bluuebunny/crossref_metadata_2025 huggingface dataset:
The combustion behavior of polyacrylate ester/graphite oxide composites
Authors: Wang Jianqi , Han Zhidong
Published: January 2006

There is an increasing interest in polymer layered silicate nanocomposites, due to the enhanced properties of these systems. An additional layered system is the graphite oxide system and this has been studied as polyacrylate ester nanocomposites. These have been characterized using X‐ray diffraction and a variety of fire tests. There is a significant change in the oxygen index for nanocomposites which is absent for microcomposites, unlike the situation for the clay‐based systems. X‐ray photoelectron spectroscopy showed that the surface was covered with a graphite oxide‐like material at high temperatures for the nanocomposites, suggesting that this nano‐dimensional material operates as a barrier, exactly as proposed for polymer‐clay systems. Copyright © 2006 John Wiley & Sons, Ltd.
Proteomic analysis of high‐density lipoprotein
Authors: Rezaee Farhad , Casetta Bruno , Levels J. Han M. , Speijer Dave , Meijers Joost C. M.
Published: January 2006

Plasma lipoproteins, such as high‐density lipoprotein (HDL), can serve as carriers for a wide range of proteins that are involved in processes such as lipid metabolism, thrombosis, inflammation and atherosclerosis. The identification of HDL‐associated proteins is essential with regards to understanding these processes at the molecular level. In this study, a combination of proteomic approaches including 1‐DE and 2‐DE MALDI‐TOF, isotope‐coded affinity tag and Western blot analysis were employed to identify proteins associated with human HDL. To minimize potential losses of HDL‐associated proteins during isolation, a one‐step ultracentrifugation technique was applied and the quality of purified HDL was confirmed by nephelometry, high‐performance gel chromatography, and Western blot analysis. MS analysis revealed the presence of 56 HDL‐associated proteins including all known apolipoproteins and lipid transport proteins. Furthermore, proteins involved in hemostasis and thrombosis, the immune and complement system were found. In addition, growth factors, receptors, hormone‐associated proteins and many other proteins were found to be associated with HDL. Our approach thus resulted in the identification of a large number of proteins associated with HDL. The combination of proteomic technologies proved to be a powerful and comprehensive tool for the identification of proteins on HDL.
Curing studies of epoxy resins with phosphorus‐containing amines
Authors: Mercado L. A. , Ribera G. , Galià M. , Cádiz V.
Published: January 2006

The curing system of diglycidyl ether of bisphenol A (DGEBA) with two phosphorus‐containing amine compounds—bis(3‐aminophenyl)methyl phosphine oxide and bis(4‐aminophenyl)‐bis(9,10‐dihydro‐9‐oxa‐10‐oxide‐10‐phosphaphenanthrene‐10‐yl)methane—was studied with differential scanning calorimetry under isothermal and nonisothermal conditions and compared with the DGEBA/diamino diphenyl methane system. The isoconversional method was used to evaluate the dependence of the effective activation energy on the extent of conversion. Modulated differential scanning calorimetry and dynamic mechanical thermal analysis were used to study the phenomena of vitrification and gelation. The thermal and flame‐retardant properties were evaluated, and the limiting oxygen index values of the phosphorylated resins, above 30, confirmed that phosphorus‐containing epoxy resins are effective flame retardants. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1676–1685, 2006
Control of diameter, morphology, and structure of PVDF nanofiber fabricated by electrospray deposition
Authors: Nasir Muhamad , Matsumoto Hidetoshi , Danno Tetsuya , Minagawa Mie , Irisawa Toshihira , Shioya Masatoshi , Tanioka Akihiko
Published: January 2006

Poly(vinylidene fluoride) (PVDF) nanofibers were prepared by electrospray deposition (ESD). To control the diameter, morphology, and structure of PVDF nanofibers, some parameters were investigated, such as polymer concentration, nozzle‐to‐ground collector distance, feeding rate of the polymer solution, and applied voltage. The fabricated fiber was 80–700 nm in diameter. The increase in the polymer concentration caused an increase in the polymer viscosity and fiber diameter. At low polymer concentration (5 wt %), polymer nanoparticles were formed. An increase in applied voltage will increase the fiber diameter. Variation in the nozzle‐to‐ground collector distance did not result in significant changes in the fiber diameter. Increase in the feeding rate of the polymer solution decreased the fiber diameter. Differential scanning calorimetry (DSC) and wide angle X‐ray diffraction (WAXD) measurements showed that the melting point and total crystallinity were decreased. Fourier transform infrared spectroscopy (FTIR) measurement revealed that ESD process induced the formation of the oriented β‐phase PVDF structures. It was also demonstrated that the addition of hydrofluorocarbon solvent to polymer solution remarkably enhanced the formation of β‐phase crystalline structure of PVDF nanofiber. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 779–786, 2006
A query on crystallization temperature‐dependent cooling function under nonisothermal condition
Authors: Shangguan Yonggang , Song Yihu , Zheng Qiang
Published: January 2006

