bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of corrugated substrates on light extraction efficiency and the mechanism of growth in pulsed laser deposited Y2O3:Eu3+ thin-film phosphors
Authors: Sohn Kee-Sun , Shin Namsoo , Kim Yoon-Chang , Do Young Rag
Published: June 2004

The luminance level of thin-film Y2O3:Eu3+ phosphors deposited by a pulsed laser deposition techniques are not candidates for field emission display because of their low extraction efficiency. A square lattice nanorod-type two-dimensional SiO2 photonic crystal layer (PCL) was built on a quartz glass substrate in an attempt to improve the efficiency of light extraction. The pitch of the PCL was varied, such that 500, 550, and 600nm pitches were produced while maintaining the depth of the PCL fixed at 200nm. The integrated photoluminescence efficiency of an Y2O2:Eu3+ thin-film phosphor deposited on the PCL was improved by 4.8 times and well matched with the calculated result based on the finite-difference time-domain method. The PCL played a significant role not only in enhancing the extraction efficiency but also aiding in the control of the film growth.
High-reflectivity AlxGa1−xN∕AlyGa1−yN distributed Bragg reflectors with peak wavelength around 350nm
Authors: Wang T. , Lynch R. J. , Parbrook P. J. , Butté R. , Alyamani A. , Sanvitto D. , Whittaker D. M. , Skolnick M. S.
Published: June 2004

Al 0.49 Ga 0.51 N ∕ Al 0.16 Ga 0.84 N distributed Bragg reflectors (DBRs), designed for the ultraviolet spectral region, are reported. The crack-free structures are grown on sapphire substrates by metalorganic chemical vapor deposition. A peak reflectivity of 91% at 353nm with a stop-band width of 17nm was obtained at 300K using a 25pair DBR. Structures at 6nm shorter wavelength show asymmetric spectra, a narrower stop band, and slightly decreased peak reflectivity. By studying the spectra as a function of temperature, the degradation is shown to arise from internal absorption at short wavelengths. Simulations based on transfer matrix theory agree well with the experimental data.
Memory effect of diamond in-plane-gated field-effect transistors
Authors: Sumikawa Yu , Banno Tokishige , Kobayashi Kensaku , Itoh Yutaka , Umezawa Hitoshi , Kawarada Hiroshi
Published: June 2004

A memory effect of in-plane-gated field-effect transistors (IPGFETs) has been observed on hydrogen-terminated and oxygen-terminated diamond surfaces. The hysteresis characteristics are achieved by the hole traps in the oxygen-terminated surface of the IPGFETs where the threshold voltage shift by the gate voltage sweep is confirmed in the Id–Vg characteristics. This feature is observed under light illumination, and depends on the radiant flux density. The hysteresis characteristics become very small under the condition of no light irradiation at room temperature. It is assumed that carrier trap sites on the insulating part of IPGFET cause the hysteresis characteristics. Radiant flux enhances carrier migration.
Tunable blue organic light emitting diode based on aluminum calixarene supramolecular complex
Authors: Legnani C. , Reyes R. , Cremona M. , Bagatin I. A , Toma H. E.
Published: June 2004

In this letter, the results of supramolecular organic light emitting diodes using a calix[4] arene complex thin film as emitter and electron transporting layer are presented. The devices were grown onto glass substrates coated with indium-tin-oxide layer and aluminum thick (150nm) cathode. By applying a dc voltage between the device electrodes in forward bias condition, a blue light emission in the active area of the device was observed. It was found that the electroluminescent emission peak can be tuned between 470 and 510nm changing the applied voltage bias from 4.3 to 5.4V. The observed tunable emission can be associated with an energy transfer from the calixarene compound.
Electrical characteristics of InGaN∕GaN light-emitting diodes grown on GaN and sapphire substrates
Authors: Cao X. A. , Teetsov J. M. , D’Evelyn M. P. , Merfeld D. W. , Yan C. H.
Published: June 2004

We report on the electrical characteristics of InGaN∕GaN multiple-quantum-well light-emitting diodes (LEDs) grown on sapphire and free-standing GaN substrates. As a result of defect reduction, the tunneling current in the homoepitaxially grown LED was remarkably suppressed and diffusion-recombination current dominated at intermediate forward bias. Temperature-dependent measurements showed that the remaining reverse current originated from carrier generation and tunneling associated with deep-level traps. In contrast, the LED on sapphire exhibited dominant tunneling characteristics over a wide range of applied bias. Nanoscale electrical characterization using conductive atomic force microscopy revealed highly localized currents at V-defects, indicating that the associated dislocations are electrically active and likely responsible for the high leakage current in the heteroepitaxially grown LED.
Fountain-pen-based laser microstructuring with gold nanoparticle inks
Authors: Choi Tae Y. , Poulikakos Dimos , Grigoropoulos Costas P.
Published: June 2004

Employing the fountain-pen principle, a micropipette is used to write an Au nanoparticle ink on glass substrates. A continuous-wave laser (488–515nm) is subsequently used as a controlled, localized energy source to evaporate the carrier liquid (toluene) in the ink and sinter the nanoparticles together thus fabricating continuous gold stripes 5μm in width and a few hundred nanometers in height. The scanning speed, the laser intensity, and the degree of defocusing are identified as important parameters to the successful manufacturing of the gold microstructures. The electrical resistivity of the stripes, within the parametric domain of the present work, is measured to be the order of 10−6Ωm.
Field emission properties of vertically aligned iron nanocluster wires grown on a glass substrate
Authors: Kim Do-Hyung , Jang Hoon-Sik , Lee Hyeong-Rag , Kim Chang-Duk , Kang Hee-Dong
Published: June 2004

