bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling Optical Changes in Perovskite Capacitor Materials Due to dc‐Field Degradation
Authors: Biegalski Michael , Trolier‐McKinstry Susan
Published: July 2010

The depth sensitivity of spectroscopic ellipsometry (SE) to the presence of oxygen vacancies (VO••), in perovskite titanates, was examined over the wavelength range from 250 to 750 nm. To determine the effect of oxygen vacancy concentration, reference optical properties of barium titanate (BaTiO3) and Fe‐doped SrTiO3 were determined for oxidized and reduced samples. These reference data were used to model the sensitivity of SE to changes due to degradation. Using these models, it was found that SE could detect reduced layers of 4 Å for BaTiO3 and an 8 Å layer for Fe‐doped SrTiO3. From the models, concentration gradients were resolvable by SE with an average diffusion depth (√Dt) of 10 Å for BaTiO3 and 50 Å for Fe‐doped SrTiO3. These models also predict that SE should be able to discern different degradation mechanisms through the way the optical properties change during degradation.
Metastable States in Alumina‐Rich La2O3:Al2O3 and Nd2O3:Al2O3
Authors: Key Thomas S. , Crist Buckley
Published: July 2010

Alumina‐rich mixtures of La2O3 and Al2O3 have equilibrium phases that are perovskite (LaAlO3) and β‐alumina (LaAl11O18). Annealing initially glassy samples with compositions 3La2O3–5Al2O3 or 11La2O3–14Al2O3 between 860° and 1075°C creates a metastable state that is clearly detected by X‐ray diffraction (XRD). While structures have not been determined, the new state appears to have two crystalline phases. This metastable state is favored by low annealing temperatures and by compositions with more rare‐earth oxide. Similar behavior is seen with Nd2O3:Al2O3 compositions, although the smaller Nd ion is less effective in promoting the metastable structure. The detection of equilibrium β‐alumina by XRD can be difficult, leading to possible misinterpretation of phases that are present.
Effect of the Ionic Size on Thermal Expansion of Low Cordierite by Molecular Dynamics Simulation
Authors: Miyake Akira
Published: July 2010

The effect of ionic size of each cation, Mg, Al, and Si, on the thermal expansion of cordierite, Mg2Al4Si5O18, was systematically investigated by using molecular dynamics simulations. The cell parameter and the thermal expansion are influenced by the ionic size. The ionic size of Al/Si ion has an opposite effect on the thermal expansion along the c‐axis to that of Mg ion, i.e., the negative thermal expansion along the c‐axis shifts to positive expansion with increasing ionic size of Mg ion and with decreasing ionic size of Al/Si ion.
Reinvestigation of Al–Si Spinel Phase in Diphasic Al2O3–SiO2 Gel
Authors: Chakraborty Akshoy Kr.
Published: July 2010

Mechanical mixture of γ‐Al2O3 and amorphous SiO2, and diphasic Al2O3/SiO2 gels of three different compositions were synthesized. They were subjected to heat treatment to various temperatures in the range 900°–1600°C. Qualitative X‐ray diffraction data show that these diphasic gels do not crystallize to a combined mixture of θ‐Al2O3 and α‐Al2O3 polymorphs at the intermediate stage, prior to mullite formation. Estimated mullite formation data show that the course of its formation from mixed oxides was different from that of diphasic gels. Results are compared with previous findings and the concept of Al–Si spinel formation in the phase transformation of stoichiometric diphasic gel system is substantiated.
The Activation Effect of K2SO4 on the Hydration of Gypsum Anhydrite, CaSO4(II)
Authors: Singh N. B.
Published: July 2010

The effect of K2SO4 activator on the hydration of chemical anhydrite obtained from burned FGD‐gypsum has been studied by different experimental techniques. Results obtained show that the degree of hydration increases when the K2SO4 concentrations increase from 0.5 to 3.3 wt%. Their heat evolution rate and maximum value also increase with the increase of K2SO4 concentration. The highest values were obtained when the hydration degree was about 50%. Also a correlation between the hydration degree and the total heat evolved was obtained. The X‐ray and SEM/EDX studies have shown that K2SO4 is adsorbed at the surface of CaSO4 even within 5 min of hydration and a syngenite—a double salt K2SO4·CaSO4·H2O is formed (even in the presence of 1.0 wt% K2SO4). Also, important changes in the morphology of the dihydrate crystal are detected. Finally, in the presence of 1.0 wt% K2SO4 (water/anhydrite (W/A) ratio=0.33), it was found that the resonance frequency, modulus of elasticity, compressive strength, and tensile strength increase with the degree of hydration whereas the total porosity decreases.
Improvement of Hydroxyapatite Sol–Gel Coating on Titanium with Ammonium Hydroxide Addition
Authors: Kim Hae‐Won , Kim Hyoun‐Ee , Knowles Jonathan C.
Published: July 2010

Small amounts (1–5 vol%) of ammonium hydroxide (NH4OH) were added to the ethanol–water‐based hydroxyapatite (HA) sol–gel solution. After aging the sol, a Ti substrate was dip‐coated and heat‐treated at 500°C for 1 h in air. The sol properties were monitored in terms of pH, viscosity, and structure changes with aging time; also, the coating phase and structure on Ti were investigated. During aging, the viscosity of the sol increased while the pH decreased, confirming the polymerization and gelation of the sol. The addition of NH4OH altered the sol properties significantly. Increase in the NH4OH concentration increased the pH and viscosity of the sol considerably, especially at short aging period, followed by a saturation with further aging. The Fourier transformed‐infrared analysis also confirmed a gradual structure change of the sol with NH4OH addition. Such changes in pH, viscosity, and structure bands of the sol driven by the NH4OH addition were attributed to the improved polymerization and gelation of the sol. The improved gelation shortened the aging time needed for crystallization of the apatite coating, i.e., increase in the NH4OH addition improved the crystallization of the coatings. Within 24 h aging time, the coatings on Ti containing over 3.5 vol% NH4OH showed characteristic HA phase and structure bands, at which period no apatite peaks were observed on the HA coating obtained without NH4OH addition.
Molecular Dynamics Computer Simulations of the Interface Structure of Calcium–Alumino–Silicate Intergranular Films between Combined Basal and Prism Planes of α‐Al2O3
Authors: Zhang Shenghong , Garofalini Stephen H.
Published: July 2010

