bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular dynamics simulation of the contact process in AFM surface observations
Authors: Shimizu J. , Zhou L. , Eda H.
Published: July 2006

In the present work, several molecular dynamics simulations have been performed to clarify dynamically the contact mechanism between the specimen surface and probe tip in surface observations by an atomic force microscope (SFM) or friction force microscope (FFM). In the simulation, a three‐dimensional model is proposed where the specimen and the probe are assumed to consist of monocrystalline copper and rigid diamond or a carbon atom, respectively. The effect of the cantilever stiffness of the AFM/FFM is also taken into consideration. The surface observation process is simulated on a well‐defined Cu{100} surface. From the simulation results it has been verified that the surface images and the two‐dimensional atomic‐scale stick‐slip phenomenon, just as is the case for real AFM/FFM surface observations, can be detected from the spring force acting on the cantilever. From the evaluation of the behaviour of specimen surface atoms, the importance of the specimen stiffness in deciding the cantilever properties can also be understood. The influence of the probe tip shape on the force images is also evaluated. From the results it can be verified that the behaviour of the specimen surface atoms as well as the solid surface images in AFM/FFM surface observations can be understood using the molecular dynamics simulation of the model presented.
A new method to simulate the elastic interactions in the tribosystems of a multi‐bar mechanism
Authors: Oprisan Cezar , Olaru Dumitru N. , Leohchi Dumitru
Published: July 2006

This paper presents a new method and criterion for predicting the occurrence of the interruption of a kinematic joint contact in a multi‐bar mechanism. The method is based on the elastic interactions in the tribosystems of the joints with imposed clearances. The method was used in a four‐bar mechanism with clearance in the joint formed from the coupler and the rocker. The analytical results were experimentally confirmed by measurement of the acceleration of the rocker.
Comparison of boundary lubrication films formed under four‐ball friction test conditions with different AW/EP Additives‐an X‐ray photoelectron spectroscopy study
Authors: Unnikrishnan R. , Christopher J. , Jain M. C. , Martin V. , Srivastava S. P.
Published: July 2006

The antiwear and extreme‐pressure properties of six different types of additive (molybdenum dialkyldithiophosphate, dibenzyl disulphide, molybdenum dialkyldithiocarbamate, zinc dialkyldithiophosphate, chlorinated paraffin wax, and triaryl phosphate) were evaluated by standard four‐ball friction and wear tests. This was followed by scanning electron microscopy (SEM), X‐ray photoelectron spectroscopy (XPS), and X‐ray photoelectron imaging (XPI) analyses of the worn surfaces to determine the structure of the boundary lubrication film and the mechanism of the tribochemical reaction occurring during the friction process. The presence of the additives in the base oil significantly increased the weld load and drastically reduced the wear‐scar diameter, suggesting antiwear and extreme‐pressure properties of the additives. The enhanced antiwear and loadcarrying capacity of the additive‐containing oils was attributed to the formation of a complex boundary lubrication film formed between the surfaces during the friction process as a result of the tribochemical reaction. The antiwear and extreme‐pressure properties of the additives were explained based on the XPS data. The studies indicated that the lubricating properties of the additives depend on their chemical nature and reactivity with metal surfaces.
Influence of test parameters on tribological measurements ‐ results from international round robin tests
Authors: Woydt Mathias , Ebrecht Johannes
Published: July 2006

A series of cooperative interlaboratory tests (‘round robins’) was conducted in 1997, 1998, 1999, 2000, and 2001 by the DIN 51834 Working Group on Tribological Tests in Translatory Oscillation Apparatus. Statistical analysis of these results showed the influence of cleaning solvent, machine model, and evaluation criteria on the tribological properties of the lubricants tested. Coefficients of friction and wear results were ranked according to the effects of ten different cleaning solvents, where isopropanol gave the lowest values and isoparaffin solvents the highest. The effect of machine model on coefficients of friction varied from about 0.2 to 0.9% of the average. Wear results were not affected. The tests also showed that the seizure criteria and methods of measuring wear required in the test procedure do not provide a suitable measure of the tribological properties of certain lubricants.
Approximate Formula for the Contact between Truncated Surfaces and Frictional Characteristics of a Journal Bearing in Mixed Lubrication
Authors: Nonogaki M. , Nakahara T.
Published: July 2006

This paper presents an approximate formula for the contact of a non‐Gaussian distribution of truncated surfaces, which is useful for mixed lubrication theory, and gives a method for the determination of the truncation parameters in this formula from a measured roughness profile. Using this approximate formula for a contact, the approximate formula for the friction coefficient of a journal bearing in mixed lubrication, which was previously proposed by the authors, is modified for truncated surfaces, and the frictional characteristics are demonstrated for various parameters of truncated roughness using the modified formula.
Optimisation of Industrial Tribological Systems with the Pin‐on‐Disc Tribometer Method
Authors: Randall N. X.
Published: July 2006

The purpose of tribology is to improve the service life and efficiency of machines and their elements. This paper describes certain tests that can be done on a modified pin‐on‐disc apparatus to match in‐service conditions more closely. The three examples considered incorporate a liquid heating function, a reciprocating modification to allow for linear sliding rather than circular sliding, and a modification to allow the simulation of different lubrication regimes.
Influence of lubricant on gear failures — test methods and application to gearboxes in practice
Authors: Michaelis Klaus , Hoehn Bernd‐Robert , Oster Peter
Published: July 2006

Base oil type, oil viscosity, and additive type and content have a strong influence on typical gear failures. As it is not possible to quantify the influence of a lubricant on load‐carrying capacity simply from a knowledge of the physical or chemical oil data, many test methods have been developed for the evaluation of mechanical—technological lubricant properties. Simple low‐cost bench test methods often show poor correlation with practice. From both experience and systematic investigation, it can be seen that testing of gear lubricants can be performed adequately only in gear test rigs using specified test gear geometry.

