Showing papers by "University of Western Australia published in 1972"

Anion adsorption by goethite and gibbsite

Abstract: Summary The relationship between adsorption and pH, termed the adsorption envelope, varies with the pKa, of the conjugate acid of the anion, for several adsorbents in presence of an excess of specifically adsorbed anions. At pH values where the acid is fully dissociated, specific adsorption occurs only to the extent of the positive charge of the surface and little specific adsorption is found at pH values more alkaline than the zero point of charge (zpc). With incompletely dissociated acids, anion adsorption can also take place at pH values more alkaline than the zpc providing the pH is somewhere near a pKa value of the acid, where the energy required to abstract a proton from the acid is at a minimum. The proton is required for the removal of a surface OH which provides a site for the anion. Specific anion adsorption (i) from a fully dissociated acid can reduce the positive charge of the surface to zero and (ii) from a weak acid can make even a negative surface more negative. Thus specific adsorption shifts the zpc to more acid values. The relationship between anion adsorption and OH release is not necessarily simple. The ideas proposed for anion adsorption have implications for cation adsorption and incorporation in an oxide surface.

Salt responses of enzymes from species differing in salt tolerance

Abstract: Enzymes which are affected by the addition of inorganic salts during in vitro assay were extracted from salt-sensitive Phaseolus vulgaris, salt-tolerant Atriplex spongiosa, and Salicornia australis and tested for sensitivity to NaCl. In each case malate dehydrogenase, aspartate transaminase, glucose 6-phosphate dehydrogenase, and isocitrate dehydrogenase showed NaCl responses similar to those found for commercially available crystalline enzymes from other organisms. Enzymes extracted from plants grown in saline cultures showed no important changes in specific activity or salt sensitivity. Interaction of pH optima and NaCl concentrations suggests that enzymes may differ in the way they respond to salt treatment.

Molecular weight and shape of humic acid from sedimentation and diffusion measurements on fractionated extracts

Abstract: Summary Whole humic acid extracts are usually too polydisperse for reliable molecular-weight measurement to be made in the ultracentrifuge by the sedimentation velocity technique. Consequently, the humic acid used in this study was fractionated with respect to molecular weight into fractions of low polydispersity by extensive use of gel-permeation chromatography and other fractionation techniques. The sedimentation and diffusion coefficients of the fractions were determined and molecular-weight values calculated. These values ranged approximately from 2 × 103 to 1.5 × 106, the higher figure not necessarily representing the upper limit for these substances. On the basis of the frictional parameters calculated from the experimental data, it is proposed that the molecule adopts the solution conformation of a randomly coiled polymer in which branching may be significant, particularly at higher molecular weights.

Drinking Patterns and Behavior of Australian Desert Birds in Relation to Their Ecology and Abundance

Abstract: Aridity is the dominant climatic feature of the Australian continent, and desert conditions exist over almost half of the total land area. The extreme physical characteristics of such an environment, high air temperatures, intense solar radiation, and scarcity of surface water, combine to pose a severe challenge to animal life. Birds are primarily diurnal and, unlike most small desert mammals, generally do not utilize the shelter afforded by underground burrows. In hot weather they must therefore reconcile the antagonistic demands of evaporative cooling and maintenance of water balance. Investigations of how Australian birds live successfully in desert areas have barely started. The success of many species must be intimately linked with their capacities for locating and utilizing surface water. To obtain information on this, we undertook field studies of the drinking habits of birds in the arid interior of Australia. Our findings are summarized in this report.

The peripheral auditory apparatus

Abstract: This review of the peripheral auditory apparatus represents an attempt to analyse critically recent developments in the field. The coverage is not exhaustive, the emphasis is on functional aspects and no attempt is made to review the anatomy of the ear. Particular emphasis is placed on three broad sections: the physiology of the middle ear, basilar membrane mechanics and the electrophysiology of the cochlea. It is in these areas that recent technical advances have led to experiments which throw doubt on traditionally held concepts. Such an advance is the application of the Mossbauer technique to the problem of middle- and inner-ear mechanics. Because of its novelty, this technique is discussed in detail. Other new methods such as laser holography are just starting to be used, as are the ion selective microelectrodes for measuring dynamic changes in endolymph concentration. After many years of slow progress there is a sudden spark of enthusiasm for peripheral auditory research, and the coming decade promises to be most exciting indeed.

Salt responses of carboxylation enzymes from species differing in salt tolerance.

