bluuebunny/crossref_metadata_2025 huggingface dataset:
On fluid‐structure interaction in transonic wind tunnels
Authors: Rašuo Boško , Bengin Aleksandar
Published: December 2008

This paper studies the interaction (influence) of perforated walls of transonic wind tunnels in two‐dimensional investigations which employ the generalized method for solving Dirichlets problem formulated for the rectangle of the transonic wind tunnel work section. The algorithm has been applied to the aerodynamic experimental results from investigations of NACA 0012 airfoil obtained at the VTI – Aeronautical Institute and the Faculty of Mechanical Engineering in Belgrade to demonstrate in two‐dimensional investigations the appropriateness of the presented advanced algorithm for the calculation of the interference of the transonic wind tunnel wall. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microcomputer‐based simulation of heat conduction between solid of tapered shape and the fluid
Authors: Shrivastava Purnima
Published: December 2008

Simulating the heat conduction in between a solid conducting body immersed in fluid at a given temperature is a difficult task, particularly when the body is tapered in shape and the costs have to be kept low.

The body in question is cylindrical, symmetrical about z‐axis, tapered in shape and has been heated to a high temperature before being immersed into the fluid. The heat conduction equation in cylindrical polar coordinates with all derivative boundary conditions is attempted to be solved in two ways – first analytically making use of Bessel's function and then by numerical modelling with the help of Finite Difference method, and equations thus formed have been solved through ADI explicit and Implicit (Peaceman Rachford) scheme on microcomputer. The paper is an account of work already done on this and includes further possibilities for general solution with analytical methods and a suitable low‐cost numerical solution. Also possible analogy with flow of fluids have been explored. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Existence of solutions to a “water‐oil” system
Authors: Ammi M. R. Sidi
Published: December 2008

In this work, we show existence of solutions of the classical system of nonlinear partial differential equations with applications in the industry of exploitation of hydrocarbons. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Inverse problems and regularization techniques in option pricing
Authors: Souza Max O. , Zubelli Jorge P.
Published: December 2008

Option‐price based calibration of stochastic volatility models under fast mean reversion poses quite challenging inverse problems. Nevertheless, in this note we remark that by an appropriate multi‐scale asymptotic analysis, one can calibrate the models in a stable way for a number of different asymptotic regimes. These regimes include, but are not restricted to, those studied by Fouque et al. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamics of fluid membranes and budding of vesicles
Authors: Arroyo Marino , DeSimone Antonio
Published: December 2008

We derive the evolution equations for a multi‐phase fluid membrane surrounded by a viscous fluid. We discuss some implications for the dynamics of lipid bilayer membranes and for physically based Willmore flows. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modeling of timing belt construction
Authors: Domek Grzegorz , Malujda Ireneusz
Published: December 2008

The frictional and profiling character of timing belt coupling with pulleys and the importance of surface state and workmanship accuracy of pulleys for the coupling quality have not been taken into account. In case of toothed cylindrical gears, operation tests have shown a huge significance of not only workmanship accuracy of pulleys, but also the technology of their working [1, 5]. Series of parameters essential for belt coupling with pulleys may be distinguished here, such as: profile of belt and pulley, surface state, barrel profile, whip and parallelism of shafts. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Acomplete classification of bifurcation diagrams of classes of multiparameter p ‐Laplacian boundary value problems
Authors: Hung Kuo‐Chih , Wang Shin‐Hwa
Published: December 2008

We study the bifurcation diagrams of positive solutions of the multiparameter p ‐Laplacian problem (φ p (u ′(x)))′ + f λ,μ (u (x)) = 0, –1 < x < 1, u (– 1) = u (1) = 0, where p > 1, φ p (y) = |y |p –2 y, (φ p (u ′))′ is the one‐dimensional p ‐Laplacian, f λ,μ (u)= g (u, λ) + h (u, μ), and λ > λ0 and μ > μ0 are two bifurcation parameters, λ0 and μ0 are two given real numbers. Assuming that functions g and h satisfy hypotheses (H1)–(H4), for fixed μ > μ0,we give a classification of totally eight qualitatively different bifurcation diagrams. We prove that, on the (λ, ∥u ∥∞)‐plane, each bifurcation diagram consists of exactly one curve which is either a monotone curve or has exactly one turning point where the curve turns to the right. Hence the problem has at most two positive solutions for each λ > λ0. More precisely, we prove the exact multiplicity of positive solutions. In addition, for all p > 1, we give interesting examples which show complete evolution of bifurcation diagrams as μ varies. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamic K‐L analysis of coherent structures based on DNS of turbulent Newtonian and viscoelastic flows (Poster Presentation)
Authors: Samanta Gaurab , Oxberry Geoffrey , Beris Antony N. , Handler Robert , Housiadas Kostas
Published: December 2008

Earlier work [1, 2], using Karhunen‐Loeve (K‐L) analysis, demonstrated a dramatic enhancement of the importance of large scale motions with increased viscoelasticity and an equally dramatic decrease in the K‐L dimension of the flow (an order of magnitude) as viscoelasticity increases versus similar Newtonian results. In this work we look into dynamics of viscoelastic turbulent flows by projecting the DNS data in time into a selected set of K‐L modes. The dynamics of the coherent structures embedded in turbulent flows were investigated through calculations of mode auto and cross correlations. This allows for a more systematic examination of the role of large‐scale structures in turbulence and drag reduction. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
International duopoly with unknown costs
Authors: Ferreira Fernanda A. , Pinto Alberto A.
Published: December 2008

