Simulating the action of zeitgebers on a coupled two-oscillator model of the human circadian system

1984 ◽  
Vol 247 (3) ◽  
pp. R418-R426
Author(s):  
P. H. Gander ◽  
R. E. Kronauer ◽  
C. A. Czeisler ◽  
M. C. Moore-Ede
Keyword(s):  
Core Temperature ◽  
Activity Rhythm ◽  
Human Subjects ◽  
Model Performance ◽  
The Other ◽  
Oscillator Model ◽  
Temporal Isolation ◽  
The Core ◽  
Temperature Rhythm ◽  
Rest Activity

Our two-oscillator model was originally designed to describe the circadian rhythms of human subjects maintained in temporal isolation. The performance of this model in response to simulated environmental synchronizing cycles (zeitgebers) is examined here. Six distinct types of synchronization are demonstrated between the x oscillator (postulated to regulate the core temperature rhythm), the y oscillator (postulated to regulate the rest-activity rhythm), and z (the zeitgeber). Four types of synchronization are identifiable, if we consider only the periods of the three oscillators. Both x and y may be synchronized by z; either may synchronize with z while the other exhibits a different period; or x, y, and z may each show different periods. Two further classes of synchronization are discernible when phase criteria are taken into account. When either x or y is on the verge of desynchronizing from the other two oscillators, it undergoes periodic phase modulations while retaining the common overall period. The type of synchronization observed depends on the periods of x, y, and z and on the strength of the z drive. The effects of modifying each of these parameters have been systematically investigated by simulation, and model performance is summarized in terms of range of entrainment "maps." These constitute extensive sets of predictions about expected patterns of entrainment of the core temperature and rest-activity rhythms of human subjects exposed to various environmental zeitgebers. Experimental data are available against which model predictions can be tested.

Modeling the action of zeitgebers on the human circadian system: comparisons of simulations and data

1984 ◽  
Vol 247 (3) ◽  
pp. R427-R444
Author(s):  
P. H. Gander ◽  
R. E. Kronauer ◽  
C. A. Czeisler ◽  
M. C. Moore-Ede
Keyword(s):  
Core Temperature ◽  
Human Subjects ◽  
Specific Model ◽  
Endogenous Rhythms ◽  
Circadian Timing ◽  
Activity Rhythms ◽  
The Core ◽  
Circadian Timing System ◽  
The Common ◽  
Rest Activity

In our two-oscillator model for the human circadian timing system, the effect of an environmental synchronizing cycle (zeitgeber) is determined by the periods of the two oscillators and of the zeitgeber and by the zeitgeber strength. The oscillators x and y are postulated to regulate the core temperature and rest-activity rhythms, respectively. From published examples of experiments in which human subjects were exposed to artificial zeitgebers, it is possible to derive estimates of the periods of the core temperature and/or the rest-activity rhythms and the zeitgeber. Two strengths of zeitgeber input to the model that correspond to two of the common zeitgeber regimes used in human entrainment studies have now been elucidated. Thus specific model simulations can be generated for each of the available examples of entrainment of human subjects by artificial zeitgebers. Such simulations indicate that the model can reproduce, with remarkable subtlety, the types of full and partial entrainment observed experimentally. The model is thus demonstrated to accommodate the period and phase control of endogenous rhythms by environmental zeitgebers, which is a crucial functional attribute of circadian timing systems.

scholarly journals An unusual titanomagnetite replacing spinel

1993 ◽  
Vol 40 ◽  
pp. 300-313
Author(s):  
Aage Jensen
Keyword(s):  
Core Temperature ◽  
Electron Microprobe ◽  
The Other ◽  
Dyke Swarm ◽  
The Core ◽  
Ti Oxides ◽  
Small Content ◽  
Good Agreement

n a recent investigation of the Fe-Ti-oxides in the Koster dyke swarm, SW Sweden, one of the dykes from sector I (41197) was omitted because the cubic Fe-Ti-oxides in this dyke were found to deviate from those in all the other dykes. The Fe-Ti-oxides in 41197 consist partly of ilmenite as free grains, and partly of titanomagnetite with sandwich as well as trellis oxyexsolution lamellae of ilmenite. Some of the titanomagnetite grains have a core of grey spine!, and there are also grains consisting mainly of spine!, but with the spine! clearly being replaced by titanomagnetite. Electron microprobe analyses of these Fe-Ti-oxides have revealed that the ilmenite as free grains has a composition quite similar to that in the other Koster dykes from sector I. Apart from a small content of Cr, the ilmenite lamellae in the titanomagne­tite grains also show good agreement with the other Koster dykes from sector I, but there are small but significant differences between the ilmenite lamellae from grain to grain within the sample. The titanomagnetite groundmass also shows small but significant differences be­tween different grains. The composition of the titanomagnetite varies from ferrofer­rites to ferrochromferrites. The grey spine! varies from ferrospinel over ferrochromspinel to ferroferrichrom­spinel. Except for the spine! grain with only incipient replacement by titanomagne­tite, the spinels have a rim which is richer in Mg, Al and Zn and poorer in Cr and Fe+++ than the core. Temperature and fO2 of coexisting pairs of ilmenite and titanomagnetite varies from 991°C, fO2 10-12-9, to 1104°C, fO2 10-11-2.