Vertically aligned nanocluster wires (NCWs) were synthesized on indium-tin-oxide-coated glass substrates via the thermal decomposition of Fe(CO)5 with a resistive heater under a magnetic field. The density of the aligned NCWs was controlled by varying the flow rate of the carrier gas. The low-density NCWs showed better field emission characteristics, with a low turn-on field of about 4V∕μm and a current density as high as 3mA∕cm2 at 7.6V∕μm. The field enhancement factor (γ) was determined to be ∼1200 for high-density NCWs and ∼1600 for low-density NCWs, which is comparable to those of carbon nanotubes.
Thin HfO2 films grown on Si(100) by atomic oxygen assisted molecular beam epitaxy
Authors: Yan Z. J. , Xu R. , Wang Y. Y. , Chen S. , Fan Y. L. , Jiang Z. M.
Published: June 2004

Thin high-k dielectric HfO2 films are deposited on Si(100) substrate by molecular beam epitaxy using Hf and atomic oxygen source. The composition of the film is determined to be stoichiometric HfO2. The very flat surface of the deposited film with a root mean square roughness less than 0.16nm without any visible pin holes down to the nanometer size can be reached. The film maintains good thermal stability after annealing at 900°C for 15min in N2 ambient. The refractive index of the film is 1.89 with a negligible extinction coefficient in the visible wavelength region and the dielectric constant is around 19. A low leakage current of 1.61×10−3A∕cm2 at −2V bias is achieved for a film with the equivalent oxide thickness of 2.4nm after annealing.
Dielectric behavior and dependence of percolation threshold on the conductivity of fillers in polymer-semiconductor composites
Authors: Dang Zhi-Min , Nan Ce-Wen , Xie Dan , Zhang Yi-He , Tjong S. C.
Published: June 2004

Polymer-semiconductor PVDF∕LNO (polyvinylidene fluoride∕Li doped NiO) composites were fabricated via simple blending and hot-molding technique. The dielectric behavior of such composites was studied over broad frequency. The results revealed the dependence of percolation threshold on the conductivity of LNO filler in the composites. And the conductivity of the LNO fillers played an important role on the dielectric properties and critical exponents of the PVDF∕LNO composites. High dielectric constants and low conductivities of the composites were observed near the percolation threshold. Finally, critical exponents were also used to explain the experimental results, and provided useful information for understanding the resultant dielectric properties.
Subpicosecond pulses from a gain-switched polymer distributed feedback laser
Authors: Goossens Mark , Ruseckas Arvydas , Turnbull Graham A. , Samuel Ifor D. W.
Published: June 2004

The emission dynamics of polymer distributed feedback lasers have been studied following excitation by femtosecond laser pulses. The lasers were found to generate pulses as short as 800fs. The dynamics were investigated as a function of pump power and excitation spot size. Simple rate equations modeling the amplification of spontaneous emission are shown to describe the behavior of the lasing dynamics observed.
Ultralow refractive index substrates–a base for photonic crystal slab waveguides
Authors: Schmidt M. , Boettger G. , Eich M. , Morgenroth W. , Huebner U. , Boucher R. , Meyer H. G. , Konjhodzic D. , Bretinger H. , Marlow F.
Published: June 2004

Out of plane radiation losses in two-dimensional (2D) photonic crystal (PC) waveguides occur due to a lack of total internal reflection at the core-substrate∕superstrate boundaries. In order to minimize these losses, either a high vertical refractive index contrast or deep etching into the substrate is required [G. Boettger, C. Liguda, M. Schmidt, and M. Eich, Appl. Phys. Lett. 81, 2517 (2002)]. The maximum vertical contrast is achieved in air bridge type PC waveguides, which are inherently fragile. In this article, we introduce a concept which combines the advantages of a high vertical index contrast of an air bridge with those of a solid substrate. This approach consists of mesoporous silica as substrate material with an ultralow refractive index (n=1.14 at 1.3μm), close to that of air. Finite 2DPC line defect resonators consisting of an optical polymer as core and mesoporous silica as substrate were fabricated. Compared to ordinary substrates with higher refractive indices like silica or amorphous Teflon [C. Liguda, G. Boettger, A. Kuligk, M. Eich, H. Roth, J. Kunert, W. Morgenroth, H. Elsner, and H. G. Meyer, Appl. Phy. Lett. 78, 2434 (2001)], measurements show significantly increased transmission at the resonance wavelength and virtually no losses on the sensitive air band side.
Facile nanocoating method: From B-doped to BN-coated one-dimensional nanostructures
Authors: Tang C. C. , Bando Y. , Golberg D. , Mitome M. , Ding X. X. , Qi S. R.
Published: June 2004

