bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of the subchondral bone layer of the medial coronoid process of the canine ulna
Authors: Wolschrijn Claudia F. , Weijs Wim A.
Published: March 2005

The medial coronoid process (MCP) of the ulna takes part in the weight‐bearing function of the elbow in quadrupedal animals. In this study, the timing of development of a solid subchondral bone layer (SBL) of the MCP in the dog is investigated, as this might be important in the pathogenesis of the fractured medial coronoid process, a common disease in young dogs of larger breeds. The SBL is considered to make an important contribution to the strength of the MCP. In this study, the SBL is visualized at the humeral articular side (H‐side) and in the radial notch (RN) via three‐dimensional reconstructions of micro‐CT scans (34 μm voxel size) in nine young golden retrievers. After micro‐CT scanning, the area was investigated histologically. Gradually, the appearance of the SBL on the H‐side changes from a trabecular aspect to an even surface with gaps and finally to a completely even surface. The surface in the RN is still rough at 24 weeks after birth, although some consolidation has occurred. Initially, the enchondral ossification activity, as observed in the histological sections, is high, but later, when the intertrabecular spaces are filled in with calcified cartilage and bone, activity is less evident. Some vessels penetrated the SBL, but it is unclear if they account for all the gaps in the surface seen in micro‐CT. In addition, the formation of a cortical structure of the proximal ulnar shaft could be visualized. The bony cortex is already even at the mediocaudal side of the proximal ulna 4 weeks after birth, but remains trabecular at the dorsal side until 6 weeks later. We hypothesize that the observed differences in the formation of an even SBL or cortex can be explained by mechanical factors. A smooth cortical layer has an even thickness and will be stronger than a cortex with varying thickness. In the MCP, compressive forces exerted by the humerus may be responsible for the early smoothening on the H‐side. In the proximal ulna, the resistance to bending in the sagittal plane will depend mainly on the caudal surface of the ulna (and dorsal surface of the radius), surfaces furthest away from the neutral axis. At least the caudal ulna smoothened first, thus providing stiffness against bending at an early age. © 2005 Wiley‐Liss, Inc.
Synthesis of alveolar bone Sharpey's fibers during experimental tooth movement in the rat
Authors: Johnson Roger B.
Published: March 2005

There is little information concerning the effects of tooth movement on the relative synthesis of bone matrix and Sharpey's fiber collagenous proteins. The purpose of this study was to investigate this situation using radioautographic techniques. The maxillary first molar tooth in rats was tipped toward the midline using an appliance and the animals were injected with 3H‐proline after 3 days and sacrificed 24 hr later. Maxillae were sectioned and silver grain proportional areas (grain density/5,000 μm2) evaluated over Sharpey's fibers and adjacent alveolar bone matrix using computerized densitometry and histomorphometric techniques. These data were compared to a group of untreated animals by Fisher's exact test. At depository surfaces of experimental tissues, the silver grain proportional area over bone matrix was significantly greater than over Sharpey's fibers (P < 0.05) and control bone matrix (P < 0.01). The silver grain proportional area over Sharpey's fibers was not different between the groups. At resorptive surfaces, the silver grain proportional area over both bone matrix and Sharpey's fibers was significantly greater in experimental tissues compared to controls (P < 0.01). Thus, movements of adjacent teeth affect both the quantity and ratios of collagenous protein incorporation into Sharpey's fibers and adjacent alveolar bone, which is dependent on the intensity and characteristics of the force. © 2005 Wiley‐Liss, Inc.
Distribution of extracellular signal‐regulated kinase 1‐ and 2‐activated neurons in the rat periaqueductal gray matter after noxious stimulation
Authors: Gioia Magda , Moscheni Claudia , Gagliano Nicoletta
Published: March 2005

The periaqueductal gray matter (PAG), the midbrain region made up of neuronal columns encircling the cerebral aqueduct, plays a key role in nociception. As the extracellular signal‐regulated kinases (ERKs) 1 and 2 are activated after noxious stimulation, we analyzed the distribution of ERK‐activated neurons in the PAG after visceral noxious stimulation. Ether‐ and urethane‐anesthetized rats received an intraperitoneal injection of acetic acid or were left untreated and were perfused after 2 hr. Serial sections immunoreacted with an antibody selective for the activated ERKs. Significant ERK activation occurred only in the ether‐anesthetized noxious stimulated rats. In these rats, we evaluated the number of ERK‐activated neurons and their density as the ratio of the number of immunolabeled neurons to the extension of the region where they were located. ERK‐activated neurons were more numerous in the lateral (LPAG) and ventrolateral (VLPAG) columns, but without significant differences. No ERK activation was seen in neurons of the most rostral PAG. The ERK‐activated neurons were significantly denser at the intermediate level of the PAG. At the caudal level, they were denser in the LPAG and VLPAG columns, and in the DPAG column at the intermediate and rostral level. These findings suggest that noxious stimulation activates ERKs in neurons involved in the different functional activities related to nociception, overlapping in the PAG columns, and strengthens the role of PAG in integration. © 2005 Wiley‐Liss, Inc.
Generation and structure determination of 5,6‐bis(methylthio)‐4,7‐diethylbenzo[1,2,3]trithiole dication MBT(2+)
Authors: Kimura Takeshi , Ito Kiyohito , Ogawa Satoshi , Sato Ryu , Kawai Yasushi
Published: March 2005

