bluuebunny/crossref_metadata_2025 huggingface dataset:
Intersubband spectroscopy of doped and undoped GaN/AlN quantum wells grown by molecular-beam epitaxy
Authors: Helman A. , Tchernycheva M. , Lusson A. , Warde E. , Julien F. H. , Moumanis Kh. , Fishman G. , Monroy E. , Daudin B. , Le Si Dang D. , Bellet-Amalric E. , Jalabert D.
Published: December 2003

We report experimental and theoretical results on interband and intersubband transitions in GaN quantum wells with strained AlN barriers. All of the samples are grown by molecular-beam epitaxy on sapphire (0001) substrates. The results show that even at room temperature, strong electron localization occurs in the plane of the quantum wells due to the combined effect of monolayer thickness fluctuations and the high internal field in the GaN layers. We also demonstrate that the intersubband absorption is systematically blueshifted in n-doped quantum wells with respect to nominally undoped samples as a result of strong many-body effects, namely the exchange interaction. The results for both undoped and doped quantum wells are in good agreement with simulations.
Doped red organic electroluminescent devices based on a cohost emitter system
Authors: Liu Tswen-Hsin , Iou Chung-Yeh , Chen Chin H.
Published: December 2003

We have developed an efficient red emitter in organic light-emitting diodes based on the fluorescent dye 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetra-methyljulolidyl-9-enyl)-4H-pyran doped in a cohost emitter system of 5,6,11,12-tetraphenylnathacene/tris(8-hydroxyquinolinato)aluminum which achieved an electroluminescence (EL) efficiency of 4.4 cd/A and 2.1 lm/W at 20 mA/cm2 and 6.8 V, with a near saturated Commission Internationale d’Eclairage coordinates (x=0.65, y=0.35). This cohost emitter system has the advantage of alleviating the current-induced fluorescence quenching often encountered in red organic EL devices and greatly improves the EL efficiency over a wide range of drive current conditions. From accelerated degradation tests, a device half-life of about 33 800 h can be projected in this system at an initial device luminance of 100 cd/m2.
Efficient electron spin manipulation in a quantum well by an in-plane electric field
Authors: Rashba E. I. , Efros Al. L.
Published: December 2003

Electron spins in a semiconductor quantum well couple to an electric field via spin–orbit interaction. We show that the standard spin–orbit coupling mechanisms can provide extraordinarily efficient electron spin manipulation by an in-plane ac electric field.
Dysprosium silicide nanowires on Si(110)
Authors: He Zhian , Stevens M. , Smith David J. , Bennett P. A.
Published: December 2003

Dysprosium deposited on Si(110) at 720 °C is observed to form self-assembled silicide nanowire (NW) structures with a single orientation and average dimensions of 15 nm wide and microns long. The NW sides grow into the substrate along inclined Si{111} planes, forming a V-shaped cross section with an interface that is coherent on one side, described by DySi2(0001)//Si(111_) and DySi2[011_0]//Si[1_10], and incoherent on the other. This type of growth represents a physical mechanism for self-assembled NW formation that does not require anisotropic lattice mismatch.
Continuous wave optically pumped lead-salt mid-infrared quantum-well vertical-cavity surface-emitting lasers
Authors: Zhao F. , Wu H. , Majumdar A. , Shi Z.
Published: December 2003

Continuous wave optically pumped mid-infrared lead-salt quantum-well vertical-cavity surface-emitting lasers with an eleven-period PbSe/PbSrSe quantum-well active region are demonstrated. The cw emissions are observed up to 230 K at the emission wavelengths around 4.03 μm. The lowest threshold pump density of 2.6 kW/cm2 appears at 190 K, 65 °C lower than that of the pulsed measurements. This indicates the temperature difference between the active region and the heat sink of the episide-up mounted on-wafer testing under cw pumping.
Rapid growth of evanescent wave by a silver superlens
Authors: Liu Zhaowei , Fang Nicholas , Yen Ta-Jen , Zhang Xiang
Published: December 2003

Recent theoretical work suggested the possibility of constructing a super-resolution diffraction-free lens by using a negative refractive index medium (NRIM). The key proposition is that evanescent waves can be greatly enhanced by increasing the thickness of the NRIM. We report here experimental evidence that confirms that the transmission of evanescent waves rapidly grows with the film thickness up to about 50 nm, after which it decays as loss becomes significant. These findings represent the first step toward the understanding and realization of a diffraction-free lens.
Polarization switching in composite-resonator vertical-cavity lasers
Authors: Grasso D. M. , Choquette K. D.
Published: December 2003

We report polarization switching in a monolithic dual-resonator vertical-cavity laser. The light output from the top ion-implanted cavity under forward bias above threshold is partitioned into two orthogonal polarizations of the fundamental transverse mode. A reverse bias of sufficient magnitude applied to the bottom oxide-confined cavity causes the abrupt suppression of the dominant polarization and simultaneous emergence of the orthogonal polarization. We find that the electro-optic birefringence of the two polarizations increases with increasing reverse bias. We show that the mechanism of the polarization switch is consistent with wavelength-dependent loss from electroabsorption in the reverse-biased quantum wells of the oxide-confined cavity.
Self-aligned mechanical attachment of carbon nanotubes to silicon dioxide structures by selective silicon dioxide chemical-vapor deposition
Authors: Whittaker Jed D. , Brink Markus , Husseini Ghaleb A. , Linford Matthew R. , Davis Robert C.
Published: December 2003

