bluuebunny/crossref_metadata_2025 huggingface dataset:
Post‐Harvest Residue Management of Creeping Red and Chewings Fescue Seed Crops
Authors: Young William C. , Gingrich Gale A. , Silberstein Thomas B , Quebbeman Bryon M.
Published: July 2010

Legislative actions in the Pacific Northwest have greatly restricted the total area of grass seed crops that can be burned each year. Grass seed growers are searching for alternatives to postharvest residue burning. In on‐farm experiments in western Oregon, we compared four postharvest residue management methods for effects on seed yield of creeping red fescue (Festuca rubra L. subsp. rubra cv. Cindy) and Chewings fescue (Festuca rubra L. subsp. commutata Gaudin cv. Center). Treatments were (i) straw residue removed and stubble flail‐chopped (flail‐chop), (ii) straw residue removed and stubble close‐clipped and vacuum‐swept (close‐clip), (iii) straw residue removed and stubble propane‐burned (propane‐burn), and (iv) residue and stubble open‐burned with full straw load (open‐burn). Seed yield components were also measured, to identify the component through which treatments affected yield. Treatment effects on seed yield of both crops interacted with years. Averaged across years, creeping red fescue seed yield was 993, 903, 804, and 620 kg ha−1 for open‐burn, propane‐burn, close‐clip, and flail‐chop treatments, respectively. The greatest treatment effect was on number of panicles, and consequently on number of floret sites and seeds produced per unit area. The number of spikelets per panicle, florets per spikelet, and seeds produced per panicle were unaffected. Open‐burn also resulted in the fewest weed seeds and the highest purity of the harvested seed. Treatments affected Chewings fescue seed yield in only one year, when seed yield was 750, 680, 477, and 553 kg ha−1 for open‐burn, propaneburn, close‐clip, and flail‐chop treatments, respectively. Treatments did not affect the number of panicles or seeds produced per unit area in Chewings fescue, the number of weed seeds, or the purity of the harvested seed. We concluded that mechanical removal of postharvest residue in Chewings fescue can maintain seed yield and seed quality similar to open‐burn. In contrast, open‐burn is required to achieve maximum seed yield and seed quality in creeping red fescue.
Intrablock Variance among Duplicate Treatments for Nearest‐Neighbor Analyses
Authors: Helms Theodore C. , Scott Roy A. , Hammond James J.
Published: July 2010

Nearest‐neighbor analysis (NNA) adjusts for spatially correlated residuals, with the goal of increasing precision. The magnitude of the block × treatment interaction mean square is commonly used to evaluate the precision of the NNA model. An alternative method of evaluating the precision of the NNA and classical unadjusted (UNADJ) randomized complete block (RCB) analysis would be to use the pooled variance between duplicate treatments within each block. We defined pure error as variation between plots that are treated alike within a block. Within each location, each genotype was randomly assigned to two plots within each block of an RCB design. The pure error of soybean [Glycine mar (L.) Merr.] genotypes was evaluated at eight locations. Our objective was to compare the block × treatment and pure error mean squares for yield, physiological maturity, and plant height to determine whether the NNA or UNADJ analysis reduces intrablock variation. The NNA analysis always decreased the magnitude of the block × treatment interaction mean squares, compared with the UNADJ analysis. In some comparisons, the pure error mean square of the NNA analysis was significantly smaller than the pure error of the UNADJ analysis. The magnitude of the block × treatment mean square is not useful for comparing the relative precision of these two analyses. When the pure error mean square was used to measure precision, the NNA was at least as precise as the UNADJ analysis.
Modifications of Soil Nitrogen Pools in Response to Alfalfa Root Systems and Shoot Mulch
Authors: Rasse Daniel P. , Smucker Alvin J. M. , Schabenberger Oliver
Published: July 2010

Decomposing alfalfa (Medicago sativa L.) shoots and roots generate large amounts of NO3‐N available to the next crop but also susceptible to deep leaching. This study was aimed at determining the specific contributions of above‐ and belowground alfalfa biomass to soil N pools. Dynamics of soil and plant N pools were studied in a Kalamazoo loam soil (fine‐loamy, mixed, mesic Typic Hapludalfs) over a 2‐yr period under bare fallow (BF), hare fallow to which alfalfa shoot mulch was applied (BFSM), living alfalfa plants with shoots removed after harvest (A), and living alfalfa with shoot mulch remaining on the soil surface after harvest (ASM). Organic N pools were monitored in alfalfa plant parts, soil‐incorporated debris, and soil organic matter to depths of 150 cm. Inorganic N pools were monitored by suction Iysimeters, soil extraction, and evaluation of soil denitrification rates. Living alfalfa stands kept soil inorganic N at very low levels, whether shoot mulch was applied or not. Soluble inorganic N concentrations decreased earlier in the fall in the upper horizons of bare fallow soils receiving alfalfa shoot mulch, suggesting enhanced leaching from bare soil under alfalfa mulch. Alfalfa crown and roots contained an average of 115 kg N ha−1 after 2 yr of treatment. In conclusion, alfalfa shoot mulch contributed little to sustained increases in soil N pools, while crowns and roots contributed larger quantities to the soil N pool.
Soybean Growth and Development Response to Rotation Sequence and Tillage System
Authors: Pedersen Palle , Lauer Joseph G.
Published: July 2010

