL) of Alcator C-Mod [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)] plasmas are made using a high-resolution spectrograph. Doppler shifts of the line emissions from either He+ at 468.6 nm or neutral deuterium at 656.1 nm from two local gas puffs are observed along radially separated, toroidally viewing chords to obtain the radial profiles of the toroidal ion and neutral flow velocities and of the temperatures in the midplane of the inner and outer SOL’s. In these experiments, the ion vertical drift due to the toroidal magnetic field gradient (ion B×∇B drift) is directed towards the lower X-point, and an outer SOL plasma flow with a velocity in the range of 5–10 km/s in the direction of the plasma current is observed at the midplane far above the divertor plates. Plasma flow in a similar direction with similar velocities is observed in the inner SOL midplane. This observation suggests a toroidal rotation of the edge plasma in a co-current direction, consistent with an Er×Bθ motion that would arise from a radially outward electric field. Interestingly, the neutral atoms in these views are observed to flow in the opposite directions in the inner and outer SOL’s, i.e., the neutrals flow in the plasma current direction in the inner SOL and in a direction opposite to the plasma current in the outer SOL. Also, the neutrals move much slower (velocities ∼2–4 km/s) in the outer SOL compared to the inner SOL (velocities ∼4–10 km/s). Temperatures determined from the Doppler broadening of the spectral lines are found to be in the range of ∼15–25 eV for the He+ ions in the inner and outer SOL’s. Much lower temperatures of ⩽2–5 eV are indicated for the deuterium atoms in both SOL’s.
Analytical solutions to estimate the stress induced polarization shift and the temperature sensitivity of optical waveguides
Authors: Huang M. , Yan X.
Published: February 2004

Polarization shift and temperature sensitivity are important issues in optical waveguides. Applying stresses is a promising method to control these optical parameters. In this article, analytical solutions are obtained to estimate the stress effects on these optical parameters. Because the refractive index variation induced by the stresses is very small, the linear approximation is used to obtain the closed-form solutions to estimate the stress induced effective index change in a slab waveguide. The solutions are, then, extended to estimate the stress induced effective index change, polarization shift, and the temperature sensitivity of a channel waveguide by use of effective index method. As an example, the optical parameters controlled by the thermal stresses, which are induced by attaching an Al plate on the bottom of the substrate, are analyzed. The results show that the polarization shift and the temperature sensitivity of the central wavelength can be tuned in a large range by varying the Al plate thickness and the curing temperature. The effects can be modified by changing the shape of the Al plate.
Local structure and persistent spectral hole burning of the Eu3+ ion in SnO2–SiO2 glass containing SnO2 nanocrystals
Authors: You Hongpeng , Nogami Masayuki
Published: February 2004

The local structure and persistent spectral hole burning (PSHB) of the Eu3+ ion in SnO2–SiO2 glass containing SnO2 nanocrystals were investigated. The excitation and emission spectra of the Eu3+ ions indicate that the Eu3+ ions are doped into the SnO2 nanocrystals and glass phases. The variation in the site symmetry of Eu3+ ions in the nanocrystal from D2h or C2h symmetry may be due to oxygen vacancies. Fluorescence line-narrowing spectra reveal that the Eu3+ ions in the glass phase have two sites, one of which exhibits a unique feature. The calculated second crystal-field parameters show that the coordinating oxygen ions of site I are closer to the Eu3+ ions with increasing excitation energy, while those of site II are farther away from the Eu3+ ions. This result leads to the opposite behavior of the fluorescence lines of the Eu3+ ions at the two sites. PSHB was also observed and multiholes with a narrow width can be burned in the SnO2–SiO2 glass containing SnO2 nanocrystals.
Simulation of light intensity dependent current characteristics of polymer solar cells
Authors: Schilinsky Pavel , Waldauf Christoph , Hauch Jens , Brabec Christoph J.
Published: February 2004

An extended replacement circuit describing the current–voltage characteristics of bulk heterojunction polymer solar cells at different light bias levels is introduced and discussed. A one diode-model is expanded by an extraction model for photogenerated carriers taking into account the effective reduction of the mean distance which the charge carriers cover when sweeping the electrical bias through the fourth quadrant of the solar cell. The model properly describes the current–voltage behavior of bulk heterojunction solar cells over more than three orders in light intensity with one set of parameters.
Humidity effects on the determination of elastic properties by atomic force acoustic microscopy
Authors: Hurley D. C. , Turner J. A.
Published: February 2004

