bluuebunny/crossref_metadata_2025 huggingface dataset:
Fyn Kinase Induces Synaptic and Cognitive Impairments in a Transgenic Mouse Model of Alzheimer's Disease
Authors: Chin Jeannie , Palop Jorge J. , Puoliväli Jukka , Massaro Catherine , Bien-Ly Nga , Gerstein Hilary , Scearce-Levie Kimberly , Masliah Eliezer , Mucke Lennart
Published: October 2005

Human amyloid precursor protein (hAPP) transgenic mice with high levels of amyloid-β (Aβ) develop behavioral deficits that correlate with the depletion of synaptic activity-related proteins in the dentate gyrus. The tyrosine kinase Fyn is altered in Alzheimer's disease brains and modulates premature mortality and synaptotoxicity in hAPP mice. To determine whether Fyn also modulates Aβ-induced behavioral deficits and depletions of synaptic activity-dependent proteins, we overexpressed Fyn in neurons of hAPP mice with moderate levels of Aβ production. Compared with nontransgenic controls and singly transgenic mice expressing hAPP or FYN alone, doubly transgenic FYN/hAPP mice had striking depletions of calbindin, Fos, and phosphorylated ERK (extracellular signal-regulated kinase), impaired neuronal induction of Arc, and impaired spatial memory retention. These deficits were qualitatively and quantitatively similar to those otherwise seen only in hAPP mice with higher Aβ levels. Surprisingly, levels of active Fyn were lower in high expresser hAPP mice than in NTG controls and lower in FYN/hAPP mice than in FYN mice. Suppression of Fyn activity may result from dephosphorylation by striatal-enriched phosphatase, which was upregulated in FYN/hAPP mice and in hAPP mice with high levels of Aβ. Thus, increased Fyn expression is sufficient to trigger prominent neuronal deficits in the context of even relatively moderate Aβ levels, and inhibition of Fyn activity may help counteract Aβ-induced impairments.
Hippocampal CA1 Circuitry Dynamically Gates Direct Cortical Inputs Preferentially at Theta Frequencies
Authors: Ang Chyze W. , Carlson Gregory C. , Coulter Douglas A.
Published: October 2005

Hippocampal CA1 pyramidal neurons receive intrahippocampal and extrahipppocampal inputs during theta cycle, whose relative timing and magnitude regulate the probability of CA1 pyramidal cell spiking. Extrahippocampal inputs, giving rise to the primary theta dipole in CA1 stratum lacunosum moleculare, are conveyed by the temporoammonic pathway. The temporoammonic pathway impinging onto the CA1 distal apical dendritic tuft is the most electrotonically distant from the perisomatic region yet is critical in regulating CA1 place cell activity during theta cycles. How does local hippocampal circuitry regulate the integration of this essential, but electrotonically distant, input within the theta period? Using whole-cell somatic recording and voltage-sensitive dye imaging with simultaneous dendritic recording of CA1 pyramidal cell responses, we demonstrate that temporoammonic EPSPs are normally compartmentalized to the apical dendritic tuft by feedforward inhibition. However, when this input is preceded at a one-half theta cycle interval by proximally targeted Schaffer collateral activity, temporoammonic EPSPs propagate to the soma through a joint, codependent mechanism involving activation of Schaffer-specific NMDA receptors and presynaptic inhibition of GABAergic terminals. These afferent interactions, tuned for synaptic inputs arriving one-half theta interval apart, are in turn modulated by feedback inhibition initiated via axon collaterals of pyramidal cells. Therefore, CA1 circuit integration of excitatory inputs endows the CA1 principal cell with a novel property: the ability to function as a temporally specific “AND” gate that provides for sequence-dependent readout of distal inputs.
Akt Contributes to Neuroprotection by Hypothermia against Cerebral Ischemia in Rats
Authors: Zhao Heng , Shimohata Takayoshi , Wang Jade Q. , Sun Guohua , Schaal David W. , Sapolsky Robert M. , Steinberg Gary K.
Published: October 2005

Activation of the Akt/protein kinase B (PKB) kinase pathway can be neuroprotective after stroke. Akt is activated by growth factors via a phosphorylation-dependent pathway involving the kinases phosphoinositide 3 (PI3) kinase and phosphoinositide-dependent protein kinase-1 (PDK1) and is negatively regulated by phosphatase and tensin homolog deleted on chromosome 10 (PTEN). Akt kinase blocks apoptosis by phosphorylating the substrates forkhead transcription factor (FKHR) and glycogen synthase kinase 3β (GSK3β). We found that intra-ischemic hypothermia (30°C) reduced infarct size and improved functional outcomes up to 2 months. Changes in phosphorylation levels of Akt, as measured by Western blots and immunostaining, differed from levels of Akt activity measured in anin vitroassay in normothermic animals. Hypothermia blocked most of these changes and maintained Akt activity. Inhibition of PI3/Akt enlarged infarct size in hypothermic animals. Hypothermia improved phosphorylation of PDK1, PTEN, and FKHR. Hypothermia did not improve GSK3β (Ser9) phosphorylation but blocked the nuclear translocation of phosphorylated β-catenin (Ser33/37/Thr41) downstream of GSK3β. Phosphorylation levels of PTEN, Akt, and Akt substrate decreased before apoptotic cytochromecrelease and degradation of microtubule-associated protein-2, a marker of neuronal survival. Hypothermia may protect from ischemic damage in part by preserving Akt activity and attenuating the apoptotic effects of PTEN, PDK1, and FKHR.
Formation of Ca–Mg–Zn bulk glassy alloy by casting into cone-shaped copper mold
Authors: Park E.S. , Kim D.H.
Published: October 2005