The standard FZG back‐to‐back gear test rig has been developed over many years and improved for different types of gear failure simulation. The standard FZG oil test A/8.3/90 is widely used for the evaluation of the scuffing properties of industrial gear oils. Automotive gear oils of GL4 level can be tested in the step test A10/16.6R/90, and axle oils of GL5 level in the shock test S‐A10/16.6R/90. For slow‐speed regimes, the C/0.05/90:120/12 wear test can be used. The influence of lubricants on the micropitting performance of gears can be evaluated in the GF‐C/8.3/90 micropitting test. Different pitting tests are available, as single‐stage (PT‐C/9:10/90) or load spectrum (PT‐C/LLS:HLS/90) tests.

The aim of this paper is to describe the influence of the lubricant on the different failure modes in gears, how to quantify this effect in adequate test methods, and how to introduce the results of such tests as determining values of the lubricant into load‐carrying capacity rating methods.
Vacuum tribological behaviour of self‐lubricating quasicrystalline composite coatings
Authors: Garc de Blas F. J. Ía , Román A. , de Miguel C. , Longo F. , Muelas R. , Agüero A.
Published: July 2006

High‐temperature‐resistant self‐lubricating coatings are needed in space vehicles for components that operate at high temperatures and/or under vacuum. Thick composite lubricant coatings containing quasicrystalline alloys as the hard phase for wear resistance can be deposited by a thermal spray technique. The coatings also contain lubricating materials (silver and BaF2CaF2 eutectic) and NiCr as the tough component. This paper describes the vacuum tribological properties of TH103, a coating of this type, with a very good microstructural quality. The coating was deposited by high‐velocity oxygen fuel spraying and tested under vacuum using a pin‐on‐disc tribometer. Different loads, linear speeds, and pin materials were studied. The pin scars and disc wear tracks were characterised using a combination of scanning electron microscopy and energy dispersive spectrometry. A minimum mean steady friction coefficient of 0.32 was obtained when employing an X750 Ni superalloy pin in vacuum conditions under 10 N load and 15 cm/s linear speed, showing moderate wear of the disc and low wear of the pin.
Power allocation and call admission control in multi‐class traffic DS‐CDMA systems with imperfect power control
Authors: Park Min Kyu , Oh Seong Keun , Lee Chaewoo
Published: July 2006

We deal with power allocation (PA) and call admission control (CAC) under imperfect power control (IPC) in the reverse link of direct sequence‐code division multiple access systems for supporting multi‐class traffic. First, we briefly review the optimum PA scheme under perfect power control (PPC) and the CAC scheme subject to an outage constraint on the total composite received power. Then, we analyze the outage degradation due to the power control error when the optimum reference power levels under PPC are used. In order to mitigate the outage degradation, we would modify the reference power levels by incorporating a call dropping strategy and an outage‐lowering strategy into the optimum PA scheme under PPC. Also, we derive a constraint inequality to determine the reverse link capacity under IPC. Finally, through numerical analyses, we compute the modified reference power levels under IPC and evaluate the reverse link capacity under IPC. Copyright © 2006 John Wiley & Sons, Ltd.
Characteristics of sensory DRG neurons innervating the wrist joint in rats
Authors: Kuniyoshi Kazuki , Ohtori Seiji , Ochiai Nobuyasu , Murata Ryo , Matsudo Takashi , Yamada Toshiyuki , Ochiai Satoko Shiozawa , Moriya Hideshige , Takahashi Kazuhisa
Published: July 2006

Background: Wrist pain can be the result of trauma, or inflammatory processes such as arthritis or synovitis. There is evidence that sensory nerve fibers are present in the wrist joints of animals and humans; however, the sensory innervation pattern of the wrist, as well as the types of nerves innervating it, have not been clarified. The purpose of this study was to characterize the types of sensory dorsal root ganglion (DRG) neurons innervating the wrist joint in the rat.

Methods: In this study, retrograde neurotransport was combined with lectin affinity histochemistry and immunohistochemistry to characterize DRG neurons innervating the wrist joint in rats. We used 3 markers: calcitonin gene‐related peptide (CGRP) as a marker of small, peptide‐containing neurons associated with inflammatory pain; the glycoprotein binding the isolectin from Griffonia simplicifolia (IB4) for small, non‐peptide‐containing neurons related to transmission of pain following nerve injury; and neurofilament 200 (NF200) for small and large myelinated fibers. IB4‐binding and CGRP‐containing neurons are typically involved in pain sensation, whereas NF200 is associated with pain and proprioception.

Results: Neurons innervating the wrist joints, retrogradely labeled with fluoro‐gold (FG), were distributed throughout DRGs from C6 to T1. Of all of the FG labeled neurons, the percentage of NF200 immunoreactive (IR) neurons and CGRP‐IR neurons were 26% and 45%, respectively. The percentage of IB4‐binding neurons was 3%, significantly less than the ratio of CGRP‐IR neurons to the total FG labeled neurons.