5,6‐Bis(methylthio)‐4,7‐diethylbenzo‐[1,2,3]‐trithiole [MBT] was oxidized with two equivalents of SbCl5 to produce a dication, MBT(2+)ċ2SbCl, as a stable, dark‐brown solid. MBT(2+) was unexpectedly silent for 1H‐NMR in CD3CN, whereas it was active for ESR, suggesting that MBT(2+) is a triplet‐state dication MBT(2+)‐T. Meanwhile, treatment of 5‐ methylsulfinyl‐6‐methylthio‐4,7‐diethylbenzo[1,2,3]‐ trithiole [MBTMO] with D2SO4 produced MBT(2+), whose 1H‐NMR gave no signals, whereas the solution is active for ESR. These results imply that MBT(2+) prepared from MBTMO is a triplet‐state dication, and a singlet‐state dication, MBT(2+)‐S, initially generated by acidification of MBTMO, isomerized to the triplet‐state dication, MBT(2+)‐T. Since MBT(2+)‐T is active for ESR at room temperature, two molecules of MBT(2+)‐T should form a spin pair in the solution with a sufficient distance between the two radical centers. The structures of MBT(2+)‐S and MBT(2+)‐T were optimized with the DFT method at the B3LYP6‐31G** level. The total energy difference between them was calculated to be 7.90 kcal/mol; MBT(2+)‐T was shown to be more stable than MBT(2+)‐S. A treatment of MBTMO with SbCl5 gave a 1:1 complex. The structure of the complex was determined with X‐ray crystallography, which showed that the complex is the corresponding sulfonium salt, MBTMOċSbCl5. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:111–222, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20078
Solvent‐free neat synthetic route to tetrahydroacridinones
Authors: Kidwai M. , Rastogi S.
Published: March 2005

An environmentally benign approach for the synthesis of acridines using inorganic solid supports and “neat reaction'' technology is described. These methodologies completely eliminate the use of solvent during the course of reaction. Moreover, microwave‐assisted reactions reduce the reaction time from hours to minutes with improved yield. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:138–222, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20080
Interaction of 1,2‐alkadienephosphonic dialkyl esters with sulfenyl‐ and selenenylbromides
Authors: Enchev Dobromir D.
Published: March 2005

The reactivity of dialkyl esters of 1, 2‐alkadienephosphonic acids toward sulfenyl‐ and selenenyl‐bromides has been investigated. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:156–222, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20083
Immune responses in mice of β‐galactosidase adsorbed or encapsulated in poly(lactic acid) and poly(lactic‐co‐glycolic acid) microspheres
Authors: Stivaktakis N. , Nikou K. , Panagi Z. , Beletsi A. , Leondiadis L. , Avgoustakis K.
Published: March 2005

The immune response induced in mice by β‐galactosidase (β‐gal) adsorbed or encapsulated on poly(lactic acid) (PLA) and poly(lactic‐co‐glycolic acid) (PLGA) microspheres was investigated. The encapsulated protein elicited higher antibody response than the protein adsorbed on the microspheres in the case of the PLA microspheres. However, the encapsulated protein elicited weaker antibody response than the adsorbed protein in the case of the PLGA (50:50) microspheres, probably because, in this case, the encapsulation process adversely affected protein immunogenicity. In the case of adsorbed β‐gal, higher antibody response was obtained with the PLA microspheres than with the PLGA (50:50) microspheres. This may be related to the lower rate of β‐gal desorption from the PLA microspheres. Based on the immunoglobulin G1/immunoglobulin G2a ratios and the stimulation indices for interferon‐γ and interleukin‐4, β‐gal encapsulated or adsorbed on PLA microspheres induced a Th1‐biased immune response whereas β‐gal encapsulated or adsorbed on PLGA (50:50) microspheres induced a Th2‐biased immune response. The results obtained indicate that more potent immune responses are obtained when the protein is encapsulated than adsorbed on the microspheres, providing that the encapsulation process does not adversely affect protein immunogenicity. Also, the type of polymer used to prepare the microspheres, but not the method of protein association with the microspheres, may affect the type of immune response. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res 73A: 332–338, 2005
Mixed layer evolution in the Sea of Okhotsk observed with profiling floats and its relation to sea ice formation
Authors: Ohshima Kay I. , Riser Stephen C. , Wakatsuchi Masaaki
Published: March 2005

The time evolution of the ocean mixed layer in the seasonal sea ice zone of the Okhotsk Sea has been observed with profiling floats. The heat storage rate in the mixed layer estimated from the float data well coincides with the surface heat flux. Mixed layer deepening and the onset of ice formation can be well reproduced by a bulk mixed layer model, suggesting that onset of ice formation can be predicted by local atmospheric conditions. This explains the remarkably high correlation of the onset day of sea ice formation with the surface heat loss in the preceding fall. The anomalously large heat loss in the fall of 2000 led to the anomalously early ice formation. Strong stratification due to the Amur River fresh water flux is indispensable for ice formation through suppression of deep convection.
Quality, compatibility, and synergy analyses of global aerosol products derived from the advanced very high resolution radiometer and Total Ozone Mapping Spectrometer
Authors: Jeong Myeong‐Jae , Li Zhanqing
Published: March 2005

