bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of molecular composition on the oxidative behaviour of group I base oils in the presence of an antioxidant additive
Authors: Adhvary A. , Erhan Sevim Z. , Singh I. D.
Published: July 2006

The response of base oil hydrocarbons to additive molecules is fundamental to any lubricant formulation. To have this understanding it is important to have complete knowledge of the base oil hydrocarbon composition. The work reported here is a study of a series of API Group I base oils showing the effect of various structural parameters during oxidation with an antioxidant additive (zinc dialkyldithiophosphate, ZDDP). To understand this complex base oil‐additive interaction pattern, a combination of chromatographic and spectroscopic methods has been adopted. The results show that certain NMR‐derived base oil structural parameters can be used as an index of the additive response in conjunction with column chromatographic and FTIR absorption data. It is also observed that saturated molecules, i.e., iso‐ and normal paraffins and naphthenes, behave differently towards an antioxidant additive, and the total additive response is the result of all the interactions in the system.
Calculation of oil‐film thickness in journal bearings running at varying rotational speeds
Authors: Kozma Mihäaly
Published: July 2006

There are many methods of calculating the properties of lubricated hydrodynamic sliding bearings running at variable loads, but, in some cases, sliding bearings of heavy‐duty machines run under constant load and at variable speeds; this can lead to reduced film thickness in the bearing and boundary lubrication. The minimum oilfilm thickness in such a bearing needs to be calculated so that the proper lubricant viscosity can be selected to reduce solid‐solid contact during machine operation. In this study, a method is presented for calculating the film thickness of sliding bearings operating with alternating rotational directions. The results of the calculations show that the squeeze effect can develop enough load‐carrying capacity to prevent solid‐solid contact between the rubbing surfaces during operation, provided the change of direction of rotation is quick enough.
The influence of surface material and topography on the wall effect of grease
Authors: Czarny Ryszard
Published: July 2006

The phenomenon of grease slip in the boundary layer of a lubricating pipe or a journal bearing is discussed here. A correlation between this phenomenon and the grease structure has been found. Based upon earlier work, it has been shown that a generalised Casson rheological model as well as a proposed yield stress distribution in the lubricant wall layer are useful for an analytical description of the phenomenon. A Couette rheometer was used for testing. As a result of the investigations it is shown that the wall material significantly affects the yield stress distribution in the boundary layer. Essential differences in the stress values are found, especially for plastics and metals.
Temperature‐dependent effects in base oils: Carbon‐13 NMR spin‐lattice relaxation time and viscometry studies
Authors: Kapur G. S. , Sarpal A. S. , Bhatnagar A. K.
Published: July 2006

Carbon‐13 NMR spin‐lattice relaxation time (T1) data have been used to study the molecular dynamic aspects of base oils with different physical properties. Relaxation time measurements have been carried out on a few model compounds and a number of mineral base oils at various temperatures (273–373 K). Effective correlation time (°C) and rotational mobility data obtained for the model compounds and base oils have provided evidence of relationships between molecular flexibility and the temperature dependence of viscosity. It is possible to determine the average carbon alkyl chain lengths and the molecular weights of the base oils from the ratio of the T1 values of Cβ and Cint carbons and the optimised value of the microviscosity factor (fr), respectively. A qualitative correlation between Arrhenius energies (Ea) for microscopic motion and macroscopic bulk properties such as viscosity and viscosity‐temperature characteristics has been observed. Base fluids having better viscosity‐temperature characteristics were also associated with lower values of Ea for micro‐ as well as macroscopic processes.
The antiwear synergism between an organotin compound and a ZnDDP
Authors: Junbing Yao
Published: July 2006

A four‐ball tester was used to evaluate the antiwear performance of an organotin compound, stannic stearate, plus a zinc dialkyldithiophospate (ZnDDP). The results indicate that stannic stearate combined with ZnDDP exhibits excellent antiwear properties in a paraffin‐based oil. The tin compound could also improve the antiwear performance of two commercial engine oils, SH/CD 15W‐50 and SE 15W‐40, which resulted in a reduction of the oil temperature and less oxidation of the oils.
Formation and frictional properties of boundary lubricating and surface‐modified layers at elevated temperatures
Authors: Konchits V. V. , Korotkevich S. V. , Kim C. K.
Published: July 2006

The influence of heating on the properties of lubricating layers formed on steel by inactive and chemically active lubricant components has been studied by electrical probe methods. Model experiments combining X‐ray photoelectron spectroscopy analysis and measurements of friction and electrical characteristics in static and dynamic point contact have shown the approach to be promising in separate studies of the properties of the physically adsorbed layer (A‐layer) and chemisorbed layer (D‐layer) of deposits.

