Omega-3 PUFA metabolism and brain modifications during aging

In Canada, 5.5 million (16% of Canadians) adults are >65 years old and projections suggest this number will be approximately 20% of Canadians by 2024. A major concern regarding old age is a decline in health, especially if this entails a loss of self-sufficiency and independence caused by a decline in cognition. The brain contains 60% of fat and is one of the most concentrated organs in long chain omega-3 fatty acids such as docosahexaenoic acid (DHA). During aging, there are physiological modifications in the metabolism of lipids that could also have consequences on brain structure and levels of DHA. This review will hence discuss the physiological modifications in the metabolism of lipids during aging with a focus on long chain omega-3 and omega-6 fatty acids and also outline the structural and functional modifications of the brain during aging including brain lipid modifications and its relation to higher levels of DHA and cognition. Therefore, in this review, we outline the importance of collecting more data on the biology of aging since it might highly improve our understanding about what are «normal» modifications occurring during aging and what can become pathological

Chemical Modification of Poly(Vinyl Alcohol) in Water

Partial chemical modification of poly(vinyl alcohol) (PVA) was performed through tosylation followed by azidation. Amine functional PVA was also prepared by grafting propargylamine using click chemistry reaction. Through this approach, a tosyl group (a good leaving group), azide group (a group used in click chemistry) and amine group (a group used for amidation) were attached to PVA polymer chains. The three chemical modifications were performed in water. FTIR and XPS analysis confirmed the chemical modification after each step. Thermogravimetric analysis (TGA) was used to study the thermal stability of the modified PVA

High strength paper production based on esterification of thermomechanical pulp fibers in the presence of poly(vinyl alcohol)

Thermomechanical pulp (TMP) fibers, generally used to produce newspapers and carton materials, have poor inter- and intra-fiber bonding contributing to low strength properties. Poly(vinyl alcohol) (PVOH) was applied as a co-additive of 1,2,3,4-butanetetracarboxylic acid (BTCA), in the presence of sodium hypophosphite (SHP) as a catalyst, to esterify paper sheets based on TMP fibers. Fourier transform infrared (FTIR) spectroscopy technique was used to confirm the formation of the ester bond. The effects of curing temperature, molar mass and mass amount of the PVOH on the tensile index were investigated. The increasing of the curing temperature improved further the wet tensile index. The presence of PVOH increased both the dry and the wet tensile index of the paper sheets. The rise of both the molar mass and the mass amount of PVOH improved the tensile index

SURFACE COMPOSITION OF GRAFTED THERMOMECHANICAL PULP THROUGH XPS MEASUREMENT

The purpose of this study is to develop an analytical method to quantify the nitrogen present at the surface of paper by using X-ray photo-electronic spectroscopy (XPS). A sample of softwood thermomechanical pulp (TMP) was treated with a cationic starch containing primary amines, while another one was treated with a cationic polymer containing quaternary amines. We also grafted monomers containing a quaternary amine to the fiber. Sheets were prepared and analyzed by XPS. The technique used allowed us to identify the type of amine and to give a semi-quantitative evaluation

Contribution of TEMPO-Oxidized Cellulose Gel in the Formation of Flower-Like Zinc Oxide Superstructures: Characterization of the TOCgel/ZnO Composite Films

In the present paper, we report on a simple and new approach for the synthesis of hierarchical flower-like zinc oxide superstructures ZnO (FL) in the presence of the TEMPO-oxidized cellulose gel (TOCgel) through a room temperature sol-gel process in aqueous medium. Resulting composite films based on TOCgel and ZnO were investigated by several techniques including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and mechanical tests. SEM images demonstrated the formation of well-shaped flower-like ZnO superstructures within the fibrous structure of the TOCgel with a uniform diameter (~5 μm). FTIR and XPS results clearly confirmed the formation of such ZnO structures. We suggested that the carboxylate groups of TOCgel fibers act as capping agents and promote the construction of such flower-like ZnO via a nucleation-growth process. A proposed mechanism based on the oriented attachment-driven growth was discussed in order to explain the formation of ZnO (FL). The photocatalytic activity of the TOCgel/ZnO composite in the degradation of methylene blue (MB) under UV irradiation was clearly confirmed. Finally, mechanical tests demonstrated that the former TOCgel/ZnO film maintained a good flexibility (bent up to ~120°) without losing its photocatalytic activity

