bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of topological properties between end-linked and statistically cross-linked polymer networks
Authors: Michalke W. , Lang M. , Kreitmeier S. , Göritz D.
Published: September 2002

This paper compares topological properties of computer-generated unimodal end-lined and statistically cross-linked polymer networks. The bond-fluctuation algorithm was used to obtain the different networks. The networks were analyzed by using knot theory. The results show that the average number of trapped entanglements increases linearly with the length of the subchains. The slope is about 2 times higher in the case of end-linked networks. Although the overall number of entanglements is higher in the end-linked case, swelling experiments reveal that the distribution of subchain lengths of statistically cross-linked networks produces inhomogeneities in the structure which lead to a stronger contribution than for the end-linked networks. A homogeneous mean-field ansatz for the influence of entanglements to the deformation modulus used by most theories therefore appears to be not applicable to statistically cross-linked networks.
Photodissociation of CFX=CHCl (X=H,F) at 193 nm by product translational spectroscopy
Authors: Ko H. S. , Lee Y. R. , Chen C. C. , Wang L. D. , Lin S. M.
Published: September 2002

In this work, we have studied the photodissociation of CFX=CHCl (X=H,F) at 193 nm using product translational spectroscopy. Results show that while the photoelimination of fast Cl, slow Cl, HCl, and HF occurs for both molecules, the cleavage of the C=C bond is only measurable for CF2=CHCl. Among these, only the fast Cl product was detected with strong angular preference with respect to polarized laser light. Product translational energy distributions P(Et) were measured for all dissociation channels. The difference in the P(Et) distributions between three-centered (3C) and four-centered (4C) molecular elimination reactions was observed. The low recoil energy for 3C HCl elimination from CF2=CHCl strongly suggests that there is no concerted isomerization from :C=CF2 to FC≡CF. Although we detected no primary C–F bond fission in the present study, a relatively large yield of the secondary dissociation products F+C2H2 was determined for the internally excited fluorovinyl radical CHCHF. The results are discussed in terms of either a direct or an indirect dissociation process arising from excitation to the ππ* state, and comparisons between the title molecules are included.
Effects of stress on electrical transport properties of nickel silicide thin layers synthesized by Ni-ion implantation
Authors: Zhang X. W. , Wong S. P. , Cheung W. Y.
Published: September 2002

Nickel disilicide layers were prepared by nickel ion implantation into silicon substrates using a metal vapor vacuum arc ion source at various beam current densities to an ion dose of 3×1017 cm−2. The as-implanted and annealed samples were characterized by using Rutherford backscattering spectrometry, x-ray diffraction, micro-Raman spectroscopy, electrical resistivity, and Hall-effect measurements. Residual stress in the NiSi2 layers was determined using the sin2 ψ method of x-ray diffraction, assuming that a biaxial stress state exists in the layers and that the elastic properties of the layers are isotropic. The temperature dependence of the sheet resistivity and the Hall mobility from 30 to 400 K showed peculiar peak and valley features varying from sample to sample, depending on the preparation conditions. However, after annealing, the differences between samples seemed to have diminished in that they all showed similar shapes in both the sheet resistivity versus temperature and the Hall mobility versus temperature curves. It was also shown that the electrical transport properties were highly correlated with the stress in the layers.
Modeling of fatigue behavior in relaxor piezocrystals: Improved characteristics by Mn substitution
Authors: Priya Shashank , Kim Hyeoung Woo , Ryu Jungho , Zhang Shujun , Shrout Thomas R. , Uchino Kenji
Published: September 2002

The functional form of the time decay of the remanent polarization under high-electrical drives, known as fatigue, has been derived for relaxor piezoelectric materials based on the hierarchical relaxation process, typical of disordered systems such as random-field and glassy states and is given in terms of normalized remanent polarization (P̄r) as P̄r(t)=P̄ot−x exp[−c(t/τ)β]. This function was verified by fitting the dynamics of the fatigue behavior in 0.92Pb(Zn1/3Nb2/3)O3–0.08 PbTiO3 (PZN–PT) relaxor-based piezoelectric system. Mn modification of a PZN–PT single crystal improved the fatigue behavior by slowing down the relaxation processes and pinning the domain wall motion.
Abnormal behavior of the dielectric parameters of Ba6−xLn8+2x/3Ti18O54 (Ln=La–Gd) solid solutions
Authors: Belous Anatolii , Ovchar Oleg , Valant Matjaz , Suvorov Danilo
Published: September 2002

The temperature dependence of the dielectric parameters ε and tan δ for the entire x range of barium lanthanide titanate solid solutions (BLT ss) using the general formula Ba6−xLn8+2x/3Ti18O54 (Ln=La, Nd, Sm, Gd) was measured over wide frequency and temperature ranges. The results show the presence of diffuse regions of ε(T) and tan δ(T) anomalies, which are located below (in the La- and Nd-containing solid solutions) or above (in the Sm- and Gd-containing solid solutions) room temperature. However, no evidence of a structural transition responsible for these anomalies could be determined by differential scanning calorimetry and x-ray diffraction analysis. To examine the nature of the abnormal temperature behavior the dielectric parameters in the systems studied were considered in terms of a simple oscillator model. Within the framework of this model correlations among the average size of the A-site ions, tilting of the oxygen octahedra, and the lattice strain are discussed, and the effect of crystallographic peculiarities on the temperature behavior of the dielectric parameters is shown. As a consequence, the changes in ε(T) and tan δ(T) behavior in the BLT ss family were shown to originate from a varying relationship between the harmonic and anharmonic contributions to the phonons of the BLT ss crystal lattice.
Influence of the passive region on zero field steps for window Josephson junctions
Authors: Benabdallah A. , Caputo J. G.
Published: September 2002