The interface structures of calcium–alumino–silicate (CAS) glassy intergranular films (IGFs) formed between the combined basal and prism orientations of α‐Al2O3 crystals were studied using molecular dynamics simulations. Preferential adsorption of specific ions from the IGFs to the contacting surfaces of the alumina crystals was observed. This segregation of specific ions to the interface enables formation of localized, ordered structures between the IGF and the crystal. However, the segregation behavior of the ions is anisotropic, depending on the orientation of the α‐Al2O3 crystals. The results show that the enrichment of Ca atoms at the basal interface inhibits growth in the 〈0001〉 direction. However, at the (1120) prism plane, Ca ions have little effect on the epitaxial adsorption of Al and O ions from the IGF onto the (1120) surface. Increasing alumina concentration in the glassy IGF enhances adsorption of Al ions onto the prism surface, with little effect on the basal surface, indicating the tendency of growth in the 〈1120〉 direction on the prism plane, but limited growth on the basal plane. These results are consistent with the experimental data regarding anisotropic grain growth in alumina sintered in the presence of CAS IGFs.
Codoping and Grain‐Boundary Cosegregation of Substitutional Cations in α‐Al2O3: A Density‐Functional‐Theory Study
Authors: Elsässer Christian , Elsässer Traude
Published: July 2010

The rhombohedral twin boundary of Corundum is used as a model interface for a theoretical case study of codoping and grain‐boundary cosegregation of substitutional aliovalent and isovalent cations in Alumina ceramics. This highly ordered interface exemplifies (a) a computationalab initioanalysis of electronic structures and total energies by means of the density functional theory, and (b) detailed microscopic insights into fundamental mechanisms of structure and bonding at interfaces related to substitutional cation impurities and dopants.
Synthesis of Nanostructured TiN Using a Two‐Step Transition Metal Halide Approach
Authors: Choi Daiwon , Kumta Prashant N.
Published: July 2010

A two‐step transition metal halide approach has been developed for synthesizing uniform ultra‐fine titanium nitride (TiN) nano‐crystallites (<10 nm) at relatively low temperatures of 400°C. The nano‐sized TiN crystallites were obtained by reacting liquid titanium tetrachloride dissolved in anhydrous chloroform with anhydrous NH3gas at room temperature followed by heat treatment under ultra‐high‐purity Ar, N2, and anhydrous NH3atmosphere. The synthesized TiN nano‐crystallites were characterized by X‐ray diffraction, Brunauer–Emmett–Teller, pycnometer, differential thermal analysis/thermo‐gravimetric analysis, and high‐resolution transmission electron microscopy. The effect of the heat treatment temperature and atmosphere (Ar, N2, and NH3) on the specific surface area, density, crystal structure, and composition is discussed.
High Piezoelectric and Dielectric Properties of La‐Doped 0.3Pb(Zn1/3Nb2/3)O3–0.7Pb(ZrxTi1−x)O3 Ceramics Near Morphotropic Phase Boundary
Authors: Deng Guochu , Yin Qingrui , Ding Aili , Zheng Xinsen , Cheng Wenxiu , Qiu Pingsun
Published: July 2010

La‐doped 0.3Pb(Zn1/3Nb2/3)O3–0.7Pb(ZrxTi1−x)O3 (x=0.5–0.53) piezoelectric ceramics with pure perovskite phase were synthesized by a two‐step hot‐pressing route. The piezoelectric properties of various compositions near the morphotropic phase boundary (MPB) were systematically investigated. Not only was the exact MPB of this system determined via X‐ray diffractometry analysis, but also the peak of piezoelectric properties was found near the MPB. The optimum piezoelectric properties of this series were observed in the specimen with Zr/Ti=51/49. The piezoelectric coefficient (d33) and electromechanical coupling factor (kp) were 845 pC/N and 0.70, respectively, which have not been reported in this system so far. Large permittivity (ɛr=4088) and permittivity maximum (ɛm=29 500) were also obtained for the poled specimens. The temperatures (Tmax) of the permittivity maxima ranged from 206° to 213°C with various Zr/Ti ratios.
Lattice Strain and Dislocations in Polished Surfaces on Sapphire
Authors: Saito Tomohiro , Hirayama Tsukasa , Yamamoto Takahisa , Ikuhara Yuichi
Published: July 2010

Polishing of ceramics, surface defects and strain are introduced that influence the mechanical properties in the final products. In this study, the sapphire surfaces with a‐plane and c‐plane were polished using several kinds of diamond slurry, and the introduced damaged zones were investigated using transmission electron microscopy (TEM), high‐resolution TEM, and TEM‐CBED (convergent beam electron diffraction). It was found that the types of slip systems and strain distribution were different between the a‐plane‐polished and the c‐plane‐polished specimens. That is, the basal slip and the prism slip were mainly activated in the c‐ and a‐plane‐polished specimens to form the different damaged zones. This difference was probably due to the difference in the direction and angle from the slip plane and applied shear stress during the polishing. On the basis of these observations, the types of introduced dislocations and distribution of strain were discussed to clarify the mechanism of polishing.
Electronic Conductivity of La‐Doped Ceria Ceramics
Authors: Shimonosono Taro , Hirata Yoshihiro , Sameshima Soichiro , Horita Teruhisa
Published: July 2010