Abstract: This paper reports effects of salts on in vitro activity of phosphoenolpyruvate carboxylase and ribulose-1,5-diphosphate carboxylase, isolated from species differing in salt tolerance.Inhibition of phosphoenolpyruvate carboxylase by the inorganic salts KCl, NaCl, and Na(4)SO(4) depended on the source of the enzyme. Phosphoenolpyruvate carboxylase isolated from leaves of C(4) plants was extremely sensitive to inorganic salts, whereas the enzyme extracted from roots of C(4) plants or from both shoots and roots of C(3) plants was much less sensitive. Ribulose-1,5-diphosphate carboxylase was less salt-sensitive than the phosphoenolpyruvate carboxylases. Differences in salt sensitivity of carboxylases were observed over a wide pH range. The results suggest substantial physical-chemical differences between phosphoenolpyruvate carboxylases functioning in photosynthesis and in CO(2) dark fixation.Among C(4) species, phosphoenolpyruvate carboxylase from halophytic species was more salt-sensitive than that from a salt-sensitive species. This anomaly, between in vitro response of enzymes and growth response of the plants, is briefly discussed.

A Comparative Analysis of Middle-Ear Function in Non-Mammalian Vertebrates

Abstract: Mossbauer techniques were used to measure response patterns of the tympanic membrane and stapes footplate in five non-mammalian vertebrates. The response amplitude in microns was calculated for both structures at 100 dB S.P.L. for tones between 62 Hz and 10.0 kHz. The response amplitude was constant for low frequencies while above 2 kHz it tended to rapidly roll-off reaching a rate of between 25–30 dB/octave. The results suggest that the limits of high frequency hearing in these species are related to the transmission characteristic of the middle-ear.

Influence of Thyroid Hormones on Enzyme Activities of Myelinating Rat Central‐Nervous Tissues

Abstract: The effects of triiodothyronine administration and of hypothyroidism on the rapidly developing enzymes UDP galactose: sphingosine galactosyltransferase and 2′:3′-nucleotide 3′-phosphohydrolase associated with central nervous system myelination were investigated. The activity of these enzymes in the spinal cords of young rats injected daily with triiodothyronine up to sacrifice on day 5 was significantly increased over control animals. In normal animals, circulating plasma thyroxine increased gradually from the second postnatal day to a maximum value at days 15–17. Rats, born of mothers treated with n-propylthiouracil from the thirteenth day of pregnancy, did not exhibit the increase in plasma thyroxine. Determination of the specific activity of these enzymes in central nervous tissue of such hypothyroid rats at day 12 showed a significant reduction compared with normal animals. Intraperitoneal injection of the hypothyroid rats with triiodothyronine on day 8 resulted in a partial restoration of the activity of the enzymes in brain and of 2′:3′-nucleotide 3′-phosphohydrolase in spinal cord when assayed on day 12. Restoration of UDPgalactose: sphingosine galactosyltransferase activity did not occur in the spinal cord of such animals. However, when hypothyroid rats were injected with triiodothyronine on days 1, 4, and 7, the psychosine-synthesising activity in their spinal cords on day 8 was restored to that of normal animals. This suggests that there is a critical period during the first 8 days of postnatal life when thyroid hormone levels must be adequate in order that spinal cord activity of this enzyme develops normally. It is concluded that the flux in circulating thyroid hormone is a factor in the normal development of these enzymes.

Use op crenulate shaped bays to stabilize coasts

Abstract: Crenulate shaped bays are the rule rather than the exception on coastal margins of oceans, inland seas or lakes where sedimentary beaches exist between headlands. They have a particular orientation to the swell or resultant wave energy vector, such that the straight tangent section is downcoast and the curved portion upcoast. The latter is a logarithmic spiral at all stages of development of the bay. When fully stable, that is no littoral drift taking place, the constant of the log-spiral equation has a specific relationship to the approach angle of the waves to the headland alignment. In this condition it is shown that diffraction and refraction are involved when waves sculpture the curved beach in the lee of the upcoast headland. A further ratio to identify stable bays appears to be the ratio of indentation length to clearance between headlands. The application of crenulate shaped bays to stabilization of a reclaimed shoreline suffering strong littoral drift on Singapore Island is described.

