Formaldehyde Resins Bearing Diaminodiphenylmethane Groups: Synthesis,Characterization and Properties

Summary: Novel formaldehyde resins bearing diaminodiphenylmethane groups were synthesized by the polymerization of a mixture of diaminodiphenylmethane (DDM), cyclohexanone (CHx) and o‐cresol (o‐Cz) with formaldehyde (FA) in the presence of an acid catalyst (HCl). The resins obtained were characterized by spectral, elemental and thermal analysis and used as a hardener for epoxy resins. The curing and temperature behavior of these epoxy resin/formaldehyde systems were investigated using differential scanning calorimetry and thermogravimetry techniques. The resins had good thermal stability and the activation energies of degradation reactions had values between 70–98 kJ · mol^?1.

The curing reaction of epoxy resins with the DDM/CHx/o‐Cz/formaldehyde resins.     

Microwave-Assisted Batch Extraction of Polyphenols from Sea Buckthorn Leaves

Extraction of polyphenols from sea buckthorn leaves using microwave-assisted extraction (MAE) is described. The influence of different parameters on the extraction process (reactor type, stirring rate, extraction time, temperature, ethanol/water ratio) was studied. The polyphenolic extracts were analyzed in order to determine the total phenolic content (TPC) either by the Folin–Ciocalteu method or by differential pulse voltammetry (DPV), and the concentration of the main polyphenolic compounds by high-performance liquid chromatography (HPLC). The specific microwave energy was also determined. MAE resulted in a shorter extraction time (7.5 versus 30 min for the conventional method). The best results for MAE were obtained at a temperature of 90°C, using a solvent/plant ratio of 20/1 and 50% ethanol in the extraction solvent. The highest values of antioxidant capacity were obtained for polyphenolic extracts resulted from microwave extraction.     

Comparison of Fenton and sono-Fenton bisphenol A degradation

Degradation of bisphenol A (BPA) was carried out with the Fenton reagent with and without additional sonochemical treatment. The Fenton and the sono-Fenton decomposition of BPA showed that ultrasound irradiation of wastewater improved the wet oxidation process of 25 mg l(-1) BPA solutions. The sonochemical degradation of BPA was monitored using UV absorption and large volume injection packed capillary LC measurements.     

Relevance of BRAF Subcellular Localization and Its Interaction with KRAS and KIT Mutations in Skin Melanoma

Although skin melanoma (SKM) represents only one-quarter of newly diagnosed skin malignant tumors, it presents a high mortality rate. Hence, new prognostic and therapeutic tools need to be developed. This study focused on investigating the prognostic value of the subcellular expression of BRAF, KRAS, and KIT in SKM in correlation with their gene-encoding interactions. In silico analysis of the abovementioned gene interactions, along with their mRNA expression, was conducted, and the results were validated at the protein level using immunohistochemical (IHC) stains. For IHC expression, the encoded protein expressions were checked on 96 consecutive SKMs and 30 nevi. The UALCAN database showed no prognostic value for the mRNA expression level of KRAS and BRAF and demonstrated a longer survival for patients with low mRNA expression of KIT in SKMs. IHC examinations of SKMs confirmed the UALCAN data and showed that KIT expression was inversely correlated with ulceration, Breslow index, mitotic rate, and pT stage. KRAS expression was also found to be inversely correlated with ulceration and perineural invasion. When the subcellular expression of BRAF protein was recorded (nuclear vs. cytoplasmatic vs. mixed nucleus + cytoplasm), a direct correlation was emphasized between nuclear positivity and lymphovascular or perineural invasion. The independent prognostic value was demonstrated for mixed expression of the BRAF protein in SKM. BRAF cytoplasmic predominance, in association with KIT’s IHC positivity, was more frequently observed in early-stage nonulcerated SKMs, which displayed a low mitotic rate and a late death event. The present study firstly verified the possible prognostic value of BRAF subcellular localization in SKMs. A low mRNA expression or IHC cytoplasmic positivity for KIT and BRAF might be used as a positive prognostic parameter of SKM. SKM’s BRAF nuclear positivity needs to be evaluated in further studies as a possible indicator of perineural and lymphovascular invasion.     

