bluuebunny/crossref_metadata_2025 huggingface dataset:
SIA spotlight on Asia
Authors: Chu Paul K. , Wu X. L. , Xie X. N. , Wee A. T. S.
Published: August 2007

There has been rapid development in science and technology in Asia in recent decades, including in the fields of surface and interface sciences. This has been facilitated by the sustained economic growth in the region, especially the growth of the semiconductor, electronic, chemical, coating and biomedical industries. Accompanying this growth is the increased use of more sophisticated analytical techniques, especially in the field of surface and interface analysis. This article reviews a selection of papers from Asia, published in major international journals in the last two years. Short reviews of each paper are presented in three sections: (i) Characterization and techniques, (ii) Materials and processing and (iii) Nanoscience and nanotechnology. Copyright © 2007 John Wiley & Sons, Ltd.
Modal ductility factors of one‐story inelastic structures with simple eccentricity
Authors: Georgoussis George K.
Published: August 2007

A simple procedure is presented for constructing modal capacity curves of one‐story monosymmetric models with elastoplastic resisting elements. These curves may be used for an approximate decomposition of the equations of motion of the assumed structural models, when subjected to ground motions. The motive of applying a modal decomposition on inelastic structures is the simplicity and the consequent attractiveness of the response spectrum technique as applied in linear structures. By applying a modal decomposition on eccentric one‐story inelastic systems, modal ductility demands may be determined for the various resisting elements and the total demands may be estimated by an appropriate combination rule. The modal capacity curves are constructed by performing a nonlinear pushover analysis using the inertia force eccentricities of each mode. As at each loading step the modal eccentricity reflects the current state of stiffness, the incremental floor movement consists of a rotation about the corresponding natural center of vibration and this simplifies the calculation of displacements throughout the loading history. The method of constructing modal capacity curves is outlined for systems with different structural parameters: uncoupled lateral frequency, uncoupled torsional‐to‐lateral frequency ratio, stiffness eccentricity and relative values of element strength. A parametric analysis is also presented, based on a three‐element single mass model that has been extensively used in the past for similar analyses. In particular, two types of model structure are examined: systems with element strengths proportional to their stiffness and systems with element strengths determined by the static equilibrium of the eccentric model. The results of the present work are in good agreement with the findings of studies published in the past. Copyright © 2007 John Wiley & Sons, Ltd.
An approximate method for static and dynamic analyses of multi‐bay coupled shear walls
Authors: Bozdogan Kanat Burak , Ozturk Duygu , Nuhoglu Ayhan
Published: August 2007

In this study an approximate method based on the continuum approach and transfer matrix method for static and dynamic analyses of multi‐bay coupled shear walls is presented. The whole structure is idealized as a sandwich beam in this method. Initially the differential equation of this equivalent sandwich beam is written, then shape functions for each storey can be obtained by the solution of differential equations. By using boundary conditions and storey transfer matrices which are obtained by these shape functions, system modes and periods can be calculated. Reliability of the study is shown with a few examples. A computer program has been developed in MATLAB and numerical samples have been solved for demonstration of the reliability of this method. The results of the samples display the agreement between the present method and the other methods given in the literature. Copyright © 2007 John Wiley & Sons, Ltd.
High frequency of missense mutations in glycogen storage disease type VI
Authors: Beauchamp N. J. , Taybert J. , Champion M. P. , Layet V. , Heinz‐Erian P. , Dalton A. , Tanner M. S. , Pronicka E. , Sharrard M. J.
Published: August 2007

Deficiency of liver glycogen phosphorylase in glycogen storage disease (GSD) type VI results in a reduced ability to mobilize glucose from glycogen. Six mutations of the PYGL gene, which encodes the liver isoform of the enzyme, have been identified in the literature. We have characterized eight patients from seven families with GSD type VI and identified 11 novel PYGL gene defects. The majority of the mutations were missense, resulting in the substitution of highly conserved residues. These could be grouped into those that were predicted to affect substrate binding (p.V456M, p.E673K, p.S675L, p.S675T), pyridoxal phosphate binding (p.R491C, p.K681T), or activation of glycogen phosphorylase (p.Q13P) or that had an unknown effect (p.N632I and p.D634H). Two mutations were predicted to result in null alleles, p.R399X and [c.1964_1969inv6;c.1969+1_+4delGTAC]. Only 7 of the 23 (30%) reported PYGL alleles carry nonsense, splice site or frameshift mutations compared to 68–80% of affected alleles of the highly homologous muscle glycogen phosphorylase gene, PYGM, that underlie McArdle disease. There was heterogeneity in the clinical symptoms observed in affected individuals. These varied from hepatomegaly and subclinical hypoglycaemia, to severe hepatomegaly with recurrent severe hypoglycaemia and postprandial lactic acidosis. We conclude that deficiency of liver glycogen phosphorylase is predominantly the result of missense mutations affecting enzyme activity. There are no common mutations and the severity of clinical symptoms varies significantly.
Roles of riparian and secondary forests in maintaining the near‐threatened butterfly, Sasakia charonda (Lepidoptera, Nymphalidae), populations in Japan
Authors: Kobayashi Takato , Nakashizuka Tohru , Kitahara Masahiko , Kubo Masako , Ito Shoko
Published: August 2007

