Circadian_rhythm

qas: question: For what do Circadian rhythms let an organism prepare?
answers: text: environmental changes

question: What can an organism that uses circadian rhythms use to its advantage that others can not?
answers: text: resources

question: By better using resources, how does that improve an organism's chances of surviving?
answers: text: selective advantage

question: By improving what processes does the use of circadian rhythms serve to benefit the individual?
answers: text: internal metabolic

question: What insect has been studied concerning the inheritability of rhythms?
answers: text: fruit flies

question: What allows organisms to anticipate and prepare for unexpected environmental changes?

question: What kind Of resources can organisms without circadian rhythms capitalize on?

question: What do circadian rhythms put at a selective disadvantage in evolutionary terms?

question: What is rhythmicity more important for regulating then it is for coordinating with the environment?
context: Circadian rhythms allow organisms to anticipate and prepare for precise and regular environmental changes. They thus enable organisms to best capitalize on environmental resources (e.g. light and food) compared to those that cannot predict such availability. It has therefore been suggested that circadian rhythms put organisms at a selective advantage in evolutionary terms. However, rhythmicity appears to be as important in regulating and coordinating internal metabolic processes, as in coordinating with the environment. This is suggested by the maintenance (heritability) of circadian rhythms in fruit flies after several hundred generations in constant laboratory conditions, as well as in creatures in constant darkness in the wild, and by the experimental elimination of behavioral, but not physiological, circadian rhythms in quail.

qas: question: What type of animals have been shown to have circadian rhythms only at certain times?
answers: text: Arctic animals

question: What daily feature do animals that show limited circadian rhythms need?
answers: text: sunrises and sunsets

question: In a study, when did reindeer at 70 degrees north only show circadian rhythms?
answers: text: autumn, winter and spring

question: At what degree north did reindeer show rhythms only in autumn and summer?
answers: text: 78 degrees

question: What aninmals  do researchers think might also show a variance in circadian rhythms in different seasons?
answers: text: other Arctic animals

question: When do subarctic animals have circadian rythms?

question: When do reindeer below 70 degrees show circadian rythems?

question: What reinder at 78 degrees do not show circadian rythems?

question: What animals show circadian rythems during the costant light of summer?
context: Norwegian researchers at the University of Tromsø have shown that some Arctic animals (ptarmigan, reindeer) show circadian rhythms only in the parts of the year that have daily sunrises and sunsets. In one study of reindeer, animals at 70 degrees North showed circadian rhythms in the autumn, winter and spring, but not in the summer. Reindeer on Svalbard at 78 degrees North showed such rhythms only in autumn and spring. The researchers suspect that other Arctic animals as well may not show circadian rhythms in the constant light of summer and the constant dark of winter.

qas: question: What produces a self-sustaining rhythm?
answers: text: central oscillator

question: When do the CCA1  and LHY function?
answers: text: morning

question: Which loop that consists of GI and ELF4 functions?
answers: text: evening

question: What was the previous belief of feedback in the gene loop?
answers: text: negative feedback loop

question: What researcher showed that the gene  feedback loop serves as a repressor?
answers: text: Andrew Millar

question: What is driven by  single feedback loop?

question: When do CCA1 ELF4 function?

question: When do GI and LHY function?

question: What does increased mRNA signals contribute to?

question: What did Andrew Millar show in 2000?
context: The central oscillator generates a self-sustaining rhythm and is driven by two interacting feedback loops that are active at different times of day. The morning loop consists of CCA1 (Circadian and Clock-Associated 1) and LHY (Late Elongated Hypocotyl), which encode closely related MYB transcription factors that regulate circadian rhythms in Arabidopsis, as well as PRR 7 and 9 (Pseudo-Response Regulators.) The evening loop consists of GI (Gigantea) and ELF4, both involved in regulation of flowering time genes. When CCA1 and LHY are overexpressed (under constant light or dark conditions), plants become arrhythmic, and mRNA signals reduce, contributing to a negative feedback loop. Gene expression of CCA1 and LHY oscillates and peaks in the early morning, whereas TOC1 gene expression oscillates and peaks in the early evening. While it was previously hypothesised that these three genes model a negative feedback loop in which over-expressed CCA1 and LHY repress TOC1 and over-expressed TOC1 is a positive regulator of CCA1 and LHY, it was shown in 2012 by Andrew Millar and others that TOC1 in fact serves as a repressor not only of CCA1, LHY, and PRR7 and 9 in the morning loop but also of GI and ELF4 in the evening loop. This finding and further computational modeling of TOC1 gene functions and interactions suggest a reframing of the plant circadian clock as a triple negative-component repressilator model rather than the positive/negative-element feedback loop characterizing the clock in mammals.

