bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal oxidation of tantalum films at various oxidation states from 300 to 700°C
Authors: Chandrasekharan Ramesh , Park Inkyu , Masel R. I. , Shannon Mark A.
Published: December 2005

This paper presents the combined use of mathematical modeling and Auger depth profiling to study and quantify the oxidation of Ta films over a wide range of temperatures. The thermal oxidation of tantalum films (∼700nm) is studied using direct measurements of species concentration by means of Auger depth profiling. The oxidation temperature range of this study extends from 300 to 700°C and the oxidation period varies from 5s to 12.5h. The Auger depth profiles revealed that the metallic film oxidizes to first form low valence oxides of Ta that progressively convert to tantalum pentoxide with increasing temperature and time. A first-order reaction diffusion model is used to quantify the diffusion of oxygen through a film that is evolving in composition. The Auger depth profiling and reaction-diffusion model are used to estimate the actual diffusivity values for oxygen in the evolving Ta/Ta-oxide thin-film matrix, rather than more conventional techniques that estimate either the initial diffusion of oxygen through a semi-infinite metal or give a depth- and time-integrated value for the diffusivity. A comparison between the actual diffusivity values estimated in this work and the depth- and time-integrated version using the same model revealed that the integrated values are higher than the actual diffusion values by greater than 300% for the temperature range tested. Moreover, these depth- and time-integrated values for diffusivity values match over the applicable temperature ranges the diffusivity values given in the literature, which are essentially integrated average values for Ta/Ta oxide matrix. Furthermore, using the Auger depth profiles, the oxide growth rates are quantified as a function of temperature and compared with available literature. The growth rate of the oxide that is observed to be logarithmic at 300°C is seen to have a parabolic growth at 500°C and then a multistep growth behavior (a combination of parabolic and linear growth) at 700°C. These growth rates and the transition from one growth type to another strongly correlate to the change in surface and film morphology and also the transition from amorphous to crystalline Ta2O5.
Numerically induced high-pass dynamics in large-eddy simulation
Authors: Geurts Bernard J. , van der Bos Fedderik
Published: December 2005

The numerical distortion of the smallest resolved-scale dynamics in large-eddy simulation may be understood in terms of the filter that is induced by the spatial discretization. At marginal subfilter resolution r=Δ∕h, with filter width Δ and grid spacing h, the character of the large-eddy closure problem is strongly influenced by the numerical method. We show that additional high-pass contributions arise from the spatial discretization. The relative importance of, on the one hand, the turbulent stresses and, on the other hand, the numerically induced contributions, is quantified for general finite differencing methods. We derive and analyze the induced filters for several popular discretization methods, including higher order central and upwind methods. The application of these induced filters to small-scale turbulent flow structures gives rise to a characteristic amplitude reduction and phase shift. Their dynamic relevance is quantified in terms of the subfilter resolution. The numerical high-pass effects are found to be negligible if the subfilter resolution is large enough (r≳4). Conversely, the numerically induced effects are comparable to, or even larger than the turbulent stresses as r=1–2.
Enhancement and limits of the photoelectrochemical response from anodic TiO2 nanotubes
Authors: Beranek R. , Tsuchiya H. , Sugishima T. , Macak J. M. , Taveira L. , Fujimoto S. , Kisch H. , Schmuki P.
Published: December 2005

Ti O 2 nanotube layers were grown on titanium by a self-organized anodic oxidation. The layers consist of arrays of individual tubes with a length of ∼2μm, a diameter of ∼100nm, and a wall thickness of ∼10nm. These layers can be annealed to an anatase structure which strongly increases the photocurrent efficiency. Moreover, the nanotube layers can—under certain conditions—exhibit a drastically enhanced photocurrent compared to compact anatase layers. These strong changes in the photoresponse are attributed to the characteristics of the space charge layer within the tube wall.
A blade-coating study using a finite-element simulation
Authors: Iliopoulos Ilias , Scriven L. E.
Published: December 2005

A computationally efficient method to describe blade-coating flows has been developed, using a Galerkin/finite-element method. Blade coating is defined by the use of a metering blade that rejects the majority of the applied continuous liquid layer on a substrate. Since the often used lubrication approximation is not valid for the region in which the flow is not rectilinear (i.e., close to the blade heel where most of the liquid is rejected), the flow field is generated by the solution of the complete Navier-Stokes equations coupled with thin inextensible elastic cylindrical shell theory for the blade deflection. The focus of this study is the elastohydrodynamic behavior of the system that is manifested through the elasticity of the blades and the non-Newtonian behavior of the coating suspensions. The approach takes into account the wear of the blade due to the impact of particles that are contained in the coating slurry. A particle tracking algorithm was developed, and upon summation of the particle impacts the erosion rate of the blades was calculated. The effect of the suspension behavior on the blade wear is explored by employing a four-parameter Carreau-type equation to describe the shear thinning behavior. To validate the model, blade samples from a pilot coater were collected at different time intervals.
Separation phenomena for gaseous mixture flowing through a long tube into vacuum
Authors: Sharipov Felix , Kalempa Denize
Published: December 2005

