bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamically dimensioned search algorithm for computationally efficient watershed model calibration
Authors: Tolson Bryan A. , Shoemaker Christine A.
Published: January 2007

A new global optimization algorithm, dynamically dimensioned search (DDS), is introduced for automatic calibration of watershed simulation models. DDS is designed for calibration problems with many parameters, requires no algorithm parameter tuning, and automatically scales the search to find good solutions within the maximum number of user‐specified function (or model) evaluations. As a result, DDS is ideally suited for computationally expensive optimization problems such as distributed watershed model calibration. DDS performance is compared to the shuffled complex evolution (SCE) algorithm for multiple optimization test functions as well as real and synthetic SWAT2000 model automatic calibration formulations. Algorithms are compared for optimization problems ranging from 6 to 30 dimensions, and each problem is solved in 1000 to 10,000 total function evaluations per optimization trial. Results are presented so that future modelers can assess algorithm performance at a computational scale relevant to their modeling case study. In all four of the computationally expensive real SWAT2000 calibration formulations considered here (14, 14, 26, and 30 calibration parameters), results show DDS to be more efficient and effective than SCE. In two cases, DDS requires only 15–20% of the number of model evaluations used by SCE in order to find equally good values of the objective function. Overall, the results also show that DDS rapidly converges to good calibration solutions and easily avoids poor local optima. The simplicity of the DDS algorithm allows for easy recoding and subsequent adoption into any watershed modeling application framework.
Groundwater convergence as a possible mechanism for multi‐year persistence in rainfall
Authors: Bierkens Marc F. P. , van den Hurk Bart J. J. M.
Published: January 2007

Yearly rainfall totals in wet‐to‐dry climate transition zones show marked multiyear periods of dry and wet anomalies. These are said to originate from large‐scale external forcings (e.g. SST anomalies) and enhanced by land‐atmosphere coupling through soil moisture, vegetation and surface albedo. We explore the hypothesis that the degree of persistence in rainfall may be partly caused by groundwater convergence, i.e. the confluence of groundwater to discharge zones that remain wet throughout the year to sustain evaporation for longer periods of time. A simple stochastic model of soil moisture‐precipitation feedback augmented with a groundwater component shows that groundwater convergence introduces long‐term persistence in rainfall. The degree of persistence (as measured by the Hurst exponent of simulated yearly rainfall totals) increases with groundwater residence time. This notion has important ramifications for multiyear drought forecasting, whereby monitoring or concurrent modeling of groundwater stores may play a role in improving predictability.
Crystallization pressures of mid‐ocean ridge basalts derived from major element variations of glasses from equilibrium and fractional crystallization experiments
Authors: Villiger Samuel , Müntener Othmar , Ulmer Peter
Published: January 2007

A new method for calculating fractionation pressures of mid‐ocean ridge basalts (MORB) that are saturated in clinopyroxene and plagioclase is presented. This mineral assemblage is the major control on the CaO versus Mg # (molar Mg/(Mg + Fetot), all Fe as Fe2+) chemical variations of basaltic liquids. By combining new equilibrium and fractional crystallization experiments on primitive mid‐ocean ridge basalts at high pressure with previously published experiments on natural basaltic systems, we derive an expression for fractionation pressures that depends only on the CaO content and the Mg # of the liquid. P (kbar) = [CaO (wt %) − 3.98(±0.17) − 14.96(±0.34) × Mg # (molar)]/[−0.260(±0.008)], r2 = 0.92. We compare our formulation of a liquid barometer with those of Grove et al. (1992), Yang et al. (1996), and Herzberg (2004). The equation can be used to predict crystallization pressures of dry tholeiitic liquids with Mg # < 0.6. Low H2O contents in the liquid (<1 wt %) do not significantly affect the calculated pressures compared to anhydrous liquids. Pressure calculations have been performed on MORB glasses for three mid‐ocean ridge systems with different spreading rates (East Pacific Rise, Mid‐Atlantic Ridge, Southwest Indian Ridge). Average pressure estimates correlate negatively with spreading rate when the MORB data are filtered for hot spot‐affected compositions. Major element variations indicate that MORB crystallizing at elevated pressures also require lower degrees of mantle partial melting. Locations and compositions of MORB glasses crystallized at elevated pressures can be explained with models where conductive cooling is enhanced, either at segmented ridges with slow spreading rates or along ridge segment terminations at fast spreading ridges.
Fibula Free Flap for Mandible Reconstruction: Analysis of 30 Consecutive Cases and Quality of Life Evaluation
Authors: Maciejewski Adam , Szymczyk Cezary
Published: January 2007

