bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical investigations of the N2H2+ cation and of its reactivity
Authors: Palaudoux J. , Hochlaf M.
Published: July 2004

Accurate ab initio calculations have been performed in order to investigate both the stable isomers and the reactivity of the N2H2+ cation. In addition to the trans-HNNH+ isomer already observed in the photoelectron studies, a formaldehyde type (isodiazene cation) and H2O2-like isomers are found. At the coupled cluster level of theory, the isodiazene cation is calculated to be as stable as trans-HNNH+. We have also studied the reactivity of N2H2+ and its implication on the reactive processes involving N2/N2+ and H2+/H2, H/H+ and HN2+/HN2, and HN and HN+ by performing suitable one-dimensional cuts of the six-dimensional potential energy functions of the lowest electronic states of H2N2+. We have pointed out the crucial role of this tetratomic intermediate cation and the importance of the short range internuclear distances during these processes. In the case of N2/N2+ and H2+/H2 reactions, we have shown that the initial orientation of the reactants may influence the N2H2+ tetratomic intermediate: One can expect to form the trans isomer preferentially if the internuclear axes of the H2/H2+ and the N2+/N2 molecules are parallel to each other when these diatoms are colliding and after intramolecular isomerization process. However, if the internuclear axes of the diatomics are perpendicular to each other, the isodiazene cation is formed preferentially. Different branching ratios are expected for each collision scheme. These reactive processes are found to involve vibronic, Renner-Teller and spin-orbit couplings between the electronic states of N2H2+. These interactions mix these electronic states, leading to the formation of atomic, diatomic, and triatomic species via the decomposition of the N2H2+ intermediate complex.
Electron pair localization function: A practical tool to visualize electron localization in molecules from quantum Monte Carlo data
Authors: Scemama Anthony , Chaquin Patrick , Caffarel Michel
Published: July 2004

In this work we introduce an electron localization function describing the pairing of electrons in a molecular system. This function, called “electron pair localization function,” is constructed to be particularly simple to evaluate within a quantum Monte Carlo framework. Two major advantages of this function are the following: (i) the simplicity and generality of its definition; and (ii) the possibility of calculating it with quantum Monte Carlo at various levels of accuracy (Hartree-Fock, multiconfigurational wave functions, valence bond, density functional theory, variational Monte Carlo with explicitly correlated trial wave functions, fixed-node diffusion Monte Carlo, etc). A number of applications of the electron pair localization function to simple atomic and molecular systems are presented and systematic comparisons with the more standard electron localization function of Becke and Edgecombe are done. Results illustrate that the electron pair localization function is a simple and practical tool for visualizing electronic localization in molecular systems.
Investigating the dominant corrections to the strong-stretching theory for dry polymeric brushes
Authors: Matsen M. W.
Published: July 2004

The accuracy of strong-stretching theory (SST) is examined against a detailed comparison to self-consistent field theory (SCFT) on dry polymeric brushes with thicknesses of up to ∼17 times the natural chain extension. The comparison provides the strongest evidence to date that SST represents the exact thick-brush limit of SCFT. More importantly, it allows us to assess the effectiveness of proposed finite-stretching corrections to SST. Including the entropy of the free ends is shown to rectify the most severe inaccuracies in SST. The proximal layer proposed by Likhtman and Semenov provides another significant improvement, and we identify one further effect of similar importance for which there is not yet an accurate treatment. Furthermore, our study provides a valuable means of rejecting mistaken refinements to SST, and indeed one such example is revealed. A proper treatment of finite-stretching corrections is vital to a wide range of phenomena that depend on a small excess free energy, such as autophobic dewetting and the interaction between opposing brushes.
Spatially-resolved electroluminescence of operating organic light-emitting diodes using conductive atomic force microscopy
Authors: Pingree L. S. C. , Hersam M. C. , Kern M. M. , Scott B. J. , Marks T. J.
Published: July 2004

A conductive atomic force microscopy (cAFM) technique has been developed that concurrently monitors topography, charge transport, and electroluminescence. This cAFM approach is particularly well suited for probing the electroluminescent response characteristics of operating organic light-emitting diodes (OLEDs) over short length scales. In a typical experiment, charge is injected into individual OLED structures with the cAFM tip, and the resulting electroluminescence and current are measured with collecting optics and a variable gain photomultiplier tube. As a proof of principle, the real-time spatial and temporal current–voltage and electroluminescence–voltage properties of 8μm×8μm OLED pixels are simultaneously imaged.
Evaluation of multicenter one-electron integrals of noninteger u screened Coulomb type potentials and their derivatives over noninteger n Slater orbitals
Authors: Guseinov I. I. , Mamedov B. A.
Published: July 2004

Multicenter integrals over noninteger n Slater type orbitals with integer and noninteger values of indices u of screened Coulomb type potentials, fu(η,r)=ru−1e−ηr, and their first and second derivatives with respect to Cartesian coordinates of the nuclei of a molecule are described. Using complete orthonormal sets of Ψα exponential type orbitals and rotation transformation of two-center overlap integrals, these integrals are expressed through the noncentral potential functions depending on the molecular auxiliary functions Ak and Bk. The series expansion formulas derived for molecular integrals of screened Coulomb potentials and their derivatives are especially useful for the computation of multicenter electronic attraction, electric field, and electric field gradient integrals. The convergence of series is tested for arbitrary values of parameters of potentials and orbitals.
Relationship between cohesive energy density and hydrophobicity
Authors: Graziano Giuseppe
Published: July 2004