A new Ca–Mg–Zn alloys having significantly improved glass-forming ability (GFA) has been developed. The ternary Ca65Mg15Zn20 bulk metallic glass with diameter of at least 15 mm is successfully fabricated by conventional copper-mold casting method in air atmosphere. The critical cooling rate for glass formation in the cone-shaped copper mold is less than 20 K/s. When compared with the GFA of Ca–Mg–M (M: Cu, Ni, and Ag) alloys, the significantly improved GFA of the Ca–Mg–Zn alloy cannot be represented by ΔTx, Trg, K, and γ parameters.
Chemical Vapor Deposition of ZnS:Mn for Thin-Film Electroluminescent Display Applications
Authors: Topol Anna W. , Dunn Kathleen A. , Barth Karl W. , Nuesca Guillermo M. , Taylor Brian K. , Dovidenko Katharine , Kaloyeros Alain E. , Tuenge Richard T. , King Chris N.
Published: October 2005

Results are presented from a systematic investigation to design and optimize a low-pressure chemical vapor deposition (CVD) process for manganese-doped zinc sulfide (ZnS:Mn) thin films for electroluminescent (EL) device applications. The CVD process used diethylzinc (DEZ), di-π-cyclopentadienyl manganese (CPMn), and hydrogen sulfide (H2S) as co-reactants and hydrogen (H2) as carrier gas. A design of experiments approach was used to derive functionality curves for the dependence of ZnS:Mn film properties on substrate temperature and flow rates (partial pressures) of DEZ, CPMn, H2S, and H2. Film physical, chemical, structural, and optical properties were examined using Rutherford backscattering spectrometry, dynamic secondary ion mass spectroscopy, x-ray photoelectron spectroscopy, nuclear-reaction analysis, x-ray diffraction, transmission electron microscopy, atomic force microscopy, and scanning electron microscopy. EL measurements were carried out on ZnS:Mn-based dielectric–sulfur–dielectric stacks incorporated into alternating-current thin-film electroluminescent devices. An optimized process window was established for the formation of films with predominantly (0 0 2) orientation, grain size larger than 0.2 μm, and Mn dopant level approximately 0.5 at.%. A brightness of 407 cd/m2 (119 fL) and efficiency of 1.6 lm/W were obtained, as measured at 40 V above threshold voltage and 60 Hz frequency.
A Comparison of Pseudomorphic Bcc Phase Stability in Zr/Nb and Ti/Nb Thin Film Multilayers
Authors: Thompson G.B. , Banerjee R. , Dregia S.A. , Miller M.K. , Fraser H.L.
Published: October 2005

A series of Nb-rich Zr/Nb and Ti/Nb multilayers were sputter deposited. Upon a reduction in thickness, a pseudomorphic bcc phase was stabilized in the Zr and Ti layers. X-ray and electron diffraction techniques were used to confirm these phase transformations. The change in phase stability was modeled by the competition between volumetric and interfacial components of the total free energy of a unit bilayer representing the multilayer. An outcome of this model is the ability to plot phase stability diagrams for multilayers, referred to as biphase diagrams, as a function of bilayer thickness and volume fraction. A comparison of the phase stability boundary between hcp/bcc and bcc/bcc for these two systems has shown that the bcc Ti’s pseudomorphic phase stabilization is maintained for a much larger layer thickness as compared to Zr. Atom probe compositional profiles of the Ti/Nb multilayers have indicated that the Nb layers interdiffused into the Ti layers thus helping to facilitate the bcc Ti phase stability in the Ti/Nb multilayers.
Nanomechanical Probing of Layered Nanoscale Polymer Films With Atomic Force Microscopy
Authors: Kovalev A. , Shulha H. , Lemieux M. , Myshkin N. , Tsukruk V.V.
Published: October 2005

The approach developed for the microindentation of layered elastic solids was adapted to analyze atomic force microscopy probing of ultrathin (1–100 nm-thick) polymer films on a solid substrate. The model for analyzing microindentation of layered solids was extended to construct two- and tri-step graded functions with the transition zones accounting for a variable gradient between layers. This “graded” approach offered a transparent consideration of the gradient of the mechanical properties between layers. Several examples of recent applications of this model to nanoscale polymer layers were presented. We considered polymer layers with elastic moduli ranging from 0.05 to 3000 MPa with different architecture in a dry state and in a solvated state. The most sophisticated case of a tri-layered polymer film with thickness of 20–50 nm was also successfully treated within this approach. In all cases, a complex shape of corresponding loading curves and elastic modulus depth profiles obtained from experimental data were fitted by the graded functions with nanomechanical parameters (elastic moduli and transition zone widths) close to independently determined microstructural parameters (thickness and composition of layers) of the layered materials.
Preparation and characterization of transparent PZN–PLZT ceramics
Authors: Yin Q.R , Ding A.L. , Zheng X.S. , Qiu P.S. , Shen M.R. , Cao W.W
Published: October 2005