It has been confirmed that D‐layers can be formed on metal surfaces at moderate temperatures (T ∼ 200°C) by both active additives and inactive components of mineral oil. Zinc dialkyldithiophosphate additives provide higher load‐bearing capacity of the A‐layer compared to pure mineral oil and can form D‐layers on steel at relatively low temperatures (of about 100°C). Lubricating layers with different physicomechanical and frictional properties can be formed depending on the chemical origin of the lubricating medium and the temperature regime.
The effects of surface irregularities on the performance characteristics of flexible finite journal bearings lubricated with couple stress fluids
Authors: Elsharkawy Abdallah A. , Guedouar Lotfi H.
Published: July 2006

A numerical solution for the elastohydrodynamic lubrication of finite journal bearings is presented. Couple stress effects resulting from blending the lubricant with various additives are considered. Elrod's cavitation algorithm, which automatically predicts film rupture and reformation in the bearings, is implemented in the solution scheme. A simple elastic model is used to describe the elastic deformation of the bearing liner. Furthermore, the effects of surface waviness on the performance of the bearing are incorporated into the analysis. A comprehensive study illustrates the effects of couple stress, liner flexibility, and surface waviness on the steady‐state performance of finite‐width journal bearings. The results show that these effects should be considered at higher values of the eccentricity ratio.
Temperature, flow, and eccentricity measurements in a journal bearing with a single axial groove at 90° to the load line
Authors: Costa L. , Miranda A. S. , Claro J. C. P. , Fillon M.
Published: July 2006

Parametric experiments were conducted to analyse the influence of some supply conditions on the performance of a steadily loaded journal bearing. The temperature distribution on the internal surface, the flow rate, and the bearing eccentricity were measured for different sets of operating conditions, under variable supply conditions. Quantitative information was provided which showed the effect of both shaft speed and applied load on maximum bush temperature and flow rate. It was observed that flow rate was moderately affected by load and significantly affected by rotational speed, oil supply temperature, and supply pressure. The maximum bush temperature was moderately affected by supply pressure and load, and significantly affected by shaft speed. For low applied loads, the attitude angle was markedly affected by supply pressure. The experimental results also showed that for a small groove length there was a variation in bush temperature in the axial direction in the groove region.
A theoretical study of two‐dimensional grease flow in regions with discontinuities
Authors: Radulescu Alexandru V. , Bonneau Dominique , Hajjam Mohammed
Published: July 2006

This paper presents a theoretical analysis of two‐dimensional grease flow through an asymmetric discontinuity. The behaviour of the fluid is described using Navier—Stokes equations, numerically solved by the finite‐element method. The FLFI program was used for this purpose. For this type of discontinuity, the velocity profile in the lubricant film, the shape and the dimensions of the stagnant core, the flow capacity, and the pressure distribution have been obtained. The results are useful in the design of bearings, if one considers the discontinuities in the carrying region as orifices, canals, or pockets for lubrication.
Tribological properties of P‐ and N‐containing organic compounds as potential extreme‐pressure and antiwear additives
Authors: Xia Yanqiu , Liu Weimin , Xue Qunji
Published: July 2006

An amine salt of an alkoxylphosphate (a P‐ and N‐containing organic compound, PN) was synthesised. Its extreme‐pressure, antiwear, and friction‐reducing properties were evaluated as an additive in liquid paraffin and a mineral oil. Tests were performed on a four‐ball friction and wear tester with an AISI 52100 steel ball self‐mated pair and the results were compared with those of sulphurised olefin (SO), zinc di‐n‐butyldithio‐phosphate (ZDDP), and dibutylphosphite (DBP). The morphologies of the worn steel surfaces were observed using a scanning electron microscope, while the binding energies of some typical elements on the worn surfaces were determined using X‐ray photoelectron spectroscopy. The additives were found to increase the load‐carrying capacity and to reduce wear and friction coefficient considerably. PN as an additive exhibits better load‐carrying, antiwear, and friction‐reducing properties than SO, ZDDP, and DBP under the same test conditions.
Composition—property correlations in some lubricating oil base stocks
Authors: Khan H. U. , Anwar M. , Nautiyal S. P. , Agrawal K. M.
Published: July 2006

The dependence of properties on the composition of lubricating oil base stocks (LOBS) available from Indian refineries has been studied. It has been observed that pour point is greatly influenced by the saturated component of the base stocks, whereas viscosity and viscosity index are greatly influenced by the aromatic content. The effect of various components on the viscosity/shear stress versus temperature behaviour of LOBS samples has also been investigated.
An investigation into the molecular orientation of sheared liquid crystalline boundary films
Authors: Nakano Ken
Published: July 2006

The molecular orientation of a nematic liquid crystal (4‐pentyl‐4′‐cyanobiphenyl, 5CB) in a shear flow between parallel plates was examined using infrared absorption spectroscopy; surface anchoring, film thickness, sliding velocity, and voltage between the parallel plates were independently investigated. Infrared absorbance of the C‐N stretch vibration was measured at the point where the direction of the vibration coincided with the long axis of each 5CB molecule. The molecular orientation depended on the product of the sliding velocity U and the film thickness D, i. e., UD. The effects of surface anchoring appeared to be stronger for lower UD. Calculated results for absorbance, based on a continuum theory, agreed well with experimental ones. The effective viscosity under the same conditions was also calculated, and was increased by a low voltage for lower UD with parallel orientation surfaces. This indicated the possibility of active control of the friction coefficient. With perpendicular orientation surfaces, even without any voltage, the effective viscosity increased with a decrease of UD, which indicated the possibility of a ‘smart lubricant’ the viscosity of which could be adequately controlled by varying the operating parameters of the mating surfaces.
The behaviour of friction modifiers under boundary and mixed EHD conditions
Authors: Castle R. C. , Bovington C. H.
Published: July 2006