Conclusion: Under physiological conditions in rats, DRG neurons transmit several types of sensation from the wrist joint including proprioception and pain. Most of the labeled neurons were CGRP‐IR peptide containing neurons. It is likely that these neurons are the predominant afferents for inflammatory pain signals from the wrist. Because peptide‐containing neurons are associated with inflammatory pain, it is likely that the inflammation in the wrist joint causes wrist joint pain.
Traffic of prion protein between different compartments on the neuronal surface, and the propagation of prion disease
Authors: Morris Roger J. , Parkyn Celia J. , Jen Angela
Published: July 2006

The key mechanism in prion disease is the conversion of cellular prion protein into an altered, pathogenic conformation, in which cellular mechanisms play a poorly understood role. Both forms of prion protein are lipid‐anchored and reside in rafts that appear to protect the native conformation against conversion. Neurons rapidly traffic their cellular prion protein out of its lipid rafts to be endocytosed via coated pits before recycling back to the cell surface. It is argued in this review that understanding the mechanism of this trafficking holds the key to understanding the cellular role in the conformational conversion of prion protein.
Relationships between the frequency of farmed Atlantic salmon, Salmo salar L., in wild salmon populations and fish farming activity in Norway, 1989–2004
Authors: Fiske Peder , Lund Roar A. , Hansen Lars P.
Published: July 2006

In Norway, there have been restrictions on salmon farming in several fjords to reduce the potential negative impact on important stocks of wild Atlantic salmon. Little is known about the incidence of escaped farmed salmon in fisheries and broodstocks relative to the extent of fish farming in nearby areas. In this study, we analysed data on the incidence of escaped farmed Atlantic salmon in angling catches and broodstock fisheries in rivers for a 16-year period (1989–2004). These data were weighted using official catch statistics and combined at the county level, and the incidence of escapees was correlated with both the stock of farmed salmon in net pens and the reported number of escapees in different Norwegian counties. Our results indicate a significant positive correlation between the incidence of escaped farmed salmon in the rivers at the county level and the intensity of salmon farming, measured as the number of farmed salmon in net pens, suggesting that protection areas may reduce the impact of escapees in salmon populations nearby.
Acute Carpal Tunnel Syndrome Secondary to Pyogenic Tenosynovitis
Authors: NOURISSAT G. , FOURNIER E. , WERTHER J. R. , DUMONTIER C. , DOURSOUNIAN L.
Published: July 2006

We report a case of acute carpal tunnel syndrome related to a spontaneous pyogenic tenosynovitis and a review of this clinical condition.
Blood splash from different diathermy instruments during tonsillectomy
Authors: Hanna B C , Thompson P , Smyth C , Gallagher G
Published: July 2006

Objective: To compare the potential risk of blood contamination of the surgeon's conjunctiva during tonsillectomy using disposable bipolar diathermy and reusable monopolar diathermy.

Design: A prospective, single-blind, randomized, controlled trial.

Methods: Elective tonsillectomy was performed using either disposable bipolar diathermy or reusable monopolar diathermy. The operating surgeon wore a ViewsafeTM protective eyeshield which was later examined under an operating microscope by a blinded observer and the number of blood spots counted.

Results: One hundred and sixty-eight patients were enrolled. The relative risk of conjunctival contamination of the surgeon using disposable bipolar diathermy was 2.8 times that with reusable monopolar diathermy (chi-squared test, p < 0.0005). A previous history of peritonsillar abscess and additional adenoidectomy were associated with increased blood splatter.

Conclusion: The use of disposable bipolar diathermy for haemostasis during tonsillectomy poses a greater risk of conjunctival contamination for the surgeon than using reusable monopolar diathermy.
Early supraglottic cancer: how extensive must surgical resection be, if used alone?
Authors: Dünne A A , Davis R K , Dalchow C V , Sesterhenn A M , Werner J A
Published: July 2006

Objectives: Two centre based evaluations of oncologic results of endoscopic resection of supraglottic cancer without post-operative irradiation.

Patients and methods: Twenty-six patients with clinical T1 (n=5) or T2 (n=21) primary squamous cell carcinomas of the supraglottic larynx and with N0 (n=24) or N1 (n=2) neck disease were treated by endoscopic supraglottic laryngectomy coupled with neck dissection(s). Endoscopic resection was standardized whereas neck dissections (NDs) varied from classical modified radical ND to selective ND of levels I to IV.

Results: Pathologically, three T2 patients were upstaged to T3, four N0 patients to N1 and one N2 patient down-staged to N1. Within an average of 42 months, there were no local failures and only one regional failure.