The cooling function (κ) in Ozawa model was investigated through theoretic analysis and experimental method. Different from the fact accepted by researchers over past decades that κ(T) depends only on the crystallization temperature (T) and consequently the parameters for nonisothermal crystallization kinetics could be obtained by plotting ln[− ln(1 − X(T))] versus ln λ at a given T, we found that κ at a given T was also dependent on onset temperature (T0) of crystallization process. Because T0 varies with cooling rate (λ) in nonisothermal crystallization, we conclude that κ is a binary function of T and λ, which was validated by our kinetic data from differential scanning calorimetry measurement in a wide λ range from 1 to 80 °C/min. It is suggested that the conventional method for calculating kinetic parameters based on Ozawa model, by plotting ln[− ln(1 − X(T))] versus ln λ, might not be exact for nonisothermal crystallization. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44:795–800, 2006
Influence of the exchange‐correlation functional in all‐electron calculations of the vibrational frequencies of corundum (α‐Al2O3)
Authors: Montanari B. , Civalleri B. , Zicovich‐Wilson C. M. , Dovesi R.
Published: January 2006

The equilibrium structural parameters, high‐ and low‐frequency dielectric tensors, Born effective charges, and Γ‐point vibrational frequencies of bulk Al2O3 corundum are calculated by using the periodic, ab initio program CRYSTAL, which adopts an all‐electron Gaussian‐type basis set. The effect of basis set and the performance of three different functionals, i.e., LDA, PW91, and B3LYP, are discussed. The mean absolute deviation from the measured frequencies is as small as 7 cm−1 for both the LDA and B3LYP functionals, indicating that these functionals perform extremely well in this case. The mean absolute deviation increases to 18 cm−1 when the PW91 functional is used. All three functionals reproduce the equilibrium geometry of corundum to a high level of accuracy, with LDA and B3LYP outperforming PW91 slightly. The comparison of the current all‐electron calculations with previous plane‐wave, pseudo‐potential calculations shows an overall similar performance. The results of isotopic substitution for both Al and O are also presented. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006
B lymphocyte‐induced maturation protein‐1 (Blimp‐1) is sufficient to trigger an unfolded protein response and XBP‐1 processing in B cells
Authors: Vallabhapurapu Duttu S. , Schimpl Anneliese , Berberich Ingolf
Published: January 2006

Terminal differentiation of B cells into antibody secreting plasma cells is an essential step for eliciting a successful humoral immune response. The two transcription factors B lymphocyte‐induced maturation protein‐1 (Blimp‐1) and X‐box‐binding protein‐1 (XBP‐1) are indispensable for this process. Hereby, XBP‐1 activation depends on Blimp‐1. However, it is not known if Blimp‐1 alone, in the absence of differentiation signals, can induce XBP‐1 processing. Here we show that ectopic expression of Blimp‐1 is sufficient to induce an unfolded protein response (UPR), as evidenced by the generation of the processed form of XBP‐1 and upregulation of the classical UPR target BIP, in both the B cell lymphoma cell line WEHI 231 and in mouse primary splenic B cells. Interestingly, the amino terminal part of Blimp‐1 comprising amino acids 1‐751 was sufficient to induce the above effects while the carboxy terminal part comprising amino acids 465‐856 had no effect. Taken together our results identify Blimp‐1 as the upstream molecule, capable of triggering the UPR in B cells resulting in XBP‐1 processing, which is an important step during plasma cell generation.
Chemical intervention in signalling networks: recent advances and applications
Authors: Tate Edward William
Published: January 2006

Chemical intervention in biological systems is a field undergoing explosive growth, and a growing number of applications in signal transduction have evolved from the rich variety of small molecule and other chemical tools now available for selective modulation of cellular processes. The key enabling factor for the majority of recent discoveries has been close collaboration between chemists and cell biologists, bringing together expertise in the development and application of novel and biologically‐relevant chemistry and an understanding of where these techniques can be brought to bear for greatest effect. The core technologies of chemical genetics, diversity oriented synthesis, high‐throughput screening and microarray technologies have recently been used in various combinations to shed light on an impressive diversity of areas, including neural lipid and auxin signalling, membrane protein co‐localisation, protein kinase engineering, and imaging signalling‐related processes. While further innovation is required to demonstrate the full potential for selective chemical intervention to complement and to a degree supersede pure genetic approaches, it will continue to stimulate ground‐breaking research, in both chemistry and biology, for many years to come.
Some North African Turning Points in Christian Apologetics
Authors: FREND W. H. C.
Published: January 2006

Apologetics take their place beside miracles of healing and courage in the face of persecution as an important means of furthering the early Christian mission. In the first two centuries AD, when the popular perception was that Christianity was closely allied to Judaism, the argument from Old Testament prophecy was important. In the third century, however, as the Church gained ground among the educated classes in east and west, the emphasis changed to an attempt to demonstrate the superiority of Christianity over its pagan rivals as a philosophy with a more convincing understanding of the role of providence. Apologists in the north African tradition, Tertullian, Minucius Felix, Arnobius and Lactantius, all played their part in this process. The prophecies of the Old Testament had to be confirmed by other prophecies, notably the Sibylline oracles and the sayings of Hermes Trismegistus. Finally, in the fourth century, many north Africans who, like Augustine for ten years, adhered to Manichaean Christianity relied wholly on these authorities, rejecting the Old Testament altogether.
Microorganisms in the Malan ice core and their relation to climatic and environmental changes
Authors: Yao Tandong , Xiang Shurong , Zhang Xiaojun , Wang Ninglian , Wang Youqing
Published: January 2006