We have investigated how ambient humidity can affect quantitative measurements of elastic properties on the nanoscale. Using an emerging technique called atomic force acoustic microscopy (AFAM), two samples were examined: a thin film of fluorosilicate glass and a section of borosilicate glass. When experimental results were analyzed using a simple model of the atomic force microscope cantilever dynamics, values of the tip–sample contact stiffness k* increased approximately linearly with relative humidity. The effect is believed to be due to the presence of a humidity-dependent layer of water on the sample. To account for this, the data analysis model was extended to include viscoelastic damping between the tip and the sample. A damping term proportional to the relative humidity was used. The revised values for k* showed virtually no dependence on humidity. Thus, the subsequent calculations of the indentation modulus M from k* yielded similar values regardless of measurement humidity. These results indicate that environmental conditions can influence quantitative nanoscale measurements of elastic properties, at least in some materials.
Vortex-type domain structure in Co-rich amorphous wires
Authors: Chizhik A. , Gonzalez J. , Yamasaki J. , Zhukov A. , Blanco J. M.
Published: February 2004

Investigation of the surface magnetic domain structure has been performed in Co-rich, nearly zero magnetostrictive, amorphous wires using magneto-optical Kerr effect magnetometry and microscopy. The formation and motion of a multidomain vortex-type structure with curved domain walls have been observed in amorphous wires. The possible origins of the existence of the vortex-type structures in these amorphous wires are discussed.
The evolution investigation of photoluminescence from a-Si:H/SiO2 to nc-Si/SiO2 multilayers
Authors: Ma Zhongyuan , Chen Kunji , Huang Xinfan , Xu Jun , Li Wei , Sui Yanping , Zhu Da , Mei Jiaxin , Feng Duan
Published: February 2004

The evolution of photoluminescence (PL) at room temperature from a-Si:H/SiO2 to nc-Si/SiO2 multilayers was observed through step-by-step post-treatment. It is found that the Si dangling bonds caused by dehydrogenation result in an intensified PL peak at 700 nm. The competition between the role of Si dangling bonds and nc-Si is the origin of the weaker PL band, including two peaks at 700 and 775 nm. The enhancement of PL intensity of the peak at 775 nm is induced by the increase of the number of nc-Si and oxygen-related defects saturated by Si–O–Si within the Si/SiO2 interface. The relation between the evolution of PL and microstructure of the samples is discussed in detail.
Diffraction stress analysis in fiber-textured TiN thin films grown by ion-beam sputtering: Application to (001) and mixed (001)+(111) texture
Authors: Abadias G. , Tse Y. Y.
Published: February 2004

The present study concerns the analysis by x-ray diffraction (XRD) of the residual stresses in fiber-textured TiN thin films grown by sputter deposition. We present an extension of the stress model of Kamminga et al. [J. Appl. Phys. 88, 6332 (2000)] to the case of sputtered thin films having a crystallographic growth texture. The state of stress is triaxial and includes an intrinsic hydrostatic component due to volumetric distortion in the growing layer caused by ion-bombardment-induced point defects, and a biaxial component imposed by the substrate on which the film adheres. Numerical illustration of the model is given for TiN films having a (001) or a mixed (001)+(111) growth texture. It is shown that in the presence of triaxial stresses, the dependence of the lattice parameter with sin2 ψ is still linear, but the stress-free lattice parameter a0 can no longer be determined from the classical strain-free direction. Nevertheless, a direct determination of a0 can be obtained graphically from the intersection of the sin2 ψ lines plotted for films with different hydrostatic stresses. When films exhibit a mixed texture, the sin2 ψ lines plotted for each subset of grains do not intersect exactly at a0. The present model is then used to analyze the XRD results of TiN fiber-textured thin films grown by a dual-ion-beam sputtering technique. The crystallite group method was used to measure the strain of crystallites having different specific fiber axis directions. The evolution of the microstructure, preferred orientation, and state of stress have been studied as a function of the film thickness, deposition temperature, and acceleration voltage Va of the Ar/N2 assistance beam. It is shown that the preferred orientation gradually changes from (001) to (111) as the thickness of the TiN films increases, with a crossover occurring between 150 and 200 nm. For films grown at T=25 °C, no significant changes in the orientational crossover or the state of stress were observed when Va was varied from 25 to 150 V. Stress analysis of TiN films having a mixed (001)+(111) texture indicates that (111) grains are more stressed than (002) ones. The present results suggest that the strain is not the dominant factor in controlling the development of preferred orientation in these films, the governing process being rather competitive growth.
Structure and magnetic characterization of La0.67Sr0.33MnO3/YBa2Cu3O7 superlattices
Authors: Przyslupski P. , Komissarov I. , Paszkowicz W. , Dluzewski P. , Minikayev R. , Sawicki M.
Published: February 2004

Oxide multilayers composed of ferromagnetic metallic layers of La0.67Sr0.33MnO3 (LSMO) and superconducting cuprate YBa2Cu3O7 (YBCO) were grown on LaAlO3 substrates by high-pressure dc sputtering. We have investigated the structural, transport, and magnetic properties of a series of samples in which the LSMO layer thickness is fixed at eight unit cells and that of YBCO varied from one to six unit cells. The superconducting transition temperature Tc0 determined from the resistance measurement is higher than the temperature of the onset of the diamagnetic response Td0. This result is discussed in the frames of the model proposed by E. B. Sonin and I. Felner [Phys. Rev. B. 57, R14000 (1998)] for a ferromagnetic superconductor. The model suggests the presence of the spontaneous vortex phase in the temperature interval Td0<T<Tc0 without an external magnetic field.
Measurement of ionic and neutral densities in amplified magnetron discharges by pulsed absorption spectroscopy
Authors: Konstantinidis S. , Ricard A. , Ganciu M. , Dauchot J. P. , Ranea C. , Hecq M.
Published: February 2004

