bluuebunny/crossref_metadata_2025 huggingface dataset:
Preliminary Identification of β-Carotene in the Vitreous Asteroid Bodies by Micro-Raman Spectroscopy and HPLC Analysis
Authors: Lin Shan-Yang , Chen Ko-Hua , Cheng Wen-Ting , Ho Chi-Tien , Wang Shun-Li
Published: March 2007

β-carotene was first identified from the vitreous asteroid bodies (ABs) excised from one patient with asteroid hyalosis (AH) by confocal Raman microspectroscopy and was also verified by high performance liquid chromatography (HPLC). Two patients had been diagnosed with AH and intervened by surgical vitrectomy due to blurred vision. The morphology and components of both AB specimens were observed by optical microscopy and determined by using confocal Raman microspectroscopy and HPLC analysis, respectively. Surprisingly, two unique peaks at 1528 and 1157 cm−1were found in the Raman spectrum for the AB specimen of patient 1 alone, which were in close agreement with that of the Raman peaks at 1525 and 1158 cm−1for β-carotene and/or lutein. However, HPLC analytical data clearly indicated that the retention time for the extracted sample from the AB specimen of patient 1 was observed at 13.685 min and just identical to that of β-carotene (13.759 min) rather than lutein (2.978 min). In addition, the lack of any peak in the HPLC profile for the AB specimen of patient 2 also confirmed the absence of Raman peaks at 1525 and 1158 cm−1. Thus this preliminary study strongly suggests that β-carotene as a unique component of ABs was specifically detected from the AB specimen of one AH patient by using confocal Raman microspectroscopy and HPLC analysis.
Analytical TEM Examinations of CoPt-TiO2 Perpendicular
Magnetic Recording Media
Authors: Risner Juliet D. , Nolan Thomas P. , Bentley James , Girt Erol , IV Samuel D. Harkness , Sinclair Robert
Published: March 2007

For this analytical TEM study, nonmagnetic oxygen-rich boundaries were
introduced into Co-Pt-alloy perpendicular recording media by cosputtering
Co and Pt with TiO2. Increasing the TiO2 content
resulted in changes to the microstructure and elemental distribution
within grains and boundaries in these films. EFTEM imaging was used to
generate composition maps spanning many tens of grains, thereby giving an
overall depiction of the changes in elemental distribution occurring with
increasing TiO2 content. Comparing EFTEM with spectrum-imaging
maps created by high-resolution STEM with EDXS and EELS enabled both
corroboration of EFTEM results and quantification of the chemical
composition within individual grain boundary areas. The difficulty of
interpreting data from EDXS for these extremely thin films is discussed.
Increasing the TiO2 content of the media was found to create
more uniformly wide Ti- and O-rich grain boundaries as well as Ti- and
O-rich regions within grains.
The therapeutic potential of gene transfer for the treatment of peripheral neuropathies
Authors: Goss James R.
Published: March 2007

Peripheral neuropathy is a common medical problem with numerous aetiologies. Unfortunately, for the majority of cases there is no available medical solution for the underlying cause, and the only option is to try to treat the resulting symptoms. Treatment options exist when neuropathy results in positive symptoms such as pain, but there is a significant lack of treatments for negative symptoms such as numbness and weakness. Systemic application of growth factor peptides has shown promise in protecting nerves from neuropathic insults in preclinical animal studies, but translation into human trials has been problematic and disappointing. Significant advancements have been made in the past few years in utilising gene therapy approaches to treat peripheral neuropathy by expressing neuroprotective gene products either systemically or in specific nervous tissues. For example, plasmids expressing vascular endothelial growth factor injected into muscle, or herpes-simplex-virus-based vectors expressing neurotrophin gene products delivered to dorsal root ganglion neurons, have been used to protect peripheral nerve function in animal models of diabetes-associated peripheral neuropathy. Many published studies support the feasibility of this approach, although several questions still need to be addressed as gene therapy to treat peripheral neuropathy moves out of the laboratory and into the clinic.
A reduction scheme for coupled multicomponent transport‐reaction problems in porous media: Generalization to problems with heterogeneous equilibrium reactions
Authors: Kräutle S. , Knabner P.
Published: March 2007

In this article a systematic approach for the efficient computation of the transport and reaction of a multispecies, multireaction system is proposed. The objective of this approach is to reformulate the given system of differential or differential‐algebraic equations in such a way that the couplings and the nonlinearities are concentrated in a reduced number of equations (if compared to the original formulation), while some linear equations decouple from the system. The resulting system is handled in the spirit of a global implicit approach (“one step method”) avoiding operator splitting techniques. The reduction of the problem size proposed in this article helps to limit the large computational costs of numerical simulations for such problems. The reduction mechanism is a generalization of the method proposed in a previous paper. Now, problems with mixed mobile/immobile species, homogeneous/heterogeneous kinetic/equilibrium reactions are considered, while the previous publication was restricted to problems without heterogeneous equilibrium reactions (such as equilibrium sorption). An application of the reduction mechanism to an example problem is given in order to investigate the reduction of the number of coupled nonlinear equations and to compare it to other methods.
Deep ocean biogeochemistry of silicic acid and nitrate
Authors: Sarmiento J. L. , Simeon J. , Gnanadesikan A. , Gruber N. , Key R. M. , Schlitzer R.
Published: March 2007