Seeded emulsion polymerization of vinyl chloride. A new approach to mechanism and kinetics

Some peculiarities concerning the mechanism and the kinetic behaviour of the vinyl chloride emulsion polymerization are described. Seeded emulsion polymerizations in the presence of an adequate mixture of anionic and non-ionic surfactants were carried out in order to avoid the micellar initiation. New kinetic parameters were determined from the experimental data as follows: (i) MSA, the minimum surface area of polymer seed particles necessary to capture all ion-oligoradicals generated in aqueous phase at a given initiator concentration; (ii) MCCI, the maximum critical concentration of initiator per unit surface of polymer particle under which the formation of new polymer particles is avoided; (iii) PVR₁, the polymer volume per active growing radical, necessary to be within the particle for 1 s. It was found that the average number of propagating radicals per particle, n, depends on the size of the polymer particle, as a resultant of entry and exit and then of the initiation and termination reactions. The practical consequences of the accurate control of the polymer particles growing during seeded emulsion polymerization of vinyl chloride were emphasized.     

Polyurethane cationomers with nitroazoaromatic groups

Novel polyurethane cationomers bearing p-nitroazoaromatic groups covalently incorporated in the polymer chain were synthesized. Their photobehavior in polymer films and solutions was investigated by electronic absorption spectroscopy and was also evaluated comparatively with an ionic azodiol model. Under UV irradiation, in the first stage of the photoprocess the trans-cis isomerization occurs, followed then by a photobleaching reaction in the second stage of the process.     

Progress in Raman spectroscopy in the fields of tissue engineering, diagnostics and toxicological testing

This review summarises progress in Raman spectroscopy and its application in diagnostics, toxicological testing and tissue engineering. Applications of Raman spectroscopy in cell biology are in the early stages of development, however, recent publications have demonstrated its utilisation as a diagnostic and development tool with the key advantage that investigations of living cells can be performed non-invasively. Some of the research highlighted here demonstrates the ability of Raman spectroscopy to accurately characterise cancer cells and distinguish between similar cell types. Many groups have used Raman spectroscopy to study tissues, but recently increased effort has gone into single cell analysis of cell lines; the advantages being that cell lines offer ease of handling and increased reproducibility over tissue studies and primary cells. The main goals of bio-Raman spectroscopy at this stage are twofold. Firstly, the aim is to further develop the diagnostic ability of Raman spectroscopy so it can be implemented in a clinical environment, producing accurate and rapid diagnoses. Secondly, the aim is to optimise the technique as a research tool for the non-invasive real time investigation of cell/material interactions in the fields of tissue engineering and toxicology testing.     

Mixed convection in laminar film flow of a micropolar fluid

In this paper, the steady mixed convection boundary layer in laminar film flow of a micropolar fluid is considered. The resulting nonlinear coupled ordinary differential equations are solved numerically using an efficient implicit finite-difference scheme. The numerical results obtained for the skin friction coefficient and the local Nusselt number, as well as the velocity, angular velocity or microrotation and temperature profiles are presented in tables and figures for different values of the material parameter K and the Richardson number Ri when the Prandtl number Pr = 0.7 and Pr = 1.     

A heatline analysis of natural convection in a square inclined enclosure filled with a CuO nanofluid under non-uniform wall heating condition

Heatline visualization technique is used to understand heat transport path in an inclined non-uniformly heated enclosure filled with water based CuO nanofluid. The cavity has square cross-section and it is non-uniformly heated from a wall and cooled from opposite wall while other walls are adiabatic. The governing equations which are continuity, momentum and energy equations are solved using finite volume method. The dimensionless heatfunction for nanofluid heat flow is defined and solved to determine heatline patterns. Calculations were performed for Rayleigh numbers of 10³, 10⁴ and 10⁵, inclination angle of 0°, 30°, 60° and 90°, and nanoparticle fraction of 0, 0.02, 0.04, 0.06, 0.08 and 0.1. It is observed that heat transfer in the cavity increases by adding nanoparticles. The rate of increase is greater for the enclosures with low Rayleigh number. Visualization of heatline is successfully applied to nanoparticle convective flows. Based on the heatline patterns, three heat transfer regions are observed and discussed in details.