Showing papers by "La Trobe University published in 1986"

What is invexity

Abstract: Recently it was shown that many results in Mathematical Programming involving convex functions actually hold for a wider class of functions, called invex. Here a simple characterization of invexity is given for both constrained and unconstrained problems. The relationship between invexity and other generalizations of convexity is illustrated. Finally, it is shown that invexity can be substituted for convexity in the saddle point problem and in the Slater constraint qualification.

Porphyroblast nucleation, growth and dissolution in regional metamorphic rocks as a function of deformation partitioning during foliation development

Abstract: In regional metamorphic rocks, the partitioning of deformation into progressive shearing and progressive shortening components results in strain and strain-rate gradients across the boundaries between the partitioned zones. These generate dislocation density gradients and hence chemical potential gradients that drive dissolution and solution transfer. Phyllosilicates and graphite are well adapted to accommodating progressive shearing without necessarily building up large dislocation density gradients within a grain, because of their uniquely layered crystal structure. However, most silicates and oxides cannot accommodate strain transitions within grains without associated dislocation density gradients, and hence are susceptible to dissolution and solution transfer. As a consequence, zones of progressive shearing become zones of dissolution of most minerals, and of concentration of phyllosilicates and graphite. Exceptions are mylonites, where strain-rates are commonly high enough for plastic deformation to dominate over diffusion rates and therefore over dissolution and solution transfer. Porphyroblastic minerals cannot nucleate and grow in zones of active progressive shearing, as they would be dissolved by the effects of shearing strain on their boundaries. However, they can nucleate and grow in zones of progressive shortening and this is aided by the propensity for microfracturing in these zones, which allows rapid access of fluids carrying the material presumed to be necessary for nucleation and growth. Zones of progessive shortening also have a number of characteristics that help to lower the activation energy barrier for nucleation, this includes a build up of stored strain-energy relative to zones of progressive shearing, in which dissolution is occuring. Porphyroblast growth is generally syndeformational, and previously accepted criteria for static growth are not valid when the role of deformation partitioning is taken into account. Porphyroblasts in a contact aureole do not grow statically either, as microfracturing, associated with emplacement, allows access of fluids in a fashion that is similar to microfracturing in zones of progressive shortening. The criteria used for porphyroblast timing can be readily accommodated in terms of deformation partitioning, reactivation of deforming foliations, and a general lack of rotation of porphyroblasts, with the spectacular exception of genuinely spiralling garnet porphyroblasts.

Molecular recognition between oligopeptides and nucleic acids: novel imidazole-containing oligopeptides related to netropsin that exhibit altered DNA sequence specificity.

Abstract: Oligopeptides have been synthesized that are structurally related to the antiviral antitumor antibiotic netropsin, but in which each of the pyrrole units is successively replaced by an imidazole moiety, as well as their di- and triimidazole-containing counterparts. These compounds bind to duplex DNA with constants in the range (1.06-1.98) X 10(6) M-1 but not to single-stranded DNA. Since they bind to T4 DNA, it is inferred that, like the parent antibiotic netropsin, they are also minor groove selective. This series of compounds exhibits a progressively decreasing preference for AT sites in binding studies with both native DNAs and synthetic oligonucleotides and a corresponding increasing acceptance of GC base pairs. Footprinting experiments utilizing a 139 base pair HindIII/NciI restriction fragment from pBR 322 DNA revealed that these lexitropsins, or information-reading oligopeptides, recognize more sites than the parent netropsin. In addition, some regions of enhanced nuclease action as the result of drug binding to the fragment were identified. The diimidazole compound in particular recognizes GC-rich sites, implying the formation of new hydrogen bonds between G-C(2)NH2 in the minor groove and the additional N3 imidazole nitrogens. It is clear however that, since the lexitropsins appear to tolerate the original (AT)4 site, an N-methylimidazole group on the ligand will permit either a GC or AT base pair in the binding sequence. Another factor that may be significant in molecular recognition is the high negative electrostatic potential of A X T regions of the minor groove, which is likely to strongly influence binding of these cationic species to DNA.(ABSTRACT TRUNCATED AT 250 WORDS)

The two alcohol dehydrogenases of Zymomonas mobilis. Purification by differential dye ligand chromatography, molecular characterisation and physiological roles.