It has been recently claimed that the large cohesive energy density of water is the ultimate cause of the poor solubility of nonpolar compounds in water. In order to test the validity of this idea, we analyze the difference in solubility between light water and heavy water of several nonpolar compounds. Even though the cohesive energy density of D2O is larger than that of H2O, nonpolar compounds are slightly more soluble in D2O than H2O. In such case experimental data do not support the correctness of the large cohesive energy density as the ultimate cause of hydrophobicity. We show that D2O is a slightly better solvent than H2O for nonpolar compounds because it is slightly less costly to create a cavity in the former liquid. This is because there is slightly more void volume in heavy water than in light water.
Approximate generation of full-dimensional ab initio van der Waals surfaces for high-resolution spectroscopy
Authors: Jankowski Piotr
Published: July 2004

A method for the generation of highly accurate, nearly-exact, full-dimensional interaction energy surfaces for weakly interacting subsystems is proposed. The method is based on the local expansion of the exact interaction energy surface in the Taylor series with respect to intramolecular coordinates. It is shown that without any significant loss of accuracy this expansion can be limited to a few low-order terms. This leads to significant savings in computations of the full-dimensional interaction energy surfaces. Also a method for the direct calculation of the interaction energy surface of reduced dimensionality, corresponding to averaging over the intramolecular vibrations, without explicit knowledge of the full-dimensional surface, is presented. The main ideas and computational features of the proposed scheme are comprehensively tested for the Ar-HF system.
Electron collisions with trifluorides: BF3 and PF3 molecules
Authors: Szmytkowski Czesław , Piotrowicz Michał , Domaracka Alicja , Kłosowski Łukasz , Ptasińska-Denga Elżbieta , Kasperski Grzegorz
Published: July 2004

Absolute total cross sections (TCSs) for electron scattering from boron trifluoride (BF3) and phosphorus trifluoride (PF3) molecules have been measured using a linear transmission method. The electron energy ranges from 0.6 to 370 eV for BF3 and from 0.5 to 370 eV for PF3. The TCS energy dependence for BF3 exhibits two very pronounced enhancements: resonantlike narrow feature located near 3.6 eV with the maximum value of 19.2×10−20 m2, and intermediate energy very broad enhancement with two humps, one centered around 21 eV (18.8×10−20 m2 in the maximum) and the other near 45 eV (19.5×10−20 m2). For PF3 the TCS has quite different low-energy dependence: at 0.5 eV it has a high value of 70×10−20 m2 and decreases steeply towards higher energies. Beyond the minimum near 5.5 eV, the TCS reveals two distinct humps: the resonant one centered near 11 eV with the peak value of 32.9×10−20 m2 and the second one much broader around 35 eV (27.9×10−20 m2). The present TCSs for trifluorides are compared to each other as well as to previous TCS data for selected perfluorides and to results for their perhydrided counterparts. The differences and similarities in the shape and magnitude of TCSs are pointed out.
Quantum tunneling dynamics in multidimensional systems: A matching-pursuit description
Authors: Wu Yinghua , Batista Victor S.
Published: July 2004

Rigorous simulations of quantum tunneling dynamics in model systems with up to 20 coupled degrees of freedom are reported. The simulations implement an extension of the recently developed matching-pursuit/split-operator Fourier-transform method to complex-valued coherent-state representations. The resulting method recursively applies the time-evolution operator, as defined by the Trotter expansion to second order accuracy, in dynamically adaptive coherent-state representations generated by an approach that combines the matching-pursuit algorithm with a gradient-based optimization method.
Photoassociation spectroscopy of ultracold Cs below the 6P1/2 limit
Authors: Pichler Marin , Chen Hongmin , Stwalley William C.
Published: July 2004

We have performed high precision photoassociation spectroscopy of ultracold cesium gas. Using trap-loss fluorescence detection and controlling the background cesium pressure we were able to photoassociate atoms into excited states of ultracold molecules with large detunings up to 56 cm−1 below the Cs(6S1/2)+Cs(6P1/2) atomic asymptote. Vibrational progressions are assigned to 0g−, 0u+, and 1g long-range states. By fitting the spectral data to the LeRoy-Bernstein expression, the effective coefficients of the leading long-range interactions and the vibrational quantum number at dissociation are obtained. In addition we have observed spectral perturbations between states of the same symmetry belonging to different asymptotes (6P1/2 and 6P3/2). The perturbations are manifested through irregular vibrational level spacings and are especially pronounced in the 0u+ symmetry. Many observed rotational levels indicate d- and higher partial wave contributions to the photoassociation cross section in the presence of trapping laser light, while spectral regions with only weak features suggest nodes in the lower state wave functions corresponding to the two ground state atoms asymptote.
Quantum dynamics calculations using symmetrized, orthogonal Weyl-Heisenberg wavelets with a phase space truncation scheme. II. Construction and optimization
Authors: Poirier Bill , Salam A.
Published: July 2004

