2011-07 How the Timing of Grade Retention Affects Outcomes: Identification and Estimation of Time-Varying Treatment Effects

We develop a new strategy to disentangle how the effects of grade retention vary over time and by student abilities. A key challenge, which the literature has not addressed, is to separate the time-varying effect of retention from dynamic selection on unobservables. Our method is a hybrid between a control function and a generalized fixed effects approach. Applying our method to nationally-representative, longitudinal data, we find evidence of dynamic selection into retention and that the treatment effect of retention varies considerably across grades and unobservable abilities of students. Our strategy can be applied more broadly to many time-varying treatment settings

Economic and welfare impacts of providing good life opportunities to farm animals

Existing animal welfare standards for legislation and food certification programmes are primarily designed to avoid harms to the livestock, with minimal consideration given to their behavioural freedoms. Recent research has shown, however, that animal welfare should not only be evaluated by the absence of negative states but also by the presence of ‘good life’ or positive experiences enjoyed by animals. The objective of the present study is to investigate the scientific validity and on-farm cost implications of utilising potential input-based measures of positive welfare as part of evaluation criteria for farm assurance schemes. Building upon the Farm Animal Welfare Council’s concept of good life opportunities, an assessment was undertaken on 49 non-caged laying hen farms across the UK by measuring on-farm resources to facilitate positive experiences alongside commonly measured metrics for welfare outcomes. The financial cost of providing these resources on each enterprise was also estimated using a farm-scale costing tool. The results suggested that 63% of resource needs that facilitate the behaviour opportunities of laying hens are already being provided by these producers, far above legal and commercial requirements. This practice attracts no reward mechanism or direct financial benefit under the current market structure. Additional provision of opportunities was positively associated with behavioural outcomes, but only limited impact was observed on health and productivity measures. Economic modelling indicated that significant room exists to further improve welfare scores on these farms, on average by 97%, without incurring additional costs. Together we argue that these results can be seen as evidence of market failure since producers are providing positive welfare value to society that is not being currently recognised. It is therefore contended that measuring and rewarding the supply of good life opportunities could be a novel policy instrument to create an effective marketplace that appropriately recognises high welfare production

Large-UU limit of a Hubbard model in a magnetic field: chiral spin interactions and paramagnetism

We consider the large-$U$ limit of the one-band Hubbard model at half-filling on a non-bipartite two-dimensional lattice. An external magnetic field can induce a three-spin chiral interaction at order $1 / U^2 ~$. We discuss situations in which, at low temperatures, the chiral term may have a larger effect than the Pauli coupling of electron spins to a magnetic field. We present a model which explicitly demonstrates this. The ground state is a singlet with a gap; hence the spin susceptibility is zero while the chiral susceptibility is finite and paramagnetic.Comment: 12 pages, plain TeX, one figure available on request, to appear in Phys. Rev.

Effect of Enzymatic Tempering of Wheat Kernels on Milling and Baking Performance

This study examined the effect of cell-wall-degrading enzymes added to temper water on wheat milling performance and flour quality. An enzyme cocktail consisting of cellulase, xylanase, and pectinase and five independent variables (enzyme concentration, incubation time, incubation temperature, tempered wheat moisture content, and tempering water pH) were manipulated in a response surface methodology (RSM) central composite design. A single pure cultivar of hard red winter wheat was tempered under defined conditions and milled on a Ross experimental laboratory mill. Some treatment combinations affected flour yield from the break rolls more than that from the reduction rolls. However, a maximum for flour yield was not found in the range of parameters studied. Though treatments did not affect the optimum water absorption for breadmaking, enzyme-treated flours produced dough exhibiting shorter mixing times and slack and sticky textures compared with the control. Regardless of differences in mixing times, specific loaf volumes were not significantly different among treatments. Crumb firmness of bread baked with flour milled from enzyme-treated wheat was comparable to the control after 1 day but became firmer during storage up to 5 days

Electromagnetic Biostimulation of Living Cultures for Biotechnology, Biofuel and Bioenergy Applications

The surge of interest in bioenergy has been marked with increasing efforts in research and development to identify new sources of biomass and to incorporate cutting-edge biotechnology to improve efficiency and increase yields. It is evident that various microorganisms will play an integral role in the development of this newly emerging industry, such as yeast for ethanol and Escherichia coli for fine chemical fermentation. However, it appears that microalgae have become the most promising prospect for biomass production due to their ability to grow fast, produce large quantities of lipids, carbohydrates and proteins, thrive in poor quality waters, sequester and recycle carbon dioxide from industrial flue gases and remove pollutants from industrial, agricultural and municipal wastewaters. In an attempt to better understand and manipulate microorganisms for optimum production capacity, many researchers have investigated alternative methods for stimulating their growth and metabolic behavior. One such novel approach is the use of electromagnetic fields for the stimulation of growth and metabolic cascades and controlling biochemical pathways. An effort has been made in this review to consolidate the information on the current status of biostimulation research to enhance microbial growth and metabolism using electromagnetic fields. It summarizes information on the biostimulatory effects on growth and other biological processes to obtain insight regarding factors and dosages that lead to the stimulation and also what kind of processes have been reportedly affected. Diverse mechanistic theories and explanations for biological effects of electromagnetic fields on intra and extracellular environment have been discussed. The foundations of biophysical interactions such as bioelectromagnetic and biophotonic communication and organization within living systems are expounded with special consideration for spatiotemporal aspects of electromagnetic topology, leading to the potential of multipolar electromagnetic systems. The future direction for the use of biostimulation using bioelectromagnetic, biophotonic and electrochemical methods have been proposed for biotechnology industries in general with emphasis on an holistic biofuel system encompassing production of algal biomass, its processing and conversion to biofuel

Investigation of the atmospheric and surface ocean pCO/sub 2/ in the Indian Ocean. Final technical report

The results of measurements for the concentration of CO/sub 2/ in the marine air and the partial pressure of CO/sub 2/ (pCO/sub 2/) in the surface ocean water obtained during the Geosecs Expedition in the north and south Indian Oceans, December 1977 through April 1978 are summarized. The area studied covers 13/sup 0/N to 64/sup 0/S in latitudes and 55/sup 0/E to 115/sup 0/E in longitudes. It has been found that the atmospheric CO/sub 2/ concentration in the southern hemisphere south of 15/sup 0/S is remarkably constant at 334 +- ppM (expressed as mole fraction of CO/sub 2/ in dry air) throughout the period of this investigation. The CO/sub 2/ concentration in the northern hemisphere from the equator to 13/sup 0/N exceeds that in the southern hemisphere by up to 5 ppM. The Inter-Tropical Convergence Zone (ITCZ) appears to represent a transition zone for the atmosphere CO/sub 2/ distribution. The surface water pCO/sub 2/ values in the Indian Ocean range from 300 microatm. to 360 microatm. The highest values were observed in the Arabian Sea, and appear to be due to the low alkalinity water flowing out of the Red Sea. The Indian equatorial water has a maximum pCO/sub 2/ value of about 335 microatm., which is about 10 microatm. (or 3%) greater than that in the atmosphere. The Indian Ocean data were combined with those previously obtained in the Pacific and Atlantic Oceans to yield a global mean pCO/sub 2/ value for the surface ocean water. It is found that the global mean pCO/sub 2/ for the world oceans is 10 +- 8 microatm. lower than the mean atmospheric pCO/sub 2/ value. This indicates that the net transfer rate of CO/sub 2/ from the atmosphere to the oceans corresponds to 50 (+-40)% of the industrial CO/sub 2/ production rate