bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimal Performance of an Endoreversible Four-Heat-Reservoir Absorption Heat-Transformer
Authors: Qin Xiaoyong , Chen Lingen , Sun Fengrui , Wu Chih
Published: July 2004

Based on an endoreversible absorption heat-transformer cycle model operating between four temperature levels with linear (Newtonian) heat transfer law, the fundamental optimal relation between the specific heating load and the coefficient of performance, the optimal temperatures of the working substance, and the optimal heat transfer surface areas of the four heat exchangers are derived by using finite-time thermodynamics. Moreover, the effects of the cycle parameters on the cycle characteristic are studied by numerical examples. The results obtained herein can provide some guidance for the optimal design of absorption heat-transformers.
Universal scaling, dynamic fragility, segmental relaxation, and vitrification in polymer melts
Authors: Saltzman Erica J. , Schweizer Kenneth S.
Published: July 2004

Our theory of dynamic barriers, slow relaxation, and the glass transition of polymers melts is numerically applied using parameters relevant to real materials. The numerical results are found to be in qualitative agreement with all the approximate analytic expressions previously derived with quantitative differences on the order of ∼20–30% or much less. The analytic prediction of a universal temperature dependence of the alpha relaxation time, and its intimate connection with the idea of a nearly universal crossover time, is established. Inter-relations between the breadth of the deeply supercooled regime, two definitions of the dynamic fragility, and the magnitude of the fast local Arrhenius process at the glass transition temperature are demonstrated and system-specific limitations identified. A quantitative application to segmental relaxation over 16 orders of magnitude in a polyvinylacetate melt yields encouraging results regarding the accuracy of the theory. The theoretical relaxation time results are well fit by multiple empirical forms (generally containing an assumed singular aspect) using parameters consistent with experimental studies. No physical significance is ascribed to this finding, but it does provide additional support for the temperature dependence of the alpha relaxation process predicted by the theory.
Ultrafast predissociation dynamics of water molecules excited to the electronic C̃ and D̃ states
Authors: Steinkellner O. , Noack F. , Ritze H.-H. , Radloff W. , Hertel I. V.
Published: July 2004

Two-photon excitation with femtosecond laser pulses in the spectral range 240–250 nm was used to prepare vapor phase H2O and D2O in the C̃ 1B1 and D̃ 1A1 states. Both states are predissociated via the B̃ 1A1 state, forming excited OH/OD(A 2Σ+) as well as ground state OH/OD(X 2Π). We used ultrashort infrared probe pulses (1.65–2.42 μm) to control the ratio between these excited and ground state fragments originating from the dissociation process. Time resolved detection of the OH/OD(A 2Σ+)→OH/OD(X 2Π) fluorescence allows us to monitor the dynamics of the predissociation. For the heterogeneous predissociation out of the C̃ 1B1 state life times of (0.5±0.1) ps and (1.2±0.1) ps were found for H2O and D2O, respectively. The purely homogeneous character of the predissociation out of the D̃ 1A1 state was monitored.
Fock space multireference coupled cluster method with full inclusion of connected triples for excitation energies
Authors: Musiał Monika , Bartlett Rodney J.
Published: July 2004

We report the initial Fock space multireference coupled cluster method with the full inclusion of single, double, and triple excitations (FS-CCSDT) for the (1,1) sector. We present pilot applications for calculating excitation energies for the N2 molecule and the Ne atom. The performance of the current model, along with the FS-CCSD one, has been studied in comparison with the equation-of-motion coupled-cluster and the similarity transformed methods.
Computer simulations of adsorption and diffusion for binary mixtures of methane and hydrogen in titanosilicates
Authors: Mitchell Martha C. , Gallo Marco , Nenoff Tina M.
Published: July 2004

Equilibrium molecular dynamics (MD) simulations of equimolar mixtures of hydrogen and methane were performed in three different titanosilicates: naturally occurring zorite and two synthetic titanosilicates, ETS-4 and ETS-10. In addition, single-component MD simulations and adsorption isotherms generated using grand canonical Monte Carlo simulations were performed to support the mixture simulations. The goal of this study was to determine the best membrane material to carry out hydrogen/methane separations. ETS-10 has a three-dimensional pore network. ETS-4 and zorite have two-dimensional pore networks. The simulations carried out in this study show that the increased porosity of ETS-10 results in self-diffusion coefficients for both hydrogen and methane that are higher in ETS-10 than in either ETS-4 or zorite. Methane only showed appreciable displacement in ETS-10. The ability of the methane molecules to move in all three directions in ETS-10 was demonstrated by the high degree of isotropy shown in the values of the x, y, and z components of the self-diffusion coefficient for methane in ETS-10. From our simulations we conclude that ETS-10 would be better suited for fast industrial separations of hydrogen and methane. However, the separation would not result in a pure hydrogen stream. In contrast, ETS-4 and zorite would act as true molecular sieves for separations of hydrogen and methane, as the methane would not move through membranes made of these materials. This was indicated by the near-zero self-diffusion coefficient of methane in ETS-4 and zorite.
Quantum dynamics calculations using symmetrized, orthogonal Weyl-Heisenberg wavelets with a phase space truncation scheme. III. Representations and calculations
Authors: Poirier Bill , Salam A.
Published: July 2004

