974 resultados para Linear potential


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Radish sprouts and broccoli sprouts have been implicated in having a potential chemoprotective effect against certain types of cancer. Each contains a glucosinolate that can be broken down to an isothiocyanate capable of inducing chemoprotective factors known as phase 2 enzymes. In the case of broccoli, the glucosinolate, glucoraphanin, is converted to an isothiocyanate, sulforaphane, while in radish a similar glucosinolate, glucoraphenin, is broken down to form the isothiocyanate, sulforaphene. When sprouts are consumed fresh (uncooked), however, the principal degradation product of broccoli is not the isothiocyanate sulforaphane, but a nitrile, a compound with little anti-cancer potential. By contrast, radish sprouts produce largely the anti-cancer isothiocyanate, sulforaphene. The reason for this difference is likely to be due to the presence in broccoli (and absence in radish) of the enzyme cofactor, epithiospecifier protein (ESP). In vitro induction of the phase 2 enzyme, quinone reductase (QR), was significantly greater for radish sprouts than broccoli sprouts when extracts were self-hydrolysed. By contrast, boiled radish sprout extracts (deactivating ESP) to which myrosinase was subsequently added, induced similar QR activity to broccoli sprouts. The implication is that radish sprouts have potentially greater chemoprotective action against carcinogens than broccoli sprouts when hydrolysed under conditions similar to that during human consumption.

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Many processes during embryonic development involve transport and reaction of molecules, or transport and proliferation of cells, within growing tissues. Mathematical models of such processes usually take the form of a reaction-diffusion partial differential equation (PDE) on a growing domain. Previous analyses of such models have mainly involved solving the PDEs numerically. Here, we present a framework for calculating the exact solution of a linear reaction-diffusion PDE on a growing domain. We derive an exact solution for a general class of one-dimensional linear reaction—diffusion process on 0

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Farmlets, each of 20 cows, were established to field test five milk production systems and provide a learning platform for farmers and researchers in a subtropical environment. The systems were developed through desktop modelling and industry consultation in response to the need for substantial increases in farm milk production following deregulation of the industry. Four of the systems were based on grazing and the continued use of existing farmland resource bases, whereas the fifth comprised a feedlot and associated forage base developed as a greenfield site. The field evaluation was conducted over 4 years under more adverse environmental conditions than anticipated with below average rainfall and restrictions on irrigation. For the grazed systems, mean annual milk yield per cow ranged from 6330 kg/year (1.9 cows/ha) for a herd based on rain-grown tropical pastures to 7617 kg/year (3.0 cows/ha) where animals were based on temperate and tropical irrigated forages. For the feedlot herd, production of 9460 kg/cow.year (4.3 cows/ha of forage base) was achieved. For all herds, the level of production achieved required annual inputs of concentrates of similar to 3 t DM/animal and purchased conserved fodder from 0.3 to 1.5 t DM/animal. This level of supplementary feeding made a major contribution to total farm nutrient inputs, contributing 50% or more of the nitrogen, phosphorus and potassium entering the farming system, and presents challenges to the management of manure and urine that results from the higher stocking rates enabled. Mean annual milk production for the five systems ranged from 88 to 105% of that predicted by the desktop modelling. This level of agreement for the grazed systems was achieved with minimal overall change in predicted feed inputs; however, the feedlot system required a substantial increase in inputs over those predicted. Reproductive performance for all systems was poorer than anticipated, particularly over the summer mating period. We conclude that the desktop model, developed as a rapid response to assist farmers modify their current farming systems, provided a reasonable prediction of inputs required and milk production. Further model development would need to consider more closely climate variability, the limitations summer temperatures place on reproductive success and the feed requirements of feedlot herds.

