Simultaneous growth of self-patterned carbon nanotube forests with dual height scales

In this study, we report on a unique, one-step fabrication technique enabling the simultaneous synthesis of vertically aligned multi-walled carbon nanotubes (VA-MWCNTs) with dual height scales through alcohol catalyzed chemical vapor deposition (ACCVD). Regions of VA-MWCNTs with different heights were well separated from each other leading to a self-patterning on the surface. We devised a unique layer-by-layer process for application of catalyst and inhibitor precursors on oxidized Si (100) surfaces before the ACCVD step to achieve a hierarchical arrangement. Patterning could be controlled by adjusting the molarity and application sequence of precursors. Contact angle measurements on these self-patterned surfaces indicated that manipulation of these hierarchical arrays resulted in a wide range of hydrophobic behavior changing from that of a sticky rose petal to a lotus leaf.     

Regulatory RNAs: A Universal Language for Inter-Domain Communication

In eukaryotes, microRNAs (miRNAs) have roles in development, homeostasis, disease and the immune response. Recent work has shown that plant and mammalian miRNAs also mediate cross-kingdom and cross-domain communications. However, these studies remain controversial and are lacking critical mechanistic explanations. Bacteria do not produce miRNAs themselves, and therefore it is unclear how these eukaryotic RNA molecules could function in the bacterial recipient. In this review, we compare and contrast the biogenesis and functions of regulatory RNAs in eukaryotes and bacteria. As a result, we discovered several conserved features and homologous components in these distinct pathways. These findings enabled us to propose novel mechanisms to explain how eukaryotic miRNAs could function in bacteria. Further understanding in this area is necessary to validate the findings of existing studies and could facilitate the use of miRNAs as novel tools for the directed remodelling of the human microbiota.     

Preparation of water‐soluble syndiotacticity‐rich high molecular weight poly(vinyl alcohol) microfibrillar fibers using copolymerization of vinyl pivalate and vinyl acetate and saponification

Water‐soluble high molecular weight (HMW) syndiotactic poly(vinyl alcohol) (s‐PVA) microfibrillar fibers were prepared by the saponification with various conditions such as amount of alkali solution, saponification temperature, and saponification concentration from copoly(vinyl pivalate (VPi)/vinyl acetate (VAc)) copolymerized using various VPi/VAc feed ratios. To produce s‐PVA microbrillar fibers having various water‐soluble temperatures for many industrial applications, the intrinsic viscosities, syndiotactic diad (S‐diad) contents, and degrees of saponification (DS)s of PVAs were finely controlled to 1.2–3.6 dL/g, 56.3–58.3%, and 91.4–98.3%, respectively. Through a series of experiments, it was found that the amount of alkali may alter the structure of the saponified polymers, primarily the DS, and the structural variation changes viscosity. That is, intrinsic viscosity was sharply decreased as the amount of alkali solution was increased. DS was increased with an increase in the amount of alkali solution. S‐diad content was increased with an increase in the VPi content. HMW s‐PVA microfibrillar fibers having S‐diad content of 56.3–58.3% prepared by the saponification of copoly(VPi/VAc) were completely soluble in water at 100°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1482–1487, 2003     

Polyurethane–poly(methyl methacrylate) block copolymer dispersions through polyurethane macroiniferters

Polyurethane macroiniferter/poly(methyl methacrylate) block copolymer dispersions with inverse core‐shell morphologies were obtained from 1,1,2,2,‐tetraphenylethane‐1,2‐diol, dimethylol propionic acid, 4,4′‐diphenylmethane diisocyanate, and poly(propylene glycol) via a living radical mechanism. Molecular weight, particle size and dispersion viscosity, and thermal, mechanical, and dynamic mechanical properties of the dispersion cast films are reported as a function of copolymerization time. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1971–1975, 2003     

Soy‐filled polyethylene fibers for modified surface and hydrophilic characteristics

By adding soy flour (soy) to linear low‐density polyethylene (LLDPE), soy‐PE fibers with enhanced hydrophilic characteristics were developed. Blends containing only soy and LLDPE had limited draw‐down, and the resulting thick fibers showed poor mechanical properties. When monoglyceride was added as a compatibilizer, thin fibers with good properties could be successfully spun due to improved dispersion of soy agglomerates in the LLDPE melt. Fibers spun from a blend containing 23/7/70 wt % of soy‐monoglyceride‐LLDPE displayed a tensile modulus and strength of 615 ± 38 and 57 ± 8 MPa, respectively. At 30% less synthetic content, these fibers still displayed mechanical properties generally comparable to those of base polyethylene fibers. Contact angle measurements showed that the soy‐based fibers had a hydrophilic surface (contact angle of 33° ± 4°). Moisture absorption studies confirmed that soy‐PE fibers gained about 20 wt % moisture in 1 h, whereas neat LLDPE fibers did not absorb any significant amount (LLDPE is hydrophobic). This hydrophilic behavior of soy‐PE fibers mimics that of natural fibers. Presence small soy agglomerates on the fiber surface also provides a textured surface and a desired tactile feel to the soy‐PE fibers, which coupled with hydrophilic behavior indicates their potential use in disposable nonwovens. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46609.     

