Selection Bias in Educational Transition Models: Theory and Empirical Evidence

Most studies which use Mare’s (1980, 1981) seminal model of educational transitions find that the effect of family background variables decreases across educational transitions. Cameron and Heckman (1998, 2001) have argued that this “waning coefficients” phenomenon might be driven by selection on unobserved variables. This paper, first, analyzes theoretically how selection on unobserved variables leads to waning coefficients and, second, illustrates empirically how selection affects estimates of the effect of family background variables on educational transitions. Our empirical analysis which uses data from the United States, United Kingdom, Denmark, and the Netherlands shows that the effect of family background variables on educational transitions is largely constant across transitions when we control for selection on unobserved variables. We also discuss the inherent difficulties in estimating educational transition models which deal effectively with selection on unobserved variables.

Jet energy scale setting with "Gamma+Jet" events at LHC energies. Detailed study of the background suppression

The possibilities of the background events suppression, based on the QCD subprocesses of qg-, gg-, qq- scattering with big cross sections, to the signal \gpj events are studied. Basing on the introduced selection criteria, the background suppression factors and signal events selection efficiencies and the number of the events, that can be collected at LHC with low luminosity L=10^{33}cm^2 s^{-1} during one month of continuous work, are determined.Comment: 23 pages, 9 figures, uses cernrep.cls style fil

Gene expression programming approach to event selection in high energy physics

Gene Expression Programming is a new evolutionary algorithm that overcomes many limitations of the more established Genetic Algorithms and Genetic Programming. Its first application to high energy physics data analysis is presented. The algorithm was successfully used for event selection on samples with both low and high background level. It allowed automatic identification of selection rules that can be interpreted as cuts applied on the input variables. The signal/background classification accuracy was over 90% in all cases

The Rise of a Magnetic Flux Tube in a Background Field: Solar Helicity Selection Rules

The buoyant transport of magnetic fields from the solar interior towards the surface plays an important role in the emergence of active regions, the formation of sunspots and the overall solar dynamo. Observations suggest that toroidal flux concentrations often referred to as "flux tubes", rise from their region of initiation likely in the solar tachocline towards the solar surface due to magnetic buoyancy. Many studies have assumed the existence of such magnetic structures and studied the buoyant rise of an isolated flux tube in a quiescent, field-free environment. Here, motivated by their formation (Cline et al. 2003; Brummell et al. 2002), we relax the latter assumption and study the rise of a toroidal flux tube embedded in a large-scale poloidal background magnetic field. We find that the presence of the large-scale background field severely affects the dynamics of the rising tube. A relatively weak background field, as low as 6% of the tube strength, can destroy the rise of a tube that would otherwise rise in the absence of the background field. Surprisingly, the rise of tubes with one sign of the twist is suppressed by a significantly weaker background field than the other. This demonstrates a potential mechanism for the selection of the preferred helicity of rising and emerging tubes for the solar case that is commensurate with many features of the hemispherical rule.Comment: 9 pages, 5 figures, accepted for publication in ApJ

The Development of the Irish Private Health Insurance Market and Evidence of Selection Effects Therein

This paper tracks the development of the Irish private health insurance market, both in terms of its legislative background and the development of competition. Literature on adverse selection and risk selection is then reviewed. Data from two surveys of consumers are then analysed to determine whether evidence exists of adverse selection or risk selection in the Irish private health insurance market. Both of these issues are relevant in the context of the debate over risk equalisation in the market in Ireland.Private health insurance, adverse selection, risk selection

Characterization, 1064 nm photon signals and background events of a tungsten TES detector for the ALPS experiment

The high efficiency, low-background, and single-photon detection with transition-edge sensors (TES) is making this type of detector attractive in widely different types of application. In this paper, we present first characterizations of a TES to be used in the Any Light Particle Search (ALPS) experiment searching for new fundamental ultra-light particles. Firstly, we describe the setup and the main components of the ALPS TES detector (TES, millikelvin-cryostat and SQUID read-out) and their performances. Secondly, we explain a dedicated analysis method for single-photon spectroscopy and rejection of non-photon background. Finally, we report on results from extensive background measurements. Considering an event-selection, optimized for a wavelength of $1064~{\rm nm}$, we achieved a background suppression of $\sim 10^{-3}$ with a $\sim 50~\%$ efficiency for photons passing the selection. The resulting overall efficiency was $23~\%$ with a dark count rate of $8.6 \cdot 10^{-3}~{\rm s}^{-1}$. We observed that pile-up events of thermal photons are the main background component.Comment: 17 pages, 9 figures. Accepted by Journal of Modern Optic