To clarify the habitat requirements of the near‐threatened butterfly, Sasakia charonda (Lepidoptera, Nymphalidae), we studied the distribution pattern of its host trees, Celtis sinensis and Celtis jessoensis, and the utilization patterns of various vegetation types by this butterfly in the Oofukasawa River basin in Hokuto City, Yamanashi Prefecture, central Japan. Two species of host trees, C. sinensis and C. jessoensis (height = 2 m or more) were found in riparian forests on sandbanks (hereinafter, riparian forest), in forest regenerated after landslides on valley walls (landslide tracks), in secondary deciduous forests consisting mainly of Quercus acutissima or Quercus serrata and in forests established at abandoned paddy fields and their periphery, where weeds and shrubs used to be mown frequently to avoid shade on the paddies before their abandonment. This suggests that they are pioneer species, and their distribution and regeneration depend on natural and/or human disturbances. Host trees above 2 m were preferred by larvae, and there were very few such trees in secondary forests. More overwintering larvae occurred in riparian forests than at other sites. The number of S. charonda adults was highest at the edge of riparian forests, and we observed a variety of behaviors such as puddling, chasing and mating there. Although the number of adult butterflies was smaller inside and at the edge of secondary forests than in riparian forests, puddling by males and roosting on the trunk of Q. acutissima or Q. serrata by females were observed more frequently there than in riparian forests. Thus, we conclude that landscapes including both riparian forests with natural disturbance and secondary forests with Quercus trees are necessary to maintain host Celtis trees and S.charonda populations.
Characteristic Oxidation Products of Choline Plasmalogens are Detectable in Cattle and Roe Deer Spermatozoa by MALDI‐TOF Mass Spectrometry
Authors: Fuchs Beate , Müller Karin , Göritz Frank , Blottner Steffen , Schiller Jürgen
Published: August 2007

Plasmalogens (1‐O‐alk‐1′‐enyl‐2‐acyl‐sn‐glycero‐3‐phosphocholines and ‐phosphoethanolamines) are important constituents of spermatozoa membranes and possess significant antioxidative properties. This particularly holds as plasmalogens from spermatozoa also possess a very high content of highly unsaturated fatty acyl residues (especially 22:6). The organic spermatozoa extracts of two different ruminants (cattle and roe deer) were analyzed for their contents of characteristic choline plasmalogen oxidation products by matrix‐assisted laser desorption and ionization time‐of‐flight (MALDI‐TOF) mass spectrometry. It will be shown that 1‐hydroxy‐2‐docosahexaenoyl‐sn‐glycero‐3‐phosphocholine (LPC 22:6) and formyl‐LPC 22:6 are reliable measures of lipid oxidation of spermatozoa and allow, accordingly, conclusions about the storage conditions. All data on spermatozoa were also confirmed by the investigation of the oxidation behavior of selected reference compounds. It will be shown that, equally if plasmalogens or diacyl PC species are used, oxidation takes place primarily at the double bond next to the glycerol backbone. These data were additionally confirmed by recording the corresponding post source decay (PSD) fragment ion spectra.
A proteomic screen reveals novel Fas ligand interacting proteins within nervous system Schwann cells
Authors: Thornhill Peter B. , Cohn Jason B. , Drury Gillian , Stanford William L. , Bernstein Alan , Desbarats Julie
Published: August 2007

Fas ligand (FasL) binds Fas (CD95) to induce apoptosis or activate other signaling pathways. In addition, FasL transduces bidirectional or ‘reverse signals’. The intracellular domain of FasL contains consensus sequences for phosphorylation and an extended proline rich region, which regulate its surface expression through undetermined mechanism(s). Here, we used a proteomics approach to identify novel FasL interacting proteins in Schwann cells to investigate signaling through and trafficking of this protein in the nervous system. We identified two novel FasL interacting proteins, sorting nexin 18 and adaptin β, as well as two proteins previously identified as FasL interacting proteins in T cells, PACSIN2 and PACSIN3. These proteins are all associated with endocytosis and trafficking, highlighting the tight regulation of cell surface expression of FasL in the nervous system.
The Printed World: Books, Publishing Culture, and Society in Late Imperial China
Authors: Meyer-Fong Tobie
Published: August 2007

Beginning in the late Ming period, China experienced a surge in the production and consumption of books. Printed pages bound into fascicles and housed in cases moved across space and through the social landscape. Their trajectories illuminate larger social, intellectual, economic, and cultural patterns. They also reveal identities under construction—by readers, writers, publishers, and consumers. This article assesses the expanding field of late imperial Chinese book history in the United States and Japan, with some reference to scholarship in China and Taiwan. It looks at the field's move away from its origins in the history of technology and its increasing engagement with social and cultural questions. In particular, the article highlights the field's focus on the “place” of publishing in late imperial China, construed both in terms of regional orientation and the social position of readers and producers of books.
Benign schwannoma in paranasal sinuses: a clinico-pathological study of five cases, emphasising diagnostic difficulties
Authors: Sheikh H Y , Chakravarthy R P , Slevin N J , Sykes A J , Banerjee S S
Published: August 2007

Objectives:

To highlight the difficulty in making a correct diagnosis of benign schwannoma in the paranasal region, to raise awareness of this rare condition, and to suggest the most appropriate treatment.

Method:

Retrieval of cases retrospectively from archives of the histopathology department of a major UK cancer centre with central review of all cases.

