Polyethylene/sepiolite fibers. Influence of drawing and nanofiller content on the crystal morphology and mechanical properties

The influence of sepiolite content (1, 2, and 3 wt%) and successive drawing steps on the final properties of polyethylene/sepiolite nanocomposite fibers are reported. Particularly the effects of these variables on crystallinity, fiber macroscopic morphology, and tensile mechanical properties are analyzed applying different experimental techniques: differential scanning calorimetry, wide angle x‐ray diffraction, scanning electronic microscopy, and tensile mechanical characterization. The study evidenced the important role of both sepiolite content and stretching on the crystalline morphology and mechanical properties of the nanocomposites fiber. Both variables favor the appearance of the monoclinic phase during polyethylene crystallization, and produce an increase of crystallinity degree (35 % with drawing steps and 10 % by the sepiolite incorporation in non drawing fiber). This change of crystal morphology influences mechanical properties enhancing with both sepiolite content and drawing steps. Thus, Young Modulus increases 17 times with drawing in pure PE fibers and 1.5 times because sepiolite presence. The strength shows similar behavior, but the elongation at break decreases 14 timed with draw steps and to a half by the sepiolite influence. The final properties of drawing nanocomposite fibers are so acceptable for textile applications and they content particles that enhance their moisture and odors absorptive capacities. POLYM. ENG. SCI., 55:1096–1103, 2015. © 2014 Society of Plastics Engineers     

Nonthermal pasteurization of liquid foods using high‐intensity pulsed electric fields

Processing foods with high‐intensity pulsed electric fields (PEF) is a new technology to inactivate microorganisms and enzymes with only a small increase in food temperature. The appearance and quality of fresh foods are not altered by the application of PEF, while microbial inactivation is caused by irreversible pore formation and destruction of the semipermeable barrier of the cell membrane. High‐intensity PEF provides an excellent alternative to conventional thermal methods, where the inactivation of the microorganisms implies the loss of valuable nutrients and sensory attributes. This article presents recent advances in the PEF technology, including microbial and enzyme inactivation, generation of pulsed high voltage, processing chambers, and batch and continuous systems, as well as the theory and its application to food pasteurization. PEF technology has the potential to improve economical and efficient use of energy, as well as provide consumers with minimally processed, microbiologically safe, nutritious and freshlike food products.     

Effects of the terminal sire type and sex on pork muscle cathepsins (B, B+L and H), cysteine proteinase inhibitors and lipolytic enzyme activities

Pork muscle cathepsins (B, B+L, and H), cysteine proteinase inhibitors and lipolytic enzyme activities were measured in the offspring of five different genetic sire types: Danish Duroc (DU), Dutch Large White (LW(D)), English Large White (LW(E)), Belgian Landrace × Landrace (BL×LR) and Belgian Landrace (BL). Cathepsin B and B+L activities were higher for LW(E) and LW(D) sires than for BL×LR and BL. Cathepsin H activity showed an opposite evolution, being higher for BL and BL×LR sires than for DU, LW(D) and LW(E). Cysteine proteinase inhibitor activity was higher for LW(E) sires than for DU and BL. In lipolytic enzymes, BL sires had a lower acid lipase activity than DU and LW(E) sires and also a lower neutral esterase activity than LW(E) and LW(D) sires. Significant differences between sexes were found for cathepsin H activity only, being higher for females.     

Regio– and Stereoselectivity of Malt Lipoxygenases LOX1 and LOX2

The characterisation of lipoxygenases LOX1 and LOX2 and hydroperoxyoctadecadienoic acid (HPODE) degrading enzymes from barley green malt is reported. Hydroxylapatite chromatography (HAC) and isoelectric focussing (IEF) were performed to separate and purify LOX isoenzymes. The regio‐ and stereo‐selectivity of LOX1 and LOX2 towards linoleic acid as substrate was characterised. HAC purified isoenzyme LOX1 showed a 9‐HPODE:13‐HPODE ratio of 75:25 and LOX2 a ratio of 39:61. IEF separated LOX1 and LOX2 transformed linoleic acid to 9‐:13‐HPODE ratios of 90:10, and 13:87, respectively. 9‐HPODE stereoisomers from LOX1 exhibited a S:R ratio of 93:7 and 13‐HPODE from LOX2 a S:R ratio of 89:11. However, the minor regioisomers were analysed with S:R = 48:52 (LOX1, 13‐HPODE) and 40:60 (LOX2, 9‐HPODE). These results indicate a complete LOX isoenzyme separation by IEF. Hydroperoxide‐metabolising enzymes, which were investigated in the IEF fractions, did not interfere with the dual position specificities of LOX isoenzymes.     