B -doped MgO nanowires were synthesized through impurity-assisted physical evaporation of a mixture of B and MgO with a small amount of Ga2O3. The B content in the mixture affectsthe morphology of MgO nanowires. B-doped MgO nanotubes and cubes were formed when B-rich mixtures were utilized. Ammonothermal treatment of as-synthesized B-doped products resulted in the formation of uniform BN coatings adherent to nanowire and nanotube surfaces. Thus a facile BN coating method was developed. Finally the growth mechanism of the present BN-coated one-dimensional nanostructures was proposed.
Enhanced light extraction in III-nitride ultraviolet photonic crystal light-emitting diodes
Authors: Shakya J. , Kim K. H. , Lin J. Y. , Jiang H. X.
Published: June 2004

III-nitride photonic crystal (PC) ultraviolet (UV) light-emitting diodes (LEDs) were fabricated. Triangular arrays of the PCs with different diameters∕periodicities were patterned using electron-beam lithography and inductively coupled plasma dry etching. The optical power output of LEDs was enhanced by a factor of 2.5 due to PC formation. It was observed that the optical enhancement factor depends strongly on the lattice constant and hole size of the PCs. The achievement of nitride PCs is expected to benefit many applications of III-nitride optoelectronics, particularly for the improvement of extraction efficiency in III-nitride deep-UV emitters (λ<340nm), which are crucial for many important applications, but presently have a very low quantum efficiency.
Pressure induced increase of particle size and resulting weakening of elastic stiffness of CeO2 nanocrystals
Authors: Wang Zhongwu , Zhao Yusheng , Schiferl David , Zha C. S. , Downs Robert T.
Published: June 2004

We demonstrate that the compressibility of cubic fluorite-structure CeO2 nanocrystals (10nm) increases at pressures above ∼20GPa. At ambient pressure, CeO2 nanocrystals exhibit larger cell parameters than micro-sized samples, and initially exhibit a higher bulk modulus of 328(12)GPa. However, above 20GPa, the bulk modulus is reduced to 230(10)GPa. Thus, a critical pressure of ∼20GPa was determined that signifies the onset of size-induced weakening of elastic stiffness in nanocrystalline CeO2. Comparison of the x-ray diffraction peaks widths between the platinum standard and CeO2 indicates that a significant increase of particle size in CeO2 appears at a pressure of ∼20GPa. It is suggested that the initial large value of the bulk modulus is a result of either an enhanced surface energy or from the pressure induced stiffness of Young’s modulus (E) and Poisson’s ratio (μ); while the weakening of the elastic stiffness above 20GPa is due to a pressure-induced increase of particle size.
Continuous-wave laser oscillation at 929nm from a Nd3+-doped LiNbO3:ZnO nonlinear laser crystal: A powerful tool for blue laser light generation
Authors: Jaque D. , Sanz García J. A. , García Solé J.
Published: June 2004

This work reports on room-temperature continuous-wave laser action at 929nm from a Nd3+:LiNbO3 nonlinear laser crystal co-doped with ZnO. The spectroscopic parameters of the quasi-three-level F3∕24→I9∕24 laser channel are discussed. In nonoptimal preliminary experiments, pump power at threshold was found to be as low as 105mW.
Vortex pinning arrays produced by nano-oxidation using an atomic force microscope
Authors: Amato J. C.
Published: June 2004

Vortex pinning arrays have been produced in thin films of the amorphous superconducting alloy Mo1−xGex by nano-oxidation with an atomic force microscope. The instrument is operated in contact mode within a controlled humidity enclosure, with an external x–y stage controlling the sample position. The pinning strength of each oxide site agrees well with theory. Because the oxide depth can be controlled by applied tip voltage and ambient humidity, and because the placement of each site is under simple software control, a wide variety of pinning landscapes can be generated easily.
Chirp characterization of ultrashort pulses utilizing molecular vibrations
Authors: Rizo Pedro Julian , Kobayashi Takayoshi
Published: June 2004

A method is presented and demonstrated for chirp characterization of ultrashort laser pulses utilizing identical setup and detection systems of common pump–probe experiments. The coherent intramolecular vibrations that can be impulsively excited in a nonresonant manner in many common solvents are used to directly measure the spectral relative delay of femtosecond pulses. For pump–probe experiments on solutions, this method has the capability of isolating the phase of the signal due to the solute from the phase due to the solvent and to uncompensated chirp in the laser pulse. The method is not restricted to pulses with optical bandwidth narrower than an octave.
Adaptive design of excitonic absorption in broken-symmetry quantum wells
Authors: Thalken Jason , Li Weifei , Haas Stephan , Levi A. F. J.
Published: June 2004

Adaptive quantum design is used to identify broken-symmetry quantum-well potential profiles with optical response properties superior to previous ad hoc solutions. This technique performs an unbiased stochastic search of configuration space. It allows us to engineer many-body excitonic wave functions and thus provides a new methodology to efficiently develop optimized quantum-confined Stark effect device structures.
Spectral focusing: High spectral resolution spectroscopy with broad-bandwidth laser pulses
Authors: Hellerer Thomas , Enejder Annika M.K. , Zumbusch Andreas
Published: June 2004

In this work, we show how broad-bandwidth femtosecond pulses can be used to achieve high spectral resolution in nonlinear spectroscopy and microscopy. Our approach is based on chirping the excitation pulses in order to focus their entire bandwidth into a narrow spectral region. We show that spectral features which are 100 times narrower than the excitation light can be resolved with this simple spectral focusing. The gain in spectral selectivity and sensitivity makes its application to nonlinear microscopy very convenient. This is demonstrated with diffraction-limited coherent anti-Stokes Raman scattering microscopy.
Solubility of nitrogen and phosphorus in 4H-SiC: A theoretical study
Authors: Bockstedte Michel , Mattausch Alexander , Pankratov Oleg
Published: June 2004

