bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Nanodomains in Polymer‐Derived SiCN Ceramics Employing Multiple Techniques
Authors: Saha A. , Raj R. , Williamson D. L. , Kleebe H.‐J.
Published: July 2010

A combination of methods, Bragg diffraction, small‐angle X‐ray scattering (SAXS), and transmission electron microscopy, is applied to the characterization of nanodomains and nanocrystals in polymer‐derived ceramics (PDCs). Detailed study of two materials, silicon carbonitride (SiCN) and a SiCN–zirconia nanocomposite, is presented. The first contains domains which can be measured only by SAXS. However, the nanocrystallites of zirconia in the second material can be quantatively studied by all three techniques. In both instances, we find the SAXS to be particularly useful because these data provide detailed information regarding the size distribution of the domains and the crystallites. This information can be valuable in understanding the materials science of PDCs: e,g., the change in the distribution and the average size of the nanoclusters can be modeled to understand the kinetic mechanisms of coarsening at high temperatures.
Controllable Crystalline Nano‐TiO2 by Homogeneous Hydrolysis with Toluene‐p‐Sulfonic Acid
Authors: Liu Wei , Chen AiPing , Lin JiaPing , Dai ZhiMing , Qiu Wei , Liu Wei , Zhu MengQin , Usuda Shouji
Published: July 2010

The homogeneous hydrolysis method was proposed to synthesize nano‐TiO2 with mixed crystal of anatase and rutile. It is remarkable that the crystal‐form‐controllable nanosize TiO2 was obtained by the addition of toluene‐p‐sulfonic acid (TSA). Two processes of the rutile phase formation were proposed. TiO2 was pure anatase crystalline in the absence of TSA. The sample with 0.2 mole ratio of TSA was mixed crystal of anatase and rutile, and characterized that the size of nanocrystalline was 19.5 nm for rutile and 13.5 nm for anatase, the specific surface area was 72.7 m2/g, and the energy of band gap was 2.83 eV. And the mechanism of the development of rutile nano‐TiO2 was presented in homogeneous hydrolysis system with TSA.
Electrically Conductive In Situ Formed Nano‐Si3N4/SiC/TiCxN1−x Ceramic Composite Consolidated by Pulse Electric Current Sintering (PECS)
Authors: Duan Ren‐Guan , Garay Javier E. , Kuntz Joshua D. , Mukherjee Amiya K.
Published: July 2010

Fully dense nano‐sized Si3N4/SiC/TiCxN1−x conductive composites have been synthesized through the reactive‐consolidation of a powder mixture of amorphous polymer precursor‐derived silicon carbonitride and nanocrystalline TiO2 by pulse electric current sintering. The nano‐Si3N4 and SiC grains, with sizes ranging from 15 to 30 nm, form large aggregate regions up to 20 μm in size. The nano‐TiC0.3N0.7 grains, ranging from 100 to 300 nm in size, form a connected matrix in which the micro‐sized Si3N4/SiC aggregate regions are distributed. The resultant ceramic composite possesses an excellent electrical conductivity, ∼3.40 × 104 (Ω·m)−1. This ceramic also exhibits favorable mechanical properties, including ∼14 GPa hardness and 6.7 MPa·m1/2 fracture toughness.
In Situ X‐Ray Diffraction Study of Electric‐Field‐Induced Domain Switching and Phase Transition in PZT‐5H
Authors: Liu Ming , Hsia K. Jimmy , Sardela Mauro R.
Published: July 2010

In situ X‐ray experiments were conducted to examine the electric‐field‐induced phase changes in PZT‐5H materials. The X‐ray diffraction profiles at different electric‐field levels were analyzed by peak fitting and were used to identify the occurrence of non‐180° domain switching and phase transition. We found that in depolarized samples, there exists a threshold electric field for the phase changes, whereas in polarized samples, no such threshold exists. The profound difference in the diffraction profile changes under positive and negative electric fields in polarized samples is responsible for the asymmetry of piezoelectric effects. Peak fitting results show phase transition as well as domain switching at different electric‐field levels. These observations further indicate the importance of residual stresses in materials' behavior.
Effects of Lanthanide Dopants on Oxygen Diffusion in Yttria‐Stabilized Zirconia
Authors: Krishnamurthy R. , Srolovitz D. J. , Kudin K. N. , Car R.
Published: July 2010

The effects of lanthanide co‐dopants on oxygen diffusion in yttria‐stabilized zirconia (YSZ) are studied using a combined first principles density functional theory (DFT)/kinetic Monte Carlo (kMC) modeling approach. DFT methods are used to calculate barrier energies for oxygen migration in different local cation environments, which are then input into kMC simulations to obtain long‐time oxygen diffusivities and activation energies. Simulation results show a substantial increase in the maximum value of the oxygen diffusivity upon co‐doping and in the dopant content at which this value is obtained for Lu‐co‐doped YSZ; while relatively little change is seen for Gd‐co‐doped YSZ. Examination of the DFT barrier energies reveals a linear scaling of barrier heights with the size of cations at the diffusion transition state. Using this strong correlation, oxygen diffusivity is examined in YSZ co‐doped with several lanthanide elements. The oxygen diffusivity decreases with dopant atomic number (and decreasing dopant ion size) for co‐dopants smaller than Y, and changes relatively little when Y is replaced by co‐dopants larger than it. These results are broadly consistent with experiment, and are explained in terms of cation‐dopant and vacancy concentration‐dependent correlation effects, with the aid of a simple analytical model.
Optical Properties of Gd–α‐Sialon Ceramics: Effect of Carbon Contamination
Authors: Chen Wei‐Wu , Su Xin‐Lu , Wang Pei‐Ling , Yan Dong‐Sheng , Cheng Yi‐Bing , Watari Koji
Published: July 2010