Observations of silicic acid and nitrate along the lower branch of the global conveyor belt circulation show that silicic acid accumulation by diatom opal dissolution occurs at 6.4 times the rate of nitrate addition by organic matter remineralization. The export of opal and organic matter from the surface ocean occurs at a Si:N mole ratio that is much smaller than this almost everywhere (cf. Sarmiento et al., 2004). The preferential increase of silicic acid over nitrate as the deep circulation progresses from the North Atlantic to the North Pacific is generally interpreted as requiring deep dissolution of opal together with shallow remineralization of organic matter (Broecker, 1991). However, Sarmiento et al. (2004) showed that the primary reason for the low silicic acid concentration of the upper ocean is that the waters feeding the main thermocline from the surface Southern Ocean are depleted in silicic acid relative to nitrate. By implication, the same Southern Ocean processes that deplete the silicic acid in the surface Southern Ocean must also be responsible for the enhanced silicic acid concentration of the deep ocean. We use observations and results from an updated version of the adjoint model of Schlitzer (2000) to confirm that this indeed the case.
Zeolite compositions as proxies for eruptive paleoenvironment
Authors: Johnson Joanne S. , Smellie John L.
Published: March 2007

We report chemical compositions of authigenic alteration minerals in subglacially erupted hyaloclastite breccias from James Ross Island, Antarctica, which provide a geochemical proxy for paleoenvironment. Analyses of zeolites (phillipsite and chabazite) from several lava‐fed deltas on the island were compared with published compositions of zeolites from known freshwater and marine environments. Using values of (Na + K)/Ca = 3.0 (for phillipsites) and 1.0 (for chabazites), the data successfully distinguish between marine and freshwater alteration. However, our study also suggests that volcanic breccias may not be sealed to fluids, even when the pore spaces are completely filled. The James Ross Island data show that, at higher elevations in lava‐fed deltas, the zeolites preserve their original freshwater‐influenced (i.e., glacial) compositions, whereas at lower elevations, (Na + K)/Ca ratios are generally higher and indicate a later marine influence. We suggest that water may penetrate several kilometers into the volcanic pile by movement along fractures and/or grain boundaries.
Diffusion plateaus in the velocity distributions of fast solar wind protons
Authors: Heuer M. , Marsch E.
Published: March 2007

In a collisionless plasma, such as the fast solar wind, wave‐particle interactions play the decisive role in determining the shape of particle velocity distribution functions (VDFs). In this paper we provide observational evidence for cyclotron‐resonant interaction of ion cyclotron Alfvén waves, which propagate outward from the Sun along the interplanetary magnetic field, with fast solar wind protons. According to quasi‐linear theory, the protons thereby diffuse in velocity space, a process leading to the formation of plateaus in the VDF. This diffusion plateau formation naturally explains the observed thermal anisotropies in the core of the proton VDFs. In this respect, we investigated a large number of data from several distinct fast solar wind streams between 0.3 and 1 AU. All measurements were made on Helios 2 during the solar minimum in 1976 and 1977. The proton VDFs as provided by the plasma instrument are modeled by a superposition of multiple Gaussians, such that the plasma dispersion relation for parallel propagating cyclotron waves can readily be solved numerically. Thus the details of the proton VDFs are well represented and are reflected in the dispersion relation, which makes our analysis as self‐consistent as possible. Proton thermal effects on the wave dispersion relation are naturally taken into account.
Stress drops and radiated seismic energies of microearthquakes in a South African gold mine
Authors: Yamada Takuji , Mori James J. , Ide Satoshi , Abercrombie Rachel E. , Kawakata Hironori , Nakatani Masao , Iio Yoshihisa , Ogasawara Hiroshi
Published: March 2007

We estimate stress drops and radiated seismic energies of 20 microearthquakes (0.0 < MW < 1.3) in a South African gold mine to investigate their rupture characteristics and scaling relationships to large earthquakes. We analyze seismograms of borehole accelerometers recorded with high sampling rate (15 kHz) within 200 m of the hypocenters at the depth of 2650 m. The waveform data have very high signal‐to‐noise ratio and no significant later phases are observed at all stations. Corner frequencies and quality factors of the anelastic attenuation Q are estimated from spectra of velocity seismograms by assuming the omega squared model of Boatwright (1978). We also investigate moment tensors for double couple solutions and volumetric components from the waveform inversion. Static stress drops of the 20 earthquakes calculated from the model of Madariaga (1976) are from 3.2 to 88 MPa and scaled energies (= ER/Mo; the ratio of the radiated energy ER to the seismic moment Mo) are from 4.2 × 10−6 to 1.1 × 10−4. We find that both the static stress drops and the scaled energies of the analyzed earthquakes are comparable to those values of larger earthquakes. Our results indicate that the dynamic rupture processes of these microearthquakes are similar to those of larger earthquakes.
On Langley plots in the presence of a systematic diurnal aerosol cycle centered at noon: A comment on recently proposed methodologies
Authors: Marenco Franco
Published: March 2007

This short paper contains a discussion on the use of Langley plots for Sun photometer and Brewer spectroradiometer calibration in the presence of a diurnal aerosol cycle. It is shown that with Langley plots alone, it is impossible to correctly identify or remove atmospheric variations having a 24‐hour periodicity with an extreme at local noon. Therefore experimentalists must either be able to exclude such a periodicity using additional measurements, or approach different calibration techniques such as the approximation by linear sections.
Global reactive nitrogen deposition from lightning NOx
Authors: Shepon A. , Gildor H. , Labrador L. J. , Butler T. , Ganzeveld L. N. , Lawrence M. G.
Published: March 2007