In this paper, we extend and elaborate upon a wavelet method first presented in a previous publication [B. Poirier, J. Theo. Comput. Chem. 2, 65 (2003)]. In particular, we focus on construction and optimization of the wavelet functions, from theoretical and numerical viewpoints, and also examine their localization properties. The wavelets used are modified Wilson-Daubechies wavelets, which in conjunction with a simple phase space truncation scheme, enable one to solve the multidimensional Schrödinger equation. This approach is ideally suited to rovibrational spectroscopy applications, but can be used in any context where differential equations are involved.
Theory of excluded volume equation of state: Higher approximations and new generation of equations of state for entire density range
Authors: Rusanov Anatoly I.
Published: July 2004

A novel theory of an equation of state based on excluded volume and formulated in two preceding papers for gases and gaseous mixtures is extended to the entire density range by considering higher (beginning from the third) approximations of the theory. The algorithm of constructing higher approximations is elaborated. Equations of state are deduced using the requirement of maximum simplicity and contain a single free parameter to be chosen by reason of convenience or simplicity or to be used as a fitting parameter with respect to the computer simulation database. In this way, precise equations of state are derived for the hard-sphere fluid in the entire density range. On the side, the theory reproduces most known earlier equations of state for hard spheres and determines their place in the hierarchy of approximations. Equations of state for van der Waals fluids are also presented, and their critical parameters are estimated.
Influence of ultraviolet exposure on the luminescence characteristics of PbS
Authors: Kang K. S.
Published: July 2004

Strong room-temperature photoluminescence is obtained from lead sulfide monomers and dimers in a UV-curable sol-gel matrix in the 510 and 810nm regimes, respectively. Luminescence at 510nm is the dominant process at low PbS concentrations and is enhanced by more than one order of magnitude as a result of matrix cross linking. As concentration increases, 810nm luminescence dominates as a result of monomer-dimer interactions. With deep UV irradiation, the 810nm transition is greatly diminished, and the 510nm emission transition dominates. There is no luminescence difference after deep UV exposure without a cross-linkable moiety.
Transient spectroscopy of InAs quantum dot molecules
Authors: Talalaev V. G. , Tomm J. W. , Zakharov N. D. , Werner P. , Novikov B. V. , Tonkikh A. A.
Published: July 2004

Coupled pairs of InAs quantum dots are grown by molecular-beam epitaxy. Structural and optical characterization is done by means of transmission electron microscopy and photoluminescence, respectively. Photoluminescence spectra consist at least of three well-separated optical transitions that are assigned to molecular energy terms and a substantial exciton lifetime increase is observed. Detailed spectral analysis of the transient luminescence behavior indicates “intraterm” transitions that could be favorably used for the creation of midinfrared light sources.
Random-field quantum spherical ferroelectric model
Authors: Gruber Christian , Zagrebnov Valentin A.
Published: July 2004

We study a (quenched) random-field quantum model of an anharmonic crystal for displacive structural phase transitions in spherical approximation: the random-field quantum spherical (ferroelectric) model. For stationary ergodic random fields its behavior depends on the quantum parameter of the model and on the expectation and covariance of the field. If quantum fluctuations are small enough not to destroy the phase transition, then it can be suppressed when the field fluctuations are large. For the field of independent identically distributed random variables and the short-range interaction we obtain that the lower critical dimensionality dl=4 (dl=2 for the zero-field) and that it decreases for long-range interactions.
Emission of electromagnetic radiation by coherent vibrational wavesin stimulated Raman scattering
Authors: Hasselbeck Michael P. , Schlie L. A. , Stalnaker D.
Published: July 2004

Electromagnetic radiation is emitted by the vibrational and collective modes of an opaque solid as the result of impulsive stimulated Raman scattering. Raman scattering of near-infrared femtosecond laser pulses produces coherent longitudinal optical phonon and plasmon oscillations in the semiconductor InSb. These oscillations radiate into free space at THz frequencies and are directly detected. The THz spectra exhibit features consistent with Raman selection rules including interference of allowed and forbidden Raman scattering.
Effect of H+ on Fe–Mg interdiffusion in olivine, (Fe,Mg)2SiO4
Authors: Wang Zhongyan , Hiraga Takehiko , Kohlstedt D. L.
Published: July 2004

To quantify the effect of hydrogen on the kinetics of Fe–Mg interdiffusion in olivine, diffusion couples composed of crystals with Mg∕(Mg+Fe) ratios of 0.91 and 0.83 were annealed under water-saturated conditions at T=1373K and P=300MPa. With fO2 buffered at the Ni–NiO phase boundary, fH2O≈300MPa. The resulting interdiffusivity, D̃Fe–Mg≈1×10−16m2∕s, is approximately one order of magnitude larger than that measured under anhydrous conditions. The enhancement in diffusivity in the presence of water results from an increase in the concentration of cation vacancies associated with the introduction of high concentrations of protons as point defects into the olivine structure.
Simplified nonplanar wafer bonding for heterogeneous device integration
Authors: Geske Jon , Bowers John E. , Riley Anton
Published: July 2004