We present a numerical and analytic study of the influence of the passive region on fluxon dynamics in a window junction. We examine the effect of the extension of the passive region and its electromagnetic characteristics, its surface inductance LI, and capacitance CI. A one dimensional model describes well the operation of the device when the velocity in the passive region vI is equal to the Swihart velocity. In the opposite case, the fluxon adapts its speed to vI. In both situations we give simple formulas for the position of the limiting voltage of the zero field steps. Large values of LI and CI lead to different types of solutions which are analyzed.
Unified compact theory of tunneling gate current in metal–oxide–semiconductor structures: Quantum and image force barrier lowering
Authors: Quan Wu-yun , Kim Dae M. , Cho Myoung Kwan
Published: September 2002

A compact model of gate current due to Fowler–Nordheim tunneling is presented, which agrees closely with the self-consistent numerical analyses of the surface inversion region of metal–oxide–semiconductor field-effect transistors (MOSFETs). The model can quantify the measured data with the accuracy practically identical to the time consuming numerical simulation. It is also shown conclusively that image force lowering of the oxide barrier height is negligible for the oxide as thin as 1 nm. The quantum barrier lowering resulting from subband splitting is rigorously incorporated, including the effect of two-dimensional electrons inverted at the higher lying subbands. Finally, it is pointed out that the compact model can be readily generalized to include the direct tunneling in deep submicron MOSFETs.
Quantitative characterization of the fabrication processes of domain-inverted layers in LiTaO3 by the line-focus-beam ultrasonic material characterization system
Authors: Miyashita Masahito , Kushibiki Jun-ichi
Published: September 2002

Application of the line-focus-beam ultrasonic material characterization system was extended to evaluate Z-cut LiTaO3 substrates with domain-inverted layers fabricated by proton exchange and quick heat treatment (QHT), and their fabrication processes and systems. Three Z-cut LiTaO3 substrates were proton-exchanged at 260 °C for 20 min; heat-treated for 30 s at 520, 540, and 560 °C, with a temperature increase rate of 80 °C/s; and annealed at 420 °C for 6 h. Slab-type domain-inverted layers with 0.50, 1.94, and 3.26-μm depths on the −Z surfaces and proton-exchanged layers on both the −Z and +Z surfaces were formed. Leaky surface acoustic wave (LSAW) velocities for both surfaces were measured in a frequency range of 100–300 MHz and found to exhibit different dispersion characteristics. Intrinsic LSAW velocity changes caused by the formation of domain-inverted layers were obtained from differences in the LSAW velocities for both surfaces. The velocity changes decreased with increases in the product fH of the ultrasonic frequency f and the domain-inverted layer thickness H. Relationships among the LSAW velocity changes, thicknesses of the domain-inverted layers, and process temperatures in QHT were experimentally obtained. An LSAW velocity variation of 2.6 m/s for the Y-axis propagation at 225 MHz was detected by a homogeneity evaluation on a specimen QHT-processed at 540 °C and annealed. This corresponded to a layer thickness variation of 0.20 μm and a QHT temperature variation of 2.9 °C.
Ternary CoxFe(1−x)Si2 and NixFe(1−x)Si2 formed by ion implantation in silicon
Authors: Fetzer Cs. , Dézsi I. , Vantomme A. , Wu M. F. , Jin S. , Bender H.
Published: September 2002

Co 1−x Fe x Si 2 and Ni1−xFexSi2 metastable ternary phases were formed by sequentially implanting Co, Ni, and Fe into Si (111) at 623 K. In order to compare the phases formed by ion implantation, the Ni1−xFexSi2 stable bulk ternary phase with a wide variety of x values was synthesized. The samples were studied by Mössbauer effect, transmission electron microscopy (TEM), x-ray diffraction, and Rutherford backscattering and channeling. X-ray diffraction and TEM results on the as-implanted samples with x=0.5 indicate a cubic (fluorite) structure. Fe57 Mössbauer spectra show three resonanceline components. Comparison of the isomer shift values of the components with those measured in the stable and metastable transition-metal silicide phases indicated three different sites for iron atoms: Fe substituting Co or Ni; Fe in the empty cubes of the fluorite-type lattices; and Fe populating sites in the CsCl-type B2 lattice. In samples of Ni1−xFexSi2 annealed at 1273 K, α-FeSi2 and a fraction of Fe dissolved in NiSi2 appeared. It was found that Fe is more soluble (maximum 30 at. %) in NiSi2 than it is in CoSi2. Implanting and annealing Co or Ni or both Co and Ni at relatively low concentration in Si already implanted with Fe resulted in β-FeSi2 with Co, Ni, and Co+Ni content, respectively. The hyperfine interaction parameters of Fe57 were slightly modified by the dissolved Co and Ni in the β-FeSi2 lattice.
Current density profile extraction of focused ion beams based on atomic force microscopy contour profiling of nanodots
Authors: Lugstein A. , Basnar B. , Hobler G. , Bertagnolli E.
Published: September 2002

