bluuebunny/crossref_metadata_2025_split huggingface dataset:
Herbicide leaching as affected by macropore flow and within‐storm rainfall intensity variation: a RZWQM simulation
Authors: Malone Robert W , Weatherington‐Rice Julie , Shipitalo Martin J , Fausey Norman , Ma Liwang , Ahuja Lajpat R , Don Wauchope R , Ma Qingli 
Published: February 2004

AbstractWithin‐event variability in rainfall intensity may affect pesticide leaching rates in soil, but most laboratory studies of pesticide leaching use a rainfall simulator operating at constant rainfall intensity, or cover the soil with ponded water. This is especially true in experiments where macropores are present—macroporous soils present experimental complexities enough without the added complexity of variable rainfall intensity. One way to get around this difficulty is to use a suitable pesticide transport model, calibrate it to describe accurately a fixed‐intensity experiment, and then explore the affects of within‐event rainfall intensity variation on pesticide leaching through macropores. We used the Root Zone Water Quality Model (RZWQM) to investigate the effect of variable rainfall intensity on alachlor and atrazine transport through macropores. Data were used from an experiment in which atrazine and alachlor were surface‐applied to 30 × 30 × 30 cm undisturbed blocks of two macroporous silt loam soils from glacial till regions. One hour later the blocks were subjected to 30‐mm simulated rain with constant intensity for 0.5 h. Percolate was collected and analyzed from 64 square cells at the base of the blocks. RZWQM was calibrated to describe accurately the atrazine and alachlor leaching data, and then a median Mid‐west variable‐intensity storm, in which the initial intensity was high, was simulated. The variable‐intensity storm more than quadrupled alachlor losses and almost doubled atrazine losses in one soil over the constant‐intensity storm of the same total depth. Also rainfall intensity may affect percolate‐producing macroporosity and consequently pesticide transport through macropores. For example, under variable rainfall intensity RZWQM predicted the alachlor concentration to be 2.7 µg ml−1 with an effective macroporosity of 2.2 E−4 cm3 cm−3 and 1.4 µg ml−1 with an effective macroporosity of 4.6 E−4 cm3 cm−3. Percolate‐producing macroporosity and herbicide leaching under different rainfall intensity patterns, however, are not well understood. Clearly, further investigation of rainfall intensity variation on pesticide leaching through macropores is needed. Published in 2004 for SCI by John Wiley & Sons, Ltd.
Photodegradation of bensulfuron‐methyl on soil surface
Authors: Si You‐Bin , Yue Yong‐De , Chen Huai‐Man , Zhou Dong‐Mei 
Published: February 2004

AbstractPhotolysis of bensulfuron‐methyl on soil surface was studied under sunlight and UV light. Seven photoproducts were isolated and characterised by spectroscopic methods. The major processes in the photolysis of bensulfuron‐methyl in soil are cleavage of the sulfonylurea bridge, scission of the SO2NH bond and contraction of the sulfuronylurea bridge. The rates of photodegradation of bensulfuron‐methyl on different soils followed first‐order rate kinetics with half lives of 21.9, 28.4, 36.9, 59.2 and 47.2 h (UV) and 23.1, 27.5, 29.1, 38.9 and 33.8 days (sunlight) for vertisol, alluvial, alfisol, red and laterite soils, respectively. The differences in rates of photodegradation were dependent upon the soil texture and organic matter content. Copyright © 2004 Society of Chemical Industry
Documenting the pesticide processes module of the ARS RZWQM agroecosystem model
Authors: Wauchope R Don , Rojas Kenneth W , Ahuja Lajpat R , Ma Qingli , Malone Robert W , Ma Liwang 
Published: February 2004

AbstractWe describe the theory and current development state of the pesticide process module of the USDA‐Agricultural Research Service Root Zone Water Quality Model, or RZWQM. Several processes which are significant in determining the fate of a pesticide application are included together in this module for the first time, including application technique, root uptake, ionic dissociation, soil depth dependence of persistence, volatilization, wicking upward in soil and aging of residues. The pesticide module requires a large number of parameters to run (as does the RZWQM model as a whole) and it is becoming clear that RZWQM will find most interest and use as part of a ‘scenario’ in which all data requirements are supplied and the predictions of the system compared with a real (usually partial) data set. Such a scenario may then be modified to examine the response of the system to changes in inputs. It also has significant potential as a technology transfer or teaching tool, providing detailed understanding of a specific agronomic system and its potential impacts on the environment. Published in 2004 for SCI by John Wiley & Sons, Ltd.
Test of the Root Zone Water Quality Model (RZWQM) for predicting runoff of atrazine, alachlor and fenamiphos species from conventional‐tillage corn mesoplots
Authors: Ma Qingli , Don Wauchope R , Ma Liwang , Rojas Kenneth W , Malone Robert W , Ahuja Lajpat R 
Published: February 2004

