Circadian system response to night work in relation to the individual circadian phase position

1979 ◽  
Vol 43 (2) ◽  
pp. 73-83 ◽  
Author(s):  
G. Hildebrandt ◽  
I. Stratmann
Keyword(s):  
Circadian System ◽  
Night Work ◽  
System Response ◽  
Circadian Phase ◽  
The Individual

scholarly journals Exercise time cues (zeitgebers) for human circadian systems can foster health and improve performance: a systematic review

2018 ◽  
Vol 4 (1) ◽  
pp. e000443 ◽  
Author(s):  
Philip Lewis ◽  
Horst W Korf ◽  
Liz Kuffer ◽  
J Valérie Groß ◽  
Thomas C Erren
Keyword(s):  
Public Health ◽  
Systematic Review ◽  
Circadian System ◽  
Eligibility Criteria ◽  
Pubmed Database ◽  
Preventative Strategy ◽  
Effects On Children ◽  
And Performance ◽  
The Individual ◽  
The Right

BackgroundCircadian system time cues (zeitgebers) acting synergistically at the right times can foster chronobiological homeostasis and ultimately health. Modern 24/7 societies are challenging chronobiological homeostasis and public health. Exercise has been discussed as a potential zeitgeber for the human circadian system. Thus, if timed correctly, exercise may help in maintenance of chronobiological homeostasis and foster public health amidst increasingly challenging 24/7 lifestyles.ObjectiveTo test, using a systematic review of the literature, the following hypothesis: exercise is a zeitgeber for the human circadian system.Data sourcesThe PubMed database was systematically searched on 19 October 2017 for relevant scientific studies and reports concerning chronobiology and exercise. Eligibility criteria were defined to include articles considering exercise as a potential zeitgeber for human circadian rhythmicity or chronobiological effects of exercise on health and/or physical performance. Cognitive effects and effects on children were excluded from the synthesis.ResultsOur systematic literature search and synthesis is compatible with the validity of the hypothesis. We report that potential exercise-zeitgeber properties may be used to improve health and performance.ConclusionsInformed timing of exercise, specific to the circadian rhythm phase and zeitgeber exposure of the individual, must be advocated in performance and disease contexts as an adjunct therapeutic or preventative strategy and physical enhancer.

Dynamic Analysis of Ball Bearings Due to Clearance Effect

2009 ◽  
Author(s):  
S. H. Upadhyay ◽  
S. C. Jain ◽  
S. P. Harsha
Keyword(s):  
Chaotic Behavior ◽  
Equations Of Motion ◽  
Peak Frequency ◽  
System Response ◽  
Ball Bearings ◽  
Outer Race ◽  
Lagrange’S Equation ◽  
Rolling Elements ◽  
Machine Systems ◽  
The Individual

In this paper, the nonlinear dynamic behavior of ball bearings due to radial internal clearance and rotor speed has been analyzed. The approach presented in this paper accounts for the contact between rolling elements and inner/outer races. The equations of motion of a ball bearing are formulated in generalized coordinates, using Lagrange’s equation considering the vibration characteristics of the individual constitute such as inner race, outer race, rolling elements. The effects of speed of rotor in which rolling element bearings shows periodic, quasi-periodic and chaotic behavior are analyzed. The results also show the intermittent chaotic behavior in the dynamic response is seen to be strongly dependent on the speed of the rotor. The results are obtained in the form of frequency responses. The validity of the proposed model verified by comparison of frequency components of the system response with those obtained from experiments. The peak-to-peak frequency response of the system for each speed is obtained. The current study provides a powerful tool design and health monitoring of machine systems.

scholarly journals Melatonin administration can entrain the free-running circadian system of blind subjects

2000 ◽  
Vol 164 (1) ◽  
pp. R1-R6 ◽  
Author(s):  
SW Lockley ◽  
DJ Skene ◽  
K James ◽  
K Thapan ◽  
J Wright ◽  
...  
Keyword(s):  
Circadian Rhythms ◽  
Core Body Temperature ◽  
Circadian System ◽  
Melatonin Treatment ◽  
Circadian Phase ◽  
Melatonin Administration ◽  
Free Running ◽  
Physiological Markers ◽  
Core Body ◽  
First Time

