bluuebunny/crossref_metadata_2025 huggingface dataset:
Unconventional control of excited states of a dimer molecule by a localized light field between metal nanostructures
Authors: Iida Takuya , Ishihara Hajime
Published: April 2009

We have made a theoretical study of the spatial interplay between the localized light field (LLF) and the electronic wavefunction of molecules. When the LLF has a nanoscale spatial variation comparable to a molecular wavefunction, this interplay is crucial to determine the optical response of molecular excited states. Such a condition can be realized in case that a molecule is lying in the vicinity of a metal nanogap. By using the calculation method applicable to arbitrary‐shaped samples, we demonstrate a drastic enhancement of the response electromagnetic field from an optical forbidden state whose magnitude is comparable to that from an allowed state. The obtained result indicates that we have a possibility to control the excited states of molecules by designing the LLF with metal nanostructures. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Homoepitaxial growth of high‐quality nonpolar ZnO films by MOCVD and evaluation of the homoepitaxial ZnO films by XRD measurement for asymmetric planes
Authors: Kashiwaba Yasuhiro , Abe Takami , Nakagawa Akira , Endo Haruyuki , Niikura Ikuo , Kashiwaba Yasube
Published: April 2009

Characteristics of homoepitaxial high‐quality nonpolar ZnO (11$ \bar 2 $0) films and a useful measurement method for determining structures of those films are described. Homoepitaxial growth of high‐quality nonpolar ZnO (11$ \bar 2 $0) films could be achieved by atmospheric‐pressure metal organic chemical vapor deposition using zinc acetylacetonate and oxygen gas. The value of full width at half‐maximum (FWHM) of X‐ray rocking curves (XRCs) of asymmetrical ZnO (20$ \bar 2 $0) and (11$ \bar 2 $2) planes increased with increase in oxygen gas flow rate, and the change in FWHM value corresponded to FWHM of near‐band‐edge emission of photoluminescence spectra. On the other hand, the FWHM value of the XRC of the symmetrical ZnO (11$ \bar 2 $0) plane did not change with change in oxygen gas flow rate, and the FWHM values of all samples were nearly equal to the FWHM value of a single crystal ZnO (11$ \bar 2 $0) substrate. The smallest FWHM values of XRCs of ZnO (11$ \bar 2 $0), (20$ \bar 2 $0) and (11$ \bar 2 $2) planes in the sample grown under the condition of an oxygen gas flow rate of 50 sccm were about 30 arcsec, 35 arcsec and 40 arcsec, respectively. These results indicate that the homoepitaxial ZnO (11$ \bar 2 $0) film has good crystallinity. XRC measurement for asymmetrical planes is useful for evaluating homoepitaxial ZnO (11$ \bar 2 $0) films. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ensemble effect on Rabi oscillations of excitons in quantum dots
Authors: Kujiraoka Mamiko , Ishi‐Hayase Junko , Akahane Kouichi , Yamamoto Naokatsu , Ema Kazuhiro , Sasaki Masahide
Published: April 2009

We observed excitonic Rabi oscillations (ROs) in quantum dots (QDs) by four‐wave mixing (FWM) and pump‐probe techniques. When a large number of QDs are excited by a spatially nonuniform laser, the inhomogeneous distribution of the transition dipole moments of the QD excitons and the spatial distribution of the input electric field induce distribution of the Rabi frequencies. We investigated this ensemble effect on the ROs of the excitonic polarization and the excitonic population observed in the FWM and pump‐probe signals. By calculating the FWM and pump‐probe signals including the Gaussian distribution of the pulse area, we first showed that a part of the ensemble effect can be cancelled out only in case of the ROs of the excitonic polarization. This reflects the differences between the characteristics of excitonic polarization and population. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sensitization efficiencies in Er‐doped SiOx films containing amorphous or crystalline silicon nanoclusters
Authors: Lenz F. , DeCorby R. , Meldrum A.
Published: April 2009

A suite of SiOx films with oxygen concentrations ranging from x = 1 to 1.8 (25 at% to 3.6 at% excess silicon) were synthesized by physical vapour deposition. Erbium was incorporated by co‐evaporation of erbium metal to a concentration of about 0.2 at%. A subsequent annealing step was performed at temperatures ranging from 400 °C to 1100 °C to induce phase separation and cluster growth, and to optically activate erbium ions. This range of compositions and annealing temperatures was used to generate a fluorescence map for nanocluster‐sensitized Er3+. Photoluminescence (PL) spectra were measured in the visible and near‐infrared wavelength regions to explore the nature of the energy transfer between Si‐NCs and Er3+ ions. The highest PL intensities for undoped films occurred for samples annealed above 1000 °C, containing silicon nanocrystals. In contrast, in Er‐doped films the strongest Er3+ emission at 1.54 μm was observed from films annealed at temperatures below 1000 °C, demonstrating that amorphous Si nanoclusters support effective energy transfer to the Er3+ ions. The sensitization was most efficient when the NC peak emission wavelength was near 660 nm (1.88 eV) matching the energy of the 4F9/2 band of Er3+ ions in a silica host. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Impact ionization in semiconductors: recent progress on non‐local effects
Authors: Marsland John S.
Published: April 2009

