Editorial for special issue: Advances in sedentary behavior research and translation

Sedentary behaviour—essentially low energy sitting time in waking hours—has emerged as an important topic in public health over the past decade or so. Although Morris and colleagues [1] analysed health outcomes of active versus seated occupations over 60 years ago, it was not until studies of TV viewing in children in the 1980s [2] that researchers started to recognise “too much sitting” as a potentially important health behaviour. Even then the rapid rise in the study of sedentary behaviour was not so evident until the early 2000s [3]–[5]. Studies on screen viewing (TV and computers), sitting at work and school, and sitting in cars have all emerged over this period, as well as a general recognition that high levels of sitting may have detrimental effects on health, and possibly be independent of levels of moderate-to-vigorous physical activity (MVPA). In the past 10–15 years there has been an exponential increase in papers addressing sedentary behaviour from the perspective of sitting, noting that many exercise physiologists still use the word 'sedentary' incorrectly by referring to those not meeting a criterion level of “sufficient” physical activity

Factors Affecting Maize Producers Adoption of Forward Pricing in Price Risk Management: The Case of Vaalharts

Logistic regression is employed to analyse the factors which influence the decision of whether or not the respondent used forward pricing methods during the 2004/05 maize production season. Forward pricing methods include cash forward contracting and hedging with futures contracts and/or options, through the South African Futures Exchange (SAFEX). Based on the results, the use of forward pricing is associated with lower levels of risk aversion and higher levels of human capital. Factor analysis is employed to reduce the dimensionality of the personal reasons which help to interpret the underlying, common factor of the personal reasons why farmers are reluctant to use forward pricing methods. Three factors were extracted and were labelled “Lack of capacityâ€, “Distrust of the marketâ€, and “Bad experiencesâ€. The results from the factor analysis confirm the finding that farmers need higher levels of human capital to use forward pricing methods and that farmers do not believe that the forward pricing market is effective. Education should furthermore, focus more on the practical application of alternative forward pricing methods and not purely on the benefits of the use of forward pricing methods.Forward pricing, Logit, Factor analysis, Agricultural Finance, Risk and Uncertainty,

Impact of capital on the growth process of a sugarcane farm in Mpumalanga

The research was conducted for a representative 50 ha farm in the Onderberg region in Mpumalanga province, where farmers use a combination of centre-pivot, drip, and dragline systems of different sizes to grow sugarcane. The main intention was to establish a multi-period linear programming model capable of economically evaluating a farm's expansion decision-making process for farmers faced with investment decisions in alternative irrigation systems, taking into account the available initial capital of the farm. A linear programming (LP) model was used to assign a mainline for a total of twelve irrigation system combinations based on the assumption that the farmer wishes to start with a 30 ha centre-pivot investment. The Generalized Algebraic Modelling System (GAMS) was used to formulate the farm growth model as mixed integer dynamic linear programming (MIDLP) for a 15-year planning horizon. Based on the results, farmers are initially forced to invest in lower-cost irrigation systems when they lack capital to start a farm business due to the time value of money. They only consider lowering operating costs by investing in capital intensive irrigation systems when they have more own capital or borrowing capacity.Agricultural Finance,

IMPACT OF CAPITAL ON THE GROWTH PROCESS OF A SUGARCANE FARM IN MPUMALANGA

The research was conducted for a representative 50 ha farm in the Onderberg region in Mpumalanga province, where farmers use a combination of centre-pivot, drip, and dragline systems of different sizes to grow sugarcane. The main intention was to establish a multi-period linear programming model capable of economically evaluating a farm expansion decision making process for farmers faced with investment decisions in alternative irrigation systems, taking in to account the available initial capital of the farm. A linear programming (LP) model was used to assign a mainline for a total of twelve irrigation system combinations based on the assumption that the farmer wishes to start with a 30 ha centre-pivot investment. Generalized Algebraic Modelling System (GAMS) was used to formulate the farm growth model as mixed integer dynamic linear programming (MIDLP) for a 15 year planning horizon. Based on the results, farmers are initially forced to invest in lower cost irrigation systems when they lack capital to start a farm business due to the time value of money. They only consider lowering operating costs by investing in expensive irrigation systems when they have more own capital or borrowing capacity.Crop Production/Industries, Land Economics/Use, Research Methods/ Statistical Methods,

