bluuebunny/crossref_metadata_2025 huggingface dataset:
On the control of filamentation of intense laser beams propagating in underdense plasma
Authors: Williams E. A.
Published: May 2006

In indirect drive inertial confinement fusion ignition designs, the laser energy is delivered into the hohlraum through the laser entrance holes (LEHs), which are sized as small as practicable to minimize x-ray radiation losses. On the other hand, deleterious laser plasma processes, such as filamentation and stimulated backscatter, typically increase with laser intensity. Ideally, therefore, the laser spot shape should be a close fit to the LEH, with uniform (envelope) intensity in the spot and minimal energy at larger radii spilling onto the LEH material. This keeps the laser intensity as low as possible, consistent with the area of the LEH aperture and the power requirements of the design. This can be achieved (at least for apertures significantly larger than the laser’s aberrated focal spot) by the use of custom-designed phase plates. However, outfitting the 192–beam National Ignition Facility [J. A. Paisner, E. M. Campbell, and W. J. Hogan, Fusion Tech. 26, 755 1994)] laser with multiple sets of phase plates optimized for a variety of different LEH aperture sizes is an expensive proposition. It is thus important to assess the impact on laser-plasma interaction processes of using phase plates with a smaller than optimum focal spot (or even no phase plates at all!) and then defocusing the beam to expand it to fill the LEH and lower its intensity. Significant effects are found from changes in the characteristic sizes of the laser speckle, from the lack of uniformity of the laser envelope out of the focal plane and on the efficacy of additional polarization smoothing and/or smoothing by spectral dispersion (SSD). These effects are quantified with analytic estimates and simulations using PF3D, our laser-plasma interaction code.
Radial compression and torque-balanced steady states of single-component plasmas in Penning-Malmberg traps
Authors: Danielson J. R. , Surko C. M.
Published: May 2006

Penning-Malmberg traps provide an excellent method to confine single-component plasmas. Specially tailored, high-density plasmas can be created in these devices by the application of azimuthally phased rf fields (i.e., the so-called “rotating wall” technique). Recently, we reported a regime of compression of electron (or positron) plasmas in which the plasma density increases until the E×B rotation frequency, ωE (with ωE∝ plasma density), approaches the applied frequency, ωRW. Good compression is achieved over a broad range of rotating wall frequencies, without the need to tune to a mode in the plasma. The resulting steady-state density is only weakly dependent on the amplitude of the rotating-wall drive. Detailed studies of these states are described, including the evolution of the plasma temperature, peak density, and density profiles during compression; and the response of the plasma, once compressed, to changes in frequency and rotating-wall amplitude. Experiments are conducted in a 4.8T magnetic field with ∼109 electrons. The plasmas have initial and final temperatures of ∼0.1eV. They can be compressed to steady-state densities >1010cm−3 and plasma radii <200μm. The outward, asymmetry-driven plasma transport rate, Γo, of the compressed plasmas is independent of density, n, in contrast to the behavior at lower densities where Γo∝n2. The implications of these results for the creation and confinement of high-density electron and positron plasmas and the creation of finely focused beams are discussed.
Advances in the numerical modeling of field-reversed configurations
Authors: Belova Elena V. , Davidson Ronald C. , Ji Hantao , Yamada Masaaki
Published: May 2006

The field-reversed configuration (FRC) is a compact torus with little or no toroidal magnetic field. A theoretical understanding of the observed FRC equilibrium and stability properties presents significant challenges due to the high plasma beta, plasma flows, large ion gyroradius, and the stochasticity of the particle orbits. Advanced numerical simulations are generally required to describe and understand the detailed behavior of FRC plasmas. Results of such simulations are presented in this paper. It is shown that 3D nonlinear hybrid simulations using the HYM code [E. V. Belova et al., Phys. Plasmas 7, 4996 (2000)] reproduce all major experimentally observed stability properties of elongated (theta-pinch-formed) FRCs. Namely, the scaling of the growth rate of the n=1 tilt mode with the S*∕E parameter (S* is the FRC kinetic parameter, E is elongation, and n is toroidal mode number), the nonlinear saturation of the tilt mode, ion toroidal spin-up, and the growth of the n=2 rotational mode have been demonstrated and studied in detail. The HYM code has also been used to study stability properties of FRCs formed by the counterhelicity spheromak merging method. A new stability regime has been found for FRCs with elongation E∼1, which requires a close-fitting conducting shell and energetic beam ion stabilization.
Chaos quasisynchronization induced by impulses with parameter mismatches
Authors: Li Chuandong , Chen Guanrong , Liao Xiaofeng , Fan Zhengping
Published: May 2006

This paper studies the effect of parameter mismatch on the impulsive synchronization of a class of coupled chaotic systems. A new definition for global quasisynchronization is introduced and used to analyze the synchronous behavior of coupled chaotic systems in the presence of parameter mismatch. Using the linear decomposition and comparison-system methods, a global synchronization error bound together with a sufficient condition is derived. Numerical simulations on the chaotic Chua’s circuit are presented to verify the theoretical results.
A model of the ethylene signaling pathway and its gene response in Arabidopsis thaliana: Pathway cross-talk and noise-filtering properties
Authors: Díaz José , Álvarez-Buylla Elena R.
Published: May 2006

