bluuebunny/crossref_metadata_2025 huggingface dataset:
TRANSPIRATION, GROWTH AND LATEX PRODUCTION OF A HEVEA BRASILIENSIS STAND FACING DROUGHT IN NORTHEAST THAILAND: THE USE OF THE WaNuLCAS MODEL AS AN EXPLORATORY TOOL
Authors: BOITHIAS L. , DO F. C. , ISARANGKOOL NA AYUTTHAYA S. , JUNJITTAKARN J. , SILTECHO S. , HAMMECKER C.
Published: September 2011

In order to get the benefit of the growing world demand for natural rubber, Hevea brasiliensis is increasingly planted in drought-prone areas, such as in the southern part of northeast Thailand. Modelling can be a useful approach in identifying key points of improvement for rubber tree cultivation in such water-limited areas. The first objective of this study was to test the possibility of using the Water Nutrients and Light Capture in Agroforestry Systems (WaNuLCAS) model as an exploratory tool to simulate water use, growth and latex production in a pure stand on a daily basis. The second was to evaluate the relative accuracy of predictions with the current model version. Finally, the third aim of this study was to identify particular parameterisations that may be adapted to improve overall prediction quality. Model outputs were compared to measurements recorded in a mature rubber tree stand of RRIM 600 clones growing in the water-limited area of northeast Thailand. The period of analysis concerned seven months of full foliation, from May to November, including a severe drought spell. Whole-tree transpiration was estimated by xylem sap flow measurement from 11 trees. The results show that the model was able to simulate daily and seasonal change of soil water content, tree transpiration, girth increment and latex production within plausible ranges. However, under detailed scrutiny, the predictions show large inaccuracies compared to the observations: soil water content (determination coefficient (R2) = 0.461, relative root mean square error (RMSErel) = 35%), tree transpiration (R2 = 0.104, RMSErel = 94%), tree girth increment (R2 = 0.916, RMSErel = 208%) and latex production (R2 = 0.423, RMSErel = 169%). As soil water content was overestimated during the driest periods, no water stress was predicted and transpiration, growth and latex production were logically overestimated during such periods. However, tree transpiration was also largely overestimated in conditions of non-limiting soil water availability with high evaporative demand. Hence, two key points of parameterisation and improvement are identified for better simulation in our conditions: the soil water balance and particularly the ratio between water infiltration and run-off, and the regulation of transpiration under high evaporative demand. In conclusion, the WaNuLCAS model is usable as an exploratory model to simulate water use, growth and production for a pure rubber tree stand. However, in our conditions of much degraded soil and high evaporative demand, the modules of soil water balance and tree transpiration require particular parameterisations and improvement.
Empirical versus exact numerical quasilinear analysis of electromagnetic instabilities driven by temperature anisotropy
Authors: YOON PETER H. , SEOUGH JUNG JOON , KIM KHAN HYUK , LEE DONG HUN
Published: September 2011

In the present paper, quasilinear development of anisotropy-driven electromagnetic instabilities is computed on the basis of recently formulated empirical wave dispersion relation and compared against exact numerical calculation based upon transcendental plasma dispersion function and exact numerical roots. Upon comparison with the exact method it is demonstrated that the empirical model provides reasonable results. The present findings may be relevant to space physical application, as the present paper provides a useful short-cut research method for self-consistent analysis of temporal development of anisotropy-driven instabilities.
Improving nutrition in home child care: are food costs a barrier?
Authors: Monsivais Pablo , Johnson Donna B
Published: September 2011

Objective

Child-care providers have a key role to play in promoting child nutrition, but the higher cost of nutritious foods may pose a barrier. The present study tested the hypothesis that higher nutritional quality of foods served was associated with higher food expenditures in child care homes participating in the Child and Adult Care Food Program (CACFP).

Design

In this cross-sectional study, nutritional quality of foods served to children and food expenditures were analysed based on 5 d menus and food shopping receipts. Nutritional quality was based on servings of whole grains, fresh whole fruits and vegetables, energy density (kJ/g) and mean nutrient adequacy (mean percentage of dietary reference intake) for seven nutrients of concern for child health. Food expenditures were calculated by linking receipt and menu data. Associations between food expenditures and menu quality were examined using bivariate statistics and multiple linear regression models.

Setting

USA in 2008–2009.

Subjects

Sixty child-care providers participating in CACFP in King County, Washington State.

Results

In bivariate analyses, higher daily food expenditures were associated with higher total food energy and higher nutritional quality of menus. Controlling for energy and other covariates, higher food expenditures were strongly and positively associated with number of portions of whole grains and fresh produce served (P= 0·001 and 0·005, respectively), with lower energy density and with higher mean nutrient adequacy of menus overall (P= 0·003 and 0·032, respectively).