A self-aligned thin-film deposition technique was developed to mechanically attach carbon nanotubes to surfaces for the fabrication of structurally robust nanotube-based nanomechanical devices. Single-walled carbon nanotubes were grown by thermal chemical-vapor deposition (CVD) across 150-nm-wide SiO2 trenches. The nanotubes were mechanically attached to the trench tops by selective silicon tetraacetate-based SiO2 CVD. No film was deposited on the nanotubes where they were suspended across the trenches.
Growth of quantum fortress structures in Si1−xGex/Si via combinatorial deposition
Authors: Vandervelde Thomas E. , Kumar Piyush , Kobayashi Takeshi , Gray Jennifer L. , Pernell Tim , Floro Jerrold A. , Hull Robert , Bean John C.
Published: December 2003

This study details the evolution of morphologies in the Si1−xGex/Si system, under kinetically controlled conditions of 550 °C growth temperature and 1 Å/s growth rate. We find that, with increasing film thickness and Ge fraction, a series of three-dimensional structures develop, starting from pits, and leading to quantum fortresses and ridges. The quantum fortress structures are of special significance because of their potential application in quantum cellular automata. We establish approximate boundaries in the parameter space of film thickness and Ge fraction, in which these structures form. We present a simple model, based on kinetics and strain, to explain the observed structures.
Generation of ultrahigh pressure using single-crystal chemical-vapor-deposition diamond anvils
Authors: Mao Wendy L. , Mao Ho-kwang , Yan Chih-shiue , Shu Jinfu , Hu Jingzhu , Hemley Russell J.
Published: December 2003

Two experiments were conducted compressing Ta, Re, Pt, and an Fe-Si alloy to ultrahigh pressures using single-crystal chemical vapor deposition (CVD) and natural diamonds. In situ energy-dispersive and angle-dispersive x-ray diffraction were used to determine pressure from known equations of state. We demonstrate that CVD diamonds can be used in diamond anvil cells to reach pressures of nearly 200 GPa.
Structuring of self-assembled three-dimensional photonic crystals by direct electron-beam lithography
Authors: Ferrand P. , Egen M. , Zentel R. , Seekamp J. , Romanov S. G. , Sotomayor Torres C. M.
Published: December 2003

An electron-beam lithography technique is described capable of structuring three-dimensional self-assembled photonic crystals. It is shown that the control of the writing depth can be achieved by varying the electron acceleration voltage. Microscopic structures with a depth from 0.4 up to 2 μm are fabricated with a typical lateral resolution of 0.4 μm. The relevance of this technique for the fabrication of deterministic defects sites in opal photonic crystals is discussed and its extension towards buried structures is suggested.
Nucleation and growth in bulk metallic glass under high pressure investigated using in situ x-ray diffraction
Authors: Wang W. H. , Wen P. , Zhao D. Q. , Pan M. X. , Okada T. , Utsumi W.
Published: December 2003

The effects of pressure up to 8.3 GPa on nucleation and growth in a Zr57Nb5Cu15.5Ni12.5Al10 bulk glass-forming alloy during heating, isothermal annealing, and cooling processes are investigated using in situ x-ray diffraction with synchrotron radiation. The metallic glass shows markedly different crystallization behaviors for different heat treatments under high pressure. Heating under high pressure can stabilize the supercooled liquid state. Isothermal high pressure annealing leads to nanocrystallization. The glass forming ability of the alloy can be enhanced by high pressure during cooling process. The effects of pressure on the nucleation and growth are discussed based on the nucleation theory.
Modulation of light by light in silicon-on-insulator waveguides
Authors: Stepanov S. , Ruschin S.
Published: December 2003

We report infrared light modulation based on direct free-carrier absorption induced by visible light irradiation in silicon-on-insulator waveguides. An amplitude modulation depth of 96% and 89% was measured for waveguide light carrier at a wavelength of 1.55 and 1.32 μm. The frequency dependence of the modulation effect was measured as well.
Plasma coating of carbon nanofibers for enhanced dispersion and interfacial bonding in polymer composites
Authors: Shi Donglu , Lian Jie , He Peng , Wang L. M. , Xiao Feng , Yang Ling , Schulz Mark J. , Mast David B.
Published: December 2003

Ultrathin films of polystyrene were deposited on the surfaces of carbon nanofibers using a plasma polymerization treatment. A small percent by weight of these surface-coated nanofibers were incorporated into polystyrene to form a polymer nanocomposite. The plasma coating greatly enhanced the dispersion of the nanofibers in the polymer matrix. High-resolution transmission-electron-microscopy (HRTEM) images revealed an extremely thin film of the polymer layer (∼3 nm) at the interface between the nanofiber and matrix. Tensile test results showed considerably increased strength in the coated nanofiber composite while an adverse effect was observed in the uncoated composites; the former exhibited shear yielding due to enhanced interfacial bonding while the latter fractured in a brittle fashion.
4H-polytype AlN grown on 4H-SiC(112̄0) substrate by polytype replication
Authors: Onojima N. , Suda J. , Kimoto T. , Matsunami H.
Published: December 2003

