The Impact of Skills on Remigration Flows

More than ten years after the seminal paper by Borjas and Bratsberg (1996) modeling the impact of skills on remigration the empirical evidence on that theory is still mixed. Our paper is to shed light on that issue. Using the GSOEP we test two hypotheses derived from Borjas and Bratsberg (1996) while allowing for endogeneity of host country specific capital. Our results give strong support for their theory. Additionally a sensitivity analysis shows that the insignificance of education in previous studies is due to the test design conducted and cannot be interpreted as falsification of Borjas’ and Bratsberg’s (1996) theory.return migration, selective return migration

A frequency-independent boundary element method for scattering by two-dimensional screens and apertures

We propose and analyse a hybrid numerical-asymptotic $hp$ boundary element method for time-harmonic scattering of an incident plane wave by an arbitrary collinear array of sound-soft two-dimensional screens. Our method uses an approximation space enriched with oscillatory basis functions, chosen to capture the high frequency asymptotics of the solution. Our numerical results suggest that fi�xed accuracy can be achieved at arbitrarily high frequencies with a frequency-independent computational cost. Our analysis does not capture this observed behaviour completely, but we provide a rigorous frequency-explicit error analysis which proves that the method converges exponentially as the number of degrees of freedom $N$ increases, and that to achieve any desired accuracy it is sufficient to increase $N$ in proportion to the square of the logarithm of the frequency as the frequency increases (standard boundary element methods require $N$ to increase at least linearly with frequency to retain accuracy). We also show how our method can be applied to the complementary "breakwater" problem of propagation through an aperture in an infinite sound-hard screen

Wave-number-explicit bounds in time-harmonic scattering

In this paper we consider the problem of scattering of time-harmonic acoustic waves by a bounded sound soft obstacle in two and three dimensions, studying dependence on the wave number in two classical formulations of this problem. The first is the standard variational/weak formulation in the part of the exterior domain contained in a large sphere, with an exact Dirichletto-Neumann map applied on the boundary. The second formulation is as a second kind boundary integral equation in which the solution is sought as a combined single- and double-layer potential. For the variational formulation we obtain, in the case when the obstacle is starlike, explicit upper and lower bounds which show that the inf-sup constant decreases like k −1 as the wave number k increases. We also give an example where the obstacle is not starlike and the inf-sup constant decreases at least as fast as k −2. For the boundary integral equation formulation, if the boundary is also Lipschitz and piecewise smooth, we show that the norm of the inverse boundary integral operator is bounded independently of k if the coupling parameter is chosen correctly. The methods we use also lead to explicit bounds on the solution of the scattering problem in the energy norm when the obstacle is starlike in which the dependence of the norm of the solution on the wave number and on the geometry are made explicit

Recovery of Polyphenols from Brewer’s Spent Grains

peer-reviewedThe recovery of antioxidant polyphenols from light, dark and mix brewer’s spent grain (BSG) using conventional maceration, microwave and ultrasound assisted extraction was investigated. Total polyphenols were measured in the crude (60% acetone), liquor extracts (saponified with 0.75% NaOH) and in their acidified ethyl acetate (EtOAc) partitioned fractions both by spectrophotometry involving Folin–Ciocalteu reagent and liquid-chromatography-tandem mass spectrometry (LC-MS/MS) methods. Irrespective of the extraction methods used, saponification of BSG yielded higher polyphenols than in the crude extracts. The EtOAc fractionations yielded the highest total phenolic content (TPC) ranging from 3.01 ± 0.19 to 4.71 ± 0.28 mg gallic acid equivalent per g of BSG dry weight. The corresponding total polyphenols quantified by LC-MS/MS ranged from 549.9 ± 41.5 to 2741.1 ± 5.2 µg/g of BSG dry weight. Microwave and ultrasound with the parameters and equipment used did not improve the total polyphenol yield when compared to the conventional maceration method. Furthermore, the spectrophotometric quantification of the liquors overestimated the TPC, while the LC-MS/MS quantification gave a closer representation of the total polyphenols in all the extracts. The total polyphenols were in the following order in the EtOAc fractions: BSG light > BSG Mix > BSG dark, and thus suggested BSG light as a sustainable, low cost source of natural antioxidants that may be tapped for applications in food and phytopharmaceutical industries