Conclusions

The results indicate that improving the nutritional quality of foods in child care may require higher food spending.
Novel lineages of Prochlorococcus and Synechococcus in the global oceans
Authors: Huang Sijun , Wilhelm Steven W , Harvey H Rodger , Taylor Karen , Jiao Nianzhi , Chen Feng
Published: September 2011

Picocyanobacteria represented by Prochlorococcus and Synechococcus have an important role in oceanic carbon fixation and nutrient cycling. In this study, we compared the community composition of picocyanobacteria from diverse marine ecosystems ranging from estuary to open oceans, tropical to polar oceans and surface to deep water, based on the sequences of 16S-23S rRNA internal transcribed spacer (ITS). A total of 1339 ITS sequences recovered from 20 samples unveiled diverse and several previously unknown clades of Prochlorococcus and Synechococcus. Six high-light (HL)-adapted Prochlorococcus clades were identified, among which clade HLVI had not been described previously. Prochlorococcus clades HLIII, HLIV and HLV, detected in the Equatorial Pacific samples, could be related to the HNLC clades recently found in the high-nutrient, low-chlorophyll (HNLC), iron-depleted tropical oceans. At least four novel Synechococcus clades (out of six clades in total) in subcluster 5.3 were found in subtropical open oceans and the South China Sea. A niche partitioning with depth was observed in the Synechococcus subcluster 5.3. Members of Synechococcus subcluster 5.2 were dominant in the high-latitude waters (northern Bering Sea and Chukchi Sea), suggesting a possible cold-adaptation of some marine Synechococcus in this subcluster. A distinct shift of the picocyanobacterial community was observed from the Bering Sea to the Chukchi Sea, which reflected the change of water temperature. Our study demonstrates that oceanic systems contain a large pool of diverse picocyanobacteria, and further suggest that new genotypes or ecotypes of picocyanobacteria will continue to emerge, as microbial consortia are explored with advanced sequencing technology.
Shifts in bacterial communities of two caribbean reef-building coral species affected by white plague disease
Authors: Cárdenas Anny , Rodriguez-R Luis M , Pizarro Valeria , Cadavid Luis F , Arévalo-Ferro Catalina
Published: September 2011

Coral reefs are deteriorating at an alarming rate mainly as a consequence of the emergence of coral diseases. The white plague disease (WPD) is the most prevalent coral disease in the southwestern Caribbean, affecting dozens of coral species. However, the identification of a single causal agent has proved problematic. This suggests more complex etiological scenarios involving alterations in the dynamic interaction between environmental factors, the coral immune system and the symbiotic microbial communities. Here we compare the microbiome of healthy and WPD-affected corals from the two reef-building species Diploria strigosa and Siderastrea siderea collected at the Tayrona National Park in the Caribbean of Colombia. Microbiomes were analyzed by combining culture-dependent methods and pyrosequencing of 16S ribosomal DNA (rDNA) V5-V6 hypervariable regions. A total of 20 410 classifiable 16S rDNA sequences reads were obtained including all samples. No significant differences in operational taxonomic unit diversity were found between healthy and affected tissues; however, a significant increase of Alphaproteobacteria and a concomitant decrease in the Beta- and Gammaproteobacteria was observed in WPD-affected corals of both species. Significant shifts were also observed in the orders Rhizobiales, Caulobacteriales, Burkholderiales, Rhodobacterales, Aleteromonadales and Xanthomonadales, although they were not consistent between the two coral species. These shifts in the microbiome structure of WPD-affected corals suggest a loss of community-mediated growth control mechanisms on bacterial populations specific for each holobiont system.
Incidental Physical Activity and Sedentary Behavior Are Not Associated With Abdominal Adipose Tissue in Inactive Adults
Authors: McGuire K. Ashlee , Ross Robert
Published: September 2011

The aim was to determine the association between objectively measured incidental physical activity (IPA) (i.e.,nonpurposeful activity accrued through activities of daily living) and sedentary behavior (SED) with abdominal obesity in a sample of inactive men and women. Participants were inactive, abdominally obese men (n = 42; waist circumference (WC) ≥102 cm) and women (n = 84; WC ≥88 cm) recruited from Kingston, Canada. Physical activity and SED were determined by accelerometry over 7 days and summarized as IPA (accelerometer counts per min (cpm) >100), light physical activity (LPA; cpm 100‐1951), sporadic moderate‐to‐vigorous physical activity (MVPA; cpm ≥1,952, accumulated in bouts <10 consecutive minutes) and SED (cpm <100). Magnetic resonance imaging was used to acquire measures of abdominal obesity, visceral adipose tissue (VAT), and subcutaneous adipose tissue (ASAT). Participants spent on average 310.2 ± 102.6 min/d in IPA and 627.8 ± 86.9 min/d in SED. Neither IPA nor SED was associated with any measure of abdominal obesity (P > 0.1). Similarly, LPA was not a significant predictor of abdominal obesity whereas sporadic MVPA was negatively associated with VAT (P < 0.05) after control for age and sex. In this study, neither IPA nor SED was associated with abdominal obesity among inactive men and women.
Impaired Insulin‐Mediated Antilipolysis and Lactate Release in Adipose Tissue of Upper‐Body Obese Women
Authors: Nellemann Birgitte , Gormsen Lars C. , Sørensen Lars P. , Christiansen Jens S. , Nielsen Søren
Published: September 2011

