An adjoint for likelihood maximization

The process of likelihood maximization can be found in many different areas of computational modelling. However, the construction of such models via likelihood maximization requires the solution of a difficult multi-modal optimization problem involving an expensive O(n3) factorization. The optimization techniques used to solve this problem may require many such factorizations and can result in a significant bottle-neck. This article derives an adjoint formulation of the likelihood employed in the construction of a kriging model via reverse algorithmic differentiation. This adjoint is found to calculate the likelihood and all of its derivatives more efficiently than the standard analytical method and can therefore be utilised within a simple local search or within a hybrid global optimization to accelerate convergence and therefore reduce the cost of the likelihood optimization

An Empirical Analysis of Income Dynamics among Men in the PSID: 1968–1989

This study uses data from the Panel Survey of Income Dynamics (PSID) to address a number of questions about life-cycle earnings mobility. It develops a dynamic reduced-form model of earnings and marital status that is nonstationary over the life-cycle. A Gibbs sampling-data augmentation algorithm facilitates use of the entire sample and provides numerical approximations to the exact posterior distribution of properties of earnings paths. This algorithm copes with the complex distribution of endogenous variables that are observed for short segments of an individual’s work history, not including the initial period. The study reaches several firm conclusions about life cycle earnings mobility. Incorporating non-Gaussian shocks makes it possible to account for transitions between low and higher earnings states, a heretofore unresolved problem. The non-Gaussian distribution substantially increases the lifetime return to postsecondary education, and substantially reduces differences in lifetime wages attributable to race. In a given year, the majority of variance in earnings not accounted for by race, education, and age is due to transitory shocks, but over a lifetime the majority is due to unobserved individual heterogeneity. Consequently, low earnings at early ages are strong predictors of low earnings later in life, even conditioning on observed individual characteristics.

Color, composition, and thermal environment of Kuiper Belt object (486958) Arrokoth

The outer Solar System object (486958) Arrokoth (provisional designation 2014 MU₆₉) has been largely undisturbed since its formation. We study its surface composition using data collected by the New Horizons spacecraft. Methanol ice is present along with organic material, which may have formed through irradiation of simple molecules. H₂O ice is not detected. This composition indicates hydrogenation of CO-rich ice and/or energetic processing of CH₄+H₂O ices in the cold, outer edge of the early Solar System. There are only small regional variations in color and spectra across the surface, suggesting Arrokoth formed from a homogeneous or well-mixed reservoir of solids. Microwave thermal emission from the winter night side is consistent with a mean brightness temperature of 29 ± 5 K

Multi-fidelity optimization via surrogate modelling

This paper demonstrates the application of correlated Gaussian process based approximations to optimization where multiple levels of analysis are available, using an extension to the geostatistical method of co-kriging. An exchange algorithm is used to choose which points of the search space to sample within each level of analysis. The derivation of the co-kriging equations is presented in an intuitive manner, along with a new variance estimator to account for varying degrees of computational ‘noise’ in the multiple levels of analysis. A multi-fidelity wing optimization is used to demonstrate the methodology

Post-weaning performance and carcass characteristics of steer progency from different suckler cow breed types

peer-reviewedIn two experiments a total of 44 steer progeny of spring-calving Charolais (C) and Hereford × Friesian (HF) suckler cows and C sires were slaughtered at approximately 2 years of age. Following weaning they were offered silage and 1 kg of concentrate per head daily during a 5 month winter after which they spent 7 months at pasture. In Experiment 1, animals were given a silage/concentrate diet during a finishing period of either 95 or 152 days. In Experiment 2, steers were offered either a daily diet of silage plus 6 kg of concentrates or concentrates to appetite plus 5 kg of silage (fresh weight) during the final 140-day finishing period. Following slaughter, an 8-rib pistola from each animal was dissected. For the two experiments combined C and HF progeny had carcass weights of 372 and 385 (s.e. 6.1) kg, proportions of carcass as pistola of 467 and 454 (s.e. 2.8) g/kg and pistola meat proportions of 676 and 642 (s.e. 5.1) g/kg, respectively. All fat traits were lower for the C than HF progeny but there was no difference in carcass conformation score. Increasing slaughter weight increased carcass weight (P < 0.001), kidney plus channel fat weight (P < 0.001), and pistola fat proportion (P < 0.001) and decreased the proportions of carcass as pistola (P < 0.05), pistola meat (P < 0.01), and bone (P < 0.05). In conclusion, breed type had no effect on carcass growth but the C progeny had higher meat yield than the HF. Increasing slaughter weight increased fatness and reduced meat yield

