Correlation between mechanical properties and orientation of the crystalline and mesomorphic phases in isotactic polypropylene fibers

The microstructure and mechanical properties of melt-spun isotactic polypropylene (iPP) fibers were studied for different take-up velocities and throughputs with a combination of small- and wide-angle X-ray scattering, calorimetry and tensile tests. With the increase of take-up velocity the mesomorphic fraction of the fibers steadily decreases while the crystalline fraction increases. The addition of an alpha-nucleating agent led to an increase of crystallinity and a slight decrease of the orientation factor. By contrast, a beta-nucleator resulted in a complete suppression of the fiber crystallinity. The orientation factor of the mesophase and/or crystalline phase is found to have a one-to-one correlation with the fiber tenacity and deformation at break. At the same time, the absolute values of crystallinity and/or mesomorphicity are fully uncorrelated with these mechanical characteristics. The observed correlations can be used for example to design and control the fiber mechanical properties by tuning the processing conditions such as take-up velocity, throughput and addition of nucleating agents.     

Potential of ionic liquids for VOC absorption and biodegradation in multiphase systems

This work aims to evaluate the feasibility of using imidazolium ionic liquids (ILs) in the design of multiphase bioreactors for the removal of volatile organic compounds (VOCs). The IL affinity for three model VOCs (dimethyl sulfide, dimethyl disulfide and toluene) was evaluated by means of the dimensionless partition coefficient (K). It was observed that ILs showed K values comparable to typical liquid solvents used in multiphase bioreactors for VOC biodegradation (K values ranged from 0.009 to 0.011, 0.0012 to 0.0013 and 0.00061 to 0.00096 for dimethyl sulfide, dimethyl disulfide and toluene, respectively). Toxicity tests showed that both ILs at concentrations of 5% and 10% (v/v) inhibited the glucose uptake of an activated sludge during approximately 24 h. After such lag period, the microorganisms were able to recover its metabolic activity. However, VOC biodegradation experiments showed that ILs at 5% (v/v) were toxic for the activated sludge and a toxic synergistic effect of the IL–VOC combination likely occurred. After acclimation to the target VOCs, only the toluene biodegradation capacity was significantly increased in the presence of ILs. These toxic effects represent a key drawback for the potential of IL-based multiphase systems devoted to VOC biodegradation. Therefore, this study suggests that microbial acclimation only to the VOCs is not enough to get an efficient biodegradation in multiphase systems including ILs as non-aqueous phases.     

Pyropheophytin a and 1,2-Diacyl-glycerols Over Time Under Different Storage Conditions in Natural Olive Oils

The effect of storage conditions (light, temperature, container types) and time on the quality of natural olive oils from different cultivars and Australian regions were studied. The oils’ changing quality was monitored through several physico-chemical methods (free fatty acids, peroxide value, UV-spectrometry (K₂₃₂, K ₂₇₀ and ΔK), induction time, total polyphenol content, bitterness, pyropheophytin a and 1,2-diacyl-glycerol content) and sensory analysis over 24 months. Pyropheophytins a and 1,2-diacyl-glycerols criteria showed very good performance as indicators of overall olive oil quality and freshness as well as highlighting any problems during the storage of the product. Pyropheophytin a increment averaged 7 % per year and the 1,2-diacyl-glycerols decreased at an average of 23 % per year at normal storage conditions over time.     

Assessing the Antimicrobial Activity of Polyisoprene Based Surfaces

There has been an intense research effort in the last decades in the field of biofouling prevention as it concerns many aspects of everyday life and causes problems to devices, the environment, and human health. Many different antifouling and antimicrobial materials have been developed to struggle against bacteria and other micro- and macro-organism attachment to different surfaces. However the “miracle solution” has still to be found. The research presented here concerns the synthesis of bio-based polymeric materials and the biological tests that showed their antifouling and, at the same time, antibacterial activity. The raw material used for the coating synthesis was natural rubber. The polyisoprene chains were fragmented to obtain oligomers, which had reactive chemical groups at their chain ends, therefore they could be modified to insert polymerizable and biocidal groups. Films were obtained by radical photopolymerization of the natural rubber derived oligomers and their structure was altered, in order to understand the mechanism of attachment inhibition and to increase the efficiency of the anti-biofouling action. The adhesion of three species of pathogenic bacteria and six strains of marine bacteria was studied. The coatings were able to inhibit bacterial attachment by contact, as it was verified that no detectable leaching of toxic molecules occurred.     