Resonant absorption diagnostic has been used to estimate densities of neutral and ionic titanium, both in ground and metastable states, in a rf coil amplified magnetron sputtering process. The conventional optical source dc supply has been replaced by a high voltage pulsed power supply to allow absorption experiments onto ionic and neutral species, in a broad range of discharge conditions (500 W are applied onto the magnetron cathode and 0–500 W on the rf coil, for a 30 mTorr argon pressure). The obtained densities are used to compare the magnetron and the amplified discharges. The total ionization degree of the metallic vapor is found to increase from ∼3% in the magnetron regime to ∼24% in the amplified magnetron discharge. The Ti (a5F) neutral metastable density is found to be partially enhanced when the rf coil is power supplied.
A simple model of interactions between electron temperature gradient and drift-wave turbulence
Authors: Holland C. , Diamond P. H.
Published: February 2004

A self-consistent theory for the interaction between electron temperature gradient (ETG) and drift-ion temperature gradient (DITG) turbulence is presented. Random shear suppression of ETG turbulence by DITG modes is studied, as well as the back-reaction of the ETG modes on the DITG turbulence via stresses. It is found that ETG dynamics can be sensitive to shearing by short-wavelength DITG modes. DITG modulations of the electron temperature gradient are also shown to be quite significant. Conversely, the back-reaction of the ETG on the DITG turbulence is found to be weak. The importance of different interactions is quantified via scalings which sensitively depend upon the electron–ion mass ratio. The findings are used to motivate a discussion of the development of a “super-grid” model for the effects of DITG turbulence on the ETG turbulence.
Time-dependent space-charge-limited conduction as a possible origin of the polarization offsets observed in compositionally graded ferroelectric films
Authors: Chan H. K. , Lam C. H. , Shin F. G.
Published: February 2004

We investigated the effects of free space charges on hysteresis-loop measurement of compositionally graded ferroelectrics and found that they are quite likely to be responsible for the “polarization offsets” observed in experiments. Taking into account conduction by those free space charges, or time-dependent space-charge-limited conduction, our computer simulation of compositionally graded lead zirconate titanate, which is placed in the Sawyer–Tower circuit and driven by an alternating applied voltage, produced shifting of measured hysteresis loops where the shift magnitudes are comparable with published experimental data. It also produced the key features as observed in experiments: The “offsets:” (a) have a monotonous increase with electric-field amplitude, (b) change in direction when the composition gradient is inverted, and (c) develop like the typical charging-up of a capacitor. All these results suggest that time-dependent space-charge-limited conduction is a possible origin of the polarization offsets observed in compositionally graded ferroelectrics.
Confined and interface phonon modes in GaN/ZnO heterostructures
Authors: Chen Chen , Dutta Mitra , Stroscio Michael A.
Published: February 2004

Confined and interface optical phonon modes in type II GaN/ZnO heterostructures are investigated in this paper. The optical phonon frequencies of the würtzite semiconductors GaN and ZnO are calculated as a function of angular variation with respect to the c-axis of these wurtzite crystals. The interface (IF) phonon frequencies of the GaN/ZnO/GaN and ZnO/GaN/ZnO heterostructures are calculated as a function of the wave vector. In addition, the confined and interface phonon-carrier interaction Hamiltonians for the Fröhlich interactions are presented. In this article, it is shown that the IF phonon interaction potentials dominate the phonon interactions in both of the heterostructures when the dimensions of the structures are small enough.
The effect of arc velocity on cold electrode erosion
Authors: Essiptchouk Alexei M. , Marotta A. , Sharakhovsky Leonid I.
Published: February 2004

Results of experimental investigations of copper cathode erosion in a magnetically driven arc versus arc rotation velocity v are presented. The erosion rate measurements were carried out with the arc burning in air, for magnetic induction values B in the range of 0.005–0.386 T, axial air gas velocity of 7.65 ms−1, and current of 292 A. It is shown that in the range of small values of v and B, the mass erosion rate diminishes with v and B. Then, the erosion remains constant for a certain range of v and B, and, subsequently, begins to grow. This information is very important for the correct use of magnetic fields to decrease erosion in arc heaters.
Poloidal momentum transport due to drift-waves in toroidal geometry
Authors: Staebler G. M.
Published: February 2004