An approach to the profile extraction of nanoscale focused ion beams is presented. It is based on contour profiling of dots patterned at various ion doses by focused ion beam exposure. While the surface contour depends on the spatial variation of the beam-solid interaction, at no single ion dose the contour reflects the current density profile of the beam itself, due to effects such as target swelling, redeposition, and angle-dependent sputtering yield. Instead, we monitor the surface deviation relative to the unimplanted case as a function of dose for the radial positions of interest, and determine scaling factors for the dose such that the scaled curves coincide for all radial positions in the regions of small milling depths. We apply the method to beam shape determination of 10 and 50 keV focused ion beams using silicon and GaAs as targets and atomic force microscopy as a contour profiling technique. Despite the different irradiation response of silicon and GaAs, the beam profiles evaluated on these substrate materials agree excellently, which demonstrates that our approach is substrate independent. It allows profile extractions of nanoscale focused ion beams with high accuracy and high sensitivity even in the tails of the beams.
Spin polarization induced by an external electric field in a hybrid magnetic-electric barrier
Authors: Wang Bin , Guo Yong , Chen Xin-Yi , Gu Bing-Lin
Published: September 2002

Recent studies indicated that under zero bias there is no spin polarization in an antiparallel magnetic-electric barrier structure, where double δ-function magnetic fields point in the opposite direction. Our research demonstrates that an external electric field can make such a hybrid structure spin polarized, however, the degree of spin polarization is smaller than 5% for the GaAs system. It is also shown that the electric barrier can greatly suppress the current density and affect the degree of spin polarization. The results can be explained by the variation of the effective potential induced by the electric field.
Photochemical reaction of divalent-germanium center in germanosilicate glasses under intense near-ultraviolet laser excitation: Origin of 5.7 eV band and site selective excitation of divalent-germanium center
Authors: Takahashi Masahide , Ichii Kentaro , Tokuda Yomei , Uchino Takashi , Yoko Toshinobu , Nishii Junji , Fujiwara Takumi
Published: September 2002

The photochemical reaction of Ge2+ in 10GeO2-90SiO2 optical fiber preform and the origin of the 5.7 eV optical absorption band induced by intense ultraviolet laser excitation have been investigated using a near-ultraviolet XeF excimer laser (3.7 eV) as the main excitation source. Based on the previous and present experimental results, it is concluded that the 5.7 eV optical absorption band does not originate from the Ge(2) electron trapped center. In place of this model, we have proposed an alternative structural model for the origin of the 5.7 eV band taking into account the experimental fact that the corresponding center is diamagnetic. In addition, it is found that the site selective excitation of the Ge2+ center can be achieved by using laser sources with different photon energies.
Effect of interfacial charge on polarization switching of lead zirconate titanate particles in lead zirconate titanate/polyurethane composites
Authors: Wong C. K. , Wong Y. W. , Shin F. G.
Published: September 2002

A simple model has been developed to include the effect of accumulated charge at the matrix–inclusion interface in ferroelectric 0–3 composites on the polarization reversal characteristics. This is used to illustrate a recent set of experimental results on initially polarized lead zirconate titanate (PZT)/polyurethane (PU) composites subjected to an increasing electric field in the reversed direction. Estimations based on previous models [e.g., T. Furukawa, K. Fujino, and E. Fukada, Jpn. J. Appl. Phys. 15, 2119 (1976)] suggest that the local electric field in the PZT particles at switching was an order smaller than the coercive field of PZT. By introducing the effect of interfacial charge and assuming that initially the charge has a magnitude which balances the depolarization field in the polarized PZT inclusions, theoretical calculation based on this image shows that the phenomenon of PZT switching at low fields can be explained as a manifestation of the depletion of interfacial charge which can no longer stabilize the original polarization.
Growth and piezoelectric properties of Pb(Yb1/2Nb1/2)O3−PbTiO3 epitaxial films
Authors: Yoshimura Takeshi , Trolier-McKinstry Susan
Published: September 2002

Epitaxial films of (1−x)Pb(Yb1/2Nb1/2)O3−xPbTiO3 (PYbN–PT, x=0.4,0.5) with SrRuO3 bottom electrodes were prepared on (100) LaAlO3, (100) SrTiO3, and (111) SrTiO3 substrates by pulsed laser deposition. It was found that vacuum annealing of the SrRuO3 before the deposition of PYbN–PT facilitated growth of perovskite PYbN–PT. With optimized growth conditions, (001) and (111) PYbN–PT epitaxial films with good phase purity were obtained in a range of 650–660 and 600–620 °C, respectively. The ferroelectric and transverse piezoelectric properties of these PYbN–PT films were investigated. In the (001) PYbN–PT (50/50) film, the highest remanent polarization (∼30 μC/cm2) and e31,f piezoelectric coefficient (−14 C/m2) were observed. The transition temperature of the (001) PYbN–PT (50/50) film was near 380 °C.
Parallel conductivity of random GaAs/AlGaAs superlattices in regime of controlled vertical disorder
Authors: Pusep Yu. A. , Chiquito A. J. , Mergulhão S. , Toropov A. I.
Published: September 2002

The transport properties of intentionally disordered short-period doped GaAs/AlGaAs superlattices were explored. We found that a redistribution of the electron density in a random potential significantly influences the electron properties of the disordered superlattices resulting in a suppression of the vertical disorder and in the increase of the in-plane mobility of the layers with increasing disorder.
Perveance of a planar diode with explosive emission finite-diameter cathodes
Authors: Saveliev Yuri M. , Sibbett Wilson , Parkes David M.
Published: September 2002

