Streamflow variations across the Andes (18°-55°S) during the instrumental era.

The rivers originating in the southern Andes (18°-55°S) support numerous ecosystems and a large number of human populations and socio-economic activities in the adjacent lowlands of Chile, Argentina and Bolivia. Here we show that ca. 75% of the total variance in the streamflow records from this extensive region can be explained by only eight spatially coherent patterns of variability. Five (three) of these Andean patterns exhibit extreme dry (wet) conditions in recent years, with strong interannual variations in northern Chile; long-term drying trends between 31° and 41°S; a transitional pattern in the central Patagonian Andes; and increasing trends in northwestern Argentina and southern Bolivia, the Fueguian Andes, and the eastern portion of the South Patagonian Icefield. Multivariate regression analyses show that large-scale indices of ENSO variability can predict 20% to 45% of annual runoff variability between 28° and 46°S. The influence of Antarctic and North Pacific indices becomes more relevant south of 43°S and in northwestern Argentina and southern Bolivia, respectively, but their overall skill as predictors of Andean streamflows is weak. The analyses provide relevant new information to improve understanding of the spatial coherence, the main temporal features, and the ocean-atmospheric forcings of surface runoff across the southern Andes.

[Subcontracting a steam sterilization activity: Impact on surgical instruments]. / Externalisation de l'activité de stérilisation : impact sur l'état des instruments chirurgicaux.

Subcontracting our institution's sterilization activity induced the implementation of an automated cleaning facility. Following this development, some of the resterilizable stainless steel needle holders started to show abnormal corrosion. Our study goal was to investigate the causes of this corrosion in order to optimize the sterilization circuit. A full sterilization process mapping and Ishikawa diagram enabled us to identify potential causes of corrosion. The needle holders' intrinsic characteristics, like steel quality and manufacturing, were analyzed as well as extrinsic factors such as the influence of preprocessing soaking conditions, steel passivation, water quality and the impact of corrosion inhibitors. Each potential factor of corrosion was tested in real conditions on needle holders' kits. The needle holders steel grade complies with medical standards and the tests showed that passivation and pre-processing conditions were not involved in the occurrence of corrosion, contrary to soaking length and use of softened rinsing water, containing more chloride than reverse osmosis water, and, thus conducive to rust formation. Moreover, corrosion inhibitors were deemed ineffective or incompatible. Due to this analysis, the incidence of corrosion was reduced by switching softened water to osmosis water and by introducing dynamic drying in the automated cleaning process. In addition, this work stresses the importance of minimizing waiting times and auditing the sterilization circuit before any subcontracting. Management Guidelines related to sterilization's outsourcing would probably have helped to limit this episode.

Climate variability 50,000 years ago in mid-latitude Chile as reconstructed from tree rings.

High-resolution proxies of past climate are essential for a better understanding of the climate system. Tree rings are routinely used to reconstruct Holocene climate variations at high temporal resolution, but only rarely have they offered insight into climate variability during earlier periods. Fitzroya cupressoides-a South American conifer which attains ages up to 3,600 years-has been shown to record summer temperatures in northern Patagonia during the past few millennia. Here we report a floating 1,229-year chronology developed from subfossil stumps of F. cupressoides in southern Chile that dates back to approximately 50,000 14C years before present. We use this chronology to calculate the spectral characteristics of climate variability in this time, which was probably an interstadial (relatively warm) period. Growth oscillations at periods of 150-250, 87-94, 45.5, 24.1, 17.8, 9.3 and 2.7-5.3 years are identified in the annual subfossil record. A comparison with the power spectra of chronologies derived from living F. cupressoides trees shows strong similarities with the 50,000-year-old chronology, indicating that similar growth forcing factors operated in this glacial interstadial phase as in the current interglacial conditions.