New features in the anti‐Stokes and Stokes Raman spectra of single‐walled carbon nanotubes that are highly separated into their semiconducting and metallic nanotube components

Surface‐enhanced Raman scattering studies were performed using nonresonant (514.5 nm) and resonant (676.4 nm) optical excitations on single‐walled carbon nanotubes thoroughly separated into semiconducting (pure 99%) and metallic (pure 98%) components. Regardless of the support (Au or Ag), the metallic nanotubes do not present an anomalous anti‐Stokes Raman emission. Regardless of whether an on‐resonant or off‐resonant optical excitation is used, only the semiconducting nanotubes produce an abnormal anti‐Stokes Raman emission that grows when increasing the excitation light intensity or temperature. The Raman studies under light polarized relative to the main nanotube axis demonstrate that only semiconducting nanotubes are sensitive toward changes in the polarization of the excitation light. Copyright © 2014 John Wiley & Sons, Ltd.     

A representation-theoretical proof of Bransonʼs classification of elliptic generalized gradients

The purpose of this paper is to present a new proof of Branson?s classification (Branson, 1997 [3]), of minimal elliptic sums of generalized gradients. The advantage of this proof is that it is local, being mainly based on representation theory and on the relationship between ellipticity and refined Kato inequalities. This approach is promising for the classification of elliptic generalized gradients of G-structures, for other subgroups G of the special orthogonal group.     

Thermal behaviour of new Cu(II) complexes with Schiff bases functionalised with 1,3,5-triazine moieties as potential antibacterial agents

New complexes of type [Cu(L¹)₂(OH₂)]·4H₂O (1), [Cu(L²)(OH₂)]·0.5H₂O (2) and [Cu₃(L³)₂(OH₂)₃]·0.5H₂O (3) were synthesized by [1 + 1], [1 + 2] and [1 + 3], respectively, template condensation of 2,4,6-triamino-1,3,5-triazine and salicylic aldehyde in the presence of copper(II). The features of complexes have been established from microanalytical, IR and UV–Vis data. The thermal analyses have evidenced the thermal intervals of stability and also the accompanying thermodynamic effects. Processes as water elimination and oxidative degradation of the organic ligands were observed. After water elimination, complexes revealed a similar thermal behaviour. The final product of decomposition was copper(II) oxide as powder X-ray diffraction indicated.     

Screening of a minimal enriched P450 BM3 mutant library for hydroxylation of cyclic and acyclic alkanes

A minimal enriched P450 BM3 library was screened for the ability to oxidize inert cyclic and acyclic alkanes. The F87A/A328V mutant was found to effectively hydroxylate cyclooctane, cyclodecane and cyclododecane. F87V/A328F with high activity towards cyclooctane hydroxylated acyclic n-octane to 2-(R)-octanol (46% ee) with high regioselectivity (92%).     

The NLS approximation for two dimensional deep gravity waves Dedicated to Professor Jean-Yves Chemin on the Occasion of His 60th Birthday

This article is concerned with in?nite depth gravity water waves in two space dimensions. We consider this system expressed in position-velocity potential holomorphic coordinates. Our goal is to study this problem with small wave packet data, and to show that this is well approximated by the cubic nonlinear Schr¨odinger equation(NLS) on the natural cubic time scale.     

Structural characteristics of some high density polyethylene/EPDM blends

Blends of ethylene propylene diene terpolymer rubber (EPDM) with high density polyethylene were obtained by melt mixing. Mechanical properties of the composites, tensile strength, hardness, resilience, elongation at break, 100% modulus and tear strength were determined. Differential scanning calorimetry and wide angle x-ray diffraction were employed to study melting behavior and crystalline structure. The surface properties were analyzed using contact angle determinations. Also, compatibilization with PE-g-MA or dynamical vulcanization using phenolic resins was applied to obtain improved mechanical properties. It was found that the crystalline structure of HDPE was not changed during blending. The vulcanized composite presents a lower degree of crystallinity. Elongation at break and hardness were significantly increased for composites containing compatibilizing agent. The morphology of EPDM composites was studied by atomic force microscopy.     

