Showing papers by "University of Sydney published in 1968"
TL;DR: It is suggested that the best classification is that which results in the briefest recording of all the attribute information, and the measurements of each thing are regarded as being a message about that thing.
Abstract: 1. The class to which each thing belongs. 2. The average properties of each class. 3. The deviations of each thing from the average properties of its parent class. If the things are found to be concentrated in a small area of the region of each class in the measurement space then the deviations will be small, and with reference to the average class properties most of the information about a thing is given by naming the class to which it belongs. In this case the information may be recorded much more briefly than if a classification had not been used. We suggest that the best classification is that which results in the briefest recording of all the attribute information. In this context, we will regard the measurements of each thing as being a message about that thing. Shannon (1948) showed that where messages may be regarded as each nominating the occurrence of a particular event among a universe of possible events, the information needed to record a series of such messages is minimised if the messages are encoded so that the length of each message is proportional to minus the logarithm of the relative frequency of occurrence of the event which it nominates. The information required is greatest when all frequencies are equal. The messages here nominate the positions in measurement space of the 5 1 points representing the attributes of the things. If the expected density of points in the measurement space is everywhere uniform, the positions of the points cannot be encoded more briefly than by a simple list of the measured values. However, if the expected density is markedly non-uniform, application
1,055 citations
TL;DR: The concept of corresponding retinal points was examined in terms of the binocular receptive fields of neurons in Area 17 of the cerebral cortex of the cat and the attempt has been made to establish the parameters of the receptive field disparities that occur within 5° of the visual axis.
Abstract: The concept of corresponding retinal points was examined in terms of the binocular receptive fields of neurons in Area 17 of the cerebral cortex of the cat. Only a proportion of the binocular receptive field pairs can be accurately superimposed at the one time in a given plane. The fields which are not corresponding are said to show receptive field disparity. The attempt has been made to establish, on a quantitative basis, the parameters of the receptive field disparities that occur within 5° of the visual axis. A new method was used for defining the zero (vertical) meridian. Very effective paralysis of the extraocular muscles was achieved and the very small residual eye movements that occurred were regularly monitored so that corrections could be applied to the plotted positions of the receptive field pairs. The distribution of the receptive field disparities about the position of maximal correspondence has a range of about ±1.2° (S.D. 0.6°) in both the horizontal and vertical directions for fields in the vicinity of the visual axis. Panum's fusional area may represent the extent to which receptive fields in the one eye, all with the same visual direction, are linked to fellow members of a pair in the other eye over a range of receptive field disparities. A naso-temporal overlap of receptive fields occurs which is probably little if any more than can be accounted for on the basis of the disparity of receptive fields lying along the zero (vertical) meridian. When the extraocular muscles are paralyzed the eyes diverge and the binocular receptive field pairs are separated on the tangent screen. The distribution of the horizontal and vertical separations of the receptive field pairs have been examined.
401 citations
TL;DR: Optimal stimulus speeds varied widely from unit to unit with a mean at 4°/sec: simple bimodal units and complex units tended to have higher optimal stimulus speeds and responded over a wider range of speeds than did simple unimmodal units.
Abstract: A quantitative study has been made of the responses to moving slit stimuli by single units in the cat striate cortex whose receptive fields lay within 5° of the visual axis. Special attention was given to finding the optimal stimulus parameters including slit width, length, orientation and speed. The analysis was largely based on averaged response vs. time histograms. Using the classification of simple and complex responses types, the units were further subdivided on the basis of the number of modes in the response and on the presence or absence of directional selectivity. Simple unimodal units with directional selectivity (SUDS) had the most specific stimulus requirements and nearly always had zero background activity. Complex units usually had a high level of background activity. SUDS units also showed a preference for horizontally- and vertically ****-orientated stimuli. Whenever the response survived reversal of contrast the directional selectivity remained independent of the change. Optimal stimulus speeds varied widely from unit to unit with a mean at 4°/sec: simple bimodal units and complex units tended to have higher optimal stimulus speeds and responded over a wider range of speeds than did simple unimodal units. While SUDS units with very small receptive fields tended to prefer slowly moving stimuli, in general there was no correlation between receptive field size and optimal stimulus speed.
348 citations
TL;DR: Averaged responses of binocularly-activated single units of the striate cortex of paralysed cats were studied using a single, moving visual stimulus and prisms of variable power to control the visual direction of each eye.
