PREDICTING OUTPUT FROM SEEMINGLY UNRELATED AREA AND YIELD EQUATIONS

Crop output can be defined as the product of area sown and yield. Given the existence of separate equations for explaining and predicting area sown and yield, in this paper we suggest predictors for output and derive expressions for the standard errors of the predictors. The methodology is applied to wheat production in the Corrigin Shire of Western Australia.Predicting a product, standard error of prediction, Crop Production/Industries,

How do You Map a Von Karman Vortex Street and How do You Use One to Generate Electricity?

Swirling structures in calmly flowing water inspire a deep, primal sense of peace and well-being. At the same time, images of Poe’s maelstrom in turbulent oceans inspire a sense of terror.1 Throughout the duration of my PhD, modelling the flow through ocean channels full of tidal turbines, I experienced both of those feelings. The mathematical beauty in my work is involved in the equations that I use to describe the ocean flowing through a tidal channel full of turbines.  A von Karman vortex street is the repeating pattern in parallel rows of swirling eddies that form in the wake of an obstruction in flowing fluid. The beauty and terror that eddies inspire in humanity is mirrored by the blessing and curse that these cause for engineers designing tidal turbines. While the fast-flowing water provides the power to drive the turbine, the turbulent vortices in the wake of a turbine put stress on downstream turbines by bending and twisting the blade as a vortex moves past the turbine. Understanding the balance between the power in the flow that can be captured by turbines and the impact on the natural flow by building these turbines was a fundamental part of my research

An Overview of the Karst Areas in British Columbia, Canada

Karst is a three-dimensional landscape that occurs in soluble bedrock (typically limestone, marble, dolostone, gypsum or halite) and is defined by a solutionally weathered surface, a subsurface drainage system (where conduit-flow dominates), and underground openings and caves. Karst can host unique flora and subsurface fauna, as well as a wide range of other scientific, recreational and cultural values. Karst and potential karst areas underlie approximately 10% of British Columbia (BC), but the distribution and extent of this landscape has yet to be fully explored and delineated. Some of the most extensive and well-developed karst areas occur within the forestedlimestone areas of coastal BC, such as on Vancouver Island and Haida Gwaii, where numerous surface karst features and caves are known. Karst in the interior plateau regions of British Columbia is less well known, being in part covered by thick deposits of glacial materials. Alpine karst regions are most apparent in the Rocky Mountains where there are limestone plateaus, karst drainages and cave systems that have close connections to past and present glacial systems. Mapping of karst is a critical component for any land-use or resource development activity in all regions of British Columbia, as the environmental impacts on karst and its associated values are potentially significant. The regional distribution of karst in BC is not well mapped, with only an office-based reconnaissance karst potential map (1:250,000-scale) and a related database completed in 1999. A renewed effort should now be made to better map karst across British Columbia using digital bedrock mapping data released in 2017, combined with more recent satellite imagery and improved field knowledge.RÉSUMÉLe karst est un paysage tridimensionnel qui se présente dans le substrat rocheux soluble (généralement calcaire, marbre, dolomite, gypse ou halite) et est défini par une surface altérée par dissolution, un système de drainage souterrain (où l’écoulement par conduit domine) et des ouvertures et cavernes souterraines. Le karst peut abriter une flore et une faune souterraine unique, ainsi qu’une grande variété d’autres ressources scientifiques, de loisir et culturelles. Les zones karstiques et potentiellement karstiques constituent environ 10% de la surface de la Colombie-Britannique, mais la répartition et l’étendue de ce paysage n’a pas été complètement explorées et circonscrites. Certaines des zones karstiques les plus étendues et les mieux développées se trouvent dans les calcaires des zones calcaires boisées de la côte de la Colombie-Britannique, telles que l’île de Vancouver et l’archipel de Haida Gwaii, où l’on connaît de nombreuses caractéristiques karstiques de surface et des cavernes. Le karst des régions des plateaux intérieurs de la Colombie-Britannique est moins bien connu, étant en partie recouvert d’épais dépôts de matériaux glaciaires. Les régions karstiques alpines sont plus apparentes dans les montagnes Rocheuses où se trouvent des plateaux calcaires, des bassins de drainage karstiques et des systèmes de cavernes étroitement liés aux systèmes glaciaires passés et contemporains. La cartographie du karst est une constituante essentielle de toute activité d’utilisation du terrain ou de développement des ressources dans toutes les régions de la Colombie-Britannique, car les impacts environnementaux sur le karst et ses bénéfices associés sont potentiellement importants. La distribution régionale et les caractéristiques des karsts en Colombie-Britannique ne sont pas bien cartographiées, avec seulement une carte de reconnaissance du potentiel karstique établie par une étude de bureau (à l’échelle de 1/250 000) et une base de données associée, complétées en 1999. Il faut aujourd’hui améliorer la cartographie de karsts en Colombie-Britannique en utilisant les données numériques de cartographie du substrat rocheux publiées en 2017, combinées avec des images satellite plus récentes et à une meilleure connaissance du terrain