The aim of this paper is to provide the theoretical framework for a quasi-linear drift-wave model of poloidal and toroidal momentum transport in magnetically confined plasmas in toroidal geometry. Axisymmetry is not required. The new feature is the inclusion of poloidal flow in the coupled equations for linear drift-wave stability and quasilinear mean field transport. It is shown how both toroidal and poloidal rotations can be included in a distribution function which is an equilibrium of the Vlasov equation in a rotating reference frame. The equations for the fluctuation driven toroidal and poloidal viscous stresses are determined and the toroidal form of the E×B and parallel velocity shear terms are found. In order to be able to follow the electric field evolution during a transport bifurcation, the neoclassical constraint on the poloidal rotation is not imposed. Instead, the common poloidal flow is evolved as part of the system of transport equations.
Hall current and Alfvén wave
Authors: Ohsaki Shuichi , Mahajan Swadesh M.
Published: February 2004

In ideal inhomogeneous magnetohydrodynamics (MHD), the Alfvén wave (the dominant low frequency mode of a magnetized plasma) displays a continuous spectrum associated with singular eigenfunctions. It is shown that the coupling of the Hall term with the sound wave induces higher (fourth) order derivative in the Alfvén mode equation, and by resolving the singularity replaces the MHD continuum by a discrete spectrum. The mode structure resulting from the Hall resolution of the singularity is compared with the standard electron-inertia approach.
Plasma-surface interaction model with secondary electron emission effects
Authors: Taccogna Francesco , Longo Savino , Capitelli Mario
Published: February 2004

This work represents the investigation of the region between a Maxwellian plasma source and a floating surface by a 1D–3V fully kinetic, electrostatic particle simulation. The electric field is self-consistently computed from the Poisson equation. The secondary electron emission is modelled rigorously by considering a realistic expression for the secondary emission coefficient dependent on the primary electron energy, the angle relative to the surface normal and surface materials and a realistic secondary electron distribution function is introduced at the collector surface. The minimum ion energy at the collector sheath edge is evaluated self-consistently by determining the plasma sheath, without the assumption of a monotonic potential. The model is able to simulate the space charge limited conditions as well as the positively charged wall cases. Results are compared with other secondary emission sheath theories and numerical models.
Dung decomposition in temperate dairy pastures. I. Changes in soil chemical properties
Authors: Aarons S. R. , O'Connor C. R. , Gourley C. J. P.
Published: February 2004

The effect of dung from cows grazing low and high input systems (2 cows/ha, 35 kg P/ha; 4 cows/ha, 140 kg P/ha) on soil chemical properties in temperate dairy pastures was investigated. Dung was used to create pads, and their effect on soil at 2 depths compared with control areas to which nothing was applied. Most dung had decomposed after 40 days in autumn, and was completely degraded by Day 60 in this temperate environment. Large quantities of the nutrients P, K, Ca, Na, Mg, and S were applied to the soil in these dung pads. The mechanism of movement of these nutrients from the pads into soil appeared to be based on their solubility in water. Phosphorus did not leach from the pads but was incorporated into the soil with the decomposing pad. Calcium, Mg, and S concentrations declined slowly in the decomposing pads. On the other hand, K and Na appeared to leach from the pads, as significant decreases in concentrations occurred during decomposition. Soil pH (1:20 soil:water) decreased under dung pads, although the effect did not last beyond 60 days and was linked to the observed increase in soil EC with depth. Extractable P and K increased considerably in soil under dung pads, but only in the upper 0–5 cm layer. Soil exchangeable aluminium and total organic P were not affected by the presence of dung pads. These results are discussed in relation to nutrient cycling in temperate Australian dairy pasture soils.
Dung decomposition in temperate dairy pastures. II. Contribution to plant-available soil phosphorus
Authors: Aarons S. R. , Hosseini H. M. , Dorling L. , Gourley C. J. P.
Published: February 2004

Changes in dung and soil inorganic and organic P pools were measured in an experiment investigating the effects of dung on soil properties in 2 grazed dairy pasture systems (low and high input). Total dung P and bicarbonate-extractable P pools were measured in decomposing pads and compared with the changes in inorganic and organic bicarbonate-extractable soil P, P sorption, and microbial P flush of soils beneath dung pads and control 'pads' where nothing was applied. Bicarbonate-extractable total P in the dung pads declined to the same level in both systems by the last sample date. Organic P comprised a similar proportion (36%) of the bicarbonate-extractable total P pool in dung from both low and high input systems. However, the transformations of dung P were different in each system, with the bicarbonate-extractable total P in the low input dung increasing by 25% before declining, and a greater decrease in percentage bicarbonate-extractable organic P in this system.Bicarbonate-extractable soil organic P did not vary under dung pads despite the large increases in Olsen and Colwell P observed. Soil Olsen P trends observed in the low and high input systems indicate a potential for leaching losses of P in high input systems compared with low. This increase in soil Olsen P was not due to decreased P sorption as dung did not reduce the sorption capacity of the soil. Microbial soil P increased under dung pads only after 60 days in this experiment. Neither the organic P nor microbial P pools contributed significantly to soil labile P pools in these temperate dairy pasture systems. The transformations of P thought to occur during the decomposition of dung are discussed.
Calibration of the Rothamsted organic carbon turnover model (RothC ver. 26.3), using measurable soil organic carbon pools
Authors: Skjemstad J. O. , Spouncer L. R. , Cowie B. , Swift R. S.
Published: February 2004

