Facile synthesis of mesoporous N doped zirconium titanium mixed oxide nanomaterial with enhanced photocatalytic activity under visible light

The present paper deals with a hydrazine mediated synthesis of high surface area and thermally stable N-doped zirconium titanium mixed oxide with enhanced photocatalytic activity towards reduction of selenium (VI) to metallic Se0 under visible light. Materials were synthesized at pH ¼ 2 by varying the hydrazine concentration and characterized by XRD, TEM, BET method, XPS, Raman spectroscopy and UV-vis solid state spectra. Presence of low amount of zirconium oxide (10 wt%) helps in phase stabilization and maintains the porous structure even at higher calcinations temperature in comparison to that of pure titania. XPS spectrum justifies the presence of nitrogen and Ti3+ in the material due to the decomposition reaction of hydrazine. Hydrazine controls the nitrogen content, surface area and the formation of oxygen vacancy in the material. Investigation of metal oxide to hydrazine ratio on the overall surface properties and photocatalytic activity indicates that the 1 : 6 ratio is the optimum composition for the best result. Surface area and pore volume increases to 298 m2/g and 0.323 cm3/g. The obtained material (TiZr-6N-400) is found to reduce selenium (VI) to selenium (0) under visible light within only 45 min of reaction. Increased photocatalytic activity under visible light is mostly due to the synergistic effect of substantial nitrogen doping, high surface area and presence of oxygen vacancy

Effect of Indole 3-butyric acid (IBA), rooting media and their interaction on different rooting and growth characteristic of air-layers in guava (Psidium guajava L. cv. L-49)

The present investigation was undertaken to study the effect of different concentrations of Indole 3-butyric acid (0, 2000, 4000, 8000 and 10000 ppm), different types of rooting media (i.e. sphagnum moss, coco peat, vermicompost, sphagnum moss + coco peat and sphagnum moss + coco peat + vermicompost) and the interaction of these in different combinations on rooting and growth characteristic of guava, cv. L-49. The results revealed that the exogenous application of Indole 3-butyric acid (IBA) 8000 ppm with media combination of sphagnum moss + coco peat + vermicompost (I3M5) significantly increased the root characters i.e. success percent of air-layers (83.3 %), callus formation (23.7), number of primary roots (24.21) and secondary roots (32.57); and growth characters i.e. number of leaves (48.17), branches (7.92) and sprouts (8.48) and survival percentages (83.18) over the other treatments and control. Among the rooting media, the combination of sphagnum moss + coco peat + vermicompost (M5) produced the highest rooting percentage (71.27), root characters and growth characters during months of July and August

ATLASGAL-selected massive clumps in the inner Galaxy: VIII. Chemistry of photodissociation regions

Aims. We study ten molecular transitions obtained from an unbiased 3 mm molecular line survey using the IRAM 30 m telescope toward 409 compact dust clumps identified by the APEX Telescope Large Area Survey of the Galaxy (ATLASGAL) to understand photodissociation regions (PDRs) associated with the clumps. The main goal of this study is to investigate whether the abundances of the selected molecules show any variations resulting from the PDR chemistry in different clump environments. Methods. We selected HCO, HOC$^+$, C$_2$H, c-C$_3$H$_2$, CN, H$^{13}$CN, HC$^{15}$N, and HN$^{13}$C as PDR tracers, and H$^{13}$CO$^+$ and C$^{18}$O as dense gas tracers. By using estimated optical depths of C$_2$H and H$^{13}$CN and assuming optically thin emission for other molecular transitions, we derived column densities of those molecules and their abundances. To assess the influence of the presence and strength of ultraviolet radiation, we compare abundances of three groups of the clumps: Hii regions, infrared bright non-Hii regions, and infrared dark non-Hii regions. Results. We detected C$^{18}$O, H$^{13}$CO$^+$, C$_2$H, c-C$_3$H$_2$, CN and HN$^{13}$C toward most of the observed dust clumps (detection rate > 94%), and H$^{13}$CN is also detected with a detection rate of 75%. On the other hand, HCO and HC$^{15}$N show detection rates of 32% and 39%, respectively, toward the clumps, which are mostly associated with Hii region sources: detection rates of HCO and HC$^{15}$N toward the Hii regions are 66% and 79%. We find that the abundances of HCO, CN, C$_2$H, and c-C$_3$H$_2$ decrease as the H$_2$ column density increase, indicating high visual extinction, while those of high density tracers (i.e., H$^{13}$CO$^+$ and HC$^{15}$N) are constant. In addition, N(HCO)/N(H$^{13}$CO$^+$) ratios significantly decrease as H$_2$ column density increase, and in particular, 82 clumps have X(HCO) $\gtrapprox$ 10$^{−10}$ and N(HCO)/N(H$^{13}$CO$^+$+) $\gtrapprox$ 1, which are the indication of far-ultraviolet (FUV) chemistry. This suggests the observed HCO abundances are likely associated with FUV radiation illuminating the PDRs. We also find that high N(c-C$_3$H$_2$)/N(C$_2$H) ratios found for Hii regions having high HCO abundances ($\gtrapprox$ 10$^{−10}$) are associated with more evolved clumps with high L$_{bol}$/M$_{clump}$. This trend might be associated with gain-surface processes, which determine initial abundances of these molecules, and time-dependent effects in the clumps corresponding to the envelopes around dense PDRs and Hii regions. In addition, some fraction of the measured abundances of the small hydrocarbons of the Hii sources can be the result of the photodissociation of PAH molecules