Thick translucent and luminescent Gd–α‐sialon ceramic disks (0.7–1.06 mm in thickness) were prepared by hot pressing. The effect of carbon atmosphere on their optical properties during sintering was explored by change packing methods. The results show that the sample with a lower carbon contamination has a higher translucence in the visible band and IR band (450–3500 nm), increasing transmission around 10% even if it is thicker. When excited at 350 nm, Gd–α‐sialon with the lower carbon contamination can produce a visible light at 450–500 nm bands, but the luminescence is very weak in the sample containing more carbon contamination. These indicate that carbon contamination causes a severe degradation of the optical properties of α‐sialon ceramics, and reduction of carbon contamination of α‐sialon ceramics is very important for the optical property improvement.
Microstructural Development on Firing Illite and Smectite Clays Compared with that in Kaolinite
Authors: McConville Caspar J. , Lee William Edward
Published: July 2010

Thermal transformation of illite and smectite group clay minerals was studied using X‐ray diffraction and transmission electron microscopy, and the results were compared with those of kaolinite. Differences were observed in the types and sizes of crystals formed at temperatures between 800° and 1400°C. Spinel‐type phases were formed after 3 h at 1000°C in all three clays, but the morphology and composition of the spinel crystals varied. Mullite crystals reached greater sizes in the illite (>10 μm needles) and smectite (>1 μm) materials than in the kaolinite (0.5 μm). Iron‐rich crystals formed in the illite and smectite materials, and feldspars present as impurities in these clays, along with interlayer cations, resulted in large quantities of liquid being formed above 1000°C. Similar thermal breakdown and phase development schemes are proposed for all three materials, with the major differences observed ascribed to the presence or absence of interlayer cations, substitutional impurities, and accessory minerals. These results provide a basis for predicting phase development on firing a given clay mineral, if its characteristics and impurity levels are known.
Initial Attempt to Characterize Oxidation Damage in C/Sic Composite Using an Ultrasonic Guided Wave Method
Authors: Roth Don J. , Verrilli Michael J. , Martin Richard E. , Cosgriff Laura M.
Published: July 2010

An ultrasonic guided wave scan system was used to non‐destructively monitor damage over time and position in a C/enhanced SiC sample that was creep tested to failure at 1200°C in air at a stress of 69 MPa (10 ksi). The use of the guided wave scan system for mapping evolving oxidation profiles (via porosity gradients resulting from oxidation) along the sample length and predicting failure location was explored. The creep‐rupture tests were interrupted for ultrasonic evaluation every two hours until failure at ∼17.5 cumulative hours.
Effect of Substitutional Monovalent and Divalent Metal Ions on Mechanical Properties of β‐Tricalcium Phosphate
Authors: Yoshida Katsumi , Kondo Naoki , Kita Hideki , Mitamura Masanori , Hashimoto Kazuaki , Toda Yoshitomo
Published: July 2010

β‐tricalcium phosphate (β‐TCP) powder doped with monovalent or divalent metal ions was hot pressed at 1100°C, and the effect of substitutional monovalent and divalent metal ions on mechanical properties of β‐TCP was investigated. The sinterability of β‐TCP would be enhanced by the substitution of monovalent and divalent metal ions for β‐TCP. Sintered β‐TCP doped with 7.6 mol% of Mg2+ ion showed a bending strength of 160 MPa. It was found that the substituition of Mg2+ ion up to 9.6 mol% and a small amount of monovalent metal ions for β‐TCP is effective to improve the mechanical strength of β‐TCP.
Monte Carlo Prediction of Non‐Newtonian Viscous Sintering: Experimental Validation for the Two‐Glass‐Cylinder System
Authors: Bordère S. , Gendron D. , Heintz J.‐M. , Bernard D.
Published: July 2010

From the Monte Carlo methodology based on a non‐discrete potential and developed to model capillary‐driven mass transport, a relation between the Monte Carlo step and the physical time has been defined as a function of the viscosity coefficient. The experimental kinetics of the shortening of a unique glass cylinder and the sintering of two‐glass cylinders at 950°C then have been compared with the numerically obtained results. The original result indicates that the active sintering mechanism for a glass under the given sintering conditions is not Newtonian viscous flow alone, a finding that corresponds perfectly well with the Monte Carlo simulation.
Synthesis and Reaction Mechanism of Ti3SiC2by Mechanical Alloying of Elemental Ti, Si, and C Powders
Authors: Li Shi‐Bo , Zhai Hong‐Xiang
Published: July 2010

Formation of titanium silicon carbide (Ti3SiC2) by mechanical alloying (MA) of Ti, Si, and C powders at room temperature was experimentally investigated. A large amount of granules less than 5 mm in size, consisting of Ti3SiC2, smaller TiC particles, and other silicides, have been obtained after ball milling for only 1.5 h. The effect of excess Si in the starting powders on the formation of Ti3SiC2was studied. The formation mechanism of Ti3SiC2was analyzed. It is believed that a mechanically induced self‐propagating reaction is ignited during the MA process. A possible reaction mechanism was proposed to explain the formation of the final products.
17O NMR Spectroscopy of α‐TeO2 and Na2TeO3
Authors: Hart Robert T. , Zwanziger Josef W.
Published: July 2010

The synthesis of 17O‐enriched α‐tellurite (α‐TeO2) is described. TeO2 is obtained stochiometrically by the reaction of tellurium isopropoxide with 17O‐enriched H2O. The reaction is mild and simple and opens the field of tellurite‐based ceramics to 17O nuclear magnetic resonance spectroscopy. We also report the first 17O nuclear magnetic resonance spectra of α‐TeO2 and Na2TeO3. Their isotropic chemical shifts, δiso, are 180 ppm and 158 ppm, respectively, and their quadrupolar coupling parameters are CQ=7.48 MHz and η=0.43 for α‐TeO2, and CQ=6.63 MHz and η=0.33. By using extended Hückel tight binding calculations, we interpret the chemical shifts of tetravalent inorganic oxide network formers (SiO2, GeO2, and TeO2) in terms of the local paramagnetic shielding effect. We also show that this is the predominant effect in determining the chemical shifts of non‐bridging oxide sites in this type of network.
Enhanced Densification of Liquid‐Phase‐Sintered WC–Co by Use of Coarse WC Powder: Experimental Support for the Pore‐Filling Theory
Authors: Kim Young‐Pil , Jung Sug‐Woo , Kang Suk‐Joong L. , Kim Byoung‐Ki
Published: July 2010