Discrete Charge Dielectric Model of Electrostatic Energy

Studies on nanoscale materials merit careful development of an electrostatics model concerning discrete point charges within dielectrics. The discrete charge dielectric model treats three unique interaction types derived from an external source: Coulomb repulsion among point charges, direct polarization between point charges and their associated surface charge elements, and indirect polarization between point charges and surface charge elements formed by other point charges. The model yields the potential energy, U(N), stored in a general $N$ point charge system differing from conventional integral formulations, $1/2\int{\bm E}\cdot{\bm D}dV$ and $1/2\int\rho\Phi dV$, in a manner significant to the treatment of few electron systems.Comment: 1 figure, 2 parts, ep

Improving the seasonal prediction of Northern Australian rainfall onset to help with grazing management decisions

The development of the Australian Community Climate and Earth-System Simulator-Seasonal prediction system version 1 (ACCESS-S1) signifies a major step towards addressing predictive limitations in multi-week to seasonal forecasting throughout Australia. It is anticipated that moving to ACCESS-S1 will provide improved skill in rainfall prediction during the dry to wet season transition period across tropical northern Australia. This is an important time for northern Australian livestock producers in terms of the decisions they make around pasture and livestock management. This study quantifies the hindcast skill of ACCESS-S1 for the northern rainfall onset (NRO), defined as the date when 50 mm of precipitation has accumulated at a given location from the 1st of September, heralding the shift towards greener pastures. We evaluate the raw model hindcasts, and compare them to hindcasts corrected for mean biases and those calibrated against observations. It is found that the raw ACCESS-S1 hindcasts broadly replicate the observed median NRO over the period 1990–2012, despite a ten- dency for earlier than observed onsets. In terms of forecasting the interannual variability of the NRO, the ca- librated hindcasts show the greatest skill, with the largest improvements over a climatological forecast in their probabilistic forecasts of an earlier or later than usual onset, with a large portion of northern Australian showing more than 10% improvement. With real-time NRO forecasts now generated by ACCESS-S1, it is expected that the calibrated predictions will help northern Australian graziers make better informed decisions around livestock management prior to the wet season

Experts react to the Spending Review: what next for the Conservative Party?

We asked experts to react to the 2015 Spending Review, with a particular focus on the Conservative Party moving forward. Tom Quinn sees a pitch for swing voters and the centre ground. Simon Griffiths points towards George Osborne’s ability as a political tactician, and Tim Bale also argues that Osborne is on target to be the next Conservative Party leader. However, Rodney Barker wonders how long it will be until the policies and rhetoric of austerity come back to bite the Chancellor. Mark Garnnett agrees and raises a further crucial point: is the Office of Budget Responsibility on its way to becoming a political tool? And finally, our commentators seem to agree – Labour in Opposition is in trouble, and the less said about that little red book, the better