The behaviour of a range of model and commercial friction modifiers (FMs) has been evaluated under elastohydrodynamic (EHD) and boundary lubrication conditions. Using a series of long‐chain carboxylic acids, it has been shown that measured boundary friction coefficients (BFCs) decrease with increasing chain length, unsaturation level, temperature, and concentration. Base oil polarity was found to have no effect under these conditions. Commercial oleate esters in synthetic base fluids gave lower BFCs than nitrogen‐containing compounds under the same conditions. This difference was observed over a range of concentrations and temperatures. The friction performance of formulated oils under mixed and full‐film EHD conditions was found to be dependent on FM, base oil, and detergent type. Under boundary conditions, friction was found to vary with FM type, but the effect of changing the base oil and the detergent system was negligible.
An indirect electric field effect on the friction of boundary‐lubricated contacts
Authors: Jiang H. , Wong P. L. , Meng Y. , Wen S.
Published: July 2006

To achieve significant friction variations by means of an externally applied voltage, it is found to be more effective to impose an electric field on the area surrounding a tribopair rather than directly through the contact. Using a new applied electric field setup, the friction behaviour of ceramic‐metal tribopairs, lubricated with an aqueous emulsion, is investigated. The potential affects the surface characteristics during the instant that the surface is out of rubbing contact. Consequently, the nominal frictional behaviour differs from that with no potential effect. The unexcited, excited, and post‐excited friction results for six different ceramic‐metal couples using a pin‐on‐disc tester are presented, and their characteristics are summarised.
Oscillations induced in EHD film thickness by a step in entrainment speed
Authors: Glovnea R. P. , Spikes H. A.
Published: July 2006

Transient elastohydrodynamic (EHD) lubrication conditions occur in the contacts of many machine elements, such as gears, cams, and reciprocating devices, as a result of their working cycles. These conditions also occur in rolling‐element bearings at the onset or cessation of motion. The aspect of film thickness in elastohydrodynamically lubricated contacts subjected to a very rapid change in entrainment speed has not received much attention from researchers, probably because it is seen as less problematic than a sudden fall of the entrainment speed, which theoretically can lead to film failure. For a sudden stop, however, it has been shown previously that the lubricant forms an entrapment, which is able to protect the contact in many cases when the motion resumes. In this paper, EHD film behaviour under sudden acceleration is investigated; the study covers three cases ‐ starting from zero film, starting from an entrapped film, and starting from a continuous, steady film.
Effect of palm oil methyl ester and its emulsions on lubricant degradation and engine component wear
Authors: Kalam M. A. , Masjuki H. H.
Published: July 2006

This paper presents the results of experimental work carried out to evaluate the effect of palm oil methyl ester also known as palm oil diesel (POD) and its emulsions, as alternative fuels, on unmodified indirect‐injection diesel engine wear and lubricant oil deterioration compared with ordinary diesel (OD). A constant 2500 rpm engine setting at half throttle was maintained throughout the wear debris and lubricant oil analysis period for 20 h for each fuel system. Samples of lubricant oil were collected through a one‐way valve connected to the crankcase sump at intervals of 4 h. The first sample was collected immediately after the engine had warmed up. The same lubricating oil, a conventional SAE 30, was used for all experiments. A multi‐element oil analyser was used to measure metal wear debris and lubricating oil additive depletion for the used lubricating oil. An ISL automatic houillon viscometer (ASTM D 445) and potentiometric titration (ASTM D 2896) were used to measure the viscosity and total base number, respectively.

The lubricant oil analysis results for POD, OD, and their emulsions containing 10% water by volume were compared. Very promising results were obtained. The accumulation of metal wear debris in crankcase oil samples was lower with POD and its emulsion compared with the OD fuel. The addition of 10% water (by volume) to POD showed a promising tendency for wear resistance.
Linear sulphonate detergents as pour point depressants
Authors: Li S. , Blackmon J. , Demange A. , Jao T.‐C.
Published: July 2006

Oil‐soluble metallic sulphonate detergents have been extensively used in automobile lubricants to keep engines clean and to extend their useful life. Calcium alkylbenzene sulphonate is widely used in the lubricant industry as a detergent. However, the authors have discovered that, uniquely, linear sulphonate detergents can play another role in lubricants, namely to depress the pour point of mineral oils. The authors have studied the relationship between the molecular structures of sulphonate detergents and pour point depression, and it has been found that, in order for a sulphonate detergent to be a pour point depressant (PPD), it must have a linear hydrocarbon tail. Other factors, such as the metal type, e.g., Ca or Mg, and the degree of overbasing, are not critical for pour point depression activity. A model is proposed to explain why sulphonate detergents with linear hydrocarbon tails can function as pour point depressants.
Investigation into the effectiveness of detergent—dispersant agents and additive packages
Authors: Vipper A. B. , Zadko I. I. , Ermolaev M. V. , Maslov L. L.
Published: July 2006

