bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical Study of Inlet-Distortion-Induced Instability of Axial Compression Systems
Authors: Lin F , Chen J
Published: June 2006

A theoretical study is performed to investigate the stall triggering mechanism of inlet-distortion-induced instability of axial compression systems. The focus is on the transient stall inception processes when the compressor is throttled from stable operating conditions to stall. By including a model for steady circumferential distortion screens, a new system model captures the non-linear interaction between inlet distortion and the axial compressor. The model is then studied with direct numerical simulation. It is found that the unstable long length-scale disturbances always grow out of the regions of the spoiled sectors of the distorted background flow, but under certain conditions they may evolve into short length-scale disturbances before rapidly triggering the full size stall. This is due to the influence of the non-linearity of the compressor characteristic and the distortion screen characteristic. The phenomenon of the long-to-short disturbance evolution shows the interplay of the initiation of the stall precursors, which is heavily related to blade passage flows, and their evolution process, which is dominated by system's non-linear characteristics, and offers an explanation to similar experimental phenomenon observed by other researchers.
Turbine Blade Cooling: The Blade Temperature Distribution
Authors: Horlock J. H. , Torbidoni L
Published: June 2006

Air cooling of high-temperature gas turbines is a standard practice; the air first cools the blading by internal convection and then by external film cooling, after ejection through holes and slots in the blade surface. In some ‘conventional’ analyses of turbine blade cooling, a ‘standard blade’ is invoked, which has a uniform blade temperature equal to the average temperature of the real blade, and estimates are made of the cooling flow required to hold the standard blade temperature to a limit set by material considerations. However, early analytical work by Ainley (for convective cooling of thin-walled blades) showed that both the coolant and blade temperatures should increase along the blade span. The current paper develops Ainley's original analysis to allow for finite blade wall thickness and thermal barrier coatings, film cooling, and variation in the mainstream gas temperature along the span. This new analysis should enable more accurate estimates to be made of cooling air flow requirements.
Experimental Study of the Effect of Drag Reduction Agents on the Performance of Jet Pumps
Authors: Gazzar M. El. , Meakhail T , Mikhail S
Published: June 2006

The overall efficiency of the jet pump is low compared with most of the other types of pumps. The majority of previous investigations concentrated on the effect of its geometric ratios on its performance. To the best of the authors’ knowledge, there are no previous investigations on the effect of adding drag reduction agents to the fluid passing on its performance, which is the objective of the present investigation. The mixing process in this case is that of two streams: the primary stream is water (Newtonian fluid), whereas the secondary stream is a solution of certain polymer (considered to be non-Newtonian). Tests are carried out to study the effect of different concentrations of additives (carboxy methyl cellulose (CMC)) on the performance of the jet pump.

The experimental results include characteristic curves for different area ratios, with different concentrations of CMC, as well as the wall static pressure distributions along the mixing chamber, diffuser, and outlet pipe. The results show that the concentration have a pronounced effect on the overall efficiency. The efficiency increases with the increase in concentration, up to a certain value, then decreases at higher value of concentration. Further, the maximum overall efficiency increases with the decrease in values of area ratio ( R).
An Advanced Oxy-Fuel Power Cycle with High Efficiency
Authors: Gou C , Cai R , Hong H
Published: June 2006

In this article, an innovative oxy-fuel power cycle is proposed as a promising CO2 emission mitigation solution. It includes two cases with different characteristics in the cycle configuration. Case 1 basically consists of a water steam Rankine cycle and a steam-CO2 recuperative-reheat cycle. Case 2 integrates some characteristics of Case 1 and a top Brayton cycle. The thermodynamic performances for the design conditions of these two cases were analysed using the advanced process simulator Aspen Plus and the results are given in detail. The corresponding exergy loss analyses were carried out to gain an understanding of the loss distribution. The MATIANT cycle, the CES cycle, and the GRAZ cycle were also evaluated as references. The results demonstrate that the proposed cycle has notable advantages in thermal efficiency, specific work, and technical feasibility compared with the reference cycles. For example, the thermal efficiency of Case 2 is 6.58 percentage points higher than that of the MATIANT cycle.
Influence of Harmonic Surface Roughness on the Fatigue Life of Elastohydrodynamic Lubricated Contacts
Authors: Chapkov A. D. , Colin F , Lubrecht A. A.
Published: June 2006

In recent years, owing to the increase in transmitted power, increase in temperature, and decrease in viscosity, elastohydrodynamic lubricated (EHL) contact conditions have become extremely severe. Consequently, roughness and surface features become increasingly important when compared with the lubricant film thickness, which can induce wear. Moreover, local pressure variations increasingly cause surface-induced fatigue. Therefore, the understanding of roughness behaviour in EHL contact performance has become important.

Three decades ago, a widely used tool to predict contact performance was proposed by Dawson and Tallian. It is based on the central film thickness to composite roughness ( h3/σ) ratio. However, engineering fatigue life models require the stress level and the stressed volume to study the contact life reduction, and neither can be extracted directly from the h3/σ ratio.

This article extends the amplitude reduction analysis. It proposes a new dimensionless parameter including central film thickness, roughness wavelength, and amplitude. It is shown that the pressure fluctuations depend solely on this parameter and that the fatigue life depends mainly on this parameter.
Effect of elastohydrodynamic film thickness on a wear model for worm gears
Authors: Sharif K. J. , Evans H. P. , Snidle R. W. , Barnett D , Egorov I. M.
Published: June 2006

Worm gears used for power transmission commonly consist of a steel worm running against a bronze or phosphor bronze worm wheel. The wheel teeth are usually manufactured using an ‘oversize’ hob so that the initial elastic contact between the teeth is in the form of an ellipse with lubricant entrainment predominantly in the major axis direction. As a result of this unfavourable contact geometry, the lubricant film generated between the worm and wheel teeth is relatively thin. The kinematic configuration is close to that of simple sliding as the velocity of the wheel tooth surface relative to the nominal contact point is very low in comparison with that of the worm. The combination of poor film forming, high sliding and a soft gear material (to avoid scuffing) leads to the continuous wear seen in these gears.