A model of the ionization pathlength PDF is reformulated with new parameters that have more physical significance and allow further investigation. The transition from the dead space effect to the dead space plus resonance effect is investigated and a new measure, the overshoot factor, is suggested as the method for indicating the degree of resonant behaviour. The non‐local model is extended for non‐uniform electric field profiles. When this extended model is fitted to Monte Carlo data derived for four different electric field profiles, a fairly consistent set of parameters is found. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Luminescence simulations of ensembles of silicon nanocrystals
Authors: Lockwood Ross , Meldrum Al
Published: April 2009

The luminescence of silicon nanocrystals (NCs) has attracted a great deal of interest due to the numerous potential photonic applications of light‐emitting silicon. However, the excitation mechanisms and cluster–cluster interactions in densely‐packed ensembles, as well as the recombination processes that influence the emission spectrum and lifetime are not yet well understood. In order to generate a more complete picture of the controlling parameters in the luminescence, a dynamic Monte Carlo model that incorporates several key physical processes for luminescent nanocrystal ensembles is developed. The model simulates Forster‐type multipole energy transfer, tunnelling interactions, radiative decay and non‐radiative trapping in physically realistic (lognormal) distributions of silicon NCs. The results of the simulation illustrate the effects of the NC size distribution, homogeneous and inhomogeneous broadening, NC packing density, and non‐radiative trapping on the ensemble luminescence spectrum. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photonic properties and applications of glass micro‐ and nanospheres
Authors: Righini Giancarlo C. , Cosi Franco , Conti Gualtiero Nunzi , Pelli Stefano , Soria Silvia , Moser Enrico , Jestin Yoann , Ferrari Maurizio , Féron Patrice , Chiasera Alessandro , Chiappini Andrea , Armellini Cristina
Published: April 2009

Fabrication, morphological and spectroscopic assessment of micro‐ and nano‐spheres are reported. Spheres with size ranging from few hundreds of nm to few hundreds of μm have been prepared by different methods, i.e. sol–gel, melting and core‐shell techniques. Pure and rare‐earth‐doped spheres find their major applications as microsensors and microlasers, respectively. We refer here to Erbium‐activated systems only: (i) coated micro spheres where the silica core, obtained by telecom fiber melting, is coated with an Er3+–70SiO2–30HfO2 film; (ii) Er3+‐activated microspheres obtained from silicate‐modified glasses and phosphate glasses using a plasma torch; (iii) sol–gel Er3+‐doped silica micro‐ and nano‐spheres. The whispering gallery mode spectra were analysed as a function of sphere diameter, thickness of coating (if any) and Erbium content. Photoluminescence spectra of different systems gave interesting indications on the potential of some activated microspheres for lasing applications. For instance, sol–gel Er3+‐activated core‐shell‐like structures exhibited a lifetime of 12.8 ms, leading to a quantum efficiency (QE) of 71%. Even higher QE (∼76%) was estimated in sol–gel Er3+‐silica spheres. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
All‐photonic switching in nanophotonic quantum wells
Authors: Singh Mahi R.
Published: April 2009

We have studied the absorption phenomenon in photonic quantum wells doped with an ensemble of three‐level nanoparticles. Photons are confined in the quantum well due to the band structure engineering. The bound states of the confined photon are calculated by using the transfer matrix method and it is found that the number of bound states in the quantum well depends on the size and the depth of the quan tum well. A probe lasers is applied to monitor the absorption spectrum. Nanoparticles are interacting with the bound photons within the quantum well. It is found that when the resonance energy of nanoparticles lies near the ground bound state, the system becomes transparent. These properties can be used to make new types of optoelectronic devices. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dipole–dipole interaction in nanoscale photonic quantum wells
Authors: Singh Mahi R.
Published: April 2009

The dipole–dipole interaction (DDI) has been studied in photonic quantum wells are simulated from two photonic crystals say A and B. An ensemble of nanoparticles is doped within the quantum well layer. Nanoparticles are interacting with each other via DDI. The absorption spectrum has been calculated by using the time dependent Schrodinger equation method. A probe field is applied to measure the absorption spectrum. Numerical simulations for the absorption coefficient have been performed. It has been found that in the absence of DDI the spectrum has two peaks and a minimum at zero detuning. However, in the presence of the large DDI coupling both peaks disappear and a large minimum appears. This means that the positions and heights of peaks can be changed due to DDI interaction. This study can be used to make new types of optical devices. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Light emission from different ZnO junctions and nanostructures
Authors: Willander M. , Lozovik Yu. E. , Wadeasa A. , Nur O. , Semenov A. G. , Vonorova N. S.
Published: April 2009