We demonstrate a simplified nonplanar wafer bonding technique for heterogeneous device integration. The improved technique can be used to laterally integrate dissimilar semiconductor device structures on a lattice-mismatched substrate. Using the technique, two different InP-based vertical-cavity surface-emitting laser active regions have been integrated onto GaAs without compromising the quality of the photoluminescence. Experimental and numerical simulation results are presented.
Photoluminescence of AlGaN grown on bulk AlN substrates
Authors: Tamulaitis G. , Yilmaz I. , Shur M. S. , Fareed Q. , Gaska R. , Khan M. A.
Published: July 2004

The photoluminescence (PL) of AlGaN quantum wells with AlN barrier layers deposited on substrates fabricated of AlN single crystals is studied in the temperature range from 11to300K under pulsed band-to-band excitation of the well material. The abnormal temperature dependence of the PL peak position and differences in the character of the peak shift with increasing excitation power density observed at low and elevated temperatures are interpreted in terms of carrier/exciton localization and screening of the built-in electric field. The formation of these localized states with narrow energy distribution and high density is favorable for efficient light emission.
Correlated diffusion of silicon and boron in thermally grown SiO2
Authors: Uematsu Masashi , Kageshima Hiroyuki , Takahashi Yasuo , Fukatsu Shigeto , Itoh Kohei M. , Shiraishi Kenji
Published: July 2004

Si self-diffusion and B diffusion in SiO2 were simultaneously investigated in thermally grown Si28O2 co-implanted with Si30 and B. The B diffusivity increases with decreasing distance between the implanted B and Si∕SiO2 interface, in the same way as Si self-diffusivity. This result together with a numerical simulation shows that SiO molecules, which are generated at the Si∕SiO2 interface and diffusing into SiO2, enhance not only Si self-diffusion, but also B diffusion. In addition, we found that the diffusivities of both Si and B increase with higher B concentration in SiO2. The experimental results can be quantitatively explained by a numerical simulation assuming that the diffusivity of SiO, which enhances the diffusivities of Si and B, increases with higher B concentration.
Nonthermal electrons and warm ions effects on oblique modulation of ion-acoustic waves
Authors: Tang Rong-An , Xue Ju-Kui
Published: July 2004

By using the standard reductive perturbation technique, a nonlinear Schrödinger equation is derived to study the instability of oblique modulation of finite amplitude ion-acoustic waves in an unmagnetized plasma consisting of warm adiabatic ions and nonthermal electrons. The effects of nonthermally distributed electrons on the modulational instability and the solitary structures are investigated. It is found that the presence of nonthermal electrons significantly changes the domain of the modulational instability in the k–θ plane.
Record saturation magnetization, Curie temperature, and magnetoresistance in Sr2FeMoO6 double perovskite synthesized by wet-chemistry techniques
Authors: Retuerto M. , Alonso J. A. , Martínez-Lope M. J. , Martínez J. L. , García-Hernández M.
Published: July 2004

Wet-chemistry techniques, involving the previous elaboration of reactive citrate precursors, have been used to prepare Sr2FeMoO6 double perovskite in polycrystalline form. This material has been characterized by x-ray and neutron powder diffraction, magnetic, and magnetotransport measurements. It exhibits a ferromagnetic Curie temperature of 416K, and an almost complete Fe∕Mo ordering at the B sublattice of the perovskite, accounting for the high saturation magnetization at 5K, of 3.97μB per formula unit. The magnetoresistance (MR) is higher than 45% at 5K, for H=9T, and the low-field MR is as high as 6.5% at room temperature for H=0.3T. These excellent features are a consequence of the good homogeneity of the samples, prepared from precursors where a perfect cationic mixing at atomic level is promoted.
V-shaped inversion domains in InN grown on c-plane sapphire
Authors: Jasinski J. , Liliental-Weber Z. , Lu H. , Schaff W. J.
Published: July 2004

Inversion domains with a V shape were found to nucleate inside a Mg-doped InN heteroepitaxial layer. They resemble Al-polarity domains, observed recently, in N-polarity AlN films. However, the angle between the sidewalls of the V-shaped domain and the c axis differs in these two cases. In InN, this angle is almost two times bigger than that reported for AlN. The origin of V-shaped inversion domains in InN film is not yet clear.
Oncostatin M-stimulated Apical Plasma Membrane Biogenesis Requires p27Kip1-Regulated Cell Cycle Dynamics
Authors: van IJzendoorn Sven C.D. , Théard Delphine , van der Wouden Johanna M. , Visser Willy , Wojtal Kacper A. , Hoekstra Dick
Published: July 2004