Results:

Five cases were identified since 1990 and clinical and pathological features are summarised. Median follow up of patients was 8.1 years. Radiological appearances of local bone invasion and histological features of tumour unencapsulation and hypercellularity could give the mistaken impression of malignant disease and lead to unnecessary over-treatment.

Conclusion:

Central pathological review and clinical awareness is required. Although local recurrence can occur, the prognosis is excellent. The treatment of choice is local excision. Radiotherapy can be considered, but in most cases it would incur unnecessary morbidity.
Relationship between tuberculous otomastoiditis and tuberculous meningitis
Authors: Sonmez G , Turhan V , Senol M G , Ozturk E , Sildiroglu H O , Mutlu H
Published: August 2007

Objective:

The aim of this study was to determine the correlation between tuberculous meningitis and tuberculous otomastoiditis.

Materials and methods:

Meningeal involvement sites were investigated by magnetic resonance imaging in 32 patients (21 males, 11 females) who had previously been diagnosed with tuberculous meningitis. Clinical and laboratory findings and responses to anti-tuberculous treatment were evaluated, and the presence of concomitant tuberculous otomastoiditis was also investigated.

Results:

The meningeal involvement site was unilateral (in the sylvian fissure and the perimesencephalic cistern) in 28 patients (87.5 per cent), and bilateral and widespread in four patients (12.5 per cent). Tuberculous otomastoiditis was found in 11 of the patients with tuberculous meningitis (34.3 per cent). Otomastoiditis was on the same side as the meningeal involvement in nine of these 11 patients. Bilateral otomastoiditis with meningeal involvement was observed in two patients.

Conclusions:

Tuberculous meningitis is frequently accompanied by otomastoiditis, although the exact causal relationship between the two conditions is unclear. Since meningitis is a serious clinical condition, concomitant otomastoiditis generally remains unrecognised. Tuberculosis should be considered in the differential diagnosis of patients with otitis or otomastoiditis who do not respond to antibiotic therapy.
Cantor sets of circles of Sierpiński curve Julia sets
Authors: DEVANEY ROBERT L.
Published: August 2007

Our goal in this paper is to give an example of a one-parameter family of rational maps for which, in the parameter plane, there is a Cantor set of simple closed curves consisting of parameters for which the corresponding Julia set is a Sierpiński curve. Hence, the Julia sets for each of these parameters are homeomorphic. However, each of the maps in this set is dynamically distinct from (i.e. not topologically conjugate to) any other map in this set (with only finitely many exceptions). We also show that, in the dynamical plane for any map drawn from a large open set in the connectedness locus in this family, there is a Cantor set of invariant simple closed curves on which the map is conjugate to the product of certain subshifts of finite type with the maps $z \mapsto \pm z^n$ on the unit circle.
ELHISA: An architecture for the integration of heterogeneous lexical information
Authors: ARTOLA XABIER , SOROA AITOR
Published: August 2007

The design and construction of lexical resources is a critical issue in Natural Language Processing (NLP). Real-world NLP systems need large-scale lexica, which provide rich information about words and word senses at all levels: morphologic, syntactic, lexical semantics, etc., but the construction of lexical resources is a difficult and costly task. The last decade has been highly influenced by the notion of reusability, that is, the use of the information of existing lexical resources in constructing new ones. It is unrealistic, however, to expect that the great variety of available lexical information resources could be converted into a single and standard representation schema in the near future. The purpose of this article is to present the ELHISA system, a software architecture for the integration of heterogeneous lexical information. We address, from the point of view of the information integration area, the problem of querying very different existing lexical information sources using a unique and common query language. The integration in ELHISA is performed in a logical way, so that the lexical resources do not suffer any modification when integrating them into the system. ELHISA is primarily defined as a consultation system for accessing structured lexical information, and therefore it does not have the capability to modify or update the underlying information. For this purpose, a General Conceptual Model (GCM) for describing diverse lexical data has been conceived. The GCM establishes a fixed vocabulary describing objects in the lexical information domain, their attributes, and the relationships among them. To integrate the lexical resources into the federation, a Source Conceptual Model (SCM) is built on the top of each one, which represents the lexical objects concurring in each particular source. To answer the user queries, ELHISA must access the integrated resources, and, hence, it must translate the query expressed in GCM terms into queries formulated in terms of the SCM of each source. The relation between the GCM and the SCMs is explicitly described by means of mapping rules called Content Description Rules. Data integration at the extensional level is achieved by means of the data cleansing process, needed if we want to compare the data arriving from different sources. In this process, the object identification step is carried out. Based on this architecture, a prototype named ELHISA has been built, and five resources covering a broad scope have been integrated into it so far for testing purposes. The fact that such heterogeneous resources have been integrated with ease into the system shows, in the opinion of the authors, the suitability of the approach taken.
Morphology and emplacement of a long channeled lava flow near Ascraeus Mons Volcano, Mars
Authors: Garry W. Brent , Zimbelman James R. , Gregg Tracy K. P.
Published: August 2007