Abstract: Averaged responses of binocularly-activated single units of the striate cortex of paralysed cats were studied using a single, moving visual stimulus and prisms of variable power to control the visual direction of each eye. Binocular facilitation, summation or occlusion of the monocular response occurred, depending on the type of unit and on the prism setting. Binocular stimulating conditions were optimal for a given unit when the prism setting superimposed, or very nearly superimposed, the receptive field pair on the same plane as the moving stimulus. Under these optimal conditions, most units showed summation or facilitation of the monocular responses, with a minority showing occlusion. When the prism setting was changed from the optimal value, binocular occlusion could be demonstrated in all units. Curves plotting binocular response against prism setting provided information on the specificity, temporal properties and symmetry of the binocular response. The binocular response of simple units showed great specificity with a sharply defined peak on the response curve at a particular prism setting. There was variation from one simple unit to another in the exact prism setting required to give the optimal response. A proportion of complex units, despite large receptive field size, showed binocular specificity with a very narrow range of facilitation, of the same order as that shown by simple units. Other complex units showed binocular facilitation over a wide range of prism settings.
340 citations
TL;DR: Pulse wave velocities calculated from values of Edyn and relative wall thickness by the Moens-Korteweg equation agreed with accepted values and a Fourier analysis of pressure and diameter waves was shown to be unsatisfactory for determining the frequency dependence of viscoelastic constants.
Abstract: Dynamic elastic moduli (Edyn) and viscous moduli (ηω) of the arterial wall were obtained at a number of sites of the systemic vascular tree of living dogs anesthetized with pentobarbital. Constants were calculated using the first harmonics of pressure and diameter obtained from a Fourier analysis of simultaneously recorded pulse waves. The means and standard errors of Edyn, in dynes cm-2 x 106, obtained at mean blood pressures ranging from 87 to 130 mm Hg and pulse frequencies from 1.1 to 2.8 cps were: 3.0±0.33 (9 midthoracic aortas), 9.8±1.2 (7 midabdominal aortas), 11.0 (4 iliac arteries), and 12.3±1.2 (11 femoral arteries). The viscous modulus was approximately 9% of Edyn in the midthoracic aorta and approximately 12% of Edyn in the abdominal and femoral arteries. Pulse wave velocities calculated from values of Edyn and relative wall thickness by the Moens-Korteweg equation agreed with accepted values. A Fourier analysis of pressure and diameter waves was shown to be unsatisfactory for determining the ...
214 citations
TL;DR: The in vitro fertilization of mouse eggs in a simple chemically defined medium is described, and the subsequent development of the fertilized eggs to 17 day old foetuses.
Abstract: THE only mammal in which in vitro fertilization has been established conclusively is the rabbit1,2. More recently, the fertilization of hamster eggs in vitro has been reported3,4, but attempts to procure development of the fertilized eggs beyond the two-cell stage have failed5. So far, in vitro fertilization of mouse eggs has not been reported6, although mouse eggs have been fertilized and cultured to the blastocyst stage within explanted Fallopian tubes maintained in organ culture7. The blastocysts developed to 17 day old foetuses when transferred to suitably prepared recipient foster mothers8. I describe the in vitro fertilization of mouse eggs in a simple chemically defined medium9, and the subsequent development of the fertilized eggs to 17 day old foetuses.
199 citations
TL;DR: In this paper, it was shown that the pulses from pulsating radio sources seem to be made up of two sub-pulses, slow, class 1, and fast, class 2.
Abstract: The pulses from pulsating radio sources seem to be made up of two subpulses, slow, class 1, and fast, class 2.
186 citations
TL;DR: Between 0 and 266 days of age the weight of the pectoral and gastrocnemius muscles of chickens increased 300–600- and 40–90-fold respectively depending on the breed and sex, which suggests that for individual fibres the cross-sectional area increased in proportion to the number of nuclei.
Abstract: Between 0 and 266 days of age the weight of the pectoral and gastrocnemius muscles of chickens increased 300–600- and 40–90-fold respectively depending on the breed and sex. In both muscles the mean cross-sectional area of the fibres and the total number of nuclei (estimated from DNA determination) maintained a constant ratio during growth. This suggests that for individual fibres the cross-sectional area increased in proportion to the number of nuclei. This phenomenon is discussed in relation to current knowledge concerning the mode of growth and multinucleation of skeletal muscle fibres.