Effects of Melatonin in Two Individuals with Alzheimer's Disease

1998 ◽  
Vol 87 (1) ◽  
pp. 331-339 ◽  
Author(s):  
Girardin Jean-Louis ◽  
Ferdinand Zizi ◽  
Hans Von Gizycki ◽  
Harvey Taub
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Circadian Rhythm ◽  
Aging Process ◽  
Activity Rhythm ◽  
The Other ◽  
Beneficial Effects ◽  
Melatonin Administration ◽  
Activity Cycles ◽  
Rest Activity

Dementia has been associated with circadian rhythm disturbances expressed in several dimensions including body temperature, hormonal concentrations, sleep and wakefulness patterns, and rest-activity cycles. These disturbances may be the result of a dampening in the amplitude of the circadian rhythm. One of the symptoms associated with the aging process has been a decline in the amplitude of the melatonin rhythm. Here, the results of melatonin administration to two patients with Alzheimer's disease are presented. Melatonin administration enhanced and stabilized the circadian rest-activity rhythm in one of the patients along with some reduction of daytime sleepiness and an improvement in mood. The other patient, who was characterized by less cognitive impairment, showed no significant changes associated with melatonin ingestion. Interestingly, the acrophase of rest-activity was delayed for about one hour in both patients. These results suggest that melatonin may have beneficial effects in some patients with Alzheimer's disease

Forced internal desynchronization between circadian temperature and activity rhythms in squirrel monkeys

1985 ◽  
Vol 248 (5) ◽  
pp. R567-R572
Author(s):  
P. H. Gander ◽  
R. Lydic ◽  
H. E. Albers ◽  
M. C. Moore-Ede
Keyword(s):  
Body Temperature ◽  
Squirrel Monkey ◽  
Activity Rhythm ◽  
The Body ◽  
Saimiri Sciureus ◽  
Dark Cycle ◽  
Temperature Rhythm ◽  
Internal Desynchronization ◽  
Body Temperature Rhythm ◽  
Rest Activity

In an attempt to force internal desynchronization between the rest-activity rhythm and the body temperature rhythm of the squirrel monkey (Saimiri sciureus), five animals were studied in a 14:14 light-dark cycle. In four animals a 28-h spectral component was found to predominate in the rest-activity rhythm, whereas an unentrained circadian component (tau = 25.9 +/- 0.4 h) predominated in the body temperature rhythm. Plots of the cycle-by-cycle acrophases of the two rhythms confirm that they desynchronize, due to the failure of the temperature rhythm to entrain to the light-dark cycle. These data from intact animals provide further support for the hypothesis that the squirrel monkey circadian timing system has at least two pacemakers. A rhythm for which the supra-chiasmatic nuclei (SCN) have previously been shown to be essential (rest-activity) simultaneously exhibited a different period from a rhythm (body temperature) that has been shown to persist after destruction of the SCN.

scholarly journals Circadian Disruption of Body Core Temperature and Rest–Activity Rhythms after General (Propofol) Anesthesia in Rats

2009 ◽  
Vol 110 (6) ◽  
pp. 1305-1315 ◽  
Author(s):  
Garance Dispersyn ◽  
Laure Pain ◽  
Yvan Touitou
Keyword(s):  
Body Temperature ◽  
Activity Rhythm ◽  
Temporal Structure ◽  
Intraperitoneal Administration ◽  
Body Core Temperature ◽  
Phase Advance ◽  
Temperature Rhythm ◽  
Temperature Rhythms ◽  
Normal Light ◽  
Rest Activity