We present results of the deposition of nitrogen compounds formed from lightning (LNOx) using the global chemical transport Model of Atmospheric Transport and Chemistry–Max Planck Institute for Chemistry version. The model indicates an approximately equal deposition of LNOx in both terrestrial and oceanic ecosystems, primarily in the tropics and midlatitudes open ocean, despite much higher intensities of lightning flashes above landmasses. The highest values of deposition are due to wet convective deposition, with highest values concentrated in the tropical continents. Nonconvective wet deposition, associated with large‐scale weather patterns, occurs over large areas of the ocean amid lower values per square meter, manifesting the long‐range transport of NOy, including long‐lived species such as HNO3 at high altitudes and PAN. Dry deposition is concentrated primarily above landmasses, yet oceanic deposition over wide areas is still observed. Combined together, the total LNOx deposition exhibits maximal influx values over land, whereas oceanic deposition over wider areas renders the integrated deposition over both ecosystems almost identical. Peaks of terrestrial deposition values (located in Africa, South America, and Asia) show seasonal variability by meridionally penetrating the northern or southern midlatitude following the corresponding summer hemisphere, in accordance with the migration of LNOx production sites. On land, wet and dry deposition rates are more or less equal with a small bias toward wet deposition, whereas above the ocean, wet deposition is markedly higher because of a small water uptake efficiency and relatively small surface roughness. Further work of modeling additional species and obtaining more information on different compounds is required.
Scattering properties of electromagnetic waves in a multilayered cylinder filled with double negative and positive materials
Authors: Yao Hai‐Ying , Li Le‐Wei , Qiu Cheng‐Wei , Wu Qun , Chen Zhi‐Ning
Published: March 2007

In this paper, a multilayered cylinder filled with double negative (DNG) material and double positive (DPS) material is studied. General formulas of electromagnetic fields in each region are derived using the eigenfunction expansion method. The expansion coefficients are determined by a recursive system that is derived from boundary conditions at the multiple interfaces. The reflection by a cylinder with (−ɛ0, −μ0) (where ɛ0 and μ0 denote the permittivity and permeability in free space, respectively) is found to be quickly diminished with its electric size. For an infinite line source, the image property is observed when the radius of this cylinder is much larger than the wavelength. The distributions of electromagnetic fields are presented when a line source is placed near a two‐layered cylinder alternately filled with DNG and DPS material. Numerical results confirm that the developed formulas are suitable to analyze the other multilayered cylindrical structures with DNG and DPS materials.
Boundary layer analysis of unsaturated seepage into cylindrical cavities
Authors: Ross Benjamin
Published: March 2007

An analytical solution has previously been published for flat capillary barriers in uniform layered rock with a quasi‐linear relative permeability function. This solution can be extended to curved surfaces with a radius of curvature that is much greater than the characteristic length of the relative permeability curve α−1 because water flows around the cavity in a relatively thin boundary layer. A simple formula is obtained for the onset of seepage into cylindrical cavities. Published solutions to the quasi‐linear seepage problem, which take the form of infinite sums of Bessel functions, agree with this formula in appropriate limits. Studies of seepage into a proposed radioactive waste repository have used a finite difference model to solve the equations of unsaturated flow explicitly. Using the boundary layer solution, the discretization error in such numerical models is calculated. The numerical estimate of the diversion capacity of a capillary barrier is shifted away from the exact solution by a factor of αd cos ϕ/sinh(αd cos ϕ), where 2d is the grid spacing and ϕ is the slope of the cavity wall.
Transcriptional bypass of bulky DNA lesions causes new mutant RNA transcripts in human cells
Authors: Marietta Cheryl , Brooks Philip J
Published: March 2007

Here, we characterize the mutant transcripts resulting from bypass of an 8,5′‐cyclo‐2′‐deoxyadenosine (cyclo‐dA) or cyclobutane pyrimidine dimer (CPD) by human RNA polymerase II (Pol II) in vivo. With the cyclo‐dA lesion, we observed two new types of mutant transcripts. In the first type, the polymerase inserted uridine opposite the lesion and then misincorporated adenosine opposite the template deoxyadenosine downstream (5′) of the lesion. The second type contained deletions of 7, 13 or 21 nucleotides (nt) after uridine incorporation opposite the lesion. The frequency of the different types of transcript from the cyclo‐dA lesion in mutant human cell lines suggests that the Cockayne syndrome B protein affects the probability of deletion transcript formation. With the CPD‐containing construct, we also detected rare transcripts containing 12 nt deletions. These results indicate that RNA pol II in living human cells can bypass helix‐distorting DNA lesions that are substrates for nucleotide excision repair, resulting in transcriptional mutagenesis.
Serum cytochrome c detection using a cytochrome c oxidase biosensor
Authors: Ashe Damian , Alleyne Trevor , Iwuoha Emmanuel
Published: March 2007