In the pectoral muscle, between 0 and 266 days, the cross-sectional area of the fibres increased in proportion to the two-thirds power of the muscle weight, which suggests that the length and diameter of the fibres maintained a constant ratio. The same relationship existed for the gastrocnemius for two months, after which the fibre cross-sectional area increased in proportion to the muscle weight, which suggests that the fibre length was then constant.
183 citations
TL;DR: Interest in the biology of selenium was focused on its properties as a naturally-occurring poison in plants grazed by stock in certain problem areas, notably in the western states of North America, and those aspects will not be considered further in this review.
Abstract: Extract Until recently, interest in the biology of selenium was focused on its properties as a naturally-occurring poison in plants grazed by stock in certain problem areas, notably in the western states of North America. The geological distribution of soils bearing seleniferous vegetation, the toxicities of various forms of selenium, including those of its inorganic salts, and the treatment and prevention of selenium poisoning have been dealt with in detail by Rosenfeld and Beath (1964), and those aspects will not be considered further in this review.
169 citations
TL;DR: In this paper, the authors derived a simple theory of free shelf waves, which, however, is more general than previous theories in that shorter as well as longer waves are taken into account.
Abstract: Taking the case of a continental shelf of exponential slope, and assuming zero horizontal divergence, the authors derive a simple theory of free shelf waves, which, however, is more general than previous theories in that shorter as well as longer waves (in comparison with previous work) are taken into account. The properties of the waves are discussed, and the dispersion curves for each mode are obtained. Although the phase velocities of shelf waves are always in the same sense as those of Kelvin waves, there is a negative group velocity for a range of wavelengths, indicating that energy can propagate in the opposite sense. A similar approach is used to derive a theory for free waves propagating on a shelf between two regions of constant depth. The limiting case of a shelf of zero width is also considered, and is compared with a limiting case of the ‘double-Kelvin’ waves discovered by Longuet-Higgins (1967).
161 citations
TL;DR: The pulsar PSR 1154-62 may be associated with a recently discovered radio supernova remnant as mentioned in this paper, which is known as PSR-PSR 1155-62.
Abstract: The pulsar PSR 1154-62 may be associated with a recently discovered radio supernova remnant
TL;DR: An experimental evaluation of Robertson's (1960) theory of limits in artificial selection was attempted, and agreement with these models was poor, as much of the response appeared to be due to a few genes (or gene combinations) with large effects on bristle number.
Abstract: 1. An experimental evaluation of Robertson's (1960) theory of limits in artificial selection was attempted. A number of lines from the Canberra base population were selected for abdominal bristle number over 50 generations with population sizes of 10, 20, and 40 pairs of parents and selection intensities of 10, 20 and 40% as well as unselected controls.2. In general, the total response obtained increased with an increase in Nī (product of population size and standardized selection differential).3. Thus, total response increased with increase in the number of individuals scored, or, for a fixed number of parents, increase in selection intensity increased both rates of response per generation and total response.4. But for the same total number scored, the response increased as selection intensity decreased. However, the proportion selected had only a small effect as compared with that of the total number scored.5. Sublines in which the population size was reduced after 16 generations of selection but with the selection intensity kept constant, immediately fell behind their parent lines and gave much less response.6. Agreement between replicate lines was generally poor, particularly for the 10- and 20-pair lines.7. Patterns of response in individual lines were frequently irregular and ‘waves of response’ were not uncommon.8. The results are discussed in terms of several theoretical models of selection limits. In general, agreement with these models was poor, as much of the response appeared to be due to a few genes (or gene combinations) with large effects on bristle number.
TL;DR: Hyperthermia induced in pregnant rats by exposures for 40 to 60 minutes in an incubator that raised deep body temperatures produced increased fetal resorptions, retardation of growth, and a number of development defects.
Abstract: Hyperthermia induced in pregnant rats by exposures for 40 to 60 minutes in an incubator that raised deep body temperatures from 381 ± 051 to 427 ± 062°C produced increased fetal resorptions, retardation of growth, and a number of development defects Grossly apparent fetal malformations included microphthalmia following hyperthermia on day 9 of pregnancy, anencephaly on day 10, and defects of tails, limbs, toes, palate, and body on days 12 to 14
TL;DR: In this article, a comparison is made between two current theories of pseudoplastic behavior (1, 2) which are based on a reaction-rate chemical equilibrium treatment, and a satisfactory description is found for the behavior of rapidly coagulating kaolinite sols with both positively and negatively charged surfaces.
