bluuebunny/crossref_metadata_2025 huggingface dataset:
A Crystalline Si3N4/Amorphous Si3N4 Composite
Authors: Reimanis Ivar E. , Petrovic John J. , Suematsu Hisayuki , Mitchell Terrence E.
Published: May 2005

A composite consisting of elongated α‐Si3N4 crystallites (5–50 (Am in diameter) embedded in an amorphous Si3N4 matrix was synthesized by chemical vapor deposition. The hardness and indentation fracture toughness of the amorphous matrix and of the composite have been evaluated at temperatures from ambient to 1200°C. It was found that the crystallites have relatively little influence on the hardness and indentation fracture toughness when the surrounding matrix is amorphous. However, a 1400°C heat treatment of the material results in a matrix consisting of small crystals (100 nm in diameter) surrounded by carbon‐containing regions which appear to be amorphous in the TEM; TEM and EELS in nearby triple points revealed the presence of amorphous carbon. After heat treatment, the indentation fracture toughness at ambient and at 1200°C is increased due to extensive microcracking. The Vickers hardness at 1200°C also increased significantly as a result of the heat treatment. The relationship between the mechanical properties and the microstructure is discussed.
Thermal Analysis of 3‐mol%‐Yttria‐Stabilized Tetragonal Zirconia Powder Doped with Copper Oxide
Authors: Seidensticker John R. , Mayo Merrilea J.
Published: May 2005

Thermal analysis was performed upon 3‐mol%‐yttria‐stabilized tetragonal zirconia polycrystals (3Y‐TZP) which had been doped with CuO using an aqueous adsorption technique. Cyclic differential thermal analysis (DTA) scans indicated that the CuO present on the powder surfaces first transforms to Cu2O and then melts. The molten Cu2O then reacts with yttria at the powder surfaces to form a new phase containing Y, Cu, and O. Because Y takes time to diffuse to the particle surfaces, the apparent melting point of this new phase appears at higher temperatures in initial DTA scans than in subsequent scans. Vaporization of the molten copper‐oxide‐rich phase at the temperatures studied causes a gradual shift in composition from Y2Cu4O5 to the less copper‐rich Y2Cu2O5 phase. The presence of the Y2Cu2O5 phase in CuO‐doped 3Y‐TZP allows for previous sintering and superplasticity results to be explained.
Sol‐Gel Synthesis of Fine Gd2CuO4 Particles: Influence of Synthesis Variables
Authors: Mahía José , Vázquez‐Vázquez Carlos , Basadre‐Pampin M. Isabel , Mira Jorge , Rivas José , López‐Quintela M. Arturo , Oseroff Saul B.
Published: May 2005

Fine particles of Gd2CuO4 were prepared by a sol‐gel reaction of an aqueous solution of metal nitrates in the presence of urea, which leads to high‐homogeneity polycrystalline powders of Gd2CuO4. We have studied the synthesis conditions, demonstrating the existence of a relationship between the calcination temperature and the heating time needed to attain the pure phase. Gd2CuO4 was obtained at temperatures of the order of 650°C, lower than temperatures employed in the conventional ceramic technique. The influence of the [urea]/[salts] ratio and an excess of Cu(II) in the starting solution was also studied and discussed. X‐ray powder diffraction, inductively coupled plasma atomic emission spectroscopy (ICPAES), photon correlation spectroscopy (PCS), and transmission electron microscopy (TEM) were used to characterize the Gd2CuO4 samples obtained.
Electrostrictive Coefficients of 0.9Pb(Mg1/3Nb2/3)O3‐0.1PbTiO3 Relaxor Ferroelectric Ceramics in the Ferroelectricity‐Dominated Temperature Range
Authors: Park Jae‐Hwan , Kim Byung‐Kook , Park Soon Ja
Published: May 2005

Polarization and strain induced by unipolar electric fields (Puni, Suni) as well as those induced by bipolar electric fields (Pbi, Sbi) were measured in 0.9Pb(Mgl/3Nb2/3)O3‐0.1PbTiO3 relaxor ferroelectric ceramics in the temperature range of −50°‐90°C to observe the phase transition in this region and calculate the electrostrictive coefficients from the purely electric‐field‐induced polarization and strain. By considering both the electrostrictive component (Funi, Suni) and the piezoelectric component (Pr, Sr), it is shown quantitatively how the transition occurs from pure electrostrictive to partially piezoelectric properties across the phase transition range. Puni represents unmixed electric‐field‐induced polarization.

while Fbi represents the summation of Puni and Pr. Similarly, Suni represents unmixed electric‐field‐induced strain, while Sbi represents the summation of Suni and Sr. The effective electrostrictive coefficient (Qeff) is calculated even in the ferroelectric region far below the phase transition temperature using Suni and Puni which are purely electric field induced. Qeff significantly increases as the temperature decreases below the phase transition temperature, which was attributed to the decreased rattling space of B‐site atoms.
Sol‐Gel Synthesis of Lithium Aluminate
Authors: Valenzuela Miguel A. , Jimenez‐Becerril Jaime , Bosch Pedro , Bulbulian Silvia , Lara Victor H.
Published: May 2005

LiAlO2 was prepared by two sol‐gel methods using simultaneous hydrolysis of the reagents: aluminum sec‐butoxide/ lithium methoxide and aluminum sec‐butoxide/LiOH. The resulting ceramic powders were compared with those prepared by two conventional methods (i.e., solid‐state fusion and peroxide). The sol‐gel method provided powders with a very high γ‐LiAlO2 content after calcining at temperatures as low as 700°C when LiOH was used. The solids were characterized by AAS, DTA, TGA, XRD, and SEM.
Synthesis of MgAl2O4 Whiskers by an Oxidation‐Reduction Reaction
Authors: Hashimoto Shinobu , Yamaguchi Akira
Published: May 2005