The Development of a Composite Based on Cellulose Fibres and Polyvinyl Alcohol in the Presence of Boric Acid

Boric acid was employed to improve the homogeneity and mechanical properties of a composite based on cellulose fibres and polyvinyl alcohol (PVOH). The influence of boric acid, under different pH values, on the mechanical properties cellulose fibres (handsheets) was investigated. The presence of the boric acid, under alkaline conditions, further improved the mechanical properties of the handsheets. A composite based on PVOH and cellulose fibres was prepared in the presence of boric acid and glycerol, a plasticizer. The employment of the boric acid, under alkaline conditions, was necessary to obtain a homogenous composite. The morphology of the final product was analysed by SEM, and their tensile properties were measured

Influence of High Shear Dispersion on the Production of Cellulose Nanofibers by Ultrasound-Assisted TEMPO-Oxidation of Kraft Pulp

Cellulose nanofibers can be produced using a combination of TEMPO, sodium bromide (NaBr) and sodium hypochlorite, and mechanical dispersion. Recently, this process has been the subject of intensive investigation. However, studies on the aspects of mechanical treatment of this process remain marginal. The main objective of this study is to evaluate the high shear dispersion parameters (e.g., consistency, stator-rotor gap, recirculation rate and pH) and determine their influences on nanocellulose production using ultrasound-assisted TEMPO-oxidation of Kraft pulp. All nanofiber gels produced in this study exhibited rheological behaviors known as shear thinning. From all the dispersion parameters, the following conditions were identified as optimal: 0.042 mm stator-rotor gap, 200 mL/min recycle rate, dispersion pH of 7 and a feed consistency of 2%. High quality cellulose gel could be produced under these conditions. This finding is surely of great interest for the pulp and paper industry

Kraft Lignin Depolymerization in an Ionic Liquid without a Catalyst

In this paper, the depolymerization of lignin was successfully achieved by the thermal treatment of kraft lignin in butyl-1,8-diazabicyclo[5.4.0]undec-7-enium chloride ([DBUC4+][Cl-]) without a catalyst. The thermal treatment experiments were performed in an oven at 150, 200, and 250 °C for 1 h. The changes in kraft lignin structure over the course of depolymerization were characterized by gel permeation chromatography (GPC), Fourier transform infrared (FTIR) spectroscopy, and 1H / 31P NMR analyses. GPC chromatograms indicated that the retention time of the original kraft lignin had shifted toward higher values after the thermal treatment, which indicated lignin depolymerization. The average molecular weight of the lignin obtained after 1 h reaction time decreased by 23, 70, and 58 wt% for the treatment at 150, 200, and 250 °C, respectively. FTIR spectra indicated the cleavage of β-O-4 bonds of kraft lignin. The 1H NMR spectra showed demethylation of all treated kraft lignins. Moreover, the 31P NMR analysis demonstrated that the demethylation phenomenon of the treated kraft lignin contributed to the formation of catechol groups

Grafting of Polycaprolactone on Oxidized Nanocelluloses by Click Chemistry

The main objective of this work is the grafting of polycaprolactone diol (PCL) on the surface of oxidized nanocelluloses (ONC) in order to enhance the compatibility between the hydrophilic cellulose nanofibres and the hydrophobic polymer matrix. This grafting was successfully realized with a new strategy known as click chemistry. In this context, the oxidized nanocelluloses bearing alkyl groups (ONC-PR) were prepared by reacting amino groups of propargylamine (PR) with carboxyl groups of ONC. In parallel, PCL was converted into azido-polycaprolactone (PCL-N3) in two steps: (i) tosylation of polycaprolactone (PCL-OTs) and (ii) conversion of PCL-OTs into PCL-N3 by nucleophilic displacement using sodium azide. Finally, ONC-PR was reacted with PCL-N3 in heterogeneous conditions through click chemistry in order to prepare polycaprolactone grafted oxidized nanocellulose (ONC-g-PCL), which could be suitable for improving the interfacial adhesion in the composite materials. The grafted samples were characterized by transmission electron microscopy and by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and Carbon-13 nuclear magnetic resonance spectroscopy (13C-NMR) spectroscopic techniques