bluuebunny/crossref_metadata_2025 huggingface dataset:
Matrix Cracking in 3D Orthogonal Melt‐Infiltrated SiC/SiC Composites with Various Z‐Fiber Types
Authors: Morscher Gregory N. , Yun Hee Mann , DiCarlo James A.
Published: July 2010

The occurrence of matrix cracks in melt‐infiltrated SiC/SiC composites with a three‐dimensional (3D) orthogonal architecture was determined at room temperature for specimens tested in tension parallel to the Y‐direction (perpendicular to Z‐bundle weave direction). The fiber types were Sylramic and Sylramic‐iBN in the X‐ and Y‐directions and lower modulus ZMI, T300, and rayon in the Z‐direction. Acoustic emission (AE) was used to monitor the matrix‐cracking activity. For Y‐direction composites, the AE data were used to determine the location (±0.25 mm) where matrix cracks occurred in the 3D orthogonal architecture. This enabled the determination of the stress‐dependent matrix crack distributions for small but repeatable matrix‐rich “unidirectional” and the matrix‐poor “cross‐ply” regions within the architecture. Matrix cracking initiated at very low stresses (∼40 MPa) in the “unidirectional” regions for the largest Z‐direction fiber tow composites. Decreasing the size of the Z‐fiber bundle increased the stress for matrix cracking in the “unidirectional” regions. Matrix cracking was analyzed on the basis that the source for through‐thickness matrix cracks (TTMC) originated in the 90° or Z‐fiber tows. It was found that matrix cracking in the “cross‐ply” regions was very similar to two‐dimensional cross‐woven composites. However, in the “unidirectional” regions, matrix cracking followed a Griffith‐type relationship, where the stress‐distribution for TTMC was inversely proportional to the square root of the height of the Z‐fiber tows.
Single‐Calcination Synthesis Mechanism of Pure‐Perovskite Pb(Ni1/3Nb2/3)O3‐PbTiO3 Using a Coating Method
Authors: Xiang Ping‐Hua , Zhong Ni , Dong Xian‐Lin , Feng Chu‐De , Wang Yong‐Ling
Published: July 2010

Pure‐perovskite 0.64Pb(Ni1/3Nb2/3)O3–0.36PbTiO3 (PNN–PT) powder has been successfully synthesized by only one‐step calcination using a coating method. SEM photograph shows that PNN–PT powder with the size of 2–4 μm is cubic and well dispersed. Based on X‐ray diffraction analysis, solid‐state reactions in the process of calcination in PbO–Nb2O5–TiO2–NiO system are investigated. In comparison with conventional solid state method, the single‐calcination synthesis mechanism of pyrochlore‐free lead‐based niobate ferroelectrics using a coating method is tentatively proposed. A typical coating structure of Ni precipitate‐coated Nb2O5 powder facilitates the formation of perovskite PNN–PT phase at a relatively low calcination temperature, resulting in the successful synthesis of pyrochlore‐free PNN–PT powder in one‐step calcination at 900°C.
Fabrication of Transparent Hydroxyapatite Sintered Body with High Crystal Orientation by Pulse Electric Current Sintering
Authors: Watanabe Yujiro , Ikoma Toshiyuki , Monkawa Akira , Suetsugu Yasushi , Yamada Hirohisa , Tanaka Junzo , Moriyoshi Yusuke
Published: July 2010

Transparent hydroxyapatite (HAp) sintered body with a high crystal orientation and a relative density of 99.7% was fabricated by the pulse electric current sintering method; the c‐axis of HAp crystals with a hexagonal column morphology and ca. 200 μm × 25 μm in size was oriented perpendicular to the pressure direction. The sintered temperature increased to 1200°C at a heating rate of 50°C/min for 10 min and a pressure of 50 MPa was applied. The orientation indexes were calculated from X‐ray diffraction patterns of the planes perpendicular and parallel to the pressure direction. The optical transmittance was greater than 70% over the wavelength of 700 nm.
Effect of Mesoporous Silica Buffer Layer on the Orientation of MFI Zeolite Membranes
Authors: Zhang Fa‐Zhi , Fuji Masayoshi , Takahashi Minoru
Published: July 2010

Growth of MFI zeolite membranes on porous α‐alumina substrates with and without precoated mesoporous silica buffer layer has been performed by in situ crystallization. A preferentially b‐oriented MFI membrane can be prepared on a mesoporous silica‐coated substrate. A membrane with a randomly oriented and eventually [h0h]‐oriented top layer is obtained on an uncoated α‐alumina substrate. The chemical properties of the substrate are suggested to have significant effects on the membrane orientation.
Effects of Aluminum and Zirconia Contents on the Sintering of Reaction‐Bonded Aluminum Oxide Ceramics
Authors: Sheedy Paul M. , Caram Hugo S. , Chan Helen M. , Harmer Martin P.
Published: July 2010

The reaction‐bonded aluminum oxide (RBAO) process is an attractive alternative to the conventional processing of Al2O3‐based ceramics. The most attractive features of the process are the high strengths, densities, and easy machinability of the green powder compacts, and the low shrinkage and high strengths of the sintered ceramics. These advantages result from the presence of aluminum in the green bodies and are enhanced further with increasing aluminum contents. However, it is apparent that ZrO2‐containing RBAO powders with higher aluminum contents (>45 vol%) are increasingly more difficult to densify, as the start of densification is delayed (shifted to higher temperatures) and the densification rates are decreased. Ultimately, this results in a decrease in the limiting density to which the RBAO ceramic may be sintered. In this study, the cooperative effects of ZrO2 and aluminum contents on the sintering of RBAO ceramics are discussed in terms of densification behavior and microstructural analysis.
Residual Stress and Microstructural Evolution in Tantalum Oxide Coatings on Silicon Nitride
Authors: Weyant C. M. , Faber K. T. , Almer J. D. , Guiheen J. V.
Published: July 2010

