bluuebunny/crossref_metadata_2025 huggingface dataset:
On the hydrodynamic lubrication analysis of piston rings
Authors: Esfahanian Mohsen , Hamrock Bernard J. , Elsharkawy Abdaliah A.
Published: July 2006

A theoretical hydrodynamic lubrication analysis of piston rings is presented. A numerical scheme is developed to solve the Reynolds' equation and the load equilibrium equation simultaneously. The hydrodynamic effects are examined in detail by considering solutions to the problem of lubricating the top compression ring in a two‐stroke diesel engine. The minimum film thickness is computed throughout a complete cycle. The pressure profiles and film shapes at different crankshaft angles are presented. In the method proposed, the camtation boundary condition within the lubricated conjunction is included in the analysis.
A study of the tribological behaviour and mechanism of actoin of bismuth dialkyldithiophosphate
Authors: Chen L. , Dong J. , Chen G.
Published: July 2006

This paper discusses the preparation of bismuth dialkyldithio‐phosphate as an oil‐soluble antiwear and extreme pressure additive for lubricants. Its tribological performance when added to an ISO VG32 mineral oil was evaluated on a four‐ball tester and a ring‐on‐block machine. The relationships between its performance and the concentrations are also given, and are compared with those of zinc dialkyldithiophosphate (ZDDP). The results show that the compound not only possesses good antiwear and friction‐reducing abilities, but also has a higher load‐carrying capacity than ZDDP. The mechanism of action of the additive was studied by surface analysis. A scanning Auger microprobe revealed a high bismuth content in the rubbing surface layers, and X‐ray photoelectron spectroscopy detected the formation of various chemical species including organic films, metallic bismuth, bismuth oxide, and bismuth sulphide. The mechanism of action is postulated on the basis of these results.
Substrate surface energy effects on a liquid lubricant film at nanometre scalesubstrate surface energy effects on a liquid lubricant film at nanometre scale
Authors: Jianbin Luo , Shizhu Wen , Xuanyu Sheng , Li Lawrence K. Y.
Published: July 2006

In this paper is discussed the effect of the physical characteristics of substrate surfaces on the lubrication properties of thin films at nanometre scale. Different coatings with different surface energies have been formed on the surface of a steel ball by means of plasma assisted sedimentation (PAS). The ball was put in a pure rolling system in point contact, where the lubricant film is measured by relative optical interference intensity (ROII). Experimental results show that the film thickness is closely related to the substrate surface energy when the film is in the nanometre scale, and that the combined surface roughness in the contact region is closely related to the liquid lubricant film thickness and the contact pressure. The thinner the film and the higher the contact pressure, the smaller will be the combined surface roughness. Lastly, the relationship between critical film thickness and its influencing factors is discussed.
A description of the lubricating action of the tribo‐active components of cutting fluids
Authors: Godlevski V. A. , Volkov A. V. , Latyshev V. N. , Maurin L. N.
Published: July 2006

A multistage mechanism of lubrication layer formation during cutting is described and the necessary conditions for the formation of a lubrication layer are formulated. It is considered that the process of physical adsorption of the tribo‐active components of the cutting fluid in the contact zone between tool and chip during metal cutting is one step in a multistage process which occurs in the interface capillary system. A mathematical model describing simultaneous diffusion and adsorption of tribo‐active components in a single interface capillary is proposed. Some parameters for a model determining the efficiency of the lubricating action of surface‐active additives are also proposed.
An analysis of the mechanisms of grease lubrication in rolling element bearings
Authors: Cann Philippa , Lubrecht A. A.
Published: July 2006

There are over eighteen billion bearings in use in the world, and most are grease lubricated. Grease is chosen for a variety of reasons: it gives low friction, is easily confined, and has a long lubricating life at low cost. In many applications, the grease is expected to lubricate effectively over a wide range of conditions and for extended periods. For such applications, lubricant failure leads to instantaneous and rapidly increasing damage of the components and eventually breakdown. Thus, an improved understanding of the fundamental aspects of grease lubrication has far‐ranging technical and economic implications. Despite the overwhelming importance of this subject, very little is known about the mechanisms of grease lubrication and the relationship between composition, lubrication performance, and life. This paper attempts to summarise current understanding of grease lubrication mechanisms in rolling element bearings and to consolidate the different aspects of this complex topic.
Preparation and tribology of aerogel silica and alumina‐silica as lubricant oil additives
Authors: Dong J. X. , Hu Z. S. , Chen G. X.
Published: July 2006

Aerogel silica and an aerogel mixture of aluminium and silica were prepared using the ethanol supercritical fluid drying technique. Their physical properties were characterised using XRD, transmission electron microscopy, (TEM), and N2 adsorption. The tribological properties of a 500 SN oil containing the aerogel and a dispersing agent were evaluated using a four‐ball machine and a block‐on‐ring tribotester. Results indicated a greater wear resistance and load‐carrying capacity and a lower friction coefficient than for the basic oil. In the oil, the aerogel worked by its deposition on the rubbing surface. Copper stearate was superior to dodecyl alcohol as a dispersing additive, and ultrasonic treatment helped promote the dispersion of the aerogel in oil. There existed an optimum ratio of aluminium isopropyl alcoholate to tetraethanol silicate. The corresponding aerogel mixture gave a maximum value of PE.
Thick‐boundary‐film formation by friction modifier additives
Authors: Anghel V. , Bovington C. , Spikes H. A.
Published: July 2006

The addition of friction modifiers to lubricants has been the subject of study for a number of years. Two main models have emerged, a thick‐film and a thin‐film or monolayer model, but it is uncertain which materials and conditions produce which results. The present work, therefore, looked at whether certain additives form thin or thick films in rolling and/or rolling‐sliding contacts; the practical effect of any thick‐film formation behaviour; and the nature and structure of boundary films formed.

