bluuebunny/crossref_metadata_2025 huggingface dataset:
High intensity fluorescence of photoactivated silver oxide from composite thin film with periodic array structure
Authors: Chuang Chih-Min , Wu Ming-Chung , Su Wei-Fang , Cheng Kuo-Chung , Chen Yang-Fang
Published: August 2006

We have fabricated a composite thin film that exhibits intense photoactivated fluorescence of silver oxide at 522 and 529nm under the irradiation of a 488nm laser. This film consists of a silver coated polymeric periodic array on indium tin oxide glass substrate. By adjusting the column diameters and lattice constants of the array to coincide with the excitation wavelength, an order increase in fluorescence intensity was obtained due to the surface plasmon polariton resonance of silver. This composite film has many potential applications in highly efficient optoelectronic devices.
Optimization problems for an elastic plate
Authors: Cuccu F. , Emamizadeh B. , Porru G.
Published: August 2006

This paper concerns optimization problems related to bi-harmonic equations subject to either Navier or Dirichlet homogeneous boundary conditions. Physically, in dimension two, our equation models the deformation of an elastic plate which is either hinged or clamped along the boundary, under load. We discuss existence, uniqueness, and properties of the optimizers.
Hybrid exchange-correlation functional for core, valence, and Rydberg excitations: Core-valence-Rydberg B3LYP
Authors: Nakata Ayako , Imamura Yutaka , Nakai Hiromi
Published: August 2006

The core-valence-Rydberg Becke’s three-parameter exchange (B3)+Lee-Yang-Parr (LYP) correlation functional (CVR-B3LYP) is proposed as a means to improve descriptions of Rydberg excitations of core-valence B3LYP (CV-B3LYP). CV-B3LYP describes excitations from both core and occupied valence orbitals to unoccupied valence orbitals with high accuracy but fails to describe those to Rydberg orbitals. CVR-B3LYP, which adopts the appropriate portions of Hartree-Fock exchange for unoccupied valence and Rydberg regions separately, overcomes the disadvantage of CV-B3LYP. Numerical assessment confirms that time-dependent density functional theory calculations with CVR-B3LYP succeed in describing not only core excitations but also Rydberg excitations with reasonable accuracy.
Experimental evidence of dynamic trapping in the scattering of H2 from Pd(110)
Authors: Barredo D. , Laurent G. , Díaz C. , Nieto P. , Busnengo H. F. , Salin A. , Farías D. , Martín F.
Published: August 2006

We have performed H2(D2) diffraction experiments on a Pd(110) surface using two different high-sensitivity set-ups. We have found that, although the total reflectivity of Pd(110) is comparable to that observed in other reactive systems, the corresponding H2(D2) diffraction patterns are quite different: no diffraction peak, including the specular one, is observed on Pd(110). This unexpected result is the consequence of dynamic trapping. Such interpretation is supported by classical dynamics calculations based on accurate ab initio potential energy surfaces.
Generalization of Wilemski-Fixman-Weiss decoupling approximation to the case involving multiple sinks of different sizes, shapes, and reactivities
Authors: Uhm Jesik , Lee Jinuk , Eun Changsun , Lee Sangyoub
Published: August 2006

We generalize the Wilemski-Fixman-Weiss decoupling approximation to calculate the transient rate of absorption of point particles into multiple sinks of different sizes, shapes, and reactivities. As an application we consider the case involving two spherical sinks. We obtain a Laplace-transform expression for the transient rate that is in excellent agreement with computer simulations. The long-time steady-state rate has a relatively simple expression, which clearly shows the dependence on the diffusion constant of the particles and on the sizes and reactivities of sinks, and its numerical result is in good agreement with the known exact result that is given in terms of recursion relations.
Accurate computational determination of the binding energy of the SO3∙H2O complex
Authors: Fliegl Heike , Glöß Andreas , Welz Oliver , Olzmann Matthias , Klopper Wim
Published: August 2006

Reliable thermochemical data for the reaction SO3+H2O⇔SO3∙H2O (1a) are of crucial importance for an adequate modeling of the homogeneous H2SO4 formation in the atmosphere. We report on high-level quantum chemical calculations to predict the binding energy of the SO3∙H2O complex. The electronic binding energy is accurately computed to De=40.9±1.0kJ∕mol=9.8±0.2kcal∕mol. By using harmonic frequencies from density functional theory calculations (B3LYP/cc-pVTZ and TPSS/def2-TZVP), zero-point and thermal energies were calculated. From these data, we estimate D0=−ΔH1a0(0K)=7.7±0.5kcal∕mol and ΔH1a0(298K)=−8.3±1.0kcal∕mol.
Spatially extended nature of resistive switching in perovskite oxide thin films
Authors: Chen Xin , Wu NaiJuan , Strozier John , Ignatiev Alex
Published: August 2006

The authors report the direct observation of the electric pulse induced resistance-change effect at the nanoscale on La1−xSrxMnO3 thin films by the current measurement of the atomic force microscopy (AFM) technique. After a switching voltage of one polarity is applied across the sample by the AFM tip, the conductivity in a local nanometer region around the AFM tip is increased, and after a switching voltage of the opposite polarity is applied, the local conductivity is reduced. This reversible resistance switching effect is observed under both continuous and short-pulse-voltage switching conditions. It is important for future nanoscale nonvolatile memory device applications.
Indication of intrinsic room-temperature ferromagnetism in Ti1−xCoxO2−δ thin film: An x-ray magnetic circular dichroism study
Authors: Mamiya K. , Koide T. , Fujimori A. , Tokano H. , Manaka H. , Tanaka A. , Toyosaki H. , Fukumura T. , Kawasaki M.
Published: August 2006

