Dye-sensitized Photooxygenation of furanosyl Furans; Synthesis of a new Pyridazine C-Nucleoside

The dye-sensitized photooxygenation of furanosyl furans easily affords C- or O-glycosides with cis-R,-unsaturated 1,4-dioxo aglycones. The reaction, performed on a ribofuranosyl furan, provides a useful new entry to a novel pyridazine C-nucleoside that can be achieved through a simple one-pot procedure

Phylogeography of Italian barbels (Cyprinidae, Barbus) inferred by mitochondrial and nuclear markers.

Species of the genus Barbus, being primary freshwater fishes intolerant of salt water, are of great value for biogeographic studies since their dispersal strictly depends on geological evolution of the landmasses (i.e. catchments watershed, mountain chains and fluctuations of sea level). In Italian peninsula four specie are formally recognized: B. caninus, B. balcanicus, B. plebejus and B. tyberinus. Their genetic relationships were assessed using both mitochondrial and nuclear markers. The study was carried out as first developing new nuclear primers for the S7 ribosomal protein and the Growth hormone genes (Gh); then performing a SNPs characterization of these loci on 18 populations (264 specimens in total). Results from nuclear sequences were then compared with those from partial sequences of the Cytochrome b mitochondrial gene (733 bp). Recovered phylogenies were congruent with the current morphology-based systematic and taxonomy. Results highlighted the close relationships between species belonging to the fluvio-lacustrine ecological group: B. plebejus and B. tyberinus and the high genetic distance between species belonging to the riverine group: B. caninus and B. balcanicus. Moreover findings were congruent with hypotheses of partial permeability of principal biogeographic barriers (Alpine and the Apennine chains) to freshwater fish fauna. Successively the influence of different ecological preferences on gene flow was tested for B. caninus and B. tyberinus on 6 and 7 populations respectively. Results pointed out that the riverine B. caninus has higher structured populations than B. tyberinus, probably due to the different dispersion ability and the different habitat colonized. Moreover, for the first time, molecular evidences were shown about hybridization events occurring between B. caninus and B. plebejus, B. tyberinus and B. barbus

Skype traffic detection and characterization

Skype is a very popular VoIP software which has recently attracted the attention of the research community and network operators; furthermore Skype uses a proprietary signalling design and its source code is unavailable. This makes its analysis really important since the classification of IP flows becomes increasingly crucial in modern network management platforms. Traditional classification systems based on packet headers are rapidly becoming ineffective. In this work after a general analysis of Skype protocol and traffic in both time and frequency domain, a new classification method is presented. It is based on statical classification of the flow, using only three basic properties of IP packets: their size, interarrival time and order of arrival. The whole process is based on a new quantity called Protocol Fingerprint. Its aim is to express these quantities in an efficient way. An important part in the classification process is taken by a Gaussian filter that smooths the protocol fingerprints avoiding misclassifications caused by any kind of noise generated in the network. Even if this technique is at an early stage of development and requires more work, it is quite promising

“Crystalline Syndiotactic Polystyrene as Reinforcing Agent of cis-1,4-Polybutadiene Rubber”

ABSTRACT: Syndiotactic polystyrene (sPS), a thermoplastic polymer characterized by high crystallinity, good chemical resistance and high modulus, has been successfully tested as a reinforcing agent for cis-1,4- polybutadiene (PB) rubber. Blends of sPS and PB have been in situ synthesized using a multistep polymerization process catalyzed by monocyclopentadienyl titanium compounds activated with MAO. This procedure assures an intimate mixing of the components and homogeneous dispersion of the sPS particles having dimension from few hundreds of nanometers to micrometers. The analysis of the mechanical properties of the sPS-PB blends obtained using this process showed enhanced Young’s modulus, toughness, σbreak and ε break: these properties were found to be 1 order of magnitude higher than those of PB and comparable to those of PB charged with inorganic filler as carbon black or silica. A multiblock copolymer (sPSB) comprising segments of sPS and PB was successfully in situ synthesized with the sPS and PB homopolymers and found to be an active compatibilizer of these blends producing a novel semicrystalline phase at the interphase between the sPS particles and the PB matrix

Structure and dynamics of catalytically competent but labile paramagnetic metal-hydrides: The Ti(iii)-H in homogeneous olefin polymerization

Metal hydride complexes find widespread application in catalysis and their properties are often understood on the basis of the available crystal structures. However, some catalytically relevant metal hydrides are only spontaneously formed in situ, cannot be isolated in large quantities or crystallised and their structure is therefore ill defined. One such example is the paramagnetic Ti(iii)-hydride involved in homogeneous Ziegler–Natta catalysis, formed upon activation of CpTi(iv)Cl(3) with modified methylalumoxane (MMAO). In this contribution, through a combined use of electron paramagnetic resonance (EPR), electron-nuclear double resonance (ENDOR) and hyperfine sublevel correlation (HYSCORE) spectroscopies we identify the nature of the ligands, their bonding interaction and the extent of the spin distribution. From the data, an atomistic and electronic model is proposed, which supports the presence of a self-assembled ion pair between a cationic terminal Ti-hydride and an aluminate anion, with a hydrodynamic radius of ca. 16 Å

Solvent- and solvothermal-induced phase transitions and crystallisations in syndiotactic polystyrene and multiblock copolymer syndiotactic polystyrene-co-cis-1,4-polybutadiene

The complex polymorphism of nanoporous syndiotactic polystyrene never stops to amaze. Simple and rapid solvent- and solvothermal-induced crystallisation of syndiotactic polystyrene (sPS) and syndiotactic polystyrene polymer segments in the multiblock copolymer syndiotactic polystyrene-co-cis-1,4-polybutadiene (sPSB) into the desired crystalline form have been disclosed and herein reported. Stirring polymer powders of sPS in the chloroform/water solvent mixture allows crystallisation of the amorphous phase and the conversion of the co-crystalline δ forms into the highly crystalline δ form; variable combinations of water with other common non-polar solvents, or of chloroform with methanol failed in this transformation. The γ form has been obtained by solvothermal treatment of the δ form by simple refluxing in acetonitrile. Stirring the γ form in chloroform/water mixture affords its rapid conversion into the ε form with elevated crystallinity. Finally, applying the chloroform/water treatment to the β form yields the δ form with high crystallinity. The complex polymorphism of the sPS was also found in sPSB copolymer, even with short styrene segments. The thermal behaviour, in terms of melting enthalpy and temperature, was investigated at the variance of styrene content