Dynamic models of molecular networks and pathways enable in silico evaluations of the consistency of proposed interactions and the outcomes of perturbations as well as of hypotheses on system-level structure and function. We postulate a continuous model of the activation dynamics of the ethylene response factor 1 (ERF1) gene in response to ethylene signaling. This activation elicits the response of the plant defensin 1 (PDF1) gene, which also responds to jasmonic acid, and the inhibition of the putative auxin responsive factor 2 (ARF2) gene, that also responds to auxin. Our model allows the effect of different ethylene concentrations in eliciting contrasting genetic and phenotypic responses to be evaluated allows the effect of different ethylene concentrations in eliciting contrasting genetic and phenotypic responses to be evaluated and seems to consider key components of the ethylene pathway because the ERF1 dose-response curve that we predict has the same qualitative form as the phenotypic dose-response curves obtained experimentally. Therefore, our model suggests that the phenotypic dose-response curves obtained experimentally could be due, at least in part, to ERF1 changes to different ethylene concentrations. Stability analyses show that the model’s results are robust to parameter estimates. Of interest is that our model predicts that the ethylene pathway may filter stochastic and rapid chaotic fluctuations in ethylene availability. This novel approach may be applied to any cellular signaling and response pathway in plants and animals.
On the definition of a kinetic equilibrium in global gyrokinetic simulations
Authors: Angelino P. , Bottino A. , Hatzky R. , Jolliet S. , Sauter O. , Tran T. M. , Villard L.
Published: May 2006

Nonlinear electrostatic global gyrokinetic simulations of collisionless ion temperature gradient (ITG) turbulence and E×B zonal flows in axisymmetric toroidal plasmas are examined for different choices of the initial distribution function. Using a local Maxwellian leads to the generation of axisymmetric E×B flows that can be so strong as to prevent ITG mode growth. A method using a canonical Maxwellian is shown to avoid this spurious generation of E×B flows. In addition, a revised δf scheme is introduced and compared to the standard δf method.
May chaos always be suppressed by parametric perturbations?
Authors: Schwalger Tilo , Dzhanoev Arsen , Loskutov Alexander
Published: May 2006

The problem of chaos suppression by parametric perturbations is considered. Despite the widespread opinion that chaotic behavior may be stabilized by perturbations of any system parameter, we construct a counterexample showing that this is not necessarily the case. In general, chaos suppression means that parametric perturbations should be applied within a set of parameters at which the system has a positive maximal Lyapunov exponent. Analyzing the known Duffing-Holmes model by a Melnikov method, we showed that chaotic dynamics cannot be suppressed by harmonic perturbations of a certain parameter, independently from the other parameter values. Thus, to stabilize the behavior of chaotic systems, the perturbation and parameters should be carefully chosen.
Efficient partitioning technique for computing the dynamics of intramolecular processes: Radiationless transitions in pyrazine
Authors: Christopher P. S. , Shapiro Moshe , Brumer Paul
Published: May 2006

An efficient QP partitioning algorithm to compute the eigenvalues, eigenvectors, and the dynamics of large molecular systems of a particular type is presented. Compared to straightforward diagonalization, the algorithm displays favorable scaling (∝NT2) as a function of NT, the size of the Hamiltonian matrix. In addition, the algorithm is trivially parallelizable, necessitating no “cross-talk” between nodes, thus enjoying the full linear speedup of parallelization. Moreover, the method requires very modest storage space, even for extremely large matrices. The method has also been enhanced through the development of a coarse-grained approximation, enabling an increase of the basis set size to unprecedented levels (108–1010 in the current application). The QP algorithm is applied to the dynamics of electronic internal conversion in a 24 vibrational-mode model of pyrazine. A performance comparison with other dynamical methods is presented, along with results for the decay dynamics of pyrazine and a discussion of resonance line shapes.
Low field magnetotransport properties of (La0.7Sr0.3MnO3)0.5:(ZnO)0.5 nanocomposite films
Authors: Kang B. S. , Wang H. , MacManus-Driscoll J. L. , Li Y. , Jia Q. X. , Mihut I. , Betts J. B.
Published: May 2006

( La 0.7 Sr 0.3 Mn O 3 ) 0.5 : ( Zn O ) 0.5 nanocomposite thin films were deposited on c-cut sapphire substrates via pulsed laser deposition. The as-grown films were composed of fine grains of 20–50nm size. The epitaxial orientation relationships between the La0.7Sr0.3MnO3 (LSMO) and the sapphire was (111)LSMO∕∕(0003)Al2O3 and ⟨112¯⟩LSMO∕∕⟨101¯0⟩Al2O3. A low field magnetoresistance (LFMR) of ∼12% was achieved at an external magnetic field of H=1T at 77K, possibly due to enhanced grain boundary effects. The postannealed film had columnar structures with well-crystallized large grains (∼200nm), and showed a low resistivity and consequently negligible LFMR similar to that of single crystal LSMO.
Measurement of cross-field power loss due to rovibrationally excited H2 in a detached hydrogen divertor plasma simulator
Authors: Hollmann E. M. , Pigarov A. Yu. , Yan Z.
Published: May 2006