Accepted: May 4, 2006

The objectives of this study were to evaluate the use of fibula free flaps (FFF) for mandible reconstruction in patients with oral cavity cancer and to assess the quality of life (QOL) of the patients who underwent reconstructive surgery. Thirty patients with T3, T4 oral cavity carcinoma underwent surgical resection of the primary tumor infiltrating the mandible or primarily originating from the mandible. According to the length (less or more than 8 cm) and localization (anterior or posterior) of the mandibular defect, patients were subdivided into four groups. In all cases an osseoseptocutaneous FFF was chosen for postresective defect reconstruction. To reconstruct anterior mandibular defects, two osteotomies were needed to give the fibula a proper shape. For extended defects, the fibula usually required more than one osteotomy. Skin islands were designed based on Doppler cutaneous perforator findings. The fibular free skin islands remained viable in all patients and no partial or total skin loss was observed. In the majority of patients (87percent) the facial artery was used for arterial anastomosis. In 6 month follow-ups, the QOL was evaluated as very good except for socioeconomic items. Pain was mild and incidental. Appearance and subjective feeling scores were excellent in two groups with mandibular defects smaller than 8 cm, although in patients with larger defects, they were still very good. Functional effects remained good, and they correlated with the size of defects. In contrast, social activities, recreation, and employment were below patients' expectations and generally reflected the current situation in Poland, but no correlation with the results of reconstruction was found. The present results show that osseocutaneous fibula free flap used in reconstructive surgery for cancer of the oral cavity allows more radical and aggressive resection with very good or excellent functional and aesthetic outcome. Estimated QOL seems an important part of evaluation of the treatment outcome.
Er
3
+
-doped BaY2F8 crystal waveguides for broadband optical amplification at 1.5μm
Authors: Toccafondo V. , Cerqueira S. A. , Faralli S. , Sani E. , Toncelli A. , Tonelli M. , Di Pasquale F.
Published: January 2007

Integrated waveguide amplifiers based on high concentration Er3+ doped BaY2F8 crystals are numerically studied by combining a full-vectorial finite element based modal analysis and propagation-rate equations. Using realistic input data, such as the absorption/emission cross sections and Er level lifetimes measured on grown crystal samples, we investigate the amplifier performance by optimizing the total Er concentration. We predict optimum gain coefficient up to 5dB∕cm and broad amplification bandwidth exceeding 80nm with 1480nm pumping.
Phase motion of accelerated electrons in vacuum laser acceleration
Authors: Hua J. F. , Lin Y. Z. , Tang Ch. X. , Ho Y. K. , Kong Q.
Published: January 2007

The phase stability in the capture and acceleration scenario (CAS) is studied and compared with that of conventional linear electron accelerators (CLEAs). For the CAS case, it has been found that a slow phase slippage occurs due to the difference between the electron velocity and the phase velocity of the longitudinal accelerating electric field. Thus, CAS electrons cannot remain in a fixed small phase region of the accelerating field to obtain a quasimonoenergy gain in contrast to the stability of phase oscillation in CLEAs. Also, the energy spread of the output electron beam for the CAS case cannot be kept as small as the CLEA because there is no good phase bunching phenomenon generated by phase oscillation.
Role of grain boundaries in ZnO nanowire field-effect transistors
Authors: Yoon Youngki , Lin Jenshan , Pearton Stephen J. , Guo Jing
Published: January 2007

ZnO nanowires have attracted strong interest for potential nanoelectronics, optoelectronics, and nanosensor applications. The role of grain boundaries (GBs) in ZnO nanowire transistors is examined by solving a two-dimensional Schrödinger equation in the nanowire cross section, coupled to a drift-diffusion equation along the nanowire. We show that a GB results in a potential barrier with the thickness determined by the gate insulator thickness and the height determined by the number of the trap states at the GB. The GB leads to a decrease of the source-drain current because the voltage drop at the GB reduces the electric field at other channel positions. The on current depends on the nanowire diameter nonmonotonically due to two competing mechanisms. Increasing the number of GBs in the channel decreases both the on current and off current. When the total number of GBs is small, its effect on the I-V characteristics can be phenomenologically viewed as an increase of the threshold voltage. When the total number of GBs is larger, it must be viewed as a combined effect of the increase of the threshold voltage and the decrease of the channel effective mobility.
Improved effective medium approach: Application to metal nanocomposites
Authors: Kochergin Vladimir , Zaporojtchenko Vladimir , Takele Haile , Faupel Franz , Föll Helmut
Published: January 2007

An improved effective medium approximation (EMA) is presented that accounts for higher order interactions between metal nanoparticles in metal-dielectric composite materials and compared to experimental results. The theoretical results of this formalism are applied to a composite material consisting of spherical gold nanoparticles randomly distributed in a dielectric matrix, which has been extensively characterized with respect to its structural and optical properties. The experimental results and theoretical predictions are compared and the results are discussed. It is shown that the modified theory expands the range to which EMA can be applied to a metal filling fraction of ∼20% at very little additional computational expenses. The improved theory also allows extracting more information from the optical characterization of the composite material such as the distribution of the interparticle distances in a composite.
High performance organic thin-film transistors with photopatterned gate dielectric
Authors: Lee Sun Hee , Choo Dong Joon , Han Seung Hoon , Kim Jun Hee , Son Young Rea , Jang Jin
Published: January 2007

The authors have fabricated high performance pentacene organic thin-film transistor (OTFT) using photopatternable poly(4-vinylphenol) gate dielectric on plastic substrate. The dielectric layer was composed of poly(vinylphenol), 1,2,4,5-tetraacetoxymethylbenzene, and 2,4-bis(trichloro methyl)-6-aryl-1,3,5-triazine. The 1,2,4,5-tetraacetoxymethylbenzene is a cross-linking material which is synthesized by a two-step reaction. The gate dielectric was patterned by spin coating and UV exposure. The OTFT with photopatterned gate dielectric exhibited a field-effect mobility of 1.23cm2∕Vs and a threshold voltage of −6.5V and an on/off current ratio of 107, so that the OTFT can be applied to make a high performance display.
Dynamic response of microcantilever-based sensors in a fluidic chamber
Authors: Decuzzi P. , Granaldi A. , Pascazio G.
Published: January 2007