Densification during liquid‐phase sintering of WC–Co with various WC powder sizes has been measured in order to identify the densification mechanism. During heating of powder compacts in the solid state, densification was enhanced with a reduction of WC powder size. However, the behavior was reversed when the densification occurred in the presence of a liquid: enhanced densification with increasing WC powder size. This result is in contradiction to a prediction of the conventional theory of liquid‐phase sintering, the contact flattening theory, but in good agreement with a prediction of the pore‐filling theory. Microstructural analysis further confirmed that the densification at the liquid‐phase sintering temperature occurred by pore filling. The calculated densification kinetics based on the pore‐filling theory also fitted well with the measured data. The observed densification behavior thus demonstrates experimentally the prediction of the pore‐filling theory that the densification is enhanced with increasing average grain size for the same pore size distribution.
Effects of Moisture on Grain‐Boundary Strength, Fracture, and Fatigue Properties of Alumina
Authors: Kruzic J. J. , Cannon R. M. , Ritchie R. O.
Published: July 2010

The role of moisture in affecting both intrinsic and extrinsic aspects of the fracture and fatigue‐crack growth resistance of a polycrystalline alumina (99.5% pure, 25 μm grain size) has been examined in both moist and dry environments at ambient temperature. The intrinsic (crack‐tip) toughness, deduced from measured crack‐opening profiles, is found to be less than for a single crystal and is 30% lower (∼0.6 MPa·m1/2) in moist air versus in dry N2, implying that the grain‐boundary theoretical strength is higher in a dry environment. Despite this, in dry atmospheres, theR‐curves (which derive from crack deflection and grain bridging) initially rose more steeply and nominal fatigue‐crack growth thresholds for short crack sizes (20–60 μm) were more than 1.3 MPa·m1/2higher. Owing to this quicker crack bridging development, strengths for natural flaws could be more than doubled in dry atmospheres, a difference that well exceeds the effect solely due to the intrinsic toughness change. After ∼2 mm of crack growth, however, theR‐curve and steady‐state fatigue behavior appeared similar in both environments, although altering the atmosphere for such fatigue cracksin situinduced large, abrupt changes in transient growth rates. The environment influences the nature of the bridging zones, with uncracked‐ligament bridges playing a larger role in dry atmospheres, while frictional bridges are predominant in moist air. Evidently, to achieve optimal toughness in bridging ceramics, the window for the requisite grain‐boundary strength may be small; whereas weak boundaries are required to induce the necessary intergranular fracture, if too weak, shallowerR‐curves, less strengthening, and poorer fatigue resistance all follow.
Preparation and Characterization of Samaria‐Doped Ceria Electrolyte Materials for Solid Oxide Fuel Cells
Authors: Fu Yen‐Pei , Wen Shaw‐Bing , Lu Chi‐Hua
Published: July 2010

The microstructure, thermal expansion, mechanical property, and ionic conductivity of samaria‐doped ceria (SDC) prepared by coprecipitation were investigated in this paper. The results revealed that the average particle size ranged from 10.9±0.4 to 13.5±0.5 nm, crystallite dimension varied from 8.6±0.3 to 10.7±0.4 nm, and the specific surface area distribution ranged from 62.6±1.8 to 76.7±2.2 m2/g for SDC powders prepared by coprecipitation. The dependence of lattice parameter, a, versus dopant concentration, x, of Sm3+ ion shows that these solid solutions obey Vegard's rule as a (x)=5.4089+0.10743x for Ce1−xSmxO2−1/2x. For SDC ceramics sintered at 1500°C for 5 h, the bulk density was over 95% of the theoretical density; the maximum ionic conductivity, σ800°C=(22.3±1.14) × 10−3 S/cm with minimum activation energy, Ea=0.89±0.02 eV, was found in the Ce0.80Sm0.20O1.90 ceramic. A dense Ce0.8Sm0.2O1.9 ceramic with a grain size distribution of 0.5–4 μm can be obtained by controlling the soaking time at 1500°C. When the soaking time was increased, the microhardness of Ce0.8Sm0.2O1.9 ceramic increased, the toughness slightly decreased, which was related to grain growth with the soaking time.
Formation Mechanism of Porous Alumina With Oriented Cylindrical Pores Fabricated by Unidirectional Solidification
Authors: Ueno Shunkichi , Lin Li M. , Nakajima Hideo
Published: July 2010

Porous alumina whose pores were aligned in one direction was fabricated by the unidirectional solidification method under a pressurized hydrogen atmosphere. The porous structure is formed at the solid–liquid interface during solidification due to a hydrogen solubility gap at the melting point. The hydrogen gas is dissolved into molten alumina according to Sieverts' law and insoluble gas that corresponds to the amount of solubility gap evolves from the solid phase at the solid–liquid interface during the unidirectional solidification to form the pores. The porosity and pore size of the solidified samples decreased with increasing total pressure where the environmental gas consisted of pure hydrogen or hydrogen–argon mixed gases. There is a reverse proportion relation between the pore diameter and the total pressure according to Boyle's law.
Two Phase Monazite/Xenotime 30LaPO4–70YPO4 Coating of Ceramic Fiber Tows
Authors: Boakye E. E. , Hay R. S. , Mogilevsky P. , Cinibulk M. K.
Published: July 2010

