Feasibility study of tomato fruit characterization by fast XRF analysis for quality assessment and food traceability.

Food product nutritional and sensory characteristics are often deeply linked to its territory of origin; therefore, its authentication by means of elemental composition becomes crucial for traceability and fighting food fraud. This study aims to establish a fast and reproducible procedure for origin and quality assessment of Sicilian tomato fruits, including PGI "Pomodoro di Pachino", by using the X-ray fluorescence (XRF) technique. Measurements were performed on different parts of PGI Pachino tomatoes belonging to the same production lot. Principal Component and Cluster Analyses show that the samples cluster accordingly with the production lot, disentangling the different parts of the fruit. This procedure, which uses XRF yield elemental pattern and statistical analysis, establishes a solid basis for characterizing elemental profiles by a fast XRF in-situ campaign, supporting the traceability system. The reliability of XRF results was confirmed by comparing elemental concentrations with ICP-MS measurements, performed for comparison, and tomato literature values.

Delayed luminescence induced by complex domains in water and in TEOS aqueous solutions.

Many recent studies on water have conjectured a complex structure composed of hydrogen bonded low- and high-density domains. In this work the structure of pure water and aqueous solutions of silica gel (TEOS) has been investigated by using delayed luminescence, which has previously shown a significant increase in aqueous salt solutions where low-density domain formation is expected. Photon emission shows an Arrhenius trend with an activation energy in water-TEOS solutions larger than in pure water and salt-water solutions. Moreover, delayed photon emission decay shows an intrinsic lifetime of about 5 µs both in solutions and in pure water that, along with secondary lifetimes induced by the presence of TEOS, could be related to the formation of different domains.

Note: Dead time causes and correction method for single photon avalanche diode devices.

Single photon avalanche diode (SPAD) is the new generation of Geiger-Muller (GM) detectors, developed with semiconductor technology, and able to detect single photons, mainly in visible range. In this work we study the signal generation process and the dead time (DT) mechanisms of the device under a constant light regime. According to our results, it is possible to discriminate low rate signals from afterpulse and noise production and, moreover, to overcome the saturation effect due to the dead time losses. Starting from hybrid DT model [S. H. Lee and R. P. Gardner, Appl. Radiat. Isot. 53, 731 (2000)] we have been able to evaluate the real amount of incident photon rate up to 10(7) cps using a passive quenched device with 0.97 mus total dead time. In this way the passive quenched SPAD achieves the same performance of the active quenched one showing that relatively complex data analysis and complex device implementation are comparable solutions for constant light measurement. We also analyze some effects, lacking in GM counter, which should be introduced in the analysis of semiconductor device, as afterpulse, reduced photon detection efficiency, and noise production.

Role of water content in dielectric properties and delayed luminescence of bovine Achilles' tendon.

In order to investigate the role of water network in collagen structure, measurement of dielectric permittivity was performed on bovine Achilles' tendon as a function of water content. The data show a sudden decrease of the permittivity at each measured frequency value when the tendon humidity decreases. A similar behaviour is shown by the total number of photons emitted in delayed luminescence (DL) experiments. The comparison of the two results is in agreement with the hypothesis that DL is connected to the excitation and subsequent decay of collective electronic states, whose properties depend on the organized structure of the system.

Delayed luminescence from bovine Achilles' tendon and its dependence on collagen structure.

Delayed luminescence from ox Achilles' tendons is found to depend on the order parameters of the collagen fibres and on both water content and the temperature, which affect those parameters.

Delayed luminescence of biological systems arising from correlated many-soliton states.

The kinetics of the delayed luminescence arising from correlated coherent many-soliton states in low-dimensional macromolecular systems, is calculated and shown to be different from the one arising from independent soliton states. The correlation between coherent electron states is essential at relatively high levels of excitation in the presence of very long macromolecules in a system. These conditions can be fulfilled in such biological systems, like algae Acetabularia Acetabulum. The cytoskeleton of this unicellular alga contains macromolecular structures (actin filaments, microtubules, etc.) of the length of several hundreds angstroms and more, in which many-soliton coherent states can exist. Indeed, the correlated coherent model is shown to give better fit of the experimental data for this type of algae in a wide range of intensities of the stimulating light, as compared with the model of noncorrelated solitons. The nonlinearity of the dependence of delayed luminescence intensity on the level of excitation increases with the increase of correlation between solitons.

Analogous features of delayed luminescence from Acetabularia acetabulum and some solid state systems.

This paper compares some features of the delayed luminescence in the seconds range emitted from an unicellular alga Acetabularia acetabulum and from some solid state systems. Results lead us to think that such delayed luminescence is connected to the dimension of the ordered structures present in both biological and solid state systems. In particular, for the biological system examined, these structures are thought to be those which contribute to the dynamic formation of the cytoskeleton.

Changes in membrane potential and delayed luminescence of Acetabularia acetabulum.

This paper examines the effect of changes in membrane potential on the critical parameters of delayed luminescence of Acetabularia acetabulum. We show that these parameters are altered by changes in membrane potential in ways that may reflect concomitant changes in energy storage and energy coupling.

Delayed luminescence from simple biological systems.

Photoinduced ultraweak photon emission in the seconds time range from several living organisms is described. Some characteristics of this phenomenon and its dependence on some physical parameters are discussed. Some experimental evidence of the connection between this phenomenon and the functional state of the biological systems is reported.

The spontaneous ultraweak luminescence of living systems.

The results of experimental research on ultraweak photon emission carried out at the Institute of Physics, Catania University, are presented here. A correlation has been demonstrated to exist between photon emission and growth activity in the germination of soya seeds and also during the exponential phase of the growth of yeast cell cultures. In addition an experiment on the self irradiation of yeast cells is reported that confirms the mitogenic effect hypothesized by Gurwitsch.