Upper‐body/visceral obesity is associated with abnormalities of free fatty acid (FFA) metabolism and greater risk of developing type 2 diabetes compared with lower‐body obesity. In lean subjects lipolysis is readily suppressed by insulin; however, metabolic inflexibility with respect to antilipolysis is a frequent finding in obesity, partly determined by body composition. This study investigates effects of insulin on regional adipose tissue lipolysis and lactate levels in upper‐body overweight/obese (UBO), lower‐body overweight/obese (LBO), and lean women. The microdialysis technique was used to assess adipose tissue glycerol and lactate concentrations in abdominal and femoral fat during a 5‐h basal period and a 2‐h hyperinsulinemic euglycemic clamp. The main findings were that the antilipolytic effect of insulin was attenuated in abdominal fat of UBO (glycerol reduction, abd (%): UBO 40.4 (−14 to 66), LBO 46.0 (−8 to 66), lean 66.2 (2–78), ANOVA, P < 0.05), and in femoral fat in both obese groups (glycerol reduction, fem (%): UBO 44.4 (35–67), LBO 44.4 (0–63), lean 65.0 (43–79), ANOVA, P < 0.05). Further, abdominal fat insulin‐mediated increase in lactate concentration was greater in lean women compared with UBO women (lactate increase, abd (%): UBO −6.1 (−37.1 to 57.4), LBO 16.5 (−32.2 to 112.5), lean 51.4 (−45.7 to 162.9), P < 0.05), whereas no differences were found between groups in femoral fat (lactate increase, fem (%), UBO −12.9 (−43 to 24), LBO 12.7 (−30.7 to 92), lean 27.6 (−9.5 to 123.8), not significant). Respiratory exchange ratio (RER) increased significantly and similarly in all groups. So, UBO women were metabolically inflexible with respect to insulins antilipolytic and lactate increasing effects in abdominal adipose tissue. These phenomena are probably both consequences of insulin resistance of adipose tissue.
Urinary F2‐Isoprostanes, Obesity, and Weight Gain in the IRAS Cohort
Authors: Il'yasova Dora , Wang Frances , Spasojevic Ivan , Base Karel , D'Agostino Ralph B. , Wagenknecht Lynne E.
Published: September 2011

Obesity has been associated with increased F2‐isoprostane (F2‐IsoP) levels cross‐sectionally. However, the prospective association may be inverse, based on our earlier finding that elevated urinary F2‐IsoP levels predict lower risk of diabetes. This earlier finding led us to hypothesize that urinary F2‐IsoPs reflect the intensity of oxidative metabolism and as such predict lower risk of both diabetes and weight gain. We examined cross‐sectional relationships with obesity and prospective relationships with weight gain using the data from 299 participants of the Insulin Resistance Atherosclerosis Study (IRAS), all of whom were free of diabetes at baseline. Four urinary F2‐IsoPs were assayed in stored baseline urine samples using liquid chromatography with tandem mass spectrometry: iPF(2α)‐III, 2,3‐dinor‐iPF(2α)‐III, iPF(2α)‐VI, and 8,12‐iso‐iPF(2α)‐VI (F2‐IsoP 1–4, respectively). Baseline F2‐IsoPs were positively associated with baseline measures of obesity; the strongest associations were found with two F2‐IsoPs: odds ratios (95% confidence intervals) for overall and abdominal obesity were 1.74 (1.26–2.40) and 1.63 (1.18–2.24) for F2‐IsoP2 and 1.47 (1.12–1.94) and 1.64 (1.22–2.20) for F2‐IsoP4. F2‐IsoP2 showed the strongest and significant inverse association with weight gain during the 5‐year follow‐up period: increase in F2‐IsoP2 equal to 1 s.d. was associated with 0.90 kg lower weight gain (P = 0.02) and the odds ratios for relative (≥5%) and absolute (≥5 kg) weight gain were 0.67 (0.47–0.96) and 0.57 (0.37–0.87), respectively. The other three F2‐IsoPs were consistently inversely associated with weight gain, although not significantly, suggesting that different F2‐IsoPs vary in their ability to detect the association with weight gain.
Cross‐Sectional Comparisons of BMI and Waist Circumference in British Children: Mixed Public Health Messages
Authors: Griffiths Claire , Gately Paul , Marchant Paul R. , Cooke Carlton B.
Published: September 2011

Research suggests that there has been a leveling off in obesity prevalence occurring in the child population. However, a concern with the evidence base is that all of the studies have relied upon the use of BMI. The purpose of this study was to compare waist circumference (WC), BMI, and waist‐to‐height ratio (WHtR) data in three different sample of children (total number: 14,697) typically aged 11–12 years. Obesity prevalence defined by BMI did not change significantly between measurement years (2005 boys 20.6%, girls 18.0%; 2006 boys 19.3%, girls 17.3%; 2007 boys 19.8%, girls 16.4%). Obesity prevalence defined by WC was considerably higher especially, in girls (2005 boys 26.3%, girls 35.6%; 2006 boys 20.3%, girls 28.2%; 2007 boys 22.1%, girls 30.1%). The prevalence of children defined as “at risk” according to WHtR (2005 boys 23.3%, girls 21.1%; 2006 boys 16.7%, girls 15.6%; 2007 boys 17.6%, girls 17.2%) was found to be between obesity prevalence, estimated using BMI and WC. This data are the most up to date collection that includes BMI and WC in three large samples of children and clearly demonstrates inconsistencies between different measurements based on current classification systems. There is a need to understand the relationship between BMI and WC, with growth and health risk to establish a consistent public health message that is easily understood by the public.
Glutathione Depletion Prevents Diet‐Induced Obesity and Enhances Insulin Sensitivity
Authors: Findeisen Hannes M. , Gizard Florence , Zhao Yue , Qing Hua , Jones Karrie L. , Cohn Dianne , Heywood Elizabeth B. , Bruemmer Dennis
Published: September 2011

Excessive accumulation of reactive oxygen species (ROS) in adipose tissue has been implicated in the development of insulin resistance and type 2 diabetes. However, emerging evidence suggests a physiologic role of ROS in cellular signaling and insulin sensitivity. In this study, we demonstrate that pharmacologic depletion of the antioxidant glutathione in mice prevents diet‐induced obesity, increases energy expenditure and locomotor activity, and enhances insulin sensitivity. These observations support a beneficial role of ROS in glucose homeostasis and warrant further research to define the regulation of metabolism and energy balance by ROS.
Band gap and electronic properties of wurtzite-structure ZnO co-doped with IIA and IIIA
Authors: Han T. , Meng F. Y. , Zhang S. , Cheng X. M. , Oh J. I.
Published: September 2011