A number of global aerosol products of varying quality, strengths, and weaknesses have been generated. Presented here are synthetic analyses with regard to the quality, compatibility, and synergy of two long‐term global (1983–2000) aerosol products derived from the advanced very high resolution radiometer (AVHRR) and the Total Ozone Mapping Spectrometer (TOMS). Four essential aerosol parameters, namely, aerosol optical thickness (AOT) from AVHRR under the Global Aerosol Climatology Project (GACP), TOMS AOT, Ångström exponent (AE) from AVHRR, and TOMS aerosol index (AI) are analyzed together with various ancillary data sets on meteorological fields, ocean color, and ground‐based AOT measurements. While the two satellite products reveal some common features, significant discrepancies exist. Reflectances measured at ultraviolet and visible wavelengths from the two sensors are incompatible in terms of the magnitude of AE computed from AOT derived from the two channels. The spatial distributions of the aerosol products from AVHRR and TOMS are complimentary in revealing different aspects of aerosol characteristics. In‐depth analyses were carried out over several regions under the influence of different types of aerosols such as biomass burning, dust, sea salt, air pollution, and their mixtures. A classification algorithm was developed to identify dominant types of aerosols around the globe using aerosol products from the two instruments. Aerosol type information is used to develop and apply relationships between the AVHRR AOT and the TOMS AOT. The latter was used to extend the AOT at 0.55 μm over land around the globe. Comparisons of monthly mean AOTs with AERONET monthly mean AOTs showed a general agreement to within an estimated error range of ±0.08 ± 0.20τ. Finally, a comparison between the estimated AOT with Moderate Resolution Imaging Spectroradiometer (MODIS) AOT over land showed good agreement in terms of magnitude and seasonality, suggesting a means of bridging past and current AOT estimations.
A global view of aerosols from merged transport models, satellite, and ground observations
Authors: Liu Hongqing , Pinker R. T. , Holben B. N.
Published: March 2005

Growing recognition of the importance of natural and anthropogenic aerosols in climate research led to numerous efforts to obtain information on aerosols based on model simulations, satellite remote sensing, and ground observations. This study describes an approach to combine information from independent sources that complement each other in their capabilities to achieve a global characterization of monthly mean clear‐sky daytime aerosol optical depth. The following sources of information have been used: simulations from the Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model; retrievals from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument on the Terra satellite; and measurements from the Aerosol Robotic Network (AERONET). Leading empirical orthogonal functions (EOFs) are used to represent the significant variation signals from model and satellite results; the EOFs are fitted to the ground observations to propagate the AERONET information at a global scale. The methodology is implemented with a 2‐year time record when collocated data from all three sources are available.
Hopping behavior in the Kuramoto–Sivashinsky equation
Authors: Blomgren Peter , Gasner Scott , Palacios Antonio
Published: March 2005

We report the first observations of numerical “hopping” cellular flame patterns found in computer simulations of the Kuramoto–Sivashinsky equation. Hopping states are characterized by nonuniform rotations of a ring of cells, in which individual cells make abrupt changes in their angular positions while they rotate around the ring. Until now, these states have been observed only in experiments but not in truly two-dimensional computer simulations. A modal decomposition analysis of the simulated patterns, via the proper orthogonal decomposition, reveals spatio-temporal behavior in which the overall temporal dynamics is similar to that of equivalent experimental states but the spatial dynamics exhibits a few more features that are not seen in the experiments. Similarities in the temporal behavior and subtle differences in the spatial dynamics between numerical hopping states and their experimental counterparts are discussed in more detail.
Analysis of the carbon-related “blue” luminescence in GaN
Authors: Armitage R. , Yang Q. , Weber E. R.
Published: March 2005

The properties of a broad 2.86-eV photoluminescence band in carbon-doped GaN were studied as a function of C-doping level, temperature, and excitation density. For GaN:C grown by molecular-beam epitaxy (MBE) the 2.86-eV band is observed in Si codoped layers exhibiting high n-type conductivity as well as in semi-insulating material. The peak position of the “blue” luminescence is constant with temperature in MBE GaN, but in semi-insulating GaN:C grown by metal-organic vapor-phase epitaxy it shifts from 3.0to2.86eV with increasing temperature in the range of 12–150K. The 2.86-eV band undergoes thermal quenching from 200to400K with an activation energy of ∼150meV. The characteristics of the 2.86-eV band are consistent with deep donor-deep acceptor recombination originating from carbon defects, under the assumption that the concentrations of these defects are low compared to the total carbon concentration in heavily C-doped samples. For low excitation density (4W∕cm2) the 2.86-eV band intensity decreases as a function of HeCd laser exposure time over a period of many minutes. However, no transient effects are observed for 20W∕cm2 excitation density. The transient behavior can be best explained using a model based on charge-trapping-induced Coulomb barriers which impede the diffusion of carriers to the 2.86-eV luminescence centers.
Magnetic hydrodynamics with asymmetric stress tensor
Authors: Billig Yuly
Published: March 2005

In this paper we study equations of magnetic hydrodynamics with a stress tensor. We interpret this system as the generalized Euler equation associated with an Abelian extension of the Lie algebra of vector fields with a nontrivial 2-cocycle. We use the Lie algebra approach to prove the energy conservation law and the conservation of cross-helicity.
On extensions of superconformal algebras
Authors: Nagi Jasbir
Published: March 2005

