bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal Denaturation of Interfacial Protein Layers
Authors: Holt S. A. , Henderson M. J. , White J. W.
Published: March 2003

We report for the first time the structural measurements at nanometre resolution of the denaturation of β-lactoglobulin and lysozyme at an air–water interface using the technique of neutron reflectivity. The incipient denaturation shown previously[1] for myogloblin is also studied for these molecules at room temperature, and denaturation is provoked by increasing the temperature of the solutions progressively to 75°C. The change in the adsorbed protein layer thickness, its scattering length density and density distribution perpendicular to the surface as a function of increased temperature are reported and the data analysed in terms of a two-state model for the denaturation process. These measurements are relevant to an understanding of the way in which proteins at interfaces act as templates, for example, in biomineralization.
Non-Alternant Hydrocarbon Polycycles: Signs of Unusual Reactivity
Authors: Langler Richard F.
Published: March 2003

A connection is developed between typical characteristic polynomial coefficient sign patterns and Δ, the difference between the numbers of π-bonding and π-antibonding molecular orbitals for hydrocarbons. A link is revealed between Δ and dominant Sachs' subgraphs for the non-zero characteristic polynomial coefficient that is closest to the end of the polynomial. Through the intermediacy of the appropriate Sachs' subgraphs, the connection between a given Lewis structure and Δ is clarified. Exploiting the Sachs' subgraphs, one can redesign non-alternant hydrocarbon structures to alter π-system stability and, therefore, the kinetic stability of interesting molecules. A PM3 test of this methodology is provided in the accompanying paper.
A PM3 Test of Kinetic Stability Predictions for Selected Sets of Non-Alternant Hydrocarbons
Authors: Langler Richard F. , McBain Adina M.
Published: March 2003

An hypothesis, developed in the preceeding paper, permits recognition of non-alternant hydrocarbons for which the number of π-bonding molecular orbitals (MOs) does not equal the number of π-antibonding MOs. PM3 results fully support expectations for the kinetic instability of those systems examined herein. Two structures are classified as anti-aromatic as a result of their very small PM3-calculated ΔEST values.
Crystal Structure of the Second-Order Nonlinear Optical Addition Complex AsI3·3S8
Authors: Kelly Julian F. , Krausz Elmars R. , Samoc Anna , Samoc Marek , Willis Anthony C.
Published: March 2003

The arsenic triiodide–sulfur adduct, AsI3·3S8 is a new nonlinear optical acceptor–donor intermolecular complex of relatively high second-order susceptibility, χ(2) ca. 10–11 m V–1. Single crystals formed by addition of AsI3, and octasulfur, S8, in the molar ratio 1 : 3 were grown from solution. The space group is R3m, a 24.739(2) Å, c 4.412(3)�Å, V 2338(1) Å3, Z 3. The arsenic triiodide molecules occupy C3v symmetry sites with the molecular three-fold symmetry axis parallel to the polar crystal c axis. S8 retains the crown conformation. Each of the three iodine atoms of the acceptor molecule, AsI3, is involved in charge-transfer contacts to the chalcogen donor atoms of the partner S8 molecules. The adduct structure has been analysed in the context of remarkable differences between nonlinear optical properties of AsI3·3S8 and the isomorphous complexes, CHI3·3S8 and SbI3·3S8.
The Synthesis of Two Combinatorial Libraries Using a 4-(2-Thienyl)-pyrrole Template
Authors: Davis Rohan A. , Carroll Anthony R. , Quinn Ronald J.
Published: March 2003

The synthesis of the novel biaryl compound, 4-(2-thienyl)-1H-pyrrole-2-carbaldehyde (1), by Suzuki–Miyaura coupling conditions is reported. Compound (1) was subsequently used as a combinatorial template in the parallel solution-phase synthesis of an amine and imine compound library. The amine library was produced using reductive amination conditions, and purification was achieved by a liquid–liquid partition followed by silica chromatography to afford ten amine analogues. The imine library consisted of five compounds, which were synthesized using volatile primary amines that allowed purification by evaporation. The synthesis of the novel and related biaryl carbaldehyde, tert-butyl-2-(5-formyl-1H-pyrrol-3-yl)-1H-pyrrole-1-carboxylate (2) is also reported.
Rapid Analysis of Trace Gases in Complex Mixtures Using Selected Ion Flow TubeMass Spectrometry
Authors: Freeman C. G. , McEwan M. J.
Published: March 2003

Although the human nose is an extremely sensitive olfactory organ, detecting some odoriferous compounds at concentrations as low as a few ppt (parts per trillion by volume) it is not quantitative. Furthermore, it cannot identify some volatile species at quite high concentrations, and neither can it recognize the individual components of many mixtures of trace volatile organic compounds (VOCs). For some considerable time the scientific community has experimented with a number of different types of olfactory devices with varying degrees of success. The advent of selected ion flow tubemass spectrometry (SIFT-MS) has revolutionized thinking in trace gas monitoring due to the simplicity of operation together with the rapidity and sensitivity of detection that this technique provides.
Preparation and Luminescence Properties of Polymeric 2,5-Bis[2´-(8´´-alkoxyquinolin-2´´-yl)ethenyl]hydroquinone Derivatives
Authors: Hsu M.-A. , Chow T. J.
Published: March 2003