Soft x-ray magnetic circular dichroism (XMCD) measurements at the Co L2,3 edges of Co-doped rutile TiO2 at room temperature revealed clear multiplet features characteristic of ferromagnetic Co2+ ions coordinated by O2− ions, being in sharp contrast to the featureless XMCD spectrum of Co metal or metallic clusters. The absorption and XMCD spectra agree well with a full atomic-multiplet calculation for the Co2+ high-spin state in the D2h-symmetry crystal field at the Ti site in rutile TiO2. The results indicate that the ferromagnetism arises from the Co2+ ions substituting the Ti4+ ions.
Computer simulations of block copolymer tethered nanoparticle self-assembly
Authors: Chan Elaine R. , Ho Lin C. , Glotzer Sharon C.
Published: August 2006

We perform molecular simulations to study the self-assembly of block copolymer tethered cubic nanoparticles. Minimal models of the tethered nanoscale building blocks (NBBs) are utilized to explore the structures arising from self-assembly. We demonstrate that attaching a rigid nanocube to a diblock copolymer affects the typical equilibrium morphologies exhibited by the pure copolymer. Lamellar and cylindrical phases are observed in both systems but not at the corresponding relative copolymer tether block fractions. The effect of nanoparticle geometry on phase behavior is investigated by comparing the self-assembled structures formed by the tethered NBBs with those of their linear ABC triblock copolymer counterparts. The tethered nanocubes exhibit the conventional triblock copolymer lamellar and cylindrical phases when the repulsive interactions between different blocks are symmetric. The rigid and bulky nature of the cube induces interfacial curvature in the tethered NBB phases compared to their linear ABC triblock copolymer counterparts. We compare our results with those structures obtained from ABC diblock copolymer tethered nanospheres to further elucidate the role of cubic nanoparticle geometry on self-assembly.
Broadband two-dimensional photonic crystal wave plate
Authors: Dai Q. F. , Li Y. W. , Wang H. Z.
Published: August 2006

It is demonstrated in this work that the phase shift of reflected wave as a function of frequency changes smoothly within the stop band of two-dimensional photonic crystal, while it changes sharply within the passband. In the stop band, the difference between the phase shift of TE and that of TM reflected wave could remain constant in a rather wide frequency region. By using the difference of phase shift, the authors obtain a kind of half-wave plate that can be used in broad spectral bandwidth. Such photonic crystal wave plates have predominance in optical and optoelectronic integration.
Depleted uranium (U23892) induced preionization for enhanced and reproducible x-ray emission from plasma focus
Authors: Ahmad S. , Shafiq M. , Zakaullah M. , Waheed A.
Published: August 2006

The effect of preionization induced by depleted uranium (U23892) around the insulator sleeve on the x-ray emission of (2.3–3.9kJ) plasma focus device is investigated by employing Quantrad Si p-i-n diodes and a multipinhole camera. X-ray emission in 4π geometry is measured as a function of charging voltage with and without preionization. It is found that the preionization enhances CuKα and total x-ray yield about 100%, broadens the x-ray emission pressure range and x-ray pulse width, and improves shot to shot reproducibility of plasma focus operation. The pinhole images of x-ray emitting zones indicate that dominant x-ray emission is from the anode tip.
Structure and stability of Al13Hn (n=1–13) clusters: Exceptional stability of Al13H13
Authors: Jung Jaehoon , Han Young-Kyu
Published: August 2006

We have performed density functional calculations for the structure and stability of Al13Hn (n=1–13) clusters. Population analysis has shown significant charge transfer occurring from the Al cluster to the H atoms. The population for Al13 varies from 0.24 (Al13H) to 2.83 (Al13H13). The shape of Al13 moieties in the Al13Hn (n⩾8) clusters is significantly distorted from the icosahedral structure of Al13 and is a “cagelike” form. Al13H13 has a capped icosahedron as the ground-state structure, similar to B13H13, while the shape of B13 (planar) is different from Al13 (icosahedral). The Al13H13 cluster is predicted to be exceptionally stable on the basis of the high stabilization energy and the negative nucleus independent chemical shift value.
Interaction potentials for Br−–Rg (Rg=He–Rn): Spectroscopy and transport coefficients
Authors: Buchachenko Alexei A. , Kłos Jacek , Szczȩśniak Małgorzata M. , Chałasiński Grzegorz , Gray Benjamin R. , Wright Timothy G. , Wood Erin L. , Viehland Larry A. , Qing Enming
Published: August 2006

High-level ab initio CCSD(T) calculations are performed in order to obtain accurate interaction potentials for the Br− anion interacting with each rare gas (Rg) atom. For the Rg atoms from He to Ar, two approaches are taken. The first one implements a relativistic core potential and an aug-cc-pVQZ basis set for bromine, an aug-cc-pV5Z basis set for Rg, and a set of bond functions placed at the midpoint of the Rg–Br distance. The second one uses the all-electron approximation with aug-cc-pV5Z bases further augmented by an extra diffuse function in each shell. Comparison reveals close similarity between both sets of results, so for Rg atoms from Kr to Rn only the second approach is exploited. Calculated potentials are assessed against the previous empirical, semiempirical, and ab initio potentials, and against available beam scattering data, zero electron kinetic energy spectroscopic data, and various sets of the measured ion mobilities and diffusion coefficients. This multiproperty analysis leads to the conclusion that the present potentials are consistently good for the whole series of Br−–Rg pairs over the whole range of internuclear distances covered.
Narrow gap HgCdTe absorption behavior near the band edge including nonparabolicity and the Urbach tail
Authors: Chang Yong , Grein Christoph H. , Sivananthan Sivalingam , Flatte M. E. , Nathan V. , Guha S.
Published: August 2006

