10 research outputs found
Results from the CERN pilot CLOUD experiment
During a 4-week run in OctoberâNovember 2006, a pilot experiment was performed at the CERN Proton Synchrotron in preparation for the Cosmics Leaving OUtdoor Droplets (CLOUD) experiment, whose aim is to study the possible influence of cosmic rays on clouds. The purpose of the pilot experiment was firstly to carry out exploratory measurements of the effect of ionising particle radiation on aerosol formation from trace H2SO4 vapour and secondly to provide technical input for the CLOUD design. A total of 44 nucleation bursts were produced and recorded, with formation rates of particles above the 3 nm detection threshold of between 0.1 and 100 cm -3 s -1, and growth rates between 2 and 37 nm h -1. The corresponding H2O concentrations were typically around 106 cm -3 or less. The experimentally-measured formation rates and htwosofour concentrations are comparable to those found in the atmosphere, supporting the idea that sulphuric acid is involved in the nucleation of atmospheric aerosols. However, sulphuric acid alone is not able to explain the observed rapid growth rates, which suggests the presence of additional trace vapours in the aerosol chamber, whose identity is unknown. By analysing the charged fraction, a few of the aerosol bursts appear to have a contribution from ion-induced nucleation and ion-ion recombination to form neutral clusters. Some indications were also found for the accelerator beam timing and intensity to influence the aerosol particle formation rate at the highest experimental SO2 concentrations of 6 ppb, although none was found at lower concentrations. Overall, the exploratory measurements provide suggestive evidence for ion-induced nucleation or ion-ion recombination as sources of aerosol particles. However in order to quantify the conditions under which ion processes become significant, improvements are needed in controlling the experimental variables and in the reproducibility of the experiments. Finally, concerning technical aspects, the most important lessons for the CLOUD design include the stringent requirement of internal cleanliness of the aerosol chamber, as well as maintenance of extremely stable temperatures (variations below 0.1 °C
The Modular Multispectral Imaging Array (MMIA) of the ASIM Payload on the International Space Station
Status Of The Development Of A Thin Foil High Throughput X-Ray Telescope For The Soviet Spectrum X-Gamma Mission
Status of the development of a thin-foil, high-throughput x-ray telescope for the Soviet Spectrum x-gamma mission
X-ray study of a test quadrant of the SODART telescopes using the expanded beam x-ray optics facility at the Daresbury synchrotron
X-ray study of a test quadrant of the SODART telescopes using the expanded beam x-ray optics facility at the Daresbury synchrotron
OBJECTIVE: To develop a predictive model to identify individuals with an
increased risk for undiagnosed diabetes, allowing for the availability of
information within the health care system. RESEARCH DESIGN AND METHODS: A
sample of participants from the Rotterdam Study (n = 1,016), aged 55-75
years, not known to have diabetes completed a questionnaire on
diabetes-related symptoms and risk factors and underwent a glucose
tolerance test. Predictive models were developed using stepwise logistic
regression analyses with the absence or presence of newly diagnosed
diabetes as the dependent variable and various items with a plausible
connection to diabetes as the independent variables. The models were
evaluated in another Dutch population-based study, the Hoorn Study (n =
2,364), in which the participants were aged 50-74 years. Performances of
the predictive models were compared by using receiver-operator
characteristics (ROC) curves. RESULTS: We developed three predictive
models (PMs), PM1 contained information routinely collected by the general
practitioner, while PM2 also contained variables obtainable by additional
questions. The third predictive model, PM3, included variables that had to
be obtained from a physical examination. These latter variables did not
have additive predictive value, resulting in a PM3 similar to PM2. The
area under the ROC curve was higher for PM2 than for PM1, but the 95% Cls
overlapped (0.74 [0.70-0.78] and 0.68 [0.64-0.72], respectively).
CONCLUSIONS: Using only information normally present in the files of a
general practitioner, a predictive model was developed that performed
similarly to one supplemented by information obtained from additional
questions. The simplicity of PM1 makes it easy to implement in the current
health care setting