The n-type dopants phosphorus and nitrogen, and their complexes with intrinsic point defects are investigated in 4H-SiC by first-principles theory. The solubility and electrical activation of the dopants in thermodynamic equilibrium are calculated. For nitrogen, a saturation of the electrical activation above a certain critical concentration is found that is driven by a preferential incorporation of nitrogen into electrically passive nitrogen-vacancy complexes. This explains the observations of recent experiments. An almost complete phosphorus activation is found up to the solubility limit. We suggest that the low phosphorus doping achieved by sublimation growth is related to the growth kinetics.
Photovoltaic effect in La0.7Ce0.3MnO3−δ∕SrTiO3-Nb heterojunction and its oxygen content dependence
Authors: Sun J. R. , Lai C. H. , Wong H. K.
Published: June 2004

The photovoltaic effect (PVE) of a heterojunction composed of a La0.7Ce0.3MnO3 (LCE) film and a 0.5wt.% Nb-doped SrTiO3 crystal has been experimentally studied. A strong PVE was observed, and the maximum photovoltage was ∼54.1mV, when the LCE film was exposed to light with a wavelength (λ) of 460nm and a power of ∼6.5μW. The PVE remains significant up to λ=660nm, though it decreases gradually with the increase of wavelength. Oxygen release of the LCE film depresses the PVE considerably and modifies the rectifying property of the junction. A logarithmic variation of photovoltage with junction resistance was observed. The weakening of the ferromagnetic order of the LCE film due to the incorporation of oxygen vacancies may be the reason for the depression of the PVE.
Silicate layer formation at Pr2O3∕Si(001) interfaces
Authors: Schmeißer D. , Müssig H.-J. , Dąbrowski J.
Published: June 2004

We studied Pr2O3∕Si(001) interfaces by synchrotron radiation photoelectron spectroscopy and by ab initio calculations. We show that the interface formed during molecular-beam epitaxy under the oxygen partial pressure above 1×10−8mbar consists of a mixed Si–Pr oxide, such as (Pr2O3)(SiO)x(SiO2)y. Neither an interfacial SiO2 nor an interfacial silicide is formed. The silicate formation is driven by a low energy of O in a PrOSi bond and by the strain in the subsurface SiOx layer. We expect that this natural interfacial Pr silicate will facilitate the integration of the high-k dielectric Pr2O3 into future complementary metal–oxide–semiconductor technologies.
Exciton and biexciton luminescence from single hexagonal GaN∕AlN self-assembled quantum dots
Authors: Kako S. , Hoshino K. , Iwamoto S. , Ishida S. , Arakawa Y.
Published: June 2004

We report single dot spectroscopy of hexagonal GaN∕AlN self-assembled quantum dots grown by metalorganic chemical vapor deposition. Through the reduction of the number of quantum dots using submicron mesa structures, we have obtained several isolated photoluminescence peaks emitted by individual quantum dots. With increasing excitation power, an additional peak emerges in the higher-energy side of an excitonic ground state. This additional peak shows quadratic power dependence, and is attributed to the photoluminescence from a biexciton state. The biexciton binding energy is negative and the magnitude is about 30meV, which is explained by the effects of a strong built-in electric field.
Electroluminescence at 7 terahertz from phosphorus donors in silicon
Authors: Lv P.-C. , Troeger R. T. , Adam T. N. , Kim S. , Kolodzey J. , Yassievich I. N. , Odnoblyudov M. A. , Kagan M. S.
Published: June 2004

Terahertz (THz) emissions corresponding to intracenter transitions of phosphorus impurities in silicon have been observed up to 30K. Electrical pulses (250ns) with a repetition rate of 413Hz were used for excitation, and the peak power was calculated to be ∼20μW∕facet for a 190×120μm2 device with a peak pumping current of 400mA at 12K. THz emission intensity increased linearly with pumping current and quenched when the sample temperature was above 30K. The current–voltage characteristics suggested a conduction and excitation mechanism by injection of electrons from a Schottky barrier followed by impact ionization of the neutral impurities.
Hysteresis loops of the energy band gap and effective g factor up to 18 000 for metamagnetic EuSe epilayers
Authors: Kirchschlager R. , Heiss W. , Lechner R. T. , Bauer G. , Springholz G.
Published: June 2004

Hysteresis effects of the fundamental energy gap as a function of applied magnetic field are studied for metamagnetic EuSe layers grown by molecular-beam epitaxy. Below the phase transition temperature, the energy gap show large step-like red shifts of up to 150meV with increasing magnetic field with pronounced hysteresis effects when the change in the magnetic field is reversed. Both, the steps and the hysteresis loops are caused by transitions between the aniferro-, ferri-, and ferromagnetic phases in EuSe. The large redshift of the band gap is directly proportional to the magnetization of the sample and results from the Zeeman spin splitting of the conduction band. The corresponding effective g factor deduced from our experiments reaches values up to 18 000 at the magnetic phase transitions.
Self-organized lattice of ordered quantum dot molecules
Authors: Lippen T. v. , Nötzel R. , Hamhuis G. J. , Wolter J. H.
Published: June 2004