We report the bandgap and electronic properties of wurtzite ZnO doped with elements IIA or/and IIIA, investigated using both theoretical and experimental methods. With wurtzite ZnO co-doped with B and Mg (denoted as ZnO:[B,Mg]) grown via metalorganic chemical vapor deposition, we have observed that both the bandgap and the conductivity can be widely tunable with the doping levels. From first-principles calculations of wurtzite ZnO:Mg, we show that IIA doping elements have a great impact on the widening of the bandgap. Also, from a newly developed calculation method for investigating the electronic properties of wurtzite ZnO:Al, we have found that IIIA doping elements play an important role in tailoring the conductivity.
Interesting features of nonlinear shock equations in dissipative pair-ion-electron plasmas
Authors: Masood W. , Rizvi H.
Published: September 2011

Two dimensional nonlinear electrostatic waves are studied in unmagnetized, dissipative pair-ion-electron plasmas in the presence of weak transverse perturbation. The dissipation in the system is taken into account by incorporating the kinematic viscosity of both positive and negative ions. In the linear case, a biquadratic dispersion relation is obtained, which yields the fast and slow modes in a pair-ion-electron plasma. It is shown that the limiting cases of electron-ion and pair-ion can be retrieved from the general biquadratic dispersion relation, and the differences in the characters of the waves propagating in both the cases are also highlighted. Using the small amplitude approximation method, the nonlinear Kadomtsev Petviashvili Burgers as well as Burgers-Kadomtsev Petviashvili equations are derived and their applicability for pair-ion-electron plasma is explained in detail. The present study may have relevance to understand the formation of two dimensional electrostatic shocks in laboratory produced pair-ion-electron plasmas.
Admittance electrical model of polyfluorene based organic light emitting diodes
Authors: Petrosino Mario , Rubino Alfredo
Published: September 2011

In order to obtain an AC electrical model of polyfluorene-PEDOT poly(3,4-ethylenedioxythiophene) based organic light emitting diodes, different devices have been realized using three PEDOT dispersions. Static current-voltage characteristics have revealed exponential like transport in all the samples and the bias has shown no dependence on admittance spectra. An electrical model is proposed and the estimated capacitance has been analyzed in terms of polyfluorene bulk intra-gap state distribution obtaining a state density of about 1016 eV−1 cm−3. The hypothesis of a space charge involving completely the polyfluorene layer has been discussed.
Bond energy analysis revisited and designed toward a rigorous methodology
Authors: Nakai Hiromi , Ohashi Hideaki , Imamura Yutaka , Kikuchi Yasuaki
Published: September 2011

The present study theoretically revisits and numerically assesses two-body energy decomposition schemes including a newly proposed one. The new decomposition scheme is designed to make the equilibrium bond distance equivalent with the minimum point of bond energies. Although the other decomposition schemes generally predict the wrong order of the C–C bond strengths of C2H2, C2H4, and C2H6, the new decomposition scheme is capable of reproducing the C–C bond strengths. Numerical assessment on a training set of molecules demonstrates that the present scheme exhibits a stronger correlation with bond dissociation energies than the other decomposition schemes do, which suggests that the new decomposition scheme is a reliable and powerful analysis methodology.
Invited Article: Millimeter-wave bolometer array receiver for the Atacama pathfinder experiment Sunyaev-Zel'dovich (APEX-SZ) instrument
Authors: Schwan D. , Ade P. A. R. , Basu K. , Bender A. N. , Bertoldi F. , Cho H.-M. , Chon G. , Clarke John , Dobbs M. , Ferrusca D. , Güsten R. , Halverson N. W. , Holzapfel W. L. , Horellou C. , Johansson D. , Johnson B. R. , Kennedy J. , Kermish Z. , Kneissl R. , Lanting T. , Lee A. T. , Lueker M. , Mehl J. , Menten K. M. , Muders D. , Pacaud F. , Plagge T. , Reichardt C. L. , Richards P. L. , Schaaf R. , Schilke P. , Sommer M. W. , Spieler H. , Tucker C. , Weiss A. , Westbrook B. , Zahn O.
Published: September 2011

The Atacama pathfinder experiment Sunyaev-Zel'dovich (APEX-SZ) instrument is a millimeter-wave cryogenic receiver designed to observe galaxy clusters via the Sunyaev-Zel'dovich effect from the 12 m APEX telescope on the Atacama plateau in Chile. The receiver contains a focal plane of 280 superconducting transition-edge sensor (TES) bolometers instrumented with a frequency-domain multiplexed readout system. The bolometers are cooled to 280 mK via a three-stage helium sorption refrigerator and a mechanical pulse-tube cooler. Three warm mirrors, two 4 K lenses, and a horn array couple the TES bolometers to the telescope. APEX-SZ observes in a single frequency band at 150 GHz with 1′ angular resolution and a 22′ field-of-view, all well suited for cluster mapping. The APEX-SZ receiver has played a key role in the introduction of several new technologies including TES bolometers, the frequency-domain multiplexed readout, and the use of a pulse-tube cooler with bolometers. As a result of these new technologies, the instrument has a higher instantaneous sensitivity and covers a larger field-of-view than earlier generations of Sunyaev-Zel'dovich instruments. The TES bolometers have a median sensitivity of 890 \documentclass[12pt]{minimal}\begin{document}$\mu {\rm K}_{\rm CMB}\sqrt{s}$\end{document}μK CMB s (NEy of 3.5 × 10−4 \documentclass[12pt]{minimal}\begin{document}$\sqrt{s}$\end{document}s). We have also demonstrated upgraded detectors with improved sensitivity of 530 \documentclass[12pt]{minimal}\begin{document}$\mu {\rm K}_{\rm CMB}\sqrt{s}$\end{document}μK CMB s (NEy of 2.2 × 10−4 \documentclass[12pt]{minimal}\begin{document}$\sqrt{s}$\end{document}s). Since its commissioning in April 2007, APEX-SZ has been used to map 48 clusters. We describe the design of the receiver and its performance when installed on the APEX telescope.
Discrete spectra for confined and unconfined −a/r + br2 potentials in d-dimensions
Authors: Hall Richard L. , Saad Nasser , Sen K. D.
Published: September 2011

