bluuebunny/crossref_metadata_2025 huggingface dataset:
Calculating the hopping times of confined fluids: Two hard disks in a box
Authors: Bowles R. K. , Mon K. K. , Percus J. K.
Published: November 2004

The dynamical transition between the anomalous single file diffusion of highly confined fluids and bulk normal diffusion can be described by a phenomenological model involving a particle hopping time τhop. We suggest a theoretical formalism that will be useful for the calculation of τhop for a variety of systems and test it using a simple model consisting of two hard disks confined to a rectangular box with hard walls. In the case where the particles are moving diffusively, we find the hopping time diverges as a power law in the threshold region with an exponent of −(3/2). Under conditions where the particles move inertially, transition state theory predicts a power law behavior with an exponent of −2. Molecular dynamics simulations confirm the transition state theory result for inertial dynamics, while Brownian dynamics simulations suggest the scaling exponent is highly sensitive to the details of the algorithm.
Evaluation of small-angle x-ray scattering data of a Raney-type Ni catalyst with computer simulation
Authors: Tóth Gergely , Körmendi Krisztina , Vrabecz Attila , Bóta Attila
Published: November 2004

A reverse Monte Carlo-type simulation method was developed for the evaluation of anomalous small-angle x-ray scattering data of a Raney-type Ni catalyst. Based on other experimental data the catalytic Ni particles were modeled as small crystalline cylinders dispersed in the matrix. The average size of the Ni particles and their pair-correlation function were determined. Despite the unknown density of the catalyst, it is shown that each particle has about 2 neighbors in the first neighboring shell independent of the modeling density, and the position of the first peak of the pair-correlation function does not depend on the modeling density. A method was elaborated to get reasonable performance of the Reverse Monte Carlo-type simulation. The scattered intensity was calculated on the basis of probe scattering atoms put inside the cylinders. The effects of the omission of the real number of the atoms, the unknown density, the lack of normalization and the uncertainties in the cross sections were unified in two constants that were determined during the simulation. The method can be used for nanoparticles with other shape, where analytic form factors are complicated, and it may be powerful in the investigation of the usually neglected or simplified inter-particle structure of these systems.
Bonding and (hyper)polarizability in the sodium dimer
Authors: Maroulis George
Published: November 2004

We report a conventional ab initio and density functional theory study of the polarizability (ααβ/e2a02Eh−1) and hyperpolarizability (γαβγδ/e4a04Eh−3) of the sodium dimer. A large [18s14p9d2f1g] basis set is thought to yield near-Hartree–Fock values for both properties: ᾱ=272.28, Δα=127.22 and γ̄=2157.6×103 at Re=3.078 87 Å. Electron correlation has a remarkable effect on the Cartesian components of γαβγδ. Our best value for the mean is γ̄=1460.1×103. The (hyper)polarizability shows very strong bond-length dependence. The effect is drastically different for the longitudinal and transverse components of the hyperpolarizability. The following first derivatives were extracted from high-level coupled cluster calculations: (dᾱ/dR)e=54.1, (dΔα/dR)e=88.1e2a0Eh−1, and (dγ̄/dR)e=210×103e4a03Eh−3. We associate the (hyper)polarizability to bonding effects between the two sodium atoms by introducing the differential property per atom Qdiff/2≡{Q[Na2(X 1Σg+)]/2−Q[Na(2S)]}. The differential (hyper)polarizability per atom is predicted to be strongly negative for the dimer at Re, as [ᾱ(Na2)/2−α(Na)]=−33.8 and [γ̄(Na2)/2−γ(Na)]=−226.3×103. The properties calculated with the widely used B3LYP and B3PW91 density functional methods differ significantly. The B3PW91 results are in reasonable agreement with the conventional ab initio values. Last, we observe that low-level ab initio and density functional theory methods underestimate the dipole polarizability anisotropy. Experimental data on this important property are highly desirable.
Monte Carlo simulation of structure and nanoscale interactions in polymer nanocomposites
Authors: Zhang Qiang , Archer Lynden A.
Published: November 2004

Off-lattice Monte Carlo simulations in the canonical ensemble are used to study polymer-particle interactions in nanocomposite materials. Specifically, nanoscale interactions between long polymer chains (N=550) and strongly adsorbing colloidal particles of comparable size to the polymer coils are quantified and their influence on nanocomposite structure and dynamics investigated. In this work, polymer-particle interactions are computed from the integrated force-distance curve on a pair of particles approaching each other in an isotropic polymer medium. Two distinct contributions to the polymer-particle interaction potential are identified: a damped oscillatory component that is due to chain density fluctuations and a steric repulsive component that arises from polymer confinement between the surfaces of approaching particles. Significantly, in systems where particles are in a dense polymer melt, the latter effect is found to be much stronger than the attractive polymer bridging effect. The polymer-particle interaction potential and the van der Waals potential between particles determine the equilibrium particle structure. Under thermodynamic equilibrium, particle aggregation is observed and there exists a fully developed polymer-particle network at a particle volume fraction of 11.3%. Near-surface polymer chain configurations deduced from our simulations are in good agreement with results from previous simulation studies.
Phase imaging and the lever-sample tilt angle in dynamic atomic force microscopy
Authors: D’Amato Matthew J. , Marcus Matthew S. , Eriksson Mark A. , Carpick Robert W.
Published: November 2004

