Effect of gamma irradiation on X‐ray absorption and photoelectron spectroscopy of Nd‐doped phosphate glass

X‐ray absorption near‐edge structure (XANES) and X‐ray photoelectron spectroscopy (XPS) of Nd‐doped phosphate glasses have been studied before and after gamma irradiation. The intensity and the location of the white line peak of the L₃‐edge XANES of Nd are found to be dependent on the ratio O/Nd in the glass matrix. Gamma irradiation changes the elemental concentration of atoms in the glass matrix, which affects the peak intensity of the white line due to changes in the covalence of the chemical bonds with Nd atoms in the glass (structural changes). Sharpening of the Nd 3d_5/2 peak profile in XPS spectra indicates a deficiency of oxygen in the glasses after gamma irradiation, which is supported by energy‐dispersive X‐ray spectroscopy measurements. The ratio of non‐bridging oxygen to total oxygen in the glass after gamma radiation has been found to be correlated to the concentration of defects in the glass samples, which are responsible for its radiation resistance as well as for its coloration.     

Graphene-based electrochemical supercapacitors

Graphenes prepared by three different methods have been investigated as electrode materials in electrochemical supercapacitors. The samples prepared by exfoliation of graphitic oxide and by the transformation of nanodiamond exhibit high specific capacitance in aq. H₂SO₄, the value reaching up to 117 F/g. By using an ionic liquid, the operating voltage has been extended to 3·5 V (instead of 1 V in the case of aq. H₂SO₄), the specific capacitance and energy density being 75 F/g and 31·9 Wh kg⁻¹ respectively. This value of the energy density is one of the highest values reported to date. The performance characteristics of the graphenes which are directly related to the quality, in terms of the number of layers and the surface area, are superior to that of single-walled and multi-walled carbon nanotubes.     

EPR and susceptibility studies on (ZnS)1-x(MnTe)x powders

(ZnS)1-x(MnTe)x luminescent powder samples with x=0.02, 0.05, 0.10, 0.15, 0.20 and 0.25 were prepared by solid-state reaction method. EPR spectra were recorded at room temperature (300K) in the frequency range 8.8-9.6GHz for samples of all compositions. The line width (DeltaH) and the number of spins increased with MnTe concentration. Room temperature dc magnetic susceptibility measurements were carried out using vibrating sample magnetometer. Susceptibility of the samples increased with MnTe content.     

Green's function of the Brinkman equation in a 2D anisotropic case

The purpose of this paper is to obtain the Green's functionof the Brinkman equation in a 2D case of hydrodynamic anisotropywith respect to the permeability. The anisotropic nature ofthe permeability is assumed to be not space or time dependent.We use the method of Fourier transform which reduces the computationof the Green's function to the computation of the fundamentalsolution of a fourth-order partial differential equation. Thisresearch work has several applications in engineering and medicineto the motion of bodies in anisotropic porous media.     

Ru(x)Pt(y)Sn(z) cluster-derived nanoparticle catalysts: spectroscopic investigation into the nature of active multinuclear single sites

Cluster-derived Ru(x)Pt(y)Sn(z) nanoparticles are active catalysts in the hydrogenation of nitrobenzene. The nature of the active sites has been elucidated by FTIR spectroscopy using CO and NO as probe molecules. A new metal carbonyl cluster precursor, Pt(2)Ru(2)(SnBu(t)(3))(2)(CO)(9)(μ-H)(2), has been synthesized to obtain a Ru(2)Pt(2)Sn(2)/SiO(2) catalyst, that displayed remarkably high levels of conversion and selectivities compared to other bi-and monometallic analogues. Spectroscopic comparisons with Ru(5)PtSn/SiO(2) indicate that both the nature and the stoichiometry of the metals play a key role in modulating the catalytic activities and selectivities. A multinuclear single-site containing Pt centers, which facilitate the hydrogen activation, coupled with a highly reactive Ru site, possibly involved in the nitrobenzene activation, can be hypothesized. The oxophilicity of tin helps with the anchoring of the nanoparticles, aids the dispersion of the other metals, and can play an important role in influencing the selectivity to aniline.     

