Designing different nanomagnets via delocalization of cobalt magnetic moment inside narrow single walled carbon nanotubes

Density functional theory calculations were employed to study the effects of chirality and diameter of single walled carbon nanotubes (SWCNTs) on electronic, structural and magnetic properties of cobalt-doped (9,0), (5,5) and (5,0) nanotube systems. The (9,0) and (5,5) SWCNTs have similar diameters but different chiralities, whereas the (5,0) tube has a very small diameter. The Co-SWCNT systems are considered with four different possible arrangements, three of which are stable and only substitution of the Co with one of the carbon atoms on the surface of the SWCNTs is an exemption. Although the quasi-metallic band gap of the (9,0) SWCNT is eliminated by the cobalt doping process, metallic features of the (5,5) and (5,0) nanotubes remain unchanged. On the other hand, delocalization of the cobalt’s magnetization and inducement of a noticeable magnetization to the tubes provide a vast area of possible total magnetizations for the Co-SWCNT systems. The results are applicable to spintronics and useful for designing other nanomagnetic systems.     

A renormalized perturbation theory for problems with non-trivial boundary conditions or backgrounds in two space–time dimensions

We discuss the effects of non-trivial boundary conditions or backgrounds, including non-perturbative ones, on the renormalization program for systems in two dimensions. We present an alternative renormalization procedure in which these non-perturbative conditions can be taken into account in a self-contained and, we believe, self-consistent manner. These conditions have profound effects on the properties of the system, in particular all of its n-point functions. To be concrete, we investigate these effects in the λ φ ⁴ model in two dimensions and show that the mass counterterms turn out to be proportional to the Green’s functions which have a non-trivial position dependence in these cases. We then compute the difference between the mass counterterms in the presence and absence of these conditions. We find that in the case of non-trivial boundary conditions this difference is minimum between the boundaries and infinite on them. The minimum approaches zero when the boundaries go to infinity. In the case of non-trivial backgrounds, we consider the kink background and show that the difference is again small and localized around the kink.     

Determination of Biogenic Amines in Cheese Using Simultaneous Derivatization and Microextraction Method Followed by Gas Chromatography–Mass Spectrometry

Microwave-assisted extraction and dispersive liquid–liquid microextraction followed by gas chromatography–mass spectrometry as a sensitive and efficient method was applied to extract and determine four biogenic amines (BAs) in Iranian Lighvan cheese samples. Carrez solutions were used for the sedimentation of proteins. Effective factors on the performance of microextraction were studied and optimized. The proposed method showed good linear ranges from 5 to 500 ng mL^?1, with the coefficients of determination higher than 0.9929. Average recoveries were between 97 and 103%. Limits of detection for all analyzed BAs ranged from 5.9 to 14.0 ng g^?1, and limits of quantitation ranged between 19.7 and 46.2 ng g^?1. Compared with previous methods, the proposed method is simple, fast, accurate, and precise and gives low detection limits for investigating trace amounts of BAs in Iranian Lighvan cheese samples. The levels of four BAs were determined in five Lighvan cheese samples. Cadaverine was found as prevailing amine in the cheese samples. Putrescine, tyramine, and histamine were present at the second, third, and fourth highest levels, respectively.     

Tributylammonium Halochromates/silica Gel:Simple Reagents for Oxidative Coupling of Thiols to Symmetrical Disulfides

New orange solid tributylammonium halochromates, (C₄H₉)₃N⁺CrO₃X^?, TBAXC (X=F, Cl) are easily synthesized by the reaction of tributylammonium fluoride and chloride with CrO₃ in a 1:1 molar ratio in the presence of HF and HCl. Tributylammonium halochromates(VI) are versatile reagent for the effective and selective oxidation of organic substrates. Silica gel supported TBAFC and TBACC are versatile reagents for the effective and selective oxidation of organic substrates, in particular, thiols, under mild conditions. Considerable improvements are observed in the presence of the absorbent, making the work‐up much more convenient.     

TiO2 as a Reusable Catalyst for the One‐Pot Synthesis of 3,4‐Dihydropyrimidin‐2(1H)‐ones under Solvent‐Free Conditions

An efficient solvent‐free method for the synthesis of various 3,4‐dihydropyrimidin‐2(1H)‐ones using TiO₂ as a recyclable heterogeneous catalyst is described. Compared to known methods, satisfactory results are obtained with excellent yields, short reaction times, and simplicity in the experimental procedure.     

Benign synthesis of carboxamide ligands,H2Me2bqb and H2Me2bpb. Preparation,characterization and electrochemistry of Ni(II) complexes: The crystal structure of [Ni(Me2bqb)]

A novel and highly efficient approach for the synthesis of H₂Me₂bqb and H₂Me₂bpb using ionic liquid as an environmentally benign reaction medium has been developed, eliminating the need for the pyridine as a toxic solvent. The Ni(II) complex of the dianionic ligand Me₂bqb²⁻, [Me₂bqb²⁻ = 1,2-bis(quinoline-2-carboxamide)-4,5-dimethyl-benzene dianion], has been synthesized and characterized by elemental analyses and spectroscopic methods, and the crystal and molecular structure of [Ni(Me₂bqb)] (1), has been determined by X-ray crystallography. The complex exhibits distorted square-planar NiN₄ coordination geometry with two short and two long Ni–N bonds (Ni–N ∼1.85 and ∼1.96 Å, respectively). The electrochemical behavior of [Ni(Me₂bqb)] (1), has been studied by cyclic voltammetry and compared with the analogous complex, [Ni(Me₂bpb)] (2).     

Metallation of tetradentate N<Subscript>2</Subscript>O<Subscript>2</Subscript> Schiff base with Mn(II), Co(II), Cu(II) and Zn(II): synthesis,characterization and formation constants measurement

Four Schiff base ligands, salabza-H₂ = N,N′-bis(salicylidene)-2-aminobenzylamine, were synthesized by condensation of one mole of 2-aminobenzylamine and two moles of salicylaldehyde and/or two moles of substituted salicylaldehyde (5-OMe, 5-Br, 5-NO₂). All the four Schiff bases and their Mn(II), Co(II), Cu(II) and Zn(II) complexes are characterized by UV-Vis, FT-IR, ¹H NMR spectroscopy, mass spectrometry and elemental analysis. The formation constants and the Gibbs free energies were measured spectrophotometrically for 1:1 complexes in methanol in constant ionic strength (I = 0.1 mol dm⁻³ NaClO₄) and at 25°C. The data refinement was carried out with the SQUAD program. The trend of formation constants of H₂L¹ with M(II) follows the order: Mn(II) (3.97) < Zn(II) (4.30) < Co(II) (4.89) < Cu(II) (5.73)     

Vibration analysis of nanorings using nonlocal continuum mechanics and shear deformable ring theory

In this article, we use shear deformable ring theory (SDRT) for the analysis of free in-plane vibration of nanorings based on nonlocal elasticity theory. The equations of motion of the nanoring are derived for the aforementioned problem by considering the small scale effect. Analytical solutions for the natural frequencies of the nanorings are presented. It is shown that the nonlocal effects play an important role in the vibration of nanorings and cannot be neglected. The effects of the small scale on the natural frequencies considering various parameters such as the radius of the nanoring, the thickness of the nanoring and mode numbers are investigated.