The phase shift in amplitude-controlled dynamic atomic force microscopy (AFM) is shown to depend on the cantilever-sample tilt angle. For a silicon sample and tip the phase shift changes by nearly 15° for a change in tilt angle of 15°. This contribution to the phase results from the oscillating tip’s motion parallel to the surface, which contributes to the overall energy dissipation. It occurs even when the measurements are carried out in the attractive regime. An off-axis dynamic AFM model incorporating van der Waals attraction and a thin viscous damping layer near the surface successfully describes the observed phase shifts. This effect must be considered to interpret phase images quantitatively.
Equilibrium free energy estimates based on nonequilibrium work relations and extended dynamics
Authors: Atılgan Erdinç , Sun Sean X.
Published: November 2004

Jarzynski’s relation and the fluctuation theorem have established important connections between nonequilibrium statistical mechanics and equilibrium thermodynamics. In particular, an exact relationship between the equilibrium free energy and the nonequilibrium work is useful for computer simulations. In this paper, we exploit the fact that the free energy is a state function, independent of the pathway taken to change the equilibrium ensemble. We show that a generalized expression is advantageous for computer simulations of free energy differences. Several methods based on this idea are proposed. The accuracy and efficiency of the proposed methods are evaluated with a model problem.
Reduction of contact resistance in pentacene thin-film transistors by direct carrier injection into a-few-molecular-layer channel
Authors: Yoneya Nobuhide , Noda Makoto , Hirai Nobukazu , Nomoto Kazumasa , Wada Masaru , Kasahara Jiro
Published: November 2004

We found an abrupt reduction of contact resistance, Rc, in pentacene bottom-contact thin-film transistors (TFTs) with Au/Ti source/drain (S/D) electrodes when Ti thickness is below ∼3nm. Our results suggest that the direct ohmic contact with a few molecular layer channel is a key to reduce the Rc of the S/D electrodes. We propose a Au/self-assembled monolayer electrode structure enabling direct ohmic contact with these few molecular layer channels, and achieved high-performance bottom-contact TFTs with an extrinsic mobility of 1.1cm2∕Vs, an on/off ratio of 106, and a subthreshold swing of 0.3 V/decade.
Growth of thick (112¯0) GaN using a metal interlayer
Authors: Tavernier P. R. , Imer B. , DenBaars S. P. , Clarke D. R.
Published: November 2004

Thick films of (112¯0)-oriented GaN have been grown on Ti-coated metal organic chemical vapor deposition templates using hydride vapor phase epitaxy. Significant reductions in crack density were observed enabling 240μm thick films to be grown on sapphire. The use of Ti interlayers was shown to generate significant fractions of voids at the interlayer regrowth interface facilitating void-assisted separation on cooling. Ti metal layers annealed under optimal conditions were found to produce a TiN nanomask suitable for lateral overgrowth during HVPE. An estimate of the void size required to allow spontaneous delamination of the substrate at the TiN–GaN interface is discussed with reference to growth conditions.
Doping of low-temperature GaAs and GaMnAs with carbon
Authors: Schott G. M. , Rüster C. , Brunner K. , Gould C. , Schmidt G. , Molenkamp L. W. , Sawicki M. , Jakiela R. , Barcz A. , Karczewski G.
Published: November 2004

The incorporation of carbon in low-temperature (LT) GaAs and GaMnAs layers deposited by molecular-beam epitaxy under various growth conditions has been investigated. The lattice parameter depends on Mn content, C content, and the growth conditions which strongly affect Mn, C, and point defect incorporation. We found optimum growth conditions (Tsub=270°C, the beam equivalent pressure ratio is 5, growth rate is 0.1nm∕s) at which high-quality GaMnAs layers with moderate Mn content as well as LT-GaAs layers were deposited, which were efficiently p-doped by carbon. LT GaAs:C revealed the same electrical activation of carbon of about 50% at a high doping level p=5×1019cm−3 as observed in high-temperature GaAs:C. The Curie temperature as well as the saturation magnetization of GaMnAs decreases with C doping. This suggests a reduced amount of Mn contributing to the ferromagnetic phase in GaMnAs:C.
Optical and electro-optical properties of submicrometer lithium niobate slab waveguides prepared by crystal ion slicing and wafer bonding
Authors: Rabiei Payam , Gunter Peter
Published: November 2004

LiNbO 3 thin film crystals have been produced using crystal ion slicing and wafer bonding. Films with a thickness of 680nm are produced on a thin layer of SiO2, which is deposited on a substrate with electrodes. The crystalline and optical qualities of the fabricated thin films are investigated and are comparable to bulk LiNbO3 single crystals. The effect of thermal annealing is studied using Rutherford backscattering. The refractive indices and the electro-optical (EO) coefficient of the fabricated films are measured using prism coupling dark line spectroscopy and modified attenuated total reflection. The EO coefficient is equal to r33=31pm∕V at λ=633nm.
Dedicated Max-Planck beamline for the in situ investigation of interfaces and thin films
Authors: Stierle A. , Steinhäuser A. , Rühm A. , Renner F. U. , Weigel R. , Kasper N. , Dosch H.
Published: November 2004

