An onset coarsening-coalescence event based on the incubation time of cylindrical mesopore formation and a significant decrease of specific surface area by 50% relative to the dry pressed samples was determined by N2 adsorption-desorption hysteresis isotherm for cassiterite SnO2 nanoparticles (rutile-type structure with bimodal size distribution). In the temperature range of 800-1100oC, the nanoparticles underwent onset sintering coupled with coarsening-coalescence without appreciable polymorphic transformation or decomposition of SnO2. The apparent activation energy of such a rapid process for SnO2 nanoparticles was estimated as 75 ¡Ó 5 kJ/mol, respectively. The minimum temperature for sintering/coarsening/coalescence of the SnO2 nanoparticles is 735oC based on the extrapolation of steady specific surface area reduction rates to null. PLA fragmentation of cassiterite SnO2 powder (rutile type, 20-50 nm in size) in water was conducted under Q-switch mode (532 nm, 400 mJ per pulse) having laser focal point fixed at 5, 10, 15 and 20 mm beneath the water level for an accumulation time of 5, 15, 20 and 30 min at 10 Hz. The 532 nm laser incidence suffered little water absorption and was effective to produce cassiterite nanocondensates as small as 5 nm in diameter and occasional nanocondensates of £\-PbO2-type structure more or less in coalescence. The combined effects of nanosize, internal compressive stress and H+ and Sn2+ co-signature in the lattice may account for a lower minimum band gap.

Thèse de doctorat : Procédés biotechnologiques et alimentaires : Vandoeuvre-les-Nancy, INPL : 2006. / Titre provenant de l'écran-titre. Bibliogr.

Reproduction de : Thèse de doctorat : Physique des agrégats : Toulouse 3 : 2007. / Titre provenant de l'écran-titre. Bibliogr. p. 207-216.

Habitat fragmentation is often regarded as a biodiversity threat associated with habitat degradation; however, research has also revealed beneficial effects on biodiversity as well, depending on the ecosystem and species community. This study examined the biodiversity of small nekton residing in seagrass meadows characterized by three levels of habitat fragmentation, and as a habitat gradient comprised of measures such as habitat amount, connectivity, patch shape, and proximity. Landscapes were mapped using recent advances in GPS and GIS technology, and analyzed using established methods from research in terrestrial ecosystems. Species richness was not significantly different as a function of fragmentation regardless of season, suggesting that the amount of habitat and configuration of several patches in fragmented habitats is sufficient to support comparable numbers of species in several patches compared to communities in large, continuous seagrass meadows. Species evenness declined significantly in fragmented habitats versus continuous ones in both seasons. Within fragmented landscapes, evenness progressively declined as habitat amount and connectivity decreased and patch isolation and density increased, suggesting that changes in landscape qualities can differentially impact processes supporting metapopulations such as dispersal and reproduction in certain species, thereby influencing community structure. Analyses that included measures of habitat connectivity, proximity, and patch density in addition to habitat amount accounted for more variability in species evenness than those just containing percent cover, and showed that fragmentation’s impacts can differ geographically. These data suggest that community resilience to fragmentation can differ between similar animal communities residing in separate locations, and that landscape configuration plays an important role in determining how communities respond to fragmentation after a threshold of change in habitat amount has been exceeded. / text

