On the stability of periodic orbits in delay equations with large delay

We prove a necessary and sufficient criterion for the exponential stability of periodic solutions of delay differential equations with large delay. We show that for sufficiently large delay the Floquet spectrum near criticality is characterized by a set of curves, which we call asymptotic continuous spectrum, that is independent on the delay.Comment: postprint versio

Quality of life in elderly ICU survivors before the COVID-19 pandemic: a systematic review and meta-analysis of cohort studies

Objectives The influence of age on intensive care unit (ICU) decision-making is complex, and it is unclear if it is based on expected subjective or objective patient outcomes. To address recent concerns over age-based ICU decision-making, we explored patient-assessed quality of life (QoL) in ICU survivors before the COVID-19 pandemic. Design A systematic review and meta-analysis of cohort studies published between January 2000 and April 2020, of elderly patients admitted to ICUs. Primary and secondary outcome measures We extracted data on self-reported QoL (EQ-5D composite score), demographic and clinical variables. Using a random-effect meta-analysis, we then compared QoL scores at follow-up to scores either before admission, age-matched population controls or younger ICU survivors. We conducted sensitivity analyses to study heterogeneity and bias and a qualitative synthesis of subscores. Results We identified 2536 studies and included 22 for qualitative synthesis and 18 for meta-analysis (n=2326 elderly survivors). Elderly survivors’ QoL was significantly worse than younger ICU survivors, with a small-to- medium effect size (d=0.35 (−0.53 and −0.16)). Elderly survivors’ QoL was also significantly greater when measured slightly before ICU, compared with follow-up, with a small effect size (d=0.26 (−0.44 and −0.08)). Finally, their QoL was also marginally significantly worse than age-matched community controls, also with a small effect size (d=0.21 (−0.43 and 0.00)). Mortality rates and length of follow-up partly explained heterogeneity. Reductions in QoL seemed primarily due to physical health, rather than mental health items. Conclusions The results suggest that the proportionality of age as a determinant of ICU resource allocation should be kept under close review and that subjective QoL outcomes should inform person-centred decision -aking in elderly ICU patients. PROSPERO registration number CRD42020181181

Analysis of the Technical and Economic Potential for Mid-Scale Distributed Wind: December 2007 - October 31, 2008

This report examines the status, restrainers, drivers, and estimated development potential of mid-scale (10 kW - 5000 kW) distributed wind energy projects

DI Diesel Engine Combustion Visualized by Combined Laser Techniques

In this work we demonstrate that the progress of the combustionccycle in a four-cylinder (in-line) 1.9 1 direct injection Diesel engine can be studied effectively using different laser visualization techniques. Direct optical access to the piston bowl was facilitated by inserting quartz windows in one of the pistons. The flow field at the time of injection was characterized by seeding the flow and illuminating the piston bowl with a laser light sheet. Fuel spray development, auto-ignition and flame propagation in a Diesel cycle were followed by laser shadowgraphy and high speed cinematography while simultaneous laser induced fluorescence (LIF) and Mie scattering images were taken to distinguish the fuel distribution in the liquid and vapor phase. In addition, two dimensional distributions of OH and NO, formed during n-heptane/air combustion in the same engine, were recorded in the pressure range 5 to 50 bar by LIF following narrowband excitation using tunable excimer lasers. Finally, further work, designed to obtain quantitative images and hence data for comparison with model calculations, is outlined.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86790/1/Sick50.pd

Delay-induced dynamics and jitter reduction of passively mode-locked semiconductor lasers subject to optical feedback

We study a passively mode-locked semiconductor ring laser subject to optical feedback from an external mirror. Using a delay differential equation model for the mode-locked laser, we are able to systematically investigate the resonance effects of the inter-spike interval time of the laser and the roundtrip time of the light in the external cavity (delay time) for intermediate and long delay times. We observe synchronization plateaus following the ordering of the well-known Farey sequence. Our results show that in agreement with the experimental results a reduction of the timing jitter is possible if the delay time is chosen close to an integer multiple of the inter-spike interval time of the laser without external feedback. Outside the main resonant regimes the timing jitter is drastically increased by the feedback.DFG, 43659573, SFB 787: Halbleiter - Nanophotonik: Materialien, Modelle, BauelementeDFG, 87159868, GRK 1558: Kollektive Dynamik im Nichtgleichgewicht: in kondensierter Materie und biologischen SystemenEC/FP7/264687/EU/Postgraduate Research on Photonics as an Enabling Technology/PROPHE

Two-Dimensional Laser Diagnostics and Modeling of Counterflow Diffusion Flames

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86756/1/Sick51.pd