Abstract-The provisioning of services in optical networks demands reliable transmission paths. This paper investigates the availability of optical connections with respect to the failure probability of the involved network components. Outages of the fiber links as well as potential hardware failures for different opaque and transparent node architectures are analyzed. The results are presented in terms of map diagrams which allow to determine the availability of a wavelength connection subject to the transmission distance and the number of traversed hops.
Background Serum neurofilament light chain (sNfL) is an established biomarker of neuro-axonal damage in multiple neurological disorders. Raised sNfL levels have been reported in adults infected with pandemic coronavirus disease 2019 (COVID-19). Levels in children infected with COVID-19 have not as yet been reported. Objective To evaluate whether sNfL is elevated in children contracting COVID-19. Methods Between May 22 and July 22, 2020, a network of outpatient pediatricians in Bavaria, Germany, the Coronavirus antibody screening in children from Bavaria study network (CoKiBa), recruited healthy children into a cross-sectional study from two sources: an ongoing prevention program for 1–14 years, and referrals of 1–17 years consulting a pediatrician for possible infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We determined sNfL levels by single molecule array immunoassay and SARS-CoV-2 antibody status by two independent quantitative methods. Results Of the 2652 included children, 148 (5.6%) were SARS-CoV-2 antibody positive with asymptomatic to moderate COVID-19 infection. Neurological symptoms—headache, dizziness, muscle aches, or loss of smell and taste—were present in 47/148 cases (31.8%). Mean sNfL levels were 5.5 pg/ml (SD 2.9) in the total cohort, 5.1 (SD 2.1) pg/ml in the children with SARS-CoV-2 antibodies, and 5.5 (SD 3.0) pg/ml in those without. Multivariate regression analysis revealed age—but neither antibody status, antibody levels, nor clinical severity—as an independent predictor of sNfL. Follow-up of children with pediatric multisystem inflammatory syndrome (n = 14) showed no association with sNfL. Conclusions In this population study, children with asymptomatic to moderate COVID-19 showed no neurochemical evidence of neuronal damage.
Today's optical networks usually still perform electrical signal processing at the nodes. However, optical switching is available which allows transparent data transmission along lightpaths. Additionally, hardware cost can be reduced by saving on transponders. We investigate different approaches for providing selective regeneration while considering the impact of physical transmission limitations. Mathematical programs are formulated to obtain optimal results.
Under span restoration or "link protection," situations arise where the end-to-end route of a restored path contains a "loopback," wherein a path doubles back on itself over part of its route following a restoration action. Investigators often independently observe this and presume that loopback detection and avoidance would thus lead to a more capacity-efficient form of span restoration. Intuitively this may be compelling and a seemingly obvious conclusion. We show, however, that this is an oversimplified view and that loopback elimination would provide none or only trivial amounts of spare capacity savings. Theoretical reasoning and experimental validations based on forcer analysis are given confirming and explaining the findings. The main insight is that while spare capacity may be used in loopbacks for one or more failure scenarios, in an efficient design, there is always one or more other failure scenarios which do use all the spare capacity without loopbacks. There is then no savings possible from loopback elimination. The benefit to the field is that for the first time a quantitative assessment of this previously only qualitatively observed effect is provided and a theoretical framework is given within which we can understand in general when loopbacks will be associated with a possible capacity penalty and when there will be no such penalty at all. This adds to our basic knowledge in the area of survivable networking science.
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