Soybean [Glycine max (L.) Merr.] benefits in yield when rotated with corn (Zea mays L.), but the mechanism of the rotation effect is not fully understood. The objective of this study was to determine effects of cropping sequence and tillage on soybean growth and plant development. A 2‐yr field study was conducted using conventional tillage and no‐tillage systems in seven different corn and soybean rotation sequences. At physiological maturity, plots of first‐year soybean after 5 yr of consecutive corn and the annually rotated soybean averaged 8% higher soil moisture content and 17% more dry matter per plant than the remaining five rotation sequences. Conventional tillage averaged 6% higher soil moisture content and 5% greater leaf area index than the no‐tillage system. In 2000, leaf area index was 29% higher for the first‐year soybean after 5‐yr corn and the annually rotated soybean than the remaining five rotation sequences. No differences in leaf area index were observed among the different rotation sequences in 2001. Soybean plants were 6% taller in first‐year soybean after 5‐yr corn, second‐year soybean, and annually rotated soybean than the remaining four rotation sequences. The no‐tillage system averaged 6% more dry matter plant per plant and 7% taller plants than the conventional tillage system. These findings support the hypothesis that growth and alterations in plant development occur when soybean is grown in different rotation sequences and tillage systems. These alterations may reflect the plant response to the corn–soybean rotation effect on soybean growth and development, but the underlying mechanism of the effect remains unknown.
Soil Response to Acid Deposition, Wind River Mountains, Wyoming: I. Soil Properties
Authors: Clayton James L. , Kennedy Debora A. , Nagel Terry
Published: July 2010

In the western USA, alpine and subalpine ecosystems with shallow soils and large areas of rock outcrop may be particularly sensitive to damaging effects from acid precipitation, especially downwind of pollutant sources. This study was conducted to characterize the capacity of subalpine soils in the Wind River Mountains of Wyoming to neutralize acid deposition through cation exchange and SO4 adsorption, and to relate buffer capacity and SO4‐adsorption isotherms to other soil properties. Although B and C horizons of one Dystric Cryochrept pedon have low exchange capacity (<6 cmolc kg−1) and low base saturation (<0.1), soils in general appear to have sufficient base‐exchange capacity to neutralize anticipated acid‐deposition rates. All other horizons sampled have base saturations in excess of 0.2. Most soils will adsorb SO4, although adsorption maxima are estimated at <1.5 mmol kg−1. High organic‐matter content of A horizons in Humic Cryaquepts interferes with SO4 adsorption. Buffer capacities above pH 4 average 4.00 cmol kg−1 pH−1; below pH 4, soils are more strongly buffered, averaging 18.7 cmol kg−1 pH−1. Base exchange is probably the dominant process controlling buffering above pH 4, and dissolution of Al (OH)3 controls buffering in the pH range 2.8 to 4.
Rubberized Asphalt for Sealing Cores of Shrinking Soil
Authors: Kluitenberg G. J. , Bilskie J. R. , Horton R.
Published: July 2010

Because many soil materials shrink as a result of soil water desorption, it is difficult to seal soil samples into containers for transport experiments when a range of soil matric potentials is to be used. In this note, we introduce the use of a rubberized asphalt product that is capable of changing shape so that a seal between the container and the soil sample can be maintained as the soil shrinks. An experiment was conducted in which the air permeability of two soil materials was measured at a series of soil matric potentials after being sealed with rubberized asphalt or paraffin. The results indicate that the asphalt was able to maintain a better seal than the rigid paraffin as the soil materials dried and shrank. Seal integrity of the asphalt was maintained as matric potentials were reduced from −50 kPa to −750 kPa for soils of moderate and high shrinkage capacity. In contrast, the air‐permeability data indicate that the paraffin failed to provide an adequate seal at −50 kPa, even before the soil was desorbed.
Water sector performance under scarcity conditions: a case study of Rajasthan, India
Authors: Reddy V. Ratna
Published: July 2010

This paper makes an attempt to assess the water sector under scarcity conditions in the State of Rajasthan. It adopts the criteria of physical, economic, financial and equity performance across sub-sectors. The assessment brought out clearly that no indicator has shown satisfactory performance in any of the sub-sectors. Though the urban drinking water sector is relatively better in performance, a lot more needs to be done in order to bring it to the threshold level of economic and financial performance. The huge expenditures incurred in this sector are not going towards real investments that would improve the performance of the sector. Despite the fact that the water sector (except groundwater) is in the hands of the government, equity goals are not achieved. An urban and rich bias is prevalent as far as access to water and public distribution of water. Apart from suggesting some short-term measures to meet the immediate demands, this paper argues that institutional reforms are critical for sustainable water resource management under scarcity conditions.
Reinsurance for High Health Costs: Benefits, Limitations, and Alternatives
Authors: Dow William H , Fulton Brent D , Baicker Katherine
Published: July 2010

Government-sponsored reinsurance for individuals with high health costs is a commonly proposed strategy to improve access and affordability in the individual and small-group health insurance markets. While reinsurance may have some benefits, other schemes may be more effective at accomplishing the same goals at lower cost. Reinsurance can be seen as a crude special case of risk-adjusted insurance subsidies. This paper estimates the effect of different reinsurance schemes on insurance premiums and insurers disincentives to enroll potentially high-cost individuals. We find that reinsurance is relatively ineffective at reducing cream-skimming incentives and argue that more sophisticated risk-adjustment schemes are more effective, particularly under community rating with guaranteed issue. Although in the past risk adjustment had been considered too complex to implement in practice, recent experience suggests that it is now feasible, and we argue that incorporation of risk adjustment would strengthen current health insurance reform efforts.
Association Between Serum IGF-1 and Diabetes Among U.S. Adults
Authors: Teppala Srinivas , Shankar Anoop
Published: July 2010

OBJECTIVE

Serum insulin-like growth factor (IGF)-1 may have a role in the maintenance of glucose homeostasis. We examined the association between serum IGF-1 and diabetes in a representative sample of U.S. adults.