A PPV-type polymer (1) incorporating 5,5�-diquinolinyl moieties is prepared by a Yamamoto homo-coupling reaction from the dibromide (2). Since all the hydroxyl groups were alkylated, this polymer showed high solubility in most organic solvents. It can be spin-coated readily to form a thin layer in the fabrication of light emitting diode (LED) devices. The adjacent quinoline rings are twisted to form a dihedral angle due to steric hindrance, so that π-conjugation is confined within each monomer unit. The emission spectra of (1) and (2) are nearly identical. The reduction potential of (1) was estimated to be –1.10 V (onset), with a band gap of 2.53 eV (490 nm). A single hetero-junction LED device fabricated by combining the films of poly(vinylkarbazol) (PVK) and (1) yielded promising results. The device ITO/PVK/(1)/Ca/Al exhibited a turn-on voltage at 6 V and reached a maximal brightness of 250 cd/m2 at 15 V. An alternate potential usage of (1) as an electron-injecting material was also explored on a green-light device using coumarin-6 as an emitter.
The Kinetics of Free-Radical Polymerization: Fundamental Aspects
Authors: Russell G. T.
Published: March 2003

Some fundamental aspects of the kinetics of free-radical polymerization are reviewed. So-called classical results for rate and molecular-weight distribution are first of all presented. It is shown how this approach can be built upon when chain-length-dependent termination is allowed, which it always should be. Various termination models are considered, and it is illustrated that although the models are different, rather remarkably they give common, model-independent behaviour. Some leading experimental results regarding the chain-length dependence of termination are summarized, before the chain-length dependence of other reactivities, the variation of reactivities with conversion, and non-steady state experiments are briefly discussed. Finally, living free-radical polymerization as effected by a reversible termination agent is considered. An outline of the kinetics of these systems is given, with the oft-neglected importance of conventional termination being stressed.
New Macrocyclic Ligands. XIV. Synthesis and X-Ray Structures of Potentially Pentadentate Ligands Incorporating Non-Symmetrically Arranged N4S-, N3OS-, N2O2S- and N2S2O-Heteroatoms
Authors: Baldwin D. S. , Bowden B. F. , Duckworth P. A. , Lindoy L. F. , McCool B. J. , Meehan G. V. , Vasilescu I. M. , Wild S. B.
Published: March 2003

The synthesis and characterization of new mixed-donor macrocyclic ligands incorporating nitrogen, sulfur and/or oxygen heteroatoms are described. The new 17- or 18-membered macrocyclic rings contain unsymmetrical arrangements of their heteroatoms in contrast to related, previously reported rings in which the donor sets are arranged symmetrically. The X-ray structures of the 17-membered rings incorporating N4O- and N4S-donor sets are presented.
The Structures of Imidazenil and Iodoimidazenil
Authors: Hambley Trevor W. , Katsifis Andrew , Knott Robert B. , Mattner Filomena , Dikic Branko
Published: March 2003

The iodinated analogue of imidazobenzodiazepine, imidazenil (1), has been prepared with the aim of radiolabelling it with iodine-123 and including it in a study to determine the role of benzodiazepine receptors in neurodegenerative diseases using single photon emission computer tomography (SPECT) imaging. A comparison of the bromo- and iodo-derivatives, as well as the conformational changes resulting from bromine–iodine substitution are described, and it is concluded that the substitution has no clear effect on the geometry. Crystal structures of (1) and iodoimidazenil (2) have been determined by X-ray diffraction methods and refined to R values of 0.059 (3817 F) and 0.048 (1318 F), respectively. The crystals of imidazenil are triclinic, space group P1–,a 12.537(4), b 18.211(6), c 7.852(2) Å, α 91.07(2), β 106.26(2), γ 77.86(2)�, Z 4, and those of iodoimidazenil are monoclinic, space group P21/a, a 12.185(2), b 7.558(2), c 18.287(2) Å, β 95.23(1)�, Z 4.
Selective Protection Strategies in the Synthesis of TRIS-Fatty Ester Derivatives
Authors: Adhikari R. , Francis C. L. , Simpson G. W. , Yang Q.
Published: March 2003

A methodology for the selective synthesis of lipophilic acyl derivatives of the glycinamido triol (1) with either one, two, or three fatty ester groups has been established. Peracylation of (1), with palmitoyl chloride gave the triacylated derivative. Conversion of (1) into the acetonide, followed by acylation with either palmitoyl chloride or lauroyl chloride, and acetal hydrolysis provided the monoacylated derivatives. Treatment of (1) with trimethyl orthoacetate gave the orthoacetate derivative. Mild hydrolysis provided the monoacetate/diol. Acylation of the two hydroxyl groups with palmitoyl chloride gave the dipalmitate/acetate. Selective cleavage of the acetate group afforded the dipalmitate of (1). Analogous chemistry with trimethyl orthoformate provided the same dipalmitate via the orthoformate, monoformate/diol, and dipalmitate/formate. A more robust synthesis of the dipalmitate was achieved by converting the hydroxyl group of the acetonide of (1) into a tert-butyldiphenylsilyl ether, followed by acetal hydrolysis, palmitoylation of the liberated hydroxyl groups, and desilylation.
Total Synthesis of Methotrexate-γ-TRIS-Fatty Acid Conjugates
Authors: Francis C. L. , Yang Q. , Hart N. K. , Widmer F. , Manthey M. K. , He-Williams H. M.
Published: March 2003

Several routes for the regiospecific synthesis of lipophilic γ-conjugates of methotrexate are described. Coupling of methotrexate-α-tert-butyl ester with glycyl-TRIS-(mono-/di-/tri-)palmitate followed by trifluoroacetic acid cleavage of the α-protection afforded the target methotrexate-γ-glycyl-TRIS-(mono-/di-/tri-)palmitate derivatives. Methotrexate-α-benzyl-γ-glycyl-TRIS-tripalmitate was prepared but no method was found to selectively cleave the α-ester. A method where the diaminopteridinylmethyl moiety was attached last was successful, but was low yielding in the final step. Coupling of 4-amino-4-deoxy-N10-methylpteroic acid with glutamoyl-γ-glycyl-TRIS-palmitate derivatives efficiently afforded the desired conjugates.
Hydrogen-Bonded Three-Dimensional Molecular Architectures Featuring Carboxylate - Imidazole - Zinc Triad Systems
Authors: Yang Jin-Hua , Zheng Shao-Liang , Tao Jun , Liu Gao-Feng , Chen Xiao-Ming
Published: March 2003