A gaseous mixture flow through a long tube into vacuum is considered assuming the pressure to be arbitrary at the tube entrance. Thus, the flow regime can vary from hydrodynamic at the entrance to free molecular at the tube exit. The distributions of density and concentration along the tube were obtained for the mixture helium–xenon at various values of the concentration and rarefaction at the tube entrance. It was shown that the variation of the concentration along the tube can be significant. The flow rates of both species determining the chemical composition in the down flow container were calculated. An analysis of these data shows that the chemical composition in the down flow container can be different from that in the up flow one, i.e., the separation phenomenon takes place. The results presented in the article can be used in practice to avoid the separation phenomenon or to intensify it if necessary.
Influences of substitution on electronic structures of oligofluorenes
Authors: Wu Chih-I , Lee Guan-Ru , Lin Chan-Tin , Chen Yu-Hung , Hong Yun-Hua , Liu Wei-Guan , Wu Chung-Chih , Wong Ken-Tsung , Chao Teng-Chih
Published: December 2005

The influences of substitutions on the electronic structures of oligofluorenes were systematically investigated. Electronic states of oligofluorenes with various types of C9 substitutions were studied by both ultraviolet photoemission spectroscopy and theoretical calculation. It is found that the substituents could have significant interaction with the backbone and substantially modify the electronic structures of oligofluorenes, depending on the types of substitutions. Consequently, the electronic properties that would affect the operations of electronic devices also considerably depend on the substitutions of the oligofluorenes.
Avalanche multiplication in AlGaN based solar-blind photodetectors
Authors: McClintock R. , Yasan A. , Minder K. , Kung P. , Razeghi M.
Published: December 2005

Avalanche multiplication has been observed in solar-blind AlGaN-based p-i-n photodiodes. Upon ultraviolet illumination, the optical gain shows a soft breakdown starting at relatively low electric fields, eventually saturating without showing a Geiger mode breakdown. The devices achieve a maximum optical gain of 700 at a reverse bias of 60 V. By modeling the device, it is found that this corresponds to an electric-field strength of 1.7MV∕cm.
Are fluorinated boron nitride nanotubes n-type semiconductors?
Authors: Xiang H. J. , Yang Jinlong , Hou J. G. , Zhu Qingshi
Published: December 2005

The structural and electronic properties of fluorine (F)-doped boron nitride nanotubes (BNNTs) are studied using density functional methods. Our results indicate that F atoms prefer to substitute N atoms, resulting in substantial changes of BN layers. However, F substitutional doping results in no shallow impurity states. The adsorption of F atoms on B sites is more stable than that on N sites. BNNTs with adsorbed F atoms are p-type semiconductors, suggesting the electronic conduction in F-doped multiwalled BNNTs with large conductivity observed experimentally might be of p-type due to the adsorbed F atoms, but not n-type as supposed before.
Sr vacancy segregation by heat treatment at SrTiO3 grain boundary
Authors: Mizoguchi Teruyasu , Sato Yukio , Buban James P. , Matsunaga Katsuyuki , Yamamoto Takahisa , Ikuhara Yuichi
Published: December 2005

Electron energy loss near-edge structures (ELNES) and first-principles band structure calculations were combined in order to identify native defects which are segregated by heat treatments at the vicinity of SrTiO3 grain boundary (GB). Spectral differences between the bulk and the vicinity of GB mainly appear around the second peak of OK ELNES. The spectral differences can be reproduced by calculating the theoretical OK ELNES from the first-nearest-neighbor oxygen to a Sr vacancy. It is therefore concluded that the Sr vacancies are concentrated in the vicinity of GB by the heat treatment.
Microfabricated high-performance microwave impedance biosensors for detection of aptamer-protein interactions
Authors: Löhndorf M. , Schlecht U. , Gronewold T. M. A. , Malavé A. , Tewes M.
Published: December 2005

High-frequency impedance biosensors with nanometer gaps have been prepared for the detection of biomolecular interactions such as protein-antibody and protein-aptamer binding. The sensor principle is based on electrical impedance changes measured at 1.2 GHz due to changes of the effective dielectric constant within the 68 nm gaps between two gold electrodes. As a model system, the specific binding of the blood clotting factor human thrombin with different concentrations to its ribonucleic acid (RNA) α-thrombin aptamer, as well as the immobilization process of the RNA-aptamer, have been detected in real time. By using a similar 68 nm-gap sensor blocked with bovine serum albumin and a reference sensor with 10μm electrode spacing, signal changes due to variations of the bulk dielectric constant due to buffer/analyte solutions, and unspecific binding events have been analyzed.
Electron traps and hysteresis in pentacene-based organic thin-film transistors
Authors: Gu Gong , Kane Michael G. , Doty James E. , Firester Arthur H.
Published: December 2005

In the absence of charge storage or slow polarization in the gate dielectric, the hysteresis in the current-voltage (I−V) characteristics of pentacene-based organic thin-film transistors (OTFTs) is dominated by trapped electrons in the semiconductor. The immobile previously stored negative charge requires extra holes to balance it, resulting in the early establishment of the channel and extra drain current. Inferred from I−V characteristics, this simple electrostatic model qualitatively explains memory effects in pentacene-based OTFTs, and was verified by a time domain measurement.
Time-resolved experimental study of carrier lifetime in GaN epilayers
Authors: Mickevičius J. , Shur M. S. , Fareed R. S. Qhalid , Zhang J. P. , Gaska R. , Tamulaitis G.
Published: December 2005