RESEARCH DESIGN AND METHODS

Third National Health and Nutrition Examination Survey (NHANES III) participants aged ≥18 years (n = 5,511) were the subjects of the study. The main outcome was the presence of diabetes (n = 387).

RESULTS

Lower serum IGF-1 levels were positively associated with diabetes after adjusting for age, sex, race/ethnicity, education, smoking, alcohol intake, BMI, hypertension, glomerular filtration rate, and serum cholesterol. Compared with quartile 4 of IGF-1 (referent), the odds ratio (OR) of diabetes associated with quartile 1 was OR 2.16 (95% CI 1.24–3.76); P-trend = 0.002. However, the observed association between IGF-1 and diabetes was present only in those <65 years of age (OR = 3.05; P-trend = 0.006) and disappeared in those ≥65 years of age (OR = 0.51; P-trend = 0.18); P-interaction = 0.0056.

CONCLUSIONS

Low IGF-1 levels are associated with diabetes among young subjects.
Colonial menageries and the exchange of exotic faunas
Authors: KISLING VERNON N.
Published: July 2010

The discovery of new worlds with their exotic faunas was part of European life during the fifteenth to nineteenth centuries. Animals representing these faunas were shipped to European menageries from the earliest discovery of the new worlds, and increased significantly during this time period with shipments to menageries throughout the world. The exchange of these exotic faunas was carried out in many different ways and was facilitated by natural history networks comprised of individuals and institutions involved in commercial, agricultural and scientific activities. Colonial menageries, first in the form of animal holding areas or acclimatization farms and later in the form of zoos, were initially dependant on the various company networks supporting botanical collecting stations. Later they were the result of official and quasi-official government efforts. These efforts evolved into the modern colonial zoological gardens. The exhibition of exotic faunas, the utilization of commercially important exotic species, and the acclimatization of domestic breeds to colonial conditions were all part of the great zoological exchange that began as a trickle in the fifteenth century and increased significantly to a flood by the nineteenth century.
Ketone and quinone-substituted polycyclic aromatic hydrocarbons in mussel tissue, sediment, urban dust, and diesel particulate matrices
Authors: Layshock Julie A. , Wilson Glenn , Anderson Kim A.
Published: July 2010

Polycyclic aromatic hydrocarbons (PAHs) substituted with a ketone or quinone functionality (OPAHs) may be important environmental contaminants. The OPAHs from environmental samples have demonstrated toxicity and may be more harmful than PAHs. Knowledge gaps concerning the occurrence of OPAHs in the total environment arise from analytical difficulties, as well as limited standards and methodologies. An optimized method was developed to quantify five ketone and four quinone OPAHs from matrices ranging from biological tissue to diesel particulates. Five National Institute of Standards and Technology Standard Reference Materials (SRMs) were analyzed. This is the first report of OPAH quantitation in SRM 2977 (mussel tissue), SRM 1944 (New York/New Jersey, USA waterway sediment), SRM 1975 (diesel extract), and SRM 1650b (diesel particulate matter) and among the few to report concentrations from SRM 1649 (urban dust). Furthermore, this is one of the first reports of OPAHs in biological tissue. Σ9OPAHs were 374 ± 59 mg/kg (mussel tissue), 5.4 ± 0.5 mg/kg (sediment), 16.9 ± 1.6 mg/kg (urban dust), 33.4 ± 0.4 mg/kg (diesel extract), and 150 ± 43 mg/kg (diesel particulate matter). In all SRMs, the levels of OPAHs were similar to or exceeded levels of PAHs. Of the OPAHs tested, the most frequently occurring in the environmental matrices were 9-fluorenone, 9,10-anthraquinone, benzofluorenone, and 7,12-benz[a]anthracenequinone. Environ. Toxicol. Chem. 2010;29:2450–2460. © 2010 SETAC
Interaction of Beclin 1 with survivin regulates sensitivity of human glioma cells to TRAIL‐induced apoptosis
Authors: Niu Ting-Kuang , Cheng Yan , Ren Xingcong , Yang Jin-Ming
Published: July 2010

MINT‐7968986, MINT‐7969161: survivin (uniprotkb:O15392) physically interacts (MI:0915) with Beclin‐1 (uniprotkb:Q14457) by anti bait coimmunoprecipitation (MI:0006)
Activation of Snake in a serine protease cascade that defines the dorsoventral axis is atypical and pipe‐independent in Drosophila embryos
Authors: Steen Pamela W. , Tian Sufang , Tully Sarah E. , Cravatt Benjamin F. , LeMosy Ellen K.
Published: July 2010