We will discuss our experimental results for optical spectra produced by hole‐injection from different p‐type organic and inorganic materials into n‐type ZnO nanowires. The influence of different growth techniques and conditions on the nanowires and their emission spectral characteristics will then be analyzed and discussed. The latest findings on the mixture of the green emission band responsible for visible light emission from ZnO and the blue light emission from the organic polymer will be presented. Different high brightness light emitting diodes (HB‐LEDs) from our grown ZnO nanowires are demonstrated. The p‐type multi layer organic structures contain PEDOT:PSS as hole injectors combined with a hole transporting layer, and in some structures, a final top electron blocking/hole barrier stepping layer is placed. The purpose of this layer is to adjust the hole and electron emission from the corresponding junction side to optimize the LED performance. Structural scanning electron microscopy (SEM), electrical (I –V characteristics), photoluminescence (PL) and electroluminescence (EL) characteristics of these devices are displayed. Theoretically, we study the superfluidity of a two‐dimensional system of excitonic polaritons in an optical microcavity with an embedded quantum well. Using the effective low‐energy action for thermodynamic phase fluctuations, we obtain an expression for the analogue of the superfluid density in the system in terms of the “current–current” correlation function. The Kosterlits–Thouless transition temperature to the superfluid state as a function of the controlling parameters is calculated. Two methods are considered for producing traps for a polariton system in an optical microcavity. The behaviour of a two‐component Bose condensate of photons and excitons is analyzed theoretically for both types of the trap. The Bose condensate is described by the coupled system of equations of the Gross–Pitaevskii type. The approximate wave functions and the spatial profiles of coupled photon and exciton condensates are obtained. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Preface: Phys. Status Solidi B 246/5
Authors: Machura Łukasz , Dajka Jerzy , Zipper Elżbieta
Published: April 2009

Every second year the Department of Theoretical Physics at the University of Silesia, Katowice, Poland, organizes the International Conference on Theoretical Physics. The XXXII meeting “Coherence and Correlations in Nanosystems” took place in September 2008 in Ustroń, Poland. The conference focused on current and important topics related to coherence and correlations in small systems. Special emphasis was given to the areas of physics at the border between theoretical solid state physics and nanophysics. The broad spectrum of topics covered during the six days of the conference can be summarized into the following five points:

1. Quantum information and computation,

2. Transport phenomena in nanosystems,

3. Superconductivity and magnetism at the nanometer scale,

4. Inhomogeneous systems,

5. Ultracold atoms in optical lattices.

The careful selection of the topics allowed the organizers of the conference to bring together distinguished scientists from different areas of physics. This in turn resulted in an effective cooperation between specialists and gave an excellent opportunity to exchange ideas. Thanks to the speakers and participants the 2008 conference maintained its international character and highest scientific quality. Both invited and contributed presentations were followed by fruitful formal and informal discussions.

We would like to express our gratitude to all authors and referees whose effort allowed us to prepare this excellent issue. We also thank the editorial staff of physica status solidi for their kind assistance (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of different sealing conditions on the seal strength of polypropylene films coated with a bio‐based thin layer
Authors: Farris Stefano , Cozzolino Carlo Alessio , Introzzi Laura , Piergiovanni Luciano
Published: April 2009

This paper presents the results of an investigation through the design of experiment technique regarding the influence of temperature, dwell time and bar pressure on the heat seal strength of oriented polypropylene films coated with a gelatin‐based thin layer. This chemometric approach allowed achieving a thorough understanding of the effect of each independent factor on the two different responses (maximum force and strain energy) considered in this work as a measure of the strength necessary to break the bond across the sealed interface. Surprisingly, the factor affecting both responses the most was the bar pressure rather than the sealing temperature. Moreover, whereas the bar pressure negatively affected the seal strength of coated polypropylene films, the sealing temperature had a positive effect. Dwell time did not have any significant influence as a main factor, while influencing negatively the seal strength as an interaction term (i.e. time × pressure), together with the further interaction temperature × pressure. The mathematical models obtained for the two responses provided different results in terms of fitting capability (R2) and prediction ability (Q2). In particular, for the maximum force response, R2 and Q2 were equal to 0.571 and 0.405, respectively, whereas the model supporting the strain energy response gave R2 = 0.932 and Q2 = 0.937, highlighting that for quantifying the seal strength, the energy necessary to break a seal is a better measure than the maximum force. The highest seal strength values obtained during this work were of 0.6615 N and 19.6 N·mm for maximum force and strain energy, respectively. Copyright © 2009 John Wiley & Sons, Ltd.
The importance of accurate interaction potentials in the melting of argon nanoclusters
Authors: Pahl E. , Calvo F. , Schwerdtfeger P.
Published: April 2009

The melting temperatures of argon clusters ArN (N = 13, 55, 147, 309, 561, and 923) and of bulk argon have been obtained from exchange Monte Carlo simulations and are compared using different two‐body interaction potentials, namely the standard Lennard–Jones (LJ), Aziz and extended Lennard–Jones (ELJ) potentials. The latter potential has many advantages: while maintaining the computational efficiency of the commonly used LJ potential, it is as accurate as the Aziz potential but the computer time scales more favorably with increasing cluster size. By applying the ELJ form and extrapolating the cluster data to the infinite system, we are able to extract the melting point of argon already in good agreement with experimental measurements. By considering the additional Axilrod–Teller three‐body contribution as well, we calculate a melting temperature of T = 84.7 K compared to the experimental value of T = 83.85 K, whereas the LJ potential underestimates the melting point by more than 7 K. Thus melting temperatures within 1 K accuracy are now feasible. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Structures of tri‐, tetra‐, and hexahydrated hydride anion clusters
Authors: Lee Han Myoung , Anick David J. , Kim Kwang S.
Published: April 2009