A fractionation scheme that provided the measurement of a labile pool (particulate organic carbon), a charcoal-carbon pool, and a humic pool by difference was tested as a means of initialising the Rothamsted organic carbon turnover model version 26.3. Equating these 3 fractions with the resistant plant material, inert organic matter, and humic pools of the model, respectively, gave good agreement between measured and modelled data for 2 long-term rotation trials in Australia using a soil depth of 30 cm. At one location, Brigalow Research Station in Queensland, there were 3 distinct soil types, two clays and a duplex soil, in a semi-arid, subtropical climate. At this site, continuous wheat with some sorghum was established after clearing land under brigalow (Acacia harpophylla) and continued for 18 years. The second location was near Tarlee, South Australia, and was established on existing agricultural land. One soil type (red brown earth) with 2 rotations (continuous wheat and wheat–fallow) were available over a period of 8 years.The modelled and measured data were in good agreement for both locations but the level of agreement was substantially improved when the resistant plant material decomposition rate was reduced from 0.3 to 0.15/year. No other modifications were required and the resulting values provided excellent agreement between the modelled and measured data not only for the total soil organic carbon but also for the individual pools. Using this fractionation scheme therefore provides an excellent means of initialising and testing the Rothamsted model, not only in Australia, but also in countries with similar soil types and climate.For the first time, the work reported here demonstrates a methodology linking measured soil carbon pools with a conceptual soil carbon turnover model. This approach has the advantage of allowing the model to be initialised at any point in the landscape without the necessity for historical data or for using the model itself to generate an initial equilibrium pool structure. The correct prediction of the changing total soil organic carbon levels, as well as the pool structure over time, acts as an internal verification and gives confidence that the model is performing as intended.
Phosphorus auditing cannot account for all of the phosphorus applied to different pasture soils
Authors: Burkitt L. L. , Gourley C. J. P. , Sale P. W. G.
Published: February 2004

Five field sites established in the high rainfall zone of southern Victoria were used to examine the downwards vertical movement of phosphorus (P) fertiliser on soils which ranged in P sorption capacity. Fertiliser was applied either as a single application of 280 kg P/ha at the beginning of the experiment (April 1998), or as 35�kg�P/ha reapplied every 6 months (totalling 210 kg P/ha by the end of the third year). Soil cores were sampled in June 2001 to a depth of 40 cm, and soil at depths of 0–5, 5–10, 10–20, 20–30, and 30–40 cm was analysed for a range of soil properties and total P concentration.Total P concentration changed very little down the profile, indicating that there was minimal vertical movement of P fertiliser below the 10 cm layer of 5 pasture soils following the single application of 280 kg P/ha or 35 kg P/ha reapplied every 6 months. Soils with low to moderate surface P sorption capacity showed a trend for higher total P concentrations at depth. However, quantitative relationships between vertical P movement and soil properties at depth were poor. A P audit resulted in variable recovery of the applied P (45–128%) in the surface 40 cm at each of the 5 sites. Consistently low P recoveries were achieved at one site, where the surface soil had a high P sorption capacity. Some applied P may have bypassed the high P sorbing surface layers at this site through macropore flow and moved beyond the 40 cm sampling zone, or have been lost to surface runoff. These results question the usefulness of P audit or mass-balance methods for accounting for P movement in a pasture-based system, as spatial heterogeneity of soil properties, both horizontally and vertically, was high in the current study.
Determination of water content in drying soils: incorporating transition from liquid phase to vapour phase
Authors: Konukcu F. , Istanbulluoglu A. , Kocaman I.
Published: February 2004

In arid and semi-arid environments, soil profiles often exhibit a liquid–vapour displacement known as evaporation front characterised by a critical matric potential (ψme) or water content (θe) located somewhere inside the unsaturated zone above a watertable (WT). The objective of this study was to determine the θe including the range of water content (θ) in the transition zone from liquid to vapour both theoretically and experimentally for different soil textures under saline and non-saline WTs. Characteristic shapes of water content and salt concentration profiles were the criteria to obtain θe experimentally, and the θ–diffusivity relationship was used to compute the θe and θ range in the transition zone. Measured θe values of 0.05 and 0.12 m3/m3 under non-saline WT and 0.07 and 0.15 m3/m3 under saline WT were in agreement with the computed values of 0.05 and 0.10 m3/m3 for sandy loam and clay loam soils, respectively. The model calculates roughly the same θe for saline and non-saline conditions. Besides experimental soils, θe and range of θ in the transition zone were calculated for silty loam and coarse sand. The lighter the soil texture, the smaller is θe and the steeper the transition zone. The results were further compared with those calculated by different authors.
Chemical characterisation of deep profile Ferrosols under sugarcane in wet tropical northern Queensland
Authors: Donn M. J. , Menzies N. W. , Rasiah V.
Published: February 2004