Two complexes, [Zn(Him)2(mpa)] (1) and [Zn(Him)2(tpa)]·H2O (2) (Him = imidazole, mpa = m-phthalate, and tpa = terephthalate), have been prepared and structurally characterized, revealing two different three-dimensional hydrogen-bonded molecular architectures. Each features [Zn(Him)2(dicarboxylate)] zigzag polymeric chains and intermolecular N–H…O hydrogen bonds between the uncoordinated Him nitrogen atoms and carboxylate oxygen atoms that are similar to the carboxylate–histidine–zinc triad systems in zinc(II) enzymes. The lattice water molecules in complex (2) play a critical role in the formation of a three-dimensional hydrogen-bonded molecular architecture.
Synthesis and X-Ray Crystal Structures of Mononuclear Complexes of 1,3-Bis(8-quinolyloxy)propane
Authors: Al-Mandhary Muna R. A. , Steel Peter J.
Published: March 2003

The preparations and X-ray crystal structures of the first transition metal complexes of 1,3-bis(8-quinolyloxy)propane (2) are described. The ligand acts as a trans-chelating N,N′-bidentate ligand in the three-coordinate silver(I) nitrate complex (3) and four-coordinate copper(II) chloride complex (4), but as an N,O,O′,N′-tetradentate ligand in the octahedral nickel(II) chloride complex (5).
Synthesis, Characterization and Complexation Studies of a Cage Ligand Bearing a Tris(bipyridyl)iron(II) Capping Group
Authors: Krenske Elizabeth , Gahan Lawrence R.
Published: March 2003

Reaction between 5-(4-amino-2-thiabutyl)-5-methyl-3,7-dithianonane-1,9-diamine (N3S3) and 5-methyl-2,2-bipyridine-5-carbaldehyde and subsequent reduction of the resulting imine with sodium borohydride results in a potentially ditopic ligand (L). Treatment of L with one equivalent of an iron(II) salt led to the monoprotonated complex [Fe(HL)]3+, isolated as the hexafluorophosphate salt. The presence of characteristic bands for the tris(bipyridyl)iron(II) chromophore in the UV/vis spectrum indicated that the iron(II) atom is coordinated octahedrally by the three bipyridyl (bipy) groups. The [Fe(bipy)3] moiety encloses a cavity composed of the N3S3 portion of the ditopic ligand. The mononuclear and monomeric nature of the complex [Fe(HL)]3+ has been established also by accurate mass analysis. [Fe(HL)]3+ displays reduced stability to base compared with the complex [Fe(bipy)3]2+. In aqueous solution [Fe(HL)]3+ exhibits irreversible electrochemical behaviour with an oxidation wave ca. 60 mV to more positive potential than [Fe(bipy)3]2+. Investigations of the interaction of [Fe(L)]2+ with copper(II), iron(II), and mercury(II) using mass spectroscopic and potentiometric methods suggested that where complexation occurred, fewer than six of the N3S3 cavity donors were involved. The high affinity of the complex [Fe(L)]2+ for protons is one reason suggested to contribute to the reluctance to coordinate a second metal ion.
Metal Complexes of 2-[1,2,3-thia(and selena)diazol-4-yl]pyridine and an Unusual Silver-induced Selenadiazole Rearrangement
Authors: Richardson Chris , Steel Peter J.
Published: March 2003

Complexes of 2-(1,2,3-thiadiazol-4-yl)pyridine (3) and 2-(1,2,3-selenadiazol-4-yl)pyridine (4) with palladium(II), nickel(II), ruthenium(II), copper(II), and silver(I) reagents are reported. In general, these ligands chelate to the metal but are curiously prone to positional disorder in the X-ray crystal structures of their complexes. With silver tetrafluoroborate, ligand (3) forms an ordered M2L4 complex that contains an unsupported Ag–Ag interaction. Treatment of (4) with excess silver nitrate leads to an intriguing molecular rearrangement that produces a silver complex of 3-formyl-1,2,3-triazolo[1,5-a]pyridine.
Understanding Homolytic Translocation Chemistry—An Ab Initio Study of Some 1,5-Transfers of Silyl, Germyl and Stannyl Groups of Synthetic Significance
Authors: Kim Sunggak , Horvat Sonia M. , Schiesser Carl H.
Published: March 2003

Ab initio molecular orbital and density functional calculations predict that 1,5-homolytic translocation reactions involving silyl, germyl and stannyl groups between two alkyl carbon atoms, between alkoxy oxygen atoms, and between alkyl and allylic carbon atoms proceed via concerted mechanisms involving frontside substitution at the higher heteroatom involved; CCSD(T)/DZP//B3LYP/DZP calculations predict energy barriers ranging from 69 to 114 kJ mol–1 depending on the system involved.
Design and Preparation of Room-Temperature Ionic Liquids Containing Biodegradable Side Chains
Authors: Gathergood N. , Scammells P. J.
Published: March 2003

Novel room-temperature ionic liquids with potential sites of enzymatic hydrolysis have been prepared and tested for biodegradable properties.
A New γ-Lactonic Acid from the Lichen Myelochroa rhytidodes
Authors: Shrestha S. , Manandhar M. D. , Elix J. A.
Published: March 2003