Although melatonin treatment has been shown to phase shift human circadian rhythms, it still remains ambiguous as to whether exogenous melatonin can entrain a free-running circadian system. We have studied seven blind male subjects with no light perception who exhibited free-running urinary 6-sulphatoxymelatonin (aMT6s) and cortisol rhythms. In a single-blind design, five subjects received placebo or 5 mg melatonin p.o. daily at 2100 h for a full circadian cycle (35-71 days). The remaining two subjects also received melatonin (35-62 days) but not placebo. Urinary aMT6s and cortisol (n=7) and core body temperature (n=1) were used as phase markers to assess the effects of melatonin on the During melatonin treatment, four of the seven free-running subjects exhibited a shortening of their cortisol circadian period (tau). Three of these had taus which were statistically indistinguishable from entrainment. In contrast, the remaining three subjects continued to free-run during the melatonin treatment at a similar tau as prior to and following treatment. The efficacy of melatonin to entrain the free-running cortisol rhythms appeared to be dependent on the circadian phase at which the melatonin treatment commenced. These results show for the first time that daily melatonin administration can entrain free-running circadian rhythms in some blind subjects assessed using reliable physiological markers of the circadian system.

scholarly journals Integration of brief light flashes varying in intensity and duration by the human circadian system

2019 ◽  
Author(s):  
Daniel S. Joyce ◽  
Manuel Spitschan ◽  
Jamie M. Zeitzer
Keyword(s):  
Phase Shift ◽  
Light Exposure ◽  
Temporal Integration ◽  
Circadian System ◽  
Flash Intensity ◽  
Flash Duration ◽  
Variable Intensity ◽  
Circadian Phase ◽  
Variable Duration ◽  
Circadian Phase Shift

AbstractThe human circadian system is exquisitely sensitive to light, through a pathway connecting the melanopsin-expressing intrinsically photosensitive retinal ganglion cells (ipRGCs) to the hypothalamic suprachiasmatic nuclei (SCN). ipRGCs are characterised by a delayed off-time following cessation of light exposure; we exploited this unusual physiologic property and examined how a sequence of flashes of bright light differing in intensity or duration presented in the biological night could delay the human circadian clock in vivo in healthy young participants (n=54). To understand the mechanism underlying circadian photoreception, we probed temporal integration by manipulating flash intensity and duration independently. In a 34-hour in-laboratory between-subjects design, we examined variable-intensity (3, 30, 95, 300, 950, 3000, or 9500 photopic lux; n=28 participants) flashes at fixed duration (2 ms), and variable-duration (10 μs, 100 μs, 1 ms, 10 ms, 100 ms, 1 sec, 10 sec) flashes at fixed intensity (2000 photopic lux; n=31 participants). We measured the phase shift of dim-light melatonin onset on the subsequent evening, and acute melatonin suppression and alertness during the flash sequence. In the variable-intensity study, we find a clear sigmoidal dose-response relationship for flash intensity and the induced circadian phase shift. In the variable-duration study, we find no parametric relationship between flash duration and induced circadian phase shift, indicating a relative insensitivity of the circadian system to flashes varying in duration. As the intermittent periods of darkness in our stimulation paradigm supports the recovery of extrinsic rod-cone signalling into the ipRGCs, our results strongly suggest rod-cone contributions into circadian photoreception.

Model Validation of Functional Responses Across Experimental Regions Using Functional Regression Extensions to the CORA Objective Rating System

2017 ◽  
Vol 2 (4) ◽  
Author(s):  
Scott M. Storm ◽  
Raymond R. Hill ◽  
Joseph J. Pignatiello ◽  
G. Geoffrey Vining ◽  
Edward D. White
Keyword(s):  
Functional Data ◽  
Rating System ◽  
System Response ◽  
Functional Regression ◽  
Response Functions ◽  
Weighted Linear Combination ◽  
Functional Responses ◽  
Parameter Configuration ◽  
Objective Rating ◽  
The Individual

As we continue to model more complex systems, the validation of dynamical responses has come to the forefront of modeling and simulation. One form of dynamic response is when the output is a function of time. The proper evaluation of functional data over an array of desired input parameters is critical to achieving a robust validation assessment of a simulation model. We extend the correlation analysis (CORA) objective rating system to validate functional data across experimental regions. Functional regression analysis is used to generate surrogate estimations of the system response functions at points within the region where experimental observations are absent. These CORA scores provide a measure of disagreement at each desired parameter configuration. An overall score for model validity is achieved using a weighted linear combination of the individual CORA scores. Finally, an improved CORA size scoring metric is introduced.

