A major goal of the Atacama Large Millimeter/submillimeter Array (ALMA) is to make accurate images with resolutions of tens of milliarcseconds, which at submillimeter (submm) wavelengths requires baselines up to ∼15 km. To develop and test this capability, a Long Baseline Campaign (LBC) was carried out from 2014 September to late November, culminating in end-to-end observations, calibrations, and imaging of selected Science Verification (SV) targets. This paper presents an overview of the campaign and its main results, including an investigation of the short-term coherence properties and systematic phase errors over the long baselines at the ALMA site, a summary of the SV targets and observations, and recommendations for science observing strategies at long baselines. Deep ALMA images of the quasar 3C 138 at 97 and 241 GHz are also compared to VLA 43 GHz results, demonstrating an agreement at a level of a few percent. As a result of the extensive program of LBC testing, the highly successful SV imaging at long baselines achieved angular resolutions as fine as 19 mas at ∼350 GHz. Observing with ALMA on baselines of up to 15 km is now possible, and opens up new parameter space for submm astronomy.

Aims. We completed observations with the Effelsberg 100-m radio telescope to measure the polarised emission from a complete sample of compact steep-spectrum sources and improve our understanding of the physical conditions inside and around regions of radio emission embedded in dense interstellar environments. Methods. We observed the sources at four different frequencies, namely 2.64 GHz, 4.85 GHz, 8.35 GHz, and 10.45 GHz, making use of the polarimeters available at the Effelsberg telescope. We complemented these measurements with polarisation parameters at 1.4 GHz derived from the NRAO VLA Sky Survey. Previous single dish measurements were taken from the catalogue of Tabara and Inoue.Results. The depolarisation index DP was computed for four pairs of frequencies. A drop in the fractional polarisation appeared in the radio emission when observing at frequencies below ∼2 GHz. Rotation measures were derived for about 25% of the sources in the sample. The values, in the source rest frame, range from about −20 rad m −2 found for 3C 138 to 3900 rad m −2 in 3C 119. In all cases, the λ 2 law is closely followed. Conclusions. The presence of a foreground screen as predicted by the Tribble model or with "partial coverage" as defined by ourselves can explain the polarimetric behaviour of the CSS sources detected in polarisation by the present observations. Indication of repolarisation at lower frequencies was found for some sources. A case of possible variability in the fractional polarisation is also suggested. The most unexpected result was found for the distribution of the fractional polarisations versus the linear sizes of the sources. Our results appear to disagree with the findings of Cotton and collaborators and Fanti and collaborators for the B3-VLA sample of CSS sources, the so-called "Cotton effect", i.e., a strong drop in polarised intensity for the most compact sources below a given frequency. This apparent contradiction may, however, be caused by the large contamination of the sample by quasars with respect to the B3-VLA.

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The bacterial canker of kiwifruit caused by Pseudomonas syringae pv. actinidiae is a severe threat to kiwifruit production worldwide. Many aspects of P. syringae pv. actinidiae biology and epidemiology still require in-depth investigation. The infection by and spread of P. syringae pv. actinidiae in xylem and phloem was investigated by carrying out artificial inoculation experiments with histological and dendrochronological analyses of naturally diseased plants in Italy. We found that the bacterium can infect host plants by entering natural openings and lesions. In naturally infected kiwifruit plants, P. syringae pv. actinidiae is present in the lenticels as well as in the dead phloem tissue beneath the lenticels, surrounded by a lesion in the periderm which appears to indicate the importance of lenticels to kiwifruit infection. Biofilm formation was observed outside and inside plants. In cases of advanced stages of P. syringae pv. actinidiae infection, neuroses of the phloem occur, which are followed by cambial dieback and most likely by infection of the xylem. Anatomical changes in wood such as reduced ring width, a drastic reduction in vessel size, and the presence of tyloses were observed within several infected sites. In the field, these changes occur only a year after the first leaf symptoms are observed suggesting a significant time lapse between primary and secondary symptoms. It was possible to study the temporal development of P. syringae pv. actinidiae-induced cambial dieback by applying dendrochronology methods which revealed that cambial dieback occurs only during the growing season.

We present new polarisation observations at 13 cm, acquired using the Westerbork Synthesis Radio Telescope (WSRT), of 65 sources, from the B3-VLA sample of Compact Steep-Spectrum sources. These new data are combined with our VLA polarisation data, at 3.6, 6 and, 21 cm, presented in a previous paper. Due to the multi-channel frequency capabilities of the WSRT, these new 13 cm observations enable a more reliable determination of integrated Rotation Measures, and of depolarisation behaviour with wavelength. The new data are inconsistent with the depolarisation models that we used earlier, and we propose an alternative model which seems to work properly. We also revise our previous model for the external Faraday screen, and its dependence on the source redshift.