A study on conformational changes by electron charges in viologen single molecules by using STM

The topography of self-assembled viologen derivatives (VC(8)SH, VC(10)SH, HSC(8)VC(8)SH, and HSC(10)VC(10)SH) molecules on an octanethiol (C(8)) self-assembled monolayer (SAM) modified gold surface was measured using ultrahigh-vacuum scanning tunneling microscopy (UHV-STM). We demonstrate here a novel matrix SAM appropriate for isolation of the viologen molecules. The C(8) was used for a matrix SAM, in which the VC(8)SH, VC(10)SH, HSC(8)VC(8)SH, and HSC(10)VC(10)SH were inserted at molecular lattice defects. The isolated single molecules of viologen derivatives inserted in the matrix SAM were observed as protrusions in STM topography using a constant current mode. We measured the topographic heights (VC(8)SH: 1.53nm, VC(10)SH: 2.01nm, HSC(8)VC(8)SH: 2.71nm, and HSC(10)VC(10)SH: 3.3nm) of the molecular protrusions using STM. Also, changes in the central axis of viologen molecules were observed as VC(8)SH (0.5-0.73nm), VC(10)SH (0.4-0.74nm), HSC(8)VC(8)SH (0.67-0.84nm), and HSC(10)VC(10)SH (0.67-0.99nm), respectively.     

Direct observation on the temperature-dependent change of magnetic domains in epitaxial MnAs film on GaAs (001)

We present a systematic change of the magnetic domain structure with temperature in epitaxial ferromagnetic MnAs film on GaAs (001), observed in a wide temperature range of 15-45 degrees C by magnetic force microscopy. Interestingly, it is found that, as temperature increases, the domain structure within the ferromagnetic alpha-MnAs stripes shows a mixture of head-on and simple domains at 15 degrees C and then, takes a complete transition to simple ones above 15 degrees C. This change could be understood by change in the demagnetizing factor of the cross-section of the ferromagnetic stripes with temperature.     

Limiting flux in microfiltration of colloidal suspensions by focusing on hydrodynamic forces in viscous sublayer

Cross‐flow microfiltration tests were performed on colloidal suspensions under turbulence conditions. By changing the particle diameter, flow rate, and channel height in the membrane housing to measure limiting fluxes, the influence of each parameter on the limiting flux was assessed from the viewpoint of hydrodynamic forces exerted on a particle in the viscous sublayer. In analyzing all the data taken, the particle Reynolds number calculated from the limiting flux is proportional to the 1.5 power of that calculated from the flow rate at the boundary between the viscous sublayer and the intermediate layer. This fact indicates that the limiting flux can be determined in situations where the drag force exerted by the flux is balanced by the lift force in the viscous sublayer. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1760–1765, 2018     

High‐Performance Triboelectric Nanogenerators Based on Electrospun Polyvinylidene Fluoride–Silver Nanowire Composite Nanofibers

The preparation of ferroelectric polymer–metallic nanowire composite nanofiber triboelectric layers is described for use in high‐performance triboelectric nanogenerators (TENGs). The electrospun polyvinylidene fluoride (PVDF)–silver nanowire (AgNW) composite and nylon nanofibers are utilized in the TENGs as the top and bottom triboelectric layers, respectively. The electrospinning process facilitates uniaxial stretching of the polymer chains, which enhances the formation of the highly oriented crystalline β‐phase that forms the most polar crystalline phase of PVDF. The addition of AgNWs further promotes the β‐phase crystal formation by introducing electrostatic interactions between the surface charges of the nanowires and the dipoles of the PVDF chains. The extent of β‐phase formation and the resulting variations in the surface charge potential upon the addition of nanowires are systematically analyzed using X‐ray diffraction (XRD) and Kelvin probe force microscopy techniques. The ability of trapping the induced tribocharges increases upon the addition of nanowires to the PVDF matrix. The enhanced surface charge potential and the charge trapping capabilities of the PVDF–AgNW composite nanofibers significantly enhance the TENG output performances. Finally, the mechanical stability of the electrospun nanofibers is dramatically enhanced while maintaining the TENG performances by applying thermal welding near the melting temperature of PVDF.     

Systemized organic functional group controls in polydiacetylenes and their effects on color changes

A variety of organic functional groups have been successfully installed into polydiacetylenes (PDAs) and applied to the color change‐controlled system of PDA sensors. Ten diacetylene compounds possessing different functionalities and lengths were systemically synthesized and fully characterized using spectroscopic methods. The polymerized vesicle solution with these compounds showed different temperatures required to induce a color change (from blue to red) depending on the functionalities installed on 10,12‐pentacosadiynoic acid (PCDA) molecules. In addition, the results reported here reveal that the intermolecular interactions of PCDA molecules and the intermolecular distance play a key role to the color of PDA system. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45011.     

Efficient dispersants for the dispersion of gallium zinc oxide nanopowder in aqueous suspensions

Appropriate dispersants for the dispersion of gallium zinc oxide (GZO) nanopowder in aqueous suspensions were identified in this study. The dispersion efficiencies and stabilization mechanisms of water‐based dispersants ammonium poly(acrylic acid) (PAA–NH₄), an anionic polyelectrolyte, and polyethylenimine (PEI), a cationic polyelectrolyte, were compared. The experimental analyses of rheology and sedimentation showed that both PAA–NH₄ and PEI were good dispersants for the dispersion of GZO. Theoretical calculations based on Derjaguin‐Landau‐Verwey‐Overbeek theory revealed that the stabilization mechanism of PEI was mainly related to the steric effect, and a very low molecular weight of 1800 g/mol was insufficient for powder stabilization. GZO was well dispersed by PEI with high molecular weight of 10 000 g/mol, but agglomeration occurred when too much PEI was added. Compared with PEI, PAA–NH₄ was more efficient because of its high contribution to the increase in electrostatic repulsion. Based on theoretical considerations on both steric and electrostatic effects, namely, the electrosteric stabilization mechanism, PAA–NH₄ is optimal for the dispersion of GZO nanopowder in aqueous suspensions.     

