Impacts of grazing management options on pasture and animal productivity in a Heteropogon contortus (black speargrass) pasture in central Queensland. 2. Population dynamics of Heteropogon contortus and Stylosanthes scabra cv. Seca.

The dynamics of Heteropogon contortus and Stylosanthes scabra cv. Seca populations were studied in a subset of treatments in an extensive grazing study conducted in central Queensland between 1988 and 2001. These treatments were 4 stocking rates in native pasture and 2 of these stocking rates in legume oversown and supplement/spring burning treatments. For the 1999-2000 summer, population data for H. contortus in 5 of these native pasture and supplement/burning treatments were compared with those for an additional burnt treatment. Seasonal rainfall throughout this study was below the long-term mean and mean annual pasture utilisation ranged from 24 to 61%. Increasing stocking rate from 5 to 2 ha/steer in native pasture reduced H. contortus plant density. Increasing stocking rate reduced seedling recruitment as a result of its effect on soil seedbanks. Seedling recruitment was the major determinant of change in plant density, although some individual H. contortus plants did survive throughout the study. Burning in spring 1999, particularly at light stocking rate, promoted seedling recruitment above that in both unburnt native and legume oversown pasture and resulted in increased H. contortus plant density. In the legume oversown treatments, S. scabra cv. Seca density increased rapidly from 15 plants/m2 in 1988 to 140 plants/m2 in 2001 following a lag phase between 1988 and 1993. This increased S. scabra density was associated with an eventual decline in H. contortus plant density through reduced seedling recruitment. It was concluded that H. contortus population density is sustainable at stocking rates of 4 and 5 ha/steer (30% pasture utilisation) and that spring burning at light stocking rate can promote H. contortus populations. Increasing densities of S. scabra need to be managed to prevent its dominance.

Heat pipes-concepts, materials and applications

The heat pipe is an innovative engineering structure characterized by its capacity to transfer large quantities of heat through relatively small cross-sectional areas with very small temperature differences; it also possesses high thermal conductance and low thermal impedance. In recent times, heat pipes in various forms and designs have found a wide variety of applications. This paper briefly presents the basic concepts of heat pipes, recent innovations in design and their applications.

The use of heat-sums to predict harvest dates following potassium chlorate (KClO3) application in longan.

The ability to initiate and manipulate flowering with KClO3 allows flowering of longan, to be triggered outside of the normal flowering season (July-September) in Australia. Fruit maturity following normal flowering will occur approximately six-eight months (180-220 days) from flowering, depending on variety. Out of season flowering will result in differing times to maturity due to different temperature regimes during the maturity period. Knowing how long fruit will take to mature from different KClO3 application dates is potentially a valuable tool for growers to use as it would allow them to time their applications with market opportunities, e.g. Chinese New Year, periods of low volumes or periods of high prices. A simple heat-sum calculation was shown to reliably quantify fruit maturity periods, 2902 and 3432 growing degree days for Kohala and Biew Kiew respectively. Growers can use heat-sum as a predictive tool to allow for efficient planning of harvesting, packaging and freight requirements.

Technical highlights: Invasive plant and animal research 2009-10

Technical highlights 2009–10, with detailed progress reports on the latest invasive plant and animal research undertaken by Biosecurity Queensland, a service unit of the Department of Employment, Economic Development and Innovation.

Technical highlights: Invasive plant and animal research 2008-09

Technical highlights 2008–09, with detailed progress reports on the latest invasive plant and animal research undertaken by Biosecurity Queensland, a service unit of the Department of Employment, Economic Development and Innovation.

Technical highlights: Invasive plant and animal research 2007-08

Technical highlights 2007–08, with detailed progress reports on the latest invasive plant and animal research undertaken by Biosecurity Queensland, a service unit of the Department of Primary Industries and Fisheries.

Axial heat conduction effects in natural convection along a vertical cylinder

MANY TRANSPORprTo cesses occur in nature and in industrial applications in which the transfer of heat is governed by the process of natural convection. Natural convection arises in fluids when the temperature changes cause density variations leading to buoyancy forces. An excellent review of natural convection flows has been given by Ede [I]. Recently, Minkowycz and Sparrow [2, 31, Cebeci [4], and Aziz and Na [S] have studied the steady, laminar, incompressible, natural convection flow over a vertical cylinder using a local nonsimilarity method, a finite-difference scheme, and an improved perturbation method, respectively. However, they did not take into account the effect ofaxial heat conduction for small Prandtl number. It is known that the axial heat conductioneffect becomesimportant for low-Prandtl-number fluids such as a liquid metal.