Exact solutions to the d-dimensional Schrödinger equation, d ⩾ 2, for Coulomb plus harmonic oscillator potentials V(r) = −a/r + br2, b > 0, and a ≠ 0 are obtained. The potential V(r) is considered both in all space, and under the condition of spherical confinement inside an impenetrable spherical box of radius R. With the aid of the asymptotic iteration method, the exact analytic solutions under certain constraints, and general approximate solutions, are obtained. These exhibit the parametric dependence of the eigenenergies on a, b, and R. The wave functions have the simple form of a product of a power function, an exponential function, and a polynomial. Polynomial solutions are found for differential equations of the form py″ + qy′ − ry = 0, where p, q, and r are given polynomials with degrees 4, 3, and 2, respectively.
Hydrodynamic dispersion in open cell polymer foam
Authors: Brosten Tyler R. , Codd Sarah L. , Maier Robert S. , Seymour Joseph D.
Published: September 2011

Nuclear magnetic resonance experiments and pore-scale lattice-Boltzmann simulation in conjunction with random-walk particle-tracking are used to probe molecular displacement statistics over a range of time and lengths within several open-cell polymer foams. Short-time molecular displacement dynamics of a flowing liquid within these structures are shown to reveal a well-defined characteristic transport length scale. The non-equilibrium statistical mechanics theory of dispersion is used to interpret the unique displacement dynamics. Scaling of data from experiment, simulation, and the non-equilibrium statistical mechanics model by the transport length scale collapses the dynamics to dimensionless scaling. Asymptotic dispersion dynamics from NMR experiment are presented as function of Peclet number defined using the transport length scale.
Four-wave mixing in InGaAs/AlAsSb intersubband transition optical waveguides
Authors: Kuwatsuka H. , Akimoto R. , Ogasawara T. , Gozu S. , Mozume T. , Hasama T. , Ishikawa H.
Published: September 2011

Four-wave mixing (FWM) in an InxGa1-xAs/AlAsySb1-y intersubband transition (ISBT) optical waveguide operating in the 1.55-μm wavelength region is discussed. The third-order optical nonlinear susceptibilities of InxGa1-xAs/AlAsySb1-y multiple quantum wells (MQWs) are estimated theoretically. ISBT excitation causes large third-order optical nonlinearity. χ(3) values of more than 1 × 1016 m2/V2 are obtained. The propagation of interacting waves for FWM in InxGa1-xAs/AlAsySb1-y ISBT optical waveguides is discussed. The interaction length is limited not only by phase matching but also by ISBT absorption. Sufficiently high FWM conversion efficiencies were obtained theoretically and experimentally for realizing coherent wavelength convertors. FWM in an InxGa1-xAs/AlAsySb1-y ISBT waveguide is a promising method for realizing compact and high-efficiency coherent wavelength conversion.
A symmetric approach to the massive nonlinear sigma model
Authors: Ferrari Ruggero
Published: September 2011

In the present paper we extend the procedure of divergences subtraction to the massive case, previously introduced for the massless nonlinear sigma model (D = 4). Perturbative expansion in the number of loops is successfully constructed. The resulting theory depends on the spontaneous symmetry breaking parameter v, on the mass m, and on the radiative correction parameter Λ. Fermions are not considered in the present work. SU(2)⊗SU(2) is the group used.
Ultra-low noise single-photon detector based on Si avalanche photodiode
Authors: Kim Yong-Su , Jeong Youn-Chang , Sauge Sebastien , Makarov Vadim , Kim Yoon-Ho
Published: September 2011

We report operation and characterization of a lab-assembled single-photon detector based on commercial silicon avalanche photodiodes (PerkinElmer C30902SH, C30921SH). Dark count rate as low as 5 Hz was achieved by cooling the photodiodes down to \documentclass[12pt]{minimal}\begin{document}$-80\,\mathrm{\protect \mathrm{\mathrm{^{\circ }}\mathrm{\mathrm{C}}}}$\end{document}−80°C. While afterpulsing increased as the photodiode temperature was decreased, total afterpulse probability did not become significant due to detector's relatively long deadtime in a passively-quenched scheme. We measured photon detection efficiency >50% at 806 nm.
Synchronization of period-doubling oscillations in vascular coupled nephrons
Authors: Laugesen J. L. , Mosekilde E. , Holstein-Rathlou N.-H.
Published: September 2011