Perveance of a planar diode with explosive emission velvet cathodes of 20–100 mm diameters in a range of diode gaps of 0.5–5 cm is investigated experimentally. An empirical universal curve linking the diode perveance and the cathode radius-to-diode gap ratio is determined thus allowing application of a Child–Langmuir model to diodes of finite dimensions. Comparison of experimental results with two-dimensional (2D) computational models is made and a simple method to translate 2D simulation results to the three-dimensional diode configurations is suggested.
Effect of annealing on formation of self-assembled (In,Ga)As quantum wires on GaAs (100) by molecular beam epitaxy
Authors: Mano T. , Nötzel R. , Hamhuis G. J. , Eijkemans T. J. , Wolter J. H.
Published: September 2002

The role of annealing for (In,Ga)As self-organized quantum wire (QWR) formation on GaAs (100) during growth of (In,Ga)As/GaAs superlattice (SL) structures is studied by x-ray diffraction (XRD), atomic force microscopy (AFM), and photoluminescence (PL) spectroscopy. XRD and AFM evidence that annealing after the supply of each layer of elongated (In,Ga)As quantum dots (QDs) in the SL is the crucial process for QWR formation. We conclude that during annealing, the shape anisotropy of the QDs is enhanced due to anisotropic mass transport and the QDs become connected along the [0-11] direction. Strain reduction by In desorption, revealed by XRD and PL, which accompanies this process, then results in well defined, uniform QWR arrays by repetition in SL growth.
Visualization of 0.1-μm-metal-oxide-semiconductor field-effect transistors by cross-sectional scanning tunneling microscopy
Authors: Okui Toshiko , Hasegawa Shigehiko , Nakashima Hisao , Fukutome Hidenobu , Arimoto Hiroshi
Published: September 2002

The device structure of 0.1-μm-metal-oxide-semiconductor field-effect transistors (MOSFETs) has been examined by cross-sectional scanning tunneling microscopy (STM). Topographic STM images display the source/drain, gate, channel, gate oxide, and spacer of the MOSFETs in terms of height, where these regions appear as though they are a different height from each other. The bias voltage dependence of the STM images shows that the contrast observed by STM reflects the differences in carrier densities between the regions in addition to that in the corrugations. The dimensions of these regions as obtained from the images are consistent with the specifications of devices in feature size that we fabricated.
Global and secondary ferroelectric minima in ordered Pb(Sc0.25Nb0.25Ti0.5)O3 alloys
Authors: Al-Barakaty A. , Bellaiche L.
Published: September 2002

A first-principles-derived approach is developed to study properties of two Pb(Sc0.25Nb0.25Ti0.5)O3 alloys that are both atomically ordered along the [001] direction. Unlike the first alloy, the second structure has differently-charged (001) B-planes. Both systems exhibit a global ferroelectric minimum of orthorhombic symmetry and a secondary ferroelectric minimum of tetragonal symmetry. Some electromechanical responses are enhanced in the secondary minimum, especially for the second structure. Mechanisms allowing a switch from the global to the secondary minimum are discussed.
Raman mapping investigations and finite element analysis of double epitaxial lateral overgrown GaN on sapphire substrates
Authors: Benyoucef M. , Kuball M. , Beaumont B. , Bousquet V.
Published: September 2002

Double epitaxial lateral overgrown (D–ELO) GaN grown by metalorganic vapor phase epitaxy on sapphire substrates was characterized using Raman mapping and finite element analysis. Reductions in stress variations at the D–ELO top surface with respect to single ELO GaN were achieved. Stress near the top surface was mainly attributed to the presence of voids on top of the upper dielectric mask.
Room-temperature epitaxial growth of AlN films
Authors: Ohta J. , Fujioka H. , Ito S. , Oshima M.
Published: September 2002

We have grown AlN films on nearly-lattice-matched (Mn,Zn)Fe2O4 (111) substrates by pulsed-laser deposition at room temperature and investigated their structural properties using reflection high-energy electron diffraction (RHEED), grazing incidence angle x-ray reflectivity (GIXR), grazing incidence angle x-ray diffraction (GIXD), and atomic force microscope. We have found that AlN grows epitaxially even at room temperature. In situ RHEED observations have shown that the room-temperature growth of AlN starts with the two-dimensional mode followed by a transition to the three-dimensional mode at the film thickness of 2 nm. GIXR and GIXD measurements have revealed that the heterointerface between AlN and (Mn,Zn)Fe2O4 is abrupt and approximately 90% of the lattice mismatch is released at the interface due to the introduction of crystalline defects such as misfit dislocations. These results indicate that the present technique solves one of the two major problems with heteroepitaxial growths of group III nitrides (mismatch in the thermal expansion coefficients) and alleviates the other problem (mismatch in the lattice constants).
Hyper-Rayleigh scattering from silver nanoparticles
Authors: Hao E. C. , Schatz G. C. , Johnson R. C. , Hupp J. T.
Published: September 2002

We experimentally demonstrate for the first time the existence of distinguishable contributions to hyper-Rayleigh scattering (HRS) intensities from Ag nanoparticles arising from electric–dipole and electric–quadrupole plasmon resonances at the emitted wavelength. We show that these results can be successfully modeled using an electromagnetic theory of HRS which assumes a surface-induced nonlinear susceptibility. In addition, we show that simple angular distribution measurements may be used to determine the relative sizes of the dipole and quadrupole contributions.
Electron stimulated solvation and reaction of water, ammonia, and methane in nanoclusters adsorbed on solid Ar substrate
Authors: Souda Ryutaro
Published: September 2002

