Thin Ice Target for 16^{16}O(p,p') experiment

A windowless and self-supporting ice target is described. An ice sheet with a thickness of 29.7 mg/cm$^2$ cooled by liquid nitrogen was placed at the target position of a magnetic spectrometer and worked stably in the $^{16}$O$(p,p')$ experiment at $E_{p}=392$ MeV. Background-free spectra were obtained.Comment: 14 pages, 4 figures, Nucl. Instr. & Meth. A (in press

Secant varieties of P^2 x P^n embedded by O(1,2)

We describe the defining ideal of the rth secant variety of P^2 x P^n embedded by O(1,2), for arbitrary n and r at most 5. We also present the Schur module decomposition of the space of generators of each such ideal. Our main results are based on a more general construction for producing explicit matrix equations that vanish on secant varieties of products of projective spaces. This extends previous work of Strassen and Ottaviani.Comment: 21 page

On the social opportunity cost of unemployment

The handling of unemployment is a central issue in cost-benefit analysis. Typically, the shadow price of employing an unemployed is derived by considering a marginal change in the employment constraint faced by an unemployed or rather an underemployed. In contrast, in this paper, we consider the discrete shift from unemployment to (full) employment. The result provides guidance how to estimate the social cost of recruiting otherwise unemployed to a project. It is shown that the social cost is overestimated by using the private reservation wage. The common practice of adding different cost items is shown to be flawed

Paying a Premium for "Green Steel": Paying for an Illusion?

The iron and steel industry generates around 10 % of global greenhouse gas emissions. The bulk of the emissions originates from the iron ore reduction. In this reduction, coal is used as a reagent. Steelmakers could switch to hydrogen-based direct reduction using hydrogen instead of coal as a reagent to reduce iron ore to pig iron. This would eliminate the CO2 emissions from the equivalent process in a traditional blast furnace. However, the process requires massive amounts of electricity. This paper looks at the economics of such a switch to "green steel." We assess a marginal increase in the production of a hypothetical green steelmaker. We also undertake an investment appraisal of a green plant, based on an ongoing installation in Northern Sweden, but also briefly consider a possible/planned investment in the US. This appraisal is complemented by computing the survival function for the net present value in a systematic sensitivity analysis. It seems highly unlikely that a green steel plant can be socially profitable. If the green plant displaces conventional steel produced within the European Union's cap-and-trade system for greenhouse gases, total emissions remain more or less unaffected; permits and emissions are simply reshuffled. Hence, if end-users of green steel pay a premium, they might pay for an illusion

Limit distributions for large P\'{o}lya urns

We consider a two-color P\'{o}lya urn in the case when a fixed number $S$ of balls is added at each step. Assume it is a large urn that is, the second eigenvalue $m$ of the replacement matrix satisfies $1/2<m/S\leq1$. After $n$ drawings, the composition vector has asymptotically a first deterministic term of order $n$ and a second random term of order $n^{m/S}$. The object of interest is the limit distribution of this random term. The method consists in embedding the discrete-time urn in continuous time, getting a two-type branching process. The dislocation equations associated with this process lead to a system of two differential equations satisfied by the Fourier transforms of the limit distributions. The resolution is carried out and it turns out that the Fourier transforms are explicitly related to Abelian integrals over the Fermat curve of degree $m$. The limit laws appear to constitute a new family of probability densities supported by the whole real line.Comment: Published in at http://dx.doi.org/10.1214/10-AAP696 the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

Computational Aspects of Optional P\'{o}lya Tree

Optional P\'{o}lya Tree (OPT) is a flexible non-parametric Bayesian model for density estimation. Despite its merits, the computation for OPT inference is challenging. In this paper we present time complexity analysis for OPT inference and propose two algorithmic improvements. The first improvement, named Limited-Lookahead Optional P\'{o}lya Tree (LL-OPT), aims at greatly accelerate the computation for OPT inference. The second improvement modifies the output of OPT or LL-OPT and produces a continuous piecewise linear density estimate. We demonstrate the performance of these two improvements using simulations