Using ultrathin‐film interferometry, tests were performed on a rig, with two commercial friction modifiers, a copper carboxylate soap, and a dimerised unsaturated carboxylic acid, in hexadecane and in a solvent‐refined mineral oil. The results showed that both additives formed thick films in high‐pressure rolling and sliding contacts at slow speeds. However, the nature of the films is determined by temperature and speed, and under certain conditions they can be destroyed.
Friction and wear behaviour of partially stabilised zirconia in reduced pressure atmospheres containing organic compounds: Potential for process lubrication of ceramics
Authors: Sasaki Shinya
Published: July 2006

Friction and wear tests were used to evaluate a partially stabilised zirconia (PSZ) disc rubbing against a PSZ pin in a high‐vacuum sliding tester. The surrounding atmosphere contained an organic compound vapour (either benzene, acetone, methane or methanol) at a reduced pressure. In order to understand the mechanism of the tribochemical reaction, the sliding conditions, velocity, and load were varied. During the sliding test, the friction coefficient, surface electrostatic voltage, and adsorption behaviour were measured dynamically. After the sliding test, the worn surfaces were analysed with EPMA and TOF‐SIMS to characterise the components and the molecular weight of the reaction products. The formation of sticky reaction products was observed on the sliding surface in benzene and acetone vapours. These products acted as lubricants, reducing the friction coefficients and wear rates. Analysis suggested that such sticky reaction products contained molecules up to 1000 atomic mass units (AMU).
Modern solid lubrication: Recent developments and applications of MoS2
Authors: Savan A. , Pflüger E. , Voumard P. , Schröer A. , Simmonds M.
Published: July 2006

An important and growing field of lubrication lies in the use of solid films, although they are in general more expensive than oils or greases, and require specialist attention both in mechanical design and in coating application techniques. In this paper, the general classification of solid lubricant types is reviewed, along with the reasons for choosing, and methods of depositing, solid lubricants, in particular MoS2. The best‐performing and most flexible technique for making MoS2 films is by physical vapour deposition (PVD), and the variants of that technology are considered. The intrinsically lubricating, lamellar structure of pure MoS2 is described, along with a brief summary of its wear and failure modes. Present applications for lubrication by MoS2 in spacecraft and dry machining are outlined, as are anti‐adhesive uses in extruding and moulding. The current state of the art of modification of MoS2 films consists in the addition of dopants (co‐sputtering), in multilayering as a series of films, each fulfilling a specific task, or in stacking repeating nano‐metre‐scale films. Composite films of MoS2 islands in a hard film matrix are also being developed.
Wear and friction behaviour of CaCO3 nanoparticles used as additives in lubricating oils
Authors: Sunqing Qiu , Junxiu Dong , Guoxu Chen
Published: July 2006

For some years, reports have been published on adding solid lubricant powder to oil to improve the tribological properties of the latter, but the results have not been satisfactory. In this paper, we describe the preparation of CaCO3 nanoparticles in a microemulsion consisting of sodium dodecyl‐sulphate (SDS)/isopentanol/cyclohexane/water, and assessment of the tribological behaviour of CaCO3 nanoparticles as additives for lubricating oils. The CaCO3 nanoparticles were characterised by transmission electron microscopy (TEM), and their tribological performance was tested in a four‐ball machine; the rubbing surface was analysed with X‐ray photoelectron microscopy (XPS). The results indicate that the size of CaCO3 nanoparticles increased with the concentration of aqueous reactant, and that CaCO3 nanoparticles exhibited good load‐carrying capacity, antiwear and friction‐reducing properties. The tribological properties of lubricating oils could be improved significantly by dispersing CaCO3 nanoparticles in 500SN base oil containing dispersants such as polyisobutene‐butanediimide (T154), calcium alkylsulphonate (T101) and methyl‐tricaprylamine chloride (aliquat 336). The improvements in friction and wear were concluded to be due to the formation of a film containing CaCO3 and CaO in the rubbing region, and the presence of nanoparticles, which may act in the same way as ball bearings, to facilitate sliding.
Friction modifiers in engine and gear oils
Authors: Herdan Jean M.
Published: July 2006

Reducing friction is an important target for any lubricant oil formulator. There are several ways, such as utilisation of multi‐grade oils with low viscosity at low temperature, or use of friction modifiers, to reduce friction in automotive engines and transmissions and thus save fuel. A good means to obtain an energy‐saving lubricant is by the addition of a friction‐reducing additive in a high‐range multigrade oil. This paper presents some considerations on the action mechanism of friction modifiers and the results obtained in engine and gear oils with two new nitrogen‐, sulphur‐, and boron‐containing additives.
Tribological evaluation and tribochemistry of some dialkyldithiomalonamides and their Mo‐S complexes as EP additives
Authors: Tripathi A. K. , Singh P. K. , Bhattacharya A. , Singh R. , Verma V. K.
Published: July 2006

The reported use of molybdenum dithiocarbamates and molybdenum dithiophosphates as antiwear and EP additives has led to attempts by the authors to synthesise certain novel Mo‐S complexes, and evaluate their effectiveness.