In a previous paper [J. Theo. Comput. Chem. 2, 65 (2003)], one of the authors (B.P.) presented a method for solving the multidimensional Schrödinger equation, using modified Wilson-Daubechies wavelets, and a simple phase space truncation scheme. Unprecedented numerical efficiency was achieved, enabling a ten-dimensional calculation of nearly 600 eigenvalues to be performed using direct matrix diagonalization techniques. In a second paper [J. Chem. Phys. 121, 1690 (2004)], and in this paper, we extend and elaborate upon the previous work in several important ways. The second paper focuses on construction and optimization of the wavelength functions, from theoretical and numerical viewpoints, and also examines their localization. This paper deals with their use in representations and eigenproblem calculations, which are extended to 15-dimensional systems. Even higher dimensionalities are possible using more sophisticated linear algebra techniques. This approach is ideally suited to rovibrational spectroscopy applications, but can be used in any context where differential equations are involved.
Field-induced resistive switching in metal-oxide interfaces
Authors: Tsui S. , Baikalov A. , Cmaidalka J. , Sun Y. Y. , Wang Y. Q. , Xue Y. Y. , Chu C. W. , Chen L. , Jacobson A. J.
Published: July 2004

We investigate the polarity-dependent field-induced resistive switching phenomenon driven by electric pulses in perovskite oxides. Our data show that the switching is a common occurrence restricted to an interfacial layer between a deposited metal electrode and the oxide. We determine through impedance spectroscopy that the interfacial layer is no thicker than 10nm and that the switch is accompanied by a small capacitance increase associated with charge accumulation. Based on interfacial I–V characterization and measurement of the temperature dependence of the resistance, we propose that a field-created crystalline defect mechanism, which is controllable for devices, drives the switch.
Percolation and gas sensitivity in nanocrystalline metal oxide films
Authors: Ulrich Markus , Bunde Armin , Kohl Claus-Dieter
Published: July 2004

We use Monte Carlo simulations to study the influence of gas adsorption on the conductance of nanocrystalline metal oxide films. The films are modeled by a network of intergranular contacts with conductances that depend on the amount of adsorbed gas molecules, and take into account a broad distribution of grain sizes and the possibility that ultrasmall nanograins can be insulating. Using percolation theory, we show that below a critical gas concentration (detection limit), the film can be insulating due to the absence of a percolating cluster of conducting grains. Above this detection limit, the conductance of the film increases rapidly. The detection limit can be tuned by the grain size and the mean coordination number in the film.
Observation of low-dimensional state tunneling in nanocrystalline silicon∕crystalline silicon heterostructures
Authors: Chen X. Y. , Shen W. Z.
Published: July 2004

We report on the observation of resonant tunneling phenomena due to the electronic transport through zero- and two-dimensional (0D and 2D) states in n-type nanocrystalline silicon (nc-Si)∕p-type crystalline silicon heterostructures. The transport information of both the 0D and 2D carriers has been extracted by the analysis of magnetic-field-dependent Hall data. Clear 2D-0D steplike and 0D-0D spikelike resonant tunneling structures have been demonstrated up to the high temperature of 220 and 50K in the natural quantum dot system, respectively. The revealed quantum tunneling information should facilitate more practical and more efficient application of nc-Si-based resonant tunneling devices.
Growth and properties of high-Curie-temperature Sr2CrReO6 thin films
Authors: Asano H. , Kozuka N. , Tsuzuki A. , Matsui M.
Published: July 2004

Thin films of ordered double-perovskite Sr2CrReO6 have been grown epitaxially onto SrTiO3 substrates by sputtering, and their microstructural, electrical, and magnetic properties are investigated. It is found that a wide growth-temperature range of at least 700–800°C can yield epitaxial films with superior magnetic properties and atomically flat surfaces. These films exhibit Curie temperatures Tc of up to 620K, and saturation magnetizations Ms of 0.9μB∕formula unit (f.u.), which is comparable to the predicted value of 1μB∕f.u. for the fully ordered half-metallic material. Owing to the wide temperature window for growth of high-quality films, the surface morphology and coercivity of Sr2CrReO6 films are highly controllable, which is favorable for fabrication of magnetic tunnel junctions.
Partial classification of modules for Lie-algebra of diffeomorphisms of d-dimensional torus
Authors: Eswara Rao S.
Published: July 2004

We consider the Lie-algebra of the group of diffeomorphisms of a d-dimensional torus which is also known to be the algebra of derivations on a Laurent polynomial ring A in d commuting variables denoted by Der A. The universal central extension of Der A for d=1 is the so-called Virasoro algebra. The connection between Virasoro algebra and physics is well known. See, for example, the book on Conformal Field Theory by Di Francesco, Mathieu, and Senechal. In this paper we classify (A, Der A) modules which are irreducible and have finite dimensional weight spaces. Earlier Larsson constructed a large class of modules, the so-called tensor fields, based on gld modules which are also A modules. We prove that they exhaust all (A, Der A) irreducible modules.
Method for the determination of the capture cross sections of electrons from space-charge-limited conduction in the dark and under illumination in amorphous semiconductors
Authors: Meaudre R. , Meaudre M.
Published: July 2004

The current transport equations describing space-charge-limited conduction in the dark and under illumination in amorphous materials have been studied. With a certain number of reasonable approximations, a very simple relation in the form Y=svX is obtained where Y and X are two quantities directly linked to the values of dark currents and photocurrents measured at two different voltages and sv is the product of capture cross section of states near the Fermi level and thermal velocity of carriers. The model is then applied to n+-i-n+ hydrogenated amorphous and polymorphous structures.
Time fractional Schrödinger equation
Authors: Naber Mark
Published: July 2004