AbstractThe Root Zone Water Quality Model (RZWQM) is a comprehensive, integrated physical, biological and chemical process model that simulates plant growth and movement of water, nutrients and pesticides in a representative area of an agricultural system. We tested the ability of RZWQM to predict surface runoff losses of atrazine, alachlor, fenamiphos and two fenamiphos oxidative degradates against results from a 2‐year mesoplot rainfall simulation experiment. Model inputs included site‐specific soil properties and weather, but default values were used for most other parameters, including pesticide properties. No attempts were made to calibrate the model except for soil crust/seal hydraulic conductivity and an adjustment of pesticide persistence in near‐surface soil. Approximately 2.5 (±0.9), 3.0 (±0.8) and 0.3 (±0.2)% of the applied alachlor, atrazine and fenamiphos were lost in surface water runoff, respectively. Runoff losses in the ‘critical’ events—those occurring 24 h after pesticide application—were respectively 91 (±5), 86 (±6) and 96 (±3)% of total runoff losses for these pesticides. RZWQM adequately predicted runoff water volumes, giving a predicted/observed ratio of 1.2 (±0.5) for all events. Predicted pesticide concentrations and loads from the ‘critical’ events were generally within a factor of 2, but atrazine losses from these events were underestimated, which was probably a formulation effect, and fenamiphos losses were overestimated due to rapid oxidation. The ratios of predicted to measured pesticide concentrations in all runoff events varied between 0.2 and 147, with an average of 7. Large over‐predictions of pesticide runoff occurred in runoff events later in the season when both loads and concentrations were small. The normalized root mean square error for pesticide runoff concentration predictions varied between 42 and 122%, with an average of 84%. Pesticide runoff loads were predicted with a similar accuracy. These results indicate that the soil‐water mixing model used in RZWQM is a robust predictor of pesticide entrainment and runoff. Published in 2004 for SCI by John Wiley & Sons, Ltd.
High stability of CdZnSSe active layers in ZnSe‐based laser diodes by introducing strain‐compensating barrier layers
Authors: Gust Arne , Klude Matthias , Ueta Akio , Roventa Elena , Hommel Detlef 
Published: February 2004

AbstractA series of four similar laser structures with an emission wavelength of 520 nm was grown by molecular beam epitaxy. The difference was the alternating implementation of an additional 5 nm thick ZnSSe layer with a high sulfur composition of 25% neighboring the quantum well on the n‐, p‐ or n‐& p‐side. A high stability of the CdZnSSe active layer was observed by introducing such a kind of strain compensating barrier layers. In lifetime measurements a large improvement was noticed by the p‐ and n‐ & p‐side barrier layers. With respect to the strain compensating effect of only one barrier layer, the p‐side layer is more effective than the n‐side one. It is assumed that the p‐side barrier layer acts not only as strain‐compensating layer, but also as blocking layer against the Cd diffusion into the p‐doped layers. A lifetime extension of one order of magnitude could be achieved. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Green monolithic II–VI vertical‐cavity surface‐emitting laser operating at room temperature
Authors: Kruse C. , Ulrich S. M. , Alexe G. , Roventa E. , Kröger R. , Brendemühl B. , Michler P. , Gutowski J. , Hommel D. 
Published: February 2004

AbstractThe realization of a monolithic all II–VI‐based vertical cavity surface emitting laser (VCSEL) for the green spectral region is reported. Optically pumped lasing operation was achieved up to room temperature using a planar VCSEL structure. Taking advantage of distributed Bragg‐reflectors based on MgS/Zn(Cd)Se superlattices as the low‐refractive index material and ZnS0.06Se0.94 layers as the high‐index material with a refractive index contrast of Δn = 0.6, a quality factor exceeding Q = 2000 is reached by using only 18 Bragg periods for the bottom DBR and 15 Bragg periods for the top DBR. The threshold power density is 0.32 MW/cm2 at a temperature of 10 K (emission wavelength 498.5 nm) and 1.9 MW/cm2 at room temperature (emission wavelength 502.3 nm). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spatial breathing of the exciton distribution in ZnSe quantum wells
Authors: Dal Don B. , Zhao Hui , Schwartz G. , Kalt H. 
Published: February 2004