The cross-field power loss due to radiation, plasma, and neutrals are measured for hydrogen discharges in a linear divertor simulator experiment. Radiation appears to be the dominant power loss channel; however, power loss due to heating of H2 neutrals is found to be quite significant, being only 2× weaker than radiation in the higher neutral pressure experiments. The H2 vibrational temperature Tvib is found to be the most important channel for carrying neutral energy out of the plasma—more important than either kinetic temperature Tkin or rotational temperature Trot. Power carried radially to the wall by plasma cross-field transport is found to be negligible when compared to neutral and radiation losses. These results demonstrate the importance of including of H2 neutrals in understanding power balance in detached tokamak divertors.
Centrosymmetric PbTe∕CdTe quantum dots coherently embedded by epitaxial precipitation
Authors: Heiss W. , Groiss H. , Kaufmann E. , Hesser G. , Böberl M. , Springholz G. , Schäffler F. , Koike K. , Harada H. , Yano M.
Published: May 2006

A concept for the fabrication of highly symmetric quantum dots that are coherently embedded in a single crystalline matrix is demonstrated. In this approach, the formation of the quantum dots is induced by a transformation of an epitaxial two dimensional quantum well into an array of isolated precipitates with dimensions of about 25nm. The formation process is driven by the immiscibility of the constituent materials resulting from their different lattice structures. The investigated PbTe∕CdTe heterosystem combines two different cubic lattices with almost identical lattice constants. Therefore, the precipitated quantum dots are almost strain-free and near thermodynamic equilibrium they exhibit the shape of small-rhombo-cubo-octahedrons. The PbTe∕CdTe quantum dots, grown on GaAs substrates, display intense room temperature luminescence at wavelength of around 3.2μm, which makes them auspicious for applications in midinfrared photonic devices.
Lateral photocurrent spectroscopy on self-assembled PbSe quantum dots
Authors: Simma M. , Fromherz T. , Raab A. , Springholz G. , Bauer G.
Published: May 2006

Wavelength- and temperature-dependent lateral photocurrent measurements were performed on self-assembled PbSe∕PbEuTe quantum-dot superlattices. The comparison of the measured data with absorption spectra calculated within the envelope function approach allows a clear identification of the different features in the photocurrent spectra. The photocurrent signal from the dots is observed over a wide temperature range and no quenching occurs even at 5 K. This indicates a type-II band alignment for the strained PbSe∕PbEuTe quantum-dots.
Organic light-emitting device luminaire for illumination applications
Authors: D’Andrade Brian W. , Brown Julie J.
Published: May 2006

The total light output of an organic light-emitting device (OLED) with a truncated square-pyramid luminaire is shown to be 1.8–2.1 times greater than the forward emission of an OLED without a luminaire. Luminaires increase the amount of outcoupled light by reducing waveguiding in the glass substrate, and they are made from 1.2-cm-thick acrylic and attached to the OLED glass substrate using index matching fluid. Based on experimental results and ray tracing models, the ratio of the OLED total emission to the OLED forward emission is found to be independent of luminaire taper angles between 30° and 80°.
Adaptive lens using liquid crystal concentration redistribution
Authors: Ren Hongwen , Lin Yi-Hsin , Wu Shin-Tson
Published: May 2006

An adaptive lens using electrically induced liquid crystal (LC)/monomer concentration redistribution is demonstrated. In the absence of an electric field, the LC/monomer mixture is homogeneously distributed. Application of an inhomogeneous electric field causes the LC molecules to diffuse towards the high field region and the liquid monomer towards the low field region. On the other hand, the LC molecules tend to diffuse from high to low concentration direction in order to balance the concentration change. A gradient LC concentration is thus obtained. Using the gradient LC concentration, we demonstrate a tunable-focus lens. Compared with a conventional LC lens, our lens has advantages in small astigmatism and without light scattering, but its response time is slower.
Strong pinning enhancement in MgB2 using very small Dy2O3 additions
Authors: Chen S. K. , Wei M. , MacManus-Driscoll J. L.
Published: May 2006

0.5 – 5.0 wt %  Dy2O3 was in situ reacted with Mg+B to form pinned MgB2. While Tc remained largely unchanged, Jc was strongly enhanced. The best sample (only 0.5wt% Dy2O3) had a Jc∼6.5×105Acm−2 at 6K, 1T and 3.5×105Acm−2 at 20K, 1T, around a factor of 4 higher compared to the pure sample, and equivalent to hot-pressed or nano-Si-added MgB2 at ⩽1T. Even distributions of nanoscale precipitates of DyB4 and MgO were observed within the grains. The room temperature resistivity decreased with Dy2O3 indicative of improved grain connectivity.
Photoluminescence and Raman scattering studies on PbTiO3 nanowires fabricated by hydrothermal method at low temperature
Authors: Hu Yongming , Gu Haoshuang , Sun Xiangcheng , You Jing , Wang John
Published: May 2006

