Design, Commissioning and Performance of the PIBETA Detector at PSI

We describe the design, construction and performance of the PIBETA detector built for the precise measurement of the branching ratio of pion beta decay, pi+ -> pi0 e+ nu, at the Paul Scherrer Institute. The central part of the detector is a 240-module spherical pure CsI calorimeter covering 3*pi sr solid angle. The calorimeter is supplemented with an active collimator/beam degrader system, an active segmented plastic target, a pair of low-mass cylindrical wire chambers and a 20-element cylindrical plastic scintillator hodoscope. The whole detector system is housed inside a temperature-controlled lead brick enclosure which in turn is lined with cosmic muon plastic veto counters. Commissioning and calibration data were taken during two three-month beam periods in 1999/2000 with pi+ stopping rates between 1.3*E3 pi+/s and 1.3*E6 pi+/s. We examine the timing, energy and angular detector resolution for photons, positrons and protons in the energy range of 5-150 MeV, as well as the response of the detector to cosmic muons. We illustrate the detector signatures for the assorted rare pion and muon decays and their associated backgrounds.Comment: 117 pages, 48 Postscript figures, 5 tables, Elsevier LaTeX, submitted to Nucl. Instrum. Meth.

Chaetopterid tubes from vent and seep sites: Implications for fossil record and evolutionary history of vent and seep annelids

Vestimentiferan tube worms living at deep-sea hydrothermal vents and cold seeps have been considered as a clade with a long and continuing evolutionary history in these ecosystems. Whereas the fossil record appears to support this view, molecular age estimates do not. The two main features that are used to identify vestimentiferan tubes in the fossil record are longitudinal ridges on the tube's surface and a tube wall constructed of multiple layers. It is shown here that chaetopterid tubes from modern vents and seeps—as well as a number of fossil tubes from shallow-water environments—also show these two features. This calls for a more cautious interpretation of tubular fossils from ancient vent and seep deposits. We suggest that: current estimates for a relatively young evolutionary age based on molecular clock methods may be more reliable than the inferences of ancient “vestimentiferans” based on putative fossils of these worms; not all of these putative fossils actually belong to this group; and that tubes from fossil seeps should be investigated for chitinous remains to substantiate claims of their potential siboglinid affinities

Irrigation-induced nitrate losses assessed in a Mediterranean irrigation district

Irrigated agriculture is crucial for productivity of major crops (mainly cereals) grown in Mediterranean countries, where extended and prolonged drought conditions adversely impact productivity. Under such conditions, irrigation and rainfall events combined with nitrogen (N) fertilization can induce nitrate (NO3) losses in irrigation return flows (IRFs). Such water-induced NO3 losses in IRFs were assessed during the 2007-2010 hydrological years in the 9495ha of the Akarsu Irrigation District (AID) of southern Turkey, with daily monitoring at three drainage gauging stations to quantify flow rates, NO3 concentrations and loads. Climatic data, soil characteristics, fertilizer N application rates to major crops, cropping patterns, and irrigation and rainfall depths were also recorded. Nitrate concentrations were higher in IRFs during winter months, ranging between 37 and 44mgNO3L-1 on average, compared to the concentrations in the irrigation season (10-23mgNO3L-1). Since most of the fertilizer N was applied in winter and early spring to wheat (2/3 of 195kgNha-1) and first crop corn (1/3 of 340kgNha-1) as preplant and surface applications; NO3 concentrations were high during these seasons because of the limited N consumption of these crops in their early growth stages. However, the NO3 load distributions in winter and summer months were similar. Annual loads of 39.7, 29.3, 55.3 and 55.2kg NO3-Nha-1 were measured in the 2007-2010 IRFs, respectively, with 45 to 57% occurring during the irrigation seasons. The consistent high NO3 over 4 years point to the potential to reduce losses and associated N pollution through better crop, irrigation and N fertilizer management. Well-established fertilizer and irrigation water management plans are critical to reduce NO3 pollution risks in Mediterranean irrigated lands. © 2014 Elsevier B.V.Sixth Framework Programme: INCO-CT-2005-015031 Firat University Scientific Research Projects Management Unit TUBITAK-108O582Authors gratefully acknowledge funding for this work by the European Commission reseach project in the context of FP6 with project acronym QUALIWATER (Project No. INCO-CT-2005-015031), IntenC project acronym MedSalin (TUBITAK and German-BMBF, TUBITAK-108O582) and partial support was received from Cukurova University Academic Research Projects Unit (Project No. ZF2006KAP1 and ZF2009KAP3). We are also thankful to Dr. Ramon Aragües at Departamento de Suelos y Riegos, CITA, Zaragoza, Spain for his in-depth review and suggestions for improvement of the manuscript