The new aliphatic acid (+)-myelochroic acid [2-(15-acetoxypentadecyl)-4-methylidene-5-oxo-2,5-tetrahydrofuran-3-carboxylic acid] (1) has been isolated from the lichen Myelochroa rhytidodes and the structure (1) deduced from a combination of spectroscopic data.
Bioactive Butyrolactones from Fungi
Authors: Hargreaves J. , Park J. , Ghisalberti E. L. , Sivasithamparam K. , Skelton B. W. , White A. H.
Published: March 2003

Investigation of a strain of an Acremonium sp fungus has led to the isolation of two butyrolactones not previously described as naturally occurring. The structures were deduced primarily by spectroscopic means, and, in the case of (2), confirmed by a single-crystal X-ray study.
25th Australasian Polymer Symposium Special Issue
Authors: Davis T. P. , Heuts J. P. A.
Published: March 2003

In February 2001 the 25th Australasian Polymer Symposium was held at the University of New England in Armidale and was attended by over 200 Australasian and international scientists; about a third of these were registered as students. Preceding the conference, a well-attended joint workshop/summer school with the theme of radical polymerization was convened in association with the Cooperative Research Centre for Polymers (CRC-P) and the ARC Key Centre for Polymer Colloids (KCPC).
Evidence for C - H…O and C - H…π Hydrogen Bonding from Comparison of the Crystal Packing of Two Dibenzo-Azacrown Ethers
Authors: Ventrice Tina , Campi Eva M. , Fallon Gary D. , Jackson W. Roy , Junk Peter C. , Nichols Peter J. , Patti Antonio F.
Published: March 2003

Crystal-packing data for a 17-membered ring NO4 dibenzo macrocycle shows interesting curvature complementarity, which is ascribed to intermolecular C–H…O and C–H…π interactions in contrast to a related 22-membered ring N2O4 dibenzo macrocycle which shows regular layer packing.
New Macrocyclic Ligands. XV. Isomeric, Benzylated and Xylyl-Linked Macrocyclic Ligands Derived from Selectively Protected N3O2-Donor Rings
Authors: Park Kyoung Ju , Kim Jin-Ho , Meehan George V. , Nishimura Tomoko , Lindoy Leonard F. , Lee Shim Sung , Park Ki-Min , Yoon Il
Published: March 2003

Direct alkylation of the N3O2-macrocycle 1,12,15-triaza-3,4 : 9,10-dibenzo-5,8-dioxacycloheptadecane (1) with benzyl bromide in the presence of sodium hydrogen carbonate (in the respective molar ratios 1.0 : 2.0 : 1.3) led to a mixture of the mono-, bis-, and tris-N-benzylated derivatives (2)–(6) which were separated using their differential solubilities in warm acetone, fractional crystallization, coupled with column chromatography on silica gel. The X-ray structure of the symmetrical dibenzylated product (4) (as its HNO3 salt) is described. In a parallel study, N-protection of (1) using 1.7 molar equivalents of di-tert-butyl dicarbonate (Boc)2O yielded a mixture from which the symmetrical and unsymmetrical di-protected isomers (8) and (9) were separated by chromatography. Reaction of the symmetrically protected derivative (8) with benzyl chloride in the presence of excess sodium carbonate, followed by removal of the Boc groups, provided an alternative route to the corresponding (symmetrical) mono-N-benzylated macrocycle (2). A similar strategy, involving the use of α,α′-dibromo-p-xylene as a dialkylating agent, was employed to bridge a pair of N-diprotected macrocycles of type (8) or (9) to yield isomeric linked products (12) and (14), respectively. Deprotection of the resulting bis-macrocyclic products gave the 'central' and 'side' linked ligands (13) and (15), respectively.
Synthesis with Glycosynthases: Cello-Oligomers of Isofagomine and a Tetrahydrooxazine as Cellulase Inhibitors
Authors: Macdonald James M. , Stick Robert V. , Tilbrook D. Matthew G. , Withers Stephen G.
Published: March 2003

Isofagomine and a carbohydrate-like tetrahydrooxazine, as their N-benzyloxycarbonyl derivatives, have been subjected to a glycosynthase in the presence of α-D-glucopyranosyl fluoride as a glucosyl donor. In each case, after protecting group removal, a mixture of 1,4-β-linked di-, tri-, and tetra-'saccharides' was obtained. These novel oligosaccharide derivatives were tested as inhibitors of the endo-glycanase Cex from Cellulomonasfimi. Affinities increased progressively as additional D-glucosyl residues were incorporated, which is consistent with the known substrate specificity of this enzyme.
Pigments of Fungi. Part 70.* Total Synthesis of (R)-Semixanthomegnin and the X-Ray Crystal Structure of (±)-7-Chloro-10-methoxy-3-methyl-3, 4-dihydro-1 H-naphtho[2,3-c]pyran-1,6,9-trione
Authors: Cotterill Ann S. , Donner Christopher D. , Gill Melvyn , White Jonathan M.
Published: March 2003

(R)-Semixanthomegnin (8), which has been converted by others to the mould metabolite (3R,3′ R)-xanthomegnin (9), is prepared in seven steps from (R)-propylene oxide (16). A single-crystal X-ray structure analysis of (±)-7-chloro-10-methoxy-3-methyl-3,4-dihydro-1H-naphtho[2,3-c]pyran-1,6,9-trione (25) confirms the regiochemistry of the cycloaddition reaction between 2,5-dichloro-1,4-benzoquinone and the new, highly oxygenated, chiral butadiene derivative (2).
Insights into Pt(II)-Hydroxamate Bonding Through the Crystal Structures of DMSO Complexes
Authors: Failes Timothy W. , Hambley Trevor W.
Published: March 2003