We consider two firms, located in different countries, selling the same homogeneous good in both countries. In each country there is a non negative tariff on imports of the good produced in the other country. We suppose that each firm has two different technologies, and uses one of them according to a certain probability distribution. The use of either one or the other technology affects the unitary production cost. We analyse the effect of the production costs uncertainty on the profits of the firms and also on the welfare of the governments. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Chemical modification of zeolite beta surface and its effect on gas permeation of mixed matrix membrane
Authors: Sirikittikul Doungporn , Fuongfuchat Asira , Booncharoen Warintorn
Published: December 2008

Chemical modification of zeolite beta (BEA) with a series of organosilane compounds [R(CH3)nSiX(3‐n), where X is a chloro or alkoxy group with n = 0 and 2, and R is an alkyl chain varying from CH3 to C18H37] was investigated. The results of FT‐IR and 29Si CP/MAS NMR indicated that the alkylsilyl species were covalently anchored onto the BEA surface. Grafting density of the alkylsilyl species was determined by CHN elemental analysis and thermogravimetric analysis (TGA). Evidently, it can be adjusted by varying the reaction time and organosilane concentration. The reaction kinetics was found to resemble the kinetics of the well‐known monolayer formation, i.e. SAMs. The kinetic plot illustrated two distinct regions, a rapid attachment followed by a gradual increase of grafting density. The degradation temperature at maximum rate (Tmax) of the surface‐grafted BEA was observed in the range of 440–460°C. The modified BEA showed surface hydrophobic characteristic by having a strong affinity to the non‐polar n‐heptane. Good particle distribution and strong interfacial adhesion were observed in the mixed matrix membranes of the BEA grafted with C3H7 to C18H37. The grafted chain length was found to have an effect on gas permeability. Carbon dioxide, oxygen, and ethylene permeabilities of the membranes containing the unmodified BEA were comparable to those of the CH3Si‐grafted BEA. Interestingly, the membranes containing the BEA grafted with C3H7 to C18H37 species showed enhancement of the carbon dioxide permeability. Affinity of the long alkyl chain to carbon dioxide probably caused the increase of carbon dioxide permeability. Copyright © 2008 John Wiley & Sons, Ltd.
Microwave‐assisted extraction of rutin and quercetin from the stalks of Euonymus alatus (Thunb.) Sieb
Authors: Zhang Fan , Yang Yi , Su Ping , Guo Zhenku
Published: December 2008

Introduction

Euonymus alatus (Thunb.) has been used as one of traditional Chinese medicines for several thousand years. Conventional methods for the extraction of rutin and quercetin from E. alatus, including solvent extraction, Soxhlet extraction and heat reflux extraction are characterised by long extraction times and consumption of large amounts of solvents.

Objective

To develop a simple and rapid method for the extraction of rutin and quercetin from the stalks of Euonymus alatus (Thunb.) Sieb using microwave‐assisted extraction (MAE) technique.

Methodology

MAE experiments were performed with a multimode microwave extraction system. The experimental variables that affect the MAE process, such as the concentration of ethanol solution, extractant volume, microwave power and extraction time were optimised. Yields were determined by HPLC. The results were compared with that obtained by classical Soxhlet and ultrasonic‐assisted extraction (UAE).

Results

From the optimised conditions for MAE of rutin and quercetin it can be concluded that the solvent is 50% ethanol (v/v) solution, the extractant volume is 40 mL, microwave power is 170 W and irradiation time is 6 min. Compared with Soxhlet extraction and ultrasonic extraction, microwave extraction is a rapid method with a higher yield and lower solvent consumption.

Conclusion

The results showed that MAE can be used as an efficient and rapid method for the extraction of the active components from plants. Copyright © 2008 John Wiley & Sons, Ltd.
The proteome of rat olfactory sensory cilia
Authors: Mayer Ulrich , Küller Alexander , Daiber Philipp C. , Neudorf Inge , Warnken Uwe , Schnölzer Martina , Frings Stephan , Möhrlen Frank
Published: December 2008

Olfactory sensory neurons expose to the inhaled air chemosensory cilia which bind odorants and operate as transduction organelles. Odorant receptors in the ciliary membrane activate a transduction cascade which uses cAMP and Ca2+ for sensory signaling in the ciliary lumen. Although the canonical transduction pathway is well established, molecular components for more complex aspects of sensory transduction, like adaptation, regulation, and termination of the receptor response have not been systematically identified. Moreover, open questions in olfactory physiology include how the cilia exchange solutes with the surrounding mucus, assemble their highly polarized set of proteins, and cope with noxious substances in the ambient air. A specific ciliary proteome would promote research efforts in all of these fields. We have improved a method to detach cilia from rat olfactory sensory neurons and have isolated a preparation specifically enriched in ciliary membrane proteins. Using LC‐ESI‐MS/MS analysis, we identified 377 proteins which constitute the olfactory cilia proteome. These proteins represent a comprehensive data set for olfactory research since more than 80% can be attributed to the characteristic functions of olfactory sensory neurons and their cilia: signal processing, protein targeting, neurogenesis, solute transport, and cytoprotection. Organellar proteomics thus yielded decisive information about the diverse physiological functions of a sensory organelle.
Proteomic identification of molecular targets of gambogic acid: Role of stathmin in hepatocellular carcinoma
Authors: Wang Xin , Chen Yangchao , Han Quan‐bin , Chan Chu‐yan , Wang Hua , Liu Zheng , Cheng Christopher Hon‐ki , Yew David T. , Lin Marie C.M. , He Ming‐liang , Xu Hong‐xi , Sung Joseph J.Y. , Kung Hsiang‐fu
Published: December 2008