Due to its coefficient of thermal expansion (CTE) and phase stability up to 1360°C, tantalum oxide (Ta2O5) was identified and investigated as a candidate environmental barrier coating for silicon nitride‐based ceramics. Ta2O5 coatings were plasma sprayed onto AS800, a silicon nitride ceramic from Honeywell International, and subjected to static and cyclic heat treatments up to 1200°C in air. Cross‐sections from coated and uncoated substrates were polished and etched to reveal the effect of heat treatments on microstructure and grain size. As‐sprayed coatings contained vertical cracks that healed after thermal exposure. Significant grain growth that was observed in the coatings led to microcracking due to the anisotropic CTE of Ta2O5. High‐energy X‐ray diffraction was used to determine the effect of heat treatment on residual stress and phases. The uncoated substrates were found to have a surface compressive layer before and after thermal cycling. Coating stresses in the as‐sprayed state were found to be tensile, but became compressive after heat treatment. The microcracking and buckling that occurred in the heat‐treated coatings led to stress relaxation after long heat treatments, but ultimately would be detrimental to the function of the coating as an environmental barrier by affording open pathways for volatile species to reach the underlying ceramic.
Gas Release of SiC Implanted with Deuterium or Helium
Authors: Aihara J. , Sawa K. , Furuya Y. , Hojo T. , Furuno S. , Yamamoto H. , Hojou K. , Ishihara M.
Published: July 2010

Helium (He+) or Deuterium (D2+) (20 keV) was implanted into polycrystalline β‐SiC with an ion dose of 7.2 × 1021 (D or He)/m2. The implanted specimens were heated at a heating rate of 10 or 20 K/min from room temperature to 1373 K, and the thermal release spectroscopic data were obtained. A sharp peak appeared at approximately 1270 K in the case of He release, and here the activation energy was estimated to be approximately 4.4 eV. Two overlapped peaks appeared at approximately 900 and 1200 K in the case of D2 release. The shapes of spectra showed strong dependence on the heating rate.
Stress Relaxation of Compression Loaded Plasma‐Sprayed 7 Wt% Y2O3–ZrO2 Stand‐Alone Coatings
Authors: Dickinson Graeme R. , Petorak Chris , Bowman Keith , Trice Rodney W.
Published: July 2010

Stand‐alone plasma‐sprayed tubes of 7 wt% Y2O3–ZrO2 made from the same starting powder but at two different sites were subject to stress‐relaxation testing in axial compression at temperatures of 25°, 1000°, 1050°, 1100°, and 1200°C and at an initial stress of 10–80 MPa. A time‐dependent stress response was observed for both coatings at all temperatures. For example, a 20 MPa stress applied at 1050°C relaxed to ∼3 MPa in 180 min. When the same initial stress was applied at 1200°C, the coating fully relaxed in 32 min. For all experimental conditions evaluated, an initial fast stress‐relaxation regime was observed (<10 min), followed by a slower second stress‐relaxation regime at later times (>10 min). Coatings with higher as‐sprayed densities exhibited a lengthened fast relaxation regime as compared with less dense coatings. A Maxwell model was modified in order to provide an accurate fit to the experimental stress‐relaxation curves. From scanning electron microscopy experiments and mechanical data, the mechanism for stress relaxation from 25°C through 1200°C, particularly during fast relaxation, was proposed to be the formation of cracks parallel with respect to the applied load. In addition to this mechanism, stress relaxation that occurred in specimens tested at 1000°C through 1200°C was proposed to be due to partial or complete closure of cracks oriented perpendicular to the applied stress.
Harmonic Analysis of Polarization Hysteresis of Aged PZTs
Authors: Srilomsak Sutham , Schulze Walter A. , Pilgrim Steven M. , Williams Francis A.
Published: July 2010

Many studies have been performed on aging of lead zirconate titanate (PZT), but a single model has not been universally accepted. An aim of this research was to determine whether harmonic analysis could distinguish among the models for the aging of PZTs. Doped and undoped PZT samples were prepared, and the aging behaviors of relative dielectric constant (K), planar coupling factor (kp), dielectric coefficient (d33), and polarization were analyzed by both weak‐field and harmonic analysis methods at 37°C. Results indicated that aging behavior, as noted by a harmonic analysis, substantially agreed with the weak‐field behavior. This finding suggests that harmonic analysis is a promising new method for studying the aging of PZTs, which may contribute to developing a better aging model for PZTs.
Density Measurements of Single Granules Using the Atomic Force Microscope
Authors: Andersson Karin M. , Bergström Lennart
Published: July 2010

The density of single spray‐dried granules has been determined with a new method based on atomic force microscopy (AFM). Spherical granules with a well‐defined diameter are attached to the AFM cantilever, which acts as a beam‐type spring, and the mass of a granule is estimated from the shift in the resonant frequency. The error of the measurements associated with the method was estimated to vary between 1% and 5%, depending on the size and shape of the granule. Density measurements of spray‐dried WC–Co granules are presented, and the effect of a polymeric binder and dispersant on the consolidation during drying is discussed.
Reactive Hot‐Pressed Alumina–Boron Nitride Composites with Y2O3 Sintering Additive
Authors: Zhang Guo‐Jun , Kita Hideki , Kondo Naoki , Ohji Tatsuki
Published: July 2010

The effect of Y2O3 addition (0–5 wt%) on the densification and properties of reactive hot‐pressed alumina (Al2O3)–boron nitride composites based on the reaction between aluminum borate (2Al2O3·B2O3) and aluminum nitride (AlN) was investigated. The densification process was very sensitive to the amount of Y2O3. Compared with a low relative density of 79.3 theoretical density (TD)% for material with no Y2O3 addition, the material density reached 98.6 TD% with 0.25% Y2O3 addition. High Y2O3 additions resulted in the formation of a new phase Al5Y3O12. The grain growth of the Al2O3 matrix was promoted by the Y2O3 addition. Owing to the high density and the small Al2O3 particle size the sample with 0.25% Y2O3 addition demonstrated the highest bending strength of 540 MPa.
Processing of Polymer‐Derived Ceramic Composite Coatings on Steel
Authors: Torrey Jessica D. , Bordia Rajendra K.
Published: July 2010