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BACKGROUND: Piperonyl butoxide (PB)-synergised natural pyrethrins (pyrethrin:PB ratio 1:4) were evaluated both as a grain protectant and a disinfestant against four Liposcelidid psocids: Liposcelis bostrychophila Badonnel, L. entomophila (Enderlein), L. decolor (Pearman) and L. paeta Pearman. These are key storage pests in Australia that are difficult to control with the registered grain protectants and are increasingly being reported as pests of stored products in other countries. Firstly, mortality and reproduction of adults were determined in wheat freshly treated at 0.0, 0.75, 1.5, 3 and 6 mg kg-1 of pyrethrins + PB (1:4) at 301C and 702% RH. Next, wheat treated at 0.0, 1.5, 3 and 6 mg kg-1 of pyrethrins + PB (1:4) was stored at 301C and 702% RH and mortality and reproduction of psocids were assessed after 0, 1.5, 3 and 4.5 months of storage. Finally, the potential of synergised pyrethrins as a disinfestant was assessed by establishing time to endpoint mortality for adult psocids exposed to wheat treated at 3 and 6 mg kg-1 of synergised pyrethrins after 0, 3, 6, 9 and 12 h of exposure. RESULTS: Synergised pyrethrins at 6 mg kg-1 provided 3 months of protection against all four Liposcelis spp., and at this rate complete adult mortality of these psocids can be achieved within 6 h of exposure. CONCLUSION: Piperonyl butoxide-synergised pyrethrins have excellent potential both as a grain protectant and as a disinfestant against Liposcelidid.

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This paper is the first of a series which will describe the development of a synthetic plant volatile-based attracticide for noctuid moths. It discusses potential sources of volatiles attractive to the cotton bollworm, Helicoverpa armigera (Hubner), and an approach to the combination of these volatiles in synthetic blends. We screened a number of known host and non-host (for larval development) plants for attractiveness to unmated male and female moths of this species, using a two-choice olfactometer system. Out of 38 plants tested, 33 were significantly attractive to both sexes. There was a strong correlation between attractiveness of plants to males and females. The Australian natives, Angophora floribunda and several Eucalyptus species were the most attractive plants. These plants have not been recorded either as larval or oviposition hosts of Helicoverpa spp., suggesting that attraction in the olfactometer might have been as nectar foraging rather than as oviposition sources. To identify potential compounds that might be useful in developing moth attractants, especially for females, collections of volatiles were made from plants that were attractive to moths in the olfactometer. Green leaf volatiles, floral volatiles, aromatic compounds, monoterpenes and sesquiterpenes were found. We propose an approach to developing synthetic attractants, here termed 'super-blending', in which compounds from all these classes, which are in common between attractive plants, might be combined in blends which do not mimic any particular attractive plant.

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In Australia, the development of rangelands has led to steady gains in pastoral productivity through more intensive and widespread land use (Stokes et al., 2006). Opportunities to benefit from intensification exist on large properties with relatively poor water and fencing infrastructure development, resulting in uneven utilisation of available forage (Ash et al.,2006). The objective of this study is to value expected economic gains from carrying out property improvements on a beef property located in Northern Australia.

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The specialist tingid, Carvalhotingis visenda, is a biological control agent for cat's claw creeper, Macfadyena unguis-cati (Bignoniaceae). Cat's claw creeper is an invasive liana with a wide climatic tolerance, and for biological control to be effective the tingid must survive and develop over a range of temperatures. We evaluated the effect of constant temperatures (0-45°C) on the survival and development of C. visenda. Adults showed tolerance for wider temperature ranges (0-45°C), but oviposition, egg hatching and nymphal development were all affected by both high (>30°C) and low (<20°C) temperatures. Temperatures between 20°C and 30°C are the most favourable for adult survival, oviposition, egg hatching and nymphal development. The ability of adults and nymphs to survive for a few days at high (40°C and 45°C) and low (0°C and 5°C) temperatures suggest that extreme temperature events, which usually occur for short durations (hours) in cat's claw creeper infested regions in Queensland and New South Wales states are not likely to affect the tingid population. The potential number of generations (egg to adult) the tingid can complete in a year in Australia ranged from three to eight, with more generations in Queensland than in New South Wales.