Abstract: 1. The two alcohol dehydrogenases found in Zymomonas mobilis have each been purified using dye-ligand chromatography and affinity elution with nucleotides. 2. The isoenzyme with lower electrophoretic mobility (ZADH-1) is a zinc enzyme with properties essentially similar to preparations described elsewhere. 3. The faster isoenzyme (ZADH-2) accounted for some 90% of the ethanol-oxidizing activity in freshly prepared extracts and corresponded to the iron-activated enzyme previously described. This enzyme was inactivated by zinc; activity could only be retained during purification by including either ferrous ions or cobaltous ions in the buffers. 4. ZADH-2 has relatively low acetaldehyde reductase activity; consequently ZADH-1 is responsible for about half of the physiological activity (acetaldehyde reduction) in Zymomonas cells. 5. Kinetic studies showed that ZADH-2 is activated by ethanol in both reaction directions; a hypothesis for the mechanism of activation is presented. 6. Metal ion analyses of ZADH-2 prepared in the presence of iron or cobalt indicated one atom of the relevant metal per subunit, with no significant zinc content. 7. N-terminal sequence analyses showed that the ZADH-1 has some homology with the Bacillus stearothermophilus enzyme, whereas ZADH-2 resembles the yeast enzyme more closely.

Dose-dependent entrainment of rat circadian rhythms by daily injection of melatonin.

Abstract: Previous work in our laboratory has shown that daily injection of large doses of the pineal hormone melatonin entrains the free-running locomotor rhythms of rats held in constant darkness and synchronizes the disrupted patterns of rats maintained in constant bright light. The present experiments determined the dose-response characteristics of entrainment to daily melatonin injections and made preliminary biochemical estimates of blood melatonin levels and half-lives after two critical doses of the hormone. The data indicated that the median effective dose for melatonin as an entraining agent in free-running rats was 5.45 +/- 1.33 micrograms/kg, considerably lower than doses previously employed and lower than doses employed in reproductive and metabolic studies in rats and hamsters. The data further indicated that the response to melatonin was quantal; rats either entrained to melatonin or they did not. No "partial entrainment" was evident, nor were there differences in phase angle, activity, or period among all effective doses. Biochemical estimates of blood melatonin after either 1 mg/kg or 1 microgram/kg of melatonin indicated that all effective doses resulted in supraphysiological levels of blood melatonin, although doses of 1 microgram/kg resulted in blood levels that were within one order of magnitude of normal nighttime values. Together, the data suggest that the rat circadian system is sensitive to the pineal hormone melatonin at or below doses required to effect rodent reproduction. Whether this sensitivity reflects a role for the pineal gland in rat circadian organization, however, still remains to be determined.

Selection in captive populations

Abstract: We have briefly reviewed types of genetic variation and selection in the wild as contrasted with selection in captive populations, along with the objectives of captive breeding programs, before recommending selection procedures for the genetic management of captive populations Although some inadvertent selection for tameness and adaptation to captive environments is inevitable in captive populations, any selection that is actively applied to captive populations should have clearly defined objectives Much of the apparent disagreement about genetic management of captive populations probably stems from the varying objectives of different captive breeding programs Objectives differ depending on whether the populations are: (1) common species for display, (2) endangered species for long-term conservation, (3) rare species being multiplied for immediate release back into the wild, or (4) rare species not yet capable of self-sustaining reproduction in captivity For all categories of populations we recommend selection to keep the genetic load under control Populations in category 1 can be selected for adaptation to captive breeding, ease of handling, and for classic species phenotype Populations in categories 2 and 3 should have no deliberate selection applied to them, apart from that to control the genetic load, so that the probability of successful release back into the wild is maximized Populations in category 4 may require selection for captive breeding success until they attain self-sustaining status Once this has been achieved they should be managed as under category 2 The special cases of species that have been subjected to introgression are discussed The multidisciplinary nature of captive population management is stressed