Starting from vector fields that preserve a differential form on a Riemann sphere with Grassmann variables, one can construct a superconformal algebra by considering central extensions of the algebra of vector fields. In this paper, the N=4 case is analyzed closely, where the presence of weight zero operators in the field theory forces the introduction of noncentral extensions. How this modifies the existing field theory, representation theory, and Gelfand–Fuchs constructions is discussed. It is also discussed how graded Riemann sphere geometry can be used to give a geometrical description of the central charge in the N=1 theory.
Relation between generalized Bogoliubov and Bogoliubov–de Gennes approaches including Nambu–Goldstone mode
Authors: Mine M. , Okumura M. , Yamanaka Y.
Published: March 2005

The two approaches of consistent quantum field theory for systems of the trapped Bose–Einstein condensates are known, one is the Bogoliubov–de Gennes approach and the other is the generalized Bogoliubov approach. In this paper, we investigate the relation between the two approaches and show that they are formally equivalent to each other. To do this one must carefully treat the Nambu–Goldstone mode which plays a crucial role in the condensation. It is emphasized that the choice of vacuum is physically relevant.
Resonances of CH2(ãA11) and their roles in unimolecular and bimolecular reactions
Authors: Lin Shi Ying , Guo Hua , Farantos Stavros C.
Published: March 2005

Low-lying resonances of the CH2(ãA11) system (J=0) in an accurate ab initio potential energy surface are studied using a filter-diagonalization method. The width of these resonances fluctuates by more than two orders of magnitude and on average increases with the energy. Analysis of the resonance states concludes that the unimolecular decay of the excited molecular system near the dissociation threshold is neither mode specific nor statistical state specific. This is apparently due to remnant regularity embedded in the largely chaotic classical phase space, as evidenced by periodic orbit analysis. As a result, the Rice–Ramsperger–Kassel–Marcus and statistical adiabatic channel models overestimate the average unimolecular decay rate. The implications of the resonances for the bimolecular C(D1)+H2 reaction are also discussed.
Partial fractions expansions and identities for products of Bessel functions
Authors: Rogers Mathew D.
Published: March 2005

We derive several partial fractions expansions for products of Bessel functions, and use them to prove algebraic relationships between infinite series involving squares of Bessel functions. We also give formulas for the Taylor series coefficients of the zeros of Bessel functions, when the zeros are regarded as functions of the order x of Jx(y).
Transformations to diagonal bases in closed-loop quantum learning control experiments
Authors: Cardoza David , Trallero-Herrero Carlos , Langhojer Florian , Rabitz Herschel , Weinacht Thomas
Published: March 2005

This paper discusses transformations between bases used in closed-loop learning control experiments. The goal is to transform to a basis in which the number of control parameters is minimized and in which the parameters act independently. We demonstrate a simple procedure for testing whether a unitary linear transformation (i.e., a rotation amongst the control variables) is sufficient to reduce the search problem to a set of globally independent variables. This concept is demonstrated with closed-loop molecular fragmentation experiments utilizing shaped, ultrafast laser pulses.
Normal and anomalous heat transport in one-dimensional classical lattices
Authors: Prosen Tomaž , Campbell David K.
Published: March 2005

We present analytic and numerical results on several models of one-dimensional (1D) classical lattices with the goal of determining the origins of anomalous heat transport and the conditions for normal transport in these systems. Some of the recent results in the literature are reviewed and several original “toy” models are added that provide key elements to determine which dynamical properties are necessary and which are sufficient for certain types of heat transport. We demonstrate with numerical examples that chaos in the sense of positivity of Lyapunov exponents is neither necessary nor sufficient to guarantee normal transport in 1D lattices. Quite surprisingly, we find that in the absence of momentum conservation, even ergodicity of an isolated system is not necessary for the normal transport. Specifically, we demonstrate clearly the validity of the Fourier law in a pseudo-integrable particle chain.
Master equation approach to charge injection and transport in organic insulators
Authors: Freire José A. , Voss Grasiela
Published: March 2005

We develop a master equation model of a disordered organic insulator sandwiched between metallic electrodes by treating as rate processes both the injection and the internal transport. We show how the master equation model allows for the inclusion of crucial correlation effects in the charge transport, particularly of the Pauli exclusion principle and of space-charge effects, besides, being dependent on just the microscopic form of the transfer rate between the localized electronic states, it allows for the investigation of different microscopic scenarios in the organic, such as polaronic hopping, correlated energy levels, interaction with image charge, etc. The model allows for a separate analysis of the injection and the recombination currents. We find that the disorder, besides increasing the injection current, eliminates the possibility of observation of a Fowler–Nordheim injection current at zero temperature, and that it does not alter the Schottky barrier size of the zero-field thermionic injection current from the value based on the energy difference between the electrode Fermi level and the highest occupied molecular orbital/lowest unoccupied molecular orbital levels in the organic, but it makes the Arrhenius temperature dependence appear at larger temperatures. We investigate how the I(V) characteristics of a device is affected by the presence of correlations in the site energy distribution and by the form of the internal hopping rate, specifically the Miller–Abrahams rate and the Marcus or small-polaron rate. We show that the disorder does not modify significantly the eβE field dependence of the net current due to the Schottky barrier lowering caused by the attraction between the charge and its image in the electrode.
A Brownian dynamics study on the self-diffusion of charged tracers in dilute polyelectrolyte solutions
Authors: Zhou Tong , Chen Shing Bor
Published: March 2005