Conclusions: Endoscopic resection of T1 and T2 supraglottic cancer without post-operative irradiation achieved good oncological results. No patients with lateralized primary cancers were found to have contralateral cancer on pathological evaluation from bilateral dissections.
Detection of an ultralow velocity zone at the core‐mantle boundary using diffracted PKKPab waves
Authors: Rost Sebastian , Garnero Edward J.
Published: July 2006

Seismic phases diffracted around Earth's core contain information about lowermost mantle wave speeds. By measuring the slowness of incident diffracted energy from array recordings, seismic velocity along the diffracted path can be estimated. Here we apply this principle to diffraction of the major arc seismic phase PKKPab recorded at the Canadian Yellowknife array to estimate P wave velocity variations along the core‐mantle boundary. We observe PKKPabdiff about 7.5° past the ray theoretical cutoff distance for PKKPab. We utilize 330 western Pacific rim earthquakes that allow us to probe the core‐mantle boundary beneath the North Atlantic and the South Pacific oceans using PKKPabdiff. Slowness and back azimuth are measured by frequency–wave number analysis. Mapping PKKPabdiff slowness variations suggest 4–19% P wave velocity reductions relative to PREM, in good agreement with the magnitude of velocity reductions previously mapped in ultralow velocity zones. The PKKPabdiff slowness and back‐azimuth variations combined with results from previous ULVZ studies using SPdiffKS imply that the lowered velocities occur at the base of the mantle beneath the North Atlantic Ocean, along the receiver side of raypaths. PKKPabdiff array measurements thus hold important potential for mapping ultralow velocity zone structure in so far unprobed regions of the lower mantle as well as for providing additional and independent information about lower mantle structure.
The Role of snow cover in the Northern Hemisphere winter to summer transition
Authors: Barriopedro David , García‐Herrera Ricardo , Hernández Emiliano
Published: July 2006

This paper examines the role of North Hemisphere snow cover in the linkage between the winter North Atlantic Oscillation (NAO) and the summer Northern Annular Mode (NAM). This transition is partially supported by the persistence of the NAO‐induced snow cover anomalies and the asymmetric thermal distribution induced by summer snow cover. We define an index of subpolar temperature difference which links winter NAO with the subsequent summer NAM. The index is also significant in the linkage between summer and winter climates and can be used as an useful predictor of the upcoming winter NAO.
Orbital motions and coherent structures in the internal tide on a steep shelf off the Pacific coast of Mexico
Authors: Filonov Anatoliy , Konyaev Konstantin
Published: July 2006

Herein we discuss the results of a study of the structure, evolution and break‐up of an internal tidal wave under conditions of a steep shelf with a slope close to that of the internal wave characteristic. Measurements were taken in Navidad Bay on Mexico's Pacific Coast. We demonstrate that, under the conditions of homogeneous density stratification, the internal tidal wave releases its energy and collapses due to resonant excitation in a sequence of third tidal harmonics. Those harmonics generate multiscale vertical bilateral steps that follow at regular intervals and feature coherent oscillations in the form of vertical jets that cover the entire water column.
Perinatal Iron Deficiency Predisposes the Developing Rat Hippocampus to Greater Injury from Mild to Moderate Hypoxia—Ischemia
Authors: Rao Raghavendra , Tkac Ivan , Townsend Elise L , Ennis Kathleen , Gruetter Rolf , Georgieff Michael K
Published: July 2006

The hippocampus is injured in both hypoxia—ischemia (HI) and perinatal iron deficiency that are co-morbidities in infants of diabetic mothers and intrauterine growth restricted infants. We hypothesized that preexisting perinatal iron deficiency predisposes the hippocampus to greater injury when exposed to a relatively mild HI injury. Iron-sufficient and iron-deficient rats (hematocrit 40% lower and brain iron concentration 55% lower) were subjected to unilateral HI injury of 15, 30, or 45 mins ( n = 12 to 13/HI duration) on postnatal day 14. Sixteen metabolite concentrations were measured from an 11 //L volume on the ipsilateral (HI) and contralateral (control) hippocampi 1 week later using in vivo1H NMR spectroscopy. The concentrations of creatine, glutamate, myo-inositol, and N-acetylaspartate were lower on the control side in the iron-deficient group ( P < 0.02, each). Magnetic resonance imaging showed hippocampal injury in the majority of the iron-deficient rats (58% versus 11%, P < 0.0001) with worsening severity with increasing durations of HI ( P = 0.0001). Glucose, glutamate, N-acetylaspartate, and taurine concentrations were decreased and glutamine, lactate and myo-inositol concentrations, and glutamate/glutamine ratio were increased on the HI side in the iron-deficient group ( P < 0.01, each), mainly in the 30 and 45 mins HI subgroups ( P < 0.02, each). These neurochemical changes likely reflect the histochemically detected neuronal injury and reactive astrocytosis in the iron-deficient group and suggest that perinatal iron deficiency predisposes the hippocampus to greater injury from exposure to a relatively mild HI insult.
Pole Position: Migrant British Women Producing ‘Selves’ through Lap Dancing Work
Authors: Bott Esther
Published: July 2006

This paper explores the motivations and experiences of British women working as lap dancers in the tourist resorts of southern Tenerife, with a particular focus on the subjective choices and processes undertaken by working-class women in the embodiment of positively evaluated identities. It uses Skeggs’ theoretical framework of ‘becoming respectable’ (1997) alongside other debates on ‘identity management’ in order to begin mapping the ways in which migrant British lap dancers produce themselves, negotiate gender and class, and seek forms of respectability, reputability and honour through their work. Drawing on empirical data, it will discuss how strong disassociations with the Other are formed, and how and why important binaries, particularly distinctions between lap dancing and prostitution and lap dancing and other ‘degraded’ forms of work and lifestyle are drawn in the dancers’ own stories of themselves. It will look at notions and processes of gaining ‘respectability’ through part of a wider migrant discourse, exploring how being a migrant lap dancer can serve as a vehicle for reproducing a ‘respectable’ and otherwise positively evaluated self on several levels.
A Hirshfeld partitioning of polarizabilities of water clusters
Authors: Krishtal A. , Senet P. , Yang M. , Van Alsenoy C.
Published: July 2006