The article presents results obtained using a model for the prediction of wear for this configuration based on the well-known Archard wear law extended to take the variation of pressure and film thickness over the contact area into account in determining the wear rate. The pressure and film thickness distributions are obtained from elastohydrodynamic lubrication (EHL) modelling of the contact over the meshing cycle. Wear patterns are presented corresponding to different film thickness sensitivities in the wear formula, and these predictions, together with the calculated increase in backlash due to wear, give a basis for calibrating the model against experimental wear tests.
Modelling thin film lubrication: Scientific versus engineering approaches
Authors: Tichy J
Published: June 2006

There have been many recent advances in lubrication experimentation from a scientific perspective - the ability to perform meaningful measurements on molecular-scale films. Likewise, impressive strides have been made in the modelling of thin film (nanometer-scale) lubrication, from molecular dynamics and other theoretical techniques, again emanating from scientific domains. Selected recent experimental and theoretical results are discussed, particularly the ‘state variable’ theories applied to simple stick-slip configuration. Continuum-based methods are traditionally thought to be of little value in describing the modes of lubrication occurring at molecular scale. However, there is considerable experimental evidence suggesting that elements of the continuum theory may be valid, in the case of films as thin as several nanometres. The behaviour of rheological models and their applicability to thin film lubrication is described. Approaching these problems from the fluid film constitutive equation perspective is less often used but appears to be promising. Such continuum methods can take advantage of the extensive existing research methodologies such as the finite-element method of the engineering tribology community.
Fretting wear of Ti(CxNy) PVD coatings under variable environmental conditions
Authors: Liskiewicz T , Rybiak R , Fouvry S , Wendler B
Published: June 2006

Fretting wear as a specific type of degradation is defined as an oscillatory motion at small amplitude between two nominally stationary solid bodies in mutual contact. Under external stresses, the interface is being damaged by debris generation and its successive ejections outside the contact area. A potential protection against fretting damage by means of hard coatings is being offered by different surface engineering techniques. For this study, TiC, TiN, and TiCN hard coatings manufactured by a physical vapour deposition method have been selected and tested against smooth polycrystalline alumina ball. A fretting test programme has been carried out at the frequency of 5 Hz, 100 N normal load, 100 μm displacement amplitude, and at three values of a relative humidity (RH): 10, 50, and 90 per cent at 295-298 K temperature. It turned out that the intensity of wear process was depending not only on loading conditions but also on environmental ones. A significant impact of RH on wear rate and friction behaviour of the coatings under investigation has been observed. Two different damage mechanisms have been identified and related to the phenomena of debris oxidation and debris adhesion to the counterbody surface. In the latter case, the debris deposited onto the surface of the alumina ball lead to a change of stress distribution at the interface and as a result to accelerated wear. In this work, experiments with variable RH increasing from 10 to 90 per cent within a single fretting test have been completed. It follows from these experiments that there exists an intermediate value of the RH at which the friction coefficient changes rapidly. Finally, a dissipated energy approach has been applied in the work to quantify and compare fretting wear rates of different hard coatings.
Wear effects and mechanisms of soot-contaminated automotive lubricants
Authors: Green D. A. , Lewis R , Dwyer-Joyce R. S.
Published: June 2006

A study has been carried out to investigate the influence of soot-contaminated automotive lubricants in the wear process of a simulated engine valve train contact. Previous research on this topic has been mainly performed from a chemical point of view in fundamental studies, with insufficient relevance to real engine conditions, i.e. load and geometry. This study investigates the conditions under which wear occurs through specimen testing. The objective of the work was to understand the wear mechanisms that occur within the contaminated contact zone, to help in future development of a predictive wear model to assist in the valve-train design process.

The effects of soot in lubricants have been tested using a reciprocating test-rig specifically designed for this application, where a steel disc is held in a bath of oil and a steel ball (replicating a valve train contact) is attached to a reciprocating arm. The materials, contact geometry and loading conditions are all related to specific conditions experienced within an engine's valve train. The testing was carried out under various contact conditions, using carbon black as a soot simulant. Wear measurements were taken during the tests and wear scar morphology was studied.

The results have revealed how varying lubrication conditions changes the wear rate of engine components and determines the wear mechanism that dominates for specific situations.
Prediction of losses in belt-type continuously variable transmission due to sliding between belt and disc
Authors: Poll G , Kruse T , Meyer C
Published: June 2006

The efficiency of belt-type continuously variable transmission (CVT) - apart from the power consumption of auxiliary systems such as hydraulics - predominantly depends on the energy dissipated during sliding at the belt-disc contacts. These sliding motions are a consequence of elastic deformations and misalignments because of clearances, resulting in a so-called spiral path of the belt elements on the discs and hence tangential and radial sliding motions.

The performance of such systems can be predicted through an iterative computation by numerically solving a set of differential equations for the forces and motions coupled with a finite-element computation of the deformations.

A comparison with elaborate measurements of deflections, belt motions, and losses shows that a relatively simple modified Coulomb type friction model with a steep gradient through the origin delivers sufficiently accurate results. The computations reveal the existence of ‘locked’ zones with extremely low ‘creeping’ motions.