Pb Ti O 3 nanowires have been successfully fabricated by a hydrothermal method at 200°C. X-ray diffraction result shows that the PbTiO3 nanowires have a tetragonal perovskite structure without any other impurity phase. Scanning electron microscopy and transmission electron microscopy investigations exhibit that the as-prepared samples are made up of large quantity nanowires with diameters of about 10–20nm and lengths reaching up to 3μm and single crystalline in nature. Photoluminescence study at room temperature for wavelength between 400 and 650nm reveals a strong blue-green emission band peaking at ca. 471.4nm (2.63eV). Raman spectroscopy study of the nanowires at room temperature demonstrates that the lifetime of the phonons is shorter compare to that of bulk materials.
Toward nκd spectroscopy: Analytic solution of the three-phase model of polarimetry in the thin-film limit
Authors: Kim I. K. , Aspnes D. E.
Published: May 2006

We find an analytic solution of the three-phase (substrate/overlayer/ambient) model of polarimetry in the thin-film limit, which allows overlayer thicknesses d and refractive indices ñ=n+iκ to be determined from measured changes Δρ∕ρ of the complex reflectance ratio ρ and ΔRp∕Rp or ΔRs∕Rs of the p- or s-polarized reflectances Rp or Rs, from a quadratic equation without the need for potentially unstable numerical methods. We also find a transformation of the data that extends the range of accuracy by up to an order of magnitude without introducing additional mathematical complications. The results are illustrated by the application to a layer of physisorbed H2O on oxidized GaAs, and show that the wavelength-by-wavelength spectroscopy of adsorbed monolayers is now within range of existing polarimetric technology.
Various low group velocity effects in photonic crystal line defect waveguides and their demonstration by laser oscillation
Authors: Kiyota Kazuaki , Kise Tomofumi , Yokouchi Noriyuki , Ide Toshihide , Baba Toshihiko
Published: May 2006

We investigated propagating modes in a two-dimensional photonic crystal slab waveguide with a line defect narrower than a single line missing hole structure from the low group velocity point of view. These modes showed low group velocities not due to the conventional distributed feedback (DFB) between a forward and a backward mode with the same lateral field distribution, but due to a DFB between modes with different lateral field distribution or property of a start point of a photonic-band-gap-guided mode. These low group velocities of over 40 were demonstrated as a Fabry-Pérot lasing oscillation due to gain enhancement.
Temperature-dependent built-in potential in organic semiconductor devices
Authors: Kemerink M. , Kramer J. M. , Gommans H. H. P. , Janssen R. A. J.
Published: May 2006

The temperature dependence of the built-in voltage of organic semiconductor devices is studied. The results are interpreted using a simple analytical model for the band bending at the electrodes. It is based on the notion that, even at zero current, diffusion may cause a significant charge density in the entire device, and hence a temperature dependent band bending. Both magnitude and temperature dependence of the built-in potential of various devices are consistently described by the model, as the effects of a thin LiF layer between cathode and active layer.
Performance of the pear (Pyrus communis) cultivar William's Bon Chretien grafted on seven rootstocks
Authors: Sotiropoulos T. E.
Published: May 2006

The performance of the pear (Pyrus communis L.) cv. William’s Bon Chretien (William’s BC) grafted on 7 rootstocks was evaluated over a period of 8 years. The scions of the cultivar William’s BC were grafted on the following 7 rootstocks: (i) P. communis seedlings, (ii) quince BA 29, (iii) quince A, (iv) Pomology Institute (PI) 1, (v) PI 5, (vi) PI 27, and (vii) quince Komotinis (iv–vii are Greek local quince seedlings). Compatibility of William’s BC with P. communis, PI 1 and PI 27 was excellent and no tree losses occurred. The highest yield per tree was recorded when William’s BC was grafted on PI 5 rootstock, although it was not significantly different from P. communis. The lowest yield was recorded when the cultivar was grafted on BA 29 rootstock. Production efficiency of William’s BC was highest when grafted on PI 27, intermediate on quince A, PI 1 and PI 5 and lowest on P. communis. Iron concentration of leaves of scions grafted on P. communis, BA 29, quince A and quince Komotinis were significantly lower than those grafted on PI 5. From the results it is concluded that the rootstocks PI 1 and PI 27 are suitable for the cv. William’s BC under Greek or other similar climatic conditions.
Root zone temperature influences growth, partitioning, leaf morphology and physiology of the peach rootstock, Green Leaf Nemaguard
Authors: Malcolm P. , Holford P. , McGlasson B. , Conroy J.
Published: May 2006

This paper examines the hypothesis that root zone temperature (RZT) affects the growth of stone fruit plants. This hypothesis was tested by growing plants of the peach rootstock, Green Leaf Nemaguard (Prunus persica L. Batsch), at a diurnally variable (26/15°C) or at constant (5, 15, 20°C) RZTs; the plants were either actively growing or emerging from dormancy when the treatments were applied. These trials demonstrated that RZT, independently of air temperature and light intensity, influences growth, dry matter partitioning, leaf morphology and physiological processes. The growth of plants emerging from dormancy was more sensitive to RZT than that of actively growing plants, therefore, phenology can influence sensitivity to RZT. The area, numbers and daily rates of expansion of leaves, correlated positively with RZT for both sets of plants. However, plants exposed to a diurnally variable 26/15°C RZT were smaller with respect to overall growth and aspects of leaf morphology than plants exposed to a constant 20°C RZT, despite the daily mean RZTs for both treatments being similar. This could be due to supraoptimal RZTs during the day and/or suboptimal RZTs at night. Root mass ratio, in both actively growing and plants exiting dormancy was highest at 20° RZT. In contrast, the stem mass ratio of actively growing plants was maximised at 5°C, and for plants exiting dormancy, the stem mass ratio was minimised at this RZT. RZTs influence the rate of leaf expansion, which in turn affects the total number of leaves and leaf area and, along with its effect on CO2 assimilation rates, results in reductions in DM production. This research illustrates the importance of RZTs, particularly in the spring, on growth and leaf development and suggests the need to incorporate RZT into development models for peaches.
Seed alkaloid concentrations are not affected by agronomic and phosphorus-nutrition treatments that reduce Pleiochaeta setosa Hughes disease on narrow-leafed lupin (Lupinus angustifolius)
Authors: Gremigni P. , Sweetingham M. W. , Cowling W. A.
Published: May 2006