The mechanisms by which the individual functional unit (nephron) of the kidney regulates the incoming blood flow give rise to a number of nonlinear dynamic phenomena, including period-doubling bifurcations and intra-nephron synchronization between two different oscillatory modes. Interaction between the nephrons produces complicated and time-dependent inter-nephron synchronization patterns. In order to understand the processes by which a pair of vascular coupled nephrons synchronize, the paper presents a detailed analysis of the bifurcations that occur at the threshold of synchronization. We show that, besides infinite cascades of saddle-node bifurcations, these transitions involve mutually connected cascades of torus and homoclinic bifurcations. To illustrate the broader range of occurrence of this bifurcation structure for coupled period-doubling systems, we show that a similar structure arises in a system of two coupled, non-identical Rössler oscillators.
Dielectric tunability transition in Ba0.6Sr0.4TiO3-based capacitors
Authors: Qiu Jie , Liu Guozhen , Sakai Joe , Gervais François , Wolfman Jérôme
Published: September 2011

Dielectric properties of Au/Ba0.6Sr0.4TiO3/La1.1Sr0.9NiO4 (Au/BST/LSNO) thin film capacitors were investigated versus excitation frequency and dc bias voltage. At low frequencies, Au/BST/LSNO capacitors exhibited a usual positive tunability [i.e., C(0V) > C(V)], while an unexpected negative tunable behavior appeared at higher frequencies. On the basis of the dielectric tunable theory and equivalent electrical circuits, a model describing the dielectric tunability of Au/BST/LSNO capacitors is proposed. The good agreement between fitted and experimental results shows that the resistance of LSNO bottom electrode in the Au/BST/LSNO capacitors plays an important role in the dielectric tunability transition from positive to negative with frequency.
Defect distributions in thin film solar cells deduced from admittance measurements under different bias voltages
Authors: Decock Koen , Khelifi Samira , Buecheler Stephan , Pianezzi Fabian , Tiwari Ayodhya N. , Burgelman Marc
Published: September 2011

The voltage dependence of the derivative of the capacitance to (the logarithm of) the measurement frequency is investigated. Relations describing this dependence are derived for the influence of carrier freeze out, of a defect distribution, and of a back contact barrier. The validity of these relations is investigated with numerical simulations.Considering the extraction of the defect density from capacitance–frequency measurements, the extension of existing formulas to different bias voltages leads to an improved accuracy and the possibility to investigate spatial non-uniformities while preserving a direct link between the defect level energy and the apparent defect density. This is illustrated with voltage dependent admittance measurements of thin film Cu(In,Ga)Se2-based solar cell devices.
Hydrogen quantum effects in hydride LaNi5H7
Authors: Kaneko Tomoaki , Tezuka Akinori , Ogawa Hiroshi , Ikeshoji Tamio
Published: September 2011

Energy eigenvalues and wave functions of hydrogen atoms in hydride LaNi5H7 are calculated. First-principles electronic structure calculations are employed to obtain the three-dimensional potential energy structure of each hydrogen site. These quantum effects are not negligibly small in evaluation of enthalpy of formation, an important property of hydrogen storage. Including the temperature effect from hydrogen gas, experimental values are well reproduced. The excitation probability of inelastic neutron scattering is also calculated using the wave functions obtained.
Fluorescence enhancement of dye-doped liquid crystal by dye-induced alignment effect
Authors: Shim Taekyu , Kim Sunghyun , Kim Doseok , Oh-e Masahito
Published: September 2011

We investigated fluorescence from hemicyanine dye molecules in a liquid crystal (4,4′-n-pentylcyanobiphenyl) (5CB) medium at different temperatures. The fluorescence decay lifetime decreased monotonically irrespective of the thermodynamic phases of the host medium as the temperature was increased. This behavior is due to an intramolecular motion of the dye promoted with the decrease in the viscosity of the medium facilitating a nonradiative decay of the excited dye molecules. By contrast, fluorescence intensity from the dyes in the nematic phase was about 3 times stronger than that in the crystalline or isotropic phase. This fluorescence enhancement in the nematic phase was found to be due to an anisotropic alignment of the dye molecules following the anisotropic alignment of the host liquid crystal medium along the pump-beam polarization direction. This light-induced liquid crystal molecular alignment was markedly enhanced by the guest dyes preferentially excited along the pump-beam polarization direction. The orientational order parameter of the dyes in the liquid-crystalline phase deduced from fluorescence anisotropy measurement was similar to the known order parameter of the liquid crystalline 5CB.
Comparison of structural and electric properties of PbZr0.2Ti0.8O3 and CoFe2O4/PbZr0.2Ti0.8O3 films on (100)LaAlO3
Authors: Zhang X. D. , Dho Joonghoe , Park Sungmin , Kwon Hyosang , Hwang Jihwan , Park Gwangseo , Kwon Daeyoung , Kim Bongju , Jin Yeryeong , Kim Bog. G. , Karpinsky D. , Kholkin A. L.
Published: September 2011

In this work, we investigated structural, electrical, and magnetic properties of ferroelectric PbZr0.2Ti0.8O3 (PZT) and ferrimagnetic/ferroelectric [CoFe2O4(CFO)/PZT] bilayers grown on (100)LaAlO3 (LAO) substrates supplied with bottom 50 nm thick LaNiO3 electrodes. Interestingly, structural and electrical properties of the PZT layer exhibited remarkable changes after the top-layer CFO deposition. X-ray diffraction data suggested that both the c- and a-domains exist in the PZT layer and the tetragonality of the PZT decreases upon the top-layer deposition. A variation in the electrical properties of the PZT layer upon the CFO deposition was investigated by polarization versus voltage (P-V), capacitance versus voltage (C-V), and capacitance versus frequency (C-f) measurements. The CFO deposition induced a slight decrease of the remnant polarization and more symmetric behavior of P-V loops as well as led to the improvement of fatigue behavior. The tentative origin of enhanced fatigue endurance is discussed based on the measurement results. These results were corroborated by local piezoelectric measurements. Ferrimagnetic property of the CFO/PZT bilayer was confirmed by magnetic measurement at room temperature.
Optimal sizing of micro grid & distributed generation units under pool electricity market
Authors: Mohammadi M. , Hosseinian S. H. , Gharehpetian G. B.
Published: September 2011