Lanthanum‐doped ceria powder with a composition Ce0.8La0.2O1.9 was prepared by heating the oxalate solid solution (Ce0.8La0.2)2(C2O4)3 at 873 K in air. As‐prepared powder was densified to 96%–97% relative density by sintering in air at 1773 K for 4 h. The electronic current of the disk sample was measured in a temperature range from 773 to 1113 K by the direct current polarization method using a Hebb–Wagner ion‐blocking cell. A linear relationship, which was theoretically predicted, was measured between log σe (electronic conductivity) and E (applied voltage) in the applied voltage range of 0.2–1.0 V. The σe was proportional to PO2−1/4.3≈PO2−1/4.6 in the oxygen partial pressure range of 10−2–10−8 Pa, and to PO2−1/6.7≈PO2−1/7.1 in the oxygen partial pressure range of 10−7.5–10−22 Pa. The apparent activation energy of the electronic conduction was 1.87–1.94 eV. The hole conduction was also measured in the Po2 range of 102–105 Pa. The transport number of oxide ion was 0.96–1.00 at 773–1113 K under an oxygen partial pressure of 10−5 Pa.
Synthesis and Characterization of Ultra‐Fine Tin Oxide Fibers Using Electrospinning
Authors: Wang Yu , Aponte Milca , Leon Neliza , Ramos Idalia , Furlan Rogerio , Pinto Nicholas , Evoy Stephane , Santiago‐Avilés Jorge J.
Published: July 2010

Ultrafine tin oxide (SnO2) fibers having a rutile structure, with diameter ranging from 100 nm to several micrometers, were synthesized using electrospinning and metallorganic decomposition techniques. In this work, we propose a precursor solution that is a mixture of pure SnO2 sol made from SnCl4:H2O:C3H7OH:2‐C3H7OH at a molar ratio of 1:9:9:6, and a viscous solution made from poly(ethylene oxide) (PEO) (molecular weight 900 000) and chloroform (CHCl3) at a ratio of 200 mg PEO/10 mL CHCl3. This solution allows to obtain an appropriate viscosity for the electrospinning process. The as‐deposited fibers were sintered at 400°, 500°, 600°, 700°, and 800°C in air for 2 h. Scanning electron microscopy, scanning probe microscopy, X‐ray diffraction, Raman microspectrometry, and X‐ray photoelectron spectroscopy (XPS) were used to characterize the sintered fibers and elucidate the chemical reaction during sintering. The results showed that up to the sintering temperature of 700°C, the synthesized fibers are composed of SnO2. XPS was found to reflect the complicate chemical changes caused by the sintering process.
Intermediate Phases in Mullite Synthesis Via Aluminum‐ and Alumina‐Filled Polymethylsiloxane
Authors: Anggono Juliana , Derby Brian
Published: July 2010

Active filler pyrolysis of polymethylsiloxane/aluminum (PMS/Al) mixtures leads to the formation of mullite at 1400°C, and by 1700°C mullite is the only crystalline phase in an amorphous matrix. These mixtures show a complex series of oxidation and reduction reactions prior to the formation of mullite. Initial oxidation of PMS at low temperatures results in the formation of an amorphous product before any significant oxidation of the Al. After melting of the Al phase, redox reactions lead to the formation of elemental Si and SiC as intermediate crystalline phases along with Al2O3 both as the crystalline α‐phase and dissolved in the amorphous matrix. Mullite formation occurs by precipitation from the matrix at temperatures above 1400°C. In contrast, PMS/Al2O3 mixtures did not show mullite formation until heat treatment at 1700°C. In this case no significant intermediate crystalline phases occur, except for some limited cristobalite crystallization from the matrix.
Mechanical Properties of Zirconia Thin Films Deposited by Filtered Cathodic Vacuum Arc
Authors: Gan Zhenghao , Yu Guoqing , Zhao Zhiwei , Tan C. M. , Tay B. K.
Published: July 2010

Surface Young's modulus (E), hardness (H), and yield strength (Y) of zirconia films deposited on Si substrate by filtered cathodic vacuum arc (FCVA) under different oxygen flow rate were studied by nano‐indentation measurement and finite element modeling. Identified by X‐ray diffraction, the structure of the films evolves from amorphous to monoclinic, and then to amorphous, with oxygen flow rate increasing from 10 to 80 standard cubic centimeters per minute, which affects the mechanical properties of the films. It is found that the elastic–perfect‐plastic constitutive model is successfully applied to the films with amorphous structure; however inadequate for the monoclinic ZrO2, indicating that dislocation‐related plasticity possibly occurs during nano‐indentation.
Ba8ZnTa6O24: A New High Q Dielectric Perovskite
Authors: Thirumal M. , Davies P. K.
Published: July 2010

The hexagonal perovskite, Ba8ZnTa6O24, was prepared in single‐phase form and was found to be a stable secondary phase, formed as a result of the loss of ZnO from Ba(Zn1/3Ta2/3)O3 microwave dielectrics. The experimental and calculated X‐ray patterns of Ba8ZnTa6O24 indicate it is isostructural with Ba8Ta6NiO24 with an 8H (cchc)2 close‐packed BaO3 stacking sequence and the lattice parameters, a=10.0825(14), c=19.0587(38)Å. High‐density ceramics of Ba8ZnTa6O24 could be prepared at temperatures considerably lower (1400°C) than those used to sinter pure Ba(Zn1/3Ta2/3)O3, and exhibit very good microwave dielectric properties with ɛ=30.5, Qf=62 300, and τf=+36 ppm/°C at 8.9 GHz.
Relationship Between Structure and Glass Transition Temperature in Low‐silica Calcium Aluminosilicate Glasses: the Origin of the Anomaly at Low Silica Content
Authors: Cormier Laurent , Neuville Daniel R. , Calas Georges
Published: July 2010

The anomalous behavior of the glass transition temperature (Tg) in low silica calcium aluminosilicate glasses has been related to the structural modifications observed by neutron and X‐ray diffraction. The diffraction data indicate that Al and Si are in tetrahedral sites and that Ca atoms are in distorted octahedral sites. By subtracting the correlation functions for glasses at constant SiO2 or constant Al2O3 content, we have shown that Si and Al atoms are introduced in a different way within the glass structure. Si is present in various Qn sites, while Al resides in Q3 and Q4 sites for glasses with high CaO content and enters fully polymerized Q4 sites with increasing SiO2 or Al2O3 content. The higher proportion of Al in Q3 positions at high CaO content yields a depolymerization of the network. The lower connectivity will contribute to a decrease of the viscosity, which may be at the origin of the decrease of Tg for glasses at low silica content.
Defects of Base Metal Electrode Layers in Multi‐Layer Ceramic Capacitor
Authors: Yu Bang‐Ying , Wei Wen‐Cheng J.
Published: July 2010