S-type granites and their probable absence in southwestern North America

Abstract: Criteria that have been (and still are) used to characterize S-type granites of the Lachlan Fold Belt (LFB) of southeastern Australia are reviewed, and comparisons are made with various peraluminous granites of southwestern North America, some of which have been classified as S-types on the basis of insufficient data. Virtually all of the vast volume of S-type granites in the LFB are near-surface, batholithic granites that are commonly associated with S-type volcanics and are not associated with regional metamorphic rocks and migmatites. They are strongly peraluminous, as shown by the presence of cordierite. Granites with primary muscovite are rare. All are low in Na, Ca, and Sr as a result of chemical weathering during formation of the sedimentary sources. Peraluminous granites of various ages in southwestern North America are distinctly different. They rarely contain cordierite (a mineral characteristic of LFB S-types), but some are highly evolved such that Fe-Mn-rich garnet has crystallized. They are dominantly two-mica granites, indicating crystallization at higher water fugacities and greater depths than most peraluminous granites of the LFB. Cordierite-bearing volcanics (S-types) have not been reported. Sodium is generally high in the peraluminous granites of southwestern North America. Some of these rocks have trondhjemitic affinities; the parent magmas seem more likely to have been produced by partial melting of altered basaltic rocks. Locally, some peraluminous rocks (marginal to metaluminous types) may owe their compositions to high-level contamination of I-types; these are not S-type rocks. No compelling evidence has been presented that any of the peraluminous granites of southwestern North America are S-types.

Fluid inclusions in skarns (carbonate replacement deposits)

Abstract: Fluid inclusions in ore skarn minerals reflect the physiochemical nature of the solutions present during the skarn-forming process. Because of the dense nature of skarn minerals and the dynamic processes operative during skarn genesis, sufficient primary fluid inclusions are usually present. Ore skarn solutions, as opposed to metamorphic skarn or ore vein solutions, have much higher CaCl2 contents and usually very high formation temperatures (>500°C) and salinities (>40 wt % T.D.S.). Temperatures and salinities generally decrease away from the solution source, both in time and space. The gradients found at greater distances from the source in distal (far from contact) skarns tend to be less (e.g. 210–350°C) for a particular skarn stage to that in proximal (near contact) skarns (e.g. 400–650°C). This information is useful for delineating the parts of such a hydrothermal system. Temperatures also tend to decrease with time, which is reflected by the superimposition of various overprinting, retrograde mineral stages. In a few areas (e.g. Naica, Mexico) intermittent boiling of ore solutions occurs, periodically elevating both temperatures and salinities, but commonly boiling only occurs early in skarn genesis just after an early, commonly lower temperature, phase. Most fluid inclusions represent a mix of‘exhaust’or reacted solutions with minor unreacted or new (pre-) ore solution components. Limited data on the distribution of elements present in fluid inclusions that do not normally take part in skarn genesis (Na, K and Cl) indicate that their proportions reflect the nature of the associated pluton. High KC1 contents are found in skarns adjacent to high K granitoids, whereas high NaCl contents are found in skarns adjacent to calcic granitoids. In many examples, daughter minerals present in minor proportions in opened fluid inclusion cavities reflect the metal characteristics of the ore solution. Small rare-earth metal, tungsten, zinc and copper daughter(?) minerals have been identified. The temperature and (or) salinity data for skarns of different metal or geological type is not particularly useful to delineate whether a skarn locality is part of a more complex, as yet unexplored system. Solutions in Pb–Zn skarns tend to be lower-temperature (150–400°C) and more dilute (<30 wt % T.D.S.) than in other skarn types, but exceptions occur.

