Cell Edges Accumulate Gamma Tubulin Complex Components and Nucleate Microtubules following Cytokinesis in Arabidopsis thaliana

Microtubules emanate from distinct organizing centers in fungal and animal cells. In plant cells, by contrast, microtubules initiate from dispersed sites in the cell cortex, where they then self-organize into parallel arrays. Previous ultrastructural evidence suggested that cell edges participate in microtubule nucleation but so far there has been no direct evidence for this. Here we use live imaging to show that components of the gamma tubulin nucleation complex (GCP2 and GCP3) localize at distinct sites along the outer periclinal edge of newly formed crosswalls, and that microtubules grow predominantly away from these edges. These data confirm a role for cell edges in microtubule nucleation, and suggest that an asymmetric distribution of microtubule nucleation factors contributes to cortical microtubule organization in plants, in a manner more similar to other kingdoms than previously thought

Radar climatology of the COPS region

A climatology of convection initiation (CI) and convective enhancements (CE) has been developed using radar reflectivity data in southwestern Germany and eastern France over the period of May�August of 2000�2006 and 2008. The study region included the Vosges Mountains of France, the Rhine Valley which straddles France and Germany, the Black ForestMountains and the SwabianMountains of Germany. Convection occurred frequently during the summer months throughout the study region. The CI density (number of initiations per square km) illustrates preferential formation in the mountain regions while the CE events spanned both mountains and valleys nearly equally. There is a strongmid-day peak of the CI events suggesting that diurnal heating is critical for CI in the region. The very strong thunderstorms (>46 dBZ) first occurred in the mountains and �2 h later in the Rhine Valley. During the summer of 2007, the Convective and Orographically-induced Precipitation Study (COPS) field campaign was conducted with the objective of obtaining improved understanding of convective processes and short-term quantitative precipitation forecasting in low-mountain regions. Comparisons were made between the radar climatology results and the COPS summer. The COPS summer exhibited preferential CI density in the mountainous regions but not as pronounced as the climatology. The COPS summer had a similar diurnal peak of CI events as climatology but the ratio of daytime to nighttime CI (1.7), or amplitude of the diurnal cycle, was less than that of climatology (3.0). While both the 8-year climatology and COPS summer were dominated by daytime, locally-forced CI occurrences, the broad distribution of daytime CI events and increase in nighttime events observed during COPS indicate a more active synoptic pattern in 2007

Operations of and Future Plans for the Pierre Auger Observatory

Technical reports on operations and features of the Pierre Auger Observatory, including ongoing and planned enhancements and the status of the future northern hemisphere portion of the Observatory. Contributions to the 31st International Cosmic Ray Conference, Lodz, Poland, July 2009.Comment: Contributions to the 31st ICRC, Lodz, Poland, July 200

Highlights from the Pierre Auger Observatory

The Pierre Auger Observatory is the world's largest cosmic ray observatory. Our current exposure reaches nearly 40,000 km$^2$ str and provides us with an unprecedented quality data set. The performance and stability of the detectors and their enhancements are described. Data analyses have led to a number of major breakthroughs. Among these we discuss the energy spectrum and the searches for large-scale anisotropies. We present analyses of our X$_{max}$ data and show how it can be interpreted in terms of mass composition. We also describe some new analyses that extract mass sensitive parameters from the 100% duty cycle SD data. A coherent interpretation of all these recent results opens new directions. The consequences regarding the cosmic ray composition and the properties of UHECR sources are briefly discussed.Comment: 9 pages, 12 figures, talk given at the 33rd International Cosmic Ray Conference, Rio de Janeiro 201

A search for point sources of EeV photons

Measurements of air showers made using the hybrid technique developed with the fluorescence and surface detectors of the Pierre Auger Observatory allow a sensitive search for point sources of EeV photons anywhere in the exposed sky. A multivariate analysis reduces the background of hadronic cosmic rays. The search is sensitive to a declination band from -85{\deg} to +20{\deg}, in an energy range from 10^17.3 eV to 10^18.5 eV. No photon point source has been detected. An upper limit on the photon flux has been derived for every direction. The mean value of the energy flux limit that results from this, assuming a photon spectral index of -2, is 0.06 eV cm^-2 s^-1, and no celestial direction exceeds 0.25 eV cm^-2 s^-1. These upper limits constrain scenarios in which EeV cosmic ray protons are emitted by non-transient sources in the Galaxy.Comment: 28 pages, 10 figures, accepted for publication in The Astrophysical Journa

Europeanisation should meet international constructivism: the Nordic Plus group and the internalisation of political conditionality by France and the United Kingdom

This article is a plausibility probe for the significance of international constructivist ‘mediating factors’ to explain variation in Europeanisation outcomes. It applies a most similar systems design (or Mill's method of difference) to show that the UK has internalised political conditionality to a larger extent than France at least partially because it has been the object of stronger socialisation pressures within the ‘Nordic Plus’ group. The article contributes to the literature on Europeanisation and development cooperation in two important ways. First, it enlarges its scope of analysis, both geographically (beyond new European Union member states) and thematically (beyond simple measures of aid quality and/or quantity). Second, it emphasises the importance of international (versus domestic) mediating factors. The empirical analysis focusses on three cases of aid sanctions in response to human rights abuses and democratic setbacks: Zimbabwe 2002, Madagascar 2009 and Mozambique 2009

Reconstruction of inclined air showers detected with the Pierre Auger Observatory

We describe the method devised to reconstruct inclined cosmic-ray air showers with zenith angles greater than $60^\circ$ detected with the surface array of the Pierre Auger Observatory. The measured signals at the ground level are fitted to muon density distributions predicted with atmospheric cascade models to obtain the relative shower size as an overall normalization parameter. The method is evaluated using simulated showers to test its performance. The energy of the cosmic rays is calibrated using a sub-sample of events reconstructed with both the fluorescence and surface array techniques. The reconstruction method described here provides the basis of complementary analyses including an independent measurement of the energy spectrum of ultra-high energy cosmic rays using very inclined events collected by the Pierre Auger Observatory.Comment: 27 pages, 19 figures, accepted for publication in Journal of Cosmology and Astroparticle Physics (JCAP

Measurement of the Depth of Maximum of Extensive Air Showers above 10^18 eV

We describe the measurement of the depth of maximum, Xmax, of the longitudinal development of air showers induced by cosmic rays. Almost four thousand events above 10^18 eV observed by the fluorescence detector of the Pierre Auger Observatory in coincidence with at least one surface detector station are selected for the analysis. The average shower maximum was found to evolve with energy at a rate of (106 +35/-21) g/cm^2/decade below 10^(18.24 +/- 0.05) eV and (24 +/- 3) g/cm^2/decade above this energy. The measured shower-to-shower fluctuations decrease from about 55 to 26 g/cm^2. The interpretation of these results in terms of the cosmic ray mass composition is briefly discussed.Comment: Accepted for publication by PR