Thus, the mechanisms of power transmission in belt-type CVT are better understood and designers have a validated tool to optimize shaft and disc geometry concerning maximum efficiency.
Occurrence of microelastohydrodynamic lubrication in simple sliding motion with transverse roughness
Authors: Wang J , Kaneta M , Guo F , Yang P
Published: June 2006

Using numerical simulations, the effect of surface roughness on elastohydrodynamic lubrication (EHL) under simple sliding point contacts is investigated. Transverse roughness is on the stationary surface. Four fluid flow models, i.e. thermal Newtonian, isothermal Newtonian, thermal Eyring, and isothermal Eyring models, are employed in the analyses. The effects of temperature rise, lubricant rheology, and amplitude and wavelength of asperities on micro-EHL films are elucidated. Behaviours of oil films with short wavelength of asperities are found to be complex. The deformations of asperities are also compared under the four fluid flow models.
Roughness in rolling-sliding elastohydrodynamic lubricated contacts
Authors: Hooke C. J.
Published: June 2006

A simplified treatment of roughness effects in rolling-sliding elastohydrodynamic lubricated (EHL) contacts was developed by the author [4]. This analysis predicted that the original amplitude would be attenuated under the conjunction and that a decaying, complementary wave would be generated at the inlet. This complementary wave would be carried through the contact at the entrainment velocity and, for sinusoidal roughness, its wavelength would be given by λ u/v, where λ is the wavelength of the original roughness, u the entrainment velocity, and v the velocity of the rough surface. This simplified analysis predicted the degree of attenuation of the original roughness and the decay rate of the complementary wave but did not determine the amplitude of the complementary wave. This paper presents a more detailed account of this analytical approach including compressibility effects together with a more accurate allowance for the coupling between the decay of the complementary wave and its wavelength. It also extends the work, using a perturbation analysis, determining accurate values for the pressures and clearance variations produced, under rolling-sliding conjunctions, by low-amplitude roughness. The perturbation results are compared with the predictions of the simplified analysis. It will be shown that the analysis is remarkably accurate. In addition, it appears to be relatively straightforward to determine the magnitude of the complementary wave for any given operating condition. The effect of low-amplitude, sinusoidal roughness on EHL contacts can then be expressed in terms of the operating conditions together with a single value for the amplitude of the complementary wave. This simplification suggests that it may be possible to produce a method for the rapid analysis of roughness effects in rolling-sliding conjunctions without the need for any detailed EHL calculations.
Lubrication in refrigeration systems: Numerical model for piston dynamics considering oil-refrigerant interaction
Authors: Grando F. P. , Priest M , Prata A. T.
Published: June 2006

Piston dynamics plays a fundamental role in several processes related to the operation of hermetic reciprocating compressors used in refrigeration. For example, the refrigerant leakage through the radial clearance between piston and cylinder, which reduces compressor pumping efficiency, and also the viscous friction associated with the lubricant film in the radial clearance, which is related to energy consumption. It is important to optimize such variables, ensuring at the same time smooth operation of the piston in its reciprocating motion, minimizing wear and increasing lifetime.

In this context, numerical models studying piston dynamics provide a useful tool for engineering design. These models usually consider an oil film filling the piston-cylinder clearance and operating in the hydrodynamic regime. Determining cavitation conditions occurring along the ringless piston represents an additional difficulty in modelling. As refrigerant is present in the compressor environment, it inevitably interacts with the oil, changing lubricant characteristics. The refrigerant can dissolve in the oil at higher pressures, reducing viscosity, and can be released at lower pressures, leading to a two-phase flow.

This work explores how the interaction of oil and refrigerant affects piston dynamics, using a numerical model that considers as the lubricant a mixture of oil and refrigerant with variable properties. Comparing the results with simulations where pure oil is considered as the lubricant and a cavitation criterion is adopted, significant differences were observed in predicting piston trajectory and power consumption along the cycle.
Bio-tribology and bio-mimetics in the operating environment
Authors: Dowson D , Neville A
Published: June 2006

The main objectives of this review are to draw attention to some of the interesting and exciting studies of human and animal tribology and to introduce the growing field of bio-mimetics.

Studies of natural and total replacement synovial joints are widely known and spectacular progress has been reported in both fields. However, it is becoming ever more important to link engineering and biology and to apply sound tribological principles in the further development of long-lasting total joint replacements.

In this article, accounts will be given for a wider range of fascinating tribological features of biological systems, embracing friction, lubrication, and wear. These include animal locomotion, swimming, adhesion and attachment to adjacent surfaces, oral tribology, skin and ocular tribology.

Bio-mimetic approaches to engineering problems, in which lessons have been learned from comparable solutions in the natural world, have been impressive, but they have not yet been widely applied in tribology. The challenge remains with prospects of ever closer association between bio-tribology and bio-mimetics.
Development of a Three-Dimensional Substructure Search Program for Organic Molecules
Authors: Kato Hiroaki , Takahashi Yoshimasa
Published: June 2006

A computer program, called SS3D, has been developed for the three-dimensional substructure searching of organic molecular structures. Our approach is based on a clique-finding algorithm that compares chemical graphs containing edges labelled with inter-atomic distances. The program allows one to specify some allowance of the distance for the geometrical matching of 3D-substructures; it also allows one to define some constraints for the query substructure or for the geometrical pattern to be used in the search. The details concerning the program are discussed and several illustrative examples are given.
Preparation and Chemical Properties of a Novel Layered Cerium(IV) Phosphate
Authors: Tsuhako Mitsutomo , Danjo Mayumi , Baba Yoshinobu , Murakami Masahiko , Nariai Hiroyuki , Motooka Itaru
Published: June 2006

A synthetic method of a novel cerium(IV) bis(hydrogenphosphate) dihydrate, Ce(HPO4)2·2H2O, hereafter referred to as CeP·2H2O, has been established by the hydrothermal reaction of cerium(IV) oxide with phosphoric acid in an autoclave. The preparation of CeP·2H2O was significantly affected by the reaction conditions: the mixing ratio (P2O5/CeO2) of CeO2 and phosphoric acid, heating temperature and time, and water vapor pressure. The optimum condition for the preparation of CeP·2H2O was the mixing ratio of 1.5—2.0, heating temperature 175—200 °C, heating time 5 h, and water vapor pressure 5.0—7.0 atm.