This paper presents an optimized design of micro grid in a distribution system including various sources such as photovoltaic array, fuel cell, and battery bank with multiple distributed generation (DG) units under pool electricity market. In this research, an algorithm has been developed for the optimization of the micro grid cost. The costs include capital cost, replacement cost, operation and maintenance cost, fuel cost, and production cost. Then, an objective function to minimize the total costs is presented. A genetic algorithm is employed to obtain the minimum cost of the micro grid during interconnected operation by optimizing the production of local DGs and power exchanges with the main distribution grid. The developed optimization algorithm is applied to a typical low voltage network operating under pool market policy.
Towards a mesoscopic model of water-like fluids with hydrodynamic interactions
Authors: Mazzitelli Irene , Venturoli Maddalena , Melchionna Simone , Succi Sauro
Published: September 2011

We present a mesoscopic lattice model for non-ideal fluid flows with directional interactions, mimicking the effects of hydrogen bonds in water. The model supports a rich and complex structural dynamics of the orientational order parameter, and exhibits the formation of disordered domains whose size and shape depend on the relative strength of directional order and thermal diffusivity. By letting the directional forces carry an inverse density dependence, the model is able to display a correlation between ordered domains and low density regions, reflecting the idea of water as a denser liquid in the disordered state than in the ordered one.
Structure-dependent band dispersion in epitaxial anthracene films
Authors: Bussolotti F. , Yamada-Takamura Y. , Wang Y. , Friedlein R.
Published: September 2011

The intermolecular band dispersion related to the highest occupied molecular orbital of epitaxial anthracene multilayer films on single-crystalline Bi(0001) has been measured using angle-resolved ultraviolet photoelectron spectroscopy. By comparing the dispersion to that of anthracene multilayers on Cu(110) [F. Bussolotti, Y. Yamada-Takamura, and R. Friedlein, Phys. Rev. B 80, 153402 (2009)10.1103/PhysRevB.80.153402], it is shown how the transfer integrals and the difference in on-site energies depend on lattice parameters and how this, in turn, affects the band curvature along high-symmetry directions.
Multiscale element mapping of buried structures by ptychographic x-ray diffraction microscopy using anomalous scattering
Authors: Takahashi Yukio , Suzuki Akihiro , Zettsu Nobuyuki , Kohmura Yoshiki , Yamauchi Kazuto , Ishikawa Tetsuya
Published: September 2011

We propose an element mapping technique of nano-meso-microscale structures buried within large and/or thick objects by ptychographic x-ray diffraction microscopy using anomalous scattering. We performed quantitative imagings of both the electron density and Au element of Au/Ag nanoparticles at the pixel resolution of better than 10 nm in a field of view larger than 5 × 5 μm2 by directly phasing ptychographic coherent diffraction patterns acquired at two x-ray energies below the Au L3 edge. This method provides us with multiscale structural and elemental information for understanding the element/property relationship linking nanoscale structures to macroscopic functional properties in material and biological systems.
High-frequency nonlinear characteristics of resonant-tunnelling diodes
Authors: Feiginov Michael , Sydlo Cezary , Cojocari Oleg , Meissner Peter
Published: September 2011

The nonlinear response of resonant-tunnelling diodes (RTDs) is analysed theoretically at high frequencies (HFs), which are far above the diode’s tunnel-relaxation-time limit. We show that the HF I-V curve in this regime is substantially different from the static one. The calculated static and oscillation characteristics of a HF RTD oscillator are in good agreement with our measurement results. Our RTD model is applicable to RTDs working at THz frequencies.
Emission control of InGaN nanocolumns grown by molecular-beam epitaxy on Si(111) substrates
Authors: Albert S. , Bengoechea-Encabo A. , Lefebvre P. , Sanchez-Garcia M. A. , Calleja E. , Jahn U. , Trampert A.
Published: September 2011

This work studies the effect of the growth temperature on the morphology and emission characteristics of self-assembled InGaN nanocolumns grown by plasma assisted molecular beam epitaxy. Morphology changes are assessed by scanning electron microscopy, while emission is measured by photoluminescence. Within the growth temperature range of 750 to 650 °C, an increase in In incorporation for decreasing temperature is observed. This effect allows tailoring the InGaN nanocolumns emission line shape by using temperature gradients during growth. Depending on the gradient rate, span, and sign, broad emission line shapes are obtained, covering the yellow to green range, even yielding white emission.
Coherent control of a THz intersubband polarization in a voltage controlled single quantum well
Authors: Wagner M. , Helm M. , Sherwin M. S. , Stehr D.
Published: September 2011

Ultrashort terahertz pulses in the far-infrared spectral region centered around 2 THz are used to coherently control an intersubband polarization in a GaAs/AlGaAs quantum well structure at low temperature. While the first pulse excites a macroscopic polarization, a second temporally delayed pulse switches the polarization off or refreshes it depending on the relative time delay. The switching is directly demonstrated in the time-domain for the few picosecond long free-induction decay of the induced polarization. Model calculations based on the optical Bloch equations agree well with the experimental data.
Gas dynamic effects on formation of carbon dimers in laser-produced plasmas
Authors: Al-Shboul K. F. , Harilal S. S. , Hassanein A.
Published: September 2011