The chemical properties of deep profile samples (up to 12 m) of Ferrosols from northern Queensland were investigated to provide an understanding of the accumulation of nitrate (NO3) within these soil profiles. The influence of other cations and anions present in the soil solution or on the exchange and the charge chemistry of the profiles were examined with respect to the NO3 accumulations. The major ions in the soil solution were Na, NO3, and chloride (Cl). Distinct regions of anion accumulation were observed; SO4 accumulated in the upper profile of all cores, whereas NO3 and Cl accumulations were restricted to the lower profile of cores with appreciable AEC (>1�cmolc/kg). Gaines-Thomas selectivity coefficients were used to indicate exchange preference for cations and anions, and are as follows: Al > Ca ~ Mg > K > Na and sulfate (SO4) > Cl ~ NO3. The selectivity of SO4 increased and the extractable SO4 decreased in the lower profile of all cores. This has important implications for the adsorption of NO3 and Cl. The NO3 and Cl accumulations were shown to correspond to a region of low SO4 occupancy of the exchange sites in the lower profile. Along with the high SO4 selectivity, this suggests that SO4 may control the positioning of the NO3 accumulations. It was concluded that the NO3 accumulations were relatively stable under current management practices, although the reduction in NO3 inputs would likely see the gradual replacement of NO3 with Cl as a result of their comparable selectivity for exchange sites.
Comparison of four methods for liberating various aggregate fractions in Vertosols to study their morphology
Authors: Field Damien J. , Sullivan Leigh A. , Cattle Stephen R. , Koppi Anthony J.
Published: February 2004

Topsoil samples from 3 Vertosols located at Narrabri, Warren, and Dalby were treated with 4 aggregate liberation methods to determine their suitability for analysis by scanning electron microscopy (SEM). In addition to the ability of each method to liberate aggregates for assessment, the potential for consequent morphological deformation was also considered. It was found that the aggregate slaking in water and modified wet sieving methods were suitable for liberating aggregates >100 μm in diameter, whereas the ultrasonic agitation method readily liberated aggregates <50 μm in diameter. End-over-end shaking is not recommended for preparing aggregates for SEM as the method appeared to cause morphological deformation of the liberated aggregates. The systematic use of the 4 aggregate liberating methods, assuming an increase in the intensity of the energy supplied, enabled the partitioning of the aggregates of these Vertosols into pragmatic aggregate size fractions defining a hierarchy, i.e. >250, 100–250, 20–100, 2–20, and <2 μm in diameter.
The effects of clay and sand additions on the strength of sandy topsoils
Authors: Harper R. J. , Gilkes R. J.
Published: February 2004

The clay contents of sandy soils in south-western Australia are often modified, either intentionally or inadvertently, as a result of management practices and erosion. Although the strength of sandy surfaced soils has previously been shown to be related to clay content, in natural soils the effects of induced changes in clay content on soil strength have not been assessed.Increasing amounts of subsoil clay were added to their respective topsoils in increments ranging from 5 to 20% by weight, and these systematically increased soil strength. A strong log–log relationship between clay content and soil strength explained 69% of the variation, with soil strength further affected by sodicity. This enhancement of soil strength has implications for the practice of claying water-repellent soils, particularly where non-uniform application or poor incorporation results in high concentrations of clay, where very high rates (e.g. 300 t/ha) of application are used, or where clayey subsoils are brought to the surface by deep cultivation or the removal of topsoils by erosion.Drift sand, with a clay content of around 1% and negligible strength, was added in increasing increments to typical topsoils, over the range of 0–100% by weight to replicate the effects of wind-induced deposition and winnowing of clay particles. Increasing additions of drift sand systematically decreased soil strength, with a log–log relationship between clay content and strength of the mixtures explaining 81% of the variation. This suggests that wind erosion, and the winnowing of clay or deposition of drift sand, permanently destabilises soil surfaces by reducing soil strength. It is feasible that strategic applications of sand on the surfaces of soils affected by hardsetting may reduce soil strength and encourage soil structure development and seedling emergence.
Inventories and elemental accumulation in peat soils of forested seabird breeding islands, southern New Zealand
Authors: Hawke D. J. , Newman J.
Published: February 2004

We determined inventories and accumulation of C, N, P, and Cd in 2 profiles from sooty shearwater (Puffinus griseus) breeding colonies. Inventories (0–70 cm, F horizon) were: 42.9 kg/m2 (C; both profiles), 1.39 and 1.95 kg/m2 (N), 2.52 and 3.99 × 10-2 kg/m2 (P), and 9.89 and 9.69 × 10-5 kg/m2 (Cd). Radiocarbon analysis for accumulation calculations was invalid in one profile due to bioturbation. Accumulation rates (95% confidence interval) for the other profile were: 61–76 g/m2.year (C), 2.0–2.4 g/m2.year (N), 0.036–0.044 g/m2.year (P), and 0.14–0.17 mg/m2.year (Cd). These accumulation data were within the range of other pristine peat systems, but lower than those with high anthropogenic inputs. Applying literature estimates of gross inputs indicated that only 0.6–2.2% of N and 0.1–0.6% of P were retained over the 567–705-year accumulation period.
Scene setting: who is the voice of nutrition in Britain?
Authors: Buttriss Judith
Published: February 2004