An analytical model describing the absorption behavior of HgCdTe is developed that simultaneously considers the contributions from nonparabolic conduction and light hole bands as calculated by a 14×14 matrix k∙p method as well as the Urbach tail. This model is capable of smoothly fitting experimental absorption coefficient curves over energies ranging from the Urbach tail region to the intrinsic absorption region up to 300meV above the band gap. Comparisons to the experimental results give good agreement.
Effect of three-body interactions on the vapor-liquid phase equilibria of binary fluid mixtures
Authors: Wang Liping , Sadus Richard J.
Published: August 2006

Gibbs-Duhem Monte Carlo simulations are reported for the vapor-liquid phase coexistence of binary argon+krypton mixtures at different temperatures. The calculations employ accurate two-body potentials in addition to contributions from three-body dispersion interactions resulting from third-order triple-dipole interactions. A comparison is made with experiment that illustrates the role of three-body interactions on the phase envelope. In all cases the simulations represent genuine predictions with input parameters obtained independently from sources other than phase equilibria data. Two-body interactions alone are insufficient to adequately describe vapor-liquid coexistence. In contrast, the addition of three-body interactions results in very good agreement with experiment. In addition to the exact calculation of three-body interactions, calculations are reported with an approximate formula for three-body interactions, which also yields good results.
Quadratic mixing of radio frequency signals using superconducting quantum interference filters
Authors: Caputo P. , Tomes J. , Oppenländer J. , Häussler Ch. , Friesch A. , Träuble T. , Schopohl N.
Published: August 2006

The authors demonstrate quadratic mixing of weak time harmonic electromagnetic fields applied to superconducting quantum interference filters (SQIFs), manufactured from high-Tc grain boundary Josephson junctions and operated in active microcooler. The authors use the parabolic shape of the dip in the dc voltage output around B=0 to mix quadratically two external rf signals, at frequencies f1 and f2 well below the Josephson frequency fJ, and detect the corresponding mixing signal at ∣f1−f2∣. Quadratic mixing also takes place when the SQIF is operated without magnetic shield. The experimental results are well described by a simple analytical model based on the adiabatic approximation.
Intense blue emission from tantalum-doped silicate glass
Authors: Meng Xiangeng , Murai Shunsuke , Fujita Koji , Tanaka Katsuhisa
Published: August 2006

The authors report on an intense blue emission centered at 420nm under ultraviolet excitation from pentavalent tantalum ion-doped silicate glasses. The blue emission is distinctly different from emission due to defects in silica glass, which is also reflected in both absorption spectrum and remarkably enhanced emission. The authors suggest that localized Ta 5d0 energy level is responsible for the blue emission.
An ab initio study on the ground and low-lying doublet electronic states of SbO2
Authors: Lee Edmond P. F. , Dyke John M. , Chau Foo-Tim , Chow Wan-Ki , Mok Daniel K. W.
Published: August 2006

Geometry optimization and harmonic vibrational frequency calculations have been carried out on the low-lying doublet electronic states of antimony dioxide (SbO2) employing a variety of ab initio methods, including the complete active space self-consistent field/multireference configuration interaction and the RCCSD(T) methods. Both large and small core relativistic effective core potentials were used for Sb in these calculations, together with valence basis sets of up to aug-cc-pV5Z quality. Contributions from outer core correlation and off-diagonal spin-orbit interaction to relative electronic energies have been calculated. The ground electronic state of SbO2 is determined to be the X̃A12 state, as is the case for dioxides of other lighter group 15 p-block (or group VA) elements. However, the ÃB22 and B̃A22 states are estimated to be only 4.1 and 10.7kcal∕mole above the X̃A12 state, respectively, at the complete basis set limit. Reliable vertical excitation energies from the X̃A12 state to low-lying excited states of SbO2 have been computed with a view to assist future spectral assignments of the absorption and/or laser-induced fluorescence spectra of SbO2, when they become available.
Time- and space-resolved fluorescence study on interfacial mobility of polymers
Authors: Tanaka Keiji , Tsuchimura Yu , Akabori Kei-ichi , Ito Fuyuki , Nagamura Toshihiko
Published: August 2006

Segmental mobility of a typical amorphous polymer, polystyrene, at the interface with a solid substrate was examined noninvasively by fluorescence lifetime measurement using evanescent wave excitation. Glass transition temperature (Tg) was discernibly higher at the interface than in the bulk. Measurements at different incident angles of excitation pulses revealed that Tg became higher the closer to the interface. This is the observation for a Tg gradient of polymers at the interface.
Defect-free 100-layer strain-balanced InAs quantum dot structure grown on InP substrate
Authors: Zhang Z. H. , Cheng K. Y. , Xu C. F. , Hsieh K. C.
Published: August 2006

A high quality 100-layer InAs quantum dot (QD) structure was successfully grown on InP substrate. The overall compressive strain caused by InAs QDs on InAlGaAs∕InP is effectively balanced by inserting tensile-strained InGaAs strain-balance layers immediately above QD layers. The cross-sectional transmission electron microscopy images show a low defect density of less than 106cm−2 and a smooth interface between QD layers throughout the whole structure. In addition, the intense room temperature photoluminescence indicates a good optical quality of the multilayer QD structure.
Phase-sensitive Brillouin light scattering spectroscopy from spin-wave packets
Authors: Serga A. A. , Schneider T. , Hillebrands B. , Demokritov S. O. , Kostylev M. P.
Published: August 2006

