8 research outputs found
Traffic engineering with OSPF-TE and RSVP-TE: Flooding reduction techniques and evaluation of processing cost
No full textThis paper considers two important aspects related to the control plane of Traffic Engineered IP/MPLS networks: the "flooding reduction" mechanisms and the evaluation of processing cost for signaling and routing protocols. The flooding reduction mechanisms are needed to reduce the amount of information exchanged by Traffic Engineering enabled routing protocols. The trade-off between the amount of information exchanged and the network performance (connection blocking probability) is discussed in the light of specific aspects of OSPF-TE routing protocol and RSVP-TE signaling protocol. Different mechanisms are analyzed and a suggestion is given for the best one. The dynamic aspects related to the time needed to distribute the routing and signaling information are considered. Finally, the combined processing cost of routing and signaling is analyzed, and the possible bottlenecks of the architecture are discussed. It is worth mentioning that the discussed results have been derived not only with simulation/analysis but also with measurements coming from a testbed implementation. (c) 2005 Elsevier B.V. All rights reserved
Cerebral fat embolism after traumatic bone fractures: a structured literature review and analysis of published case reports
Get PDFBackground: The incidence of cerebral fat embolism (CFE) ranges from 0.9–11%, with a mean mortality rate of around 10%. Although no univocal explanation has been identified for the resulting fat embolism syndrome (FES), two hypotheses are widely thought: the ‘mechanical theory’, and the ‘chemical theory’. The present article provides a systematic review of published case reports of FES following a bone fracture. Methods: We searched MEDLINE, Web of Science and Scopus to find any article related to FES. Inclusion criteria were: trauma patients; age ≥ 18 years; and the clinical diagnosis of CFE or FES. Studies were excluded if the bone fracture site was not specified. Results: One hundred and seventy studies were included (268 cases). The male gender was most prominent (81.6% vs. 18.4%). The average age was 33 years (±18). The mean age for males (29 ± 14) was significantly lower than for females (51 ± 26) (p < 0.001). The femur was the most common fracture site (71% of cases). PFO was found in 12% of all cases. Univariate and multivariate regression analyses showed the male gender to be a risk factor for FES: RR 1.87 and 1.41, respectively (95%CI 1.27–2.48, p < 0.001; 95%CI 0.48–2.34, p < 0.001). Conclusions: FES is most frequent in young men in the third decades of life following multiple leg fractures. FES may be more frequent after a burst fracture. The presence of PFO may be responsible for the acute presentation of cerebral embolisms, whereas FES is mostly delayed by 48–72 h
Italian multicenter validation of cystic fibrosis questionnaire-R by A.L.Quittner and coll.
No full textGe-on-Si single-photon avalanche diode detectors: design, modeling, fabrication, and characterization at wavelengths 1310 and 1550 nm
Get PDFThe design, modeling, fabrication, and characterization of single-photon avalanche diode detectors with an epitaxial Ge absorption region grown directly on Si are presented. At 100 K, a single-photon detection efficiency of 4% at 1310 nm wavelength was measured with a dark count rate of ~ 6 megacounts/s, resulting in the lowest reported noise-equivalent power for a Ge-on-Si single-photon avalanche diode detector (1×10-14 WHz-1/2). The first report of 1550 nm wavelength detection efficiency measurements with such a device is presented. A jitter of 300 ps was measured, and preliminary tests on after-pulsing showed only a small increase (a factor of 2) in the normalized dark count rate when the gating frequency was increased from 1 kHz to 1 MHz. These initial results suggest that optimized devices integrated on Si substrates could potentially provide performance comparable to or better than that of many commercially available discrete technologies
Study of the response of silicon photomultipliers in presence of strong cross-talk noise
No full textAbstract Silicon Photomultipliers (SiPM) are interesting detectors for beam diagnostics applications due to their reduced dimensions and costs, and higher photon detection efficiency. Possible applications include longitudinal beam profile measurements by synchrotron light imaging, detection of optical transition radiation for energy spectrum measurements and medical imaging. However, quantitative measurement with SiPMs are jeopardized by the systematic reading error due to Optical Cross-talk (OC), i.e. optical coupling between neighbouring diodes in the array. OC results in overestimation of the impinging light level, and reflects the probability of a triggered avalanche creating a photon of suitable energy and direction to fire a second avalanche in another diode. In this paper, we derive a generalized response distribution for SiPM in presence of OC noise, which overcomes the limitations of assumptions currently made in literature and provides a correction of the SiPM response distribution valid for arbitrary large levels of OC
Optimization of epitaxial growth for thick Ge-on-Si structures used for single photon avalanche diode applications
No full textSPAD structures have been grown by RP-CVD and shown to have: excellent crystallinity, with low TDD; a smooth surface, suitable for device incorporation; and sharp doping profiles required to maximize performance. Device measurements have produced the highest SPDE of any Ge on Si SPAD recorded.</p
Design and performance of a prototype mesa-geometry Ge-on-Si single-photon avalanche diode detector at 1310 nm and 1550 nm wavelengths
No full textGe-on-Si single-photon detectors are fabricated and characterized at 1310 and 1550 nm. 4 % single-photon detection efficiency is observed at 1310 nm demonstrating the lowest reported noise equivalent power for Ge-on-Si single-photon detectors (1×10-14 WHz-1/2)
