Variable-range hopping in Fe70Pt30 catalyzed multi-walled carbon nanotubes film

Using low-pressure chemical vapour deposition (LPCVD), multi-walled carbon nanotubes (MWNTs) are grown on nanocrystalline Fe₇₀Pt₃₀ film. The Fe₇₀Pt₃₀ nanocrystalline film is deposited by vapour condensation technique. The size of the nanoparticles varies from 5–10 nm, as inferred from SEM micrographs of Fe₇₀Pt₃₀ film. SEM and TEM observations of as-grown CNTs film reveal that these are multi-walled and their diameter varies from 30–80 nm and length is of the order of several micrometers respectively. There is a structural change from ordinary geometry of CNTs to bamboo shaped as suggested by TEM image. Raman spectra shows sharp G and D bands with a higher intensity of G band showing the presence of graphitic nature of the nanotubes. An experimental study of the temperature dependence of electrical conductivity of MWNTs film is done over a wide temperature range from (293–4 K). The measured data gives a good fit to variable-range hopping (VRH) and the results are interpreted using Mott's (VRH) model. The conduction mechanism of the MWNTs film shows a crossover from the exp[ -(T_o/T)^1/4] law in the temperature range (293–110 K) to exp[ -(T_m/T)^1/3] in the low temperature range (110–4 K). This behaviour is attributed to temperature-induced transition from three-dimension (3D) to two-dimension (2D) VRH. Various Mott's parameters like characteristic temperature (T_m), density of states at Fermi level N(E_F), localization length (ξ), hopping distance (R), hopping energy (W) have also been calculated using above-mentioned model.     

Hydrogen tunneling steps in cyclooxygenase-2 catalysis

Cyclooxygenases-1 and -2 are tyrosyl radical (Y·)-utilizing hemoproteins responsible for the biosynthesis of lipid-derived autocoids. COX-2, in particular, is a primary mediator of inflammation and believed to be up-regulated in many forms of cancer. Described here are first-of-a-kind studies of COX-2-catalyzed oxidation of the substrate analogue linoleic acid. Very large (≥20) temperature-independent deuterium kinetic isotope effects (KIEs) on the rate constant for enzyme turnover were observed, due to hydrogen atom abstraction from the bisallylic C-H(D) of the fatty acid. The magnitude of the KIE depends on the O(2) concentration, consistent with reversible H/D tunneling mediated by the catalytic Y·. At physiological levels of O(2), retention of the hydrogen initially abstracted by the catalytic tyrosine results in strongly temperature-dependent KIEs on O-H(D) homolysis, also characteristic of nuclear tunneling.     

Small polaron hopping conduction mechanism in Fe doped LaMnO3

The structural and electrical transport properties of LaMn(1-x)Fe(x)O(3) (0.1 ≤ x ≤ 0.6) bulk samples have been investigated. The powder x-ray diffraction patterns at room temperature show that all samples are formed in single phase. The temperature dependent resistivity data have been fitted with the Mott's variable-range hopping (VRH) model for an entire studied range of the temperature (77-300 K) to calculate the hopping distance (R(h)) and the density of states at Fermi level (N(E(F))). It is found that all parameters vary systematically with the increase in Fe concentration. Moreover, the resistivity data were also fitted in the small polaron hopping (SPH) model. The non-adiabatic SPH conduction mechanism is followed by all samples. This type conduction mechanism is far accompanied by subtle electronically induced structural changes involving in Fe-O-Fe and Fe-O-Mn bond angles and bond lengths. Thus we suggest that the transport properties can be explained according to the additional localization of charge carriers induced by Fe doping.     