Magnesium aluminate whiskers were synthesized by an oxidation—reduction reaction between MgO, C, and Al in a CO and CO2 atmosphere. The oxygen partial pressure suitable for MgAl2O4 whisker growth ranged from 10−12.1 to 10−11.5 MPa. The average whisker diameter and length formed at 1500°C for 8 h were ∼3.1 μm and ∼4 mm, respectively. The whiskers grew in the [111] direction.
High‐Temperature Corrosion Resistance of Chemically Vapor Deposited Silicon Carbide against Hydrogen Chloride and Hydrogen Gaseous Environments
Authors: Kim Dong‐Joo , Choi Doo‐Jin
Published: May 2005

Silicon carbide (SiC) films deposited by chemical vapor deposition were exposed to hydrogen chloride and hydrogen gaseous mixture (5% HCl and 95% H2) at 1200°C with a total pressure of 101 kPa in order to investigate their durability against the corrosive gas. Corrosion resistance against the HCl and H2 gaseous mixture was related to the micro‐structure and preferred orientation of the SiC films, which depend on the deposition conditions. The stratified structure with a small crystallite had higher corrosion resistance than the faceted columnar structure, and (111) oriented films had higher resistance than (220) oriented films.
Transparent Cr4+‐Doped YAG Ceramics for Tunable Lasers
Authors: Ikesue Akio , Yoshida Kunio , Kamata Kiichiro
Published: May 2005

Transparent Cr4+:YAG (Y3AlSO12) ceramics doped with Ca and Mg as counterions and SiO2 as a sintering aid were fabricated by a solid‐state reaction method using high‐purity powders of Al2O3, Y2O3, and Cr2O3. The mixed powder compacts were sintered at 1750°C for 10 h in oxygen, or 1750°C for 10 h under vacuum, and then annealed at 1400°C for 10 h in oxygen. Cr‐doped YAG ceramics sintered in oxygen had a brown color and characteristic absorption by Cr4+ ions, whereas these YAG ceramics sintered under different conditions (vacuum + oxygen) had a green color and absorption at ∼590 and 430 nm by Cr3+ ions. The absorption behavior of YAG ceramics sintered in oxygen was almost equivalent to that of Cr4+:YAG single crystals fabricated by the Czochralski method.
Aqueous Emulsion Acrylic Binders for Low‐Foaming Ceramic Slips
Authors: Tang Xun , Donate Antonio T.
Published: May 2005

Experiments are reported to fundamentally understand foaming in ceramic slips. Adsorption of two different types of surfactants, one anionic and another nonionic, onto alumina powders was studied. The most significant observation was that while the anionic surfactant strongly adsorbed onto alumina powders, the nonionic surfactant had essentially no adsorption. A model polymer based on the anionic surfactant was synthesized and compared with a similar polymer prepared with the nonionic surfactant. The comparison demonstrated that while the model polymer foamed severely in its neat form, it produced a very low‐foaming ceramic slip when formulated with alumina powder because the surface‐active agents in the binder strongly adsorbed onto the powder. Based on these fundamental understandings, a series of aqueous emulsion acrylic Duramax binders were developed. The influence of these binders on foaming in alumina slips is reported.
Oxidation of TiB2 Powders below 900°C
Authors: Kulpa Alina , Troczynski Tom
Published: May 2005

Oxidation studies have been performed on titanium dibor‐ide (TiB2) powders, from room temperature up to 900°C. The studies were performed at low partial pressures of oxygen, at 10 and 0. 05 ppm of O2 in argon, simulating furnace atmosphere with flowing neutral gas of medium and high purity, and in air. It has been found that titanium borate (TiBO3) is formed in these processes. It has also been revealed that the oxidation process starts below 400°C and is reversible in this low temperature range from 100° to 400°C.
Oxygen Vacancy Motion in Perovskite Oxides
Authors: Warren William L. , Vanheusden Karel , Dimos Duane , Pike Gordon E. , Tuttle Bruce A.
Published: May 2005

Using electron paramagnetic resonance, the motion of oxygen vacancies within the oxygen octahedron in perovskite BaTiO3 is observed via the alignment of oxygen vacancyrelated defect dipoles induced by bias/heat combinations. The vacancy motion is found to have an activation energy of 0.91 eV, in excellent agreement with that predicted. It is found that the onset of resistance degradation is also concurrent with oxygen vacancy motion. This result spectroscopically demonstrates that oxygen vacancy migration in the lattice is likely responsible for the observed degradation.
Surface Properties of Ceramic Laminates Fabricated by Die Pressing
Authors: Wang Hui , Hu Xiaozhi
Published: May 2005

The simple die‐pressing technique has been used to fabricate thick‐layer zirconia/alumina ceramic laminates in the forms of film/substrate and multilayer systems. A “vibration sieve” method is used to achieve uniform layer thickness. In order to suppress surface crack initiation and propagation, the laminates are designed to retain residual compressive stresses in the surface layers. As a result, the surface fracture/fatigue resistance has been significantly improved, and the microhardness of the surface layer has also been increased to a certain degree.
Surface Modification of Silicon Nitride Powder with Aluminum
Authors: Han K. R. , Lim C. S. , Hong M. J. , Choi S. K. , Kwon S. H.
Published: May 2005