Antifouling and antipredatory activity of natural products of the seaweeds Dictyota dichotoma and Chaetomorpha linoides

The seaweeds Dictyota dichotoma and Chaetomorpha linoides from the southeast coast of India were screened for anti-microfouling activity against biofilm bacteria, anti-macrofouling activity against brown mussels and feeding deterrence activity against the sea angel Monodactylus kottelati. The surface associated epiphytic bacteria were also isolated from seaweeds and screened for activity against biofilm bacteria. The acetone extracts showed a wide spectrum activity against biofilm bacteria and the algal metabolite was surface concentrated and non-polar in nature. The seaweeds also inhibited byssus production and attachment in brown mussels, and deterred feeding in the sea angel. The lower epiphytic bacterial number on the seaweed's surface compared to the surrounding seawater medium indicated selective inhibition or surface mediation. The epiphytic bacteria, which showed activity against biofilm bacteria, might also possibly play a role in seaweed defence strategies. The 50% deterrence of feeding activity at lower concentrations was not proportionate to the 100% inhibition concentration, which could be attributed to the adaptability of the fishes, an indication that the active substances are inhibitory in nature. This was further substantiated with the 100% recovery of mussels in a toxicity assay and the lower EC(50) values than LC(50) values in the mussel bioassay. The study indicates that the metabolites of both seaweeds have ecological significance and could possibly play a multifunctional role.     

Capture of sunflower seedlings lipase using polyclonal antibodies

True lipolytic activity is observed in different subcellular fractions of germinating sunflower seedlings (Helianthus annuus L.) in delipidated oleosomes and microsomes. Triacylglycerol lipase (EC. 3.1.1.3) catalyses the first catabolic step of lipolysis. To our knowledge, this plant lipase has not yet been identified. Our aim was to develop a method to collect the lipase for further studies. An immunological method was used to capture sunflower seedling lipase from oleosomes and microsomes. This method uses an immunoaffinity column prepared with polyclonal antibodies (anti-P-61) directed against oleosomal activity. Our results verify that we have successfully adapted a purification procedure of plant lipase using anti-P-61. Since the eluted lipolytic activity is distributed among diverse proteic peaks, we changed the elution procedure: the introduction of CHAPS, a zwitterionic detergent, allowed us to recover all the lipolytic activity in a single proteic peak. This may help us to characterise the studied lipase.     

Unique emission from norbornene derived terpyridine--a selective chemodosimeter for G-type nerve agent surrogates

A new chemodosimeter for a G-type agent that exploits norbornene derived terpyridine (NDT)-lanthanide unique emission is reported. The unusual emission between terpyridine and norbornene motifs of NDT is attributed to the significant difference in the position of the HOMO and LUMO wave functions that prevents the non-radiative relaxation pathway. An interesting magenta emission from NDT along with Eu(III) is utilized as a new fluorometric chemodosimeter that selectively detects (by changing the observed magenta emission to blue) G-type agent surrogates. A detection limit of 40 ppb is obtained and the selectivity for reactive surrogates over a variety of other close chemical analogs is demonstrated.     

A HYSCORE investigation of bimetallic titanium-vanadium microporous catalysts: elucidating the nature of the active sites

Vanadium and titanium bimetallic AlPO-5 molecular sieves have been synthesized and characterized by means of Electron Spin Echo detected EPR and Hyperfine Sublevel Correlation (HYSCORE) spectroscopy. Direct evidence for framework substitution of redox-active Ti ions and VO(2+) units at Al sites is provided through the detection of large (31)P hyperfine couplings.     

Repeated dose 28-days oral toxicity study of Carica papaya L. leaf extract in Sprague Dawley rats

Carica papaya L. leaves have been used in ethnomedicine for the treatment of fevers and cancers. Despite its benefits, very few studies on their potential toxicity have been described. The aim of the present study was to characterize the chemical composition of the leaf extract from 'Sekaki' C. papaya cultivar by UPLC-TripleTOF-ESI-MS and to investigate the sub-acute oral toxicity in Sprague Dawley rats at doses of 0.01, 0.14 and 2 g/kg by examining the general behavior, clinical signs, hematological parameters, serum biochemistry and histopathology changes. A total of twelve compounds consisting of one piperidine alkaloid, two organic acids, six malic acid derivatives, and four flavonol glycosides were characterized or tentatively identified in the C. papaya leaf extract. In the sub-acute study, the C. papaya extract did not cause mortality nor were treatment-related changes in body weight, food intake, water level, and hematological parameters observed between treatment and control groups. Some biochemical parameters such as the total protein, HDL-cholesterol, AST, ALT and ALP were elevated in a non-dose dependent manner. Histopathological examination of all organs including liver did not reveal morphological alteration. Other parameters showed non-significant differences between treatment and control groups. The present results suggest that C. papaya leaf extract at a dose up to fourteen times the levels employed in practical use in traditional medicine in Malaysia could be considered safe as a medicinal agent.