Ordered groups of InAs quantum dots (QDs), lateral QD molecules, are created by self-organized anisotropic strain engineering of a (In,Ga)As∕GaAs superlattice (SL) template on GaAs (311)B in molecular-beam epitaxy. During stacking, the SL template self-organizes into a two-dimensionally ordered strain modulated network on a mesoscopic length scale. InAs QDs preferentially grow on top of the nodes of the network due to local strain recognition. The QDs form a lattice of separated groups of closely spaced ordered QDs whose number can be controlled by the GaAs separation layer thickness on top of the SL template. The QD groups exhibit excellent optical properties up to room temperature.
Epitaxial GaN on Si(111): Process control of SiNx interlayer formation
Authors: Rawdanowicz T. A. , Narayan J.
Published: June 2004

The heteroepitaxial growth of (0001) GaN thin films directly on (111) Si by laser-molecular beam epitaxy without the formation of a SiNx interlayer at the GaN∕Si interface is reported. We also find that SiNx can be formed subsequently as a result of nitrogen diffusion to the GaN∕Si(111) interface. The orientation relationship of GaN on Si(111) was determined using x-ray diffraction and selected area electron diffraction. The atomic structure of the interfaces was studied by high resolution transmission electron microscopy. A Fourier filtered image of the cross-sectional GaN∕Si(111) interface demonstrated domain matching epitaxy of 6:5. Distributions of N and Ga concentrations near the GaN∕Si interface were determined using electron energy loss spectroscopy.
The effects of soil type and seasonal rainfall on the optimum seed rate for wheat in Western Australia
Authors: Cima R. Del , D'Antuono M. F. , Anderson W. K.
Published: June 2004

Seventeen experiments were conducted in 1996, 1997 and 1998 in the central and northern wheatbelt of Western Australia, covering a range of soil types, seasonal rainfall, cultivars and sowing times. The objective of the experiments was to investigate how these factors affect the range of optimum seed rates derived from seeding rate experiments and, thus, to improve advice to farmers. Our results suggest that soil type and seasonal rainfall were the major factors influencing the differences in optimum seed rate. Regression tree methods were used to show that experiments in clay loam soils had higher optimum seed rates (52–76 kg/ha, depending on the cultivars used). In sandier soils, the optimum seed rate was lower (35–60 kg/ha, depending on cultivar and sowing time) but higher (67�kg/ha) at higher seasonal rainfall (>450 mm). We found some cultivars were grouped into consistent response patterns. Sowing time also influenced optimum seed rate; later sowing required higher seed rates, to maximise grain yield. A positive correlation was not observed between grain yield and optimum seed rate, possibly due to the narrow range of yields recorded in the experiments. Our data showed that the percentage of establishment fell off rapidly at higher seed rates. This implies that lower establishment percentages should be used when calculating the seed rates required to produce high plant populations in the field.
The potential for extended lactations in Victorian dairying: a review
Authors: Borman J. M. , Macmillan K. L. , Fahey J.
Published: June 2004

This review examines the potential for extended lactations on Victorian dairy farms in the context of (i)�the advantages and disadvantages of existing seasonal milk production systems; (ii) projected future changes to Victorian dairy farming; (iii) the mechanics of extended lactations; (iv) the change in costs associated with extended lactations; and (v) how extended lactations might be successfully implemented. Traditionally, Victorian dairying has been characterised by seasonal, low input, pasture-based milk production reliant on family labour. Successful implementation of this type of milk production system requires cows to calve in accordance with seasonal pasture supply. Recently a number of economic (static or falling milk prices), management (larger herds, increased labour expense, lower labour availability) and social pressures (animal welfare and environmental regulation) have emerged that question the viability of pasture-based dairying in a number of countries including Australia. Some of these threats to dairying may increase the attractiveness of systems that exploit the production potential of high yielding cows in larger herds, with increased supplementation of pasture-based diets over extended lactations. It is generally concluded that 12-month calving intervals are the most economic, based on the shape of the lactation curve and the perceived costs of extended lactations. However, these fundamentals have been changed by years of intensive selection for high milk production and the recent implementation of new management techniques such as Bovine somatotrophin, total mixed rations and increased milking frequency. Modern high yielding cows can maintain high daily yields for a much longer proportion of lactation than previously, but these cows are also largely unsuited to seasonal production systems due to a prolonged period of negative energy balance after calving and consequent low fertility. We have identified that calving and pregnancy incur substantial costs that are often hidden but need to be accounted for in valid economic comparisons. It is evident that seasonal pasture-based dairying requires disciplined management where certain tasks must be achieved in a timely manner if the system is to operate efficiently. Where the system does break down, often due to infertility for example, new management approaches are required. It is of concern that farmers may adopt a default position of extended lactations without realising or exploiting the potential benefits. Among the advantages of extended lactation management would be a more even spread in labour requirements, input costs and income across the year. In conclusion, extended lactations are a suitable option for some Victorian dairy enterprises. That suitability will depend on a number of factors; particularly, cow milk production potential, ability to grow pasture or feed supplements economically, management expertise, environmental constraints, herd size and labour availability.
Phosphorus uptake and growth promotion of chickpea by co-inoculation of mineral phosphate solubilising bacteria and a mixed rhizobial culture
Authors: Gull M. , Hafeez F. Y. , Saleem M. , Malik K. A.
Published: June 2004