The results of X-ray powder diffraction, fluorescent X-ray analysis, differential thermal analysis and thermogravimetry (DTA-TG), IR spectrum, and phase transition showed that CeP·2H2O is a novel crystalline layered cerium(IV) phosphate having a interlayer distance d = 18.0 Å, longer than any layered phosphates (zirconium(IV), titanium(IV), and tin(IV) phosphates) so far reported.

The reversible phase transition of CeP·2H2O occurred as follows, when exposed to various relative humidities:

CeP·2H2O dissolved slightly in distilled water and hydrochloric acid, and much more in aqueous sodium hydroxide and aqueous ammonia. CeP·2H2O effectively adsorbed ammonia in an aqueous solution and ammonia gas.
Molecular Structures of HMPA-Coordinated Samarium(II) and Ytterbium(II) Iodide Complexes. A Structural Basis for the HMPA Effects in SmI2-Promoted Reactions
Authors: Hou Zhaomin , Zhang Yugen , Wakatsuki Yasuo
Published: June 2006

The reaction of ytterbium(II) iodide (YbI2) with 4.5 equiv of hexamethylphosphoric triamide (hmpa) in tetrahydrofuran (thf) gave [Yb(hmpa)4(thf)2]I2 (1) as yellow crystals. A similar reaction of SmI2 with hmpa afforded black-purple [SmI2(hmpa)4] (2) after recrystallization from toluene. When 10 equiv of hmpa were used in the reaction with SmI2, [Sm(hmpa)6]I2 (3) was obtained as purple blocks. Complexes 1—3 have been structurally characterized by crystallographic studies. The structural data of these complexes satisfactorily explain the hmpa effects observed in SmI2-promoted reactions, and also provide a guideline for the use of HMPA in these reactions.
Modified Borohydride Agents, (1,4-Diazabicyclo[2.2.2]octane)(tetrahydroborato)zinc Complex [Zn(BH4)2(dabco)]. A New Ligand Metal Borohydride as a Stable, Efficient, and Versatile Reducing Agent
Authors: Firouzabadi Habib , Zeynizadeh Behzad
Published: June 2006

(1,4-Diazabicyclo[2.2.2]octane)(tetrahydroborato)zinc complex is a stable compound which has been used for the selective reduction of aldehydes, ketones, α,β-unsaturated carbonyl compounds, α-diketones, acyloins and acyl chlorides to their alcohols and aldehydes in THF or CH2Cl2/hexane at room temperature or under reflux conditions.
Side-Chain Liquid-Crystalline Polyoxetanes with a Spacer-Separated Azobenzene Moiety. II. Preparation and Characterization of Polyoxetanes Derived from 4-(4-Alkoxyphenylazo)phenyl 4-[7-(3-Methyl-3-oxetanyl)-1,6-dioxaheptyl]benzoates
Authors: Ogawa Hiroshi , Hosomi Tetsuya , Kosaka Toshiaki , Kanoh Shigeyoshi , Ueyama Akihiko , Motoi Masatoshi
Published: June 2006

A series of polyoxetanes were prepared by the cationic ring-opening polymerization of 4-(4-alkoxyphenylazo)phenyl 4-[7-(3-methyl-3-oxetanyl)-1,6-dioxaheptyl]benzoates using 0.08 molar amount of THF·BF3 in dichloromethane at 20 to 30 °C. Although the product polymers indicated GPC-average molecular weights of around 9000 to 23000, in most cases, they did not have an unimodal molecular weight dispersity. The liquid-crystalline mesophases of the polymers were examined by differential scanning calorimetry and polarized optical microscopy; these textures were observed due to nematic and/or smectic mesophases over a wide temperature range from about 250 °C to room temperature. The benzoate moiety, the longer p-substituted alkoxy tails, and the oxetane main chain play important roles in maintaining highly ordered, stable mesophases.
N,N,N′,N′-Tetraalkyl-2,2′-dihydroxy-1,1′-binaphthyl-3,3′-dicarboxamides: Novel Chiral Auxiliaries for Asymmetric Simmons–Smith Cyclopropanation of Allylic Alcohols and for Asymmetric Diethylzinc Addition to Aldehydes
Authors: Kitajima Hiroshi , Ito Katsuji , Aoki Yuko , Katsuki Tsutomu
Published: June 2006

The newly introduced title compounds were found to be efficient chiral auxiliaries for the asymmetric Simmons–Smith cyclopropanation of allylic alcohols and for asymmetric addition of diethylzinc to aldehydes. For example, Simmons-Smith cyclopropanation of cinnamyl alcohol in the presence of N,N,N′,N′-tetraethyl-2,2′-dihydroxy-1,1′-binaphthyl-3,3′-dicarboxamide (1b) proceeded with high enantioselectivity of 94% ee and addition of diethylzinc to benzaldehyde in the presence of N,N,N′,N′-tetraisopropyl-2,2′-dihydroxy-1,1′-binaphthyl-3,3′-dicarboxamide (1e) proceeded with enantioselectivity of 99% ee. Although the reaction mechanism of these reactions is still nuclear, a monomeric seven-membered 2,2′-dihydroxy-1,1′ -binaphthyl-3,3′-dicarboxamide (1)–Zn complex is considered to be an active species which catalyzes the above reactions, on the basis of NMR experiments.
Oxidative Anion Metatheses in Diaryliodonium Iodides and Chlorides
Authors: Kazmierczak Pawel , Skulski Lech
Published: June 2006