Transparent Pb(Zn1/3Nb2/3)O3–(Pb1-xLax)(Zr1-yTiy)O3 (PZN–PLZT) ferroelectric ceramics have successfully been prepared by hot-pressed sintering in oxygen atmosphere. Uniform cylindrical samples with diameter as large as Φ = 50 mm can readily be obtained. X-ray analysis and scanning electron microscopy experiments showed a pure perovskite phase, thin grain boundaries, and uniform dense microstructures. Very good transparency was reached for wavelength from near ultraviolet to infrared. The dielectric constant was also measured as a function of temperature and frequency. Some novel phenomena such as good piezoelectric and electro-optical properties have been observed.
A Thermo-Chemical Surface Treatment of AlN Powder for the Aqueous Processing of AlN Ceramics
Authors: Olhero S.M. , Novak S. , Oliveira M. , Krnel K. , Kosmac T. , Ferreira J.M.F.
Published: October 2005

Dense aluminum nitride ceramics were prepared by sintering green bodies at 1750 °C for 2 h. These green bodies were prepared by aqueous slip-casting from a powder that was surface-treated to prevent hydrolysis. The surface treatment of the aluminum nitride (AlN) powder consisted of dispersing the powder in warm-water solutions of aluminum dihydrogenphosphate Al(H2PO4)3. Different treatment temperatures in the range 30–80 °C were tested. For all the tested temperatures, the surface-treated AlN powder was found to be water-resistant, even after drying and/or redispersion. Various commercial dispersants were tested for their effectiveness, and the amount of dispersant was optimized in terms of a high solids loading of the suspension and an acceptable viscosity for slip casting. Based on these studies, a stable aqueous suspension of AlN powder, treated at 60 °C, with a total solids loading of 50 vol%, was prepared using CaF2 as a sintering additive. The well-dispersed powder made it possible to prepare green samples with close particle packing and relatively high sintered densities; that is, more than 96% of the theoretical density.
Atomistic Structure of Calcium Silicate Intergranular Films Between Prism and Basal Planes in Silicon Nitride: A Molecular Dynamics Study
Authors: Su Xiaotao , Garofalini Stephen H.
Published: October 2005

Molecular dynamics simulations of approximately 15 Å thick intergranular films (IGFs) containing SiO2 and CaO in contact with two surface terminations of the prism (10¯10) and basal planes (0001) of Si3N4 were performed using a multibody interatomic potential. Samples with the same composition (1.5 mol% CaO) and number of atoms but different crystal planes (i.e., the prism and basal planes of Si3N4) were studied. In both the prism and basal cases, the IGF in the final configuration is well-ordered in the interface region. A small number of N ions from the crystal moved into the IGF near the interface, and O ions moved into the N sites in the crystal, indicating the formation of a Si–O–N interface. In addition, Ca ions do not segregate to the IGF–crystal interface. The bonding characteristics of the O ions at the interface with neighbor Si ions are different in the prism and basal cases. Such difference may be explained by the difference in the two crystal Si3N4 surfaces. The Si–O bond length of the IGF has a range from 1.62 Å to 1.64 Å, consistent with recent experimental findings.
Secondary Mullite Formation in Kaolin–Al2O3 Ceramics
Authors: Chen Yung-Feng , Wang Moo-Chin , Hon Min-Hsiung
Published: October 2005

Secondary mullite has been formed in 60 wt% kaolin–40 wt% Al2O3 ceramics by solution-precipitation in the glassy phase in contact with Al2O3 particle, showing a plate-like morphology, at temperatures above 1673 K. The lattice constant modification of secondary mullite has been determined: the lattice parameters of orthorhombic structure of a, b, and c axes decrease from 8.653, 8.770, and 3.167 Å to 7.958, 8.064, and 2.926 Å, respectively. The Al2O3 content in the secondary mullite crystals increases from 59.69 to 70.41 wt% when the grain width increases from 15 to 40 nm. Both the formation of secondary mullite and its grain growth are intimately related to the presence of the glassy phase originated from impurity (K2O) in the kaolin. Their locations as well as their chemical composition of mullite grains, Al2O3 grains, and glassy phase are provided by the meticulous experiments using high-resolution transmission electron microscopy, selected-area electron diffraction, and energy dispersive spectroscopy techniques.
Reduction of Surface Oxide Films in Al–Mg Alloy Powders by Pulse Electric Current Sintering
Authors: Xie Guoqiang , Ohashi Osamu , Yamaguchi Norio , Song Minghui , Mitsuishi Kazutaka , Furuya Kazuo , Noda Tetsuji
Published: October 2005

The reduction mechanism of particle surface oxide films on Al–Mg alloy specimens sintered by the pulse electric current sintering (PECS) process was investigated via transmission electron microscopy, energy dispersive x-ray spectroscopy, and thermodynamic calculation. The reduction products were either MgAl2O4or MgO or both, which is dependent on the sintering temperature and Mg content in Al–Mg alloy. Comparing the experimental temperature of the reduction products with that from thermodynamic calculation, it was suggested that the temperature at interfaces between particles was higher than that inside particles. This difference of temperature enhanced reduction of surface oxide films of Al–Mg alloy powders and hence accelerated the sintering in the PECS process.
Uniaxial Compressive Stress Dependence of the High-Field Dielectric and Piezoelectric Performance of Soft PZT Piezoceramics
Authors: Zhou Dayu , Kamlah Marc , Munz Dietrich
Published: October 2005