The dynamic response of a microcantilever beam used as a transducer in a biomechanical sensor for molecule detection is analyzed. The cantilever motion is modeled using the classical Euler-Bernoulli beam theory coupled to the Reynolds equation of lubrication accounting for the hydrodynamic interactions. The beam is oscillated by an electrostatic harmonic force in close proximity to a rigid wall in an analysis chamber. It is shown that the dynamic response of the beam can be accurately predicted by a simple equivalent damped harmonic oscillator whose quality factor has been estimated as a function of the beam-wall gap. As the gap is reduced the quality factor is reduced and damping becomes more and more important. A transduction relationship between the frequency shift and the mass of molecules adherent on the beam is proposed which accounts for the beam-fluid-substrate interactions.
Magnetic presheath in a weakly turbulent multicomponent plasma
Authors: Stanojević Mladen , Duhovnik Jože , Jelić Nikola , Kuhn Siegbert
Published: January 2007

A fluid model of the magnetic presheath in a weakly turbulent multicomponent plasma consisting of electrons and several positive ion components is presented. Turbulent particle source terms in the continuity equations and turbulent momentum source terms in the momentum balance equations for the ion components are derived from basic principles [Plasma Phys. Controlled Fusion 47, 685 (2005)], i.e., by means of the ensemble averaging procedure from the statistical theory of plasma turbulence. Then the unknown correlations between the fluctuating quantities occurring in the turbulent source terms derived are replaced with phenomenological expressions based on analogy with classical transport. The remaining correlation terms in the momentum balance equations, which are responsible for explicit coupling of the equations for different ion components, reduce to the corresponding classical terms when the turbulent transport corrections are negligible (i.e., for “quiescent” plasmas). Under certain conditions regarding the nature of the boundary plasma turbulence, the analysis of the planar magnetic presheath performed in this study yields results for the ion component fluid velocities and particle flux densities at the magnetic presheath entrance that are directly applicable to the boundary conditions of multifluid plasma transport and turbulence codes. A fluid formulation of the Bohm criterion, valid for weakly turbulent multicomponent plasmas as treated in this study, is also derived.
Migration of holes: Numerical algorithms and implementation
Authors: Breidbach J. , Cederbaum L. S.
Published: January 2007

A hole created in a system, for instance by ionization, can migrate through the system solely driven by many-electron effects. The implementation of the theory of charge migration and the numerical algorithms used are described in detail. A description of the ab initio calculation of charge migration in realistic systems is presented for several examples and the underlying mechanisms of charge migration are identified and interpreted using theoretical models. In all cases studied the migration is found to be ultrafast.
Ag
In
Se
2
nanorods: A semiconducting material for saturable absorber
Authors: Elim Hendry I. , Ji Wei , Ng Meng-Tack , Vittal Jagadese J.
Published: January 2007

Ag In Se 2 nanorods (NRs) with a diameter of 15nm have been investigated for their nonlinear optical responses by using Z-scan and transient absorption techniques with femtosecond laser pulses of photon energy greater than the band gap. At excitation irradiance of 20GW∕cm2, AgInSe2 NRs reveal saturation in the nonlinear absorption and optical Kerr nonlinearity with a recovery time determined to be a few tens of picoseconds. Such large saturable absorption and Kerr nonlinearity exhibit a third-order susceptibility of 1.2×10−8esu and a figure of merit of 0.04esucms−1, making AgInSe2 NRs a promising candidate for saturable absorption devices.
Dielectric response of soft mode in ferroelectric SrTiO3
Authors: Han Jiaguang , Wan Fan , Zhu Zhiyuan , Zhang Weili
Published: January 2007

The authors report far-infrared dielectric properties of powder form ferroelectric SrTiO3. Terahertz time-domain spectroscopy (TDS) measurement reveals that the low-frequency dielectric response of SrTiO3 is a consequence of the lowest transverse optical (TO) soft mode TO1 at 2.70THz (90.0cm−1), which is directly verified by Raman spectroscopy. This result provides a better understanding of the relation of low-frequency dielectric function with the optical phonon soft mode for ferroelectric materials. Combining terahertz TDS with Raman spectra, the overall low-frequency optical phonon response of SrTiO3 is presented in an extended spectral range from 6.7to1000.0cm−1.
Investigation of drain current transient in BCB- and SiN-passivated Al0.25Ga0.75As∕In0.2Ga0.8As pseudomorphic high electron mobility transistors
Authors: Tan Chee Leong , Wang Hong , Radhakrishnan K.
Published: January 2007

The authors report on the drain current transient of Al0.25Ga0.75As∕In0.2Ga0.8As pseudomorphic high electron mobility transistors passivated by low-k benzocyclobutene (BCB). Compared to the more commonly used silicon nitride, BCB has a lower dielectric constant and loss tangent and is becoming popular for passivation. However, its effect on the device drain current transient has not been studied so far. In this work, the effectiveness of BCB as a passivation material was investigated in relation to the device drain current transient response. The surface trap model was also used to describe the transient behavior quantitatively.
Floral development in three species of Acacia (Leguminosae, Mimosoideae)
Authors: Gómez-Acevedo Sandra Luz , Magallón Susana , Rico-Arce Lourdes
Published: January 2007