Oncostatin M regulates membrane traffic and stimulates apicalization of the cell surface in hepatoma cells in a protein kinase A-dependent manner. Here, we show that oncostatin M enhances the expression of the cyclin-dependent kinase (cdk)2 inhibitor p27Kip1, which inhibits G1-S phase progression. Forced G1-S-phase transition effectively renders presynchronized cells insensitive to the apicalization-stimulating effect of oncostatin M. G1-S-phase transition prevents oncostatin M-mediated recruitment of protein kinase A to the centrosomal region and precludes the oncostatin M-mediated activation of a protein kinase A-dependent transport route to the apical surface, which exits the subapical compartment (SAC). This transport route has previously been shown to be crucial for apical plasma membrane biogenesis. Together, our data indicate that oncostatin M-stimulated apicalization of the cell surface is critically dependent on the ability of oncostatin M to control p27Kip1/cdk2-mediated G1-S-phase progression and suggest that the regulation of apical plasma membrane-directed traffic from SAC is coupled to centrosome-associated signaling pathways.
Promoter-dependent Roles for the Srb10 Cyclin-dependent Kinase and the Hda1 Deacetylase in Tup1-mediated Repression inSaccharomyces cerevisiae
Authors: Green Sarah R. , Johnson Alexander D.
Published: July 2004

The Tup1-Ssn6 complex has been well characterized as a Saccharomyces cerevisiae general transcriptional repressor with functionally conserved homologues in metazoans. These homologues are essential for cell differentiation and many other developmental processes. The mechanism of repression of all of these proteins remains poorly understood. Srb10 (a cyclin-dependent kinase associated with the Mediator complex) and Hda1 (a class I histone deacetylase) have each been implicated in Tup1-mediated repression. We present a statistically based genome-wide analysis that reveals that Hda1 partially represses roughly 30% of Tup1-repressed genes, whereas Srb10 kinase activity contributes to the repression of ∼15% of Tup1-repressed genes. These effects only partially overlap, suggesting that different Tup1-repression mechanisms predominate at different promoters. We also demonstrate a distinction between histone deacetylation and transcriptional repression. In an HDA1 deletion, many Tup1-repressed genes are hyperacetylated at lysine 18 of histone H3, yet are not derepressed, indicating deacetylation alone is not sufficient to repress most Tup1-controlled genes. In a strain lacking both Srb10 and Hda1 functions, more than half of the Tup1-repressed genes are still repressed, suggesting that Tup1-mediated repression occurs by multiple, partially overlapping mechanisms, at least one of which is unknown.
Neither ancient nor modern: Wallis and Barrow on the composition of continua. Part two: The seventeenth-century context: The struggle between ancient and modern
Authors: Hill Katherine
Published: July 2004

In the the first part of this article* it was shown that neither John Wallis nor Isaac Barrow fits precisely into the modern or traditional categories commonly used by historians. Yet other kinds of tension between tradition and innovation did exist in the wider intellectual community of early modern England that might have some bearing on the state of mathematics. We therefore need to explore how the opposition between ancient and modern was expressed in the seventeenth century. First, there was the religiously based belief in the decay of nature; supporters of this belief regarded traditional methods to be superior. The defenders of the moderns, on the other hand, did not consider the Bible to rule out contemporary improvements on ancient techniques. But the very idea that knowledge could be advanced, particularly beyond the classical works, was still new and strange in this period.1 Second, the dispute surrounding educational reform included the rejection of traditional educational methods. Social and economic pressures led reformers to propose an increased concern with utility and practical methods, which might increase employment. Once the context of the tension between the supporters of the ancients and the supporters of the moderns has been explored, we can ascertain whether Wallis and Barrow stood on different sides in the conflict, and how this may have have influenced their mathematics.
The Royal Society and post-Galilean Science in Italy
Authors: López Susana Gómez
Published: July 2004

When the Royal Society was established in London in 1660, one of the objectives of its founders was to set up a scientific communications network. During its first years of existence the Society tried to initiate a complex system of diffusion of information and ideas. Oldenburg's prolific international correspondence, the publication of
Philosophical Transactions
and repeated petitions for scientific correspondence from all over Europe are just a few examples of the latitudinarian spirit of the Royal Society's founders. However, this attempt to open intellectual frontiers was destined to be continuously hampered by the various political, religious and cultural situations that characterized European history at the time.
Thomas Henshaw and Sir Robert Paston's pursuit of the red elixir: An early collaboration between fellows of The Royal Society
Authors: Dickson Donald R.
Published: July 2004

The problems involved in using Baconian categories to understand the great instauration Bacon hoped to foster are now well known. Natural philosophers were, for Bacon, empiricists, who tested their observations of nature openly, and their foes were superstitious dogmatists, who speculated by conjuring hypotheses in secret. As Joseph Agassi has wryly remarked, ‘once a person, historian or not, accepts a division of mankind into open-minded and closed-minded, he almost invariably finds himself on the right side’.1We now appreciate how broad even the Royal Society's conception of natural philosophy was, given the hermetic interests of many of its early members.2 By examining an early collaborative effort of Thomas Henshaw and Sir Robert Paston, who were both respected Fellows of the Royal Society as well as ‘chemical alchemists’ or ‘chemical philosophers’ following a rigorous, quantitative programme of experimentation, this essay will confirm that the actual practice of natural philosophy was broad indeed, and hardly revolutionary.3 Our view of these shadowy figures is usually obscured by the backdrop against which they are set, a backdrop that was created as the category of ‘natural magic’ disappeared, with part becoming science and the rest being discarded as superstition. The evidence to be examined includes an alchemical treatise in the British Library (Sloane 2222) and Henshaw's correspondence discussing it. Although the status of alchemy certainly changed during the course of the seventeenth century, it did so because more rigorous experimentation proved the alchemist's claims to be unverifiable, not because any underlying theories had been altered. The letters, especially, illustrate this process and also shed light on the differences between the closed world of alchemy and the more open culture of science then emerging.
Darwin's illness and systemic lupus erythematosus
Authors: Young D.A.B.
Published: July 2004