Brownian dynamics simulations with hydrodynamic interactions are conducted to investigate the self-diffusion of charged tracer particles in a dilute solution of charged polymers, which are modeled by bead-spring chains. The Debye–Hückel approximation is used for the electrostatic interactions. The hydrodynamic interactions are implemented by the Ewald summation of the Rotne–Prager tensor. Our simulations find that the difference in short- and long-time diffusivities is very slight in uncharged short-chain solutions. For charged systems, to the contrary, the difference becomes considerable. The short-time diffusivity is found to increase with increasing chain length, while an opposite behavior is obtained for the long-time diffusivity. The former is attributed to the hydrodynamic screening among beads in a same chain due to the bead connectivity. The latter is explained by the memory effect arising from the electrostatic repulsion and chain length. The incorporation of hydrodynamic interactions improves the agreement between the simulation prediction and the experimental result.
A comparison of Hartree–Fock and exact diagonalization solutions for a model two-electron system
Authors: Thompson David C. , Alavi Ali
Published: March 2005

We compare the restricted (RHF) and unrestricted (UHF) Hartree–Fock solutions with the exact configuration interaction (CI) solutions for the model problem of two interacting electrons confined within an infinite spherical potential of radius R. An investigation of the ground state energy, electron density, and a population analysis of the wave functions reveals that the UHF solution compares favorably with the CI one in both the small and large R limits. The Coulson–Fischer transition (the point at which the RHF and UHF solutions are no longer degenerate) occurs at an rs≡R∕21∕3≈6a.u., close to the crossover rs where the exact CI density acquires a minimum at the sphere center; this behavior captures the onset of Wigner molecule formation. In this regime, however, the HF densities and energies are not quantitatively accurate when compared to the CI ones. This failure is further quantified by computing Ec∕E to determine the ability of each method at capturing the exact correlation energy; we conclude that the UHF solutions can be reasonably accurate at both high and low densities, but not at intermediate rs.
High-pressure phase transitions in SnO2
Authors: Ono S. , Funakoshi K. , Nozawa A. , Kikegawa T.
Published: March 2005

In situ observations of the phase transition in SnO2 were carried out in both a multianvil and a diamond-anvil cell high-pressure apparatus using synchrotron radiation. The phase transition from the α-PbO2-type (space group: Pbcn) to the pyrite-type (space group: Pa-3) structure was observed at high pressures and high temperatures. The phase boundary between the α-PbO2-type and pyrite-type structures in the temperature range of 800–1500 K was found to be given by the relation P(GPa)=16.7(±0.5)−0.0021(±0.0015)[T(K)−1000]. The negative slope of the transition is consistent with the calculated phase boundary between the α-PbO2-type and pyrite-type structures of silica (SiO2). However, our results do not agree with the slope of the phase boundary of germanium dioxide (GeO2), which was reported to have a positive slope. The Birch–Murnaghan equation of state for the pyrite-type phase of SnO2 was determined from the experimental unit-cell parameters, with K0=307(±10)GPa and V0=128.1(±0.3)Å3 with the value of K0′ set to 4.
Effects of nitrogen incorporation on the properties of GaInNAs∕GaAs quantum well structures
Authors: Zhao Q. X. , Wang S. M. , Sadeghi M. , Larsson A. , Willander M. , Yang J. H.
Published: March 2005

We report results from theoretical and experimental investigations of GaInNAs∕GaAs quantum well structures. Optical transition energies for samples with different In and N concentrations were determined by photoluminescence measurements. The results show that the reduction of the ground-state transition energy by the introduction of N decreases with increasing In concentration. The experimental data are compared with calculations using the effective-mass approximation. Modifications of the band-gap energy due to N incorporation were accounted for using the two-level repulsion model. Proper effective-mass and band offset values, based on recent experimental work, were used. Calculated and measured transition energies show good agreement. The critical thickness, lattice constant, strain, and optical transition energies are discussed for GaInNAs∕GaAs quantum well structures tuned for emission at 1.3 and 1.55μm, in particular. Such a simple model, within the effective-mass approximation, is a very useful guide for device design.
Spectroscopic analysis of a-C and a-CNx films prepared by ultrafast high repetition rate pulsed laser deposition
Authors: McCann R. , Roy S. S. , Papakonstantinou P. , McLaughlin J. A. , Ray S. C.
Published: March 2005

The effect of nitrogen partial pressure on amorphous carbon nitride (a-CNx) (0.0⩽x⩽0.17) and laser fluence on amorphous carbon (a-C) films prepared by ultrafast high repetition rate pulsed laser deposition has been studied. The chemical bonding structure of the films was investigated by x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and Fourier transform infrared (FTIR) analysis. XPS studies of films revealed an increase in the CN sites at the expense of CC bonded carbon sites as nitrogen content in the films increased. Films (a-C) prepared as a function of laser fluence showed an increase in sp3-bonded carbon as laser fluence was increased from 0.36 to 1.7J∕cm2. The ID∕IG ratio and G peak position increased as a function of nitrogen whereas the full width at half maximum (FWHM) of the G peak decreased. This is indicative of either an increase in the size or number of the sp2 sites. Films prepared as a function of laser fluence revealed a decrease of the ID∕IG ratio and an increase in the FWHM of the G peak. The use of two visible excitation wavelengths when analyzing the samples indicated a resonant process. FTIR analysis revealed an increase in the peaks attributed to CN bonds as well as indicated a tiny amount of CN bonds within the nitrogen-doped films. Additionally, surface morphology analysis showed a greater particle density on films prepared at the highest laser energy in comparison to those prepared at lower fluences. Film hardness characterized by nanoindentation revealed that films became softer as a function of nitrogen content.
Thermal mismatch strains in sidewall functionalized carbon nanotube/polystyrene nanocomposites
Authors: Hadjiev V. G. , Mitchell C. A. , Arepalli S. , Bahr J. L. , Tour J. M. , Krishnamoorti R.
Published: March 2005