Time-resolved photoluminescence and light-induced transient grating measurements of GaN epilayers show that the photoluminescence decay can be described by two coupled exponential terms and that carrier mobility and lifetime in GaN epilayers are correlated within the model which accounts for nonradiative carrier recombination predominantly at dislocations. The obtained results demonstrate that migration-enhanced metalorganic chemical vapor deposition (MEMOCVD™) allows for growth of high-quality GaN epilayers on sapphire substrates with the dislocation density close to 108cm−2, carrier lifetime as long as 2 ns, and ambipolar diffusion coefficient of 2.1cm2s−1 corresponding to the hole mobility of approximately 40cm2V−1s−1.
Raman characterization of electronic properties of self-assembled GaN nanorods grown by plasma-assisted molecular-beam epitaxy
Authors: Wang D. , Tin C. -C. , Williams J. R. , Park M. , Park Y. S. , Park C. M. , Kang T. W. , Yang W. -C.
Published: December 2005

We have investigated the Raman scattering of the aligned gallium nitride (GaN) nanorods grown by plasma-assisted molecular-beam epitaxy. It was determined by Raman spectroscopy that the GaN nanorods are relatively strain free. The free carrier concentration, as well as electron mobility of the GaN nanorods, was obtained by the line shape analysis of the coupled A1longitudinal-optical(LO) phonon-plasmon mode. The electron concentration and mobility of electron obtained from line shape analysis are 3.3×1017cm−3 and 140cm2Vs, respectively. The local temperature of the nanorod sample was estimated based on the ratio of Stokes to anti-Stokes Raman peak intensity. Since the position of the LO phonon peak was found to be dependent on both the temperature and the LO phonon-plasmon coupling, it is crucial to consider the temperature effect in determining the frequency of the uncoupled LO phonon mode for the line shape analysis. The frequency of the A1(LO) mode of an undoped bulk GaN was used as a reference to determine the frequency of the uncoupled A1(LO) phonon mode of the GaN nanorods.
Time-delayed, time-resolved Langmuir probe diagnostics of pulsed plasmas
Authors: Qin Shu , McTeer Allen
Published: December 2005

A method called time-delayed, time-resolved Langmuir probe measurement is used to measure pulsed plasmas to overcome the secondary electron emission during high-voltage pulses. The plasma densities of the pulsed-mode plasma or any plasmas with secondary electron issues can be measured and analyzed by using this method.
A Rapid Method for Determining Lipid Fraction Ratios of Hard Corals under Varying Sediment and Light Regimes
Authors: Saunders Sandra M. , Radford Ben , Bourke Sarah A. , Thiele Zoe , Bech Tina , Mardon Jerome
Published: December 2005

Environmental Context.Monitoring the health of coral reef systems is vitally important to maintain and manage these threatened, complex and biodiverse natural ecosystems. Although total lipid content has been suggested as a potential index of coral condition, current methods of measurement are time consuming, technically challenging and expensive. These limitations have prohibited the application of coral lipid content as an impact-monitoring tool. The development of a practical and rapid method to determine lipid fraction ratios has the potential to lead towards an effective tool for coral reef monitoring. Abstract.Lipid content has been used as a measure of energetic status and condition in a number of fish and invertebrate species and can potentially be applied to hard corals. However, common methods for measuring lipid content are time consuming, technically challenging and expensive and these limitations have prohibited the application of lipid content as an impact-monitoring tool. To overcome these limitations, a rapid low-tech method for determining neutral to polar lipid ratios from hard coral tissue samples has been developed. This paper describes the development of the method together with a preliminary application of the technique carried out in a field study to determine whether the relative amounts of non-polar storage lipid to polar structural lipid may provide insight into the nutritional condition of individual coral colonies under differing environmental stresses. Variation in the lipid ratios of the hard coral Acropora nobilis, collected from the Montebello Islands off Western Australia, was correlated with local light and sediment regimes. This initial application of the method has demonstrated the viability of the technique, which subsequently has the potential to be applied in the analysis of a large number of samples as would be required in environmental monitoring.
Direct Measurements of New-Particle Fluxes in the Coastal Environment
Authors: Flanagan Robert J. , Geever Michael , O'Dowd Colin D.
Published: December 2005

Environmental Context.The formation of new secondary aerosol particles in the natural atmosphere is important in terms of controlling the background aerosol population, which significantly impacts on climate. The coastal zone is perhaps the strongest natural source of new secondary aerosol particles, driven by the release of biogenic vapours, which, after undergoing photochemical reactions, lead to the massive production of nucleation mode aerosols, with concentrations often reaching in excess of 106 cm−3. Quantification of this source strength is important, particularly on a regional scale, in terms of estimating the impact of aerosols on climate.
Abstract.Measurements of the flux of new secondary aerosol particles during nucleation events in the coastal environment using an eddy-correlation technique are reported for the first time. Events are divided into two types based on the prevailing wind direction. During tidal-related nucleation events, new-particle upward fluxes are typically of the order of 109–1010 particles m−2 s−1. A close correlation (r2 = 0.86) was found between total particle concentration and total (positive) flux when air masses were not affected by multiple sources. This would suggest that continuous measurements of particle number concentration at Mace Head can be translated into a flux using the resulting parameterization. It is expected that parameterizations obtained from similar data and analysis would be equally feasible at other coastal locations.
Marine Aerosol Iodine Chemistry: The Importance of Soluble Organic Iodine
Authors: Baker Alex R.
Published: December 2005