Isolation of phosphate solubilising bacterial strains was carried out from rhizosphere, roots and nodules of chickpea, to study the viability for solubilisation of tri-calcium phosphate and the effect on growth of chickpea plants. The potential of isolated bacterial strains to solubilise phosphate was qualitatively evaluated by the measurement of a clear zone around the colonies. The diameter of this zone ranged from 21 to 83 mm. Phosphate solubilisation, by phosphate solubilising bacterial isolates, was quantified by spectrophotometry and was found to range from 65 to 130.5 μg/mL. The drop in pH ranged from 5.6 to 3.6. The plant growth, shoot phosphorus and nitrogen concentrations, nodulation efficiency and nitrogenase activity were significantly enhanced, showing the positive effect of phosphate solubilising bacteria inoculation. Phosphate solubilising bacterial strains CPS-2, CPS-3 and Ca-18 had the maximum positive effect on shoot length, shoot dry weight and nodulation of chickpea plants. Treatments inoculated with non-phosphate solubilising bacterial strains IFA1 and IFA2 showed the minimum values in all the parameters.
Effects of feeding magnesium sulfate to dry pregnant dairy cows with different body condition scores on intake in late gestation, periparturient blood calcium concentrations and production in early lactation
Authors: Stockdale C. R.
Published: June 2004

An experiment was conducted to investigate the interaction between the responses of cows fed magnesium sulfate during late gestation and body condition score (BCS). Cows were fed a total mixed ration before calving and a pasture-based diet in early lactation. Seventy-two cows were fed differentially to achieve target BCS, on an 8-point scale, of about 4, 5 and 6 units, 1 month before calving. Cows were individually fed a total mixed ration of maize silage, crushed barley, canola meal and barley straw at about 1.6 kg dry matter (DM)/100 kg liveweight during the 27 days, on average, before parturition. In each BCS treatment, half the cows were fed 105–155 g magnesium sulfate (depending on liveweight) in the last 3 weeks while the remaining cows were provided with 18–27 g magnesium oxide, maintaining similar levels of magnesium in both diets.The dietary cation–anion difference of the control and magnesium sulfate diets averaged +5.1 and –5.5�cmol(+)/kg, respectively, while urine pH values were 6.4 and 5.4, respectively. The cows fed the control diet, on average, calved in better condition (P<0.05) than those fed magnesium sulfate (BCS at calving were 5.1 and 4.7 units for the control and the magnesium sulfate treatments, respectively). The feed intake of cows that did not receive magnesium sulfate was maintained until the day before calving whereas the feed intake of cows fed magnesium sulfate declined sharply from about a week before calving, and was always lower (P<0.05) than the control group. During the 4 weeks before parturition, the cows in the medium BCS group generally consumed more DM than did those in the other 2 BCS treatments (8.9 v. 7.4 and 8.2 kg DM/cow.day; P<0.05). During the 2 days before calving, all cows had similar intakes (7.7 kg DM/cow.day; P>0.05). The control diet resulted in lower concentrations of total blood serum calcium but only immediately after calving (1.90 v. 2.02 mmol/L; P<0.05). The production data indicated that magnesium sulfate had no effect (P>0.05) on either milk yield or milk composition even though the use of magnesium sulfate reduced the incidence of subclinical hypocalcaemia from 64 to 46%. However, there was a positive relationship between BCS at calving and milk fat concentration (P<0.05). There were no significant (P>0.05) interactions between dietary additives and the BCS of the cows. In conclusion, the use of magnesium sulfate resulted in the relative maintenance of blood calcium concentrations, reducing the incidence of subclinical hypocalcaemia at calving, while having a negative effect on intake before calving. However, these effects were not translated into benefits in animal production.
An integrated numerical system to estimate air quality effects of forest fires
Authors: Miranda A. I.
Published: June 2004

Forest fires are an important source of various gases and particles emitted into the atmosphere that may affect the air quality on a local and/or larger scale. Currently, there is a growing awareness that smoke from wildland fires exposes individuals and populations to hazardous air pollutants. In order to understand and to simulate forest fire effects on air quality, several issues should be analysed and integrated: fire progression, fire emissions, atmospheric flow, smoke dispersion and chemical reactions. In spite of the available models to simulate smoke dispersion and the existence of some systems already covering the main questions, there still remains a lack of integration concerning fire progression. Photochemical pollution is also not included in these modelling systems. AIRFIRE is a numerical system, developed to estimate the effects of forest fires on air quality, integrating several components of the problem through the inclusion of different modules, namely the mesoscale meteorological model MEMO, the photochemical model MARS, and the Rothermel fire spread model. The system was applied to simulate plume dispersion from a wildfire that occurred in a coastal area, close to Lisbon city, at the end of September 1991. Results, namely the obtained pollutants concentration fields, point to a significant impact on the local air quality. Obtained wind fields and concentration patterns revealed the presence of sea breezes and also the influence of the fire in the atmospheric flow. Estimated carbon monoxide concentration levels were very high, exceeding the recommended hourly limit value of the World Health Organization, and ozone concentration values pointed to photochemical production.
The post-fire measurement of fire severity and intensity in the Christmas 2001 Sydney wildfires
Authors: Chafer Chris J. , Noonan Mark , Macnaught Eloys
Published: June 2004