A new Hirshfeld partitioning of cluster polarizability into intrinsic polarizabilities and charge delocalization contributions is presented. For water clusters, density-functional theory calculations demonstrate that the total polarizability of a water molecule in a cluster depends upon the number and type of hydrogen bonds the molecule makes with its neighbors. The intrinsic contribution to the molecular polarizability is transferable between water molecules displaying the same H-bond scheme in clusters of different sizes, and geometries, while the charge delocalization contribution also depends on the cluster size. These results could be used to improve the existing force fields.
Comment on “Global thermodynamics of hydrophobic cavitation, dewetting, and hydration” [J. Chem. Phys. 123, 184504 (2005)]
Authors: Graziano Giuseppe
Published: July 2006

It is pointed out that in a Ben-Amotz in a recent article [J. Chem. Phys.123, 184504 (2005)] attributed a noncorrect meaning to the entropy convergence temperature, claiming that the latter corresponds to the temperature at which the hydration entropy of a series of solutes crosses zero. A short resumé of the entropy convergence phenomenon and of the provided statistical mechanical analyses is accomplished. In addition, it is brought out that the different temperature dependence of the cavity entropy change on increasing the cavity diameter, pointed out by Ben-Amotz, originates from the assumption that the work of cavity creation should be proportional to the experimental surface tension of liquid water for cavities large on a molecular scale.
Theoretical and experimental exploration of rules for combining transport parameters in laminar membranes
Authors: Liang Wenquan , Siegel Ronald A.
Published: July 2006

Permeabilities, time lags, and mean first passage times were measured in silastic (Sil) and ethylene vinyl acetate copolymer (EVAc) membranes and in the series composites Sil/EVAc and EVAc/Sil. These measurements were used to test phenomenological rules derived previously [R. A. Siegel, J. Phys. Chem. 95, 2556 (1991)] relating the parameters of the constituent membranes to the same parameters for the membrane composites. Reasonable agreement was found between experimental results and these rules. As predicted, permeability and time lag are the same in either direction of transport through the series composite, while mean first passage time is direction dependent. In addition to the experimental results, the combination rules are rederived using the partition/diffusion model of membrane transport, and certain new theoretical connections are noted.
Activated hopping and dynamical fluctuation effects in hard sphere suspensions and fluids
Authors: Saltzman Erica J. , Schweizer Kenneth S.
Published: July 2006

Single particle Brownian dynamics simulation methods are employed to establish the full trajectory level predictions of our nonlinear stochastic Langevin equation theory of activated hopping dynamics in glassy hard sphere suspensions and fluids. The consequences of thermal noise driven mobility fluctuations associated with the barrier hopping process are determined for various ensemble-averaged properties and their distributions. The predicted mean square displacements show classic signatures of transient trapping and anomalous diffusion on intermediate time and length scales. A crossover to a stronger volume fraction dependence of the apparent nondiffusive exponent occurs when the entropic barrier is of order the thermal energy. The volume fraction dependences of various mean relaxation times and rates can be fitted by empirical critical power laws with parameters consistent with ideal mode-coupling theory. However, the results of our divergence-free theory are largely a consequence of activated dynamics. The experimentally measurable alpha relaxation time is found to be very similar to the theoretically defined mean reaction time for escape from the barrier-dominated regime. Various measures of decoupling have been studied. For fluid states with small or nonexistent barriers, relaxation times obey a simple log-normal distribution, while for high volume fractions the relaxation time distributions become Poissonian. The product of the self-diffusion constant and mean alpha relaxation time increases roughly as a logarithmic function of the alpha relaxation time. The cage scale incoherent dynamic structure factor exhibits nonexponential decay with a modest degree of stretching. A nearly universal collapse of the different volume fraction results occurs if time is scaled by the mean alpha relaxation time. Hence, time-volume fraction superposition holds quite well, despite the presence of stretching and volume fraction dependent decoupling associated with the stochastic barrier hopping process. The relevance of other origins of dynamic heterogeneity (e.g., mesoscopic domains), and comparison of our results with experiments, simulations, and alternative theories, is discussed.
Representation of state property systems
Authors: Aerts D. , Pulmannová S.
Published: July 2006

A “state property system” is the mathematical structure which models an arbitrary physical system by means of its set of states, its set of properties, and a relation of “actuality of a certain property for a certain state.” We work out a new axiomatization for standard quantum mechanics, starting with the basic notion of state property system, and making use of a generalization of the standard quantum mechanical notion of “superposition” for state property systems.
Unifying kinetic approach to phoretic forces and torques onto moving and rotating convex particles
Authors: Kröger Martin , Hütter Markus
Published: July 2006