Gamboge has been developed as an injectable drug for cancer treatment in China. In this study, the inhibition ratio and their IC50 values of two derivatives from Gamboge in hepatocellular carcinoma (HCC) were determined. Proteomic approach was employed to reveal the target proteins of these two derivatives, gambogic acid (GA), and gambogenic acid (GEA). HCC cells were cultured under varied conditions with the addition of either GA or GEA. Twenty differentially expressed proteins were identified and the four most distinctly expressed proteins were further validated by Western blotting. GA and GEA revealed inhibitory effects on HCC cell proliferation. The expression of cyclin‐dependent kinase 4 inhibitor A and guanine nucleotide‐binding protein β subunit 1 were upregulated by both xanthones, whilst the expression of 14‐3‐3 protein sigma and stathmin 1 (STMN1) were downregulated. Furthermore, overexpression of STMN1 in HCC cells decreased their sensitivity, whilst small interfering RNAs targeting STMN1 enhanced their sensitivity to GA and GEA. In conclusion, our study suggested for the first time that STMN1 might be a major target for GA and GEA in combating HCC. Further investigation may lead to a new generation of anticancer drugs exerting synergistic effect with conventional therapy, thus to promote treatment efficacy.
On the mechanisms of cadmium stress alleviation in Medicago truncatula by arbuscular mycorrhizal symbiosis: A root proteomic study
Authors: Aloui Achref , Recorbet Ghislaine , Gollotte Armelle , Robert Franck , Valot Benoît , Gianinazzi‐Pearson Vivienne , Aschi‐Smiti Samira , Dumas‐Gaudot Eliane
Published: December 2008

The arbuscular mycorrhizal (AM) symbiosis belongs to the strategies plants have developed to cope with adverse environmental conditions including contamination by heavy metals such as cadmium (Cd). In the present work, we report on the protective effect conferred by AM symbiosis to the model legume Medicago truncatula grown in presence of Cd, and on the 2‐D‐based proteomic approach further used to compare the proteomes of M. truncatula roots either colonised or not with the AM fungus Glomus intraradices in Cd‐free and Cd‐contaminated substrates. The results indicated that at the proteome level, 9 out of the 15 cadmium‐induced changes in nonmycorrhizal roots were absent or inverse in those Cd‐treated and colonized by G. intraradices, including the G. intraradices‐dependent down‐accumulation of Cd stress‐responsive proteins. Out of the twenty‐six mycorrhiza‐related proteins that were identified, only six displayed changes in abundance upon Cd exposure, suggesting that part of the symbiotic program, which displays low sensitivity to Cd, may be recruited to counteract Cd toxicity through the mycorrhiza‐dependent synthesis of proteins having functions putatively involved in alleviating oxidative damages, including a cyclophilin, a guanine nucleotide‐binding protein, an ubiquitin carboxyl‐terminal hydrolase, a thiazole biosynthetic enzyme, an annexin, a glutathione S‐transferase (GST)‐like protein, and a S‐adenosylmethionine (SAM) synthase.
Formation of Jets by Shaped Charges with Metal Powder Liners
Authors: Zygmunt Bogdan , Wilk Zenon
Published: December 2008

The characteristics of shaped charges with metal powder liners for perforating borehole pipes are described. The liners were manufactured using powder metallurgy technology. Two types of powder liners were made: a homogeneous one made of copper powder and a heavy one made of copper and tungsten powder blend. Laminar liners consisting of two layers made from powders of different densities were also examined. X‐ray pulse technique was applied to research the process of jet stream formation. Radiograms revealed the discontinuous (discrete) structure of jets formed from powder liners. The corresponding computer simulations of jet formation are presented.
Novel γ‐ and X‐ray scintillator research: on the emission wavelength, light yield and time response of Ce3+ doped halide scintillators
Authors: Birowosuto M. D. , Dorenbos P.
Published: December 2008

This work reviews the scintillation properties of many Ce3+ doped halide compounds studied during the past two decades with the aim to find new relationships between scintillation performance and materials properties. Three major types of compounds are reviewed; lanthanide trihalides LnX3, (pseudo)‐elpasolites M2ALnX6 and ternary halides Am Lnn Xo where M and A are alkali cations, Ln is a rare earth cation and X is a halide anion. We will address the relationship of the emission wavelength of Ce3+ and its Stokes shift with the structure, type of anions, coordination number, band gap etc. A comparison between the observed absolute scintillation yield with the fundamental limits will be made. Scintillation losses due to thermal ionization processes and the relationship between Stokes shift, self absorption, and decay time lengthening are treated. Various trends will be identified that may guide us in the continuing quest for better scintillators. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Methane gas sensor application of cuprous oxide synthesized by thermal oxidation
Authors: Jayatissa Ahalapitiya H. , Samarasekara P. , Kun Guo
Published: December 2008