Using pre- and post-fire satellite imagery from SPOT2, we examined the fire severity and intensity of the Christmas 2001 wildfires in the greater Sydney Basin, Australia. We computed a Normalised Difference Vegetation Index (NDVI) from the two satellite images captured before (November 2001) and after (January 2002) the wildfires, then subtracted the later from the former to produce a difference image (NDVIdiff) which was subsequently classified into six fire severity classes (unburnt, low, moderate, high, very high and extreme severity). We then tested the fire severity classification on 342 sample sites within the 225 000ha fire affected area using a qualitative visual assessment guide. We found that the NDVIdiff classification produced an accuracy of at least 88% (K
hat = 0.86), with the greatest discrepancy being between the low and moderate classification. Knowledge of rate of spread over some of the affected area, coupled with a complete knowledge of fuel loads, was used to retrospectively model fire intensity, which in areas of extreme fire intensity, produced heat energy levels exceeding 70 000 kW m–1. Importantly, we found no positive effect of topography on fire severity, in fact finding an inverse relationship between slope and fire severity and no effect due to aspect. Further analysis showed that flat to moderate slopes less than 18° across all aspects suffered the greatest vegetal destruction, and there was no relationship between north-westerly aspects and fire severity. We also introduce a relatively simple method for estimating fuel load biomass using a combination of satellite image and rapid field assessment. We found 79% accuracy for this method based on 125 sample sites. It is postulated that this type of analysis can greatly improve our understanding of the spatial impact of fire, how natural areas within the fire ground were impacted, and how remote sensing and GIS technologies can be efficiently used in fire management planning and post-fire analysis.
Slope and wind effects on fire propagation
Authors: Viegas Domingos X.
Published: June 2004

The vectoring of wind and slope effects on a flame front is considered. Mathematical methods for vectoring are presented and compared to results of laboratory experiments. The concept of multiple standard fire spread directions is presented. The experimental laboratory study, included effects of variable wind velocity and direction on point source flame fronts on a 30° inclined fuel bed.
A semi-transparent model of bushfire flames to predict radiant heat flux
Authors: Knight I.K. , Sullivan A.L.
Published: June 2004

The radiation emitted by a body is related through the Stefan-Boltzmann equation to the temperature of the emitting element. In the case of flame, the emitting elements are carbon particles. Existing models of bushfire flame radiation assume, however, that the flame radiates as a surface with an emissivity of 1 (i.e. a blackbody). This is only true when the flame is thick enough to provide a continuous wall of radiating carbon particles.
In this paper we propose a semi-physical model of radiant heat flux from bushfire flame that calculates the emissivity of the flame front based on its geometry and the optical properties of the flame. This model is calibrated using conservation of energy principles and empirical information about the radiant heat energy as a percentage of total energy of the flame. Comparisons are made with the flames generated by a propane-fuelled bushfire flame front simulator.
Harvest rate of sooty shearwaters (Puffinus griseus) by Rakiura Māori: a potential tool to monitor population trends?
Authors: Kitson Jane Catherine
Published: June 2004

Sooty shearwaters (tītī, muttonbird, Puffinus griseus) are highly abundant migratory seabirds, which return to breeding colonies in New Zealand. The Rakiura Māori annual chick harvest on islands adjacent to Rakiura (Stewart Island), is one of the last large-scale customary uses of native wildlife in New Zealand. This study aimed to establish whether the rate at which muttonbirders can extract chicks from their breeding burrows indicates population trends of sooty shearwaters. Harvest rates increased slightly with increasing chick densities on Putauhinu Island. Birders' harvest rates vary in their sensitivities to changing chick density. Therefore a monitoring panel requires careful screening to ensure that harvest rates of the birders selected are sensitive to chick density, and represents a cross-section of different islands. Though harvest rates can provide only a general index of population change, it can provide an inexpensive and feasible way to measure population trends. Detecting trends is the first step to assessing the long-term sustainability of the harvest.
Autecology of the yellow-footed antechinus (Antechinus flavipes) in a fragmented landscape in southern Australia
Authors: Marchesan Doreen , Carthew Susan M.
Published: June 2004

Autecological data were collected on southern populations of the yellow-footed antechinus (Antechinus flavipes), during a wider study on the persistence of this species in a highly fragmented landscape of the southern Mt Lofty Ranges, South Australia. Data are presented to provide information on this species in the southern part of its range, to present a comparison with populations in other, more northern regions, and to provide an insight into the species' persistence in a fragmented system. Resulting recapture rates lend support to the presence of a male-biased dispersal strategy, which is the first published indication of such a strategy for the species. New information was also recorded for nest sites, with most sites occurring in tall Xanthorrhoea semiplana tateana, and only 33% found in tree cavities. Other results showed mostly comparable population densities and weights with other, more northern populations. However, differences were apparent with respect to juvenile dispersal behaviour and, to some extent, breeding times. Within-study populations also showed variation with regard to weights, density and breeding times. Forest animals were lighter, were largely of lower population densities, and were generally later breeders than animals that inhabited patches and strips of remnant vegetation. Such differences in weight and density may have been due to favourable 'edge effects' in patches and strips, while variations in breeding times may be due to local climatic or habitat factors. The life-history strategies and tolerance of habitat edges shown by A.�flavipes (presently and historically) provide some explanation for the species' persistence in this fragmented system.
Change in abundance of dugongs in Shark Bay, Ningaloo and Exmouth Gulf, Western Australia: evidence for large-scale migration
Authors: Gales Nick , McCauley Robert D. , Lanyon Janet , Holley Dave
Published: June 2004

