Atomistic simulations to study crack tip behaviour in single crystal of bcc niobium and hcp zirconium

In this article, molecular dynamics based simulations were carried out to study the fracture toughness of single crystals of niobium (Nb) and zirconium (Zr). Separate set of simulations were performed with different orientations of crack plane in Nb and Zr. In each case, efforts were made to align the crack front with principal planes of corresponding crystal structure, that was bcc for Nb and hcp for Zr. Deformation in single crystal of Nb and Zr was governed either by twinning or emergence of dislocations from the crack tip and surfaces. The deformation mechanism in single crystal of Nb and Zr also helps in governing the overall toughness of the material, while deforming via twinning leads to higher change in the crack length, whereas dislocations emerging from the crack tip blunts the opening and improves the toughness.     

1‐[2‐(4‐Nitro­phenoxy)­acetyl]­pyrroli­din‐2‐one: an antiamnesic agent

The title compound, C₁₂H₁₂N₂O₅, is a potential antiamnesic agent. The pyrrolidinone ring has an envelope conformation, and the central moiety is almost coplanar with the planes of the phenyl and pyrrolidinone rings. In the crystal structure, weak intermolecular C—H...O interactions link the mol­ecules into a complex network that can be described by (X) rings (X = 16, 20 and 26) and a C(12) chain.     

DNP by thermal mixing under optimized conditions yields >60,000-fold enhancement of 89Y NMR signal

Hyperpolarized (89)Y complexes are attractive NMR spectroscopy and MR imaging probes due to the exceptionally long spin-lattice relaxation time (T(1) ≈ 10 min) of the (89)Y nucleus. However, in vivo imaging of (89)Y has not yet been realized because of the low NMR signal enhancement levels previously achieved for this ultra low-γ(n) nucleus. Here, we report liquid-state (89)Y NMR signal enhancements over 60,000 times the thermal signal at 298 K in a 9.4 T magnet, achieved after the dynamic nuclear polarization (DNP) of Y(III) complex of 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA) samples at 3.35 T and 1.4 K. The (89)Y DNP was shown to proceed by thermal mixing and the liquid state (89)Y NMR signal enhancement was maximized by (i) establishing the optimal microwave irradiation frequency, (ii) optimizing the glassing matrix, (iii) choosing a radical with negligible inhomogeneous line broadening contribution to the ESR linewidth, and (iv) addition of an electron T(1e) relaxation agent. The highest enhancements were achieved using a trityl OX063 radical combined with a gadolinium relaxation agent in water-glycerol matrix. Co-polarization of (89)YDOTA and sodium [1-(13)C]pyruvate showed that both (89)Y and (13)C nuclear species acquired the same spin temperature, consistent with thermal mixing theory of DNP. This methodology may be applicable for the optimization of DNP of other low-γ(n) nuclei.     

Quantitative investigation, stability and in vitro release studies of anti-TB drugs in Triton niosomes

The highly stable innocuous niosomes composed of four components (Triton X 100, polyethylene glycol 2000, water, Span 80) have been prepared successfully and characterized using particle size analyzer, transmission and scanning electron microscopy. The mean size has been found to be in the range 200-300 nm. The optimization of niosomes has been carried out using fluorescence spectroscopy. An attempt has been made to incorporate anti-tuberculosis drugs (ATD's) in the prepared niosomes. The stability and encapsulation efficiency of these drugs in the niosome have also been assessed and high encapsulation efficiency is observed. Such high encapsulation efficiency will serve as an advantage to solve the problem of multi-drug resistance in case of tuberculosis. Release studies and kinetics have been carried out to investigate the release behavior of drugs from the prepared niosomes. Fickian or diffusional release has been observed for rifampicin and isoniazid and a non-Fickian release mechanism for pyrazinamide. Fluorescence probe quenching technique has been used to determine the location and distribution coefficient of the ATD's in niosome/water system.     

Solvothermally synthesized europium-doped CdS nanorods: applications as phosphors

To exploit the photoluminescent behavior of CdS at nanoscale with different doping concentration of europium—a rare earth element, we report the synthesis of Eu-doped CdS nanorods by using low temperature solvothermal process by using ethylenediamine. The outcomes can have future applications as phosphors, photovoltaic cells, lasers, light emitting diodes, bio-imaging, and sensors. The doping was confirmed by electron dispersive spectroscopy supported by X-ray diffraction. From scanning electron microscopy and transmission electron microscopy analysis it was observed that the average diameter of the Cd_1−x Eu _x S nanorods is about 10–12 nm having lengths in the range of 50–100 nm. UV–Visible spectroscopy study was carried out to determine the band gap of the nanorods and the absorbance peaks showed blue shift with respect to the bulk CdS. The blue shift was also observed as the doping concentration of Eu increases. From photoluminescence (PL) studies at λ_ex = 450 nm, peaks at 528 and 540 nm were observed due to CdS, peak at 570 nm is due to defects related transitions, while the peak at 613 nm is due to Eu. As the doping concentration of Eu is increased the intensity of the luminescent peak at 613 nm is increased. Thermogravimetric analysis showed the nanorods are thermally stable up to 300 °C. The traces of impurities adsorbed on the nanorods were confirmed by Fourier transform infrared spectroscopy.     

On the role of liquid phase stability and GFA parameters

Role of liquid phase stability on the glass forming ability (GFA) has been reviewed and the alloy systems have been analyzed by introducing a contribution factor (w_g) to the characteristic temperature T_g, in the γ parameter. The kinetics of glass formation for various alloy systems has been found to vary with liquid phase stability in metastable state. The GFA of a fragile liquid is found to be more responsive to the contribution of metastable stability compared to strong liquid.     

Synthesis,spectral analysis and in vitro cytotoxicity of diorganotin (IV) complexes derived from indole-3-butyric hydrazide

A series ( 1–20 ) of diorganotin (IV) complexes with general formula R₂SnL were formed by the reaction of R₂SnCl₂ (where R = Me, Et, Bu and Ph) with Schiff base ligands ( H ₂ L ^1–4 ) derived from the reaction of indole-3-butyric hydrazide with the salicylaldehyde and its derivatives. The structure elucidation of compounds were done by using UV–Vis, FT-IR, NMR (¹H, ¹³C, ¹¹⁹Sn), Mass spectrometry and thermal gravimetric analysis. Spectroscopic evidences suggested tridentate nature (ONO) of Schiff base ligands and coordinated to the dialkyl/diaryltin (IV) moieties through nitrogen and oxygen donor sites giving pentacoordinated geometry to complexes. The compounds were tested for the antimicrobial activity against bacterial and fungal strains which showed promising biological activity with compound 20 (Ph₂SnL⁴) as most active against microbes. The in silico study of the compounds was carried and observed that the compounds are used as orally active drugs and promote the formation of different hydrazide based drugs. The synthesized compounds were tested against human carcinoma cell lines namely A549, MCF7 and one normal cell line IMR 90 using MTT assay. The diethyl and dibutyltin complexes of Schiff bases displayed good cytotoxic activities. Compound 3 (H₂L³) and 10 (Et₂SnL²) were most potent against cancer cell lines with lowest IC₅₀ values and 7–8 times less toxic against the normal cell line.     

Risk assessment from gamma dose rate in Balod District of Chhattisgarh,India

Journal of Radioanalytical and Nuclear Chemistry - People are generally exposed to the natural radiation that presents inside and outside the houses. This investigation has been carried out gamma...