We have reinvestigated the structures of hydrated hydride anion clusters, using density functional theory and high‐level ab initio theory. We find new low‐lying energy structures for H−(H2O)n=3,4,6 which are compatible with previously reported structures. The binding energies, electronic properties, and IR spectra of these competing low‐energy hydrated hydride anion clusters are reported to facilitate experiments. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
A theoretical study of molecular conduction. V. NEGF‐based MP2 approach
Authors: Shimazaki Tomomi , Yamashita Koichi
Published: April 2009

The conductivity of single molecules has received much attention, because achieving it is a fundamental requirement for developing molecular‐scale electronics. On the other hand, electron correlation is very important to investigate various features of molecules. We report on a nonequilibrium Green's function (NEGF)‐based second‐order Møller–Plesset (MP2) approach to accommodate the effect of electron correlation. The NEGF‐based MP2 method reduces to an ordinary MP2 method for an isolated molecule, if the molecule does not interact with semi‐infinite electrodes. Moreover, we calculate the theoretical current and the conductance of benzenedithiol and fluoro‐benzenedithiol molecules using this technique. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Electronic structures of lanthanide monofluorides in the ground state: Frozen‐core Dirac–Fock–Roothaan calculations
Authors: Wasada‐Tsutsui Yuko , Watanabe Yoshihiro , Tatewaki Hiroshi
Published: April 2009

We discuss the ground states of LnF for all the lanthanides, based on Dirac–Fock–Roothaan (DFR) calculations with average‐configuration in the reduced frozen‐core approximation. The electron configurations of the ground states are (4f)n−1(5d)1(6s)1 for LaF ∼ NdF, (4f)n(6s)1 for PmF and SmF, and (4f)n−1(6s)2 for EuF ∼ LuF, in contrast to the (4f)n(6s)1 configurations of the gaseous cation, Ln+. Although the ground state configuration varies, the bonding character in the ground states is ionic for all LnF; a single electron is transferred from the Ln atom to the F atom. We also discuss the excited states having configurations (4f)n−1(6s)2, (4f)n−1(5d)1(6s)1, and (4f)n (6s)1. The complete active space configuration interaction calculations were performed for GdF, using two kinds of DFR spinor sets, one of which is a nonrelativistic‐like spinor set and the other relativistic one. The nonrelativistic‐like spinor set gives 8Σ− like (nonrelativistic like) ground state, which is consistent with the experiment. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Quasi‐classical trajectory study on He+H/D/T reactions
Authors: Xu Wen‐Wu , Liu Xin‐Guo , Luan Shi‐Xia , Zhang Qing‐Gang
Published: April 2009

The trajectory calculations of He+H, He+D and He+T reactions on the Palmieri potential energy surface (Palmieri et al., Mol Phys, 2000, 98, 1835) have been carried out to study the isotope effect on stereodynamics at the collision energy of 50 kcal/mol. The distributions of dihedral angle P (ϕr) and the distributions of angle between and ′, P (θr) are discussed. The product rotational alignment parameters 〈P2(′●)〉 for the title reactions are compared with the mass factors. Furthermore, the angular distributions of the product rotational vectors in the form of polar plot in θr and ϕr are calculated. The calculations indicate that the stereodynamics properties of the title reactions are sensitive to the mass factor and the long range interaction of ion‐molecule reaction. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010
Potential energy surface of the 12A′ Li2 + Li doublet ground state
Authors: Byrd Jason N. , Montgomery John A. , Michels H. Harvey , Côté Robin
Published: April 2009

The lowest doublet electronic state for the lithium trimer (12A′) is calculated for use in three‐body scattering calculations using the valence electron FCI method with atomic cores represented using an effective core potential. It is shown that an accurate description of core‐valence correlation is necessary for accurate calculations of molecular bond lengths, frequencies and dissociation energies. Interpolation between 12A′ ab initio surface data points in a sparse grid is done using the global interpolant moving least squares method with a smooth radial data cutoff function included in the fitting weights and bivariate polynomials as a basis set. The Jahn–Teller splitting of the 12E′ surface into the 12A1 and 12B2 states is investigated using a combination of both CASSCF and FCI levels of theory. Additionally, preliminary calculations of the 12A″ surface are also presented using second order spin restricted open‐shell Møller–Plesset perturbation level of theory. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
On intramolecular average 13C chemical shift in nonanes
Authors: Randić Milan , Novič Marjana , Vikić‐Topić Dražen , Plavšić Dejan
Published: April 2009

Partial ordering is a tool that allows finding regularities in variations in physico‐chemical properties among isomers as well as in structure‐activity relationship among structurally related compounds. By comparison of variations in molecular properties with variation of their mathematical descriptors, one may arrive at novel insights and novel interpretations of experimental data. By using partial ordering, we have re‐examined the relative magnitudes of 13C chemical shift sum (or average intra‐molecular chemical shifts) in nonane isomers. As a result, one obtains some understanding of structural factors of importance for the observed isomeric variations of the average 13C chemical shift among nonanes. In contrast, more elaborate models, which give better numerical precision, do not offer comparable insights into structure‐property relationship. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009
Improved exponential stability for stochastic Markovian jump systems with nonlinearity and time‐varying delay
Authors: He Yong , Zhang Yan , Wu Min , She Jin‐Hua
Published: April 2009