Application of cuprous oxide (Cu2O) thin films for methane gas sensors was investigated. The Cu2O films were prepared by the thermal oxidation of Cu films under reduced partial pressure of oxygen. The XRD and AFM measurements were performed to investigate crystal structure and the surface properties of synthesized Cu2O films. According to the XRD patterns, the films had a preferred (111) orientation. Sensors were fabricated using synthesized Cu2O films and their sensitivity, response times, and recovery times were measured at different temperatures for different methane concentrations. The sensor exhibited a high sensitivity, a fast response time, and a fast recovery time for methane gas at an operation temperature as low as 180 °C. The Cu2O has unique characteristics, such as has p‐type conduction, high conductivity, and high carrier mobility. The fast and high response of Cu2O sensor for methane was explained as due to the increase of resistance in intrinsic p‐type Cu2O in the presence of methane gas. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of manganese silicide layers on Si substrates using MnCl2 source
Authors: Junhua Hu , Kurokawa Takanori , Suemasu Takashi , Takahara Shogo , Itakura Masaru , Tatsuoka Hirokazu
Published: December 2008

Manganese silicide layers were grown on Si(111) substrates by exposure of the Si substrates to MnCl2 vapor. The thermal treatment temperature of 500 °C provided the appropriate growth conditions to form the Mnx Siy (y /x ∼ 2) similar to MnSi1.7 phase. The epitaxial Mnx Siy (y /x ∼ 2) islands grew during the initial growth stage. As the heat treatment time increased, the epitaxial layer became continuous and covered the entire Si(111) substrate surface at the appropriate heat treatment temperature of 500 °C, even though the additional growth of the Mnx Siy (y /x ∼ 1) deposit similar to MnSi phase occurred when the thickness of Mn‐silicide layers exceeded the limited layer thickness. These results encouraged us to grow large area Mnx Siy (y /x ∼ 2) layers on Si substrates using this simple growth technique. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Highly efficient broad‐area blue and white light‐emitting diodes on bulk GaN substrates
Authors: Vampola Kenneth J. , Fellows Natalie N. , Masui Hisashi , Brinkley Stuart E. , Furukawa Motoko , Chung Roy B. , Sato Hitoshi , Sonoda Junichi , Hirasawa Hirohiko , Iza Michael , DenBaars Steven P. , Nakamura Shuji
Published: December 2008

Highly efficient light emitting diodes (LEDs) with peak emission wavelengths of nominally 450 nm were grown, fabricated and tested. The growth was performed by metal organic chemical vapour deposition. The LEDs were grown on c ‐plane (0001) bulk GaN substrates and fabricated into broad‐area devices with active area 0.01 cm2. Considerations were made to improve extraction efficiency, including transparent contacts, suspended mirror‐less packaging and encapsulation in a truncated pyramid optic.

These factors resulted in LEDs with high peak external quantum efficiency and reduced efficiency droop. The output power and external quantum efficiency at 20 mA were 38.5 mW and 68.9%. At 100 mA, they were 170 mW and 60.9%. White LEDs were fabricated by application of a yellow phosphor to the blue LEDs. The white LED luminous flux and efficacy at 20 mA was 9.6 lm and 128 lm/W. The chromaticity coordinates and correlated colour temperature were (0.348 K, 0.378 K) and 4998 K. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth behavior and microstructure of ZnO epilayer on γ‐LiAlO2(100) substrate by chemical vapor deposition
Authors: Chang Liuwen , Chou Mitch M. C. , Hwang Teng‐Hsing , Chen Chun‐Wei
Published: December 2008

Low lattice‐mismatched γ‐LiAlO2(100) substrates were employed to grow ZnO epitaxial films by chemical vapor deposition. The influence of growth temperature on growth behavior of ZnO was investigated. Results indicated that the low lattice‐matched (10$ \bar 1 $0) crystallites nucleate on substrate at all growth temperatures employed. However, a second type of crystallites having an (0001) orientation can also nucleate on substrate at low growth temperature of 575 °C and 640 °C. The growth rate of the later crystallite is, however, higher than that of the (10$ \bar 1 $0) one and finally results in a single crystalline ZnO film having an [0001] azimuthal orientation. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Properties and prospects of blue–green emitting II–VI‐based monolithic microcavities
Authors: Sebald K. , Kruse C. , Wiersig J.
Published: December 2008

In this paper we review basic optical properties of II–VI‐based monolithic microcavities with quantum wells or quantum dots embedded. The epitaxial growth of high‐reflectivity distributed Bragg reflectors for the blue–green spectral range is discussed since they are a key component for micropillar cavities. The pillar structured samples reveal three‐dimensionally confined optical modes with high quality factors and small mode volumes making them appropriate to investigate cavity quantum electrodynamic effects. The II–VI material system is very promising for the utilization of this effect for technological applications due to the large exciton oscillator strength and carrier confinement. The theoretical methods needed to describe light–matter interaction in such systems is reviewed. For the quantum well based cavities single‐mode stimulated emission at near room temperature is realized. Furthermore, the relatively large cavity polariton stability makes it possible to observe polariton condensation in this kind of samples. For the quantum dot based microcavities a strong enhancement of the emission intensity for quantum dots being in spectral resonance with the cavity modes is observed. To realize the necessary spectral matching a target fine tuning can be achieved by temperature variation or by post fabrication focused ion beam milling. A pronounced enhancement of the spontaneous emission rate of quantum dots coupled to the discrete optical modes of the cavities is demonstrated by the occurrence of the Purcell effect. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An empirical model for bulk modulus and cohesive energy of rocksalt‐, zincblende‐ and chalcopyrite‐structured solids
Authors: Verma A. S.
Published: December 2008