A 102‐m‐long ice core retrieved from the Malan Ice Cap on the Tibetan Plateau provides us with a historical record of the microorganisms trapped in the ice. The microorganisms in the Malan ice core are identified as α, β, and γ‐Proteobacteia, and the LGC, HGC, and CFB group by means of the results of 16S rRNA sequence analysis and physiological characteristics, while the eukaryotes in the ice core are mainly composed of Chlamydomonas sp. and Pseudochlorella sp. based on the phylogenetic examination of the 18S rRNA gene. The microbial populations show observable differences at different depths in the ice core, reflecting the effects of climatic and environmental changes on the distribution of the microorganisms in the glacier. Examination of the Malan ice core shows four general periods of microbial concentration, which correspond to four phases of temperature revealed by δ18O values in the core. Observations also indicate that microorganism concentrations tend to be negatively correlated with the temperature at a relatively long timescale and, to some extent, positively correlated with mineral concentrations. The present study demonstrates that more microorganisms are associated with colder periods while fewer microorganisms are associated with warm periods, which provides us with a new proxy for the reconstruction of past climatic and environmental changes by means of ice core analysis.
From spatial variation of fracture patterns to fold kinematics: A geomechanical approach
Authors: Bellahsen N. , Fiore P. E. , Pollard D. D.
Published: January 2006

A vertical, compression‐parallel joint set apparently formed at Sheep Mountain Anticline (SMA) during the early Laramide orogeny, prior to significant folding. Field data indicate that these joints occur in fewer locations in the forelimb than in the hinge and backlimb. Using three‐dimensional elastic dislocation models, we show that early slip along an underlying thrust fault can locally perturb the surrounding stress field, inhibiting joint formation above the fault. Thus, we are able to constrain the forelimb kinematics finding that the forelimb was originally located in the hangingwall, above the thrust fault. Furthermore the mode of folding at SMA is constrained: the anticline developed with a fixed hinge and rotating limbs, while the underlying basement rocks deformed internally.
Non‐Newtonian viscosity of basaltic magma
Authors: Sonder I. , Zimanowski B. , Büttner R.
Published: January 2006

Basaltic melt drives most of earth's volcanism. Understanding its rheology is crucial for any model of magma transport and volcanic eruption. Basaltic magma is generally treated as a quasi Newtonian liquid, but there are observations of Non‐Newtonian behaviour. With a method, that allows measurement of Non‐Newtonian viscosity of a representative melt (molten basaltic rock), we found a strong shear rate dependency of viscosity in a wide range of temperatures. The temperature‐viscosity dependency indicates properties of the molten phase as the cause. The viscosity data are in good agreement with a power law model.
Equation of state of antigorite, stability field of serpentines, and seismicity in subduction zones
Authors: Hilairet Nadège , Daniel Isabelle , Reynard Bruno
Published: January 2006

Antigorite, the high‐pressure variety of serpentine, is a major water carrier in subduction zones. Its equation of state, which controls its stability field at high pressure, was determined at ambient temperature up to 10 GPa by in situ synchrotron X‐Ray diffraction in a diamond‐anvil cell. No amorphization, phase transition or hysteresis were detected during compression or decompression. Compression is anisotropic, with the c axis twice as compressible as the others. A fit to the second order Birch‐Murnaghan equation of state gave V0 = 2926.23(50) Å3 and K0 = 67.27(123) GPa. In antigorite the atomic assemblage is denser than in lizardite, which may influence phase stability. The antigorite K0 value obtained here is significantly higher than currently assumed in thermodynamic databases. Antigorite P‐T stability field is re‐evaluated, with major dehydration reaction (and associated potential earthquake) loci occurring at lower pressures, and is found to be consistent with the latest experimental results.
Controls on ocean productivity and air‐sea carbon flux: An adjoint model sensitivity study
Authors: Dutkiewicz S. , Follows M. J. , Heimbach P. , Marshall J.
Published: January 2006

We use the adjoint of a global model of coupled oceanic cycles of carbon, phosphorus and iron to comprehensively and efficiently map the sensitivity of global biological productivity and air‐sea carbon fluxes to local perturbations of the atmospheric iron source sustained for a decade or more. Modeled productivity and carbon flux are found to be most sensitive to enhanced iron sources in high nitrate low chlorophyll regions. The relative response of productivity to an enhanced iron source is greatest in the Equatorial Pacific. Although surface macro‐nutrients are more abundant in the Southern Ocean, nutrient utilization here is critically regulated by light limitation. Our results differ from those of previous studies which imposed depletion of surface nutrients and ignore the availability of light. However, the enhancement of oceanic carbon storage per unit increase in productivity is strongest in the high latitude oceans.
Modeling ocean processes below Fimbulisen, Antarctica
Authors: Smedsrud Lars H. , Jenkins Adrian , Holland David M. , Nøst Ole A.
Published: January 2006