Three-terminal devices to examine single molecule conductance switching

We report electronic transport measurements of single-molecule transistor devices incorporating bipyridyl-dinitro oligophenylene-ethynylene dithiol (BPDN-DT), a molecule known to exhibit conductance switching in other measurement configurations. We observe hysteretic conductance switching in 8% of devices with measurable currents, and find that dependence of the switching properties on gate voltage is rare when compared to other single-molecule transistor devices. This suggests that polaron formation is unlikely to be responsible for switching in these devices. We discuss this and alternative switching mechanisms.Comment: 5 pages, 4 figures. Supporting material available upon reques

Optimising The Response To Supplementary Concentrates By Beef Cattle In Winter

End of project reportConcentrates are a major component of feed costs in winter finishing of beef cattle. Two separate experiments were carried out to evaluate the response to increasing supplementary concentrate level with grass silage and the effects of feeding the silage and concentrates separately or as a total mixed ration (TMR). In experiment 1, a total of 117 finishing steers (initial live weight 538 kg, s.d. 35.5) were assigned to a preexperimental slaughter group of 9 animals and to 6 feeding treatments of 18 animals each. The feeding treatments were: 1) silage (SO) only offered ad libitum, 2) SO plus a low level of concentrates offered separately (LS), 3) SO plus a low level of concentrates offered as a TMR (LM), 4) SO plus a medium level of concentrates offered separately (MS), 5) SO plus a medium level of concentrates offered as a TMR (MM), and 6) concentrates ad libitum plus a restricted silage allowance (AL). Low and medium target concentrate levels were 3 and 6 kg dry matter (DM) per head daily. When silage and concentrates were fed separately, the daily concentrate allowance was given in one morning feed. The animals were individually fed for a mean period of 132 days. After slaughter, carcasses were weighed and graded and the ribs joint was dissected into its component tissues. Silage DM intake decreased but total DM intake increased with increasing concentrate level. Live weight gains for SO, LS, LM, MS, MM and AL were 0.34, 0.86, 0.86, 1.02, 1.00 and 1.12 (s.e. 0.064) kg/day, respectively. Corresponding carcass weight gains were 0.25, 0.58, 0.58, 0.71, 0.68 and 0.82 (s.e. 0.028) kg/day. All measures of fatness increased, ribs joint bone proportion decreased, and muscle proportion was not significantly affected by dietary concentrate level. There were no significant interactions between concentrate level and method of feeding. Compared with offering the feeds separately, feeding a TMR increased silage DM intake by proportionately 0.06 and total DM intake by proportionately 0.04. Otherwise, method of feeding had no significant effect on performance, slaughter or carcass traits. Mean rumen pH decreased while ammonia concentration tended to increase with increasing concentrate level. Total volatile fatty acids and the acetate to propionate ratio were lowest for SO. Method of feeding had no significant effect on rumen fermentation

The new scramble for Africa: towards a human-rights based approach to large-scale land acquisitions in the Southern African Development Community (SADC) sub-region

The chapter examines the implications of a contemporary ‘land grab’ in the SADC region, or the growing acquisition of lands by foreign investors at the behest of Asian or Middle Eastern states, to produce crops for their own consumption and security in the wake of the global food crisis. The analysis provides a rights-based approach to large-scale land acquisition, particularly looking at the right to food and land rights for the local communities, including an exploration of the meaning and reach of customary land rights. It also examines the right to development, which is used as a justification for leasing lands, and highlights that this right concurrently confers obligations on SADC states to protect the rights of peoples to control decisions which affect their economic and social development. Overall the aim is to signal the alarming move towards large-scale land acquisitions in the SADC region, and the potential for human rights to provide a regulatory framework. It is suggested that the issue could galvanise the international movement towards non-state actor accountability, which has been evolving for several decades