In this paper we present empirical models for ground‐state properties such as bulk modulus and cohesive energy of rocksalt‐, zincblende‐ and chalcopyrite‐structured solids. The bulk moduli and cohesive energy of these solids exhibit a linear relationship when plotted on a log–log scale versus the nearest‐neighbor distance d (Å), but fall on different straight lines according to the product of valence electrons of the solids. We have applied the proposed relations to alkali halides, alkaline‐earth chalcogenides, binary and ternary tetrahedral semiconductors and found a better agreement with experimental data as compared to the values evaluated by earlier researchers. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of hydrostatic pressure on the conduction‐electron g ‐factor in GaAs–Ga1–xAlx As quantum wells
Authors: Porras‐Montenegro N. , Raigoza N. , Reyes‐Gómez E. , Duque C. A. , Oliveira L. E.
Published: December 2008

The effects of hydrostatic pressure on the conduction‐electron effective Landé g ‐factor in semiconductor GaAs–Ga1–x Alx As quantum wells under growth‐direction and in‐plane magnetic fields are studied. Calculations are performed by using the Ogg–McCombe effective Hamiltonian in order to take into account the non‐parabolicity and anisotropy of the conduction band. Numerical results are obtained as functions of the ap‐ plied hydrostatic pressure and magnetic fields. Present results are in quite good agreement with experimental measurements in GaAs–Ga1–x Alx As quantum wells in the absence of hydrostatic pressure, and indicate new possibilities for manipulating the electron‐effective g ‐factor in semiconductor low‐dimensional systems. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Unusual B1–B2 transition in PbSe under high pressure: evidence for two intermediate phases; transport, structural, and optical properties
Authors: Ovsyannikov Sergey V. , Shchennikov Vladimir V. , Manakov Andrei Y. , Likhacheva Anna Y. , Ponosov Yuri S. , Mogilenskikh Viktor E. , Vokhmyanin Alexander P. , Ancharov Alexey I. , Skipetrov Eugenii P.
Published: December 2008

We report the results of a study of the thermoelectric power (Seebeck effect), the electrical resistivity, X‐ray diffraction, and Raman spectroscopy under high pressure (P) to 15 GPa for binary and tin‐doped lead selenide (PbSe and Pb1–x Snx Se (x = 0.125)). The gathered data were inconsistent with previous models suggesting only one intermediate phase between the ambient NaCl (B1) lattice and a high‐pressure metal CsCl (B2) lattice. Furthermore, the data hint at the existence of two competing intermediate phases. From the thermopower we established that a phase that is characterized by n‐type conductivity is dominating, while the other one – of p‐type conductivity is probably optional. The electrical conductivity in both of the phases is semiconducting. In the X‐ray diffraction studies in one of the three investigated samples of Pb0.875Sn0.125Se we could refine a pattern of the intermediate phase taken at ∼9.5 GPa in the Cmcm space group. This corresponds to the symmetry of earlier proposed structural types of TlI and CrB. The patterns of the intermediate phase in the two other samples show additional strong reflexes that are not related to either the NaCl or the CsCl lattices. This presents evidence of the presence of one more undetermined phase. The Raman spectra of the intermediate phase showed a dependence on a pressure‐transmitting medium (methanol‐ethanol or KCl). The pressure‐driven NaCl → CsCl transition and a pressure dependence of the semiconductor energy gap of PbSe are compared with those of other lead salts, namely, PbTe and PbS (galena). It is surmised that there is no interrelation between the closure of the energy gap at the NaCl phase and the phase transition to the intermediate phase. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Excitons in coupled quantum dots: hydrostatic pressure and electric field effects
Authors: López S. Y. , Porras‐Montenegro N. , Duque C. A.
Published: December 2008

The variational procedure, in the effective‐mass and parabolic‐band approximations, is used in order to investigate the effects of hydrostatic pressure and in‐growth direction applied electric field on the exciton states in vertically GaAs–Ga1–x Alx As coupled quantum dots. We have found that when the symmetrical lengths and radius of each QD are comparable with the Bohr radius of the GaAs material and for a finite value of the applied electric field, the binding energy always diminishes with the length of the central barrier because the two carriers in the exciton are localized in two well defined different regions of the system. However, for the zero electric field the binding energy decreases with the barrier width from the limit value corresponding to the exciton confined in one quantum dot of volume V up to reach a minimum and then increases to a value which corresponds to that of the exciton confined in an isolated quantum dot of volume V /2. Additionally, we have found that the applied electric field caninduce that the lowest structure in the photoluminescence‐peak energy transitions be associated to spatially indirect excitons, situation which in the zero limit of the electric field and independent of the dimensions of the two coupled dots, always corresponds to spatially direct excitons. The main hydrostatic pressure effect reveals an increasing in the exciton binding energy, without modifying the direct or indirect exciton regime, and a well defined rigid blue‐shift in the photoluminescence peak energy transitions in the presence of an applied electric field. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical properties of di‐octyl substituted polyfluorene under hydrostatic pressure
Authors: Paudel K. , Arif M. , Chandrasekhar M. , Guha S.
Published: December 2008