The severity of brown spot caused by the fungus Pleiochaeta setosa (Kirchn.) Hughes in narrow-leafed lupin (Lupinus angustifolius L.) is reduced by improving phosphorus (P) nutrition and using agronomic treatments that extend crop rotation or increase cereal stubble retention. The aim of this work was to investigate the impact of these treatments on the alkaloid concentrations of the harvested seed of 3 sweet cultivars of L. angustifolius that differed in their susceptibility to this fungal disease: Merrit (susceptible), Tallerack and Myallie (both moderately resistant). Because abiotic and biotic stresses appear to stimulate plant alkaloid biosynthesis, we hypothesised that higher levels of disease pressure may increase alkaloid concentrations in the harvested seed, particularly in the disease-susceptible Merrit.
The main effects of P nutrition, cereal stubble retention, genotype and crop rotation were significant for the severity of brown spot and plant biomass of narrow-leafed lupin in a field trial in Wongan Hills, Western Australia, but were not significant for total alkaloid concentrations or the relative proportions of individual alkaloids of the harvested seed. Seed total alkaloid concentrations were in most cases below the maximum permitted concentration established for lupin seed (200 mg/kg dry matter) and were independent of the severity of brown spot on leaves. The great fluctuations of seed total alkaloid concentrations observed in grower deliveries to bulk handling facilities and in lupin cultivar yield testing trials are unlikely to result from the nutritional and agronomic treatments such as those investigated in this experiment, or the various disease levels that resulted from these treatments.
Selenoprotein deficiency accelerates prostate carcinogenesis in a transgenic model
Authors: Diwadkar-Navsariwala Veda , Prins Gail S. , Swanson Steven M. , Birch Lynn A. , Ray Vera H. , Hedayat Samad , Lantvit Daniel L. , Diamond Alan M.
Published: May 2006

Considerable animal and human data have indicated that selenium is effective in reducing the incidence of several different types of cancer, including that of the prostate. However, the mechanism by which selenium inhibits carcinogenesis remains unknown. One possibility is that dietary selenium influences the levels of selenium-containing proteins, or selenoproteins. Selenoproteins contain selenium in the form of selenocysteine and perform a variety of cellular functions, including antioxidant defense. To determine whether the levels of selenoproteins can influence carcinogenesis independent of selenium intake, a unique mouse model was developed by breeding two transgenic animals: mice with reduced selenoprotein levels because of the expression of an altered selenocysteine-tRNA (i
6
A
−
) and mice that develop prostate cancer because of the targeted expression of the SV40 large T and small t oncogenes to that organ [
C3(1)/Tag
]. The resulting bigenic animals (
i
6
A
−
/
Tag
) and control WT/
Tag
mice were assessed for the presence, degree, and progression of prostatic epithelial hyperplasia and nuclear atypia. The selenoprotein-deficient mice exhibited accelerated development of lesions associated with prostate cancer progression, implicating selenoproteins in cancer risk and development and raising the possibility that selenium prevents cancer by modulating the levels of these selenoproteins.
Proposed Mode of Action for In Utero Effects of Some Phthalate Esters on the Developing Male Reproductive Tract
Authors: David Raymond M.
Published: May 2006

Phthalate esters containing a straight-chain backbone of 4–6 carbons have demonstrated testicular toxicity and infertility in adult and pre-adolescent rats, mice, hamsters, and ferrets. In recent years, these same phthalates have been shown to interfere with the normal development of the male reproductive tract in rodents and rabbits. The review presented here summarizes studies that provide evidence of a mode of action for these effects. The data indicate that C4–C6 phthalate esters inhibit processes in the Leydig cell, such as the synthesis of testosterone (T) and production of insulin-like factor 3 (insl3), both of which are required for normal development of male genitalia. A proposed secondary effect of reduced androgen production is on Sertoli cells, resulting in failure to proliferate and interference with cell-cell communication (gap-junction intracellular communication) leading to the development of large multinucleate gonocytes. The possibility that phthalates act directly on the Sertoli cells to interfere with intracellular communication is not excluded. The strength, consistency, and plausibility of the proposed mode of action and alternate modes of action are discussed.
The Nose Revisited: A Brief Review of the Comparative Structure, Function, and Toxicologic Pathology of the Nasal Epithelium
Authors: Harkema Jack R. , Carey Stephan A. , Wagner James G.
Published: May 2006