The PML for rough surface scattering

In this paper we investigate the use of the perfectly matched layer (PML) to truncate a time harmonic rough surface scattering problem in the direction away from the scatterer. We prove existence and uniqueness of the solution of the truncated problem as well as an error estimate depending on the thickness and composition of the layer. This global error estimate predicts a linear rate of convergence (under some conditions on the relative size of the real and imaginary parts of the PML function) rather than the usual exponential rate. We then consider scattering by a half-space and show that the solution of the PML truncated problem converges globally at most quadratically (up to logarithmic factors), providing support for our general theory. However we also prove exponential convergence on compact subsets. We continue by proposing an iterative correction method for the PML truncated problem and, using our estimate for the PML approximation, prove convergence of this method. Finally we provide some numerical results in 2D.(C) 2008 IMACS. Published by Elsevier B.V. All rights reserved

Growth, decline and locational change in the English silk industry of the nineteenth century: a study in historical geography

The English silk industry, by its extreme fluctuations in profitability and its widespread distribution makes an interesting geographical case study of some of the forces which affected the location of industry during the Industrial Revolution. This thesis sets out to analyse the industry's changing location in times of expansion and contraction, particularly in its mechanised branches, during the nineteenth century. The broad locational pattern of the silk industry was established during the eighteenth century when a considerable increase in the size of the industry was accompanied by spatial expansion: the old concentrations of manufacturing in London declined in importance and new centres, particularly in the Pennine province, but also in parts of southern England assumed greater significance. The first four chapters examine the factors, for example power supplies and competition for labour, which influenced its location. Because of its uncertain profitability, there were few districts in which silk could dominate the local labour force and so secure a measure of protection from stronger industries. Its labour force was thus liable to be eroded during the industry's frequent recessions and was only rebuilt with difficulty in subsequent booms. The supply of labour is therefore seen as a major factor affecting the changing location of silk manufacture, though competition for other resources, such as power and factory space were also significant, particularly in the Pennine province. The broad pattern of the industry's distribution had been established by the mid-nineteenth century and from this time there is a wealth of statistical information available for the size and distribution of the industry in the Factory Inspectors' Returns and the Census. Chapter 5 uses these sources to give a systematic account of the distribution and structure of the industry in about 1850. Despite its widespread distribution it is evident that there existed compact localities in which silk manufacturing was concentrated and that here the domestic, as well as the factory workers were found. Moreover, there were four districts, London, Lancashine the South West Pennines and Coventry which were the dominant centres of the trade and together accounted for most of the industry's employment. From an analysis of the technical data contained in the Factory Inspectors' Returns it is possible to distinguish some regional contrasts in the technical advancement and organisation of the industry. Chapter 6 concludes that in general silk manufacturing in the south was labour intensive and technically backward while in the Pennines contact and competition with the other textile trades made for a more advanced industry. Chapters 7 and 8 analyse the reaction in the various regions to one of the most extreme fluctuations in fortune that the industry experienced, in terms both of changing techniques and organisation and of the size and distribution of the labour force. Differences between the throwing and weaving branches in their response to boom and slump were apparent and the greater strength of the Pennine industry was again demonstrated. Finally Chapter 9 examines the long term decline of the industry after the Free Trade Treaty of 1860. Competition exposed the weaknesses of the industry and at a national level contraction was inevitable. But some of the regional specialisms had the ability to persist despite the general malaise, and it was not until the twentieth century that silk manufacturing was located almost entirely in one region, the South West Pennines

Masculinity, Medicine and Mechanization. The Construction of Occupational Health in Northern Ontario