The complexes [Pt(bha-H)(DMSO)2] and [Pt(sha-H)(DMSO)2], where bhaH is benzohydroxamic acid and shaH is salicylhydroxamic acid, were prepared and the crystal structures determined (both monoclinic, space group Pca21). These complexes provide support for the argument that hydroxamates will only bind to Pt(II) when ligands with soft-donor atoms lie trans to the hydroxamate in the doubly deprotonated hydroximate form. Comparison of the Pt–O bond lengths between these and related structures reveals significant ionic contributions to the bonding.
Synthesis of Collinin, an Antiviral Coumarin
Authors: Curini Massimo , Epifano Francesco , Maltese Federica , Marcotullio Maria Carla , Gonzales Sylvia Prieto , Rodriguez Juan Carlos
Published: March 2003

Collinin (1), a geranyloxycoumarin, has been synthesized in three steps and 24.6% overall yield from pyrogallol (2) and propiolic acid (3).
Synthesis of Some 3-Furylamine Derivatives
Authors: Lingham Anthony R. , Rook Trevor J. , Hügel Helmut M.
Published: March 2003

A general and efficient method for the synthesis of 3-furylamines via Michael addition of amines to acyclic keto alkynol precursors has been achieved. The preparation of various 3-furylamines has been carried out using a flexible methodology which also allows modification of the substituent at the 5-position.
Complexation of Zinc(II) and Cadmium(II) by Hydroxyethyl- and Bis(hydroxyethyl)-1,4,7-triazacyclononane in Water
Authors: Creaser Steffen P. , Pyke Simon M. , Lincoln Stephen F.
Published: March 2003

The complexation of Zn2+ by hydroxyethyl- and bis(hydroxyethyl)-1,4,7-triazacyclononane ((2) and (3)) in aqueous solution at 298.2 K and I = 0.10 mol dm−3 (NaNO3) is characterized by log(K/dm3 mol−1) = 10.45 ± 0.05 and 11.32 ± 0.02 and a deprotonation assigned to coordinated water is characterized by pKa = 8.87 ± 0.11 and 8.50 ± 0.03, respectively. For the analogous Cd2+ complexes log(K/dm3 mol−1) = 8.74 ± 0.02 and 9.79 ± 0.02, respectively, and no deprotonation of coordinated water is detected. The synthesis of (2) is described.
A heated air quarantine disinfestation treatment against Queensland fruit fly (Diptera: Tephritidae) for tomatoes
Authors: Heather N. W. , Kopittke R. A. , Pike E. A.
Published: March 2003

A circulated heated-air treatment at 92% RH to achieve and maintain a minimum fruit core temperature of 44°C for 2 h is shown to disinfest tomatoes against Queensland fruit fly, Bactrocera tryoni (Froggatt) for market access quarantine purposes. The efficacy of the treatment exceeded 99.99%, tested at the 95% confidence level. An estimated 78 439 eggs were used for large-scale trials, as the stage of the pest most tolerant of heat at the treatment temperature.
Dryland salinity in the Upper Kent River catchment of Western Australia: farmer perceptions and practices
Authors: Kington E. A. , Pannell D. J.
Published: March 2003

Dryland salinity, resulting from extensive land clearing, has been increasingly recognised as a serious environmental and economic problem in Western Australia. Policy initiatives at the state and national level in Australia have attempted to influence farmers' choices of land management practices to reduce the threat of salinity. This study examines, for a particular catchment, what farmers' salinity management practices have been and are likely to be, how farmers view the salinity problem and its recommended treatments, and farmers' perceptions of why the salinity problem continues to worsen. We found that the farmers had high levels of knowledge about salinity and its treatment, although their perceptions appeared to be overly optimistic on a number of aspects of the problem. As a group they were highly uncertain about its extent and the rate of worsening, and they highlighted the complexity, modest effectiveness and relatively poor economic performance of available treatment options. It appears that the scale of salinity prevention practices in the catchment is insufficient for preventing ongoing increases in the area of saline land.
Recognising a climate for sustainability: extension beyond transfer of technology
Authors: Fliert E. van de
Published: March 2003

Sustainable agriculture emphasises the fundamental role of the human component in a production system, as opposed to conventional agriculture, which centres on technologies. Therefore, it is characterised by the abilities and behaviours that farmers display, including the knowledge and skills they possess, decision-making processes they apply, and individual and collective actions they take. This has strong implications for extension development and organisation, in that the methodologies applied should be oriented towards enhancing farmer capacities favourable to sustainable agriculture, rather than towards achieving adoption of standardised technologies. These capacities include sound ecological knowledge, observational, analytical and experimental skills, and inclination towards collectivity to allow farmers to make better, informed decisions for location-specific agro-ecosystem management. Extension approaches favouring this type of learning are participatory, experience-based and adaptable. Needs and opportunity assessment, participatory technology development, defining the implications for farmers of the implementation of an innovation, and development of a learning curriculum (first for farmers and then for facilitators) are among the sequential phases for solid extension development for sustainable agriculture. Applying underlying principles of participatory capacity development, rather than fixed, condition-specific models, provides a generic framework for extension development under diverse ecological and socio-cultural settings.
Lamb production from Merino ewes mated to Merino or Damara rams
Authors: Fleet M. R. , Bennie M. J. , Dunsford G. N. , Cook G. R. , Smith D. H.
Published: March 2003