qas: question: What is the Drosophila gene the cause of?
answers: text: sleep disorder FASPS

question: What is the Drosophila gene also known as?
answers: text: period

question: What is Familial advanced sleep phase syndrome?
answers: text: FASPS

question: What kind of clock have genetic functions?
answers: text: biological clock

question: What does the body interpret from the gene feedback loop?
answers: text: time of the day

question: What Jean is responsible for the circadian rhythm?

question: What kind of clock does not have genetic functions?

question: How do cells of the body interpret fluctuations in light?

question: What does a defect in the period genome cause?
context: A defect in the human homologue of the Drosophila "period" gene was identified as a cause of the sleep disorder FASPS (Familial advanced sleep phase syndrome), underscoring the conserved nature of the molecular circadian clock through evolution. Many more genetic components of the biological clock are now known. Their interactions result in an interlocked feedback loop of gene products resulting in periodic fluctuations that the cells of the body interpret as a specific time of the day.[citation needed]

qas: question: Whose work habits and environment prevents them from maintaining a regular sleep pattern?
answers: text: airline pilots

question: What can the lack of regular sleep patterns cause?
answers: text: fatigue

question: What organizations cites this disruption of sleep patterns as a cause of accidents?
answers: text: NTSB

question: What has the NTSB conducted to find the cause of pilot fatigue?
answers: text: research studies

question: Of what does the NTSB want to find a means of doing?
answers: text: combating fatigue

question: Who follows a very natural human circadian rhythem?

question: what does a natural circadian rhythem lead to?

question: Who conducted studies on sewardes fatigue?
context: Due to the work nature of airline pilots, who often cross several timezones and regions of sunlight and darkness in one day, and spend many hours awake both day and night, they are often unable to maintain sleep patterns that correspond to the natural human circadian rhythm; this situation can easily lead to fatigue. The NTSB cites this as contributing to many accidents[unreliable medical source?]  and has conducted several research studies in order to find methods of combating fatigue in pilots.

qas: question: What is the earliest recorded instance of circadian rhythm?
answers: text: 4th century B.C.E

question: What ship captain described daily leaf movements?
answers: text: Androsthenes

question: What tree leaves did Androsthenes describe?
answers: text: tamarind

question: What type of Chinese texts mention circadian process in humans?
answers: text: medical

question: When did the Chinese use diurnal rhythms to remember Acu-points?
answers: text: 13th century

question: What was first recorded in 400 BC?

question: What did Alexander the great described?

question: What philosophers first described the diurnal process in humans?

question: What was first described in medical texts during the 1300s?

question: What did Androsthenes use the noon and midnight manual for?
context: The earliest recorded account of a circadian process dates from the 4th century B.C.E., when Androsthenes, a ship captain serving under Alexander the Great, described diurnal leaf movements of the tamarind tree. The observation of a circadian or diurnal process in humans is mentioned in Chinese medical texts dated to around the 13th century, including the Noon and Midnight Manual and the Mnemonic Rhyme to Aid in the Selection of Acu-points According to the Diurnal Cycle, the Day of the Month and the Season of the Year.

qas: question: What is the plant expression of circadian rhythm?
answers: text: when to flower

question: What do plants need to attract to their flowering?
answers: text: pollinators

question:  With what feature of environment do plants need to be in sync?
answers: text: light cycle

question: What does adaptive advantage allow for plants?
answers: text: Anticipation of changes

question: Where can an understanding of circadian rhythms of plants be an advantage?
answers: text: agriculture

question: What plant behavior is not controlled by circadian rythems??