We present an unusual temperature dependence of thermal strains in 4-(10-hydroxy)decyl benzoate (HDB) modified SWNT∕PS (SWNT—single wall carbon nanotube, PS—polystyrene) nanocomposites. The strain transfer from the matrix to nanotubes in these nanocomposites, inferred from the frequency change of the Raman active tangential modes of the nanotubes, is enhanced strongly below 300 K, whereas it is vanishingly small at higher temperatures. The increased strain transfer is suggestive of reinforcement of the HDB-SWNT∕PS nanocomposites at low temperatures. On the other hand, the pristine SWNTs couple weakly to the PS matrix over the entire temperature range of 4.5–410 K. We argue that the strain transfer in HDB-SWNT∕PS is determined by the thermomechanical properties of the interface region composed of polystyrene plasticized by the tethered alkanelike modifier.
A characterization of Rhodamine 640 for optical amplification: Collinear pump and signal gain properties in solutions, thin-film polymer dispersions, and waveguides
Authors: Ramon M. C. , Ariu M. , Xia R. , Bradley D. D. C. , Reilly M. A. , Marinelli C. , Morgan C. N. , Penty R. V. , White I. H.
Published: March 2005

We report a study of the optical signal amplification properties of Rhodamine 640 in solution, in thin-film format dispersed within a poly(methyl methacrylate) (PMMA) polymer matrix, and in a waveguiding structure created by coating polymer-dispersed Rhodamine 640 onto a patterned quartz substrate. The optical signal amplification experiments were carried out using a collinear pump and signal setup. Depending on both pump and signal energies, gains of up to 41 dB were achieved in solution, while 1% by weight dye-doped PMMA films showed net gains of 54cm−1, and associated losses of 16cm−1. Using the same concentration dye/PMMA dispersions, waveguide structures were fabricated with a 120×1μm2 cross section and a length of 1.2 cm. The internal optical gain values measured at 625 and 650 nm were found to be as high as 26 and 8 dB, respectively. The corresponding signal-to-noise ratio was in the 7–21-dB range at 625 nm and in the 3–21-dB range at 650 nm. Both in solution and in the waveguide structures we found that amplified spontaneous emission had a detrimental effect on the optical gain characteristics through a decrease in the signal-to-noise ratio.
Structure and strain relaxation mechanisms of ultrathin epitaxial Pr2O3 films on Si(111)
Authors: Schroeder T. , Lee T.-L. , Libralesso L. , Joumard I. , Zegenhagen J. , Zaumseil P. , Wenger C. , Lupina G. , Lippert G. , Dabrowski J. , Müssig H.-J.
Published: March 2005

The structure of ultrathin epitaxial Pr2O3 films on Si(111) was studied by synchrotron radiation-grazing incidence x-ray diffraction. The oxide film grows as hexagonal Pr2O3 phase with its (0001) plane attached to the Si(111) substrate. The hexagonal (0001) Pr2O3 plane matches the in-plane symmetry of the hexagonal Si(111) surface unit cell by aligning the ⟨101¯0⟩Pr2O3 along the ⟨112¯⟩ Si directions. The small lattice mismatch of 0.5% results in the growth of pseudomorphic oxide films of high crystalline quality with an average domain size of about 50 nm. The critical thickness tc for pseudomorphic growth amounts to 3.0±0.5nm. The relaxation of the oxide film from pseudomorphism to bulk behavior beyond tc causes the introduction of misfit dislocations, the formation of an in-plane small angle mosaicity structure, and the occurence of a phase transition towards a (111) oriented cubic Pr2O3 film structure. The observed phase transition highlights the influence of the epitaxial interface energy on the stability of Pr2O3 phases on Si(111). A mechanism is proposed which transforms the hexagonal (0001) into the cubic (111) Pr2O3 epilayer structure by rearranging the oxygen network but leaving the Pr sublattice almost unmodified.
Work-function changes of treated indium-tin-oxide films for organic light-emitting diodes investigated using scanning surface-potential microscopy
Authors: Chen Sy-Hann
Published: March 2005

Local surface work-function (WF) measurement on indium-tin-oxide (ITO) films prepared by different cleaning methods for use as anode materials in organic light-emitting diodes were studied using scanning surface-potential microscopy. The ITO WF changes with standard wet-cleaning treatment correspond directly to asperities on the film surface. The maximum difference value (MDV) in the local WF reached 0.41eV. However, after wet-cleaning ITO with the ultraviolet ozone or O-plasma treatment, the WF distribution is more uniform than the original distribution. Owing to the sufficient ITO surface oxidization, the mean local WF value increases effectively to more than 5.00eV and the MDV is less than 0.05eV. Furthermore, the changes in roughness and conductivity on the ITO surface at different treatment times are also discussed. The proper exposure time for the O-plasma treatment can thereby be determined.
On the local and nonlocal Camassa–Holm hierarchies
Authors: Casati Paolo , Lorenzoni Paolo , Ortenzi Giovanni , Pedroni Marco
Published: March 2005