During Drosophila embryogenesis, establishment of ventral and lateral cell fates requires spatial regulation of an extracellular serine protease cascade composed of Nudel, Gastrulation Defective (GD), Snake, and Easter. Pipe, a sulfotransferase expressed ventrally during oogenesis, sulfates secreted targets that somehow confer positive spatial input to this cascade. Nudel and GD activation are pipe‐independent, while Easter activation requires pipe. The effect of pipe on Snake activation has been unknown. Here we show that Snake activation is cascade‐dependent but pipe‐independent. These findings support a conclusion that Snake's activation of Easter is the first spatially regulated step in the dorsoventral protease cascade.
Effects of prenatal stress and exercise on dentate granule cells maturation and spatial memory in adolescent mice
Authors: Bustamante Carlos , Bilbao Pamela , Contreras William , Martínez Mauricio , Mendoza Antonio , Reyes Álvaro , Pascual Rodrigo
Published: July 2010

Exposure to prenatal stress (PS) increases the risk of developing neurobehavioral disturbances later in life. Previous work has shown that exercise can exert beneficial effects on brain damage; however, it is unknown whether voluntary wheel running (VWR) can ameliorate the neurobehavioral impairments induced by PS in adolescent offspring. Pregnant CF‐1 mice were randomly assigned to control (n = 5) or stressed (n = 5) groups. Pregnant dams were subjected to restraint stress between gestational days 14 and 21 (G14–21), whereas controls remained undisturbed in their home cages. On postnatal day 21 (P21), male pups were randomly assigned to the following experimental groups: control (n = 5), stressed (n = 5), and stressed mice + daily submitted to VWR (n = 4). At P52, all groups were behaviorally evaluated in the Morris water maze. Animals were then sacrificed, and Golgi‐impregnated granule cells were morphometrically analyzed. The results indicate that PS produced significant behavioral and neuronal impairments in adolescent offspring and that VWR significantly offset these deleterious effects.
Interference effects in the sum frequency generation spectra of thin organic films. I. Theoretical modeling and simulation
Authors: Tong Yujin , Zhao Yanbao , Li Na , Osawa Masatoshi , Davies Paul B. , Ye Shen
Published: July 2010

A general theoretical calculation is described for predicting the interference effect in the sum frequency generation (SFG) spectra from a model thin-film system as a function of film thickness. The calculations were carried out for a three-layer thin film consisting of an organic monolayer, a dielectric thin film of variable thickness, and a gold substrate. This system comprises two sources of SFG, namely, a resonant contribution from the monolayer/dielectric film interface and a nonresonant contribution from the dielectric film/gold interface. The calculation shows that both the spectral intensity and the shape of the SFG spectra vary significantly with the thickness of the dielectric layer due to interference effects in the thin film. The intensity changes at a particular frequency were explained in terms of the changes in the local field factors (L factors) as a function of the dielectric film thickness. The L factor for each beam changes periodically with the thickness of the dielectric film. However, the combined L factor for the three beams shows complicated thickness dependent features and no clear periodicity was found. On the other hand, if the susceptibilities of both the resonant and nonresonant terms are fixed, changes in the spectral shape will be mainly due to changes in the phase differences between the two terms with the film thickness. The interference behavior also depends strongly on the polarization combinations of the sum frequency, visible, and infrared beams. A general method is provided for predicting changes in the spectral shapes at different film thicknesses by taking into account the relative intensities and phases of the SFG signals from the two interfaces. The model calculation provides important insights for understanding the nonlinear optical responses from any thin-film system and is an essential tool for quantitatively revealing the nonlinear susceptibilities, which are directly related to the actual structure of the interfacial molecules from the observed SFG spectra after quantitative removal of the L factors.
Superelastic response of [111] and [101] oriented NiTi micropillars
Authors: Manjeri R. M. , Qiu S. , Mara N. , Misra A. , Vaidyanathan R.
Published: July 2010

A combination of microcompression experiments on single crystal micron-scaled pillars of NiTi of known orientations and in situ neutron diffraction during loading of the same NiTi but in bulk, polycrystalline form are carried out to understand the stress-induced transformation associated with superelasticity at reduced length scales. At the length scales investigated, there is evidence through this work of a fully reversible stress-induced transformation from B2 to B19′ NiTi that does not involve additional dislocation activity or irrecoverable strains. The orientation dependence of the elastic deformation of the B2 phase, the onset of its transformation to the B19′ phase, the gradient and the hysteresis in the stress-strain response during transformation, the elastic modulus of the stress-induced B19′ phase and the onset of plasticity are quantified and analyzed in these experiments by examining the crystallography of the B2 to B19′ transformation.
An effective rate equation approach to reaction kinetics in small volumes: Theory and application to biochemical reactions in nonequilibrium steady-state conditions
Authors: Grima R.
Published: July 2010

