Search Results

You are looking at 111 - 120 of 12,228 items for :

  • All content x
Clear All
Acta Veterinaria Hungarica
Authors: Orsolya Erdősi, Katalin Szakmár, Olivér Reichart, Zsuzsanna Szili, Noémi László, Péter Székely Körmöczy, and Péter Laczay

55 Garrido, A., Chapela, M., Román, B., Fajardo, P., Lago, J. and Vieites, J. M. (2013): A new multiplex real-time PCR developed method for Salmonella spp. and Listeria monocytogenes

Restricted access

Abstract  

Results of a self-observation of the working time distribution of an university teacher for a period of 28 years are reported. Averaged over the whole period, the teaching activities take 18%, scientific work −20%, and the various kinds of administrative, organizational and technical activities −51% of the working time. The changes of the working time distribution and of the working day duration during the years and the respective data related to the months in the year are presented. The working time data are compared with the growth of the scientific production of the observed person.

Restricted access

Abstract  

All nuclear spectroscopy systems, whether measuring charged particles, X-rays, or gamma-rays, exhibit dead time losses during the counting process due to pulse processing in the electronics. Several techniques have been employed in an effort to reduce the effects of dead time losses on a spectroscopy system including live time clocks and loss-free counting modules. Live time extension techniques give accurate results when measuring samples in which the activity remains roughly constant during the measuring process (i.e., the dead time does not change significantly during a single measurement period). The loss-free counting method of correcting for dead time losses, as introduced by HARMS and improved by WESTPHAL (US Patent No. 4,476,384) give better results than live time extension techniques when the counting rate changes significantly during the measurement. However, loss-free counting methods are limited by the fact that an estimation of the uncertainty associated with the spectral counts can not be easily determined, because the corrected data no longer obeys Poisson statistics. Therefore, accurate analysis of the spectral data including the uncertainty calculations is difficult to achieve. The Ortec® DSPECPLUS implements an improved zero dead time method that accurately predicts the uncertainty from counting statistics and overcomes the limitations of previous loss-free counting methods. The uncertainty in the dead-time corrected spectrum is calculated and stored with the spectral data (Patent Pending). The GammaVision-32® analysis algorithm has been improved to propagate this uncertainty through the activity calculation. Two experiments are set up to verify these innovations. The experiments show that the new method gives the same reported activity and associated uncertainties as the well-proven Gedcke-Hale live time clock. It is thus shown that over a wide range of dead times the new ZDT method tracks the true counting rate as if it had zero dead time, and yields an accurate estimation of the statistical uncertainty in the reported counts.

Restricted access

Abstract  

Integro-differential inequalities with initial time difference arediscussed. They play an important role in the investigation of initial value problems of integro-differential equations where the initial time differs. The existence of extremal solutions is investigated by the monotone iterative technique.

Restricted access

Abstract  

A new approach to the problem of the dead-time of pulse detection systems is proposed. The presented method of the correction for counting losses is based on the evaluation of the shortest time interval between two successive output pulses.

Restricted access

Determination of power-time curves of bacterial growth

Study of lowest growth temperature

Journal of Thermal Analysis and Calorimetry
Authors: Sun Haitao, Nan Zhaodong, Liu Yongjun, Zhang Honglin, and Zhang Tonglei

Bacterial growth power-time curves were determined with a 2277 Thermal Activity Monitor. Bacterial multiplication curves were measured at different temperatures and an experimental model was established. Both growth rate constants and lowest growth temperatures were calculated.

Restricted access

Abstract  

Some of the techniques used in atom-at-a-time investigations of both nuclear and chemical properties of transactinide elements will be discussed. Constraints on the systems that are valid for exploring chemical properties when only a few atoms at a time are available and recent developments in instrumentation are considered. The current status of investigations of the chemical properties of the transactinides is summarized and prospects for additional studies are evaluated.

Restricted access

Abstract  

Positron annihilation lifetime spectroscopy was used to study the time dependence of the ortho-positronium lifetime and intensity and the ortho-positronium lifetime distribution in a poly(ethylene oxide)/poly(methyl methacrylate) blend after heat treatment. The recently introduced maximum entropy for lifetime analysis (MELT) program and the POSITRONFIT program were used for evaluation of the spectra. The blend shows a large excess in free volume hole size shortly after cooling from the melt. Withi time, the hole size decreases, while the orthio-positronium intensity remains constant. The lifetime distribution width does njot vary systematically with time. Differential scanning calorimetry measurements show that crystallisation of the poly(ethylene oxide) phase occurs parallel to the decrease in ortho-positronium lifetime.

Restricted access

Abstract  

It is a well-known empirical fact that when informetric processes are observed over an extending period of time, the entire shape of the distribution changes. In particular, it has been shown that concentration aspects change. In this paper the recently introduced co-concentration coefficient (C-CC) is investigated via simple stochastic models of informetric processes to investigate its time-dependence. It is shown that it is important to distinguish between situations where the zero-producers can be counted and those where they cannot. A previously published data set is used to illustrate how the empirical C-CC develops in time and the general features are compared with those derived from the theoretical model.

Restricted access

Abstract  

A novel method for the determination of rate constants of reactions, the time-variable method, is proposed in this paper. The method needs only three time points (t), peak heights () and pre-peak areas (), obtained from the measured thermoanalytical curve. It does not require the thermokinetic reaction to be completed. It utilizes data-processing on a computer to give the rate constants. Four reaction systems, including a first-order reaction, second-order reactions (with equal concentrations and with unequal concentrations) and a third-order reaction, were studied with this method. The method was validated and its theoretical basis was verified by the experimental results.

Restricted access