In the present paper, the synthesis of certain 1,5‐dialkyl‐2,4‐dithiomalonamides and their Mo‐S complexes, namely, bis(1,5‐dialkyl‐2,4‐dithiomalonamido)‐dioxo‐molybdenum (VI), and the tribological evaluation of their 0.5% w/v admixtures in paraffin oil by a four‐ball test are reported, and the results compared with a dioxo‐bis(N,N‐diethyldithiocarbamato)‐molybdenum(VI) reference additive.

The additive, bis(1,5‐diethylhexyl‐2,4‐dithiomalonamido)‐dioxo‐molybdenum(VI), has been found to reduce significantly both coefficient of friction and wear‐scar values, and to give higher load wear index values and flash temperatures, and has been found to be equally effective with alloy steel balls of three different compositions. However, all the Mo‐S complexes afforded smaller wear‐scar diameters in a one‐hour wear test.

The wear spots on the used steel ball specimens were subjected to SEM and AES surface analysis for understanding the additive‐metal interaction tribochemistry.
Advances in solid lubrication with MoS2 multilayered coatings
Authors: Voumard P. , Savan A. , Pflüger E.
Published: July 2006

The general classification of solid lubricant types is reviewed, along with the reasons for choosing and methods of depositing solid lubricants, in particular MoS2. The best‐performing and most flexible technique for making MoS2 films is by physical vapour deposition (PVD), and the variants of that technology are considered. The intrinsically‐lubricating, lamellar structure of pure MoS2 is described, along with a brief summary of the wear and failure modes. Present applications for lubrication by MoS2 in spacecraft and dry machining are described. Anti‐adhesion uses in extruding and moulding are also mentioned. The current modification of MoS2 films is by addition of dopants (co‐sputtering), by multilayering as a series of films each fulfilling a specific task, or by stacking repeating nanometre‐scale films. Composite films of MoS2 islands in a hard film matrix are also being developed.
Mechanisms of wear of metal by nitrile rubber under boundary lubrication conditions
Authors: Siwei Zhang , Qiongjun Liu , Renyang He
Published: July 2006

The wear mechanisms for metal being worn by nitrile rubber under boundary lubrication conditions were investigated. We examined the surface profiles of both metal and rubber with SEM, and studied the chemical states of the elements in both surfaces with XPS. The functional groups in the rubber were analysed with FT‐IR. Under the action of shear forces, the metal lattice was disordered and new dislocations were formed; as a result, the chemical activity of the metal was increased. The macromolecular chains of the nitrile rubber and the alkane chains of the mineral oil were broken at stress concentration sites. These broken macromolecular chains produced active macromolecular free radicals, which reacted with the activated iron atoms and iron oxides, and generated a metal‐polymer film on the metal surface. This metal‐polymer film was destroyed and removed by the action of the debris on the sliding surface. Thus the rubber wore away the metal. Under boundary lubrication conditions with mineral oil, the physical processes of wear of T10 steel by nitrile rubber are microcutting and surface peeling.
Calcium cyclohexoxylborate: A new type of antiwear oil additive
Authors: Fenfang Li , Boshui Chen , Weijiu Huang , Diansen Gao , Junxiu Dong
Published: July 2006

Calcium cyclohexoxylborate (CaCHOB) was prepared, and its antiwear and friction‐reducing properties were investigated on a four‐ball tester and an HQ‐1 friction machine. X‐ray photo‐electron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to determine the chemical states of the tribo‐logical species on the rubbing surfaces. The results indicate that CaCHOB demonstrates good tribological performance. XPS and SEM analyses showed that surface films containing CaO and B2O3 were formed. These films were deposited on the rubbing surface and improved the lubricating state of the friction surface.
Development of a statistical method to formulate high‐VI hydraulic oils
Authors: Neveu Christian D. , Schweder Roland
Published: July 2006

Mobile hydraulic equipment is often subjected to a wide range of operating temperatures, and so must be lubricated with oils with a high viscosity index (VI) in order to maximise efficiency. Formulating high‐VI hydraulic oils is a complex task that requires testing numerous intermediate blends in order to achieve the desired viscosity at both low and high temperatures. With the introduction of the ASTM D 6080 hydraulic oil classification, which defines a separate grade at low and high temperature for high‐VI oils, and further includes VI and viscosity measurements after the sonic shear test, formulating high‐VI hydraulic oils has become even more complex.