Autoxidation of humic acid under alkaline conditions

Abstract: Summary Humic acid was treated for 30 days with normal NaOH under either N2 or O2. In both cases some acid-soluble material resulted which was enriched with free and peptide α-amino N and also with total N. The molecular weight of the humic acid fell under alkaline conditions, while there was a decrease in total UV and visible absorption due to the production of less-coloured material which was largely present in the acid soluble fraction. Under O2 these effects were considerably enhanced and simultaneously a significant arnount of O2 was consumed. Other changes produced by O2 were an increase in the cation-exchange capacity, particularly of the acid-soluble fraction, the production of carbonate, an increase in the Oxidation state of the acid, and a lessening of the resemblance of the acid to lignin as shown by the infra-red and UV spectra. In the main the changes produced by O2 are similar to those observed for humic acids of decreasing molecular weight that can be extracted from a soil, either by differential extraction or by extraction followed by fractionation into different molecular-weight classes.

Calibration of gel permeation chromatography materials for use with humic acid

Abstract: Summary Three common gel-chromatography materials have been calibrated for humic acid, using fractionated samples the molecular weights of which were calculated by combining sedimentation coefficients determined on the ultracentrifuge with diffusion coefficients. The gel materials were found to have the following fractionation ranges for humic acid when tris buffer was used: Sephadex G-100, 2500 to 100000; Bio Gel P-150, below 1000 to 40000; Sepharose 6B, 1500 to 2500000. Borax buffer appeared to extend the range of Sephadex G-100 to lower molecular weights. A brief comparison is made of the retention behaviours of humic acid, proteins, and dextrans on the gel materials.

The Oxidation of Octahedral Iron in Biotite

Abstract: Oxidation of octahedral ferrous iron in biotite by saturated bromine water results in a loss of both octahedral and interlayer cations. The hydroxyl adjacent to vacant octahedral cation sites adopt an inclined orientation resulting in a more stable environment for interlayer cations. The only structural change accompanying these processes is a decrease in b-axis dimension which is linearly related to octahedral ferric iron content. These findings are in agreement with observations made on naturally weathered biotites.

Nitrogen, phosphorus and sulphur contents of humic acids fractionated with respect to molecular weight

Abstract: Summary Two humic acids, extracted from widely different soils, have been fractionated with respect to molecular weight by means of gel chromatography. The resulting fractions were assayed for total nitrogen, amino acid nitrogen, phosphorus and sulphur. Nitrogen and phosphorus contents were greatest in the high molecular weight fractions and decreased considerably with decreasing humic acid molecular weight. The change in nitrogen content was accounted for mainly by the loss of amino acid nitrogen. By contrast, sulphur contents remained constant throughout the molecular weight range. These changes may reflect part of the process whereby nutrient elements, combined organically within humic acid, are made available for plant growth.

Thermal Anomalies in the Eastern Indian Ocean

Abstract: STANDARD works on oceanography usually show water temperatures for February and August, on the normally valid assumption that these months represent the seasonal extremes. Various aspects of water circulation and climatic rhythm in the Western Australian region are quite anomalous1,2 and cannot be explained in terms of atmospheric or terrestrial factors alone. In the course of this investigation, it seemed advisable to determine the time of mean highest and lowest temperatures at the surface of the ocean. The US Naval Oceanographic Office's charts3 were used because they embodied the most numerous data.

Age effects in the acquisition and retention of active and passive avoidance learning by rats.

Abstract: Three groups of 8 male albino rats within each of the age ranges 24, 50, and 100 days were trained on an active avoidance task to a criterion of 10 successive avoidances. The number of trials to criterion was found to be a monotonic function of age. One group at each age was tested immediately thereafter for passive avoidance of the conditioning chamber, another group was tested for passive avoidance after 25 days, and the third was tested for retention of active avoidance after 25 days. Groups at 50, 75, and 125 days were used as controls for the active avoidance retention groups. All animals took significantly fewer trials to relearn the active avoidance after 25 days than did controls on the acquisition of the original learning task. On passive avoidance 24-day olds performed less efficiently than the older groups and failed to show any retention after 25 days.

Arrian's Literary Development

Abstract: There is relative agreement among modern scholars that the bulk of Arrian's literary activity came late in his life. What has become the standard theory was evolved by Eduard Schwartz, who maintained that it was only after the end of his public career that Arrian turned to writing. According to this hypothesis the Пєρίπλους of 131/ A.D. was a tentative preliminary monograph, which was followed in 136/7 by a work of similar genre, the .

The electrophysiology of the utricle.