Channeled lava flows, hundreds of kilometers long, are common on the lower flanks of the Tharsis Montes on Mars. Our analysis of a 690‐km‐long lava flow along the southwest perimeter of Ascraeus Mons shows that it was emplaced on low local slopes (<0.3°), with a deep channel (∼20 m), and at high effusion rates (19,000–29,000 m3/s) calculated from the Graetz number. These parameters are similar to conditions needed to yield rapidly emplaced terrestrial flows >100 km in length, but the maximum effusion rates necessary on Earth are essentially the minimum for Martian flows. On the basis of our calculated effusion rates, the eruption duration was 3 to 7 Earth months, assuming a constant effusion rate and continuous eruption. The morphology of the Ascraeus Mons flow shows similarities to terrestrial and simulated channeled flows. Downstream changes in morphology resemble those observed in the 1907 flow, Mauna Loa Volcano, Hawaii and channeled polyethylene glycol (PEG) flows. Braided sections of the channel in the Ascraeus Mons flow contain islands which are hundreds of meters across and resemble features observed in the 1907 and 1984 flows on Mauna Loa Volcano. Crosscutting relationships suggest islands in the proximal section were shaped by thermal and mechanical erosion, whereas islands in the medial section are inferred to be material rafted by surges of lava through the channel. Overall, understanding the morphology of long lava flows on Mars is essential to the interpretation of their emplacement and constraining eruption conditions in the saddle regions of the Tharsis volcanoes.
Fluctuations of radio occultation signals in X/K band in the presence of anisotropic turbulence and differential transmission retrieval performance
Authors: Gorbunov M. E. , Kirchengast G.
Published: August 2007

We investigated amplitude fluctuations and differential transmission errors for radio occultation (RO) measurements performed in X/K band for Low‐Earth Orbiter – Low‐Earth Orbiter (LEO–LEO) cross‐links. We performed a series of high‐resolution numerical simulations using a quasi‐realistic anisotropic turbulence model with European Centre for Medium‐Range Weather Forecast (ECMWF) ERA40 reanalyses as the background fields. Three test cases were simulated: high, middle, and low latitudes, with turbulence intensity profile being estimated based on high‐resolution radio sonde data. The numerical end‐to‐end simulations were based on the multiple phase screens technique (forward modeling) and the canonical transform amplitude ratioing method (differential transmission retrieval). The anisotropy coefficient was varied from 3 to 50. We found the dependences of the scintillation index on anisotropy in the area of weak fluctuations to be consistent with previous theoretical studies: scintillation index is approximately proportional to the square root of the anisotropy coefficient. For strong fluctuations this dependence becomes weaker. The type of dependence of differential transmission errors from anisotropy is more sensitive to the fluctuation strength. Generally, it increases with anisotropy, but the dependence saturates for stronger anisotropy and becomes flat or even slightly reverse. At all fluctuation levels, including the strongest ones, the differential transmission error is found smaller than 5% (smaller than 1–2.5% for all weak and moderately strong fluctuations) for ∼1 km height resolution, reinforcing the results of the previous studies that X/K band RO phase delay and transmission are a promising future source for accurate temperature and humidity profiling.
Resonant modes of circular microstrip radiator loaded with varactor diode
Authors: Chakravarty T. , Sanyal S. K. , De A.
Published: August 2007

In this paper, a novel configuration of postvaractor loaded circular microstrip antenna is presented. A comprehensive cavity model analysis of such electrically thin antenna leads to very interesting results like compactness and high tunability. In earlier published works, varactor diode had been directly connected between the antenna and the ground plane. In this case, however, a metallic post is used to help connect the varactor diode in SOT‐23 package to the ground. The metallic post acts as an inductance, and therefore the circuit changes from capacitive loading to series L‐C loading resulting in vastly different results. The numerical results agree well with experimental results.
Solution of volume‐surface integral equations using higher‐order hierarchical Legendre basis functions
Authors: Kim O. S. , Meincke P. , Breinbjerg O. , Jørgensen E.
Published: August 2007

The problem of electromagnetic scattering by composite metallic and dielectric objects is solved using the coupled volume‐surface integral equation (VSIE). The method of moments (MoM) based on higher‐order hierarchical Legendre basis functions and higher‐order curvilinear geometrical elements is applied to transform the VSIE into a system of linear equations. The higher‐order MoM provides significant reduction in the number of unknowns in comparison with standard MoM formulations using low‐order basis functions, such as RWG functions. Owing to the orthogonal nature of the higher‐order Legendre basis functions, the continuity condition at the interface between metal and dielectric can be satisfied explicitly, which further reduces the number of unknowns as well as improves the accuracy of the solution. Numerical results for a metallic sphere with dielectric coating show excellent agreement with the analytical Mie series solution. Scattering by more complex metal‐dielectric objects is also considered to compare the presented technique with other numerical methods.
Effects of Ascochyta blight (Mycosphaerella pinodes) on the photosynthesizing leaf area and the photosynthetic efficiency of the green leaf area of dried‐pea (Pisum sativum)
Authors: Garry G. , Jeuffroy M. H. , Ney B. , Tivoli B.
Published: August 2007

