Setting up a business in the Netherlands

Onderzoekt de kenmerken van mensen die de plannen voor het starten van een onderneming realiseren, vergeleken met de mensen die opgeven of bezig blijven met het opzetten van de onderneming.

QCD and spin effects in black hole airshowers

In models with large extra dimensions, black holes may be produced in high-energy particle collisions. We revisit the physics of black hole formation in extensive airshowers from ultrahigh-energy cosmic rays, focusing on collisional QCD and black hole emissivity effects. New results for rotating black holes are presented. Monte Carlo simulations show that QCD effects and black hole spin produce no observable signatures in airshowers. These results further confirm that the main characteristics of black hole-induced airshowers do not depend on the fine details of micro black hole models.Comment: 6 pages, 2 figures, accepted for publication in Physical Review

Encountered Problems and Outcome Status in Nascent Entrepreneurship

Post-printThe relationship between outcome status and encountered problems in the business start-up process is investigated. Contrary to expectations, we find that starters do not substantially differ from quitters in number and type of problems encountered, and that problems encountered generally do not affect outcome status. This research is based on a sample of 414 Dutch nascent entrepreneurs followed over a three year period. Its design is comparable to the U.S. PSED (Panel Study of Entrepreneurial Dynamics)

Deconvolution of Images from BLAST 2005: Insight into the K3-50 and IC 5146 Star-forming Regions

We present an implementation of the iterative flux-conserving Lucy-Richardson (L-R) deconvolution method of image restoration for maps produced by the Balloon-borne Large Aperture Submillimeter Telescope (BLAST). Compared to the direct Fourier transform method of deconvolution, the L-R operation restores images with better-controlled background noise and increases source detectability. Intermediate iterated images are useful for studying extended diffuse structures, while the later iterations truly enhance point sources to near the designed diffraction limit of the telescope. The L-R method of deconvolution is efficient in resolving compact sources in crowded regions while simultaneously conserving their respective flux densities. We have analyzed its performance and convergence extensively through simulations and cross-correlations of the deconvolved images with available high-resolution maps. We present new science results from two BLAST surveys, in the Galactic regions K3-50 and IC 5146, further demonstrating the benefits of performing this deconvolution. We have resolved three clumps within a radius of 4'.5 inside the star-forming molecular cloud containing K3-50. Combining the well-resolved dust emission map with available multi-wavelength data, we have constrained the spectral energy distributions (SEDs) of five clumps to obtain masses (M), bolometric luminosities (L), and dust temperatures (T). The L-M diagram has been used as a diagnostic tool to estimate the evolutionary stages of the clumps. There are close relationships between dust continuum emission and both 21 cm radio continuum and ^(12)CO molecular line emission. The restored extended large-scale structures in the Northern Streamer of IC 5146 have a strong spatial correlation with both SCUBA and high-resolution extinction images. A dust temperature of 12 K has been obtained for the central filament. We report physical properties of ten compact sources, including six associated protostars, by fitting SEDs to multi-wavelength data. All of these compact sources are still quite cold (typical temperature below ~ 16 K) and are above the critical Bonner-Ebert mass. They have associated low-power young stellar objects. Further evidence for starless clumps has also been found in the IC 5146 region

Success and risk factors in the pre-startup phase

Why does one person actually succeed in starting a business, while a second person gives up? In order to answer this question, a sample of 517 nascent entrepreneurs (people in the process of setting up a business) was followed over a three-year period. After this period, it was established that 195 efforts were successful and that 115 startup efforts were abandoned. Our research focuses on estimating the relative importance of a variety of approaches and variables in explaining pre-startup success. These influences are organised in terms of Gartner's framework of new venture creation. This framework suggests that start-up efforts differ in terms of the characteristics of the individual(s) who start the venture, the organisation which they create, the environment surrounding the new venture, and the process by which the new venture is started. Logistic regression analyses are run for the sample as a whole as well as for subgroups within the sample, namely for those with high ambition vs. low ambition and for those with substantial vs. limited experience. The results point to the importance of perceived risk of the market as a predictor of getting started vs. abandoning the startup effort.