Currently the public is being inundated daily with information about diet and health, which is often conflicting and frequently not based on good quality evidence. This situation is fuelled by the ready access to information of variable quality via the internet, which has short circuited the previous checks and balances applied by researchers and the peer review process, whereby scientific findings were batted around and refined within the confines of the scientific research community, occasionally emerging to be incorporated into the advice given by health professionals. This situation, coupled with concern about the growing trend whereby detailed nutrition advice is sold to the public by self-styled 'experts' with no formal degree-level training in the subject, prompted a conference that highlighted the importance of ensuring that nutrition advice is evidence-based, using a series of topical overviews. In recent years the Nutrition Society has played an active role in establishing mechanisms to assist the public in their search for high-quality dietary advice by badging individuals appropriately qualified to offer sound and relevant advice on nutrition.
Is there more to folates than neural-tube defects?
Authors: Finglas Paul M. , Wright Anthony J. A. , Wolfe Caroline A. , Hart David J. , Wright Dawn M. , Dainty Jack R.
Published: February 2004

The purpose of the present paper is to review our current understanding of the chemistry and biochemistry of folic acid and related folates, and to discuss their impact on public health beyond that already established in relation to neural-tube defects. Our understanding of the fascinating world of folates and C1metabolism, and their role in health and disease, has come a long way since the discovery of the B-vitamin folic acid by Wills (1931), and its first isolation by Mitchellet al. (1941). However, there is still much to do in perfecting methods for the measurement of folate bioavailability, and status, with a high extent of precision and accuracy. Currently, examination of the relationships between common gene polymorphisms involved in C1metabolism and folate bioavailability and folate status, morbidity, mortality and longevity is evaluated as a series of individual associations. However, in the future, examination of the concurrent effects of such common gene polymorphisms may be more beneficial.
Diet and cardiovascular disease in the UK: are the messages getting across?
Authors: Kelly C. N. M. , Stanner S. A.
Published: February 2004

Cardiovascular disease (CVD) is a leading cause of premature death in the UK and a major cause of ill health and disability. Whilst death rates from CVD have been falling since the late 1970's in the UK, levels of morbidity (such as angina) do not seem to be falling and may even be rising in some age-groups, especially as the population ages. There is broad consensus that lifestyle factors, including physical activity and diet, are fundamental determinants of heart disease risk. Current recommendations to reduce cardiovascular risk include maintaining a healthy body weight, eating five or more portions of fruit and vegetables each day, reducing intake of fat (particularly saturated fatty acids), reducing salt intake and eating one portion of oily fish per week. Although some improvements have been made in recent years (e.g. a reduction in total fat intake), national studies suggest that more effective campaigns are required to increase awareness of the benefits of these dietary changes. The present paper will discuss how the dietary messages relating to CVD are best communicated to the general public and will identify some of the main barriers to their implementation.
Home enteral-tube feeding: The changing role of the dietitian
Authors: Madigan Sharon M.
Published: February 2004

Enteral feeding in primary care has increased markedly over the last decade. It allows patients to be discharged to home or residential care who previously would have remained in hospital. Difficulties do arise for patients, their carers and health professionals, as care of these patients and support for health professionals is often patchy or non-existent. Dietitians are uniquely placed to participate in the management of tube feeding in primary care, provide support and education to patients and their carers, evaluate treatment and promote better outcomes for patients receiving tube feeding.
Nutrition and cancer prevention: diet-gene interactions
Authors: Mathers John C.
Published: February 2004

Cancer is the major cause of death in the UK, and the Government has set a target to reduce death rate from cancer in individuals 75 years by ≥20% by 2010. Whilst earlier diagnosis and more effective treatments will contribute to meeting this target, there are considerable opportunities to prevent cancer by improving diet and other aspects of lifestyle. There is now a good understanding of the biological basis of carcinogenesis, which is providing the basis for mechanistic investigation of the chemo-preventive properties of certain foods and food components. It is becoming increasingly clear that there are important interactions between an individual's genotype (characterised by single nucleotide polymorphisms in particular genes) and habitual diet that modulate the risk of developing cancer. The technology to support this post-genomic revolution in nutrition research is now widely available, but brings with it considerable challenges in terms of study design and ethics. However, in the absence of a robust body of evidence on which dietary strategies will benefit which individuals, soundly based genetically-targeted nutrition advice to the public on cancer prevention is a little way in the future.
Plant polyphenols: are they the new magic bullet?
Authors: Duthie Garry G. , Gardner Peter T. , Kyle Janet A. M.
Published: February 2004