Comparative tests of more than 15 detergents (calcium sulphonates and phenates) of different basicity and dispersants (succinimides) were carried out using laboratory test methods. The effectiveness of the detergent and dispersant action of the test additives, their thermal, hydrolytic, and colloidal stability, and their influence on the antioxidant properties of engine oils were evaluated. The results obtained showed that it is possible to differentiate additives of various types, and demonstrated the relative efficiency of additives belonging to the same class. The effectiveness of certain additive packages was evaluated using a new approach: in addition to the laboratory methods, the retention of the dispersing ability of additive packages was evaluated in previously oxidised additivated engine oils. This allowed the efficiency of engine oils of different categories to be characterised.
Effect of MoDDP on the antioxidative properties of ZnDDP in mineral oil
Authors: Du D. C. , Kim S. S. , Suh C. M. , Chun J. S. , Moon W. S. , Kwon W. S.
Published: July 2006

The antioxidative actions of zinc and molybdenum dithiophosphates and their mixtures were evaluated using the RBOT (rotary bomb oxidation test) and the ISOT (Indiana stirring oxidation test). The results showed a synergistic effect on the antioxidative action with certain mixtures of the additives in mineral oil. FTIR spectra indicated the presence of some oxidation products and the degradation of the additives in the additive‐containing oils.
EP/AW performance evaluation of some zinc alkyl/dialkyl/alkylaryl‐dithiocarbamates in four‐ball tests
Authors: Verma V. K. , Singh R. , Srivastava Vandana , Singh P. K.
Published: July 2006

Tribochemistry, the chemistry of interacting surfaces under the influence of a lubricant, helps in the appropriate selection of suitable lubricant additives for specific uses. Modern lubricants are usually formulated from a range of petroleum base oils or synthetic fluids incorporating a variety of chemical additives for performance enhancement. Extreme‐pressure (EP) and anti‐wear (AW) additives are used extensively in lubricants for hypoid gears and metal cutting and forming operations to reduce wear, modify friction, and prevent scuffing of moving metallic parts.

The present paper includes the synthesis and the evaluation of the tribological properties of 0.5% (w/v) solutions of some zinc bis‐(alkyl/dialkyl/alkylaryldithiocarbamates) in paraffin oil using 12.7 mm diameter steel bearing ball specimens in four‐ball tests. All the synthesised zinc dithiocarbamate additives in general, and zinc bis‐(morpholinodithio‐carbamate) (A4) in particular, exhibited good AW, EP, and friction‐reducing properties. Additive A4 especially gave low values of wear‐scar diameter and coefficient of friction at higher loads and higher values of load wear index and flash temperature parameter during EP tests (ASTM D 2783) and afforded lower values of wear‐scar diameter in a one‐hour wear test (ASTM D 2266–67).

The surface topography of the wear‐scar matrix of the used ball specimens was investigated by scanning electron microscopy.
Surface‐capped molybdenum sulphide nanoparticles — a novel type of lubricant additive
Authors: Bakunin V. N. , Suslov A. Y. , Kuz'mina G. N. , Vedeneeva L. M. , Parenago O. P. , Migdal C. A. , Stott P. E.
Published: July 2006

Compounds containing molybdenum sulphide are widely employed as friction‐modifying and antioxidant additives in lubricants. However, the synthesis of these types of compound can often be complex and expensive. Tribologically active lubricant additives can be prepared as inorganic nanosized surface‐capped particles, the surfaces being coated with compounds that interact and/or react with the inorganic material.

This paper reports on the synthesis and characterisation of surface‐capped molybdenum trisulphide nanoparticles. The synthesis was carried out using a reverse micellar system. The size and composition of the nanoparticles were determined, and their tribological properties as lubricant additives were compared with those of commercially available additives. It was found that the surface‐capped molybdenum sulphide nanoparticles show good friction‐modifying and anti‐scuffing behaviour.
A simple formula for the dielectric relaxation time—temperature—pressure relationship of lubricating oils and its application to viscosity prediction
Authors: Suzuki Akihito , Masuko Masabumi
Published: July 2006

The dielectric constant and the loss factor for several lubricating oils were both measured within the frequency range of 100 Hz–1.5 MHz. Measurements were made at atmospheric pressure with varying temperature, and at fixed temperature with varying pressure. The temperature dependence of the dielectric relaxation time could be expressed by the Vogel—Fulcher—Tammann (VFT) equation. In order to express the dielectric relaxation time as a function of temperature and pressure, a pressure‐dependent term was introduced into the characteristic temperature of the VFT equation. The experimental relaxation time could then be represented by a simple formula. Moreover, high‐pressure viscosity was calculated from the dielectric relaxation data by introducing the pressure dependence of the bulk modulus. The predicted results showed fairly good agreement with the viscosity data.
Molecular dynamics study of the interfacial slip phenomenon in ultrathin lubricating films
Authors: Wang H. , Hu Y. Z. , Guo Y.
Published: July 2006

