Probability distributions for economic surplus changes: the case of technical change in the Australian wool industry

Mullen, Alston and Wohlgenant (1989) (MAW) examined the distribution of the benefits of technical change in the Australian wool industry. Their conclusions are revisited by examining the probability distributions of changes in the welfare measures, given uncertainty about their model parameters. Subjective probability distributions are specified for the parameters and correlations among some of the parameters are imposed. Hierarchical distributions are also used to model diverse views about the specification of the subjective distributions. A sensitivity elasticity is defined through the estimation of a response surface to measure the sensitivity of the estimated research benefits to individual parameters. MAW’s conclusions are found to be robust under the stochastic approach to sensitivity analysis demonstrated in this article.Livestock Production/Industries,

How and Why Are Cancers Acidic? Carbonic Anhydrase IX and the Homeostatic Control of Tumour Extracellular pH.

The acidic tumour microenvironment is now recognized as a tumour phenotype that drives cancer somatic evolution and disease progression, causing cancer cells to become more invasive and to metastasise. This property of solid tumours reflects a complex interplay between cellular carbon metabolism and acid removal that is mediated by cell membrane carbonic anhydrases and various transport proteins, interstitial fluid buffering, and abnormal tumour-associated vessels. In the past two decades, a convergence of advances in the experimental and mathematical modelling of human cancers, as well as non-invasive pH-imaging techniques, has yielded new insights into the physiological mechanisms that govern tumour extracellular pH (pHe). In this review, we examine the mechanisms by which solid tumours maintain a low pHe, with a focus on carbonic anhydrase IX (CAIX), a cancer-associated cell surface enzyme. We also review the accumulating evidence that suggest a role for CAIX as a biological pH-stat by which solid tumours stabilize their pHe. Finally, we highlight the prospects for the clinical translation of CAIX-targeted therapies in oncology

Particle formation and interaction

A wide variety of experiments can be conducted on the Space Station that involve the physics of small particles of planetary significance. Processes of interest include nucleation and condensation of particles from a gas, aggregation of small particles into larger ones, and low velocity collisions of particles. All of these processes could be investigated with a general purpose facility on the Space Station. The microgravity environment would be necessary to perform many experiments, as they generally require that particles be suspended for periods substantially longer than are practical at 1 g. Only experiments relevant to planetary processes will be discussed in detail here, but it is important to stress that a particle facility will be useful to a wide variety of scientific disciplines, and can be used to address many scientific problems

Supergiant Shells and Molecular Cloud Formation in the LMC

We investigate the influence of large-scale stellar feedback on the formation of molecular clouds in the Large Magellanic Cloud (LMC). Examining the relationship between HI and 12CO(J=1-0) in supergiant shells (SGSs), we find that the molecular fraction in the total volume occupied by SGSs is not enhanced with respect to the rest of the LMC disk. However, the majority of objects (~70% by mass) are more molecular than their local surroundings, implying that the presence of a supergiant shell does on average have a positive effect on the molecular gas fraction. Averaged over the full SGS sample, our results suggest that ~12-25% of the molecular mass in supergiant shell systems was formed as a direct result of the stellar feedback that created the shells. This corresponds to ~4-11% of the total molecular mass of the galaxy. These figures are an approximate lower limit to the total contribution of stellar feedback to molecular cloud formation in the LMC, and constitute one of the first quantitative measurements of feedback-triggered molecular cloud formation in a galactic system.Comment: 14 pages, 6 figures. Accepted for publication in Ap

HIF-1-Independent Mechanisms Regulating Metabolic Adaptation in Hypoxic Cancer Cells.

In solid tumours, cancer cells exist within hypoxic microenvironments, and their metabolic adaptation to this hypoxia is driven by HIF-1 transcription factor, which is overexpressed in a broad range of human cancers. HIF inhibitors are under pre-clinical investigation and clinical trials, but there is evidence that hypoxic cancer cells can adapt metabolically to HIF-1 inhibition, which would provide a potential route for drug resistance. Here, we review accumulating evidence of such adaptions in carbohydrate and creatine metabolism and other HIF-1-independent mechanisms that might allow cancers to survive hypoxia despite anti-HIF-1 therapy. These include pathways in glucose, glutamine, and lipid metabolism; epigenetic mechanisms; post-translational protein modifications; spatial reorganization of enzymes; signalling pathways such as Myc, PI3K-Akt, 2-hyxdroxyglutarate and AMP-activated protein kinase (AMPK); and activation of the HIF-2 pathway. All of these should be investigated in future work on hypoxia bypass mechanisms in anti-HIF-1 cancer therapy. In principle, agents targeted toward HIF-1β rather than HIF-1α might be advantageous, as both HIF-1 and HIF-2 require HIF-1β for activation. However, HIF-1β is also the aryl hydrocarbon nuclear transporter (ARNT), which has functions in many tissues, so off-target effects should be expected. In general, cancer therapy by HIF inhibition will need careful attention to potential resistance mechanisms