A dedicated beamline for the Max-Planck-Institut für Metallforschung was recently taken into operation at the Ångstro/mquelle Karlsruhe (ANKA). Here we describe the layout of the beamline optics and the experimental end-station, consisting of a heavy duty multiple circle diffractometer. For both a new design was realized, combining a maximum flexibility in the beam properties [white, pink, (focused) monochromatic, energy range 6–20 keV] with a special diffractometer for heavy sample environments up to 500 kg, that can be run in different geometrical modes. In addition the angular-reciprocal space transformations for the diffractometer in use are derived, which allows an operation of the instrument in the convenient six circle mode. As an example, results from surface x-ray diffraction on a Cu3Au(111) single crystal are presented.
Direct determination of the equilibrium unbinding potential profile for a short DNA duplex from force spectroscopy data
Authors: Noy Aleksandr
Published: November 2004

Modern force microscopy techniques allow researchers to use mechanical forces to probe interactions between biomolecules. However, such measurements often happen in nonequilibrium regime, which precludes straightforward extraction of the equilibrium energy information. Here we use the work-averaging method based on Jarzynski equality to reconstruct the equilibrium interaction potential from the unbinding of a complementary 14-mer DNA duplex from the results of nonequilibrium single-molecule measurements. The reconstructed potential reproduces most of the features of the DNA stretching transition, previously observed only in equilibrium stretching of long DNA sequences. We also compare the reconstructed potential with the thermodynamic parameters of DNA duplex unbinding and show that the reconstruction accurately predicts duplex melting enthalpy.
Memory effect from charge trapping in layered organic structures
Authors: Kang Sung Hoon , Crisp Todd , Kymissis Ioannis , Bulović Vladimir
Published: November 2004

We demonstrate organic light emitting devices (OLEDs) with a charge trap layer that show memory behavior. These OLEDs demonstrate that organic heterojunction structures can controllably trap and release electronic charges. The trap layer is either 5-nm-thick clustered silver islands, or a 10-nm-thick organic laser dye DCM2 ([2-methyl-6-[2-(2,3,6,7-tetrahydro-1H,5H-benzo[i,j]quinolizin-9-yl)-ethenyl]-4H-pyran-4-ylidene] propane-dinitrile) doped into TPD (N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine). Predictions of the energy band structure indicate that both DCM2 sites and the metal islands can trap charge, consistent with the measured current–voltage characteristics. Trap sites are charged by applying reverse bias over the OLEDs. For devices with DCM2 traps we observe quenching of DCM2 photoluminescence upon charging, which allows us to quantify the charged trap density as approximately 10% of the trap sites or 1018cm−3. From time resolved measurements we observe that the charge retention time exceeds 2h.
Laser action in Eu-doped GaN thin-film cavity at room temperature
Authors: Park J. H. , Steckl A. J.
Published: November 2004

Rare-earth-based lasing action in GaN is demonstrated. Room-temperature stimulated emission (SE) was obtained at 620 nm from an optical cavity formed by growing in situ Eu-doped GaN thin films on sapphire substrates. The SE threshold for optical pumping of a ∼1 at.  % Eu-doped GaN sample was ∼10kW∕cm2. The SE threshold was accompanied by reductions in the emission linewidth and lifetime. A modal gain of ∼43cm−1 and a modal loss of ∼20cm−1 were obtained.
Electromigration lifetime and critical void volume
Authors: He Jun , Suo Z. , Marieb T. N. , Maiz J. A.
Published: November 2004

We study electromigration in copper lines encapsulated in an organosilicate glass. A line fails when a void near the upstream via grows to a critical volume. We calculate the void volume as a function of time. The statistical distribution of the critical volume (DCV) is taken to be independent of testing variables, such as line length and electric current density. By contrast, the distribution of the lifetime (DLT) strongly depends on these testing variables. We deduce the DCV from the experimentally measured DLT. Once deduced, the DCV can predict the DLT under untested conditions.
Kinetic measurement of ribosome motor stalling force
Authors: Sinha Deepak Kumar , Bhalla U. S. , Shivashankar G. V.
Published: November 2004

We measure the ribosome motor stalling forces to unzip mRNA polymers during gene expression. An approach of using the changes in the reaction rate constants to determine the molecular motor forces is presented. Specific antisense DNA oligomers complementary to mRNA templates are used as kinetic barriers for estimating the ribosome forces using real time bioluminescence detection of luciferase gene expression. The rate constants are determined by comparing the experimental data with numerical simulation of gene expression to deduce the ribosome force (26.5±1pN) required to unzip mRNA polymers. Understanding the forces generated by the ribosome may also enable the construction of information-based artificial nanoscale machines.
Phase separation and magnetic properties of half-metal-type Co2Cr1−xFexAl alloys
Authors: Kobayashi K. , Umetsu R. Y. , Kainuma R. , Ishida K. , Oyamada T. , Fujita A. , Fukamichi K.
Published: November 2004