The nose is a very complex organ with multiple functions that include not only olfaction, but also the conditioning (e.g., humidifying, warming, and filtering) of inhaled air. The nose is also a “scrubbing tower” that removes inhaled chemicals that may be harmful to the more sensitive tissues in the lower tracheobronchial airways and pulmonary parenchyma. Because the nasal airway may also be a prime target for many inhaled toxicants, it is important to understand the comparative aspects of nasal structure and function among laboratory animals commonly used in inhalation toxicology studies, and how nasal tissues and cells in these mammalian species may respond to inhaled toxicants. The surface epithelium lining the nasal passages is often the first tissue in the nose to be directly injured by inhaled toxicants. Five morphologically and functionally distinct epithelia line the mammalian nasal passages—olfactory, respiratory, squamous, transitional, and lymphoepithelial—and each nasal epithelium may be injured by an inhaled toxicant. Toxicant-induced epithelial lesions in the nasal passages of laboratory animals (and humans) are often site-specific and dependent on the intranasal regional dose of the inhaled chemical and the sensitivity of the nasal epithelial tissue to the specific chemical. In this brief review, we present examples of nonneoplastic epithelial lesions (e.g., cell death, hyperplasia, metaplasia) caused by single or repeated exposure to various inhaled chemical toxicants. In addition, we provide examples of how nasal maps may be used to record the character, magnitude and distribution of toxicant-induced epithelial injury in the nasal airways of laboratory animals. Intranasal mapping of nasal histopathology (or molecular and biochemical alterations to the nasal mucosa) may be used along with innovative dosimetric models to determine dose/response relationships and to understand if site-specific lesions are driven primarily by airflow, by tissue sensitivity, or by another mechanism of toxicity. The present review provides a brief overview of comparative nasal structure, function and toxicologic pathology of the mammalian nasal epithelium and a brief discussion on how data from animal toxicology studies have been used to estimate the risk of inhaled chemicals to human health.
Design-Based Sampling and Quantitation of the Respiratory Airways
Authors: Hyde Dallas M. , Harkema Jack R. , Tyler Nancy K. , Plopper Charles G.
Published: May 2006

Design-based quantitation of the nasal cavity, larynx and tracheobronchial conducting airways after exposure to inhaled toxicants requires complete measurement of all respiratory airways or appropriate sampling followed by morphometric measurements. In vivo imaging (MRI or CT) of the nasal cavity, larynx and conducting airways provides anatomical detail of all the airways down to the distal airways. Since inhaled toxicants show predictable deposition patterns in the airways, identification and sampling of conducting airways becomes essential in a precise toxicological evaluation. Lengths, diameters and luminal surface areas can be directly measured on fixed specimens using a steromicroscope. Estimates of cell numbers, extracellular matrix volumes and vessel/nerve lengths per airway or epithelial basal laminar surface are estimated stereologically. Selected airways are cut into smaller pieces using a “fractionator” for uniform sampling of the airways. Cell numbers are estimated using a “disector.” Volumes are estimated using point probes, while length and surface areas are estimated by isotropically oriented sections with plane and line probes; an approach free of assumptions of shape, size or spatial orientation. True biological variance and the average sampling variance of the stereological measurement define the minimal sampling required to achieve precise estimates of the nasal cavity, larynx and conducting airways.
Exogenous Influences on Task Set Activation in Task Switching
Authors: Rubin Orit , Koch Iring
Published: May 2006

To explore the effect of exogenous processes on cognitive control, we used a cueing task-switching paradigm with two spatial judgement tasks and added an irrelevant colour attribute to the task-relevant spatial attribute of the target. The colour was not related to any specific Stimulus–Response relation in the tasks. A correlation was created between stimulus colour and task identity. This correlation was strong but imperfect in Experiment 1 and perfect in Experiment 2. As a result of the colour–task correlation, stimuli contained redundant information about task identity. By changing the correlation pattern every few blocks we caused this information to be sometimes invalid. In both experiments, performance was worse when the information carried by the target was invalid than when it was valid. However, this effect was exclusive to conditions with short task preparation time. By comparing performance with a control group, which had no colour–task correlation (in Experiment 2) we established that the colour manipulation did not cause a qualitative change in preparation strategy, and that the exogenous effect was stronger in switch trials than in repetition trials. We conclude that exogenous processes that are related to task set affect performance primarily if they are presented before endogenous processes of task set preparation have been launched.
Prevalence of recurrent complaints of pain among Greek schoolchildren and associated factors: A population‐based study
Authors: Bakoula Chryssa , Kapi Aikaterini , Veltsista Alexandra , Kavadias George , Kolaitis Gerasimos
Published: May 2006

Aim: To determine the prevalence of recurrent complaints of pain (RCP) in Greek children, and to examine associations with socio‐demographic characteristics and psychosocial factors. Methods: Cross‐sectional study comprising a nationally representative population of 8130 7‐y‐old Greek schoolchildren. Data were collected by mailed questionnaires (response rate 89%). RCP was defined as present if at least one of the complaints of headache, abdominal pain or limb pain occurred at least once a week. Results: The RCP prevalence rate was 7.2%, with significant gender differences (8.8% of girls, 5.7% of boys; p<0.001). RCP was significantly positively associated with a chronic health problem among the children, frequent change of residence, poor school performance, often watching TV and rarely playing with other children. There were no statistically significant associations of RCP with family structure and socio‐economic status.