The tribological performance of thin films of a liquid alkane has been studied through a molecular dynamics simulation with particular attention being paid to the phenomenon of interfacial slip. The model system for the simulation consists of two solid walls, with the lubricant molecules confined between them. Molecules of n‐decane (C10H22) were chosen to represent the lubricant molecules. The results of the simulation show: the average velocity of decane molecules in a Couette flow exhibits largely a linear distribution, but with a slip velocity at the solid‐liquid interface; when the simulations are performed at different temperatures, the slip ratios were found to vary with temperature; slip behaviour depends strongly on the solid‐fluid interaction; and slip ratios increase with decreasing film thickness, suggesting that slip in the thin films is a confinement‐related phenomenon.
Temperature—friction characteristics of cylinder lubrication in large, slow, cross‐head marine diesel engines under boundary lubrication conditions
Authors: Stolarski T. A. , Zhou Q. , Smart M. , Green D. , Allen R. W.
Published: July 2006

In large, slow, cross‐head marine diesel engines research has increasingly shown that the lubrication regime between piston rings and cylinder liner at top dead centre is of the boundary lubrication type due to the high gas pressure, low sliding speed, and high temperature. This means that the tribological properties of piston ring, cylinder liner, and cylinder lubricant in these types of engine under boundary lubrication conditions should be considered simultaneously when friction and wear between the piston ring and cylinder liner are studied. Until now there has been no standard method to evaluate boundary lubrication performance. There are a few traditional methods used in lubricant research, but their results are not correlated with service conditions. It is important to find a suitable method to evaluate the boundary lubrication performance of lubricants at the laboratory testing stage or before the engine testing stage. The important parameters, such as sliding speed, normal load, materials of the contacting pairs, and lubricant, need all to be controlled.

In this paper a systematic experimental procedure, the ‘five times heating and cooling test’, is introduced to assess lubricant properties under boundary lubrication conditions. Most of the parameters mentioned above are controlled. The model contact, of pin‐on‐plate form, is made from the actual piston and liner materials used in a large‐bore, slow, cross‐head marine diesel engine. The temperature characteristics of different blends of lubricants are investigated under boundary lubrication conditions using a pin‐on‐plate reciprocating test rig. These blends of lubricants have the same additives but different base fluids; they nevertheless fulfil the physical and chemical requirements of a real marine diesel engine. The test temperature range is from room temperature to the working temperature of the top piston ring.

The experiments show that there are different temperature—friction characteristics for lubricants with different bases and the same additive package and there are also different temperature—friction characteristics during heating up and cooling down for each blend. Single‐base lubricants have more promising temperature—friction characteristics than those of a blend of a high‐viscosity base and a low‐viscosity base at high temperature.
Engine oil compositions based on PIB—succinimide combinations
Authors: Bartha L. , Kis G. , Hancsók J. , Baladincz J.
Published: July 2006

Additive packages for engine oils were prepared using PIB—succinimide combinations with different properties. PIB—succinimide‐type dispersants of various average molecular weights and dominant side effects were selected for preparing multifunctional additive combinations. A high‐molecular‐weight PIB—polysuccinimide type as viscosity‐index improver, a PIB—polysuccinimide with strong basic character as a highly effective sludge dispersant, molybdenum‐containing poly‐alkylene—polysuccinic anhydride derivatives as dispersants with complementary antifriction efficiency, and some conventional detergent, antioxidant, antiwear, and anticorrosion engine oil additives were used in engine oil compositions of various viscosity grades. The technical and economic advantages of appropriately selected and balanced additive combinations were shown by bench test results of the rheological, detergent—dispersant, and antifriction properties of the test oils.
A comparative study of phenol‐type antioxidants in methyl oleate with quantum calculations and experiments
Authors: Zhang Y. Y. , Wang H. D. , Ren T. H. , Yi M. R.
Published: July 2006

Chemical software (Gaussian 98w) was used to calculate the highest occupied molecular orbital (HOMO) energy level of three phenol‐type antioxidants to evaluate their oxidation resistance performance. The conclusion drawn from the quantum calculations was that the decreasing order of the oxidation resistance effectiveness was 4,4‐methylene‐di(2,6‐di‐t‐butyl‐phenol) (T511)>2,6‐di‐t‐butyl‐4‐methylphenol (BHT)>phenol. Pressure differential scanning calorimetry (PDSC) and the rotary bomb oxidation test were also used to assess the antioxidants in a methyl oleate base oil. According to the experimental results, the oxidation resistance capability of the three antioxidants decreased in the order BHT > T511 > phenol. The results indicated that the quantum calculation method could be used to screen antioxidants with regard to their oxidation resistance effectiveness.
Synthesis of molybdenum polyisobutenyl succinate (MoPIBS) and a study of its tribological characteristics
Authors: Fu S. F. , Tao D. H. , Zhang J. H.
Published: July 2006

