Cover Image,Volume 138, Issue 9

Blends of polypropylene (PP), polyamide 6 (PA6), and biodegradable polymers (BPs) such as poly(D,L-lactic acid) (PDLLA), poly(lactic acid-co-ε-caprolactone) (poly[LA-co-ε-CL]) and poly(ε-caprolactone) (PCL) were prepared using a twin-screw mini-extruder. The composition of the blend PP/PA6 was fixed at a mass proportion of 70/30, and the compatibilized blends contain 5 wt% of each BP. The morphology observed through scanning electronic microscopy, the dynamic mechanical thermal properties (DMTA), and the biodegradation test after composting and performing optical microscopy (OM) of the blends were investigated. The blend PP/PA6 compatibilized with polypropylene grafted with maleic anhydride (PPMA) was also obtained and used as a reference. The results showed that the PP/PA6/PPMA revealed a more homogeneous morphology and resulted in higher modulus; nevertheless, the sample obtained with the lower molar mass PDLLA as an alternative for PPMA showed a storage modulus behavior close to the reference material. Poly(LA-co-ε-CL) and PCL also showed changes in the morphology of the PA6 dispersed phase. Positive results were observed in the biodegradation test examined by OM for all samples containing BPs. The novelty of this work was to employ BPs as compatibilizing agents of the blends comprising PP/PA6, producing ternary blends with superior mechanical properties due to the better dispersion of the phases.     

Effect of carbon nanotubes functionalization on properties of their nanocomposites with polycarbonate/poly(acrylonitrile-butadiene-styrene) matrix

In this work, a comparative study evaluating the influence of different functionalization of carbon nanotubes on the properties of nanocomposites with polymeric matrix was performed. A 50/50 wt% polycarbonate (PC)/poly(acrylonitrile-butadiene-styrene) (ABS) blend was used as polymeric matrix of the nanocomposites. The comparison was made between nanocomposites reinforced with covalently functionalized multiwall carbon nanotubes (MWCNTf) and MWCNTf/nanoclay hybrid functionalization. The effect on the mechanical and morphological properties of the nanocomposites was evaluated through tensile and Izod impact tests and scanning electron microscopy and transmission electron microscopy (TEM) analyses. The thermal characterization of PC/ABS blends and nanocomposites was performed by differential scanning calorimetry (DSC). Results showed that both methods of functionalization of MWCNTs increased the stiffness and impact resistance of the nanocomposites. TEM micrographs indicated the preferred location of the reinforcements in the SAN phase of ABS. Results from DSC indicated an increase in the thermal resistance of the nanocomposites.     

Improving the Binding Affinity of in‐Vitro‐Evolved Cyclic Peptides by Inserting Atoms into the Macrocycle Backbone

Cyclic peptides binding to targets of interest can be generated efficiently with powerful in vitro display techniques, such as phage display or mRNA display. The cyclic peptide libraries screened with these methods are generated by altering in a combinatorial fashion the amino acid sequence of the peptides, the number of amino acids in the macrocycle rings, and the cyclization chemistry. A structural element that cannot easily be varied in the cyclic peptides is the backbone, which is built from amino acids, each of which contributes three atoms to the macrocyclic ring structure. Here, we proposed to improve the affinity of a phage‐selected bicyclic peptide inhibitor of coagulation factor XII (FXII) by screening variants with one or two carbon atoms inserted into different positions of the backbone, and thus tapping into a structural space that was not sampled by phage display. Two mutants showed 4.7‐ and 2.5‐fold improved K_i values. The better one blocked FXII with a K_i of 1.5±0.1 nm and inhibited activation of the intrinsic coagulation pathway (EC_2x 1.7 μm) . The strategy of ring size variation by one or several atoms should be generally applicable for the affinity maturation of in‐vitro‐evolved cyclic peptides.     

Synthesis of poly(lactic acid) by heterogeneous acid catalysis from <Emphasis Type="SmallCaps">d</Emphasis>,<Emphasis Type="SmallCaps">l</Emphasis>-lactic acid

Poly(lactic acid) (PLA) is an important polymer because of its significant biocompatibility and biodegradability. Supported H₃PW₁₂O₄₀ (H₃PW) on activated carbon was utilized for the catalytic polymerization of D,L-lactic acid, resulting in blends of PLA. The stability of the polymer was monitored by thermogravimetry (TGA), and the decomposition temperature (T_d) was used to determine the optimal production conditions (i.e., temperature of 180 °C for 15 h; 0.1 wt. % catalyst; 20 wt. % H₃PW/carbon calcined at 400 °C). The best catalyst was reused three times with good activity and recovery (95 %) and was analyzed to confirm the consistency of its Keggin structure, dispersion, and acidity, which are important parameters that affect the catalyst’s activity. The obtained polymer was characterized by gel permeation chromatography (GPC), Fourier-transform infrared spectroscopy (FT-IR), ¹H/¹³C nuclear magnetic resonance (NMR) spectroscopy, specific optical rotation ([α]_D ²⁵), powder X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The average molar mass of the polymer was 17,400 g mol^?1. Blends of poly(lactic acid) with 85 % poly(L-lactic acid) stereospecific isomer were obtained.

