Saturating Exponential Function Research Articles

ESR dating of the quaternary deep-sea sediment core RC17-177

The deep-sea sediment core RC17-177 from the west equatorial Pacific was dated with ESR using the signal at g = 2.0036 of foraminifera. The measured dose rate parameters were: U-, Th- and K-concentrations, 234U- 230Th- and 231Pa-excess (initial values were assumed to be constant), average water content (derived from carbonate content) and a k α -factor of 0.1 ± 0.02 (own experiment). The ESR-signal growth curves on γ-irradiation have been fitted by single exponential saturation functions. However, significant deviations from a single exponential form have been observed for larger γ-doses. Agreement between ESR ages from the signal at g = 2.0036 and those from an independent δ 18O stratigraphy was observed up to 800 ka. The existence of outliers could be explained by variable initial Th-excess or water content at different depths. On the contrary, the signal at g = 2.0006 delivered ADs (and corresponding ages) that are far too small due to a low thermal stability.

Effect of sleep deprivation on EEG slow wave activity within non-REM sleep episodes in the rat

Recordings of 10 rats were obtained during the first 8 h of the light period under control conditions and after 24 h of sleep deprivation (SD). Non-rapid eye movement sleep (non-REMS) and EEG spectra in the range of 0.5–4.0 Hz were analyzed for 4 sec epochs. The time course of EEG slow wave activity within non-REMS episodes was closely approximated by a saturating exponential function. The time constant of approx. 50 sec varied little over consecutive 2 h periods and was not significantly changed by SD. The maximal level of EEG slow wave activity attained within non-REMS episodes (corresponding to the asymptote level of the fitted function) decreased over consecutive 2 h periods and was massively enhanced after SD. The study documents both the invariant and the homeostatically regulated aspect of the intraepisodic build-up of EEG slow wave activity.

Extrapolation of thermoluminescence— laboratory dose curves obeying the saturating exponential equation

Abstract A scheme is presented for calculating confidence contours for the parameters of the saturating exponential function fitted to experimental TL-dose data. The contours are accurate but, because of the non-linearity of the function, the corresponding probabilities are not. The conditions for obtaining good precision without excessive effort are explored. A reasonable prescription is six equally-spaced doses, with the largest about six times the intercept on the TL-dose plot, and with eight and seven replicates at the lowest doses of the first- and second-glow data sets respectively, and two replicates at all other doses.

Electroencephalogram analysis of non-rapid eye movement sleep in rats.

Sleep states and power spectra of the electroencephalogram were determined for consecutive 4-s epochs during 24 h in rats that had been implanted with electrodes under deep pentobarbital anesthesia. The power spectra in non-rapid eye movement sleep (NREMS) showed marked trends: low-frequency activity (0.75-7.0 Hz) declined progressively throughout the 12-h light period (L) and remained low during most of the 12-h dark period (D); high-frequency activity (10.25-25.0 Hz) rose toward the end of L and reached a maximum at the beginning of D. Within a single NREMS episode (duration 0.5-5.0 min), slow-wave activity (0.75-4.0 Hz) increased progressively to a plateau level. The rise was approximated by a saturating exponential function: although the asymptote level of the function showed a prominent 24-h rhythm, the time constant remained relatively stable (approximately 40 s). After short interruptions of NREMS episodes, slow-wave activity rose more steeply than after long interruptions. The marked 24-h variation of maximum slow-wave activity within NREMS episodes may reflect the level of a homeostatic sleep process.

Proton-induced coloring of multicomponent glasses

Proton-induced absorption over the 280-700-nm region and growth of that coloring with increasing dosage of proton radiation were determined for three Schott glasses used as focusing elements in the International Ultraviolet Explorer. It was found that the absorption spectra for each glass can be fitted with three Gaussian shaped bands in the near UV-visible range, while a fourth Gaussian characterizes the absorption edge. For doses up to 10(7) rads, the dependence of the induced absorption alpha on total dose Phi is accurately described by the saturating exponential function alpha(lambda,Phi) = alpha(s)[1 - exp(-bPhi)], where alpha(s) and b are constants dependent on the wavelength and glass type. The proton irradiation results were then compared to the effects of electron irradiation on those same three types of glass. For any one glass, it was determined that electrons and protons produced absorption bands with peaks at the same energies but with different saturation levels. For the glasses and wavelength region investigated, proton irradiation induced higher absorption saturation levels alpha(s) in the longer wavelengths, while electron irradiation induced greater absorption in the shorter wavelengths.

Performance of a high-sensitivity chromatographic argon lonization system as determined by calibration with a pulse technique using a solid sample injector

The response of a small argon detector to varied amounts of fatty acid esters injected onto GLC columns is examined. In the field intensified current region, the ionization current increase of the detector is strictly linear with the concentration of the solute moving through the cell up to a generated peak height current of about 3 nA (Tables 1 and 2, as well as Figure 2). Small quantities of substances with homologous structures and of similar size give rise to current responses that correspond to their molar concentrations. Larger solute concentrations elicit a detector response following an exponential saturation function, as had become previously evident in a steady-state calibration study with propane-argon gas mixtures. A procedure for converting the present peak to the prior established time-invariant detector responses is out-lined. We thus demonstrated that the response for argon detectors, deduced from measurements of varying concentrations of propane, is also applicable to peak currents resulting from slug-injections of high-boiling solutes onto standard GLC columns.