An Algorithmic Measurement of Technical Progress

In this paper we propose a measure of technological progress which is based on the information embedded in standard input-output tables. Well known duality properties enables one to establish a connection between the quantities necessary as inputs and the associated output and some auxiliary prices (like the wage-profit curves). We claim that properly tailored wage-profit frontiers may provide a basis for the measurement of technological progress. But the computation of these wage-profit frontiers is not trivial. A brute force algorithm for the computation of the wage-profit frontiers has high combinatorial complexity that would make its precise computation intractable. But thanks to an efficient algorithm that we have been able to devise we can now compute it. We consider this to be an important and original contribution. Here we present and apply this algorithm. Due to this improvement we can now use these wage-profit frontiers as benchmarks against which to measure technological progress: two new indices have been defined. These new tools have have been applied to the OECD input-output data 1970-2005 and the reslts are presented here.Technological Change, Convergence, Input-output analysis, Technological Frontier, Computational Techniques

Development and Characterisation of Strontium-containing Bioactive Glasses and Aluminium-free Glass Polyalkenoate Cements

Bioactive glass (BG) reactivity is the result of a special silicate structure, disrupted by the presence of alkali and earth-alkali metal ions. These glasses dissolve in body fluids and form a hydroxy-carbonated apatite (HCA) on their surface, which mimics the composition and structure of the mineral phase of bone. This feature, coupled with the release of biologically active ions, explains their excellent osseointegration. In the first part of this thesis, we investigated the effect of substituting strontium for calcium in a BG system based on SiO2-P2O5-Na2O-CaO. The reason for introducing strontium in a BG was driven by its strengthening effect on bone in the treatment of osteoporosis. The glass structure and physical properties were investigated by X-ray diffraction (XRD), solid state nuclear magnetic resonance (NMR), Fourier transform infrared (FTIR) spectroscopy and thermal analysis. Dissolution profiles and in vitro bioactivity of Sr-BG were investigated in Tris buffer and simulated body fluid by inductively coupled plasma (ICP) spectroscopy, XRD and FTIR. Glass cytotoxicity was assessed by culturing osteoblast-like cells (SaOs-2) on Sr-BG discs for 14 days. It was found that substitution of Sr for Ca does not modify the Q2 silicate structure of the glass, nor its orthophosphate environment. However, it expands and weakens the glass network, thus the glasses dissolved more rapidly with higher strontium content and formed more HCA. A live/dead cellular assay showed an increased cell proliferation for higher strontium containing glasses. Glass polyalkenoate cements (GPCs) also use the potential of reactive glasses to release multivalent cations, which cross-link the carboxylic groups of polyacid chains in aqueous solution to form a hard cement. GPCs do not shrink, do not have significant exotherm and have good adhesive properties. However, the use of commercial GPCs, based on fluoro-alumino-silicate glasses, has been limited to dentistry and minor surgery due to biocompatibility issues. Aluminium is known to have neurotoxic effect and inhibits remineralisation. The aim of the second part of this study was to investigate new glass compositions for the development of aluminium-free GPCs for orthopaedic applications. Sr-BG compositions were adapted for cement forming purpose by removing soda and including Mg2+, Zn2+ and Fe3+ to provide an alternative to Al3+. The selected cations are all naturally present in the body and can potentially enter into the glass network, mimicking the formation of Al- O-Si bonds present in conventional GPCs. The mechanical properties of the cements were assessed by performing compression and bonding strength tests, whereas their working (WT) and setting times were measured with an oscillating rheometer. Finally, cement cytotoxicity was evaluated by culturing SaOs-2 cells on cement discs. It was established that only high zinc containing glasses lead to cements with suitable mechanical properties to be used as bone cements. WT was short but increased up to two minutes by using citric acid as a chelating agent. The high Zn release from the cements induced cytotoxicity and predominated over the potential positive effect of Sr on cells

Desafíos y necesidades en la enseñanza del ladino entre diez activistas de la revitalización de la lengua

