Revising the Cannabis Use Disorders Identification Test (CUDIT) by means of Item Response Theory.

Cannabis use among adolescents and young adults has become a major public health challenge. Several European countries are currently developing short screening instruments to identify 'problematic' forms of cannabis use in general population surveys. One such instrument is the Cannabis Use Disorders Identification Test (CUDIT), a 10-item questionnaire based on the Alcohol Use Disorders Identification Test. Previous research found that some CUDIT items did not perform well psychometrically. In the interests of improving the psychometric properties of the CUDIT, this study replaces the poorly performing items with new items that specifically address cannabis use. Analyses are based on a sub-sample of 558 recent cannabis users from a representative population sample of 5722 individuals (aged 13-32) who were surveyed in the 2007 Swiss Cannabis Monitoring Study. Four new items were added to the original CUDIT. Psychometric properties of all 14 items, as well as the dimensionality of the supplemented CUDIT were then examined using Item Response Theory. Results indicate the unidimensionality of CUDIT and an improvement in its psychometric performance when three original items (usual hours being stoned; injuries; guilt) are replaced by new ones (motives for using cannabis; missing out leisure time activities; difficulties at work/school). However, improvements were limited to cannabis users with a high problem score. For epidemiological purposes, any further revision of CUDIT should therefore include a greater number of 'easier' items.

Job satisfaction and life satisfaction: Analysis of a reciprocal model with social demographic moderators

The general objective of the study was to empirically test a reciprocal model of job satisfaction and life satisfaction while controlling for some social demographic variables. 827 employees working in 34 car dealerships in Northern Quebec (56% responses rate) were surveyed. The multiple item questionnaires were analysed using correlation analysis, chi square and ANOVAs. Results show interesting patterns emerging for the relationships between job and life satisfaction of which 49.2% of all individuals have spillover, 43.5% compensation, and 7.3% segmentation type of relationships. Results, nonetheless, are far richer and the model becomes much more refined when social demographic indicators are taken into account. Globally, social demographic variables demonstrate some effects on each satisfaction individually but also on the interrelation (nature of the relations) between life and work satisfaction.

Entrepreneurship, organization and economic performance among Spanish firms, 1930-1975. The case of the motor industry

Before the Civil War (1936-1939), Spain had seen the emergence offirms of complex organizational forms. However, the conflict andthe postwar years changed this pattern. The argument put forwardin this paper is based on historical experience, the efforts willbe addressed to explain the development of Spanish entrepreneurshipduring the second half of the twentieth century. To illustrate thechange in entrepreneurship and organizational patterns among theSpanish firms during the Francoist regime we will turn to the caseof the motor vehicle industry.

Intellectual property rights and efficient firm organization

I show that intellectual property rights yield static efficiency gains, irrespective oftheir dynamic role in fostering innovation. I develop a property-rights model of firmorganization with two dimensions of non-contractible investment. In equilibrium, thefirst best is attained if and only if ownership of tangible and intangible assets is equallyprotected. If IP rights are weaker, firm structure is distorted and efficiency declines:the entrepreneur must either integrate her suppliers, which prompts a decline in theirinvestment; or else risk their defection, which entails a waste of her human capital. Mymodel predicts greater prevalence of vertical integration where IP rights are weaker,and a switch from integration to outsourcing over the product cycle. Both empiricalpredictions are consistent with evidence on multinational companies. As a normativeimplication, I find that IP rights should be strong but narrowly defined, to protect abusiness without holding up its potential spin-offs.

A simple permutation test for clusteredness

Hierarchical clustering is a popular method for finding structure in multivariate data,resulting in a binary tree constructed on the particular objects of the study, usually samplingunits. The user faces the decision where to cut the binary tree in order to determine the numberof clusters to interpret and there are various ad hoc rules for arriving at a decision. A simplepermutation test is presented that diagnoses whether non-random levels of clustering are presentin the set of objects and, if so, indicates the specific level at which the tree can be cut. The test isvalidated against random matrices to verify the type I error probability and a power study isperformed on data sets with known clusteredness to study the type II error.

What do outside experts bring to a committee? Evidence from the Bank of England

We test whether outside experts have information not available to insiders by usingthe voting record of the Bank of England's Monetary Policy Committee. Memberswith more private information should vote more often against conventional wisdom,which we measure as the average belief of market economists about future interest rates. We find evidence that external members indeed have information notavailable to internals, but also use a quasi-natural experiment to show they mayexaggerate their expertise to obtain reappointment. This implies that an optimalcommittee, even outside monetary policy, should potentially include outsiders, butneeds to manage career concerns.

Expression of foraging and Gp-9 are associated with social organization in the fire ant Solenopsis invicta.

The aim of this study was to investigate levels of expression of two major genes, the odorant binding protein Gp-9 (general protein-9) and foraging, that have been shown to be associated with behavioural polymorphisms in ants. We analysed workers and young nonreproductive queens collected from nests of the monogyne (single reproductive queen per nest) and polygyne (multiple reproductive queens) social forms of Solenopsis invicta. In workers but not young queens, the level of foraging expression was significantly associated with social form and the task performed (ie localization in the nest or foraging area). The level of expression of Gp-9 was also associated with social form and worker localization. In addition there was a higher level of expression of the Gp-9(b) allele compared with the Gp-9(B) allele in the heterozygote workers and the young nonreproductive queens. Finally, in the polygyne colonies the level of expression of foraging was not significantly associated with the Gp-9 genotype for either workers or young nonreproductive queens, suggesting that both genes have independent non-epistatic effects on behaviour in S. invicta.