We derive general expressions and present several examples for the phoretic forces and torques acting on a translationally moving and rotating convex tracer particle, usually a submicrosized aerosol particle, assumed to be small compared to the mean free path of the surrounding nonequilibrium gas. Point of departure is an expression of the stress tensor in terms of half-sphere integrals to be evaluated with the inhomogeneous velocity distribution function of the surrounding gas, more specifically, its approximation in terms of a finite number of moments. A worked out example covers Grad’s 13 moment approximation in and out of the so-called hydrodynamic approximation. We implement an accommodation coefficient characterizing the collision process in order to derive the tracer particle’s complete equations of motion in a form which offers the possibility for immediate numerical implementation, and the analytical exploration of the effect of particle shape and size on phoretic drift velocity. Explicit expressions for axisymmetric, spherical, cylindrical, and also cuboidal particles are presented, discussed, and successfully compared with the rarely available, previously treated special cases, thus supporting the unifying approach presented in this manuscript.
Vibrational properties of inclusion complexes: The case of indomethacin-cyclodextrin
Authors: Rossi Barbara , Verrocchio Paolo , Viliani Gabriele , Scarduelli Giorgina , Guella Graziano , Mancini Ines
Published: July 2006

Vibrational properties of inclusion complexes with cyclodextrins are studied by means of Raman spectroscopy and numerical simulation. In particular, Raman spectra of the nonsteroidal, anti-inflammatory drug indomethacin undergo notable changes in the energy range between 1600 and 1700cm−1 when inclusion complexes with cyclodextrins are formed. By using both ab initio quantum chemical calculations and molecular dynamics, we studied how to relate such changes to the geometry of the inclusion process, disentangling single-molecule effects, from changes in the solid state structure or dimerization processes.
Diffusional anomaly and network dynamics in liquid silica
Authors: Sharma Ruchi , Mudi Anirban , Chakravarty Charusita
Published: July 2006

The present study applies the power spectral analysis technique to understand the diffusional anomaly in liquid silica, modeled using the Beest-Kramer-van Santen (BKS) potential. Molecular-dynamics simulations have been carried out to show that power spectrum of tagged particle potential energy of silica shows a regime with 1∕fα dependence on frequency f which is the characteristic signature of multiple time scale behaviour in networks. As demonstrated earlier in the case of water [J. Chem. Phys. 122, 104507 (2005)], the variations in the mobility associated with the diffusional anomaly are mirrored in the scaling exponent α associated with this multiple time scale behavior. Our results indicate that in the anomalous regime, as the local tetrahedral order decreases with temperature or pressure, the coupling of local modes to network reorganizations increases and so does the diffusivity. This symmetry-dependence of the vibrational couplings is responsible for the connection between the structural and diffusional anomalies.
Excitation of a surface plasmon with an elastomeric grating
Authors: Kocabas A. , Dâna A. , Aydinli A.
Published: July 2006

We report on a new method to excite surface plasmon polaritons on a thin metal slab surface using an elastomeric grating which is fabricated by replica molding technique. The grating is placed on the metal surface which creates a periodic perturbation on the surface matching the momentum of the incident light to that of the surface plasmon. The conformal contact between the metal surface and the elastomeric grating changes the dielectric medium periodically and allows the observation of an effective surface plasmon polariton at the metal-air and metal-polymer interfaces of the grating. To clarify the nature of the observed plasmon, comparison of the elastomeric grating with elastomeric slabs was performed with the attenuated total reflection method.
Coupled resonator optical waveguides based on silicon-on-insulator photonic wires
Authors: Xia Fengnian , Sekaric Lidija , O’Boyle Martin , Vlasov Yurii
Published: July 2006

Coupled resonator optical waveguides (CROWs) comprised of up to 16 racetrack resonators based on silicon-on-insulator (SOI) photonic wires were fabricated and characterized. The optical properties of the CROWs were simulated using measured single resonator parameters based on a matrix approach. The group delay property of CROWs was also analyzed. The SOI based CROWs consisting of multiple resonators have extremely small footprints and can find applications in optical filtering, dispersion compensation, and optical buffering. Moreover, such CROW structure is a promising candidate for exploration of low light level nonlinear optics due to its resonant nature and compact mode size (∼0.1μm2) in photonic wire.
Optical manipulation of single electron spin in doped and undoped quantum dots
Authors: Jin Jinshuang , Li Xin-Qi , Yan YiJing
Published: July 2006

The optical manipulation of electron spins is of great benefit to solid-state quantum information processing. In this letter, we provide a comparative study on the ultrafast optical manipulation of single electron spin in the doped and undoped quantum dots. The study indicates that the experimental breakthrough can be preliminarily made in the undoped quantum dots, because of the relatively less demand.
Improved luminance intensity of InGaN–GaN light-emitting diode by roughening both the p-GaN surface and the undoped-GaN surface
Authors: Peng Wei Chih , Wu Yew Chung Sermon
Published: July 2006

The InGaN–GaN epitaxial films were grown by low-pressure metal-organic chemical vapor deposition on a sapphire substrate, and then the light-emitting diode (LED) with double roughened (p-GaN and undoped-GaN) surfaces was fabricated by surface-roughening, wafer-bonding, and laser lift-off technologies. It was found that the front side luminance intensity of double roughened LED was 2.77 times higher than that of the conventional LED at an injection current of 20mA. The backside luminance intensity was 2.37 times higher than that of the conventional LED. This is because the double roughened surfaces can provide photons multiple chances to escape from the LED surface, and redirect photons, which were originally emitted out of the escape cone, back into the escape cone.
Bright semipolar GaInN∕GaN blue light emitting diode on side facets of selectively grown GaN stripes
Authors: Wunderer Thomas , Brückner Peter , Neubert Barbara , Scholz Ferdinand , Feneberg Martin , Lipski Frank , Schirra Martin , Thonke Klaus
Published: July 2006