The Schrödinger equation is considered with the first order time derivative changed to a Caputo fractional derivative, the time fractional Schrödinger equation. The resulting Hamiltonian is found to be non-Hermitian and nonlocal in time. The resulting wave functions are thus not invariant under time reversal. The time fractional Schrödinger equation is solved for a free particle and for a potential well. Probability and the resulting energy levels are found to increase over time to a limiting value depending on the order of the time derivative. New identities for the Mittag–Leffler function are also found and presented in an Appendix.
Field-controlled domain-wall resistance in magnetic nanojunctions
Authors: Burton J. D. , Kashyap A. , Zhuravlev M. Ye. , Skomski R. , Tsymbal E. Y. , Jaswal S. S. , Mryasov O. N. , Chantrell R. W.
Published: July 2004

The electrical resistance of a constrained domain wall in a nanojunction is investigated using micromagnetic modeling and ballistic conductance calculations. The nanojunction represents two ferromagnetic electrodes connected by a ferromagnetic wire of 10 nm in length and of a few nanometers in cross section. We find that the anisotropy of the electrodes favors a localization of the domain wall within the constriction (wire) revealing a positive domain-wall resistance. An applied magnetic field moves the domain wall toward one of the electrodes and reduces its width. This compression of the domain wall leads to a sizeable enhancement of the domain-wall resistance.
Initial growth of interfacial oxide during deposition of HfO2 on silicon
Authors: Choi K. , Temkin H. , Harris H. , Gangopadhyay S. , Xie L. , White M.
Published: July 2004

Interfacial chemistry of Hf∕Si, HfO2∕SiO2∕Si, and HfO2∕Si is investigated by x-ray photoelectron spectroscopy in order to understand the interfacial layer formation mechanism. Deposition of Hf and HfO2 films was carried out on Si wafers by electron-beam evaporation with oxygen backfill. We show that the interfacial layer formation takes place predominantly at the initial stage of the HfO2 film deposition. Temporary direct bonding between Hf metal and Si is proposed to be the source of the catalytic reaction resuting in formation of interfacial layer. Formation of interfacial layer was suppressed by chemically grown thin oxide blocking the direct Si–Hf bonding. We also demonstrate reduced interfacial layer after modified Shiraki surface etch, compared to the Radio Corporation of America clean. This indicates that a more complete hydrogen termination and atomically smoother surface can delay the onset of interfacial layer formation.
Pb
0.3
Sr
0.7
TiO
3
thin films for high-frequency phase shifter applications
Authors: Jain M. , Karan N. K. , Katiyar R. S. , Bhalla A. S. , Miranda F. A. , Keuls F. W. Van
Published: July 2004

Pb 0.3 Sr 0.7 TiO 3 ( PST 30 ) thin films were synthesized on platinized silicon (Pt∕Si) and lanthanum aluminate (LAO) substrates using chemical solution deposition technique. The films on LAO substrate were highly (100) oriented, whereas the films on Pt∕Si substrate were polycrystalline. The low dielectric loss in the PST30∕LAO films makes them attractive for fabricating tunable dielectric devices. An eight-element coupled microstrip phase shifter was fabricated on PST30∕LAO film and tested in the frequency range ∼15–17GHz. The maximum figure of merit (κ=phase shift per dB loss) of ∼56°∕dB was obtained for PST30 film, which was better than commonly observed value in pure barium strontium titanate films. This makes PST30 a potential candidate material for further investigations for microwave applications.
Orientation dependence of the converse piezoelectric constantsfor epitaxial single domain ferroelectric films
Authors: Ouyang Jun , Yang S. Y. , Chen L. , Ramesh R. , Roytburd A. L.
Published: July 2004

The orientation dependence of the converse piezoelectric constants in epitaxial single domain piezoelectric films constrained by substrate is calculated. The calculations are supported by the experimental measuring results of longitudinal piezoelectric constants of ferroelectric tetragonal Pb(Zr0.2Ti0.8)O3 thin films with (001), (011), and (111) orientations.
Efficient light absorption in metal–semiconductor–metal nanostructures
Authors: Collin Stéphane , Pardo Fabrice , Teissier Roland , Pelouard Jean-Luc
Published: July 2004

A nanoscale metal–semiconductor grating is proposed for efficient and ultrafast photodetection. Theoretical and experimental results of efficient absorption in nanoscopic semiconductor wires are presented. The strong confinement of light in subwavelength metal–semiconductor gratings is achieved by Fabry–Pérot resonances involving vertical transverse magnetic surface-plasmon waves and transverse electric guided waves. Photodetectors have been fabricated with 40×100nm cross sections of Ag and GaAs wires. The reflectivity and photocurrent mesurements are in good agreement with theoretical estimates.
The Lerch function and the thermodynamical functions of the ideal quantum gases
Authors: Ciccariello Salvino
Published: July 2004