Background General anesthesia is commonly associated with sleep disorders, fatigue, drowsiness, and mood alterations in patients. The authors examined whether general (propofol) anesthesia can impact the circadian temporal structure by disturbing circadian rest-activity and body temperature rhythms under normal light-dark conditions (light-dark 12:12 h) in rats. Methods A group of rats was anesthetized with propofol, and another was injected with 10% Intralipid, which was used as a control lipidic solution. The authors examined six groups of rats according to the Zeitgeber time of intraperitoneal administration (ZT6, ZT10, ZT16) and the substance injected (propofol or Intralipid). Results On the day after anesthesia, propofol induced a significant 60- to 80-min phase advance of both rest-activity and body temperature rhythms. A significant 45- to 60-min phase advance of body temperature and a significant 20-min phase advance of rest-activity were still observed on the second day after anesthesia. The amplitudes of both rest-activity and body temperature rhythms were decreased on the first and second days after anesthesia. The 24-h mean rest-activity rhythm was decreased on the day after anesthesia, whereas the 24-h mean body temperature rhythm was not modified. Conclusion The results demonstrate the disturbing effects of propofol anesthesia on the circadian time structure in rats under normal light conditions.

The Salvage of Ideas: Schumpeter and the Core Problems Still Confronting Economics

2003 ◽  
pp. 15-26
Author(s):  
P. Wynarczyk
Keyword(s):  
The Other ◽  
The Core ◽  
Other Hand ◽  
The One

Two aspects of Schumpeter' legacy are analyzed in the article. On the one hand, he can be viewed as the custodian of the neoclassical harvest supplementing to its stock of inherited knowledge. On the other hand, the innovative character of his works is emphasized that allows to consider him a proponent of hetherodoxy. It is stressed that Schumpeter's revolutionary challenge can lead to radical changes in modern economics.

The Final ‘Thank You’

Derrida Today ◽  
2010 ◽  
Vol 3 (1) ◽  
pp. 21-36
Author(s):  
Grant Farred
Keyword(s):  
South Africa ◽  
South African ◽  
Jacques Derrida ◽  
Political Transition ◽  
The Other ◽  
World Cup ◽  
The Core ◽  
Nelson Mandela ◽  
Black President ◽  
The Moment

‘The Final “Thank You”’ uses the work of Jacques Derrida and Friedrich Nietzsche to think the occasion of the 1995 rugby World Cup, hosted by the newly democratic South Africa. This paper deploys Nietzsche's Zarathustra to critique how a figure such as Nelson Mandela is understood as a ‘Superman’ or an ‘Overhuman’ in the moment of political transition. The philosophical focus of the paper, however, turns on the ‘thank yous’ exchanged by the white South African rugby captain, François Pienaar, and the black president at the event of the Springbok victory. It is the value, and the proximity and negation, of the ‘thank yous’ – the relation of one to the other – that constitutes the core of the article. 1

Analysis (Hans Morgenthau) to the concept of power and applied to the units of the international system

2019 ◽  
Vol 1 (1) ◽  
pp. 138
Author(s):  
Saif Nasrat Tawfiq Al - Haramazi
Keyword(s):  
Applied Sciences ◽  
International System ◽  
The Other ◽  
Human Sciences ◽  
Basic Requirement ◽  
The Core ◽  
Hans Morgenthau

The theoretical curriculum in all disciplines is a basic requirement that nourishes the minds of the intellectual and cognitive recipients in the various scientific and cognitive stages. This is the framework that distinguishes the academic understanding of the anarchic, which is one of the most important and important keys in thinking and success in that jurisdiction or field, , Because it is unreasonable and logical to get into the core of any subject without searching and searching for its intellectual and historical bases to find out the reasons and reasons that surrounded this idea which was later recognized as an important contribution to the field of human sciences. Applied Sciences and other from the other side.

AFRICAN WOMEN AND FORBIDDEN GROUNDS: FEMALE SEXUALITY AND SELF-DETERMINATION IN AFRICAN LITERATURE

Imbizo ◽  
2017 ◽  
Vol 7 (1) ◽  
pp. 40-54
Author(s):  
Oyeh O. Otu
Keyword(s):  
Female Sexuality ◽  
Sense Of Self ◽  
African Literature ◽  
The Other ◽  
Self Determination ◽  
African Women ◽  
The Core ◽  
The Many ◽  
The One ◽  
Sexual Repression

This article examines how female conditioning and sexual repression affect the woman’s sense of self, womanhood, identity and her place in society. It argues that the woman’s body is at the core of the many sites of gender struggles/ politics. Accordingly, the woman’s body must be decolonised for her to attain true emancipation. On the one hand, this study identifies the grave consequences of sexual repression, how it robs women of their freedom to choose whom to love or marry, the freedom to seek legal redress against sexual abuse and terror, and how it hinders their quest for self-determination. On the other hand, it underscores the need to give women sexual freedom that must be respected and enforced by law for the overall good of society.

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