4H-polytype AlN has been grown on a 4H-SiC substrate with the (112̄0) face via plasma-assisted molecular-beam epitaxy. The microscopic structure of the AlN/4H-SiC interface was examined using high-resolution transmission electron microscopy, and the polytype replication of the 4H structure from the 4H-SiC(112̄0) substrate was evidently confirmed. The x-ray rocking curve of (112̄0) diffraction for the single crystalline 4H-AlN epilayer exhibited a very small linewidth of 90 arc sec, suggesting noticeably small tilting around the [112̄0] direction. The excellent crystalline quality is probably owing to the polytype matching between the 4H-AlN epilayer and the 4H-SiC substrate, which resulted in remarkable reduction of defects at the interface.
Surface-relief diffraction gratings based on selective etching of periodically poled lithium niobate
Authors: Capmany J. , Fernández-Pousa C. R. , Diéguez E. , Bermúdez V.
Published: December 2003

This work reports the use of selective etching in a periodically poled crystal of LiNbO3 (MgO):Yb3+ to engineer a surface-relief diffraction grating. A 35.1%–64.9% fill factor (domain duty cycle) grating with a 6.86 μm domain period is presented. The diffraction grating created provides a simple tool for accurate characterization of domain size and structure homogeneity. Following a similar process, arbitrary surface-relief two-level binary diffractive optical elements can be patterned in domain-engineered lithium niobate crystals.
Soil surface temperature and mortality in land snails: implications for successful management
Authors: Kempster V. , Charwat S.
Published: December 2003

Three species of land snails, Theba pisana (Müller, 1774), Cernuella virgata (Da Costa, 1778) and Cochlicella acuta (Müller, 1774), introduced to Australia from the Mediterranean region, cause significant economic problems in harvested crops in southern Australia. One of the strategies for post-harvest control of these snails involves stubble management to knock the snails onto the hot ground during summer. Farmers report variable results with this strategy, which could be due to varying heat tolerances between the 3 species. In a series of laboratory experiments, field-collected snails of the 3 species were tested for their ability to survive high surface temperatures for varying periods of time. The results reported here indicate differences between the 3 species in their tolerance of soil surface temperatures, and suggest that the variable results noted in the field are due at least in part to the differing heat tolerances of the 3 species. When adult snails were placed in incubators at a constant temperature, all T. pisana died after 3 h at 55°C, while C. virgata and C. acuta survived longer, with 100% mortality only after 2 successive 6-h exposures at 55°C. Weight loss of snails was measured after heat treatment to estimate water loss under these conditions. Recommendations are made for more effective mechanical control strategies for snails in the field during summer.
Tissue testing to assess the sulfur requirements of subterranean clover on very sandy soils in high rainfall areas of south-western Australia
Authors: Bolland M. D. A. , Yeates J. S. , Codling B. J. , Clarke M. F.
Published: December 2003

Tissue testing was studied in field experiments between 1979 and 1985 to predict when sulfur (S) fertiliser was required for pastures in high rainfall (>650 mm annual average) areas of south-western Australia. The pastures comprised about half subterranean clover and annual ryegrass (Lolium rigidum Gaud.), the major pasture species in the region. Tissue testing was done for each species, using: (i) whole shoots, the present method used by commercial laboratories in Western Australia; (ii) youngest open leaves (legumes, YOLs) or youngest expanded blades (grass, YEBs); (iii) old leaves and blades (leaves that were not YOLs or YEBs); and (iv) stems (left after removal of YOLs, YEBs, old leaves and blades). Dried tissue was measured for total S, sulfate S, the total nitrogen : total S ratio and the sulfate S : total S ratio. For each pasture species, tissue test values were related to yield of dried herbage of that species measured for plants cut at ground level. Fertiliser nitrogen was not applied in the experiments.Annual ryegrass showed no significant yield responses to applied fertiliser S for all harvests in all experiments. Subterranean clover showed significant yield responses for most harvests of all experiments. At each site in each year, yield responses to applied S tended to become larger as the growing season progressed. For subterranean clover critical S values related to 90% of the maximum (relative) yield varied for different harvests of the same experiment within and between years, and for different experiments in the same and different years. As determined from all data, critical S values were similar for all plant parts (whole shoots, YOLs, old tissue, stems), with no consistent, systematic trend with plant age, and were: total S, range 0.10–0.30% S, mean 0.23%; sulfate S, range 0.01–0.14%, mean 0.04%; total N : total S ratio, range 11–30, mean 19; sulfate S : total S ratio, range 0.01–0.48, mean 0.27. The exception was that total S was lower for clover stems, the range being 0.06–0.20%, and mean 0.13%. Therefore, % total S in clover shoots can continue to be used as an indicator of sulfur deficiency in subterranean clover in the region.
First year seed softening in three Hedysarum spp. in southern Queensland
Authors: Bell L. W. , Lloyd D. L. , Bell K. L. , Johnson B. , Teasdale K. C.
Published: December 2003