AbstractWe measured the transport dynamics of excitons in ZnSe quantum wells with help of a time‐resolved nanophotoluminescence setup. Right after picosecond excitation, the excitons move out of the laser spot, but then they reverse the direction of propagation, and finally spread out again. We attribute this “spatial breathing” of the exciton population to acoustic phonon emission, which is a predominantly backward scattering event. This permits us to detect the first inelastic scattering event after the fast excitation generation, causing the end of the coherent transport regime. Using this method, we can determine simultaneously the coherence time and length of excitons in an 8nm well to 29 ps and 800 nm, respectively. We can reproduce the results with help of a Monte‐Carlo simulation of the exciton dynamics in the well. The obtained values for coherence length and time are consistent with other, independent experiments. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of linear and nonlinear optical spectra of various ZnO epitaxial layers and of bulk material obtained by different experimental techniques
Authors: Priller H. , Brückner J. , Gruber Th. , Klingshirn C. , Kalt H. , Waag A. , Ko H. J. , Yao T. 
Published: February 2004

AbstractWe investigate ZnO epitaxial layers grown by MBE (Molecular Beam Epitaxy) and MOVPE (Metal Organic Vapor Phase Epitaxy) techniques. The samples show similar optical behavior in temperature dependent photoluminescence measurements, reflection and photoluminescence excitation spectroscopy in the low density regime. High excitation measurements show different behavior. While the MBE sample leads to stimulated emission from the exciton‐exciton‐scattering, an electron hole plasma is formed in the MOVPE sample which leads to stimulated emission at higher excitation intensities. The gain value measured by the variable stripe length method is much higher for the MBE grown sample. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth by MBE and characterization of metastable group II sulphides
Authors: Prior K. A. , Bradford C. , David L. , Tang X. , Cavenett B. C. 
Published: February 2004

AbstractMany group II sulphides semiconductors have the rocksalt structure as their stable crystal structure. In the case of MgS and MnS it has been demonstrated that these compounds can be grown in the metastable zinc blende structure. Recently, at Heriot–Watt we have shown that a simple MBE growth procedure can be used to increase the thickness of these metastable layers to over 130 nm. In this paper, we summarise some of the results we have obtained and describe some of the structures which we have grown using these materials. The aim is to demonstrate that the growth method is simple, and that MgS in particular is a material with useful properties that can be incorporated into a variety of structures. Finally, we describe some potential uses of these compounds which we have not yet explored, and suggest other compounds which may be successfully grown with this method. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of heterostructures containing MnS grown by MBE
Authors: David L. , Tang X. , Beamson G. , Wolverson D. , Prior K. A. , Cavenett B. C. 
Published: February 2004

AbstractMnS can be grown lattice matched to GaAs and ZnSe in the metastable zinc blende structure. Recently, layers of MnS over 100nm thick have been produced which are thick enough for structural characterisation. In this paper we report measurements obtained from X‐ray diffraction, Raman and X‐ray Photoelectron Spectroscopy. X‐ray diffraction has been used to obtain a value of Poisson's ratio of 0.475. This is unusually high and has implications for the stability of the material. Raman spectroscopy has been used to determine a value for the LO phonon frequency of 380 cm−1 which is in line with the value estimated from its reduced mass. XPS has been used to determine a value for the Valence Band offset. Unlike previous measurements on this compound we have found that the MnS growth must start with Mn, and not S. This presumably reflects the differences between our growth method and that used previously to grow zinc blende MnS. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
MBE growth and optical properties of ZnO on GaAs(111) substrates
Authors: Matsumoto Takashi , Nishimura Kazuto , Nabetani Yoichi , Kato Takamasa 
Published: February 2004

AbstractHexagonal ZnO layers were grown by plasma assisted MBE on GaAs(111)B substrates. The substrate was chemically etched and no buffer layer was introduced. The epitaxial orientation relationships was ZnO(0001)//GaAs(111) and ZnO[11–20]//GaAs[01–1]. The layer–substrate interface was investigated by transmission electron microscope (TEM) observation, and 2–3 monolayer thick contrast band was found at the interface. The lattice constant c was smaller than that of bulk ZnO and changed systematically with the layer thickness. Low temperature photoluminescence (PL) spectra was dominated by a donor bund exciton band at 3.360 eV. Another bound exciton band was found around 3.330 eV. The relative intensity of the PL bands changed with growth conditions. PL peak energies became smaller as the lattice constant c became smaller. The lattice strain dependence of the exciton energy was derived.
MBE growth of ZnSSeO alloy using ZnS as a sulfur source
Authors: Nabetani Y. , Ito Y. , Mukawa T. , Okuno T. , Kato T. , Matsumoto T. , Hirai T. 
Published: February 2004

