Electronic Transport Properties of Pentacene Single Crystals upon Exposure to Air

We report the effect of air exposure on the electronic properties of pentacene single crystals. Air can diffuse reversibly in and out of the crystals and controls the physical properties. We discern two competing mechanisms that modulate the electronic transport. The presence of oxygen increases the hole conduction, as in dark four O2 molecules introduce one charge carrier. This effect is enhanced by the presence of visible light. Contrarily, water, present in ambient air, is incorporated in the crystal lattice and forms trapping sites for injected charges.Comment: 16 pages, 3 figure

Measure of National Return in International Science Cooperation

In the decades since science and technology measures were crafted and adopted by governments, R&D has increasingly taken place across national boundaries. This leaves a gap for policy makers in how to account for the benefits to national governments of supporting international collaboration in science. This article seeks to address this gap by suggesting a measure for the impact of international collaboration in science using fractionalized field-weighted citations and analysing these in relationship to public spending and researcher mobility

A combined model of aggregation, fragmentation, and exchange processes: insights from analytical calculations

We introduce a mean-field framework for the study of systems of interacting particles sharing a conserved quantity. The work generalises and unites the existing fields of asset-exchange models, often applied to socio-economic systems, and aggregation-fragmentation models, typically used in modelling the dynamics of clusters. An initial model includes only two-body collisions, which is then extended to include many-body collisions and spontaneous fragmentation. We derive self-consistency equations for the steady-state distribution, which can be solved using a population dynamics algorithm, as well as a full solution for the time evolution of the moments, corroborated with numerical simulations. The generality of the model makes it applicable to many problems and allows for the study of systems exhibiting more complex interactions that those typically considered. The work is relevant to the modelling of barchan dune fields in which interactions between the bedforms and spontaneous fragmentation due to changes in the wind are thought to lead to size-selection. Our work could also be applied in finding wealth distributions when agents can both combine assets as well as split into multiple subsidiaries.Comment: 19 pages, 5 figures. To be published in Journal of Statistical Mechanics: Theory and Experiment (JSTAT

(Aan)raken. De rol van lichamelijke interactie in partnerdans: inzichten voor het bewerkstelligen van verbinding in geestelijke begeleiding.

Een centraal element in humanistisch geestelijk raadswerk is de verbinding tussen de geestelijk begeleider en de cliënt. Deze verbinding is gebaseerd op de therapeutische relatie uit de rogeriaanse methodiek, bestaande uit congruentie, onvoorwaardelijke acceptatie en empathie. Ondanks de grote rol van lichamelijke interactie in het tot stand brengen van verbinding tussen begeleider en cliënt, ontbreekt een theoretische uitwerking van de toepassing van lichamelijkheid binnen geestelijk raadswerk. Deze thesis onderzoekt aan de hand van partnerdans – een vorm van contact gebaseerd op lichamelijke interactie – de mogelijkheden met betrekking tot de inzet van lichamelijke interactie voor het bewerkstelligen van verbinding in geestelijke begeleiding. Dit kwalitatieve, exploratieve onderzoek tracht middels negen diepteinterviews en zes participerende observaties binnen de setting van een danspaleis inzicht te vergaren in de lichamelijke invulling van de rogeriaanse kernaspecten van verbinding. De onderzoeksvraag is: Welke rol speelt lichamelijke interactie in het tot stand komen van verbinding in partnerdans? De resultaten laten zien dat congruentie, onvoorwaardelijke acceptatie en empathie in partnerdans een lichamelijke invulling kennen, die geestelijk begeleiders handvatten kan bieden voor het inzetten van lichamelijke interactie in contact met cliënten. Lichamelijke congruentie bestaat uit lijfelijke reflectie: hoe reageert het eigen lichaam op wat er gebeurt? En lukt het om daar trouw aan te blijven? Lichamelijke onvoorwaardelijk acceptatie gaat over fysieke nabijheid, ongeacht hoe iemand ruikt, beweegt, eruit ziet of mentaal functioneert. De lichamelijke invulling van empathie bestaat uit lichamelijke volgzaamheid: het inleven in en aansluiten bij de belevingswereld van de ander, door diens lichamelijke signalen af te lezen en daar fysiek dan wel verbaal op af te stemmen. Non-verbale afstemming bestaat hoofdzakelijk uit het overnemen van de bewegingen (spiegelen) en aanraking. Het inleven in de ander vergt moed en (zintuigelijke) inspanning. In het maken van verbinding wisselen leiden (een directieve houding) en volgen (een non-directieve houding) elkaar af. Een focus op de lichamelijke mogelijkheden van de ander kan eraan bijdragen dat iemand zich comfortabeler voelt in zijn eigen lichaam

Genetic Parameters for Lean Growth Rate and Its Components in U.S. Landrace Pigs

Records on 65,536 Landrace pigs collected between 1985 and 1999 in herds on the National Swine Registry STAGES program were used to estimate additive genetic (animal), common environmental (litter), and residual variances and covariances for days to 250 lb, backfat, loin eye area, and lean growth rate. Analysis was by the REMLf90 program of I. Misztal using a multiple-trait animal model with fixed effects of contemporary group and sex and random effects of animal, litter, and residual error. Heritability estimates were 0.54, 0.39, 0.49, and 0.48 for days to 250 lb, backfat, loin eye area, and lean growth rate, respectively. Genetic correlations for lean growth rate with days to 250, backfat, and loin eye area were -0.83, -0.38, and 0.40, respectively. Phenotypic correlations for lean growth rate with days to 250 lb, backfat, and loin eye area were -0.80, -0.40, and 0.56, respectively. Litter effects were large only for days to 250 lb. Lean growth rate should be used as an important selection criteria in genetic improvement in pigs

Reproducing size distributions of swarms of barchan dunes on Mars and Earth using a mean-field model

We apply a mean-field model of interactions between migrating barchan dunes, the CAFE model, which includes spontaneous calving, aggregation, fragmentation, and mass-exchange, yielding a steady-state size distribution that can be resolved for different choices of interaction parameters. The CAFE model is applied to empirically measured distributions of dune sizes in two barchan swarms in the north circumpolar region of Mars, three swarms in Morocco, and one in Mauritania, each containing more than 1000 bedforms. When the sizes of bedforms are rescaled by the mean size in each zone two attractor states appear, with the Tarfaya zones all displaying a common distribution and the Martian and Mauritanian zones sharing a different distribution. Comparison of these attractor states with the outputs of the CAFE model reveals that the Tarfaya-type distribution results from a preference for aggregation and fragmentation interactions whereas the Mars-Mauritania distribution is more likely a result of exchange-dominated interactions. We observe that there appears to be a greater number of collisions happening in Tarfaya than in the other areas which is consistent with a greater rate of aggregation-fragmentation processes as suggested by our model. Our comparison with the CAFE model also predicts a universal rule for the outputs of the different types of interactions with exchange interactions favouring the production of two dunes roughly equal in size. Fragmentation interactions often result in three bedforms with volumes approximately in the ratio 1:1:2. Finally, we find that spontaneous calving of dunes does not play an important role in shaping the size distributions in barchan swarms

Molecular gas temperature and density in spiral galaxies

We combine beam-matched CO-13, CO-12 J = 3 yields 2 and J = 2 yields 1 line data to infer the molecular gas excitation conditions in the central 500 to 1600 pc diameters of a small sample of infrared-bright external galaxies: NGC253, IC342, M 83, Maffei 2, and NGC6946. Additional observations of the J = 1 yields 0 lines of C-18O and CO-13 set limits on the opacity of the CO-13 J = 1 yields 0 line averaged over the central kiloparsec of these spiral galaxies