The influence of uniaxial prestress on dielectric and piezoelectric performance was studied for soft lead zirconate titanate piezoceramics. High electric field induced polarization and longitudinal/transverse strain were measured at different compression preload levels of up to −400 MPa. The parameters evaluated included polarization/strain outputs, dielectric permittivity, piezoelectric constants, and dissipation energy as a function of the mechanical preload and electric-field strength. The results indicate a significant enhancement of the dielectric and piezoelectric performance within a certain prestress loading range. At much higher stress levels, the predominant mechanical depolarization effect makes the material exhibit hardly any piezoeffect. However, the enhanced performance achieved by a small stress preload is accompanied by an unfavorable increased hysteresis, and consequently, increased energy loss, which is attributed to a larger extrinsic contribution due to more non-180° domain switching induced by the combined electromechanical load.
Effect of Nano-Sized Sm2BaCuO5 Particles Addition on the Pinning Mechanism of Sm–Ba–Cu–O Materials
Authors: Chen Shih-Yun , Hseih Ping-Chi , Chen In-Gann , Wu Mow-Kuen
Published: October 2005

The superconducting properties of air-processed melt-textured growth Sm–Ba–Cu–O samples with addition of small amounts (0.004 wt%, 0.4 wt%, 4 wt%) of nano-sized Sm2BaCuO5 particles (nm211) were studied. The microstructure observations show that the size distribution and morphology of the 211-particles of the nm211-doped samples are similar to that of the control (undoped) samples. However, except for the 4 wt% nm211-doped sample, both Tc (critical temperature) and Jc (H, T) (critical current density) are enhanced in nm211-doped samples, and the Jc–H curves are different from those of control samples. The effect of nm211 particles on Jc enhancement is larger at high magnetic fields (>1 T at 77 K) than at low magnetic fields (0∼1 T). The dominant pinning mechanism by analyzing the Jc (H, T) data using the scaling theory indicate that the nm211-doped samples are originated from Δκ pinning (i.e., Tc variation); on the other hand, the control samples are originated from normal pinning (i.e., nonsuperconducting crystalline defects). It is proposed that nano-sized compositional fluctuations in the RE1+x Ba2−x Cu3O
y matrix, which are products of nm211 particles and liquid peritectic reaction, act as the source of Δκ pinning centers.
Influence of Nanoparticle Surfaces on the Electrical Breakdown Strength of Nanoparticle-Filled Low-Density Polyethylene
Authors: Ma Dongling , Siegel Richard W. , Hong Jung-Il , Schadler Linda S. , Mårtensson Eva , Önneby Carina
Published: October 2005

The electrical breakdown strength of TiO2nanoparticle-filled low-density polyethylene (LDPE) nanocomposites was investigated. It was found that the surface water on the nanoparticles played a very important role in determining the breakdown strength. The breakdown strength at 63.2% cumulative failure probability (E0) for the composites filled with dried nanoscale TiO2was similar to that of neat LDPE and 50% higher than that for the samples filled with as-received nanoscale TiO2. This increase was due to a better dispersion, a better interface, and a morphology change of the matrix. It was also found that surface modification of nanoscale TiO2had a significant influence on the breakdown strength.N-(2-aminoethyl) 3-aminopropyl-trimethoxysilane (AEAPS)-coated TiO2-filled samples showed about 40% higherE0than that of uncoated, as-received TiO2-filled samples. This was mainly due to enhanced electron scattering because of the presence of polar groups in AEAPS.
Conventional and Microcontact Impedance Studies of Mn–Zn Ferrite Ceramics
Authors: Lee Jong-Sook , Fleig Jürgen , Maier Joachim , Kim Doh-Yeon
Published: October 2005

Microcontact impedance spectroscopy in conjunction with conventional impedance techniques has been performed to elucidate microstructural and compositional inhomogeneities in polycrystalline Mn–Zn ferrites. Microcontact studies reveal the occurrence of oxygen stoichiometry gradients in these typically prepared ferrite ceramics together with a strong spatial resistance variation from boundary to boundary. This leads to a reinterpretation of the conventional impedance spectra of ferrites.
Kinetics of borosilicate glass deposition
Authors: Biernacki Joseph J. , Kannan Pravin , Meyer Harry , Blue Criag
Published: October 2005

The kinetics of borosilicate glass film deposition on silicon using boron nitride as a solid source was investigated. Experimental data on the thickness of deposited films as a function of temperature and process times under controlled atmospheric conditions was obtained. A 33-kW rapid thermal processing infrared furnace was used to minimize temperature and gas phase transients experienced on the commercial scale. The thickness and composition of the borosilicate glass films were measured using scanning Auger spectroscopy, and the thickness of the films as a function of time for various temperatures are presented. The results suggest a rapid transition to diffusion-controlled deposition with an activation energy of 2.77 ± 0.5 eV. The partial pressure of water vapor was found to have a potentially significant effect on the rate of film growth.
Exploring Biological Surfaces by Nanoindentation
Authors: Enders S. , Barbakadse N. , Gorb S.N. , Arzt E.
Published: October 2005

With the help of instrumented indentation, the mechanical behavior of a variety of biological systems was studied: the waxy zone of the pitcher plant (Nephenthes alata) adapted for attachment prevention, the head-to-thorax articulation system of a beetle (Pachnoda marginata) as an example of friction minimization, and the wing arresting system of the dung beetle (Geotrupes stercorarius) adapted for mechanical interlocking. We demonstrate that nanoindentation can successfully be applied to compliant and highly structured biological composite materials. Measuring the mechanical performance of these surfaces can provide important information for understanding the overall functioning of these systems. Tests on fresh and dried samples show the influence of desiccation on the results and point out the importance of native conditions during the measurements. However, these preliminary results also point to current limits of the test method and the need for adapting it and current theories to meet the specific requirements of biological materials.
Effect of Sol-Gel Thin Coatings on the Fracture Strength of Glass
Authors: Sánchez-González Estíbaliz , Miranda Pedro , Díaz-Parralejo Antonio , Pajares Antonia , Guiberteau Fernando
Published: October 2005