Chemical master equations provide a mathematical description of stochastic reaction kinetics in well-mixed conditions. They are a valid description over length scales that are larger than the reactive mean free path and thus describe kinetics in compartments of mesoscopic and macroscopic dimensions. The trajectories of the stochastic chemical processes described by the master equation can be ensemble-averaged to obtain the average number density of chemical species, i.e., the true concentration, at any spatial scale of interest. For macroscopic volumes, the true concentration is very well approximated by the solution of the corresponding deterministic and macroscopic rate equations, i.e., the macroscopic concentration. However, this equivalence breaks down for mesoscopic volumes. These deviations are particularly significant for open systems and cannot be calculated via the Fokker–Planck or linear-noise approximations of the master equation. We utilize the system-size expansion including terms of the order of Ω−1/2 to derive a set of differential equations whose solution approximates the true concentration as given by the master equation. These equations are valid in any open or closed chemical reaction network and at both the mesoscopic and macroscopic scales. In the limit of large volumes, the effective mesoscopic rate equations become precisely equal to the conventional macroscopic rate equations. We compare the three formalisms of effective mesoscopic rate equations, conventional rate equations, and chemical master equations by applying them to several biochemical reaction systems (homodimeric and heterodimeric protein-protein interactions, series of sequential enzyme reactions, and positive feedback loops) in nonequilibrium steady-state conditions. In all cases, we find that the effective mesoscopic rate equations can predict very well the true concentration of a chemical species. This provides a useful method by which one can quickly determine the regions of parameter space in which there are maximum differences between the solutions of the master equation and the corresponding rate equations. We show that these differences depend sensitively on the Fano factors and on the inherent structure and topology of the chemical network. The theory of effective mesoscopic rate equations generalizes the conventional rate equations of physical chemistry to describe kinetics in systems of mesoscopic size such as biological cells.
Logarithm second-order many-body perturbation method for extended systems
Authors: Ohnishi Yu-ya , Hirata So
Published: July 2010

We propose progressive downsampling of wave vectors in the Brillouin zone integrations occurring in the second-order many-body or Møller–Plesset perturbation (MP2) method for extended systems of one-dimensional periodicity. Higher-lying unoccupied and lower-lying occupied Bloch orbitals are subject to downsampling by an exponentially increasing factor (with base n), making the total number of Bloch orbitals included in the MP2 lattice sums grow only logarithmically with respect to the number of basis functions per unit cell. Unlike the mod n downsampling scheme proposed earlier, this log n scheme reduces the scaling of the computational cost and thus achieves a greater speedup as the unit cell size increases. Correct band indexing is essential for accuracy. Two-electron integrals entering the MP2 energy and quasiparticle energy expressions must be multiplied by quadrature weights that are a function of the energy bands involved, and an algorithm to compute the weights is proposed. A combined use of the log n and mod n schemes can speedup the MP2/6-31G∗∗ calculation of polyacetylene typically by a factor of 20 with an error in the correlation energy within a few percent relative to the conventional calculation. Similar combinations can reproduce the MP2 quasiparticle energy bands accurately at a fraction of the usual computational cost.
Mixed potentials in radiative stellar collapse
Authors: Thirukkanesh S. , Maharaj S. D.
Published: July 2010

We study the behavior of a radiating star when the interior expanding, shearing fluid particles are traveling in geodesic motion. We demonstrate that it is possible to obtain new classes of exact solutions in terms of elementary functions without assuming a separable form for the gravitational potentials or initially fixing the temporal evolution of the model unlike earlier treatments. A systematic approach enables us to write the junction condition as a Riccati equation which under particular conditions may be transformed into a separable equation. New classes of solutions are generated which allow for mixed spatial and temporal dependence in the metric functions. We regain particular models found previously from our general classes of solutions.
Global mode analysis of a pipe flow through a 1:2 axisymmetric sudden expansion
Authors: Sanmiguel-Rojas E. , del Pino C. , Gutiérrez-Montes C.
Published: July 2010

We report the results of the global mode analysis to characterize the onset of unsteadiness in a circular pipe flow through an axisymmetric sudden expansion of inlet-to-outlet diameter ratio of d/D=0.5. We find that the axisymmetric state becomes linearly unstable at a significantly higher critical Reynolds number than the one reported in previous experimental works. This unstable global mode corresponds to an oscillatory bifurcation with wavenumber |m|=1 located at the end of the recirculation region.
Asymmetric ground state spin configuration of transverse domain wall on symmetrically notched ferromagnetic nanowires
Authors: Djuhana Dede , Piao Hong-Guang , Lee Sang-Hyuk , Kim Dong-Hyun , Ahn Sung-Min , Choe Sug-Bong
Published: July 2010

We report that a ground state spin configuration around a notch of ferromagnetic nanowires can have either symmetric or asymmetric transverse domain wall structure depending on the notch geometry by means of micromagnetic simulation with a systematic variation in the notch aspect ratio. An asymmetric off-centered domain wall configuration becomes stable for a certain range of the notch aspect ratio.
Dynamics of polarized photoluminescence in m-plane InGaN/GaN quantum wells
Authors: Liuolia Vytautas , Marcinkevičius Saulius , Lin You-Da , Ohta Hiroaki , DenBaars Steven P. , Nakamura Shuji
Published: July 2010

Spectrally-, polarization-, and time-resolved photoluminescence (PL) experiments have been performed on 2.5 nm thick m-plane single InGaN quantum wells. It has been found that PL decay is mainly determined by nonradiative recombination through several types of recombination centers, while PL rise is largely affected by exciton transfer into localization minima. Prolonged PL rise times and time-dependent spectral shift were used to study exciton transfer into the localization centers. Characteristic time of the exciton transfer is 80–100 ps at lower temperatures and about 50 ps at room temperature, which corresponds to the exciton diffusion length of 200–500 nm. Degree of PL linear polarization was found to decrease at a similar rate. Decreased PL polarization for the localized excitons suggests that the localization centers are related to areas with relaxed strain.
Surface enhanced Raman scattering optimization of gold nanocylinder arrays: Influence of the localized surface plasmon resonance and excitation wavelength
Authors: Guillot N. , Shen H. , Frémaux B. , Péron O. , Rinnert E. , Toury T. , Lamy de la Chapelle M.
Published: July 2010