In view of the increasing awareness of the need for environmental protection, it is considered important to have more low‐ or non‐phosphorus additives in engine oils. To this end, molybdenum polyisobutenyl succinate (MoPIBS) was synthesised and its structure investigated using spectroscopy. The antiwear and friction‐reducing behaviour of MoPIBS as an oil additive was investigated and compared to that of zinc dialkyldithio‐phosphate (ZnDDP) using a four‐ball tester. The results indicated that MoPIBS in white oil exhibits very good antiwear and friction‐reducing properties, better than those of ZnDDP, but that the load‐carrying capacity is poorer than that of ZnDDP. The worn surfaces were investigated using Auger electron spectroscopy (AES) and X‐ray photoelectron spectroscopy (XPS). It was found that the boundary lubrication film on the worn surfaces was mainly composed of MoO3 and Fe2O3, which contributed to improving the tribological properties of MoPIBS as an additive in white oil.
Study of the tribological performance of a rare earth naphthenate as a lubricant additive
Authors: Liu R. D. , Tao D. H. , Zhang J. H. , Cao W. G. , Fu S. F.
Published: July 2006

The tribological behaviour of a rare earth naphthenate (REN) as a lubricant oil additive in VG26 white oil and the complexes of REN and organo‐sulphur or organo‐phosphate compounds have been evaluated with a four‐ball friction and wear tester. The chemical features and elemental composition of the boundary lubricating film were examined by means of Auger electron spectroscopy (AES) and X‐ray photoelectron spectrometry (XPS). The results show that REN exhibits good antiwear, load‐carrying, and friction‐reducing properties in the base stock. When 2.0% REN is added, the wear‐scar diameter value reduces to 54.7% of that for the base stock alone and the maximum non‐seizure load increases 2.95 times. A synergistic effect is found for the load‐carrying capability of the complex of REN and organo‐sulphur while poor compatibility is exhibited for the complex of REN and organo‐phosphate. The analytical results of AES and XPS indicate that the good performance of REN is attributable to the formation of a boundary lubricating film mainly composed of naphthenic acid, rare earth oxide, and complexes of rare earth metals, which is formed on a rubbed surface when lubricated by oil containing the REN additive.
Recent achievements in the synthesis and application of inorganic nanoparticles as lubricant components
Authors: Bakunin V. N. , Suslov A. Yu. , Kuzmina G. N. , Parenago O. P.
Published: July 2006

Recent advances made in the chemistry and technology of nano‐metric inorganic particles allow the synthesis of various metal oxides, chalcogenides, phosphates, and so on. Surface modification of nanoparticles in some cases allows the formation of stable dispersions in liquid hydrocarbons. The state of the art in the field of inorganic nanoparticle synthesis and their application in tribology are discussed in this paper. Special attention is paid to the synthesis of surface‐capped and bare molybdenum sulphide nanoparticles and to the testing thereof as friction‐modifying additives for liquid lubricants. Differences in the mechanism of action of MoSx nanoparticles and molecular molybdenum complexes (e.g., molybdenum dithiocarbamate) are discussed. Future trends in the use of inorganic nanoparticles as lubricant additives are suggested.
Characterisation and nano‐friction behaviour of molecular deposition films
Authors: Zhang S. W. , Wang Q. B. , Gao M. L.
Published: July 2006

The structure and the nano‐friction behaviour of a new kind of ultrathin film, a molecular deposition (MD) film, on an Au substrate were studied. The MD film is formed by the electrostatic attraction between opposite charges of cationic and anionic compounds, and a multilayer film can be built through alternating deposition of bipolar cationic and anionic compounds. Monolayer, bilayer, trilayer, and tetralayer MD films on Au substrates were examined. MD films with an alkyl terminal group were also investigated. It was found that while the MD film on an Au substrate reduced the friction, its nano‐friction behaviour was unstable because of the active terminal group. However, if the MD film was formed with an alkyl terminal group, its nano‐friction behaviour became stable and its friction decreased markedly. Therefore, this film termination method could contribute to the nano‐tribological application of MD films.
Rheological properties of high‐viscosity‐index mineral base oils for automotive engine lubricants
Authors: Muraki M. , Dong D.
Published: July 2006

Viscosity‐pressure‐temperature relations for paraffinic mineral base oils at pressures up to 0.7 GPa and temperatures between 30 and 90°C were determined using a falling‐ball‐type viscometer. The oils used were solvent refined oils, hydrocracked oils, and an oil produced by a wax isomerisation process. The viscosity at pressures higher than those possible with the viscometer was then derived by applying a simplified solution to the traction curves determined using an elastohydrodynamic disc‐on‐ball tester. When the measured viscosity and the calculated viscosity were plotted against pressure, for the oils with a viscosity index higher than 120 the viscosity derived from traction measurements followed the curve extrapolated to the high‐pressure region using either the Yasutomi or Roelands equations (the parameters for which were obtained using the viscometer). However, the calculated viscosity for the lower‐viscosity‐index oils deviated upwards from the extrapolated curve.
The mechanical generation of emulsions
Authors: Dalmazzone C.
Published: July 2006

Emulsions are complex systems frequently encountered in our daily lives and in most industrial sectors, including the oil industry. An understanding of the mechanisms of emulsion formation is essential both to create them and to treat them. The present work describes the main phenomena that come into play in emulsifying. The break‐up of droplets in either laminar or turbulent flow is discussed, and certain correlations, from which the diameter of the droplets formed can be predicted, are given. The role of surfactants is also examined, as are the typical time scales of the various processes involved.
Cover Picture: Macromol. Rapid Commun. 15/2006
Authors: Benkoski Jason J. , Hu Hua , Karim Alamgir
Published: July 2006