Motivation based policies for an entrepreneurial EU economy

This paper investigates the impact of various entrepreneurial motives and institutional conditions on entrepreneurial aspirations in terms of innovativeness, job growth expectations and export orientation. We estimate a two-equation model explaining entrepreneurial motivations and entrepreneurial aspirations, while taking into account the interrelationship between both groups of variables. We use data from the Global Entrepreneurship Monitor (GEM) and find that entrepreneurial aspirations are different for various types of entrepreneurial motives. For example, we find that the increase wealth motive as a prime driver for becoming selfemployed is positively related to innovation and growth ambitions, whereas we find no evidence of a relation between the independence motive and entrepreneurial aspirations. On the basis of our findings policy directions are presented for an entrepreneurial EU economy. An updated version of this paper is numbered H200710.

Drivers of entrepreneurial aspirations at the country lever: the role of start-up motivations and social security

This paper investigates whether start-up motivations and the level of social security can explain entrepreneurial aspirations. We use country-level data from the Global Entrepreneurship Monitor (GEM) for the year 2005. We distinguish between the necessity motive, independence motive and increase wealth motive and look at entrepreneurial aspirations in terms of innovativeness, job growth expectations and export orientation. As an indicator of a country?s level of social security we take the social security contribution rate (for employer?s and employees) from the World Competitiveness Yearbook. Previous research has found a negative relationship between the level of entrepreneurial activity and social security contributions, suggesting that social security increases the opportunity costs for entrepreneurship. The results of this study complement these previous findings by indicating that social security contributions have a negative influence on the supply of ambitious entrepreneurship in terms of new product or service introductions, job growth and export orientation. Furthermore, our findings indicate that entrepreneurial aspirations in terms of job growth and export relate positively to the increase wealth motive, whereas no significant relationship is found between our aspiration variables and the independence and necessity motives. On the basis of our findings policy directions are presented for an entrepreneurial economy. This is an update of paper H200627.

Butterfly abundance in a warming climate: patterns in space and time are not congruent

We present a model of butterfly abundance on transects in England. The model indicates a significant role for climate, but the direction of association is counter to expectation: butterfly population density is higher on sites with a cooler climate. However, the effect is highly heterogeneous, with one in five species displaying a net positive association. We use this model to project the population-level effects of climate warming for the year 2080, using a medium emissions scenario. The results suggest that most populations and species will decline markedly, but that the total number of butterflies will increase as communities become dominated by a few common species. In particular, Maniola jurtina is predicted to make up nearly half of all butterflies on UK Butterfly Monitoring Scheme (UKBMS) transects by 2080. These results contradict the accepted wisdom that most insect populations will grow as the climate becomes warmer. Indeed, our predictions contrast strongly with those derived from inter-annual variation in abundance, emphasizing that we lack a mechanistic understanding about the factors driving butterfly population dynamics over large spatial and temporal scales. Our study underscores the difficulty of predicting future population trends and reveals the naivety of simple space-for-time substitutions, which our projections share with species distribution modelling

The Balloon-Borne Large Aperture Submillimeter Telescope (BLAST) 2005: A 10 deg^2 Survey of Star Formation in Cygnus X

We present Cygnus X in a new multi-wavelength perspective based on an unbiased BLAST survey at 250, 350, and 500 μm, combined with rich data sets for this well-studied region. Our primary goal is to investigate the early stages of high-mass star formation. We have detected 184 compact sources in various stages of evolution across all three BLAST bands. From their well-constrained spectral energy distributions, we obtain the physical properties mass, surface density, bolometric luminosity, and dust temperature. Some of the bright sources reaching 40 K contain well-known compact H_(II) regions. We relate these to other sources at earlier stages of evolution via the energetics as deduced from their position in the luminosity-mass (L-M) diagram. The BLAST spectral coverage, near the peak of the spectral energy distribution of the dust, reveals fainter sources too cool (~10 K) to be seen by earlier shorter-wavelength surveys like IRAS. We detect thermal emission from infrared dark clouds and investigate the phenomenon of cold "starless cores" more generally. Spitzer images of these cold sources often show stellar nurseries, but these potential sites for massive star formation are "starless" in the sense that to date there is no massive protostar in a vigorous accretion phase. We discuss evolution in the context of the L-M diagram. Theory raises some interesting possibilities: some cold massive compact sources might never form a cluster containing massive stars, and clusters with massive stars might not have an identifiable compact cold massive precursor