An ultra‐thin Ni‐based metal used as the electrode layer in multilayer ceramic capacitor determines the dielectric performance of the capacitor. The warpage and the continuity of the inner electrode layers, and a dihedral angle between BaTiO3 layers and metal electrodes of two ceramic capacitors (X7R and X5R) were characterized by optical microscopy and scanning/transmission electron microscopes. The results show that the warpage of the chips is closely related to the discontinuity of the inner electrode. The discontinuity takes place mainly because of Rayleigh instability of the Ni layer, but is less induced by the tensile stress from sintering.
Broadband Complex Dielectric Permittivity of Porous Aluminum Silicate–Pyrolytic Carbon Composites
Authors: Calame Jeffrey P. , Abe David K. , Levush Baruch , Lobas David
Published: July 2010

The broadband (10 kHz–18 GHz) complex dielectric permittivity of electrically lossy aluminum silicate–pyrolytic carbon composites is studied as a function of carbon content. The composites are made from a commercial machinable ceramic that is treated by oxalic acid refluxing, followed by sucrose pyrolysis within the open porosity. The resulting composites have a slightly percolating conductor configuration that exhibits non‐Debye dielectric properties. Such composites are useful as microwave absorbers in vacuum electronic amplifiers, for suppressing spurious oscillations, and for bandwidth control. Four contributions to the dielectric response were observed and analyzed. These consist of a direct current conductivity contribution that is significant only at frequencies below 1 MHz, an irregular low‐frequency relaxation, a strong non‐Debye, high‐frequency relaxation with its upper portions extending into the microwave regime, and an underlying, broadband loss consistent with a universal dielectric response. The microwave behavior is dominated by changes in the position, intensity, and Cole–Cole exponent of the high‐frequency relaxation as the carbon content increases.
Electrical Conductivity of Epitaxial SrTiO3 Thin Films as a Function of Oxygen Partial Pressure and Temperature
Authors: Ohly Christian , Hoffmann‐Eifert Susanne , Guo Xin , Schubert Jürgen , Waser Rainer
Published: July 2010

SrTiO3 (100) epitaxial films with thicknesses of 3, 1 μm, and 250 nm were prepared on MgO (100) substrates by pulsed‐laser deposition. The electrical conductivities of the thin films were systematically investigated as a function of temperature and ambient oxygen partial pressure. This was made possible by using a specially designed measurement setup, allowing the reliable determination of resistances of up to 25 GΩ in the temperature range of 600°–1000°C under continuously adjustable oxygen partial pressures ranging from 10−20 to 1 bar. The capabilities of the measurement setup were tested thoroughly by measuring a SrTiO3 single crystal. The well‐known characteristics, e.g., the decline of the conductivity with a slope of –1/4 under reducing conditions and the opposite +1/4 behavior in oxidizing atmospheres, are found in the log(σ)–log(pO2) profiles of the epitaxial films. However, the p‐type conductivity decreases, and the n‐type conductivity increases with decreasing film thickness. This phenomenon is attributed to the charge carrier redistribution in the surface space charge layers. Owing to the high surface‐to‐volume ratio, the space charge layers play an important role in thin films.
Modeling Electrophoretic Deposition on Porous Non‐Conducting Substrates Using Statistical Design of Experiments
Authors: Compson Charles , Liu Meilin , Besra Laxmidhar , Earl David
Published: July 2010

Statistical design of experiments was used to model electrophoretic deposition of yittria‐stabilized zirconia (YSZ) particles on porous, non‐conducting NiO–YSZ substrates. A 23–full‐factorial matrix with three repetitions of the centerpoint was augmented with six axial runs and two additional centerpoints to form an inscribed central composite design. Fixed ranges of substrate firing temperature (1100°–1300°C), deposition voltage (50–300 V), and deposition time (1–5 min) were used as the independent design variables to model responses of YSZ deposition thickness, area‐specific interfacial resistance (ASR), and power density. Regression equations were determined, which were used to optimize deposition parameters based on the desired responses of low interfacial polarization resistance and high‐power density. Low substrate firing temperature (1100°C) combined with a low voltage (50 V) and minimal deposition time (1 min) resulted in a 6 μm‐thick YSZ film, a power density of 628 mW/cm2, and an ASR of 0.21 Ω·cm2. Increasing the substrate firing temperature, voltage, and time to 1174°C, 215 V, and 3 minutes, respectively, reduced the ASR to 0.19 Ω·cm2, increased YSZ film thickness to 25 μm, but had only a negligible effect on power density (600 mW/cm2).
Pressureless Sintering of ZrB2–SiC Ceramics
Authors: Zhang Shi C. , Hilmas Greg E. , Fahrenholtz William G.
Published: July 2010

A pressureless sintering process was developed for the densification of zirconium diboride ceramics containing 10–30 vol% silicon carbide particles. Initially, boron carbide was evaluated as a sintering aid. However, the formation of a borosilicate glass led to significant coarsening, which inhibited densification. Based on thermodynamic calculations, a combination of carbon and boron carbide was added, which enabled densification (relative density >98%) by solid‐state sintering at temperatures as low as 1950°C. Varying the size of the starting silicon carbide particles allowed the final silicon carbide particle morphology to be controlled from equiaxed to whisker‐like. The mechanical properties of sintered ceramics were comparable with hot‐pressed materials with Vickers hardness of 22 GPa, elastic modulus of 460 GPa, and fracture toughness of ∼4 MPa·m1/2. Flexure strength was ∼460 MPa, which is at the low end of the range reported for similar materials, due to the relatively large size (∼13 μm long) of the silicon carbide inclusions.
Growth and Properties of a Thulium, Holmium‐Codoped LuLiF4 Single Crystal
Authors: Jing Fangli , Shimamura Kiyoshi , Víllora Encarnación G. , Medvedev Andrey , Kitamura Kenji , Asai Kazuhiro , Sato Atsushi
Published: July 2010