Spectral, magnetic and thermal characterisation of new Co(II), Ni(II) and Cu(II) complexes with Schiff base 5-bromo-N,N′-bis-(salicylidene)-o-tolidine

Starting from 5-bromo-N,N′-bis-(salicylidene)-o-tolidine (H₂L) new complexes with Co(II), Ni(II) and Cu(II) were synthesised and characterised. The features of complexes have been assigned from microanalytical, IR, UV–Vis–NIR and EPR spectra, magnetic data at room temperature as well as thermal analysis. IR data are in accordance with bischelate nature of the deprotonated ligand that coordinates through azomethinic nitrogen and phenolic oxygen. The electronic spectra display the characteristic pattern of tetrahedral stereochemistry for [CoL]·H₂O complex and octahedral one for [NiL(OH₂)₂]·H₂O complex. The electronic spectra correlated with magnetic susceptibility measurements indicate a square-planar surrounding for [ML] (M:Ni, Cu) species, while the EPR spectrum of copper complex sustains the proposed stereochemistry. The thermal analysis evidenced that thermal transformations are complex processes according to TG, DTA and DTG curves including (crystallization or coordination) water elimination, thermolyses and oxidative degradation of Schiff base. All these processes lead to the most stable metallic oxides as final product.     

Thermal study on complexes with Schiff base derived from 1,2,4-triazole as potential antimicrobial agents

In order to develop new metallo-antimicrobials the complexes of type MLCl·nH₂O ((1) M: Co, n = 0; (2) M: Ni, n = 2; (3) M: Cu, n = 2.5; (4) M: Zn, n = 0, HL: Schiff base derived from acetylacetone and 3-amino-4H-1,2,4-triazole) were synthesized by template condensation. The features of complexes have been assigned from microanalytical, IR and UV–Vis-NIR data. The species heating in air evidenced processes as melting, water and hydrochloride endothermic elimination as well as oxidative degradation of the Schiff base. The temperature ranges as well as modification in the electronic spectra of dehydrated intermediates indicate the presence of both coordination and crystallisation water molecules. The final product of decomposition was the most stable metal oxide as powder X-ray diffraction indicated.     

Synthesis, spectral and thermal study on new Fe(III) complexes with N,N-dimethylbiguanide as antibacterial agents

New complexes [FeO(DMBG)]₂ and [Fe(DMBG)₂]Cl·0.5H₂O (HDMBG: N,N-dimethylbiguanide) have been synthesized and characterized by microanalytical, IR and UV–Vis data. Electronic spectra of the complexes are characteristic for a tetrahedral stereochemistry, whilst the modifications in the IR spectra indicate the presence of the DMBG anion as chelate. The thermal decomposition investigated in air by thermal analysis confirmed the proposed formulas for the complexes and provided information concerning the modifications during heating and also the thermodynamic effects accompanying them. The thermal transformations are complex, according to TG and DTG curves including dehydration, hydrochloric acid elimination, oxidative degradation and condensation of –C=N– unit. The final product of decomposition was iron (III) oxide as powder XRD indicates. Complexes were screened for their antimicrobial properties against Gram-positive, Gram-negative bacterial, as well as fungal pathogenic strains. The results indicate that Fe(III) complexes exhibit an improved antibacterial activity against S. aureus and E. coli strains in comparison with free biguanide. The Fe(III) complexes also inhibit the ability of S. aureus, B. subtilis, P. aeruginosa and E. coli strains to colonize the inert substratum, accounting for their possible use as anti-biofilm agents.     

Physico-chemical and thermal characterisation of new Co(II) complexes with pyrazole derivatives

Four new complexes having general formula [CoL₂(acr)₂] (L: 1H-pyrazole (Hpz) (1); 3-methyl-1H-pyrazole (3-Me-Hpz) (2); 4-methyl-1H-pyrazole (4-Me-Hpz) (3); 3,5-dimethyl-1H-pyrazole (Hdmpz) (4); acr: acrylato ion) were synthesised and characterised. The infrared and UV–vis spectral data indicate that these pyrazole derivatives act as unidentate while acrylato ions act as bidentate chelate ligands generating Co(II) complexes with octahedral stereochemistry. TG experiments revealed the nature of complex species as anhydrous and confirmed those compositions. The biological assays revealed a good activity against Bacillus subtilis for all complexes.