We here emphasize that the surface enhanced Raman scattering (SERS) intensity has to be optimized by choosing the appropriate gold nanoparticles size for two excitation wavelengths; 632.8 and 785 nm. We discuss the role of the position and of the order of the localized surface plasmon resonance (LSPR) in such optimization for both wavelengths. At 632.8 nm, the best SERS intensity is reached for a LSPR located between the excitation and Raman wavelengths whereas at 785 nm, the LSPR should be placed outside this range. The third order of LSPR is shown to have no influence on the SERS intensity.
Terahertz response of InGaAs field effect transistors in quantizing magnetic fields
Authors: Klimenko O. A. , Mityagin Yu. A. , Videlier H. , Teppe F. , Dyakonova N. V. , Consejo C. , Bollaert S. , Murzin V. N. , Knap W.
Published: July 2010

Terahertz (THz) detection by plasma wave mechanism in InGaAs field effect transistors is studied in high/quantizing magnetic fields regime. The correlation between the photovoltaic response and magnetoresistance is revealed. It allows explaining the dominant physical mechanism responsible for strong oscillations observed in the transistor THz photoresponse. The results indicate also a serious discrepancy between experimental data and existing theoretical model.
Intergrain connectivity of MgB2 ceramics studied by impedance analysis
Authors: Wang C. C. , Wang C. , Zeng R. , Dou S. X.
Published: July 2010

First, by using of the conventional Rowell analysis, we demonstrated that the addition of nano BN particles can effectively eliminate MgO and pores in MgB2 resulting in a very high density and good connectivity of BN-doped MgB2. Then, another method—low-frequency dielectric impedance analysis—was introduced to characterize the properties of the grain boundaries of MgB2. A comparative impedance study was performed in the frequency range from 100 Hz to 100 MHz on pure and nano BN-doped MgB2. The study revealed some following interesting results: (1) a dielectric resonance around frequency of 108 in both samples was observed, which was argued to be related to an inductance-capacitance and (2) the pure sample has two dielectric relaxations originating from intergrains, while the doped sample has only one intergranular contribution. This convinces that the electric connectivity of the doped sample is really improved by the addition of nano BN particles. Our results indicate that dielectric technique may be a useful tool to characterize the grain boundary properties and grain boundary-related properties of MgB2.
Electrical field induced direct-to-indirect bandgap transition in ZnO nanowires
Authors: Li S. , Li J. L. , Jiang Q. , Yang G. W.
Published: July 2010

As a wide bandgap (3.37 eV) compound semiconductor with the exciton binding energy of 60 meV, ZnO nanowires have attracted considerable interest because of great potential applications in micro-optoelectronics and nano-optoelectronics. However, ZnO nanowires as basic units of microelectronic and optoelectronic nanodevices usually work in the circumstance of the electrical field. Therefore, the influence of electrical field on the electronic structure of ZnO nanowires partly determines the performance of nanodevices. For this issue, we inhere have studied the effects of the applied electrical field on the electronic structure of ZnO nanowires using the density functional theory. It was found that the applied electrical field cannot only effectively modulate the bandgap of ZnO nanowires but also leads to the bandgap transition from direct to indirect. Meanwhile, the above effects of electrical field depend on the size and shape of ZnO nanowires. The physical understanding of the electrical field effects of the energy band structure of ZnO nanowires is attributed to the bond length changes in lattice and the charge transfer between Zn and O atoms. Thus, these valuable investigations are important for designing the microelectronic and optoelectronic nanodevices based on ZnO nanowires.
Field-dependent ultrafast dynamics and mechanism of magnetization reversal across ferrimagnetic compensation points in GdFeCo amorphous alloy films
Authors: Chen Zhifeng , Gao Ruixin , Wang Zixin , Xu Chudong , Chen Daxin , Lai Tianshu
Published: July 2010

Ultrafast dynamics of genuine magneto-optical recording across ferrimagnetic compensation points is demonstrated in GdFeCo films using time-resolved polar Kerr spectroscopy combined with a laser-synchronized sinusoidal alternating magnetic field which can reinitialize irreversible initial magnetization state to laser radiating. The external field dependence of magnetization reversal dynamics is measured and shows that reversal rate accelerates with increasing external fields. Analysis of the magnetization reversal dynamics with Bloch equation shows the magnetization reversal rate is linearly dependent on the external fields within experimental errors, which supports quantitatively that the mechanism of magneto-optical recording in rare earth-transition metal ferromagnetic films is related to the formation and growth of the reversed domains. It is also shown that nucleation field is obviously larger than hot coercivity shown in the anomalous hysteresis loop.
Numerical simulation of current density induced magnetic failure for giant magnetoresistance spin valve read sensors
Authors: Zeng Ding Gui , Chung Kyung-Won , Judy Jack H. , Bae Seongtae
Published: July 2010