This paper is concerned with delay‐dependent exponential stability for stochastic Markovian jump systems with nonlinearity and time‐varying delay. An improved exponential stability criterion for stochastic Markovian jump systems with nonlinearity and time‐varying delay is proposed without ignoring any terms by considering the relationship among the time‐varying delay, its upper bound and their difference, and using both Itô's differential formula and Lyapunov stability theory. A numerical example is given to illustrate the effectiveness and the benefits of the proposed method. Copyright © 2009 John Wiley & Sons, Ltd.
A hybrid feedback for a benchmark problem of idle speed control
Authors: Balluchi A. , D'Apice C. , Gaeta M. , Piccoli B. , Sangiovanni Vincentelli A. L. , Zadarnowska K.
Published: April 2009

The ever increasing demands on passengers' comfort, safety, emissions and fuel consumption imposed by car manufacturers and regulations call for advanced techniques and the use of cycle‐accurate models in automotive control. In this paper, we focus on such approach to the idle speed control. It is natural to resort to hybrid methodologies, because of the rich combination of time and event‐based behaviors exhibited by a controlled engine. A hybrid benchmark problem is considered and addressed first by analyzing the equilibria of the system and then testing a simple hybrid feedback strategy. Copyright © 2009 John Wiley & Sons, Ltd.
Effects of a surface oriented travelling screen and water abstraction practices on downstream migrating salmonidae smolts in a lowland stream
Authors: Svendsen Jon C. , Aarestrup Kim , Deacon Michael G. , Christensen Rune H. B.
Published: April 2009

Downstream migration of immature salmonids (smolts) may be associated with severe mortalities in anthropogenically altered channels. In Pacific salmon, several investigations have suggested the use of the dominating surface orientation of smolts to improve fish by‐pass structures in large and deep hydroelectric reservoirs. The present study tested the use of a surface orientated travelling screen to guide Atlantic salmon (Salmo salar L.) and brown trout (Salmo trutta L.) smolts past a water abstraction site in a shallow lowland stream. The percentage of total discharge abstracted from the stream was included in the analyses. Indigenous migrating smolts were trapped, PIT tagged and subsequently released upstream of the water abstraction site. Releases shifted between a present or absent travelling screen. The migration success of the released smolts was evaluated using a trap situated downstream of the water abstraction site. There was no evidence that the surface oriented travelling screen had any influence on the probability of fish passing the water abstraction site. However, for both species, the probability of successful migration past the water abstraction site correlated negatively with the abstracted percentage of the total daily stream discharge. These findings may have important management implications because they suggest that short term changes in the percentage of total stream discharge abstracted may have consequences for the downstream migration success of smolts. Copyright © 2009 John Wiley & Sons, Ltd.
Robust power control for IEEE 802.15.4 wireless sensor networks with round‐trip time‐delay uncertainty
Authors: Mahdi Alavi S. M. , Walsh M. J. , Hayes M. J.
Published: April 2009

This paper presents a novel, practically implementable robust Power Control (PC) technique that is generally applicable to a variety of IEEE 802.15.4 infrastructure and peer‐to‐peer wireless sensor networks (WSNs) where there is a round‐trip time‐delay uncertainty. In this methodology, robust stabilityandperformance constraints are cast as a set of exclusion regions on the Nichols chart. The desired PC strategy is achieved through an iterative shaping of the system frequency response until these constraints are satisfied. A Smith Predictor (SP) is also adopted to mitigate the effects of time delay that occurs quite naturally in this type of problem. Such an approach is shown to be entirely appropriate for the discrete time controller design problem at hand. The designs are validated experimentally using a fully compliant 802.15.4 testbed where mobility is introduced using autonomous robots. This testbed provides a good basis for a formal comparison of the new approach against a number of existing strategies. Copyright © 2009 John Wiley & Sons, Ltd.
Link layer solutions for supporting real‐time traffic over CDMA wireless mesh networks
Authors: Alsabaan Maazen , Zhuang Weihua , Wang Ping
Published: April 2009

With recent advances in the development of wireless communication networks, wireless mesh networks (WMNs) have been receiving considerable research interests in recent years. The need to support integrated services and ensure quality of service (QoS) satisfaction for various applications is one of the fundamental challenges for successful WMN deployment. In order to provide differentiated services, medium access control (MAC) should have priority management at the link layer. In code division multiple access (CDMA)‐based WMNs, the interference phenomenon and simultaneous transmissions must be considered. We propose two priority schemes for MAC in a distributed CDMA‐based WMN, taking into account interference, multimedia services, QoS requirements, and simultaneous transmissions. The first priority scheme is within a node. Each node has an independent queue for each traffic class. According to QoS requirements, the queue that should be served first is determined. The second priority scheme is among neighbor nodes. It is proposed for multiple simultaneous transmissions in the CDMA network. This scheme gives a larger chance of correct transmission to high priority traffic than low priority traffic. In addition, we propose to use adaptive spreading gain and a frame structure to achieve high resource utilization. Simulation results demonstrate that the proposed schemes can achieve effective QoS guarantee. Copyright © 2009 John Wiley & Sons, Ltd.
Placing and maintaining a core node in wirelessad hocnetworks
Authors: Dvir A. , Segal M.
Published: April 2009