Conifer Diterpene Resin Acids Disrupt Juvenile Hormone-Mediated Endocrine Regulation in the Indian Meal Moth <Emphasis Type="Italic">Plodia interpunctella</Emphasis>

Diterpene resin acids (DRAs) are important components of oleoresin and greatly contribute to the defense strategies of conifers against herbivorous insects. In the present study, we determined that DRAs function as insect juvenile hormone (JH) antagonists that interfere with the juvenile hormone-mediated binding of the JH receptor Methoprene-tolerant (Met) and steroid receptor coactivator (SRC). Using a yeast two-hybrid system transformed with Met and SRC from the Indian meal moth Plodia interpunctella, we tested the interfering activity of 3704 plant extracts against JH III-mediated Met-SRC binding. Plant extracts from conifers, especially members of the Pinaceae, exhibited strong interfering activity, and four active interfering DRAs (7α-dehydroabietic acid, 7-oxodehydroabietic acid, dehydroabietic acid, and sandaracopimaric acid) were isolated from roots of the Japanese pine Pinus densiflora. The four isolated DRAs, along with abietic acid, disrupted the juvenile hormone-mediated binding of P. interpunctella Met and SRC, although only 7-oxodehydroabietic acid disrupted larval development. These results demonstrate that DRAs may play a defensive role against herbivorous insects via insect endocrine-disrupting activity.     

Effects of an external electric field on the collection efficiency of air filters: Filtration mechanisms with an external e-field

An external electric field was applied on the filter to improve its collection efficiency, and the collection efficiencies of the different filters under various conditions were evaluated. Dominant electrical filtration mechanisms for each condition were investigated using experimental and theoretical approaches. Four types of air filters were used as test filters: a charged fiber filter, a low-grade filter with 50% collection efficiency in the most penetration particle size (MPPS) zone, and two high-grade filters with more than 95% collection efficiency in the MPPS zone. Three different particle charge states—neutralized, single-charged and uncharged—were considered. For neutralized particles, the external electric field led to a 14.5%p. and 2.5%p. increase in the collection efficiencies of the low-grade filter and charged fiber filter, respectively. With the electric field, the collection efficiency of the low-grade filter increased by 30%p. for single-charged particles. The electric field also affected the collection efficiencies of the charged filter and high-grade filters, but the effect was not significant. For uncharged particles, the electric field did not lead to a remarkable increase in the collection efficiencies of any of the filters. Through experimental and theoretical analysis, it was found that the polarization force imposed on the charged fiber was the dominant factor for the charged fiber filter regardless of application of the external electric field. The Coulombic force imposed on the electric field was the dominant factor for the low-grade filter, while both the Coulombic and the polarization forces affected the collection efficiency of the high-grade filter.

Copyright © 2017 American Association for Aerosol Research     

Harvesting of <Emphasis Type="Italic">Scenedesmus obliquus</Emphasis> cultivated in seawater using electro-flotation

Seawater, when supplemented to a growth medium, appears to stimulate auto-flocculation of a certain microalgae species like Scenedesmus obliquus and thus renders its harvesting easy. To make use of this unique response for the purpose of biomass harvesting, S. obliquus was grown in a seawater-added medium and then collected in electrochemically- mediated ways. Significantly higher harvesting efficiency and energy saving were observed with electroflotation (EF) than with electro-coagulation-flotation (ECF) and the standard BG11 medium. An optimal EF condition, the highest recovery rate with least energy use, was found with a supply of 0.5 A. Seawater amendment was most beneficial in a level of 10%. All this clearly showed that applying EF to cells cultivated in the seawater-supplemented medium is a promising harvesting means that enables one to obtain algae biomass without interfering with the downstream process of biodiesel production.     

Verification of the performance of rotatable jig for a single cantilever beam method using the finite element analysis

The performance of new jig for single cantilever beam test method was verified by finite element analysis. Two types of jig were designed for a small specimen that had relatively short length compared to the width of cantilever; one was simple fixed jig and the other was specially designed rotatable jig. The rotatable jig has a rotatable seesaw which adjusts the experimental misalignments between the specimen and test machine. Among the three translational and three rotational misalignments, following three important factors were considered; rotation about x-axis, rotation about z-axis, and translation in y-axis. Adhesive layer was modeled by cohesive zone element, and crack propagation behavior and the deviation of energy release rate were investigated. The fixed jig showed undesired asymmetric crack propagation and large deviation of energy release rate when it had rotational misalignment about x-axis. However, the proposed new rotatable jig showed almost symmetrical crack propagation and small deviation of energy release rate regardless of misalignments. Rotational motion of the seesaw automatically compensated the rotational misalignment of the specimen. The rotatable jig also showed relatively small deviation of energy release rate compared with the fixed jig by the rotational misalignment about the z-axis. In contrast, the rotatable jig showed deviation of energy release rate by translational misalignments in the y-axis. However, the magnitude of the deviation was very small within the controllable range of experimental misalignment. In conclusion, it was found out that the proposed jig was appropriate for the measurement of adhesion of a small specimen by single cantilever beam method.