TL;DR: The fluidity of blood and of the packed blood cells can be explained only by the very low internal viscosity of the red cell.
Abstract: BLOOD is known to be viscous and thixotropic1,2 and its viscosity decreases as the flow velocity, or velocity gradient, increases. While at near zero flow velocities, human blood may exhibit viscosities from 100 to 10,000 times that of water; at high flow velocities, it is only two to ten times that of water3,4. Perhaps the most remarkable aspect of blood is the fact that it remains fluid even at haematocrits of 95–100 per cent. If the red cells were rigid particles, the consistency of blood at high haematocrits would be that of a brick. It therefore seemed5 both obvious and simple that the fluidity of blood and of the packed blood cells can be explained only by the very low internal viscosity of the red cell.
TL;DR: In this article, Groenvlei pollen diagrams are considered to cover a period of ca. 8,000 years, covering the earliest period recorded, forest was much restricted, a dry steppe-like heath occupied most of the area and the 400 mm isohyet lay some 100 km east of its present position.
TL;DR: The summing properties of ganglion cells in the cat's retina have been examined, using as stimuli two stationary, flashing spots of light both positioned within the center regions of the cells' receptive fields and found to be non-linear in both cases.
TL;DR: Electrophysiological studies support the hypothesis that all or most of the Optic Nerve fibres supplying Lateral Geniculate Nucleus (LGN) bifurcate to supply Anterior Colliculus (AC) and three similar groups of fibres are activated in ON by stimulating either in AC or in LGN.
TL;DR: Attempts to examine sensory relationships in the recognition of ewes by their lambs established that recognition did exist but that the senses involved could not be isolated in the T maze.
TL;DR: In this article, the Muller-Lyer illusion was found to be a confounding of the ecological and developmental variables within cultures and the significant influence of each variable on susceptibility to the Muller Lyer illusion when eliminated.
Abstract: Two separate traditions of research into the Muller-Lyer illusion have existed for at least 70 years: the ecological and the developmental. To assess the ecological hypothesis, a sufficient range in visual ecology typically has been sought in cross-cultural comparisons; however, many of these comparisons have been inconclusive, especially when other ethnic variables have been held constant. These insignificant findings are considered to result from a confounding of the ecological and developmental variables. Appropriate sampling from Temne and Eskimo populations (enabling, in turn, one variable to be matched while the other is varied) demonstrates this confounding within cultures and, when eliminated, the significant influence of each variable on susceptibility to the Muller-Lyer illusion. Further work, however, is needed to discover other factors which will account for variance in susceptibility between cultures.
TL;DR: In this paper, a theory of saturated homomorphs and formations for finite-dimensional soluble Lie algebras was developed, a theory analogous to the theories developed for finite soluble groups by Gaschtitz, Lubeseder, Schunck, Barnes and Kegel.
Abstract: In this paper, we develop for finite-dimensional soluble Lie algebras, a theory of saturated homomorphs and formations and of functors analogous to the theories developed for finite soluble groups by Gaschtitz, Lubeseder, Schunck, Barnes and Kegel. Much of this requires little more than verbal alteration of the group theory form, replacing the words \"group\" and \"normal subgroup\" by \"algebra\" and \"ideal\" wherever they occur. Even where this translation is completely routine, for the sake of completeness, we give at least brief indications of the proofs. All algebras in the following are finite-dimensional soluble Lie algebras over some fixed ground field F. Except where specifically stated, no assumptions are made about the field F. We write A c L, A
TL;DR: In this article, the authors deal with factors that contribute to the emergence of egalitarian ideologies, tracing the social processes they entail and analysing their consequences for social life, including the consequences of these processes.
Abstract: This essay deals with factors that contribute to the emergence of egalitarian ideologies, tracing the social processes they entail and analysing their consequences for social life.
TL;DR: It has been demonstrated that the male of Dacus tryoni (Frogg) produces a sex pheromone which is released at the same time as stridulation, and this discovery is particularly interesting, for it not only provides a further example of a species in which the male produces asex phersomone, but also is the only known case in which a sexphersone is stored in a special reservoir before release.