The third in a series of five-yearly aerial surveys for dugongs in Shark Bay, Ningaloo Reef and Exmouth Gulf was conducted in July 1999. The first two surveys provided evidence of an apparently stable population of dugongs, with ~1000 animals in each of Exmouth Gulf and Ningaloo Reef, and 10 000 in Shark Bay. We report estimates of less than 200 for each of Exmouth Gulf and Ningaloo Reef and ~14 000 for Shark Bay. This is an apparent overall increase in the dugong population over this whole region, but with a distributional shift of animals to the south. The most plausible hypothesis to account for a large component of this apparent population shift is that animals in Exmouth Gulf and Ningaloo Reef moved to Shark Bay, most likely after Tropical Cyclone Vance impacted available dugong forage in the northern habitat. Bias associated with survey estimate methodology, and normal changes in population demographics may also have contributed to the change. The movement of large numbers of dugongs over the scale we suggest has important management implications. First, such habitat-driven shifts in regional abundance will need to be incorporated in assessing the effectiveness of marine protected areas that aim to protect dugongs and their habitat. Second, in circumstances where aerial surveys are used to estimate relative trends in abundance of dugongs, animal movements of the type we propose could lead to errors in interpretation.
Australian fur seals (Arctocephalus pusillus doriferus) breeding in Tasmania: population size and status
Authors: Pemberton David , Gales Rosemary
Published: June 2004

This study confirms the persistence of five major breeding colonies of Australian fur seals (Arctocephalus pusillus doriferus) in Tasmanian Bass Strait waters. Incidental births also occasionally occur in very low numbers at other sites. Data collected between 1989 and 1999 shows that estimates of the minimum number of pups born at the major colonies varies considerably between sites and years. No colony has shown a consistent trend in pup production over the last 11 seasons. The most recent count for all Tasmanian colonies for the 1999 breeding season provided a minimum estimate of 3254 pups produced, similar to the estimate of 3373 in 1989. The highest estimate was recorded in 1995 when at least 6024 pups were born. Combining the most recent counts with the numbers estimated for the four Victorian colonies (13 872) gives a minimum pup production of 17 126 for the species, with only one-fifth of all pups being born on Tasmanian islands. Application of population estimators to translate pup numbers to population size for the species results in a conservative estimate of 68 500 individuals with upper and lower bounds of 60 000 and 77 000 Australian fur seals. Numbers of Australian fur seals remain low relative to other fur seal populations, with Australian fur seals being less numerous by an order of magnitude compared with their South African counterpart (A. p. pusillus). The current estimate of the total population of Australian fur seals is approximately half that of pre-sealing levels. The current number of breeding colonies in Tasmania indicates that the population of Australian fur seals breeding in Tasmanian waters has stabilised at well below their historic pre-sealing levels, with at least four sites remaining vacant. The species remains vulnerable due to its small population size, with Tasmanian breeding colonies being particularly vulnerable because of low numbers and due to the profound influence of weather events on pup survival.
The liberation, distribution, abundance and management of wild deer in Australia
Authors: Moriarty Andrew
Published: June 2004

Deer species (fallow, red, sambar, chital, rusa and hog deer) have formed wild populations in Australian habitats ranging from arid woodland to rainforest and are a growing management issue. Data were obtained via an Australia-wide land-manager survey that collected information on the liberation, distribution, abundance and management of wild deer in Australia. It is estimated that there are 218 wild deer herds in Australia with 7% of these herds originating from acclimatisation society releases, 35% from deer farm escapes/releases and 58% from translocations (deliberate releases). On average, herds released by acclimatisation societies are estimated to be 107 years old, herds that have escaped from (or been released from) deer farms are 9 years old, and transplanted herds are 6 years old. It is estimated that Australia currently has 200 000 wild deer, with 85% of these deer originally released by acclimatisation societies, 6% through escapes/releases from deer farms and 9% by translocation. Poor knowledge of the impacts of wild deer by land managers and the absence of consistent legislation governing the management of farmed and wild deer are factors that have exacerbated deliberate releases of deer and the escape of deer from farms. Management strategies for wild deer in Australia need to be developed by land managers to address the escape and release of deer from farms, the illegal translocation of deer into the wild and the management of existing wild deer herds.
Koalas on Kangaroo Island: from introduction to pest status in less than a century
Authors: Masters Pip , Duka Toni , Berris Steve , Moss Graeme
Published: June 2004

In less than a century the ecological profile of koalas on Kangaroo Island has shifted from that of a species introduced for conservation purposes to one of pest status. Between 1923 and 1925, 18 koalas were released on Kangaroo Island. Their numbers increased rapidly and in 1997 a population-control program was implemented based on a population estimate of 5000 koalas. During the course of this program, it became clear that the koala population on Kangaroo Island was much greater and more widely distributed than previously thought, hence a more comprehensive population survey was carried out.In 2000–01 the koala population size was calculated using a stratified sampling approach based on five 'catchment units' and three habitat classifications that were known to support koalas. The koala population was estimated to be ~27 000 koalas in 2001. There were substantial differences in koala density in the low-, medium- and high-quality habitat within each catchment unit, and therefore large differences in the spatial distribution of koalas across Kangaroo Island. This revised population estimate has substantial ramifications for the Kangaroo Island Koala Management Program that was set in place in 1997.