One person in the battlefield is not a warrior: Self-construal, perceived ability to make a difference, and socially responsible behavior

We suggest that cultivating an individual's connectedness to others promotes sociallyresponsible behavior both directly and indirectly through increased perceived abilityto make a difference. Individuals whose interdependent self is more prominent feel theyhave more of an impact on larger scale societal outcomes and, therefore, engage more insocially responsible behaviors than do individuals whose independent self is moreprominent. We test these hypotheses in two experiments in which participants makefinancial contributions or exert an effort for a social cause. In a survey, we find thatperceived effectiveness mediates the effect of self-construal on socially responsibleconsumption.

Endogenous spillovers, increased competition and re-organization waves

We consider an entrepreneur that is the sole producer of a costreducing skill, but the entrepreneur that hires a team to usethe skill cannot prevent collusive trade for the innovation related knowledge between employees and competitors. We showthat there are two types of diffusion avoiding strategies forthe entrepreneur to preempt collusive communication i) settingup a large productive capacity (the traditional firm) and ii)keeping a small team (the lean firm). The traditional firm ischaracterized by its many "marginal" employees that work shortdays, receive flat wages and are incompletely informed about the innovation. The lean firm is small in number of employees,engages in complete information sharing among members, that are paid with stock option schemes. We find that the lean firm is superior to the traditional firm when technological entry costsare low and when the sector is immature.

Testing Spatial Autocorrelation in Weighted Networks : the Modes Permutation Test

In a weighted spatial network, as specified by an exchange matrix, the variances of the spatial values are inversely proportional to the size of the regions. Spatial values are no more exchangeable under independence, thus weakening the rationale for ordinary permutation and bootstrap tests of spatial autocorrelation. We propose an alternative permutation test for spatial autocorrelation, based upon exchangeable spatial modes, constructed as linear orthogonal combinations of spatial values. The coefficients obtain as eigenvectors of the standardised exchange matrix appearing in spectral clustering, and generalise to the weighted case the concept of spatial filtering for connectivity matrices. Also, two proposals aimed at transforming an acessibility matrix into a exchange matrix with with a priori fixed margins are presented. Two examples (inter-regional migratory flows and binary adjacency networks) illustrate the formalism, rooted in the theory of spectral decomposition for reversible Markov chains.

Relative and absolute reliability of the clinical version of the Narrow Path Walking Test (NPWT) under single and dual task conditions.

Decline in gait stability has been associated with increased fall risk in older adults. Reliable and clinically feasible methods of gait instability assessment are needed. This study evaluated the relative and absolute reliability and concurrent validity of the testing procedure of the clinical version of the Narrow Path Walking Test (NPWT) under single task (ST) and dual task (DT) conditions. Thirty independent community-dwelling older adults (65-87 years) were tested twice. Participants were instructed to walk within the 6-m narrow path without stepping out. Trial time, number of steps, trial velocity, number of step errors, and number of cognitive task errors were determined. Intraclass correlation coefficients (ICCs) were calculated as indices of agreement, and a graphic approach called "mountain plot" was applied to help interpret the direction and magnitude of disagreements between testing procedures. Smallest detectable change and smallest real difference (SRD) were computed to determine clinically relevant improvement at group and individual levels, respectively. Concurrent validity was assessed using Performance Oriented Mobility Assessment Tool (POMA) and the Short Physical Performance Battery (SPPB). Test-retest agreement (ICC1,2) varied from 0.77 to 0.92 in ST and from 0.78 to 0.92 in DT conditions, with no apparent systematic differences between testing procedures demonstrated by the mountain plot graphs. Smallest detectable change and smallest real change were small for motor task performance and larger for cognitive errors. Significant correlations were observed for trial velocity and trial time with POMA and SPPB. The present results indicate that the NPWT testing procedure is highly reliable and reproducible.

Après votre arrêt cardiaque, vous prendrez bien un peu d'élixir de (sur)vie [After your heart arrest, would you like to test a medicinal elixir?].

So far, cardiac arrest is still associated with high mortality or severe neurological disability in survivors. At the tissue level, cardiac arrest results into an acute condition of generalized hypoxia. A better understanding of the pathophysiology of ischemia-reperfusion and of the inflammatory response that develops after cardiac arrest could help to design novel therapeutic strategies in the future. It seems unlikely that a single drug, acting as a <magic bullet>, might be able to improve survival or neurological prognosis. Lessons learned from pathophysiological mechanisms rather indicate that combined therapies, involving thrombolysis, neuroprotective agents, antioxidants and anti-inflammatory molecules, together with temperature cooling, might represent helpful strategies to improve patient's outcome after cardiac arrest.

Three essays on organizations and their external environment

Abstract: The literature on the various links between organizations and their external environment is very extensive and fragmented. This thesis is comprised of three separate essays, each examining specific research questions related to these links. The first essay deals with the notion of industry life cycle and how the geographical concentration of an industry is linked to the particular life cycle stage in which the industry finds itself. The aim of this first essay is firstly to verify if the evolution of the Swiss hotel industry fits some of the stylized facts of the industry life cycle. The second aim is to verify if there is evidence of geographical clustering of the hotel industry, and by extension of tourism. The third aim is to verify a hypothesis that industry decline manifests itself mainly by company closures in decentralized locations. The importance for organizational survival and performance of adapting and reacting to environmental changes has long been ascertained. This adaptation requires managers, under conditions of uncertainty, to identify relevant changes in their external environment and to interpret the possible effects of those changes on their organization. Furthermore, it requires finding and adopting organizational responses in reaction to the environmental changes. The second essay explores how managers perceive their environment by reporting the results of two workshops held with managers from the European hotel industry. In the third essay we examine in more detail the role of uncertainty in the interpretation by executives of environmental changes. We integrate existing theories of interpretation and uncertainty into one framework, which we then test using national survey data from the hotel industry. In all three essays we are able to provide some evidence to support our main hypotheses, but.also make suggestions far further research into the topics examined.