Mechanical and physico-chemical characterization of cyclodextrin finished polyamide fibers

We present the study of the cyclodextrin (CDs) finishing of polyamide fibers (PA) by means of citric acid (CTR) as crosslinking agent. We observed that the mode of grafting happened by the formation of a crosslinked polymer formed between CTR and CDs. This polymer physically adhered to the fibers network and was resistant to hot water washings. Modified fibers were characterized by evaluating the contact angle with a polar liquid and by studying the hysteresis of damping of PA fibers (Cahn balance) with various grafting rates and by studying the absorptivity of grafted fabrics via the technique of the posed drop (Digidrop^® instrument). Then a mechanical characterization of the PA fabrics grafted with various proportions of CDs was accomplished, by traction and tear tests by using a tensile-test bench Lohmergy. Finally a topographic study of PA grafted surfaces was approached by atomic force microscopy (AFM and LFM; contact and non-contact mode) which permitted to evaluate the roughness and the chemical heterogeneity of the grafted surfaces.     

Characterization of internal structure of hydrated agar and gelatin matrices by cryo‐SEM

There has been a considerable interest in recent years in developing polymer gel matrices for many important applications such as 2DE for quantization and separation of a variety of proteins and drug delivery system to control the release of active agents. However, a well‐defined knowledge of the ultrastructures of the gels has been elusive. In this study, we report the characterization of two different polymers used in 2DE: Gelatin, a naturally occurring polymer derived from collagen (protein) and agar, a polymer of polysaccharide (sugar) origin. Low‐temperature SEM is used to examine the internal structure of these gels in their frozen natural hydrated states. Results of this study show that both polymers have an array of hollow cells that resembles honeycomb structures. While agar pores are almost circular, the corresponding Gaussian curve is very broad exhibiting a range of radii from nearly 370 to 700 nm. Gelatin pores are smaller and more homogeneous reflecting a narrower distribution from nearly 320 to 650 nm. Overall, these ultrastructural findings could be used to correlate with functions of the polymers.     

Hydroxytyrosol Acyl Esters: Biosynthesis and Activities

We previously reported the production of high yields of hydroxytyrosol through the bioconversion of tyrosol. In the present work, hydroxytyrosol was subjected to the lipase catalyzed acylation aiming for the recovery of more lipophilic esters that might be easily incorporated in cosmetic and food preparations. Hydroxytyrosyl acetate and hydroxytyrosyl oleate were produced with respective molar esterification yields of 98% and 78%. DPPH free radical quenching potency demonstrated that the acylation of hydroxytyrosol did not alter its antioxidant activity. The acylated esters were shown to be more effective than the natural antioxidant: caffeic acid and two synthetic ones as BHA and BHT. Antiproliferative activity on human cervical cells (HeLa) resulted in IC₅₀ values of 0.46, 0.42 and 0.33 mM for hydroxytyrosol and its acetyl and oleyl esters, respectively. Additionally, when used at a non-cytotoxic concentration (100 μM), these compounds showed significant effectiveness in preventing iron-induced oxidative stress, resulting in a reduction of 30%, 36% and 38% in thiobarbituric acid-reactive substance production, respectively.     

Phase behavior and rheological properties of enzymatically synthesized trehalose decanoate aqueous solutions