The effects of Ascochyta blight (caused byMycosphaerella pinodes) on the net photosynthetic rate of glasshouse‐grown dried pea were studied on foliar discs and whole plants in pots showing different disease intensities, assessed visually using a disease scale (scores 0 to 5) or by an estimation of the fraction of leaf area with necrosis using an image analyser. The photosynthetic rate of foliar discs was measured using a leaf disc electrode; for plants it was assessed by CO2exchange rate measurements in a closed chamber. A reduction in the net photosynthetic rate of diseased plants was correlated with an increase in disease score. A 53–56% reduction was found in foliar discs with a mean disease score of 3. On whole plants, mean scores of 3.5 and 4.0 were associated with reductions of 36% and 98% respectively. The disease also induced a decrease in the photosynthetic efficiency of the non‐necrotic leaf area. The photosynthetic rate was zero when 30–40% of foliar area was necrotic on foliar discs and on whole plants. A function was derived from the foliar disc data that described the dependence of photosynthetic rate on the fraction of leaf area without necrosis. The model is discussed with reference to data obtained from entire plants and other pathosystems.
Polymer induced drag reduction in exact coherent structures of plane Poiseuille flow
Authors: Li Wei , Graham Michael D.
Published: August 2007

Nonlinear traveling waves that are precursors to laminar-turbulent transition and capture the main structures of the turbulent buffer layer have recently been found to exist in all the canonical parallel flow geometries. The present work examines the effect of polymer additives on these “exact coherent states” (ECS) in the plane Poiseuille geometry, using the FENE-P constitutive model for polymer solutions. In experiments with a given fluid, Reynolds and Weissenberg numbers are linearly related (i.e., Wi∕Re=const). In this situation, we study the effects of viscoelasticity on velocity field and polymer stress field along some experimental paths, which represent different flow behaviors as Re (and Wi) increases. The changes to the velocity field for the viscoelastic nonlinear traveling waves qualitatively capture many of those experimentally observed in fully turbulent flows of polymer solutions at low to moderate levels of drag reduction: drag is reduced, streamwise velocity fluctuations increase, and wall-normal and spanwise velocity fluctuations decrease. The mechanism underlying these observations is the suppression of streamwise vortices by the polymer forces exerted on the fluid. Specifically, at sufficiently high wall shear rates, viscoelasticity completely suppresses these streamwise vortices in the near-wall region, as is found in experiments in the maximum drag reduction regime. The mean shear stress balance for the nonlinear traveling waves shows that Reynolds shear stress decreases and polymer stress increases monotonically with the increase of viscoelasticity, as is found in full turbulence. The study of the influence of the viscoelasticity on the turbulent kinetic energy and Reynolds stress budgets shows that as Re (and Wi) increases, there is a consistent decrease in the production, diffusion, and dissipation of turbulent kinetic energy. The decrease in the velocity pressure gradient term leads to a redistribution of the turbulent kinetic energy among the streamwise, wall-normal and spanwise directions. The influence of the rheological parameters on the viscoelastic ECS is analyzed. It is found that the degree of drag reduction is determined primarily by the extensional viscosity and Weissenberg number. The optimum wavelength conditions under which the viscoelastic ECS first come into existence are also investigated. The wavelengths in streamwise and spanwise directions and the wall-normal extent of the ECS all increase monotonically with the increase of viscoelasticity, as is found in experiments.
Initiation of granular surface flows in a narrow channel
Authors: Jop Pierre , Forterre Yoël , Pouliquen Olivier
Published: August 2007

We experimentally investigate how a long granular pile confined in a narrow channel destabilizes when it is inclined above the angle of repose. A uniform flow then develops, which is localized at the free surface. It first accelerates before reaching a steady uniform regime. During this process, an apparent erosion is observed and the thickness of the flowing layer increases. We precisely study the evolution of the vertical velocity profile in this transient regime. The measurements are compared with the prediction of a viscoplastic model [Jop et al., Nature 441, 727 (2006)].
Vibrational energy levels with arbitrary potentials using the Eckart-Watson Hamiltonians and the discrete variable representation
Authors: Mátyus Edit , Czakó Gábor , Sutcliffe Brian T. , Császár Attila G.
Published: August 2007

An effective and general algorithm is suggested for variational vibrational calculations of N-atomic molecules using orthogonal, rectilinear internal coordinates. The protocol has three essential parts. First, it advocates the use of the Eckart-Watson Hamiltonians of nonlinear or linear reference configuration. Second, with the help of an exact expression of curvilinear internal coordinates (e.g., valence coordinates) in terms of orthogonal, rectilinear internal coordinates (e.g., normal coordinates), any high-accuracy potential or force field expressed in curvilinear internal coordinates can be used in the calculations. Third, the matrix representation of the appropriate Eckart-Watson Hamiltonian is constructed in a discrete variable representation, in which the matrix of the potential energy operator is always diagonal, whatever complicated form the potential function assumes, and the matrix of the kinetic energy operator is a sparse matrix of special structure. Details of the suggested algorithm as well as results obtained for linear and nonlinear test cases including H2O, H3+, CO2, HCN∕HNC, and CH4 are presented.
Impulsive excitation of electrostatic waves at the upper hybrid branch: A boundary value problem
Authors: Randriamboarison Orélien C.
Published: August 2007

The problem of impulsive excitation of longitudinal waves at the upper hybrid branch of a bounded cold magnetized plasma is considered. The disturbing antenna is supposed to be a point source localized at the center of a plasma-filled circular cylindrical cavity with perfectly conducting walls. The boundary conditions at the edge of the cavity naturally characterize the space discrete spectral composition for the emanated electrostatic waves. We describe a formalism that allows an analytical treatment of the temporal evolution equation of the magnetized plasma response. Particular attention is paid to the statement of the initial values of the generated electrostatic eigenmodes. On the basis of the technique of solving the Volterra integral equation, an algebraic expression of the solution is inferred.
Verification of gyrokinetic δf simulations of electron temperature gradient turbulence
Authors: Nevins W. M. , Parker S. E. , Chen Y. , Candy J. , Dimits A. , Dorland W. , Hammett G. W. , Jenko F.
Published: August 2007