Oxidative anion metatheses in the crude title iodides and chlorides produced the corresponding pure hydrogensulfates, nitrates, tetrafluoroborates, triflates, tosylates, as well as bromides and chlorides (only from the iodides) in 54—86% yields. These procedures are easier and shorter than earlier methods. By using modified oxidative metatheses in the title iodides (in the presence of HBr or HCl) it was possible either to isolate, or to detect only, the intermediate dihaloiodates(I), [Ar2I]+[IX2]− (X = Br or Cl). A complex Ph2I+Cl−·1/2I2 was also obtained in 56% yield. Tetraethylammonium iodide was similarly converted into pure tetrafluoroborate or dibromoiodate(I) in 75 and 76% yields, respectively.
Manganese-Catalyzed Silylmagnesiation of Acetylenes and 1,3-Dienes
Authors: Tang Jun , Shinokubo Hiroshi , Oshima Koichiro
Published: June 2006

The treatment of 4-benzyloxy-1-butyne with PhMe2SiMgMe in the presence of a catalytic amount of MnCl2 gave a monosilylated product, (E)-PhCH2OCH2CH2CH=CHSiMe2Ph, selectively after an aqueous workup. Meanwhile, the reaction of isoprene with PhMe2SiMgMe under manganese catalysis and the subsequent addition of iodomethane afforded 4-dimethylphenylsilyl-2,3-dimethyl-1-butene in good yield.
Highly Efficient Energy Transfer from Tryptophans in Avidin Tetramer to Biotin-Linked Pyrenylalanine
Authors: Kuragaki Masahiro , Sisido Masahiko
Published: June 2006

Highly efficient energy transfer from tryptophan units of an avidin tetramer to biotin-linked pyrenylalanine was observed. The energy transfer efficiency reached 85% when two of the four subunits were occupied with biotin-linked pyrenylalanine. The transfer efficiency vs. pyrenylalanine/binding site curve was simulated taking the distribution of the biotin derivatives among the four binding sites and the difference of Förster’s r0 values for polar and nonpolar tryptophans, into account. The results showed a qualitative agreement with the experimental data.
Excited State Intramolecular Proton Transfer Reactions in 2-(2-Hydroxyphenyl)benzimidazole in Micellar Solutions
Authors: Das Somes Kumar , Bansal Ashish , Dogra Sneh Kumar
Published: June 2006

Spectral characteristics of 2-(2-hydroxyphenyl)benzimidazole (HPBI) have been studied in solutions containing different compositions of dioxane–water mixtures, aqueous sodium dodecyl sulfate (SDS), hexadecyltrimethylammonium bromide (HTAB), and Triton X-100 (TX-100). The correlation curve between the fluorescence band maxima () and the dielectric constant of dioxane–water solutions provides a better rule than the pure solvents to find the polarity at the binding site of the fluorophore in micelles. The effective dielectric constant at the binding sites of SDS, HTAB, and TX-100 are found to be 40, 20, and 20, respectively. The values of the binding constants of HPBI to these micelles conform to the above results. pKa values for various proton transfer reactions were determined at different concentrations of SDS, HTAB, and TX-100, both in the ground and singlet states, and these are discussed.
Physical and Donor–Acceptor Properties of 3-Propyl-4-ethylsydnone
Authors: Handa Minoru , Kataoka Mayumi , Wakaumi Makoto , Sasaki Yukio
Published: June 2006

The physical properties of 3-propyl-4-ethylsydnone at various temperatures were investigated by dielectric constant (ε), refractive index (nD), density (ρ), and viscosity (η) measurements. The dielectric constant of 3-propyl-4-ethylsydnone was very high compared with those of many organic solvents. For example, it was found to be 64.6 at 25 °C, close to that of propylene carbonate (64.9), a typical nonaqueous polar solvent with a high dielectric constant. The refractive index and density for 3-propyl-4-ethylsydnone decreased linearly with increasing temperature. The viscosity of 3-propyl-4-ethylsydnone at 25 °C was 11.2 cP (1 cP = 10−3 N s m−2). This was larger than those of many organic solvents and close to that of phenol (11.6 cP at 20 °C). From a line for log η vs. 1/T, the activation energy (Eη) for the viscosity of 3-propyl-4-ethylsydnone was found to be 29.7 kJ mol−1. The estimation of donor (DN) and acceptor (AN) numbers for 3-propyl-4-ethylsydnone were also done from 29Si and 13C NMR spectroscopies, respectively. Donor number of 3-propyl-4-ethylsydnone was about 25, and its acceptor number was approximately about 20. Both numbers were large in many organic solvents. Both physical and donor–acceptor properties were influenced by alkyl substituent groups in the 3-, 4-positions of the sydnone ring.
A Unified Theory of Uniaxially- and Biaxially-Stretched Film Methods: Three-Dimensional Reduced Spectra of Perylene
Authors: Kobayashi Michio , Yuan Xinghai , Shinbo Norio , Watanabe Masashi , Matsumoto Masunori , Miura Masanori , Yoshioka Ikuko , Tanizaki Yoshie
Published: June 2006