The authors demonstrate the fabrication and evaluation of bright semipolar GaInN∕GaN blue light emitting diodes (LEDs). The structures are realized by growing five GaInN∕GaN quantum wells on the {11¯01} side facets of selectively grown n-GaN stripes with triangular shape running along the ⟨112¯0⟩ direction covered with a Mg-doped GaN top layer. The growth was done by metal organic vapor phase epitaxy using a conventional [0001] sapphire substrate. The devices have circular mesa structures with diameters between 70 and 140μm. Continuous wave on-wafer optical output powers as high as 700μW and 3mW could be achieved under dc conditions for 20 and 110mA, respectively. The current dependent blueshift of the peak emission wavelength caused by screening effects of the piezoelectric field was only 1.5nm for currents between 1 and 50mA. This is less than half the value measured on c-plane LEDs and confirms the reduced piezoelectric field in our LED structures.
Carcinogens induce genome-wide loss of heterozygosity in normal stem cells without persistent chromosomal instability
Authors: Donahue Sarah L. , Lin Qing , Cao Shang , Ruley H. Earl
Published: July 2006

Widespread losses of heterozygosity (LOH) in human cancer have been thought to result from chromosomal instability caused by mutations affecting DNA repair/genome maintenance. However, the origin of LOH in most tumors is unknown. The present study examined the ability of carcinogenic agents to induce LOH at 53 sites throughout the genome of normal diploid mouse ES cells. Brief exposures to nontoxic levels of methylnitrosourea, diepoxybutane, mitomycin C, hydroxyurea, doxorubicin, and UV light stimulated LOH at all loci at frequencies ranging from 1–8 × 10
−3
per cell (10–123 times higher than in untreated cells). This greatly exceeds the frequencies at which these agents have been reported to induce point mutations and is comparable to the rates of LOH observed in ES cells lacking the gene responsible for Bloom syndrome, an inherited DNA repair defect that results in greatly increased risk of cancer. These results suggest that LOH contributes significantly to the carcinogenicity of a variety of mutagens and raises the possibility that genome-wide LOH observed in some human cancers may reflect prior exposure to genotoxic agents rather than a state of chromosomal instability during the carcinogenic process. Finally, as a practical matter, chemically induced LOH is expected to enhance the recovery of homozygous recessive mutants from phenotype-based genetic screens in mammalian cells.
Genome analysis of the smallest free-living eukaryote
Ostreococcus tauri
unveils many unique features
Authors: Derelle Evelyne , Ferraz Conchita , Rombauts Stephane , Rouzé Pierre , Worden Alexandra Z. , Robbens Steven , Partensky Frédéric , Degroeve Sven , Echeynié Sophie , Cooke Richard , Saeys Yvan , Wuyts Jan , Jabbari Kamel , Bowler Chris , Panaud Olivier , Piégu Benoît , Ball Steven G. , Ral Jean-Philippe , Bouget François-Yves , Piganeau Gwenael , De Baets Bernard , Picard André , Delseny Michel , Demaille Jacques , Van de Peer Yves , Moreau Hervé
Published: July 2006

The green lineage is reportedly 1,500 million years old, evolving shortly after the endosymbiosis event that gave rise to early photosynthetic eukaryotes. In this study, we unveil the complete genome sequence of an ancient member of this lineage, the unicellular green alga
Ostreococcus tauri
(Prasinophyceae). This cosmopolitan marine primary producer is the world’s smallest free-living eukaryote known to date. Features likely reflecting optimization of environmentally relevant pathways, including resource acquisition, unusual photosynthesis apparatus, and genes potentially involved in C
4
photosynthesis, were observed, as was downsizing of many gene families. Overall, the 12.56-Mb nuclear genome has an extremely high gene density, in part because of extensive reduction of intergenic regions and other forms of compaction such as gene fusion. However, the genome is structurally complex. It exhibits previously unobserved levels of heterogeneity for a eukaryote. Two chromosomes differ structurally from the other eighteen. Both have a significantly biased G+C content, and, remarkably, they contain the majority of transposable elements. Many chromosome 2 genes also have unique codon usage and splicing, but phylogenetic analysis and composition do not support alien gene origin. In contrast, most chromosome 19 genes show no similarity to green lineage genes and a large number of them are specialized in cell surface processes. Taken together, the complete genome sequence, unusual features, and downsized gene families, make
O. tauri
an ideal model system for research on eukaryotic genome evolution, including chromosome specialization and green lineage ancestry.
E2-25K mediates US11-triggered retro-translocation of MHC class I heavy chains in a permeabilized cell system
Authors: Flierman Dennis , Coleman Catherine S. , Pickart Cecile M. , Rapoport Tom A. , Chau Vincent
Published: July 2006