Seed softening was investigated in 41 lines of Hedysarum coronarium, 5 lines of H. carnosum and 8�lines of H. flexuosum grown at Oakey, Queensland in 2000. After testing for initial hard seed content in each line, the remaining hard seeds were placed on the soil surface at Kingsthorpe on 15 January 2001. Changes in hard seed levels over the ensuing summer-autumn seed softening period were measured. The initial hard seed content in each species ranged from 20 to 79% in H. coronarium; 31 to 79% in H. carnosum; and 54 to 83% in H. flexuosum. No significant difference in the time of seed softening between accessions or species was identified. Despite the similar timing, the extent of softening varied greatly between accessions and species. The proportion of initially hard seed that softened ranged from 54 to 95% in H. coronarium; 27 to 45% in H. carnosum; and 50 to 74% in H. flexuosum. Accessions of H. coronarium and H. flexuosum softened the greatest proportion of seed between 15 January and 22�February with reducing amounts thereafter. Accessions of H. carnosum softened less seed over this period, appearing to display a slower, more constant rate of softening. Although total hard seed levels were relatively low, there was sufficient variability in hard seed levels to provide some scope for selection of desired hard seed characteristics.
Improved slope adjustment functions for soil erosion prediction
Authors: Sheridan G. J. , So H. B. , Loch R. J.
Published: December 2003

Numerous studies in the last 60 years have investigated the relationship between land slope and soil erosion rates. However, relatively few of these have investigated slope gradient responses: (a) for steep slopes, (b)�for specific erosion processes, and (c) as a function of soil properties. Simulated rainfall was applied in the laboratory on 16 soils and 16 overburdens at 100 mm/h to 3 replicates of unconsolidated flume plots 3 m long by 0.8 m wide and 0.15 m deep at slopes of 20, 5, 10, 15, and 30% slope in that order. Sediment delivery at each slope was measured to determine the relationship between slope steepness and erosion rate. Data from this study were evaluated alongside data and existing slope adjustment functions from more than 55 other studies from the literature. Data and the literature strongly support a logistic slope adjustment function of the form S = A + B/[1 + exp (C – D sin θ)] where S is the slope adjustment factor and A, B, C, and D are coefficients that depend on the dominant detachment and transport processes. Average coefficient values when interill-only processes are active are A –1.50, B 6.51, C 0.94, and D 5.30 (r2 = 0.99). When rill erosion is also potentially active, the average slope response is greater and coefficient values are A –1.12, B 16.05, C 2.61, and D 8.32 (r2 = 0.93). The interill-only function predicts increases in sediment delivery rates from 5 to 30% slope that are approximately double the predictions based on existing published interill functions. The rill + interill function is similar to a previously reported value. The above relationships represent a mean slope response for all soils, yet the response of individual soils varied substantially from a 2.5-fold to a 50-fold increase over the range of slopes studied. The magnitude of the slope response was found to be inversely related (log–log linear) to the dispersed silt and clay content of the soil, and 3 slope adjustment equations are proposed that provide a better estimate of slope response when this soil property is known. Evaluation of the slope adjustment equations proposed in this paper using independent datasets showed that the new equations can improve soil erosion predictions.
Effect of polyacrylamide additions on infiltration and erosion of disturbed lands
Authors: Vacher C. A. , Loch R. J. , Raine S. R.
Published: December 2003

The removal of vegetation and disturbance of the soil surface due to a range of human activities results in the potential for soil structure degradation and sediment movement. Polyacrylamides have been used to improve infiltration and reduce erosion on agricultural lands. However, they are not commonly used as part of management and rehabilitation programs on land disturbed by construction or mining activities in Australia. A study was undertaken to investigate the potential for polyacrylamides to improve infiltration and reduce erosion of soil material from 3 Australian mine sites. The polyacrylamides were found to significantly (P < 0.05) increase total infiltration under rainfall, reduce surface hardness, and reduce sediment entrainment and erosion by both rainfall and overland flows. The effectiveness of the polyacrylamide was found to be related to clay content of the soil as well as the molecular weight and charge density of the polyacrylamide. The implications of these results for the management and rehabilitation of disturbed lands are discussed.
Soil sampling strategies for spatial prediction by correlation with auxiliary maps
Authors: Hengl Tomislav , Rossiter David G. , Stein Alfred
Published: December 2003

The paper evaluates spreading of observations in feature and geographical spaces as a key to sampling optimisation for spatial prediction by correlation with auxiliary maps. Although auxiliary data are commonly used for mapping soil variables, problems associated with the design of sampling strategies are rarely examined. When generalised least-squares estimation is used, the overall prediction error depends upon spreading of points in both feature and geographical space. Allocation of points uniformly over the feature space range proportionally to the distribution of predictor (equal range stratification, or ER design) is suggested as a prudent sampling strategy when the regression model between the soil and auxiliary variables is unknown. An existing 100-observation sample from a 50 by 50 km soil survey in central Croatia was used to illustrate these concepts. It was re-sampled to 25-point datasets using different experimental designs: ER and 2 response surface designs. The designs were compared for their performance in predicting soil organic matter from elevation (univariate example) using the overall prediction error as an evaluation criterion. The ER design gave overall prediction error similar to the minmax design, suggesting that it is a good compromise between accurate model estimation and minimisation of spatial autocorrelation of residuals. In addition, the ER design was extended to the multivariate case. Four predictors (elevation, temperature, wetness index, and NDVI) were transformed to standardised principal components. The sampling points were then assigned to the components in proportion to the variance explained by a principal component analysis and following the ER design. Since stratification of the feature space results in a large number of possible points in each cluster, the spreading in geographical space can also be maximised by selecting the best of several realisations.
Potassium - calcium exchange in electropositive oxisols: description of exchange sites
Authors: Alves M. E. , Lavorenti A.
Published: December 2003

