Optoelectronic properties of sexithiophene single crystals

UV—Vis absorption, photoluminescence (PL) and photoconductivity (PC) measurements have been carried out on sexithiophene (6T) single crystals grown from the vapor phase. UV—Vis absorption data were used to determine the absorption coefficient and refraction index under polarized light. The spectrum at polarization perpendicular to the unique axis b is similar to that measured on polycrystalline films, whereas that at light polarized parallel to b presents a weak structured absorption. The refractive index is 1.656, independent of the wavelength, under parallel polarization, and follows the Sellmeier equation, with n_∞ = 1.867, under perpendicular polarization. The PL excitation spectrum with parallel polarization follows exactly the corresponding weak absorption, whereas, at perpendicular polarization, it saturates when the absorption length compares the crystal thickness, and then decreases down to a minimum at 3.5 eV. This lowering mirrors a decrease of the PL yield at higher energies. The PC action spectrum shows an opposite behavior: it presents first a rise at 2.4 eV, parallel to the absorption onset, then a second rise at 3.0 eV up to a maximum at 3.3 eV. The first rise corresponds to the generation of singlet excitons, which then give birth to charges, through either exciton breaking, or more likely charge detrapping. The second rise could correspond to a direct ionization process. The magnetic field effect on PC has been studied. A relative decrease of up to 6% at a field of 4000 G has been detected. The decrease is attributed to the lowering of the triplet—doublet interaction constant R.     

Development of a rapid method based on front face fluorescence spectroscopy for the monitoring of egg freshness: 1—evolution of thick and thin egg albumens

In this preliminary study, the intrinsic fluorescence of thick and thin egg albumens was evaluated as a possible rapid method for the monitoring of egg freshness. The fluorescence emission spectra of tryptophan residues (excitation: 290 nm; emission: 305–430 nm) of proteins and fluorescent Maillard reaction products (excitation: 360; emission: 380–580 nm) were recorded directly on thick and thin albumen samples within 2–3, 4, 5, 9, 10, 12, 16, 18, 23, 25 and 29 days of storage. Principal component analysis (PCA) and factorial discriminant analysis (FDA) were applied to the spectra data sets. Considering tryptophan fluorescence spectra recorded on thick egg albumen, correct classification was observed for 62.8 and 54.3% for the calibration and the validation sets, respectively. Better classification was obtained from thin egg albumen since 67.3 and 69.1% of samples were correctly classified. Considering fluorescent Maillard reaction products, the similarity map determined by the principal components (PCs) 1 and 2 showed a discrimination of eggs as a function of their storage time on both thick and thin albumens. The percentage of samples correctly classified into four groups by the FDA was 97.4 and 91.4% for the calibration and validation thick albumen samples, respectively. It was concluded that fluorescent Maillard reaction products could be considered as fingerprints that may allow the discrimination between fresh and aged eggs.     

Improvement of Mullite and Magnesia‐Based Refractory Castables Through Addition of Nano‐Spinel Powder

Two different commercial refractory castables based on mullite or magnesia aggregates have been improved through addition of 0–25 wt.% nano‐magnesium aluminate spinel (MA) powder. Physico‐mechanical and refractory properties were tested at different firing temperatures. The phase composition, thermal analysis, and microstructure of these refractory castables were detected using X‐ray diffraction (XRD), differential thermal analysis (DTA), as well as scanning electron microscope (SEM) attached with energy dispersive X‐ray unit, respectively. The castable sample mix containing 10 wt.% nano‐MA spinel powder was chosen as an optimum composition according to its good sintering, mechanical as well as refractory properties.     

Hybrid solar still by heat pump compression

Our study is related to an experimental work and modelling of a simple solar still (SSS), green house type, asymmetrical and a hybrid system of a solar still connected to a heat pump (SSSHP). Simple solar stills have in general very low efficiency and our study aims in improving that incorporation by heat pump. This will increase vapor condensation, improve efficiency and consequently the output per m² of still surface area. Data obtained from our experimental research are used to determine convective and evaporative heat transfer coefficients such as the experimental and theoretical efficiencies. The nom of the hybrid system is HSSHP. Daily output increased from 2 l/m² for the SSS up to 12 l/m² for the HSSHP and average efficiency increased from 20% to 80%.     

Extensive malignant schwannoma of the sciatic nerve. Contribution of imaging techniques

The authors reports a case of malignant schwannoma of sciatic nerve. Clinically, this tumor was manifested by a progressive tumefaction of the leg, and moderate pain, without functional signs. The origin of the sciatic nerve has been suspected by computed tomography, because its location, the vascular contacts, and the lesion's extension. Biopsy leads to confirm the nerve tumor, and precised the histologic type: malignant schwannoma. Local, regional and general extension did not premise treatment.     

A Distributed Artificial Network Solving Complex and Multiple Causal Associations

Causal reasoning (known also as abduction) is a hard task that cognitive agents perform reliably and quickly. A particular class of causal reasoning that raises several difficulties is the cancellation class. Cancellation occurs when a set of causes (hypotheses) cancel each other's explanation with respect to a given effect (observation). For example, a cloudy sky may suggest a rainy weather; whereas a shiny sky may suggest the absence of rain. In the current paper, we extend a recent neural model to handle cancellation interactions. We conduct a sensitivity analysis of this proposal on ad hoc problems put at extreme cases. Finally, we test the model on a large database and propose objective criteria to quantitatively evaluate its performance. Simulation results are very satisfactory and should encourage research.