Environmental Context.Ozone concentrations play a large part in controlling the oxidation capacity of the marine boundary layer, while the production of new aerosol particles affects atmospheric radiative balance. Iodine has a complex chemistry in the marine atmosphere which impacts on both these processes. Much of this iodine chemistry, especially the chemical speciation of iodine in aerosol, is only poorly understood. This study explores the occurrence and abundance of organic forms of iodine, a topic that has received very little attention to date.
Abstract.Iodine has a complex chemistry in aerosols in the marine boundary layer (MBL), and is involved in both ozone destruction and new aerosol particle formation processes. Work in this area has focussed almost exclusively on inorganic iodine chemistry. Results from two research cruises in the Atlantic Ocean, covering wide longitude (60°W to 0°W) and latitude (50°N to 50°S) ranges indicate that soluble organic iodine species are both widespread and abundant in marine aerosol. The reactivity of these species is yet to be determined, but may influence the concentrations of some aerosol inorganic iodine species, and may also impact on MBL ozone destruction reactions.
Marine Organic Halide and Isoprene Emissions Near Mace Head, Ireland
Authors: Greenberg James P. , Guenther Alex B. , Turnipseed Andrew
Published: December 2005

Environmental Context.Atmospheric aerosols have received increasing attention, not only because they include cloud condensation nuclei, essential for precipitation, but also because of their absorption and scattering of radiation, which may affect climate. The process of aerosol formation, however, is not well understood. This paper describes measurements of the fluxes into the atmosphere of several possible biogenic precursors to primary aerosol production.
Abstract.Vertical profiles of the concentration of several alkyl halides, as well as isoprene, were made from the surface to 200 m, using a tethered balloon platform, near Mace Head, Ireland in September–October 2003. Profiles indicate a surface source of several alkyl halides. Alkyl halides have been proposed as a source of new particles in the atmosphere. Estimates of emission rates (μg m−2 h−1) were made using a flux-gradient technique for CH2Br2 (0.8), CHBr3 (6), CH2IBr (0.1), CH2I2 (0.1), and isoprene (24).
Quantification of Coastal New Ultra-Fine Particles Formation from In situ and Chamber Measurements during the BIOFLUX Campaign
Authors: Sellegri K. , Yoon Y. J. , Jennings S. G. , O'Dowd C. D. , Pirjola L. , Cautenet S. , Chen Hongwei , Hoffmann Thorsten
Published: December 2005

Environmental Context.Secondary processes leading to the production of ultra-fine particles by nucleation are still poorly understood. A fraction of new particles formed can grow into radiatively active sizes, where they can directly scatter incoming solar radiation and, if partly water soluble, contribute to the cloud condensation nuclei population. New particle formation events have been frequently observed at the Mace Head Atmospheric Research Station (western Ireland), under low tide and sunny conditions, leading to the hypothesis that new particles are formed from iodo-species emitted from macroalgae.
Abstract.New particle formation processes were studied during the BIOFLUX campaign in September 2003 and June 2004. The goals were to bring new information on the role of I2 in new particle formation from seaweeds and to quantify the amount of I2 emitted and new particles formed by a given amount of seaweed. These two goals were achieved by using a simulation chamber filled with selected species of seaweeds from the Mace Head area and flushed with particle-free atmospheric air. It was found that total particle concentrations and particles in the 3–3.4 nm size range produced in the chamber are positively correlated with gaseous I2 concentrations emitted by the seaweeds, with a typical source rate of 2800 particles cm−3 ppt(I2)−1 in the 3–3.4 nm size range. In fact, I2 and particle concentrations are also both directly positively correlated with the seaweed mass (64 300 particles cm−3 formed per kg of seaweed, and 24 ppt of I2 per kg of seaweeds) until saturation was reached for a seaweed biomass of 7.5 kg m−2. From the chamber experiments, the flux of 3–3.4 nm particles was calculated to be 2.5 × 1010 m−2 s−1 for a seaweed loading of 2.5 kg m−2 (representative of a typical seaweed field density), decreasing to 1 × 1010 m−2 s−1 for a seaweed loading of 1 kg m−2. At a seaweed loading of 2.5 kg m−2, the growth rate of particles produced in the chamber was calculated to be 1.2 nm min−1. The source rates and growth rates determined from the chamber experiments were used in conjunction with seaweed coverage in and around Mace Head to produce local emission inventories for a meso-scale dispersion model. Comparison of the resulting aerosol size distributions from the model simulations and those observed exhibited good agreement suggesting that the chamber fluxes and growth rates are consistent with those associated with the tidal emission areas in and around Mace Head.
Coastal New Particle Formation: A Review of the Current State-Of-The-Art
Authors: O'Dowd Colin D. , Hoffmann Thorsten
Published: December 2005