LuLiF4 single crystals codoped with thulium (Tm) and holmium (Ho) were successfully grown by the Czochralski method. The excellent laser performance, in terms of highest slope efficiency, and highest optical‐to‐optical efficiency and lower laser threshold, was studied in comparison with 5% Tm, 0.5% Ho‐codoped YLiF4, and Lu3Al5O12 under the same conditions.
Rheological Characterization and Coagulation Casting of Al2O3–Nano Zirconia Suspensions
Authors: Santacruz Isabel , Binner Jon
Published: July 2010

The rheological behavior of electrosterically dispersed aqueous suspensions composed of submicrometer alumina and nano zirconia particles in different ratios and solids contents (from 34 to 40 vol%) has been studied during in situ coagulation casting. Glucono‐δ‐lactone was used as the coagulant to achieve destabilization of the ceramic suspensions by acidifying the suspension so that the pH became close to the isoelectric point for both powders. The effects of the lactone content (from 0.5 to 6.7 wt%) and the solids loading on the rheological parameters (dynamic and static measurements) during the coagulation process were studied. Dynamic measurements showed an increasing elastic modulus, G′, with time and lactone content (viz. 180 and 340 kPa for 6.7 wt% lactone addition after 40 and 60 min, respectively, and 57.3 kPa for 0.5 wt% lactone after 60 min), suggesting the formation of stronger green bodies at higher additions and longer times. The conditions were optimized to yield homogeneous green samples with a uniform nanozirconia distribution and densities between 58% and 60% of the theoretical. These were subsequently sintered to yield composites with a final density up to 97%.
Low‐Temperature Fabrication of Porous β‐SiC Ceramics in Sodium Vapor
Authors: Kawamura Fumihiro , Yamane Hisanori , Yamada Takahiro , Yin Shu , Sato Tsugio
Published: July 2010

β‐silicon carbide (SiC) porous ceramics were synthesized from pelletized powder mixtures of silicon (Si) and fullerene or Si and amorphous carbon (carbon black) at 1000 K for 24 h in sodium (Na) vapor. The relative density of the ceramics was 29%–34% of the theoretical density of SiC. Scanning electron microscopic observation of the fracture surface showed that the ceramics prepared with fullerene were agglomerates of submicrometer‐sized SiC particles and open spaces. The samples prepared with carbon black had a smooth fracture surface with cavities and voids. Using transmission electron microscopy, grains of over 250 nm and a diffuse electron diffraction ring pattern of β‐SiC were observed for the sample prepared with fullerene, and grains of 10–20 nm with a β‐SiC spot ring pattern for the sample prepared with carbon black. A surface area of 11–17 m2/g and a mesopore size distribution in the range of 2–10 nm were shown by a nitrogen adsorption technique. Energy‐dispersive X‐ray analysis detected 1–5 at.% of Na against Si on the fracture surface of the ceramics.
Change in the Thermal Expansion of a Perovskite‐Type Mixed Conductor Upon Sample Density
Authors: Nagai Toru , Ito Wataru , Sakon Tadashi
Published: July 2010

Thermal expansions (TEs) of dense and porous samples were studied for mixed conductor Sr(Co0.9Nb0.1)O3−δ (SCNb). In Ar, the TEs of the porous samples were almost the same as those of a dense sample, which had the character of conventional TEs. In air, on the other hand, the TEs of porous samples were larger than the dense sample. The difference of TE in air resulted from a change in the chemical expansion, which originated from the variation of oxygen vacancy concentration. On decreasing the density, oxygen incorporation from air into SCNb took place at a lower temperature, and the length change upon chemical expansion was increased.
Equilibrium Dependence of the Conductivity of Pure and Tin‐Doped Indium Oxide on Oxygen Partial Pressure and Formation of an Intrinsic Defect Cluster
Authors: Ohya Yutaka , Yamamoto Tomonori , Ban Takayuki
Published: July 2010

The dependence of the electrical conductivity of pure (99.999%) and tin‐doped indium oxide (In2O3) ceramics on oxygen partial pressure

was investigated at 800° and 850°C. The doping amount of tin was 100–1000 ppm, which is within the solubility limit at the temperatures measured. The conductivity of doped ceramics was independent of
, and the carrier concentration was almost the same as the estimated value from the tin content. The conductivity of the pure In2O3 ceramic was proportional to. By considering a singly charged defect cluster of interstitial indium and interstitial oxygen, , the conductivity dependence is deduced to be proportional to. There are large and three adjacent vacant sites, 8a and 16c, in the In2O3 structure to enter indium and oxygen.
Tailoring of a γ‐Alumina Membrane with a Bimodal Pore Size Distribution for Improved Permeability
Authors: Ahmad A. L. , Leo C. P. , Abd. Shukor S. R.
Published: July 2010

Porous γ‐alumina with a bimodal pore size distribution has been developed by adding nanosized polystyrene beads to boehmite sol as templating units. The primary pore diameter is in the range of 4–6 nm and the secondary pore diameter is ca. 50 nm with minor pore shrinkage. The unsupported γ‐alumina with different porous structures are characterized using thermogravimetric analysis, Fourier transform infrared spectra, X‐ray diffraction, N2 adsorption/desorption, and transmission electron microscopy. γ‐alumina with a bimodal porous structure shows reduced transport resistance compared with γ‐alumina with a unimodal porous structure in the dye adsorption test. Although the thickness of γ‐alumina thin layer increases when more secondary pores are generated, a γ‐alumina membrane with a bimodal pore size distribution shows diminution of transport resistance in the water permeability study also.
Energetics of Aluminum Vacancies and Incorporation of Foreign Trivalent Ions in γ‐Al2O3: An Atomistic Simulation Study
Authors: Maglia Filippo , Gennari Silvia , Buscaglia Vincenzo
Published: July 2010