Potassium–calcium exchange was studied in batch experiments carried out with 2 oxisols exhibiting positive charge balance. The experimental data were quantitatively described with the Rothmund–Kornfeld formulation of the Gaines–Thomas approach, and the permanent and variable surface negative charges were measured using the caesium-adsorption method. For both soils, no appreciable involvement of permanent negative charges was observed in the potassium–calcium exchange, which, in turn, seemed to occur solely on the variable negative charges. The preference for potassium over calcium exhibited by both soils was well described by the Rothmund–Kornfeld formulation of the Gaines–Thomas approach. It was hypothesised that the exchange sites could be divided into 2 groups with different potassium selectivities. The proportions and selectivities of these exchange site groups were estimated combining the Rothmund–Kornfeld formulation with the Dufey–Delvaux multisite model. For both soils, there was excellent agreement between experimental and modelled data and it was possible to estimate the amounts of exchange sites (cmolc/kg) presenting greater and lower potassium selectivity. The existence of variable negative charge pools more accessible to K than to Ca ions but not evenly accessible to the former was considered as a possible cause of the non-ideal behaviour of the studied soils in relation to the potassium–calcium exchange.
Effect of centrifuge conditions on water and total dissolved phosphorus extraction from soil
Authors: Toifl Melissa , Nash David , Roddick Felicity , Porter Nichola
Published: December 2003

Centrifugation of soils to extract soil water is widely used to investigate the chemical properties of soil water. However, no single set of standard operating conditions in terms of centrifuge time and speed have been defined. This study investigated centrifuge conditions on the effect of volume of soil water and phosphorus concentrations extracted to determine a set of standard operating conditions that could be used for soil water extraction in the future.Two contrasting soils that had been dried and rewet, a Ferrosol and a Dermosol, were used to investigate centrifuge speed (1000–3000 r.p.m.) and centrifuge time (5–30 min) on the extraction of soil water. Centrifuge speeds of 1000, 2000, and 3000 r.p.m. were trialed in this study giving relative centrifugal forces of 220, 881, and 1982g respectively. Increasing centrifuge time significantly increased (P < 0.001) the volume of soil water extracted. Almost twice as much soil water was extracted when the centrifuge time was increased from 5 to 30 min. Centrifuge speed was also a highly significant factor (P < 0.001) in increasing the volume of soil water extracted. The amount of soil water extracted increased by up to 15% when the centrifuge speed was increased from 1000 to 3000 r.p.m.The concentration of total dissolved phosphorus (TDP) did not change significantly with either centrifuge speed or time. The most important factor in determining the concentration of TDP was the soil type.The conditions that gave an adequate volume of soil water for analyses from field-moist soils in the shortest amount of time were a centrifuge force of 1982g and a time of 10 min.
Using radiometric data to identify æolian dust additions to topsoil of the Hillston district, western NSW
Authors: Cattle S. R. , Meakin S. N. , Ruszkowski P. , Cameron R. G.
Published: December 2003

The identification and characterisation of æolian dust additions to Australian soil profiles has been attempted using a wide range of analytical techniques. Such techniques are often reliant on specialised equipment and operator expertise, but do not necessarily yield information on the spatial distribution of deposited dust across the landscape. An airborne geophysical technique which measures naturally occurring gamma-rays may now assist in the rapid assessment of dust accumulation sites at the catchment scale. This technique, known as gamma ray spectrometry or radiometrics, assesses the potassium (K), uranium (U), and thorium (Th) contents of the Earth's surface, and may potentially distinguish æolian sediments from the underlying rock or in situ developed soil profile by their differing K, U, and/or Th-bearing mineral suites. This paper summarises a study of this technique for identifying æolian dust in topsoils of the Hillston district in western New South Wales. Using airborne with follow-up ground-based radiometric data, a variable relationship was established between large K signatures and apparent topsoil dust accumulations, which were identified as containing appreciable feldspar and illite. The previously established correlation between topsoil clay content and eTh (equivalent Th) concentration was also observed in this region, indicating that the technique may allow for rapid identification of landform features with significant clay and silt enrichment, as often occurs with dust accession. Despite the ubiquity of æolian sediments in this region, the radiometric data were moderately effective in discriminating different dune systems and may therefore represent a useful initial technique for discerning likely areas of dust accumulation in this environment. However, in areas influenced by fluvial sediments, the radiometric signatures were not necessarily indicative of the topsoil dust content.
Predicting unsaturated hydraulic conductivity functions of three Indian soils from particle size distribution data
Authors: Chaudhari S. K. , Batta R. K.
Published: December 2003

The present study compares experimental unsaturated hydraulic conductivity functions, K(θ), of 9 soils of Maharashtra State of India, 3 each in the clay, clay loam, and loam textural classes, all predicted by a particle size distribution (PSD) based model. PSD data were transformed into pore-size distribution using Aryas' modified model. Experimental K(θ) curves were determined by the horizontal infiltration method. Fifteen soils, 5 each with clay, clay loam, and loam texture, were used to evaluate the parameters of flow model (i.e. qi = crix) empirically. These parameters deviated from Hagen-Poiseuilles' equation for an idealised porous medium. An effort was made to interpret the deviation in the logc and x values in relation to changes in hydro-physical behaviour of these soils. The model includes packing density and pore tortuosity as a scaling factor, α, of the Arya-Paris model. The model predicted hydraulic conductivity of these soils quite satisfactorily with R2 values for log-transformed experimental and predicted hydraulic conductivity being 0.85, 0.97, 0.94, and 0.92 for clay, clay loam, loam, and all textures together, respectively. The root mean square residues for the soils ranged from 0.067 to 0.724, with an average of 0.428. Prediction uncertainties in intra- and inter-textural classes were attributed to differences in hydro-physical behaviour of the soils.
Cattle treading and phosphorus and sediment loss in overland flow from grazed cropland
Authors: McDowell R. W. , Drewry J. J. , Muirhead R. W. , Paton R. J.
Published: December 2003