A Dynamic Risk Optimization Model for Evaluating Profitable and Feasible Water Management Plans

Currently the South African government is advocating the cultivation of high valued crops and more efficient use of available water resources through the adoption o f more efficient irrigation technology and irrigation scheduling. A requirement of the National Water Act (Act 36 of 1998) is the compilation of water management plans. The main objective of this paper is to develop a multiperiod mathematical risk programming model able of assisting water user associations with the compilation of water management plans that are both profitable and feasible. Special care was taken to represent canal capacities and irrigation system application rates in the model. Risk simulation procedures are used to generate an appropriately correlated inter- and intra-temporal risk matrix for the programming model. A combination of subjectively elicited distributions of crop yield and objective data on crop prices were used to characterize risk. The model was applied to a representative flood irrigation farm in the Vaalharts irrigation scheme South Africa to demonstrate the capability of the model to optimize water use over a 15 year planning horizon. Model results clearly indicated the potential of high value crops and more efficient irrigation technology to soften the impact of water shortages. Furthermore infrastructure, the financial position of the farmer and the level of risk averseness have significantly impacted on the results. Policy makers and government authorities should take cognizance of these factors when evaluating water use efficiency and water management plans of different water user associations. Improvements in the adopted modeling procedure are also made.Dynamic Linear Programming, risk, irrigation, feasibility, South Africa, Resource /Energy Economics and Policy, C6, Q15, Q12,

Scaling of the critical current in ITER type niobium-tin superconductors in relation to the applied field, temperature and uni-axial applied strain

The three dimensional surface of the critical current density versus field and temperature Jc(B,T) of niobium-tin is a function of the strain state of the superconductor. A brief review of literature on this subject is presented. The Jc(B) function is described by the relations for flux pinning. The temperature and strain dependencies are added to this relation, This results in a unifying scaling law for A15 materials, which is verified for different niobium-tin conductors with respect to all the relevant variables, i.e. field, temperature and uni-axial strain. Nb3Sn conductors from 9 manufacturers are measured in the frame work of the third ITER benchmark tests on critical current. The investigated ranges are: applied field from 7 to 13 T, temperature from 4.2 to 8 K and applied strain from -0.4 to +0.8%. Special attention is paid to the region of compressive axial strain, which is the most relevant state of strain for superconductors under thermal compression in practical application

Compressive and tensile axial strain reduced critical currents in Bi-2212 conductors

Mono and multifilamentary wires of BSCCO-2212 in Ag matrix are investigated in an axial strain experiment. The superconducting samples are soldered to a substrate that is bend in order to achieve a compressive or tensile axial strain. The I/sub c/-strain dependence is measured in magnetic fields up to 16 T at 4.2 K and the strain is varied from -2% to +1.2%. In these Bi-2122 samples any strain-induced I/sub c/ reduction is irreversible. Moreover a significant rise in I/sub c/ was never observed after changing the strain. Special attention is paid to the tensile axial strain regime (0 to 0.4%). A small but significant reduction in I/sub c/ is found in this case. The strain behaviour of these wires indicates that the I/sub c/ reduction is due to fractures in the superconducting filament

Small and repetitive axial strain reducing the critical current in BSCCO/Ag superconductors

The critical current in two types of axially deformed BSCCO/Ag tape conductors is investigated. An Ic reduction is observed for small axial strains (ranging from 0 to 0.3%) with a characteristic slope dic/d&epsiv;=-5±1 (relative Ic, change per relative change in length). In the case of an axial compression there is a more pronounced Ic reduction. For small axial strains (<0.3%) a certain reversible change in Ic is observed. This reversible behaviour occurs in combination with an irreversible reduction that increases when the number of strain cycles is increased. The reversible part of the Ic change remains for a large number of strain cycles (>10000) and has a similar negative slope for both compressive and tensile strains. It is proposed that the reversible Ic change is correlated to a non-hydrostatic lattice deformation. The Ic versus strain behaviour is in good agreement with an earlier proposed mode

Bookstore Names For Fun and Profit

If the Internet has done anything, it has caused a proliferation of bookish activity - dusting off, re-reading, swapping, borrowing, buying and selling. I, for one, has gotten caught up in this melee. My general modus operandi is to do garage sales and pass the wonderful bargains I find on to other anxious Internet book freaks