The phase stability and magnetic properties of the half-metal-type Co2Cr1−xFexAl alloy system were investigated. It was found that the occurrence of two-phase separation is unavoidable in a concentration range of less than x=0.4, leading to deviation of the saturation magnetic moments from the generalized Slater–Pauling line. The L21-type phase becomes stable in a concentration range of more than x=0.7, where no half-metallic behaviors are present. Consequently, it is concluded that the most favorable concentration for applications to spintronic devices is located around x=0.4 in Co2Cr1−xFexAl alloys having the B2-type phase.
Clamping effects in the Al2O3(112¯0)∕Nb(110)∕Eu(110) epitaxial system
Authors: Soriano S. , Dufour C. , Dumesnil K. , Borchers J. A. , Mangin Ph.
Published: November 2004

In-plane and out-of-plane lattice parameters of Nb and Eu have been measured as a function of temperature between 10 and 300 K in the Al2O3(112¯0)∕Nb(110)∕Eu(110) epitaxial system. It is shown that the Nb lattice is clamped in the growth plane to the sapphire substrate, in the whole temperature range. On its own, the Eu lattice is totally free to expand isotropically above a clamping temperature Tcl, below which in-plane parameters also freeze to an almost constant value. This well-defined clamping temperature strongly depends on the Eu thickness and likely is related to the thermal mobility of interface defects.
A phase retrieval algorithm for shifting illumination
Authors: Rodenburg J. M. , Faulkner H. M. L.
Published: November 2004

We propose a method of iterative phase retrieval that uses measured intensities in the diffraction plane to solve the phase problem in a way that bypasses the problem of lens aberration, leading to greatly improved spatial resolution. This method is stable, easy to implement experimentally, and can be used to view a large area of the specimen when that is desired.
Wavelength shifting in photonic bandgap microcavities with isotropic media
Authors: Di Falco Andrea , Conti Claudio , Assanto Gaetano
Published: November 2004

By coupled mode theory in the time domain and a finite-difference time-domain code, we investigate wavelength shifting and frequency conversion via four-wave mixing inside a photonic crystal wire in an isotropic Kerr material. The three-dimensional time-resolved analysis yields ultrafast and all-optically tunable frequency conversion of a signal/channel about the pump frequency.
Time-division multiplexing of high-resolution x-ray microcalorimeters: Four pixels and beyond
Authors: Doriese W. B. , Beall J. A. , Deiker S. , Duncan W. D. , Ferreira L. , Hilton G. C. , Irwin K. D. , Reintsema C. D. , Ullom J. N. , Vale L. R. , Xu Y.
Published: November 2004

We present experimental results from a four-pixel array of transition-edge-sensor, x-ray microcalorimeters read out through a single amplifier channel via a time-division superconducting quantum interference device multiplexer. We map the dependence of the x-ray energy resolution of the microcalorimeters on multiplexer timing parameters. We achieve multiplexed, four-pixel resolution of 6.94±0.05eV full width at half maximum of the MnKα complex near 5.9keV, which is a degradation of only 0.44eV from nonmultiplexed operation. An analysis of straightforward upgrades to the multiplexer predicts that a linear array of 32 of these pixels could be multiplexed with a degradation in resolution of only 0.1eV. These results, the first demonstration of a time-division multiplexer for x-ray detectors, establish a clear path to the instrumentation of a kilopixel microcalorimeter array.
Applied field Mössbauer study of shape anisotropy in Fe nanowire arrays
Authors: Zhan Qing-feng , He Wei , Ma Xiao , Liang Ya-qiong , Kou Zhi-qi , Di Nai-li , Cheng Zhao-hua
Published: November 2004

In order to investigate the magnetic anisotropy of Fe nanowire arrays from microscopic point of view, Fe57 Mössbauer spectra were measured at various magnetic fields along and perpendicular to the nanowire axis, respectively. On the basis of the absorption intensities of the second and the fifth lines of sextet, the orientation of Fe magnetic moments can be detected. It was found that the shape anisotropy dominates the overall magnetic anisotropy in the Fe nanowires. Furthermore, the longitudinal and transverse demagnetizing fields of Fe nanowire, respectively, were deduced from the effective hyperfine field at Fe57 nuclei as a function of applied field. The chain-of-spheres model in conjunction with symmetric fanning mechanism was adopted to interpret the domain structure and the parallel coercivity of magnetic nanowire arrays.
Differential effects of certain phenoxyacetic acid compounds and phenylcarbamates on plant species. I. Effect of applications to the soil prior to emergence
Authors: Moore RM
Published: November 2004

Investigations were conducted in glass-house and field to determine the effects of pre-emergence applications of certain phenoxyacetates and phenylcarbamates on plant species. The effects of both types of compounds on the establishment of all monocotyledons and dicotyledons tested and on the ear formation and grain yield of a cereal Triticum vulgare, are described. The phenoxyacetates, applied in 0.1 per cent. concentrations, markedly inhibited all the dicotyledonous species. Monocotyledons were, in general, more tolerant than the dicotyledons but were affected at the higher concentrations. The phenylcarbamates produced toxic responses, in varying degrees of intensity, on all the graminaceous species tested but affected only one dicotyledon, viz. Linum usitatissimum. Symptoms of toxicity are described and some factors which appeared to govern their intensity are noted.
Seedling blight. II. Soil in relation to seedling blight of opium poppy and peas
Authors: Angell HR
Published: November 2004

