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Anodic TiO 2 nanotubes (NTs) have been studied extensively for many years. However, the growth kinetics still remains unclear, because it is hardly derived by direct in situ methods. Here, an interesting approach is proposed to overcome this challenge. A combinatorial anodization was exploited to monitor the pore initiation and nanotube growth under a preformed compact surface layer (CSL). The preformed CSL and the NTs under the CSL (UCSL-NTs) were formed in fluoride-free and fluoride-containing electrolytes, respectively. The forming process of UCSL-NTs was discussed as compared with that of the general NTs, mainly focusing on the differences of current-time curves and electric charge quantity (Coulomb). The results show that pore embryos of UCSL-NTs have already been achieved under the CSL before the CSL is dissolved. There are five stages in the current-time curve of UCSL-NTs, which is significantly different from three stages of the general NTs. A new growth model, based on a comprehensive review of the existing theories, is proposed to explain the current decrease and increase. And the forming process of TiO 2 NTs is considered to be dominated by the oxide plastic flow around the oxygen bubbles.Anodic TiO 2 nanotubes (NTs) and other porous anodic oxides have attracted considerable scientific interests due to their various applications (e.g., solar energy materials, magnetic semiconductors and biosensors) 1-3 and mysterious formation mechanisms. 4,5 Different mechanisms of TiO 2 NTs have been reported in many electrochemical journals in recent years. 4-8 It is well known that field-assisted dissolution (FAD) (TiO 2 + 6F − + 4H + → [TiF 6 ] 2− + 2H 2 O) of the oxide leads to pore formation in anodic titania films, 8-10 similar to that in porous anodic alumina (PAA) films (Al 2 O 3 + 6H + → 2Al 3 + + 3H 2 O), 11-14 despite a lack of direct experimental evidence that confirms this expectation. 14 As the formation mechanism is impossible to be derived by direct in situ experimental methods, much remains to be done along these directions. 15 Garcia-Vergara et al. 16,17 proposed the field-assisted 'plastic flow' model, the constant thickness of the barrier layer is maintained by flow of oxide from the pore bottom toward the pore wall, driven by compressive stresses from electrostriction and possibly through volume expansion. 16 In fact, the plastic flow is contrary to expectations of the FAD. 16 The behavior of incorporated species in PAA is always incompatible with the FAD model. 16 The flow model has been recognized and exploited for explaining the formation of TiO 2 NTs and serrated nanochannels. 18,19 However, Zhou et al. 12 indicated that both the FAD and the flow models cannot explain the formation of gaps among nanotubes. In recent tracer studies on Ti thin films, the expansion factors increase from 1.5 to 3.0, 20,21 these findings cannot be clarified. Furthermore, anodized TiO 2 NTs have been achieved in an aqueous H 2 SO 4 solution as well as other fluoride free solutions, 12,22,23 this fact puts the flu...

A nanohybrid comprising silver nanoparticles within third-generation dendritic poly(amidoamine) (PAMAM) grafted onto multiwalled carbon nanotubes (MWNTs) was applied as an antimicrobial agent in solution. The high abundance of amine groups on the dendrimer-modified MWNTs (d-MWNTs) provided sites for reduction and precipitation of silver nanoparticles from silver acetate aqueous solution, resulting in carbon nanotubes/ Ag nanohybrids (d-MWNTs/Ag). The content of PAMAM grafted on d-MWNTs determined by using a thermal gravimetric analyzer (TGA) was about 45%. The silver nanoparticles produced were determined to be face-centered cubic silver nanocrystals by X-ray powder diffraction (XRD). The nanohybrids were investigated with scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, and X-ray energy dispersive spectroscopy (EDS). The antimicrobial properties of acid-treated MWNTs (MWNTs-COOH), d-MWNTs, and d-MWNTs/ Ag were investigated against Staphylococcus aureus (S. aureus), Escherichia coli (E. coli), and Pseudomonas aeruginosa (P. aeruginosa). Against E. coli and P. aeruginosa which are Gram-negative, d-MWNTs and d-MWNTs/Ag which are equally effective were found to have a stronger antimicrobial effect than MWNTs-COOH. Against S. aureus (Gram-positive), d-MWNTs/Ag showed a stronger antimicrobial effect than d-MWNTs (92.3% kill versus 71.6% kill), while MWNTs-COOH only killed 15.4% of this bacteria. Possible mechanisms are proposed to explain the higher antimicrobial activity by d-MWNTs/Ag nanohybrids. These findings suggest that PAMAM/Ag grafted onto insoluble MWNTs may be used as effective antimicrobial materials.

Manganese is an essential metal for plant growth. A number of transporters involved in the uptake of manganese from soils, and its translocation to the shoot, have been identified in Arabidopsis and rice. However, the transporter responsible for the radial transport of manganese out of root exodermis and endodermis cells and into the root stele remains unknown. Here, we show that metal tolerance protein 9 (MTP9), a member of the cation diffusion facilitator family, is a critical player in this process in rice (Oryza sativa). We find that MTP9 is mainly expressed in roots, and that the resulting protein is localized to the plasma membrane of exo- and endodermis cells, at the proximal side of these cell layers (opposite the manganese uptake transporter Nramp5, which is found at the distal side). We demonstrate that MTP9 has manganese transport activity by expression in proteoliposomes and yeast, and show that knockout of MTP9 in rice reduces manganese uptake and its translocation to shoots. We conclude that at least in rice MTP9 is required for manganese translocation to the root stele, and thereby manganese uptake.