A unified theory of uniaxially- and biaxially-stretched film methods has been proposed. This theory allows the decomposition of the electronic absorption spectrum into three-dimensional reduced spectra polarized along the molecular orientation axes. A transformation theory has also been proposed to transform these reduced spectra to the three-dimensional reduced spectra polarized along the molecular axes, assuming that there exist a pure band and an overlapping band in the spectrum. These theories were applied to get the three-dimensional reduced spectra of perylene.
Thermochromism of the Crystals of 2,3-Bis(phenylthio)-1,4-naphthoquinone
Authors: Tanaka Masashi , Hayashi Hisahiro , Matsumoto Shingo , Kashino Setsuo , Mogi Kouichi
Published: June 2006

The crystals of 2,3-bis(phenylthio)-1,4-naphthoquinone have the dimorphs of red and violet forms. The crystal structures of a monoclinic form (violet form) and an orthorhombic form (red form) have been determined by the X-ray diffraction method. In the orthorhombic form, two phenylthio groups are located on the same side of the naphthoquinone plane, while in the monoclinic form one phenylthio group is located on the naphthoquinone plane and the other phenylthio group is located under the plane. The violet form changes to the red form upon heating. The thermochromism of these crystals was studied, based on the crystal structures of the dimorphs and the solid state CP-NMR and IR and visible absorption spectra and the differential scanning calorimetry together with the theoretical analysis of the data of IR and visible absorption spectra.
Highly Efficient and Selective Membrane Transport of Silver(I) Ion by a Cooperative Carrier Composed of Aza-18-crown-6 and Palmitic Acid
Authors: Shamsipur Mojtaba , Akhond Morteza
Published: June 2006

A given mixture of aza-18-crown-6 and plamitic acid was found to be an excellent cooperative carrier for the efficient transport of Ag+ ions through a bulk liquid membrane. In the presence S2O32− ion, as a suitable metal ion acceptor in the receiving phase, the amount of silver transported across the liquid membrane after 90 min was 93.6 ± 1.5%. The selectivity and efficiency of silver transport from aqueous solutions containing other cations such as Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Pb2+, and Fe2+ ions were investigated. In the presence of diphosphate as a suitable masking agent in the source phase, the interfering effect of Cd2+ ion was eliminated.
Synthesis, Crystal Structure, and Characterization of Layered Aluminum Methylphosphonate
Authors: Maeda Kazuyuki , Hashiguchi Yoshie , Kiyozumi Yoshimichi , Mizukami Fujio
Published: June 2006

The first aluminum methylphosphonate with a layered structure, designated AlMepO-ζ, giving an ideal composition of Al(OH)(O3PCH3)·H2O was synthesized with a hydrothermal procedure. AlMepO-ζ is monoclinic, space group P21/c, with a = 7.8676(7), b = 7.0744(13), c = 9.4789(7), β = 106.599(6)°. The framework in a sheet containing unidimensional [–Al–(OH)–Al–] chain is topologically the same as VO(O3PC6H5)·H2O. Methyl groups protrude into the interlamellar space. TG-DTA and MAS-NMR results revealed the decomposition mechanism.
Total Internal Reflection Fluorometric Study of the Ion-Association Adsorption of Ionic Derivatives of Porphyrin at Liquid–Liquid Interface
Authors: Saitoh Yoriko , Watarai Hitoshi
Published: June 2006

Interfacial ion-association adsorption of 5,10,15,20-tetrakis(4-sulfonatophenyl)-21H,23H-porphine (H2tpps4−) with hexadecyltrimethylammonium ion and 5,10,15,20-tetrakis(1-methyl-4-pyridinio)-21H,23H-porphine (H2tmpyp4+) with 1-hexadecanesulfonate was measured by means of a total internal reflection fluorometry at toluene/water systems. The adsorptivity of the porphyrins was negligibly small in the absence of the ionic surfactants, but it was increased by the addition of the surfactants in the 10−8—10−7 M concentration. The adsorptivity was governed by the positive or negative charge of the surface-active counter ion and its concentration, which determined the electrostatic potential of the interface. Further, it was found that zinc(II)-1,10-phenanthroline, a hydrophobic complex cation, remarkably enhanced the interfacial adsorption of [Zntpps]4− ion, but showed no positive effect on the adsorption of [Zntmpyp]4+ ion.
Kinetics of the Formation and Decay of Benzidine Mono Radical Cation in Aqueous Solution
Authors: Aravindan Ponnu , Maruthamuthu Pichai , Dharmalingam Periasamy
Published: June 2006

The oxidation of benzidine by Ce(IV); the oxoanions MnO4− and Cr2O72−; peroxides, namely potassium peroxomonosulfate (KHSO5), peroxodisulfate (S2O82−) and H2O2; and halogens viz., Cl2, Br2, and I2, to the benzidine mono radical cation (benzidine•+) and further oxidation to the benzidine diradical cation (+•benzidine•+) by the above-mentioned oxidants, except for Br2 and I2, were investigated by a stopped-flow technique. The kinetics of both reactions, the formation and decay of benzidine•+, were monitored by following the absorption of the radical cation at λmax = 603 nm. The reactions were found to follow a total second-order kinetics, first-order each with respect to [benzidine] or [benzidine•+] and the [oxidant]. The effects of the pH and temperature on the formation and decay of benzidine•+ were also investigated. The kinetic and transition-state parameters were evaluated with a suitable reaction mechanism. The radical cation benzidine•+ was converted back to the parent compound, benzidine, by such reducing agents as sulfite (SO32−), thiosulfate (S2O32−), dithionite (S2O42−), and disulfite (S2O52−). The rate constants for these reactions were also estimated. The experimentally determined rate constants for the oxidative electron-transfer reactions were correlated theoretically using Marcus theory; the observed and calculated rate constants show good agreement.
“Syn-Effect” in the Desulfonylation Reaction of α,α-Dialkylated (E)-Allylic Sulfones
Authors: Shibayama Atsushi , Nakamura Tetsuya , Asada Takahiro , Shintani Takehiko , Ukaji Yutaka , Kinoshita Hideki , Inomata Katsuhiko
Published: June 2006