Three steamed soils, limed and not limed, two hosts, and one isolate of Pythium ultimum were used in an experiment. The organism, isolated from peas germinating in limed Belanglo soil, was pathogenic to both hosts. The incidence of seedling blight of peas in the three reinfested soils varied significantly. On poppy, on two of the reinfested soils, it also varied significantly, but inversely to the incidence on peas. On peas in the first sowing it was not affected by liming the soil; on poppy it was significantly reduced. Seedling blight of both hosts was associated with one organism. The contrasting results could not be correlated with the uniform conditions of soil temperature, air temperature, and soil moisture; on any one soil or soil treatment they could not be ascribed to the prevailing uniform aeration, reaction, microflora, and microbial antagonism The only conditioning factor that was varied was the steamed soil, or steamed soil modified by adding lime. Differences in the incidence of disease were associated with variation of the conditioning factor and the host. Seedling blight of peas, resulting from natural reinfestation, occurred in earlier resowings in limed than in unlimed soils. Physiogenic seedling blight of poppy also occurred, causing total loss on one soil and smaller percentages of loss on the other soils.
The effect of the dietary plane upon the reactions of two breeds of sheep during short exposures to hot environments
Authors: Riek RF , Hardy MH , Lee DHK , Carter HB
Published: November 2004

Five Camden Park Merino and six Corriedale ewes, each breed divided into three groups and offered the food corresponding respectively to high, medium, and low dietary levels, were exposed for seven hours a day, one to three days a week, to each of several selected hot atmospheres over a range of temperatures 30 to 45°C, and a range of vapour pressures 15 to 40 mm.Hg. Observations were made on the rectal temperature, pulse rate, respiratory rate, respiratory volume, evaporative water loss, food and water consumption, body weight, and behaviour. These sheep were relatively tolerant of the hot conditions, only the highplane Corriedales having to be removed before the completion of the seven hours' exposure from the atmosphere 40°C./40 mm.Hg., with a rectal temperature over 107° F. A sharp rise in respiratory rate followed commencement of the exposure, the rate in the Merino being the higher under all hot conditions above the mildest (300 °C./30 mm.Hg.). The average maximum rates obtained for four sheep were 370/min. for the Merinos and 290/min. for the Corriedales. Pulse rates showed little change from normal rates of 60-65min. until air temperate or humidity reached high levels. The rise in vapour pressure at an air temperature of 40°C., which produced the same effect as a rise of 1°C. in air temperature at a vapour pressure of 30 mm.Hg., was 0.25 mm.Hg. for rectal temperature, 1.7 mm.Hg. for respiratory rate, and 2.3 mm.Hg. for respiratory volume. A high-plane diet reduced the heat tolerance of sheep, and heavy individuals actually lost weight during the experimental period. A very low diet, on the other hand, also impaired heat regulation, probably as part of a general depression of function. Sheep on a medium-plane diet fared best. It is difficult to account for observed water losses under hot conditions unless sweating is admitted.
Volatile fatty acid metabolism of ruminants, with particular reference to the lactating bovine mammary gland and the composition of milk fat
Authors: McClymont GL
Published: November 2004

Studies are reported on the volatile fatty acid (V.F.A.) metabolism of sheep and bovines with particular reference to the association between (i) ingestion of food and ruminal levels of V.F.A.s and arterial levels of acetic acid and (ii) the utilization of arterial acetic acid by the bovine mammary gland and the association between this utilization and the proportion of lower fatty acids (Reichert-Meissl value) in the milk fat. Ruminal levels of V.F.A. and arterial levels of acetic acid were found to be similar in cattle and sheep, and similar to those reported by earlier workers for sheep. There was a close association between changes in ruminal V.F.A. and arterial acetic acid levels. Arterial acetic acid levels were found on the feeds studied to reach a maximum value of 8-14 mg. per cent. by 2-5 hours after feeding, declining to 5-8 mg. per cent. by 8 hours after feeding and to 2-6 mg. per cent. by 16 hours after feeding. On starvation for approximately 72 hours, values fell as low as 1.5 mg. per cent. Acetic acid was found to be a major metabolite of the bovine mammary gland, arterio-venous (A-V.) differences being directly dependent on the arterial level and of the order of 2-6 mg. per cent. or 40-80 per cent. of the arterial level in the fed animal. Arterial levels and mammary A-V. differences of acetic acid were unaffected by cod-liver oil feeding or low roughage-high concentrate diets, both of which depressed the fat percentage and the Reichert- Meissl (R-M.) value of the milk fat. Hyperinsulinism and recent or delayed milking also had no effect on the A-V. differences. The depression in R-M. value during fasting was not reversed by intraruminal or intravenous acetic acid infusions despite the maintenance of high blood levels of acetic acid. There was no detectable correlation between carbon dioxide output by the mammary gland and the acetic acid uptake of the gland, indicating that the acid served some 'useful' purpose in the gland. It is concluded, taking into account other evidence, that acetic acid is utilized in the gland for fat synthesis and oxidation, depending on the requirements of the gland, but that the proportion of lower fatty acids in milk fat is not dependent on the uptake of acetic acid.
Some effects of no cultivation on the yield and growth of citrus trees
Authors: Frith HJ
Published: November 2004