Equiaxed yttrium–lanthanum phosphate nanoparticles (Y0.7,La0.3)PO4·0.7H2O were made and used to continuously coat Nextel™ 720 fiber tows. The particles were precipitated from a mixture of yttrium and lanthanum citrate chelate and phosphoric acid (H3PO4), and characterized with differential thermal analysis and thermogravimetric analysis, X‐ray diffraction, transmission electron microscopy, and scanning electron microscopy. The coated fibers were heat treated at 1000°–1300°C for 1, 10, and 100 h. Coating grain growth kinetics and coated fiber strengths were determined and compared with equiaxed La‐monazite coatings. The relationships between coating porosity, coating hermeticity, and coated fiber strength are discussed.
Methane Oxidation on Perovskite‐Type Ca(Mn1−xTix)O3−δ
Authors: Taguchi Hideki , Nakade Katsuyuki , Yosinaga Masashi , Kato Masaki , Hirota Ken
Published: July 2010

X‐ray photoelectron spectroscopy was performed to elucidate the catalytic activity of CH4 oxidation on perovskite‐type Ca(Mn1−xTix)O3−δ synthesized at 1173 K in a flow of oxygen from a gel with citric acid and ethylene glycol. The Mn ion content decreases and the ratio of the Mn3+ ion in the Mn ion increases with increases in x. Ca(Mn1−xTix)O3−δ has a high catalytic activity of CH4 oxidation at x=0.4. These results indicate that the catalytic activity strongly depends on the Mn3+ ion content of the surface.
Optically Transparent Polycrystalline Al2O3 Produced by Spark Plasma Sintering
Authors: Jiang DongTao , Hulbert Dustin M. , Anselmi‐Tamburini Umberto , Ng Terry , Land Donald , Mukherjee Amiya K.
Published: July 2010

The spark plasma sintering (SPS) technique was used to produce mid‐infrared (IR) transparent alumina with the desired transmittance. An excellent transmittance of 85% has been obtained in a sample sintered at 1300°C for 5 min. The heating rate, sintering time, and annealing have a significant influence on IR transmittance. The improvement in transmission may be attributed to the progressive elimination of residual porosity when applying a slower heating rate, longer sintering time during SPS, and postsinter annealing. It is suggested that localized residual strain/stress at grain boundaries and oxygen vacancy concentration are other factors influencing the optical properties of the SPS‐sintered alumina.
Synthesis of Highly Dispersed Barium Titanate Nanoparticles by a Novel Solvothermal Method
Authors: Wei Xiao , Xu Gang , Ren Zhaohui , Wang Yonggang , Shen Ge , Han Gaorong
Published: July 2010

A novel solvothermal route has been developed to synthesize highly dispersed nanocrystalline barium titanate (BaTiO3), using a mixture of ethylenediamine and ethanolamine as a solvent. The as‐synthesized BaTiO3 nanoparticles were characterized by X‐ray powder diffraction, transmission electron microscopy (TEM), high‐resolution TEM, Fourier transform infrared spectroscopy, and thermal analysis. Based on the results of characterizations, the organic solvent was found to influence strongly the crystal growth and dispersibility of BaTiO3. The BaTiO3 nanoparticles obtained were highly dispersed and crystalline with a cubic perovskite structure. The particle size derived from the TEM ranged from 5 to 20 nm.
Phase Structure and Electrical Properties of (K0.48Na0.52)(Nb0.95Ta0.05)O3‐LiSbO3 Lead‐Free Piezoelectric Ceramics
Authors: Wu Jiagang , Peng Ting , Wang Yuanyu , Xiao Dingquan , Zhu Jumu , Jin Yong , Zhu Jianguo , Yu Ping , Wu Lang , Jiang Yihang
Published: July 2010

(1−x)(K0.48Na0.52)(Nb0.95Ta0.05)O3–xLiSbO3 [(1−x)KNNT−xLS] lead‐free piezoelectric ceramics were prepared by the conventional solid‐state sintering method. A morphotropic phase boundary (MPB) between orthorhombic and tetragonal phases was identified in the composition range of 0.03<x<0.05. The ceramics near the MPB exhibit a strong compositional dependence and enhanced electrical properties. The (1−x)KNNT–xLS (x=0.04) ceramics exhibit good electrical properties (d33=250 pC/N, kp=45.1%, kt=46.3%, Tc=348°C, To−t=74°C, Pr=25.9 μC/cm2, Ec=10.7 kV/cm, ɛr∼1352, tan δ∼3%). These results show that (1−x)KNNT–xLS ceramic is a promising lead‐free piezoelectric material.
Low‐Temperature Sintering of La(Ca)CrO3Powder Prepared through the Combustion Process
Authors: Nair Sathi Rajachandran , Purohit Ram Dayal , Tyagi Avesh Kumar , Sinha Pankaj Kumar , Sharma Beant Prakash
Published: July 2010

Ultrafine La(Ca)CrO3(LCC) powder was prepared through the glycine–nitrate gel combustion process. It was shown for the first time that the use of relatively inexpensive CrO3as a starting material for chromium has potential for the bulk preparation of sinter‐active LCC powder. As‐prepared powder, when calcined at 700°C, resulted in LCC along with a small amount of CaCrO4. The calcined powder was found to be composed of soft agglomerates with a particle size of ≈70–290 nm. The cold pressing and sintering of the calcined powder at 1200°C resulted in the mono‐phasic La0.7Ca0.3CrO3with density ≈98% of its theoretical value. This is the lowest sintering temperature ever reported for La0.7Ca0.3CrO3. The conductivity of the sintered La0.7Ca0.3CrO3at 1000°C was found to be ≈57 S/cm in air. The sintering and electrical behavior achieved for La0.7Ca0.3CrO3may find application as an interconnect material for high‐temperature solid oxide fuel cells if problems with chemical expansion and poor conductivity in fuel can be overcome.
Preparation of Porous Tin Oxide Nanobelts Using the Electrospinning Technique
Authors: Yang An , Tao Xiaoming , Pang Geoffrey Kin Hung , Siu Kenneth Guei Gu
Published: July 2010