Polymer‐derived ceramic composites are being investigated as environmental barrier coatings to protect stainless steel from oxidation and carburization. Coatings have been produced using poly(hydridomethylsiloxane) as a preceramic polymer and titanium disilicide as an expansion agent. Processing parameters have been optimized and a relationship has been derived to predict the final coating thickness based on slurry viscosity and dip coating withdrawal speed. Microstructural analysis reveals a composite coating of oxidized filler particles in a silica matrix. A diffusion layer is visible at the coating–steel interface, indicating good bonding. The optimized coatings are ∼18 μm thick, and have some residual porosity and a density of 2.56 g/cm3.
Two‐Step Sintering of Nanocrystalline ZnO Compacts: Effect of Temperature on Densification and Grain Growth
Authors: Mazaheri Mehdi , Zahedi A. M. , Sadrnezhaad S. K.
Published: July 2010

Two‐step sintering (TSS) was applied on nanocrystalline zinc oxide (ZnO) to control the accelerated grain growth occurring during the final stage of sintering. The grain size of a high‐density (>98%) ZnO compact produced by the TSS was smaller than 1 μm, while the grain size of those formed by the conventional sintering method was ∼4 μm. The results showed that the temperature of both sintering steps plays a significant role in densification and grain growth of the nanocrystalline ZnO compacts. Several TSS regimes were analyzed. Based on the results obtained, the optimum regime consisted of heating at 800°C (step 1) and 750°C (step 2), resulting in the formation of a structure containing submicrometer grains (0.68 μm). Heating at 850°C (step 1) and then at 750°C (step 2) resulted in densification and grain growth similar to the conventional sintering process. Lower temperatures, e.g., 800°C (step 1) and 700°C (step 2), resulted in exhaustion of the densification at a relative density of 86%, above which the grains continued to grow. Thermogravimetric analysis results were used to propose a mechanism for sintering of the samples with transmission electron micrographs showing the junctions that pin the boundaries of growing grains and the triple‐point drags that result in the grain‐boundary curvature.
Crystallization Kinetics and Microwave Properties of Bi0.5Y2.5Fe5O12 Via the Coprecipitation Process
Authors: Fu Yen‐Pei , Cheng Chih‐Wen , Hung Dung‐Shing , Yao Yeong‐Der
Published: July 2010

The crystallization kinetics of Bi0.5Y2.5Fe5O12 powders prepared by the coprecipitation process have been investigated. The activation energy of crystallization was calculated on the basis of differential scanning calorimetry at different heating rates. Analysis of nonisothermal DSC data yielded a value of 823.8 kJ/mol and 2.25 for the activation energy of crystallization and the Avrami exponent, respectively. This value for the Avrami exponent was consistent with surface and internal crystallization occurring simultaneously. The complex permittivity and permeability of Bi0.5Y2.5Fe5O12 was measured at the X‐band (8–12 GHz) using the cavity perturbation technique. For dielectric properties, the real part of permittivity, ɛ′, was obtained in the range of 13.57–16.37. For magnetic properties, the real part of permeability, μ′, was obtained in the range of 21.61–16.90.
Structure, Properties, and Impedance Spectroscopy of CaCu3Ti4O12 Ceramics Prepared by Sol–Gel Process
Authors: Sun Dun‐Lu , Wu Ai‐Ying , Yin Shao‐Tang
Published: July 2010

CaCu3Ti4O12 (CCTO) ceramics with high dielectric constant (2–4 × 104) and low loss (0.04) were prepared by the sol–gel process and sintered at 1050°C for different times. The sintering time has a sensitive influence on the values of the dielectric constant and nonlinear coefficient. Tailored dielectric constant and nonlinear coefficient can be obtained by selecting a suitable sintering time according to different desired device application. The result of current–voltage characteristics and Cole–Cole plots in a broad temperature range (60–400 K) provide more effective evidence of the high dielectric constant supported by the grain boundary barrier layer (GBBL) capacitors model. Below 150 K, the GBBL capacitors effect weakens and gradually disappears with further decrease of temperature, thus leading the dielectric constant to decrease rapidly. Two values of grain activation energy acting at different temperature for each sample were obtained.
Isothermal Section of a Cu2O–Al2O3–SiO2 Pseudo‐Ternary System at 1150°C in Air
Authors: Xiao Qiuguo , Ma Hui , Zhao Xinhua
Published: July 2010

In this study, the isothermal section of a Cu2O–Al2O3–SiO2 pseudo‐ternary phase diagram at 1150°C was analyzed by means of a scanning electronic microscope and powder X‐ray diffraction of the quenched samples qualitatively, and the compositions of the tie‐points of the tie‐planes as well as their regions were determined by in situ high‐temperature quantitative X‐ray diffraction analysis and energy‐dispersive X‐ray spectroscopy. Then, the isothermal section of the Cu2O–Al2O3–SiO2 pseudo‐ternary phase diagram at 1150°C was constructed; it was found that the isothermal section is composed of two single liquid‐phase regions, five two‐phase regions, and six three‐phase regions.
Growth Kinetic and Characterization of RF‐Sputtered ZnO:Al Nanostructures
Authors: Choopun Supab , Hongsith Niyom , Wongrat Ekasiddh , Kamwanna Teerasak , Singkarat Somsorn , Mangkorntong Pongsri , Mangkorntong Nikorn , Chairuangsri Torranin
Published: July 2010