For most of his adult life Charles Darwin, F.R.S. (1809-1882) suffered from a chronic indisposition, the nature of which has remained a mystery. Until Colp's exhaustive account of the illness, the principal symptoms cited were palpitation, dyspepsia, headache, weakness and exhaustion. Such symptoms suggested to many a psychosomatic disorder, although this has not gone uncriticized. The only physical diagnosis to have received attention was Chagas' disease, an infection to which Darwin might have been exposed to in Argentina. However, since Woodruff's effective intervention, that diagnosis finds little support; and today the psychogenic hypothesis holds the field. But how reliable is this presumption in the light of the much fuller medical information available in Colp's review, much of it derived from unpublished letters, which subsequently have been or are being published?10 The important impression gained from Colp's account is the severity of the repeated attacks Darwin endured for over 35 years. He knew he was truly ill, as did his family, friends and at least some of his doctors. The desperation of his efforts on many occasions to pursue his scientific work despite prostration makes nonsense of the suggestion, for example, that he induced vomiting attacks merely to avoid going to dinner parties.
Viral evolution and the emergence of SARS coronavirus
Authors: Holmes Edward C. , Rambaut Andrew
Published: July 2004

The recent appearance of severe acute respiratory syndrome coronavirus (SARS–CoV) highlights the continual threat to human health posed by emerging viruses. However, the central processes in the evolution of emerging viruses are unclear, particularly the selection pressures faced by viruses in new host species. We outline some of the key evolutionary genetic aspects of viral emergence. We emphasize that, although the high mutation rates of RNA viruses provide them with great adaptability and explain why they are the main cause of emerging diseases, their limited genome size means that they are also subject to major evolutionary constraints. Understanding the mechanistic basis of these constraints, particularly the roles played by epistasis and pleiotropy, is likely to be central in explaining why some RNA viruses are more able than others to cross species boundaries. Viral genetic factors have also been implicated in the emergence of SARS–CoV, with the suggestion that this virus is a recombinant between mammalian and avian coronaviruses. We show, however, that the phylogenetic patterns cited as evidence for recombination are more probably caused by a variation in substitution rate among lineages and that recombination is unlikely to explain the appearance of SARS in humans.
The experience of the 2003 SARS outbreak as a traumatic stress among frontline healthcare workers in Toronto: lessons learned
Authors: Maunder Robert
Published: July 2004

The outbreak of severe acute respiratory syndrome (SARS) in the first half of 2003 in Canada was unprecedented in several respects. Understanding the psychological impact of the outbreak on healthcare workers, especially those in hospitals, is important in planning for future outbreaks of emerging infectious diseases. This review draws upon qualitative and quantitative studies of the SARS outbreak in Toronto to outline the factors that contributed to healthcare workers' experiencing the outbreak as a psychological trauma. Overall, it is estimated that a high degree of distress was experienced by 29–35% of hospital workers. Three categories of contributory factors were identified. Relevant contextual factors were being a nurse, having contact with SARS patients and having children. Contributing attitudinal factors and processes were experiencing job stress, perceiving stigmatization, coping by avoiding crowds and colleagues, and feeling scrutinized. Pre–existing trait factors also contributed to vulnerability. Lessons learned from the outbreak include: (i) that effort is required to mitigate the psychological impact of infection control procedures, especially the interpersonal isolation that these procedures promote; (ii) that effective risk communication is a priority early in an outbreak; (iii) that healthcare workers may have a role in influencing patterns of media coverage that increase or decrease morale; (iv) that healthcare workers benefit from resources that facilitate reflection on the effects of extraordinary stressors; and (v) that healthcare workers benefit from practical interventions that demonstrate tangible support from institutions.
Preparedness for SARS in the UK in 2003
Authors: Harper David R.
Published: July 2004

Severe acute respiratory syndrome (SARS) has been described as the first major emerging infectious disease of the twenty–first century. Having initially emerged, almost unnoticed, in southern China, it rapidly spread across the globe. It severely tested national public health and health systems. However, it also resulted in rapid, intensive international collaboration, led by the World Health Organization, to elucidate its characteristics and cause and to contain its spread. The UK mounted a vigorous public health response. Some particular issues concerned: the practicalities of implementing exit screening had this been required; the likely efficacy of this and other control measures; the legal base for public health action; and the surge capacity in all systems should the disease have taken hold in the UK. We have used this experience of 2003 to inform our preparation of a framework for an integrated, escalating response to a future re–emergence of SARS according to the levels of disease activity worldwide. Recent cases confirm that SARS has not ‘gone away’. We cannot be complacent about our contingency planning.
Informed consent and public health
Authors: O'Neill Onora
Published: July 2004