question: What are constant but not self sustaining?

question: What needs to be in sync with ambient temperatures?
context: Plant circadian rhythms tell the plant what season it is and when to flower for the best chance of attracting pollinators. Behaviors showing rhythms include leaf movement, growth, germination, stomatal/gas exchange, enzyme activity, photosynthetic activity, and fragrance emission, among others. Circadian rhythms occur as a plant entrains to synchronize with the light cycle of its surrounding environment. These rhythms are endogenously generated and self-sustaining and are relatively constant over a range of ambient temperatures. Important features include two interacting transcription-translation feedback loops: proteins containing PAS domains, which facilitate protein-protein interactions; and several photoreceptors that fine-tune the clock to different light conditions. Anticipation of changes in the environment allows appropriate changes in a plant's physiological state, conferring an adaptive advantage. A better understanding of plant circadian rhythms has applications in agriculture, such as helping farmers stagger crop harvests to extend crop availability and securing against massive losses due to weather.

qas: question: What has the simplest known circadian clock?
answers: text: prokaryotic cyanobacteria

question: With how many proteins can the circadian clock of Synechococcus elongatus are needed to reproduce its effect?
answers: text: three proteins

question: What type of feedback mechanism was previously thought to be needed to sustain the clock?
answers: text: DNA

question: How long a rhythm were researchers able to sustain in the in vitro experiment?
answers: text: 22-hour

question: What were the only proteins necessary to the circadian timekeeper experiment?
answers: text: KaiA, KaiB, KaiC

question: What organism has the most complex circadian clock?

question: Where can the circadian clock of theprokaryotic cyanobacteria be reconstituted?

question: What was the minimum amount of time the clock could be sustained in vitro?

question: What three proteins needed to be removed to sustain the in vitro clock?
context: The simplest known circadian clock is that of the prokaryotic cyanobacteria. Recent research has demonstrated that the circadian clock of Synechococcus elongatus can be reconstituted in vitro with just the three proteins (KaiA, KaiB, KaiC) of their central oscillator. This clock has been shown to sustain a 22-hour rhythm over several days upon the addition of ATP. Previous explanations of the prokaryotic circadian timekeeper were dependent upon a DNA transcription/translation feedback mechanism.[citation needed]

qas: question: To what is the circadian rhythm tied?
answers: text: light–dark cycle

question: What conditions will produce a free-running rhythm in humans?
answers: text: total darkness

question: What are the environmental factors that can change the rhythm?
answers: text: zeitgebers

question: What do blind mole rats have in place of vision?
answers: text: photoreceptors

question: What cycle is seperate from the circadian rythem?

question: What does total light cause in humans?

question: What is the term for the environmental cues that dertermine daily rythems?

question: What kind of mammals need external stimuli to maintain their endogenous clock?
context: The rhythm is linked to the light–dark cycle. Animals, including humans, kept in total darkness for extended periods eventually function with a free-running rhythm. Their sleep cycle is pushed back or forward each "day", depending on whether their "day", their endogenous period, is shorter or longer than 24 hours. The environmental cues that reset the rhythms each day are called zeitgebers (from the German, "time-givers"). Totally blind subterranean mammals (e.g., blind mole rat Spalax sp.) are able to maintain their endogenous clocks in the apparent absence of external stimuli. Although they lack image-forming eyes, their photoreceptors (which detect light) are still functional; they do surface periodically as well.[page needed]

qas: question: What chemical is absent or low during daylight?
answers: text: Melatonin

question: When is the melatonin onset?
answers: text: 9 p.m

question: At its onset, what can be measured in blood or saliva?
answers: text: Melatonin

question: The presence of what is a circadian marker?
answers: text: hormone

question: What are the more reliable markers in determining sleep timing?
answers: text: melatonin phase

question: When is Meletonin found in the system?

question: What starts to decrease at 9 p.m.