Environmental Context.Atmospheric aerosols play an important role in determining the earth’s radiative budget, climate change and air quality levels. Much effort has been spent on quantifying the impact of aerosols on climate change; however, the largest gap in our knowledge relates to quantifying natural aerosol systems and the new particle formation process associated with these systems. The marine aerosol system is of particular interest due to the 70% ocean coverage of the earth’s surface. Coastal new particle formation events are though to be more frequent and of stronger intensity compared with open ocean events and thus have been studied in detail to identify possible processes leading to open ocean new particle production.
Abstract.New particle formation via secondary gas-to-particle conversion processes over the oceans is one of the main mechanisms controlling the marine aerosol number population; however, despite extensive effort over the years, this phenomenon is still not well quantified. Coastal new particle formation events are more frequent than open ocean events and consequently have been studied in greater detail. This review article summarizes the recent studies into coastal new particle formation events and summarizes the linkage of these events to iodine emissions and ultimate particle formation via iodine oxide nucleation processes. The current state of knowledge may be summarized by concluding that, in general, coastal nucleation events are driven by biogenic emissions of iodine vapours that undergo rapid chemical reactions to produce condensable iodine oxides leading to nucleation and growth of new particles. The primary source of the condensable iodine vapours is thought to be molecular iodine (I2). The role of iodine oxides in open-ocean new particle production still remains an open question and is the most pressing next step to undertake.
Iodine and Halocarbon Response of Laminaria digitata to Oxidative Stress and Links to Atmospheric New Particle Production
Authors: Palmer Carl J. , Anders Thorsten L. , Carpenter Lucy J. , Küpper Frithjof C. , McFiggans Gordon B.
Published: December 2005

Environmental Context.Various organic iodine compounds (including CH3I, CH2ClI, CH2BrI, CH2I2) are present throughout the marine boundary layer as a result of their production from seaweeds, phytoplankton, and photolysis reactions occurring in seawater. In air, these compounds rapidly photolyse to give atomic I which subsequently reacts with ozone to form iodine oxide, potentially leading to perturbations of the tropospheric oxidative capacity and nucleation of atmospheric particles. Recent research has identified molecular iodine as an additional source of iodine atoms to coastal areas. Here we study the relative roles and controls of gaseous organic and molecular iodine release from the seaweed Laminaria digitata.
Abstract.Changes in the halocarbon, I2 and particle production of the brown algal kelp Laminaria digitata as a response to different chemical stresses have been investigated. Oxidative stress (caused by either exogenous hydrogen peroxide, gaseous ozone or a solution of oligoguluronates, known elicitors of oxidative stress) caused increased halocarbon and I2 production by the seaweed. The maximum I2 release was observed under exposure to O3 (at several hundred parts per billion by volume (ppbv)), whereas oligoguluronates elicited the highest release of iodine-containing halocarbons including CH2I2. Significantly greater production of I2, compared to CH2I2, was observed at atmospheric levels of ozone. Particle production was observed only when the Laminaria samples were exposed to ozone (up to 16 000 cm−3 s−1 per gram fresh weight (FW) of seaweed with a ~2 min residence time and with a total I atom flux of 1.6 × 108 cm−3 s−1 g−1 FW from photolysis of I2); passing O3-free air over the unstressed seaweed followed by secondary mixing with ozone did not result in any measurable particle formation. Our limited data indicate that ozone elicits abiotic production of I2 from Laminaria and that there is a direct relationship between the amount of I2 released and the number of particles formed. The results support the recent hypothesis that molecular iodine rather than volatile organic iodine (e.g. CH2I2) release from exposed seaweeds is the major source of coastal new particle production.
Formation Pathways and Composition of Iodine Oxide Ultra-Fine Particles
Authors: Saunders Russell W. , Plane John M. C.
Published: December 2005

Environmental Context.Bursts of ultra-fine particles (diameter < 10 nm) in the daytime coastal marine boundary layer at low tide coincide with the observation of iodine oxide radicals. The detection of iodine in the particles suggests a direct link between the biogenic emission of iodine-containing vapours and subsequent particle nucleation and growth. These coastal aerosols are therefore most likely iodine oxide polymers. However, the reaction pathways leading to the homogeneous nucleation of these particles are currently an area of uncertainty, as is their final composition. These ultra-fine particles are potentially important as a source of cloud condensation nuclei, and as a major pathway for enriching iodine in marine aerosol.
Abstract.Iodine oxide nanoparticles were generated photochemically from I2 in the presence of O3, and their morphology and composition analyzed by transmission electron microscopy (TEM). The particles exhibit fractal morphologies consistent with agglomerative coagulation, and have an O/I ratio of 2.45 ± 0.08, indicating that they are composed of I2O5. Quantum calculations show that gas-phase I2O5 could be formed by a series of exothermic reactions involving the oxidation of I2O2, I2O3 and I2O4 by O3. In order to form pure I2O5 particles, modelling calculations indicate that the rate coefficients for these reactions probably need to be faster than 6 × 10−13 cm3 molecule−1 s−1 at 295 K. Applying this model to the atmosphere shows that ultra-fine iodine oxide particles formed in the coastal marine boundary layer would then consist of I2O5.
Chemical characterisation of bog peat and dried peat of the Australian Alps
Authors: Grover S. P. P. , McKenzie B. M. , Baldock J. A. , Papst W. A.
Published: December 2005