The unified description of the main thermodynamical functions of the Bose and Fermi ideal gases, obtained by Lee [J. Math. Phys. 36, 1217 (1995)] in terms of the polylogarithmic functions, can also be obtained by analytic continuation in the chemical potential owing to the analytic properties of the Lerch function that is simply related to the polylogarithmic ones. By this procedure we also show that the Fourier coefficients of the thermal Green function of the ideal Bose gas convert into those of the Fermi one.
Observation of ion-acoustic shock waves undergoing Landau damping
Authors: Nakamura Y. , Bailung H. , Saitou Y.
Published: July 2004

Numerical results of a modified Korteweg–de Vries equation with an integral term which describes Landau damping have been compared with the experimental findings. In the linear regime, the wave damping rate is proportional to wave number, which conforms to a kinetic dispersion relation. Transition of an oscillatory ion-acoustic shocklike structure into a monotonic shock has been observed when Landau damping is introduced by mixing H2 ions with an Ar plasma. Quenching of the oscillatory stucture behind the wave front is identified as a dissipation charateristic governed by the strength of Landau damping.
Uniaxial in-plane magnetic anisotropy of Ga1−xMnxAs
Authors: Welp U. , Vlasko-Vlasov V. K. , Menzel A. , You H. D. , Liu X. , Furdyna J. K. , Wojtowicz T.
Published: July 2004

The anisotropic magnetic properties of a series of epitaxial Ga1−xMnxAs films with thicknesses ranging from 0.2to6.8μm were investigated using magnetometry and x-ray diffraction. The films all show a distinct uniaxial contribution to the magnetic anisotropy along the in-plane [110] direction, whose relative importance increases with the temperature. The uniaxial anisotropy field is found to be essentially thickness independent, ruling out the possibility that this is an effect produced by a single surface or interface due to well-known surface reconstruction. Furthermore, even the very thick samples are found to be tetragonal and coherently strained to the GaAs substrate. Our results suggest that the uniaxial anisotropy arises from surface reconstruction induced preferential Mn incorporation occurring at every step of layer-by-layer growth and thus uniformly penetrates the entire sample.
Two-photon absorption in InP substrates in the 1.55μm range
Authors: Vignaud D. , Lampin J. F. , Mollot F.
Published: July 2004

The nonlinear optical absorption has been studied in three different InP substrates (semi-insulating Fe-doped, n-type S-doped, and p-type Zn-doped) by subpicosecond pump-probe differential transmission experiments at 1.6μm. A strong negative differential transmission peak is observed at zero delay, induced by an autocorrelation effect: it is related to two-photon absorption, but not to the occurrence of transitions involving any midgap level (noticeably the Fe-related one). The experimental two-photon absorption coefficient β for InP stands in the range between 24 and 33cm∕GW.
Strong enhancement of terahertz radiation from semiconductor surfaces using MgO hemispherical lens coupler
Authors: Nakajima M. , Uchida K. , Tani M. , Hangyo M.
Published: July 2004

We report an enhancement of terahertz radiation power from InAs surfaces excited by ultrashort laser pulses using an MgO hemispherical lens coupler. The power of the terahertz radiation from the InAs surface with the MgO lens coupler is 50 times larger than that from the InAs surface without the MgO lens coupler. The enhancement is explained mainly by the increase of the transmission efficiency of the THz wave from InAs to free space.
Optical switching of single-electron tunneling in SiO2∕molecule∕SiO2 multilayer on Si(100)
Authors: Wakayama Y. , Ogawa K. , Kubota T. , Suzuki H. , Kamikado T. , Mashiko S.
Published: July 2004

Porphyrin-based molecules inserted into the oxide layer of a metal–oxide–semiconductor structure served as Coulomb islands. A Coulomb staircase originating from the single-electron tunneling was observed in a current–voltage curve. We found that light irradiation induced a shift in the Coulomb staircase. This shift was reversible; the shifted Coulomb staircase returned to its original position when the light irradiation was turned off. We thus demonstrated optical switching of a tunneling current. This result indicates that the molecular Coulomb islands have the potential to provide a range of optical functionality in single-electron tunneling devices.
Low-frequency negative capacitance effect in systems of metallic nanoparticles embedded in dielectric matrix
Authors: Parravicini G. B. , Stella A. , Ungureanu M. C. , Kofman R.
Published: July 2004

A negative capacitance (NC) effect in a low-frequency range (4–8×105Hz), previously shown to take place mainly in semiconductor structures, is evidenced in a nanometric system constituted by metallic (Ga) nanoparticles embedded in an insulating (SiOxwithx~1) matrix. The dependence of the NC phenomenon on the time-dependent transient current through the system is evidenced. A remarkable enhancement of the effect with size reduction of the nanoparticles is manifested. The physical mechanism responsible for the current inertia appears to be related to the space charges located at the multiple insulator–metal interfaces.
Freestanding vertically aligned arrays of individual carbon nanotubes on metallic substrates for field emission cathodes
Authors: Mauger M. , Binh Vu Thien , Levesque A. , Guillot D.
Published: July 2004

Direct growth of individual and vertically aligned carbon nanotubes (CNTs) onto a metallic tip apex using a two-chamber radio-frequency plasma-enhanced chemical vapor deposition is reported. Individual Ni nanocatalysts, obtained by a sol–gel combustion technique, were dots for the nucleation of individual CNTs that were freestanding, clean, and vertically aligned by the presence of a controlled applied field. The arrays of CNTs obtained, having a low-density spatial distribution to avoid mutual electrostatic field screening, gave uniform stable overall field emission patterns after a conditioning process. Effective total current densities up to 1A∕cm2 can be extracted.
Temperature dependence of hydrogen-induced exfoliation of InP
Authors: Hayashi S. , Bruno D. , Goorsky M. S.
Published: July 2004