ZnO:Al nanostructures with 1% by mole of Al were prepared by radio frequency sputtering on copper and quartz substrates. The ZnO:Al nanostructures obtained exhibited needle‐ or tree‐like structures with the diameter ranging from 30 to 100 nm. It was suggested that these ZnO:Al nanostructures could be single‐crystalline hexagonal structures growing along the

direction with branching along the 〈0001〉 direction. From Hall measurement, ZnO:Al nanostructures had a resistivity in the order of 10−2Ω·cm, a carrier concentration of 1020 cm−3, and a Hall mobility of 3 cm2·(V·s)−1. From X‐ray diffraction, transmission electron microscopy and Raman results, ZnO:Al nanostructures had

direction perpendicular to the surface, whereas ZnO nanobelts had the c‐axis perpendicular to the surface. In addition, the growth mechanism of the wire and belt‐like nanostructure could be explained by kinetics of anisotropic growth via a vapor–solid mechanism. This information would be useful for further applications of ZnO:Al nanostructures.
First Observation of α‐Ca2[SiO3(OH)](OH)–Ca6[Si2O7][SiO4](OH)2 Phase Transformation upon Thermal Treatment in Air
Authors: Garbev Krassimir , Gasharova Biliana , Beuchle Günter , Kreisz Siegfried , Stemmermann Peter
Published: July 2010

Thermal treatment transforms α‐Ca2[SiO3(OH)](OH) (α‐C2SH) into hydraulic Ca2SiO4 polymorphs, which is a process of considerable interest to the cement chemistry community. The thermal behavior of differently synthesized samples of α‐C2SH in air at ambient pressure has been investigated in detail by high‐temperature powder X‐ray diffraction (XRD), synchrotron‐based infrared (IR) microspectroscopy of single crystals, trimethylsilylation method (TMSM), and thermal analysis. Powder XRD data on α‐C2SH samples heated to different temperatures between 300° and 500°C suggest coexistance of α‐C2SH and dellaite, Ca6[Si2O7][SiO4](OH)2. IR absorption bands typical for the initial α‐C2SH phase diminish over the course of thermal treatment, accompanied by the appearance of bands characteristic for dellaite. The partial polymerization of the isolated SiO3(OH) tetrahedra present in α‐C2SH to [Si2O7] dimers, as expected for dellaite, was proven by the presence of an IR band at 1050 cm−1 and by TMSM. For the first time, dellaite, along with x‐Ca2SiO4, was observed as an intermediate product of the dehydration of α‐C2SH. Until now, dellaite was believed to be only a high‐pressure phase. Dellaite coexists with x‐Ca2SiO4 up to 560°–620°C and decomposes to x‐Ca2SiO4 at higher temperatures. Upon further heating, the latter phase transforms into α′l‐Ca2SiO4, and finally gives β‐Ca2SiO4 after cooling to room temperature. The thermal decomposition of α‐C2SH is a much more complicated process than reported previously. Different factors, such as the source of Ca and the presence of NaOH during synthesis, seem to control the mechanism of its dehydration. The presence of dellaite is shown to lower the temperature of formation of β‐Ca2SiO4.
A Novel Method of Predicting Ultrasonic and Elastic Properties of Isotropic Ceramic Materials after Sintering from the Properties of Partially Sintered or Green Compacts
Authors: Phani Kalyan Kumar
Published: July 2010

A novel method for predicting the porosity dependence of ultrasonic and elastic properties of isotropic ceramics after sintering based on the properties of green or partially sintered compacts has been proposed. The method is based on the observation that the ratio of ultrasonic shear wave to longitudinal wave velocity is a function of porosity only and varies linearly with the longitudinal wave velocity. It is also shown that the predicted trend of variation of Poisson's ratio with porosity agrees with the predictions of the Mori–Tanaka mean field approach. The method can be used as a quality control tool during the preparation of ceramic materials.
Development of a Dense Electrolyte Thin Film by the Ink‐Jet Printing Technique for a Porous LSM Substrate
Authors: El‐Toni Ahmed Mohamed , Yamaguchi Toshiaki , Shimizu Sota , Fujishiro Yoshinobu , Awano Masanobu
Published: July 2010

Recently, the fabrication and development of novel solid oxide fuel cell (SOFC) structures were conducted with the aim of enhancing power generation. Newly cathode‐supported honeycomb‐type SOFC with a promising power/volume ratio is under development. However, the conventional processing techniques used for the fabrication of different SOFC cell components (electrolyte and electrode) are not compatible with the newly constructed honeycomb structure. The ink‐jet printing technique may offer the ability to design and fabricate SOFC components on honeycomb substrates and complex 3D structures. In this study, the formation of a dense Gadolinium‐doped ceria thin film on a cathode‐supported LaSrMnO3 substrate by the ink‐jet printing technique was investigated.
Bronchopulmonary dysplasia – prevalence, severity and predictive factors in a national cohort of extremely premature infants
Authors: Farstad T , Bratlid D , Medbø S , Markestad T ,   The Norwegian Extreme Prematurity Study Group*
Published: July 2010

Aim:  To study prevalence and predictive factors of bronchopulmonary dysplasia (BPD) in a cohort of preterm infants with a high incidence of prenatal steroid and surfactant treatment.

Methods:  BPD was analysed in a national cohort of infants with gestational age (GA) of 22–27 completed weeks (wks) or birth weight (BW) of 500–999 g. Of 464 infants who were transferred to a NICU, 377 infants with GA ≤ 30 wks and survived beyond 28 days were included in the study.

Results:  Moderate or severe BPD was strongly related to GA. Of infants with GA 22–25 wks, 67.3% developed BPD compared to 36.6% at GA 26–30 wks. Overall, moderate and severe BPD was significantly more common in boys (63.3%) than in girls (36.6%) (p = 0.0004), but female gender was not a protective factor in infants with GA 22–25 wks. In multivariate analyses, BPD was significantly associated with gender, surfactant treatment and treatment for PDA.

