Model Specifications for Analyzing the Role and Long-Run Impacts of Resources, the Environment, and Technological Change on the Food Production System

A recent working paper by Pierre Crosson ("Resources, Technology and Environment in Agricultural Development." WP-79-103, October 1979) provides an intellectual background for research being undertaken by FAP on "Limits and Consequences of Food Production Technologies". The primary focus of this research effort will be on developing a set of models that will increase understanding of the short and long-run impacts of policies on the resources-technology-environment (R-T-E) system in agricultural production. This paper briefly sketches two model specifications that could be used to analyze the R-T-E issues discussed by Crosson. One model is specified to determine the "socially" optimal allocation of resources over time under R-T-E constraints, while the second model is specified to trace out the temporal R-T-E effects of agricultural producers' decisions under various R-T-E policies and assumptions. Both models are rather ambitious from a computational viewpoint and in terms of data requirements. It is suggested that initial modeling efforts focus on a few regions or watersheds, rather than countries. Then, as experience is gained with these small area models and information developed about the extremely complex R-T-E constraints, the modeling effort could be expanded to country models. Finally, country models could be linked to form a world R-T-E model

Meningiomas occurring during long-term survival after treatment for childhood cancer

Childhood cancer is rare but improvements in treatment over the past five decades have resulted in a cohort of more than 30,000 long-term survivors of childhood cancer in the UK with more added annually. These long-term survivors are at risk of late effects of cancer treatment which replace original tumour recurrence as the leading cause of premature death. Second neoplasms are a particular risk and in the central nervous system meningiomas occur increasingly with increased radiation dose to central nervous system tissue and length of time after exposure, resulting in a 500-fold increase above that expected in the normal population by 40 years of follow up. This multidisciplinary author group and others met to discuss the issue. Our pooled information, and consensus that screening should only follow symptoms, was published online by the Royal College of Radiologists in 2013. We outline here the current knowledge and management of these neoplasms secondary to childhood cancer treatment

Socially Optimal Agricultural Erosion-Sedimentation Control Considering both Soil Conservation and Water Quality

Social concern about erosion and sedimentation arises principally from two factors. One factor is the future social costs in the form of reduced productivity that arise from erosion, while the second is the current and to some extent future social costs resulting from sediment pollution. This paper presents a dynamic non-linear optimization model that can be used to determine the socially optimal level of soil conservation when both of the above factors are considered. The objective function in the model is the present value of consumers' plus producers' surplus less off-site sediment damages, over a long planning horizon. The model is applied to a watershed that is fairly representative of the Corn Belt. Results indicate that substantially more soil conservation than presently occurs is justified from society's viewpoint

Bronchodilator tolerance and rebound bronchoconstriction during regular inhaled β -agonist treatment

AbstractThere is uncertainty about the development of airway tolerance to β -agonists and the phenomenon of rebound bronchoconstriction on β -agonist withdrawal. We have recently completed a study of the regular terbutaline and budesonide treatment in asthma. We report our observations on the effect of starting and stopping terbutaline treatment on morning and evening peak flows.The study was a randomized four-way, double-dummy, cross-over comparison of regular inhaled terbutaline (500–1000 μ g four times daily), budesonide, combined treatment and matching placebo. Each treatment was given for 6 weeks following a 4 week single-blind placebo washout. Ipratropium was used for symptom relief. No other asthma medication was permitted during either the treatment or wash-out periods. Evaluable data were obtained from 52 subjects for both placebo and terbutaline treatment. Changes in mean morning and evening peak flows during terbutaline treatment were compared to the baseline peak flows during the last 2 weeks of the preceding washout. The peak flow changes on stopping terbutaline were also analysed.Mean morning peak flow was not significantly different during terbutaline treatment when compared to either baseline or placebo treatment. Evening peak flows were significantly higher during terbutaline treatment [mean increase 23·1l min−1(95%CI=18·8, 27·4)]. Analysis of the peak flow changes on a day-by-day basis revealed an initial increase in morning peak flows for the first 2 days of treatment of 19·2 and 13·4l min−1[increases of 25·0 and 17·3l min−1in comparison with the corresponding values during placebo (P<0·01)] followed by a return to baseline. The increase in evening peak flows was also greater for the first 2 days of treatment than for the remainder of the treatment period (P<0·01). On ceasing terbutaline treatment there was a fall in mean morning peak flow below the baseline on the following morning of 21·6l min−1(P<0·05 compared to placebo).The temporary increase in morning peak flows and greater than expected rise in evening peak flows for the first 2 days of treatment suggest the development of tolerance to the bronchodilator effect of terbutaline. Similarly, the fall in morning peak flows on treatment withdrawal suggests rebound bronchoconstriction. These effects are likely to be mediated by downregulation of the β -receptor during treatment. The clinical significance of these changes is uncertain in view of the stability of overall asthma control during terbutaline treatment, but sudden withdrawal of β -agonist treatment could conceivably lead to a deterioration in asthma control

