Structural studies and T c dependence in La2−x Dy x Ca y Ba2Cu4+y O z type mixed oxide superconductors

A new series of mixed oxide superconductors with the stoichiometric composition La_2−x Dy _x Ca _y Ba₂Cu_4+y O _z (x=0.0 − 0.5, y=2x) has been studied for structural and superconductiong properties. Our earlier studies on La_2−x (Y/Er) _x Ca _y Ba₂Cu_4+y O _z series, show a strong dependence of T _c on hole concentration (p _sh). In the present work, the results of the analysis of the neutron diffraction measurements at room temprerature on x=0.3 and 0.5 samples are reported. It is interesting to know that Ca substitutes for both La and Ba site with concomitant displacement of La onto Ba site. Superconductivity studies show that maximum T _c is obtained for x=0.5, y=1.0 sample (T _c ∼ 75 K), for La_1.5Dy_0.5Ca₁Ba₂Cu₅O _z (La-2125).     

Structural characteristics of different types of nanoparticles synthesised in mesomorphic metal alkanoates

The class of thermotropic ionic liquid crystals (LCs) of the metal alkanoates possesses a number of unique properties, such as intrinsic ionic conductivity, high dissolving ability and ability to form time-stable mesomorphic glasses. These ionic LCs can be used as nanoreactors for the synthesis and stabilisation of different types of nanoparticles (NPs). Thus, some semiconductors, metals and core/shell NPs were chemically synthesised in the thermotropic ionic liquid crystalline phase (smectic A) of the cadmium octanoate (CdC₈) and of the cobalt octanoate (CoC₈). By applying the scanning electron microscopy, the cadmium and cobalt octanoate composites containing CdS, Au, Ag and core/shell Au/CdS NPs have been studied. NPs’ sizes and dispersion distribution of the NPs’ size in the nanocomposites have been obtained.     

Vasopressin-dependent flank marking in golden hamsters is suppressed by drugs used in the treatment of obsessive-compulsive disorder

Background  

Alterations in arginine vasopressin regulation and secretion have been proposed as one possible biochemical abnormality in patients with obsessive-compulsive disorder. In golden hamsters, arginine vasopressin microinjections into the anterior hypothalamus trigger robust grooming and flank marking, a stereotyped scent marking behaviors. The intensity and repetition of the behaviors induced by arginine vasopressin is somewhat reminiscent of Obsessive Compulsive Disorder in humans. The present experiments were carried out to test whether pharmacological agents used to alleviate obsessive compulsive disorder could inhibit arginine vasopressin-induced flank marking and grooming.     

The dynamics of partial oxidation of ethane over platinum

Catalysts are increasingly finding application in fuel reformation leading to more reactive blends, micro-combustors and nano-catalysts aimed at improving application performance. In the current work, the interactions of surface and gas phase reactions in C₂H₆/O₂/N₂ mixtures over a supported platinum catalyst are reported. Experiments were combined with computations featuring comprehensive detailed chemistry for both phases in order to explore the dynamics of the conversion processes using high superficial gas velocities, extended Al₂O₃ foam monoliths up to 60 mm in length and with variable Pt loading of 1% and 3% by weight. The residence time was varied between 1 and 3 ms at different oxygen to carbon weight (0.5 < O/C < 0.8) ratios and a constant molar hydrogen to oxygen (H₂/O₂ = 2) ratio. The applied gas phase chemistry features a detailed C₁–C₂ mechanism including low-temperature chemistry. The heterogeneous chemistry is analysed using two independently developed detailed heterogeneous reaction mechanisms [1] and [2]. The study confirms that the heterogeneous chemistry is essential in providing reaction stability and initially contributes to the formation of C₂H₄. It is also shown that increased residence times can result in a consistent heterogeneous consumption of ethylene principally leading to methane, carbon monoxide and carbon deposition. The surface chemistry is analysed in detail and it is shown that residence times can be used to mitigate C₂H₄ loss with the need to balance the stability of the process.