This article presents results from interviews with ten teachers engaged in Ladino (Judaeo-Spanish) revitalisation. The purpose of the study is to collect Ladino teachers’ experiences to understand the challenges they face and the needs they express to continue their activities. Challenges were related to students’ linguistic backgrounds, students’ and teachers’ confidence about expressing themselves in Ladino, and to views on language normativity. The teachers expressed needs concerning finding stable teacher positions, about creating a Ladino proficiency test and certificate, developing resources for language teaching, and updating Ladino’s vocabulary to reflect contemporary life. Creating venues for learners to use the language, and opportunities for Ladino teachers to meet and discuss pedagogical issues were seen as important. The teachers’ views differed considerably regarding questions on language norms, and an official language proficiency certificate. The results point to the need for further discussions, and for teacher development initiatives.Este artículo presenta los resultados de entrevistas con diez profesores comprometidos con la revitalización del ladino (judeoespañol). El propósito del estudio es recopilar las experiencias de docentes de ladino para comprender los desafíos que enfrentan y las necesidades que expresan para continuar con sus actividades. Los desafíos estaban relacionados con el perfil lingüístico de los estudiantes, con la confianza de los estudiantes y de los profesores para expresarse en ladino y con opiniones normativas sobre la lengua. Los maestros expresaron necesidades relacionadas con la búsqueda de puestos docentes estables, con la creación de una prueba y un certificado de dominio del ladino, con el desarrollo de recursos para la enseñanza del idioma y con la actualización del vocabulario del ladino para reflejar la vida contemporánea. Se consideró importante crear espacios para que los estudiantes puedan practicar la lengua y oportunidades para que los docentes se puedan reunir y discutir cuestiones didácticas. Los puntos de vista de los docentes diferían considerablemente en cuanto a normas lingüísticas, y la deseabilidad de un certificado oficial de dominio del idioma. Los resultados apuntan a la necesidad de más discusiones y de iniciativas de perfeccionamiento pedagógico

The North Atlantic: The Norwegian Sea, A Scandinavian Security Problem

A little more than a year ago the then Norwegian Defense Minister Hellesen announced, in a report to the Norwegian Parliament, that Rus­sian military activity near Norwegian waters and airspace had substantially increased. He also made it clear in his report that the number of units in the Russian Arctic Fleet had increased sharply and that the fighting power of the vessels was much improved. Numer­ous air and amphibious exercises sug­gested that Russian forces could con­duct offensive operations on very short notice

Using Formal Methods. A practical comparison between Z/EVES and PVS

This paper consists of a review and comparison between Z/EVES and PVS--two tools designed for analyzing formal specifications. Z/EVES is a tool for analyzing specifications written in Z. PVS is a general theorem prover for a language that consists of higher order logic together with set theory. The review has its focus on the possibility to use these tools in an industrial context. The plan for the review was to get acquainted with the tools on a general level and then to use them to partially validate a formal specification of requirements for the safety function of railway signaling systems. The conclusion is that PVS is clearly superior to Z/EVES. PVS has such a good performance that it can be recommended for industrial use in the area of formal methods. Concerning Z/EVES, its applicability seems more restricted

The Quark Propagator from the Dyson-Schwinger Equations: I. the Chiral Solution

Within the framework of the Dyson-Schwinger equations in the axial gauge, we study the effect that non-perturbative glue has on the quark propagator. We show that Ward-Takahashi identities, combined with the requirement of matching perturbative QCD at high momentum transfer, guarantee the multiplicative renormalisability of the answer. Technically, the matching with perturbation theory is accomplished by the introduction of a transverse part to the quark-gluon vertex. We show that this transverse vertex is crucial for chiral symmetry breaking, and that massless solutions exist below a critical value of the strong coupling constant. Using the gluon propagator that we previously calculated, we obtain small corrections to the quark propagator, which keeps a pole at the origin in the chiral phase.Comment: 21 pages, 6 figures; McGill/94-24, SHEP 93/94-26 We generalise our results by showing that they are not sensitive to the specific choice that we make for the transverse vertex. We illustrate that fact in two new figure