Model simulations of circulation and melting beneath Fimbulisen, Antarctica, obtained using an isopycnic coordinate ocean model, are presented. Model results compare well with available observations of currents and hydrography in the open ocean to the north of Fimbulisen and suggest that Warm Deep Water exists above the level of a sub‐ice‐shelf bedrock sill, the principal pathway for warm waters to enter the sub‐ice‐shelf cavity. The model shows a southward inflow of Warm Deep Water over this sill and into the cavity, producing a mean cavity temperature close to −1.0°C. This leads to high levels of basal melting (>10 m/a) at the grounding line of Jutulstraumen and an average melting over the ice shelf base close to 1.9 m/a. The southward inflow is a compensating flow caused by the northward outflow of fresh, cold water produced by the basal melting. Results on inflow and melting are difficult to validate since no in situ measurements yet exist in the cavity. If such high melt rates are realistic, the mass balance of Fimbulisen must be significantly negative, and the ice shelves along Dronning Maud Land must contribute about 4.4 mSv of melt water to the Weddell Sea, about 15% of the total Antarctic meltwater input to the Southern Ocean.
A reversible minimum-to-minimum mapping method for the calculation of free-energy differences
Authors: Theodorou Doros N.
Published: January 2006

A general method is introduced for the calculation of the free-energy difference between two systems, 0 and 1, with configuration spaces Ω(0), Ω(1) of the same dimensionality. The method relies upon establishing a bijective mapping between disjoint subsets Γi(0) of Ω(0) and corresponding disjoint subsets Γi(1) of Ω(1), and averaging a function of the ratio of configurational integrals over Γi(0) and Γi(1) with respect to the probability densities of the two systems. The mapped subsets Γi(0) and Γi(1) need not span the entire configuration spaces Ω(0) and Ω(1). The method is applied for the calculation of the excess chemical potential μex in a Lennard-Jones (LJ) fluid. In this case, Ω(0) is the configuration space of a (N−1) real molecule plus one ideal-gas molecule system, while Ω(1) is the configuration space of a N real molecule system occupying the same volume. Γi(0) and Γi(1) are constructed from hyperspheres of the same radius centered at minimum-energy configurations of a set of “active” molecules lying within distance a from the ideal-gas molecule and the last real molecule, respectively. An algorithm is described for sampling Γi(0) and Γi(1) given a point in Ω(0) or in Ω(1). The algorithm encompasses three steps: “quenching” (minimization with respect to the active-molecule degrees of freedom), “mutation” (gradual conversion of the ideal-gas molecule into a real molecule, with simultaneous minimization of the energy with respect to the active-molecule degrees of freedom), and “excitation” (generation of points on a hypersphere centered at the active-molecule energy minimum). These steps are also carried out in reverse, as required by the bijective nature of the mapping. The mutation step, which establishes a reversible mapping between energy minima with respect to the active degrees of freedom of systems 0 and 1, ensures that excluded volume interactions emerging in the process of converting the ideal-gas molecule into a real molecule are relieved through appropriate rearrangement of the surrounding active molecules. Thus, the insertion problem plaguing traditional methods for the calculation of chemical potential at high densities is alleviated. Results are presented at two state points of the LJ system for a variety of radii a of the active domain. It is shown that the estimated values of μex are correct in all cases and subject to an order of magnitude lower statistical uncertainty than values based on the same number of Widom [J. Chem. Phys. 39, 2808 (1963)] insertions at high fluid densities. Optimal settings for the new algorithm are identified and distributions of the quantities involved in it [number of active molecules, energy at the sampled minima of systems 0 and 1, and free-energy differences between subsets Γi(0) and Γi(1) that are mapped onto each other] are explored.
Catalytic spatiotemporal thermal patterns during CO oxidation on cylindrical surfaces: Experiments and simulations
Authors: Digilov Rafael M. , Nekhamkina Olga , Sheintuch Moshe
Published: January 2006

Dynamics of spatiotemporal thermal patterns during the catalytic CO oxidation over Pd supported on a glass-fiber catalytic cloth rolled into a tube of 20 mm diameter and 80 mm length has been studied in a continuous flow reactor by IR thermography. A specially designed aluminum mirror built in the reactor provided image of the entire surface of the horizontally held catalytic tube. With flow in the main axial direction and through the tube surface, we observed periodic motions of a pulse, which was born downstream and propagated upstream. The temperature pulse motion was accompanied by conversion oscillations of CO2. With flow in the main axial direction, parallel to the surface, we observed a stationary hot zone after an oscillatory transient. These patterns can be simulated with a plug-flow-reactor-like heterogeneous reactor model that incorporates previously determined kinetic and transport parameters.
Recursive parametrization and invariant phases of unitary matrices
Authors: Jarlskog C.
Published: January 2006

We present further properties of a previously proposed recursive scheme for parametrization of n-by-n unitary matrices. We show that the factors in the recursive formula may be introduced in any desired order. The method is used to study the invariant phases of unitary matrices. The case of four-by-four unitary matrices is investigated in detail. We also address the question of how to construct symmetric unitary matrices (i.e., unitary matrices U that satisfy the condition Uij=Uji) using the recursive approach.
Elastic light scattering from nanoparticles by monochromatic vacuum-ultraviolet radiation
Authors: Shu Jinian , Wilson Kevin R. , Ahmed Musahid , Leone Stephen R. , Graf Christina , Rühl Eckart
Published: January 2006