Stimulation of liver tryptophan pyrrolase during heat exposure

Exposure of rats to heat (39 +/- 1 degree C) stimulated liver tryptophan pyrrolase 2-fold between 3 and 48 h. Plasma corticosterone increased 2-fold after 1 h of heat exposure and decreased to a low value of 50% by 16 h. The effect of heat exposure on the enzyme was obtained in adrenalectomized animals. Stimulation by cortisol and tryptophan of the enzyme was also obtained in heat exposure, and the effects seemed to be additive. The concentration of tryptophan in the liver remained unchanged, and that in the plasma decreased to about 50% at 8 h exposure to heat and reverted to normal by 46 h. Simultaneous administration of noradrenaline to heat-exposed rats had no effect, whereas that of thyroxine partly prevented the stimulation of the enzyme activity. Hypothyroid conditions obtained by thyroidectomy or treatment with propylthiouracil significantly stimulated the enzyme activity. Cycloheximide treatment of heat-exposed rats did not prevent the stimulation of the enzyme activity. The results indicate that the effect of heat exposure on liver tryptophan pyrrolase is obtained, due to the accompanying hypothyroid condition, by increasing the activity of the existing protein by a mechanism possibly different from those known at present.

Heat exposure and hypothyroid conditions decrease hydrogen peroxide generation in liver mitochondria

Exposure of rats to heat (39 +/- 1 degree C) decreased H2O2 generation in mitochondria of the liver, but not of the kidney or the heart. The effect was obtained with three substrates, succinate, glycerol 1-phosphate and choline, with a decrease to 50% in the first 2-3 days of exposure, and a further decrease on longer exposure. The dehydrogenase activity with only glycerol 1-phosphate decreased, which is indicative of the hypothyroid condition, whereas choline dehydrogenase activity remained unchanged and that of succinate dehydrogenase decreased on long exposure. The serum concentration of thyroxine decreased in heat-exposed rats. Thyroxine treatment of rats increased H2O2 generation. Hypothyroid conditions obtained by treatment with propylthiouracil or thyroidectomy caused a decrease in H2O2 generation and changes in dehydrogenase activities similar to those with heat exposure. Treatment of heat-exposed or thyroidectomized rats with thyroxine stimulated H2O2 generation by a mechanism apparently involving fresh protein synthesis. The results indicate that H2O2 generation in mitochondria of heat-exposed animals is determined by thyroid status.

Fluctuation Theory Of The Specific-Heat Of Normal Liquid-3He

The measured specific heat of normal liquid 3He shows a plateau for 0.15<1 K; below 0.15 K and above 1 K, it rises linearly with temperature. However, the slope on the high-temperature side is very much reduced compared with the free-Fermi-gas value. We explain these features through a microscopic, thermal spin- and density-fluctuation model. The plateau is due to spin fluctuations which have a low characteristic energy in 3He. Because of the low compressibility, the density fluctuations are highly suppressed; this leads to a reduced slope for CV(T) for high temperatures.

Heat-Capacity Measurements - Progress In Experimental-Techniques

The heat capacity of a substance is related to the structure and constitution of the material and its measurement is a standard technique of physical investigation. In this review, the classical methods are first analyzed briefly and their recent extensions are summarized. The merits and demerits of these methods are pointed out. The newer techniques such as the a.c. method, the relaxation method, the pulse methods, the laser flash calorimetry and other methods developed to extend the heat capacity measurements to newer classes of materials and to extreme conditions of sample geometry, pressure and temperature are comprehensively reviewed. Examples of recent work and details of the experimental systems are provided for each method. The introduction of automation in control systems for the monitoring of the experiments and for data processing is also discussed. Two hundred and eight references and 18 figures are used to illustrate the various techniques.

Vapour heat treatment of honey gold mango

Vapour heat treatment of honey gold mango for access to the Japanese market.

Heat acclimation for protection from exertional heat stress (Protocol)

This is the protocol for a review and there is no abstract. The objectives are as follows: To assess the effects of heat acclimation interventions aimed at protecting health and performance from exertional heat stress.