The Importance of Monitoring Sleep within Adolescent Athletes: Athletic, Academic, and Health Considerations

Opinion piece

Sleep Medication and Athletic Performance—The Evidence for Practitioners and Future Research Directions

Opinion piece

Yang-Mills Action from Open Superstring Field Theory

We calculate the effective action for nonabelian gauge bosons up to quartic order using WZW-like open superstring field theory. After including level zero and level one contributions, we obtain with 75% accuracy the Yang-Mills quartic term. We then prove that the complete effective action reproduces the exact Yang-Mills quartic term by analytically performing a summation over the intermediate massive states.Comment: 10 page

The influence of polarity on flux and rejection behaviour in solvent resistant nanofiltration - experimental observations

The separation characteristics of a dense polydimethylsiloxane (PDMS) membrane were studied using mixtures comprising xylene, cyclohexane or n-heptane with oxygenate components at concentrations up to 75%. The effects of polarity on flux and rejection performance were determined through a test matrix of solvent type, concentration, filtration pressure, crossflow rate and the degree of membrane crosslinking. In all cases involving alcohols, the more polar compound in the feed mixture was partially rejected by the membrane and the extent of rejection was dependent on the polarity as quantified by solubility parameter. The rejection-concentration profiles for several alcohol/solvent mixtures exhibited a maximum, with the highest rejection around 30%. Mixtures containing MTBE did not separate, i.e. no rejection was observed. Rejection increased with increasing pressure and crossflow rate but was largely unaffected by the degree of membrane crosslinking. Component flux was affected by the oxygenate concentration in the mixture, which was attributed in part to changes in the degree of membrane swelling with composition. Experimental findings suggest that the separation is primarily governed by multicomponent solvent/oxygenate/membrane swelling equilibria, and results compare favourably with swelling isotherms available in the open literature

Magnetically Stabilized Luminescent Excitations in Hexagonal Boron Nitride

Magnetically stabilized luminescence is observed in hexagonal boron nitride. The luminescence is induced by absorption of cold neutrons and is in the visible region. In the absence of a magnetic field, the photon emission level is observed to decay over several hundred seconds. A fraction of this luminescence can be suppressed if the temperature is T <~ 0.6 K and the magnetic field is B >~ 1.0 T. Subsequent to irradiation and suppression, luminescence can be induced by an increase in T or lowering of B. Possible explanations include stabilization of triplet states or the localization and stabilization of excitons.Comment: 11 pages, 7 figures, to appear in the Journal of Luminescenc

Time Evolution in Superstring Field Theory on non-BPS brane.I. Rolling Tachyon and Energy-Momentum Conservation

We derive equations of motion for the tachyon field living on an unstable non-BPS D-brane in the level truncated open cubic superstring field theory in the first non-trivial approximation. We construct a special time dependent solution to this equation which describes the rolling tachyon. It starts from the perturbative vacuum and approaches one of stable vacua in infinite time. We investigate conserved energy functional and show that its different parts dominate in different stages of the evolution. We show that the pressure for this solution has its minimum at zero time and goes to minus energy at infinite time.Comment: 16 pages, 5 figures; minor correction