High-performance nanocomposites based on polyetherketones

Polyetherketones, PEKs, are an important family of high-performance thermoplastic materials that display a unique combination of toughness, stiffness, thermooxidative stability, chemical and solvent resistance, flame retardancy, and retention of physical properties at high temperatures. A relevant step forward in the development of these materials has been the recent incorporation of nanofillers to extend their utility in advanced technological applications. This review provides an extensive overview of the research on PEK-based nanocomposites with a special emphasis on both carbon-based nanofillers, such as nanotubes or nanofibers, and inorganic nanoparticles. Nanocomposites can be fabricated by simple, low-cost conventional techniques such as extrusion and compression molding, generally combined with pre-processing stages involving mechanochemical treatments in organic solvents. Different strategies employed to efficiently incorporate carbon nanofillers into these matrices, including polymer functionalization, covalent grafting and nanofiller wrapping in compatibilizing systems are described. The analysis of the influence of the preparation and processing conditions as well as the nanofiller type, attributes and loading on the structure and properties of the resulting materials is also considered. Composites incorporating carbon nanofillers display remarkably improved thermal stability, electrical and thermal conductivity as well as mechanical property enhancements compared to the neat polymers. On the other hand, the incorporation of inorganic nanoparticles such as WS₂, SiO₂ or Al₂O₃ significantly enhances the tribological properties of the matrix, mainly the coefficient of friction and wear resistance. Finally, current and potential applications of these multifunctional nanocomposite materials in fields such as medicine, telecommunications, electronics, aerospace, automobile and chemical industries are described.     

Quick high-temperature hydrothermal synthesis of mesoporous materials with 3D cubic structure for the adsorption of lysozyme

Three-dimensional cage-like mesoporous FDU-12 materials with large tuneable pore sizes ranging from 9.9 to 15.6 nm were prepared by varying the synthesis temperature from 100 to 200 °C for the aging time of just 2 h using a tri-block copolymer F-127(EO₁₀₆PO₇₀EO₁₀₆) as the surfactant and 1,3,5-trimethyl benzene as the swelling agent in an acidic condition. The mesoporous structure and textural features of FDU-12-HX (where H denotes the hydrothermal method and X denotes the synthesis temperature) samples were elucidated and probed using x-ray diffraction, N₂ adsorption, ²⁹Si magic angle spinning nuclear magnetic resonance, scanning electron microscopy and transmission electron microscopy. It has been demonstrated that the aging time can be significantly reduced from 72 to 2 h without affecting the structural order of the FDU-12 materials with a simple adjustment of the synthesis temperature from 100 to 200 °C. Among the materials prepared, the samples prepared at 200 °C had the highest pore volume and the largest pore diameter. Lysozyme adsorption experiments were conducted over FDU-12 samples prepared at different temperatures in order to understand their biomolecule adsorption capacity, where the FDU-12-HX samples displayed high adsorption performance of 29 μmol g⁻¹ in spite of shortening the actual synthesis time from 72 to 2 h. Further, the influence of surface area, pore volume and pore diameter on the adsorption capacity of FDU-12-HX samples has been investigated and results are discussed in correlation with the textural parameters of the FDU-12-HX and other mesoporous adsorbents including SBA-15, MCM-41, KIT-5, KIT-6 and CMK-3.     

Serine Protease Inhibitors as Good Predictors of Meat Tenderness: Which Are They and What Are Their Functions?

Since years, serine proteases and their inhibitors were an enigma to meat scientists. They were indeed considered to be extracellular and to play no role in postmortem muscle proteolysis. In the 1990's, we observed that protease inhibitors levels in muscles are a better predictor of meat tenderness than their target enzymes. From a practical point of view, we therefore choose to look for serine protease inhibitors rather than their target enzymes, i.e. serine proteases and the purpose of this report was to overview the findings obtained. Fractionation of a muscle crude extract by gel filtration revealed three major trypsin inhibitory fractions designed as F1 (Mr:50–70 kDa), F2 (Mr:40–60 kDa) and F3 (Mr:10–15kD) which were analyzed separately. Besides antithrombin III, an heparin dependent thrombin inhibitor, F1 and F2 comprised a large set of closely related trypsin inhibitors encoded by at least 8 genes bovSERPINA3-1 to A3-8 and able to inhibit also strongly initiator and effector caspases. They all belong to the serpin superfamily, known to form covalent complexes with their target enzymes, were located within muscle cells and found in all tissues and fluids examined irrespective of the animal species. Potential biological functions in living and postmortem muscle were proposed for all of them. In contrast to F1 and F2 which have been more extensively investigated only preliminary findings were provided for F3. Taken together, these results tend to ascertain the onset of apoptosis in postmortem muscle. However, the exact mechanisms driving the cell towards apoptosis and how apoptosis, an energy dependent process, can be completed postmortem remain still unclear.     