This 1-year study investigated the effect of dairy cow treading on soil physical properties and sediment and phosphorus (P) loss via overland flow from pasture and cultivated soil used for wintering dairy cows in southern New Zealand. Treading decreased soil macroporosity and Ksat, and increased overland flow volumes. Treading increased mean suspended sediment concentration in overland flow in the cultivated + trodden treatment (2.6 g/L) compared with ungrazed pasture (0.44 g/L) and ungrazed cultivated (0.98 g/L) treatments over 2 slope positions. Following grazing in the cultivated + trodden treatment, only 25% more sediment was lost in subsequent overland flow events (2.09 and 2.63 g before and after grazing, respectively), and mean total P (TP) losses increased by >250% (from 0.7 to 2.5 mg P). Meanwhile in the cultivated but ungrazed treatment, sediment and TP loss decreased. The increased loss of sediment and P following grazing in the cultivated + trodden treatment was attributed to P from cattle dung, and soil disturbance. Consequently, wintering of animals on cultivated paddocks with forage crops increases the risk of losing much P, especially in particulate form.
Cover-runoff equations to improve simulation of runoff in pasture growth models
Authors: Owens J. S. , Silburn D. M. , McKeon G. M. , Carroll C. , Willcocks J. , deVoil R.
Published: December 2003

An Australian native pasture growth–water balance model (GRASP) was modified to include the USDA curve number runoff method from PERFECT, with the aim of providing a more general model than the regionally derived Scanlan runoff approach used previously and to improve runoff and water balance prediction. The modified model was calibrated against measured runoff and soil water data for a range of pasture treatments in Central Queensland. Optimised curve numbers were related to cover; curve number reduced from 97 for bare conditions to a minimum of 57 for 53% cover, with no difference between soils (mudstone or sandstone derived, or eroded phases) or types of cover (grass biomass and litter, or tree litter). In the modified model this equation provides feedback of effects of grazing management and tree density on cover to the water balance.Runoff prediction using the Scanlan runoff sub-model (derived for soils in the Burdekin catchment) was satisfactory (r21:1 = 0.70), indicating that soils at the Central Queensland site had similar runoff responses to those in the Burdekin. Addition of the curve number sub-model improved runoff prediction (r21:1 = 0.87). Adjusting curve number each day according to cover improved runoff predictions for low cover situations where cover varied through time, which is important in degraded pastures. Total soil water prediction was very good using the Scanlan runoff sub-model (r21:1 = 0.88) and slightly improved using the modified model (r21:1 = 0.91). Soil water in the surface layer was predicted well, giving confidence in prediction of soil evaporation.This study provides important new runoff parameter values for modelling water balance and degradation of hard setting soils under pasture. The parameters derived from this study can be used with historical climate data to provide a long-term assessment of effects of grazing management on runoff on such soils.
Influence of diazotrophic inoculations on nitrogen nutrition of rice
Authors: Das A. C. , Saha D.
Published: December 2003

An experiment was conducted in microplots (7 by 7m) to investigate the effect of 2 non-symbiotic N2-fixing bacteria [Azotobacter (strain CS1) and Azospirillum (strain CM4)] in the presence of 50 kg N/ha on the performances of the diazotrophs with respect to nitrogen accretion and its transformation in the rhizosphere soils of rice (Oryza sativa L. cv. IR-36). In most cases, a successful inoculation of the diazotrophs was recorded, with the proliferation of Azotobacter and Azospirillum, either alone or in combination, in the rhizosphere soils, and nitrogenase activity (C2H2 reduction) of the microbes was present in rice roots. The uninoculated soil receiving 100 kg N/ha recorded the highest amount of total nitrogen, non-hydrolysable organic nitrogen, available nitrogen, and hydrolysable organic nitrogen content in the rhizosphere soils, resulting in greater yield of the crop. Inoculation of the diazotrophs substantially increased different fractions of nitrogen content in the rhizosphere soils, and the increase in total nitrogen, non-hydrolysable organic nitrogen, and hydrolysable organic nitrogen was greater due to Azotobacter than either Azospirillum or a combination of Azotobacter and Azospirillum. Total and mineral nitrogen content increased at maximum tillering to flowering stages of the crop, followed by a decline at maturity, whereas, hydrolysable organic nitrogen decreased with a concomitant increase in non-hydrolysable fraction with the age of the crop.
Balancing different types of actin polymerization at distinct sites
Authors: Grevengoed Elizabeth E. , Fox Donald T. , Gates Julie , Peifer Mark
Published: December 2003