The electrospinning method is adopted to prepare utralong PEO/stannic hydroxide composite nanofibers. Tin‐oxide nanobelts can be obtained by calcination of the composite nanofibers in an open atmosphere. The nanobelts were characterized by a field emission scanning electron microscope, X‐ray diffraction, a transmission electron microscope, a Raman spectromicroscope, and Fourier transform infrared spectroscopy. Microstructural analysis has shown that the nanobelts prepared consist of a continuous network of interconnected SnO2 grains. As a result, the SnO2 nanobelts possess a high surface area and continuous porosity, which may be applied for the fabrication of sensitive gas sensors.
Modifications of the C–S–H Gel by Hydration at 40°C of Belite Cements from Coal Fly Ash Class C
Authors: Goñi Sara , Guerrero Ana
Published: July 2010

The influence of the temperature on two types of hydrated fly ash belite cement (FABC) pastes were investigated at a nanoscale (1–100 nm) by measuring the specific surface area and pore‐size distribution by the sorption isotherms of nitrogen gas and the BET method, and at a microscale from the pore‐size distribution measured by mercury intrusion porosimetry. The two belite cements were fabricated by the hydrothermal–calcination route of fly ash class C in NaOH 1Msolution (FABC‐2‐N) and demineralized water (FABC‐2‐W). In the case of FABC‐2‐W, a densification of the C–S–H gel was produced at the temperature of 40°C, which favored the formation of pores ∼3 nm in diameter leading to higher surface area values, compared with the C–S–H gel formed at 20°C. At a microscale, the temperature led to an increase of capillary porosity (>0.05 μm) at a later age of hydration and, consequently, a decrease of compressive mechanical strength. In the case of FABC‐2‐N, the densification of the gel was less evident, but the increase of capillary porosity (pores of diameter >0.05 μm) was higher. Significant direct linear quantitative correlations were found among these nanostructure characteristics of the C–S–H gel and macrostructural engineering property such as the compressive mechanical strength, for the two FABC‐2‐W and FABC‐2‐N cements under normal conditions. At 40°C, the correlations were not so clear probably due to another microstructural factor such as the increase of the larger capillary porosity (>0.05 μm).
THE PRO SE LITIGANT'S STRUGGLE FOR ACCESS TO JUSTICE
Authors: Goldschmidt Jona
Published: July 2010

Just as the growth of pro se litigation is a challenge for the courts, so, too, is the bench and bar's resistance to pro se assistance programs and policies a challenge to court reformers seeking to improve access to justice. Even where progressive courts have been able to implement court‐annexed pro se assistance programs, judicial and bar resistance to pro se assistance in the courtroom remains. This paper explores the reasons for such resistance, and argues that pro se litigants have a right to receive—and judges have an obligation to provide—reasonable judicial assistance, particularly in cases involving a represented and an unrepresented party. A set of recommendations is offered which will result in pro se litigants being given more basic legal information than previously provided, better preparation of pro se cases, and a more active judge to ensure that all parties have equal access to justice.
UNBUNDLING LEGAL SERVICES IN MEDIATION
Authors: Garfield Franklin R.
Published: July 2010

The adversarial model for resolving family disputes is seriously flawed. The judicial system is inefficient and uneconomical. The vast majority of litigants cannot afford to have their cases handled by a lawyer, and, as a result, they end up representing themselves. However, divorcing spouses want and need legal services. They should not be forced to choose between full services and no services. As mediation moves toward acceptance as the preferred method for resolving family disputes, attorneys have an opportunity to offer a menu of legal services from which clients may order a la carte. This is the essence of unbundling. This article explores how unbundling enables mediation clients to obtain the legal services they request at an affordable cost and relieves consulting attorneys who perform discrete tasks of responsibility for the outcome of the case.
WHEN PARENTS ARE ON A LEVEL PLAYING FIELD, COURTS CRY FOUL AT SMOKING
Authors: Tondo Carrie‐Anne
Published: July 2010

Should courts regulated a parent's legal smoking habit because it is in the best interests of the children? This article explores the historical views of smoking and the potential and probable health hazards associated with cigarette smoking. By a review of the dangers associated with smoking as well as court cases that have considered smoking as endangement to children, this note suggests that courts do have the power to curtail a parent's smoking habit and in turn should regulate such behavior, especially when it is medically proven that it is in the best interests of the children.
Valuation in Emerging Markets: A Simulation Approach
Authors: García‐Sánchez Javier , Preve Lorenzo , Sarria‐Allende Virginia
Published: July 2010

Most of the foundations of valuation theory have been designed for use in developed markets. Because of the greater, and in some cases different, risks associated with emerging markets (although recent experience might suggest otherwise), investors and corporate managers are often uncomfortable using traditional methods. The typical way of capturing emerging‐market risks is to increase the discount rate in the standard valuation model. But, as the authors argue, such adjustments have the effect of undermining some of the basic assumptions of the CAPM‐based discounted cash flow model.

The standard theory of capital budgeting suggests that estimates of unconditional expected cash flows should be discounted at CAPM discount rates (or betas) that reflect only “systematic,” or “nondiversifiable,” market‐wide risks. In practice, however, analysts tend to take what are really estimates of “conditional” expected cash flows—that is, conditional on the firm or its country avoiding a crisis—and discount them at higher rates that reflect not only systematic risks, but diversifiable risks that typically involve a higher probability of crisis‐driven costs of default. But there is almost no basis in theory for the size of the increases in discount rates.

