Period clock

Expression of the period clock gene within different cell types in the brain of Drosophila adults and mosaic analysis of these cells influence on circadian behavioral rhythms. J. Neurosci. 12 3321-49. 

James, A.A., J. Ewer, P. Reddy, J.C. Hall M. Rosbash. 1986. Embryonic expression of the period clock gene in the central nervous system of Drosophila melanogaster. EMBO J. 5 2313-20. 

Reddy, P., A.C. Jacquier, N. Abovich, G. Petersen M. Rosbash. 1986. The period clock locus of D. melanogaster codes for a proteoglyctm. Cell 46 53-61. 

As described above, PYP is part of a family of proteins named Xanthopsins, which thus far have only been identified in proteobacteria. Nevertheless, PYP also shows striking similarities to the much larger family of PAS domains. These PAS domains were identified in proteins from all three kingdoms of fife, i.e., in the Bacteria, the Archaea, and the Eucarya. PAS is an acronym formed from the names of the proteins in which the PAS motive was first recognized the Drosophila period clock protein (PER), the vertebrate aryl hydrocarbon receptor nuclear translocator (ARNT), and the Drosophila single-minded protein (SIM). 

The simplest manifestation of nonlinear kinetics is the clock reaction—a reaction exliibiting an identifiable mduction period , during which the overall reaction rate (the rate of removal of reactants or production of final products) may be practically indistinguishable from zero, followed by a comparatively sharp reaction event during which reactants are converted more or less directly to the final products. A schematic evolution of the reactant, product and intenuediate species concentrations and of the reaction rate is represented in figure A3.14.2. Two typical mechanisms may operate to produce clock behaviour. 

Figure A3.14.2. Characteristic features of a clock reaction, illustrated for the Landolt reaction, showing (a) variation of product concentration witii induction period followed by sharp reaction event (b) variation of overall reaction rate witli course of reaction.

The Landolt reaction (iodate + reductant) is prototypical of an autocatalytic clock reaction. During the induction period, the absence of the feedback species (Irere iodide ion, assumed to have virtually zero initial concentration and fomred from the reactant iodate only via very slow initiation steps) causes the reaction mixture to become kinetically frozen . There is reaction, but the intemiediate species evolve on concentration scales many orders of magnitude less than those of the reactant. The induction period depends on the initial concentrations of the major reactants in a maimer predicted by integrating the overall rate cubic autocatalytic rate law, given in section A3.14.1.1. 

Clock-type induction periods occur in the spontaneous ignition of hydrocarbon-oxygen mixtures [2], in the setting of concrete and the curing of polymers [3]. A related phenomenon is the induction period exhibited... 

A high throughput of instructions was achieved by pipelining the processing of instructions. The execution of instructions was divided into 12 suboperations that used 10 different circuits. When flowing smoothly, a new instruction could be taken every two clock periods (or 64 nanoseconds) and therefore up to six instructions were simultaneously in different phases of execution, and could be said to be in parallel execution (1). 

Real-time clocks (RTCs). Real-time systems are required to respond to events, as they occur, in a timely manner. This is especially crucial in process control systems where control actions applied at the wrong time may amplify process deviations or destabilize the processes. The nodes in the systems are interrupted periodically by the real-time clocks to maintain the ac tual elapsed times. 

Bad laboratory analyses are not always the fault of the laboratory.. Sampling plays a big role. One plant superintendent investigated every instance of suspect analyses in his plant using elaborate around-the-clock methods over a considerable period. His results revealed that over one half of the bad analyses were not the fault of the laboratory. We are all human and bad analyses will result from time to time. Rather than resubmit samples, it may be well to spend a few minutes using the following methods as referees to evaluate the reasonableness of the results. 

The dependence of reaction rates on pH and on the relative and absolute concentrations of reacting species, coupled with the possibility of autocatalysis and induction periods, has led to the discovery of some spectacular kinetic effects such as H. Landolt s chemical clock (1885) an acidified solution of Na2S03 is reacted with an excess of iodic acid solution in the presence of starch indicator — the induction period before the appearance of the deep-blue starch-iodine colour can be increased systematically from seconds to minutes by appropriate dilution of the solutions before mixing. With an excess of sulfite, free iodine may appear and then disappear as a single pulse due to the following sequence of reactions ... 

Period 1) Clock gene and transcriptional repressor and negative limb (complex with CRY, PER2) of molecular circadian oscillators, essential for circadian clock plasticity and entrainment. 

OxyContin is a controlled-released form of oxycodone and indicated for the management of moderate to severe pain when a continuous, around-the-clock analgesic is needed for an extended period of time OxyContin is not intended for use as a PRN analgesic The patient may experience fewer adverse reactions with oxycodone tlian morphine, and the drug is effective and safe for the elderly. The tablets are to be swallowed whole and are not to be broken, chewed, or crushed. 

The binary pulsar PSR1913+16. In 1974 Russell Hulse and Joseph Taylor discovered a very special pulsar PSR1916+13. A striking feature that was revealed just after its discovery was a large shift of the pulses rate with a period of a few hours. This was explained by Doppler shift, so PSR1916-H13 is in fact a binary system in which a pulsar orbits about the center of mass of the system. Thanks to the presence of this very stable local clock, Hulse and Taylor were able to obtain all the orbital parameters of this system. By studying the variations of those parameters over nearly twenty years, they... 

Commercial production of food products is conducted in large-scale processing plants. As already mentioned, tomatoes are processed in plants continuously from June to late fall (autumn), 24 h per day, 7 days per week. This is also true of potatoes, wheat, soybeans, corn, and other large-scale commodity crops. Some crops, such as grapes, that might have a relatively short harvest season, may be processed around the clock to generate intermediate products, such as juice or young wine that can be stored for extended periods of time, whereas final products, which can be made from the intermediate products, may be produced over time as consumer demand requires. Final products may also be stored in their final retail or food service containers until demand requires distribution. 

When operators are used around the clock, at least 4 men are needed for each post and an extra man is often required as a substitute for vacation periods, sickness, and other absences. This extra person may be used as a substitute for more than one position. 

In Gubbio, Italy, a 1 cm layer of clay between extensive limestone formations marks the boundary between the Cretaceous and Tertiary Periods. This clay layer was known to have been deposited about 65 million years ago when many life forms became extinct, but the length of time associated with the deposition was not known. In an attempt to measure this time with normally deposited meteoritic material as a clock, extensive measurements of iridium abundances (and those of many other elements) were made on the Gubbio rocks. Neutron activation analysis was the principal tool used in these studies. About 50 elements were searched for in materials like the earth s crust, about 40 were detected and about 30 were measured with useful precision [26-28]2. 

Nelson I think it affects the bursting. There is another clock here. If we add iberiotoxin to bladder strips, the amplitudes and durations of the phasic contractions increase. We also observe a slowing of the phasic contraction frequency. This suggests that it is some sort of slow Ca2+ dependent process that causes longer periods between contractions. The net effect of iberiotoxin is a large increase in force amplitude and duration rise, the frequency goes down. 

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