Photoinitiated cationic polymerisation of multifunctional systems

Different types of tridimensional polymer networks have been synthetised by photoinitiated cationic polymerisation of vinyl ether and epoxy-functionalised oligomers and polymers. The polymerisation kinetics was followed by real-time infrared (RTIR) spectroscopy, a technique that records directly conversion versus time profiles in a timescale as short as 1 s. The addition of a diacrylate monomer was shown to accelerate the ring-opening polymerisation of epoxidized polyisoprene, with formation of interpenetrating polymer networks having well contrasted properties. A dual polymer network has been generated by photocrosslinking of a polyisoprene functionalised with both epoxy and acrylate groups.     

Differential effects of various trivalent and pentavalent organic and inorganic arsenic species on glucose metabolism in isolated kidney cells

We have compared the acute toxicities of the trivalent arsenic species arsenite, oxophenylarsine (PhAsO), 2-chlorovinyloxoarsine (ClvinAsO), methyloxoarsine (MeAsO), and of the pentavalent arsenic species arsenate, methyl- and phenyl-arsonic acid in rat kidney tubules (RKT) and Madin-Darby canine kidney (MDCK) cells. In RKT, PhAsO (1 μmol I⁻¹, 60 min) almost completely (>90%) blocked gluconeogenesis without affecting cell viability as assessed by dye exclusion. In MDCK cells, PhAsO (2 μmol I⁻¹) markedly inhibited glucose uptake (60% of controls) within 30 min, while cell viability, as assessed by formazan formation, was not affected within 180 min. MeAsO and CIvinAsO were similarly effective to PhAsO in both RKT and MDCK cells. Estimated IC₅₀ values for the inhibition of gluconeogenesis were 0.55 (PhAsO), 0.69 (CIvinAsO) and 0.99 μmol I⁻¹ (MeAsO) and for the inhibition of glucose uptake 1.23 (PhAsO). 2.62 (CIvinAsO) and 6.99 μmol I⁻¹ (MeAsO). At longer storage times, aqueous solutions of MeAsO and of CIvinAsO, but not of PhAsO, gradually lost toxic activity in RKT and MDCK cells, especially at alkaline pH. Concomitantly, a gradual decrease in content as assessed by HPLC was detected. Roughly 10-fold higher concentrations of arsenite than of PhAsO were required for comparable effects on gluconeogenesis in RKT, whereas in MDCK cells about 100-fold higher concentrations were needed for similar inhibition of glucose uptake. Pentavalent arsenate and phenylarsonate were two orders of magnitude less effective than PhAsO in RKT, while methylarsonate had virtually no influence on gluconeogenic activity. In MDCK cells the pentavalent arsenic species showed effects only in the millimolar range. It is concluded (1) that different mechanisms are involved in the acute toxicity of oxoarsines and inorganic arsenic and (2) that PhAsO offers advantages as a model substance for mono-substituted trivalent arsenicals, because it is more stable and more readily detectable.     

Ring-opening metathesis copolymerization employing ruthenium-based metathesis catalysts

The copolymerization of both high- and low-strain cyclic olefins employing three ruthenium-based metathesis catalysts is desribed. The effect of the ligand environment as well as the nature of the carbene on the copolymerizations is discussed.     

Target Design of Novel Histone Deacetylase 6 Selective Inhibitors with 2-Mercaptoquinazolinone as the Cap Moiety

Epigenetic alterations found in all human cancers are promising targets for anticancer therapy. In this sense, histone deacetylase inhibitors (HDACIs) are interesting anticancer agents that play an important role in the epigenetic regulation of cancer cells. Here, we report 15 novel hydroxamic acid-based histone deacetylase inhibitors with quinazolinone core structures. Five compounds exhibited antiproliferative activity with IC₅₀ values of 3.4–37.8 µM. Compound 8 with a 2-mercaptoquinazolinone cap moiety displayed the highest antiproliferative efficacy against MCF-7 cells. For the HDAC6 target selectivity study, compound 8 displayed an IC₅₀ value of 2.3 µM, which is 29.3 times higher than those of HDAC3, HDAC4, HDAC8, and HDAC11. Western blot assay proved that compound 8 strongly inhibited tubulin acetylation, a substrate of HDAC6. Compound 8 also displayed stronger inhibition activity against HDAC11 than the control drug Belinostat. The inhibitory mechanism of action of compound 8 on HDAC enzymes was then explored using molecular docking study. The data revealed a high binding affinity (−7.92 kcal/mol) of compound 8 toward HDAC6. In addition, dock pose analysis also proved that compound 8 might serve as a potent inhibitor of HDAC11.     