In order to determine the most effective VI improver to meet a given set of viscosity requirements, a large statistically designed experiment has been carried out. Empirical equations have been obtained that can be used to model the blending efficiency of VI improvers at different temperatures and to estimate their shear stability. This paper shows how the results obtained for 42 hydraulic oils have been used to develop a computer program aimed at facilitating the formulation of high‐VI hydraulic oils.
Effect of mechanical shear on the thin‐film properties of base oil‐polymer mixtures
Authors: Devlin M. T. , Hammock T. , Jao T. ‐C.
Published: July 2006

The thickness and frictional characteristics of thin lubricant films are known to affect the fuel economy properties of oils. The base oil and polymer compositions of the lubricant are generally considered to be critical chemical factors that can influence these thin‐film lubricant properties in new oils. However, it is important to produce lubricants with good fuel economy properties that are maintained after the lubricant is degraded. Lubricants in use can undergo oxidation and mechanical shear degradation. The effect of oxidation degradation on thin‐film physical properties has previously been studied. This paper investigates the effect of mechanical shearing on thin‐film properties. Dispersant olefin copolymers are found to reduce thin‐film friction in simple mixtures and in fully formulated oils. In simple mixtures, shearing the dispersant olefin copolymers does not affect the friction‐reducing ability of these polymers. In fully formulated oils, even though shearing diminishes to a degree the friction‐reducing ability of dispersant olefin copolymers, these copolymers can still provide significant friction reduction.
Additive‐additive interactions: The search for synergistic antioxidant—antiwear phosphorodithioate compositions
Authors: Swami K. K. , Prakash S. , Mondal P. K. , Dohhen K. C. , Sarin R. , Tuli D. K. , Bhatnagar A. K.
Published: July 2006

Additive‐additive interactions between zinc dialkylphosphorodithioates and ashless alkylaminophosphorodithioates have been studied with the object of reducing the zinc level in the lubricant formulations. Various combinations of these components were evaluated for their antiwear and antioxidant properties using four‐ball and differential scanning calorimetry techniques.
Development of ashless multifunctional additives from cashew nutshell liquid
Authors: Swami K. K. , Prakash S. , Sarin R. , Tuli D. K. , Bhatnagar A. K.
Published: July 2006

Aminodi(alkylphenyl) phosphorodithioates have been synthes‐ised by the condensation of di (alkylphenyl) phosphorodithioic acid, which was derived from a renewable, biodegradable, low‐cost, naturally occurring vegetable product, cashew nutshell liquid, with various amines. These ashless aminodi (alkyl‐phenyl) phosphorodithioates have been evaluated as anti‐oxidant, antiwear, friction‐modifying, and extreme‐pressure additives in lubricant compositions.
Basics of mixed lubrication
Authors: Spikes H. A. , Olver A. V.
Published: July 2006

This paper reviews recent research in mixed lubrication, focusing on the current understanding of lubricant entrainment, and thus film thickness, and of friction in thin‐film, rough‐surface lubricated contacts. By combining research using optical interferometry on the experimental side and numerical modelling on the theoretical side, we now have a reasonable understanding of micro‐elastohydrodynamic lubrication, although design rules are still lacking. The regime of true mixed lubrication, where there are both elastohydrodynamic and boundary lubricated regions within a single contact, remains quite poorly understood. New experimental techniques as well as new information about very thin‐film rheology under high‐strain and high‐pressure conditions are probably needed before much further progress can be made in this area.
Mechanism of boundary film formation from n‐hexadecane
Authors: Makowska M. , Kajdas C. , Gradkowski M.
Published: July 2006

It is widely acknowledged that the process of surface film formation by tribological additives is very complex, because even saturated hydrocarbons — as major components of lubricating oils — undergo chemical changes under boundary lubrication conditions. To gain a better understanding of the tribochemical changes of paraffinic hydrocarbons, research was carried out using n‐hexadecane, which is widely used as a low‐viscosity model base oil. It has been hypothesised that the interactions between the products of n‐hexadecane triboreactions and steel surfaces are mostly initiated by the mechanical action of the system. Wear tests were performed, using a pin‐on‐disc machine. Fourier transform infrared microspectrophotometry and X‐ray photoelectron spectroscopy were used to analyse the wear tracks on the steel discs. Based on the analytical data obtained, a model of boundary film formation from aliphatic hydrocarbons is proposed.
Analysis of rough line contacts operating under mixed elastohydrodynamic lubrication conditions
Authors: Bakolas V. , Mihailidis A.
Published: July 2006

Heavily loaded machine elements, such as gears, usually operate in the mixed lubrication regime. Surface roughness has a significant effect on the pressure distribution, the subsurface stress field, and the friction coefficient. Based on the superposition of a dry rough and a fully flooded smooth contact, a mixed lubrication model has been developed. The roughness profile is assumed to be known. Surface deformation is calculated by taking into account the pressure distribution that is built up by asperity contacts, asperity interactions, and lubricant flow. Thermal and sliding effects are incorporated into the analysis. Non‐Newtonian lubricant behaviour is considered by using a power‐law rheological model. The pressure distribution, subsurface stress field, and friction coefficient were calculated from the model at several points along the contact path for an FZG type C gear pair. It was shown that a significant part of the load is carried by the contacting asperities. The position of the maximum shear stress is very close to the surface.
Additive efficiency and micellar structure of lubricants
Authors: Bakunin V. N. , Kuz'mina G. N. , Parenago O. P.
Published: July 2006