Elastic light scattering is reported using monochromatic vacuum-ultraviolet radiation to study free, spherical silica nanoparticles prepared by approaches from colloidal chemistry, with diameters between 100 and 240nm. The colloidal nanoparticles of defined size are transferred from an aqueous solution into the gas phase using a particle beam experiment. After focusing of the particle beam by an aerodynamic lens, the scattered light from monochromatic synchrotron radiation is measured. Angle-resolved elastically scattered light is detected, showing a strong forward-scattering component. Additional evidence for the detection of elastically scattered light comes from plotting the scattered light intensity as a function of the dimensionless parameter qR, where q is the magnitude of the scattering wave vector and R is the particle radius. This yields different power-law regimes that are assigned to scattering from the surface and the bulk of the nanoparticles. Furthermore, there is evidence for modulations in the scattered light intensity as a function of scattering angle, which is clearly distinguished from the forward-scattering component. The experimental results are compared to Mie scattering simulations for isolated particles, yielding general agreement with the experimental results. Deviations from Mie simulations are observed for samples consisting of significant amounts of aggregates. The present results indicate that the optical properties of free nanoparticles are sensitively probed by vacuum-ultraviolet radiation.
Determinant representation of correlation functions for the Uq(gl(1∣1)) free Fermion model
Authors: Zhao Shao-You , Yang Wen-Li , Zhang Yao-Zhong
Published: January 2006

With the help of the factorizing F-matrix, the scalar products of the Uq(gl(1∣1)) free fermion model are represented by determinants. By means of these results, we obtain the determinant representations of correlation functions of the model.
Distributed Gaussian polynomials as q-oscillator eigenfunctions
Authors: Karabulut Hasan
Published: January 2006

Karabulut and Sibert [J. Math. Phys. 38, 4815 (1997)] have constructed an orthogonal set of functions from linear combinations of equally spaced Gaussians. In this paper we show that they are actually eigenfunctions of a q-oscillator in coordinate representation. We also reinterpret the coordinate representation example of q-oscillator given by Macfarlane as the functions orthogonal with respect to an unusual inner product definition. It is shown that the eigenfunctions in both q-oscillator examples are infinitely degenerate.
0.9
T
static magnetic field and temperature-controlled specimen environment for use with general-purpose optical microscopes
Authors: Harroun T. A. , Desrochers C. M. , Nieh M.-P. , Watson M. J. , Katsaras J.
Published: January 2006

We describe the addition of a simple, low-cost 0.9T fixed magnetic field to a commercially available, variable-temperature sample environment suitable for optical microscopy. The magnetic field is achieved with the use of Fe–Nd–B rare-earth permanent magnets and steel yoke assembly, packaged into a Linkam Scientific Instruments model THMS600 heating and cooling stage. We demonstrate its effectiveness with examples of magnetic ordering of a lipid/water system doped with paramagnetic Tm3+ ions in the presence and absence of the applied magnetic field and at different temperatures.
Complementarity and clustering in a simple model mixed bilayer
Authors: Khanna Kunal , Chang Ted T. , Kindt James T.
Published: January 2006

A bilayer of uniform thickness containing a mixture of long and short lipids is simulated using a parallel hard-rod model to illustrate the effect of transbilayer repulsions between the tails of the long component. Monte Carlo simulations show considerable entropy-driven clustering within each layer. Demixing reaches a maximum at the highest packing fraction of the liquid state and decreases as the system orders. The formation of complementary clusters of long and short rods on opposite sides of the bilayer increases translational freedom within each cluster by reducing constraints imposed by the opposing leaflet, an effect that becomes less important as rods lock into facing hexagonally ordered arrays.
Modeling of band gap properties of GaInNP alloys lattice matched to GaAs
Authors: Buyanova I. A. , Izadifard M. , Chen W. M. , Hong Y. G. , Tu C. W.
Published: January 2006

Compositional and temperature dependences of the band gap energies of GaInNP alloys, which are lattice matched to GaAs, are determined and modeled by a band anticrossing (BAC) interaction between the localized state of the isolated NP and extended host states. The BAC parameters are deduced as EN=2.1±0.1eV and CMN=1.7±0.2eV. The low value of the coupling parameter CMN implies weaker coupling of the N level with the host matrix, presumably due to short range ordering effects, similar to the case of GaInNAs alloys with a high In content. The obtained information is important for future modeling of the electronic structure of the alloys.
Metamaterial with randomized patterns for negative refraction of electromagnetic waves
Authors: Chen H. , Ran L. , Wang D. , Huangfu J. , Jiang Q. , Kong J. A.
Published: January 2006

Artificial metamaterials made to date are all periodic in structure. Here we show that by randomizing contour patterns deposited lithographically on circuit board materials, a metamaterial characterized by a constitutive relation with negative constitutive parameters is produced in solid-state form. We clearly demonstrate the phenomenon of negative refraction to show that it is not produced by periodicity. This underlines the importance of using constitutive relations for media characterization in electromagnetic theory and suggests that metamaterials could be realized with composite materials or fabricated with various techniques by using versatile hosting materials.
Electrospinning of silica nanochannels for single molecule detection
Authors: Wang Miao , Jing Nan , Su Chin B. , Kameoka Jun , Chou Chao-Kai , Hung Mien-Chie , Chang Kuang-An
Published: January 2006