We investigated the effect of helium and nitrogen pressures on the dynamics of molecular species formation during laser ablation of carbon. For producing plasmas, planar carbon targets were irradiated with 1064 nm, 6 ns pulses from an Nd:yttrium aluminum garnet laser. The emission from excited C2 and CN molecules was studied using space resolved optical time-of-flight emission spectroscopy and spectrally resolved fast imaging. The intensity oscillations in C2 and CN monochromatic fast imaging and their emission space-time contours suggest that recombination is the major mechanism of C2 formation within the laser ablation carbon plumes in the presence of ambient gas.
Spin transistor using magnetic tunnel junctions with half-metallic Co2MnSi Heusler alloy electrodes
Authors: Ohdaira Y. , Oogane M. , Naganuma H. , Ando Y.
Published: September 2011

We fabricated a spin transistor structure that consisted of two magnetic tunnel junctions with half-metallic Co2MnSi electrodes. Transient responses were observed by applying pulsing gate voltage. Output currents were controlled by both the source-drain and gate voltage and magnetic configuration of the Co2MnSi. The drain current increased around 3000 times at a source-drain voltage of 0.01 V and anti-parallel magnetic configuration, when a gate voltage of 1 V peak-to-peak was applied. In addition, the maximum magnetocurrent ratios were 215% at 6 K. Expected operation properties are observed in our proposed spin transistor.
Coronal Streamers Revealed during Solar Eclipses: Seeing is not Believing, and Pictures Can Lie
Authors: Woo Richard
Published: September 2011

For those fortunate enough to have personally witnessed and photographed the visible corona surrounding the Sun during a solar eclipse, pictures are usually a let down for not living up to the visual view. After 150 years of investigating the corona, we understand it more fully and now know this difference to be real. The difference stems from our inability to either see or image the true distribution of simultaneous brightness because of its large dynamic range (eg, Rodriguez, Woods, 2008 Digital Image Processing, Upper Saddle River: Pearson Prentice Hall). Brightness in the corona is unprecedented, as it falls by three orders of magnitude over a distance of only one solar radius from the Sun.
City Histories in Medieval Iran
Authors: Bulliet Richard W.
Published: September 2011

The object of this article is to open up to speculation a historiographical problem which the serious student of Iranian urban history necessarily encounters. This is the problem of the motivation of the authors of medieval urban histories. In studying any single work or city, it may be possible to work around the problem; but as soon as a broader approach is attempted, encompassing several cities and numerous works, it looms as a major obstacle.

The root of the problem is essentially the very richness and volume of medieval urban historical writing itself, for that is what makes the comparative study of Iranian cities potentially so rewarding. There is hardly a single major city in the Persian speaking world that has not been the subject of at least one local history. Many of these works are extant, published or unpublished; but many, many more that at one time existed have disappeared.
From Model to Crop: Functional Analysis of a STAY-GREEN Gene in the Model Legume Medicago truncatula and Effective Use of the Gene for Alfalfa Improvement
Authors: Zhou Chuanen , Han Lu , Pislariu Catalina , Nakashima Jin , Fu Chunxiang , Jiang Qingzhen , Quan Li , Blancaflor Elison B. , Tang Yuhong , Bouton Joseph H. , Udvardi Michael , Xia Guangmin , Wang Zeng-Yu
Published: September 2011

Medicago truncatula has been developed into a model legume. Its close relative alfalfa (Medicago sativa) is the most widely grown forage legume crop in the United States. By screening a large population of M. truncatula mutants tagged with the transposable element of tobacco (Nicotiana tabacum) cell type1 (Tnt1), we identified a mutant line (NF2089) that maintained green leaves and showed green anthers, central carpels, mature pods, and seeds during senescence. Genetic and molecular analyses revealed that the mutation was caused by Tnt1 insertion in a STAY-GREEN (MtSGR) gene. Transcript profiling analysis of the mutant showed that loss of the MtSGR function affected the expression of a large number of genes involved in different biological processes. Further analyses revealed that SGR is implicated in nodule development and senescence. MtSGR expression was detected across all nodule developmental zones and was higher in the senescence zone. The number of young nodules on the mutant roots was higher than in the wild type. Expression levels of several nodule senescence markers were reduced in the sgr mutant. Based on the MtSGR sequence, an alfalfa SGR gene (MsSGR) was cloned, and transgenic alfalfa lines were produced by RNA interference. Silencing of MsSGR led to the production of stay-green transgenic alfalfa. This beneficial trait offers the opportunity to produce premium alfalfa hay with a more greenish appearance. In addition, most of the transgenic alfalfa lines retained more than 50% of chlorophylls during senescence and had increased crude protein content. This study illustrates the effective use of knowledge gained from a model system for the genetic improvement of an important commercial crop.
The inverse problem of bimorph mirror tuning on a beamline
Authors: Huang Rong
Published: September 2011

One of the challenges of tuning bimorph mirrors with many electrodes is that the calculated focusing voltages can be different by more than the safety limit (such as 500 V for the mirrors used at 17-ID at the Advanced Photon Source) between adjacent electrodes. A study of this problem at 17-ID revealed that the inverse problem of the tuningin situ, using X-rays, became ill-conditioned when the number of electrodes was large and the calculated focusing voltages were contaminated with measurement errors. Increasing the number of beamlets during the tuning could reduce the matrix condition number in the problem, but obtaining voltages with variation below the safety limit was still not always guaranteed and multiple iterations of tuning were often required. Applying Tikhonov regularization and using the L-curve criterion for the determination of the regularization parameter made it straightforward to obtain focusing voltages with well behaved variations. Some characteristics of the tuning results obtained using Tikhonov regularization are given in this paper.