It was found that the desulfonylation reaction of α,α-dialkylated (E)-allylic sulfones with a base preferentially affords the sterically unfavorable (Z)-alkadienes. The relative degree of the “syn-effect”, which is herein defined as an effect which stabilizes the syn-conformation, leading to (Z)-products, in the transition state against the steric hindrance, was revealed for various substituents at the δ-position of the (E)-allylic sulfones to be as follows: RO– >> CH3– > RS– > –CH2– > (CH3)2CH– >> (CH3)3C– > C6H5–. This finding is in accord with a previously found tendency in the conversion of (E)-vinylic sulfones to the corresponding allylic sulfones under basic conditions.
Mechanism for the Production and Reaction of Active-Oxygen Species from Photoexcited Hematoporphyrin Adsorbed on a Biological Heterogeneous System
Authors: Noda Hiroyuki , Ohya-Nishiguchi Hiroaki , Kamada Hitoshi
Published: June 2006

The electronic states of hematoporphyrin (HP) adsorbed on the cell wall of yeast [biological heterogeneous (BH) system] have been characterized based on its fluorescence spectra, in comparison with those of the HP monomer and oligomer in a homogeneous system. The formation of some adsorption structures of HP on a BH system was confirmed from the fluorescence excitation spectra. An ESR method has also been applied to clarify the mechanism for the production and reaction of active-oxygen species from photoexcited HP on a BH system. The hydroxyl radical derived through a three-electron reduction of oxygen was the major product. The mechanism for producing the hydroxyl radical from photoexcited HP on a BH system is discussed as a characteristic feature for the formation of a heterogeneous system containing monomeric HP.
Reactivities of Stable Rotamers. XXXIX. Thermal Decomposition of t-Butyl 3-Methyl-3-(substituted 9-triptycyl)peroxybutanoate Rotamers
Authors: Oki Michinori , Fujino Ichiro , Kawaguchi Daisuke , Chuda Kazumasa , Moritaka Yoko , Yamamoto Yasunori , Tsuda Shingo , Akinaga Tadashi , Aki Michihiko , Kojima Hiroharu , Morita Nobuhiro , Sakurai Makoto , Toyota Shinji , Tanaka Yasuhiro , Tanuma Toshihiro , Yamamto Gaku
Published: June 2006

The ap and sc rotamers of the title compound, where substituents are 1,4-dimethyl, 1,4-dimethoxy, 1,2,3,4-tetrafluoro, and 1,2,3,4-tetrachloro, were thermolyzed in toluene solutions to examine the effects of interactions between the radical center and the substituent. The rates of thermolyses were affected neither by the substituent nor by the rotameric positions, but the product distributions showed dependence on the substituent. In the ap-forms, the effectively bulkier the substituent at the 1-position, the higher the yields of the 5-membered ring compound. This was attributed to the degree of the tilting of the 9-substituent, which forces the radical center to be pushed into the triptycene skeleton. For the sc-forms, the chloro and the methyl substituents exhibited special effects, the former affording a colligation product between benzyl and 2-(1,2,3,4-tetrachloro-9-triptycyl)-2-methylpropyl radicals and the latter showing a tendency of radical migration to the benzylic position. Comparison of the results of thermolyses of the 1,4-dimethyl peroxyester with those of 2(1H)-thioxo-1-pyridyl 3-(1,4-dimethyl-9-triptycyl)-3-methylbutanoate indicates that, although it is believed that these precursors afford the same 2-(1,4-dimethyl-9-triptycyl)-2-methylpropyl radicals, the product distributions were significantly different from each other. These results were attributed to the stabilizing effects of the sulfur compound on the radical in the solvent cage in the latter.
Regioselective Coupling Reaction of Allylic Barium Reagents with Epoxides
Authors: Yasue Katsutaka , Yanagisawa Akira , Yamamoto Hisashi
Published: June 2006

The regioselective coupling reaction of epoxides with allylic barium reagents was achieved. All reactions resulted in high yields with remarkable α-selectivities. 2-Propynylbarium reagent afforded exclusively the corresponding acetylenic alcohol.
First Synthesis and Reactivities of Isolable Dithiiranes and Their 1-Oxides
Authors: Ishii Akihiko , Akazawa Toru , Ding Meng-Xin , Honjo Takanari , Maruta Teruo , Nakamura Shin-ya , Nagaya Hidenori , Ogura Miho , Teramoto Katsuhiko , Shiro Motoo , Hoshino Masamatsu , Nakayama Juzo
Published: June 2006

The reaction of the 6-exo-oxide of 2,2,4,4-tetramethyl-1,5-diphenyl-6,7-dithiabicyclo[3.1.1]heptane (2) with 2KHSO5·KHSO4·K2SO4 gave the first isolable dithiirane oxide, (1RS, 3SR)-3-phenyl-3-(1,1,3,3-tetramethyl-4-oxo-4-phenylbutyl)dithiirane 1-oxide (1), while the 6-endo-oxide of 2 gave both 1 and its (1RS, 3RS)-isomer 10. Under similar reaction conditions, 2 yielded the first isolable, unoxidized dithiirane, 3-phenyl-3-(1,1,3,3-tetramethyl-4-oxo-4-phenylbutyl)dithiirane (3). The dithiirane 3 was also obtained by treatment of 2 with NaOCl–NaClO4. The X-ray structure analyses were performed for 1, 3, and 10. Treatment of unsymmetrical 8,8-dimethyl-1,9-diphenyl-10,11-dithiatricyclo[7.1.1.02,7]undeca-2,4,6-triene with NaOCl–NaClO4gave 3-[1-(o-benzoylphenyl)-1-methylethyl]-3-phenyldithiirane selectively in good yield. However, 1,3-dithietanes, prepared from adamantane-2-thiones, failed to give the corresponding dithiiranes by treatment with 2KHSO5·KHSO4·K2SO4 or NaOCl–NaClO4. The dithiirane 3 thermally isomerized to 2,2,4,4-tetramethyl-1,5-diphenyl-8-oxa-6,7-dithiabicyclo[3.2.1]octane probably via 2,2,4,4-tetramethyl-1,5-diphenyl-5-thioxo-1-pentanone S-sulfide.
NMR Spectroscopy of Cyclodextrin–Inorganic Anion Systems
Authors: Matsui Yoshihisa , Ono Masaharu , Tokunaga Shuichi
Published: June 2006