Damara sheep have recently been imported to Australia and are being crossed with Merino ewes as a diversification from wool to fat tail sheep production for live sheep export or meat markets. A comparison was made of the lamb outputs from Merino ewes mated to 2 Merino rams and 2 Damara fat tail rams. There were more multiple litters produced in the matings with the Damara rams than from the Merino rams (P = 0.01). The 5-month weights of the crossbred lamb groups (36.3 and 38.9 kg) were higher (P<0.05) than the Merino groups (33.4 and 32.3 kg). Ram lambs were slaughtered at 7 months of age and the carcasses dissected into 'trim lamb' lean portions, fat trims, bone and other oddments. Dressing percentage at slaughter of the crossbred lambs was 3–4% higher (P<0.001), reflecting lower wool production, than the Merino lambs. After adjustment for chilled carcass weight, there were no differences (P>0.05) between rams for the total amount of lean meat. However, the crossbred groups had more external carcass fat (2.59 and 2.64 kg) than the Merino groups (2.14 and 2.15 kg) and, in addition, had fat tail weights of 0.52 and 0.36 kg.
Sustaining productivity of a Vertisol at Warra, Queensland, with fertilisers, no-tillage or legumes. 6. Production and nitrogen benefits from annual medic in rotation with wheat
Authors: Weston E. J. , Dalal R. C. , Strong W. M. , Lehane K. J. , Cooper J. E. , King A. J. , Holmes C. J.
Published: March 2003

Continuous cereal production in the summer-dominant rainfall region of north-eastern Australia has depleted native soil nitrogen fertility to a level where corrective strategies are required to sustain wheat grain yields and high protein levels for domestic and export markets. Annual medic pastures, along with other strategies, were evaluated from 1986 to 1998 on a Vertisol at Warra, southern Queensland, for their benefit to subsequent grain yield and protein content of wheat.Annual medic production and nitrogen yields were closely correlated with the growing season rainfall (March–September). Each 100 mm of growing season rainfall resulted in 1.39 t/ha of dry matter and 40 kg/ha of N yield. There were significant increases in soil mineralisable nitrogen following annual medic leys compared with continuous wheat in most years, but increases in total soil nitrogen were only observed in 1990, 1991 and 1992. However, pre-plant nitrate-nitrogen following an annual medic ley was always higher than that of continuous wheat without nitrogen fertiliser. This resulted in significant increases in wheat yield (6 of 9 seasons) and grain protein (in all seasons) compared with continuous wheat. The overall responses in yield and protein were similar to those of 50� kg/ha of fertiliser nitrogen applied to continuous wheat crops. A nitrogen harvest budget for the annual medic–wheat rotation over 11 years showed that it contributed 131 kg N/ha more than continuous wheat. Thus, using the seasonal conditions experienced from 1987 to 1998 as a reasonable representation of the rainfall range in the region, sustainable productivity can be maintained where annual medics are grown in short rotations with wheat.
Mineral content of honeybee-collected pollen from southern New South Wales
Authors: Somerville D. C. , Nicol H. I.
Published: March 2003

The mineral content of honeybee-collected pollen from 34 floral species was analysed for 10 elements. The mean concentrations (mg/kg) of major and minor elements were the following: potassium (K) 5530, phosphorus (P) 4600, sulfur (S) 2378, calcium (Ca) 1146, magnesium (Mg) 716, sodium (Na) 82, iron (Fe) 67, zinc�(Zn) 58, manganese (Mn) 33 and copper (Cu) 12. Close correlations existed between Mn and Cu, P and S, K and S and K and Zn. Single species demonstrated similar element profiles. Echium plantagineum pollen had a high mean concentration of P (7411 mg/kg) and S (3133 mg/kg) when compared with the mean of the total; Brassica�napus pollen had high concentration of Mg (1400 mg/kg) and Ca (1750 mg/kg) and low concentration of Fe (27 mg/kg); Hypochoeris radicata had low concentrations of 6 elements — Fe (4.5 mg/kg), Zn (20 mg/kg), Mg�(240 mg/kg), S (1400 mg/kg), P (2066 mg/kg) and K (2433 mg/kg). Asphodelus fistulosus had the highest concentration of K at 38 000 mg/kg, the next highest value of 8200 mg/kg being for Prunus dulcis.
Wheat genotypes differ in growth and phosphorus uptake when supplied with different sources and rates of phosphorus banded or mixed in soil in pots
Authors: Valizadeh G. R. , Rengel Z. , Rate A. W.
Published: March 2003

The growth response of wheat genotypes supplied with phosphorus fertiliser at different rates (banded or mixed throughout the soil) and sparingly soluble phosphorus sources (aluminium phosphate and iron phosphate) is not known. Eleven wheat genotypes and 1 rye genotype were tested at 3 rates of phosphorus fertiliser application (5, 10 and 20 mg P/kg soil) in a pot study. Another experiment compared 4 wheat genotypes at 2 rates of phosphorus application (deficient and sufficient) and 2 application methods (banding and mixing throughout the soil). The selected wheat genotypes were also used to investigate growth and root exudation response to iron phosphate and aluminium phosphate supply. Banding of phosphorus fertiliser increased the uptake of phosphorus and wheat growth compared with mixing phosphorus throughout the soil. Wheat genotypes did not differ significantly in growth and phosphorus uptake at the low rate of application. With increasing rates of phosphorus supply, the 2 phosphorus-fertiliser-responsive wheat genotypes (Wawht 2074 and Aroona) had significantly increased phosphorus uptake and root and shoot weights. When supplied with aluminium phosphate and iron phosphate, the 2 phosphorus-fertiliser-responsive genotypes had larger roots and higher concentration of phosphorus in the shoots and roots, while the phosphorus utilisation-efficient wheat genotypes (Westonia and Gutha) had higher shoot weights than phosphorus fertiliser-responsive ones. All wheat genotypes produced quantitatively and qualitatively similar root exudates in the iron phosphate, aluminium phosphate and zero-phosphorus treatments. The aluminium phosphate treatment caused genotypes to increase root exudation of oxalic anions, uptake of phosphorus and growth, compared with the iron phosphate treatment. It was concluded that the choice of genotypes for achieving increased wheat growth would depend on the phosphorus source in soil and the rate of application of phosphorus fertiliser.
Role of phosphorus fertiliser banding and the ratio of nitrate to ammonium on the uptake of phosphorus and wheat growth: a glasshouse study
Authors: Valizadeh G. R. , Rengel Z. , Rate A. W.
Published: March 2003