Electron stimulated desorption of cations from H2O, NH3, and CH4 molecules adsorbed on the solid Ar surface has been investigated to explore the behavior of excess protons as well as proton transfer reactions in solvent. In a submonolayer coverage regime, cluster ions are ejected from H2O and NH3 molecules in the form of solvated protons whereas fragmentation occurs preferentially for CH4. Reacted species assignable to methyl alcohol, formaldehyde, and formic acid are emitted in the protonated or hydrated form by electronic excitation of a H2O nanocluster including CH4 or CO additives.
Lucerne in crop rotations on the Riverine Plains. 2. Biomass and grain yields, water use efficiency, soil nitrogen, and profitability
Authors: Hirth J. R. , Haines P. J. , Ridley A. M. , Wilson K. F.
Published: September 2002

In a field experiment in north-eastern Victoria (average annual rainfall 598
mm), the impact of 2–4 years of lucerne growth on the following
3–4 crops was assessed. Controls of continuous lucerne, annual pasture,
and continuous crop were compared with 5 lucerne–crop rotations.
Above-ground biomass and water use efficiency of lucerne, annual pasture, and
crops were assessed, as were the soil N status, grain yields, and
profitability of crops after lucerne. Lucerne grew more slowly over the
autumn–spring growing season (20 kg DM/ha.day) than did annual
pastures and crops (41 and 58 kg DM/ha.day, respectively), while over the
spring–autumn period, it grew at a mean 26 kg DM/ha.day. The summer
growth rates of lucerne were, however, highly variable (1–52 kg
DM/ha.day). Despite large changes in temperature and water availability
over the year, the biomass water use efficiency (WUEB)
of lucerne was similar over the winter and summer growth seasons (16 and 10 kg
DM/ha.mm, respectively) and averaged 13 kg DM/ha.mm for the whole
year. In contrast, the WUEB of wheat, canola, and annual
pasture over their respective growth seasons averaged 36, 38, and 26 kg
DM/ha.mm. When calculated over a whole year, however, they were much
closer to lucerne at 23, 14, and 17 kg DM/ha.mm, respectively.
Autumn removal of lucerne left soils initially low in mineral N (mean 82 kg
N/ha.m depth in April) for the establishment of the first crop, but this
was not reflected in the subsequent N contents of crop biomass and grain.
Autumn mineral N concentrations peaked 1–2 years after lucerne removal
(mean 141 kg N/ha.m depth). Yields of first crops after lucerne were
strongly dependent on growing season rainfall. When sowing commenced in a wet
year, they were similar to, or greater than, the control, but when sown in a
dry year, were substantially lower. When sowing commenced in a wet year,
lucerne supplied additional N for a minimum of 2 crops. At least 3 crops were
supplied with lucerne N when cropping commenced in a dry year. The inclusion
of 2–3 years of lucerne into a continuous cropping sequence only
decreased annual profitability by $AU40/ha. This work shows that
short phases of lucerne (minimum of 3 years) followed by 3–4 crops can
provide economically viable options for farmers and produce better
hydrological outcomes than current annual-plant based cropping systems.
Improvement of two locally adapted cotton cultivars in earliness by induced mutations
Authors: Xanthopoulos F. P. , Kechagia U. E.
Published: September 2002

Seeds from two locally adapted cotton cultivars, Eva and Zeta-2, were
irradiated by 300 Gy γ-irradiation in order to create useful variability
for earliness within each cultivar, and then to select for desirable
recombinations. Selection for earliness was applied in the
M2 generation and the earliest 2% of the mutants
were selfed for further evaluation. After eliminating the undesirable
phenotypes, the remaining material was sown in progeny rows as the
M3 generation. Selection for earliness based upon
morphological and physiological characteristics resulted in 5 early mutants
from cv. Eva and 3 early mutants from cv. Zeta-2. These lines were further
evaluated the following year for earliness, yield, fibre, and seed quality in
3 locations across the Greek cotton belt, using a randomised complete block
experimental design with 4 replications. Among the 5 early mutants of cv. Eva,
only one was consistently early at all 3 locations, whereas the other 4
mutants showed significant differences in the first growth stages. From the 3
early mutants of cv. Zeta-2, one was consistently early at all 3 locations.
Plant height, lint yield, length, micronaire, strength, etc., as well as oil
%, protein %, and gossypol %, were not significantly
different from the untreated checks.
Impact of pugging by dairy cows on pastures and indicators of pugging damage to pasture soil in south-western Victoria
Authors: Nie Z. N. , Ward G. N. , Michael A. T.
Published: September 2002

Pugging damage by cows in wet winters is an important limitation for dairying
in Victoria and Tasmania. A grazing trial was conducted to identify the
effects of pugging by dairy cows on pasture yield and utilisation in
south-western Victoria, Australia. A series of pugging severity treatments (no
pugging, light, medium, and heavy pugging) were imposed by varying stocking
density at different soil moisture levels. Medium–heavy pugging in
winter reduced pasture yield in the following spring by 40–42%,
pasture utilisation by 34–40%, and perennial ryegrass
(Lolium perenne L.) tiller density by
39–54%. Light pugging had no effect on pasture yield,
utilisation, and perennial ryegrass tiller density. Pasture growth rate showed
a similar pattern between treatments; however, the impact was greater in the
first 9 weeks after pugging than later (9–14 weeks). With heavy stocking
density, there could be a potential risk of pugging damage when soil strength
is <700 kPa. Indicators of pugging severity (pugging score, depth, and soil
surface roughness) were highly correlated. The relationship between pugging
severity and pasture yield, utilisation, and ryegrass tiller density was best
described by a negative linear regression when pugging scores were 0–2.
Leaf modification delays panicle initiation and anthesis in grain sorghum
Authors: Ockerby S. E. , Midmore D. J. , Yule D. F.
Published: September 2002