This paper reports on the influence of the micellar structure of additives, for example antioxidant additives, on their performance in lubricants. It is well known that hydrocarbon lubricants have a complex liquid structure depending on the composition of the base oils and the additive packages used. The authors have elsewhere suggested a micellar inhibition mechanism that functions in cases where lubricant compositions comprise both antioxidant and detergent additives. A similar situation is created in strongly degraded lubricants when the micellar‐like structure of the hydrocarbons is due to the interaction of oxidation and degradation products. The mechanism of reverse micelle formation and its influence on the oxidation mechanism and oxidation inhibition activity of different additive types are discussed. The influence of the hydrocarbon chain length of the additives on their activity is also discussed.
Laser stimulation of the auditory nerve
Authors: Izzo Agnella D. , Richter Claus‐Peter , Jansen E. Duco , Walsh Joseph T.
Published: July 2006

Background and Objectives

For centuries, electric current has been used to stimulate neurons. Shortcomings of electrical stimulation include the contact between the stimulating electrode and the tissue, and the non‐selective stimulation of the tissue. In contrast to electric stimulation, optical radiation can provide spatially selective neural stimulation without tissue contact.

Study Design/Materials and Methods

Acute in vivo experiments using gerbils were conducted to record optically evoked compound action potentials (CAPs) from the cochlea.

Results

Optical radiation evokes CAPs in normal hearing animals and in deafened animals, in which cochleae lack outer and inner hair cells. Stimulation threshold was measured as 0.018±0.003 J/cm2 (mean±SE). Laser radiation could be increased by 30–40 dB until drastic changes were seen in cochlear function. Cochlear response amplitudes to optical radiation were stable over extended stimulation times.

Conclusions

We have demonstrated that the auditory nerve can be stimulated by optical radiation. One potential clinical use of this technology would be for cochlear implants. Lasers Surg. Med. 38:745–753, 2006. © 2006 Wiley‐Liss, Inc.
Chain Orientation in Polyethylene Fibers Prepared by Ethylene Nanoextrusion Polymerization
Authors: Ye Zhibin , Zhu Shiping , Britten James F.
Published: July 2006

Summary: Ethylene nanoextrusion polymerization has been demonstrated to be a novel nanofabrication concept for the preparation of polyethylene (PE) fibers directly from ethylene monomers without any post‐processing procedures. For PE fibers, chain orientation is a critical parameter that affects performance and application of the fibrous materials. In this communication, we report an investigation on chain orientation in PE fibrous samples prepared through nanoextrusion polymerization using a two‐dimensional wide angle X‐ray diffraction (2D WAXRD) technique. Two types of fibrous samples, including individual microfibers and microfiber aggregates, were sampled randomly and studied. For individual PE microfibers, anisotropic diffraction patterns were observed, suggesting chain orientation along the microfiber axial direction. Some microfibers showed the most desired diffraction pattern often found in high‐modulus high‐strength PE fibers. These samples possessed a very high degree of chain orientation along the fiber axis. Owing to a random aggregation of anisotropic microfibers, microfiber aggregates exhibited isotropic diffraction patterns. This work provided further experimental evidence for the proposed nanoextrusion polymerization concept.

2D WAXRD diffraction pattern of a PE microfiber.

magnified image

2D WAXRD diffraction pattern of a PE microfiber.
New heuristic methods for the capacitated multi‐facility Weber problem
Authors: Aras Necati , Altınel İ. Kuban , Orbay Metin
Published: July 2006

In this paper we consider the capacitated multi‐facility Weber problem with the Euclidean, squared Euclidean, and ℓp‐distances. This problem is concerned with locating m capacitated facilities in the Euclidean plane to satisfy the demand of n customers with the minimum total transportation cost. The demand and location of each customer are known a priori and the transportation cost between customers and facilities is proportional to the distance between them. We first present a mixed integer linear programming approximation of the problem. We then propose new heuristic solution methods based on this approximation. Computational results on benchmark instances indicate that the new methods are both accurate and efficient. © 2006 Wiley Periodicals, Inc. Naval Research Logistics 2006
Perinatal findings and molecular cytogenetic analyses of de novo interstitial deletion of 9q (9q22.3→q31.3) associated with Gorlin syndrome
Authors: Chen Chih‐Ping , Lin Shuan‐Pei , Wang Tzu‐Hao , Chen Yann‐Jang , Chen Ming , Wang Wayseen
Published: July 2006

Objectives

To present the perinatal findings and the molecular cytogenetic analyses of a de novo interstitial deletion of 9q (9q22.3→q31.3) associated with Gorlin syndrome.