Almost all polyfluorene (PF) derivatives utilize solubilizing side chain substituents for tailoring their optical and electronic properties. Side chain substitution, in addition to improving the solution processing and film forming characteristics, confers new functionality and dictates the backbone structure of polymers. The backbone conformation in di‐octyl substituted PF (PF8) is strongly dependent upon the conformation of the alkyl side chain. In this paper we present photoluminescence and Raman scattering studies of bulk PF8 as a function of hydrostatic pressure. These results are further contrasted with the optical studies of a branched side group substituted PF under hydrostatic pressure. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Luminescent detection of Cu(II) ions in aqueous solution using CdSe and CdSe‐ZnS quantum dots functionalised with mercaptosuccinic acid
Authors: Callan John F. , Mulrooney Ray C.
Published: December 2008

CdSe (core) and CdSe‐ZnS (core‐shell) Quantum Dots (QD's) surface functionalised with mercaptosuccinic acid ligands were prepared. The conjugates were screened against a variety of common metal ions in aqueous solution and selectivity was established for Cu(II) ions based on an “On‐Off” change in fluorescence intensity. The presence of the ZnS shell was found to have a significant effect on both the sensitivity and the range of Cu2+ induced quenching. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Few‐electron semiconductor quantum dots in magnetic field
Authors: Ciftja Orion
Published: December 2008

Usually, semiconductor quantum dots represent a twodimensional nanoscale system with few electrons confined in a semiconductor host crystal. Properties of fewelectron quantum dots in the weak magnetic regime are explained well through single‐electron theory concepts. However, as the strength of the external magnetic field increases the confined electrons in the quantum dot start to manifest collective quantum behavior as seen in the integer and fractional quantum Hall effect regime.

In the limit of strong magnetic field, we see the confined electronic states in a semiconductor quantum dot transforming into Laughlin‐like states that describe strongly correlated electronic systems in the quantum Hall regime. While this is expected, our calculations further indicate that even a classical model of confined electrons provides quite an accurate presentation, suggesting that in this regime electrons stabilize in relatively rigid geometric structures. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transport mechanism in the quantum well embedded with quantum dots
Authors: Kannan E. S. , Kim Gil‐Ho , Farrer I. , Ritchie D. A.
Published: December 2008

Electron transport in single and double quantum well system embedded with InAs quantum dots is investigated by carrying out magnetoresistance measurements at 1.2 K. At low carrier densities, the electrons are strongly localized due to disorder and undergo magnetic field induced insulator to quantum Hall liquid transitions characterized by temperature independent crossing points. At higher carrier densities no such magnetic field induced transition are observed. The potential induced by the electrons in the quantum dots were found to enhance the scattering between the edge states resulting in the substantial reduction of the width of the Hall plateau in the single quantum well system. In the double quantum well system, instead of plateaus abrupt increase in the Hall resistance is observed at integer filling factors. On sweeping the gate bias at fixed magnetic field, hysteresis effect was observed in the double quantum well system due to the charge trapping in the defect levels. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Emission spectrum of a quantum dot embedded in a nanocavity
Authors: Tarel Guillaume , Savona Vincenzo
Published: December 2008

We model the emission spectrum of a quantum dot embedded in a (e.g. photonic crystal) nanocavity, using a semi‐classical approach to describe the matter‐field interaction. We start from the simple model of a quantum dot as a two‐level system, and recover the result expected from cavity quantum electrodynamics. Then, we study the influence of electron‐acoustic‐phonons interaction. We show that the surrounding semiconductor plays an essential role in the emission spectrum in strong coupling. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth behaviour of InGaN/GaN self‐assembled quantum dots with different growth conditions in horizontal MOCVD
Authors: Jung Woo‐Gwang , Jang Jae‐Min , Choi Seung‐Kyu , Kim Jin‐Yeol
Published: December 2008

InGaN/GaN self‐assembled quantum dots (QDs) were grown on (0001) sapphire substrates by low pressure metalorganic chemical vapor deposition. The growth behavior of the InGaN/GaN QDs was examined under different experimental conditions. The InGaN/GaN QDs were formed in Stranski‐Krastanow growth mode by the continuous supply of metalorganic (MO) sources, whereas they were formed in the Volmer‐Weber growth mode by the periodic interruption of the MO sources. In addition, a quantum ring (QRs) structure was confirmed during the formation of InGaN QDs. The In content in the InGaN QDs appeared to increase with decreasing temperature. The photoluminescence spectrum (PL) showed peaks for the GaN buffer layer and the InGaN QDs layer at 362.2 nm (3.41 eV) and between 420–460 nm (2.96–2.70 eV), respectively. The composition of InGaN QDs was estimated from the PL peak position to be In0.12‐0.15Ga0.88‐0.85N. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
InP‐quantum dots in Al0.20Ga0.80InP with different barrier configurations
Authors: Schulz Wolfgang‐Michael , Roßbach Robert , Reischle Matthias , Beirne Gareth J. , Jetter Michael , Michler Peter
Published: December 2008