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Convex potential minimisation is the de facto approach to binary classification. However, Long and Servedio [2008] proved that under symmetric label noise (SLN), minimisation of any convex potential over a linear function class can result in classification performance equivalent to random guessing. This ostensibly shows that convex losses are not SLN-robust. In this paper, we propose a convex, classification-calibrated loss and prove that it is SLN-robust. The loss avoids the Long and Servedio [2008] result by virtue of being negatively unbounded. The loss is a modification of the hinge loss, where one does not clamp at zero; hence, we call it the unhinged loss. We show that the optimal unhinged solution is equivalent to that of a strongly regularised SVM, and is the limiting solution for any convex potential; this implies that strong l2 regularisation makes most standard learners SLN-robust. Experiments confirm the unhinged loss’ SLN-robustness.

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Galerkin representations and integral representations are obtained for the linearized system of coupled differential equations governing steady incompressible flow of a micropolar fluid. The special case of 2-dimensional Stokes flows is then examined and further representation formulae as well as asymptotic expressions, are generated for both the microrotation and velocity vectors. With the aid of these formulae, the Stokes Paradox for micropolar fluids is established.

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Only three of the 11 species in the genus Zoysia Willd. have thus far contributed to commercially available turfgrass varieties. One of the neglected taxa is Z. macrantha Desv., an Australian native species further divided into two subspecies. The coarser Z. macrantha subsp. macrantha occurs on sand dunes, headlands and tidal areas along eastern and southeastern coasts from about 23 to 38°S latitude. The shorter, denser-growing Z. macrantha subsp. walshii M.E. Nightingale is found on the southern mainland (South Australia and Victoria from longitude 137° to 148°E and at latitudes higher than 36°S), adjacent offshore islands, and northern, eastern and central Tasmania to 43°S growing on the edges of coastal, sub-coastal and even inland salt lakes, in riverine environments, and from moist grassy depressions (both coastal and inland) to rocky headlands. The latter subspecies has the more discontinuous and specialised distribution, largely determined by the need for an appropriate level of peat, clay or silt in the soil to maintain adequate moisture during the dry summers in southern Australia while at the same time avoiding anything more than temporary waterlogging. It grows on low fertility soils ranging from strongly acid to neutral or mildly alkaline, and is often very closely grazed by marsupials. Both subspecies are salt and drought tolerant, but not notably shade tolerant. Their potential to add greater drought tolerance in particular to the Asian Zoysia material in current use through future breeding programs is discussed.

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Androgen receptor (AR) is necessary for normal male phenotype development and essential for spermatogenesis. AR is a classical steroid receptor mediating actions of male sex steroids testosterone and 5-alpha-dihydrotestosterone. Numerous coregulators interact with the receptor and regulate AR activity on target genes. This study deals with the characterization of androgen receptor-interacting protein 4 (ARIP4). ARIP4 binds DNA, interacts with AR in vitro and in cultured yeast and mammalian cells, and modulates AR-dependent transactivation. ARIP4 is an active DNA-dependent ATPase, and this enzymatic activity is essential for the ability of ARIP4 to modulate AR function. On the basis of sequence homology in its ATPase domain, ARIP4 belongs to the SNF2 family of proteins involved in chromatin remodeling, DNA repair, and homologous recombination. Similar to its closest homologs ATRX and Rad54, ARIP4 does not seem to be a classical chromatin remodeling protein in that it does not appear to form large protein complexes in vivo or remodel mononucleosomes in vitro. However, ARIP4 is able to generate superhelical torsion on linear DNA fragments. ARIP4 is covalently modified by SUMO-1, and mutation of six potential SUMO attachment sites abolishes the ability of ARIP4 to bind DNA, hydrolyze ATP, and activate AR function. ARIP4 expression starts in early embryonic development. In mouse embryo ARIP4 is present mainly in the neural tube and limb buds. In adult mouse tissues ARIP4 expression is virtually ubiquitous. In mouse testis ARIP4 is expressed in the nuclei of Sertoli cells in a stage-dependent manner. ARIP4 is also present in the nuclei of Leydig cells, spermatogonia, pachytene and diplotene spermatocytes. Testicular expression pattern of ARIP4 does not differ significantly in wild-type, FSHRKO, and LuRKO mice. In the testis of hpg mice, ARIP4 is found mainly in interstitial cells and has very low, if any, expression in Sertoli and germ cells. Heterozygous Arip4+/ mice are fertile and appear normal; however, they are haploinsufficient with regard to androgen action in Sertoli cells. In contrast, Arip4 / embryos are not viable. They have significantly reduced body size at E9.5 and die by E11.5. Compared to wild-type littermates, Arip4 / embryos possess a higher percentage of apoptotic cells at E9.5 and E10.5. Fibroblasts derived from Arip4 / embryos cease growing after 2-3 passages and exhibit a significantly increased apoptosis and decreased proliferation rate than cells from wild-type embryos. Our findings demonstrate that ARIP4 plays an essential role in mouse embryonic development. In addition, testicular expression and AR coregulatory activity of ARIP4 suggest a role of ARIP4-AR interaction in the somatic cells of the testis.