To investigate the mechanisms of hydrogen-induced blistering in III–V materials, a standard splitting dose of 5×1016H2+∕cm2 at 150keV was implanted into InP substrates cooled to −20°C. Substrate cooling during the implantation improved the reproducibility of this approach by limiting hydrogen mobility during ion implantation. The implant profile and defect structure of unbonded wafers were studied for various annealing schedules with double-axis x-ray diffraction and transmission electron microscopy. It was found that exfoliation was greatly facilitated by a combined lower-temperature (150°C) “defect nucleation” step, followed by a higher-temperature anneal (300°C). The nucleation of defects in the lower-temperature regime, which did not occur if the initial anneal was conducted only at higher temperatures, was attributed to defect trapping of hydrogen. This annealing sequence presents a means by which to (i) improve the interfacial bond strength at low temperatures while the “nucleation” occurs and (ii) promote efficient exfoliation at high temperature.
Myofibroblast Development Is Characterized by Specific Cell-Cell Adherens Junctions
Authors: Hinz B. , Pittet P. , Smith-Clerc J. , Chaponnier C. , Meister J.-J.
Published: July 2004

Myofibroblasts of wound granulation tissue, in contrast to dermal fibroblasts, join stress fibers at sites of cadherin-type intercellular adherens junctions (AJs). However, the function of myofibroblast AJs, their molecular composition, and the mechanisms of their formation are largely unknown. We demonstrate that fibroblasts change cadherin expression from N-cadherin in early wounds to OB-cadherin in contractile wounds, populated with α-smooth muscle actin (α-SMA)-positive myofibroblasts. A similar shift occurs during myofibroblast differentiation in culture and seems to be responsible for the homotypic segregation of α-SMA-positive and -negative fibroblasts in suspension. AJs of plated myofibroblasts are reinforced by α-SMA–mediated contractile activity, resulting in high mechanical resistance as demonstrated by subjecting cell pairs to hydrodynamic forces in a flow chamber. A peptide that inhibits α-SMA–mediated contractile force causes the reorganization of large stripe-like AJs to belt-like contacts as shown for enhanced green fluorescent protein-α–catenin-transfected cells and is associated with a reduced mechanical resistance. Anti-OB-cadherin but not anti-N-cadherin peptides reduce the contraction of myofibroblast-populated collagen gels, suggesting that AJs are instrumental for myofibroblast contractile activity.
Ladies in the Scientific Revolution
Authors: Cook Alan
Published: July 2004

Two exhibitions were recently held in the Library of the Society, one on Women in Science and another on the Archives of the Scientific Revolution. The first did not go so far back as the scientific revolution, with one exception, the translation of Newton's
Principia
by the Marquise du Chàtelet. Yet it was in the scientific revolution, conveniently taken as running from the middle of the seventeenth to the middle of the eighteenth century, that women are first known to have engaged in natural philosophy. Eight ladies certainly had some part in the scientific revolution, not just as tricoteuses watching the heads roll, but themselves helping to bring down the guillotine upon Aristotelians, Cartesians, astrologers, hermetics and mystics.
Robert Hooke: A fractographic study of Kettering–stone
Authors: Hull Derek
Published: July 2004

Observ. XV. illustrated by Schem. IX. Figur:1 (figure 1 of this paper) in Robert Hooke's Micrographia (1665)1 is a description of Kettering–stone ‘which is brought from Kettering in Northampton–shire, and digg’d out of a Quarry, as I am inform'd’. As Curator of Experiments for the Royal Society from 1662, Hooke was charged by the Society to bring in at every meeting one microscopical observation at least. The minutes of the Society2 record that on 15 April 1663 ‘Mr Hooke showed the Company two Microscopicall Schemas; one representing the Pores of Cork … the other a Kettering Stone, appearing to be composed of Globules; and those hollow ones, each having 3 Coatings, sticking to one another, and so making up one entire firm stone’.
Address of the President, Sir Aaron Klug, O.M., P.R.S., given at the Anniversary Meeting on 29 November 1996
Authors: Klug Aaron
Published: July 2004

At the Anniversary Meeting of the Royal Society held on 29 November 1996, the President, Sir Aaron Klug, O.M., following the presentation of medals for 1996, continued:
Epidemiology, transmission dynamics and control of SARS: the 2002–2003 epidemic
Authors: Anderson Roy M. , Fraser Christophe , Ghani Azra C. , Donnelly Christl A. , Riley Steven , Ferguson Neil M. , Leung Gabriel M. , Lam T. H. , Hedley Anthony J.
Published: July 2004

This paper reviews current understanding of the epidemiology, transmission dynamics and control of the aetiological agent of severe acute respiratory syndrome (SARS). We present analyses of data on key parameters and distributions and discuss the processes of data capture, analysis and public health policy formulation during the SARS epidemic are discussed. The low transmissibility of the virus, combined with the onset of peak infectiousness following the onset of clinical symptoms of disease, transpired to make simple public health measures, such as isolating patients and quarantining their contacts, very effective in the control of the SARS epidemic. We conclude that we were lucky this time round, but may not be so with the next epidemic outbreak of a novel aetiological agent. We present analyses that help to further understanding of what intervention measures are likely to work best with infectious agents of defined biological and epidemiological properties. These lessons learnt from the SARS experience are presented in an epidemiological and public health context.
Management and prevention of SARS in China
Authors: Zhong Nanshan
Published: July 2004