While it is known that nitrogen fertilisers improve phosphorus uptake depending on soil type and pH, the role in phosphorus uptake of the ratio of nitrate to ammonium in nitrogen fertiliser banded with phosphorus fertiliser is unclear. The present glasshouse study investigated the wheat growth response to different rates of application and banding depths (5 and 15 cm) of nitrogen and phosphorus, and mixing of phosphorus fertiliser with soil. The effect of 2 forms of nitrogen (ammonium and nitrate) banded with phosphorus fertiliser was also studied.Both banding depths increased phosphorus uptake and wheat growth more than mixing fertiliser throughout the soil. Banding at the 5 cm depth increased phosphorus uptake efficiency and wheat growth more than banding at the 15 cm depth. The highest shoot and root growth and phosphorus content were found when the nitrate : ammonium ratio was 50 : 50 and 75 : 25, with a slight decline at 100 : 0. The treatments with a large proportion of ammonium suppressed the growth of wheat and, consequently, reduced total phosphorus content. It was concluded that banding nitrate and ammonium at ratios 50 : 50, 75 : 25 and 100 : 0 with phosphorus fertiliser at 5 cm depth was optimal for increasing phosphorus uptake and wheat growth.
Nodulation and growth of pasture legumes with naturalised soil rhizobia.2. Balansa clover (Trifolium michelianum Savi)
Authors: Ballard R. A. , Craig A. D. , Charman N.
Published: March 2003

Balansa clover (Trifolium michelianum Savi) is grown widely across southern and eastern Australia. The presence of suitable rhizobia (Rhizobium leguminosarum bv. trifolii) for this species of clover, and their ability to form an effective symbiosis, was assessed in a survey of 43 soils collected from across Australia. The effectiveness of the soil rhizobia is compared with that of strains WU95 and WSM409. The study confirmed the widespread occurrence of clover rhizobia in Australian soils. No clover rhizobia were detected in 6 of the 43 soils and this was probably associated with a history of clover absence at these soil locations. Thirty of the soils contained more than 500 rhizobia per gram. These rhizobia varied from highly effective for soil T2 (128% of WSM409) through to ineffective for soil V9 (22% of WSM409). Few soil inoculants were more effective than strain WSM409. Commercial inoculant strain WSM409 was generally more effective than former inoculant strain WU95.The suboptimal performance of the rhizobia in many of the soils indicates that there is an opportunity to improve the level of nitrogen fixation by balansa clover in the field. Bearing in mind the difficulties associated with the introduction and persistence of applied inoculant strains, cultivar selection is considered as an approach to improve the symbiosis. However, this study indicated little variation in the performance of the 3 commercial cultivars, Frontier, Paradana and Bolta, in this regard.
Crop growth, yield and water use in long fallow and continuous cropping sequences in the Victorian mallee
Authors: O'Connell M. G. , Connor D. J. , O'Leary G. J.
Published: March 2003

The agronomic implications of substituting mustard (Brassica juncea) for long (winter) fallows were investigated in a 6-year field experiment by comparing 2 cropping sequences (fallow–wheat–pea v. mustard–wheat–pea) in the semi-arid Victorian mallee. Production and water use of wheat, pea and mustard were measured. Grain yields ranged from 0.1 to 2.4 t/ha for wheat (mean 1.72 t/ha after fallow and 1.22 t/ha after mustard); from 0 to 0.6 t/ha (mean 0.22 t/ha) for mustard and from 0 to 1.4 t/ha (mean 0.8 t/ha) for field pea, strongly reflecting variable seasonal conditions (in-crop rainfall range from 84 to 231 mm). Mustard was shown to be a potential replacement for long fallow producing additional yield benefit (mustard + wheat) in one year. However, under drought conditions it introduces severe penalties to wheat growth and yield compared with the traditional fallow cropping system. Further, mustard did not affect water use, growth, or yield of the second crop after wheat (in our case field pea). This study highlights a conflict between developing farming systems that are productive, environmentally and socially acceptable under variable weather conditions and yet uphold the regional need to reduce dependence on fallowing. Further analyses of weather patterns and other crop choice strategies are needed to help develop better management strategies for the mallee region of Australia.
Effect of timing of pasture grass removal on subsequent take-all incidence and yield in wheat in southern New South Wales
Authors: Kidd C. R. , Murray G. M. , Pratley J. E. , Leys A. R.
Published: March 2003