We construct the local and nonlocal conserved densities for the Camassa–Holm equation by solving a suitable Riccati equation. We also define a Kadomtsev–Petviashvili extension for the local Camassa–Holm hierarchy.
Coherent anti-Stokes Raman scattering microscopy with spectrally tailored ultrafast pulses
Authors: Porter Rhiannon , Shan Fang , Guo Ting
Published: March 2005

We report a coherenti-Stokes Raman scattering (CARS) microscopy method using tailored ultrafast pulses from a broadband chirped-pulse-amplification Ti: Sapphire laser. Three input waves were obtained at the pulse compressing stage. An air-spaced etalon was used to generate the narrow band waves (2ω1), and a hard aperture mask was used to produce the broadband wave (ω2). Spectral resolution as high as 7cm−1 can be achieved with the etalon, and the temporal resolution was ∼1 picosecond. Two-dimensional (2D) time-resolved vibrational CARS spectrographs covering 820–1500cm−1 were obtained from opaque and transparent thin films.
Size, shape, and ordering of SiGe/Si(001) islands grown by means of liquid phase epitaxy under far-nonequilibrium growth conditions
Authors: Hanke M. , Boeck T. , Gerlitzke A.-K. , Syrowatka F. , Heyroth F. , Köhler R.
Published: March 2005

Applying scanning electron microscopy, we have studied the evolution of shape and lateral positional correlation of Si1−xGex/Si(001) Stranski–Krastanov islands grown by means of liquid phase epitaxy (LPE). However, in contrast to conventional near-equilibrium LPE, a distinctly higher cooling rate of 10 K/min ensures extremly nonequilibrium growth conditions. The facet inclination of subsequent island stages decreases from nearly vertical sidewalls toward {111}- and {101}-type facets. Energy dispersive x-ray microanalysis yields a size-independent germanium content of 8.9% within islands between 760 and 1700 nm base width which is—by more than a factor of 2—smaller than islands of the same concentration grown in a near-equilibrium LPE process. Square-like formations of subsequently smaller islands around a large central island indicate only next to island interactions during the lateral self-assembling.
Examining the screening limit of field effect devices via the metal-insulator transition
Authors: Hong X. , Posadas A. , Ahn C. H.
Published: March 2005

The electronic screening length, the distance over which an electric field is attenuated in a material, imposes a lower physical bound on the lateral size scaling of semiconductor field effect devices. Alternatives will be needed to achieve devices whose characteristic dimensions approach a nanometer. In this work, we demonstrate the atomic-scale nature of screening at high electron densities, using the polarization field of a ferroelectric oxide, Pb(Zr,Ti)O3, to electrostatically modulate the metallicity of ultrathin manganite La1−xSrxMnO3 (LSMO) films near the metal-insulator transition. Within the screening length, the transport characteristics of LSMO vary sharply at the scale of a single atomic layer.
A long-range attraction between aggregating 3T3 cells mediated by near-infrared light scattering
Authors: Albrecht-Buehler Guenter
Published: March 2005

At what range can a mammalian cell sense the presence of another cell and through what medium? To approach these questions, the formation of aggregates of a 3T3 cell variant (3T3
x
cells) grown on solid substrates was studied. Each of the aggregates consisted of cells that, at the time of their seeding, were single and located randomly. Yet somehow they seemed to detect each other within a certain range (
R
a
) and move together to form aggregates. The article describes a simple assay to measure the value of
R
a
. When applied to 3T3
x
cells with altered intensities of near-infrared light scattering (
I
sc
) the assay showed that (
i
)
R
a
was much larger than one cell diameter, and (
ii
)
R
a
was directly related to
I
sc
. The results suggest that near-infrared light scattering by the cells mediate a long-range attraction between them, which does not require physical contact and enables them to detect each other's presence.
Character sheaves on disconnected groups, VII
Authors: Lusztig G.
Published: March 2005

We define and study convolution of parabolic character sheaves. As an application, we attach to any parabolic character sheaf the orbit of a tame local system on the maximal torus under a subgroup of the Weyl group.
Parkinsonism as an initial manifestation of dural arteriovenous fistula
Authors: Lee P. H. , Lee J. S. , Shin D. H. , Kim B. M. , Huh K.
Published: March 2005

Parkinsonism associated with dural arteriovenous fistula (DAVF) has been described rarely; however, isolated parkinsonism as the presenting symptom of DAVF has not been reported. Here, we describe a patient with DAVF showing reversible isolated parkinsonism after embolization, which was well correlated with perfusion status of basal ganglia, suggesting that a perfusion defect was responsible for the pathogenesis of the parkinsonism in our DAVF patient.
Cerebrospinal fluid and serum neuron‐specific enolase concentrations in a normal population*
Authors: Casmiro M. , Maitan S. , De Pasquale F. , Cova V. , Scarpa E. , Vignatelli L. ,   on behalf of the NSE Study Group
Published: March 2005