The case fatality was the lowest (3.8%) among 1512 cases with severe acute respiratory syndrome (SARS) in Guangdong Province, China. Rational use of corticosteroid, non–invasive ventilation and the integration of traditional Chinese medicine and modern medicine may partly have contributed to the lowest fatality figure. There was a close linkage between civet cats and humans in terms of transmission of SARS. Strict control of the wild–animal market may be significant in preventing a new outbreak of SARS this year.
Mate choice in the predaceous mite Phytoseiulus persimilis: evidence of self‐referent phenotype matching?
Authors: Enigl Monika , Schausberger Peter
Published: July 2004

Close inbreeding may have negative fitness effects. Consequently, organisms have evolved various mechanisms, which enable them to avoid close inbreeding. In no‐choice and choice experiments we assessed whether the predaceous mite Phytoseiulus persimilis Athias‐Henriot (Acari: Phytoseiidae) avoids close inbreeding by kin recognition. No‐choice experiments demonstrated that virgin females more readily accept unrelated males than they accept related ones, which suggests a female preference for unrelated mates. Because each female had been reared in isolation prior to experiments, females most likely imprinted on themselves, and later used self‐referent phenotype matching to assess potential mating partners. In contrast, neither female nor male choice experiments indicated a preference. Analyses of female and male behavior revealed that in choice experiments, female preference for unrelated males was probably confounded by male competition and/or altered by the different ecological context posed by choice experiments.
Wing morph development and reproduction of the ectoparasitoid Melittobia digitata: nutritional and hormonal effects
Authors: Cônsoli Fernando L. , Vinson S. Bradleigh
Published: July 2004

Manipulation studies of the temporal availability of nutrients during parasitoid larval development (high‐quality host vs. host deprivation) demonstrated that parasitoid access to nutrition affected the wing morph development of Melittobia digitata Dahms (Hymenoptera: Eulophidae), but not the parasitoid's ovarian development. Around 70% of programmed short wing morph larvae (SWM) that had been host‐deprived at 120 h after host parasitization shifted their development and emerged as long wing morphs (LWM). A reversion in morph development of programmed LWM was also found when the larvae were offered new hosts after up to 120 h of development, and both programmed SWM or LWM larvae that differentiated as SWMs had a similar egg load. Although precocene treatment of programmed SWM induced 30% of LWM development, morph development of programmed LWM remained unaltered if treated with methoprene, a juvenile hormone analogue (JHA), indicating that the morph development of M. digitata does not appear to be under juvenile hormone control. However, both precocene and JHA affected the ovarian development of the emerging female. We hypothesize that specific nutrients from the host hemolymph, or changes in the host internal composition at the parasitoid larval sensitive stage (120–123 h) induce changes in pathways that control parasitoid metabolism and nutrient allocation decisions during the cell growth and development of imaginal discs.
Double Entry Bookkeeping and the Distributional Properties of a Firm's Financial Ratios
Authors: Ashton David , Dunmore Paul , Tippett Mark
Published: July 2004

Our purpose here is to assess whether the innate properties of the double entry bookkeeping system are such that financial ratios, calculated from the balance sheet summary measures implied by it, will be generated by distributional forms with non‐convergent moments. Our analysis begins with a brief summary of some important analytical properties of the debt and equity components of the double entry bookkeeping system. We then use these to determine the time series and distributional properties of the debt to equity ratio itself. Our analysis shows that even when the evolution of balance sheet summary measures like debt and equity can be described by ‘well behaved’ distributional processes, there is a distinct possibility that ratios derived from them will evolve in terms of distributional forms with non‐convergent moments. We argue that this has serious implications for parameter estimation as well as the integrity of the regression and/or discriminant procedures which underscore bankruptcy and financial distress prediction models based on financial ratios derived from the double entry bookkeeping system.
Intra Day Bid‐Ask Spreads, Trading Volume and Volatility: Recent Empirical Evidence from the London Stock Exchange
Authors: Cai Charlie X. , Hudson Robert , Keasey Kevin
Published: July 2004

With the benefit of very high frequency (25 million 1 minute observations) and recent data (2001) for the UK, this paper explores a number of intra day patterns of stock market behaviour. More specifically, a distinct reverse J shaped bid‐ask spread pattern is noted for SETS securities, a declining bid‐ask spread pattern for non‐SETS securities, a two hump pattern for trading volume and a U‐shaped pattern for returns volatility for all securities. In terms of complementing the existing literature, the paper shows that differences in trading systems may affect the bid‐ask spread patterns, while differences in market environments (i.e. US and UK markets) seems to affect the trading volume pattern. The paper suggests avenues for future research, in particular, the need to consider what factors are significant in determining intra day patterns for different trading systems and the need for additional cross‐market comparisons to identify how institutional factors affect the behaviour of investors on an intra day basis.
Female Earnings and Divorce Rates: Some Australian Evidence
Authors: Phillips Bruce , Griffiths William
Published: July 2004