The importance of bogs in the catchment hydrology of the Australian Alps has been long recognised but little studied. Damaged bogs are thought to be the source of dried peats now common throughout the Alps. We described the characteristics of a bog peat and a dried peat, to better understand the relationship between the two. Standard chemical properties of peat were measured: pH, loss on ignition, gravimetric contents of carbon and nitrogen, and electrical conductivity. We also measured the concentrations of total and plant-available elements, and the chemical composition of the organic carbon, leading to a measure of the extent of decomposition. The results suggest that this is a typical Sphagnum bog peat—low pH, high carbon content—and the distribution of carbon groups and other elements reflect the stable water source of this groundwater-fed Sphagnum bog. The properties of the dried peat were most similar to the catotelm (lower layer) of the bog peat. This resemblance, combined with decades of field observations, indicates that dried peat may form from the catotelm of bog peat, after the acrotelm (upper layer) dries and erodes. These results have implications for the management of Alps catchments, and further studies are needed to ascertain the hydrologic and carbon cycling roles of organic soils in the Australian Alps.
Handling the water content discontinuity at the interface between layered soils within a numerical scheme
Authors: Matthews C. J. , Cook F. J. , Knight J. H. , Braddock R. D.
Published: December 2005

In general, the water content (θ) form of Richards’ equation is not used when modeling water flow through layered soil since θ is discontinuous across soil layers. Within the literature, there have been some examples of models developed for layered soils using the θ-form of Richards’ equation. However, these models usually rely on an approximation of the discontinuity at the soil layer interface. For the first time, we will develop an iterative scheme based on Newton’s method, to explicitly solve for θ at the interface between 2 soils within a numerical scheme. The numerical scheme used here is the Method of Lines (MoL); however, the principles of the iterative solution could be used in other numerical techniques. It will be shown that the iterative scheme is highly effective, converging within 1 to 2 iterations. To ensure the convergence behaviour holds, the numerical scheme will be tested on a fine-over-coarse and a coarse-over-fine soil with highly contrasting soil properties. For each case, the contrast between the soil types will be controlled artificially to extend and decrease the extent of the θ discontinuity. In addition, the numerical solution will be compared against a steady-state analytical solution and a numerical solution from the literature.
Soil P in a forested seabird colony: inventories, parent material contributions, and N : P stoichiometry
Authors: Hawke David J.
Published: December 2005

Guano from breeding seabirds provides a large external source of nutrients to the soils of breeding colonies. However, little is known of guano P retention relative to N or the relative importance of guano and soil parent material as P sources. Soil profile N and P inventories (0–0.60 m, n = 4; 0–0.36 m, n = 1) and guano N and P concentrations were measured at a Westland petrel colony, and the parent material contributions of P were calculated using Ca, Al, Fe, Ti, and Zr as reference elements. Median inventories (0–0.60 m) were 1.49 kg N/m2 and 332 × 10–3 kg P/m2, the N result being similar to that from a seabird colony on peat soil where N retention was very low. Calculated parent material contributions were smallest (32–66% of soil P) when based on Ca and largest (47–102% of soil P) when based on Zr. Contributions were similar for Al, Fe, and Ti; Al (41–87% soil P) was selected for subsequent calculations. Regardless of the reference element, parent material therefore contributed a large part of soil P. Phosphorus in excess of parent material supply (Pexcess) was significantly correlated with soil C, implying that guano P is held primarily in organic form. The median soil N : P molar ratios were 9.6 : 1 based on total P and 11.2 : 1 based on Pexcess, compared with ratios for Westland petrel guano of 4.1 : 1 (when birds were consuming fisheries waste) and 16.4 : 1 (when fisheries waste was replaced by fish). The similarity between soil and guano N : P ratios implies that both N and P are lost from soil at similar rates, although volatilisation of N would enrich soil drainage water in P. Calculations using guano deposition rates from the literature yielded P residence times of 4–15 years (Pexcess) and 11–41 years (total P), consistent with a highly dynamic soil system.
Beyond the olfactory bulb: An odotopic map in the forebrain
Authors: Nikonov Alexander A. , Finger Thomas E. , Caprio John
Published: December 2005

We report electrophysiological evidence that a simple odotopy, the spatial mapping of different odorants, is maintained above the level of the olfactory bulb (OB). Three classes of biologically relevant odorants for fish are processed in distinct regions of the forebrain (FB) in the channel catfish. Feeding cues, mainly amino acids and nucleotides, are represented in lateral, pallial portions of the FB, equivalent to the olfactory cortex of amniote vertebrates, whereas social signals mediated by bile salts are represented in medial FB centers, possibly homologous to portions of the amygdala. As in the OB, the different odorant classes map onto different territories; however, the response properties of units of the olfactory areas of the FB do not simply mirror those of the OB. For some units, distinctive response properties emerged, because the FB is the first center where odors subserving a common behavioral function (i.e., food function) converge.
Auditory-visual fusion in speech perception in children with cochlear implants
Authors: Schorr Efrat A. , Fox Nathan A. , van Wassenhove Virginie , Knudsen Eric I.
Published: December 2005

