1,069 research outputs found
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
BIOBIO â Betriebsmanagement-Indikatoren fĂŒr BiodiversitĂ€t in biologischen und extensiven Anbausystemen
In dem EU FP7-Projekt âBioBioâ soll ein allgemeines Set von Indikatoren fĂŒr BiodiversitĂ€t in biologischen und extensiven Anbausystemen in Europa entwickelt und getestet werden. Neben direkten Indikatoren fĂŒr Habitat-, Arten- und genetische DiversitĂ€t werden auch indirekte Indikatoren zur Bewirtschaftung der landwirtschaftlichen Betriebe und FlĂ€chen erfasst. In Fallstudien wird der Zusammenhang zwischen den ausgewĂ€hlten Indikatoren, den Betriebsystemen und direkten Indikatoren untersucht. Die Auswahl der Indikatoren erfolgte nach wissenschaftlichen Kriterien sowie nach Gesichtspunkten der PraktikabilitĂ€t und Anwendbarkeit. Hauptergebnis des Projektes wird ein Handbuch mit Factsheets der ausgewĂ€hlten Indikatoren sein
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 survivorsâ QoL was significantly
worse than younger ICU survivors, with a small-to-
medium
effect size (d=0.35 (â0.53 and â0.16)). Elderly survivorsâ
QoL was also significantly greater when measured slightly
before ICU, compared with follow-up,
with a small effect
size (d=0.26 (â0.44 and â0.08)). Finally, their QoL was
also marginally significantly worse than age-matched
community controls, also with a small effect size (d=0.21
(â0.43 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
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
Two-Dimensional Laser Diagnostics and Modeling of Counterflow Diffusion Flames
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86756/1/Sick51.pd
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