It was numerically demonstrated that current-in-plane (CIP) and current-perpendicular-to-plane (CPP) Ir20Mn80 based giant magnetoresistance spin valve read sensors operating at an extremely high current density (J≥1×108 A/cm2) show completely different electrical and magnetic failure mechanisms: (1) CIP read sensors, electromigration-induced Cu spacer diffusion and correspondingly degraded interlayer coupling were primarily responsible for the failures; while, (2) CPP read sensors, the deterioration of exchange bias due to thermomigration-induced Mn interdiffusion at the Co80Fe20/Ir20Mn80 interface was found to be dominant. The different temperature and current distribution resulting in different mass-transport mechanisms are the main physical reasons for the failure.
Terahertz metamaterials with VO2 cut-wires for thermal tunability
Authors: Wen Qi-Ye , Zhang Huai-Wu , Yang Qing-Hui , Xie Yun-Song , Chen Kang , Liu Ying-Li
Published: July 2010

An active terahertz (THz) metamaterial with vanadium dioxide (VO2) cut-wire resonators fabricated on glass substrate was proposed, and THz time-domain spectroscopy was used to probe the temperature-tuned electromagnetic properties. By thermal-triggering the insulator-metal phase transition of VO2, THz transmission signals through the metamaterial exhibit a significant decline with amplitude over 65%. Numerical simulations confirm the observations are due to the metallization of the VO2 film with increasing temperature.
Fast three dimensional ac electro-osmotic pumps with nonphotolithographic electrode patterning
Authors: Senousy Y. M. , Harnett C. K.
Published: July 2010

Three dimensional (3D) stepped electrodes dramatically improve the flow rate and frequency range of ac electro-osmotic pumps, compared to planar electrodes. However, the fabrication of 3D stepped electrodes for ac electro-osmosis (ACEO) pumps usually involves several processing steps. This paper demonstrates results from ACEO pumps produced by a faster and less expensive method to fabricate the 3D electrodes—extending the previous work to disposable devices. The method is based on shadowed evaporation of metal on an insulating substrate that can be injection molded. Flow velocities through the 3D ACEO pump are similar to those seen in the previous work.
Three-color electrowetting display device for electronic paper
Authors: You H. , Steckl A. J.
Published: July 2010

Three-color electrowetting (EW) reflective display devices have been achieved using a vertical stack structure with colored oils. Fundamental properties (interface tension and geometry) of the EW process were investigated. Arrays of ∼1000–2000 pixels were constructed with pixel sizes of 200×600 and 300×900 μm2. Each color layer can be switched independently. Open (oil-free) area fraction of ∼80% in each cell is achieved at ∼10–12 V. Switch-on times range from 5 to 15 ms, suitable for video content display. These characteristics demonstrate that the EW vertical structure has the potential to produce attractive video-speed color reflective electronic paper devices.
Multicatalytic, asymmetric Michael/Stetter reaction of salicylaldehydes and activated alkynes
Authors: Filloux Claire M. , Lathrop Stephen P. , Rovis Tomislav
Published: July 2010

We report the development of a multicatalytic, one-pot, asymmetric Michael/Stetter reaction between salicylaldehydes and electron-deficient alkynes. The cascade proceeds via amine-mediated Michael addition followed by an
N
-heterocyclic carbene-promoted intramolecular Stetter reaction. A variety of salicylaldehydes, doubly activated alkynes, and terminal, electrophilic allenes participate in a one-step or two-step protocol to give a variety of benzofuranone products in moderate to good yields and good to excellent enantioselectivities. The origin of enantioselectivity in the reaction is also explored;
E
/
Z
geometry of the reaction intermediate as well as the presence of catalytic amounts of catechol additive are found to influence reaction enantioselectivity.
Structural basis for the specific inhibition of heterotrimeric G
q
protein by a small molecule
Authors: Nishimura Akiyuki , Kitano Ken , Takasaki Jun , Taniguchi Masatoshi , Mizuno Norikazu , Tago Kenji , Hakoshima Toshio , Itoh Hiroshi
Published: July 2010

Heterotrimeric GTP-binding proteins (G proteins) transmit extracellular stimuli perceived by G protein-coupled receptors (GPCRs) to intracellular signaling cascades. Hundreds of GPCRs exist in humans and are the targets of a large percentage of the pharmaceutical drugs used today. Because G proteins are regulated by GPCRs, small molecules that directly modulate G proteins have the potential to become therapeutic agents. However, strategies to develop modulators have been hampered by a lack of structural knowledge of targeting sites for specific modulator binding. Here we present the mechanism of action of the cyclic depsipeptide YM-254890, which is a recently discovered G
q
-selective inhibitor. YM-254890 specifically inhibits the GDP/GTP exchange reaction of α subunit of G
q
protein (Gα
q
) by inhibiting the GDP release from Gα
q
. X-ray crystal structure analysis of the Gα
q
βγ–YM-254890 complex shows that YM-254890 binds the hydrophobic cleft between two interdomain linkers connecting the GTPase and helical domains of the Gα
q
. The binding stabilizes an inactive GDP-bound form through direct interactions with switch I and impairs the linker flexibility. Our studies provide a novel targeting site for the development of small molecules that selectively inhibit each Gα subunit and an insight into the molecular mechanism of G protein activation.
Coupling growth-factor engineering with nanotechnology for therapeutic angiogenesis
Authors: Sinha Roy Rituparna , Soni Shivani , Harfouche Rania , Vasudevan Pooja R. , Holmes Oliver , de Jonge Hugo , Rowe Arthur , Paraskar Abhimanyu , Hentschel Dirk M. , Chirgadze Dimitri , Blundell Tom L. , Gherardi Ermanno , Mashelkar Raghunath A. , Sengupta Shiladitya
Published: July 2010