Synthesis and spectroscopic characterization of coumarin 440 dye doped silica gel rods

We have studied silica gel by sol–gel technique for the preparation of new dye-laser materials. Silica gel rods with dimension 50 × 10 mm² have been prepared successfully without breaking. It shows high transparency and good mechanical strength. Tetraethylorthosilicate (TEOS), formamide in molar ratio (0.25:0.70), 80 ml ethanol, 20 ml dimethylformamide (DMF), 10 ml water, hydrochloric acid as a catalyst (at pH 6), and 0.5 ml silicone defoaming agent/surfactant have been used. The synthesis has been carried out in a beaker and the reaction mixture is caste in to the flat bottom glass tubes at 40 °C after thoroughly mixing of all the ingredients. These complex reactions, that carried out by hydrolysis and condensation in the silica gel formation show less gel time ∼8–10 h at 40 °C. Coumarin. 440 dye was doped during the preparation of all the ingredients solution mixture. It has been observed that that the compatibility of Nile blue dyes with silica-gel promise good homogeneity with transparency.     

Enhanced Electrocatalytic Reduction of Oxadiargyl and Its Determination on 2‐(4‐((4‐Acetylphenyl)diazenyl)phenylamino)‐ethanol Modified Graphene‐Paste Electrode

The electrochemical behavior of oxadiargyl at a graphene‐paste electrode modified with an azo dye, 2‐(4‐((4‐acetylphenyl)diazenyl)phenylamino)ethanol (ADPE), ADPE/MGRPE was investigated. The modified electrode showed high electrocatalytic activity toward oxadiargyl. The apparent electron transfer rate constant (k_s) and charge transfer coefficient (α) between electrode and ADPE were 1.16 s^?1 and 0.41, respectively. The differential pulse voltammetry response of the modified graphene‐paste electrode was linear against the concentration of oxadiargyl in the range from 0.03 to 1.4 mg L^?1. The limit of detection was found to be 1.3 µg L^?1 (S/N=3). The practical analytical utility of this electrode was demonstrated by measurement of oxadiargyl in river water, soil and rice samples.     

Microwave assisted synthesis of 3-benzazepin-2-ones as building blocks for 2,3-disubstituted tetrahydro-3-benzazepines

Microwave assisted condensation of primary amines with keto acids 1a–c provided directly 3,4-disubstituted 1,3-dihydro-3-benzazepin-2-ones 2. Whereas small amine size, such as NH₃ afforded high yields of secondary lactams 2a, 2d, and 2g, primary amines with larger substituents in α-position led to lower yields of 2 or even to regioisomeric indanone derivatives 4. However, subsequent alkylation of 2a, 2d, and 2g with various alkyl halides provided the corresponding N-substituted 3-benzazepin-2-ones 2 in good yields. Hydrogenation of 2 followed by BH₃ reduction led to 3-benzazepines 9. 3-Benzyl-2-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine (9c) reveals high σ₁ affinity and selectivity over σ₂ and NMDA receptors.     

Potential Therapeutic Targets of Resveratrol,a Plant Polyphenol,and Its Role in the Therapy of Various Types of Cancer

Cancer is among the most prominent causes of mortality worldwide. Different cancer therapy modes employed, including chemotherapy and radiotherapy, have been reported to be significant in cancer management, but the side effects associated with these treatment strategies are still a health problem. Therefore, alternative anticancer drugs based on medicinal plants or their active compounds have been generating attention because of their less serious side effects. Medicinal plants are an excellent source of phytochemicals that have been recognized to have health-prompting effects through modulating cell signaling pathways. Resveratrol is a well-known polyphenolic molecule with antioxidant, anti-inflammatory, and health-prompting effects among which its anticancer role has been best defined. Additionally, this polyphenol has confirmed its role in cancer management because it activates tumor suppressor genes, suppresses cell proliferation, induces apoptosis, inhibits angiogenesis, and modulates several other cell signaling molecules. The anticancer potential of resveratrol is recognized in numerous in vivo and in vitro studies. Previous experimental data suggested that resveratrol may be valuable in cancer management or improve the efficacy of drugs when given with anticancer drugs. This review emphasizes the potential role of resveratrol as an anticancer drug by modulating numerous cells signaling pathways in different types of cancer.