Methods

Amniocentesis was performed at 18 weeks' gestation on a 27‐year‐old woman at a community hospital because of a high Down syndrome risk of 1/178, a low maternal serum α‐fetoprotein (MSAFP) level of 0.66 multiples of the median (MoM), and a high maternal serum human chorionic gonadotrophin (MShCG) level of 3.13 MoM. The karyotype was initially determined to be 46,XY. However, fetal macrocephaly and overgrowth were found at 30 weeks' gestation. Postnatally, the infant manifested characteristic features of Gorlin syndrome. High‐resolution chromosomal bandings of the peripheral blood lymphocytes, polymorphic DNA marker analysis to determine the parental origin of the deletion, array comparative genomic hybridization (CGH) to determine the extent of the chromosomal deletion, and fluorescence in situ hybridization (FISH) to determine the deletion of the PTCH gene were performed.

Results

The 850‐band level of resolution showed an interstitial deletion of 9q (9q22.3→q31.3). The parental karyotypes were normal. The karyotype of the proband was 46,XY,del(9)(q22.3q31.3)de novo. Polymorphic DNA marker analysis revealed that the deletion was of paternal origin. Array CGH revealed that the deleted region was about 12 Mb, encompassing the segment from 9q22.32 to 9q31.3. FISH analysis using the BAC probe RP11‐34D4 and the probe RP11‐43505 indicated the deletion of the PTCH gene.

Conclusions

Fetuses with an interstitial deletion of 9q (9q22.3→q31.3) may be associated with a low level of MSAFP and a high level of MShCG in the second trimester, and sonographic findings of overgrowth and macrocephaly in the third trimester. Copyright © 2006 John Wiley & Sons, Ltd.
Isothermal crystallization behavior of poly(L‐lactide) in poly(L‐lactide)‐block‐poly(ethylene glycol) diblock copolymers
Authors: Huang Ching‐I , Tsai Shang‐Hsiu , Chen Chih‐Ming
Published: July 2006

The crystal unit‐cell structures and the isothermal crystallization kinetics of poly(L‐lactide) in biodegradable poly(L‐lactide)‐block‐methoxy poly(ethylene glycol) (PLLA‐b‐MePEG) diblock copolymers have been analyzed by wide‐angle X‐ray diffraction and differential scanning calorimetry. In particular, the effects due to the presence of MePEG that is chemically connected to PLLA as well as the PLLA crystallization temperature TC are examined. Though we observe no variation of both the PLLA and MePEG crystal unit‐cell structures with the block ratio between PLLA and MePEG and TC, the isothermal crystallization kinetics of PLLA is greatly influenced by the presence of MePEG that is connected to it. In particular, the equilibrium melting temperature of PLLA, T, significantly decreases in the diblock copolymers. When the TC is high so that the crystallization is controlled by nucleation, because of the decreasing T and thereafter the nucleation density with decreasing PLLA molecular weight, the crystallinity of PLLA also decreases with a decrease in the PLLA molecular weight. While, for the lower crystallization temperature regime controlled by the growth mechanism, the crystallizability of PLLA in copolymers is greater than that of pure PLLA. This suggests that the activation energy for the PLLA segment diffusing to the crystallization site decreases in the diblocks. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2438–2448, 2006
Preparation of antimicrobial poly(vinyl alcohol) nanofibers containing silver nanoparticles
Authors: Hong Kyung Hwa , Park Jong Lyoul , Sul In Hwan , Youk Ji Ho , Kang Tae Jin
Published: July 2006

Polyvinyl alcohol (PVA) nanofibers containing Ag nanoparticles were prepared by electrospinning PVA/silver nitrate (AgNO3) aqueous solutions, followed by short heat treatment, and their antimicrobial activity was investigated for wound dressing applications. Since PVA is a water soluble and biocompatible polymer, it is one of the best materials for the preparation of wound dressing nanofibers. After heat treatment at 155 °C for 3 min, the PVA/AgNO3 nanofibers became insoluble, while the Ag+ ions therein were reduced so as to produce a large number of Ag nanoparticles situated preferentially on their surface. The residual Ag+ ions were reduced by subsequent UV irradiation for 3 h. The average diameter of the Ag nanoparticles after the heat treatment was 5.9 nm and this value increased slightly to 6.3 nm after UV irradiation. It was found that most of the Ag+ ions were reduced by the simple heat treatment. The PVA nanofibers containing Ag nanoparticles showed very strong antimicrobial activity. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2468–2474, 2006
Exhaled breath condensate nitrite/nitrate and pH in relation to pediatric asthma control and exhaled nitric oxide
Authors: Ratnawati  , Morton John , Henry Richard L. , Thomas Paul S.
Published: July 2006

Background

Combining exhaled breath condensate (EBC) and exhaled nitric oxide (eNO) may be a useful, non‐invasive method to assess airway inflammation in pediatric asthma. This cross‐sectional study evaluated the relationship of both EBC nitrite/nitrate (NOx) and EBC pH with asthma control and eNO in asthmatic, normal, and atopic children.

Methods

A total of 92 children were recruited, comprising 62 with asthma, 14 with atopy only, and 16 who were normal and non‐atopic. All completed a questionnaire for asthma symptoms and control. Variables measured were spirometry, EBC NOx, pH, and eNO.