Surface tension properties of an enzymatically synthesized equimolar mixture of trehalose mono- and didecanoate in aqueous solutions have been determined. At 20 degrees C a critical micellar concentration (CMC) of 50 micromol/l and a minimal surface tension of 28 mN/m have been obtained. Above the CMC, it has been shown that up to a concentration of 42 wt%, and in a 20-60 degrees C temperature range the sugar ester aqueous solutions do not form any crystalline structure, nor present any phase transition, and the trehalose decanoate molecules form an isotropic worm-like micellar phase. The rheological properties indicate however a more complicated picture in the same concentration and temperature ranges. In steady shear, the viscosity of the trehalose decanoate solutions do not exhibit any shear rate dependence from 1 to 100 s(-1) for concentrations up to 42 wt%. Below 0.8 wt%, the viscosity remains constant and close to that of water; then, between 0.8 and 23 wt%, the viscosity shows a quadratic increase with surfactant concentration. For higher concentrations, up to 42 wt%, no further significant increase in viscosity is observed. In oscillatory shear experiments, the solutions exhibit viscoelastic properties. The observed rheological behavior as a function of concentration and temperature may be due to a progressive evolution of the trehalose decanoate molecular associations: as the concentration increases, the system evolves towards an entangled and/or partially branched or cross-linked micellar network, and eventually a multiconnected network of cross-linked micelles.     

Physicochemical characterizations and semiconducting properties of a manganese tungstate MnWO4 obtained by hydrothermal route

Journal of Solid State Electrochemistry - Manganese tungstate (MnWO4) synthesized by hydrothermal method is characterized by many physicochemical techniques. X-ray diffraction pattern (XRD)...     

On Uniqueness for the Harmonic Map Heat Flow in Supercritical Dimensions

We examine the question of uniqueness for the equivariant reduction of the harmonic map heat flow in the energy supercritical dimension d ≥ 3. It is shown that, generically, singular data can give rise to two distinct solutions that are both stable and satisfy the local energy inequality. We also discuss how uniqueness can be retrieved. © 2017 Wiley Periodicals, Inc.     

Evaluation of the ice ratio formed during quasi-adiabatic pressure shift freezing

Abstract

Pressure shift freezing consists in cooling a biological substance (mainly containing water) under pressure without phase change followed by a sudden release of the pressure. The high supercooling obtained during the quasi adiabatic depressurisation permits to achieve a rapid and uniform ice nucleation. The ice fraction formed during the pressure release of a sample of pure water has been calculated using a mathematical model. In addition, this fraction was experimentally evaluated by isothermal calorimetry. The calculations and measurements were carried out at 3 different initial points of the ice I melting curve. A relatively good agreement is observed between the experimental and calculated ice ratio which were between 0.117 and 0.402 (kg ice/kg ice-water mixture) for an initial temperature-pressure values of -10°C/1 15 MPa and -21°C/210 MPa respectively.     

Unusual rearrangement in the reactions of phenylmalonic acid dihydrazide with 1, 3‐Diketones

Phenylmalonic acid dihydrazide reacted with 2,4‐pentanedione to give, unexpectedly, 5,7‐dimethyl‐1,3‐dioxo‐2‐phenyl‐2,3‐dihydro‐1H‐pyrazolo[1,2‐a]pyrazole‐4‐ylium 5. The structure of the product is confirmed by X‐ray crystallography.     

Sol–gel synthesis and luminescent properties of SiO2/Zn2SiO4 and SiO2/Zn2SiO4:V composite materials

Undoped and vanadium-doped Zn₂SiO₄ particles embedded in silica host matrix were prepared by a simple solid-phase reaction after the incorporation of ZnO and ZnO:V nanoparticles, respectively, in silica monolith using the sol–gel method with supercritical drying of ethyl alcohol in two steps. After supercritical drying and annealing in the temperature range between 1423 and 1473 K in an air atmosphere, the photoluminescence (PL) measurements show a band centered at about 760 nm in the case of non-doped Zn₂SiO₄ which is attributed to energy transfer from Zn₂SiO₄ particles to NBOHs interface defects. In the case of vanadium doped Zn₂SiO₄, the PL reveals a band centered at about 540 nm attributed to the vanadium in the interfaces between Zn₂SiO₄ particles and SiO₂ host matrix. Photoluminescence excitation (PLE) measurements show different origins of the emission bands. The PLE band (～240–350 nm) may be understood as an energy transfer process from O^2? to V⁵⁺ which occurs intrinsically in the vanadyl group.