question: What is more stable than the melatonin offset?

question: What is melatonin phase not a reliable marker for?
context: Melatonin is absent from the system or undetectably low during daytime. Its onset in dim light, dim-light melatonin onset (DLMO), at roughly 21:00 (9 p.m.) can be measured in the blood or the saliva. Its major metabolite can also be measured in morning urine. Both DLMO and the midpoint (in time) of the presence of the hormone in the blood or saliva have been used as circadian markers. However, newer research indicates that the melatonin offset may be the more reliable marker. Benloucif et al. found that melatonin phase markers were more stable and more highly correlated with the timing of sleep than the core temperature minimum. They found that both sleep offset and melatonin offset are more strongly correlated with phase markers than the onset of sleep. In addition, the declining phase of the melatonin levels is more reliable and stable than the termination of melatonin synthesis.

qas: question: What physical factor must be continuously monitored during temperature studies> 
answers: text: temperatures

question: At what time does the average adult human reach his lowest temperature?
answers: text: 05:00

question: How long before wake time is the lowest temperature reached?
answers: text: two hours

question: When does the temperature of morning type young adults reach its lowest?
answers: text: 04:00

question: What is the time of lowest temperature for evening type young adults?
answers: text: 06:00

question: What physical factor must be periodicly monitored in temperature studies?

question: What do evening types reach at 4:00 a.m?

question: What occurs close to waking for morning types?

question: Who reaches their minimum temperature in the middle of their waking hours?
context: For temperature studies, subjects must remain awake but calm and semi-reclined in near darkness while their rectal temperatures are taken continuously. Though variation is great among normal chronotypes, the average human adult's temperature reaches its minimum at about 05:00 (5 a.m.), about two hours before habitual wake time. Baehr et al. found that, in young adults, the daily body temperature minimum occurred at about 04:00 (4 a.m.) for morning types but at about 06:00 (6 a.m.) for evening types. This minimum occurred at approximately the middle of the eight hour sleep period for morning types, but closer to waking in evening types.

qas: question: Who noticed that sleepiness increases and decreases in a 24 hour period?
answers: text: Patrick and Gilbert

question: Who showed the animals could maintain activity in the absence of light and temperature changes?
answers: text: J.S. Szymanski

question: What animals rhythmic feeding times were studied in the early 20th century ?
answers: text: bees

question: What gene did Konopka and Benzer map in the early 1970 s?
answers: text: "period"

question: What mutation did Takahashi discover in 1994?
answers: text: circadian clock

question: Who observed that sleepiness remained steady over twenty-four hour period?

question: What did Patrick and Gilbert show in 1918?

question: What was noticed in the rhythmic feeding time of birds in the early twentieth century?

question: What did Ingeborg Beling and Oskar Wahl isolate in the early 1970s?
context: In 1896, Patrick and Gilbert observed that during a prolonged period of sleep deprivation, sleepiness increases and decreases with a period of approximately 24 hours. In 1918, J.S. Szymanski showed that animals are capable of maintaining 24-hour activity patterns in the absence of external cues such as light and changes in temperature. In the early 20th century, circadian rhythms were noticed in the rhythmic feeding times of bees. Extensive experiments were done by Auguste Forel, Ingeborg Beling, and Oskar Wahl to see whether this rhythm was due to an endogenous clock.[citation needed] Ron Konopka and Seymour Benzer isolated the first clock mutant in Drosophila in the early 1970s and mapped the "period" gene, the first discovered genetic determinant of behavioral rhythmicity. Joseph Takahashi discovered the first mammalian circadian clock mutation (clockΔ19) using mice in 1994. However, recent studies show that deletion of clock does not lead to a behavioral phenotype (the animals still have normal circadian rhythms), which questions its importance in rhythm generation.

qas: question: Inside of what can the molecular circadian clock operate?
answers: text: single cell

question: By functioning within a single, what is the system?
answers: text: cell-autonomous

question: What section of the brain periodically releases hormones?
answers: text: endocrine glands

question: How are sleep and wake cycles as well as body functions coordinated?
answers: text: biological clock

question: What do body hormone receptors do with the body's organs?
answers: text: synchronise

question: What requires multiple cells to function?