The complete sequence of floral development in three species of Acacia was analysed. These species were sampled from each of the three Acacia subgenera. The species were Acacia berlandieri Benth. (subg. Aculeiferum), A. pennatula (Schltdl. & Cham.) Benth. (subg. Acacia) and A. saligna (Labill.) H.L.Wendl. (subg. Phyllodineae). The aim of the study was to determine whether the different subgenera share developmental pathways during flower formation. This study showed that development in the genus Acacia is heterogeneous. Each species studied showed different inception patterns of the calyx and androecium, whereas the inception patterns of the corolla and gynoecium were similar. These differences of inception in the calyx are not necessarily constant within each subgenus. Nevertheless, each subgenus was differentiated on the basis of inception patterns of the androecium, and other features such as the presence or absence of congenital or postgenital fusion in the calyx and corolla, and the time of differentiation of calyx and corolla tubes and the style.
Optimising storage and in vitro germination of Eucalyptus pollen
Authors: Horsley Tasmien N. , Johnson Steven D. , Stanger Terrence K.
Published: January 2007

The best sucrose solution for maximum in vitro germination of Eucalyptus pollen was investigated in order to evaluate pollen germination rate as an indicator of pollen viability. In vitro germination of both freshly collected and 1-year-old pollen (stored at 4°C) of Eucalyptus grandis, E. smithii, E. nitens, E. dunnii and E. macarthurii was carried out in 0, 10, 20, 30, 40 and 50% (w/v) sucrose solutions, either with (0.15 mg L–1) or without boric acid. Similar trends were obtained for both fresh and 1-year-old pollen, with all species responding most favourably to 30% (w/v) sucrose and 0.15 mg L–1 boric acid. When an optimal in vitro germination medium had been established, the viabilities (%germination) of E. smithii, E. nitens and E. grandis pollen, stored at room (25°C), fridge (4°C), freezer (–10°C) and liquid nitrogen (–196°C) temperatures, were compared. For all tested species, germination declined as storage temperature increased, and by 8 months, the highest survival was obtained with cryostored pollen.
Grazing and fire in two subalpine peatlands
Authors: McDougall Keith L.
Published: January 2007

The floristic composition and structure of peatland vegetation in adjoining subalpine catchments of the Bogong High Plains (north-eastern Victoria) were monitored between 1979 and 2006. Grazing by cattle had been excluded from one catchment since 1946, when it was fenced. Peatland vegetation in both catchments was partially burnt in a wildfire in 2003. Between 1979 and 1999, in the ungrazed peatland, the cover of Sphagnum cristatum Hampe and Baeckea gunniana Schauer increased and the cover of pools decreased, whereas in the grazed peatland the cover of B. gunniana and Epacris paludosa R.Br. decreased and the cover of Empodisma minus (Hook.f.) L.A.S.Johnson & D.F.Cutler increased. The cover of all recorded species decreased following a fire in 2003. Between 2004 and 2006, a significant increase in cover was detected in two of eight species measured in burnt areas. In burnt areas, the number of native species per quadrat increased in the grazed peatland and the numbers of exotic species per quadrat increased in both peatlands over that period. By 2006, the peatlands had largely recovered floristically from the 2003 fires but it is likely to be decades before the cover of S. cristatum and Richea continentis B.L.Burtt. reaches pre-fire levels. Control of several exotic species that established after the fire (especially Salix cinerea L. and Juncus spp.) may be required.
The Aryl hydrocarbon receptor is activated by modified low-density lipoprotein
Authors: McMillan Brian J. , Bradfield Christopher A.
Published: January 2007

Endogenous activation of the aryl hydrocarbon receptor (AHR) is required for normal vascular development. This biology led us to investigate the interplay between the AHR and vascular physiology by using an
in vitro
model of fluid shear stress. Using this system, we show that fluid flow induces a robust AHR-mediated increase in
CYP1
expression. Furthermore, we demonstrate that incubation with sheared bovine or human sera is sufficient for AHR activation, indicating that direct cellular exposure to shear stress is not required for this response. Fractionation of sera by size and density revealed the AHR-activating factor to be low-density lipoprotein (LDL). Purified LDL (0.1 mg/ml) from sheared sera induces a 6-fold increase in AHR-mediated signaling as compared with LDL purified from static sera. Similar results were obtained by exposing a purified fraction of LDL to fluid flow, suggesting that shear stress is capable of directly modifying LDL structure and/or function. In addition, we show that LDL can be converted to an AHR-activating species by conventional methods of lipoprotein modification, such as NaOCl oxidation. Finally, we demonstrate that an increased level of AHR-activating LDL is present in the sera of AHR null mice as compared with heterozygous littermates, suggesting a role for the
Ahr
locus in the physiological response to modified LDL
in vivo
. Overall, these data demonstrate a previously undescribed relationship between LDL modification and AHR biology and provide a potential explanation for the vascular abnormalities observed in AHR null mice.
T cell self-reactivity forms a cytokine milieu for spontaneous development of IL-17+ Th cells that cause autoimmune arthritis
Authors: Hirota Keiji , Hashimoto Motomu , Yoshitomi Hiroyuki , Tanaka Satoshi , Nomura Takashi , Yamaguchi Tomoyuki , Iwakura Yoichiro , Sakaguchi Noriko , Sakaguchi Shimon
Published: January 2007

