Cryogenic Thermometer Calibration Facility at CERN

A cryogenic thermometer calibration facility has been designed and is being commissioned in preparation for the very stringent requirements on the temperature control of the LHC superconducting magnets. The temperature is traceable in the 1.5 to 30 K range to standards maintained in a national metrological laboratory by using a set of Rhodium-Iron temperature sensors of metrological quality. The calibration facility is designed for calibrating simultaneously 60 industrial cryogenic thermometers in the 1.5 K to 300 K temperature range, a thermometer being a device that includes both a temperature sensor and the wires heat-intercept. The thermometers can be calibrated in good and degraded vacuum or immersed in the surrounding fluid and at different Joule self-heating conditions that match those imposed by signal conditioners used in large cryogenic machinery. The calibration facility can be operated in an automatic mode and all the control and safety routines are handled by a Programmable Logic Controller (PLC). LabVIEW is used both as the PLC operator interface and for configuring and reading the thermometric data sampled by the higher accuracy laboratory equipment. The isothermal support onto which the thermometers are mounted is thermally anchored through the wiring to a helium bath. The calibration procedure begins once the temperature of the support is stabilized. Measured data is presented and it is possible to infer that the absolute accuracy that can be obtained is better than ± 5 mK for the full temperature range

Clinical features and outcomes of elderly hospitalised patients with chronic obstructive pulmonary disease, heart failure or both

Background and objective: Chronic obstructive pulmonary disease (COPD) and heart failure (HF) mutually increase the risk of being present in the same patient, especially if older. Whether or not this coexistence may be associated with a worse prognosis is debated. Therefore, employing data derived from the REPOSI register, we evaluated the clinical features and outcomes in a population of elderly patients admitted to internal medicine wards and having COPD, HF or COPD + HF. Methods: We measured socio-demographic and anthropometric characteristics, severity and prevalence of comorbidities, clinical and laboratory features during hospitalization, mood disorders, functional independence, drug prescriptions and discharge destination. The primary study outcome was the risk of death. Results: We considered 2,343 elderly hospitalized patients (median age 81 years), of whom 1,154 (49%) had COPD, 813 (35%) HF, and 376 (16%) COPD + HF. Patients with COPD + HF had different characteristics than those with COPD or HF, such as a higher prevalence of previous hospitalizations, comorbidities (especially chronic kidney disease), higher respiratory rate at admission and number of prescribed drugs. Patients with COPD + HF (hazard ratio HR 1.74, 95% confidence intervals CI 1.16-2.61) and patients with dementia (HR 1.75, 95% CI 1.06-2.90) had a higher risk of death at one year. The Kaplan-Meier curves showed a higher mortality risk in the group of patients with COPD + HF for all causes (p = 0.010), respiratory causes (p = 0.006), cardiovascular causes (p = 0.046) and respiratory plus cardiovascular causes (p = 0.009). Conclusion: In this real-life cohort of hospitalized elderly patients, the coexistence of COPD and HF significantly worsened prognosis at one year. This finding may help to better define the care needs of this population

Current self-distribution effects in oxide-confined vertical-cavity surface-emitting lasers

We develop a self-consistent electro-optical model for oxide-confined Vertical-Cavity Surface-Emitting Lasers, including optical polarization and spin-flip dynamics. When subject to large signal modulation, current self-distribution effects reduce the amount of spatial-hole burning in the device, leading to a reduced overshoot during transients and an increased damping of the relaxation oscillations. © 2009 Springer Science+Business Media, LLC.Peer Reviewe

Theoretical study of colliding pulse passively mode-locked semiconductor ring lasers with an intracavity Mach–Zehnder modulator

In this paper, we theoretically study the impact of an intracavity filter based on a Mach-Zehnder interferometer (MZI) on the pulses emitted by InGaAsP/InP passively mode-locked quantum well ring lasers. The filter allows to control the net gain curvature in the device, hereby providing for control over the modes that participate in the dynamics. Simulations of a traveling-wave model indicate that the pulsewidth can be controlled and reduced down to 500 fs. We present and verify a simple algorithm, which can be used for calculating the optimum values of the MZI parameters. The optimum parameters are then used in the study of an MZI passive-mode-locked laser under various operating condition

Theoretical study of colliding pulse passively mode-locked semiconductor ring lasers with an intracavity Mach–Zehnder modulator

In this paper, we theoretically study the impact of an intracavity filter based on a Mach-Zehnder interferometer (MZI) on the pulses emitted by InGaAsP/InP passively mode-locked quantum well ring lasers. The filter allows to control the net gain curvature in the device, hereby providing for control over the modes that participate in the dynamics. Simulations of a traveling-wave model indicate that the pulsewidth can be controlled and reduced down to 500 fs. We present and verify a simple algorithm, which can be used for calculating the optimum values of the MZI parameters. The optimum parameters are then used in the study of an MZI passive-mode-locked laser under various operating condition