Wirelessad hocnetworks are characterized by several performance metrics, such asbandwidth, transport, delay, power, etc. These networks are examined by constructing a tree network. A core node is usually chosen to be themedianorcenterof the multicast tree network with a tendency to minimize a performance metric, such as delay or transport. In this paper, we present a new efficient strategy for constructing and maintaining a core node in a multicast tree for wirelessad hocnetworks undergoing dynamic changes, based on local information. The new core (centdian) function is defined by a convex combination signifying total transport and delay metrics. We provide two bounds ofO(d) andO(d+l) time for maintaining the centdian using local updates, wherelis the hop count between the new center and the new centdian, anddis the diameter of the tree network. We also show anO(n log n) time solution for finding the centdian in the Euclidian complete network. Finally, an extensive simulation for the construction algorithm and the maintenance algorithm is presented along with an interesting observation. Copyright © 2009 John Wiley & Sons, Ltd.
Dedicated to Professor Reinhard Nesper on the Occasion of His 60th Birthday
Authors: Jansen Martin , Klapötke Thomas , Limberg Christian
Published: April 2009

Reinhard Nesper, professor at the Laboratory for Inorganic Chemistry of the ETH Zürich, celebrated his 60th birthday on April 9, 2009. On this occasion the editors, the publisher, his friends and colleagues congratulate cordially and dedicate to him this “Festheft” in amity and recognition.
Benefits Versus Risks: A Prospective Audit
Authors: Gupta Vikas
Published: April 2009

Background

The purpose of this prospectively collected database is to evaluate the safety, efficacy, and utility of postoperative jejunostomy feeding in terms of achieving nutritional goals and evaluating gastrointestinal and mechanical complications in patients undergoing esophagectomy.

Methods

The study included 204 consecutive patients who underwent esophagectomy for various benign and malignant conditions. All patients underwent Witzel feeding jejunostomy at the time of laparotomy. Patients were followed prospectively to record nutritional intake, type of feed administered, rate progression, tolerance, and complications either mechanical or gastrointestinal.

Results

Feeding jejunostomy could be performed in 99.5% patients; 6.0% of the patients had a blocked catheter during the course of feeding. The target calorie requirement could be achieved in 78% of patients by third day. In all, 95% of patients could be successfully fed exclusively by jejunostomy catheter during the postoperative period. Minor gastrointestinal complications developed in 15% of the patients and were managed by slowing the rate of infusion or administering medication. Patients spent a mean of 16.67 ± 22.00 days (range 0–46 days) on jejunostomy feeding after surgery; however, 13% required prolonged jejunostomy feeding beyond 30 days. Altogether, 64% of the patients with an anastomotic leak and 50% of the patients with postoperative complications required catheter jejunostomy feeding beyond 30 days. The mean duration for which jejunostomy tube feeding was used was significantly higher for patients who developed anastomotic disruptions (33.05 ± 16.24 vs. 14.69 ± 19.04 days; p = 0.000) and postoperative complications (26.67 ± 25.56 vs. 14.52 ± 18.64 days; p = 0.000) when compared to those without disruption or complications. There were no serious complications related to the feeding catheter that required reintervention. There was no difference in the mean body weight or weight deficit at the end of 10 days and at 1 month in patients who developed complications or anastomotic disruption when compared to their counterparts. No patient died as a result of a complication related to the feeding jejunostomy.

Conclusions

Tube jejunostomy feeding is an effective method for providing nutritional support in patients undergoing esophagectomy, and it allows home support for the subset who fail to thrive. Prolonged tube feeding was continued in patients developing anastomotic disruptions and postoperative complications. Feeding jejunostomy has a definitive role to play in the management of the patients undergoing esophagectomy.
Enzyme analysis for Pompe disease in leukocytes; superior results with natural substrate compared with artificial substrates
Authors: van Diggelen O. P. , Oemardien L. F. , van der Beek N. A. M. E. , Kroos M. A. , Wind H. K. , Voznyi Y. V. , Burke D. , Jackson M. , Winchester B. G. , Reuser A. J. J.
Published: April 2009

Enzyme analysis for Pompe disease in leukocytes has been greatly improved by the introduction of acarbose, a powerful inhibitor of interfering α‐glucosidases, which are present in granulocytes but not in lymphocytes. Here we show that the application of acarbose in the enzymatic assay employing the artificial substrate 4‐methylumbelliferyl‐α‐d‐glucoside (MU‐αGlc) is insufficient to clearly distinguish patients from healthy individuals in all cases. Also, the ratios of the activities without/with acarbose only marginally discriminated Pompe patients and healthy individuals. By contrast, when the natural substrate glycogen is used, the activity in leukocytes from patients (n = 82) with Pompe disease is at most 17% of the lowest control value. The use of artificial substrate in an assay with isolated lymphocytes instead of total leukocytes is a poor alternative as blood samples older than one day invariably yield lymphocyte preparations that are contaminated with granulocytes. To diagnose Pompe disease in leukocytes we recommend the use of glycogen as substrate in the presence of acarbose. This assay unequivocally excludes Pompe disease. To also exclude pseudo‐deficiency of acid α‐glucosidase caused by the sequence change c.271G>A (p.D91N or GAA2; homozygosity in approximately 1:1000 caucasians), a second assay employing MU‐αGlc substrate plus acarbose or DNA analysis is required.
When Cognitive Diagnosis Meets Computerized Adaptive Testing: CD-CAT
Authors: Cheng Ying
Published: April 2009