Water stress at anthesis is the major cause of yield reduction or crop failure
in grain sorghum [Sorghum bicolor (L.) Moench]
in central Queensland. Rainfall is difficult to predict and it is impractical
to substantially alter the timing and amount of water stored in the soil, so
we focussed on whether crop ontogeny could be managed, ultimately giving
farmers some capability to align anthesis with in-crop rain. It is widely
considered that a signal, transported from the leaf to the shoot apical
meristem, is integral to the onset of panicle initiation and reproductive
development. We hypothesised that modifying the leaves may interrupt the
signal and cause a delay in the onset of reproductive development. Delays in
sorghum anthesis associated with leaf modification treatments applied before
panicle initiation were found to be a consequence of delays in panicle
initiation. The longest delays in panicle initiation were obtained by
twice-weekly defoliation above the second ligule (15–45 days); delays
were shorter when plants were defoliated above the third ligule (10–41
days) or when only the fully exposed leaves were removed (0–13 days),
depending on genotype. Although panicle initiation was delayed, leaf
initiation continued, so extra leaves were produced. Defoliation of fully
irrigated plants, however, generally reduced green leaf area, plant dry weight
at anthesis, and grain yield, all by 30–50%. The application of
ethephon also delayed anthesis, and changed the pattern but not the area of
leaf produced, and did not alter grain yield. In rain-fed agriculture, where
grain yields are frequently <50% of irrigated controls, delaying
panicle initiation by 2 weeks may provide a better rainfall environment during
which anthesis and grain-filling will occur. Reductions in green leaf area,
although reducing yield potential, may promote a more balanced use of water
between vegetative and grain growth. There was sufficient evidence to indicate
that defoliation before panicle initiation could provide simple post-sowing
management to achieve this scenario.
Incidence of virus infection in experimental plots, commercial crops, and seed stocks of cool season crop legumes
Authors: Latham L. J. , Jones R. A. C.
Published: September 2002

Experimental plots of cool season crop legumes growing at diverse locations in
Western Australia were inspected for plants with suspect virus symptoms over 4
growing seasons (1994, 1997, 1998, 1999), and plant samples were tested for
infection with alfalfa mosaic (AMV), bean yellow mosaic (BYMV), cucumber
mosaic (CMV), and pea seed-borne mosaic (PSbMV) viruses. All 4 viruses were
detected in faba bean (Vicia faba); BYMV, CMV, and PSbMV
in field pea (Pisum sativum); AMV, CMV, and PSbMV in
lentil (Lens culinaris); and AMV and CMV in chickpea
(Cicer arietinum). Among minor crop species, AMV, BYMV,
and CMV were found in narbon bean (V. narbonensis) and
grass pea (Lathyrus sativus); BYMV and CMV in dwarf
chickling (L. cicera); BYMV in bitter vetch
(V. e r v i l i a ) and
L. clymenum; and AMV in fenugreek
(Trigonella foenum-graecum). Incidences of individual
viruses varied widely from site to site but plot infection sometimes reached
100%. Symptom severity varied widely with virus–crop combination.
In large-scale surveys of commercial crops of field pea and faba bean over 2
(1998, 1999) and 3 (1994, 1998, 1999) growing seasons, respectively, randomly
collected samples from each crop were tested for presence of AMV, BYMV, CMV,
and PSbMV. In 1999 they were also tested for beet western yellows virus
(BWYV). All 5 viruses were detected in both species. BWYV was found in
35% of faba bean and 56% of the field pea crops sampled in 1999,
with incidences of infection in individual crops up to 40% and
49%, respectively. PSbMV was found in 42% and BYMV in 18%
of field pea crops in 1999. In individual crops, highest infection incidences
of BYMV and PSbMV detected were 31% for BYMV in faba bean in 1998 and
9% for PSbMV in field pea in 1999. CMV and AMV incidences in both
species never exceeded 7% of crops or 4% of plants within
individual crops. Infection by 2 different viruses within individual crops was
common, even 3 were sometimes found. Cultivars infected with most viruses were
Fiesta and Fiord for faba bean, and Dundale, Laura, and Magnet for field pea.
BYMV was detected in the crop tested of dwarf chickling. In tests on seed
samples from Western Australia of 30 commercial seed stocks of field pea, 11
of faba bean, and 50 of chickpea, PSbMV was detected in 11, 1, and 1,
respectively; CMV in 1, 1, and 3; BYMV in 3, 1, and 0; and AMV in 0, 0, and 1.
This appears to be the first record of seed transmission of CMV in pea and
faba bean. Seed samples from Victoria were also found to contain viruses:
PSbMV in pea and AMV in lentil.
Widespread infection with viruses in evaluation plots and commercial crops of
cool season crop legumes is a cause for concern, especially where individual
crop incidences are high and 2 or more viruses are present. Sowing of infected
seed stocks leads to introduction of randomly dispersed sources of virus
infection within the crop sown, resulting in spread of infection and yield
losses. Appropriate control measures are discussed.
Environmental factors influencing maturation and release of ascospores of Venturia pirina in Victoria, Australia
Authors: Villalta O. N. , Washington W. S. , Rimmington G. M. , MacHardy W. E.
Published: September 2002