Surface modification of Si3N4 with alumina was tried. It was achieved by simply mixing Si3N4 powder with an alumina sol up to ∼2 wt% as alumina in an aqueous medium, dried, and followed by calcination at 400°C for 1 h. A TEM micrograph showed a coating layer of ∼15 nm thickness. The isoelectric point of the modified Si3N4 powder with porous alumina was at pH 7.8, which is different from 5.8 and 8.6 for Si3N4 and amorphous alumina, respectively.
Barium Holmium Zirconate, A New Perovskite Oxide: II, Synthesis as Nanoparticles through a Modified Combustion Process
Authors: Jose Rajan , John Asha Mary , Divakar Ramachandran , Koshy Jacob
Published: May 2005

Nanoparticles of barium holmium zirconate, a new complex perovskite ceramic oxide, has been synthesized using a modified self‐propagating combustion process. The solid combustion products obtained were characterized by X‐ray diffraction (XRD), electron diffraction, differential thermal analysis, thermogravimetric analysis, infrared spectroscopy, particle size analysis, surface area determination, and high‐resolution transmission electron microscopy. The XRD and electron diffraction studies have shown that the as‐prepared powder is phase pure Ba2HoZrO5.5 and has a complex cubic perovskite (A2BB′O6) structure with a lattice constant a= 8.428 Å. The transmission electron microscopic investigation has shown that the particle size of the as‐prepared powder was in the range 4–16 nm with a mean grain size of 8.2 nm. The nanoparticles of Ba2HoZrO5.5 obtained by the present method could be sintered to 98% theoretical density at 1500°C.
Effect of the Cobalt Ion and Polyethyleneimine Adsorption on the Surface Forces between Tungsten Oxide and Cobalt Oxide in Aqueous Media
Authors: Andersson Karin M. , Bergström Lennart
Published: May 2005

We used the colloidal probe technique with atomic force microscopy to study the interactions between a tungsten oxide sphere, WO3, and flat oxidized tungsten and cobalt surfaces in aqueous electrolytes. We investigated the effects of adsorption of cobalt ions to tungsten oxide surfaces and adsorption of polyethyleneimine (PEI). Low concentrations of cobalt ions added to a WO3 system resulted in extended hydration forces and a lowering of the absolute value of the surface potential. PEI was shown to adsorb to the WO3 surfaces and induce an electrosteric repulsion in both the symmetric (WO3–WO3) and asymmetric (WO3–CoOOH) systems. The possible complexation of cobalt ions with PEI does not significantly influence the thickness of the adsorbed layer.
Mechanical Activation of the Decomposition and Sintering of Kyanite
Authors: Aguilar‐Santillán Joaquín , Cuenca‐Alvarez Ricardo , Balmori‐Ramírez Heberto , Bradt Richard C.
Published: May 2005

The influence of attrition milling on the thermal decomposition of kyanite (Al2O3·SiO2) to mullite (3Al2O3·2SiO2) and SiO2, and its subsequent sintering, was studied. A commercial kyanite was attrition‐milled for times up to 12 h. Dilatometry confirmed that as‐received unmilled kyanite decomposes between 1300° and 1435°C. The decomposition reaction is slow initially and accelerates during the later stages until about one‐half of the decomposition occurs in the last 35°C. For the attrition‐milled kyanite, the onset decomposition temperature decreases, the transformation temperature interval is reduced, and both the decomposition reaction and subsequent sintering are accelerated. A dense microstructure of fine equiaxed mullite grains in the 1 μm size range, evenly dispersed in a glassy matrix, is obtained by sintering the attrition‐milled kyanites. These results are explained in terms of the energy accumulated during attrition milling, a reduction of the milled kyanite particle size, and the presence of a liquid phase during sintering.
Transparent Alumina with Submicrometer Grains by Float Packing and Sintering
Authors: Godlinski Dirk , Kuntz Meinhard , Grathwohl Georg
Published: May 2005

Commercially available α‐alumina powder with high‐purity, submicrometer particle size and narrow particle‐size distribution is used as starting material to prepare dense ceramic parts with transparent properties. The powder is dispersed and stabilized in a water‐based suspension. Controlled consolidation and drying by float packing leads to homogeneous green compacts, which can be densified without additives by sintering in air at 1275°C to transparency, while the mean grain size remains at 0.4 μm. The in‐line transmittance for wavelengths of 300–450 nm is comparable to commercial polycrystalline alumina tubes for lighting technologies, whose grain sizes are larger by a factor of 40.
Model Apatite Systems for the Stabilization of Toxic Metals: I, Calcium Lead Vanadate
Authors: Dong Zhili , White Timothy J. , Wei Bing , Laursen Karin
Published: May 2005

Apatites of composition (Ca10−xPbx)(VO4)6F2 with 0 ≤x≤ 9 were synthesized by sintering in air at 800°C the oxides of calcium, lead, and vanadium that were mixed with calcium fluoride. Variations in lattice parameters, grain size, and durability were monitored as a function of composition. The expected dilation in unit cell edges with increasing replacement of calcium (IR = 1.26 Å) by lead (IR = 1.45 Å) was observed. The a cell edge (in angstroms) varied linearly (0.0458 x+ 9.7068) with x, while c followed the binomial function 0.0018x2+ 0.0279x+ 7.0118. Average grain sizes increased from approximately 5 μm (x= 0) to 25 μm (x= 9) as grain growth was enhanced due to incipient melting of the lead‐rich compositions. For x < 5 the materials were biphasic. Overall dissolution, as determined by the toxicity characteristic leaching procedure (TCLP), was faster in calcium‐rich apatites. Etching of well‐crystallized apatite grains occurred preferentially on {1010} faces. These leach losses were augmented through the more rapid removal of cryptocrystalline regions and intergranular thin films.
Crystal Morphology of Mesoporous Silica Thin Films Synthesized by the Spin‐Coating Method Using PEO–PPO–PEO Triblock Copolymer
Authors: Park Gyeong‐Su , Ahn Chi‐Won , Kim Mahn‐Won
Published: May 2005