Computerized adaptive testing (CAT) is a mode of testing which enables more efficient and accurate recovery of one or more latent traits. Traditionally, CAT is built upon Item Response Theory (IRT) models that assume unidimensionality. However, the problem of how to build CAT upon latent class models (LCM) has not been investigated until recently, when Tatsuoka (J. R. Stat. Soc., Ser. C, Appl. Stat. 51:337–350, 2002) and Tatsuoka and Ferguson (J. R. Stat., Ser. B 65:143–157, 2003) established a general theorem on the asymptotically optimal sequential selection of experiments to classify finite, partially ordered sets. Xu, Chang, and Douglas (Paper presented at the annual meeting of National Council on Measurement in Education, Montreal, Canada, 2003) then tested two heuristics in a simulation study based on Tatsuoka’s theoretical work in the context of computerized adaptive testing. One of the heuristics was developed based on Kullback–Leibler information, and the other based on Shannon entropy. In this paper, we showcase the application of the optimal sequential selection methodology in item selection of CAT that is built upon cognitive diagnostic models. Two new heuristics are proposed, and are compared against the randomized item selection method and the two heuristics investigated in Xu et al. (Paper presented at the annual meeting of National Council on Measurement in Education, Montreal, Canada, 2003). Finally, we show the connection between the Kullback–Leibler-information-based approaches and the Shannon-entropy-based approach, as well as the connection between algorithms built upon LCM and those built upon IRT models.
Fabrication of Antireflective Sub-Wavelength Structures on Silicon Nitride Using Nano Cluster Mask for Solar Cell Application
Authors: Sahoo Kartika Chandra , Lin Men-Ku , Chang Edward-Yi , Lu Yi-Yao , Chen Chun-Chi , Huang Jin-Hua , Chang Chun-Wei
Published: April 2009

We have developed a simple and scalable approach for fabricating sub-wavelength structures (SWS) on silicon nitride by means of self-assembled nickel nanoparticle masks and inductively coupled plasma (ICP) ion etching. Silicon nitride SWS surfaces with diameter of 160–200 nm and a height of 140–150 nm were obtained. A low reflectivity below 1% was observed over wavelength from 590 to 680 nm. Using the measured reflectivity data in PC1D, the solar cell characteristics has been compared for single layer anti-reflection (SLAR) coatings and SWS and a 0.8% improvement in efficiency has been seen.
Drive-style emissions testing on the latest two Honda hybrid technologies
Authors: Alessandrini Adriano , Orecchini Fabio , Ortenzi Fernando , Villatico Campbell Federico
Published: April 2009

Introduction

Hybrid technology is seen by many as a potential solution to reduce vehicle emissions in cities. However type approval tests of hybrid vehicles measure emission levels comparable to those of conventional cars in the same market segment. It has been argued that type approval tests do not represent the reality of emission in cities therefore, to quantify the real emission of hybrids and to compare them with those of conventional vehicles in the same conditions, an emission measurement campaign was organised.

Acquisition campaign

Three Honda cars, one conventional (the Civic 2.0) and two hybrids (the Civic IMA and the Civic Hybrid), equipped to collect emissions as well as the engine and vehicle working parameters were driven three times by twenty drivers on the same urban route. Drivers were asked to drive normally and not requested to do anything special but to scrupulously follow the given itinerary.

Results

Two main results were obtained: average and maximum emission levels for the three cars are quantified; the effects of the drivers on such levels assessed. The conventional car (with two people and 250 kg of measurement tools onboard) consumes an average of 12.6 l/100 km, its CO2 emissions range between 200 g/km and 300 g/km with an average of 260 g/km. CO emissions range between 0.25 g/km and 6.25 g/km (Euro IV limit is 1 g/km) with an average of 2 g/km. The most recent of the two tested hybrids consume in average 8.23 l/100 km and emits between 150 and 230 g/km of CO2 with an average of about 180 g/km; it emits virtually no CO in the majority of cases but can reach up to 1.8 g/km and average CO emissions are about 0.2 g/km. The hybrid performs always better than the conventional; in terms of CO2 and consumption it can have up to a 30% reduction and in terms of CO up to 90% reduction.