Transparent polycrystalline alumina obtained by SPS: Green bodies processing effect

Starting from a commercial slurry of high purity α-Al₂O₃, freeze-dried powders, cast, filter-pressed or cold isostatically pressed samples were produced. Resulting powders or green bodies showing different particles packing were densified by spark plasma sintering (SPS) to obtain transparent polycrystalline α-Al₂O₃. Microstructure and real in-line transmittance (RIT) after SPS were dependent on the particles packing quality. Avoiding large agglomerates, narrowing the pore size distribution, reducing the most-frequent pore size (D_mode) and avoiding macroscopic heterogeneities within the green bodies enabled high RIT values to be achieved in the visible and near-infrared spectrum. However, a limit was achieved in the preparation of green bodies for which reducing the D_mode had no more influence on the optical behaviour of samples sintered by SPS. Finally, pure α-Al₂O₃ samples presenting a high RIT_640 nm value of 53% were produced from all the green bodies obtained by the following techniques: filter-pressing, slip casting and cold isostatic pressing.     

Shear-induced migration and axial development of particles in channel flows of non-Brownian suspensions

We present an experimental study on the shear-induced migration and axial development of particles in the channel flows of non-Brownian suspensions. The suspending fluid is Newtonian. We investigate fracturing flows with a Hele-Shaw type scaling through building a unique channel setup and an advanced optical system. The local particle concentration profiles are measured via the refractive-index matching technique for a wide range of bulk volume fraction, that is, . Simultaneously, the particle image velocimetry is performed to determine the velocity profile of the particle phase. We compare our experimental results with the available two-phase continuum frameworks and show discrepancies and similarities in the fully developed and axial development of the solid volume fraction profiles. We discuss directions in which the continuum frameworks require improvements.     

Processing of CaLa2S4 infrared transparent ceramics: A comparative study of HP and FAST/SPS techniques

The densification of CaLa₂S₄ (CLS) powders prepared by combustion method was investigated by the use of Field-Assisted Sintering Technique (FAST) and Hot Pressing (HP). CLS powders were sintered using FAST at 1000°C at different pressures and heating rates and sintered by HP under 120 MPa from 800°C to 1100°C for 6 hours with a heating rate of 10°C/min. Comparison of both techniques was further realized by use of the same conditions of pressure, dwell time, and heating rate. Complementary techniques (XRD, SEM-EDS, density measurements, FTIR spectroscopy) were employed to correlate the sintering processes/parameters to the microstructural/compositional developments and optical transmission of the ceramics. Both sintering techniques produce ceramics with submicrometer grain size and relative density of about 99%. Nevertheless, HP is more suitable to densify CLS ceramics without fragmentation and also reach higher transmission than FAST. Transmission of 40%–45% was measured out of a possible maximum of 69% based on the Fresnel losses in the 8-14 μm window when HP is applied at 1000°C for 6 hours under 120 MPa. In both techniques, ceramics undergo reduction issues that originate from graphitic sintering atmosphere.     

Synthesis and Anticancer Properties of Oxazepines Related to Azaisoerianin and IsoCoQuines

In this article, we report the synthesis and biological properties of a series of novel oxazepines related to isoCA-4 having significant antitumor properties. Among them, three oxazepin-9-ol derivatives display a nanomolar or a sub-nanomolar cytotoxicity level against five human cancer cell lines (HCT116, U87, A549, MCF7, and K562). It was demonstrated that the lead compound in this series inhibits tubulin assembly with an IC₅₀ value of 1 μM and totally arrests the cellular cycle in the G2/M phase at the low concentration of 5 nM in HCT116 and K562 cells. Molecular modeling studies perfectly corroborates these promising results.     

Development of the Acidity of Zirconia-Supported Niobia Catalysts

A series of NbO _x /ZrO₂ catalysts containing up to 2.67wt Nb (ca. 80 nominal surface coverage) was prepared by incipient wetness impregnation from niobium oxalate and oxalic acid solution. The structure of the catalysts was monitored by X-ray diffraction and Raman spectroscopy. The results indicated the presence of a surface Nb phase. No evidence for the formation of crystalline Nb₂O₅ species was found. The development of the acidity as a function of Nb loading was monitored by adsorption of a basic probe molecule followed by infrared spectroscopy. The results indicated the appearance of Brnsted acid sites for a threshold of Nb loading. The abundance of Brnsted acid sites correlated well with the isopropanol dehydration activity. The overall behavior was very similar to that reported earlier for the WO _x /ZrO₂ system.