A meta-analysis of wage-risk estimates of the value of a statistical life

This paper presents the results of a meta-analysis of estimates of the value of statistical life (VOSL). Data on the sample characteristics, data sources and analytical approach used to derive some 60 separate estimates in 17 published papers are used in the analysis. Tests lead us to reject the hypothesis that this sample shows evidence of publication bias. A meta-regression of these estimates provides evidence that VOSL is increasing in income but is invariant with respect to baseline risk. Controlling for aspects of the sample, data sources and analytical approach allows us to derive a best estimate of the VOSL of around $7 million

Simple models and concepts as tools for the study of sustained soil productivity in long-term experiments. I. New soil organic matter and residual effect of P from fertilizers and farmyard manure in Kabete, Kenya

The rough outcomes of a long-term experiment in Kenya were (re-)interpreted using simple models to find causes of success or failure with regard to sustained soil productivity. A two- pools model calculated the development of soil organic matter, and a practical equation estimated the residual effect of fertilizer P. Relative mineralization rate was 4 and 8% y(-1) for original and newly formed soil organic carbon (SOC). Maize yielded 0.25 and 1.1 t ha(-1) per g kg(-1) of original and new SOC, respectively. Yields of fertilized maize increased initially as a result of increasing residual effects of applied P, but decreased later presumably because SOC declined to below a critical level of 16 g kg(-1). To maintain SOC above this level, about 10 tons of farmyard manure (dry matter) must be applied annually. Agronomic nutrient use efficiencies for fertilizer N and P were low, but the residual effect of P was high. The simple model outlined half a century ago adequately calculated build-up of new soil organic matter. The estimated residual effect of fertilizer P explained increasing crop responses to repeated P applications. The absence of data on nutrient uptake by the crop strongly limited the understanding of the experimental results

Do scenario context and question order influence WTP? The application of a model of uncertain WTP to the CV of the morbidity impacts of air pollution

This paper presents a general framework for modelling responses to contingent valuation questions when respondents are uncertain about their ‘true’ WTP. These models are applied to a contingent valuation data set recording respondents’ WTP to avoid episodes of ill-health. Two issues are addressed. First, whether the order in which a respondent answers a series of contingent valuation questions influences their WTP. Second, whether the context in which a good is valued (in this case the information the respondent is given concerning the cause of the ill-health episode or the policy put into place to avoid that episode) influences respondents’ WTP. The results of the modelling exercise suggest that neither valuation order nor the context included in the valuation scenario impact on the precision with which respondents answer the contingent valuation questions. Similarly, valuation order does not appear to influence the mean or median WTP of the sample. In contrast, it is shown that in some cases, the inclusion of richer context significantly shifts both the mean and median WTP of the sample. This result has implications for the application of benefits transfer. Since, WTP to avoid an episode of ill-health cannot be shown to be independent of the context in which it is valued, the validity of transferring benefits of avoided ill-health episodes from one policy context to another must be called into question

Simple models and concepts as tools for the study of sustained soil productivity in long-term experiments. II. Crop nutrient equivalents, balanced supplies of available nutrients, and NPK triangles

Two NPK factorial trials, one in Vietnam and one in The Netherlands were (re-)analyzed to find causes of success or failure with regard to sustained soil productivity, using the concept of crop nutrient equivalents (CNE). A (k)CNE is the quantity of a nutrient that, under conditions of balanced nutrition, has the same effect on yield as 1 (k)g of nitrogen. The percentages the nutrients take in the (k)CNE sum of N, P and K are plotted along the sides of a triangle. Soil, crop and input NPK are indicated in the triangle. Balanced crop NPK is found in the centre of the triangle, and required NPK inputs are on a straight line in the extension of the line trough the point of soil NPK and the centre. Experimental inputs were compared with inputs required for balanced NPK. In Vietnam, responses to P and soil available N:P:K pointed to severe shortage of P. Rice yields increased over time in dry but not in wet seasons. The lower yields in wet seasons were ascribed to insufficiently long periods between the dry and the next wet seasons for replenishment of labile soil P. In the Netherlands, four crops were grown in rotation on a former sea bottom. Only N had a strong effect on yield. Soil available N:P:K revealed low N, very high K and medium P. Recovery of fertilizer N was high because of capillary rise of groundwater and absence of leaching. In both trials, first-season chemical crop analysis would directly have detected disproportions of soil available N, P and K. This knowledge could have improved the experimental designs, optimized nutrient use efficiency and minimized losses of N and K to the environmen