Atomistic simulation methods based on pair‐wise interatomic potentials and energy minimization have been applied to elucidate the energetics of cation vacancies and the incorporation of 13 trivalent M3+cations (Cr3+, Ga3+, Fe3+, Lu3+, Yb3+, Er3+, Y3+, Tb3+, Gd3+, Eu3+, Sm3+, Nd3+, La3+) in γ‐Al2O3. Calculations have been carried out using Al64O96defect spinel supercells containing eight aluminum vacancies. The lowest energy configurations correspond to a random distribution of tetrahedral and octahedral vacancies. The energy gain in comparison with exclusive tetrahedral or octahedral vacancies is rather small (0.03 and 0.09 eV/Al2O3, respectively). Unit cell volume, density, and lattice properties of optimized structures are in good agreement with the experimental values or the results of high‐quality density functional theory calculations. The trends observed for the solution energy of the M2O3oxides in the supercell with minimum energy indicate the preferential incorporation of the foreign ions at the tetrahedral site and an increase of the solubility of M2O3in the defect spinel in comparison with α‐Al2O3. Configurations with the lowest energy have negative solution energies and, consequently, incorporation of trivalent ions can improve the thermodynamic stability of γ‐Al2O3in comparison with α‐Al2O3and increase the γ→α transition temperature.
Replicated association of the NR4A3 gene with smoking behaviour in schizophrenia and in bipolar disorder
Authors: Novak G. , Zai C. C. , Mirkhani M. , Shaikh S. , Vincent J. B. , Meltzer H. , Lieberman J. A. , Strauss J. , Lévesque D. , Kennedy J. L. , Le Foll B.
Published: July 2010

Schizophrenia and bipolar disorder are associated with dopamine neurotransmission and show high comorbidity with tobacco dependence. Recent evidence indicates that the family of the NR4A orphan nuclear receptors, which are expressed in dopamine neurons and in dopaminoceptive brain areas, may play a role in dopamine‐mediated effects. We have, therefore, analysed the association of six single nucleotide polymorphisms (SNPs) within the three genes belonging to the NR4A orphan nuclear receptor family, NR4A1 (rs2603751, rs2701124), NR4A2 (rs12803, rs834835) and NR4A3 (rs1131339, rs1405209), with the degree of smoking in a sample of 204 unrelated schizophrenia patients, which included 126 smokers and 78 non‐smokers. SNPs within the NR4A3 gene (rs1131339 and rs1405209) were significantly associated with heavy smoking in this cohort, using a stepwise analysis of the escalated number of cigarettes smoked per day (P = 0.008 and 0.006, respectively; satisfying the Nyholt significance threshold of 0.009, an adjustment for multiple testing). We then repeated the association analysis of the NR4A3 markers (rs1131339 and rs1405209) in a larger cohort of 319 patients with bipolar disorder, which included 167 smokers and 152 non‐smokers. We have replicated the positive association with smoking of the NR4A3 SNP rs1131339 in this group (P = 0.04), providing an important confirmation of the involvement of the NR4A3 gene in nicotine addiction in patients with mental health disease, a population significantly at risk for nicotine addiction.
The brain‐derived neutrophic factor val66met polymorphism and sudden unexpected infant death
Authors: Opdal SH , Melien Ø , Hynnekleiv T , Rognum TO
Published: July 2010

Aim:  Findings of hypoxia prior to death and involvement of a dysregulation of the serotonergic network in sudden infant death syndrome (SIDS) may indicate that brain‐derived neutrophic factor (BDNF) also is of importance with regard to sudden unexpected infant death. Based on this, the purpose of this study was to investigate the BDNF val66met polymorphism in SIDS cases, cases of infectious death and controls.

Methods:  The polymorphism was investigated in 163 SIDS cases, 34 cases of infectious death and 121 controls, using real‐time PCR and fluorescence melting curve analysis.

Results:  There were no differences in val66met genotype distribution between neither the SIDS cases nor the cases of infectious death and controls (p = 0.95 and p = 0.52, respectively).

Conclusion:  The study indicates that the val66met polymorphism is not important for sudden unexpected infant death. However, several other SNPs in the BDNF gene, as well as in other genes involved in this pathway, including G‐protein, have to be investigated to fully exclude any involvement of BDNF in SIDS.
PROFLAVINE‐SENSITIZED PHOTOOXIDATION OF TRYPTOPHAN AND RELATED PEPTIDES
Authors: Banassi C. A. , Scoffone E. , Galiazzo G. , Iori G.
Published: July 2010

Abstract— The photodynamic action of proflavine on the amino acids cystine, rnethionine, tyrosine, histidine, tryptophan and related peptides was tested in anhydrous formic and acetic acids. Only rnethionine and tryptophan were found to be photooxidized: the former, whether free or bound in a polypeptide chain, is quantitatively converted to methioninesulphoxide; the latter, when free, is fragmented to several compounds, which may be divided into two main classes: melanines and kynurenine derivatives.