This report shows that highly self-reactive T cells produced in mice as a result of genetically altered thymic T cell selection spontaneously differentiate into interleukin (IL)-17–secreting CD4+ helper T (Th) cells (Th17 cells), which mediate an autoimmune arthritis that clinically and immunologically resembles rheumatoid arthritis (RA). The thymus-produced self-reactive T cells, which become activated in the periphery via recognition of major histocompatibility complex/self-peptide complexes, stimulate antigen-presenting cells (APCs) to secrete IL-6. APC-derived IL-6, together with T cell–derived IL-6, drives naive self-reactive T cells to differentiate into arthritogenic Th17 cells. Deficiency of either IL-17 or IL-6 completely inhibits arthritis development, whereas interferon (IFN)-γ deficiency exacerbates it. The generation, differentiation, and persistence of arthritogenic Th17 cells per se are, however, insufficient for producing overt autoimmune arthritis. Yet overt disease is precipitated by further expansion and activation of autoimmune Th17 cells, for example, via IFN-γ deficiency, homeostatic proliferation, or stimulation of innate immunity by microbial products. Thus, a genetically determined T cell self-reactivity forms a cytokine milieu that facilitates preferential differentiation of self-reactive T cells into Th17 cells. Extrinsic or intrinsic stimuli further expand these cells, thereby triggering autoimmune disease. Intervention in these events at cellular and molecular levels is useful to treat and prevent autoimmune disease, in particular RA.
Structure model and small-angle scattering cross sections of latent ion tracks in dielectric solids
Authors: Eyal Yehuda , Abu Saleh Sameer
Published: January 2007

Knowledge of the morphology of ion damage trails, `latent ion tracks', typically a few nanometres wide and 10–125 µm long, created along wakes of swift heavy ions in dielectric solids, is a prerequisite for advancement of track applications in nanotechnology. Modeling the tracks as depleted columnar structures with soft to hard boundaries and cylindrical symmetry, the derivation of theoretical track small-angle X-ray scattering cross sections is reported. These quantities enable the determination of track structure parameters, specifically the track electron density function and its radial dispersion, from empirical scattering intensities. The derived expressions can be readily adopted for analysis of small-angle neutron scattering data.
Parametric Rietveld refinement
Authors: Stinton Graham W. , Evans John S. O.
Published: January 2007

In this paper the method of parametric Rietveld refinement is described, in which an ensemble of diffraction data collected as a function of time, temperature, pressure or any other variable are fitted to a single evolving structural model. Parametric refinement offers a number of potential benefits over independent or sequential analysis. It can lead to higher precision of refined parameters, offers the possibility of applying physically realistic models during data analysis, allows the refinement of `non-crystallographic' quantities such as temperature or rate constants directly from diffraction data, and can help avoid false minima.
High-resolution synchrotron radiation studies on natural and thermally annealed scleractinian coral biominerals
Authors: Stolarski J. , Przeniosło R. , Mazur M. , Brunelli M.
Published: January 2007

The structural phase transition from aragonite to calcite in biogenic samples extracted from the skeletons of selected scleractinian corals has been studied by synchrotron radiation diffraction. Biogenic aragonite samples were extracteden blocwithout pulverization from two ecologically different scleractinian taxa:Desmophyllum(deep-water, solitary and azooxanthellate) andFavia(shallow-water, colonial, zooxanthellate). It was found that natural (not pulverized) samples contribute to narrow Bragg peaks with Δd/dvalues as low as 1 × 10−3, which allows the exploitation of the high resolution of synchrotron radiation diffraction. A precise determination of the lattice parameters of biogenic scleractinian coral aragonite shows the same type of changes of thea,b,clattice parameter ratios as that reported for aragonite extracted from other invertebrates [Pokroy, Quintana, Caspi, Berner & Zolotoyabko (2004).Nat. Mater.3, 900–902]. It is believed that the crystal structure of biogenic samples is influenced by interactions with organic molecules that are initially present in the biomineralization hydrogel. The calcite phase obtained by annealing the coral samples has a considerably different unit-cell volume and lattice parameter ratioc/aas compared with reference geological calcite and annealed synthetic aragonite. The internal strain in the calcite structure obtained by thermal annealing of the biomineral samples is about two times larger than that found in the natural aragonite structure. This effect is observed despite slow heating and cooling of the sample.
New solutions to the problems of chain orientation and chain continuity in structure analysis of fibrous polymers. A reconsideration of the structure of polyisobutene
Authors: Immirzi Attilio , Alfano Davide , Tedesco Consiglia
Published: January 2007

Two points of general interest in structural refinement of polymers based on internal coordinates are discussed: the chain orientation and the chain continuity. Using a proprietary computer program, based on revised approaches to these questions, the structure of polyisobutene has been reconsidered, using new X-ray diffraction measurements (Fuji image plate) and performing a structure refinement based on internal coordinates. Three refinement schemes, with a decreasing number of degrees of freedom, have been considered, with the conclusion that the distortion from the 83regular helix, claimed by Tadokoro [(1979).Structure of Crystalline Polymers, p. 136. New York: Wiley-Interscience], is confirmed, though lower than supposed. The new procedures implemented for chain orientation and chain continuity work excellently.
Thermal properties of monoclinic crystal Er3+:Yb3+:Ca4YO(BO3)3
Authors: Ge W. W. , Zhang H. J. , Wang J. Y. , Jiang M. H. , Sun S. Q. , Ran D. G. , Xia H. R. , Boughton R. I.
Published: January 2007