Rural settlement in the Age of Reason

2001 ◽  
Vol 8 (1) ◽  
pp. 2-23 ◽  
Author(s):  
Chris Dalglish
Keyword(s):  
Social Relations ◽  
Social Practice ◽  
Private Property ◽  
System Response ◽  
Routine Practice ◽  
Scottish Highlands ◽  
Age Of Reason ◽  
The Social ◽  
Material Environment ◽  
The Individual

AbstractThis paper discusses the project of an archaeology of capitalism through a case study situated in the southern Scottish Highlands. It is argued that archaeology as a discipline has a significant contribution to make to discussions of the emergence and development of the social relations of capitalism. This is because archaeology has as one of its main concerns mundane social practice or routine. Changes in everyday routine and the associated material environment made the ideological aspects of capitalism, focusing on the individual and private property, conceivable for some. These changes to the everyday environment were instigated by the landlords, inspired by enlightenment thought, in order to secure their ownership of certain estates as private property, which had been in dispute under the clan system. Response of the rural population to Improvement was varied and their continuing relationship with their landlord evolved with reference to certain key structuring dispositions. The essential issue for the farming population was land rights. The major conclusion of this paper as concerns archaeologies of capitalism is that we must distinguish between capitalism (an ideology of the individual made knowable in routine practice) and capitalist societies (those societies where capitalism is widespread but not necessarily universal). This allows consideration of varied experience of and interaction with capitalism in the past.

Individual differences in subjective and objective alertness during sleep deprivation are stable and unrelated

2003 ◽  
Vol 284 (2) ◽  
pp. R280-R290 ◽  
Author(s):  
Rachel Leproult ◽  
Egidio F. Colecchia ◽  
Anna Maria Berardi ◽  
Robert Stickgold ◽  
Stephen M. Kosslyn ◽  
...  
Keyword(s):  
Sleep Deprivation ◽  
Performance Tasks ◽  
Performance Deficits ◽  
Circadian Phase ◽  
Eyes Closed ◽  
Eyes Open ◽  
And Performance ◽  
Independent Effects ◽  
The Individual ◽  
Subjective Alertness

This study examines the individual reproducibility of alterations of subjective, objective, and EEG measures of alertness during 27 h of continuous wakefulness and analyzes their interrelationships. Eight subjects were studied twice under similar constant-routine conditions. Scales and performance tasks were administered at hourly intervals to define temporal changes in subjective and objective alertness. The wake EEG was recorded every 2 h, 2 min with eyes open and 2 min with eyes closed. Plasma glucose and melatonin levels were measured to estimate brain glucose utilization and individual circadian phase, respectively. Decrements of subjective alertness and performance deficits were found to be highly reproducible for a given individual. Remarkably, there was no relationship between the impairments of subjective and objective alertness. With increased duration of wakefulness, EEG activity with eyes closed increased in the delta range and decreased in the alpha range, but the magnitudes of these changes were also unrelated. These findings indicate that sleep deprivation has highly reproducible, but independent, effects on brain mechanisms controlling subjective and objective alertness.

scholarly journals Validation of Computational Fluid-Structure Interaction Analysis Methods to Determine Hydrodynamic Coefficients of a BOP Stack

2015 ◽  
Author(s):  
Raj Venuturumilli ◽  
Michael Tognarelli ◽  
Samir Khanna ◽  
Michael Triantafyllou
Keyword(s):  
Interaction Analysis ◽  
Fluid Structure Interaction ◽  
System Response ◽  
Hydrodynamic Coefficients ◽  
Element Analysis ◽  
Detailed Model ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Sixth Generation ◽  
The Individual