The effect of ZrO2–3 mol/ Y2O3sol-gel thin coatings on the fracture of soda-lime glass is investigated. For this purpose, a recently developed strength measurement procedure—based on making a brittle material flex on top of a soft substrate by applying a load with a spherical indenter to the top surface of the system—is used. Results suggest significant variation of both the average fracture strength and the Weibull modulus on coated glass slides. It is suggested that the origin of such variations can be attributed to a certain chemical degradation of the glass during the coating process. This chemical attack produces a highly homogeneous flaw population on the glass surface which governs its fracture behavior. Implications of this work for the practical use of coated glass layers are discussed.
Bulk Glass Formation in an Fe-Based Fe–Y–Zr–M (M = Cr, Co, Al)–Mo–B System
Authors: Lu Z.P. , Liu C.T. , Carmichael C.A. , Porter W.D. , Deevi S.C.
Published: October 2005

Several new bulk metallic glasses based on Fe–Y–Zr–(Co, Cr, Al)–Mo–B, which have a glass-forming ability superior to the best composition Fe61Zr10Co7Mo5W2B15 reported recently, have been successfully developed. The as-cast bulk amorphous alloys showed a distinctly high thermal stability with glass-transition temperatures above 900 K, supercooled liquid regions above 60 K, and high strength with Vickers hardness values larger than HV 1200. The suppression of the growth of primary phases in the molten liquids and the resultant low liquidus temperatures were found to be responsible for the superior glass-forming ability in these new alloys. It was found that the addition of 2% Y not only facilitated bulk glass formation, but the neutralizing effect of Y with oxygen in the molten liquids also improved the manufacturability of these amorphous alloys.
Deformation Behavior of Ti–Zr–Ni–Cu–Be Metallic Glass and Composite in the Supercooled Liquid Region
Authors: Bae D.H. , Park J.M. , Na J.H. , Kim D.H. , Kim Y.C. , Lee J.K.
Published: October 2005

The deformation behavior of Ti-based bulk metallic glass (BMG) and metallic glass matrix composite (MGMC), both having a multistep crystallization behavior upon heating, has been investigated in the supercooled liquid region. The BMG deforms homogeneously and exhibits moderate elongation to failure due to its multistep crystallization behavior, but shows a significant variation of the flow stress during deformation. For the MGMC containing an in situ β-phase, a stress-overshoot characteristic, observed in the BMG, is not presented, but elongation to failure is rather limited because the crystalline β-phase prevents the viscous flow of the amorphous phase. The different presence of the crystalline phases in the metallic glasses can differently affect the flow behavior of metallic glass in the supercooled liquid region.
Role of Sr Addition on the Structure Stability and Electrical Conductivity of Sr-Doped Lanthanum Copper Oxide Perovskites
Authors: Yu Ho-Chieh , Fung Kuan-Zong
Published: October 2005

The structural and electrical properties of lanthanum copper oxide were examined as a function of Sr addition. It was observed that the lanthanum oxide and copper oxide formed La2CuO4 with K2NiF4 structure when the powder mixture was heated at 800 °C in ambient pressure. Interestingly, the samples of Sr-doped (15∼25%) lanthanum copper oxides showed single perovskite-based phase after being heated at 800 °C. Without Sr addition, a single-perovskite phase of lanthanum copper oxide was observed only under the oxygen pressure as high as 65 kbar. The stabilization of perovskite structure in lanthanum copper oxide was effectively achieved by the addition of Sr. Based on the titration analysis and pertinent defect reactions, the enhancement of perovskite stability was due to the presence of trivalent copper ions that were created to balance the electrical charge of doping ion (SrLa′). With the increasing concentration of trivalent copper ions (or electron holes equivalently) in Sr-doped samples, lanthanum copper oxide also changed from a semiconductor to metallic conductor. When the Sr dopant exceeded its solubility limit of approximately 25% in the A-site sublattice, the Sr-rich second phases, La2SrCu2O6 and Cu2SrO3, appeared and suppressed the electronic conduction drastically.
Nanostructured Gold Thin Films Prepared by Pulsed Laser Deposition
Authors: Irissou Eric , Le Drogoff Boris , Chaker Mohammed , Trudeau Michel , Guay Daniel
Published: October 2005

A structural and morphological study of nanostructured gold thin films prepared by pulsed laser deposition in the presence of several inert background gases (Ar, He, and N2) and at various pressures (from 10 mTorr to 1 Torr) and target-to-substrate distances (from 1 to 10 cm) is presented. Structural and morphological analyses were undertaken using semiquantitative x-ray diffraction, scanning tunneling microscopy, and transmission electron microscopy. For each set of deposition conditions, the kinetic energy of the neutral gold species [Au(I)] present in the plasma plume was determined by time-of-flight emission spectroscopy and used to characterize the plasma dynamics. It is shown that all films exhibit a transition from highly [111] oriented to polycrystalline as the Au(I) kinetic energy decreases. The polycrystalline phase ratio is close to 0% for Au(I) kinetic energy larger than approximately 3.0 eV/atom and approximately 86 ± 10% for Au(I) kinetic energy smaller than approximately 0.30 eV/atom, irrespective of the background gas atmosphere. The mean crystallite size of both phases and the mean roughness of the films also follow a unique relation with the Au(I) kinetic energy, independently of the nature of the background gas, and nanocrystalline films with crystallite size as small as 12 nm are obtained for Au(I) kinetic energy smaller than 0.3 eV/atom.
Preparation of Lutetium Nitride by Direct Nitridation
Authors: Suehiro Takayuki , Hirosaki Naoto , Yamamoto Yoshinobu , Nishimura Toshiyuki , Mitomo Mamoru , Takahashi Junichi , Yamane Hisanori
Published: October 2005