The authors report on the implementation of phase sensitivity into Brillouin light scattering spectroscopy from propagating spin-wave packets. In order to access phase information, interference between the light inelastically scattered by the spin-wave and a frequency shifted coherent reference beam is used. This approach allows for access to quantities such as the space- and time-resolved phase profile and the wave front of spin-wave packets and beams. The authors apply the developed method to investigations of the phase profiles of linear and nonlinear (soliton) spin-wave pulses. In particular, the constant phase profile characteristics for an envelope spin-wave soliton are demonstrated.
Indium oxide “rods in dots” nanostructures
Authors: Ding G. Q. , Shen W. Z. , Zheng M. J. , Zhou Z. B.
Published: August 2006

The authors have demonstrated a special indium oxide (In2O3) “rods in dots” nanostructure with high nanorod sheet density of over 1012cm−2. The approach has been realized through depositing controllable individual In2O3 nanorods in both number and shape within a single porous alumina membrane (PAM) nanochannel under radio frequency magnetron sputtering. The authors further discussed in detail effects of the PAM configurations (pore diameter and thickness) and sputtering conditions (substrate temperature and argon pressure) on the formation of the In2O3 nanostructure.
Noise in carbon nanotube field effect transistor
Authors: Liu Fei , Wang Kang L. , Zhang Daihua , Zhou Chongwu
Published: August 2006

Low frequency noise power spectrum density of carbon nanotubes is presented. It is shown that the input-referred noise of carbon nanotubes increases quadratically as gate voltage is overdriven, suggesting that mobility fluctuation is the dominant mechanism contributing to the noise in carbon nanotube field effect transistors. The comparison of source-drain current noise power spectrum densities of carbon nanotubes in air and in vacuum indicates that a part of device noise is due to charge fluctuations from attached air molecules.
Characteristics of a Si dual-band detector responding in both near- and very-long-wavelength-infrared regions
Authors: Ariyawansa G. , Rinzan M. B. M. , Matsik S. G. , Hastings G. , Perera A. G. U. , Liu H. C. , Buchanan M. , Sproule G. I. , Gavrilenko V. I. , Kuznetsov V. P.
Published: August 2006

A p-type Si homojunction detector responding in both near- and very-long-wavelength-infrared (NIR and VLWIR) ranges is demonstrated. The detector consists of a p++-Si top contact layer, a p+-Si emitter, an undoped Si barrier, and a p++-Si bottom contact layer grown on a Si substrate. Interband and intraband transitions lead to NIR and VLWIR responses, respectively. The responsivity, quantum efficiency, and detectivity at −1V bias and 4.6K are ∼0.024A∕W, 3.7%, and ∼1.7×109cmHz1∕2∕W at 0.8μm, while they are 1.8A∕W, 8.8%, and ∼1.2×1011cmHz1∕2∕W at 25μm, respectively. The background limited infrared performance temperature at ±0.9V bias is 25K.
Catalyst-free growth of In(As)P nanowires on silicon
Authors: Mattila M. , Hakkarainen T. , Lipsanen H. , Jiang H. , Kauppinen E. I.
Published: August 2006

The catalyst-free metal organic vapor phase epitaxial growth of In(As)P nanowires on silicon substrates is investigated using in situ deposited In droplets as seeds for nanowire growth. The thin substrate native oxide is found to play a crucial role in the nanowire formation. The structure of the nanowires is characterized by photoluminescence and electron microscopy measurements. The crystal structure of the InP nanowires is wurtzite with its c axis perpendicular to the nanowire axis. Adding arsenic precursor to the gas phase during growth results in a bimodal photoluminescence spectrum exhibiting peak at the InAsP and InP band gap energies.
Effects of tensile stress induced by SiO2 passivation layer on the properties of AlGaN∕GaN heterostructure photodiode
Authors: You Da , Tang Yingwen , Xu Jintong , Li Xue , Li Xiangyang , Gong Haimei
Published: August 2006

The effects of tensile stress induced by SiO2 passivation layer on AlxGa1−xN∕GaN heterostructure photodiode are investigated. The photodiode, with SiO2 layer annealed at 650°C for 30min in O2, shows that reverse current has decreased to 6.16nA∕cm−2 under −10V, two orders lower than that of the device without annealing technique. The responsivity also increases to 0.212A∕W at zero bias. The high-resolution x-ray diffraction, Hall measurements are taken to investigate the surface strain and electrical properties of p-AlGaN surface. These observations indicate that tensile stress induced by SiO2 annealing technique can improve performances of this photodiode greatly.
Surface-emitting distributed-feedback dye laser of a polymeric multilayer fabricated by spin coating
Authors: Komikado Toshiyuki , Yoshida Shuhei , Umegaki Shinsuke
Published: August 2006

A distributed-feedback laser was demonstrated by using a fluorescent dye-doped polymer. The periodic structure of a one-dimensional photonic crystal was fabricated through spin coating and alternate stacking of high and low refractive-index polymers. The rhodamine-6G-doped multilayer showed a photonic band gap in the transmissivity spectrum at the fluorescent wavelength range. Laser emission from the surface of the multilayer was attained at the band edge for a pump of the second harmonic of a neodymium-doped yttrium aluminum garnet laser. Wavelength tuning was possible by spin coating a multilayer onto a concave substrate.
Characteristics of millimeter wave microstrip antennas with left-handed materials substrates
Authors: Yang Rui , Xie Yong-Jun , Wang Peng , Li Lei
Published: August 2006