Drilling riser systems are subjected to hydrodynamic loads from vessel motions, waves, steady currents and vortex-induced motions. This necessitates a proper structural analysis during the design phase using techniques such as finite element analysis (FEA). Common approaches within the FEA packages approximate the individual components including BOP/LMRP (Blow-Out Preventer/Lower Marine Riser Package), subsea tree and wellhead using 2D or 3D beam/pipe elements with approximated effective mass and damping coefficients. Predicted system response can be very sensitive to the mass, hydrodynamic added mass and drag of the large LMRP/BOP/Tree components above the wellhead. In the past, gross conservative estimates on the hydrodynamic coefficients were made and despite this, design criteria were generally met. With the advent of large sixth-generation BOP stacks with the possibility of additional capping stacks, such approximations are no longer acceptable. Therefore, the possibility of relying on the more detailed capability of computational fluid-structure interaction (FSI) analysis for a better calculation of these coefficients is investigated. In this paper, we describe a detailed model developed for a 38:1 scaled down BOP and discuss the subsequent predictions of the hydrodynamic coefficients. The model output is compared against the data from the concurrent tests conducted in an experimental tow tank. The comparison demonstrates that computational FSI can be an effective and accurate tool for calculating the hydrodynamic coefficients of complex structures like BOPs.

scholarly journals Exploring light exposure of hospital nurses working rapidly rotating shifts in relation to sleepiness and sleep

2021 ◽  
Vol 2042 (1) ◽  
pp. 012111
Author(s):  
Mariëlle P.J. Aarts ◽  
Steffen L. Hartmeyer ◽  
Kars Morsink ◽  
Helianthe S.M. Kort
Keyword(s):  
Visual Inspection ◽  
Intervention Studies ◽  
Light Exposure ◽  
Hospital Nurses ◽  
Negative Effects ◽  
Limited Sample ◽  
Circadian Phase ◽  
Exposure Patterns ◽  
The Individual ◽  
Careful Manipulation

Abstract Nightshift work can negatively impact sleep, performance, and health. Careful manipulation of light exposure patterns can help reduce these negative effects but is challenging in conditions of rapidly rotating shiftwork and due to individual differences. As chronotype is related to shiftwork tolerance, we explored patterns of sleep, sleepiness, and light exposure during the first day of nightshift work between earlier and later chronotypes, based on data from an observational field study among rapidly rotating hospital nurses. Due to the limited sample size, only descriptive analyses and visual inspection were conducted. In line with findings of lower shiftwork tolerance, earlier chronotypes (N=6) seemed to be sleepier during work and sleep less than later types (N=7). Differences were also observed in light exposure patterns, revealing potential for light exposure interventions, and suggesting a contribution to shiftwork tolerance. For future intervention studies in aiming to identify a light exposure strategy, our findings highlight the importance of investigating light exposure relative to the individual circadian phase.

scholarly journals cpmA, a Gene Involved in an Output Pathway of the Cyanobacterial Circadian System

1999 ◽  
Vol 181 (11) ◽  
pp. 3516-3524 ◽  
Author(s):  
Mitsunori Katayama ◽  
Nicholas F. Tsinoremas ◽  
Takao Kondo ◽  
Susan S. Golden
Keyword(s):  
Vibrio Harveyi ◽  
Circadian System ◽  
Open Reading Frame ◽  
Circadian Gene ◽  
Reading Frame ◽  
Circadian Phase ◽  
System A ◽  
Reporter Strains ◽  
Pcc 7942 ◽  
Low Amplitude

ABSTRACT We generated random mutations in Synechococcus sp. strain PCC 7942 to look for genes of output pathways in the cyanobacterial circadian system. A derivative of transposon Tn5 was introduced into the chromosomes of reporter strains in which cyanobacterial promoters drive the Vibrio harveyi luxAB genes and produce an oscillation of bioluminescence as a function of circadian gene expression. Among low-amplitude mutants, one mutant, tnp6, had an insertion in a 780-bp open reading frame. The tnp6 mutation produced an altered circadian phasing phenotype in the expression rhythms of psbAI::luxAB,psbAII::luxAB, andkaiA::luxAB but had no or little effect on those of psbAIII::luxAB,purF::luxAB,kaiB::luxAB,rpoD2::luxAB,ndhD::luxAB, andconII::luxAB. This suggests that the interrupted gene in tnp6, named cpmA (circadian phase modifier), is part of a circadian output pathway that regulates the expression rhythms of psbAI, psbAII, andkaiA.

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