The influence of moisture, light, and temperature on
Venturia pirina ascospore maturation and discharge was
studied during 1992–99 in 2 pear-growing regions in Victoria. In each
year and site, mature ascospores were trapped over a 3-month period beginning
a few days before or at the green-tip stage of pear tree development in early
September and ending in late November, with the majority of ascospores
((>80%) trapped between green-tip and petal-fall. Ascospore
discharge was associated with rain and dew, with 90–98% of the
season’s total number of ascospores trapped during rain events and
2–10% trapped during dew events in the 12 data sets examined.
Most ascospores were trapped (82.5– 99.9%) during daytime
(0600–1800 hours). The 0.1–17.5% of ascospores detected
during night time (1900–0500 hours) were trapped mainly within 1–3
h of dawn or dusk. There were linear relationships between the logit of
cumulative percentage of ascospore maturation and temperature accumulation
(above 0 degree-days), calculated both daily and for days with
>= 0.2 mm of rainfall. Six linear regression equations were
formulated with 10 years of field data and using the 2 methods of accumulating
degree-days, to predict the cumulative percentage of matured ascospores.
Predictions were compared with additional field and laboratory observations
not used in the formulation of the linear equations. The importance of the
temperature-based linear equations is discussed in relation to the prediction
of pear scab ascospore maturity for use in a pear scab management program.
Changes in protein composition during grain development in wheat
Authors: Panozzo J. F. , Eagles H. A. , Wootton M.
Published: September 2002

Changes in glutenin, gliadin, glutenin subunit composition, and polymer size
distribution were monitored for 4 cultivars of wheat
(Triticum aestivum L.) throughout grain filling in an
irrigated and non-irrigated environment over 2 seasons. The synthesis of
glutenin and gliadin was modelled using a logistic function to determine the
rate and duration of synthesis in response to environmental conditions. The
maximum rate of synthesis of glutenin occurred approximately 6–8 days
after the maximum rate of gliadins, with the duration extended by a similar
period. High molecular weight glutenin subunits (HMWGS) were detected earlier
than low molecular weight glutenin subunits (LMWGS). After the initial
synthesis of HMWGS, there was a period at approximately mid grain filling when
the rate of synthesis was reduced, followed by a period of more rapid
synthesis in the latter stages of grain filling. In contrast, once detected,
LMWGS increased at a faster rate than, and were in excess with respect to,
HMWGS.
Cultivar and environmental differences were observed, but in all cases the
average molecular weight of polymeric glutenin increased throughout grain
filling. Large polymers (>400 kD) increased continuously during grain
filling, whereas polymers in the range 150–400 kD remained relatively
constant and smaller polymers <150 kD decreased. As grain filling
approached physiological maturity, there was a rapid increase in the synthesis
of large polymers. The gliadin to glutenin ratio was almost the same in grain
from adjacent irrigated and non-irrigated environments subjected to high
temperatures at mid grain f illing, but the proportion of highly polymeric
glutenin was greater from the non-irrigated environment.
Effects of sowing time and nitrogen fertiliser on canola and wheat, and nitrogen fertiliser on Indian mustard. II. Nitrogen concentrations, N accumulation, and N fertiliser use efficiency
Authors: Hocking P. J. , Stapper M.
Published: September 2002

Canola, Indian mustard, and wheat were grown at Ariah Park and Cowra (canola
only) in the cropping belt of New South Wales, Australia, to determine the
effects of sowing time (canola and wheat) and nitrogen (N) fertiliser on N
concentrations and N accumulation in shoots, N fertiliser use-efficiency, and
N removal in grain of the crops. Concentrations of N in shoots of all crops
decreased during the season, irrespective of sowing time or N fertiliser rate.
Late sowing decreased N accumulation by 55% and 40% for canola
and wheat, respectively, at Ariah Park, and by 50% for canola at Cowra,
but increased canola and wheat grain N (protein) concentrations more than the
applied N. All crops accumulated most of their N before anthesis, and there
was little N accumulation after the end of flowering; however, sowing canola
late increased the proportion of N accumulated during flowering. Indices of N
fertiliser use efficiency were reduced by sowing late, but N use efficiencies
of the oilseeds at each sowing time were similar to values for wheat after
accounting for differences in the biosynthetic costs of grain and straw
production. Removal of N in canola grain from an April sowing was 35%
greater than N removal by wheat grain sown at the same time, but was similar
for both crops from late May and July sowings. Consequently, more N fertiliser
should be applied to canola than wheat to obtain high grain yields when both
crops are sown early in the season. It was concluded that sowing early was
essential to achieve high N use efficiency, reduce potential losses of N, and
maximise economic returns from N fertiliser.
Yield performance and adaptation of some Australian and CIMMYT/ICARDA developed wheat genotypes in the West Asia North Africa (WANA) region
Authors: Sivapalan S. , O'Brien L. , Ortiz-Ferrara G. , Hollamby G. J. , Barclay I. , Martin P. J.
Published: September 2002

A set of 29 advanced breeding lines and named cultivars from different
breeding programs in Australia was compared with 18 genotypes developed by the
CIMMYT/ICARDA breeding programs for their adaptation and yield performance
using 5 locations in the WANA region for 2 years. Classification analysis
identified 13 CIMMYT/ICARDA genotypes that had a pattern in yield
performance similar to 2 Australian cultivars, Leichhardt and Hartog. The
classification of environments effectively identified trials that experienced
heat stress and received supplementary irrigation. Most of the genotypes
developed by the CIMMYT/ICARDA breeding programs showed wide adaptation in
the WANA region. Genotypes developed for Australian Mediterranean environments
failed to show wide adaptation in the WANA region. However, many Australian
genotypes showed specific adaptation to heat-stressed environments. Variation
among Australian genotypes for disease resistance and heat tolerance couldbe
used for wheat improvement in the WANA region.
Near infrared reflectance spectroscopy as a potential surrogate method for the analysis of D13C in mature kernels of durum wheat
Authors: Ferrio J. P. , Bertran E. , Nachit M. , Royo C. , Araus J. L.
Published: September 2002