Mesoporous thin films on Si substrates with thicknesses of about 460–610 nm have been synthesized by the spin‐coating method using a Pluronic EO77PO29EO77 (F68), EO104PO39EO104 (F88), and EO133PO50EO133 (F108) triblock copolymer system. The triblock copolymers were preserved within the synthesized mesoporous thin films. Transmission electron microscopy (TEM) characterization of these films clearly demonstrates that long‐range mesostructural ordering strongly depends on the molecular weight of the poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide) (PEO–PPO–PEO) triblock copolymer, with lower molecular weight producing higher degrees of order. Plane and cross‐sectional high‐resolution TEM studies coupled with X‐ray diffraction (XRD) analysis also show that highly ordered F68 mesoporous silica thin film forms a cubic structure with a lattice spacing a= 6.70 nm.
Electrostatic and Entropic Interactions between Parallel Interfaces Separated by a Glassy Film
Authors: Johnston Karen , Finnis Michael W.
Published: May 2005

A simple classical density functional model is set up to describe the electrostatic and entropic interactions between two parallel planar charged interfaces separated by a thin film of a phase (the glass) containing a distribution of charged ions. The total charge in the system is zero. Three cases are treated: (1) the two interfaces carry a fixed surface charge; (2) the first interface carries a fixed surface charge, simulating a ceramic, while the second is held at zero potential, simulating a metal; and (3) both interfaces are held at zero potential. A discretized form of the nonlinear Poisson–Boltzmann equation is derived and solved by a Newton–Raphson method. The continuum approximation is compared with a model in which the ions are only allowed to occupy discrete planes. The effect of correlation among the ions is included within the local density approximation. Inserting parameters appropriate to the copper–alumina interface, we find that the attractive image force between the ceramic and metal dominates the entropic (DLVO) repulsive force in the 1–2 nm range.
Crystallization Kinetics and Mechanism of Low‐Expansion Lithium Aluminosilicate Glass‐Ceramics by Dilatometry
Authors: Karmakar Basudeb , Kundu Paritosh , Jana Sunirmal , Dwivedi Ravindra Nath
Published: May 2005

The crystallization kinetics and mechanism of a precursor glass of lithium aluminosilicate (LAS)‐based commercial low‐expansion glass‐ceramics were investigated using a dilatometer. The isothermal crystallization behavior of β‐quartz solid solution (ss) was found to obey the Avrami equation. Nonisothermal crystallization data were analyzed by the Ozawa method and modified Kissinger equation. The value of the Avrami exponent (n) was ∼1.5, and the apparent activation energy (Ea) was ∼500 kJ/mol, which was close to that of the diffusion of silicon and aluminum ions as well as metal–oxygen bond strengths, suggesting a three‐dimensional (3D) diffusion‐controlled reaction mechanism.
Fabrication of Stainless‐Steel‐Fiber‐Reinforced Cordierite‐Matrix Composites of Tubular Shape Using Electrophoretic Deposition
Authors: Kaya Cengiz , Kaya Figen , Boccaccini Aldo R.
Published: May 2005

Stainless‐steel (316L) fiber mats shaped into tubular geometry were used to reinforce cordierite. The cordierite‐matrix composites were manufactured using electrophoretic deposition and pressureless sintering. The sintered composites, which had an internal and external deposit thickness of ∼1 mm, were free of surface cracks when a deposition time of 2.5 min was used. Metal‐fiber‐reinforced cordierite composites such as those developed here may constitute a promising alternative for manufacturing damage‐tolerant tubular components for applications at temperatures up to ∼900°C.
Fabrication of Macrochannelled‐Hydroxyapatite Bioceramic by a Coextrusion Process
Authors: Koh Young‐Hag , Kim Hae‐Won , Kim Hyoun‐Ee , Halloran John W.
Published: May 2005

A coextrusion process was used to fabricate macrochannelled hydroxyapatite (HA). To improve the powder characteristics, the HA powder was calcined at 900°C in air for 1 h. A feedrod composed of HA (shell) and carbon black (core) was coextruded at 120°C through a symmetric 8:1 square reduction die. After the first coextrusion, the individual pieces were bundled, warm‐pressed, and then coextruded again. After removing the binder, the billet was sintered at 1350°C for 1h in air. Uniform, 27 vol% macrochannels with a diameter of 270 μm were formed in the dense HA through removal of the carbon black. The compressive strength of the test specimens was strongly dependent on the macrochannel direction due to the stress concentrations related to the macrochannel geometry.
Diffusion of Neodymium into Sputtered Films of Tantalum Pentoxide
Authors: Sager David A. , Apostolopoulos Vasilis , Wilkinson James S.
Published: May 2005

In this communication the diffusion of neodymium into rf‐sputtered films of tantalum pentoxide (Ta2O5) has been investigated using the SIMS technique. The diffusion characteristics were obtained for a temperature of 1100°C, and the results showed a time‐dependent diffusion coefficient that reflects a transition of the sputtered films from the amorphous to the crystalline phase. The potential for doping films of Ta2O5 with neodymium by diffusion, for the realization of novel active optical devices, is also discussed.
Crystallization of Polymer‐Derived Silicon Carbonitride at 1873 K under Nitrogen Overpressure
Authors: Friess Martin , Bill Joachim , Golczewski Jerzy , Zimmermann Andre , Aldinger Fritz , Riedel Ralf , Raj Rishi
Published: May 2005