Within the last ten years it has emerged that the release of cytochrome c plays a critical role in the important process of programmed cell death. It has also been shown that this protein is released into the circulating blood following MIs (myocardial infarctions). Methods for the detection of this protein have therefore become important. The enzyme cytochrome c oxidase is specific for cytochrome c. Bovine cytochrome c oxidase was successfully immobilized in a didodecyldimethylammonium bromide vesicular system on to gold electrodes and its interaction with cytochrome c was studied. Square‐wave‐voltammetric analysis of the biosensor showed two redox couples with midpoint potential, E0′, values of +182 and +414 mV compared with Ag/AgCl. The redox couple with E0′ of +414 mV showed a cathodic sensitivity to the presence of cytochrome c in both buffer solution and human serum. Responses of the cytochrome c oxidase biosensor to oxidized cytochrome c followed hyperbolic electrochemical Michaelis–Menten kinetics with a Km of 1.57 μM and maximum current (Imax) of 1.38×10−6 μA. The detection limit of the biosensor in human serum was 0.2 μM, which is well below the lowest physiological concentration of 0.8 μM previously reported for MIs [Alleyne, Joseph and Sampson (2001) Appl. Biochem. Biotechnol. 90, 97–105]. These results indicate that the cytochrome c oxidase biosensors could be used to determine variations in cytochrome c concentration and thus have potential to be used as a diagnostic tool in the detection of MIs and possibly also in the study of programmed cell death.
Electrical properties of germanium/metal-oxide gate stacks with atomic layer deposition grown hafnium-dioxide and plasma-synthesized interface layers
Authors: Sugawara Takuya , Oshima Yasuhiro , Sreenivasan Raghavasimhan , McIntyre Paul C.
Published: March 2007

The electrical properties of metal-oxide-semiconductor (MOS) capacitors composed of atomic-layer-deposited (ALD) hafnium-dioxide (HfO2) dielectrics and plasma-synthesized interface layers were investigated. MOS capacitor with oxynitride interface layer shows negative flatband voltage (Vfb) shift from the ideal value. Hafnium-alkylamide ALD process performed on a plasma nitrided silicon surface causes negative Vfb shift. Germanium MOS capacitors show additional negative Vfb shift (−0.5V). X-ray photoelectron spectroscopy shows evidence of germanium diffusion into the HfO2 layer. Germanium MOS capacitor with tantalum-oxynitride (TaON) interface layer shows superior electrical properties. These results indicate that the selection of the interface layer strongly influences germanium MOS capacitor electrical properties.
Richtmyer-Meshkov instability induced by the interaction of a shock wave with a rectangular block of SF6
Authors: Bates K. R. , Nikiforakis N. , Holder D.
Published: March 2007

In this article the interaction of a shock wave with a rectangular block of sulphur hexafluoride (SF6), occupying part of the test section of a shock tube, is studied by experimental and numerical means. The difference between the ratios of the specific heats of the two gases (air and SF6) gives rise to numerical problems (generation of spurious waves at their interface). This necessitated the development of a multifluid algorithm (augmented Navier-Stokes formulation). The governing equations are based on a thermodynamically consistent and fully conservative formulation. A Riemann-problem-based scheme (the weighted average flux method) is used to integrate the hyperbolic part of the system. To this end, a new approximate Riemann problem solver has been formulated to account for the variable ratio of specific heats. The resulting algorithm was implemented in an adaptive mesh refinement code, which allowed high-resolution simulations to be performed on desktop computers. The evolution of the flow is well captured by the two-dimensional numerical solution, up to the point at which dimensionality effects become significant. The experimental evidence and numerical solutions complement each other to allow the time-evolving features present to be accurately identified and tracked, and the resulting flow physics to be discussed. Where possible, quantitative geometric comparison is made between both sets of results and good agreement demonstrated.
Coupling in the singular limit of thin quantum waveguides
Authors: Albeverio Sergio , Cacciapuoti Claudio , Finco Domenico
Published: March 2007

We analyze the problem of approximating a smooth quantum waveguide with a quantum graph. We consider a planar curve with compactly supported curvature and a strip of constant width around the curve. We rescale the curvature and the width in such a way that the strip can be approximated by a singular limit curve, consisting of one vertex and two infinite, straight edges, i.e., a broken line. We discuss the convergence of the Laplacian, with Dirichlet boundary conditions on the strip, in a suitable sense and we obtain two possible limits: the Laplacian on the line with Dirichlet boundary conditions in the origin and a nontrivial family of point perturbations of the Laplacian on the line. The first case generically occurs and corresponds to the decoupling of the two components of the limit curve, while in the second case a coupling takes place. We present also two families of curves which give rise to coupling.
Low temperature magnetron sputter deposition of polycrystalline silicon thin films using high flux ion bombardment
Authors: Gerbi Jennifer E. , Abelson John R.
Published: March 2007

We demonstrate that the microstructure of polycrystalline silicon thin films depends strongly on the flux of low energy ions that bombard the growth surface during magnetron sputter deposition. The deposition system is equipped with external electromagnetic coils which, through the unbalanced magnetron effect, provide direct control of the ion flux independent of the ion energy. We report the influence of low energy (<27eV) Ar+ on the low temperature (<450°C) growth of polycrystalline silicon thin films onto amorphous substrates. We use spectroscopic ellipsometry, Raman scattering, x-ray diffraction, and cross sectional transmission electron microscopy to analyze the film microstructure. We demonstrate that increasing the flux ratio of Ar+ ions to silicon neutrals (J+∕J0) during growth by an order of magnitude (from 3 to 30) enables the direct nucleation of polycrystalline Si on glass and SiO2 coated Si at temperatures below 400°C. We discuss possible mechanisms for this enhancement of crystalline microstructure, including the roles of enhanced adatom mobility and the formation of shallow, mobile defects.
Nonlinear spin wave magnetization of solution synthesized Ni nanoparticles
Authors: Vitta Satish
Published: March 2007

