Delay-dependent Stabilization Conditions of Controlled Positive Continuous-time Systems

The stabilization problem for a class of linear continuous-time systems with time-varying non differentiable delay is solved while imposing positivity in closed-loop. In particular, the synthesis of state-feedback controllers is studied by giving sufficient conditions in terms of linear matrix inequalities(LMIs). The obtained results are then extended to systems with non positive delay matrix by applying a memory controller. The effectiveness of the proposed method is shown by using numerical examples.     

Some color aspects of Parian bodies

The two coloring oxides, CoO and NiO were included separately in a self-glazed parian body ?highly feldspathic porcelain? in 5 different concentration between 1 and 10 wt%. The host body consisted of 75% feldspar and 25% kaolin. The mixes were pressed and matured between 1125°C and 1150°C. The produced colors were characterized visually as well as in reference to the CIE system. The densification of the blue and green bodies were slightly reduced, although higher density values were achieved. This was attributed to the effect of the Co²⁺ or Ni²⁺ dense aluminate or silicate. However, their influence was counter balanced by the enhanced leucite formation and higher porosity glassy phase. Various shades of blue were obtained by introducing Co²⁺. Maximum difference in color Δ E = 12.97 Judds was obtained by incorporating 5 wt % and firing at 1125°C while a value of 11.69 Judds was obtained upon firing a specimen with only 1 wt % at 1150°C. The latter value is comparable to that obtained by incorporating 10% of blue stain. Ni²⁺ produced various shades of green with a maximum of Δ E = 5.44 Judds upon firing a sample with 5 wt % at 1150°C. The results are discussed in view of the ligand field theory as well as X-ray diffraction analysis.     

Development of biomimetic coatings on Sm oxide doped ELB (Eu–Li–borate) glasses

The in-vitro biomineralization of Eu/Li–borate glasses containing Sm₂O₃ was investigated by immersion in simulated body fluid (SBF) up to 72 h. Back scattering scanning electron microscope supplemented with EDX was used to follow the development of the phosphatic layer post 72 h SBF immersion. Biochemical analyses of calcium and inorganic phosphorus (Ca²⁺ and iP) ions were conducted using relevant biochemical kits and spectrophotometer. Spectra of TF-X-ray analyses and Fourier transform infrared were obtained for the samples post 72 h immersion and compared to the host one.The role of Sm₂O₃ in the biomineralization and crystallinity of the (ELB) borate glasses is proved by the developed rounded nano particles and the presence of elemental Eu and Sm in the formed layer beside Ca and P as presented by EDX. The continuous reduced values of ionic iP accompanying the adsorption and release of Ca ions in SBF with time assured the biolayer formation. The formed phosphatic layer presented shifted XRD peaks due to ionic incorporations especially of Sm³⁺. FT-IR proved the selectivity of BO₃ group for phosphatic deposition. Deconvolution of ν₄ and ν₃ regions, for carbonates and phosphates, respectively, proved the enhanced peak areas with increased Sm³⁺ content.     

The fate of indigenous microbiota, starter cultures, Escherichia coli, Listeria innocua and Staphylococcus aureus in Danish raw milk and cheeses determined by pyrosequencing and quantitative real time (qRT)-PCR

The purpose of this work was to study the bacterial communities in raw milk and in Danish raw milk cheeses using pyrosequencing of tagged amplicons of the V3 and V4 regions of the 16S rDNA and cDNA. Furthermore, the effects of acidification and ripening starter cultures, cooking temperatures and rate of acidification on survival of added Escherichia coli, Listeria innocua and Staphylococcus aureus in cheeses at different stages of ripening were studied by pyrosequencing and quantitative real time (qRT)-PCR. A high diversity of bacterial species was detected in raw milk. Lactococcus lactis, Streptococcus thermophilus, Lactobacillus casei and Lactobacillus rhamnosus were the main bacteria detected in raw milk and cheeses. Bacteria belonging to the genera Brevibacterium, Staphylococcus, Escherichia, Weissella, Leuconostoc, Pediococcus were also detected in both 16S rDNA and cDNA obtained from raw milk and cheeses. E. coli, which was added to milk used for production of some cheeses, was detected in both DNA and RNA extracted from cheeses at different stages of ripening showing the highest percentage of the total sequence reads at 7 days of ripening and decreased again in the later ripening stages. Growth of E. coli in cheeses appeared to be affected by the cooking temperature and the rate of acidification but not by the ripening starter cultures applied or the indigenous microbiota of raw milk. Growth of L. innocua and S. aureus added to milks was inhibited in all cheeses at different stages of ripening. The use of 16S rRNA gene pyrosequencing and qRT-PCR allows a deeper understanding of the behavior of indigenous microbiota, starter cultures and pathogenic bacteria in raw milk and cheeses.     