We have fabricated silica nanochannels with inner diameter as small as 20nm using a scanned coaxial electrospinning and demonstrated their application for single molecule detection. A coaxial jet, with the use of motor oil as the core and silica sol-gel solution as the shell, is extruded through a coaxial source and deposited on the rotating collector as oriented nanofibers. They are then annealed to cross-link silica and eliminate motor oil, thereby forming nanochannels. Subsequently, a fluorescent dye was injected into the individual nanochannels via a capillary force and single molecule detection was performed by monitoring the photon signals from 5-Iodoacetamidofluorescein.
Optical phase characterization of active semiconductor microdisk resonators in transmission
Authors: Stapleton Andrew , Farrell Stephen , Akhavan Hooman , Shafiiha Roshanak , Peng Zhen , Choi Seung-June , O’Brien John , Dapkus P. Daniel , Marshall William
Published: January 2006

The optical phase characteristics of an indium phosphide (InP) vertically coupled microdisk were experimentally demonstrated. Overcoming the material losses by injecting current into the active quantum well microdisk layer has allowed us to observe the phase behavior in all three coupling regimes. The ability to tune the resonant wavelength of this device makes it suitable for use as a phase modulator or tunable optical delay element.
Catchment characteristics and chemical limnology of small lakes, tarns and mire pools in New Zealand (South Island) and Tasmania
Authors: Vanhoutte Koenraad , Verleyen Elie , Kilroy Cathy , Sabbe Koen , Dasseville Renaat , Vyverman Wim
Published: January 2006

Small alpine water bodies can play a large role in defining patterns of biological and landscape diversity, and may be particularly sensitive to climate change. A large limnological dataset, consisting of 65 and 6 water bodies, respectively, on South Island and Stewart Island (New Zealand) and 76 and 12 water bodies, respectively, in the Tasmanian highlands and coastal areas (Australia), was constructed to assess patterns of variation in alpine and subalpine lakes in the Australasian region. With the exception of the coastal systems, most lakes were very dilute. In general, lake water chemistry resembled world average seawater cationic ratios (WASW). In addition, some New Zealand lakes fell close to the world average freshwater cationic ratios (WAFW), due to relatively high calcium concentrations, and some were dominated by magnesium due to the presence of serpentine bedrock in the catchment area. Multivariate analyses of the joint dataset revealed that the variation in chemical limnological variables was dominated by gradients in conductivity, pH and gilvin. The concurrent relationships between pH, calcium and gilvin, which enabled the differentiation of Tasmanian water bodies into limnological provinces, were absent in New Zealand. In the latter, pH and gilvin contents were not coincident, as clear-water acidic systems occurred in New Zealand. The higher diversity of freshwater bodies in New Zealand will enable independent assessment of the effects of pH and gilvin on the distribution and diversity of biota.
The brain-specific double-stranded RNA-binding protein Staufen2 is required for dendritic spine morphogenesis
Authors: Goetze Bernhard , Tuebing Fabian , Xie Yunli , Dorostkar Mario M. , Thomas Sabine , Pehl Ulrich , Boehm Stefan , Macchi Paolo , Kiebler Michael A.
Published: January 2006

Mammalian Staufen2 (Stau2) is a member of the double-stranded RNA-binding protein family. Its expression is largely restricted to the brain. It is thought to play a role in the delivery of RNA to dendrites of polarized neurons. To investigate the function of Stau2 in mature neurons, we interfered with Stau2 expression by RNA interference (RNAi). Mature neurons lacking Stau2 displayed a significant reduction in the number of dendritic spines and an increase in filopodia-like structures. The number of PSD95-positive synapses and miniature excitatory postsynaptic currents were markedly reduced in Stau2 down-regulated neurons. Akin effects were caused by overexpression of dominant-negative Stau2. The observed phenotype could be rescued by overexpression of two RNAi cleavage-resistant Stau2 isoforms. In situ hybridization revealed reduced expression levels of β-actin mRNA and fewer dendritic β-actin mRNPs in Stau2 down-regulated neurons. Thus, our data suggest an important role for Stau2 in the formation and maintenance of dendritic spines of hippocampal neurons.
Structural transitions in the synaptic SNARE complex during Ca2+-triggered exocytosis
Authors: Han Xue , Jackson Meyer B.
Published: January 2006

The synaptic SNARE complex is a highly stable four-helix bundle that links the vesicle and plasma membranes and plays an essential role in the Ca2+-triggered release of neurotransmitters and hormones. An understanding has yet to be achieved of how this complex assembles and undergoes structural transitions during exocytosis. To investigate this question, we have mutated residues within the hydrophobic core of the SNARE complex along the entire length of all four chains and examined the consequences using amperometry to measure fusion pore opening and dilation. Mutations throughout the SNARE complex reduced two distinct rate processes before fusion pore opening to different degrees. These results suggest that two distinct, fully assembled conformations of the SNARE complex drive transitions leading to open fusion pores. In contrast, a smaller number of mutations that were scattered through the SNARE complex but were somewhat concentrated in the membrane-distal half stabilized open fusion pores. These results suggest that a structural transition within a partially disassembled complex drives the dilation of open fusion pores. The dependence of these three rate processes on position within the SNARE complex does not support vectorial SNARE complex zipping during exocytosis.
CMPZ– an algorithm for the efficient comparison of periodic structures
Authors: Hundt R. , Schön J. C. , Jansen M.
Published: January 2006