The magnetic properties of Ni nanoparticles synthesized using a soft chemical method followed by heat treatment in H2 atmosphere have been studied in detail. The powder consists of pure Ni with no additional phase and the average crystallite size is 30±5nm, determined using the modified Scherer relation. The crystallites tend to agglomerate into large particles of sizes 50–100nm, as observed by transmission electron microscopy. The saturation magnetization is found to be 46.42emug−1 at 5K, about 80% of the bulk magnetization value. The temperature dependence of saturation magnetization for T<0.5TC is found to deviate from the linear Bloch’s T3∕2 law indicating that spin wave interactions needs to be considered to understand the behavior. The spin wave stiffness constant obtained by fitting the saturation magnetization decay to a nonlinear spin wave model is lower by an order of magnitude compared to that of bulk Ni. The coercivity on the other hand decreases from 67Oe at 5Kto36Oe at 300K with a temperature dependence slower than the T1∕2 behavior predicted for noninteracting superparamagnetic particles.
How really transverse is the filamentation instability?
Authors: Bret A. , Gremillet L. , Bellido J. C.
Published: March 2007

It is generally considered that the linear filamentation instability encountered when two counter streaming electron beams interpenetrate is purely transverse. Exact and approximated results are derived in the relativistic fluid approximation showing that within some parameter range, filamentation can be indeed almost longitudinal with cos(k,Ê)≲1−3.1∕γb, where γb is the relativistic factor of the beam. Temperature effects are then evaluated through relativistic kinetic theory and yield even fewer transverse filamentation modes. In the cold case, the transverse approximation overestimates the growth rate by a factor ∝γb.
Heteroepitaxial growth of sixfold symmetric osmium on Si (111) and Si (100)
Authors: Peng Tai-Yen , Lo C. K. , Yao Y. D. , Chen San-Yuan
Published: March 2007

Growing sixfold symmetric osmium (Os) epitaxial films with suitable buffer layers was developed. Using a Cu buffer layer, the lattice mismatch between Os (0002) and Si (100) was significantly reduced from >30% to ∼7% to grow Os films with twin relationships and weak sixfold symmetries. On the other hand, the Cu∕Au buffer layer was selected to form a fcc (111) surface mesh on H–Si (111)-1×1, and therefore sixfold symmetric Os films were grown due to the lower lattice mismatch. Such growth properties may be applied in the high density magnetic random access memory manufacturing processes to connect the magnetic tunnel junction growth and Cu metal line directly.
Ultraviolet light-emitting diodes with self-assembled InGaN quantum dots
Authors: Park Il-Kyu , Kwon Min-Ki , Seo Seong-Bum , Kim Ja-Yeon , Lim Jae-Hong , Park Seong-Ju
Published: March 2007

A photoluminescence study showed that the self-assembled InGaN quantum dots (QDs) provide strongly localized recombination sites for carriers and that the piezoelectric field-induced quantum-confined Stark effect (QCSE) is small because the height of QDs is too small to separate the wave functions of electrons and holes. The InGaN QD light-emitting diode (LED) showed an emission peak at 400nm, and the peak was redshifted with increasing injection current, indicating a small QCSE. The light output power of an InGaN QD LED increased linearly with increasing injection current due to the strongly localized recombination sites of the InGaN QDs.
Motion analysis of grip and release with fingers using simple magnetic detection system
Authors: Kandori Akihiko , Miyashita Tsuyoshi , Hosono Noboru , Yokoe Masaru , Ogata Kuniomi , Abe Kazuo , Sakoda Saburo
Published: March 2007

We have developed a magnetic grip-and-release motion detection system to measure time differences among fingers during motion. We designed a magnetic sensing system consisting of a magnetic oscillation coil, sensing coil, and circuit unit. We measured wave forms of grip-and-release motion (15s) of seven healthy volunteers using the system. To provide the grip-and-release timing of each finger, we used the reference voltage of each subject in the state of grasping a rod with a 30mm diameter. Using the reference voltage, the time differences in the finger movements of all volunteers were detected. The detected grip-and-release time difference of both dominant and nondominant hands had a main tendency in which the closing movement of the little finger is fast, within 10ms, and the opening movement is slow, within 13ms. Our data suggest that the new magnetic sensing system has the potential to detect the quantitative value of the time difference in grip-and-release motion among fingers.
Determination of Young’s modulus of individual electrospun nanofibers by microcantilever vibration method
Authors: Yuya Philip A. , Wen Yongkui , Turner Joseph A. , Dzenis Yuris A. , Li Zheng
Published: March 2007

