Microstructure,thermooxidation and mechanical behavior of a novel highly linear,vitamin E stabilized,UHMWPE

A novel, vitamin E-stabilized, medical grade ultra-high molecular polyethylene, MG003 (DSM Biomedical; The Netherlands), has been very recently introduced for use in total joint replacements. This homopolymer resin features average molecular weight similar to that of conventional GUR 1050 resin (5.5–6*10⁶ g/mol), but a higher degree of linearity. The aim of this study was to characterize the microstructure, thermal and thermooxidation properties as well as the mechanical behavior of this novel MG003 resin before and after gamma irradiation in air to 90 kGy. For this purpose, a combination of experimental techniques were performed including differential scanning calorimetry (DSC), thermogravimetry (TG), transmission electron microscopy (TEM), X-Ray Diffraction, electron paramagnetic resonance (EPR), and uniaxial tensile tests. As-consolidated MG003 materials exhibited higher crystalline contents (~ 62%), transition temperatures (~ 140 °C), crystal thickness (~ 36 nm), yield stress (~ 25 MPa) and elastic modulus (~ 400 MPa) than GUR 1050 controls (55%, 136 °C, 27 nm, 19 MPa, and 353 MPa, respectively). Irradiation produced similar changes in both MG003 and GUR 1050 materials, specifically increased crystallinity (63% and 60%, respectively), crystal thickness (39 nm and 30 nm), yield stress (27 MPa and 21 MPa), but, above of all, loss of elongation to breakage (down to 442 and 469%, respectively). Thermogravimetric and EPR results suggest comparable susceptibilities to oxidation for both MG003 and GUR 1050 polyethylenes. Based on the present findings, MG003 appears as a promising alternative medical grade polyethylene and it may satisfactorily contribute to the performance of total joint replacements.     

Synthesizing higher nitride of molybdenum (Mo) and iron (Fe) in ammonia (NH3) gas stream under irradiation of concentrated solar beam in a solar furnace

Flowing gaseous ammonia NH₃ with suppressed extent of dissociation (un‐cracked NH₃) is acknowledged to function as a powerful nitriding medium to realize formation of metal nitride MN_x with considerably high N/M ratio x that cannot be achieved through reaction of M with N₂ gas. For example, mono‐nitride δ‐MoN of Mo and ε‐FeN_x phase of Fe with x = 0.33 ? 0.50 (i. e. hypo‐stoichiometric sub‐nitride ε‐Fe₂N) were reported to be difficult to prepare in N₂ gas environment even at elevated pressure but might be synthesized in flowing NH₃ gas at normal pressure when reaction temperature and NH₃ gas flow rate were set adequately. In the present work, nitriding experiments for Mo and Fe were carried out in flowing NH₃ gas under irradiation with concentrated solar beam. The acquired experimental evidences demonstrated that temperature range for formation of δ‐MoN was somewhat extended in flowing NH₃ gas under heating with concentrated solar beam compared with that under heating in conventional laboratory or industrial electric furnace. On the other hand, no such merit of extending temperature range for formation of ε‐Fe₂N in flowing NH₃ gas was detected in the present work under heating with concentrated solar beam.     

Hydrothermal Synthesis and Characterization of Europium-doped Barium Titanate Nanocrystallites

Nano-Micro Letters - Barium titanate nanocrystallites were synthesized by a hydrothermal technique from barium chloride and tetrabutyl titanate. Single-crystalline cubic perovskite BaTiO3...     

Hydrogel-based piezoresistive pH sensors: investigations using FT-IR attenuated total reflection spectroscopic imaging

The strong swelling ability of the pH-responsive poly(acrylic acid)/poly(vinyl alcohol) (PAA/PVA) hydrogel makes the development of a new type of sensor possible, which combines piezoresistive-responsive elements as mechanoelectrical transducers and the phase transition behavior of hydrogels as a chemomechanical transducer. The sensor consists of a pH-responsive PAA/PVA hydrogel and a standard pressure sensor chip. However, a time-dependent sensor output voltage mirrors only the physical swelling process of the hydrogel but not the corresponding chemical reactions. Therefore, an investigation of the swelling behavior of this hydrogel is essential for the optimization of sensor design. In this work, Fourier transform infrared (FT-IR) spectroscopic imaging was used to study the swelling of the hydrogel under in situ conditions. In particular, laterally and time-resolved FT-IR images were obtained in the attenuated total reflection mode and the entire data set of more than 80,000 FT-IR spectra was evaluated by principal component analysis (PCA). The first and third principal components (PCs) indicate the swelling process. Molecular changes within the carboxyl groups were observed in the second and fourth PC and identified as key processes for the swelling behavior. It was found that time-dependent molecular changes are similar to the electrical sensor output signal. The results of the FT-IR spectroscopic images render an improved chemical sensor possible and demonstrate that in situ FT-IR imaging is a powerful method for the characterization of molecular processes within chemical-sensitive materials.     