The chemical stability of an amorphous silicon carbonitride ceramic, having the composition 0.57SiC·0.43Si3N4·0.49C is studied as a function of nitrogen overpressure at 1873 K. The ceramic suffers a weight loss at pN2 < 3.5 bar (1 bar = 100 kPa), does not show a weight change from 3.5 to 11 bar, and gains weight above 11 bar. The structure of the ceramic changes with pressure: it is crystalline from 1 to 6 bar, amorphous at ∼10 bar, and is crystalline above ∼10 bar. The weight‐loss transition, at 3.5 bar, is in excellent agreement with the prediction from thermodynamic analysis when the activities of carbon, SiC, and Si3N4 are set equal to those of the crystalline forms; this implies that the material crystallizes before decomposition. The amorphous to crystalline transition that occurs at ∼10 bar, and which is accompanied by weight gain, is likely to have taken place by a different mechanism. A nucleation and growth reaction with the atmospheric nitrogen is proposed as the likely mechanism. The supersaturation required to nucleate α‐Si3N4 crystals is calculated to be 30 kJ/mol.
Increased leaf area dominates carbon flux response to elevated CO2in stands ofPopulus deltoides(Bartr.)
Authors: Murthy Ramesh , Barron‐Gafford Greg , Dougherty Phillip M. , Engel Victor C. , Grieve Katie , Handley Linda , Klimas Christie , Potosnak Mark J. , Zarnoch Stanley J. , Zhang Jianwei
Published: May 2005

We examined the effects of atmospheric vapor pressure deficit (VPD) and soil moisture stress (SMS) on leaf‐ and stand‐level CO2exchange in model 3‐year‐old coppiced cottonwood (Populus deltoidesBartr.) plantations using the large‐scale, controlled environments of the Biosphere 2 Laboratory. A short‐term experiment was imposed on top of continuing, long‐term CO2treatments (43 and 120 Pa), at the end of the growing season. For the experiment, the plantations were exposed for 6–14 days to low and high VPD (0.6 and 2.5 kPa) at low and high volumetric soil moisture contents (25–39%). When system gross CO2assimilation was corrected for leaf area, system net CO2exchange (SNCE), integrated daily SNCE, and system respiration increased in response to elevated CO2. The increases were mainly as a result of the larger leaf area developed during growth at high CO2, before the short‐term experiment; the observed decline in responses to SMS and high VPD treatments was partly because of leaf area reduction. Elevated CO2ameliorated the gas exchange consequences of water stress at the stand level, in all treatments. The initial slope of light response curves of stand photosynthesis (efficiency of light use by the stand) increased in response to elevated CO2under all treatments. Leaf‐level net CO2assimilation rate and apparent quantum efficiency were consistently higher, and stomatal conductance and transpiration were significantly lower, under high CO2in all soil moisture and VPD combinations (except for conductance and transpiration in high soil moisture, low VPD). Comparisons of leaf‐ and stand‐level gross CO2exchange indicated that the limitation of assimilation because of canopy light environment (in well‐irrigated stands; ratio of leaf : stand=3.2–3.5) switched to a predominantly individual leaf limitation (because of stomatal closure) in response to water stress (leaf : stand=0.8–1.3). These observations enabled a good prediction of whole stand assimilation from leaf‐level data under water‐stressed conditions; the predictive ability was less under well‐watered conditions. The data also demonstrated the need for a better understanding of the relationship between leaf water potential, leaf abscission, and stand LAI.
Influence of drought‐induced acidification on the mobility of dissolved organic carbon in peat soils
Authors: Clark Joanna M. , Chapman Pippa J. , Adamson John K. , Lane Stuart N.
Published: May 2005

A strong relationship between dissolved organic carbon (DOC) and sulphate (SO42−) dynamics under drought conditions has been revealed from analysis of a 10‐year time series (1993–2002). Soil solution from a blanket peat at 10 cm depth and stream water were collected at biweekly and weekly intervals, respectively, by the Environmental Change Network at Moor House‐Upper Teesdale National Nature Reserve in the North Pennine uplands of Britain. DOC concentrations in soil solution and stream water were closely coupled, displaying a strong seasonal cycle with lowest concentrations in early spring and highest in late summer/early autumn. Soil solution DOC correlated strongly with seasonal variations in soil temperature at the same depth 4‐weeks prior to sampling. Deviation from this relationship was seen, however, in years with significant water table drawdown (>−25 cm), such that DOC concentrations were up to 60% lower than expected. Periods of drought also resulted in the release of SO42−, because of the oxidation of inorganic/organic sulphur stored in the peat, which was accompanied by a decrease in pH and increase in ionic strength. As both pH and ionic strength are known to control the solubility of DOC, inclusion of a function to account for DOC suppression because of drought‐induced acidification accounted for more of the variability of DOC in soil solution (R2=0.81) than temperature alone (R2=0.58). This statistical model of peat soil solution DOC at 10 cm depth was extended to reproduce 74% of the variation in stream DOC over this period. Analysis of annual budgets showed that the soil was the main source of SO42−during droughts, while atmospheric deposition was the main source in other years. Mass balance calculations also showed that most of the DOC originated from the peat. The DOC flux was also lower in the drought years of 1994 and 1995, reflecting low DOC concentrations in soil and stream water. The analysis presented in this paper suggests that lower concentrations of DOC in both soil and stream waters during drought years can be explained in terms of drought‐induced acidification. As future climate change scenarios suggest an increase in the magnitude and frequency of drought events, these results imply potential for a related increase in DOC suppression by episodic acidification.
Productivity of high‐latitude lakes: climate effect inferred from altitude gradient
Authors: Karlsson Jan , Jonsson Anders , Jansson Mats
Published: May 2005