The authors report a technique for measuring Young’s modulus of a single electrospun nanofiber using the vibrations of two microcantilevers coupled with the nanofiber. The modulus is calculated from the resonant frequency shift resulting from the nanofiber. Polyacrylonitrile nanofibers (200nm diameter) were collected during electrospinning and wrapped on two similar microcantilevers causing a shift in first resonance from 10.0to19.4kHz. Finite element analysis was used to analyze the frequency shift using images from a scanning electron microscope giving a modulus of the as-spun polyacrylonitrile nanofiber of 26.8GPa.
Ferroelectric all-polymer hollow Bragg fibers for terahertz guidance
Authors: Skorobogatiy Maksim , Dupuis Alexandre
Published: March 2007

Design of hollow all-polymer Bragg fibers using periodic multilayers of ferroelectric polyvinylidene fluoride (PVDF) polymer and a low loss polycarbonate (PC) polymer is demonstrated. Efficient band gap guiding is predicted near the transverse optical frequency of a PVDF material in the terahertz regime. Optimal reflector designs are investigated in the whole terahertz region. Depending on frequency, the lowest loss hollow Bragg fiber can be one of the following: a photonic crystal fiber guiding in the band gap regime, a metamaterial fiber with a subwavelength reflector period, a single PC, or a PVDF tube.
Regular arrangement of nanoparticles from the gas phase on bacterial surface-protein layers
Authors: Queitsch Ute , Mohn Elias , Schäffel Franziska , Schultz Ludwig , Rellinghaus Bernd , Blüher Anja , Mertig Michael
Published: March 2007

FePt nanoparticles from the gas phase are deposited onto the two-dimensional crystalline surface layer protein from the bacterium Bacillus sphaericus NCTC 9602. The potential of this protein layer to facilitate the ordered spatial arrangement of the otherwise statistically distributed nanoparticles on the substrate is studied. Transmission electron microscopy reveals the particles positions to be directed by the regular protein template.
Structure stability, fracture, and tuning mechanism of CdSe nanobelts
Authors: Wang Zhongwu , Finkelstein Ken , Ma Chris , Wang Zhong Lin
Published: March 2007

High pressure synchrotron x-ray diffraction studies have been conducted to explore the structural stability, phase transformation, and resulting mechanisms of CdSe nanobelts. 25-nm-thick wurtzite CdSe nanobelts transform to a rocksalt structure with in situ fracture at 4.0GPa; this is greater than the transition pressure of 2.5GPa in bulk and 25nm nanoparticle. Decompression results in the formation of wurtzite and sphalerite at 1.2GPa. Total Gibbs free energy calculations demonstrate that the low surface energy ±{21¯0} facets are fully responsible for the enhancement of structure stability. A strongest particle size for the rocksalt phase was determined ∼12nm, providing a significant constraint for the fracture of nanobelts and size-tuned enhancement of mechanical properties.
Size-dependent planar colloidal crystals guided by alternating electric field
Authors: Zhang Ke-Qin , Liu Xiang Y.
Published: March 2007

The authors demonstrate that two-dimensional crystals can be assembled from suspensions of colloidal spheres subjected to an alternating electric field on the surface of electrodes. The order parameters of monolayer colloidal crystals, which are extracted from the translational correlation function g(r) and bond-orientational correlation function g6(r), are employed to quantitatively characterize the ordering of the colloidal assemblies. This method has been applied on colloidal spheres of various sizes ranging from 450nmto5.0μm. In particular, high-quality crystals of spheres sized differently are controlled by different domains of frequency. This technique could be a rational method to assemble micro- or submicron colloidal spheres.
Modeling magnetic fields measured by surface probes embedded in a cylindrical flux conserver
Authors: Golingo R. P.
Published: March 2007

Calculating magnetic fields at the surface of a flux conserver, perfect conductor, for displaced plasma currents is useful for understanding modes of a Z-pinch. The magnetic fields measured at the flux conserver are a sum of the magnetic fields from the plasma current and the eddy currents which form in the walls to keep the flux constant. While the magnetic field at the wall from the plasma current alone is easily calculated using the Biot–Savart law, finding the eddy currents in the flux conserver which satisfy the boundary conditions can be a tedious process. A simple method of calculating the surface magnetic field for a given Z-pinch displacement off-axis is derived for a cylindrical flux conserver. This relationship does not require the explicit calculation of the eddy currents, saving time when analyzing surface magnetic probe measurements. Analytic expressions can be used to describe the surface magnetic field which increase the understanding of the magnetic probe measurements.
Effects of morphology and optical contrast in organic distributed feedback lasers
Authors: Salerno M. , Gigli G. , Zavelani-Rossi M. , Perissinotto S. , Lanzani G.
Published: March 2007

Optically pumped organic distributed feedback lasers, based on the same cavity geometry and polymeric active material, but patterned with different methods, are compared. In one case, the pattern is transferred into the polymer by spin coating the latter on top of a silica master. In the other case, the master is used as a mold to imprint a polymer film. The comparison shows that the imprinted structures, even though a lower quality copy of the master at morphological level, exhibit better performance. This result is checked for different laser cavities, and a qualitative explanation in terms of optical contrast is provided.
Photoluminescence from low temperature grown InAs∕GaAs quantum dots
Authors: Sreenivasan D. , Haverkort J. E. M. , Eijkemans T. J. , Nötzel R.
Published: March 2007