Winter cleaning is the removal of grasses from pasture using selective herbicides applied during winter. We compared the effectiveness of an early (June) and late (July) winter cleaning with an early spring herbicide fallow (September), spring (October) herbicide and no disturbance of the pasture on development of the root disease take-all in the subsequent wheat crop. Experiments were done at 5 sites in the eastern Riverina of New South Wales in 1990 and 1991. The winter clean treatments reduced soil inoculum of Gaeumannomyces graminis var. tritici (Ggt) compared with the other treatments at all sites as measured by a bioassay, with reductions from the undisturbed treatments of 52–79% over 5 sites. The winter clean treatments also significantly reduced the amount of take-all that developed in the subsequent wheat crop by between 52 and 83%. The early and late winter clean treatments increased the number of heads/m2 at 3 and 1 sites, respectively. Dry matter at anthesis was increased by the winter clean treatments at 3 sites. Grain yield was increased by the winter cleaning treatments over the other treatments at the 4 sites harvested, with yield increases of the early winter clean over the undisturbed treatment from 13 to 56%. The autumn bioassay of Ggt was positively correlated with spring take-all and negatively correlated with grain yield of the subsequent wheat crop at each site. However, there was a significant site and site × bioassay interaction so that the autumn bioassay could not be used to predict the amount of take-all that would develop.
Blood cell profiles of steer progeny from parents selected for and against residual feed intake
Authors: Richardson E. C. , Herd R. M. , Colditz I. G. , Archer J. A. , Arthur P. F.
Published: March 2003

This study examined whether a single generation of divergent selection for residual feed intake was accompanied by differences in red and white blood cell parameters that could assist in the early identification of animals likely to perform well in a test for residual feed intake. Two cohorts of steer progeny born in 1996 (n = 74) and 1998 (n = 120) of parents selected for low residual feed intake (high efficiency) and high residual feed intake (low efficiency) were used. The steers grazed on pasture before feedlot entry and subsequent feed intake test. Blood samples were collected from the 1998 born cattle at pasture the day before feedlot induction, and for all cattle, at the start, middle and end of their feed intake test. Statistically significant regressions between sire estimated breeding value for residual feed intake and white blood cell count, haemoglobin level, haematocrit and percentage monocytes measured on their progeny over a feed intake test were evidence for a genetic association between these blood parameters and residual feed intake. Of the cell parameters measured in the blood samples collected from cattle at pasture before feedlot entry, only white blood cell count (r = –0.20, P<0.05) and neutrophil count (r = –0.29, P<0.01) were correlated with steer residual feed intake in the feedlot, none (P>0.05) were correlated with sire estimated breeding value for residual feed intake. Cell parameters measured in the blood samples collected from cattle at the start of the feed intake test were not correlated (P>0.05) with steer residual feed intake in the feedlot or with sire estimated breeding value for residual feed intake. It is doubtful that blood parameters in a blood sample taken at pasture before feedlot entry or at the start of a feed intake test can be used to predict residual feed intake of individual steers or sire progeny groups in feed intake tests.
The impact of rabbits on a grazing system in eastern New South Wales.1. Ground cover and pastures
Authors: Croft J. D. , Fleming P. J. S. , Ven R. van de
Published: March 2003

Although there have been a number of studies that have examined the effects of rabbits on pasture, the relationship between rabbit density and pasture degradation caused by rabbits has never been quantified. An experiment was conducted at Cowra, New South Wales, from October 1984 to October 1987, to determine the impact various densities of rabbits have on pasture composition, indices of pasture biomass and ground cover. Using plots set stocked with the equivalent of 8 sheep/ha (the district average) and 4 densities of rabbits as treatments, 0,�24, 48 and 72 rabbits/ha, the consequences of rabbit grazing were investigated.Pasture composition changed with season, year and rabbit density. Cumulative effects were also evident. Rabbits severely depleted improved pastures of legumes (subterranean clover particularly), with grass cover increasing proportionate to rabbit density. In the final year of the experiment, the rabbit-free treatment had 31% legumes and 25.2% grasses, whereas the highest rabbit density treatment had 6.2% legumes and 47.4% grasses. Indices of pasture biomass were highest in the zero rabbits/ha treatment and lowest in the 72 rabbits/ha treatment. More bare soil was exposed in the highest rabbit density treatment. Once seasonal and year effects were accounted for, the relationship between rabbit density and percentage damage was positive.
The impact of rabbits on a grazing system in eastern New South Wales. 2. Sheep production
Authors: Fleming P. J. S. , Croft J. D. , Nicol H. I.
Published: March 2003

Much research, time and money have been invested in the control of rabbits in Australia, yet the relationship between rabbit density and livestock production losses has not been quantified. We experimentally investigated the variations in sheep production parameters caused by 4 densities of rabbits, 0, 24, 48 and 72 rabbits/ha. Medium to strong wool merino wethers were run at a constant stocking rate in replicated plots with rabbits at 4� different densities. Sheep liveweight and body condition and wool production variables were measured over 3�years. Low to medium densities of rabbits were not found to reduce liveweights of wethers, whereas wethers run with the high density of rabbits were significantly lighter. The presence of rabbits reduced the body condition of sympatric sheep with the lowest body condition recorded at the high rabbit density. Mean greasy fleece weights, wool yields and clean-fleece weights were significantly different between densities of rabbits. Wethers run with the high rabbit density grew less wool than the wethers run with the other 3 densities of rabbits. The cumulative gross return per ha from wool production was highest for the medium rabbit density and lowest at high rabbit density. At the conclusion of this short-term experiment, the presence of some rabbits enhanced returns from wool production because of lower fibre diameter and comparable clean-fleece weights of fleeces grown at low and medium rabbit densities. These production characteristics might have been caused by synergistic effects on pasture growth or a sheep stocking rate that was too conservative for the prevailing seasonal conditions. At high rabbit density, competition for pasture between rabbits and sheep overrode possible synergistic and understocking effects. The economic implications of the presence of rabbits on merino sheep production are discussed.