Systematic ensemble photoluminescence studies have been performed on type‐I InP‐quantum dots in Al0.20Ga0.80InP barriers, emitting at approximately 1.85 eV at 5 K. The influence of different barrier configurations as well as the incorporation of additional tunnel barriers on the optical properties has been investigated. The confinement energy between the dot barrier and the surrounding barrier layers, which is the sum of the band discontinuities for the valence and the conduction bands, was chosen to be approximately 190 meV by using Al0.50Ga0.50InP. In combination with 2 nm thick AlInP tunnel barriers, the internal quantum efficiency of these barrier configurations can be increased by up to a factor of 20 at elevated temperatures with respect to quantum dots without such layers. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Coherent manipulation of excitons in a pair of quantum dots coupled by the dipole‐dipole interaction
Authors: Al‐Ahmadi Ameenah N.
Published: December 2008

We investigate coherent coupling effects that are generated between excitons (EXs) and biexcitons (BXs) in colloidal quantum dot system. We used the density matrix method to study the EX–BX system in a dimer consisting of two QDs coupled via dipole‐dipole interaction. The EX and BX levels in the donor dot are controlled by resonant picoseconds excitation, giving rise to Rabi oscillation. The resonant energy transfer processes keep memory of coherent donor interaction with the optical field and result in “Rabi oscillation memory”. Decoherence of Rabi oscillation of the donor dot is caused by biexciton, and population leakage to the acceptor dot via Förster coupling. The quality factor of the induced Rabi oscillation in the acceptor yields information on the energy transfer rate between the two dots. The effect of the BX levels is realized to be very week in such system. These results provide information about the properties of BX coherence that is important for quantum device application. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Atomic force microscopy based room temperature photocurrent‐spectroscopy of single subsurface InAs quantum dots
Authors: Brezna W. , Fasching G. , Unterrainer K. , Strasser G. , Smoliner J.
Published: December 2008

In this work, we present a scheme for room temperature detection of single subsurface InAs quantum dots buried in GaAs by Atomic Force Microscopy based local photocurrent spectroscopy. The measurements were performed at room temperature and ambient conditions. The AFM was used as a nanopositioning system and the AFM tip was used to create a nano‐scale Schottky contact in the vicinity of a QD. The photocurrent spectra clearly showed peaks from quantum dots located in the vicinity of the AFM tip. The spatial resolution of the method was determined to be in between 100 nm and 1000 nm. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quantum dots to double concentric quantum ring structures transition
Authors: Bietti S. , Somaschini C. , Abbarchi M. , Koguchi N. , Sanguinetti S. , Poliani E. , Bonfanti M. , Gurioli M. , Vinattieri A. , Kuroda T. , Mano T. , Sakoda S.
Published: December 2008

Making use of the droplet–epitaxial technique, we realized a series of GaAs/AlGaAs nanostructured samples, starting from the same initial Ga droplet configuration, in which the nanostructure morphologies are progressively changed, via the As partial pressure provided during the growth, from islands, to single rings and, eventually, to concentric ring structures. We report a detailed characterization of the different structure morphologies, electronic structures and carrier dynamics via AFM and photoluminescence measurements as well as through theoretical simulations. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evolution of InAs quantum dots grown on cross‐hatch substrates
Authors: Limwongse T. , Panyakeow S. , Kanjanachuchai S.
Published: December 2008

InAs quantum dots (QDs) are grown on In0.2Ga0.8As/GaAs cross‐hatch layer by molecular beam epitaxy. The self‐assembled QDs form with the deposition of approximately 0.8 monolayer (ML) of InAs. The QDs distribute on the cross‐hatch surface unevenly: more are found along the [1‐10] crystallographic direction than the orthogonal [110] direction, while there exists even lower density of QDs on the flat areas. Height analyses indicate that QDs first form at the hatches' intersections, then they form along the [1‐10] direction, the [110] direction, and on the flat areas, respectively. This orderly evolution of QDs is attributed to the characteristic strain distribution of the cross‐hatch surface, giving rise to position‐ and orientation‐dependent critical thickness for QD formation. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Formation of nanoscale magnetic field by nuclear spin polarization in individual quantum dots
Authors: Sasakura H. , Adachi S. , Kaji R. , Muto S.
Published: December 2008

We demonstrated the creation of nanoscale magnetic field into the two isolated semiconductor quantum dots in spatially‐confined mesa structure of ∼150 nm diameter using an optical pumping of the nuclear spins. The amplitude of nuclear field between two isolated quantum dots under same pumping condition were clearly difference, suggesting that the nanoscale‐locality of the nuclear field was found to be around 100 nm. This method is based on the sensitivity of the critical magnitudes of the external magnetic field to the quantum dot properties in the bistable behavior of nuclear spin polarization. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Differential photoelectron holography of Cu(100) surface using laboratory‐level X‐ray sources
Authors: Hashimoto A. , Suzuki A. , Kisaka Y. , Miyasaka S. , Nojima M. , Owari M. , Nihei Y.
Published: December 2008