The authors investigated a set of self-assembled InAs∕GaAs quantum dots (QDs) formed by molecular beam epitaxy at low temperature (LT, 250°C) and postgrowth annealing. A QD photoluminescence (PL) peak around 1.01eV was observed. The PL efficiency quickly quenches between 6 and 40K due to the tunneling out of the QD into traps within the GaAs barrier. The PL efficiency increases by a factor of 45–280 when exciting below the GaAs band gap, directly into the InAs QD layer. This points towards good optical quality QDs, which are embedded in a LT-GaAs barrier with a high trapping efficiency.
Weak coupling interactions of colloidal lead sulphide nanocrystals with silicon photonic crystal nanocavities near 1.55μm at room temperature
Authors: Bose Ranojoy , Yang Xiaodong , Chatterjee Rohit , Gao Jie , Wong Chee Wei
Published: March 2007

The authors observe the weak coupling of lead sulphide nanocrystals to localized defect modes of two-dimensional silicon nanocavities. Cavity resonances characterized with ensemble nanocrystals are verified with cold-cavity measurements using integrated waveguides. Polarization dependence of the cavity field modes is observed. The linewidths measured in coupling experiments are broadened in comparison to the cold-cavity characterization, partly due to large homogeneous linewidths of the nanocrystals. The calculated Purcell factor [Phys. Rev. 69, 681 (1946)] for a single exciton is 100, showing promise toward applications in single photon systems. These novel light sources operate near 1.55μm wavelengths at room temperature, permitting integration with current fiber communication networks.
Electromigration-induced Kirkendall voids at the Cu∕Cu3Sn interface in flip-chip Cu∕Sn∕Cu joints
Authors: Liu C. Y. , Chen J. T. , Chuang Y. C. , Ke Lin , Wang S. J.
Published: March 2007

Polarity void formation has been observed at the Cu3Sn∕Cu interfaces in current-stressed Cu∕Sn∕Cu flip-chip joints. Electromigration voids were observed at the Cu3Sn∕Cu anode interface, but no voids were found at the Cu3Sn∕Cu cathode interface. The backstress in the anode’s Cu trace line caused a vacancy backflow toward the Cu3Sn∕Cu anode interface, which led to serious void formation. In the opposite Cu3Sn∕Cu cathode interface, Cu atoms in the cathode’s Cu trace line electromigrated toward the Cu3Sn∕Cu cathode interface, which alleviated or healed possible Kirkendall void formation due to the normal annealing process.
Deep level defects which limit current gain in 4H SiC bipolar junction transistors
Authors: Cochrane C. J. , Lenahan P. M. , Lelis A. J.
Published: March 2007

The authors employ a very sensitive electrically detected electron spin resonance technique called spin dependent recombination to observe recombination centers in fully processed 4H SiC n-p-n bipolar junction transistors. Their measurements indicate that the observed dominating recombination defect in these transistors is an intrinsic center of high symmetry, most likely a vacancy. This defect likely plays a dominating role in limiting the current gain in these 4H SiC devices.
Polarized optical feedback from an extremely short external cavity for controlling and stabilizing the polarization of vertical cavity surface emitting lasers
Authors: Arizaleta Arteaga Mikel , Parriaux Olivier , López-Amo Manuel , Thienpont Hugo , Panajotov Krassimir
Published: March 2007

The authors present experimental results showing that polarization selective optical feedback from an extremely short external cavity induces switching between the two fundamental transverse modes with orthogonal linear polarization of the otherwise (without optical feedback) polarization stable vertical cavity surface emitting laser. Moreover, when properly selecting the external cavity length within a subwavelength range the polarization state of the emitted light can be chosen in either of the two fundamental transverse modes and stabilized against injection current variations. The numerical results reported are in good agreement with experiments.
Short wavelength (λ=2.13μm) intersubband luminescence from GaN∕AlN quantum wells at room temperature
Authors: Nevou L. , Tchernycheva M. , Julien F. H. , Guillot F. , Monroy E.
Published: March 2007

The authors report the observation of room-temperature intersubband luminescence at λ=2.13μm from GaN∕AlN quantum wells under optical pumping at λ=0.98μm. The quantum wells are designed to exhibit three bound states in the conduction band. The emission arises from the e3e2 intersubband transition. Photoluminescence excitation spectroscopy shows that the emission is only observed for p-polarized excitation at wavelengths corresponding to the e1e3 intersubband transition. The measured external quantum efficiency is 10pW∕W.
Observation of superluminal propagation at negative group velocity in C60 solution
Authors: Wang Hao , Zhang Yundong , Wang Nan , Yan Wenlong , Tian He , Qiu Wei , Yuan Ping
Published: March 2007

The authors observed the superluminal propagation at negative group velocity in C60 toluene solution firstly. The theoretical analysis was made based on density matrix model of superluminal propagation. The simulation result was well consistent with experimental measurement. The largest time advancement of 3.58ms was got at 5.6×10−4mol∕l of sample concentration; the corresponding group velocity is −0.28m∕s.
Anomalous thermal stability of cubic tin confined in a nanotube
Authors: Wang B. , Ouyang G. , Yang Y. H. , Yang G. W.
Published: March 2007

In situ observations of transmission electron microscopy have indicated that the cubic Sn phase confined in a nanotube has extreme stability even when the temperature is more than 700°C, significantly higher than the melting point (231.9°C) of tin. A thermodynamic model was established to pursue the physical origins of the anomalous stability of the confined cubic Sn phase. It was found that the epitaxial interface confinement of SnO2∕Sn and the difference of thermal expansion between the core and shell play crucial roles in the unusual stability of the cubic Sn at high temperature.
Observation of negative bias stressing interface trapping centers in metal gate hafnium oxide field effect transistors using spin dependent recombination
Authors: Cochrane C. J. , Lenahan P. M. , Campbell J. P. , Bersuker G. , Neugroschel A.
Published: March 2007