The aim of this study was to determine cerebrospinal fluid (CSF) and serum neuron‐specific enolase (NSE) concentrations in a normal population and to analyse their relationship with sex and age. The sample was recruited among patients undergoing spinal anaesthesia, without neurological diseases. NSE was determined by means of immunometric assay. One hundred and eight patients (68 men) were recruited. CSF‐NSE concentration was (mean ± SD) 17.3 ± 4.6 ng/ml (men 17.4 ± 4.2, women 17.0 ± 5.2, P = 0.62); serum concentration was 8.7 ± 3.9 ng/ml (men 8.9 ± 3.9, women 8.3 ± 4.0, P = 0.06). The mean CSF/serum NSE ratio was 2.3 ± 0.8 (men 2.2 ± 0.8, women 2.4 ± 0.9, P = 0.22). In both sexes, simple regression analysis showed not significantly increasing concentrations with advancing age for both CSF and serum NSE. Serum and CSF concentrations did not correlate in both sexes. In our study, CSF‐NSE was twice the serum concentration; both were not influenced by sex or age. Serum and CSF‐NSE values vary widely among different studies on normal populations because of different determination methods; therefore, each laboratory should obtain its own reference values. Finally, serum NSE should be used with caution as an indicator of CSF concentration as no correlation could be demonstrated between them in our study.
Central command and the cutaneous vascular response to isometric exercise in heated humans
Authors: Shibasaki Manabu , Secher Niels H. , Johnson John M. , Crandall Craig G.
Published: March 2005

Cutaneous vascular conductance (CVC) decreases during isometric handgrip exercise in heat stressed individuals, and we hypothesized that central command is involved in this response. Seven subjects performed 2 min of isometric handgrip exercise (35% of maximal voluntary contraction) followed by postexercise ischaemia in normothermia and during heat stress (increase in internal temperature ∼1°C). To augment the contribution of central command independent of force generation, on a separate day the protocol was repeated following partial neuromuscular blockade (PNB; i.v. cisatracurium). Forearm skin blood flow was measured by laser‐Doppler flowmetry, and CVC was the ratio of skin blood flow to mean arterial pressure. The PNB attenuated force production despite encouragement to attain the same workload. During the heat stress trials, isometric exercise decreased CVC by ∼12% for both conditions, but did not change CVC in either of the normothermic trials. During isometric exercise in the heat, the increase in mean arterial pressure (MAP) was greater during the control trial relative to the PNB trial (31.0 ± 9.8 versus 18.6 ± 6.4 mmHg, P < 0.01), while the elevation of heart rate tended to be lower (19.4 ± 10.4 versus 27.4 ± 8.1 b.p.m., P= 0.15). During postexercise ischaemia, CVC and MAP returned to pre‐exercise levels in the PNB trial but remained reduced in the control trial. These findings suggest that central command, as well as muscle metabo‐sensitive afferent stimulation, contributes to forearm cutaneous vascular responses in heat stressed humans.
A Constraint Satisfaction Problem Approach Linking Function and Grammar-Based Design Generation to Assembly
Authors: Schmidt Linda C. , Shi Hai , Kerkar Sameer
Published: March 2005

This work presents a constraint satisfaction problem (CSP) approach to design, integrating a function-based design generation algorithm to a geometric modeler. Our long-term goal is to create a unified graph-grammar based designer assistance tool that generates geometrically valid designs from functionally feasible design concepts. This paper introduces the Assembler, a graph-grammar based algorithm that takes a functionally valid but geometrically ambiguous design of a cart made of Meccano Erector Set components and converts it into geometrically valid models of cart designs. Assembler uses grammars to implement solving the CSP formulation of the assembly problem. From the exploration of Assembler’s geometric models, we conclude that the assembly problems of our carts require more sophisticated constraining to generate more realistic designs.
Static Analysis of Tensegrity Structures
Authors: Crane Carl D. , Duffy Joseph , Correa Julio C.
Published: March 2005

Two problems are addressed in this paper. First, the mathematical model to perform the static analysis of an antiprism tensegrity structure subjected to a wide variety of external loads is presented. The virtual work approach is used to deduce the equilibrium equations and a method based on Newton’s Third Law is used to verify the numerical results. Two numerical examples are provided to demonstrate the use of the mathematical model, as well as the verification method. The second problem deals with the development of a mathematical model to perform the static analysis of a prestressed antiprism tensegrity structure subjected to an arbitrary length reduction of its connecting ties. Again, a virtual work approach is used to deduce the equilibrium equations and the numerical results are verified using a Newtonian approach. One example is provided to illustrate the mathematical model.
Finding Geometric Invariants From Time-Based Invariants for Spherical and Spatial Motions
Authors: Roth Bernard
Published: March 2005

This paper shows how the instantaneous invariants for time-independent motions can be obtained from time-dependent motions. Relationships are derived between those parameters that define a time-dependent motion and the parameters that define its geometrically equivalent time-independent motion. The time-independent formulations have the advantage of being simpler than the time dependent ones, and thereby lead to more elegant and parsimonious descriptions of motions properties. The paper starts with a review of the choice of canonical coordinate systems and instantaneous invariants for time-based spherical and spatial motions. It then shows how to convert these descriptions to time-independent motions with the same geometric trajectories. New equations are given that allow the computation of the geometric invariants from time-based invariants. The paper concludes with a detailed example of the third-order motion analysis of the trajectories of an open, spatial R-R chain.