Results

EBC NOx in those with asthma (mean 8.4 µM, CI 7.5–9.4) was significantly elevated when compared with normal (4.8 µM, CI 3.4–6.2, P = 0.0007) and atopic children (6.5 µM, CI 4.0–9.1, P = 0.02). The mean level of eNO was significantly higher in those with asthma (43.7 ppb, CI 34.7–51.1, P < 0.001) and atopy (24 ppb, CI 16.7–31.2, P < 0.05) when compared with normal children (11.5 ppb, CI 6.7–16.2). There was a significantly lower pH in those with asthma and a FEV1 < 80% predicted (P = 0.03), but no significant overall differences in EBC pH between the three groups of children. There was a significant correlation between eNO and EBC NOx in the group as a whole, but not between eNO and EBC pH.

Conclusions

Mean EBC NOx levels differ between children with asthma, atopy, and those who are normal, but it is not interchangeable with eNO. EBC pH may be an additional marker of asthma control. Pediatr Pulmonol. 2006, 41:929–936. © 2006 Wiley‐Liss, Inc.
Case study: Providing evidence‐based behavioral and nutrition treatment to a toddler with cystic fibrosis and multiple food allergies via telehealth
Authors: Piazza‐Waggoner Carrie , Ferguson Kathleen S. , Daines Cori , Acton James D. , Powers Scott W.
Published: July 2006

Barriers to successful outcome for cystic fibrosis (CF) therapies can include distance from a CF care center, co‐morbid conditions that require individualized alterations to the prescribed treatment, and patient‐provider interactions, among others. We present the case of a 21‐month‐old female with CF for whom modifications of an efficacious behavioral and nutrition treatment were made due to food allergies and distance from the CF care center. She was classified as at‐risk nutritionally. Following treatment a significant increase in energy intake (calories) was observed in addition to her meeting weight and height growth rates for a child of this age and gender who is growing normally at the 50th percentile. Pediatr Pulmonol. 2006, 41:1001–1004. © 2006 Wiley‐Liss, Inc.
Long‐term follow‐up of oropharyngeal dysphagia in children without apparent risk factors
Authors: Lefton‐Greif Maureen A. , Carroll John L. , Loughlin Gerald M.
Published: July 2006

Background

The presence of swallowing dysfunction in children without obvious risk factors remains under appreciated. Early identification and prompt initiation of appropriate treatments are critical for reduction of morbidities associated with dysphagia.

Objective.

To describe the clinical presentations, radiologic characteristics, and long‐term outcomes in children with oropharyngeal dysphagia presenting as unexplained respiratory problems. We completed a retrospective chart review of all children without known dysphagic risk factors upon presentation to Speech‐Language Pathology (December 1991–April 1995) for feeding/swallowing evaluations because of refractory respiratory problems and dysphagic concerns, and who subsequently were diagnosed with dysphagia on Videofluoroscopic Swallow Study (VFSS). In August 2002, follow‐up telephone interviews were conducted with caregivers of 14 children.

Results.

We identified 19 children (mean age 1.14 years; range 0.9–5.75) with dysphagia presenting as unexplained respiratory problems. On VFSS, delayed pharyngeal swallow onset was the most common abnormal radiologic finding and always preceded penetration or tracheal aspiration. Eleven (57.9%) children aspirated. Aspiration occurred only with liquids and 100% of aspiration events were silent (i.e., no cough). Dysphagia was not a concern in 11 children at a mean age 3.2 years (range 0.7–10) and persisted in three children who were 9 years or older.

Conclusions.

Oropharyngeal dysphagia should be considered in the differential diagnosis of young children without known risk factors associated with swallowing dysfunction when they present with unexplained respiratory problems. Although the prognosis for resolution of dysphagic concerns is very good, it may take several years. Pediatr Pulmonol. 2006, 41:1040–1048. © 2006 Wiley‐Liss, Inc.
The etiology of tracheal mucosal injury in proximal esophageal atresia plus distal tracheoesophageal fistula: An animal study
Authors: Ateş Oğuz , Hakgüder Gülce , Olguner Mustafa , Özer Erdener , Akgür Feza M.
Published: July 2006

Tracheal mucosal damage has been reported in autopsy specimens of cases with proximal esophageal atresia and distal tracheoesophageal fistula (EA‐TEF) (Gross classification type C). Such changes have not been reported for isolated EA (Gross classification type A). Our hypothesis is that passage of amniotic fluid (AF) through fistula via larynx and trachea may damage tracheal mucosa. An experimental study was conducted to investigate this hypothesis in the Adriamycin‐induced EA‐TEF model. In the first stage of the study, we tested whether the fetuses with EA‐TEF associated with pyloric atresia cannot swallow AF whereas the fetuses EA‐TEF without intestinal atresia can swallow AF. Carbon solution was injected into the AF for this purpose. In the second stage of study, at the 21st day of their gestation, fetuses were extirpated and dissected under microscope. In both stages, fetuses were divided into four groups as control, fetuses without tracheoesophageal abnormalities, fetuses with EA‐TEF only, fetuses with pyloric atresia associated with EA‐TEF. Lungs and tracheas of the all fetuses were removed for histopathological examination. While carbon particles were present in the trachea, stomachs of the fetuses without tracheoesophageal anomalies, with EA‐TEF only and control fetuses, carbon particles were absent in both trachea and stomachs of the fetuses with pyloric atresia associated with EA‐TEF. Histopatological examination of the tracheal mucosa showed damage throughout the trachea in the fetuses with EA‐TEF only group. Tracheal mucosa was found to be normal in other groups. Bronchial mucosa and lung tissues were found to be normal in all groups. Amniotic fluid swallowed through the TEF causes histopathological changes in the tracheal mucosa of the fetuses with EA‐TEF only group. These findings may also contribute to the development of new fetal treatment modalities. Pediatr Pulmonol. 2006, 41:1049–1052. © 2006 Wiley‐Liss, Inc.
Correlated Ab initio electron propagators in the study of molecular wires
Authors: Dolgounitcheva O. , Zakrzewski V. G. , Sterling Mark R. , Kletsov A. , Dahnovsky Yu. , Ortiz J. V.
Published: July 2006