In cells expressing human cytomegalovirus US11 protein, newly synthesized MHC class I heavy chains (HCs) are rapidly dislocated from the endoplasmic reticulum (ER) and degraded in the cytosol, a process that is similar to ER-associated degradation (ERAD), the pathway used for degradation of misfolded ER proteins. US11-triggered movement of HCs into the cytosol requires polyubiquitination, but it is unknown which ubiquitin-conjugating and ubiquitin-ligase enzymes are involved. To identify the ubiquitin-conjugating enzyme (E2) required for dislocation, we used a permeabilized cell system, in which endogenous cytosol can be replaced by cow liver cytosol. By fractionating the cytosol, we show that E2-25K can serve as the sole E2 required for dislocation of HCs
in vitro
. Purified recombinant E2-25K, together with components that convert this E2 to the active E2-ubiquitin thiolester form, can substitute for crude cytosol. E2-25K cannot be replaced by the conjugating enzymes HsUbc7/Ube2G2 or Ube2G1, even though HsUbc7/Ube2G2 and its yeast homolog Ubc7p are known to participate in ERAD. The activity of E2-25K, as measured by ubiquitin dimer formation, is strikingly enhanced when added to permeabilized cells, likely by membrane-bound ubiquitin protein ligases. To identify these ligases, we tested RING domains of various ligases for their activation of E2-25K
in vitro
. We found that RING domains of gp78/AMFR, a ligase previously implicated in ERAD, and MARCHVII/axotrophin, a ligase of unknown function, greatly enhanced the activity of E2-25K. We conclude that in permeabilized, US11-expressing cells polyubiquitination of the HC substrate can be catalyzed by E2-25K, perhaps in cooperation with the ligase MARCHVII/axotrophin.
Impact of different land uses on the migration of two herbicides in a silt loam soil: unsaturated soil column displacement studies
Authors: Vincent A. , Benoit P. , Pot V. , Madrigal I. , Delgado‐Moreno L. , Labat C.
Published: July 2006

Displacement experiments of bromide and two herbicides, isoproturon and metribuzin, were performed in unsaturated undisturbed soil cores sampled on a unique site under (i) conventional wheat/maize rotation, (ii) 10‐year‐old grassed strip and (iii) 80‐year‐old oak/chestnut forest. Steady state conditions at constant rainfall intensity were used to compare the effect of the different land uses on soil herbicide transport and dissipation parameters. For each herbicide, mobility was similar between grassed strip and cultivated soils while it was reduced in the forest soils. The descriptive and moment analyses of the experimental breakthrough curves of bromide and herbicides demonstrated a similar degree of physical non‐equilibrium transport for the cropped and grassland soil columns, with transport ranging from a less intense physical non‐equilibrium status to the complete physical equilibrium state for the forest soil columns. Chemical non‐equilibrium transport was shown for the three situations. Degradation occurred in some columns as demonstrated by the elution of a metabolite of isoproturon. Previous data on sorption and degradation of isoproturon on the same soils were used to explain the differences observed in the analysis of the elution curves between grassed strip, forest and cultivated soil. Averaging Kd values from individual soil layers of each profile gave a satisfying understanding of isoproturon retardation factors. Sorption on soil organic matter was the main factor in herbicide mobility. However, other phenomena such as degradation and formation of non‐extractable residues were involved in the differences observed in leached masses of isoproturon between the three situations.
Cardiovascular disease and Alzheimer's disease: common links
Authors: STAMPFER M. J.
Published: July 2006

Growing evidence supports a strong and likely causal association between cardiovascular disease (CVD), and its risk factors, with incidence of cognitive decline and Alzheimer's disease. Individuals with subclinical CVD are at higher risk for dementia and Alzheimer's. Several cardiovascular risk factors are also risk factors for dementia, including hypertension, high LDL cholesterol, low HDL cholesterol and especially diabetes. Moderate alcohol appears to be protective for both CVD and dementia. In contrast, inflammatory markers predict cardiovascular risk, but not dementia, despite biological plausibility for such a link. The substantial overlap in risk factors points to new avenues for research and prevention.
Correlation of amino acid variations within nonstructural 4B protein with initial viral kinetics during interferon‐alpha‐based therapy in HCV‐1b‐infected patients
Authors: Welker M.‐W. , Hofmann W.‐P. , Welsch C. , Von Wagner M. , Herrmann E. , Lengauer T. , Zeuzem S. , Sarrazin C.
Published: July 2006

Summary.  Chronic hepatitis C is a major cause of liver cirrhosis leading to chronic liver failure and hepatocellular carcinoma. Different hepatitis C virus (HCV) proteins have been associated with resistance to interferon‐alpha‐based therapy. However, the exact mechanisms of virus‐mediated interferon resistance are not completely understood. The importance of amino acid (aa) variations within the HCV nonstructural (NS)4B protein for replication efficiency and viral decline during the therapy is unknown. We investigated pretreatment sera from 42 patients with known outcome to interferon‐based therapy. The complete NS4B gene was amplified and sequenced. Mutational analyses of predicted conformational, functional, structural and phylogenetic properties of the deduced aa sequences were performed. The complete NS4B protein was highly conserved with a median frequency of 0.015 ± 0.009 aa exchanges (median ± SD, 4.00 ± 2.31). Especially within the predicted transmembranous domains of the NS4B protein, the mean number of aa variations was low (median frequency, 0.013 ± 0.013). Neither the number of aa variations nor specific aa exchanges were correlated with HCV RNA serum concentration at baseline. A rapid initial HCV RNA decline of ≥1.5 log10 IU/mL at week 2 of interferon‐based therapy was associated with a higher frequency of nonconservative aa exchanges within the complete NS4B protein in comparison with patients with a nonrapid HCV RNA decline (median frequency, 0.011 ± 0.005 vs 0.004 ± 0.003, P = 0.006). Overall, the aa sequence of the NS4B protein was highly conserved, indicating an important role for replication in vivo. Amino acid variations with relevant changes of physicochemical properties may influence replication efficiency, associated with a rapid early virological response.