This dissertation examines workplace issues and events that shaped men’s health, and the healthcare services in support of them, in northern Ontario’s resource extraction industries. Between 1890 and 1925 there were important transformations in the hardrock mining sector including: technological innovations and refinements of the materials and devices used to extract ores; the healthcare mandated and legislatively prescribed but challenging to deliver to frontier workspaces; and how the complex interactions of the men, their work, their communities, wartime demands and collective bargaining combined to construct new definitions of masculinity. Using quantitative data from the Ontario Bureau of Mines on the numbers of annual accidents and fatalities, a clearer understanding emerges that reveals how workingmen’s bodies were understood over time. Together with newspaper accounts, the reports of coroners’ juries, personal papers, doctors’ memoirs and popular histories, the role of work and workplace conditions clarifies how health was managed or how it suffered as the exploitation of the provinces natural resources began in earnest. The impact of World War One caused a wholesale change in the scale and importance of the mines and the men that worked them. This was seen in their solidarity, strength and successful strike immediately after the war and in fewer accidents and fatalities. The pace of change however faded in the post-war era. The gains that were made were kept and men’s health and safety never again saw the alarming losses as those enumerated here

Entropy Bound for the Classical Capacity of a Quantum Channel Assisted by Classical Feedback

We prove that the classical capacity of an arbitrary quantum channel assisted by a free classical feedback channel is bounded from above by the maximum average output entropy of the quantum channel. As a consequence of this bound, we conclude that a classical feedback channel does not improve the classical capacity of a quantum erasure channel, and by taking into account energy constraints, we conclude the same for a pure-loss bosonic channel. The method for establishing the aforementioned entropy bound involves identifying an information measure having two key properties: 1) it does not increase under a one-way local operations and classical communication channel from the receiver to the sender and 2) a quantum channel from sender to receiver cannot increase the information measure by more than the maximum output entropy of the channel. This information measure can be understood as the sum of two terms, with one corresponding to classical correlation and the other to entanglement.Comment: v2: 6 pages, 1 figure, final version published in conference proceeding

Development and validation of a fast gas chromatography combustion isotope ratio mass spectrometry method for the detection of epiandrosterone sulfate in urine

In doping control, to confirm the exogenous origin of exogenously administered anabolic androgenic steroids (AAS), a gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS) analysis is performed. Recently published work suggests that epiandrosterone sulfate (EpiAS) is a promising IRMS target compound for the detection of AAS, capable of prolonging the detection window. However, EpiAS is only excreted in urine in its sulfoconjugated form, while all other IRMS target compounds are excreted glucuronidated, meaning that EpiAS cannot be incorporated in the existing IRMS methods. A separate extensive sample preparation needs to be performed on this compound with a different hydrolysis and extraction procedure and a different liquid chromatography (LC) clean-up. The current work presents a new, fast, and easy to implement EpiAS IRMS method. The approach was based on the direct GC analysis of non-hydrolyzed EpiAS, making the solid phase extraction, hydrolysis, and acetylation step redundant. Sample preparation consisted of a simple liquid-liquid extraction, followed by LC fraction collection. A population study was performed to check compliance with the criteria drafted by the World Anti-Doping Agency (WADA). To verify the applicability of the developed approach, the method was applied to the samples of four administration studies (i.e. dehydroepiandrosterone (DHEA), testosterone gel (T gel), androstenedione (ADION), and intramuscular testosterone undecanoate. In contrast to previously published data, the strength of EpiAS as the target compound and the prolongation of the detection window in comparison with the conventional IRMS target compounds was less pronounced

Enumerating and indexing many-body intramolecular interactions:a graph theoretic approach

The central idea observes a recursive mapping of -body intramolecular interactions to -body terms that is consistent with the molecular topology. Iterative application of the line graph transformation is identified as a natural and elegant tool to accomplish the recursion. The procedure readily generalizes to arbitrary -body potentials. In particular, the method yields a complete characterization of -body interactions. The hierarchical structure of atomic index lists for each interaction order is compactly expressed as a directed acyclic graph. A pseudo-code description of the generating algorithm is given. With suitable data structures (e.g., edge lists or adjacency matrices), automatic enumeration and indexing of -body interactions can be implemented straightforwardly to handle large bio-molecular systems. Explicit examples are discussed, including a chemically relevant effective potential model of taurocholate bile salt