Climate change is predicted to be dramatic at high latitudes. Still, climate impact on high latitude lake ecosystems is poorly understood. We studied 15 subarctic lakes located in a climate gradient comprising an air temperature difference of about 6°C. We show that lake water productivity varied by one order of magnitude along the temperature gradient. This variation was mainly caused by variations in the length of the ice‐free period and, more importantly, in the supply of organic carbon and inorganic nutrients, which followed differences in terrestrial vegetation cover along the gradient. The results imply that warming will have rapid effects on the productivity of high latitude lakes, by prolongation of ice‐free periods. However, a more pronounced consequence will be a delayed stimulation of the productivity following upon changes of the lakes terrestrial surroundings and subsequent increasing input of elements that stimulate the production of lake biota.
Effects of simulated long‐term climatic change on the bryophytes of a limestone grassland community
Authors: Bates Jeffrey W. , Thompson Ken , Grime J. Philip
Published: May 2005

The bryophyte vegetation of upland limestone grassland at Buxton in the southern Pennine Hills (UK) was studied following seven years' continuous simulated climate change treatments. The experimental design involved two temperature regimes (ambient, winter warming by 3°C) in factorial combination with three moisture regimes (normal, summer drought, supplemented summer rainfall) and with five replicate blocks. Percentage cover of the bryophytes was estimated visually using 15 randomly positioned quadrats (30 cm × 30 cm) within each of the 30 3 m × 3 m plots. Significant treatment effects were found but these were relatively modest. Total bryophyte cover and cover of Calliergonella cuspidata and Rhytidiadelphus squarrosus responded negatively to drought, whereas Fissidens dubius increased in the droughted plots. Campyliadelphus chrysophyllus increased with winter warming, while R. squarrosus, Lophocolea bidentata and species richness all decreased. The effects on the total bryophyte flora were further studied by canonical correspondence analysis, which yielded a first axis reflecting the combined effects of the moisture and temperature treatments. However, this analysis and a detrended correspondence analysis of the plot data also revealed that natural factors were more important causes of variation in the grassland community than the simulated climate treatments. It was concluded that dewfall may be an important source of moisture for grassland bryophytes and that this factor may have reduced the impact of the moisture treatments. The absence of some thermophilous species such as Homalothecium lutescens in the plots initially may also have reduced their scope for major vegetational change.
Species enrichment in an agriculturally improved grassland and its effects on botanical composition, yield and forage quality
Authors: Hofmann M. , Isselstein J.
Published: May 2005

In a field experiment, the effects of different management treatments on the botanical development and productivity of a previously species‐poor, intensively managed, lowland permanent grass sward were investigated over a 4‐year period. Fertilizer inputs were stopped and nine main treatments, based on three pre‐sowing and three post‐sowing cutting regimes, were applied. Half of each treatment plot was oversown with a mixture of forb (wildflower) species and half left unsown. The aims were: (1) to investigate the effect of cutting regimes on the establishment of introduced forb species, (2) to assess the development and dry‐matter (DM) yield potential of these introduced species, and (3) to compare the DM yield and forage quality of swards with and without introduced species. Seedling establishment was recorded until the end of the second year. From the third year onwards, a common twice‐yearly cutting regime was imposed on all treatments, and the development of the introduced species was recorded. The DM yield of the nine oversown sub‐treatments was compared with the sub‐treatments not oversown. Frequent cutting after oversowing resulted in the greatest number of established plants and three times greater harvested DM yield of introduced species, compared with infrequent cutting. Plantago lanceolata and Trifolium pratense were the best performing introduced species. By years 3 and 4, there was proportionately 0·15 and 0·23, respectively, additional herbage DM yield harvested from the oversown treatments compared with unsown treatments, and up to 0·60 more in some treatments. The introduction of forbs increased the crude protein concentration, but decreased the digestibility of the forage.
Factors reducing yield of organic white clover seed production in Denmark
Authors: Langer V. , Rohde B.
Published: May 2005

Factors reducing yield of organic white clover seed production were investigated in Denmark. In thirty‐six fields from different regions, density of flower heads, and weevils of the genera Apion and Hypera, hatching from flower heads, were assessed. In fifteen of these fields, additional measurements were made in order to calculate potential yield and yield‐reducing factors. Flower heads had a mean of ninety‐two florets per head, of which proportionately 0·59 were intact, 0·08 were not pollinated and 0·34 damaged by weevils; 0·16 of the florets contained larvae of Apion species. In intact florets the mean number of seeds was 3·6. Density and size of flower heads were correlated with low density of flower heads leading to significantly more florets per head. The number of seeds per intact floret was correlated with the proportion of unpollinated florets. The number of insect‐damaged florets was influenced by both larvae of Apion in and the numbers of Hypera nigrirostris (Fabr.) hatched from flower heads. One larva of H. nigrirostris caused approximately ten times the damage of a larva of Apion. Densities of Apion and Hypera were influenced by location, with fields with adjacent weevil sources being most at risk. An estimate of potential seed yield showed that, even under good harvest conditions, only a small part of potential seed yield is realized and that under suboptimal harvest conditions seed loss is high. The main factors responsible for low yields in Danish organic white clover seed production were identified as unfavourable harvest conditions and weevil damage.
Potential risks when spreading anaerobic digestion residues on grass silage crops – survival of bacteria, moulds and viruses
Authors: Johansson M. , Emmoth E. , Salomonsson A.‐C. , Albihn A.
Published: May 2005