The GEM gyrokinetic δf simulation code [Y. Chen and S. Parker, J. Comput. Phys. 189, 463 (2003); Y. Chen and S. Parker, J. Comput. Phys.220, 839 (2007)] is shown to reproduce electron temperature gradient turbulence at the benchmark operating point established in previous work [W. M. Nevins, J. Candy, S. Cowley, T. Dannert, A. Dimits, W. Dorland, C. Estrada-Mila, G. W. Hammett, F. Jenko, M. J. Pueschel, and D. E. Shumaker, Phys. Plasmas 13, 122306 (2006)]. The electron thermal transport is within 10% of the expected value, while the turbulent fluctuation spectrum is shown to have the expected intensity and two-point correlation function.
Flow-induced instability of double-walled carbon nanotubes based on an elastic shell model
Authors: Yan Y. , He X. Q. , Zhang L. X. , Wang Q.
Published: August 2007

Double-walled carbon nanotubes (DWCNTs) are modeled based on Donnell’s shell theory, and flow-induced instability that is induced when pressure-driven fluid goes through the inner tube at a steady flow velocity is studied. The van der Waals (vdW) interaction between the inner and outer walls is taken into account in the modeling. The numerical simulations show that the vdW interaction has significant effects on the flow-induced instability of DWCNTs. The critical flow velocities and loss of stability are closely related to the ratio of the length to the outer radius. Donnell’s shell model for carbon nanotubes (CNTs) is preferred in simulations because it takes into account the shear effects in the walls. A comparison between the CNTs that are based on a Eulerian beam model and those that are based on Donnell’s shell model shows that when the 50-nm-radius tube length is shorter than 10 μm, the comparative errors between the Eulerian beam and Donnell’s shell models are greatly increased.
Magnetoresistance in epitaxially grown MnAs films on GaAs substrates
Authors: Manago Takashi , Sinsarp Asawin , Akinaga Hiro
Published: August 2007

Magnetotransport properties of epitaxially grown MnAs(1¯100) films on GaAs(001) substrates were investigated. The thickness of the films was adjusted to 250 nm, which is the characteristic thickness for showing a clear ladder-type magnetic domain structure. The broad magnetoresistance (MR) behaviors depend on the magnetic field directions, and they follow the magnetization process well. Detailed investigation of MR in low magnetic fields along the magnetic easy axis revealed that the additional MR effect around 0 T depends on the current direction. The MR in low magnetic fields reflects the characteristic domain structures of the MnAs films.
Self-assembled Ge nanocrystals on high-k cubic Pr2O3(111)∕Si(111) support systems
Authors: Schroeder T. , Costina I. , Giussani A. , Weidner G. , Seifarth O. , Wenger Ch. , Zaumseil P. , Mocuta C. , Metzger T. H. , Geiger D. , Lichte H.
Published: August 2007

The stoichiometry, structure, and defects of self-assembled heteroepitaxial Ge nanodots on twin-free type B oriented cubic Pr2O3(111) layers on Si(111) substrates are studied to shed light on the fundamental physics of nanocrystal based nonvolatile memory effects. X-ray photoelectron spectroscopy studies prove the high stoichiometric purity of the Ge nanodots on the cubic Pr2O3(111)∕Si(111) support system. Synchrotron based x-ray diffraction, including anomalous scattering techniques, was applied to determine the epitaxial relationship, showing that the heteroepitaxial Ge(111) nanodots crystallize in the cubic diamond structure with an exclusive type A stacking configuration with respect to Si(111). Grazing incidence small angle x-ray scattering was used in addition to analyze the average shape, size, and distance parameters of the single crystalline Ge nanocrystal ensemble. Furthermore, transmission electron micrographs report that partial dislocations are the prevailing extended defect structure in the Ge nanodots, mainly induced by surface roughness on the atomic scale of the cubic Pr2O3(111) support.
Insights on fundamental mechanisms impacting Ge metal oxide semiconductor capacitors with high-k/metal gate stacks
Authors: Batude P. , Garros X. , Clavelier L. , Le Royer C. , Hartmann J. M. , Loup V. , Besson P. , Vandroux L. , Campidelli Y. , Deleonibus S. , Boulanger F.
Published: August 2007

Capacitance-voltage (CV) measurements on germanium metal oxide semiconductor (MOS) structures show unusual frequency behavior compared to their silicon counterparts—a low-frequency behavior of the high-frequency CV characteristics is observed in the inversion regime, and the experimental CV curves in the depletion regime exhibit large features that have been attributed to high densities of interface defects (Dit). In this paper, an electrical model is proposed to give insights on the fundamental mechanisms impacting Ge structures from a careful analysis of these CV measurements. Thanks to this analytical model, both CV and GV (conductance-voltage) characteristics have been accurately simulated over a large range of gate voltages and frequencies. The modeling of the strong inversion regime confirms that the generation-recombination of minority carriers is assisted by bulk traps and shows that a small level of impurities in Ge—in the 1015–1016percm3 range—can explain the frequency dispersion observed in the CV curves. The modeling in the depletion regime takes into account the fast minority carrier response in Ge. This clearly shows that the filling of the interface traps by minority carriers is essential for explaining the large features observed in the weak inversion regime and consequently that common Dit extraction techniques used on Si cannot be applied any longer to Ge MOS structures.
Effect of preionization, fluorine concentration, and current density on the discharge uniformity in F2 excimer laser gas mixtures
Authors: Mathew D. , Bastiaens H. M. J. , Boller K. J. , Peters P. J. M.
Published: August 2007