question: What results in a synchronized output electrical signals?

question: what section of the brain rarely releases hormones?

question: Where in the body are receptors for electrical signals located?

question: What is timed independently of the biological clock?
context: It is now known that the molecular circadian clock can function within a single cell; i.e., it is cell-autonomous. This was shown by Gene Block in isolated mollusk BRNs.[clarification needed] At the same time, different cells may communicate with each other resulting in a synchronised output of electrical signaling. These may interface with endocrine glands of the brain to result in periodic release of hormones. The receptors for these hormones may be located far across the body and synchronise the peripheral clocks of various organs. Thus, the information of the time of the day as relayed by the eyes travels to the clock in the brain, and, through that, clocks in the rest of the body may be synchronised. This is how the timing of, for example, sleep/wake, body temperature, thirst, and appetite are coordinately controlled by the biological clock.[citation needed]

qas: question: What signals plants to synchronize their internal clocks?
answers: text: Light

question: What do plants use to sense light?
answers: text: photoreceptors

question: What receptors absorb red and blue light in plants?
answers: text: phytochromes and cryptochromes

question: Which phytochrome found in seedlings deteriorates with light and growth?
answers: text: phyA

question: What is the main phytochrome found in seedling grown in light?
answers: text: phyB

question: What absorbes white light for plants?

question: What does Cry 1 degrade to?

question: What is Cry 1 is the main phytochtome for?

question: What photochromes are less stable than phyA?
context: Light is the signal by which plants synchronize their internal clocks to their environment and is sensed by a wide variety of photoreceptors. Red and blue light are absorbed through several phytochromes and cryptochromes. One phytochrome, phyA, is the main phytochrome in seedlings grown in the dark but rapidly degrades in light to produce Cry1. Phytochromes B–E are more stable with phyB, the main phytochrome in seedlings grown in the light. The cryptochrome (cry) gene is also a light-sensitive component of the circadian clock and is thought to be involved both as a photoreceptor and as part of the clock's endogenous pacemaker mechanism. Cryptochromes 1–2 (involved in blue–UVA) help to maintain the period length in the clock through a whole range of light conditions.

qas: question: What time cycle did studies in 1938 and 1990s use on humans?
answers: text: 28-hour

question: What conditions were suppressed in the 28 hour wake-sleep cycle studies ?
answers: text: time cues

question: How long did the suppression of time clues study last?
answers: text: month

question: What is this forced type of study called?
answers: text: forced desynchrony

question: When in the cycle do wake-sleep cycles break off from the circadian period?
answers: text: 24.18 hours

question: What did Kleitman do in the 1990's?

question: Whar dir Czeisler do in 1938?

question: When can normal people adjust to a 28 hr sleep cycle?

question: What happens at 24.5 hours?
context: Studies by Nathaniel Kleitman in 1938 and by Derk-Jan Dijk and Charles Czeisler in the 1990s put human subjects on enforced 28-hour sleep–wake cycles, in constant dim light and with other time cues suppressed, for over a month. Because normal people cannot entrain to a 28-hour day in dim light if at all,[citation needed] this is referred to as a forced desynchrony protocol. Sleep and wake episodes are uncoupled from the endogenous circadian period of about 24.18 hours and researchers are allowed to assess the effects of circadian phase on aspects of sleep and wakefulness including sleep latency and other functions.[page needed]

qas: question: What effect does jet-lag and shift-work have on the human body?
answers: text: profound consequences

question: Animals that eat during resting periods show what body increase?
answers: text: body mass

question: How does irregular eating during shift-work effect insulin?
answers: text: insulin sensitivity

question: Besides insulin sensitivity, what other effect does shift-work have on the body?
answers: text: higher body mass

question: What type of work can lead to heart, hypertension and inflammation?
answers: text: Shift-work

question: What does shift work have little effect on?

question: What causes animals to have decreased body mass?

question: What decreases insulin sensativity?