A factorial field experiment is described in which cultural, irrigation, and nitrogen treatments were tested on citrus trees of different stocks and scions. The sod treatment quickly caused decreases in growth of the trees and the yield and quality of the fruit produced. The plots where bare soil was maintained have given large healthy trees with high yields of good-quality fruit, in spite of an observed deterioration of soil structure in these plots. Nitrogen treatments improved the yield and health of the trees in the sod treatments but have had no effect on the other cultural treatments. Root distribution, soil fertility, and leaf analysis studies, undertaken to try to explain the reasons for the yield differences noted, are described and it is concluded that nitrogen effects could explain all differences recorded to date.
Selection for economic characters in Australian Merino sheep. II. Relative efficiency of certain aids to selection.
Authors: Morley FHW
Published: November 2004

Theoretical consequences of the use of progeny testing, sib testing, and mass selection are examined in a flock of 1,000 ewes producing 700 progeny of breeding age each year. Selection based on a combination of individual merit and merit of half-sibs should result in approximately the same annual improvement as that achieved by optimum use of progeny-tested sires. In large flocks extensive use of outstanding sires by artificial insemination may increase progress for traits with heritability of about 0.3 by a factor of about 1.2 as compared with mass selection. The advantages to be gained by progeny testing and artificial insemination may be outweighed by the dangers of inbreeding, and the cost involved would have to be considered. As most of these advantages should be achieved by combination or even by mass selection, which avoid inbreeding and much of the cost, progeny testing with wide use of progeny-tested sires is unlikely to be the most economical road to flock improvement.
Growth of wool fibres in sheep.
Authors: Fraser AS
Published: November 2004

The tips of birthcoat fibres in sheep range in shape from a definite sickle tip to one with no definite shape. The different shapes of tip are related to different types of follicle. The shapes of the tips are explained as the result of competition between follicles. The intensity of competition is not uniform, as follicles enter the follicle population in sequence.
Growth of the N-type fleece.
Authors: Fraser AS
Published: November 2004

The rates of growth of wool fibres are compared between normal and N-type Romney Marsh sheep. The three types of follicles — primaries and first- and second-wave secondaries — form their fibres at rates of the same order in normal Romneys. The N and nr genes cause an increase in the rate of growth of the early, primary fibres, and a decrease in the rate of growth of late fibres, having no marked effect on fibres initiated between these two periods. It is argued that. the primary effect of these genes is to increase the efficiency of competition of the early initiated follicles, resulting in an increased growth rate of their fibres, which, owing to competition between follicles, results in a proportionate decrease in the growth rate of the late fibres.
Spotted-wilt development in resistant and susceptible Lycopersicon species.
Authors: Hutton EM , Peak AR
Published: November 2004

Studies have been made of the development of the spotted-wilt virus In the inoculated leaves and non-inoculated parts of three Lycopersicon species. At temperatures of 60°F to 87°F. L. pimpinellifolium (Porter's strain), L. peruvanum, and the L. esculentum variety Rey de los Tempranos, exhibit different degrees of resistance to virus multiplication when compared with the susceptible Bonny Best variety. Infected plants of Porter's strain and Rey de los Tempranos are able to develop new growth free from virus. Resistance appears to depend on the presence of a virus-inactivating system which functions more actively when plants are maintained at a temperature of 90°F. Although the resistance of Porter's strain can be transmitted to hybrids, Rey de los Tempranos appears more promising as a parent for the development of spotted-wilt-resistant tomato varieties. A method for the selection of the resistant phenotypes in hybrid progenies is suggested.
Competition and weedicide studies of Mintweed (Salvia reflexa Hornem).
Authors: Bisset WJ
Published: November 2004

Experiments to determine the value of selective herbicides and improved soil fertility for the control of mintweed in competition with crop and pasture species are described. Under glass-house conditions mintweed and Queensland blue grass gave a lesser response to added sulphate of ammonia than did Rhodes grass; the contrast was more marked where water supply was limited. Rhodes grass competed more strongly with mintweed than did Queensland blue grass. Where mintweed was controlled by a selective herbicide the yield of sorghum and French millet was increased significantly.
Availability of trace elements from rocks and minerals.
Authors: Swaby RJ , Passey BI
Published: November 2004

Fifteen rocks and 65 minerals were bioassayed for the amounts of Fe, Zn, Cu, Mn, and Mo available to Aspergillus niger. The micronutrients most commonly released were Fe and Mo, followed by Mn, then Cu, and least of all Zn. Some rocks and minerals contained traces of all micronutrient elements, but rarely in sufficient quantity for optimal growth of the mould. Among the rocks, the igneous types were better sources of micronutrients than the metamorphic and the sedimentary. Among the minerals, those featuring micronutrient elements in their chemical formulae tended to be fairly good suppliers of these elements, but certain minerals not suspected of containing micronutrients were also found to provide them in moderate amounts. The quantity of trace elements released from ferro-magnesium silicates varied considerably, so that they are imperfect indices of the micronutrient status of soils.
Bare-patch disease and associated problems in subterranean clover pastures in South Australia.
Authors: Ludbrook WV , Brockwell J , Riceman DS
Published: November 2004