Testing, tracing and isolation in compartmental models

Existing compartmental mathematical modelling methods for epidemics, such as SEIR models, cannot accurately represent effects of contact tracing. This makes them inappropriate for evaluating testing and contact tracing strategies to contain an outbreak. An alternative used in practice is the application of agent- or individual-based models (ABM). However ABMs are complex, less well-understood and much more computationally expensive. This paper presents a new method for accurately including the effects of Testing, contact-Tracing and Isolation (TTI) strategies in standard compartmental models. We derive our method using a careful probabilistic argument to show how contact tracing at the individual level is reflected in aggregate on the population level. We show that the resultant SEIR-TTI model accurately approximates the behaviour of a mechanistic agent-based model at far less computational cost. The computational efficiency is such that it can be easily and cheaply used for exploratory modelling to quantify the required levels of testing and tracing, alone and with other interventions, to assist adaptive planning for managing disease outbreaks

Book Reviews

Book Review 1Book Title: Zoological Catalogue of Australia Vol. 34. Hemichordata, Tunicata, CephalochordataBook Authors: Editors A. Wells & W.W.K. Houston1998. CSIRO Publishing, Melbourne. 298pp.Book Review 2Book Title: Biodiversity dynamics and conservation: the freshwater fish of tropical AfricaBook Author: Christian Léveque 1997. ISBN 0 521 570336. Cambridge University Press, Cambridge.Book Review 3Book Title: Biology and ecology in southern African estuariesBook Author: Alan K. Whitfield Ichthyological Monographs of the J.L.B. Smith Institute of Ichthyology, No.2. 1998. ISBN 0-86810-333-0. Hardcover, 223 pp.Book Review 4Book Title: The Southern synthesis. Fauna of Australia Vol. 5Book Authors: P.L. Beesley, G.J.B. Ross & A. Wells 1998. CSIRO Publishing, Melbourne.Book Review 5Book Title: The Kingdon field guide to African mammalsBook Author: Jonathan Kingdon1997. Academic Press (locally available at Russell & Friedman. Box 73, Halfway House) 465pp. ISBN 0-12-408355-2.Book Review 6Book Title: Cooperative breeding in mammalsBook Authors: Edited by Nancy G. Solomon & Jeffrey A. FrenchCambridge University Press, Cambridge, UK. 1997. 390 pp. ISBN 0521 4591 3

Soil microbial communities with greater investment in resource acquisition have lower growth yield

Resource acquisition and growth yield are fundamental microbial traits that affect biogeochemical processes and have consequences for ecosystem functioning. However, there is a lack of empirical observations linking these traits. Using a landscape-scale survey of temperate near-neutral pH soils, we show tradeoffs in key community-level parameters linked to these traits. Increased investment into extracellular enzymes estimated using specific potential enzyme activity was associated with reduced growth yield obtained using carbon use efficiency measures from stable isotope tracing. Reduction in growth yield was linked more to carbon than nitrogen acquisition highlighting smaller stoichiometric than energetic constraints on community metabolism in examined soils

Demonstrating 24-hour continuous vertical monitoring of atmospheric optical turbulence

We report what is believed to be the first example of fully continuous, 24-hour vertical monitoring of atmospheric optical turbulence. This is achieved using a novel instrument, the 24-hour Shack-Hartmann Image Motion Monitor (24hSHIMM). Optical turbulence is a fundamental limitation for applications such as free-space optical communications, where it limits the achievable bandwidth, and ground-based optical astronomy, restricting the observational precision. Knowledge of the turbulence enables us to select the best sites, design optical instrumentation and optimise the operation of ground-based optical systems. The 24hSHIMM estimates the vertical optical turbulence coherence length, time, angle and Rytov variance from the measurement of a four-layer vertical turbulence profile and a wind speed profile retrieved from meteorological forecasts. To illustrate our advance we show the values of these parameters recorded during a 36-hour, continuous demonstration of the instrument. Due to its portability and ability to work in stronger turbulence, the 24hSHIMM can also operate in urban locations, providing the field with a truly continuous, versatile turbulence monitor for all but the most demanding of applications