A large Er3+–Yb3+co-doped yttrium calcium oxoborate [Er3+:Yb3+:Ca4YO(BO3)3, abbreviated as Er:Yb:YCOB] single crystal, with dimensions of 2.5 cm in diameter and 9.0 cm in length, has been grown along the crystallographicbaxis by the Czochralski method. X-ray powder diffraction results show that the as-grown Er:Yb:YCOB crystal belongs to the monoclinic system with space groupCm; the unit-cell constants area= 8.085,b= 16.048,c= 3.528 Å and β = 101.11°. The high crystalline quality of the as-grown single crystal was confirmed by high-resolution X-ray diffraction, which showed the full width at half-maximum of the rocking curves to be less than 20 arcseconds on the (060) and (\overline 201) diffraction planes. The measurement and calculation of the symmetrical second-rank tensor for the monoclinic crystal are described in detail in this paper. The principal coefficients of thermal expansion of the as-grown Er:Yb:YCOB crystal are αI= 11.95 × 10−6 K−1, αII= 9.20 × 10−6 K−1and αIII= 18.93 × 10−6 K−1over the temperature range 303.15–873.15 K. The specific heat of the crystal is 725.6 J kg−1 K−1at 328.15 K. The principal thermal conductivity parameters areKI= 2.882 W m−1 K−1,KII= 2.687 W m−1 K−1andKIII= 2.692 W m−1 K−1at 328.15 K.
Simulation of small-angle scattering curves by numerical Fourier transformation
Authors: Schmidt-Rohr Klaus
Published: January 2007

A simple numerical approach for calculating theq-dependence of the scattering intensity in small-angle X-ray or neutron scattering (SAXS/SANS) is discussed. For a user-defined scattering density on a lattice, the scattering intensityI(q) (qis the modulus of the scattering vector) is calculated by three-dimensional (or two-dimensional) numerical Fourier transformation and spherical summation inqspace, with a simple smoothing algorithm. An exact and simple correction for continuous rather than discrete (lattice-point) scattering density is described. Applications to relatively densely packed particles in solids (e.g.nanocomposites) are shown, where correlation effects make single-particle (pure form-factor) calculations invalid. The algorithm can be applied to particles of any shape that can be defined on the chosen cubic lattice and with any size distribution, while those features pose difficulties to a traditional treatment in terms of form and structure factors. For particles of identical but potentially complex shapes, numerical calculation of the form factor is described. Long parallel rods and platelets of various cross-section shapes are particularly convenient to treat, since the calculation is reduced to two dimensions. The method is used to demonstrate that the scattering intensity from `randomly' parallel-packed long cylinders is not described by simple 1/qand 1/q4power laws, but at cylinder volume fractions of more than ∼25% includes a correlation peak. The simulations highlight that the traditional evaluation of the peak position overestimates the cylinder thickness by a factor of ∼1.5. It is also shown that a mix of various relatively densely packed long boards can produceI(q) ≃ 1/q, usually observed for rod-shaped particles, without a correlation peak.
Resolution functions of time-of-flight small-angle neutron scattering instruments with rectangular apertures
Authors: Grabcev B.
Published: January 2007

Analytic forms are found for resolution functions of small-angle neutron scattering instruments. The expressions are developed as a function of momentum transfer (Q) rather than separately in terms of neutron wavelength (λ) and scattering angle (θ). Effects caused by the gravitational field as well as by quasi-elastic scattering are included. Explicit analytic forms for the transmission functions are proposed for both the incident and scattered beams, enabling careful analysis of any problem regarding small-angle scattering experiments. Due to the reciprocal mathematical relationship between λ, θ andQ, [λ, θ] space is employed to approach different aspects of the topic. Applications to time-of-flight instruments with rectangular apertures, including the choice of the most convenient instrumental parameters, the analysis of smearing effects and the data reduction toQspace, are presented.
Contrast variation in small-angle scattering experiments on polydisperse and superparamagnetic systems: basic functions approach
Authors: Avdeev Mikhail V.
Published: January 2007

The development of the basic functions approach [Stuhrmann (1995).Modern Aspects of Small-Angle Scattering, edited by H. Brumberger, pp. 221–254. Dordrecht: Kluwer Academic Publishers] for the contrast variation technique in small-angle scattering from systems of polydisperse and superparamagnetic non-interacting particles is presented. For polydisperse systems the modified contrast is introduced as the difference between the effective mean scattering length density (corresponding to the minimum of the scattering intensity as the function of the scattering length density of the solvent) and the density of the solvent. Then, the general expression for the scattering intensity is written in the classical way through the modified basic functions. It is shown that the shape scattering from the particle volume can be reliably obtained. Modifications of classical expressions describing changes in integral parameters of the scattering (intensity at zero angle, radius of gyration, Porod integral) with the contrast are analyzed. In comparison with the monodisperse case, the residual scattering in the minimum of intensity as a function of contrast (effective match point) in polydisperse systems makes it possible to treat the Guinier region of scattering curves around the effective match point quite precisely from the statistical viewpoint. However, limitations of such treatment exist, which are emphasized in the paper. In addition, the effect of magnetic scattering in small-angle neutron scattering from superparamagnetic nanoparticles is considered in the context of the basic functions approach. Conceptually, modifications of the integral parameters of the scattering in this case are similar to those obtained for polydisperse multicomponent particles. Various cases are considered, including monodisperse non-homogeneous and homogeneous magnetic particles, and polydisperse non-homogeneous and homogeneous magnetic particles. The developed approach is verified for two models representing the main types of magnetic fluids – systems of polydisperse superparamagnetic particles located in liquid carriers.
Improvement of data treatment in small-angle neutron scattering
Authors: Brûlet Annie , Lairez Didier , Lapp Alain , Cotton Jean-Pierre
Published: January 2007