The systematic comparison of the atomic structure of solid compounds has become an important task in crystallography, chemistry, physics and materials science, in particular in the context of structure prediction and structure determination of crystalline solids. In this work, an efficient and robust algorithm for the comparison of periodic structures is presented, which is based on the mapping of the point patterns of the two structures into each other. This algorithm has been implemented as the moduleCMPZin the structure visualization and analysis programKPLOT.
Structure of the quaternary alloy Zn0.6Mn0.4In2S4from synchrotron powder diffraction and electron transmission microscopy
Authors: Ávila-Godoy Rosario , Mora Asiloé J. , Acosta-Najarro Dwight R. , Delgado Gerzon E. , López-Rivera Santos A. , Fitch Andrew N. , Mora Andrés E. , Steeds John W.
Published: January 2006

The aim of the present work was to determine the structure of the quaternary alloy Zn0.6Mn0.4In2S4and to locate the Mn2+. This was accomplished by means of powder synchrotron X-ray diffraction, high-resolution microscopy and convergent-beam electron diffraction (CBED). The powder X-ray diffraction pattern was indexed in a rhombohedral cell, with cell constantsa= 3.875 (2),c= 37.208 (4) Å, and possible space groupsR\bar{3}morR3m. Rietveld refinements using different cationic arrangements in these space groups were performed. A model in space groupR3m, in which the tetrahedral and octahedral sites were occupied by different proportions of Zn, Mn and In atoms, gave the best result. The Rietveld refinement of this model led to figures of meritRwp= 9.8%,Rp= 9.1% and χ2= 11.1. Selected-area electron diffraction patterns and high-resolution transmission electron micrographs along [001] reveal the rhombohedral configuration. CBED patterns perpendicular to [001], showing the distinctive 3msymmetry, confirmed space groupR3mand the breaking of the centrosymmetry of the parent compound, ZnIn2S4.
On the reliability of fully automatic indexing of electron diffraction patterns obtained in a transmission electron microscope
Authors: Morawiec A. , Bouzy E.
Published: January 2006

Orientation maps similar to electron backscatter diffraction maps can be obtained in a transmission electron microscope. A method of such mapping by automatic indexing of electron diffraction patterns has been proposed recently. The procedure is relatively simple and fast but it does not avoid the 180° ambiguity. Using tests on simulated patterns, it is shown that under current practice automatic indexing may give a considerable fraction of erroneous solutions. Optimization of measurement conditions leading to a reduction of that fraction is considered.
A simple method of shielding area detectors from unwanted Bragg diffraction
Authors: Fábry Jan , Kopecký Miloš , Kub Jiří
Published: January 2006

Shielding of unwanted Bragg diffraction is performed by tiny permanent magnets made from SmCo5. The magnets are situated on a non-absorbing foil that is fixed tightly in a metal frame situated between the sample and the detector.
Analytic determination of the three-dimensional distribution of dislocations using synchrotron X-ray topography
Authors: Yi J. M. , Chu Y. S. , Argunova T. S. , Je J. H.
Published: January 2006

A technique, using a symmetric reflectionviaazimuthal rotation of a sample, is presented for characterization of the three-dimensional distribution of dislocations in single crystals. An analytic formula is derived to transform the three-dimensional geometry of a straight dislocation into its two-dimensional projection onto the detector plane. By fitting topographs to the formula, the orientations and locations of dislocations are quantitatively determined. The dislocations in a thermally stressed Si wafer are examined as an example.
SAXS instruments with slit collimation: investigation of resolution and flux
Authors: Fritz Gerhard , Bergmann Alexander
Published: January 2006

Six small-angle X-ray cameras with block collimation systems were simulated, namely the original Kratky camera, a high-flux version of the Kratky camera, a SAXSess (Anton Parr) camera with a focusing mirror in a linear collimation setup and in a pin-hole setup, as well as a similar camera with a parallelizing mirror in a linear and a pin-hole setup. Their performance was examined using Monte Carlo ray-tracing. The Kratky and the SAXSess camera gave resolutions of 64–65 nm, the high-flux Kratky camera gave a resolution of 44 nm, and the camera with parallelizing mirror gave a resolution of 32 nm. The flux of the camera with parallelizing mirror was 1.47 times higher than for the SAXSess camera, and 18.6 times the flux of the Kratky camera. On changing the alignment, the camera with parallelizing mirror exhibited the best performance up to a resolution of 44 nm; the SAXSess camera was better for higher resolutions. Experimental flux measurements agree if no collimation system is added. Measurements of beam profiles and flux including collimation systems show only qualitative agreement because of user-dependent factors during alignment.
Design and implementation of a simple and inexpensive GISAXS sample chamber
Authors: Groves Michael N. , Singh Marsha A. , Beydaghyan Gisia , Muller Matthew S. , Sheridan Emily , Schneider Dieter K.
Published: January 2006

Anin situsample chamber designed for synchrotron grazing-incidence small-angle X-ray scattering measurements of polymer film microstructure as a function of temperature is described. The chamber operates in a He environment and can be used to perform thermal quenching measurements for time-dependent monitoring of phase transformation kinetics. Preliminary data on a symmetric styrene–butadiene polymer are presented.
Measurement of the mechanical properties of the skin using the suction test
Authors: Khatyr Fouad , Imberdis Claude , Varchon Daniel , Lagarde Jean‐Michel , Josse Gwendal
Published: January 2006