Conclusions:  BPD remains a severe complication of extreme prematurity in spite of prenatal steroids and surfactant treatment. Whether associations with surfactant and PDA treatment simply reflect severity of early lung disease or have causal relationships should probably be studied in randomized controlled trials.
PHYTOCHROME‐MEDIATED GERMINATION: EFFECTS OF BRIEF HIGH TEMPERATURE TREATMENTS
Authors: McDonough Walter T.
Published: July 2010

Abstract— Brief high temperature treatments, applied early in the pregerminative period to radiation‐requiring seeds of lettuce, inhibited both dark and radiation‐induced germination. The inhibition increased with increasing incubation temperature. There was little difference in the germination percentage whether the inductive irradiation was applied before or after the high temperature treatment. When the high temperature treatment preceded induction, there was an increase in the radiation dosage required for maximum germination. These findings are interpreted in terms of lability of physiologically active phytochrome to higher temperatures.
AMPHIPHILIC COPOLYMERS AS MEDIA FOR LIGHT‐INDUCED ELECTRON TRANSFER–I. ELECTROSTATIC EFFECT ON THE FORWARD REACTION AS STUDIED BY FLUORESCENCE QUENCHING
Authors: Itoh Yoshihiro , Morishima Yotaro , Nozakura Shun‐ichi
Published: July 2010

Abstract— Fluorescence quenching of amphiphilic copolymers, poly(9‐vinylphenanthrene‐co‐sodium 2‐acrylamido‐2‐methylpropanesulfonate) (APh) and poly(9‐vinylphenanthrene‐co‐3‐methacrylamidopropyltrimethylammonium methyl sulfate) (QPh), in aqueous solution, was studied using methyl viologen (MV2+) or 4,4'‐bipyridinium‐1, 1'‐bis(trimethylenesulfonate) (SPV) as oxidative quenchers. The fluorescence of the excited phenanthrene groups in APh was found to be efficiently quenched by MV2+. The apparent second‐order rate constant for the quenching, kq, ranged in the magnitude of 1011 ‐1012M‐1 s‐1, which are well beyond the diffusion‐controlled limit. This is presumably due to an increase of the effective concentration of MV2+ around the fluorophore in the copolymer resulting from electrostatic attraction between MV2+ and anionic segments of APh. This strong electrostatic interaction also favors the formation of ground‐state EDA (electron donor acceptor) complex between the phenanthrene residue and MV2+. Such striking behaviors were not observed with the related model compound. Unexpectedly, the quenching with SPV, a zwitterionic quencher, was also enhanced in the polymer system (kq= 2–6 × 1010M‐1 s‐1), suggesting the presence of some attractive interaction between APh and SPV. Contrary to the APh system, the fluorescence quenching of the corresponding cationic polymer (QPh) with MV2+ was strongly diminished (kq= 5 × 108M‐1 s‐1). This indicates that the polycation of QPh effectively prevents the access of MV2+ to the polymer.
OXYGEN REQUIREMENT FOR NEAR‐UV MEDIATED CYTOTOXICITY OF PHENYLHEPTATRIYNE TOEscherichia coli
Authors: Kagan Jacques , Tadema‐Wielandt Katrina , Chan Ging , Dhawan Som N. , Jaworsky Jeffrey , Prakash Indra , Arora Sudershan K.
Published: July 2010

Abstract—Phenylheptatriyne (PHT) is a good singlet oxygen sensitizerin vitro. In vivo, its phototoxicity towardE. coli Bhas been proved unequivocally to depend on the presence of oxygen. The literature reports indicating that phenylheptatriyne was representative of a new class of sensitizers were probably based on experiments conducted under conditions which were not strictly anaerobic.
PHOTOREACTIVITY OF PHOTOTOXIC ANTIMALARIAL COMPOUNDS
Authors: Epling Gary A. , Yoon Ung Chan , Ayengar Narayan K. N.
Published: July 2010

Abstract— The photochemical reactivity of six phototoxic 2‐arylquinolinemethanol antimalarials was examined to understand the chemical mechanism of reaction that causes the in vivo phototoxicity. All of these compounds were found to be photochemically reactive, giving products of photochemical fragmentation involving cleavage of the side chain. The products which are formed, the variation in product distribution with change of solvent and presence of thiols, and photolyses in deuterium‐labeled solvents indicate that free radicals are involved in the photofragmentation. There is a good correlation between the quantum efficiency of the photofragmentation reaction and the phototoxicity of the compounds; the more phototoxic compounds react most efficiently, while the less phototoxic compounds react less efficiently. It appears that in vivo free radical reactions caused by the photofragmentation of these compounds are the source of their phototoxicity.
THE TRANSVERSE LOCATION OF FLUOROPHORES IN LIPID BILAYERS AND MICELLES AS DETERMINED BY FLUORESCENCE QUENCHING TECHNIQUES
Authors: Blatt Edward , Chatelier Ronald C. , Sawyer William H.
Published: July 2010

Abstract— A fluorescence quenching technique has been used to determine the absolute partition coefficients of a set of n‐doxyl stearates which partition between the aqueous and lipid phases of a phospholipid dispersion, and it is shown that the values of the coefficients vary in a systematic way depending on the position of the doxyl group on the acyl chain of the fatty acid. The n‐doxyl stearates quench the fluorescence of n‐(9‐anthroyloxy) fatty acids in lipid bilayers, and consideration of the absolute partition coefficients of the quencher and of the microviscosity of the bilayer is necessary to extract information about the proximity of the fluorophore and quencher. In addition, quenching of the fluorescent fatty acids with a quencher which is small relative to the width of the lipid bilayer allows determination of both the absolute and local partition coefficients, the latter referring to a subvolume of the bilayer within which quenching occurs. The relationship between absolute and local partition coefficients is defined for micelles and bilayers and a method for determining the relative transverse positions of the anthroyloxy rings in these structures is described.
PHOTOSENSITIZATION BY ANTITUMOR AGENTS–7. CORRELATION BETWEEN ANTHRACENEDIONE‐PHOTOSENSITIZED DNA DAMAGE, NADH OXIDATION AND OXYGEN CONSUMPTION FOLLOWING VISIBLE LIGHT ILLUMINATION
Authors: Hartley John A. , Reszka Krzysztof , Lown, * J. William
Published: July 2010