question: What kind of work leads to lower body mass?
context: Shift-work or chronic jet-lag have profound consequences on circadian and metabolic events in the body. Animals that are forced to eat during their resting period show increased body mass and altered expression of clock and metabolic genes.[medical citation needed] In humans, shift-work that favors irregular eating times is associated with altered insulin sensitivity and higher body mass. Shift-work also leads to increased metabolic risks for cardio-metabolic syndrome, hypertension, inflammation.

qas: question: What do studies show has a bidirectional relationship with the circadian system?
answers: text: abusive drugs

question: What do abusive drugs effect in the circadian system?
answers: text: circadian pacemaker

question: What do drug abusers show in their circadian processes?
answers: text: disrupted rhythms

question: What can the disrupted circadian system cause?
answers: text: abuse and relapse

question: What can disruption to genetics and environment in the sleep cycle cause?
answers: text: susceptibility to addiction

question: What studies show a minor relationship between the circadian system and drug abuse?

question: What is displayed by individuals when not abusing drugs?

question: What do steady rhythms increase?

question: What may be increased by a person's normal sleep and wake cycle?
context: Studies conducted on both animals and humans show major bidirectional relationships between the circadian system and abusive drugs. It is indicated that these abusive drugs affect the central circadian pacemaker. Individuals suffering from substance abuse display disrupted rhythms. These disrupted rhythms can increase the risk for substance abuse and relapse. It is possible that genetic and/or environmental disturbances to the normal sleep and wake cycle can increase the susceptibility to addiction.

qas: question: What is theorized to have evolved with circadian rhythms?
answers: text: photosensitive proteins

question: What is thought that circadian rhythm evolved to protect?
answers: text: replicating DNA

question: From what did  DNA need to be protected in the earliest cells? 
answers: text: ultraviolet radiation

question: One possible reason for the development of the circadian system is the need to counteract what ?
answers: text: redox reactions

question: What environmental event occurred 2.3 million years ago?
answers: text: Great Oxidation Event

question: What type of proteins developed as a result of circadian rhythms?

question: What developed to protect replicating DNA from ultraviolet radiation and night?

question: What type of replication is only done during the day?

question: What simple organism provides evidence the DNA replicates at night?

question: What event occurred approximately 2.3 million years ago?
context: What drove circadian rhythms to evolve has been an enigmatic question. Previous hypotheses emphasized that photosensitive proteins and circadian rhythms may have originated together in the earliest cells, with the purpose of protecting replicating DNA from high levels of damaging ultraviolet radiation during the daytime. As a result, replication was relegated to the dark. However, evidence for this is lacking, since the simplest organisms with a circadian rhythm, the cyanobacteria, do the opposite of this - they divide more in the daytime. Recent studies instead highlight the importance of co-evolution of redox proteins with circadian oscillators in all three kingdoms of life following the Great Oxidation Event approximately 2.3 billion years ago. The current view is that circadian changes in environmental oxygen levels and the production of reactive oxygen species (ROS) in the presence of daylight are likely to have driven a need to evolve circadian rhythms to preempt, and therefore counteract, damaging redox reactions on a daily basis.

qas: question: What is the body clock gene in animals necessary to ensure?
answers: text: cellular/metabolic events

question: What do mice without the clock gene become?
answers: text: hyperphagic and obese

question: Beside obesity, how else does the lack of a circadian clock effect   the mice?
answers: text: glucose metabolism

question: How certain is it that these circadian clock  effects are the same in humans?
answers: text: not clear

question: What gene needs to be deleted to cause obesity in mice?
answers: text: Rev-ErbA alpha clock

question: What does thhe addition of the clock gene in mice demonstrate?

question: what happens to mice with the clock gene?

question: what facilitates nondiiet induced obesity in mice?

question: what effects are proven to be identical in mice and humans?