The discharge homogeneity in F2-based excimer laser gas mixtures and its dependence on various key parameters, such as the degree of preionization, preionization delay time, F2 concentration and current density, is investigated in a small x-ray preionized discharge chamber. The spatial and temporal evolution of the discharges is monitored by taking photographs of the discharge fluorescence with a fast intensified CCD camera. It is found that a preionization electron density of about 107 cm−3 bar−1 is sufficient to initiate a streamer-free homogeneous discharge in gas mixtures of helium and fluorine with multiatmospheric gas pressure. The accompanying optimum time delay between the application of the x-ray pulse and voltage across the discharge electrodes is determined to be about 20 ns. It is shown that in spite of these optimum initial conditions, a homogeneous glow discharge eventually transforms into an inhomogeneous discharge containing numerous filaments. Our experiments show that the higher the initial F2 concentration, the initial current density or the pump power density, the shorter the time interval over which the discharge stays homogeneous. By a quantitative characterization and defining a detailed measure of the observed discharge inhomogeneity we find that halogen depletion, as suggested from the theory, is responsible for the temporal instability of discharges in such laser gas mixtures, as the experimental results are in good agreement with the theory on the halogen depletion instability mechanism.
Limits of size confinement in silicon thin films and wires
Authors: Pascual-Gutiérrez José A. , Murthy Jayathi Y. , Viskanta Raymond
Published: August 2007

Physically confined structures such as thin films and nanowires are becoming increasingly important in nanoscale energy conversion and nanoelectronics. The main focus of this work is to determine the size threshold below which the volumetric specific heat and group velocity of one- and two-dimensionally confined silicon nanostructures begin to differ significantly with respect to bulk silicon and to quantify these changes. The dynamical matrix approach subject to free-standing boundary conditions is employed to determine the phonon normal modes of vibration of the structures. The environment-dependent interatomic potential under the harmonic approximation is used to model interatomic forces. We find that above 10nm thickness, silicon [111]-films yield specific heats and group velocities which exhibit size-invariant behavior; for [111]-silicon nanowires, the limit is approximately 5nm. Moreover, we show that computed phonon group velocities using the dynamical matrix approach are affected by geometry-specific modes beyond confinement, and that size effects are mainly manifested through the volumetric specific heat at low temperatures. Furthermore, we conclude that confinement effects, when present, are only relevant at low temperatures, below 100K, when the predominant phonon wavelength becomes larger than the confined dimension.
Heat treatment parameters effecting the fractal dimensions of AuGe metallization on GaAs
Authors: Mojzes Imre , Dominkovics Csaba , Harsányi Gábor , Nagy Szilvia , Pipek János , Dobos László
Published: August 2007

Correlation was detected between the thermal treatment parameters of the AuGe–GaAs system and surface fractal structure. Structural entropic calculations were used to confirm the results obtained by fractal calculations.
Circular photogalvanic effect of the two-dimensional electron gas in AlxGa1−xN∕GaN heterostructures under uniaxial strain
Authors: He X. W. , Shen B. , Tang Y. Q. , Tang N. , Yin C. M. , Xu F. J. , Yang Z. J. , Zhang G. Y. , Chen Y. H. , Tang C. G. , Wang Z. G.
Published: August 2007

The circular photogalvanic effect (CPGE) of the two-dimensional electron gas (2DEG) in Al0.25Ga0.75N∕GaN heterostructures induced by infrared radiation has been investigated under uniaxial strain. The observed photocurrent consists of the superposition of the CPGE and the linear photogalvanic effect currents, both of which are up to 10−2nA. The amplitude of the CPGE current increases linearly with additional strain and is enhanced by 18.6% with a strain of 2.2×10−3. Based on the experimental results, the contribution of bulk-inversion asymmetry (BIA) and structure-inversion asymmetry (SIA) spin splitting of the 2DEG to the CPGE current in the heterostructures is separated, and the ratio of SIA and BIA terms is estimated to be about 13.2, indicating that the SIA is the dominant mechanism to induce the k-linear spin splitting of the subbands in the triangular quantum well at AlxGa1−xN∕GaN heterointerfaces.
Effect of Cr substitution for Fe on the spin polarization of Co2CrxFe1−xSi Heusler alloys
Authors: Karthik S. V. , Rajanikanth A. , Nakatani T. M. , Gercsi Z. , Takahashi Y. K. , Furubayashi T. , Inomata K. , Hono K.
Published: August 2007