Estimation of the thickness and the optical parameters of several stacked thin films using optimization

The reverse engineering problem addressed in the present research consists of estimating the thicknesses and the optical constants of two thin films deposited on a transparent substrate using only transmittance data through the whole stack. No functional dispersion relation assumptions are made on the complex refractive index. Instead, minimal physical constraints are employed, as in previous works of some of the authors where only one film was considered in the retrieval algorithm. To our knowledge this is the first report on the retrieval of the optical constants and the thickness of multiple film structures using only transmittance data that does not make use of dispersion relations. The same methodology may be used if the available data correspond to normal reflectance. The software used in this work is freely available through the PUMA Project web page (http://www.ime.usp.br/~egbirgin/puma/).     

Surface enhanced fluorescence of anti-tumoral drug emodin adsorbed on silver nanoparticles and loaded on porous silicon

Fluorescence spectra of anti-tumoral drug emodin loaded on nanostructured porous silicon have been recorded. The use of colloidal nanoparticles allowed embedding of the drug without previous porous silicon functionalization and leads to the observation of an enhancement of fluorescence of the drug. Mean pore size of porous silicon matrices was 60 nm, while silver nanoparticles mean diameter was 50 nm. Atmospheric and vacuum conditions at room temperature were used to infiltrate emodin-silver nanoparticles complexes into porous silicon matrices. The drug was loaded after adsorption on metal surface, alone, and bound to bovine serum albumin. Methanol and water were used as solvents. Spectra with 1 μm spatial resolution of cross-section of porous silicon layers were recorded to observe the penetration of the drug. A maximum fluorescence enhancement factor of 24 was obtained when protein was loaded bound to albumin, and atmospheric conditions of inclusion were used. A better penetration was obtained using methanol as solvent when comparing with water. Complexes of emodin remain loaded for 30 days after preparation without an apparent degradation of the drug, although a decrease in the enhancement factor is observed. The study reported here constitutes the basis for designing a new drug delivery system with future applications in medicine and pharmacy.     

Influence of the pH on the synthesis of reduced graphene oxide under hydrothermal conditions

Here we describe the important role played by the pH on the morphology and structure of the reduced graphite oxide (rGO) samples obtained by hydrothermal treatment of the previously prepared GO. The nature of the resulting samples has been studied on the basis of a complete battery of experimental techniques.     

The effect of NaCl-free processing and high pressure on the fate of Listeria monocytogenes and Salmonella on sliced smoked dry-cured ham

NaCl is an important multifunctional ingredient applied in dry-cured ham elaboration. However, its excessive intake has been linked to serious cardiovascular diseases causing a recent increase in the development of reduced salt products. In the present study Listeria monocytogenes and Salmonella, food-borne pathogens which can cross-contaminate post processed products, were spiked with < 100 CFU/g on slices of both standard (S) and NaCl-free processed (F) (elaborated with KCl + potassium lactate instead of NaCl) smoked dry-cured ham. Although L. monocytogenes and Salmonella counts decreased faster in S ham, pathogens were present in both types of non-pressure treated ham during the entire refrigerated storage period (112 days). Pressurisation at 600 MPa for 5 min caused the elimination of both pathogens in S ham after 14 days. In contrast, Salmonella and L. monocytogenes were present in F ham until days 28 and 56, respectively, indicating that the NaCl-free processed dry-cured ham had lower stability than standard smoked dry-cured ham.     

Short communication: Production of antihypertensive peptide HLPLP by enzymatic hydrolysis: optimization by response surface methodology

This study evaluates the potential ability of proteolytic enzymes to release the antihypertensive peptide HLPLP, β-casein f(134–138), from caseinate. Corolase PP (Röhm GmbH &; Co. KG, Darmstadt, Germany) was found as the most appropriate enzyme to produce this peptide. The optimization of the main experimental variables involved in the process [concentration of Corolase PP, concentration of Peptidase 433P (Biocatalysts Ltd., Parc Nantgarw, UK), and the hydrolysis time on the HLPLP concentration, expressed as area of peak] were studied using a central composite face design. The optimum conditions to obtain the maximum concentration of HLPLP provided by the statistical program were a concentration of Corolase PP of 60 mg/g of protein and hydrolysis time of 24 h. The use of the Peptidase 433P did not increase the amount of the active peptide. The obtained hydrolysate might be used as functional ingredient with antihypertensive properties.