Millimeter wave microstrip antennas with left-handed materials substrates are studied with method of moments. Discrete complex image method is extended to the computation of Green’s function in microstrip circuits with left-handed materials substrates. It is shown that this kind of antennas will achieve similar radiation patterns to the ones of conventional millimeter wave microstrip antennas in some cases, and can obtain radiation patterns characteristic of narrow main lobes with low elevation angles in other cases. Potential applications for directive antennas with these unusual radiation patterns of this kind of antennas are proposed.
Ferroelectric properties in KNbO3 thin films probed by optical second harmonic generation
Authors: Murzina T. V. , Savinov S. A. , Ezhov A. A. , Aktsipetrov O. A. , Korsakov I. E. , Bolshakov I. A. , Kaul A. R.
Published: August 2006

Ferroelectric phase transitions and the structure of KNbO3 nanometer-thick films deposited by Metal-organic chemical-vapor deposition technique on a MgO(100) substrate are studied. Thin KNbO3 films of the average thickness from 20to150nm possess a grainlike structure with a lateral grain size of about 250nm. Such films reveal ferroelectric properties similar to KNbO3 single crystal. Temperature dependencies of optical second harmonic generation intensity show that the Curie temperature TC of the nanometer-thick KNbO3 films is about 30°C lower than the TC of KNbO3 single crystal, which is attributed to size effects in KNbO3 nanograins.
A molecular phylogeny of the Australian monitor lizards (Squamata:Varanidae) inferred from mitochondrial DNA sequences
Authors: Fitch A. J. , Goodman A. E. , Donnellan S. C.
Published: August 2006

To date no complete phylogeny of all of the currently recognised Indo-Australian varanid species and subspecies has been published. This paper presents a comprehensive mitochondrial gene phylogeny of these lizards. A portion of the mitochondrial genome comprising part of the ND4 gene and three adjacent tRNA genes (hereafter referred to as ND4) was analysed alone and, for a subset of the taxa, combined with previously published mitochondrial data. Similar tree topologies were produced by both datasets although combining the data helped resolve some of the unresolved or weakly supported nodes in the ND4 analyses. The monophyly of the Indo-Australian group was strongly supported in all analyses. This group comprised three major lineages: the gouldii group, the Odatria group and the varius group. Mitochondrial ND4 nucleotide sequences were successfully amplified from all of the Indo-Australian monitor species and subspecies currently recognised and, as such, is the first comprehensive phylogenetic study of the Australian monitor lizards published. Analysis of the tempo of diversification and evolution of preferred habitat use identified six episodes of increased net speciation rate, with two closely adjacent episodes showing the highest rates of diversification and correlating with the appearance of all preferred habitat types. The comprehensive molecular phylogenetic framework will also be useful for the identification of varanid species and traded products derived from monitors and, as such, has important applications for wildlife management and conservation.
Digestive plasticity of the small intestine and the fermentative hindgut in a marsupial herbivore, the tammar wallaby (Macropus eugenii)
Authors: Munn Adam J. , Banks Peter , Hume Ian D.
Published: August 2006

We investigated the effects of a ground, pelleted diet versus natural forage on the gross morphology of the gastrointestinal tract of a medium-sized (5–7 kg body mass) macropodid marsupial, the tammar wallaby (Macropus eugenii). The empty wet mass (g) of the small intestine of tammar wallabies maintained on a pelleted diet for 6 weeks was 22% greater than that of animals maintained on natural forage, once body mass was taken into account by ANCOVA. Similarly, the body-mass-adjusted length of the tammar wallaby caecum and proximal colon combined was 25% longer in animals maintained on the pelleted diet compared with those maintained on forage. Our data suggest that food particle size may be directly involved in controlling the size of the post-gastric alimentary tract in tammar wallabies, and thus in their diet choice and nutritional ecology. Notably, this is the first study that links phenotypic plasticity of the gut directly to diet in a marsupial and we conclude that the tammar wallaby is an excellent model for exploring the causes and consequences of digestive plasticity in macropodid marsupials.
How to become a uropathogen: Comparative genomic analysis of extraintestinal pathogenic
Escherichia coli
strains
Authors: Brzuszkiewicz Elzbieta , Brüggemann Holger , Liesegang Heiko , Emmerth Melanie , Ölschläger Tobias , Nagy Gábor , Albermann Kaj , Wagner Christian , Buchrieser Carmen , Emődy Levente , Gottschalk Gerhard , Hacker Jörg , Dobrindt Ulrich
Published: August 2006

Uropathogenic
Escherichia coli
(UPEC) strain 536 (O6:K15:H31) is one of the model organisms of extraintestinal pathogenic
E. coli
(ExPEC). To analyze this strain's genetic basis of urovirulence, we sequenced the entire genome and compared the data with the genome sequence of UPEC strain CFT073 (O6:K2:H1) and to the available genomes of nonpathogenic
E. coli
strain MG1655 (K-12) and enterohemorrhagic
E. coli
. The genome of strain 536 is ≈292 kb smaller than that of strain CFT073. Genomic differences between both UPEC are mainly restricted to large pathogenicity islands, parts of which are unique to strain 536 or CFT073. Genome comparison underlines that repeated insertions and deletions in certain parts of the genome contribute to genome evolution. Furthermore, 427 and 432 genes are only present in strain 536 or in both UPEC, respectively. The majority of the latter genes is encoded within smaller horizontally acquired DNA regions scattered all over the genome. Several of these genes are involved in increasing the pathogens' fitness and adaptability. Analysis of virulence-associated traits expressed in the two UPEC O6 strains, together with genome comparison, demonstrate the marked genetic and phenotypic variability among UPEC. The ability to accumulate and express a variety of virulence-associated genes distinguishes ExPEC from many commensals and forms the basis for the individual virulence potential of ExPEC. Accordingly, instead of a common virulence mechanism, different ways exist among ExPEC to cause disease.
Topical interests and the mitigation of search engine bias
Authors: Fortunato S. , Flammini A. , Menczer F. , Vespignani A.
Published: August 2006