The addition of alkali salts of chaotropic anions such as Br−, I−, SCN−, N3−, ClO4−, and NO3− to an α-cyclodextrin (α-CD) solution in D2O caused marked downfield shifts in the 1H NMR signal of the C(5)–H located in the interior of the α-CD cavity, whereas the signal showed no or only small upfield shifts upon the addition of alkali salts of antichaotropic anions such as F−, HCO3−, H2PO4−, HPO42−, and SO42−. The effects of the inorganic salts on the chemical shifts (δ) for the other protons of α-CD were significant but smaller than that on δ for C(5)–H. These facts indicate that the chaotropic anions are included within the α-CD cavity and held in the vicinity of C(5)–H. Similar, but smaller, effects of the inorganic salts were observed for β- and γ-CD. The binding constants and thermodynamic parameters determined for complexation of CD’s with some chaotropic anions suggest that hydrophobic and van der Waals interactions, as well as a conformational change of CD macrocycles and the desolvation of CD’s and/or the anions upon complexation, play important roles in complex stabilization. The effect of inorganic salts on the spin-lattice relaxation times of α-CD protons also supports the above conclusion.
A Generalized Fokker–Planck Equation Treatment of Inertia and Non-Markovian Effects on the Short-Time Dynamics of a Collision-Induced Reaction
Authors: Ibuki Kazuyasu , Ueno Masakatsu
Published: June 2006

The inertia and non-Markovian effects on the short-time dynamics of a diffusion-controlled reaction were studied using a generalized Fokker–Planck equation with a boundary condition suitable for a collision-induced reaction. The approximation of half-range Maxwellian velocity distributions was employed to calculate the time-dependent rate constant. At time zero, the rate constant obtained analytically exhibits a limiting value which is independent of the friction kernels, and is smaller than that of the Smoluchowski–Collins–Kimball (SCK) theory. At finite times, the rate constant is obtained numerically, and its initial decay is slower than that of the SCK theory even when only the inertia effect is taken into account. When a non-Markovian effect is also taken into account, the initial slow decay becomes more pronounced. We have also found that the theoretical rate constant is sensitive to the boundary condition for the velocity distribution at the reaction radius. In order to test the results, we carried out a computer simulation of an encounter reaction between a test particle and hard-sphere reactants in a hard-sphere fluid, and obtained the survival probabilities of the test particle. Our results agree excellently with the simulation results.
Phase Separation in Silica Sol–Gel System Containing Poly(ethylene oxide) II. Effects of Molecular Weight and Temperature
Authors: Nakanishi Kazuki , Soga Naohiro
Published: June 2006

Phase separation and gelation behaviors have been studied for acid-catalyzed, alkoxide-based silica systems containing poly(ethylene oxide), PEO. In order to clarify the role of PEO in a phase-separating sol–gel system, the effects of the molecular weight of PEO and the reaction temperature were investigated in detail. The PEO concentration of the highest phase-separation tendency slightly increased along with a decrease in the molecular weight, suggesting that the phase-separation behavior is mainly governed by an interaction between PEO and the solvent mixture. The reaction temperature affected the morphology-composition relationship mainly by its effect on the sol–gel transition kinetics.
Synthesis of New Cationic Schiff Base Complexes of Copper(II) and Their Selective Binding with DNA
Authors: Tanaka Tomohide , Tsurutani Keiko , Komatsu Atsushi , Ito Toyofumi , Iida Kazumi , Fujii Yuki , Nakano Yoshiharu , Usui Yoshiharu , Fukuda Yutaka , Chikira Makoto
Published: June 2006

A series of cationic salen-type Schiff base complexes of copper(II), the general formula of which is [Cu{R3N+–CH2–C6H3(O−)–CH=N–}2X]Br2 (R: CH3, C2H5, C3H7, C4H9; X: C2H4, C3H6, C6H10, C6H4, C10H6), was newly prepared, and the molecular structure of complex 1 (R = CH3, X = C2H4) was determined by an X-ray crystal structure analysis. The binding mode and binding constants (Kb) of all the complexes with calf thymus DNA were investigated at an ionic strength of I = 0.05(NaCl + HEPES buffer, pH = 7.2) using induced CD and the UV-vis spectra. Those complexes with aliphatic X group selectively bound to the groove of DNA, and the Kb’s were in the range of 102—103 mol dm−3 (site size base pairs n = 7.2—7.4). However, those with aromatic X group selectivity intercalated to the base pairs, and the Kb’s were in the range of 104—105mol dm−3 (n = 2.8—4.0). These binding modes were confirmed based on the salt dependence of Kb’s. In addition, 1 and 10 (R = CH3, X = C6H4) were found to exhibit AT-sequence affinity from the induced CD spectra and Kb’s for poly(dA-dT)–poly(dA-dT), poly(dG-dC)–poly(dG-dC), and poly(dA-dC)–poly(dT-dG).