Lutetium nitride (LuN), an end member of a new quaternary system Si3N4–SiO2–Lu2O3–LuN, was synthesized by direct nitridation of a lutetium metal. The nitridation extent of the lutetium ingot (10 × 5 × 2 mm) reached about 97% by heating at 1600 °C for 8 h with an applied N2 pressure of 0.92 MPa; the initial shape of the bulk metal was maintained in the course of nitridation. The resulting nitrided lutetium possessed a moderately low oxygen content (∼0.7 wt%), which enables the preparation of uncharacterized high nitrogen-containing phases in the Lu–Si–O–N system.
The 2.0 Å Crystal Structure of a Pocilloporin at pH 3.5: The Structural Basis for the Linkage Between Color Transition and Halide Binding
Authors: Wilmannt Pascal G. , Battad Jion , Beddoe Travis , Olsen Seth , Smith Sean C. , Dove Sophie , Devenish Rodney J. , Rossjohn Jamie , Prescott Mark
Published: October 2005

The pocilloporin Rtms5 and an engineered variant Rtms5H146S undergo distinct color transitions (from blue to red to yellow to colorless) in a pH‐dependent manner. pKa, values of 4.1 and 3.2 were determined for the blue (absorption λmax, 590 nm) to yellow (absorption λmax, ∼453 nm) transitions of Rtms5 and Rtms5H146. The pKa for the blue‐yellow transition of Rtms5H146S increased by 1.4 U in the presence of 0.1 M KI, whereas the pKa for the same transition of Rtms5 was relatively insensitive to added halides. To understand the structural basis for these observations, we have determined to 2.0 Å resolution the crystal structure of a yellow form of Rtms5H146S at pH 3.5 in the presence of iodide. Iodide was found occupying a pocket in the structure with a pH of 3.5, forming van der Waals contacts with the tyrosyl moiety of the chromophore. Elsewhere, it was determined that this pocket is occupied by a water molecule in the Rtms5H146S structure (pH 8.0) and by the side chain of histidine 146 in the wild‐type Rtms5 structure. Collectively, our data provide an explanation for the observed linkage between color transitions for Rtms5H146S and binding to halides.
Accuracy of Diver Counts of Fluvial Rainbow Trout Relative to Horizontal Underwater Visibility
Authors: Hagen John , Baxter James S.
Published: October 2005

We investigated the effects of variation in underwater visibility on the accuracy of diver counts of rainbow trout Oncorhynchus mykiss in the Salmo River, British Columbia, over a 3-year time period. A four-man team of divers, drifting in a downstream direction, made periodic counts of trout along a study reach in which radio-tagged fish that had also received a visual mark were present. Observer efficiency of divers (number of tags seen relative to the number known to be present) was significantly related to horizontal underwater Secchi disk visibility during 2002 and 2003 but only poorly so for the first year of the study in 2001. Overall, horizontal visibility in the 3 years' combined data set was significantly related to observer efficiency, explaining 62% of the variation. Diver counts of untagged trout confirmed these patterns. Diver counts of trout greater than 30 cm and greater than 40 cm showed precise, significant relationships with horizontal visibility for both 2002 and 2003. Horizontal visibility changes explained 94% and 93% of the variation in counts of trout greater than 30 cm and greater than 40 cm, respectively, in 2002 and 94% and 87% of the variation for the same size categories in 2003. The poor-quality, nonsignificant relationships between counts of trout and visibility in 2001 were consistent with the poor observer efficiency relationship for that year as estimated from the observations of the radio-tagged fish. Taken together, these poor-quality relationships for the first year of the study point to either crew inexperience or some other factor(s) as an important source of error in addition to water clarity.
Electrofishing Catchability of Walleyes, Largemouth Bass, Smallmouth Bass, Northern Pike, and Muskellunge in Wisconsin Lakes
Authors: Schoenebeck Casey W. , Hansen Michael J.
Published: October 2005

We sought to determine whether electrofishing catchability was density dependent and varied with physical and biological factors for walleyes Sander vitreus, largemouth bass Micropterus salmoides, smallmouth bass M. dolomieu, northern pike Esox lucius, and muskellunge E. masquinongy in Wisconsin lakes. Electrofishing catch rate (number of fish caught per shoreline mile) was linearly related to population density (number of fish per acre) in spring for largemouth bass, northern pike, and muskellunge and in fall for walleyes, largemouth bass, and smallmouth bass. In contrast, gear saturation caused the electrofishing catch rate to be nonlinearly related (hyperstable) to population density for walleyes and smallmouth bass during spring. Catchability was higher during spring than fall for walleyes, largemouth bass, and smallmouth bass. Catchability of walleyes during fall was positively related to the percentage of littoral zone, whereas catchability of largemouth bass, smallmouth bass, and muskellunge was negatively related to the shoreline development index. Other physical and chemical variables failed to describe significant residual variation in catchability of any other species in any other season. We conclude that population density cannot be accurately estimated from the electrofishing catch rates of walleyes and smallmouth bass during spring. Therefore, mark–recapture methods must still be used to estimate population density if managers choose to sample those species during spring in Wisconsin lakes.
Evaluation of Sampling Techniques for Age-0 Lake Sturgeon in a Lake Michigan Tributary
Authors: Benson Angela C. , Sutton Trent M. , Elliott Robert F. , Meronek Thomas G.
Published: October 2005