Whereas masking the carboxyl group of tryptophan has no effect on the photooxidation products, N‐substituted derivatives of tryptophan are converted in high yields to the corre‐sponding kynurenine compounds. The possible applications of the method to biologically active polypeptides are discussed.
THE IRRADIATION OF SOME GLYCINE‐CONTAINING DIPEPTIDES ON SILICA GEL
Authors: Rivett D. E. , Wilshire J. F. K.
Published: July 2010

Abstract— When glycylphenylalanine and phenylalanylglycine were irradiated on thin layers of silica gel G, peptide bond fission, diketopiperazine formation and deamination occured. The products were identified by thin‐layer chromatogrpahy on the same plate, procedure which enables very small quantities of material to be irradiated.
A NEW GLOW PEAK, IN RHODOPSEUDOMONAS SPHAEROIDES
Authors: Govindjee  , Desai T. S. , Tatake V. G. , Sane P. V.
Published: July 2010

Abstract— A new glow peak at 120 K has been observed in Rhodopseudomanas sphaeroides and in its carotenoidless green mutant. This peak (labelled Zn), which is composed of two peaks at 120 and 150 K, appears when the bacteria are illuminated with white light while being cooled to 77 K and then warmed in darkness at a heating rate of 10 K per min. Delayed light emission and prompt fluorescence spectra show peaks around 530, 610 and 660 nm. The action spectra of light emission show a major peak at 410 nm and a smaller peak around 545 nm. The pigment responsible for the light emission is also leached out in the suspension medium. The chromophore responsible for the light emission appears to be magnesium protoporphyrin IX, not bacteriochlorophyll.
INDEPENDENT EFFECTS OF PHYTOCHROME AND NITRATE ON NITRATE REDUCTASE AND NITRITE REDUCTASE ACTIVITIES IN MAIZE
Authors: Sharma Arun Kumar , Sopory Sudhir K.
Published: July 2010

Abstract— Involvement of phytochrome in the regulation of nitrate reductase (NR) and nitrite reductase (NIR) activities in excised, etiolated leaves of Zea mays (L.) variety ‘Ganga‐5’ is demonstrated using low energy and high irradiance responses of phytochrome action. Photoreversibility by far‐red light of red light stimulated increases in NR and NIR activities was lost by 2 h. Red light given to the leaves, when induction by NO‐3, was saturated, further increased both enzyme activities. Even if red light was given 4–8 h before NO‐3, it still increased both NR and NIR activities.
MAGNETIC FIELD EFFECT ON THE HYDROGEN ABSTRACTION OF ANTHRAQUINONES IN SDS MICELLAR SOLUTIONS
Authors: T0animoto Yoshifumi , Shimizu Katsuko , Itoh Michiya
Published: July 2010

Abstract— The magnetic field effect (≤2600 G) on the hydrogen abstraction of three anthraquinones in SDS micellar solutions was studied by steady‐state photolysis. The relative quantum yield of disappearance of quinones is significantly reduced (? 30%) in a magnetic field (2600 G). The observation was interpreted in terms of the radical pair model.
4,4',6‐TRIMETHYLANGELICIN, A NEW VERY PHOTOREACTIVE AND NON SKIN‐PHOTOTOXIC MONOFUNCTIONAL FUROCOUMARIN
Authors: Baccichetti F. , Carlassare F. , Bordinα F. , Guiotto A. , Rodighiero P. , Vedaldi D. , Tamaro M. , DallAcqua F.
Published: July 2010

Abstract— 4,4',6‐Trimethylangelicin is a new monofunctional furocoumarin which appears to be a very promising potential agent for the photochemotherapy of psoriasis. Actually, it is capable of photoreacting with DNA to a large extent (four times more than 8‐MOP), forming only monoadducts; it produces singlet oxygen to an insignificant extent. Its antiproliferative effect (tested in Ehrlich ascites tunior cells) appears to be several times higher than that induced by the most active angelicins now known and by 8‐MOP itself. In spite of this high photosensitized effect, 4,4',6‐trimethylangelicin seems to be non‐phototoxic on guinea‐pig skin and much less mutagenic than 8‐MOP in E. coli WP2 uvr‐A, a strain in which cross‐links show lethality rather than mutations.
UV MUTAGENIC PHOTOPRODUCTS IN Escherichia coli AND HUMAN CELLS: A MOLECULAR GENETICS PERSPECTIVE ON HUMAN SKIN CANCER*
Authors: Brash Douglas E.
Published: July 2010

Abstract— The relevance of photoproducts produced by 254 nm irradiation to human skin cancer is first critically evaluated. Experiments identifying the mutagenic photoproducts at 254 nm are then described. Mutations are primarily due to the(6–4) photoproduct and the cyclobutane pyrimidine dimer, both in E. coli and in human cells. The(6–4) photoproduct may be more important in E. coli and the cyclobutane dimer more important in mammalian cells. In human cells, mutations occur at the C of a TC, CT, or CC cyclobutane dimer, but not at TT cyclobutane dimers, and also appear to occur, less frequently, at the C of TC and CC(6–4) photoproducts. The local structure of DNA is more important in determining the frequency of mutation at a site than is the photoproduct frequency at that site. The effect of DNA structure appears to be due to site‐specific lethality.
IN SITU GENERATION OF PSORALENS BY PHOTOLYSIS OF WATER‐SOLDBLE PRECURSORS
Authors: Mohammad Taj , Morrison Harry
Published: July 2010

Abstract— The poor water solubility of typical photochemotherapeutic psoralens restricts their utility in aqueous solutions and commonly requires the use of organic co‐solvents in photobiological studies. This paper describes the preparation of readily water‐soluble “pre‐psoralens”, (Z)‐3‐[5‐(4,6‐dimethoxy)benzofuranyl]propenoic acid (3) and (Z)‐3‐[5‐(6,7‐dimethoxy)benzofuranyl]propenoic acid (4), and their novel photocyclization in aqueous media to give 5‐methoxypsoralen (5‐MOP) and 8‐methoxypsoralen (8‐MOP), respectively. Quantum efficiencies, measured at 308 nm for the cyclization, are 12. 1 × 10‐3 for 3 → 5‐MOP and 2.7 × 10‐3 for 4 → 8‐MOP. 5‐Methoxyisopsoralen (5‐MOiP, 5) is a side product from the photolysis of 3. Photocross‐linking of calf thymus DNA is effected when the “pre‐psoralens” are irradiated with 308 or 355 nm (3 only) light.
TWO NEW STERICALLY HINDERED PHTHALOCYANINES: SYNTHETIC AND PHOTODYNAMIC ASPECTS
Authors: Rihter Boris D. , Bohorquez Maria D. , J.Rodgers Michael A. , Kenney Malcolm E.
Published: July 2010