Short-term changes in global cloud cover and in cosmic radiation

Galactic cosmic rays (GCR) have been suggested as a possible contributory mechanism to cloud formation. If these are significant then, in addition to the similarity between long-term (years) changes in GCR and cloud cover, there should also be a similarity over shorter (days) time scales. This paper reports an analysis of changes in global cloud cover and GCR recorded at 3 hourly intervals over 22 years. There is a significant correlation between short-term changes in low cloud cover over northern and southern hemispheres, consistent with about 3% of the variation arising from common factors. However, GCR is not a major factor responsible for cloud cover changes. There is an association between short-term changes in low cloud cover and galactic cosmic radiation over a period of several days. This could arise if approximately 3% of the variations in cloud cover resulted from GCR

The curve complex and covers via hyperbolic 3-manifolds

Rafi and Schleimer recently proved that the natural relation between curve complexes induced by a covering map between two surfaces is a quasi-isometric embedding. We offer another proof of this result using a distance estimate via hyperbolic 3-manifolds.Comment: 5 page

Characteristics of a production route for filamentary Nb3Sn superconductors based on a reaction between niobium and Nb6Sn5

Monofilamentary Nb3Sn superconductors have been made by application of a reaction between Nb6Sn5 powder and niobium. The layer thickness of Nb3Sn shows a parabolic time dependence, implying diffusion-controlled layer growth. The activation energy for diffusion is 268 kJ mol−1. The critical temperature Tc is about 17.5 K and the overall critical current density Jc is about 5 × 108 A m−2at 8 T, both after annealing at 675 °C. These values are comparable with those obtained for so-called ECN-type superconductors, which are based on a reaction between NbSn2 powder and niobium. An advantage of the use of Nb6Sn5 powder in comparison with NbSn2 is the kinetics of growth of Nb3Sn, which allows a lowering of the reaction temperature to 600–625 °C for filament diameters of about 30 μm

Travelling waves in nonlinear diffusion-convection-reaction

The study of travelling waves or fronts has become an essential part of the mathematical analysis of nonlinear diffusion-convection-reaction processes. Whether or not a nonlinear second-order scalar reaction-convection-diffusion equation admits a travelling-wave solution can be determined by the study of a singular nonlinear integral equation. This article is devoted to demonstrating how this correspondence unifies and generalizes previous results on the occurrence of travelling-wave solutions of such partial differential equations. The detailed comparison with earlier results simultaneously provides a survey of the topic. It covers travelling-wave solutions of generalizations of the Fisher, Newell-Whitehead, Zeldovich, KPP and Nagumo equations, the Burgers and nonlinear Fokker-Planck equations, and extensions of the porous media equation. \u

Localization and blow-up of thermal waves in nonlinear heat conduction with peaking

The authors consider the initial-boundary value problem for the porous medium equation ut =(um)xx in (0,∞)×(0,T), where m>1, 00}as t↑T under the hypothesis that ψ(t)↑∞ as t↑T is investigated. The effect of localization of the blowing-up boundary function when lim sup t↑T ζ(t)<∞ is investigated. It is established that localization occurs if and only if lim sup t↑T (∫ t 0 ψ m (s)ds)/ψ(t)<∞, and some estimates concerning the asymptotic behaviour of the solution near the singular point t=T and in the blow-up set Ω={x≥0: lim sup t↑T u(x,t)=∞} are given. Various estimates from above and below on the length ω=supΩ of the blow-up set are obtained. These theorems make more precise some previous results concerning the localization of the boundary blowing-up function which were given in the book by A. A. Samarskiĭ, the reviewer et al. [Peaking modes in problems for quasilinear parabolic equations(Russian), "Nauka'', Moscow, 1987]. Proofs of the theorems are based on comparison with some explicit solutions and on construction of different kinds of weak sub- and supersolutions. The authors use some special integral identities and estimates of the solution and its derivatives by means of the maximum principle. A special comparison theorem above blow-up sets for different boundary functions is proved