Introduction: Intracytoplasmic sperm injection (ICSI) has been a successful assisted reproductive technique for men with severe male-factor infertility. However, ICSI requires the subjective selection of normal looking sperm, which does not preclude the transmission of genetically abnormal sperm. Correlation between abnormal sperm morphology and chromosomal abnormalities has been suggested but not been conclusive and less is known about the connection between sperm morphology and DNA integrity. Sperm morphology will be evaluated on its ability to identify the level of chromosomal abnormalities or fragmented DNA in sperm. To further focus this investigation on sperm morphology, men with infertility isolated to abnormal sperm morphology (isolated teratozoopsermia) are examined. Materials and Methods: Sperm from isolated teratozoopsermic men (n=10) were analysed by fluorescent in situ hybridization (FISH) and terminal dUTP nick-end labelling (TUNEL) assays to determine the level of aneuploidy and DNA fragmentation, respectively. These results were also compared to that of sperm from control men (n=9) of proven fertility and normal seminal parameters. Results: Sperm from teratozoospermic men, compared to control men, had higher rates of total chromosomal abnormality (5.90±3.74% vs. 2.35±0.87%, P=0.0128), total aneuploidy (4.90±2.82% vs. 1.99±0.65%, P=0.0087), and chromosome 13 disomy (0.77±0.50% vs. 0.20±0.14%, P=0.0046). In control samples, incidence of tapered heads associated with supernumerary chromosomal abnormalities (rs=0.9747, P=0.0167). In teratozoospermic samples, incidence of amorphous heads associated to chromosome 13 disomy and sex chromosome aneuploidy (rs=0.6391, P= 0.0466; rs=0.8049, P=0.0050, respectively). Tail abnormalities were associated with chromosomal abnormalities (bent tail-disomy 13: rs=0.7939, P=0.0061; 2-tailed-disomy 13: rs=0.8193, P=0.0037; 2-tailed-supernumerary chromosomal abnormalities: rs=0.7534, P=0.0119). Levels of DNA fragmented sperm were higher in teratozoospermic men than control men (60.28±21.40% vs. 32.40±17.20%, P=0.0121). DNA fragmentation in sperm positively correlated with the incidence of sperm with bent necks in control samples (rs=0.8571, P=0.0238) and round headed sperm in teratozoospermic samples (rs=0.6727, P=0.0390). Conclusions: Sperm of isolated teratozoospermic men have elevated rates of chromosomal abnormalities and DNA fragmentation compared to that of fertile controls. Specific abnormal sperm morphology can be correlated wiht chromosomal abnormalities and level of DNA fragmentation in sperm and this may prove useful in sperm selection for ICSI when applied to isolated teratozoospermic patients.

Copolymers of N-(2-hydroxypropyl)methacrylamide (HPMA) and N-hydroxysuccinimide methacrylate (NMS) were synthesized by reversible addition-fragmentation transfer (RAFT) polymerization using a semi-batch method. The copolymers were prepared in a wide range of molecular weights (Mn= 4,200-14,000 g/mol) with narrow polydispersities (1.2-1.4). A new approach was developed to prepare a modified RAFT chain transfer agent, a naphthalimide-dyelabeled dithiobenzoate. It was used to prepare a naphthalimide-dye end-labeled poly(HPMA-co-NMS). The copolymer was characterized by four different methods, 1H NMR spectroscopy via end group characterization and using 3-(trimethylsilyl)propionic acid-d4 sodium salt (TSP)external standard, end group analysis by UV-Vis spectroscopy and by GPC. The results obtained from these measurements are in good agreement.

No description available.

No description available.

One of the most interesting features of fragmentation models is a possibility to breach / Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2008.

Copolymers of N-(2-hydroxypropyl)methacrylamide (HPMA) and N-hydroxysuccinimide methacrylate (NMS) were synthesized by reversible addition-fragmentation transfer (RAFT) polymerization using a semi-batch method. The copolymers were prepared in a wide range of molecular weights (Mn= 4,200-14,000 g/mol) with narrow polydispersities (1.2-1.4). A new approach was developed to prepare a modified RAFT chain transfer agent, a naphthalimide-dyelabeled dithiobenzoate. It was used to prepare a naphthalimide-dye end-labeled poly(HPMA-co-NMS). The copolymer was characterized by four different methods, 1H NMR spectroscopy via end group characterization and using 3-(trimethylsilyl)propionic acid-d4 sodium salt (TSP)external standard, end group analysis by UV-Vis spectroscopy and by GPC. The results obtained from these measurements are in good agreement.