Primary structure of the (1→3,1→4)-β-D-glucan 4-glucohydrolase from barley aleurone

Abstract: During germination of barley grains, the cell walls of the starchy endosperm are degraded by (1→3,1→4)-β-glucanases (EC 3.2.1.73) secreted from the aleurone and scutellar tissues. The complete sequence of the aleurone (1→3,1→4)-β-glucanase isoenzyme II comprises 306 amino acids and was determined by sequencing nine tryptic peptides (110 residues) and aligning them with the amino acid sequence deduced from a cDNA clone encoding the 291 NH2-terminal residues. Although no amino acid sequence homology with a bacterial (1→3)(1→4)-β-glucanase is apparent, close to 50% homology is found with two large regions of a (1→3)-β-glucanase from tobacco pith tissue. The gene for barley (1→3,1→4)-β-glucanase isoenzyme II shares with that for the α-amylase isoenzyme 1 a strongly preferred use of codons with G and C in the wobble position (94% and 90%, respectively). Both enzymes are secreted from the aleurone cells during germination. Such one-sided codon usage is not characteristic for the gene encoding the (1→3)-β-glucanase of tobacco pith tissue or the hor2-4 gene encoding the B1 hordein storage protein in the endosperm.

Attention deficit disorder with hyperactivity: a critique

Abstract: The DSM III category of Attention Deficit Disorder with Hyperactivity is considered within a framework of Rutter's (1977) outline of criteria for adequacy of psychiatry classification. Discussion of problems with the operationalization and definition of 'attention deficit' and the difficulty of using this rubric in distinguishing between ADDH and other related childhood disorders, along with the consequent failure to meet other important criteria, leads to the conclusion that the concept needs re-appraisal.

DNA cleavage specificity of a group of cationic metalloporphyrins.

Abstract: The ability of a group of water-soluble metalloporphyrins to cleave DNA has been investigated. Incubation of Mn3+, Fe3+, or Co3+ complexes of meso-tetrakis(N-methyl-4-pyridiniumyl)porphine (H2T4MPyP) with DNA in the presence of ascorbate, superoxide ion, or iodosobenzene results in DNA breakage. Comparisons between the rates of porphyrin autodestruction with the rates of strand scission of covalently closed circular PM2 DNA indicate that the porphyrins remain intact during the cleavage process. Analysis of the porphyrin-mediated strand scissions on a 139-base-pair restriction fragment of pBR322 DNA using gel electrophoresis/autoradiography/microdensitometry reveals that the minimum porphyrin cleavage site is (A X T)3. The cleavage pattern within a given site was found to be asymmetric, indicating that porphyrin binding and the strand scission process are highly directional in nature. In addition to an analysis of the mechanism of porphyrin-mediated strand breakage in terms of the DNA cleavage mechanism of methidium-propyl-iron-EDTA and Fe-bleomycin, the potential of the cationic metalloporphyrins as footprinting probes and as new "reporter ligands" for DNA is presented and discussed.

Visual and auditory attention performance in hyperactive children: Competence or compliance

Abstract: The effect of self-control and compliance on the attentional performance of hyperactive children was assessed. Visual and auditory attention tasks were presented in conditions in which the experimenter was either absent and therefore not imposing external control, or present and therefore imposing some degree of control. There was no difference in performance between hyperactives and controls when the experimenter was present, but the hyperactives' performance showed a greater deterioration than controls when the experimenter was absent. The amount of movement displayed during the tasks was greater for hyperactives and increased more for this group during experimenter-absent conditions. The results support the contention that noncompliance is a major contributor to the poor performance of hyperactive children, which can be seen as an "application" deficit rather than an "ability" deficit. These findings have relevance for the current debate on the association between hyperactivity and conduct disorder, and from an applied perspective they serve to stress the importance of situational contributors to the problem behaviors of hyperactive children.