The survival of pathogenic and spoilage micro‐organisms in soil and on grass fertilized with spiked anaerobic digestion residue (ADR) was investigated in a climate chamber during periods of up to 56 d. In addition, the survival of these organisms over time was investigated during ensiling of grass at 390 g dry matter (DM) kg−1 or 610 g DM kg−1. Micro‐organisms included in these studies were: Clostridium tyrobutyricum, Salmonella serotype Typhimurium, Listeria monocytogenes, Campylobacter jejuni, Escherichia coli, Talaromyces emersonii, Byssochlamys nivea, Porcine parvovirus and Swine vesicular disease virus. Soil and grass still contained high numbers of E. coli, Cl. tyrobutyricum and T. emersonii (1·9–5·4 log10) 49 and 56 d after fertilization with spiked ADR. Listeria monocytogenes and S. Typhimurium were generally found in the samples. This indicates that, within this time span, there is a risk of silage contamination by bacteria, moulds and viruses present in ADR spread on grassland. An increase in DM content of the crop decreased its ensilability as measured by pH and short‐chain fatty acid content. However, no clear differences were found in survival of pathogenic and spoilage micro‐organisms between the two silages with different DM contents, regardless of storage time. The lack of moisture and oxygen was probably sufficient to cause the reduction in vegetative bacteria in the 610 g DM kg−1 silage. However, bacterial and fungal spores and the viruses studied were not significantly inactivated by ensiling at these high DM contents and could, therefore, pose a health risk to farm animals fed on the silage if present in ADR applied to crops prior to ensilage.
Seedling recruitment dynamics of forage and weed species under continuous and rotational sheep grazing in a temperate New Zealand pasture
Authors: Edwards G. R. , Hay M. J. M. , Brock J. L.
Published: May 2005

Understanding the grazing conditions under which plant populations are limited by seed availability (seed limitation) is important for devising management schemes that aim to manipulate the establishment of weed and forage species. Seeds of three weed species (Cirsium arvense, C. vulgare and Rumex obtusifolius) and five forage species (Lolium perenne, Lotus uliginosus syn. L. pedunculatus, Paspalum dilatatum, Plantago lanceolata and Trifolium repens) were broadcast sown into L. perenne–T. repens pastures in Manawatu, New Zealand and five sheep‐grazing and two slug‐grazing (with and without molluscicide) treatments were imposed in a split‐plot design. Of the five sheep‐grazing treatments, four compared continuous grazing with rotational grazing at intervals of 12, 24 and 36 d in spring, with all four grazed under a common rotation for the remainder of the year. The fifth treatment was continuous grazing all year. Seed sowing increased seedling emergence of C. vulgare, L. perenne, P. lanceolata, R. obtusifolius and T. repens under all sheep‐ and slug‐grazing treatments, with differences in seedling densities persisting for at least 21 months. Seed sowing did not increase seedling densities of C. arvense, L. uliginosus or P. dilatatum. The effects of sheep‐grazing management on seedling emergence and survival were uncoupled. For the five seed‐limited species, seedling emergence was greater on pastures that were rotationally grazed during spring compared with those that were continuously grazed. However, seedling survival was lower in pastures grazed rotationally during summer, autumn and winter, so that after 21 months seedling numbers were greater on plots that were continuously grazed all year. Exclusion of slugs increased seedling recruitment of T. repens but had no impact on the other species. As weed and forage species responded in a similar way to sheep‐grazing management (increased under continuous, decreased under rotational), it is unlikely that the goals of reducing weed invasions and enhancing forage species establishment could be carried out concurrently in established pastures with the same management.
Human CD8+ T cells specific for influenza A virus M1 display broad expression of maturation‐associated phenotypic markers and chemokine receptors
Authors: Hoji Aki , R. Rinaldo Charles
Published: May 2005

To define the role of memory T cells in a non‐persistent viral infection, we have delineated the phenotype of memory CD8+ T cells specific for influenza A virus (FluA; matrix protein M158−66) based on the expression of several memory/effector lineage markers and relevant chemokine receptors. We found a majority of FluA‐specific CD8+ T cells expressed CD27 and CD28, and variably expressed CD45RA, CD62L, CD94 and granzyme A. A majority of FluA‐specific CD8+ T cells expressed high levels of CXCR3, and moderate levels of CCR5 and CXCR4, whereas a limited proportion expressed CCR7, CCR6 and CXCR5. A phenotypic profile based on these observations showed that there are both immature and mature memory CD8+ T cells specific for FluA.
Increased carrageenan‐induced acute lung inflammation in old rats
Authors: Corsini Emanuela , Di Paola Rosanna , Viviani Barbara , Genovese Tiziana , Mazzon Emanuela , Lucchi Laura , Marinovich Marina , Galli Corrado Lodovico , Cuzzocrea Salvatore
Published: May 2005