Search engines have become key media for our scientific, economic, and social activities by enabling people to access information on the web despite its size and complexity. On the down side, search engines bias the traffic of users according to their page ranking strategies, and it has been argued that they create a vicious cycle that amplifies the dominance of established and already popular sites. This bias could lead to a dangerous monopoly of information. We show that, contrary to intuition, empirical data do not support this conclusion; popular sites receive far less traffic than predicted. We discuss a model that accurately predicts traffic data patterns by taking into consideration the topical interests of users and their searching behavior in addition to the way search engines rank pages. The heterogeneity of user interests explains the observed mitigation of search engines’ popularity bias.
“Modern” Masculinities: Ethnicity, Education, and Gender in Macedonia
Authors: Dimova Rozita
Published: August 2006

In 2000, when conducting a household survey as part of my research on consumption and ethnicity in the small western Macedonian town of Kumanovo, I received explicit proof of how important education has become for ethnic Albanians. It was a Friday afternoon on a hot summer day. I was in my top-floor apartment, working with my research assistant, Adnan, a 28-year-old ethnic Albanian man who had been helping me for the past year. We had grown to be a well-synchronized team. It was his turn to dictate while I entered data from the survey into the computer. The questionnaire concerned interior decorations, but it began with several general questions about the ages, education, and number of family members. After we finished entering around thirty of the questionnaires completed in Albanian, Adnan suddenly stood up without a word. He went into the kitchen, and started drinking water from the first thing he saw, which was an empty olive jar drying on the dish rack. Then he came back, clearly upset. He wiped the sweat from his forehead with the upper part of his hand, and exclaimed,

There is something not right here. I cannot believe that, in a family of eight, six members have college degrees and they all live together in one house. Bullshit! I would have known that family. I know most of the Albanians here and, trust me, this is not true. This is all exaggerations and lies.
Potential self-selection bias in a nested case-control study on indoor environmental factors and their association with asthma and allergic symptoms among pre-school children
Authors: Bornehag Carl-Gustaf , Sundell Jan , Sigsgaard Torben , Janson Staffan
Published: August 2006

Selection bias means a systematic difference between the characteristics of selected and non-selected individuals in epidemiological studies. Such bias may be introduced if participants select themselves for a study. The present study aims at identifying differences in family characteristics, including health, building characteristics of the home, and socioeconomic factors between participating and non-participating families in a nested case-control study on asthma and allergy among children. Information was collected in a baseline questionnaire to the parents of 14,077 children aged 1—6 years in a first step. In a second step 2,156 of the children were invited to participate in a case-control study. Of these, 198 cases and 202 controls were finally selected. For identifying potential selection bias, information concerning all invited families in the case-control study was obtained from the baseline questionnaire. Results show that there are several possible biases due to self-selection involved in an extensive study on the impact of the home environment on asthma and allergy among children. Factors associated with participating were high socioeconomic status of the family, more health problems in the case families, and health-related lifestyle factors, such as non-smoking parents. The overall conclusion of this study is that there are selection biases involved in studies that need close cooperation with the families involved. One solution to this problem is stratification, i.e. investigating associations between exposures and health in the same socioeconomic strata.
Rural—urban differences in health and health behaviour: A baseline description of a community health-promotion programme for the elderly
Authors: Fogelholm Mikael , Valve Raisa , Absetz Pilvikki , Heinonen Heikki , Uutela Antti , Patja Kristiina , Karisto Antti , Konttinen Riikka , Mäkelä Tiina , Nissinen Aulikki , Jallinoja Piia , Nummela Olli , Talja Martti
Published: August 2006

Study objective: To (1) describe the setting and design of the Good Ageing in Lahti Region (GOAL) programme; (2) by using the baseline results of the GOAL cohort study, to examine whether living in urban, semi-urban, or rural communities is related to risk factors for chronic diseases and functional disability in ageing individuals. Design: The baseline data of a cohort study of ageing individuals living in three community types (urban, semi-urban, rural). Data were collected by two questionnaires and laboratory assessments. Setting: Fourteen municipalities in the Lahti region (Päijät-Häme County) in Finland. Participants: A regionally and locally stratified random sample of men and women born in 1946—50, 1936—40, and 1926—30. A total of 4,272 were invited and 2,815 (66%) participated. Main results: Elevated serum cholesterol, obesity, disability, sedentary lifestyle (<2 times/week walking), and high fat intake were more prevalent in rural vs. urban and semi-urban communities. After adjustment for sex, age, education, obesity, diet, physical activity, smoking, and alcohol use, rural communities remained the only community type with increased (p<0.05) probability for high BMI (OR 1.33) and high waist circumference (OR 1.43). Conclusions: The unfavourable health and lifestyle profile, together with an old population, makes health promotion for elderly citizens a special challenge for rural communities such as those in Päijät-Häme County, Finland. Most, if not all, of the differences in health between the three community types were explained by educational background, physical activity, and smoking.
On a certain class of linear Hamiltonian maps
Authors: Otsuki Nobukazu , Suzuki Sintaro
Published: August 2006