Abstract— The synthesis and the properties of l,4‐dibutoxy‐2,3‐dicyanotriptycene, of a metal‐free tetradibenzobarrelenooctabutoxyphthalocyanine, and of the corresponding zinc phthalocyanine are described. The two phthalocyanines do not aggregate when dissolved in benzene at concentrations up to 450 μM. For the metal‐free and the zinc compounds, the red band maxima are at 736 and 757 nm, the triplet maxima are at 590 and 605 nm, the triplet state lifetimes are 58 and 177μs, and the protoporphyrin‐IX dimethyl ester‐to‐compound bimolecular rate constants for triplet energy transfer are 2.61 × 108 and 1.47 × 108 M‐1 s‐1. Triplet energy transfer from the metal‐free compound to O2 is endoergonic by 1.0 kcal mol‐1. The potential of the zinc compound for photodynamic therapy is touched upon.
PHOTO‐INDUCED ELECTRON TRANSFER FROM NUCLEOTIDES TO RUTHENIUM‐TRIS‐1,4,5,8TETRAAZAPHENANTHRENE: MODEL FOR PHOTOSENSITIZED DNA OXIDATION
Authors: Lecomte Jean‐Paul , Mesmaeker Andrée Kirsch‐De , Kelly John M. , Tossi Alex B. , Görner Helmut
Published: July 2010

Abstract— The luminescence quenching of ruthenium‐tris‐l,4,5,8‐tetraazaphenanthrene [Ru(tap)32+] by nucleotides approaches the diffusion rate only with guanosine‐5′‐monophosphate (GMP), the most reducing nucleotide, and leads to an electron transfer with the production of the monoreduced complex and the oxidized base. The resulting deprotonated GMP(‐H)radical recombines with the monoreduced complex according to a bimolecular equimolar process.

The pH dependence of the decay of the transient reduced complex, in the presence of an oxidant (oxygen or benzoquinone) indicates the formation of Ru(tap)2(tapH)2+i.e. the reduced protonated species, subsequent to the electron transfer, with a pKa of 7.6 as confirmed from pulse radiolysis experiments. As the non‐protonated reduced complex, Ru(tap)2(tap2)+ has a higher reducing power than the protonated one, oxygen is able to reoxidize only the non‐protonated species, whereas benzoquinone reoxidizes both species but with different rate constants.

The flash photolysis of Ru(tap),2+ in the presence of DNA and the effect of Mg2+ ions and GMP as supplementary additives also show the existence of a photo‐induced electron transfer with the nucleic acid, which can be correlated to the photosensitized cleavage of DNA by this complex.
DOSE‐RESPONSE OF CHRONIC ULTRAVIOLET EXPOSURE ON EPIDERMAL FORWARD SCATTERING‐ABSORPTION IN SK‐1 HAIRLESS MOUSE SKIN
Authors: Menter Julian M. , Acin Patricia P. , Sayre Robert M. , Willis Isaac
Published: July 2010

Abstract— This work provides a dose‐response model of UV‐induced epidermal‐stratum corneum thickening induced by irradiation at wavelength X. This model assumes that photobiochemical reaction(s) can give rise to hyperplasia in a manner which is predictable from a simple photochemical kinetic scheme. In this work, we derive an equation which predicts an approximately linear relationship between the logarithm of the increase in optical skin thickening measured at 320 nm (ΔOD320) and total cumulative dose (DT) seen by the target cells in or near the basal layer. For each excitation wavelength Λ, the slope R(Λ) of the log ΔOD320vs DT plot is proportional to ε(Λ) φrx where ε(Λ) is the extinction coefficient for the target chromophore at excitation wavelength, and φrx is the quantum yield for the photochemical reaction(s) leading to hyperplasia. Our data previously obtained from irradiation of SK‐1 hairless mice with “monochromatic” UV wavebands at 280, 290, 300, 307 and 313 nm (Menter et al., 1988, Photochem. Photobiol. 47, 225–260.) and data from Sterenborg and van der Leun at 254 and 313 nm (1988, Photodermatology 5, 71–82) are in good agreement with this model, except for 254 and 280 nm excitation, which are greatly attenuated by epidermis‐stratum corneum. For excitation at the latter wavelengths, “dark” regressive processes successfully compete with the “light” reaction(s) which lead to (pre)cancerous lesion. This difficulty notwithstanding, the “intrinsic” action spectrum for hyperplasia derived from these measurements indicates that the target chromophore preferentially absorbs in the UV‐C region.

Assuming ε(Λ) ≅ 1000 M‐1 cm‐1 of 280 nm, our values of R(Λ) indicate that the photochemical reaction(s) leading to hyperplasia are roughly as efficient as thymine photodimerization in aqueous solution, with φrx≅ 4 × 10–4. This work is important because it illustrates that, to a first approximation, even complex photobiological processes may be rationalized on the basis of fundamental photochemical processes, as occurring in “simple” homogeneous photochemical reactions in solution.
CLEARANCE TIMES OF PORPHYRIN DERIVATIVES FROM MICE AS MEASURED BY in vivo FLUORESCENCE SPECTROSCOPY
Authors: Kennedy J. C. , Nadeau P. , Petryka4 Z. J. , Porrier R. H. , Weagle G.
Published: July 2010

Abstract— The clearance times of 17 different porphyrin derivatives from SKH:HR‐1 mice have been measured using the technique of in vivo fluorescence spectroscopy. This technique monitors the in vivo porphyrin fluorescence observed from the external skin surface. Most hydrophilic porphyrin derivatives show relatively short clearance times, in the order of 2.5–6 h. The dicarboxylic acid porphyrins, proto‐, hydroxyethylvinyldeutero‐and hematoporphyrin IX have clearance times of 7.8, 12.2 and 14.7 h respectively. The mixture hematoporphyrin derivative has an intermediate clearance time of 12.6 h. N‐methylated porphyrins show clearance times in the vicinity of 15–22 h. Monoaspartyl chlorin e6 shows the longest clearance time of all porphyrin derivatives measured (30.3 h).