Program clocks in small mammals

Complex patterns of time, direction, and speed of running by small nocturnal mammals in activity wheels sometimes are duplicated almost exactly from night to night. These activity pattern repetitions disclose: (i) previously unknown capabilities of biological clocks to act as sequence programmers for behavior; (ii) that animals can retain a record of the sequence and timing of their activities covering an entire night; and (iii) that the activities of one night can bias an animal toward similar behavior on subsequent nights.     

Synchronizing rock clocks of Earth history

Calibration of the geological time scale is achieved by independent radioisotopic and astronomical dating, but these techniques yield discrepancies of approximately 1.0% or more, limiting our ability to reconstruct Earth history. To overcome this fundamental setback, we compared astronomical and 40Ar/39Ar ages of tephras in marine deposits in Morocco to calibrate the age of Fish Canyon sanidine, the most widely used standard in 40Ar/39Ar geochronology. This calibration results in a more precise older age of 28.201 +/- 0.046 million years ago (Ma) and reduces the 40Ar/39Ar method's absolute uncertainty from approximately 2.5 to 0.25%. In addition, this calibration provides tight constraints for the astronomical tuning of pre-Neogene successions, resulting in a mutually consistent age of approximately 65.95 Ma for the Cretaceous/Tertiary boundary.     

Trapped ions, laser cooling, and better clocks

Ions that are stored in electromagnetic "traps" provid the basis for extremely high resolution spectroscopy. By using lasers, the kinetic energy of the ions can be cooled to millikelvin temperatures, thereby suppressing Doppler frequency shifts. Potential accuracies of frequency standards and clocks based on such experiments are anticipated to be better than one part in 10(15).     

Circadian clocks in daily and seasonal control of development

The rotation of the earth results in regular changes in the light environment, and organisms have evolved a molecular oscillator that allows them to anticipate these changes. This daily molecular oscillator, known as the circadian clock, regulates a diverse array of physiologies across a wide variety of organisms. This review highlights a few of the insights we have into circadian clock regulation of development, in both plants and animals. A common thread linking plants and animals is the use of the circadian clock to sense changes in day length and to mediate a diverse number of photoperiodic responses.