Topologically controlled growth of magnetic-metal-functionalized semiconductor oxide nanorods

Colloidal semiconductor-magnetic hybrid nanocrystals with topologically controlled composition are fabricated by heterogeneous nucleation of spherical epsilon-Co domains onto anatase TiO2 nanorods. The latter can be selectively decorated at either their tips or at multiple locations along their longitudinal sidewalls, forming lattice-matched heterointerfaces regardless of the metal deposition sites. The possibility of switching between either heterostructure growth modes arises from the facet-dependent chemical reactivity of the oxide seeds, which is governed mainly by selective adhesion of the surfactants rather than by small differences in misfit-induced interfacial strain at the relevant junction points.     

Polyblend fibers from polypropylene and mercapto-modified EVA

Polyblend fibers were made from mixtures of polypropylene (PP) and ethylene-vinyl acetate copolymers (EVA) or their mercapto-modified products [poly(ethylene-co-vinyl acetate-co-vinyl mercaptoacetate)] (EVASH). The presence of few EVA or EVASH in the PP fibers results in an increasing of the elastic modulus, indicating a reinforcing action of these functional polymers. The composition surface of the modified PP fibers was analyzed by X-ray photoelectron spectroscopy and diffuse reflectance infrared Fourier transform spectroscopy. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 2243–2249, 1997     

The effect of hydroxyl‐terminated polybutadiene‐grafted carbon fiber on the impact performance of carbon fiber–epoxy resin composites

Carbon fiber (CF) containing 1.4 and 2.1 mmol/g of —COOH and —OH groups, respectively, was functionalized by using an excess of tolylene‐2,4‐diisocyanate. The NCO‐modified CF was submitted to a graft reaction with hydroxyl‐terminated polybutadiene (HTPB). The HTPB‐grafted carbon fiber was employed as reinforcing agent for epoxy resin‐based composites. The presence of the flexible HTPB at the interface between the fiber and the matrix resulted in a substantial improvement on impact strength. Additional improvement on toughness was achieved by using epoxy matrix containing dispersed phase of HTPB. The composite morphology was also studied by scanning electron microscopy. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1424–1431, 1999     

Evaluating and comparing three community small-scale wind electrification projects

Electrification systems based on renewable energy have proven suitable for providing electricity autonomously to rural communities. Among the technical options available, wind systems are increasingly getting attention. In the northern mountains of Peru, at 3800 m.a.s.l., three community wind electrification projects have been implemented. The technical solutions used in each project are different: wind vs. hybrid photovoltaic-wind systems; individual equipment vs. microgrids. This study aims to describe, evaluate and compare these three small-scale community wind electrification projects. The evaluation of the three projects was carried out by comparing previous and present scenario; attention has been focused on project design and technical aspects, socio-economic impacts and sustainability and management model. These three examples shed light on both the advantages and disadvantages of different technological options as well as on appropriate community-level management models.     

Effect of branched PP content on the physical properties and cell growth during foaming of TPOs

Linear/branched PP blends at various ratios were used as the matrix for thermoplastic olefin (TPO) compounds, containing an ethylene–octene copolymer dispersed phase. A detailed investigation of the physical properties of these blends revealed that addition of branched PP (BPP) resulted in improved stiffness and flexural properties. Given that the phase morphology of the blends and the interfacial tension between their components remained virtually unaffected, these improvements are attributed to the higher stiffness of the BPP‐containing matrices. Talc‐filled TPOs containing branched PPs exhibited further improvements in the stiffness and flexural properties. An investigation into the bubble growth process during foaming using a batch foaming simulation system revealed that the presence of BPP resulted in a slight delay in cell nucleation, whereas the rate of bubble growth was not significantly altered. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Novel spectropolarimeter employing fixed polarizers for the determination of optically active samples

A novel spectropolarimeter, based on modification of an ordinary, inexpensive, multiwavelength ultraviolet (UV)-visible-near-infrared (NIR) spectrophotometer, is described and applied to the determination of sucrose, sucrose inversion, and enantiomeric composition of solutions of (R)-(+)-limonene and (S)-(-)-limonene. The instrument has no moving parts, and optical rotation measurements are encoded as an apparent absorbance. Apparent absorbance measurements can be combined with multivariate statistical analysis over a wide spectral range, and a background correction technique that employs the sample as its own blank provides an effective means of correcting for the presence of chromophores that also absorb over the wavelengths of interest. The instrument was tested against an ordinary polarimeter and showed good performance with both colorless and colored samples.     

Morphoanatomical and phytochemical studies of Salvia lachnostachys (Lamiaceae)

Salvia lachnostachys Benth., Lamiaceae, is a endemic species from southern Brazil. The essential oil of its leaves and flowers is mainly constituted by aliphatic compounds, such as dodecanoic acid, with sesquiterpenes as minor constituents. This work evaluated the morphology, anatomy, microchemistry, and phytochemistry of S. lachnostachys to provide advanced knowledge of Brazilian plants with medicinal potential. Light and scanning electron microscopy techniques were used in the anatomical and microchemical studies. Compounds were isolated by chromatographic techniques, identified by analysis of their NMR spectra and compared with published data. S. lachnostachys can be distinguished from other related species mainly by its petiolate leaves, terminal inflorescence, persistent bracts, and villous‐glandular corolla. The stem and leaves of S. lachnostachys display anatomical characteristics common to the family Lamiaceae. However, this species can be distinguished from other family members by the morphology and the presence of eglandular and glandular trichomes, as well as the organization of the vascular bundles of the petiole. The phytochemical results revealed that S. lacnostachys produces oleanolic and ursolic acids in addition to the diterpene fruticuline A, which is a rare compound, previously found only in Salvia fruticulosa Benth. and S. corrugata Vahl. Ursolic and oleanolic acids are bioactive triterpenes that exhibit antiatherosclerotic, anticancer, antihypertensive, antinflammatory, antileukemic, antimutagenic, antioxidant, antiproliferative, and antiviral activities, and fruticuline A has antibacterial activity. Microsc. Res. Tech. © 2012 Wiley Periodicals, Inc.     

Exploring the Origin of the Temperature‐Dependent Behavior of PbS Nanocrystal Thin Films and Solar Cells

Temperature‐dependent studies of the electrical and optical properties of cross‐linked PbS nanocrystal (NC) solar cells can provide deeper insight into their working mechanisms. It is demonstrated that the overall effect of temperature on the device efficiency originates from the temperature dependence of the open‐circuit voltage and the short‐circuit current, while the fill factor remains approximately constant. Extensive modeling provides signs of band‐like transport in the inhomogeneously coupled NC active layer and shows that the charge transport is dominated by diffusion. Moreover, via low temperature absorption and photoluminescence (PL) measurements, it is shown that the optical properties of PbS thin films before and after benzenedithiol (BDT) treatment exhibit very distinct behavior. After BDT treatment, both the optical density (OD) and PL are shifted to lower energies, indicating the occurrence of electronic wave function overlap between adjacent NCs. Decrease of the temperature leads to additional red‐shift of the OD and PL spectra, which is explained by the well‐known temperature dependence of the PbS NCs' bandgap. Moreover, BDT treated PbS NCs show unusual properties, such as decrease of the PL signal and broadening of the spectra at low temperatures. These features can be attributed to the partial relaxation of the quantum confinement and the opening of new radiative and nonradiative pathways for recombination at lower temperatures due to the presence of trap states.