Correlated ab initio electron propagators provide a systematic approach to treating correlation effects in the study of molecular wires. Some preliminary formal and computational steps toward the application of such methods to electron transport problems in nanoscience are presented. Retarded and advanced Green functions are expressed in terms of a general electron propagator for a bridge molecule. Terminal and Green function matrices of any rank may be employed. An analytical expression for the current depends on correlated electron binding energies, pole strengths, and Dyson orbitals that may be produced with readily available software. Calculations on benzene dithiolate between gold atoms illustrate the capabilities of this approach. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
A new approach to the Noack volatility test
Authors: Selby T. W. , Reichenbach E. A. , Hall R. H.
Published: July 2006

This paper reports on the method and preliminary results of a significant modification of the Noack volatility test. This modification permits collection and examination of the volatile products as well as of the residue. The analysis of such volatiles by chromatography and spectroscopy revealed surprising information that is especially relevant in the face of increasingly difficult automotive and heavy duty engine emission limitations. The data also showed very close agreement with the Unified Test Method for the Noack Volatility Test now covered by CEC L‐40‐T‐87. Important to operators, the authors' modified Noack apparatus avoids the use of the toxic Wood's Metal of the earlier Noack apparatus.
Laboratories at work: Tribology at BAM, Berlin
Authors: Santner Erich
Published: July 2006

The tribology laboratories described here are part of the Bundesanstalt für Materialforschung und ‐prüfung (Federal Institute for Materials Research and Testing), known as ‘BAM’.
Laser particle sizing of diesel soots in two formulated oils after different engine tests
Authors: Constans B. , Bezot P.
Published: July 2006

Soots of four types were extracted from two different formulated diesel oils, namely oil ‘A’, a 15W40, and oil ‘B’, a 20W40, after engine (50 h) and tribological (20 h + 20 h) tests. The soots were dispersed into four different model solvents and base oils, and analysed by Photon Correlation Technique.

In a first study, soot particle size measurements were conducted after dilution in n‐heptane, Kerdane solvent, 60N and 130N base oils. The influences of engine running‐time and solvent nature have been particularly considered. The second study has been devoted to the aggregation kinetic of soots in these solvents.

These data are important for a better understanding of soot dispersion stability and the rheology of used oils in diesel engines.
Computer support in tribology ‐ experiments and database
Authors: Santner E.
Published: July 2006

As in all other areas of research today, so in tribology, computers play an important role. The exact analysis of tribological systems needs finite element methods (FEM) for calculation. Analysis of worn surfaces by SEM, AUGER, ESCA, XRS and the interpretation and documentation of measurements is performed with computers. The new approach to the basis of tribology by the use of scanning tunnelling microscopy (STM) and lateral force microscopy (LFM) would not be possible without computers. This paper points out the opportune tasks for computers in tribological simulation tests, such as complex test cycles, long time runs, automatic sensor calibration, measurements of fast varying signals, control and correction of mutual influences, and mentions the databases TRIBO (Tribology Index) for literature and Tribocollect for tribological data.
The laboratory simulation of abrasive wear
Authors: Williams J. A.
Published: July 2006

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two‐ and three‐body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.
Hot oil oxidation test (HOOT) — a laboratory simulation of ASTM Sequence IIID/IIIE engine tests
Authors: Ramakumar S. S. V. , Madhusudhana Rao A. , Srivastava S. P. , Bhatnagar A. K.
Published: July 2006

Reliable laboratory screening tests are an important stage in the development of automotive oils, because these oils are required to pass expensive engine tests to establish their performance credentials. The oxidation stability of crankcase lubricants is a vital parameter which defines the longevity of these oils in service. ASTM Sequence IIID and IIIE tests are used in the industry to evaluate this parameter. The present paper describes the development of a simple, bubbling oxygen, glassware, catalyst inhibited, type oxidation test. The test conditions have been optimised to get better discretion in the results, and the test results, when statistically correlated with the corresponding ASTM Sequence IIID and IIIE data, indicate that a 50–375% viscosity rise in HOOT will ensure a comfortable IIID pass with 98% confidence. However, in the case of IIIE, a viscosity rise of HOOT below 50% may indicate a IIID+ or IIIE performance with only 50% confidence. Improvement of the correlation between HOOT and IIIE can only be achieved by increasing the severity of the test conditions.