Rehabilitation of lake sturgeon Acipenser fulvescens in the Great Lakes would benefit from a greater understanding of early life stage attributes. The objectives of this study were to determine the efficacy of active and passive sampling gears for capturing age-0 lake sturgeon and evaluate whether the most effective gear types were size selective. Fish were collected by means of active (i.e., wading, haul-seine, backpack electrofishing, snorkeling surveys, and bottom trawls) and passive (i.e., gill nets, set lines, and fyke nets) sampling gears from June to November of 2002 and 2003 in the lower Peshtigo River, Wisconsin, and nearshore waters of Green Bay. Mean catch per unit effort (CPUE) was greatest for day wading (0.036 fish/min), followed by day haul-seine surveys (0.029 fish/min), night wading (0.020 fish/min), and night haul-seine surveys (0.015 fish/min). Night wading surveys captured the greatest number of fish (N = 118). Day and night electrofishing (CPUE = 0.008 and 0.013 fish/min, respectively), snorkeling (CPUE = 0.010 fish/ min), and gill nets (CPUE = 0.026 fish/d) were less effective gear types, while bottom trawls, set lines, and fyke nets did not capture fish. Smaller fish were captured during day wading and haul-seine surveys (median = 71 and 68 mm, respectively) than during night wading and haul-seine surveys (median = 120 and 133 mm, respectively). Based on these results, we recommend the use of wading and haul-seine surveys to collect age-0 lake sturgeon in shallow lotic and lentic systems, such as the lower Peshtigo River and Green Bay, that are characterized by low current velocity and high water clarity.
Comparison of Interval and Aerial Count Methods for Estimating Fisher Boating Effort
Authors: Lockwood Roger N. , Rakoczy Gerald P.
Published: October 2005

Interval and aerial angler creel survey counting methods were compared for a statistical district of Lake Michigan (MM-6) to evaluate potential underestimation of the interval method. Two 0.5-h boat (i.e., interval) counts were made per sample day at five access ports within MM-6, and on the same day, boats in 3 out of 18 MM-6 grids were counted from aircraft. Seasonal and monthly day-type (weekday or weekend day) estimates of boating effort by count method were compared. Seasonal boating effort estimates during open-water periods were not significantly different for aerial versus interval counts: 250,387 versus 247,117 in 2000 and 177,532 versus 219,097 in 2001. Similarly, comparisons of boating effort by monthly day type (i.e., weekday or weekend day) within each year did not indicate significant differences. Aerial precision estimates (2 SEs/estimate; 14.84% in 2000 and 15.53% in 2001) were more precise than interval estimates (21.42% in 2000 and 24.54% in 2001). Similarly, predicted power (1 − β) was greater for aerial estimates than for interval estimates. The potential power of future interval estimates to detect a 25% change in boating effort with α = 0.05 was 0.38 for 2000 data and 0.30 for 2001 data. Aerial estimates provided power estimates of 0.66 for 2000 data and 0.62 for 2001 data. At least four interval counts per sample day are needed to match the precision and power of three aerial counts. Although both count types were made on the same sample days and at approximately the same (random) times each sample day, each method relied on unique estimation methods. Comparable, independent estimates establish the reliability of these two methods.
Interactions between Walleyes and Four Fish Species with Implications for Walleye Stocking
Authors: Fayram Andrew H. , Hansen Michael J. , Ehlinger Timothy J.
Published: October 2005

We used a number of different data sets and four criteria to evaluate evidence of competition and predation between walleye Sander vitreus and northern pike Esox lucius, muskellunge E. masquinongy, smallmouth bass Micropterus dolomieu, and largemouth bass M. salmoides in northern Wisconsin lakes. The four criteria were as follows: (1) indices of population abundance were inversely related, (2) two species had shared resources or one species preyed on the other, (3) competition or predation was strong enough to produce a measurable effect, and (4) experimental manipulations produced results consistent with the hypothesis of competition or predation. Using these criteria, we identified which species interact most strongly with walleyes, determined the most likely mechanism for interaction (predation, competition, or both), and characterized the effects of walleye stocking on these species. Largemouth bass was the only species that strongly interacted with walleyes: (1) indices of largemouth bass and walleye population abundance were inversely related in lakes with self-sustaining walleye populations; (2) the diet of largemouth bass included juvenile walleyes; (3) walleye growth was positively related to indices of largemouth bass abundance; and (4) survival of stocked walleyes was negatively related to indices of largemouth bass abundance, and indices of largemouth bass abundances increased as an index of walleye stocking intensity increased. A bioenergetics analysis of one lake that was stocked with 39,300 juvenile walleyes, but also has some natural reproduction of walleyes, suggested that the largemouth bass population could consume up to 82,500 juvenile walleyes per year. Our findings suggest that largemouth bass interact strongly with walleyes through predation, that they can limit the survival of stocked walleyes, and that walleye stocking can result in increased largemouth bass populations. Therefore, management goals seeking to simultaneously maximize largemouth bass and walleye populations may be unrealistic.
Shear and torsion interaction in prestressed hollow core units
Authors: Broo H. , Lundgren K. , Engström B.
Published: October 2005