Introduction: The suction test is commonly used to study the mechanical properties of human skin in vivo. The unevenness of the stress fields complicates obtaining the intrinsic mechanical parameters of the skin in vivo because the values of the local stresses and deformations cannot be calculated directly from the displacements and forces applied by the test apparatus. In general, users only take into account the negative pressure applied and the elevation of the dome of skin drawn up in order to deduce the properties of the skin. This method has the major disadvantage of being dependent on the experimental conditions used: in particular, the size of the suction cup and the negative pressure applied. Here, we propose a full mechanical study of the test to provide rigorous results. We compare the frequently used geometric method (making the thin plate hypothesis), Timoshenko's method (which can take greater plate thicknesses into account) and finally various results obtained by the finite elements (FE) technique.

Methods: The suction test was modelled by FE with large displacements and large deformations both for orthotropic and isotropic plates. The results obtained in the elastic domain for various values of Young's modulus and of applied negative pressure were used as references and were compared with methods using analytical relationships.

Results: The geometric method generally used in the interpretation of suction tests gives results, which in certain configurations, are very different from those obtained by FE. The method of Timoshenko is suited to thick plates ‘in contact’ or embedded round the edge, the elevation of the dome and the tension and flexion stresss are analytically accessible through relationships involving four constants that are dependent on the limit conditions. Comparison with the FE results enabled the optimisation of the coefficients to adapt the relationships to the particular conditions of the suction trials.

Conclusion: We showed the limits of the geometrical method and proposed a solution, which while remaining simple to use, gives results that are closer to reality both for the calculation of the modulus and for the determination of the state of the stresses obtained.
Digital camera images obtained using a light‐emitting diode illuminator and their dermatological applications
Authors: Ahn Hyo Hyun , Kim Soo Nam , Kye Young Chul
Published: January 2006

Background/purpose: Although digital cameras have powerful macrocapabilities, flash macrophotographs are often unsatisfactory. The aim of this study was to develop a light‐emitting diode (LED) illuminator for macro digital photography that allows colorimetric investigations of the skin.

Methods: We devised an LED illuminator suitable for acquiring super‐macro digital images of the skin. Reference CIELAB color chart values were compared statistically with computed values from digital images in order to obtain equations for real CIELAB values. Using these, we acquired and analyzed images of various dermatological conditions using an LED illuminator.

Results: The images obtained with the devised LED illuminator were more reproducible than flash‐assisted photographs. With proper camera settings, the devised LED illuminator and the color analysis method developed during this study provided digital skin images containing colorimetric information.

Conclusion: A digital camera equipped with an LED illuminator is a useful tool for dermatological research and clinical practice.
High‐resolution ultrasound reflex transmission imaging and digital photography: potential tools for the quantitative assessment of pigmented lesions
Authors: Rallan D. , Dickson M. , Bush N. L. , Harland C. C. , Mortimer P. , Bamber J. C.
Published: January 2006

Background/aims: High‐resolution ultrasound (HRU) is a relatively cheap imaging method that shows small quantitative differences between benign naevi and melanoma. Previous studies using B‐mode display suggest that these arise from their differing attenuating properties. Attenuation characteristics, however, are better evaluated using reflex transmission imaging (RTI). White light clinical (WLC) photography is an even cheaper imaging method that is routinely used for monitoring but less frequently in everyday diagnosis. As features from each method may have an independent origin, two such modalities may be of greater diagnostic value than either method alone. However, although quantitative analysis of digital photographs is being developed to aid tumour diagnosis, in vivo RTI for the evaluation of pigmented skin lesions has not previously been described. This paper presents the feasibility of performing RTI in vivo and evaluates the reliability of the objective features used. The potential of the combination of quantitative RTI and white light (WL) digital photography data for the classification of pigmented lesions was assessed.

Methods: Randomly selected patients were recruited via a skin cancer screening clinic. RTI data were acquired from each index lesion with a 20 MHz single‐element scanner. WL images were taken using a high‐resolution (2.8 Mpixels) digital camera. Quantitative features calculated from both images were used to derive a discriminant rule. This equation was then applied to reclassify each case based on its quantitative criteria. The resultant classification was compared with histological diagnosis.

Results: Twenty‐four lesions (10 melanoma and 14 naevi) were studied. On RTI, no subjective differences were observed between benign naevi and melanoma. Many lesions were either not visible on RTI or lacked clearly definable borders. Consequently, the WL photographs were used to draw lesion boundaries on RT images for feature calculation. Melanoma were less attenuating than naevi on RTI (P=0.026) and had greater red colour variegation on WL imaging (P=0.016). The combination of quantitative parameters (two from RTI and four from photographs) improved sensitivity for this sample without compromising the specificity of 100% compared with either modality alone. The procedure is highly reproducible (r=0.85 between two operators).

Conclusions: Pigmented skin lesions can be quantitatively defined from RTI data acquired in vivo and a significant difference in attenuation is shown. However, accurate registration of the RT image with a corresponding photograph was crucial for this purpose and only possible when corresponding points could be reliably identified on both images. Combination of features from ultrasound and optical images may synergistically improve diagnostic accuracy and a larger study is warranted to investigate this.