Effect of aromatic substitution on the cure reaction and network properties of anhydride cured triphenyl ether tetraglycidyl epoxy resins

A systemic study of the impact of aromatic substitution on the reaction rate and network properties of the isomers of a tetraglycidylaniline triphenyl ether epoxy resin cured with anhydride hardeners is presented here. The epoxy resins synthesized in this work were based upon N,N,N,N‐tetraglycidyl bis(aminophenoxy)benzene (TGAPB), where the glycidyl aniline and ether groups change from being all meta (133 TGAPB), to meta and para (134 TGAPB), and finally to an all para substituted epoxy resin (144 TGAPB). Increasing para substitution increased reaction rate, promoted the onset of vitrification and increased epoxide conversion. Thermal properties such as glass transition temperatures (T_g) and coefficients of thermal expansion (CTE) both increased consistently with increasing para substitution, although thermal stability as measured via thermogravimetric analysis decreased. Mechanical properties also varied systematically with flexural strength and ductility increasing with increased para substitution, while the modulus decreased. Indeed, the ductility almost doubled, as measured by the work of fracture and displacement at failure highlighting the importance of substitution on properties.     

Applying Hybrid ARIMA-SGARCH in Algorithmic Investment Strategies on S&P500 Index

This research aims to compare the performance of ARIMA as a linear model with that of the combination of ARIMA and GARCH family models to forecast S&P500 log returns in order to construct algorithmic investment strategies on this index. We used the data collected from Yahoo Finance with daily frequency for the period from 1 January 2000 to 31 December 2019. By using a rolling window approach, we compared ARIMA with the hybrid models to examine whether hybrid ARIMA-SGARCH and ARIMA-EGARCH can really reflect the specific time-series characteristics and have better predictive power than the simple ARIMA model. In order to assess the precision and quality of these models in forecasting, we compared their equity lines, their forecasting error metrics (MAE, MAPE, RMSE, MAPE), and their performance metrics (annualized return compounded, annualized standard deviation, maximum drawdown, information ratio, and adjusted information ratio). The main contribution of this research is to show that the hybrid models outperform ARIMA and the benchmark (Buy&Hold strategy on S&P500 index) over the long term. These results are not sensitive to varying window sizes, the type of distribution, and the type of the GARCH model.     

Effects of surfactants on properties of polymer-coated magnetic nanoparticles for drug delivery application

The objective of this research was to compare the effects of two different surfactants on the physicochemical properties of thermo-responsive poly(N-isopropylacrylamide-acrylamide-allylamine) (PNIPAAm-AAm-AH)-coated magnetic nanoparticles (MNPs). Sodium dodecyl sulfate (SDS) as a commonly used surfactant in nanoparticle formulation process and Pluronic F127 as an FDA approved material were used as surfactants to synthesize PNIPAAm-AAm-AH-coated MNPs (PMNPs). The properties of PMNPs synthesized using SDS (PMNPs-SDS) and PF127 (PMNPs-PF127) were compared in terms of size, polydispersity, surface charge, drug loading efficiency, drug release profile, biocompatibility, cellular uptake, and ligand conjugation efficiency. These nanoparticles had a stable core–shell structure with about a 100-nm diameter and were superparamagnetic in behavior with no difference in the magnetic properties in both types of nanoparticles. In vitro cell studies showed that PMNPs-PF127 were more cytocompatible and taken up more by prostate cancer cells than that of PMNPs-SDS. Cells internalized with these nanoparticles generated a dark negative contrast in agarose phantoms for magnetic resonance imaging. Furthermore, a higher doxorubicin release at 40 °C was observed from PMNPs-PF127, and the released drugs were pharmacologically active in killing cancer cells. Finally, surfactant type did not affect the conjugation efficiency to the nanoparticles when folic acid was used as a targeting ligand model. These results indicate that PF127 might be a better surfactant to form polymer-coated magnetic nanoparticles for targeted and controlled drug delivery.     

High-spin structure in154Er

High spin states in the nucleus¹⁵⁴Er have been reinvestigated using the¹²³Sb(³⁵Cl, 4n) reaction and a variety of spectroscopic techniques including excitation functions,γ-γ coincidences,γ angular distribution and linear polarization measurements. From the measured energies, relative intensities and transition multipolarities a new level scheme has been deduced up to an excitation energy of ～12 MeV and spin 36. An interpretation of the experimental results is given in terms of the deformed Woods-Saxon orbitals. Gigantic backbending (superdeformation) effect is studied theoretically within the cranking model.