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Graphical Abstract Stereoselective synthesis of 85 % PLLA from polymerization of d,l-lactic acid using 12-tungstophosphoric acid supported on carbon as a catalyst

     

Very High Cycle Fatigue of Two Ductile Iron Grades

Two ductile iron grades, EN‐GJS‐600‐3 a ferritic–pearlitic grade, and EN‐GJS‐600‐10 a silicon strengthened ferritic nodular iron grade, are studied in the very high cycle fatigue range using a 20 kHz ultrasonic test equipment. Fatigue strengths and SN‐curves are achieved, and fracture surfaces and microstructures are investigated. The ferritic grade with higher ductility displays a lower fatigue strength at 10⁸ load cycles than the ferritic–pearlitic grade, 142 and 167 MPa, respectively. Examination of fracture surfaces shows that fatigue failures are controlled by micropores in both of the ductile iron grades, while the graphite nodule distributions do not seem to influence the difference in fatigue strengths. Prediction of the fatigue strengths, using a model for ductile iron proposed by Endo and Yanase, indicates a large potential for improvement in particular for the ferritic grade.     

Terror management and religion: Evidence that intrinsic religiousness mitigates worldview defense following mortality salience.

Terror management theory suggests that people cope with awareness of death by investing in some kind of literal or symbolic immortality. Given the centrality of death transcendence beliefs in most religions, the authors hypothesized that religious beliefs play a protective role in managing terror of death. The authors report three studies suggesting that affirming intrinsic religiousness reduces both death-thought accessibility following mortality salience and the use of terror management defenses with regard to a secular belief system. Study 1 showed that after a naturally occurring reminder of mortality, people who scored high on intrinsic religiousness did not react with worldview defense, whereas people low on intrinsic religiousness did. Study 2 specified that intrinsic religious belief mitigated worldview defense only if participants had the opportunity to affirm their religious beliefs. Study 3 illustrated that affirmation of religious belief decreased death-thought accessibility following mortality salience only for those participants who scored high on the intrinsic religiousness scale. Taken as a whole, these results suggest that only those people who are intrinsically vested in their religion derive terror management benefits from religious beliefs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Transformation Textures in As‐hot rolled TRIP Steels

The microstructures of TRIP steels finish‐rolled above and below the recrystallization‐stop temperature (T_nr) are compared. Here, the retained austenite grains are equiaxed or elongated, respectively, according to whether final rolling was carried out above or below the T_nr. The recrystallized austenite did not contain a sharp texture, the best defined component of which was the cube. The bainite that formed in this case was characterized by weak concentrations of the Goss and rotated Goss and a fairly strong concentration of the rotated cube. It also displayed the transformation products of a retained rolling fibre in the prior austenite. The deformed austenite contained the typical fcc rolling texture, where the copper is considerably more intense than the brass under these conditions. After transformation to bainite, the presence of a strong transformed copper component is evident, together with somewhat less intense contributions from the three transformed brass components. The data indicate that strong variant selection took place in the deformed austenite and that it was also present in the recrystallized material, but to a lesser extent. The latter displayed evidence of incomplete recrystallization in that the transformation texture included components obtained from both “recrystallized” and “deformed” austenite.     

Possibilities to reduce pavement rehabilitation cost of a collision-free road investment using an LCCA design procedure

In the past decades, many single carriageway roads in Sweden have been converted to collision-free roads as a cost-effective alternative to conventional motorways. Investigations have concluded that the road type has been successful in reducing the number of fatal accidents, despite increased operation and maintenance costs. In recent years, the focus has shifted to converting narrower roads, which are anticipated to further increase pavement rehabilitation cost but also complicate traffic management during road works. This paper first examines the consequences in terms of road agency and road user costs; second, the possibilities to influence future costs by design alternatives. A life cycle cost analysis was employed to study future costs. The analysis indicated significant increase in life cycle cost compared to a single carriageway road. The analysis of design alternatives also indicated that future agency and road user cost can be substantially improved by finding an optimal alternative.     

Adsorbed Eutectic GaIn Structures on a Neoprene Foam for Stretchable MRI Coils

Stretchable conductors based on eutectic gallium–indium (eGaIn) alloy are patterned on a polychloroprene substrate (neoprene foam) using stencil printing. By tuning the amount of eGaIn on the neoprene substrate, different strain‐sensitivity of electrical resistance is achieved. Conductors with a layer of eGaIn, which adsorbs to the walls of 60–100 µm wide neoprene cells, change their electrical resistance for 5% at 100% strain. When the amount of eGaIn is increased, the cells are filled with eGaIn and the strain‐sensitivity of the electrical resistance rises to 300% at 100% strain. The developed conductors are patterned as stretchable on‐body coils for receiving magnetic signals in a clinical magnetic resonance imaging setup. First images with a stretchable coil are acquired on an orange and compared to the images that are recorded using a rigid copper coil of the same size.     

Sterilizing photocurable materials by irradiation: preserving UV-curing properties of photopolymers following E-beam,gamma, or X-ray exposure

We have developed novel photopolymer gels to function as separators in blood collection tubes. By incorporating antioxidants such as α-tocopherol and nitroxides (TEMPO and TEMPOL), the new formulation can be sterilized with electron beam or gamma rays at a dose level of 17?kGy, without inducing premature curing of the photopolymers. For the blood separator gels that contain α-tocopherol, our results show that α-tocopherol plays a decisive role in impeding C-centered free radical propagation reactions through an H^?transfer mechanism. This mechanism involves the transfer of an H-atom from the hydroxyl group (OH) of α-tocopherol to the propagating C-centered radical leading to the termination of the polymerization. The sterilization radiation-induced premature curing of the photopolymer was also prevented in the blood separator gel containing nitroxides. For the gels containing TEMPO or TEMPOL, inhibition of the premature curing was achieved through an addition reaction or an H-transfer reaction, respectively. Our results also show that while α-tocopherol is not a contributing factor in the subsequent (time-of-use) UV curing of the gels, nitroxides enhance the UV curing process through nitroxide-mediated living free radical polymerization reactions leading to a decrease in UV curing time. The photopolymer separator gels are shown to function advantageously in clinical laboratory testing, especially for cell-free DNA measurements in blood.