AbstractWe have grown quaternary alloy semiconductor ZnSSeO by molecular beam epitaxy. Large band gap bowing due to large electronegativity of O is expected in this alloy. The growth of ZnSSeO was proceeded by supplying RF‐excited oxygen during the growth of ZnSSe. The lattice constant of ZnSSeO decreased with increasing O2 flow rate. X‐ray diffraction peak was separated when O2 flow rate was high. However, controllable range of lattice constant without phase separation was expanded compared with ZnSeO ternary alloy. It was shown that S composition parasitically increased with O composition. We have explained the enhancement of S incorporation in terms of reduction of strain energy. The band gap energy decreased with increasing O2 flow rate regardless of phase separation. The amount of band gap bowing was slightly less than that found in ZnSeO. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Molecular beam epitaxy of MgxZn1−xO layers without wurzite‐rocksalt phase mixing from x = 0 to 1 as an effect of ZnO buffer layer
Authors: Fujita Shizuo , Takagi Tsuyoshi , Tanaka Hiroshi , Fujita Shigeo 
Published: February 2004

AbstractMgxZn1−xO (0 ≤ x ≤ 1) layers without wurzite‐rocksalt phase mixing have been successfully grown by MBE on a‐plane sapphire substrates with ZnO buffer layers. The layers of x < 0.5 take wurzite (0001) structure eliminating the problem of wurzite‐rocksalt phase mixing reported previously between x = 0.35 and 0,45, while those of x > 0.5 rocksalt (001) with wurzite (0001) structure only at the initial stage of the growth (<25 nm). The rocksalt (001) rather than (111) which has been generally seen on sapphire without ZnO buffer layers can be explained by the model showing successive transition from wurzite (0001) to rocksalt (001) with the tensile and compressive deformation of the lattices along a‐ and b‐axes, respectively. The band gap energy of MgxZn1−xO has been continuously tuned without the problem of unstable phase mixing. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
MBE growth and characterization of hexagonal ZnCdMgSe layers and ZnCdSe/ZnCdMgSe QW structures on GaAs (111) substrates
Authors: Suzuki S. , Kaifuchi Y. , Kumada H. , Ishitani Y. , Yoshikawa A. 
Published: February 2004

AbstractZnCdMgSe epilayers and ZnCdSe/ZnCdMgSe quantum well structures were grown on GaAs(111)A and B substrates by MBE using a low‐temperature‐grown CdS buffer layer. X‐ray reciprocal space maps demonstrated that ZnCdMgSe epilayers grown on CdS buffer layers were predominantly hexagonal structures. In the quantum well structures, in‐situ RHEED pattern also demonstrated the hexagonal structure during the growth. X‐ray diffraction results showed that the crystalline quality of the ZnCdMgSe epilayers grown on GaAs(111)A surface was much better than that on the (111)B surface. Low temperature photoluminescence of ZnCdMgSe epilayers were dominated by the deep and shallow donor–acceptor pair emissions for the case of GaAs(111)A and B, respectively. The peak energy positions of the photoluminescence spectra increased with increasing the growth temperature. Although strong emissions from ZnCdMgSe barriers were observed, emissions from the ZnCdSe QW structure were very weak. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Development of yellow‐green LEDs and LDs using MgZnCdSe‐BeZnTe superlattices on InP substrates by MBE
Authors: Che Song‐Bek , Nomura Ichirou , Kikuchi Akihiko , Kishino Katsumi 
Published: February 2004

AbstractWe have fabricated yellow‐green light emitting diodes (LEDs) and laser diodes (LDs) by using II–VI compounds grown on an InP substrate. A separate confinement hetero‐structure was fabricated by means of Cl‐doped MgSe/ZnCdSe SuperLattices(SLs) for n‐side layers, a ZnCdSe Single Quantum Well (SQW) for an active region, and N‐doped MgSe/BeZnTe SLs for p‐side layers. Lasing emission around 560 nm could be observed at a current density over 2.5 kA/cm2 under the pulsed current injection at 77 K. In order to obtain a lasing operation at room temperature, it is necessary to decrease the resistance of the LD and to suppress the current leakage at the interface between the active region and the p‐side region. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Epitaxial growth and optical properties for ultraviolet regionof BeMgZnSe on GaP(001) substrate
Authors: Niiyama Yuuki , Yokoyama Takeshi , Watanabe Masahiro 
Published: February 2004