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Although agriculture generates 16% of Australia's greenhouse gas emissions, it also has the potential to sequester large quantities of emissions through land use management options such as agroforestry. Whilst there is an extensive amount of agroforestry literature, little has been written on the economic consequences of adopting silvopastoral systems in northern Australia. This paper reports the financial viability of adopting complementary agroforestry systems in the low rainfall region of northern Australia. The analysis incorporates the dynamic tradeoffs between tree and pasture growth, likely forest product yields, carbon sequestration and livestock methane emissions in a bioeconomic model. The results suggest there are financial benefits for landholders who integrate complementary agroforestry activities into existing grazing operations at even modest carbon prices.

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To experimentally investigate the potential of mixed species polycultures for bioremediation of nutrient rich prawn farm effluent, a series of experiments was performed with banana prawns Penaeus (Fenneropenaeus) merguiensis, sea mullet Mugil cephalus and rabbitfish Siganus nebulosus to determine their compatibilities during particular life stages. Rabbitfish demonstrated a high tendency to prey upon banana prawn juveniles when no other food was available. Mullet of various sizes did not appear to prey upon banana prawn postlarvae (PL16) or juveniles in a fed or unfed environment. The study confirms the good potential for mullet and banana prawn polycultures.

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The biological function of nitric oxide and its oxidized forms has received a great deal of attention over the past two decades. However much less attention has been focused on the reduced nitric oxide, nitroxyl (HNO). Unlike NO, HNO is highly reactive species and thus it needs to be generated by using donor compounds under experimental conditions. Currently there is only one donor available, Angeli s salt, which releases HNO in a controlled fashion under pysiological conditions. Prior studies have shown the pro-oxidative and cytotoxic potential of Angeli s salt compared to NO donors. The high reactivity of HNO with cysteine thiols is considered to form the biochemical basis for its unique properties compared to other nitrogen oxides. Such thiol modification cold result in disturbances of vital cellular functions and subsequently to death of disturbance sensitive cells, such as neurons. Therefore modification of proteins and lipids was studied in vitro and the potential neurotoxicity was studied in vivo by local infusion of Angeli s salt into the rat central nervous system. The results show that under aerobic in vitro conditions, HNO can, subsequent to autoxidation, cause irreversible oxidative modification of proteins and lipids. These effects are not however seen in cell culture or following infusion of Angeli s salt directly into the rat central nervous tissue likely due to presence of lower oxygen and higher thiol concentration. However, due to high reactivity with thiols, HNO can cause irreversible inactivation of cysteine modification sensitive enzymes such as cysteine proteases papain in vitro and cathepsin B in cell culture. Furthermore it was shown that infusion of HNO releasing Angeli s salt into the rat central nervous system causes necrotic cell death and motor dysfunction following infusion into the lumbal intrathecal space. In conclusion, the acute neurotoxic potential of Angeli s salt was shown to be relatively low, but still higher compared to NO donors. HNO was shown to affect numerous cellular processes which could result in neurotoxicity if HNO was produced in vivo.

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We analyze recent experimental results of Sundström and Gillbro by using the theory of Bagchi, Fleming and Oxtoby. The experimental results are in good agreement with this theory, but not with the earlier theory of Förster and Hoffmann. By fitting the new experimental results to the theory, we obtain approximate estimates of the frequency of the excited surface (assumed harmonic) and the width of the sink function.