Therapeutic angiogenesis is an emerging paradigm for the management of ischemic pathologies. Proangiogenic Therapy is limited, however, by the current inability to deliver angiogenic factors in a sustained manner at the site of pathology. In this study, we investigated a unique nonglycosylated active fragment of hepatocyte growth factor/scatter factor, 1K1, which acts as a potent angiogenic agent in vitro and in a zebrafish embryo and a murine matrigel implant model. Furthermore, we demonstrate that nanoformulating 1K1 for sustained release temporally alters downstream signaling through the mitogen activated protein kinase pathway, and amplifies the angiogenic outcome. Merging protein engineering and nanotechnology offers exciting possibilities for the treatment of ischemic disease, and furthermore allows the selective targeting of downstream signaling pathways, which translates into discrete phenotypes.
NLR family member NLRC5 is a transcriptional regulator of MHC class I genes
Authors: Meissner Torsten B. , Li Amy , Biswas Amlan , Lee Kyoung-Hee , Liu Yuen-Joyce , Bayir Erkan , Iliopoulos Dimitrios , van den Elsen Peter J. , Kobayashi Koichi S.
Published: July 2010

MHC class I plays a critical role in the immune defense against viruses and tumors by presenting antigens to CD8 T cells. An NLR protein, class II transactivator (CIITA), is a key regulator of MHC class II gene expression that associates and cooperates with transcription factors in the MHC class II promoter. Although CIITA also transactivates MHC class I gene promoters, loss of CIITA in humans and mice results in the severe reduction of only MHC class II expression, suggesting that additional mechanisms regulate the expression of MHC class I. Here, we identify another member of the NLR protein family, NLRC5, as a transcriptional regulator of MHC class I genes. Similar to CIITA, NLRC5 is an IFN-γ–inducible nuclear protein, and the expression of NLRC5 resulted in enhanced MHC class I expression in lymphoid as well as epithelial cell lines. Using chromatin immunoprecipitation and reporter gene assays, we show that NLRC5 associates with and activates the promoters of MHC class I genes. Furthermore, we show that the IFN-γ–induced up-regulation of MHC class I requires NLRC5, because knockdown ofNLRC5specifically impaired the expression of MHC class I. In addition to MHC class I genes, NLRC5 also induced the expression of β2-microglobulin, transporter associated with antigen processing, and large multifunctional protease, which are essential for MHC class I antigen presentation. Our results suggest that NLRC5 is a transcriptional regulator, orchestrating the concerted expression of critical components in the MHC class I pathway.
Land Use Changes and Forest Degradation in a Himalayan Watershed: Analysis and Policy Alternatives
Authors: Sharma Rakesh Kumar , Sankhayan Prem Lall , Singh Ranveer
Published: July 2010

Agriculture, horticulture, and forestry are the mainstays of the economy of the Indian state of Himachal Pradesh. The economic, technological, and institutional factors that affect land use need to be analyzed in a holistic way, especially in view of fast changing cropping patterns and declining forest density. The use of a bio-economic programming model incorporating economic and ecological factors appears to be a highly attractive tool for analysis at a micro watershed scale. The objective function of the model is to maximize the discounted gross margins from different sets of activities, namely, agricultural, livestock, and forestry over a 20 year model horizon. The model becomes non-linear by incorporating a variance and co-variance matrix of gross returns over the last five years. The model investigates the effects of alternate policy scenarios on income levels, cropping patterns, biomass use and its growth, and labour and capital requirements over next 20 years by using the General Algebraic Modelling Systems (GAMS). The biomass growth is based on a logistic growth model. Though there is a sharp increase in income by replacing traditional crops with horticultural crops, such changes are also accompanied with increased income risk. Results show a diversification strategy on the part of farmers in the study watershed rather than only maximizing profits. The biomass growth becomes sustainable if there is an increase in emigration rate, use of liquefied petroleum gas (LPG), and substitution of improved livestock. More such response through government policies can improve long term sustainability.
Social Norms, Social Capital, and the Sustainability of Small Scale Economies
Authors: Ranjan Ram
Published: July 2010

This paper develops a conceptual model to link social norms and social capital with key socio-ecological characteristics of small scale economies in order to derive implications for the sustainability of natural resources and survival of these economies. Specifically, the extent of punishment required to deter defection is derived as a function of group size, rewards from defection, resource stock, and the risk of groundwater loss. Social norms which ordain collective participation and punishments can be endogenous, dynamic, and exhibit resilience. The implication of these possibilities on the sustainability of small scale economies is also evaluated.
Analyzing Water Institutions in the 21st Century: Guidelines for Water Researchers and Professionals
Authors: Poirier Bryan A. , de Loë Robert C.
Published: July 2010

Institutional barriers (as opposed to technical challenges) were identified in the early 1980s as being at the root of many of the world's most challenging water resource problems. To what extent does this claim hold true today? We investigate and report on some major developments which have occurred in the field of institutional analysis over the past 25 years. An article published by Helen Ingram and colleagues in 1984 offering practical advice for water planners undertaking institutional analyses, provides the lens through which we examine changes in the field. Major developments since that article was published include an increasing sensitivity to the importance of context, a heightened awareness of the complex nature of social-ecological systems, and a growing appreciation of the dynamic nature of institutions. Much of the advice offered by Ingram and her colleagues continues to be sound, but we suggest that new insights from the past 25 years of work in this field can enhance the challenge of institutional analyses.