Moisture sorption isotherms – Experimental and mathematical investigations of orange (Citrus sinensis) peel and leaves

The aims of this work were to determine chemical composition and sorption isotherms of Tunisian orange peel and leaves of the “Maltaise” variety. These by-products were found to be rich in fibre, soluble sugars, protein, minerals and phenols. The equilibrium moisture contents of “Maltaise” peel and leaves were measured using the static gravimetric method at three temperatures (40, 50 and 60 °C) and in wide range of water activity (0.109–0.891). Desorption and adsorption data of peel and leaves were best fitted by the Peleg model at 40, 50 and 60 °C. The net isosteric heats of desorption and adsorption were determined from sorption isotherms. For both peel and leaves, the net isosteric heat of desorption was higher than the net isosteric heat of adsorption and both decreased continuously with increasing of the equilibrium moisture content.     

Immunosuppressive activity of bovine seminal plasma on bovine lymphocytes in vitro

Pooled seminal plasma obtained from six bulls was tested for its immunosuppressive activities in vitro on blastogenesis of bovine lymphocytes. Lymphocyte stimulation assay and mixed lymphocyte reaction were used as test procedures. Concanavalin A and phytohemagglutinin were utilized in the lymphocyte stimulation assays as nonspecific stimuli. Tritiated thymidine uptake by the lymphocytes was measured after incubation for 5 d with seminal plasma. Undiluted seminal plasma was cytotoxic to lymphocytes up to and at 1/100 dilution but not at 1/400. Undiluted seminal plasma was immunosuppressive at a 1/400 dilution. Lyophilization of seminal plasma without prior dialysis resulted in loss of immunosuppressive activity. After dialysis and lyophilization, the reconstituted seminal plasma suppressed thymidine uptake by Concanavalin A and phytohemagglutinin-stimulated bovine lymphocytes while being noncytotoxic. This paper documents that bovine seminal plasma is immunosuppressive and also cytotoxic to the bovine cells that generate an immune response.     

Maximuma posteriori fast fading channel estimation for alamouti’s space-time transmit diversity

This paper considers the Alamouti’s two-branch transmit diversity scheme. This scheme supports a maximum likelihood detection based on linear processing at the receiver. When no knowledge of the channel is available — at the transmitter and the receiver- the above scheme requires in general the estimation of the two discrete propagation channels seen from the two transmit antennas. Our objective is to evaluate the Alamouti’s technique of diversity with a realistic estimation algorithm considering a very fast time-varying channel. For a robust channel estimation, we propose an EM-based maximuma posteriori semi-blind algorithm. This algorithm requires a convenient representation of the time-varying fading channel using a discrete version of the Karhunen-Loève expansion theorem. The iterative receiver optimally uses pilot as well as unknown data symbols for improving channel estimation quality. The validity of the proposed algorithm is highlighted by simulation results. Moreover, a complexity evaluation of this algorithm and a comparison is provided for different scenarii.     

Studies of deep centers in dilute GaAsN and InGaAsN films grown by molecular beam epitaxy

Deep levels spectra DLTS, 77 K photoluminescence (PL) spectra and photosensitivity were measured for GaAsN and InGaAsN films with low N and In concentration grown by molecular beam epitaxy and in GaAs films grown on GaAsN buffer. It is shown that the bandedge luminescence intensity is greatly decreased in GaAsN, GaAs/GaAsN and particularly in InGaAsN structures compared to the homoepitaxial GaAs. Comparison of the DLTS and PL spectra strongly suggests that the main recombination center in such films is the EL3-like electron trap whose concentration greatly increases upon In and N incorporation into the solid solution. Based on published results the trap is associated with substitutional oxygen on As site and the results are discussed in view of such possible assignment.     

Nitrobenzene as a material for the fast-respond degenerate four-wave mixing

We have revealed a possibility of using nitrobenzene (NB) as a promising for time-resolving degenerate four-wave mixing (DFWM). The DFWM efficiency versus time delay between the probe and pump beams was revealed. The four time-retarded maxima of the DFWM are caused by specific electron–vibration interactions in the NB. An essential contribution of acoustical vibrations is demonstrated. Molecular dynamics geometry optimisation of the NB molecule is done taking into account intermolecular interactions. Superposition of all possible molecular conformations with appropriate weighting factors and higher-order intermolecular multiple interactions is considered. The observed DFWM behavior is explained within the framework of ab inito quantum chemical calculations with inclusion of excited configuration interaction (CI) states. We considered both harmonic as well anharmonic electron–vibration interactions. The average lifetime of MO levels contributing to the third-order nonlinear and time kinetics of the observed DFWM dependences is estimated. Advantages and drawbacks of the prosposed method are discussed.     

Wireless network resource management for Web-based multimedia document services

Advances in wireless technology and availability of portable devices with networking capabilities have enabled ubiquitous Web accessibility. This has created the need to provide advance Internet services to mobile users without causing service failures due to connection migration or handoffs. However, scarcity of wireless resources restricts the provision of multimedia services in wireless networks. We address the issue of managing wireless resources to support Web-based multimedia document services including MPEG-4-based applications, in wireless networks with a high degree of user mobility. In particular, we formulate the resource management problem in wireless networks as an optimization problem with an objective function comprising different quality of presentation parameters.     

Interface properties and deep levels in InGaAsN/GaAs and GaAsN/GaAs heterojunctions

Interface properties of dilute slightly lattice mismatched GaAsN/GaAs (0.35 at.% N) and closely lattice matched InGaAsN (1 at.% In, 0.35 at.% N) heterojunctions (HJs) were studied by means of capacitance–voltage profiling, deep levels transient spectroscopy (DLTS) and current–voltage measurements. It is found that the lattice matched HJs show no electrical breakdown when the space charge region crosses the interface. The carrier concentration profiles in such HJ show, as expected, the accumulation region on the low-bandgap side and the depletion region on the high-bandgap side of the HJ. This is not the case for the GaAsN/GaAs (GaAsN layer on top) and the GaAs/GaAsN (GaAs layer on top) HJ. The density of deep traps in GaAsN, InGaAsN films and in GaAs films grown on GaAsN underlayers was very much higher than in epitaxial GaAs films. The dominant deep centers were the EL6 and the EL3 electron traps. The interface regions of the GaAs/GaAsN and the InGaAsN/GaAs HJs were shown to be enriched by EL3 traps, while for the GaAsN/GaAs HJ those regions were enriched by EL6 traps which was associated with the former films being Ga-rich and thus facilitating incorporation of oxygen on As sites.