Viviparous (live-bearing) vertebrates have evolved repeatedly within otherwise oviparous (egg-laying) clades. Over two-thirds of these changes in vertebrate reproductive parity mode happened in squamate reptiles, where the transition has happened between 98 and 129 times. The transition from oviparity to viviparity requires numerous physiological, morphological, and immunological changes to the female reproductive tract, including eggshell reduction, delayed oviposition, placental development for supply of water and nutrition to the embryo by the mother, enhanced gas exchange, and suppression of maternal immune rejection of the embryo. We performed genomic and transcriptomic analyses of a closely related oviparous–viviparous pair of lizards (Phrynocephalus przewalskii and Phrynocephalus vlangalii) to examine these transitions. Expression patterns of maternal oviduct through reproductive development of the egg and embryo differ markedly between the two species. We found changes in expression patterns of appropriate genes that account for each of the major aspects of the oviparity to viviparity transition. In addition, we compared the gene sequences in transcriptomes of four oviparous–viviparous pairs of lizards in different genera (Phrynocephalus, Eremias, Scincella, and Sphenomorphus) to look for possible gene convergence at the sequence level. We discovered low levels of convergence in both amino acid replacement and evolutionary rate shift. This suggests that most of the changes that produce the oviparity–viviparity transition are changes in gene expression, so occasional reversals to oviparity from viviparity may not be as difficult to achieve as has been previously suggested.

Single-walled carbon nanotubes functionalized with generation (n) 0-2 dendritic poly(amidoamine) (denoted as SWNTs-G n -NH 2 , n ) 0, 1, or 2) were used as filler in thermosetting epoxy to prepare anisotropic microscale diameter fibers by reactive spinning. Dendritic poly(amidoamine) (PAMAM) was "grafted from" acid-modified and toluene 2,4-diisocyanate-activated SWNTs by repeating amidation of terminal ester groups via ethylenediamine (EDA) and Michael addition of methyl acrylate (MA) to amino groups. Fourier transform infrared (FTIR) and hydrogen nuclear magnetic resonance ( 1 H NMR) spectroscopy and thermogravimetric analysis (TGA) confirmed the successful grafting and generation buildup. Optical and scanning electron microscope (SEM) observations revealed that PAMAMfunctionalized SWNTs dispersed in epoxy much more uniformly than pristine nanotubes. The dispersibility improved with increasing generation number. Microsized fibers made of epoxy reinforced with aligned SWNTs-G 2 -NH 2 by reactive spinning show high tensile strength and Young's modulus per unit weight fraction (dσ/dW NT and dE/dW NT ). The respective measures are 7022 MPa and 118.0 GPa, which is a high reinforcement efficacy in comparison to other fillers. The nanotube alignment and grafting of dendritic PAMAM play a crucial role in the enhancement of the tensile strength of these reinforced composite fibers.

1, 2-Distearoyl-sn-glycero-3-phosphoethanolamine-Poly(ethylene glycol) (DSPE- PEG) is a widely used phospholipids-polymer conjugate in drug delivery applications. It is a biocompatible, biodegradable and amphiphilic material which can also be functionalized with various biomolecules for specific functions. With the emerging interest in use of nanocarriers for therapeutic drug delivery and imaging DSPE-PEG has become a very useful material for the formulation of these nanocarriers for achieving prolonged blood circulation time, improved stability and enhanced encapsulation efficiency. This review will focus on the relationships between the structure of DSPEPEG and its noticeable effects on these nanocarriers' properties, and the recent progress on the development of DSPE-PEG and its derivatives in delivery systems.

To improve the interlaminar shear strength (ILSS) of carbon fiber reinforced epoxy composite, networks of multiwalled carbon nanotubes (MWNTs) were grown on micron-sized carbon fibers and single-walled carbon nanotubes (SWNTs) were dispersed into the epoxy matrix so that these two types of carbon nanotubes entangle at the carbon fiber (CF)/epoxy matrix interface. The MWNTs on the CF fiber (CF-MWNTs) were grown by chemical vapor deposition (CVD), while the single-walled carbon nanotubes (SWNTs) were finely dispersed in the epoxy matrix precursor with the aid of a dispersing agent polyimide-graft-bisphenol A diglyceryl acrylate (PI-BDA) copolymer. Using vacuum assisted resin transfer molding, the SWNT-laden epoxy matrix precursor was forced into intimate contact with the "hairy" surface of the CF-MWNT fiber. The tube density and the average tube length of the MWNT layer on CF was controlled by the CVD growth time. The ILSS of the CF-MWNT/epoxy resin composite was examined using the short beam shear test. With addition of MWNTs onto the CF surface as well as SWNTs into the epoxy matrix, the ILSS of CF/epoxy resin composite was 47.59 ± 2.26 MPa, which represented a ∼103% increase compared with the composite made with pristine CF and pristine epoxy matrix (without any SWNT filler). FESEM established that the enhanced composite did not fail at the CF/epoxy matrix interface.