Abstract: The Na+ concentration in utricular endolymph of guinea pigs was measured with Na+ specific electrodes and found to be 12.6±5.8 mEqu/l. The utricular potential was 1.8±4.4 mV. Permanent anoxia resulting in the death of the animal caused the potential to fall by 15 mV and the Na+ concentration to rise at a rate of 0.4 mEqu/l per minute. The utricular potential could be maintained during anoxia by bubbling the surrounding perilymph with air or oxygen. Maintenance of the Na+ concentration and the utricular potential did not depend on the integrity of the first turn of the cochlea. It was concluded that the utricle produced its own endolymph and potential and was effectively isolated from the cochlea. The access resistance of the utricle was measured to be 2±1.1 kohms.

A Calcium-Citro-Phosphate Technique for the Histochemical Localization of Myosin ATPase

Abstract: A simple and sensitive calcium precipitation method is described for the histochemical demonstration of myosin ATPase in striated muscle. In this technique inorganic pyrophosphate is incorporated in the fixative to protect the sites of myosin ATPase activity, thus minimizing enzymatic inactivation during fixation. The incubation medium used contains Ca++ (70 mM) as the capturing agent, ATP (4 mM) as substrate, citric acid (7.5 mM) and gelatin. During incubation, the enzyme catalyzes the hydrolysis of ATP to ADP and inorganic phosphate. The liberated phosphate is precipitated as “calcium-citro-phosphate”. The latter is then converted to black cobalt sulphide. The calcium-citro-phosphate is rapidly formed during incubation (within 10 min) and can not be washed off the tissue sections.

Middle-ear function in a monotreme: The echidna (Tachyglossus aculeatus)†

Abstract: The mechanics of the middle ear bones of echidna (Tachyglossus aculeatus) were studied using the Mossbauer technique. A small radioactive source was placed on the stapes and the alterations in the frequency of the emitted γ-ray, which occurred when the stapes vibrated during sound stimulation, were detected by a proportional counting system and absorber. In this way the velocity of stapes motion could be measured in response to different acoustic frequencies and intensities. The ossicular system of echidna consists of a large malleus with an anteromedially directed process, the processus gracilus; an incus which is ankylosed to the malleus, and a columelliform stapes. The tympanic bone supports the eardrum and appears firmly locked to the processus gracilus. The malleus and incus are tightly attached, at their lateralmost corner, to the periotic bone. This latter attachment causes the middle ear chain to be very stiff. The velocity of stapes motion at 100 dB SPL is very low (0.0014 mm/sec) at 100 Hz and rises to a peak at 6 kHz (0.1 mm/sec). Velocity decreases at approximately 12 dB/octave as frequency is increased beyond 6 kHz. Amplitude of stapes motion is relatively constant at about 0.002–0.004 μ for 100 dB SPL between 100 Hz and 6 kHz and drops off at 18 dB/octave at higher frequencies. Comparison of these results with those for some lizards and placental mammals reveals that the echinda middle ear bones are considerably less efficient in transmitting airborne vibrations than those of the other animals.

Surface Charge Characteristics of Hydroxyapatite and Fluorapatite

Abstract: THE crystal and solution chemistry of apatites has been studied intensively by medical, biological and earth scientists but studies of the electrochemistry of apatite surfaces have not been extensive. The few studies of the surface charge characteristics of hydroxyapatite [Ca10(OH)2(PO4)6] and fluorapatite [Ca10F2(PO4)6] show that H+ and OH− are potential determining ions, but estimates of the pH at the point of zero charge (PZC) have varied widely from 4.3 to 7.6 for hydroxyapatite1–5 and from 4 to >12 for fluorapatite6–8.

Continuous Topological Variation of Coordination in Crystals: Structural Relations and Possible Transformation Mechanisms

Abstract: An attempt is made to provide plausible model mechanisms for some high-pressure transformations. Topological distortions of three-dimensional anion nets are considered in simplified terms involving single layers and their stacking. Prototype structures with the same stoichiometry but different cation-coordination numbers are seen to be simply related to one another.

Temperature dependence of the proton nuclear magnetic resonance spectra of some diamagnetic N,N-dialkyldithiocarbamate complexes of transition metals

Abstract: Unusual structure and temperature dependent behavior of the proton nmr spectrum in a number of diamagnetic N,Ndialkyldithiocarbamate complexes of di- and trivalent transition metal ions, [M(CSLNRZ)~n ]=, 2, 3 may be accounted for by a total line-shape analysis in terms of an appropriate and general two-proton exchange model using a density matrix formalism. This has been done in detail for a limited range of basic, well-defined, simple, and representative members of the above series, using the diethyl-, di-n-propyl-, diisopropyl-, diisobutyl-, and dibenzyldithiocarbamates of nickel(I1) and cobalt(II1) Where possible a tentative physical interpretation of the model is given.