We discovered a certain class of linear Hamiltonian maps which are defined by explicit time dependent Hamiltonian functions. Our method is the analogy of Moser’s construction in 1986, although it is not so difficult, but we think the results are new.
Rigidity of certain holomorphic foliations
Authors: Marín David
Published: August 2006

There is a well-known rigidity theorem of Y. Ilyashenko for (singular) holomorphic foliations in

C
P

2

\mathbb {CP}^2

and also the extension given by Gómez-Mont and Ortíz-Bobadilla (1989). Here we present a different generalization of the result of Ilyashenko: some cohomological and (generic) dynamical conditions on a foliation

F

\mathcal {F}

on a fibred complex surface imply the d-rigidity of

F

\mathcal {F}

, i.e. any topologically trivial deformation of

F

\mathcal {F}

is also analytically trivial. We particularize this result to the case of ruled surfaces. In this context, the foliations not verifying the cohomological hypothesis above were completely classified in an earlier work by X. Gómez-Mont (1989). Hence we obtain a (generic) characterization of non-d-rigid foliations in ruled surfaces. We point out that the widest class of them are Riccati foliations.
Universal localization of triangular matrix rings
Authors: Sheiham Desmond
Published: August 2006

If

R
R

is a triangular

2
×
2

2\times 2

matrix ring, the columns

P
P

and

Q
Q

are f.g. projective

R
R

-modules. We describe the universal localization of

R
R

which makes invertible an

R
R

-module morphism

σ
:
P
→
Q

\sigma :P\to Q

, generalizing a theorem of A. Schofield. We also describe the universal localization of

R
R

-modules.
Periodic groups whose simple modules have finite central endomorphism dimension
Authors: Snider Robert
Published: August 2006

Theorem. If

k
k

is an uncountable field and

G
G

is a periodic group with no elements of order the characteristic of

k
k

and if all simple

k
[
G
]

k[G]

modules have finite central endomorphism dimension, then

G
G

has an abelian subgroup of finite index.
The monic integer transfinite diameter
Authors: Hare K. , Smyth C.
Published: August 2006

We study the problem of finding nonconstant monic integer polynomials, normalized by their degree, with small supremum on an interval

I
I

. The monic integer transfinite diameter

t

M

(
I
)

t_{\mathrm {M}}(I)

is defined as the infimum of all such supremums. We show that if

I
I

has length

1
1

, then

t

M

(
I
)
=

1
2

t_{\mathrm {M}}(I) = \tfrac {1}{2}

. We make three general conjectures relating to the value of

t

M

(
I
)

t_{\mathrm {M}}(I)

for intervals

I
I

of length less than

4
4

. We also conjecture a value for

t

M

(
[
0
,
b
]
)

t_{\mathrm {M}}([0,b])

where

0
>
b
≤
1

0>b\le 1

. We give some partial results, as well as computational evidence, to support these conjectures. We define functions

L

−

(
t
)

L_{-}(t)

and

L

+

(
t
)

L_{+}(t)

, which measure properties of the lengths of intervals

I
I

with

t

M

(
I
)

t_{\mathrm {M}}(I)

on either side of

t
t

. Upper and lower bounds are given for these functions. We also consider the problem of determining

t

M

(
I
)

t_{\mathrm {M}}(I)

when

I
I

is a Farey interval. We prove that a conjecture of Borwein, Pinner and Pritsker concerning this value is true for an infinite family of Farey intervals.
Iterated function systems, Ruelle operators, and invariant projective measures
Authors: Dutkay Dorin , Jorgensen Palle
Published: August 2006

We introduce a Fourier-based harmonic analysis for a class of discrete dynamical systems which arise from Iterated Function Systems. Our starting point is the following pair of special features of these systems. (1) We assume that a measurable space

X
X

comes with a finite-to-one endomorphism

r
:
X
→
X

r\colon X\rightarrow X

which is onto but not one-to-one. (2) In the case of affine Iterated Function Systems (IFSs) in

R

d

\mathbb {R}^d

, this harmonic analysis arises naturally as a spectral duality defined from a given pair of finite subsets

B
,
L

B, L

in

R

d

\mathbb {R}^d

of the same cardinality which generate complex Hadamard matrices.

Our harmonic analysis for these iterated function systems (IFS)

(
X
,
μ
)

(X, \mu )

is based on a Markov process on certain paths. The probabilities are determined by a weight function

W
W

on

X
X

. From

W
W

we define a transition operator

R
W

R_W

acting on functions on

X
X

, and a corresponding class

H
H

of continuous

R
W

R_W

-harmonic functions. The properties of the functions in

H
H

are analyzed, and they determine the spectral theory of

L
2

(
μ
)

L^2(\mu )

. For affine IFSs we establish orthogonal bases in

L
2

(
μ
)

L^2(\mu )

. These bases are generated by paths with infinite repetition of finite words. We use this in the last section to analyze tiles in

R

d

\mathbb {R}^d

.
Continuous-time Kreiss resolvent condition on infinite-dimensional spaces
Authors: Eisner Tatjana , Zwart Hans
Published: August 2006

Given the infinitesimal generator

A
A

of a

C
0

C_0

-semigroup on the Banach space

X
X

which satisfies the Kreiss resolvent condition, i.e., there exists an

M
>
0

M>0

such that
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" alttext="double-vertical-bar left-parenthesis s upper I minus upper A right-parenthesis Superscript negative 1 Baseline double-vertical-bar less-than-or-equal-to StartFraction upper M Over normal upper R normal e left-parenthesis s right-parenthesis EndFraction">