Abstract—The 1,4‐diamino‐substituted anthraquinones mitoxantrone and ametantrone do not photosensitize DNA damage following illumination with visible light. In contrast, both the 1,5‐ and 1,8‐bis[[(diethylamino)ethyl]amino]anthraquinones, AMI and AM2 respectively, sensitized DNA single‐strand break formation in closed‐circular plasmid DNA upon exposure to visible light. The presence of an electron donor such as NADH is required in the case of AMI, and enhances the effect with AM2. At increasing DNA base pair to drug ratios the rate of oxygen consumption decreased rapidly suggesting that the drug photosensitizing properties are lost upon binding or intercalation into DNA. A direct correlation between oxygen consumption, NADH oxidation and extent of DNA damage was established at different DNA base pair to drug ratios.
THE RELATIVE BIOLOGICAL IMPORTANCE OF CYCLOBUTANE AND(6–4) PYRIMIDINE‐PYRIMIDONE DIMER PHOTOPRODUCTS IN HUMAN CELLS: EVIDENCE FROM A XERODERMA PIGMENTOSUM REVERTANT*
Authors: Cleaver James E. , Cortés Felipe , Karentz Deneb , Lutze Louise H. , Morgan William F. , Player Audrey N. , Vuksanovic Ljiljana , Mitchell David L.
Published: July 2010

Abstract— The relative biological importance of(5–5,6–6) cyclobutane and(6–4) pyrimidine‐pyrimidone dimers in mammalian cells has been determined in a xeroderma pigmentosum (XP) revertant that repairs only the(6–4) photoproduct. Surprisingly, the majority of biological effects of UV light, including cell killing, sister chromatid exchange, mutagenesis, and inhibition and recovery of DNA and RNA synthesis, appear to be due to the(6–4) photoproduct and not to the cyclobutane dimer. Although the XP revertant repairs its own genomic DNA, it fails to repair damage in shuttle vectors, including the pZ189 mutational and chloramphenicol acetyl transferase transcriptional assay systems. The revertant is therefore a cell line for which shuttle vectors are inappropriate as models for genomic DNA repair, and may highlight a general weakness of shuttle vectors for the study of infrequent DNA lesions.
RHYTHMIC OSCILLATION OF CYCLIC 3′,5′AMP AND ‐GMP CONCENTRATION AND STIMULATION OF FLOWERING BY CYCLIC 3′,5′‐GMP IN Lemna paucicostata 381
Authors: Hasunuma Kohji , Funadera Kanako , Furukawa Kazuhiko , Miyamoto‐Shinohara Yukie
Published: July 2010

Abstract— Rhythmic oscillation of the concentration of cyclic 3′,5′‐AMP and ‐GMP in a short day plant, Lemna paucicostata 381 in continuous darkness was detected after 2 cycles of 12 h dark and 12 h light entrainment. Cyclic 3′,5′‐AMP and ‐GMP, extracted from whole plant showed parallel oscillations in their concentrations for initial 36 h in continuous darkness and the oscillation in the concentration of cyclic 3′,5′‐AMP was roughly circadian. Their concentrations decreased during the initial 12 h (subjective night) and increased during 12 to 28 h. Exogenous addition of 2 μ.M of cyclic 3′,5′‐GMP or the dibutyryl derivative of it stimulated floral induction by 20 to 30%, when the plants were grown under 12 h light and 12 h dark regime. Cyclic 3′,5′‐AMP or the dibutyryl derivative of it showed little effect on flowering.
PROPERTIES OF IMMOBILIZED THYLAKOID MEMBRANES IN A PHOTOSYNTHETIC PHOTOELECTROCHEMICAL CELL
Authors: Lemieux Sylvie , Carpentier Robert
Published: July 2010

Abstract— Thylakoid membranes isolated from spinach were immobilized in a cross‐linked albumin‐glutaraldehyde matrix. Their properties in a single‐compartment photoelectrochemical cell using platinum electrodes in potentiostatic mode were compared with the native material. The porous network of the immobilized tissue retained a relatively significant quantity of aqueous media which could be modified at will by aspiration of the proper media. In the presence of the acceptor potassium ferricyanide the photocurrent generation was enhanced up to a value of one hundred times higher than the maximum output of thylakoids entrapped in a polyvinyl alcohol film deposited on a Sn02 electrode. Immobilization in the albumin‐glutaraldehyde matrix resulted in a better resistance to high pH, elevated temperatures and continuous exposure to high light intensity in potentiostatic mode (working conditions) in the electrochemical cell.
REVERSIBLE BLEACHING OF Chlamydomonas reinhardtii RHODOPSIN in vivo
Authors: Hegemann P. , Hegemann U. , Foster K. W.
Published: July 2010

Abstract— The effect of hydroxylamine on the phototactic activity of Chlamydomonas reinhardtii was investigated. The following results were obtained: (1) wild type cells, irradiated for 10 min with green light immediately after addition of 1 mM hydroxylamine, showed a 20 min transient loss of phototactic activity, (2) irradiation of cells, preincubated in the dark with 4 mM. hydroxylamine for 30 min, diminished the phototactic sensitivity permanently by more than 100‐fold without loss of cell motility. (3) The phototactic sensitivity completely recovered within 3(1 min of the removal of hydroxylamin from carotenoid‐containing cells or from carotenoid‐negative cells upon addition of 11‐cis or all‐trans retinal. Our explanation is bleaching of rhodopsin by more than 99% and reconstitution by de novo synthesized or by added retinal.
COMPARATIVE STUDIES ON THE LETHAL, MUTAGENIC, AND RECOMBINOGENIC EFFECTS OF ULTRAVIOLET‐A,‐B,‐C, AND VISIBLE LIGHT WITH AND WITHOUT 8‐METHOXYPSORALEN IN Saccharomyces cerevisiae
Authors: Mondon P. , Shahin Majdi M.
Published: July 2010