Epidemiological evidence suggests that diets rich in fruit and vegetables decrease the risk of premature mortality from major clinical conditions, including cancer and heart disease. However, it is not yet clear which components or combination of components in fruit and vegetables are protective and what is their mechanism of action. Such scientific uncertainty does not seem to inhibit the marketing of a huge range of plant-based concoctions, promoted as ‘magic bullets’ for optimum health. For example, the purported health-giving properties of plant polyphenols represent a case in which enthusiastic marketing claims may far exceed the current scientific evidence. Even when good experimental evidence exists, results need to be interpreted with caution in relation to human health benefits, as polyphenols may have limited bioavailability and may also be extensively metabolised. In addition, some polyphenols can be toxic and mutagenic in some cell culture systems. Until more is known about the activity and metabolic fate of polyphenols in the body, it would be better for the consumer to increase fruit and vegetable intake, and also to be wary of claims that these compounds are a panacea for good health.
Uncoupling protein 3 and physical activity: the role of uncoupling protein 3 in energy metabolism revisited
Authors: Schrauwen Patrick , Hesselink Matthijs
Published: February 2004

Physical activity influences energy metabolism in human subjects by increasing activity-induced energy expenditure and resting metabolic rate for several hours after exercise. On the other hand, physical activity increases mechanical energy efficiency, suggesting that trained subjects would need less energy for daily activities. The underlying mechanism by which physical activity influences energy metabolism is largely unknown. The skeletal muscle-specific homologue of uncoupling protein (UCP) 1, UCP3, could possibly play a major role in energy expenditure. UCP3 is, like UCP1, able to uncouple respiration from ATP production. A strong link or association between theUCP3gene and energy metabolism was found. Furthermore, UCP3 mRNA expression is related to sleeping metabolic rate, and thyroid hormone, a powerful stimulator of energy expenditure, up regulates UCP3. Finally, mice overexpressing UCP3 are hyperphagic but lean. These findings indicated that UCP3 is related to energy metabolism and that UCP3 could have a role in the effect of physical activity on energy expenditure. Thus, acute exercise up regulates UCP3, whereas endurance training results in the down-regulation of UCP3 protein content. Only a minimal amount of physical activity is needed for down-regulation of UCP3. Moreover, there is very strong evidence that UCP3 is negatively related to mechanical energy efficiency, suggesting that the down-regulation of UCP3 with training increases mechanical energy efficiency. Taken together, although the exact function of UCP3 is still unknown, exercise and training studies clearly show that under certain circumstances UCP3 is strongly related to human energy metabolism, possibly as a secondary effect of its (yet) unknown primary function.
Improving communication to tackle obesity in the UK
Authors: Jebb Susan A. , Lang Rebecca , Penrose Adrian
Published: February 2004

Obesity is a serious health issue. In the UK the prevalence of obesity has trebled in the last 20 years and today one in five adults is clinically obese. Research shows that obesity is a predictable response to an environment that favours the consumption of energy-dense foods and allows minimal physical activity. This finding implies that the efficacy of public health messages to individuals to inform their lifestyle choices will be enhanced by environmental changes that support and facilitate healthy options. The present paper focuses on the importance of communicating scientific knowledge to the stakeholders with a responsibility for tackling obesity and addresses some of the barriers that are encountered.
Impacts of vigorous and non-vigorous activity on daily energy expenditure
Authors: Westerterp Klaas R.
Published: February 2004

Activity intensity is a potential determinant of activity-induced energy expenditure. Tri-axial accelerometery is the most objective measurement technique for the assessment of activity intensity, in combination with doubly-labelled water for the measurement of energy expenditure under free-living conditions. Data on the effects of subject characteristics, including body size and age, and exercise training on the relationship between activity intensity and daily energy expenditure are reviewed. Average daily metabolic rate and non-basal energy expenditure are positively related to body size. The duration and intensity of physical activities do not need to be equivalent to the energy spent on activity. Obese subjects spend more energy on physical activity but can perform fewer activities, especially high-intensity (weight-bearing) activities, because of their higher body weight. Physical activity generally declines gradually from about 60 years of age onwards. Most subjects >80 years have an activity level well below the level defined for sedentary middle-aged adults. Spending relatively more time on low-intensity activities has a negative effect on the mean physical activity level. To obtain a higher physical activity level does not necessarily imply high-intensity activities. In an average subject 25% of the activity-induced energy expenditure may be attributed to high-intensity activities. Exercise training, as a form of high-intensity activity, affects the physical activity level more in younger subjects than in elderly subjects.
Energy expenditure, physical activity and body-weight control
Authors: Tappy L. , Binnert C. , Schneiter Ph.
Published: February 2004

Regular physical exercise and endurance training are associated with low body weight and low body fat mass. The relationship between exercise and body-weight control is complex and incompletely understood. Regular exercise may decrease energy balance through an increase in energy expenditure or an increase in fat oxidation. It may also contribute to weight loss by modulating nutrient intake. An intriguing question that remains unresolved is whether changes in nutrient intake or body composition secondarily affect spontaneous physical activity. If this were the case, physical activity would represent a major adaptative mechanism for body-weight control.