During the past 25 years, medical ethics has concentrated largely on clinical medicine and the treatment of individual patients. This focus permits a view of medical provision as a (quasi–) consumer good, whose distribution can be or should be contingent on individual choice. The approach cannot be extended to public health provision. Public health provision, including measures for limiting the spread of infectious diseases, is a public good and can be provided for some only if provided for many. The provision or non–provision of public goods cannot be contingent on individual informed consent, so must be in some respects compulsory. An adequate ethics of public health needs to set aside debates about informed consent and to consider the permissible limits of just compulsion for various types of public good. It will therefore gain more from engaging with work in political philosophy than with individualistic work in ethics.
Introduction
Authors: McLean A. R. , May R. M. , Pattison J. , Weiss R. A.
Published: July 2004

In the summer of 2003, as the first global severe acute respiratory syndrome (SARS) epidemic stuttered to a close, The Royal Society set about organizing a meeting that would take stock of the year's events and ask ‘what can we learn from SARS about emerging infections in general?’ Emerging infections are more than just a current biological fashion. The bitter ongoing experience of AIDS and the looming threat of an influenza pandemic teach us that the control of infectious disease is a problem we have not yet solved. It is a problem that needs to be addressed by a broad community. Scientists, policy makers and health care workers all need to be prepared, but prepared to do what? The purpose of the meeting was to use SARS as an example to enumerate the generic issues that must be considered when planning for the control of emerging infections.
Laboratory diagnosis of SARS
Authors: Bermingham A. , Heinen P. , Iturriza-Gómara M. , Gray J. , Appleton H. , Zambon M. C.
Published: July 2004

The emergence of new viral infections of man requires the development of robust diagnostic tests that can be applied in the differential diagnosis of acute illness, or to determine past exposure, so as to establish the true burden of disease. Since the recognition in April 2003 of the severe acute respiratory syndrome coronavirus (SARS–CoV) as the causative agent of severe acute respiratory syndrome (SARS), enormous efforts have been applied to develop molecular and serological tests for SARS which can assist rapid detection of cases, accurate diagnosis of illness and the application of control measures. International progress in the laboratory diagnosis of SARS–CoV infection during acute illness has led to internationally agreed World Health Organization criteria for the confirmation of SARS. Developments in the dissection of the human immune response to SARS indicate that serological tests on convalescent sera are essential to confirm SARS infection, given the sub–optimal predictive value of molecular detection tests performed during acute SARS illness.
Plant preference in relation to life history traits in the zoophytophagous predator Dicyphus hesperus
Authors: Sanchez Juan Antonio , Gillespie David R. , McGregor Robert R.
Published: July 2004

Dicyphus hesperus Knight (Heteroptera: Miridae) is an omnivorous predator used to control pests of greenhouse vegetables. Plant preferences and life history traits were studied using nine plant species: Lycopersicon esculentum Mill. (Solanaceae), Capsicum annuum L. (Solanaceae), Verbascum thapsus L. (Scrophulariaceae), Nepeta cataria L. (Lamiaceae), Stachys albotomentosa (Lamiaceae), Nicotiana tabacum L. (Solanaceae), Vicia sativa L. (Fabaceae), Zea mays L. (Gramineae), and Chrysanthemum coronarium L. (Asteraceae). Plants were selected from among potential target crops, natural hosts, plants used for mass rearing, and plants on which D. hesperus has not been reported. Plant preference was measured by multi‐choice host plant selection and oviposition assays. Development and reproduction were measured on each of the plant species on both a plant diet alone and on a plant diet supplemented with Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs. Dicyphus hesperus females and nymphs expressed a preference for some plants over others. Plant preference ranged from low preference plants, such as Z. mays, V. sativa, C. coronarium, and C. annuum, to high preference plants such as V. thapsus, N. tabacum, and S. albotomentosa. When E. kuehniella eggs were supplied, there were few differences in the development time and fecundity of D. hesperus among plants, with the exception of corn and broad bean, where fecundity was lower. On a plant diet alone, nymphs were able to complete their development on V. thapsus, C. annuum, and N. cataria. However, mortality and development time were much lower on V. thapsus than on C. annuum and N. cataria. On most of the plant species D. hesperus did not lay any eggs when fed on a plant diet alone. On V. thapsus, females laid a few eggs and lived longer than when fed on prey. Dicyphus hesperus females tended to prefer host plants on which nymph survival without prey was greatest.
Significance of shelter traps for spring monitoring of Anthonomus pomorum in apple orchards
Authors: Hausmann Claudia , Samietz Jörg , Dorn Silvia
Published: July 2004