Hollow core units are mainly designed to resist bending and shear. There are, however, many applications in which they are also subjected to torsion. The present calculation method for shear and torsion in the European Standard EN 1168 adds stresses from multiple influences without taking into account the softening of cracking concrete; therefore it is probably conservative. The main purpose of this work is to investigate the response of prestressed hollow core units subjected to selected combinations of shear and torsion by using non-linear finite element (FE) analyses. In previous work by the present authors, three-dimensional FE models of hollow core units were developed and validated by full-scale experiments. This paper shows how similar models were analysed for several load combinations of shear and torsion ratios. One load combination was validated by full-scale tests. The results from the FE analyses made it possible to present shear and torsion capacities in interaction diagrams useful in practical design. Moreover, the influences of the shear span and the prestressing transfer zone on the shear and torsion capacity were evaluated. It was concluded that the boundaries affected the capacity: shorter shear span gave higher capacity. The curved interaction diagrams obtained from the FE analyses were compared with linear diagrams from the analytical model in EN 1168. For most combinations the FE analyses showed higher capacities, except for combinations close to pure torsion, and pure shear for one of the geometries investigated.
Vulnerability assessment of corrosion-affected concrete structures
Authors: Li C. Q. , Melchers R. E. , Lawanwisut W.
Published: October 2005

Reinforcement corrosion in concrete is the predominant causal factor for the premature deterioration of reinforced concrete structures, causing various degrees of damage to the structure and leading to final structural collapse. The existence of reinforcement corrosion in concrete structures makes them increasingly vulnerable over time. This ultimately poses a potential risk to the public. The intention of the present paper is to propose a method to assess the vulnerability of reinforced concrete structures deteriorating over time due to reinforcement corrosion. The application of the proposed method to corrosion-affected flexural members is demonstrated, while in practice the limitations of the proposed approach need to be recognised due to the complexity of the corrosion process in real structures. The effect of design variables of reinforced concrete structures on their vulnerability is also studied using two sensitivity analysis techniques. It is found that corrosion-induced deterioration is the most important single factor that makes reinforced concrete structures vulnerable. The method presented in the paper can assist engineers, operators and asset managers in developing a risk-informed and cost-effective maintenance strategy in the asset management of corroded concrete infrastructure.
Reinfestation of Endophtye‐Infected Tall Fescue in Renovated Endophyte‐Free Pastures under Rotational Stocking
Authors: Tracy Benjamin F. , Renne Ian J.
Published: October 2005

Endophyte‐infected (E+) tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbyshire] is problematic in pastures because it produces alkaloids that can be toxic to cattle (Bos taurus). Replacement of E+ tall fescue pasture with endophyte‐free (E−) fescue may effectively eliminate this problem. Endophyte‐free cultivars, however, are less competitive than E+ fescue and are usually displaced over time. The main objective of this study was to determine whether E+ fescue would reinfest pastures planted with mixtures of E− fescue and other species and grazed under rotational stocking. In 2001, nine tall fescue pastures in western Illinois were renovated and planted with mixtures that contained E− fescue (Barcel) and two, four, or seven additional species. Pastures were grazed by beef cattle over 3 yr. Tall fescue tillers were collected each September and subjected to microscopic analysis for endophyte presence. After renovation, E+ still accounted for 18 to 38% of tall fescue. Relative to all other species, however, E+ fescue was <10% of pasture communities. The species mixtures sown with E− fescue had little influence on E+ fescue reinfestation (P = 0.70). Contrary to other studies, percentage of E+ fescue in E− pastures did not increase in the 3 yr of this study. Moderate grazing pressure under rotational stocking combined with relatively wet growing seasons likely favored E− fescue and suppressed E+ reinfestation. We also suggest that if pasture renovation can reduce E+ fescue percentage to <10%, it is unlikely that E+ fescue will reinfest pastures to an extent that may cause fescue toxicosis in cattle.
Spatial Variability of the Illinois Soil Nitrogen Test: Implications for Soil Sampling
Authors: Ruffo Matías L. , Bollero Germán A. , Hoeft Robert G. , Bullock Donald G.
Published: October 2005

The Illinois Soil Nitrogen Test (ISNT) is a recently developed test that has shown promise for corn (Zea maysL.) N fertilization. However, among‐field and within‐field spatial variability of this test is unknown and sampling recommendations have not been defined. The objectives of this study were to estimate the spatial variability and structure of the ISNT to provide sampling recommendations and to determine the short‐term effect of N fertilizer on this test. Soil samples were collected on 14 production fields and analyzed for the ISNT. Data was analyzed with traditional statistics and with geostatistical techniques. In the short term, N fertilization did not have a significant effect on the ISNT (p> 0.3). The ISNT was normally distributed in 12 fields and showed a relatively low coefficient of variation (18% on average). Field mean ISNT ranged from 98 to 255 mg kg−1and tended to be higher in Mollisols than in Alfisols. On average across fields, at least 10 samples are required to determine the mean ISNT for a given field with a precision of 24 mg kg−1. The geostatistical analysis revealed that the ISNT has strong spatial structure, as indicated by the bounded variograms, the relatively low nugget/sill ratio (<30% in 10 fields) and the mean range of 150 m. The spatial variability indicates that the ISNT can be mapped with a relatively sparse sampling grid and with a low number of samples, critical characteristics when assessing the economic implication for variable and uniform rate N fertilization.