Determination of methyl gallate in Bauhinia retusa extract by high-performance liquid and thin-layer chromatography

Two stability-indicating chromatographic methods are reported for the determination of methyl gallate in crude extracts of Bauhinia retusa. Separation by high performance thin layer chromatography was conducted on silica gel aluminum sheets using 9.5:0.5:0.2 (v/v/v) chloroform:methanol:acetic acid at 280 nm. The results from the 2–40 µg/band were used to prepare a linear calibration graph. The limits of detection and quantitation were 0.5 and 1.5 µg/band, respectively. The reverse phase high performance liquid chromatographic isolation of methyl gallate was performed at ambient temperature with an injection volume of 10 μL. The mobile phase consisted of 40:60 (v/v) methanol:0.1% ortho-phosphoric acid. The separation was performed at 1 mL/min using a detection wavelength of 280 nm. The calibration graph for methyl gallate was rectilinear from 0.02–40 µg/mL with limits of detection and quantitation of 0.004 and 0.010 µg/mL, respectively. For both methods, intra-day and inter-day precision were evaluated and the relative standard deviation was less than 2%, indicating good precision. The robustness was evaluated by making small and deliberate changes to appropriate parameters and the calculated relative standard deviation was less than 2%.The chromatographic methods were employed to determine methyl gallate in crude Bauhinia retusa extracts.     

Chryseobacterium meningosepticum in a parapneumonic effusion in a chronic kidney disease patient on hemodialysis

Chryseobacterium meningosepticum is an uncommon human pathogen, which is an inhabitant of soil and water. It should be included in the list of suspected nosocomial infections, especially in patients with immunocompromised status. C. meningosepticum infections are not common but are clinically important because the organism is naturally resistant to multiple antibiotics. We report a case where the bacterium was isolated from the pleural fluid from a chronic kidney disease patient on hemodialysis, who developed pneumonia with complicated parapneumonic effusion. To the best of our knowedge, this is the first case where C. meningosepticum is isolated from the pleural effusion, from India.     

Cardiovascular disease research in Saudi Arabia: a bibliometric analysis

In the previous three decades, in Saudi Arabia, prevalence of cardiovascular diseases (CVD) has increased and the government has invested significantly in education, healthcare, and research. This study examined the research productivity trends and characterized the types and focus of the all CVD research studies from Saudi Arabia. Data were extracted from studies published up until December 2015 and indexed in the PubMed database. Study eligibility criteria included: (1) sample selected within Saudi Arabia, and (2) CVD or a risk factor for CVD as an outcome, or (3) patients with CVD as study participants. Bibliometric data and study characteristics were extracted from each study; examples include authorship (number, gender, affiliation), journal, publication year, study location, research design, sample size, sample type (general or patient), sample composition (male or female), and sampling strategy (random or non-random). Analysis included 295 studies that pertained to 19 types of CVD; the most common were coronary artery disease (18%), hypertension (16%), stroke (14%), peripheral artery disease (11%), and congenital heart disease (10%). In the past 30 years, the overall productivity, use of a hypothesis-testing design (i.e. case–control, cohort, or trial), international collaborations, and funding increased incrementally. The experimental design constituted only 3% of all studies and less than 10% of the hypothesis-testing design studies. The scientific literature from Saudi Arabia addressed many of the CVD types. However, there were very few experimental studies conducted to date. Funding agencies should consider patronizing more studies with a hypothesis-testing design.     

Automatic analysis of human posture equilibrium using empirical mode decomposition

The present study proposes a new approach for the assessment of the human balance control. This approach is based on the decomposition of the center of pressure displacement using empirical mode decomposition (EMD) that provides an effective time-frequency analysis of non-stationary signals. Twenty-eight healthy subjects performed quiet standing in four conditions—feet apart/together with respect to eyes open/closed—while recording the stabilometric signals in the anteroposterior (AP) and mediolateral (ML) directions. The EMD method decomposes each stabilometric signal into several subsignals called intrinsic mode functions (IMFs). Stabilogram-diffusion analysis technique is applied to generate the diffusion curve of each IMF signal. Each diffusion curve is modeled as a second-order system and provides representative features, such as the gain parameter. Analysis of the gain parameter shows the major effect of visual input and feet conditions on the strategy to control/stabilize the balance. Significant differences were found between young and elderly, and between women and men. In addition, the impact of feet position seems to be higher in ML direction than in AP direction.     

Failure Investigation of Cracks in Bolted Flange

Cracks were observed on the outer diameter of the bolted flanges of a number of large control valves in high temperature service. An investigation was launched to determine the cause of cracking and propose corrective action. Metallurgical failure analysis and finite element analysis techniques were used to investigate the fracture, and concluded that the failures occurred due to thermal fatigue. A structural assessment performed on a cracked flange concluded that the cracks do not have an adverse effect on the integrity of the flange and it was concluded that the cracked flanges could be safely returned to service.