Three diseases new to subterranean clover pastures have been observed in the Coonalpyn Downs, South Australia. Rhizoctonia solani is shown to be the cause of "bare patch" and Meloidogyne marioni of "root-knot patch". The third disease, "unthriftiness", is a complex problem. There is some evidence that Corticium praticola may be associated as a parasite, but it appears that there are other contributing factors. The implications of widespread establishment of these diseases are discussed and suggestions for control are made.
Some correlation studies of Australian rainfall.
Authors: Treloar HM , Grant AM
Published: November 2004

Statistical relations between rainfall and other climatological elements described by earlier workers have been extended for different districts and stations, different time lags, and more recent data. The latter study shows that practically all the correlations have decreased considerably in magnitude. The implications for the correlation method of seasonal forecasting are briefly discussed.
Studies of intervarietal hybridization in subterranean clover (Trifolium subterraneum L.).
Authors: Hutton EM , Peak JW
Published: November 2004

Subterranean clover pollen germinates freely on an agar medium at relative humidities above 95 per cent. and at temperatures between 20 and 25°C. Temperature was not as critical as relative humidity, since pollen germinated freely a t 4°C. Based on these findings an improved technique for the artificial hybridization of subterranean clover varieties was developed. With this technique 35.3 per cent. of the emasculated and cross-pollinated florets set seed in 18 different intervarietal crosses. Varying degrees of compatibility exist between different varieties. The percentage of emasculated florets in Tallarook which set seed from pollinations with different male parents varied from 75 per cent. for Dwalganup to 6.5 per cent. for Wenigup. The characteristics of a number of the F1 hybrids are described. The extent to which different parental characters were dominant in the hybrids is indicated.
Experiments on the control of the Lucerne flea (Sminthurus viridis (L) and the Red-Legged earth mite (Halotydeus destructor (Tuck.)) in pastures in Western Australia.
Authors: Wallace MMH
Published: November 2004

Experiments with BHC, chlordane, and parathion against the lucerne flea (Sminhurus viridis (L.)) and the red-legged earth mite (Halotydeus destructor (Tuck.)) in pastures are described. All insecticides were applied by means of a low-volume boom spray delivering 5 gal per acre. BHC applied at the rate of 2 lb 50 per cent. dispersible powder per acre had no effect on the lucerne flea population but killed approximately 90 per cent. of the earth mites present. Chlordane applied a t the rate of ½ lb per acre achieved no control of either pest. Parathion applied at the rate of ¼ pt of 20 per cent. emulsion per acre gave practically 100 per cent. control of lucerne fleas. Its residual effects were negligible and fleas hatching from eggs laid prior to spraying were not harmed. Equally good immediate control was achieved by applications of parathion at one-half the above concentration. The addition of DDT to the spray ensured the destruction of all earth mites as well as the lucerne flea. DDT gave no evidence of control of the lucerne flea in previous experiments. The experiments show that parathion is a highly effective insecticide against the lucerne flea but for maximum efficiency it should be applied early in the season before any eggs have been laid. The toxicity of the parathion sprays to grazing stock is discussed.
Development of the skin follicle population in Merino sheep.
Authors: Fraser AS
Published: November 2004

Skin samples were taken at intervals from birth to several months of age, and counts made of the ratio of secondary to primary follicles. This ratio, which is of the order of 2-4 at birth, increases to about 13-18 by 30-40 days after birth and then increases slowly to the mature value of 18-24 over several months.
The post-natal development of the skin follicle population of a strain of Merino sheep.
Authors: Schinckel PG
Published: November 2004

Observations are reported on the development of the follicle population during post-natal life in three groups of sheep from a strain of Australian Merino. The primary follicle number is complete by birth, and changes in density thereafter merely reflect the normal skin expansion accompanying growth. This constancy with time of the primary follicle number validates the use of the ratio of secondary to primary follicles (S/P) as a measure of the development of the secondary follicles. The S/P ratio followed a sigmoid curve characterized by a small increase in the ratio during the first week, a large increase in the second, and a progressive decline in the rate of development of secondary follicles thereafter.
Interactions of genotype and environment in determining sexual maturity in the domestic fowl.
Authors: Skaller F , Sheldon BL
Published: November 2004

Sexual maturity data of 1762 pullets from four differently bred flocks a t the Poultry Research Centre, Werribee, were examined for interaction between genotype for age at sexual maturity and the environment as represented by different hatching dates. Interaction was significant in two of the flocks studied and there was some interaction, though not significant, in the other flocks. Progressively later hatching caused significant increases in age at maturity in all flocks, but large differences in sexual maturity between sire families did not occur. The occurrence of interaction in other flocks and its effects on current poultry breeding methods are discussed. It is concluded that interactions of the order of those reported in this paper are not of a sufficient magnitude to warrant revision of present methods.
A technique for the collection of large numbers of Paramphistome (Trematoda) metacercariae.
Authors: Durie PH
Published: November 2004

A technique is described for the collection of large numbers of paramphistome metacercariae. The technique is based on the attraction of the cercariae to an illuminated, yellow surface.
Studies on the sultana vine. 4. A pruning experiment with number of buds per vine varied, number of buds per cane constant
Authors: Antcliff AJ , Webster WJ , May P
Published: November 2004