The significance of the apple blossom weevil, Anthonomus pomorum L. (Coleoptera: Curculionidae), as a potential threat to apple, Malus domestica Borkh., has increased over the past two decades in many regions of Europe. The apple blossom weevil immigrates into orchards and colonises apple trees in early spring. Females deposit single eggs into closed blossom buds, which leads to capped blossoms. This study was designed to test the suitability of transparent shelter traps for the surveillance of colonisation under different population pressures, and to assess the quantitative relationship between number of weevils caught and: (1) absolute injury, expressed as number of infested buds, as well as (2) relative injury, expressed as a percentage of infested buds relative to all buds on the tree. The findings with the new shelter traps were contrasted to results from limb jarring. Numbers of weevils caught with the transparent shelter trap were positively correlated with absolute injury, as well as with relative injury across the five study sites, whereas weevil counts with limb jarring were not correlated with absolute injury, but only with relative injury. Our data validate the transparent shelter trap as a method for accurately monitoring the course of spring colonisation of A. pomorum and demonstrate its potential for predicting injury by the weevils to blossom buds. In contrast, the significance of limb jarring for monitoring both the time course of colonisation and subsequent injury is limited. The significant linear relationship between the number of weevils caught in shelter traps and the relative injury allows for predictions of potential damage before oviposition takes place, i.e., early enough for an insecticide application where necessary.
Effects of post‐application irrigation and substrate moisture on the efficacy of entomopathogenic nematodes against western flower thrips, Frankliniella occidentalis
Authors: Ebssa Lemma , Borgemeister Christian , Poehling Hans‐Michael
Published: July 2004

The efficacy of entomomatogenic nematodes (Steinernema bicornutum Tallosi, Peters and Ehlers and/or Heterorhabditis indica LN2 Poinar, Karunakar and David) against the soil‐dwelling life stages of western flower thrips Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) was assessed under different moisture conditions in a commercial plant‐growing substrate in laboratory experiments. In the first experiment, both nematode species were tested at substrate moisture ranges of 67, 78, 88, or 95% relative moisture content, that were maintained before applying the nematodes at 100 or 400 infective juveniles (IJs) cm−2. In the second experiment, 10, 25, 50, 100, or 120 ml irrigation water, resulting in relative moisture contents of 72, 81, 90, 99%, or more than the saturation level of the substrate, respectively, was applied to the substrate. Heterorhabditis indica LN2 was applied either in 3 ml water and followed by irrigation, or by suspending the infective juveniles in the water amounts indicated above to apply the nematodes in higher volume. Results indicated that at the higher application rate, initial moisture content did not significantly affect the efficacy of H. indica LN2. On the other hand, increasing moisture content resulted in an improved efficacy of H. indica LN2 and S. bicornutum at lower and higher application rates, respectively. Similar thrips control levels of 44 and 60% at the lower and higher application rate of H. indica LN2, respectively, were obtained at 88% relative moisture content. In the second experiment, higher and statistically similar thrips mortality of 40 and 50% at lower and higher application rates of H. indica LN2, respectively, were obtained when the infective juveniles were applied in a high volume suspension of 100 ml, or when followed by irrigation with 25 ml water, resulting in both cases in 81% relative moisture content. Generally, efficacies of the nematodes for thrips control can be improved by using an appropriate moisture content and/or post‐application irrigation. Thus, the high nematode application rates required for successful F. occidentalis control can be partly attributed to substrate moisture content and/or post‐application irrigation.
Predicting Corporate Failure in the UK: A Multidimensional Scaling Approach
Authors: Neophytou Evi , Molinero Cecilio Mar
Published: July 2004

Scaling techniques are proposed as a tool for the analysis and prediction of corporate failure. This approach, while keeping a strong theoretical basis, has the advantage of visualising the main features of the data in the form of statistical maps that lend themselves to intuitive interpretation. The maps contain directional statistics to help with interpretation. The methodology is demonstrated using a sample of UK industrial companies. A future‐dated holdout sample is also employed to illustrate how the Multidimensional Scaling technique can aid practitioners when assessing the financial health of a company.
Determinants of the Capital Structures of European SMEs
Authors: Hall Graham C. , Hutchinson Patrick J. , Michaelas Nicos
Published: July 2004

The aim of this paper is to examine the degree to which the determinants of SMEs’ capital structures differ between European countries. The study is based on data for four thousand SMEs, five hundred from each of eight European countries. Regressions were run using short‐term and long‐term debt as dependent variables and profitability, growth, asset structure, size and age as independent variables. A key feature of this paper is the use of restricted and unrestricted regressions to isolate the country‐effect from the firm‐specific‐effect. The results show that variations are likely to be due to country differences as well as firm‐specific ones.
A Note on the Intraday Patterns of Initial Public Offerings: Evidence from Hong Kong
Authors: Cheng Wai‐yan , Cheung Yan‐Leung , Po Ka‐kit
Published: July 2004

This paper examines the intraday patterns of IPOs in Hong Kong during the period 1995–1998. The results reveal that the well‐known under‐pricing phenomenon of IPOs occurs only at the opening trading of new issues and vanishes afterwards. The return volatility of IPOs is found to be high during the first trading session, and declines rapidly during the rest of the first trading day until the end of the trading day. The intraday return volatility of IPOs is found to follow a double U‐shape pattern, which is similar to that of the general market. A great deal of trading activity was recorded during the first five minutes of the trading day. Consistent results are obtained for IPOs registered during the pre‐crisis and post‐crisis periods. This paper has practical implications for investors. Investors can benefit from the under‐pricing only if they subscribe for new shares in the primary market. There is, however, no profit‐making opportunity for day traders who buy shares on the first trading day. This shows that the Hong Kong market is efficient in adjusting for the IPO under‐pricing. In addition, it is likely that, because of Hong Kong's share allotment method, only big investors who apply for large numbers of shares can benefit from this under‐pricing phenomenon.