Carbon isotope discrimination (Δ13C) in grain is
a potentially useful trait in breeding programs that aim to increase the yield
of wheat and other cereals. Near infrared reflectance spectroscopy (NIRS) is
used in routine assays to determine grain and flour quality. This study
assesses the ability of NIRS to predict Δ13C in
mature kernels of durum wheat. Plants were grown in north-west Syria as this
location provided 3 distinct Mediterranean trials that covered a wide range
for Δ13C values in grains (from about
12.9‰ to 17.6‰). We measured the spectral reflectance signature
between 1100 and 2500 nm in samples from the same flour used in the
conventional (i.e. mass spectrometry) determinations of
Δ13C. By using principal components regression
and partial least squares regression (PLSR), a model of the association
between conventional laboratory analysis and these spectra was produced.
Global regressions, which included samples from all 3 trials, and local
models, which used samples from only one trial, were built and then validated
with sample sets not included in calibration procedures. In global models,
strong significant correlations (P < 0.001) were
found between NIRS-predicted Δ13C and measured
Δ13C values. PLSR gave r
2 values of 0.86 and 0.82 for calibration and validation
sets, respectively. Although less strongly correlated, all local models
selected for a subset of samples with significantly higher
Δ13C values. Local models also performed well
when selecting samples from the other 2 trials. The advantages and possible
limitations of NIRS are further discussed.
Involvement of root inhibitory Pseudomonas spp. in the poor early growth of direct drilled wheat: studies in intact cores
Authors: Simpfendorfer S. , Kirkegaard J. A. , Heenan D. P. , Wong P. T. W.
Published: September 2002

Wheat seedlings were grown in intact cores of soil removed from 26 sites
throughout southern New South Wales where slower seedling growth in
direct-drilled (DD) soil than in cultivated soil had been commonly reported.
Experiments were conducted in a controlled environment using soil cultivation
and fumigation to assess the role of physical and biological constraints to
growth under direct drilling. Populations of various microbial groups
(especially Pythium and
Pseudomonas spp.) were assessed for their involvement in
the growth reductions.
Soil cultivation increased the growth of seedlings relative to the DD
treatment in cores from 18 of the 26 sites (mean increase 43%), while
sterilisation increased growth in DD cores from 25 of the sites (mean increase
68%). The growth response to cultivation was less than that to
sterilisation in cores from most sites, suggesting that cultivation only
partially removes the growth limitation. With the exception of one site,
cultivating sterilised cores provided no additional growth benefits over the
sterilised DD treatment, indicating that biological rather than physical
factors per se were predominantly responsible for the
reduced growth.
The reduced growth in DD cores was not associated with the presence of any of
the common soil-borne fungal pathogens of wheat. Averaged across sites,
Pseudomonas populations in the rhizosphere of seedlings
grown in cultivated cores were reduced by 50% compared with the DD
treatment, while sterilisation reduced populations by 65%. An
assessment of the inhibitory activity of pseudomonads towards wheat seedlings
in a test-tube bioassay indicated that reduced growth in DD cores was more
closely related to the deleterious activity of
Pseudomonas spp. toward root growth than to their
population in the rhizosphere. A close relationship existed between the
inhibitory activity of Pseudomonas spp. and the response
of wheat seedlings to both cultivation (r =
0.859) and sterilisation (r mp;equals; 0.842).
A methodology for analysis of sugarcane productivity trends. I. Analysis across districts
Authors: Ellis R. N. , Basford K. E. , Cooper M. , Leslie J. K. , Byth the late D. E.
Published: September 2002

Historically, few articles have addressed the use of district level mill
production data for analysing the effect of varietal change on sugarcane
productivity trends. This appears to be due to lack of compiled district data
sets and appropriate methods by which to analyse these data. Recently,
varietal data on tonnes of sugarcane per hectare (TCH), sugar content (CCS),
and their product, tonnes of sugar content per hectare (TSH) on a district
basis, have been compiled. This study was conducted to develop a methodology
for regular analysis of such data from mill districts to assess productivity
trends over time, accounting for variety and variety environment interaction
effects for 3 mill districts (Mulgrave, Babinda, and Tully) from 1958 to 1995.
Restricted maximum likelihood methodology was used to analyse the district
level data and best linear unbiased predictors for random effects, and best
linear unbiased estimates for fixed effects were computed in a mixed model
analysis. In the combined analysis over districts, Q124 was the top ranking
variety for TCH, and Q120 was top ranking for both CCS and TSH. Overall
production for TCH increased over the 38-year period investigated. Some of
this increase can be attributed to varietal improvement, although the
predictors for TCH have shown little progress since the introduction of Q99 in
1976. Although smaller gains have been made in varietal improvement for CCS,
overall production for CCS decreased over the 38 years due to non-varietal
factors. Varietal improvement in TSH appears to have peaked in the mid-1980s.
Overall production for TSH remained stable over time due to the varietal
increase in TCH and the nonvarietal decrease in CCS.