Conclusion: The results are indicative of the prevalence of RCP in Greek schoolchildren. This study enlightens the psychosocial component of RCP and emphasizes the importance of gathering information on children's social background in medical settings.
Fast improvement of verbal memory function after left temporal tumour resection
Authors: Moser Sonya Jourdan , Schneider Jacques , Lütschg Jürg , Weber Peter
Published: May 2006

Case report: A 7‐y‐old, right‐handed girl presented at our clinic with complex partial seizures, behavioural problems and word‐finding difficulties. Clinical examination was normal, but electroencephalogram revealed bilateral epileptic discharges in the temporal and paracentral leads. Magnetic resonance imaging showed an intracerebral mass in the left mesial temporal lobe in the areas of the gyrus temporooccipitalis medialis and gyrus parahippocampalis. Neuropsychological testing brought to light an above‐average general intelligence, but the girl performed below average in verbal memory tests and average in figural memory tests. Results: The tumour was completely removed by surgery. Neuropsychological testing 3 and 11 wk after tumour resection demonstrated above‐average verbal learning and memory abilities and improved visual memory. The emotional disturbances, seizures and electroencephalogram abnormalities disappeared completely during the postoperative follow‐up.

Conclusion: After resection of a left temporal brain tumour, the patient was free of seizures, and neuropsychological functions recovered completely within weeks.
Are the symptoms and severity of head injury predictive of clinical findings three months later?
Authors: FALK ANN‐CHARLOTTE , CEDERFJÄLL CLAES , VON WENDT LENNART , KLANG BIRGITTA
Published: May 2006

Aim: To describe symptoms and functional disabilities 3 mo after a minimal, mild or moderate head injury in children, and to analyse relationships between these and initial symptoms and management documented at the time of the injury. Methods: The sample consisted of all children (0–15 y) admitted to an emergency department during a 1‐mo period with a history of head injury. Data were collected from the medical records at the time of the injury, and questionnaires about symptoms/change and functional problems 3 mo after the injury. Results: Symptoms and functional problems were reported in 35% of the children 3 mo after a head injury. Documented altered consciousness (in children less than 5 y) and disorientation (in children 5 y of age or older) at the emergency department were correlated with changes in behaviour at 3 mo. The initial duration of unconsciousness was not predictive of subsequent behaviour. Conclusion: The difficulties in predicting outcomes in head‐injured children, especially younger ones, indicate the need for a follow‐up appointment in order to identify children with special needs. Further studies are needed regarding the early signs and symptoms in different age groups.

Conclusion: The difficulties in predicting outcomes in head‐injured children, especially younger ones, indicate the need for a follow‐up appointment in order to identify children with special needs. Further studies are needed regarding the early signs and symptoms in different age groups.
Short Article: What do we know about Psycholinguistic Effects?
Authors: Lewis Michael B. , Vladeanu Matei
Published: May 2006

Identifying clear and unequivocal psycholinguistic effects for lexical retrieval tasks has been the aim of a significant proportion of recent research activity. Debates have erupted concerning the existence or otherwise of particular effects on particular lexical tasks. Here, it is suggested that the reason for these debates is that researchers exercise choice in what variables they consider in their analysis. It is further illustrated that methods that have been employed for comparing the size of these effects between tasks can only lead to inconclusive results. It is suggested that psycholinguistic data may be better analysed using structural equation modelling methodologies. An example of such an approach is presented.
Short Article: The Impact of Letter Detection on Eye Movement Patterns during Reading: Reconsidering Lexical Analysis in Connected Text as a Function of Task
Authors: Greenberg Seth N. , Inhoff Albrecht W. , Weger Ulrich W.
Published: May 2006

A comparison was made between reading tasks performed with and without the additional requirement of detecting target letters. At issue was whether eye movement measures are affected by the additional requirement of detection. Global comparisons showed robust effects of task type with longer fixations and fewer word skippings when letter detection was required. Detailed analyses of target words, however, further showed that reading with and without letter detection yielded virtually identical effects of word class and text predictability for word-skipping rate and similar effects for different word viewing duration measures. The overall oculomotor pattern suggested that detection does not substantially shift normal reading movements in response to lexical cues and thereby indicated that detection tasks are informative about word and specifically word class processing in normal reading.
Inferring the distribution of mutational effects on fitness inDrosophila
Authors: Loewe Laurence , Charlesworth Brian
Published: May 2006

The properties of the distribution of deleterious mutational effects on fitness (DDME) are of fundamental importance for evolutionary genetics. Since it is extremely difficult to determine the nature of this distribution, several methods using various assumptions about the DDME have been developed, for the purpose of parameter estimation. We apply a newly developed method to DNA sequence polymorphism data from twoDrosophilaspecies and compare estimates of the parameters of the distribution of the heterozygous fitness effects of amino acid mutations for several different distribution functions. The results exclude normal and gamma distributions, since these predict too few effectively lethal mutations and power-law distributions as a result of predicting too many lethals. Only the lognormal distribution appears to fit both the diversity data and the frequency of lethals. This DDME arises naturally in complex systems when independent factors contribute multiplicatively to an increase in fitness-reducing damage. Several important parameters, such as the fraction of effectively neutral non-synonymous mutations and the harmonic mean of non-neutral selection coefficients, are robust to the form of the DDME. Our results suggest that the majority of non-synonymous mutations inDrosophilaare under effective purifying selection.
Thermally induced torpor in fullterm lizard embryos synchronizes hatching with ambient conditions
Authors: Radder Rajkumar , Shine Richard
Published: May 2006