Effect of zone drawing on the structure and properties of melt‐spun poly(trimethylene terephthalate) fiber

Melt‐spun poly(trimethylene terephthalate) (PTT) fibers were zone‐drawn and the structures and properties of the fibers were investigated in consideration of the spinning and zone‐drawing conditions. The draw ratio increased up to 4 with increasing drawing temperature to 180°C, at a maximum drawing stress of 220 MPa. Higher take‐up velocity gave lower drawability of the fiber. The PTT fiber taken up at 4000 rpm was hardly drawn, in spite of using maximum drawing stress, because a high degree of orientation had been achieved in the spinning procedure. However, an additional enhancement of birefringence was observed, indicating a further orientation of PTT molecules by zone drawing. The exotherm peak at 60°C disappeared and was shifted to a lower temperature with an increase in the take‐up velocity, which means that the orientation and crystallinity of the fiber increased. The d‐spacing of (002) plane increased with increasing take‐up velocity and draw ratio, whereas those of (010) and (001) planes decreased. In all cases, the crystal size increased with take‐up velocity and draw ratio. The cold‐drawn PTT fiber revealed a kink band structure, which disappeared as the drawing temperature was raised. The physical properties of zone‐drawn PTT fibers were improved as the draw ratio and take‐up velocity increased. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3471–3480, 2001     

Marine n-3 fatty acids: Basic features and background

There is some evidence from epidemiology that intake of n-3 polyunsaturated fatty acids (PUFA) from seafood may protect against coronary artery disease (CAD). This hypothesis is further supported from animal data showing a beneficial effect of n-3 PUFA on thrombosis and atherosclerosis in animals fed fish oils in most, but not all, studies. There are several mechanisms by which an increased intake of marine n-3 PUFA may protect against CAD; the most universal finding is a reduction of plasma triglycerides. It is puzzling, however, that a very low amount of n-3 PUFA, with no known beneficial biochemical effects, seems to be cardioprotective. It has therefore been of paramount interest to perform clinical trials. Such evidence and trials are discussed in later chapters, and the results have been very encouraging.     

Analytical and numerical assessments of local overpressure from hydrogen gas explosions in petrochemical plants

Accurate prediction of pressure rise is important for safety assessments of a petrochemical plant in the event of an explosion accident. The sudden pressures arising from gas explosions at various hydrogen concentrations in air have been predicted analytically and numerically. These solutions were compared against experimental data. The analytical solution, based on the self‐similar solution for pointwise strong explosions in an open space, which assumed no energy loss and premixed fuel‐air mixture, reasonably predicted the explosive‐ignition detonation case while the numerical solutions were more suitable to model spark‐ignition deflagration cases that accounted for the effect of turbulence arising from three‐dimensionality and presence of obstacles in the computational domain. Comparison of both analytical and numerical results against experimental data indicates that their differences are within a 30% margin. The analytical model presented herein can be useful for field engineers who want conservative estimates of the overpressure resulting from explosive‐ignition detonation. Copyright © 2016 John Wiley & Sons, Ltd.     

The effect of polypropylene maleic anhydride on polypropylene/(recycled acrylonitrile butadiene rubber)/(sugarcane bagasse) composite

The effect of polypropylene maleic anhydride (PPMAH) on the tensile properties and morphology of polypropylene (PP)/(recycled acrylonitrile butadiene rubber) (NBRr)/(sugarcane bagasse) (SCB) composites has been studied. Six different composites (100/0/10, 80/20/10, 70/30/10, 60/40/10, 50/50/10, and 40/60/10), with fixed 5 wt% of PPMAH compatibilizer and without PPMAH addition, were carried out. The composites were prepared through melt‐mixing technique at 180^oC for 9 min using a rotor speed of 15 rpm. The specimens were analyzed for mechanical properties and examined with scanning electron microscopy. The tensile strength was found to decrease with increasing filler content. However, tensile strength and Young's modulus of the PPMAH compatibilized composites were found to increase, while the elongation at break showed the opposite trend as compared with the control composites. The morphology results support the tensile properties and indicated a better interaction between the SCB filler and PP/NBRr matrices with the presence of PPMAH as a compatibilizer. This is due to the esterification bonding between the SCB filler and PP matrix in the presence of PP/NBRr matrices. J. VINYL ADDIT. TECHNOL., 23:228–233, 2017. © 2015 Society of Plastics Engineers