AbstractEpitaxial growth of high energy BeMgZnSe lattice matched to GaP(001) substrate was demonstrated using BeZnSe buffer layer with molecular beam epitaxy (MBE). BeZnSe buffer layers were introduced to suppress phase separation on GaP substrate even at high‐Mg and Be content region maintaining lattice match. Full‐width at half‐maximum (FWHM) (ω‐scan (004)) of Be0.47Mg0.15Zn0.38Se was 662.4 arcsec although we didn't observe photoluminescence. One possible explanation of this result is that the transition mechanism changes from direct to indirect for Mg content 8–15%. It was also found that the direct gap of BeMgZnSe has approximately 3.80 eV under lattice matched to GaP substrate. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of ZnCdSeTe/MgZnSeTe materials for ZnTe‐based visible optical devices
Authors: Nomura Ichirou , Ochiai Yasutomo , Toyomura Naobumi , Manoshiro Asuka , Kikuchi Akihiko , Kishino Katsumi 
Published: February 2004

AbstractBandgap energy and refractive indices of ZnTe‐based II–VI compounds such as ZnCdTe, ZnCdSeTe, and MgZnSeTe were systematically investigated. The refractive index data were approximated by the modified single effective oscillator method. Especially the approximation for MgZnSeTe made it possible to estimate the refractive index values for any Mg composition in any wavelength of the transmission region. Using the refractive index data, waveguide analysis and design of ZnCdTe/MgZnSeTe laser structures were performed to obtain confinement factors more than 4.5%. ZnCdTe/MgZnSeTe light emitting diodes were fabricated on ZnTe substrates observing yellow light emissions around 583 nm. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Proposal of a novel BeZnSeTe quaternary for II‐VI middle range visible light emitting devices on InP substrates
Authors: Takashima Yasushi , Nomura Ichirou , Nakai Yuki , Kikuchi Akihiko , Kishino Katsumi 
Published: February 2004

AbstractA novel BeZnSeTe quaternary has been proposed for active layers of II–VI visible light emitting devices on InP substrates. BeZnSeTe, which lattice parameters were matched to InP, were grown on InP substrates by molecular beam epitaxy (MBE). The Be composition was changed from 0.11 to 0.35. The photoluminescence (PL) spectra of these samples at 15 K showed single peak emissions with wavelengths from 487 to 506 nm without any deep level emission. From the reflectivity and PL spectra at 15 K, the Γ–Γ direct and Γ–X indirect bandgaps of BeZnSeTe were evaluated, and it is shown that the crossover point from direct to indirect is around Be composition of 0.3. Applying the BeZnSeTe for the active layer, visible light emitting diodes (LEDs) were fabricated on InP substrates by MBE, resulting in yellow light single peak emissions around 575 nm at room temperature. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical and interface phonons of different kind in BeTe/ZnSe superlattices
Authors: Reshina I. I. , Ivanov S. V. , Kosobukin V. A. , Sorokin S. V. , Toropov A. A. 
Published: February 2004

AbstractWe have studied Raman scattering for a number of type II novel superlattices BeTe/ZnSe, which have no common cation or anion atoms at the interfaces. Under off‐resonant excitation LO‐phonons in BeTe and ZnSe layers were observed as well as a high‐frequency mode due probably to the “wrong bond” BeSe at the interface. Under excitation resonant with the direct exciton in ZnSe layers we observed ZnSe LO‐phonons of different orders and electrostatic interface modes of the Fuchs–Kliever type. Calculated frequencies of the interface modes are compared with the experimental ones. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tuning the optical and magnetic properties of II–VI quantum dots by post‐growth rapid thermal annealing
Authors: Gurung T. , Mackowski S. , Jackson H. E. , Smith L. M. , Heiss W. , Kossut J. , Karczewski G. 
Published: February 2004

AbstractWe show that both the optical and magnetic properties of CdTe‐based quantum dots (QDs) can be tuned by post‐growth annealing. With increasing of annealing temperature, the photoluminescence of CdTe and CdMnTe QDs shifts towards high energies. At the same time, we observe a narrowing of the QD ensemble emission linewidth due to the improved homogeneity of the QD ensemble. We find that for annealed CdTe QDs the exciton diamagnetic shift is about two times larger that for the as‐grown ones, suggesting an increase of the average dot size upon annealing. In the case of CdMnTe QDs the emission lines of individual quantum dots narrow significantly from 3 meV down to 0.25 meV showing that effect of spin fluctuations is much reduced probably due to an increase of the average dot size. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)