The purpose of this article is to examine whether female earnings have influenced divorce rates in Australia, using state‐level data for the past four decades. Following a recent study by Ressler and Waters (2000), which concludes from comparable US data that female earnings and divorce rates may be jointly endogenous, initial testing is performed to identify whether female earnings can be treated as exogenous. A Hausman specification error test finds no evidence of a simultaneous relationship in the Australian data, in contrast to the findings of Ressler and Waters. The test result supports the hypothesis that other underlying factors affect female earnings, of which higher divorce rates are merely another symptom. A divorce rate equation is estimated. In accordance with much of the literature, the rise in female earnings over the past four decades is found to have increased Australian divorce rates.
Minimum Wages and Employment: Comment
Authors: Watson Ian
Published: July 2004

Does increasing the minimum wage lead to employment losses? For many years most economists thought that the answer to this was a straightforward ‘yes’. However, research during the 1990s began to overturn this conventional wisdom and showed that increases in the minimum wage did not automatically lead to employment losses. A recent Australian study, by Leigh (2003), examined the impact of statutory minimum wages in Western Australia and reached conclusions which supported the conventional view. However, close scrutiny of Leigh's article shows that it is fundamentally flawed. Despite Leigh's efforts, it remains the case that we simply do not know a great deal about the employment impact of Australia's system of minimum wages.
Minimum Wages and Employment: Reply
Authors: Leigh Andrew
Published: July 2004

The results of my study (Leigh 2003, 2004) on the effect of minimum wages on employment have been brought into question by Watson (2004), which raises some potential methodological concerns. Careful reanalysis of the Western Australian minimum wage experiment demonstrates that this critique is not well founded. Further checks show that the results are robust to a number of alternative specifications, in addition to those presented in the original article.
Plasma Assisted Milling of Heat-Resistant Superalloys
Authors: Lo´pez de Lacalle L. N. , Sa´nchez J. A. , Lamikiz A. , Celaya A.
Published: July 2004

The term Thermal Enhanced Machining refers to a conventional cutting process in which an external energy source is used to enhance the chip-generation mechanism. The work presented here analyzes the basic aspects and the experimental results obtained when applying an assisting plasma jet to the milling process. This process, known as PAM (Plasma Assisted Milling) has been applied to the machining of three very low machinability materials: a Ni-base alloy (Inconel 718), a Co-base alloy (Haynes 25), (both belonging to the group of the heat-resistant alloys) and the Ti-base alloy Ti6Al4V. The study focuses on two major topics. First, the efficiency of the milling operation in terms of cutting speed, feed, axial and radial depths of cut and the plasma operating parameters has been addressed. Second, a study on the alterations of the metallurgical structure and the properties of materials after the PAM has also been performed. The process conditions for the above-mentioned Ni-base and Co-base alloys are detailed. The study under these conditions has shown an excellent performance of the whisker reinforced ceramic tools. In fact, cutting speeds as high as 970 m/min and large radial and axial depths of cuts are possible, driving to a cost-effective machining process. The absence of changes in the metallurgical structure of the alloys after applying the PAM process is also addressed. Therefore, it can be stated that this is a feasible approach to the optimization of the machining process of heat-resistant alloys. Finally, the results obtained in the PAM of Ti6Al4V are detailed. In this experimentation, a certain level of degradation was observed in the microstructure of the alloy when undergoing the PAM process, therefore the use of this technique is not recommended for this material.
Boundary Conformed Toolpath Generation via Laplace Based Parametric Redistribution Method
Authors: Oulee T. H. , Yang Daniel C. H. , Chuang J. J.
Published: July 2004

A new approach for boundary conformed toolpath generation is presented in this paper. The approach combines the numerical Laplace solution for initial parametrization and a parametric redistribution algorithm for improved toolpath generation. The Laplace parametrization can be applied to any 2D surface domain without anomalies. Our parametric redistribution algorithm can then be used to reduce the unevenness that usually occurs in Laplace parametrization. The adequacy of computational robustness and efficiency of the parametric redistribution method are tested in this paper. By applying the parametric redistribution method, both the machining efficiency and uniformity of the resultant toolpaths can be improved. The advantages of this boundary conformed toolpath generation approach are successfully demonstrated on several typical examples.
Warpage Analysis of Underfilled Wafers
Authors: Ding Hai , Ume I. Charles , Zhang Cheng
Published: July 2004

Wafer-level packaging (WLP) is one of the future trends in electronic packaging. Since 1994, many companies have released various WLP licenses. One of the common concerns of WLP is wafer warpage. Warpage of wafers tends to introduce cracking or delamination during dicing and low temperature storage processes. After wafer dicing, warpage could affect the quality of the dies and shorten the life of each packaged product. Many documented works indicated that in the design and implementation of multilayer structured electronic packaging products, some key parameters must be carefully considered and closely controlled to ensure the best packaging quality with the minimum warpage. During the wafer-level flip chip assembly process, the application of underfill on the whole wafer is a critical step. In this step, the key underfill parameters that affect wafer warpage are Young’s modulus, thickness, and coefficient of thermal expansion (CTE). In this paper, an experimental design and statistical methods were used to identify the model structure and parameters that are critical to the warpage of wafers. Bilinear regression models were identified based on the data obtained from finite element analysis (FEA) that was verified by shadow moire´ experiments. In FEA, the underfilled wafer structure is simplified to consisting of two layers of linear elastic materials. According to the models, the CTE, the coupling of Young’s modulus and CTE, and the coupling of thickness and CTE primarily determine wafer warpage. Further FEA and shadow moire´ experiments indicate that the models are capable of predicting wafer warpage in the WLP processes.
Continuous Optimal Infeed Control for Cylindrical Plunge Grinding, Part 1: Methodology
Authors: Dong Shaoqiang , Danai Kourosh , Malkin Stephen , Deshmukh Abhijit
Published: July 2004