Eggs inside an underground nest have limited access to information about above-ground conditions that might affect the survival of emerging hatchlings. Our measurements of heart rates of embryos inside the intact eggs of montane lizards (Bassiana duperreyi, Scincidae) show that low temperatures induce torpor in fullterm embryos, but do not do so during earlier embryogenesis or later, post-hatching. Because above-ground conditions affect soil temperatures, this stage-dependent torpor effectively restricts hatching to periods of high ambient temperatures above ground. Torpor thus can function not only to synchronize activity with suitable environmental conditions during post-hatching life (as reported for many species), but also can occur in embryos, to synchronize hatching with above-ground conditions that facilitate successful emergence from the nest.
Two-dimensional empirical mode decomposition by finite elements
Authors: Xu Y , Liu B , Liu J , Riemenschneider S
Published: May 2006

Empirical mode decomposition (EMD) is a powerful tool for analysis of non-stationary and nonlinear signals, and has drawn significant attention in various engineering application areas. This paper presents a finite element-based EMD method for two-dimensional data analysis. Specifically, we represent the local mean surface of the data, a key step in EMD, as a linear combination of a set of two-dimensional linear basis functions smoothed with bi-cubic spline interpolation. The coefficients of the basis functions in the linear combination are obtained from the local extrema of the data using a generalized low-pass filter. By taking advantage of the principle of finite-element analysis, we develop a fast algorithm for implementation of the EMD. The proposed method provides an effective approach to overcome several challenging difficulties in extending the original one-dimensional EMD to the two-dimensional EMD. Numerical experiments using both simulated and practical texture images show that the proposed method works well.
Geological constraints on detecting the earliest life on Earth: a perspective from the Early Archaean (older than 3.7 Gyr) of southwest Greenland
Authors: Fedo Christopher M , Whitehouse Martin J , Kamber Balz S
Published: May 2006

At greater than 3.7 Gyr, Earth's oldest known supracrustal rocks, comprised dominantly of mafic igneous with less common sedimentary units including banded iron formation (BIF), are exposed in southwest Greenland. Regionally, they were intruded by younger tonalites, and then both were intensely dynamothermally metamorphosed to granulite facies (the highest pressures and temperatures generally encountered in the Earth's crust during metamorphism) in the Archaean and subsequently at lower grades until about 1500 Myr ago. Claims for the first preserved life on Earth have been based on the occurrence of greater than 3.8 Gyr isotopically light C occurring as graphite inclusions within apatite crystals from a 5 m thick purported BIF on the island of Akilia. Detailed geologic mapping and observations there indicate that the banding, first claimed to be depositional, is clearly deformational in origin. Furthermore, the mineralogy of the supposed BIF, being dominated by pyroxene, amphibole and quartz, is unlike well-known BIF from the Isua Greenstone Belt (IGB), but resembles enclosing mafic and ultramafic igneous rocks modified by metasomatism and repeated metamorphic recrystallization. This scenario parsimoniously links the geology, whole-rock geochemistry, 2.7 Gyr single crystal zircon ages in the unit, an approximately 1500 Myr age for apatites that lack any graphite, non-MIF sulphur isotopes in the unit and an inconclusive Fe isotope signature. Although both putative body fossils and carbon-12 enriched isotopes in graphite described at Isua are better explained by abiotic processes, more fruitful targets for examining the earliest stages in the emergence of life remain within greater than 3.7 Gyr IGB, which preserves BIF and other rocks that unambiguously formed at Earth's surface.
Comparative genomic analysis of two strains of human adenovirus type 3 isolated from children with acute respiratory infection in southern China
Authors: Zhang Qiwei , Su Xiaobo , Gong Sitang , Zeng Qiyi , Zhu Bing , Wu Zaohe , Peng Tao , Zhang Chuyu , Zhou Rong
Published: May 2006

Human adenovirus type 3 (HAdV-3) is a causative agent of acute respiratory disease, which is prevalent throughout the world, especially in Asia. Here, the complete genome sequences of two field strains of HAdV-3 (strains GZ1 and GZ2) isolated from children with acute respiratory infection in southern China are reported (GenBank accession nos DQ099432 and DQ105654, respectively). The genomes were 35 273 bp (GZ1) and 35 269 bp (GZ2) and both had a G+C content of 51 mol%. They shared 99 % nucleotide identity and the four early and five late regions that are characteristic of human adenoviruses. Thirty-nine protein- and two RNA-coding sequences were identified in the genome sequences of both strains. Protein pX had a predicted molecular mass of 8.3 kDa in strain GZ1; this was lower (7.6 kDa) in strain GZ2. Both strains contained 10 short inverted repeats, in addition to their inverted terminal repeats (111 bp). Comparative whole-genome analysis revealed 93 mismatches and four insertions/deletions between the two strains. Strain GZ1 infection produced a typical cytopathic effect, whereas strain GZ2 did not; non-synonymous substitutions in proteins of GZ2 may be responsible for this difference.