Development of (1→3,1→4)-β-d-Glucan Endohydrolase Isoenzymes in Isolated Scutella and Aleurone Layers of Barley (Hordeum vulgare)

Abstract: An immunological assay has been used to investigate the synthesis of (1→3,1→4)-β-glucanase (EC 3.2.1.73) isoenzymes from isolated barley aleurone layers and scutella. Enzyme release from both tissues is enhanced by 1 micromolar gibberellic acid and 10 millimolar Ca2+, although increases induced by gibberellic acid are observed only in the presence of Ca2+. Isoenzyme I is synthesized predominantly in the scutellum, while isoenzyme II is synthesized exclusively in the aleurone. A third, putative isoenzyme III has been detected in significant proportions in scutellar secretions and may also be secreted from aleurone layers. Both gibberellic acid and Ca2+ appear to preferentially enhance isoenzyme II secretion from the aleurone and isoenzyme III secretion from scutella. The patterns of isoenzyme secretion are suggestive of tissue-specific differences in expression of the genes which code for (1→3,1→4)-β-glucanase isoenzymes. Qualitatively similar results were obtained with barley cultivars harvested in Australia and North America.

A factor of 2 reduction in theoretical F2 peak electron density due to enhanced vibrational excitation of N2 in summer at solar maximum

Abstract: The degree to which the O(+) + N2 reaction rate is increased as a result of enhanced vibrational excitation of the N2 molecule in the thermosphere was investigated. It is found that the reaction rate may be sufficiently elevated in summer at solar maximum to decrease the peak O(+) density by a factor of 2, but there is only a small reduction in the winter peak density. Therefore the vibrational excitation of N2 acts to increase the magnitude of the seasonal anomaly. This work emphasizes the need for more laboratory work to clear up uncertainties in some of the key parameters.

Correction of finite element estimates for Stum-Liouville eigenvalues

Abstract: It is shown that a simple asymptotic correction technique of Paine, de Hoog and Anderssen reduces the error in the estimate of thekth eigenvalue of a regular Sturm-Liouville problem obtained by the finite element method, with linear hat functions and mesh lengthh, fromO(k 4 h 2) toO(k h 2). The result still holds when the matrix elements are evaluated by Simpson's rule, but if the trapezoidal rule is used the error isO(k 2 h 2). Numerical results demonstrate the usefulness of the correction even for low values ofk.

The typification and status of Phymatolithon (Corallinaceae, Rhodophyta)

Abstract: The taxonomy and nomenclature of Phymatolithon Foslie, 1898 (Corallinaceae, Rhodophyta) have been reassessed on the basis of studies of the designated generitype and other critical specimens. Phymatolithon was based on P. polymorphum (L.) Foslie whose basionym, Millepora polymorpha Linnaeus, is one of several superfluous substitute names for Millepora calcarea Pallas. A neotype for M. calcarea is designated and described and the concept of Phymatolithon is reviewed and amended in the light of information from the neotype. The generic name Phymatolithon is proposed for conservation against Apora Gunnerus 1768 and Nullipora Lamarck 1801, both of which are also based on Millepora polymorpha and hence on M. calcarea. The name Phymatolithon polymorphum has been misapplied for many years to a quite different species of Phymatolithon, the correct name for which is P. purpureum (P. & H. Crouan) comb. nov. (Basionym: Lithothamnion purpureum P. & H. Crouan). The taxonomic status of Phymatolithon is discussed briefl...

Mammalian X chromosome inactivation: Testing the hypothesis of transcriptional control

Abstract: Mammalian X chromosome inactivation is generally considered to be a good example of stable transcriptional repression; however, there has been no satisfactory evidence for transcriptional control. We have made a test of the hypothesis of transcriptional control by Northern blot analysis of RNA from a woman heterozygous for a mutant Hpt allele which shows no detectable transcription of wild-type mRNA. Cells from this Hpt+ Hpt- woman were separated into HPRT+ and HPRT- subpopulations by selection in HAT or thioguanine. The HPRT+ population (in which the Hpt+ is on the active X) transcribed normal Hpt mRNA, while the HPRT- population (in which the Hpt+ allele is on the inactive X) did not. These results provide strong support for the hypothesis of transcriptional control.