In this article, the authors propose that analysts in emerging markets avoid this discount rate problem by using simulation techniques to capture emerging‐market risks in their estimates of unconditional expected cash flows—in other words, estimates that directly incorporate the possibility of an emerging‐market crisis and its consequences. Having produced such estimates, analysts can then discount them using the standard Global CAPM.
Relationship between Electrical and Thermal Conductivities for Evaluating Thermal Regime of Gas Hydrate Bearing Sedimentary Layers
Authors: MATSUBAYASHI OSAMU , EDWARDS R. NIGEL
Published: July 2010

Abstract: In an attempt to explore the potential use of electrical resistivity data combined with seafloor heat flow measurements as an alternative predictor of bottom of gas hydrate stability (BGHS) in marine gas hydrate‐bearing geological environments, a model for conversion of electrical conductivity to thermal conductivity has been formulated. It was found that a thermal conductivity versus electrical conductivity model assuming hydrate‐coated‐grains gives lower thermal conductivity than other models, because gas hydrates characteristically have a low value of thermal conductivity compared with sediment grains. The authors consider the hydrate‐coated‐grain model more realistic than other models. Once we can establish a relationship between electrical resistivity and thermal resistivity of sedimentary formations like that proposed in this paper, it will be possible to provide an independent source of information about the depth of BGHSs even with an absence of seismic BSR data.
ON THE EMERSON ENHANCEMENT EFFECT IN THE FERRICYANIDE HILL REACTION IN CHLOROPLAST FRAGMENTS*
Authors: Govindjee  , Bazzaz Maarib
Published: July 2010

Abstract— The Emerson effect is demonstrated in the ferricyanide Hill reaction when the rates of steady‐state oxygen evolution are measured in spinach chlorplast fragments exposed to red (650 nm) and far‐red (700 nm) light of high but not saturating intensity. However, at very low light intensity, the Emerson effect could not be observed. These experiments suggest that ferricyanide can be reduced at two sites. At low light intensity, the rate at one site predominates and at this site one photochemical system is active. At high light intensity, however, the action at a site that is dependent on the cooperation of two photochemical systems predominates.

The action spectra of the ferricyanide Hill reaction measured in the presence of an excess of 650 nm or in the excess of 700 nm light show two peaks: one at 650 nm due to chlorophyll b and the other around 675 nm due to chlorophyll a. The ratio of chlorophyll a to chlorophyll b peaks is about 1.4 when 650 nm background light is used; the same ratio is about 0.7 with 700 nm background light. The two pigment systems seem to contain both chlorophyll a and chlorophyll b but in different proportions.
LIGHT‐INDUCED SHIFTS IN THE ABSORPTION SPECTRUM OF CAROTENOIDS IN RED AND BROWN ALGAE
Authors: Fork David C. , Amesz Jan
Published: July 2010

Abstract— Changes in light absorption in the region 450–540 nm were observed upon illumination of the red algae Iridaea splendens, Schizymenia pacifica and Porphyra perforata and the brown alga Pheostrophion irregulare. The difference spectra of these changes in Iridaea and Schizymenia showed maxima and minima at about 465, 480, 495, 515 nm. The spectra were similar to difference spectra earlier observed in photosynthetic bacteria, and the location of the maxima and minima suggested a shift towards longer wavelength of a compound with absorption maxima at about 440, 470, and 500 nm, probably a carotenoid. Similar, but more distorted difference spectra were observed in the other algae. Time courses and size of the signals induced by light of different wavelengths suggest that excitation of both photosynthetic pigment systems causes a shift in carotenoid absorption, with kinetics which appear to be similar to those of the well‐known change at 515 nm in green plants.
THE PHOTOCHEMICAL YIELD OF SINGLET OXYGEN FROM PORPHYRINS IN DIFFERENT STATES OF AGGREGATION
Authors: Moan Johan
Published: July 2010

Abstract— Aqueous solutions of hematoporphyrin and hematoporphyrin derivatives were exposed to light. When present in such solutions tryptophan is degraded by a singlet oxygen mechanism. This is true for excitation at 396 nm, where porphyrin monomers have their absorption maximum, as well as for excitation at 360 nm, where porphyrin aggregates seem to absorb strongly. The quantum yield of singlet oxygen production is similar within 25% for excitation at 396 and 360 nm while the fluorescence quantum yield is more than a factor 2 lower for excitation at 360 nm than for excitation at 396 nm. Photoexcitation of the clinically used hematopotophyrin derivatives photofrin I and photofrin II produces singlet oxygen with significantly smaller yields than photoexcitation of hematoporphyrin. Thus, the aggregates present in solutions of photofrin I and photofrin II are of a different nature than those present in aqueous solutions of hematoporphyrin.
SOLVENT EFFECTS ON INTRAMOLECULAR EXCIMER FORMATION IN N‐ACETYL‐BIS(PYRENYLALANINE)‐METHYLESTER
Authors: Goedeweeck R. , Schryver F. C. De
Published: July 2010

Abstract— The synthesis, absorption and emission properties of threo and erythro N‐acetyl‐bis‐(pyrenylalanine)‐methylester are discussed. The intensity of excimer emission is very dependent on the tendency of the solvent to interact with the peptide function by hydrogen bonding. Hydrogen accepting solvents shift the equilibrium between the different conformations, adopted by these dipeptides, towards a random coil conformation, which is unfavourable for excimer formation. In strongly hydrogen donating solvents however, a very intense excimer emission is observed due to a reduction of the partial double bond character of the peptide bond by an hydrogen bridge with the solvent molecules.
COMPARISON OF THE PHOTOTOXICITY OF α‐TERTHIENYL WITH THAT OF A SELENIUM AND OF AN OXYGEN ANALOGUE
Authors: Garcia F. J. , Yamamoto E. , Abramowski Z. , Downum K. , Towers G. H. N.
Published: July 2010

Abstract— Two analogues of α‐terthienyl, namely 2, 5di(2'‐thienyl) selenophene and 2, 5di(2'‐thienyl) furan have been prepared and their phototoxicities toward several microorganisms have been compared. Dose response studies with Escherichia coli indicate that α‐terthienyl is more active than these analogues. α‐Terthienyl was shown to be the most effective of the three compounds in the photoinactivation of yeast alcohol dehydrogenase. Diagnostic tests showed the participation of singlet oxygen in the photosensitization to different extents by these three thiophenes.
THE PHOTOPHYSICS AND PHOTOCHEMISTRY OF THE NEAR‐UV ABSORBING AMINO ACIDS–II. TYROSINE AND ITS SIMPLE DERIVATIVES
Authors: Creed David
Published: July 2010