The proto-oncogenic kinase Abelson (Abl) regulates actin in response to cell signaling. Drosophila Abl is required in the nervous system, and also in epithelial cells, where it regulates adherens junction stability and actin organization. Abl acts at least in part via the actin regulator Enabled (Ena), but the mechanism by which Abl regulates Ena is unknown. We describe a novel role for Abl in early Drosophila development, where it regulates the site and type of actin structures produced. In Abl's absence, excess actin is polymerized in apical microvilli, whereas too little actin is assembled into pseudocleavage and cellularization furrows. These effects involve Ena misregulation. In abl mutants, Ena accumulates ectopically at the apical cortex where excess actin is observed, suggesting that Abl regulates Ena's subcellular localization. We also examined other actin regulators. Loss of Abl leads to changes in the localization of the Arp2/3 complex and the formin Diaphanous, and mutations in diaphanous or capping protein β enhance abl phenotypes.
A Unique Region of RILP Distinguishes It from Its Related Proteins in Its Regulation of Lysosomal Morphology and Interaction with Rab7 and Rab34
Authors: Wang Tuanlao , Wong Ka Khuen , Hong Wanjin
Published: December 2003

Rab7 and Rab34 are implicated in regulation of lysosomal morphology and they share a common effector referred to as the RILP (Rab-interacting lysosomal protein). Two novel proteins related to RILP were identified and are tentatively referred to as RLP1 and RLP2 (for RILP-like protein 1 and 2, respectively). Overexpression of RILP caused enlarged lysosomes that are positioned more centrally in the cell. However, the morphology and distribution of lysosomes were not affected by overexpression of either RLP1 or RLP2. The molecular basis for the effect of RILP on lysosomes was investigated, leading to the demonstration that a 62-residue region (amino acids 272-333) of RILP is necessary for RILP's role in regulating lysosomal morphology. Remarkably, transferring this 62-residue region unique to RILP into corresponding sites in RLP1 rendered the chimeric protein capable of regulating lysosome morphology. A correlation between the interaction with GTP-bound form of both Rab proteins and the capability of regulating lysosomes was established. These results define a unique region in RILP responsible for its specific role in regulating lysosomal morphology as well as in its interaction with Rab7 and Rab34.
Phosphorylation of High-Mobility Group Protein A2 by Nek2 Kinase during the First Meiotic Division in Mouse Spermatocytes
Authors: Di Agostino Silvia , Fedele Monica , Chieffi Paolo , Fusco Alfredo , Rossi Pellegrino , Geremia Raffaele , Sette Claudio
Published: December 2003

The mitogen-activated protein kinase (MAPK) pathway is required for maintaining the chromatin condensed during the two meiotic divisions and to avoid a second round of DNA duplication. However, molecular targets of the MAPK pathway on chromatin have not yet been identified. Here, we show that the architectural chromatin protein HMGA2 is highly expressed in male meiotic cells. Furthermore, Nek2, a serine-threonine kinase activated by the MAPK pathway in mouse pachytene spermatocytes, directly interacts with HMGA2 in vitro and in mouse spermatocytes. The interaction does not depend on the activity of Nek2 and seems constitutive. On progression from pachytene to metaphase, Nek2 is activated and HMGA2 is phosphorylated in an MAPK-dependent manner. We also show that Nek2 phosphorylates in vitro HMGA2 and that this phosphorylation decreases the affinity of HMGA2 for DNA and might favor its release from the chromatin. Indeed, we find that most HMGA2 associates with chromatin in mouse pachytene spermatocytes, whereas it is excluded from the chromatin upon the G2/M progression. Because hmga2-/- mice are sterile and show a dramatic impairment of spermatogenesis, it is possible that the functional interaction between HMGA2 and Nek2 plays a crucial role in the correct process of chromatin condensation in meiosis.
EFA6, Exchange Factor for ARF6, Regulates the Actin Cytoskeleton and Associated Tight Junction in Response to E-Cadherin Engagement
Authors: Luton Frédéric , Klein Stéphanie , Chauvin Jean-Paul , Le Bivic André , Bourgoin Sylvain , Franco Michel , Chardin Pierre
Published: December 2003

We addressed the role of EFA6, exchange factor for ARF6, during the development of epithelial cell polarity in Madin-Darby canine kidney cells. EFA6 is located primarily at the apical pole of polarized cells, including the plasma membrane. After calcium-triggered E-cadherin–mediated cell adhesion, EFA6 is recruited to a Triton X-100–insoluble fraction and its protein level is increased concomitantly to the accelerated formation of a functional tight junction (TJ). The expression of EFA6 results in the selective retention at the cell surface of the TJ protein occludin. This effect is due to EFA6 capacities to promote selectively the stability of the apical actin ring onto which the TJ is anchored, resulting in the exclusion of TJ proteins from endocytosis. Finally, our data suggest that EFA6 effects are achieved by the coordinate action of both its exchange activity and its actin remodeling C-terminal domain. We conclude that EFA6 is a signaling molecule that responds to E-cadherin engagement and is involved in TJ formation and stability.
The TWEAK Is Weak for Alcohol Screening Among Female Veterans Affairs Outpatients
Authors: Bush Kristen R. , Kivlahan Daniel R. , Davis Tania M. , Dobie Dorcas J. , Sporleder Jennifer L. , Epler Amee J. , Bradley Katharine A.
Published: December 2003

Background: The optimal brief questionnaire for alcohol screening among female patients has not yet been identified. This study compared the performance of the TWEAK (tolerance, worried, eye‐opener, amnesia, cutdown), the Alcohol Use Disorders Identification Test (AUDIT), and the AUDIT Consumption (AUDIT‐C) as self‐administered screening tests for hazardous drinking and/or active alcohol abuse or dependence among female Veterans Affairs (VA) outpatients.