Abstract— Genetic effects of UV‐A, UV‐B, UV‐C, and the combination of 8‐methoxypsoralen (8MOP) with UV‐A or visible light were studied in the haploid strain XV185–14C and diploid strain D5 of Saccharomyces cerevisiae. The induction of his+, lys+, and horn+ reverse mutations was measured in strain XV185–14C. In strain D5 we measured the induction of genetically altered colonies, particularly twin spot colonies arising from a mitotic crossing‐over. UV‐C and UV‐B induced point mutations at the three loci in the haploid strain and mitotic crossing‐over and other genetic alterations in the diploid strain. UV‐C was more mutagenic and recombinogenic than UV‐B. UV‐A or visible light alone did not induce genotoxic effects at the doses tested. However, UV‐A plus 8‐MOP produced lethal and mutagenic effects in the haploid strain XV185–14C, although mutagenic activity was less than that of UV‐B. Visible light plus 8‐MOP also induced genotoxic effects in strain XV185–14C. In the diploid strain D5, UV‐A plus 8‐MOP induced a higher frequency of genetic alterations than UV‐B at comparative doses. Visible light plus 8‐MOP was also genetically active in strain D5. The haploid strain was more sensitive to the lethal effects of UV‐C, UV‐B, UV‐A, and impure visible light plus 8‐MOP than the diploid strain.
FURTHER CHARACTERIZATION OF MONOCLONAL ANTIBODY INDICATES SPECIFICITY FOR (6–4)‐DIPYRIMIDINE PHOTOPRODUCTS
Authors: Strickland P. T. , Nikaioo O. , Matsunaga T. , Boyle J. M.
Published: July 2010

Abstract— Monoclonal antibody aUVssDNA‐1 is produced by hybridoma cell line 25JF.C3B6 originally selected from cell fusions using spleen cells from mice immunized with UV‐irradiated polydeoxynucleotides (Strickland and Boyle, Photochem. Photobiol.34, 595–601, 1981). Original and subsequent studies of the binding characteristics of aUVssDNA‐1 indicated that it was specific for cyclobuta‐dithymidine photoproducts. Those investigations examined action spectrum, short‐wavelength photo‐reversal, nucleotide sequence effects, and photoreactivation using E. coli photolyase and incandescent tight. However, the more recent studies reported here examined acetophenone‐UV‐B photosensitization, UV‐B photoisomerization, and photoreactivation using cloned E. coli photolyase and filtered incandescent light. The results indicate that aUVssDNA‐1 recognizes photoproducts with characteristics of (6–4)‐dipyrimidines. Thus, previous studies in which relatively rapid repair of cyclobuta‐dithymidine photoproducts was inferred using this antibody, require re‐interpretation in light of these new findings.
STUDIES ON HUMAN LENS: I. ORIGIN AND DEVELOPMENT OF FLUORESCENT PIGMENTS
Authors: Sen Asok C. , Ueno Norio , Chakrabarti Bireswar
Published: July 2010

Abstract— Fluorescence spectra of normal mature human lenses have been measured and at least eight species with distinct emission characteristics identified. To determine the specific photochemical and photophysical processes responsible for the origin and development of these fluorophores, emission behavior of the products generated by successive irradiation of young human lenses (3–6 y old) as well as of L‐tryptophan solution have been systematically monitored. Fluorescent products that resulted from this irradiation were comparable to many of the fluorophores detected in aged lenses, indicating that light plays a major role in the development of these pigments. In addition to photogenerated species, there are other compounds in human lenses, presumably advanced glycosylated end products, with marked fluorescence properties.

Several oxidation products of tryptophan including N‐formylkynurenine or its derivatives, β‐carboline or its derivatives, and anthranilic acid have been identified in the mature human lens. The development of several photoproducts also was attributed to endogenous ascorbate‐mediated Maillard reaction products, which undergo photoconversion by the visible light. Although some of these chromophores could act as photosensitaizers, the sensitizing efficiency of many are low. Conversely, the near‐UV filtering capability of these colored compounds conceivably could protect the vitreous and retina from development of any photochemical lesion.
ANALYSIS OF MULTIPLE PHOTORECEPTOR PIGMENTS FOR PHOTOTROPISM IN A MUTANT OF Arabidopsis thaliana
Authors: Konjević Radomir , Khurana Jitendra P. , Poff Kenneth L.
Published: July 2010

Abstract— The shape of the fluence‐response relationship for the phototropic response of the JK224 strain of Arabidopsis thaliana depends on the fluence rate and wavelength of the actinic light. At low fluence rate (0.1 μmol m‐2s‐1), the response to 450‐nm light is characterized by a single maximum at about 9 μmol m‐2. At higher fluence rate (0.4 μmol m‐2s‐1), the response shows two maxima, at 4.5 and 9 μmol m‐2. The response to 510‐nm light shows a single maximum at 4.5 μmol m‐2. Unilateral preirradiation with high fluence rate (25 μmol m‐2s‐1) 510‐nm light eliminates the maximum at 4.5 μmol m‐2 in the fluence response curve to a subsequent unilateral 450‐nm irradiation, while the second maximum at 9 μmol m‐2 is unaffected. Based on these results, it is concluded that a single photoreceptor pigment has been altered in the JK224 strain of Arabidopsis thaliana.
IMPAIRED ACCUMULATION OF A CATIONIC PHOTOSENSITIZING AGENT BY A CELL LINE EXHIBITING MULTIDRUG RESISTANCE
Authors: Kessel David , Woodburn Kathryn , Skalkos Dimitris
Published: July 2010

