CORN HYBRID SELECTION AND CLIMATIC VARIABILITY: GAMBLING WITH NATURE?

Farmer adaptation to climatic variability is explored via an analysis of corn hybrid selection in southern Ontario. Corn hybrid varieties are available for a wide range of conditions, including accumulated heat, measured as Corn Heat Units (chus). Hybrids with higher chu ratings generally have higher yields, so long as there is sufficient heat for them to mature. Farmers choose their hybrid varieties prior to the growing season, in the face of uncertainty about the chus that will accumulate at their location. Farmers in the sample counties showed a consistent tendency to adjust their hybrid selection on the basis of the previous year's growing conditions. After the high chu year of 1991, farmers chose significantly more longer-maturing and potentially higher-yielding, but riskier varieties. After the lower chu years of 1992 and 1993, farmers' hybrid selections became markedly more conservative. L'étude de I'adaptation des fermiers aux changements climatiques se fait par une analyse de /'hybridation du maïs au sud de l'Ontario. Les variétés de maïs hybrides conviennent à différentes conditions climatiques in-cluant la chaleur accumulée, mesurée en Unitées de Chaleur de Maïs (ucms). Les hybrides ayant une valeur ucm plus élevée donnent généralement un rendement plus élevéà condition qu'ils bénéficient d'assez de chaleur pour mûrir. Les fermiers des comtés sélectionnés ont démontré une tendance persistante à baser leurs sélections d'hybrides en fonction des conditions de crois-sance de I'année précédente. Depuis 1991, année ayant connu un taux élevé d'UCM, les fermiers ont opté pour un type d'hybride à croissance prolongée, au potentiel de rendement plus élevé mats également plus risqué. Les années 1992 et 1993 ayant connu un niveau ucm moins élevé, les fermiers ont alors sélectionné des hybrides plus traditionnels.     

Degradation processes in colourless Roman glass: cases from the Bocholtz burial

A group of Roman glass objects from the Bocholtz burial in the SW of Limburg (The Netherlands) was found to have been subject to varying degrees of degradation. Many of the 25 colourless glass objects were fragmented to pieces <0.1 cm (“sugared”), whereas the three transparent blue-green glass objects were in near-pristine state. Analyses using SEM, XRF and EDS revealed that the fragmentation was the direct result of the intense leaching of Na₂O from the glass structure and its replacement with water. The resulting gel layers with low-Na₂O contents and large amounts of water are sensitive to cracking when they dry out. Thin-walled glass appears to be less sensitive to cracking from the resulting stress than thick-walled glass. Local differences in the moisture regime during burial also influence the severity of the glass degradation. Glass with low concentrations of CaO seems to be the most sensitive to this form of degradation. The typical blue-green Roman glass is less sensitive as it generally has considerably higher concentrations of CaO.     

Stocking Up: The Role of Temporal and Spatial R&D Stocks

Endogenous growth models are built around the concept of a knowledge stock. This knowledge stock can also be interpreted as a localized stock that operates at the regional level, as is common in the regional innovation systems literature. We use data from the second, third and fourth Community Innovation Surveys (covering 1994–1996, 1998–2000 and 2002–2004) to measure the build-up of knowledge at a very low regional aggregation level (“across streets and hallways”) in the Netherlands. In doing so, we account for regional agglomeration effects. We find that such local knowledge stocks have a small influence on innovation and are far outweighed by firm-specific characteristics.     

Oculus ecclesiae or the eyes of the people. Church and society in medieval Frisia

Medieval Frisia, also known as the ‘Seven Frisian Sea Lands’, consisted of clearly distinguishable parts: West Friesland (now part of the Dutch province of Holland), West-Lauwers Friesland (the present-day Dutch Province of Friesland), the Lands between the Lauwers and the Eems (the present-day province of Groningen) also called East Friesland, together with German East Friesland (Fig. 1). This study is concerned with the Lands between the Lauwers and the Eems; its main emphasis is on the lands (terrae) of Fivelgo and Hunsingo (Fig. 2).The history of medieval Friesland is not considered here in terms of modern political theory; instead, emphasis is on the forms of society and administration as they really existed, and on actual family and communal relationships. Viewed in this light the peace and truces inspired by the Church are seen to have played an important role.     

REGIONAL WAGE DIFFERENCES IN THE NETHERLANDS: MICRO EVIDENCE ON AGGLOMERATION EXTERNALITIES

Based on micro data on individual workers for the period 2000–2005, we show that wage differentials in the Netherlands are small but present. A large part of these differentials can be attributed to individual characteristics. Remaining effects are partially explained by variations in employment density, with an elasticity of about 4.8 percent, and by Marshall‐Arrow‐Romer externalities, where doubling the local share of a (two‐digit) industry results in a 2.9 percent higher productivity. We also find evidence for small negative effects of competition (Porter externalities) and diversity (Jacobs externalities).