‖
(
s
I
−
A

)

−
1

‖
≤

M

R
e

(
s
)

\| (sI-A)^{-1}\| \leq \frac {M}{\mathrm {Re}(s)}

for all complex

s
s

with positive real part, we show that for general Banach spaces this condition does not give any information on the growth of the associated

C
0

C_0

-semigroup. For Hilbert spaces the situation is less dramatic. In particular, we show that the semigroup can grow at most like

t
t

. Furthermore, we show that for every

γ
∈
(
0
,
1
)

\gamma \in (0,1)

there exists an infinitesimal generator satisfying the Kreiss resolvent condition, but whose semigroup grows at least like

t
γ

t^\gamma

. As a consequence, we find that for

R

N

{\mathbb R}^N

with the standard Euclidian norm the estimate

‖
exp
⁡
(
A
t
)
‖
≤

M
1

min
(
N
,
t
)

\|\exp (At)\| \leq M_1 \min (N,t)

cannot be replaced by a lower power of

N
N

or

t
t

.
An a priori error analysis for the coupling of local discontinuous Galerkin and boundary element methods
Authors: Gatica Gabriel , Sayas Francisco-Javier
Published: August 2006

In this paper we analyze the coupling of local discontinuous Galerkin (LDG) and boundary element methods as applied to linear exterior boundary value problems in the plane. As a model problem we consider a Poisson equation in an annular polygonal domain coupled with a Laplace equation in the surrounding unbounded exterior region. The technique resembles the usual coupling of finite elements and boundary elements, but the corresponding analysis becomes quite different. In particular, in order to deal with the weak continuity of the traces at the interface boundary, we need to define a mortar-type auxiliary unknown representing an interior approximation of the normal derivative. We prove the stability of the resulting discrete scheme with respect to a mesh-dependent norm and derive a Strang-type estimate for the associated error. Finally, we apply local and global approximation properties of the subspaces involved to obtain the a priori error estimate in the energy norm.
Order of convergence of second order schemes based on the minmod limiter
Authors: Popov Bojan , Trifonov Ognian
Published: August 2006

Many second order accurate nonoscillatory schemes are based on the minmod limiter, e.g., the Nessyahu–Tadmor scheme. It is well known that the

L
p

L_p

-error of monotone finite difference methods for the linear advection equation is of order

1

/

2

1/2

for initial data in

W
1

(

L
p

)

W^1(L_p)

,

1
≤
p
≤
∞

1\leq p\leq \infty

. For second or higher order nonoscillatory schemes very little is known because they are nonlinear even for the simple advection equation. In this paper, in the case of a linear advection equation with monotone initial data, it is shown that the order of the

L
2

L_2

-error for a class of second order schemes based on the minmod limiter is of order at least

5

/

8

5/8

in contrast to the

1

/

2

1/2

order for any formally first order scheme.
Significant sequence similarities in promoters and precursors of Arabidopsis thaliana non-conserved microRNAs
Authors: Wang Yu , Hindemitt Tobias , Mayer Klaus F. X.
Published: August 2006

Some plant microRNAs have been shown to be de novo generated by inverted duplication from their target genes. Subsequent duplication events potentially generate multigene microRNA families. Within this article we provide supportive evidence for the inverted duplication model of plant microRNA evolution. First, we report that the precursors of four Arabidopsis thaliana microRNA families, miR157, miR158, miR405 and miR447 share nearly identical nucleotide sequences throughout the whole miRNA precursor between the family members. The extent and degree of sequence conservation is suggestive of recent evolutionary duplication events. Furthermore we found that sequence similarities are not restricted to the transcribed part but extend into the promoter regions. Thus the duplication event most probably included the promoter regions as well. Conserved elements in upstream regions of miR163 and its targets were also detected. This implies that the inverted duplication of target genes, at least in certain cases, had included the promoters of the target genes. Sequence conservation within promoters of miRNA families as well as between miRNA and its potential progenitor gene can be exploited for understanding the regulation of microRNA genes.

Contact:  Kmayer@gsf.de

Supplementary Material: Web supplementary information is available at . Further supplementary material is available on Bioinformatics online.
A bizarre new toothed mysticete (Cetacea) from Australia and the early evolution of baleen whales
Authors: Fitzgerald Erich M.G
Published: August 2006

Extant baleen whales (Cetacea, Mysticeti) are all large filter-feeding marine mammals that lack teeth as adults, instead possessing baleen, and feed on small marine animals in bulk. The early evolution of these superlative mammals, and their unique feeding method, has hitherto remained enigmatic. Here, I report a new toothed mysticete from the Late Oligocene of Australia that is more archaic than any previously described. Unlike all other mysticetes, this new whale was small, had enormous eyes and lacked derived adaptations for bulk filter-feeding. Several morphological features suggest that this mysticete was a macrophagous predator, being convergent on some Mesozoic marine reptiles and the extant leopard seal (Hydrurga leptonyx). It thus refutes the notions that all stem mysticetes were filter-feeders, and that the origins and initial radiation of mysticetes was linked to the evolution of filter-feeding. Mysticetes evidently radiated into a variety of disparate forms and feeding ecologies before the evolution of baleen or filter-feeding. The phylogenetic context of the new whale indicates that basal mysticetes were macrophagous predators that did not employ filter-feeding or echolocation, and that the evolution of characters associated with bulk filter-feeding was gradual.