A new methodology is developed for optimal infeed control of cylindrical plunge grinding cycles. Unlike conventional cycles having a few sequential stages with discrete infeed rates, the new methodology allows for continuous variation of the infeed rate to further reduce the cycle time. Distinctive characteristics of optimal grinding cycles with variable infeed rates were investigated by applying dynamic programming to a simulation of the grinding cycle. The simulated optimal cycles were found to consist of distinct segments with predominant constraints. This provided the basis for an optimal control policy whereby the infeed rate is determined according to the active constraint at each segment of the cycle. Accordingly, the controller is designed to identify the state of the cycle at each sampling instant from on-line measurements of power and size, and to then compute the infeed rate according to the optimal policy associated with that state. The optimization policy is described in this paper, and the controller design and its implementation are presented in the following paper [1].
Aging Effects on Microstructure and Tensile Property of Sn3.9Ag0.6Cu Solder Alloy
Authors: Xiao Qiang , Bailey Harold J. , Armstrong William D.
Published: July 2004

Relationships between microstructural and mechanical aging effects in eutectic PbSn and Pb-free solder alloy Sn3.9Ag0.6Cu are reported and compared. The room temperature aged Sn3.9Ag0.6Cu alloy continually age-softened, this softening correlated with the growth of relatively large tin-rich crystals. The 180°C aged Sn3.9Ag0.6Cu alloy initially age-softened, and the minimum flow strength was reached after one day at 180°C. This softening correlated with the growth of relatively large tin-rich crystals and with the coarsening of Ag3Sn particles. When aged at 180°C beyond one day the Sn3.9Ag0.6Cu alloy age-hardened, the hardening correlated with the dispersion of Ag3Sn particles into tin-rich crystals which previously had not contained intermetallic precipitates.
Compact Modeling of Fluid Flow and Heat Transfer in Straight Fin Heat Sinks
Authors: Kim Duckjong , Kim Sung Jin
Published: July 2004

In the present work, a compact modeling method based on a volume-averaging technique is presented. Its application to an analysis of fluid flow and heat transfer in straight fin heat sinks is then analyzed. In this study, the straight fin heat sink is modeled as a porous medium through which fluid flows. The volume-averaged momentum and energy equations for developing flow in these heat sinks are obtained using the local volume-averaging method. The permeability and the interstitial heat transfer coefficient required to solve these equations are determined analytically from forced convective flow between infinite parallel plates. To validate the compact model proposed in this paper, three aluminum straight fin heat sinks having a base size of 101.43mm×101.43mm are tested with an inlet velocity ranging from 0.5 m/s to 2 m/s. In the experimental investigation, the heat sink is heated uniformly at the bottom. The resulting pressure drop across the heat sink and the temperature distribution at its bottom are then measured and are compared with those obtained through the porous medium approach. Upon comparison, the porous medium approach is shown to accurately predict the pressure drop and heat transfer characteristics of straight fin heat sinks. In addition, evidence indicates that the entrance effect should be considered in the thermal design of heat sinks when Re Dh/L>∼O10.
Use of transmission electron microscopy in the characterization of GaInNAs(Sb) quantum well structures grown by molecular beam epitaxy
Authors: Gugov Tihomir , Gambin Vincent , Wistey Mark , Yuen Homan , Bank Seth , Harris James S.
Published: July 2004

The quaternary GaInNAs alloy is a very promising material system for lasers in the 1.2–1.6 μm range with application in telecommunication fiber-optic networks. While good quality laser material has been demonstrated at 1.3 μm, pushing the emission beyond 1.5 μm by adding up to 40% In and 2% N has been unsuccessful. Recently, the addition of small amounts of Sb has put this alloy back on track for the 1.5 μm challenge by dramatically improving the luminescence efficiency of the material. In this work, high-resolution transmission electron microscopy (TEM), energy-filtered TEM, dark-field TEM, and energy-dispersive x-ray spectroscopy were used to structurally characterize both GaInNAs and GaInNAsSb quantum well structures. The results provide insight into the role of antimony in improving the optical properties of the material, namely reducing the local compositional fluctuations of In.
Field emission from carbon nanotube Mat
Authors: Zhao W. J. , Rochanachivapar W. , Takai M.
Published: July 2004

Field emission characteristics of both top and bottom surfaces of carbon nanotube mats (CNT-Mats) or sheet-like CNTs were investigated. The emission characteristics of the CNT-Mat were compared with those of screen-printed CNT emitters before and after UV laser irradiation. Screen-printed CNT emitters have very low emission current density without proper surface treatment, although after UV laser irradiation, the emission current densities increased drastically. On the other hand, the CNT-Mats have excellent field emission characteristics even without any surface treatment. With an applied electric field of 3.47 V/μm, the emission current density of the top surface of CNT-Mat reached 1.99 mA/cm2, which was six times higher than that of screen-printed CNT emitters after UV laser irradiation. The field emission stability of CNT-Mat and screen-printed CNT emitters in various pressures were also investigated. Both CNT emitters have stable field emissions at and below 1×10−4 Pa.