Abstract: Dacus tryoni (Frogg.) mates at dusk. During courtship, males stridulate by drawing their wings across a pair of combs formed from large bristles on the third abdominal tergite. This produces a high pitched buzz, audible to the human ear, which is considered to be a mating call1. It has now been demonstrated that the male also produces a sex pheromone which is released at the same time as stridulation. This discovery is particularly interesting, for it not only provides a further example of a species in which the male produces a sex pheromone, but also is the only known case in which a sex pheromone is stored in a special reservoir before release. This communication briefly describes some of the experimental work which has been carried out with the pheromone.
TL;DR: In this paper, a simple formula is derived expressing the compression f in terms of the pressure and incompressibility at internal points of the Earth, which is free from certain limitations in an earlier formula used by Birch, and is not restricted to the mantle.
Abstract: Using Birch's development of finite-strain theory for the Earth, a simple formula is derived expressing the compression f in terms of the pressure and incompressibility at internal points of the Earth. The formula is free from certain limitations in an earlier formula used by Birch, and is not restricted to the mantle. The formula is applied to determining values of f for six representative Earth models, and preferred estimates of f are set down for the Earth. The results are compared with Birch's earlier estimates of f for the mantle. The computed values of f do not significantly exceed 0·13 in the mantle or 0·20 in the core. Across the mantle-core boundary, f is likely to be nearly continuous; any sudden change is likely to be less than about 5 per cent. The results are subject to the reliability of Birch's form of equation of state for the internal regions of the Earth and, as in Birch's method, neglect possible effects of phase changes.
TL;DR: In this paper, a quadratic representation of the incompressibility k in terms of the pressure p for the materials of the Earth inside the pressure range 0.4 < p < 3.2 × 1012 dyn/cm2 was derived.
Abstract: Summary
A quadratic representation of the incompressibility k in terms of the pressure p for the materials of the Earth inside the pressure range 0.4 < p < 3.2 × 1012 dyn/cm2 was empirically derived some years ago on the basis of seismic and other evidence. The numerical coefficients in the representation have been revised in the present paper, taking account of recent observational evidence. The revised quadratic law applies to the whole Earth below 1000 km. The new evidence includes the recently revised estimate of the Earth's moment of inertia, revised seismic evidence on the lower core, and data from free Earth oscillations. The quadratic model is compared with linear models derived for the lower mantle and core separately. Attention is drawn to errors made when any of these models is applied at pressures less than 0.4 × 1012 dyn/cm2. It is pointed out that unqualified application of Birch's finite-strain formulae leads to some results for the Earth's deeper interior that are somewhat discordant with the empirical evidence here used.
TL;DR: Sensory stimuli utilized by both rams and oestrous ewes in partner-seeking activity were examined using deaf, anosmic and blindfolded animals mated with tethered or free partners, and Blindfolding may have influenced ewe partner- seeking behaviour directly by impairment of visual contact or indirectly by restriction of random movement.
TL;DR: Thick sections of the peripheral coronal areas of the mature dental pulp were examined under light microscopy and thin sections prepared for electron microscopy after fixation in Palade's osmium tetroxide to identify three types of nerve endings.
TL;DR: Air pollution may be a contributing factor in the genesis and maintenance of the prevalent nontuberculous lung disease in New Guinea highlanders.
Abstract: The degree of air pollution in native huts in the New Guinea Highlands has been assessed The “average” concentrations of smoke density, aldehydes, and carbon monoxide measured in the Eastern Highlands, at an altitude of 7,200 feet, were 666 μg/m3 1.08 ppm and 21.3 ppm, respectively, but these figures do not include peak values of 4,862 μg/m3, 3.8 ppm and 150 ppm which were obtained on one occasion soon after startup of the fire. Comparable “average” values in the Western Highlands, at 4,000 to 5,200 feet were 359 μg/cum, 0.67 ppm and 11.3 ppm, respectively. Smoke density was highly correlated with aldehyde concentrations in both areas, r = +0.93 and + 0.88, and with carbon monoxide, r = + 0.87 and +0.72. Air pollution may be a contributing factor in the genesis and maintenance of the prevalent nontuberculous lung disease in New Guinea highlanders.