Cover: Hierarchical assemblies can be built up from nanoscale building blocks through manipulation of the oil/water interface. By choosing a monomer as the oil phase, one can preserve a rich variety of structures by UV flash curing. We show here a surface created by iteratively crosslinking several generations of particle‐stabilized emulsions. Further details can be found in the article by J. J. Benkoski,* H. Hu, and A. Karim on page 1212.
Friction and nanowear of polystyrene against hydrophobic and hydrophilic substrates
Authors: Ghorbal Achraf , Bistac Sophie , Schmitt Marjorie
Published: July 2006

The ambition of this study is to analyze the role of interfacial interactions in friction and nanowear of polystyrene, by comparing friction against hydrophobic wafers (methyl‐terminated) and hydrophilic wafers (hydroxyl‐terminated) as a function of sliding velocity and normal force. Friction experiments are performed with a translation tribometer and nanowear investigation is achieved by using atomic force microscopy (AFM) analysis of the wafer surfaces after friction. Experimental results show that the friction coefficients measured on hydrophilic surfaces are always larger than those obtained with hydrophobic surfaces, indicating a relationship between friction and interfacial interactions. Elsewhere, AFM analysis shows that polystyrene transfer appears for a higher normal force in the case of hydrophobic substrates compared to hydrophilic one. However, the corresponding tangential (or friction) force necessary to detect transfer is quite similar for both types of substrates, indicating that the initial wear of polystyrene occurs for a similar threshold interfacial shear. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2449–2454, 2006
Should we use criteria or eyeballing to reject post‐interruption tracings?
Authors: Veugelers Rebekka , Penning Corine , Grootscholten Stefan P.J. , Merkus Peter J.F.M. , Arets Hubertus G.M. , Rieken Rob , Brussee Jessica E. , Jilderda‐Janssen Mayke , Tibboel Dick , Evenhuis Heleen M.
Published: July 2006

During the analysis of interrupter resistance (Rint)‐measurements, most authors reject post‐interruption tracings based on the shape of the pressure‐time and flow‐time curves. However, objective criteria for rejection are lacking. We aimed to formulate explicit rejection criteria that correspond to eyeballing the curve pattern (daily practice), in order to simplify the analysis. Inter‐observer agreement within and between both methods was studied. Results obtained with the developed rejection criteria were compared to those of current practice (eyeballing) using 54 measurements (807 interruptions) of children with severe neurological impairment. Inter‐observer agreement on rejection was similar using the criteria or eyeballing (85.6% vs. 82.8%). Using the criteria, more individual interruptions were rejected (43.4% vs. 29.8% using eyeballing), while discarding total measurements (<5 remaining interruptions) was similar (9.2% vs. 7.4% using eyeballing). Results using only the criteria for pressure‐time curves were comparable to eyeballing. Outcome values were comparable between any of the used rejection methods and not rejecting at all. In this first detailed study on rejection of post‐interruption tracings, explicit rejection criteria were developed. None of the rejection methods influenced the outcome value relevantly. However, rejection criteria can contribute to the standardization of the Rint technique and simplify decision‐making in daily practice. Pediatr Pulmonol. 2006, 41:937–946. © 2006 Wiley‐Liss, Inc.
Association of transient tachypnea of the newborn and childhood asthma
Authors: Birnkrant David J. , Picone Charlene , Markowitz Wendy , El Khwad Mohammed , Shen Wen Hsin , Tafari Nebiat
Published: July 2006

Objective:

To determine if transient tachypnea of the newborn (TTN) is independently associated with childhood asthma.

Methods:

The sampling frame was a computerized database on 18,379 term infants born between January 1, 1996 and December 31, 2000 in an urban tertiary care hospital. This was a case‐control study nested in a cohort of all term newborns who were subsequently diagnosed with asthma (n = 2137) and a similar number of birthday‐matched controls. The International Classification of Diseases, Ninth Revision code was used to identify the infants with TTN and those who developed asthma. Logistic regression was used to adjust for potentially confounding variables. Stratified multivariate analysis was undertaken on subgroups to assess possible effect modification by factors known to influence the incidence of asthma: race, gender, domicile, and maternal asthma.

Results:

After adjustment for potential confounding, TTN was significantly associated with the diagnosis of childhood asthma (adjusted OR = 1.50, 95% CI: 1.13–1.99; P = 0.0052). The association of TTN and asthma was statistically strongest among male infants, especially among males whose mothers lived at an urban address, males of non‐white race, and males whose mothers did not have asthma. The pattern of association of TTN and asthma was similar for infants diagnosed with asthma once compared with those diagnosed with asthma recurrently.