Fatigue of glass reinforced plastics under complex stresses

Many failure theories have been postulated to predict the behaviour of glass reinforced plastics (GRP) under complex stresses. However, the efficient use of these theories for design purposes is inhibited because the experimental complex stress data needed to verify and discriminate between them is not available. This thesis presents some of the experimental data required. Uniaxial stress test results from flat laminates, and biaxial stress test results from thin-walled tubes under combined internal pressure and axial force, are presented for various damage states under both static and fatigue loading for a plane isotropic material and an orthotropic material. The data were then used to establish which failure theory provided the most acceptable prediction of the observed behaviour. For ultimate strength, the Norris Failure theory gave adequate predictions, but not for resin cracking. The most generally acceptable predictions, for both materials, were given by those theories whose equations contain a constant which is derived from complex stress data, these being the modified Marin and the strength tensor theories. For the orthotropic material, three-dimensional representations of the plane stress ultimate strength and damage failure surfaces are presented for both static and fatigue loading. However, even though a considerable number of specimens were tested, only very few failure surface sections were experimentally established. It was found for both materials that fatigue loading was more damaging than static loading, for both uniaxial and biaxial stress conditions, and that the behaviour of the materials was dependent upon the ratio of the biaxial stresses. Jointed reinforcement layers severely affect the zero-tension fatigue behaviour of the plane isotropic material, but the effect on the orthotropic material decreases with increasing fatigue life. The effect of macro-voids on crack initiation should be acknowledged if damage is used as a design criterion

HI Emission and Absorption in the Southern Galactic Plane Survey

We present preliminary results from the Southern Galactic Plane Survey (SGPS) Test Region and Parkes data. As part of the pilot project for the Southern Galactic Plane Survey, observations of a Test Region (325.5 deg < l < 333.5 deg; -0.5 deg < b < 3.5 deg) were completed in December 1998. Single dish observations of the full survey region (253 deg < l < 358 deg; |b| <1 deg) with the Parkes Radio Telescope were completed in March 2000. We present a sample of SGPS HI data with particular attention to the smallest and largest scale structures seen in absorption and emission, respectively. On the large scale, we detect many prominent HI shells. On the small scale, we note extremely compact, cold clouds seen in HI self-absorption. We explore how these two classes of objects probe opposite ends of the HI spatial power spectrum.Comment: 9 pages, 3 embedded postscript & 4 jpeg figures. Presented at the Astronomical Society of Australia, Hobart, Tasmania, July 4-7 2000. To appear in PASA Vol. 18(1

Fatigue of glass reinforced plastics under complex stresses

Many failure theories have been postulated to predict the behaviour of glass reinforced plastics (GRP) under complex stresses. However, the efficient use of these theories for design purposes is inhibited because the experimental complex stress data needed to verify and discriminate between them is not available. This thesis presents some of the experimental data required. Uniaxial stress test results from flat laminates, and biaxial stress test results from thin-walled tubes under combined internal pressure and axial force, are presented for various damage states under both static and fatigue loading for a plane isotropic material and an orthotropic material. The data were then used to establish which failure theory provided the most acceptable prediction of the observed behaviour. For ultimate strength, the Norris Failure theory gave adequate predictions, but not for resin cracking. The most generally acceptable predictions, for both materials, were given by those theories whose equations contain a constant which is derived from complex stress data, these being the modified Marin and the strength tensor theories. For the orthotropic material, three-dimensional representations of the plane stress ultimate strength and damage failure surfaces are presented for both static and fatigue loading. However, even though a considerable number of specimens were tested, only very few failure surface sections were experimentally established. It was found for both materials that fatigue loading was more damaging than static loading, for both uniaxial and biaxial stress conditions, and that the behaviour of the materials was dependent upon the ratio of the biaxial stresses. Jointed reinforcement layers severely affect the zero-tension fatigue behaviour of the plane isotropic material, but the effect on the orthotropic material decreases with increasing fatigue life. The effect of macro-voids on crack initiation should be acknowledged if damage is used as a design criterion

Stellar Populations at the Center of IC 1613

We have observed the center of the Local Group dwarf irregular galaxy IC 1613 with WFPC2 aboard the Hubble Space Telescope in the F439W, F555W, and F814W filters. We find a dominant old stellar population (aged ~7 Gyr), identifiable by the strong red giant branch (RGB) and red clump populations. From the (V-I) color of the RGB, we estimate a mean metallicity of the intermediate-age stellar population [Fe/H] = -1.38 +/- 0.31. We confirm a distance of 715 +/- 40 kpc using the I-magnitude of the RGB tip. The main-sequence luminosity function down to I ~25 provides evidence for a roughly constant SFR of approximately 0.00035 solar masses per year across the WFPC2 field of view (0.22 square kpc) during the past 250-350 Myr. Structure in the blue loop luminosity function implies that the SFR was ~50% higher 400-900 Myr ago than today. The mean heavy element abundance of these young stars is 1/10th solar. The best explanation for a red spur on the main-sequence at I = 24.7 is the blue horizontal branch component of a very old stellar population at the center of IC 1613. We have also imaged a broader area of IC 1613 using the 3.5-meter WIYN telescope under excellent seeing conditions. The AGB-star luminosity function is consistent with a period of continuous star formation over at least the age range 2-10 Gyr. We present an approximate age-metallicity relation for IC 1613, which appears similar to that of the Small Magellanic Cloud. We compare the Hess diagram of IC 1613 to similar data for three other Local Group dwarf galaxies, and find that it most closely resembles the nearby, transition-type dwarf galaxy Pegasus (DDO 216).Comment: To appear in the September 1999 Astronomical Journal. LaTeX, uses AASTeX v4.0, emulateapj style file, 19 pages, 12 postscript figures, 2 tables. 5 of the figures available separately via the WW