Speech, for most of us, is a bimodal percept whenever we both hear the voice and see the lip movements of a speaker. Children who are born deaf never have this bimodal experience. We tested children who had been deaf from birth and who subsequently received cochlear implants for their ability to fuse the auditory information provided by their implants with visual information about lip movements for speech perception. For most of the children with implants (92%), perception was dominated by vision when visual and auditory speech information conflicted. For some, bimodal fusion was strong and consistent, demonstrating a remarkable plasticity in their ability to form auditory-visual associations despite the atypical stimulation provided by implants. The likelihood of consistent auditory-visual fusion declined with age at implant beyond 2.5 years, suggesting a sensitive period for bimodal integration in speech perception.
Meat consumption reduces the risk of nutritional rickets and osteomalacia
Authors: Dunnigan Matthew G. , Henderson Janet B. , Hole David J. , Mawer E. Barbara , Berry Jacqueline L.
Published: December 2005

Endogenous vitamin D deficiency (low serum 25(OH)D3) is a necessary but insufficient requirement for the genesis of vitamin D-deficiency rickets and osteomalacia. The magnitude of the independent contributions of dietary factors to rachitic and osteomalacic risk remains uncertain. We reanalysed two weighed dietary surveys of sixty-two cases of rickets and osteomalacia and 113 normal women and children. The independent associations of four dietary variables (vitamin D, Ca, fibre and meat intakes) and daylight outdoor exposure with rachitic and osteomalacic relative risk were estimated by multivariate logistic regression. Meat and fibre intakes showed significant negative and positive associations respectively with rachitic and osteomalacic relative risk (RR; zero meat intake: RR 29·8 (95 % CI 4·96, 181),P<0·001; fibre intake: RR 1·53 (95 % CI 1·01, 2·32),P+0·043). The negative association of meat intakes with rachitic and osteomalacic relative risk was curvilinear; relative risk did not fall further at meat intakes above 60 g daily. Daylight outdoor exposure showed a significant negative association with combined relative risk (RR 0·33 (95 % CI 0·17, 0·66),P<0·001). Operation of the meat and fibre risk factors was related to sex, age and dietary pattern (omnivore/lactovegetarian), mainly determined by religious affiliation. The mechanism by which meat reduces rachitic and osteomalacic risk is uncertain and appears independent of revised estimates of meat vitamin D content. The meat content of the omnivore Western diet may explain its high degree of protection against nutritional rickets and osteomalacia from infancy to old age in the presence of endogenous vitamin D deficiency.
The effect of selenium on thyroid status in a population with marginal selenium and iodine status
Authors: Thomson Christine D. , McLachlan Sarah K. , Grant Andrea M. , Paterson Elaine , Lillico Anna J.
Published: December 2005

The effects of Se on thyroid metabolism in a New Zealand population are investigated, including (a) the relationship between Se and thyroid status, and (b) the effect of Se supplementation on thyroid status. The data used come from two cross-sectional studies of Se, I, thyroid hormones and thyroid volume (studies 1 and 4), and three Se intervention studies in which thyroid hormones, Se and glutathione peroxidase (GPx) activities were measured (studies 2, 3 and 5). There were no significant correlations between Se status and measures of thyroid status after controlling for sex at baseline or after supplementation in any of the studies. When data from study 4 were divided into two groups according to plasma Se, plasma thyroxine (T4) was lower in males with higher plasma Se levels (P=0·009). Se supplementation increased plasma Se and GPx activity, but produced only small changes in plasma T4and triiodothyronine (T3):T4ratio. In study 2, there was a significant reduction in plasma T4(P=0·0045). In studies 3 and 5 there were small decreases in plasma T4and a small increase in the T3:T4ratio, which were not significantly different from placebo groups. Lack of significant associations between plasma Se and thyroid status, and only small changes in T4suggest that Se status in New Zealand is close to adequate for the optimal function of deiodinases. Adequate plasma Se may be approximately 0·82–0·90 μmol/l, compared with 1·00–1·14 μmol/l for maximal GPx activities.
Lactation decreases pancreatic lipase mRNA level in the rat
Authors: Birk Ruth Z. , Regan Karen S. , Brannon Patsy M.
Published: December 2005

Lactation alters maternal metabolism and increases food intake in rats to support milk production. Pancreatic lipase (PL) is primarily responsible for fat digestion in adults and is regulated by dietary fat. The present research determined the regulation of PL by lactation and dietary fat. In Expt 1, eighteen Sprague–Dawley dams and twelve age-matched virgins (controls) were fed a low-fat diet (LF; 11 % energy as safflower oil) for 7–63 d. At postpartum (day 0), peak lactation (day 15) and post-lactation (day 56) and after 7 d in virgins, the pancreas was removed for mRNA and enzyme analyses. In Expt 2, thirty-six Sprague–Dawley dams were fed LF until day 9 postpartum when dams were divided into three groups of twelve; one continued to be fed LF, one was fed a moderate-fat diet (MF; 40 % energy as safflower oil); and one was fed a high-fat diet (HF; 67 % energy as safflower oil) diet. At peak lactation (day 15) and post-lactation (day 56), the pancreas was removed for mRNA and enzyme analyses. Expt 1 revealed that lactation and post-lactation significantly (P<0·001) decreased PL mRNA (67 % and 76 %, respectively), but only post-lactation decreased PL activity. Increased dietary fat in Expt 2 significantly increased PL mRNA (LF<MF<HF,P<0·001) and PL activity (LF<MF=HF,P<0·02) in both lactation and post-lactation. In summary, lactation and post-lactation decreased PL mRNA significantly even though dietary fat still regulated PL activity and mRNA in lactation and post-lactation.
Diet-related variation in cellular retinol-binding protein type II gene expression in rat jejunum
Authors: Suruga Kazuhito , Kitagawa Masaaki , Yasutake Hiromitsu , Takase Sachiko , Goda Toshinao
Published: December 2005