Methods: Women were included in the study if they received care at VA Puget Sound and completed both a self‐administered survey containing the AUDIT and TWEAK screening questionnaires and subsequent in‐person interviews with the Alcohol Use Disorders and Associated Disabilities Interview Schedule. Sensitivities, specificities, positive and negative likelihood ratios, and areas under Receiver Operating Characteristic curves were computed for each screening questionnaire compared with two interview‐based comparison standards: (1) active DSM‐IV alcohol abuse or dependence and (2) hazardous drinking and/or active DSM‐IV alcohol abuse or dependence, the more appropriate target for primary care screening.

Results: Of 393 women who completed screening questionnaires and interviews, 39 (9.9%) met diagnostic criteria for alcohol abuse or dependence, and 89 (22.7%) met criteria for hazardous drinking or alcohol abuse or dependence. The TWEAK had relatively low sensitivities (0.62 and 0.44) but adequate specificities (0.86 and 0.89) for both interview‐based comparison standards, even at its lowest cut‐point (≥1). The AUDIT and AUDIT‐C were superior, with the following areas under the receiver operating characteristic curve for active alcohol abuse or dependence and hazardous drinking and/or active alcohol abuse or dependence, respectively: AUDIT, 0.90 [95% confidence interval (CI), 0.85–0.95] and 0.87 (95% CI, 0.84–0.91); AUDIT‐C, 0.91 (95% CI, 0.88–0.95) and 0.91 (95% CI, 0.88–0.94); and TWEAK, 0.76 (95% CI, 0.66–0.86) and 0.67 (95% CI, 0.60–0.74).

Conclusions: The TWEAK has low sensitivity as an alcohol‐screening questionnaire among female VA outpatients and should be evaluated further before being used in other female primary care populations. The three‐item AUDIT‐C was the optimal brief alcohol‐screening questionnaire in this study.
Association Between Sweet Preference and Paternal History of Alcoholism in Psychiatric and Substance Abuse Patients
Authors: Kampov‐Polevoy A. B. , Ziedonis D. , Steinberg M. L. , Pinsky I. , Krejci J. , Eick C. , Boland G. , Khalitov E. , Crews F. T.
Published: December 2003

Background:The relationship between preference for stronger sweet solutions and propensity to excessive alcohol drinking is supported by both animal and human studies. This study was designed to test the hypothesis that sweet preference is associated with the genetic risk of alcoholism as measured by a paternal history of alcoholism.

Methods:Participants were 180 patients admitted to a residential treatment program for the treatment of alcoholism, drug dependence, or psychiatric conditions. In addition to a routine medical examination, patients completed the standard sweet preference test twice (on the 9th and 24th days after admission), and the family history of alcoholism was evaluated.

Results:Sweet preference was shown to be stable over time. It was strongly associated with a paternal history of alcoholism, with family history–positive patients approximately 5 times more likely to prefer stronger sweet solutions than family history–negative subjects. Such factors as dependence on alcohol, cocaine, opiates, cannabis, other drugs (including prescription drugs), and tobacco smoking, as well as demographics (gender and age), did not significantly interfere with association between sweet preference and paternal history of alcoholism.

Conclusions:These findings provide some support for the hypothesis that preference for stronger sweet solutions is associated with a genetic predisposition to alcoholism as measured by a paternal history of alcoholism.
Identification of a Retinoid Receptor Response Element in the Human Aldehyde Dehydrogenase‐2 Promoter
Authors: Pinaire Jane , Chou Wan‐Yin , Morton Michael , You Min , Zeng Yan , Cho Won Kyoo , Galli Andrea , Everett Lynn , Breen Heather , Dumaual Natividad , Smith Jennifer R. , Crabb David
Published: December 2003

Background: The human aldehyde dehydrogenase‐2 promoter contains sites that bind members of the nuclear receptor family, and one (designated FP330–3′) is predicted to bind retinoic acid receptors.

Methods: Binding of retinoid receptors to the FP330–3′ oligonucleotide duplex and point mutations thereof was assayed using electrophoretic mobility shift assays. The function of the promoter element was determined in transfection assays.

Results: Heterodimers of retinoic acid receptor (RAR)α, β, and γ with retinoid X receptor (RXR)α bound the FP330–3′ site. Mutagenesis of the FP330–3′ site suggested that either the upstream DR‐5 or downstream DR‐1 could mediate binding of RAR/RXR. FP330–3′ oligonucleotide duplexes were not bound by in vitro translated RXR homodimers but weakly competed with a synthetic DR‐1 oligonucleotide duplex for binding by RXR. A reporter construct carrying four copies of the FP330–3′ element was induced by cotransfection of rat hepatoma cells with a construct encoding RARα, when the RAR‐specific ligand AM580 was present. Each of the three RXR isoforms α, β, and γ stimulated the expression of reporter constructs containing the FP330–3′ sites in a 9‐cis retinoic acid‐dependent fashion in cells in culture. This was confirmed in the case of RXRα using the RXR‐specific ligand methoprene.

Conclusion: The human aldehyde dehydrogenase‐2 promoter contains a retinoid response element, which may contribute to regulation of the gene.