Abstract—The photophysics and photochemistry of tyrosine and some of its simple analogues and derivatives are comprehensively reviewed. Topics discussed include emission spectroscopy, formation of photoproducts in direct and sensitized reactions, photooxidations, and mechanistics studies using steady state kinetic methods, flash photolysis, and electron spin resonance. Energy and electron transfer processes involving tyrosine and other molecules of biological interest are briefly summarized.
THE PHOTOPHYSICS AND PHOTOCHEMISTRY OF THE NEAR‐UV ABSORBING AMINO ACIDS‐III. CYSTINE AND ITS SIMPLE DERIVATIVES
Authors: Creed David
Published: July 2010

Abstract— The photochemistry of cystine and some of its analogues is reviewed. Topics discussed include the absorption spectra of disulfides, the photochemistry of alkyl disulfides and other more highly substituted disulfides including cystine, photooxidation of disulfides, and photochemical interactions of cystine derivatives with other molecules of biological interest.
PORPHYRIN‐LIPOSOME INTERACTIONS: INFLUENCE OF THE PHYSICO‐CHEMICAL PROPERTIES OF THE PHOSPHOLIPID BILAYER
Authors: Ricchelli* Fernanda , Stevanin Daniela , Jori Giulio
Published: July 2010

Abstract— The quenching of the fluorescence emitted by hematoporphyrin incorporated into unilamellar liposomes of dipalmitoyl‐phosphatidylcholine and dimyristoyl‐phosphatidylcholine, was studied by using methylviologen, 9,10‐anthraquinone‐2,6‐disulfonate and 9,10‐anthraquinone‐2‐sulfonate as quenchers, in order to assess how the distribution of the porphyrin and the interaction mode of the various quenchers with the porphyrin is affected by the physico‐chemical properties of the vesicles.

The results obtained indicate that, below the critical temperature for the phase transition of the lipids, hematoporphyrin is preferentially distributed in the outer lipid monolayer of liposomes of dipalmitoyl‐phosphatidylcholine while most hematoporphyrin molecules are located in the inner monolayer in liposomes of dimyristoyl‐phosphatidylcholine. This distribution is only slightly changed when the external mean radius of liposomes increases from 26 to 50 nm.

The rise of temperature above the critical value for the liquid‐gel phase transition causes a shift of the hematoporphyrin molecules toward the inner phospholipid monolayer. This shift is more pronounced in liposomes of dimyristoyl‐phosphatidylcholine.

Studies on model systems, i.e. neutral and ionic micelles, indicate that methylviologen and anthra‐quinone‐type quenchers drastically differ in their interaction mechanism with hematoporphyrin. In particular, methylviologen is the only quencher which can discriminate different hematoporphyrin populations in liposomes of dimyristoyl‐phosphatidylcholine and dipalmitoyl‐phosphatidylcholine in both the liquid and gel phase. Anthraquinone‐type quenchers interact with both hematoporphyrin populations when the lipids are in the gel phase. When the lipids are in a fluid state, the quenching occurs only on the external hematoporphyrin population in liposomes of dipalmitoyl‐phosphatidylcho‐line while in liposomes of dimyristoyl‐phosphatidylcholine no discrimination is observed. The influence of the liposomal structure at different temperatures and of the length of the hydrocarbon chains is discussed.
THE RELATIVE CYTOTOXICITY OF(6–4) PHOTOPRODUCTS AND CYCLOBUTANE DIMERS IN MAMMALIAN CELLS*
Authors: Mitchell David L.
Published: July 2010

Abstract— The significance of the pyrimidine(6‐4)pyrimidone photoproduct in mammalian cell killing is considered. Photochemical data indicate that the(6–4) photoproduct is induced at a substantial frequency compared to the cyclobutane dimer and that the action spectra for the induction of both lesions are equivalent. The repair of(6–4) photoproducts in various normal and UV‐hypcrsensitive mammalian cell lines, including several recently derived somatic cell hybrids and transformants, is presented. The sensitivity of these cells to ultraviolet irradiation correlates better with the capacity to repair(6–4) photoproducts than cyclobutane dimers. These data are used to support that idea that the(6–4) photoproduct is one of the major cytotoxic lesions induced in DNA by ultraviolet light.
CONFIGURATIONS OF NEUROSPORENE ISOMERS ISOLATED FROM THE REACTION CENTER AND THE LIGHT‐HARVESTING COMPLEX OF Rhodobacter spheroides G1C. A RESONANCE RAMAN, ELECTRONIC ABSORPTION, AND1H‐NMR STUDY
Authors: Koyama Yasushi , Kanaji Mariko , Shimamura Toshio
Published: July 2010

Abstract—HPLC analysis of neurosporene extracted from the chromatophore membranes ofRhodobacter spheroidesG1C showed two isomeric components 1 and 2. Extract from the light‐harvesting complex (LH) gave only component 2, while extract from the reaction center (RC) mainly gave component 1. Both components were isolated, and their configurations were determined by means of (1) resonance Raman, (2) electronic absorption, and (3)1H‐HMR spectroscopy. The configuration of component 2 originating from LH was determined to be all‐transand that of component 1 from RC was determined to be 15‐cis. Thus, our previous configurational prediction of this particular carotenoid bound to RC, by means of resonance Raman spectroscopy, to be15‐cis[Y. Koyama, T. Takii, K. Saiki and K. Tsukida,Photobiochem. Photobiophys.5(1983)139–150] is confirmed.
QUENCHING OF SINGLET MOLECULAR OXYGEN BY PHTHALOCYANINES AND NAPHTHALOCYANINES
Authors: Krasnovsky A. A. , Rodgers M. A. J. , Galpern M. G. , Rihter B. , Kenney M. E. , Lukjanetz E. A.
Published: July 2010