Small-angle neutron scattering has been successfully used since the 1970s. As a general rule, methods to extract the useful signal from that received by the detector are well known and give good results. At the Laboratoire Léon Brillouin, for example, these methods have been employed for a long time. However, the data reduction software has been changed for the following reasons. Problems are encountered if the container of the sample gives a spurious signal or if the scattering angle is so large that its cosine cannot be approximated by 1. In the present paper, generalizations of formulas are made in order to account for these difficulties. The decrease of scattered intensity delivered by an incoherent sample that is often observed at large angles is shown to be only due to a geometrical effect. The consequent modifications of the relations used for the normalization of cells of position-sensitive detectors and for the absolute calibration are given. As for the inherent background of the sample, the contribution of density fluctuations is usually neglected. This contribution is formally given as a function of the contrast lengths and of the isothermal compressibility of the sample. This new result allows numerical evaluations of the different terms of the inherent sample background. Practical examples are given. Finally, several methods, developed at the Laboratoire Léon Brillouin, are given to determine the background properly. They are based on systematic measurements of transmissions and background levels of suitably prepared blank samples.
Comparison of time and frequency domain measures of RSA in ambulatory recordings
Authors: Goedhart Annebet D. , Van Der Sluis Sophie , Houtveen Jan H. , Willemsen Gonneke , De Geus Eco J.C.
Published: January 2007

The extent to which various measures of ambulatory respiratory sinus arrhythmia (RSA) capture the same information across conditions in different subjects remains unclear. In this study the root mean square of successive differences (RMSSD), peak valley RSA (pvRSA), and high frequency power (HF power) were assessed during ambulatory recording in 84 subjects, of which 64 were retested after about 3 years. We used covariance structure modeling to test the equality of the correlations among three RSA measures over two test days and three conditions (daytime sitting or walking and nighttime sleep) and in groups with low, medium, and high mean heart rate (HR), or low, medium, and high mean respiration rate (RR). Results showed that ambulatory RMSSD, pvRSA, and HF power are highly correlated and that their correlation is stable across time, ambulatory conditions, and a wide range of resting HR and RR values. RMSSD appears to be the most cost‐efficient measure of RSA.
Effects of protozoa on the antioxidant activity in the ruminal fluid and blood plasma of cattle
Authors: GAZI Masudur R. , YOKOTA Masato , TANAKA Yuichi , KANDA Shuhei , ITABASHI Hisao
Published: January 2007

The objective of this study was to investigate the antioxidant status in ruminal fluid and blood plasma among three faunated and two defaunated (protozoa‐free) cattle (average bodyweight of 225 kg), fed hay plus concentrate. The extra cellular antioxidant activity of the mixed protozoa and bacteria suspensions were also studied in vitro. The antioxidant activity was detected by means of the free radical scavenging ability. The activity (units/microbial nitrogen) of the protozoal suspension increased from 59 (0 h) to 318 (18 h), and decreased to 40 (24 h) during incubation. The activity of the bacterial suspension also increased from 111 (0 h) to 644 (18 h), and decreased to 533 (24 h). The antioxidant activity (units/mL, U/mL) in the ruminal fluid of faunated (ranging from 116 to 254) and defaunated (ranging from 66 to 110) cattle was increased after 2 h and decreased after 5 h of feeding, being significantly higher in the faunated cattle. The antioxidant activity of blood plasma (U/mL) ranged from 248 to 316 in the faunated and 121–170 in the defaunated cattle during 0–5 h after feeding, being significantly higher in the faunated cattle. Therefore, defaunation possibly causes a decrease in the antioxidant level in the ruminal fluid, and may impair the health and performance of ruminants through an oxidant–antioxidant imbalance.
Effects of cecectomy on digestion and retention time of digesta in rats
Authors: KUROSAWA Akira , IKEDA Shuhei , HAGIWARA Tomoko , SUKEMORI Seizi , KURIHARA Yoshio
Published: January 2007

The present experiment aimed to obtain basic knowledge of the role of the cecum in the digestion of protein, fiber and energy, and in the retention of digesta in rats. Twelve healthy male Sprague–Dawley strain rats were used. The experiment lasted for 8 weeks following preliminary feeding. Crude protein [CP], acid detergent fiber [ADF], and energy digestibilities were measured in weeks 1, 4, and 7 of the experiment, while the digesta retention time was measured in weeks 2, 5, and 8. At the end of the test, the colon capacity was measured after killing the rats with diethyl ether. The effects of the cecectomy were not recognized in bodyweight gain, even while the feed intake was high and the feed efficiency was low due to the cecectomy. However these effects were not recognized in the latter half of the test periods. The mean retention time of digesta for the cecectomized rats was about 2 h shorter than that for the control group of rats, while the retention time of digesta in week 8 increased compared to weeks 2 and 5. The digestibility of each substance was significantly lower following the cecectomy. The colon became swollen because of the cecectomy and this swollen colon made up for the capacity of the dissected cecum. It had been considered that the cecum does not play a role in the digestion of nutrition for growth, however, the present results showed two types of effects of cecectomy: one that disappears in accordance with time after surgery (i.e. feed intake and feed efficiency), and another that continues for a longer period (i.e. digestibility, retention time of digesta).
Roles of central histaminergic system in glucose metabolisms and food intake in sheep
Authors: KUROSE Yohei , TERASHIMA Yoshiaki
Published: January 2007