Cellular retinol-binding protein type II (CRBPII) is involved in the transport of vitamin A and its metabolism in the small intestine. In the present study, we demonstrated diet-related variations in CRBPII expression in rat jejunum. The CRBPII protein and mRNA levels increased in parallel after the start of feeding period regardless of whether the feeding period was restricted to the hours of darkness or of light. In addition, this variation was observed in the rats fed high-fat diet or low-fat diets, but not in those fed a fat-free diet or in fasted rats. A similar diet-induced variation was seen in the mRNA of liver-type fatty acid-binding protein in rat jejunum. In the transient transfection experiment, unsaturated fatty acid increased rat CRBPII gene promoter activity via the PPARα/retinoid X receptor-α heterodimer. Taken together, these results suggest that the diet-related variation in CRBPII expression in rat jejunum may be brought about by the transcriptional induction of CRBPII gene expression mainly triggered by dietary fatty acids.
Dietary fibre-rich oat-based products affect serum lipids, microbiota, formation of short-chain fatty acids and steroids in rats
Authors: Drzikova Barbora , Dongowski Gerhard , Gebhardt Erich
Published: December 2005

Wistar rats (ten per group) were fed either an oat-free control diet or a dietary fibre-rich test diet containing 500 g oat-based products/kg for 6 weeks. The oat-based products, containing 4–128 g/kg resistant starch, 30–92 g/kg β-glucan and 122–304 g/kg total dietary fibre, were oat flour extrudate, flour/Novelose (commercial resistant starch) extrudate (80:20 w/w), oat bran, bran/Novelose extrudate (80:20 w/w) and autoclaved oat flour. Serum total cholesterol decreased in the groups fed flour, flour/Novelose and bran/Novelose (P<0·05). In most of the test groups, count numbers of bifidobacteria were higher (P<0·001) and of coliforms were lower (P<0·05). The mass of the caecum walls and contents was greater in groups fed Novelose- and bran-containing diets (P<0·005). In all the test groups, pH values were lower in the intestinal contents (P<0·001), and caecal concentrations of acetate (P<0·001), propionate (P<0·05), butyrate (P<0·005) and total SCFA (P<0·001) were higher. The lowest concentrations of steroids were found in rats fed the autoclaved flour. In the other test groups, more bile acids appeared in the caecal (P<0·001) and colonic contents (P<0·005), as well as in the faeces, at week 6 (P<0·001). The highest bile acid excretion was found after feeding bran-containing diets. In the intestinal contents of all the test groups, more primary bile acids (P<0·001) appeared than in the control group. The excretion of steroids increased within the experimental period. Using extrusion technology, dietary fibre-rich oat-based products, which have beneficial physiological effects in rats, can be produced. Oat flour and bran are excellent sources for the preparation of directly edible oat products. Their nutritional properties can be further improved by the addition of resistant starch.
Effect of apolipoprotein E genotype on vitamin K status in healthy older adults from China and the UK
Authors: Yan Liya , Zhou Bo. , Nigdikar Shailja , Wang Xiaohong , Bennett Janet , Prentice Ann
Published: December 2005

The vitamin K concentration in the circulation and the availability of vitamin K to bone may be affected by factors influencing lipoprotein metabolism, such as apoE genotype. The relationships between markers of vitamin K status, bone mineral content and apoE genotype were studied in healthy older men and women aged 60–83 years, 177 from Shenyang, China, and 132 from Cambridge, UK. Fasting plasma was analysed for vitamin K1, triacylglycerol, total osteocalcin, undercarboxylated osteocalcin (ucOC) and apoE genotype. Hip bone mineral content was measured using dual-energy X-ray absorptiometry. Subjects were grouped according to apoE genotype as E2/3, E3/3 and [E3/4+E4/4]. The mean plasma vitamin K1concentration of the three genotype groups was significantly higher and the percentage ucOC was lower in the Chinese than in the British subjects (P<0·01). A higher vitamin K1concentration was found in subjects with [E3/4+E4/4] than those with either E2/3 or E3/3 in Cambridge (32·2 (SE 14·6) %,P=0·03; 24·6 (SE 10·7) %,P=0·02). Similar trends were observed although were not statistically significant in Shenyang (26·5 (18·9) %,P=0·16; 23·1 (13·0) %,P=0·08). Subjects with [E3/4+E4/4] had a lower percentage ucOC (total osteocalcin adjusted) than did those with either E2/3 or E3/3 in Shenyang (65·1 (27·2) %,P=0·02; 49·6 (19·9) %,P=0·01 respectively) but not in Cambridge. This study demonstrates that a superior vitamin K status is associated with the apoE4 genotype in healthy older individuals from China and the UK.