Conclusions

The wideness of the measured ranges depends mostly on the drivers. Women tend to consume and emit less than men. The reason for this is the different way they use the accelerator pedal; they push it less and keep it steadier. In other word the standard deviation of the accelerator position (or throttle) is lower. It is here shown how a correlation exist between the throttle standard deviation and the emissions which justify using such parameter as the indicator of drive-style.
Financial progress and the stability of long‐run money demand: Implications for the conduct of monetary policy in emerging economies
Authors: Darrat Ali F. , Al‐Sowaidi Saif S.
Published: April 2009

This paper examines whether recent financial changes in three emerging market economies in the Gulf region (Bahrain, the UAE, and Qatar) have distorted the character and the stability of their underlying long‐run money demand relations. Money demand instability prompts concerns about the appropriateness of targeting monetary aggregates and could weaken the presumed link between monetary policy and its ultimate objectives. Our results suggest that the quick pace of financial changes in the three emerging market economies did not cause undue shifts in their equilibrium money demand relations. Further evidence from direct tests of cointegration stability indicates the superiority of targeting M1 in the UAE and M2 for Qatar. In Bahrain, both M1 and M2 prove equally appropriate to guide monetary policy. Thus, despite the wave of financial developments that have recently swept the three Gulf economies, the evidence suggests that monetary authorities in these countries should maintain a close watch on monetary growth as a principal policy guide.
‘Banks is the villain!’? Sir Joseph Banks and the governance of the Society of Antiquaries
Authors: Morgan Evans Dai
Published: April 2009

The name of Sir Joseph Banks (1743–1820) is well known in scientific and exploration circles – he is undeservedly much less well known as an antiquary. This study considers his roles in relation to the premier antiquarian society of the time, the Society of Antiquaries of London. Using the Society’s records, Sir Joseph Banks is considered as an ordinary Fellow, as a member of Council, as an auditor of the finances and as a scrutator at elections. The relations between the Royal and Antiquarian Societies on first moving into Somerset House and the contemporary question of whether they might have merged is also examined. Joseph Banks’s role in the circumstances of the three contested presidential elections of 1785, 1799 and 1812 is especially considered, and these are seen not just to represent internal squabbling amongst the Fellows, but to reflect the wider social and political strains of the time. In producing the narrative of these elections, significant past mistakes are corrected. Lastly the relationship between Georgeiiiand the Society of Antiquaries is touched upon.
Does Sentiment Drive the Retail Demand for IPOs?
Authors: Dorn Daniel
Published: April 2009

Individual and institutional investors can trade German initial public equity offerings on an as-if/when-issued basis before the start of secondary trading. Using actual when-issued trades made by a sample of clients at a large German retail broker during 1999 and 2000, the paper documents that retail buyers consistently overpay for initial public offerings (IPOs) in the when-issued market relative to the immediate aftermarket. The observed willingness to overpay points to sentiment as a driver of retail trading decisions. Consistent with this interpretation and with sentiment affecting prices, IPOs that are aggressively bought by individuals in the when-issued market exhibit high first-day returns as well as poor aftermarket returns relative to benchmarks of similar stocks.
Understanding the Penalties Associated with Corporate Misconduct: An Empirical Examination of Earnings and Risk
Authors: Murphy Deborah L. , Shrieves Ronald E. , Tibbs Samuel L.
Published: April 2009

We examine the relationship between allegations of corporate misconduct and changes in profitability and risk of the alleged offender. Profitability is measured as reported earnings and analysts’ earnings forecasts. Risk is measured as stock return volatility and concordance among analysts’ forecasts. Decreases in earnings and increases in risk are found to accompany allegations of misconduct, and although the results are somewhat sensitive to the earnings and risk metrics used, the changes are found to be consistently greater for related-party offenses. The importance of reputational penalties is underscored by analysis of the association between allegation-related changes in firm value and changes in earnings and risk.
Is the Value Premium a Proxy for Time-Varying Investment Opportunities? Some Time-Series Evidence
Authors: Guo Hui , Savickas Robert , Wang Zijun , Yang Jian
Published: April 2009

We uncover a positive stock market risk-return tradeoff after controlling for the covariance of market returns with the value premium. Fama and French (1996) conjecture that the value premium proxies for investment opportunities; therefore, by ignoring it, early specifications suffer from an omitted variable problem that causes a downward bias in the risk-return tradeoff estimation. We also document a positive relation between the value premium and its conditional variance, and the estimated conditional value premium is strongly countercyclical. The latter evidence supports the view that value is riskier than growth in bad times, when the price of risk is high.
The Information Content of Idiosyncratic Volatility
Authors: Jiang George J. , Xu Danielle , Yao Tong
Published: April 2009

Ang, Hodrick, Xing, and Zhang (2006a) show that stocks with high idiosyncratic return volatility tend to have low future returns. This paper further documents that idiosyncratic volatility is inversely related to future earning shocks, and more importantly, that the return-predictive power of idiosyncratic volatility is induced by its information content about future earnings. We examine various explanations of the triangular relation among idiosyncratic volatility, future earning shocks, and future stock returns. Our results show that the idiosyncratic volatility anomaly is not a simple manifestation of previously documented market anomalies related to excessive extrapolation on firm growth, over-investment tendency, accounting accruals, or investor underreaction to earnings news. On the other hand, there is evidence that the idiosyncratic volatility anomaly is related to corporate selective disclosure, and the anomaly is stronger among stocks with a less sophisticated investor base.