The neurotransmitter histamine is thought to be involved in the homeostatic regulation of energy balance. The present study was conducted to examine whether the central histaminergic system is involved in the regulation glucose metabolisms and food intake in ruminants. Thioperamide, a presynaptic H3‐receptor antagonist, was intracerebroventricularly infused at a rate of 68 μg/min for 3 h, beginning at 11.00 hours, into castrated Suffolk rams (48–55 kg bodyweight) accustomed to being fed alfalfa hay cubes (2% of body weight) at 12.00 hours. The food intake was measured every 60 min for 2 h after the commencement of feeding (12.00 hours). Blood samples were taken through a jugular vein catheter every 10 or 20 min during the experiment. Plasma glucose levels were significantly (P < 0.05) greater in the thioperamide‐treated group than in the control. The post‐prandial insulin increment was significantly (P < 0.05) greater in the thioperamide‐treated group than in the saline‐treated control. The food intake of the thioperamide‐treated group was significantly (P < 0.05) less than that of the control in the period from 60 to 120 min after feeding. In conclusion, the central histaminergic system is involved in the regulation of glucose metabolisms and food intake in ruminants.
Lived Experiences of Mothers Caring for Children With Thalassemia Major in Thailand
Authors: Prasomsuk Suksiri , Jetsrisuparp Arunee , Ratanasiri Thawalwong , Ratanasiri Amornrat
Published: January 2007

ISSUES AND PURPOSE.  Thalassemic patients must be given continuous treatment throughout their lives due to the physical and psychological effects of their disorder; their families also are impacted. This qualitative study explored the lived experiences of 15 mothers of children with thalassemia major by conducting semistructured interviews; the data were analyzed utilizing content analysis.

CONCLUSION.  Six themes were identified: lack of knowledge about thalassemia, psychosocial problems, concerns for the future, social support systems, financial difficulty, and the effectiveness of healthcare services.

PRACTICE IMPLICATIONS.  These findings suggest that a holistic, culturally sensitive nursing approach should be considered when caring for children with thalassemia.
Evaluation of foliar fungal endophyte incidence in field-grown transgenicBtwhite spruce trees
Authors: Stefani F.O.P. , Bérubé J.A.
Published: January 2007

A total of 770 transgenic Bt white spruce needles were collected and plated on potato dextrose agar to determine their foliar endophyte diversity. The ribosomal internal transcribed spacer regions for 310 foliar endophytes were amplified by polymerase chain reaction (PCR) and digested using CfoI and MspI, which created 21 restriction groups. Isolates from each restriction group were sequenced and compared with reference sequences in GenBank. Eighteen sequence groups were obtained, of which five were identified at the species level. The most common endophytic fungi identified by PCR-RFLP was Lophodermium piceae (incidence of 74.5%). The second and third most common ones were Hypoxylon fragiforme (3.63%) and Lophodermium nitens (3.18%). A statistical analysis performed on the most common endophyte groups showed no statistical difference in endophyte frequency or distribution between the control white spruce needles (nontransgenic) and saplings with constructs containing the reporter gene GUS or the Bt Cry1A(b) gene and kanamycin.
Isotopic constraints on the thermal history of the Wind River Range, Wyoming: implications for Archean metamorphism
Authors: Keane Stephen D , Hall Chris M , Essene Eric J , Cosca Michael A , DeWolf Charles P , Halliday Alex N
Published: January 2007

Precise U–Pb monazite and 40Ar/39Ar hornblende ages have been obtained from three locations in the high-grade Archean core of the Wind River Range, Wyoming. Monazites from metapelites in the Paradise Basin, Medina Mountain, and Crescent Lake have U–Pb ages of 2718 ± 1, 2633 ± 5, and 2657 ± 2 Ma, respectively. Hornblendes from amphibolites and granulites from the same locations yield plateau 40Ar/39Ar isotope ages of 2652 ± 11, 2572 ± 9, and 2527 ± 8 Ma, respectively, and are interpreted as cooling ages from the last thermal event. The three localities experienced similar peak pressure–temperature conditions. The timing of high-grade metamorphism in the Paradise Basin is older than the emplacement of large subjacent batholiths at 2.63–2.67 Ga. Calculated cooling rates based on monazite–hornblende pairs of 3.4 ± 1.0 °C/Ma for Paradise Basin, 3.8 ± 1.2 °C/Ma for Medina Mountain, and 1.7 ± 0.4 °C/Ma for Crescent Lake cannot be used to rule out reheating during subsequent pluton emplacement. The markedly slower cooling rate inferred for Crescent Lake may indicate early differential uplift or may demark another regional metamorphic event. The difference in 40Ar/39Ar ages between hornblende (2652 ± 11 Ma) and biotite (2637 ± 11 Ma) suggests a more rapid cooling rate, 11 °C/Ma, for Paradise Basin between 2.65 and 2.63 Ga, which may be related to the time of large-scale batholith emplacement elsewhere in the terrane. Combining new data with other ages in the Wind River Range reveals an extended metamorphic history, punctuated by thermal events over a time interval of at least 700 Ma.