The authors combine metal oxide semiconductor (MOS) gated diode measurements and very sensitive electrically detected electron spin resonance measurements to detect and identify negative bias temperature instability (NBTI) generated defect centers in fully processed HfO2 pMOS field effect transistors. Both short and long term stressing defects are different from those generated by NBTI in Si∕SiO2 devices. The spectra generated by long term stressing differ from the short term stressing signals and are somewhat similar to those observed in plasma nitrided oxide Si∕SiO2 devices. The results suggest that NBTI defects are located in the interfacial SiO2 layer of these HfO2 devices.
Institutional Innovations, Asymmetric Decentralization, and Local Economic Development: A Case Study of Kunshan, in Post-Mao China
Authors: Chien Shiuh-Shen
Published: March 2007

The author provides an understanding of the concept of institutional innovations for local economic development in post-Mao China. With Kunshan, one of the most dramatically developed regions in Yangtze Delta, used as a case study, the aim is to understand how, under what circumstances, and by whom, locally initiated projects can be institutionalized and evolved in the context of China's transition. ‘Projects’ here refer to those reforms implemented by local governments initially without any permission from the centre. It is argued that the development of those projects can be understood as an evolutionary process, consisting of three mechanisms of local-central interactions: state's intention to connive; ex-post state endorsement, and ex-ante state adoption. Moreover, the innovations would be successful not only because of general contexts such as marketization, liberalization, and globalization, but also because of a particular process of economic decentralization to the local and political centralization under the party, or, as is proposed, asymmetric decentralization. Careerist local officials would like to utilize their decentralized resources to strive for more development opportunities, which could in turn become their ‘political capital’, enabling them to attract the attentions of upper level governments and hence gain promotion.
Plant-macrofossil assemblages during Pliocene uplift, South Island, New Zealand
Authors: Pole Mike
Published: March 2007

Organically preserved plant macrofossils, which accumulated during the period of late Neogene tectonic uplift, were documented from four localities in the South Island. These include Arapito Road (near Karamea), Waitahu River (near Reefton), Tadmor (south of Nelson) and Grey River (north of Christchurch). The assemblages from these localities were species-poor compared with older Cenozoic assemblages, but included a range of conifers and angiosperms. Of note was the presence of Acmopyle (currently extinct in New Zealand) and Cupressaceae in all four localities. At least two new species of Acmopyle were present, with leaf shapes distinctly different from any currently known. One of them (A. kirrileeae sp. nov.) had unflattened, awl-like foliage, whereas the other (A. biformis sp. nov.) had dimorphic foliage, including very distinct bilaterally flattened leaves with a mucronate apex. Both of these were distinct from the flattened foliage, which predominates on extant Acmopyle. Other conifers included Araucaria, Dacrycarpus, Dacrydium, Phyllocladus and Libocedrus. Angiosperms included Beauprea (now extinct in New Zealand) Beilschmiedia, Knightia sp., Metrosideros, Nothofagus and probably Pseudowintera, Pseudopanax and Cunoniaceae. The assemblages suggest temperate conditions.
Histomorphometry and expression of Cdc47 and caspase-3 in hyperthyroid rat uteri and placentas during gestation and postpartum associated with fetal development
Authors: Freitas E. S. , Leite E. D. , Souza C. A. , Ocarino N. M. , Ferreira E. , Cassali G. D. , Gomes M. G. , Serakides R.
Published: March 2007

In two different experiments, the effects of hyperthyroidism on the histomorphometry and expression of Cdc47 and caspase-3 were evaluated in the uteri and placentas during gestation and postpartum. Fetal development was also evaluated during gestation. In the first experiment, 36 adult female Wistar rats were divided into two groups of 18 animals each: (1) hyperthyroid; and (2) euthyroid (control). Female rats were mated and killed at 7, 14 and 19 days of gestation. Uteri and placentas were weighed and subjected to histomorphometric and immunohistochemical evaluation to determine the expression of Cdc47 and caspase-3. Ovaries were also evaluated for weight and subjected to morphometric analysis. Fetuses were quantified and weighed individually. In the second experiment, 12 adult female Wistar rats were divided into two groups of six animals each: (1) hyperthyroid; and (2) euthyroid (control). Female rats were mated and killed 2 days postpartum. Uteri were evaluated in the same way as for the first experiment. Hyperthyroidism increased ovulation and conception rates without disturbing the size and viability of the fetuses. In the pregnant uteri, hyperthyroidism did not change the thickness of the layers or the expression of Cdc47 and caspase-3. However, in the placentas, hyperthyroidism increased the medium diameter of trophoblast cells, as well as the thickness and the expression of Cdc47 of spongiotrophoblast cells, at 14 days of gestation. During uterine involution, hyperthyroidism significantly increased the expression of Cdc47 and reduced the expression of caspase-3 in the uterine layers. In conclusion, hyperthyroidism increased the conception rate because of an ovulation gain, induced significant placental changes during pregnancy and, in the uterus, increased Cdc47 expression and decreased caspase-3 expression after parturition.