Recursive neural networks prediction of glass transition temperature from monomer structure: an application to acrylic and methacrylic polymers

We propose a new method based on a Recursive Neural Network (RecNN) for predicting polymer properties from their structured molecular representations. RecNN allows for a completely novel approach to QSPR analysis by direct adaptive processing of molecular graphs. This model joins the representational power of structured domains with Neural Network ability to capture underlying complex relationships in the data by a process of training from examples. To this aim, a structured representation was designed for the modelling of polymer structures. The adopted representation can account also for average macromolecule characteristics, such as degree of polymerization, stereoregularity, comonomer distribution. To begin with, this model was applied to the prediction of the glass transition temperature of (meth)acrylic polymers with different degree of main chain tacticity. The results so far obtained indicate that the proposed representation of polymer structure can convey information on both the repeating unit structure and average polymer features. The ability of the proposed RecNN method of treating this structured representation makes this method more general and flexible with respect to standard literature methods. Moreover, the same model can handle at the same time the Tg of polymer samples present in only one tacticity form together with that of polymer with different stereoregularity.     

Tritium measurements by AMS and applications

The Accelerator mass spectrometry (AMS) analysing method is described with applications for the detection of tritium leaks, detection of pollution and for research in the fusion experiments. The special requirements for an experiment of AMS with tritium are also presented. This paper concludes by showing the possibilities for each AMS facility to perform applications for detecting and preventing the environment pollution with tritium.     

Functionalization of multi-walled carbon nanotubes with coumarin derivatives and their biological evaluation

We report the synthesis and the characterization of different multi-walled carbon nanotubes (MWCNTs) linked to natural molecules, 5,7-coumarins and/or oleic acid, obtained from purified pristine MWCNTs by a cascade of chemical functionalization. The activities of these modified MWCNTs were investigated in vitro on human umbilical vein endothelial cells (HUVECs) by evaluating their ability to influence cell viability and to induce cell apoptosis. Our data showed that pristine MWCNTs are markedly cytotoxic; conversely, the carboxylated carbon nanotubes, much more readily dispersed in aqueous solutions and CNT-Link, the key intermediate designed by us for the drug anchorage, are biocompatible at the tested concentrations (1 and 10 μg ml(-1)).     

Fabrication of Stiffness Gradients of GelMA Hydrogels Using a 3D Printed Micromixer

Many properties in both healthy and pathological tissues are highly influenced by the mechanical properties of the extracellular matrix. Stiffness gradient hydrogels are frequently used for exploring these complex relationships in mechanobiology. In this study, the fabrication of a simple, cost‐efficient, and versatile system is reported for creation of stiffness gradients from photoactive hydrogels like gelatin‐methacryloyl (GelMA). The setup includes syringe pumps for gradient generation and a 3D printed microfluidic device for homogenous mixing of GelMA precursors with different crosslinker concentration. The stiffness gradient is investigated by using rheology. A co‐culture consisting of human adipose tissue‐derived mesenchymal stem cells (hAD‐MSCs) and human umbilical cord vein endothelial cells (HUVECs) is encapsulated in the gradient construct. It is possible to locate the stiffness ranges at which the studied cells displayed specific spreading morphology and migration rates. With the help of the described system, variable mechanical gradient constructs can be created and optimal 3D cell culture conditions can be experientially identified.     

Amphotropic Properties of Cyclic Scyllitol Hexaesters [1]

Abstract

The new Scyllitol hexaesters with cyclic fragments in lateral substituents of series 1 were synthesized and their thermo- and lyotropic properties (with various organic linear or cyclic solvents) have been studied. It was established that the presence of benzene fragments in the substituents of the scyllitol hexaesters (1a-e) reduces the ability of the mesophase formation. The cyclohexane unit instead (sf. 1f) increases the thermostability of mesophase. While using above mentioned solvents a lot of cases of the induction of mesomorphic properties for non-mesogenic compounds of series 1 have been described. With cyclic solvents lyotropic mesophases were induced in binary mixtures of the hexaester 1a which showed mesomorphic properties neither under thermotropic conditions nor in binary mixtures with linear alkanes.     

Synthesis of anabasine-containing aminomethyl derivatives of 6-hydroxyaurones

Chemistry of Heterocyclic Compounds - Aminomethylation of aurones was studied by using anabasine. The reaction in the case of 6-hydroxyaurones was shown to selectively provide...     

Non-linear viscoelastic behavior of polymer melts interpreted by fractional viscoelastic model

Very recently, researchers dealing with constitutive law pertinent viscoelastic materials put forward the successful idea to introduce viscoelastic laws embedded with fractional calculus, relating the stress function to a real order derivative of the strain function. The latter consideration leads to represent both, relaxation and creep functions, through a power law function. In literature there are many papers in which the best fitting of the peculiar viscoelastic functions using a fractional model is performed. However there are not present studies about best fitting of relaxation function and/or creep function of materials that exhibit a non-linear viscoelastic behavior, as polymer melts, using a fractional model. In this paper the authors propose an advanced model for capturing the non-linear trend of the shear viscosity of polymer melts as function of the shear rate. Results obtained with the fractional model are compared with those obtained using a classical model which involves classical Maxwell elements. The comparison between experimental data and the theoretical model shows a good agreement, emphasizing that fractional model is proper for studying viscoelasticity, even if the material exhibits a non-linear behavior.     

Direct Derivation of Corrective Terms in SDE Through Nonlinear Transformation on Fokker–Planck Equation

This paper examines the problem of probabilistic characterization of nonlinear systems driven by normal and Poissonian white noise. By means of classical nonlinear transformation the stochastic differential equation driven by external input is transformed into a parametric-type stochastic differential equation. Such equations are commonly handled with Itô-type stochastic differential equations and Itô's rule is used to find the response statistics. Here a different approach is proposed, which mainly consists in transforming the Fokker–Planck equation for the original system driven by external input, in the transformed probability density function of the new state variable. It will be shown that the Wong–Zakay or Stratonovich corrective term and the hierarchy of correction terms in the case of Poissonian white noise arise in a natural way.     

Histamine and spontaneously released mast cell granules affect the cell growth of human hepatocellular carcinoma cells

The role of mast cells in tumor growth is still controversial. In this study we analyzed the effects of both histamine and pre-formed mediators spontaneously released by mast cells on the growth of two human hepatocellular carcinoma cell lines, HA22T/VGH and HuH-6, with different characteristics of differentiation, biological behavior and genetic defects. We showed that total mast cell releasate, exocytosed granules (granule remnants) and histamine reduced cell viability and proliferation in HuH-6 cells. In contrast, in HA22T/VGH cells granule remnants and histamine induced a weak but significant increase in cell growth. We showed that both cell lines expressed histamine receptors H(1) and H(2) and that the selective H(1) antagonist terfenadine reverted the histamine-induced inhibition of HuH-6 cell growth, whereas the selective H(2) antagonist ranitidine inhibited the histamine-induced cell growth of HA22T/VGH cells. We demonstrated that histamine down-regulated the expression of beta-catenin, COX-2 and survivin in HuH-6 cells and that this was associated with caspase-3 activation and PARP cleavage. On the contrary, in HA22T/VGH cells expression of survivin and beta-catenin increased after treatment with granule remnants and histamine. Overall, our results suggest that mediators stored in mast cell granules and histamine may affect the growth of liver cancer cells. However, mast cells and histamine may play different roles depending on the tumor cell features. Finally, these data suggest that histamine and histamine receptor agonists/antagonists might be considered as "new therapeutic" drugs to inhibit liver tumor growth.