Ageing is associated with increased susceptibility to lung infections and delayed resolution of pulmonary infiltrates. The purpose of this study was to investigate the effect of age on the onset of carrageenan‐induced lung inflammation. When compared with carrageenan‐treated young rats (3 months old), old rats (> 18 months old) exhibited a preponderance of pleural exudation and polymorphonuclear cell infiltration. Lung myeloperoxidase activity, an index of neutrophil infiltration and activation, was significantly increased in old rats in comparison with young rats. Consistent with the biochemical markers of inflammation, increased lung damage, as assessed by nitrosative stress and lipid peroxidation, was observed in carrageenan‐treated old rats. In the lung exudate obtained from old rats, a significant reduction in interleukin‐10 (IL‐10) was observed, while similar expression of monocyte chemotactic protein‐1 was induced, suggesting that a decrease in IL‐10 rather than increased chemotaxis may account for the preponderance of the inflammatory cellular infiltrate in old rats. Similar to the in vivo situation, freshly isolated alveolar macrophages obtained from old rats produced less IL‐10. This defective IL‐10 production could be explained by a reduction in the cAMP‐dependent signalling pathway, which mediates IL‐10 production. Indeed, we found decreased cAMP‐responsive element binding protein (CREB) and phosphorous‐CREB (P‐CREB) expression in old rats, which may account for reduced IL‐10 production in old rats.
CpG motif acts as a ‘danger signal’ and provides a T helper type 1‐biased microenvironment for DNA vaccination
Authors: Liu Ling , Zhou Xiaohui , Liu Hua , Xiang Li , Yuan Zhenghong
Published: May 2005

The method of delivering a DNA vaccine can influence the type of immune response induced by the vaccine. Application of a DNA vaccine by gene gun typically induces a T helper type 2 (Th2)‐type reaction, whereas needle inoculation triggers a Th1 response. In the present study, we found that physical trauma, gold‐particle bombardment and the CpG motif can act as ‘danger signals’ that recruit inflammatory cells to damaged tissues. Analysis of the cytokine profiles of draining lymph nodes or lymph‐node‐derived mononuclear cells from different groups by real‐time reverse transcription–polymerase chain reaction revealed that, while gene‐gun‐bombardment induced a Th2‐type cytokine microenvironment with increased interleukin‐4 (IL‐4) and IL‐10 mRNA expression and almost no increase in IL‐12 and interferon‐γ mRNA expression in draining lymph nodes, intradermal injection as well as subcutaneous injection of muscle induced the opposite. We further studied whether the addition of the CpG motif can switch the Th2‐type cytokine microenvironment produced by gene‐gun bombardment in draining lymph nodes. Results showed that the addition of the CpG motif can increase IL‐12 mRNA expression in draining lymph nodes whether induced by intradermal injection, intramuscular injection, or gene‐gun bombardment. These data suggest that delivery of the CpG motif induced a Th1‐biased microenvironment in draining lymph nodes. Taken together, the CpG motif can act as a ‘danger signal’ and Th1 immune response enhancer in DNA vaccination. These results may help to explain the mechanism of different types of immune response induced by DNA vaccines delivered by different routes and facilitate the application of DNA vaccines.
Long‐term sickness absence: women's opinions about health and rehabilitation
Authors: Ockander Marlene , Timpka Toomas
Published: May 2005

Aims.  This paper reports a study to identify associations between ideas of health and rehabilitation in groups of women having first‐hand experience of long‐term sickness absence.

Background.  As a central part of their work, nurses have to be able to understand people in distress. When someone is unable to work because of illness, nurses are one of the central professional categories involved in their rehabilitation.

Methods.  Data were collected by Q‐sort grid and biographical interviews from 82 women aged 30–49 years who had either been absent from work because of sickness for 60 days or more, or were receiving a disability pension. The data were first analysed by patterns and structures obtained from a modified factor analysis. The second phase of the analysis dealt with relocating the results from the statistical analyses to their social context.

Results.  Six opinions representing different conceptions of health, illness, and rehabilitation were identified. These ranged from reflecting high levels of trust in the health care system to reliance on ‘nature's course’ and emphasizing the meaning of ‘feeling all right’.

Conclusions.  For women on long‐term sick leave, it is reasonable to expect that their communication with rehabilitation professionals will be founded in a mutual understanding of basic concepts. However, the disparate opinions about health and rehabilitation identified in this study show that future studies need to investigate the prospective value of this categorization to see whether and how these conceptions affect rehabilitation practices.
The dorsal raphe nucleus in schizophrenia: a post mortem study of 5‐hydroxytryptamine neurones
Authors: Craven R. M. , Priddle T. H. , Cooper S. J. , Crow T. J. , Esiri M. M.
Published: May 2005

The 5‐hydroxytryptamine (5‐HT, serotonin) system has been implicated in the pathophysiology and treatment of schizophrenia. In this study, we addressed the hypothesis that a deficit of 5‐HT neurones, either inherited or acquired, is central to the developmental pathology of the disorder. We examined putative 5‐HT neurones of the dorsal raphe nucleus (DRN) in post mortem, formalin‐fixed tissue from 15 schizophrenic patients and 20 control subjects matched for age and gender. No significant difference was detected between these groups in the number or size (cross‐sectional area or diameter) of tryptophan‐hydroxylase‐immunoreactive cell profiles viewed in transverse sections collected from the level of the trochlear decussation to the emergence of the trigeminal nerve. Profile number was not affected by age, gender, side of the brainstem (left or right) or post mortem interval; however, time in formalin correlated negatively with the number of neurones counted. Moreover, a significant negative correlation was detected between time in formalin and the levels of immunoreaction product (optical density), which in turn correlated positively with our profile counts. A positive correlation was found between the age of subjects and our estimates of cell size. Our results do not support the proposal that an abnormality in the number and/or size of DRN 5‐HT neurones is central to the aetiopathology of schizophrenia.