A pruning experiment is described in which the number of buds per vine was varied by varying the number of canes retained, the number of buds per cane being held constant. With increasing number of canes per vine, per cent. bud burst generally showed a linear decrease, and per cent. fruitful shoots, although generally not affected, showed a similar effect after years of high fruitfulness. Bunch number and weight of fresh fruit harvested increased linearly with increasing cane number. Sugar content decreased and number of mature buds produced increased with increasing cane number. Weight of fresh fruit was positively correlated with bunch number, and negatively correlated with sugar content and number of mature buds. Bunch number was positively correlated with per cent. bud burst. The yield from 10 canes in a year of low fruitfulness was no greater than the yield from 4 canes in a year of high fruitfulness. In the high year evidence suggesting overloading on vines with more than seven canes was obtained from the sugar content and bud number results. Vines returned to uniform pruning treatment after a year of high fruitfulness, the third year of the experiment, showed residual effects in the first season but not thereafter. It is concluded that by regulating the number of canes according to the potential fruitfulness found by microscopical examination before pruning, overloading can be avoided in very fruitful seasons and the crop can be improved in years of low fruitfulness. However, complete uniformity of crop from year to year cannot be achieved.
Investigations on brown rot of apricots caused by Sclerotinia fructicola (Wint.) Rehm. II. The relationship of the potassium status of apricot trees to brown rot susceptibility
Authors: Wade GC
Published: November 2004

It is shown that under Tasmanian conditions there is a negative relation between the potassium status of apricot trees and their susceptibility to brown rot. From regression equations calculated, it is suggested that trees with a potassium content of about 4.6 per cent. in oven-dry leaves would be resistant to brown rot. Difficulty was experienced in increasing the potassium content of the trees by soil or spray applications of potassium fertilizer, but when this was achieved, some reduction in brown rot incidence occurred. Regular annual soil dressings of potassium chloride at the rate of 2 lb per tree was the most satisfactory treatment tested.
The development of the testis, epididymis, and penis in the young Merino ram
Authors: Watson RH , Sapsford CS , McCance I
Published: November 2004

Observations were made on 110 Merino rams aged between 1 and 64 weeks. They comprised four groups, the animals of which experienced different rates of growth. The weight of the testes a t any one age varied widely. It was closely related to body weight. This relation was similar in all groups. As body weight increased from 23 to 27 kg, the relative increase in the weight of the testes was much greater than that a t higher or lower body weight. The general histological characteristics of the testes were closely related to their weight, and, like it, to body weight. The tubules were present as solid or but slightly vacuolated cords in all animals which weighed less than 21 kg. Spermatozoa were not seen in the lumen of the tubules in any animal which weighed less than 27 kg, and they were present in all but three of those which weighed more than 28 kg. The relative cross-sectional area of the seminiferous tubules increased directly with the relative increase in the weight of the testes until the testes weighed at least 300 g. The weight of the epididymides was more closely related to the weight of the testes than to age or body weight. Its relation to the weight of the testes varied in the different groups. Irrespective of the age a t which the particular body weight was attained, little separation of the prepuce from the penis had occurred in animals which were lighter than 18 kg, and separation was more or less complete in most animals which were heavier than 27 kg.
A study of clay mineralogy and particle size
Authors: Hosking JS , Neilson ME , Carthew AR
Published: November 2004

A study of the mineralogy of the clay, silt, and sand fractions of 24 soils has shown that the clay minerals are distributed through all fractions of the soils. In granitic and other soils which are characterized by kaolinite, with mica, illite, or montmorillonoids sometimes present though subsidiary, the clay mineral content of the silts may be as high as in the clay fraction though on the average it is about 50 per cent.; in the sands, however, clay minerals are negligible. In basaltic or basic soils which are characterized by halloysite or nontronite or both, with other types subsidiary, the clay mineral content of the silts is somewhat less than that in granitic soils, but persists a t an average of 20 per cent, in the sands. The higher concentration of kaolinite in the silt fractions reflects the larger particle size of this mineral. The concentration of halloysite or nontronite in the sand fractions, and even the concentrations reached in the silts of soils containing these minerals, reflect their fibrous nature which allows the formation of stable interlaced aggregates. Overall the two types of mineral, altered (authigenic) and residual (allogenic), vary continuously with particle size; the former, constituting the bulk of the colloids, decrease to small amounts in the coarse sand, while the latter necessarily show the reverse effect. The silts contain both types of mineral in about equal amounts and thus represent the intermediate particle size of mechanical breakdown and chemical alteration.
Bunch spear grass dominance in burnt pastures in South-Eastern Queensland
Authors: Shaw NH
Published: November 2004

The results are reported of a study of the effect of annual burning, in the absence of grazing, on the botanical composition of a native pasture in south-eastern Queensland. The main effect of burning was to give dominance of Heteropogon contortus (L.) Beauv. ex R. & S. This appeared to be due to three main causes: established plants were resistant to fire; fire favoured the germination of seed; and fire reduced the basal ground cover of other species. The effects on other species and on the proportion of bare ground are reported. The significance of the results in relation to the present distribution of H. contortus-dominant pastures is discussed.