Conclusion:

TTN was independently and significantly associated with the subsequent diagnosis of childhood asthma, especially among male infants. TTN may be a marker of deficient pulmonary function reflecting inherited susceptibility to asthma. Pediatr Pulmonol. 2006, 41:978–984. © 2006 Wiley‐Liss, Inc.
Validation of a hand‐held exhaled nitric oxide analyzer for use in children
Authors: McGill Claire , Malik Gulshan , Turner Stephen W.
Published: July 2006

Measurements of exhaled nitric oxide (FENO) may be useful in the diagnosis and management of asthma in children. A new hand‐held device (MINO®, Aerocrine) for measuring FENO has been marketed but has not been validated in a pediatric population. The objective is to validate the MINO® against the NIOX® analyzer. This was a randomized cross‐over study where FENO was measured in a single assessment using the MINO® and NIOX®. Children were recruited from a respiratory clinic and had six attempts to provide a FENO measurement with each analyzer. Fifty‐five children were enrolled, 33 boys, median age 9 years. A mean FENO value was obtained in 39 children with MINO® and 44 with NIOX®. Paired mean FENO values were obtained in 34 children and the values were higher for the NIOX® (mean difference 3.9 ppb limits of agreement −1.1, 8.9). The differences between analyzers became greater at higher FENO values. The first FENO value using the MINO® was 24 ppb and the mean of all FENO values using the MINO® was 27 ppb (difference not significant). Exhaled NO values were comparable between the two analyzers although there was greater consistency at lower values. The findings of the study do not contradict the manufacturer's recommendation that only one FENO value is required with the MINO®, however, we suggest that the mean of at least two values should be reported in children. Pediatr Pulmonol. 2006, 41:1053–1057. © 2006 Wiley‐Liss, Inc.
Coupling of the electronic band structure with Ag phonon modes in Y123 and Y124 systems
Authors: Khosroabadi H. , Mossalla B. , Akhavan M.
Published: July 2006

Ab initio frozen‐phonon calculations have been performed for k = 0 Ag Raman modes of two superconducting systems Y123 and Y124. We have used the local density approximation pseudopotential method in our calculations by VASP code. Results have been compared with other computational and experimental data for similar systems. Then we present changes of electronic band structure with the change of ionic positions in each Ag mode for both systems. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ultrafast photoresponse of superconductor/ferromagnet Nb/NiCu heterostructures
Authors: Pepe Giovanni Piero , Amanti Maria , De Lisio Corrado , Latempa Rossella , Marrocco Nicola , Parlato Loredana , Peluso Giuseppe , Barone Antonio , Sobolewski Roman , Taneda Takahiro
Published: July 2006

We report on femtosecond optical pump‐probe studies of proximized ferromagnet/superconductor (F/S) hybrids, consisting of Ni0.5Cu0.5 layers deposited on top of Nb films. The weak ferromagnetic nature of the completely proximised Ni0.5Cu0.5 film makes possible to observe the dynamics of the nonequilibrium superconductivity through the near‐surface optical reflectivity change measurements. The time‐resolved photoresponse transient of the NiCu(21 nm)/Nb bilayer in the superconducting state shows strongly suppressed slow bolometric component. The fast relaxation time is also discussed accordingly to current theories on S/F heterostructures. The proposed S/F nanobilayers represent a new, artificially designed superconductor with the features (sub‐picosecond photoresponse with suppressed bolometric component) very desirable for superconducting photodetectors and photon counters. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Fluctuation conductivity analysis on the Bi‐based superconductors processed under same conditions
Authors: Ben Azzouz F. , Zouaoui M. , Annabi M. , Ben Salem M.
Published: July 2006

We report electrical conductivity fluctuation measurements on different Bismuth‐based granular samples synthesized under same processing conditions.Using the fluctuation conductivity Δσ as a function of the reduced temperature ϵ in the range –7 < ln ϵ < 1, we identified Gaussian and critical fluctuation conductivity in (Bi,Pb)‐2223 and Bi‐2212 samples. Within the mean field region, samples show predominately two dimensional (2D) behaviour with exponent λ = –1. Closer to critical temperature T C, we have observed a crossover of λ from –2/3 to –1/3 in the critical region. The obtained exponents are consistent with 3D‐XY model predictions. The regime with the critical exponent –2/3 is dominate in the case of (Bi,Pb)‐2223 sample. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interplay of electron–phonon and Coulomb interaction in semiconductor quantum dots
Authors: Förstner J. , Knorr A. , Moloney J. V.
Published: July 2006

The cover picture of this issue of physica status solidi (c) has been taken from the article [1]. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of hybrid density functional, Hartree–Fock, and GW calculations on NiO
Authors: Patterson C. H.
Published: July 2006

The electronic band structure of NiO in the ferromagnetic state is calculated using the B3LYP hybrid density functional, the Hartree–Fock (HF) method, and the GW approximation (GWA) with dielectric functions constructed using either B3LYP or HF wave functions and energy eigenvalues. The band structure from the GWA calculation based on B3LYP wave functions is quite similar to the parent B3LYP band structure; the main differences are in valence bandwidth and in the upward shift of the empty minority spin Ni 3d bands relative to the same bands in the B3LYP calculation. The band structure from the GWA calculation based on HF wave functions differs in that there are large upward shifts in valence band positions in the GWA calculation relative to the HF calculation, which result from screening of the bare exchange term in the Fock operator. Matrix elements of the HF exchange operator are obtained using wave functions from self‐consistent HF or B3LYP calculations. Magnitudes of these matrix elements for several states at the Γ point of the Brillouin zone are compared, and it is found that the only major difference occurs in the empty minority spin bands derived from Ni 3d states of e symmetry. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006