We have investigated the effect of Cr substitution for Fe on the spin polarization, P, of Co2CrxFe1−xSi alloys using the point contact Andreev reflection method. A steep increase from P=0.57 to P=0.64 occurs by a small substitution of Cr for Fe of x=0.02, thereafter P values are constant for higher Cr concentrations up to x=0.4. The increase in spin polarization can be attributed to both the improved L21 ordering found experimentally as well as the half-metallicity predicted by ab initio calculations in the composition range of 0≤x≤0.5. We propose the composition range of 0.02≤x≤0.1 is the most promising for ferromagnetic electrodes of magnetic tunneling junctions to achieve high tunneling magnetoresistance.
Highly efficient and stable white light organic light-emitting devices
Authors: Lin Mei-Fang , Wang Lei , Wong Wai-Kwok , Cheah Kok-Wai , TAM Hoi-Lam , Lee Meng-Ting , Ho Meng-Huan , Chen Chin H.
Published: August 2007

A highly efficient two-element white light organic light-emitting device with a sky blue dopant BUBD-1 and a yellow dopant TBRb was fabricated. The device achieved an electroluminescence efficiency of 17.1cd∕A and 7.9lm∕W at 20mA∕cm2. From 112 to 32 010 nits, the CIEx,y coordinates variation was Δ(x,y)<±(0.01,0.01), which is superior to common white light organic light-emitting devices (OLEDs) that tend to change color with drive conditions. Moreover, the device reached a half-decay t1∕2 lifetime over 40000h at an initial luminance of 300cd∕m2. This result is among the best records of fluorescent white light OLEDs.
Local retention behaviors of epitaxial and polycrystalline PbMg1∕3Nb2∕3O3–PbTiO3 thin films by scanning force microscopy
Authors: Lee J. H. , Choi M. R. , Oh Y. J. , Jo W.
Published: August 2007

The authors report the results of retention in epitaxial and polycrystalline PbMg1∕3Nb2∕3O3–PbTiO3 (PMN-PT) thin films on SrRuO3 (SRO) and Pt. The SRO electrodes were deposited by pulsed laser deposition and the PMN-PT thin films were coated by a sol-gel method. Local poling behaviors of the PMN-PT domains were investigated as a function of time in both single-poled and reverse-poled regions by scanning force microscopy. An extended exponential decay is observed in the PMN-PT/SRO heterostructures while a fluctuated relaxation is shown in the PMN-PT/Pt films, suggesting that crystal orientation and grain growth is critical to understand retention of relaxor ferroelectrics.
Effect of tensile stress on the various components of the off current of n-channel metal-oxide-semiconductor transistors
Authors: Yang Peizhen , Lau W. S. , Ho V. , Loh C. H. , Siah S. Y. , Chan L.
Published: August 2007

The authors found that tensile stress actually slightly increases the on current and the subthreshold off current but it slightly decreases the gate leakage current and the drain junction leakage current for n-channel metal-oxide-semiconductor transistors. For short transistors, the subthreshold off current dominates over the other two components of the off current such that tensile stress slightly increases both the on current and the off current. However, in the on current versus the logarithm of off current plot, tensile stress increases the on current for a constant off current such that the overall effect of tensile stress is an improvement.
Double capping of molecular beam epitaxy grown InAs∕InP quantum dots studied by cross-sectional scanning tunneling microscopy
Authors: Ulloa J. M. , Koenraad P. M. , Gapihan E. , Létoublon A. , Bertru N.
Published: August 2007

Cross-sectional scanning tunneling microscopy was used to study at the atomic scale the double capping process of self-assembled InAs∕InP quantum dots (QDs) grown by molecular beam epitaxy on a (311)B substrate. The thickness of the first capping layer is found to play a mayor role in determining the final results of the process. For first capping layers up to 3.5nm, the height of the QDs correspond to the thickness of the first capping layer. Nevertheless, for thicknesses higher than 3.5nm, a reduction in the dot height compared to the thickness of the first capping layer is observed. These results are interpreted in terms of a transition from a double capping to a classical capping process when the first capping layer is thick enough to completely cover the dots.
Electron and hole dynamics of InAs∕GaAs quantum dot semiconductor optical amplifiers
Authors: O’Driscoll I. , Piwonski T. , Schleussner C.-F. , Houlihan J. , Huyet G. , Manning R. J.
Published: August 2007

Single-color and two-color pump-probe measurements are used to analyze carrier dynamics in InAs∕GaAs quantum dot amplifiers. The study reveals that hole recovery and intradot electron relaxation occur on a picosecond time scale, while the electron capture time is on the order of 10ps. A longer time scale of hundreds of picoseconds is associated with carrier recovery in the wetting layer, similar to that observed in quantum well semiconductor amplifiers.
Effect of excess bismuth concentration on dielectric and electrical properties of fully crystallized Bi2Mg2∕3Nb4∕3O7 thin films
Authors: Seong Nak-Jin , Park Jong-Hyun , Yoon Soon-Gil
Published: August 2007

The fully crystallized Bi2Mg2∕3Nb4∕3O7 (BMN) films deposited at 400°C were characterized as a function of excess bismuth amount. The films with 15mol% excess bismuth amount were fully crystallized having a monoclinic structure at 300°C. The dielectric constant of the films deposited at 400°C increases with increasing excess bismuth amount and the films with 15mol% excess bismuth exhibit a dielectric constant of 128 and a dissipation factor of 0.2%. The crystallized BMN films with 170nm thickness exhibit breakdown strengths above 600kV∕cm (⩾10V), irrespective of excess bismuth amount and a leakage current density of 2×10−8A∕cm2 at 590kV∕cm. The conduction of crystallized BMN films was controlled by Schottky emission mechanism having a Schottky barrier height of 0.2–0.35eV.