Classification of moroccan olive cultivars by linear discriminant analysis applied to ATR–FTIR spectra of endocarps

The potential of FTIR combined with chemometrics was studied to classify five Moroccan varieties of olives by analysis on the endocarps. Attenuated total reflectance (ATR) enabled the samples to be examined directly in the solid state. The spectral data were subjected to a preliminary derivative elaboration based on the Norris gap algorithm to reduce the noise and extract larger analytical information. Linear discriminant analysis (LDA) was adopted as classification method, and Principle component analysis (PCA) was employed to compress the original data set into a reduced new set of variables before LDA. The calibration set was built by using the IR data from seventy‐five samples scanned in reflectance mode, and the ranges 3000–2400 and 2300–600 cm^?1 were selected because furnishing the most useful analytical information. PCA allowed clustering the samples in five classes by using the first two principal components with an explained variance of 98.16%. Application of LDA on an external test set of twenty‐five samples enabled to classify them into five variety groups with a correct classification of 92.0%.     

Lithia porcelains as promising breeder candidates - II. Structural changes induced by fast neutron irradiation

The promise of lithia ceramics as candidate breeder materials necessitates investigations on radiation damage induced structural variations. Prepared porcelain systems consisting of β-eucryptite (Li₂O.Al₂O₃.2SiO₂), its solid-solution (Li₂O.Al₂O₃.3SiO₂) and β-spodumene (Li₂O.Al₂O₃4SiO₂), previously characterized, were irradiated by fast neutrons at room temperature. A ²⁵²Cf source (2 MeV) was used to give fluences of 1 × 10⁵, 1 × 10⁸ or 1 × 10¹⁰ n/cm². Samples of each group received fluences in a one-shot technique, i.e. new samples were used for each fluence before being subjected to structural testing. Damage was assessed by X-ray diffraction (XRD) and infrared (IR) spectral analyses. Relevance dilatation changes were followed through coefficient of change with temperature up to 1000 °C. Surface morphologies were examined using scanning electron microscopy (SEM) and selected area electron diffraction (SAED).

XRD patterns revealed various degrees of imperfections that were reflected as shifts in lattice planes. The IR spectral bands suffered shift, especially in the fingerprint region, parallel with the fluence intensity. Coefficient of contraction and/ or expansion evidenced various degree of damage, which upon intense irradiation annealed to the original values. SEM micrographs revealed that large grains comprising either β-eucryptite or β-spodumene bodies are much more affected by fast neutrons compared to smaller grains detected in the body containing the solid-solution. Additional evidence was obtained by the SAED results, where the continuous polycrystalline rings of both β-eucryptite and β-spodumene turned upon irradiation to the amorphous metamict state simulating the initial solidsolution structure. The latter acquired higher crystalline order, as well as polycrystalline habit. The degrees of induced imperfections were found to be dependent on initial crystallinity. The higher sensitivity to fast neutrons of β-eucryptite was related to its higher lithia content rather than its hexagonal spiral structure compared to the tetragonal β-spodumene. Intense irradiation caused annealing of the produced damage observed by fragmentation of the grains and various degree of amorphism.     

Atmospheric plasma‐aided biocidal finishes for nonwoven polypropylene fabrics. I. Synthesis and characterization

Novel biocidal fabrics were synthesized by the graft copolymerization of glycidyl methacrylate (GMA) onto plasma‐treated nonwoven polypropylene (PP) to produce PP/GMA grafts. Atmospheric oxygenated helium plasma was used to enhance the PP fabrics' initiation before GMA grafting. The grafted PP/GMA epoxide group was reacted with β‐cyclodextrin, monochlorotrizynyl‐β‐cyclodextrins, or a quaternary ammonium chitosan derivative [N‐(2 hydroxy propyl) 3‐trimethylammonium chitosan chloride]. Some interesting biocidal agents were complexed into the cyclodextrin (CD) cavity of PP/GMA/CD grafted fabrics. Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and optical and scanning electron microscopies were used to characterize the grafted complexed fabrics. These synthesized biocidal fabrics proved to be antistatic, antimicrobial, and insect‐repelling (see part II of this study). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1900–1910, 2007