Abstract— Using the direct measurement of the photosensitized luminescence of singlet molecular oxygen (1O2) the rate constants (kq) have been determined for 1O2 quenching by the monomeric molecules of the following phthalocyanines and naphthalocyanines in chloroform: tetra‐(4‐tert‐butyl) phthalocyanine (I); octa‐(3,6‐butoxy) phthalocyanine (II), tetra‐(6‐tert‐butyl)‐2,3 naphthalocyanine (III), aluminium tetra‐(l‐tert‐phenyl)‐2,3 naphthalocyanine (IV), tri‐(n‐hexyl‐siloxy) derivatives of silicon‐(V), tin‐(VI), aluminium‐(VII) and gallium‐(VIII) 2,3 naphthalocyanine. The following kq values were obtained (kq× 10–8M‐1 s‐1): 2.9 (I), 59 (II), 100 (III), 20 (IV), 3.9 (V), 53 (VI), 33 (VII), 110 (VIII). As most of the quenchers have the low‐lying triplet levels, a contribution of the quenching mechanism based on the energy transfer from 1O2 to these levels has been analysed. A formula is proposed describing the relation between kq values caused by this mechanism, and photophysical constants of the quencher triplet state. This formula was applied to phthalocyanines, naphthalocyanines, p‐carotene and bacterochlorophyll a. The data suggest that the energy transfer can fully explain the activity of V and strongly contributes into the activities of II, III and VI‐VIII. A charge transfer interaction might be an additional mechanism involved in 1O2 quenching by compounds studied. As some phthalocyanines and naphthalocyanines are strong physical quenchers of singlet oxygen they can be used as efficient inhibitors for photodestructive processes in photochemical systems.
EVALUATION OF PORPHYRIN CHARACTERISTICS REQUIRED FOR PHOTODYNAMIC THERAPY
Authors: Woooburn K. W. , Vardaxis N. J. , Hill J. S. , Kaye A. H. , Reiss J. A. , Phillips D. R.
Published: July 2010

Abstract— The cytotoxicity (in the dark), phototoxicity (red light) and subcellular localization (using confocal laser scanning microscopy) were determined for 15 porphyrins (1–15) in C6 glioma cells. The partition coefficient in 2‐octanol was also determined for each porphyrin at pH 7.4. The cytotoxicity increased with π (log of partition coefficient) up to π values of +2. The 7 porphyrins with cationic side chains exhibited a classical parabolic correlation between phototoxicity and π, with maximal activity at a π value of approximately 1.0. There was also a significant correlation between subcellular localization and degree of phototoxicity, with the three most photosensitive porphyrins all possessing cationic side chains, and all three localizing in mitochondria.
THE ROLE OF ARGININES 82 AND 227 IN THE BACTERIORHODOPSIN PROTON PUMP*
Authors: Drachev L. A. , Kaulen A. D. , Khorana H. G. , Moci T. , Postanogova N. V. , Skulachev V. P. , Stern L. J.
Published: July 2010

Abstract— Arginine residues 82 and 227 in bacteriorhodopsin were replaced by glutamine residues, using the site‐directed mutagenesis techniques. Mutant bacteriorhodopsins were found to be competent in formation and decomposition of the photocycle M412 intermediate as well as in generation of photoelectric potential provided that pH of the medium is sufficiently high. Lowering of pH results in transition of bacteriorhodopsin into a blue acidic form which cannot produce M412 and photo‐potential. The pK values of these transitions for Arg‐227 → Gln and Arg‐82 → Gln mutants are shifted correspondently for 1 and 4 pH units to a higher pH region in comparison with native bacteriorhodopsin. The rate of the M412 formation in both mutants was similar to that in the native protein. As to M412 decay, it is much slower in Arg‐227 → Gln mutant than in native and Arg‐82 → Gln bacteriorhodopsins. In all cases, the decay depends only slightly upon pH. It is concluded that Arg‐82 is involved in maintenance of a bacteriorhodopsin structure that is resistant to the pH decrease down to 4 whereas Arg‐227 is required first of all for the process of Schiff base reprotonation.
A PHOTORECEPTOR SYSTEM REGULATING in vivo AND in vitro PHOSPHORYLATION OF A PEA PLASMA MEMBRANE PROTEIN*
Authors: Short Timothy W. , Porst Markus , Brigg Winslow R.
Published: July 2010

Abstract— We have continued to characterize the blue light‐regulated phosphorylation of a 120 kDa pea plasma membrane protein thought to be involved in sensory transduction for phototropism (Short and Briggs, 1990, Plant Physiol.92, 179–185). By incubating pea stem sections in 32P‐phosphate, we show that the 120 kDa protein is phosphorylated in vivo only after blue light irradiation and that the photosensitive fluence range matches that for phototropism. Blue light induces phosphorylation of the protein in vitro as well, but the fluences required to elicit the response are at least 30‐fold higher. Triton solubilization of the plasma membrane vesicles does not further alter the fluence‐response relationship. Very little turnover was detected over 20 min phosphorylation time courses or by pulse‐chase experiments on unirradiated, blue light pulse‐irradiated, or continuously irradiated membranes. Experiments with a dark period intervening between irradiation and addition of adenosine triphosphate show the light‐induced change to persist for several minutes at 30°c. Agents that disrupt the normal photochemistry of flavins preferentially inhibit the light‐induced enhancement of phosphorylation, suggesting a flavin chromophore. However, exogenous free flavins do not affect the sensitivity of the response. Staphylococcus aureus V‐8 proteolysis of the phosphorylated protein from membranes subjected to a range of fluences before phosphorylation shows that the radiolabel on each of three peptides increases in proportion to the phosphorylation level of the undigested polypeptide. These studies may be valuable for assessing the nature of the photoreceptor and for unravelling the early sensory transduction steps in phototropism.