Effects of gamma irradiation on the viability and phenotypic characteristics of Salmonella Enteritidis inoculated into specific-pathogen-free eggs

The goal of this study was to determine the effects of various levels of gamma irradiation on the phenotypic characteristics of 20 strains of Salmonella Enteritidis inoculated separately into specific-pathogen-free shell eggs. Bacterial strains were inoculated into egg yolks and exposed to (60)Co radiation at doses of 0.49 to 5.0 kGy. The eggs were maintained at 25°C and analyzed for the presence of Salmonella on days 1, 2, 4, and 7, and the recovered Salmonella isolates were characterized biochemically. All strains were resistant to doses of 0.49, 0.54, 0.59, 0.8, and 1 kGy; colony counts were ≥10(5) CFU/ml of egg yolk except for one strain, which was detected at 96 h and at 7 days after irradiation at 1 kGy, with a population reduction of 2 log CFU/ml. For the other evaluated doses, 12 strains (60.0%) were resistant at 1.5 kGy and 7 strains (35.0%) were resistant at 3.0 kGy. Among all analyzed strains, 5.0 kGy was more effective for reducing and/or eliminating the inoculated bacteria; only two (10%) strains were resistant to this level of irradiation. Salmonella colony counts were significantly reduced (P < 0.01) with increasing doses from the day 1 to 7 of observation, when microbial growth peaked. Loss of mobility, lactose fermentation, citrate utilization, and hydrogen sulfide production occurred in some strains after irradiation independent of dose and postirradiation storage time. Increases in antibiotic susceptibility also occurred: seven strains became sensitive to β-lactams, two strains became sensitive to antifolates, and one strain each became sensitive to fluoroquinolone, phenicol, nitrofurans, tetracyclines, and aminoglycosides. The results indicate that up to 5.0 kGy of radiation applied to shell eggs inoculated with Salmonella Enteritidis at 4 log CFU per egg is not sufficient for complete elimination of this pathogen from this food matrix.     

Seasonal changes of α-tocopherol in green marine algae (Caulerpa genus)

Abstract: Marine algae are a promising source of beneficial compounds for human use. Among these, pro‐vitamin A carotenoids and vitamins B, C, and E stand out. The objective of this study was to investigate seasonal variation of α‐tocopherol levels in 5 species of green marine algae of the Caulerpa genus. This research was carried out with both fresh and dry specimens; and, in addition, differences arising as a result of the drying process were examined. Analyses were carried out by high‐performance liquid chromatography (HPLC) using an isocratic system and a reversed‐phase C‐18 column. The distribution of α‐tocopherol throughout the year in Caulerpa genus was variable. All samples of both fresh and dried algae contained α‐tocopherol, except for the dried C. racemosa from March 2006. The drying process was responsible for losses of α‐tocopherol ranging from 21% to 93%.     

钢框架结构优化设计的多集约束和自动构件分组

对于结构优化问题,如钢框架结构的用钢量最小化,设计尺寸取决于构件横截面面积。构件横截面面积可从一些可行性表格中查得,如美国钢结构协会(AISC)提供的表格。构件的横截面尺寸bf,tf,d和tw(可为分散的或连续的)能独立确定。讨论关于设计尺寸变量的框架结构优化问题,提出一种获得理想构件分组法则。此法则考虑了制作、检查、装配和焊接的优势,而这些因素在传统预算里并没有被考虑。运用先前提出的适应性损失法,增强结构优化中的机械约束。     

Morphology of the stifle in agouti (Dasyprocta prymnolopha,Wagler 1831)

The agouti (Dasyprocta prymnolopha, Wagler 1831) is a wild rodent of great zootechnical potential, a fact that enables anatomical and morphological studies to support management actions with this animal. In this perspective, this study aimed to describe the anatomy and histology of the agouti stifle joint. Four adult agoutis were used, two females and two males. The animals were submitted to dissection and identification of the structures of the stifle joint. For light microscopy study, samples of the patellar ligament, cranial and caudal cruciate ligaments, medial and lateral collateral ligaments were used. Agouti has a highly congruent patellofemoral joint; elongated patella; medial and lateral fabellae at the proximal insertion of the gastrocnemius muscle; medial and lateral meniscus with lunula; in addition to the presence of the following ligament structures: patellar ligament, cranial and caudal cruciate ligaments, medial and lateral collateral ligaments, meniscofemoral ligament, caudal meniscal ligament of the medial meniscus, and medial and lateral cranial ligaments. The patellar ligament presents bundles of parallel collagen fibers with a straight path and coated fibroblasts; collateral and cruciate ligaments had loose and dense connective tissue, coated fibroblasts and collagen bundle undulations, the latter most expressive in the caudal cruciate ligament. Thus, except for the shape and angulation of the stifle, which allows specific movements, the agouti stifle has structures analogous to that of other rodents and domestic animals.