question: Deletion of what gene in himans causes diabetes?
context: Mutations or deletions of clock gene in mice have demonstrated the importance of body clocks to ensure the proper timing of cellular/metabolic events; clock-mutant mice are hyperphagic and obese, and have altered glucose metabolism. In mice, deletion of the Rev-ErbA alpha clock gene facilitates diet-induced obesity and changes the balance between glucose and lipid utilization predisposing to diabetes. However, it is not clear whether there is a strong association between clock gene polymorphisms in humans and the susceptibility to develop the metabolic syndrome.

qas: question: Where is the primary circadian gene located in humans?
answers: text: suprachiasmatic nucleus

question: Where are these cell groups found in humans?
answers: text: hypothalamus

question: What would the loss of the SCN cells cause in the sleep-wake rhythm?
answers: text: complete absence

question: What provides information to the SCN?
answers: text: eyes

question: What special cells in the eyes communicate directly to the SCN cells?
answers: text: ganglion

question: Where is the secondary circadian clocl located?

question: What surrounds the hypothalamus?

question: What do the SCN cells cause in the sleep-wake rythem?

question: What do the SCN recieve through the skin?

question: What does the pupil contain that are directly photosensative?
context: The primary circadian "clock" in mammals is located in the suprachiasmatic nucleus (or nuclei) (SCN), a pair of distinct groups of cells located in the hypothalamus. Destruction of the SCN results in the complete absence of a regular sleep–wake rhythm. The SCN receives information about illumination through the eyes. The retina of the eye contains "classical" photoreceptors ("rods" and "cones"), which are used for conventional vision. But the retina also contains specialized ganglion cells that are directly photosensitive, and project directly to the SCN, where they help in the entrainment (synchronization) of this master circadian clock.

qas: question: What did early research show people preferred as a day length?
answers: text: 25 hours

question: What was the fault not considered in the early theories of day length?
answers: text: artificial light

question: What did electric lighting in the evening do to the test subjects circadian phase?
answers: text: delayed

question: When did more stringent testing determine that humans preferred a 24 hour day? 
answers: text: 1999

question: To what is the 24 hours, 11 minutes day outcome of research closest ?
answers: text: solar day

question: Who prefers a 25 hour day when exposed to stimuli like daylight?

question: What did the research shield the participants from?

question: Who was aware of the phase-delaying effect of indoor ekectric lights?

question: When did testing determine peple preferred a 25 hour day?

question: Who estimated the human rythem was in perfect sinc with the solar day?
context: Early research into circadian rhythms suggested that most people preferred a day closer to 25 hours when isolated from external stimuli like daylight and timekeeping. However, this research was faulty because it failed to shield the participants from artificial light. Although subjects were shielded from time cues (like clocks) and daylight, the researchers were not aware of the phase-delaying effects of indoor electric lights.[dubious – discuss] The subjects were allowed to turn on light when they were awake and to turn it off when they wanted to sleep. Electric light in the evening delayed their circadian phase.[citation needed] A more stringent study conducted in 1999 by Harvard University estimated the natural human rhythm to be closer to 24 hours, 11 minutes: much closer to the solar day but still not perfectly in sync.

qas: question: Where else beside the SCN cells are independent circadian rhythms also found?
answers: text: organs and cells

question: What is the term for the independent clocks?
answers: text: peripheral oscillators

question: What is the SCN considered to be in comparison to the peripheral oscillators?
answers: text: master clock

question: In what body gland are the peripheral oscillators located?
answers: text: adrenal gland

question: To what do oscillators in the skin respond?
answers: text: light

question: Where are dependent circadian rythems found?

question: What is the term for dependent clocks?

question: What in the skin responds to temperature?

question: What structures are strong oscillators?
context: More-or-less independent circadian rhythms are found in many organs and cells in the body outside the suprachiasmatic nuclei (SCN), the "master clock". These clocks, called peripheral oscillators, are found in the adrenal gland,[citation needed] oesophagus, lungs, liver, pancreas, spleen, thymus, and skin.[citation needed] Though oscillators in the skin respond to light, a systemic influence has not been proven. There is also some evidence that the olfactory bulb and prostate may experience oscillations when cultured, suggesting that these structures may also be weak oscillators.[citation needed]