Stabilization of clayey soil using fibre reinforcement

The paper presents experimental and numerical investigations on crack evolution during desiccation, on unsaturated, compacted and reinforced clay using natural Alfa fibres. The effect of fibre content is investigated and a comparison between experimental and numerical simulations is made. A modified model for tensile strength is updated in the finite element program CODE_BRIGHT and used to predict tensile cracks induced by desiccation on reinforced soil. The results show that the soil desiccation cracking behaviour is significantly influenced by fibre inclusion and that experimental and numerical results are in good agreement.Postprint (published version

The emergence of quantum capacitance in epitaxial graphene

We found an intrinsic redistribution of charge arises between epitaxial graphene, which has intrinsically n-type doping, and an undoped substrate. In particular, we studied in detail epitaxial graphene layers thermally elaborated on C-terminated $4H$-$SiC$ ($4H$-$SiC$ ($000{\bar{1}}$)). We have investigated the charge distribution in graphene-substrate systems using Raman spectroscopy. The influence of the substrate plasmons on the longitudinal optical phonons of the $SiC$ substrates has been detected. The associated charge redistribution reveals the formation of a capacitance between the graphene and the substrate. Thus, we give for the first time direct evidence that the excess negative charge in epitaxial monolayer graphene could be self-compensated by the $SiC$ substrate without initial doping. This induced a previously unseen redistribution of the charge-carrier density at the substrate-graphene interface. There a quantum capacitor appears, without resorting to any intentional external doping, as is fundamentally required for epitaxial graphene. Although we have determined the electric field existing inside the capacitor and revealed the presence of a minigap ($\approx 4.3meV$) for epitaxial graphene on $4H$-$SiC$ face terminated carbon, it remains small in comparison to that obtained for graphene on face terminated $Si$. The fundamental electronic properties found here in graphene on $SiC$ substrates may be important for developing the next generation of quantum technologies and electronic/plasmonic devices.Comment: 26 pages, 8 figures, available online as uncorrected proof, Journal of Materials Chemistry C (2016

Biochemical composition of three Tunisian silverside (fish) populations caught in open sea, lagoon and island coasts

Fatty acid and amino acid profiles were determined in three silverside populations caught in Tunisian waters Atherina boyeri (open sea), Atherina lagunae (lagoon) and Atherina sp. (island coasts). Saturated fatty acids reached in total lipids 43.54%, 36.96% in marine and 33.64% in insular silverside and A. lagunae, in which eicosapentaenoic acid, docosahexaenoic acid and linoleic acid were the prominent fatty acids. The n-3/n-6 index showed a significant level indicating a tendency to accumulate n-3 fatty acids in A. boyeri and A. lagunae and n-6 fatty acids in Atherina sp. Total amino acid content ranged from 528 to 588 mg/g crude protein, in which, glutamic acid was the most abundant. Methionine had the lowest essential amino acid score in A. boyeri and Atherina sp. (0.73 and 0.71, respectively)while tryptophan had the lowest in A. lagunae (0.07)

Block to granular-like transition in dense bubble flows

We have experimentally investigated 2-dimensional dense bubble flows underneath inclined planes. Velocity profiles and velocity fluctuations have been measured. A broad second-order phase transition between two dynamical regimes is observed as a function of the tilt angle $\theta$. For low $\theta$ values, a block motion is observed. For high $\theta$ values, the velocity profile becomes curved and a shear velocity gradient appears in the flow.Comment: Europhys. Lett. (2003) in pres

Computational Laser Spectroscopy in a Biological Tissue

We present a numerical spectroscopic study of visible and infrared laser radiation in a biological tissue. We derive a solution of a general two-dimensional time dependent radiative transfer equation in a tissue-like medium. The used model is suitable for many situations especially when the external source is time-dependent or continuous. We use a control volume-discrete ordinate method associated with an implicit three-level second-order time differencing scheme. We consider a very thin rectangular biological-tissue-like medium submitted to a visible or a near infrared light sources. The RTE is solved for a set of different wavelength source. All sources are assumed to be monochromatic and collimated. The energetic fluence rate is computed at a set of detector points on the boundaries. According to the source type, we investigate either the steady-state or transient response of the medium. The used model is validated in the case of a heterogeneous tissue-like medium using referencing experimental results from the literature. Also, the developed model is used to study changes on transmitted light in a rat-liver tissue-like medium. Optical properties depend on the source wavelength and they are taken from the literature. In particular, light-transmission in the medium is studied for continuous wave and for short pulse

Oxygen-vacancy-related giant permittivity and ethanol sensing response in SrTiO3-δ ceramics

The ethanol sensing properties of SrTiO3-δ (δ = 0.075 and 0.125) ceramics was analyzed by dielectric measurements. The ceramics were prepared by solid state reaction method followed by the creation of oxygen vacancies-δ, through a thermal activated process. The crystal symmetry, space group and unit cell dimensions were derived from the X-ray diffraction (XRD) data using FullProf software whereas grain's size distribution was assessed by scanning electron microscopy (SEM). The prepared samples have been analyzed by impedance spectroscopy over the frequency range from 100 Hz to 1 MHz and temperature range from 240 to 340 K. The dielectric properties of SrTiO3-δ ceramics showed a quite remarkable stability of giant permittivity (>104) as well as a low dielectric loss, which open ways for several applications such as over voltage protections of electronic devices. A low-frequency dielectric relaxation behavior was found, and the carriers for electrical conduction result from the first-ionization of oxygen vacancies. The conductivity and gas sensitivity of SrTiO3-δ-based sensors were investigated. Results demonstrated that the conductivity decreases after the introduction of the ethanol gas, and p-type semiconductor gas-sensing materials were obtained. Both characteristics present higher responses at lower optimal operating temperatures.publishe