Abstract—Transport and accumulation of copper benzochlorin iminium salt (CDSl), a cationic photosensitizing agent, were examined using the P388/ADR murine leukemia, which exhibits the MDR (multidrug resistance) phe‐notype, and the wild‐type parent cell line, P388. The recent availability of radioactive CDSl permitted kinetic studies at drug levels in the submicromolar range. Exclusion of CDSl by P38WADR cells could be demonstrated, indicating that this agent is a substrate for the outward transport system associated with MDR. These results have implications with regard to the efficacy of cationic photosensitizers against this common neoplastic phenotype. The CDSl was readily accumulated by P388 cells and by P388/ADR cells: when the outward transport system was inhibited. Under these conditions, CDSl was tightly bound and could not be washed out even when the outward transport system was reactivated.
PURIFICATION AND CHARACTERIZATION OF A RIBOFLAVIN‐BINDING PROTEIN FROM FLAGELLA OF Euglena grcrcilis
Authors: Neumann Ralf , Hertel* Rainer
Published: July 2010

Abstract—Phototaxis of the flagellate Euglena gracilis has been thought to be mediated by flavin photoreceptor molecules localized in the paraflagellar body (PFB). From isolated flagella of Euglena a riboflavin (RF)‐binding protein was solubilized and purified using nonionic detergents, high ionic strength, affinity Chromatography and standard column separations. Sodium dodecyl sulfate gel electrophoresis showed an apparent molecular weight of 68 kDa for the binding protein. Its hydrophobicity was confirmed by Triton X‐114 phase partitioning. Binding affinity for tritiated RF was high in the oxidized state (KD= 4 nM) as well as under reducing conditions in the presence of dithionite (Kd= 6 nM). Affinities towards flavin mononucleotide and flavin adenine dinucleotide were lower. Based on binding data and on estimates of the purified 68 kDa polypeptide, approximately lo6 flavin‐binding sites were determined per one flagellum. Evidence is discussed that the flavin‐binding protein is part of the entire flagellar membrane and does not reside in the PFB. If not the photoreceptor, the flagellar RF‐binding protein may have a functional role in the biochemical chain leading from the reception of the phototactic stimulus to the motile response.
A LABORATORY INVESTIGATION OF TWO ULTRAVIOLET SPECTRORADIOMETERS
Authors: Webb A. R. , Gardiner B. G. , Blumthaler M. , Forster P. , Huber M. , Krrsch P. J.
Published: July 2010

Abstract—Spectral measurements of the solar UV irradiance at the earth's surface depend critically on the characteristics of the spectroradiometers and the procedures used in their calibration. Two UV spectroradiometers were subjected to a series of laboratory tests to investigate which factors were most significant in limiting the reliability of the absolute irradiance measurements. Three independent standards of spectral irradiance were scanned by both instruments under a range of bench conditions. The results were consistent to within about 3%, most of the uncertainty being due to scattered light in the laboratory. An UV laser was used to determine the slit function of each spectrometer and the influence of internal stray light. Significant departures from the ideal cosine and azimuth responses were measured by a xenon lamp. Both spectroradiometers were kept indoors throughout the experiments. The relevance of these laboratory results is discussed with respect to the task of measuring solar UV radiation in the field.
SOLAR UVR EXPOSURES OF THREE GROUPS OF OUTDOOR WORKERS ON THE SUNSHINE COAST, QUEENSLAND
Authors: Gies H. P. , Roy C. R. , Toomey S. , Maclennan R. , Watson M.
Published: July 2010

The solar ultraviolet radiation (UVR) exposures of three groups of outdoor workers, physical education (PE) teachers, ground staff/gardeners and lifeguards were measured using UVR‐sensitive polysulfone (PS) film badges. The exposures all took place on the Sunshine Coast, Queensland over 5 consecutive weekdays in November 1992. For the three groups, the shoulder badges received greater UVR exposures than the chest badges, in agreement with previous studies. The PE teachers received the highest UVR exposures while the lifeguards received the least. One of the 5 days of the study was overcast with some rain showers and UVR doses for this day for all groups were significantly lower than on the other 4 days, however the ratio of exposure to ambient remained relatively constant. All groups had measured UVR exposures in excess of occupational guidelines, indicating that protective measures, including education and behavior modification, which are becoming much more common in occupational situations in Australia, are both timely and necessary.
PHOTODYNAMIC ACTIVITIES and SKIN PHOTOSENSITIVITY OF THE bis(DIMETHYLTHEXYLSILOXY)SILICON 2,3‐NAPHTHALOCYANINE IN MICE
Authors: Brasseur Nicole , Ouellet Rene , Lewis Karina , Potter William R. , Lier Johan E. van
Published: July 2010

The photodynamic therapy (PDT) activity of the bis(dimethylthexylsiloxy)silicon 2,3‐na‐phthalocyanine (SiNc 8) was evaluated against the EMT‐6 tumor implanted intradermally in BALB/c mice. The SiNc 8 was formulated in aqueous emulsions based on Cremophor EL or Solutol HS 15. The formulation was shown to affect plasma clearance and overall pharmacokinetics. Compared to Cremophor, Solutol promoted rapid plasma clearance and high liver retention of the dye, combined with a slight increase of dye tumor concentrations. The PDT action spectrum for tumor response of SiNc 8 in Cremophor (190 mW cm2, 200 J cm2, 24 h postinjection [p.i.] of 1 (jimol kg1) showed a maximum at 780 nm, which corresponds to the absorption maximum of the monomelic dye as well as the in vivo maximum change in the “diffuse optical density” produced by the dye. The extent of tumor necrosis increased with augmented dye and light doses. Regardless of the formulation, at 1 h p.i. of 0.1 μmol kg−! SiNc 8, PDT efficiency (190 mW cm'2, 400 J cm2) was high but accompanied by severe damage to normal tissues, at 24 h PDT resulted in complete tumor regression in 80% of the animals without adverse effects to adjacent tissues, while at 72 h p.i. PDT induced no tumor response with Cremophor and only a partial response with Solutol. At the latter time point, plasma dye clearance was nearly complete while tumor tissue levels remained high, suggesting that tumor response correlates with plasma rather than tumor dye levels. Skin sensitivity of SKhl mice to solar‐simulated radiation was lower with SiNc 8 as compared to Photofrin®. Our data suggest the potential of SiNc 8 as a far‐red absorbing photosensitizer in clinical PDT.