X‐ray photoelectron diffraction (XPED) is a useful tool to analyze the surface structure. In order to reconstruct a three‐dimensional atomic structure, some methods based on photoelectron holography were studied. In our group, differential photoelectron holography (DPH) was proposed to reduce artifacts. DPH can be carried out by the subtraction of XPED patterns excited by different X‐ray energies. It was reported that DPH is a very effective technique with large‐scale synchrotron radiation. In this study, we developed a stripe‐type X‐ray target that can generate two different X‐rays alternately at the laboratory level. Subsequently, DPH was applied to obtain the atomic image of the Cu(100) surface by the stripe‐type target. Copyright © 2008 John Wiley & Sons, Ltd.
Wavefunctional analysis of electron transfers in 2D nanostructures under external fields
Authors: Tomiya Mitsuyoshi , Sakamoto Shoichi , Kusumoto Hanako , Nishikawa Masaki
Published: December 2008

The time‐evolution of the wave packet inside chaotic and integrable two‐dimensional nanostructures is numerically studied. Recently the time‐evolution of quantum states is seriously considered to treat the dynamical property of nanostructures. By computer simulation, we have found the enhancement around the classical periodic orbits, which has been theoretically predicted. It is similar to the scars in the standing wave of the chaotic billiards and is also beyond the naive prediction of the random nodal patterns from the chaotic nanostructure. The initial position and velocity and the shape of the wave packet are crucial for the enhancement, however, we can observe that the remnant of the initial wave packet travels along the unstable periodic orbit. Then the wave packet gradually diffuses around the structure. This behavior has close relation to the dynamical properties of electrons in the structure, e.g., the conductivity, the magneto‐resistance etc. Copyright © 2008 John Wiley & Sons, Ltd.
A Bayesian sensitivity model for intention‐to‐treat analysis on binary outcomes with dropouts
Authors: Kaciroti Niko A. , Schork M. Anthony , Raghunathan Trivellore , Julius Stevo
Published: December 2008

Intention‐to‐treat (ITT) analysis is commonly used in randomized clinical trials. However, the use of ITT analysis presents a challenge: how to deal with subjects who drop out. Here we focus on randomized trials where the primary outcome is a binary endpoint. Several approaches are available for including the dropout subject in the ITT analysis, mainly chosen prior to unblinding the study. These approaches reduce the potential bias due to breaking the randomization code. However, the validity of the results will highly depend on untestable assumptions about the dropout mechanism. Thus, it is important to evaluate the sensitivity of the results across different missing‐data mechanisms. We propose here a Bayesian pattern‐mixture model for ITT analysis of binary outcomes with dropouts that applies over different types of missing‐data mechanisms. We introduce a new parameterization to identify the model, which is then used for sensitivity analysis. The parameterization is defined as the odds ratio of having an endpoint between the subjects who dropped out and those who completed the study. Such parameterization is intuitive and easy to use in sensitivity analysis; it also incorporates most of the available methods as special cases. The model is applied to TRial Of Preventing HYpertension. Copyright © 2008 John Wiley & Sons, Ltd.
Dynamic changes in salivary cortisol and secretory immunoglobulin A response to acute stress
Authors: Fan Yaxin , Tang Yiyuan , Lu Qilin , Feng Shigang , Yu Qingbao , Sui Danni , Zhao Qingbai , Ma Yinghua , Li Song
Published: December 2008

Psychological stress leads to the secretion of cortisol. While this psychoneuroendocrine response helps to maintain physiological as well as psychological homeostasis under stress, exaggerated release of cortisol can suppress aspects of immune function and have negative effects on health. The present study set out to investigate the dynamic changes in salivary secretory immunoglobulin A (sIgA) and cortisol before and after acute stress, and to analyse the relationship between sIgA and cortisol trend. Thirty‐five healthy subjects took part in this study. All subjects underwent an acute stress test (mental arithmetic task). Salivary cortisol and sIgA responses were assessed repeatedly before the stress test, immediately after the stress test and 20 min after the stress test. The levels of salivary cortisol and sIgA both significantly increased after the acute mental arithmetic challenge. However, the increase of sIgA is transient; the sIgA fall was significantly correlated with the cortisol rise during the 20 min after stress (r = 0.569, p < 0.001). These results may help determine the timing of effective intervention in order to reduce the hypersecretion of cortisol and improve mucosal immune function. Copyright © 2008 John Wiley & Sons, Ltd.
Dealing with a ‘hidden stressor’: emotional disclosure as a coping strategy to overcome the negative effects of motive incongruence on health
Authors: Schüler Julia , Job Veronika , Fröhlich Stephanie M. , Brandstätter Veronika
Published: December 2008

Taking the affiliation motive as an example, present research examines whether the negative effects of implicit–explicit motive incongruence on health is moderated by emotional disclosure. Starting from the point of view that motive incongruence works as a chronic stressor and therefore causes impairment of health, we predicted that participants who use the stress‐reducing coping strategy of emotional disclosure should be less affected by the negative effects of motive incongruence on health than participants who do not use this stress‐coping strategy. Two studies confirmed this hypothesis. Participants with affiliation motive incongruence who practiced emotional disclosure used less medication (Study 1, n = 85) and reported lower somatization symptoms (Study 2, n = 102) than motive incongruent individuals who did not disclose their emotions to others. Copyright © 2008 John Wiley & Sons, Ltd.