Passive polarization converter in SiON technology

A passive polarization converter has been realized in silicon oxynitride (SiON) technology. The device is a grating assisted codirectional coupler consisting of segments of asymmetrically etched ridge waveguides. By using a double-masking technique, the fabrication of the device is tolerant with respect to the alignment of the required masks. Conversion efficiencies up to 0.98 (TE¿TM and TM¿TE) and insertion losses of 3 dB/cm have been measured. Using 2-D beam propagation method simulations, an observed beat pattern in the converter could be explained as due to a leaky mode, which is captured in the grating structur

Prediction of thickness limits of ideal polar ultrathin films

Competition between electronic and atomic reconstruction is a constantly recurring theme in transition-metal oxides. We use density functional theory calculations to study this competition for a model system consisting of a thin film of the polar, infinite-layer structure ACuO2 (A=Ca, Sr, Ba) grown on a nonpolar, perovskite SrTiO3 substrate. A transition from the bulk planar structure to a chain-type thin film accompanied by substantial changes to the electronic structure is predicted for a SrCuO2 film fewer than five unit cells thick. An analytical model explains why atomic reconstruction becomes more favorable than electronic reconstruction as the film becomes thinner, and suggests that similar considerations should be valid for other polar films

Sticking together or falling apart? Solidarity in an era of individualization and globalization

"This book examines, both theoretically and empirically, the impact of globalization and individualization on social solidarity. It focuses both on informal solidarity, such as volunteering, charitable giving, and informal care, and on formal solidarity, such as social benefits and development aid. It challenges the common belief that social solidarity is endangered by the increasing competition and capital flows between countries and by growing selfishness of modern citizens. The book scrutinizes the theoretical arguments that both informal solidarity and social solidarity organized through the welfare state are eroding. Empirically, it is the first thorough study of international comparative data on solidarity, globalization and individualization. The book concludes that, overall, solidarity is rising rather than declining. The impact of globalization and individualization is much more ambiguous than is often contended. While particular aspects of globalization and individualization might harm solidarity, other elements foster solidarity instead." [author's abstract]Dit boek onderzoekt in theoretisch en empirisch opzicht welke gevolgen globalisering en individualisering hebben voor solidariteit. Het besteedt aandacht aan informele solidariteit, zoals vrijwilligerswerk en mantelzorg, en aan formele solidariteit, zoals sociale uitkeringen en ontwikkelingshulp. Het plaatst kanttekeningen bij het wijd verbreide geloof dat de groeiende internationale concurrentie en kapitaalstromen en het toenemende egocentrisme van moderne burgers de solidariteit ondergraven

Tetragonal CuO: A new end member of the 3d transition metal monoxides

Monoclinic CuO is anomalous both structurally as well as electronically in the 3$d$ transition metal oxide series. All the others have the cubic rock salt structure. Here we report the synthesis and electronic property determination of a tetragonal (elongated rock salt) form of CuO created using an epitaxial thin film deposition approach. In situ photoelectron spectroscopy suggests an enhanced charge transfer gap $\Delta$ with the overall bonding more ionic. As an end member of the 3d transition monoxides, its magnetic properties should be that of a high $T_N$ antiferromagnet

HOW CRITICAL IS THE CHOICE OF DISTANCE-BASED MEASURES IN STUDYING TUMBLE TURN PERFORMANCE?

The turn is a crucial part of swim races and therefore requires systematic investigation. Yet, many different measures of turn performance are used in the literature. This study aimed to examine the level of agreement and the sensitivity of six fixed-distance based performance measures of the tumble turn. Tumble turn data of 10 Dutch elite level swimmers were analysed using those measures. The overall level of agreement was high between all measures (R ranging from 0.91 to 0.99). However, if the swimmers were ranked according to each of those measures, not all performance measures resulted in the same ranking. In particular, the rankings for measures with an exist distance of 10 m deviated from those for measures with an exit distance of 5 or 15 m. This finding suggests that the performance measures of interest are sensitive to different phases of the turn

Authentication and authorisation in entrusted unions

This paper reports on the status of a project whose aim is to implement and demonstrate in a real-life environment an integrated eAuthentication and eAuthorisation framework to enable trusted collaborations and delivery of services across different organisational/governmental jurisdictions. This aim will be achieved by designing a framework with assurance of claims, trust indicators, policy enforcement mechanisms and processing under encryption to address the security and confidentiality requirements of large distributed infrastructures. The framework supports collaborative secure distributed storage, secure data processing and management in both the cloud and offline scenarios and is intended to be deployed and tested in two pilot studies in two different domains, viz, Bio-security incident management and Ambient Assisted Living (eHealth). Interim results in terms of security requirements, privacy preserving authentication, and authorisation are reported

You cannot regulate empty houses away

Posted by Christian Hilber (SERC & LSE), Paul Cheshire (SERC & LSE) and Hans Koster (VU Amsterdam) “Almost 57,000 homes in London stand empty…” writes David Smith in the Guardian on May 4th. This he claims is a significant cause of London’s housing problem and the “Key to this is tackling buy-to-leave investing.” The answer to this ‘problem’ is for the mayor to refuse planning permission and for Boroughs ”…to introduce planning restrictions …to prohibit the deliberate practice of letting properties lie empty.“ This is not a view unique to David Smith. For example, the well-known architect Lord Rogers in arguing against the desirability of permitting offices to be converted to housing to help with London’s housing shortage noted: “Why should we rush to convert office blocks when we already have three-quarters of a million homes in England lying empty.

Regulating housing vacancies away? The paradoxical effects of mismatch

Policy makers agree that vacant houses are undesirable. Moreover the existence of empty houses is used as an argument for allocating less land for new construction. So higher vacancy rates tend to trigger tighter restrictions on the supply of land. Such tighter restrictions lead to higher prices and, because of the incentives this creates for occupying housing, to lower housing vacancies (‘opportunity cost effect’). There is, however, a second effect ignored by planners: more restrictive planning policies impede the matching process in housing markets so leading to higher vacancies (‘mismatch effect’). Which of these two forces dominates is an empirical question. This is our focus here. Addressing potential reverse causation and other endogeneity concerns, we use a unique panel data set on land use regulation for 350 Local Authorities in England from 1981 to 2011. Our results show that tighter local planning constraints increase local housing vacancy rates, suggesting that the mismatch effect dominates. A one standard deviation increase in local regulatory restrictiveness causes the average local vacancy rate to increase by about 0.9 percentage points (23 percent). The results are economically meaningful and show that pointing to the existence of vacant houses as a reason for being more restrictive in allocating land for housing is counterproductive