Five Dimensional Cosmological Models in General Relativity

A Five dimensional Kaluza-Klein space-time is considered in the presence of a perfect fluid source with variable G and $\Lambda$. An expanding universe is found by using a relation between the metric potential and an equation of state. The gravitational constant is found to decrease with time as $G \sim t^{-(1-\omega)}$ whereas the variation for the cosmological constant follows as $\Lambda \sim t^{-2}$, $\Lambda \sim (\dot R/R)^2$ and $\Lambda \sim \ddot R/R$ where $\omega$ is the equation of state parameter and $R$ is the scale factor.Comment: 13 pages, 4 figures, accepted in Int. J. Theor. Phy

Theory of band gap bowing of disordered substitutional II-VI and III-V semiconductor alloys

For a wide class of technologically relevant compound III-V and II-VI semiconductor materials AC and BC mixed crystals (alloys) of the type A(x)B(1-x)C can be realized. As the electronic properties like the bulk band gap vary continuously with x, any band gap in between that of the pure AC and BC systems can be obtained by choosing the appropriate concentration x, granted that the respective ratio is miscible and thermodynamically stable. In most cases the band gap does not vary linearly with x, but a pronounced bowing behavior as a function of the concentration is observed. In this paper we show that the electronic properties of such A(x)B(1-x)C semiconductors and, in particular, the band gap bowing can well be described and understood starting from empirical tight binding models for the pure AC and BC systems. The electronic properties of the A(x)B(1-x)C system can be described by choosing the tight-binding parameters of the AC or BC system with probabilities x and 1-x, respectively. We demonstrate this by exact diagonalization of finite but large supercells and by means of calculations within the established coherent potential approximation (CPA). We apply this treatment to the II-VI system Cd(x)Zn(1-x)Se, to the III-V system In(x)Ga(1-x)As and to the III-nitride system Ga(x)Al(1-x)N.Comment: 14 pages, 10 figure

Bianchi Type III Anisotropic Dark Energy Models with Constant Deceleration Parameter

The Bianchi type III dark energy models with constant deceleration parameter are investigated. The equation of state parameter $\omega$ is found to be time dependent and its existing range for this model is consistent with the recent observations of SN Ia data, SN Ia data (with CMBR anisotropy) and galaxy clustering statistics. The physical aspect of the dark energy models are discussed.Comment: 12 pages, 2 figures, Accepted version of IJT

Some anisotropic universes in the presence of imperfect fluid coupling with spatial curvature

We consider Bianchi VI spacetime, which also can be reduced to Bianchi types VI0-V-III-I. We initially consider the most general form of the energy-momentum tensor which yields anisotropic stress and heat flow. We then derive an energy-momentum tensor that couples with the spatial curvature in a way so as to cancel out the terms that arise due to the spatial curvature in the evolution equations of the Einstein field equations. We obtain exact solutions for the universes indefinetly expanding with constant mean deceleration parameter. The solutions are beriefly discussed for each Bianchi type. The dynamics of the models and fluid are examined briefly, and the models that can approach to isotropy are determined. We conclude that even if the observed universe is almost isotropic, this does not necessarily imply the isotropy of the fluid (e.g., dark energy) affecting the evolution of the universe within the context of general relativity.Comment: 17 pages, no figures; to appear in International Journal of Theoretical Physics; in this version (which is more concise) an equation added, some references updated and adde

A Statistical Study on Photospheric Magnetic Nonpotentiality of Active Regions and Its Relationship with Flares during Solar Cycles 22-23

A statistical study is carried out on the photospheric magnetic nonpotentiality in solar active regions and its relationship with associated flares. We select 2173 photospheric vector magnetograms from 1106 active regions observed by the Solar Magnetic Field Telescope at Huairou Solar Observing Station, National Astronomical Observatories of China, in the period of 1988-2008, which covers most of the 22nd and 23rd solar cycles. We have computed the mean planar magnetic shear angle (\bar{\Delta\phi}), mean shear angle of the vector magnetic field (\bar{\Delta\psi}), mean absolute vertical current density (\bar{|J_{z}|}), mean absolute current helicity density (\bar{|h_{c}|}), absolute twist parameter (|\alpha_{av}|), mean free magnetic energy density (\bar{\rho_{free}}), effective distance of the longitudinal magnetic field (d_{E}), and modified effective distance (d_{Em}) of each photospheric vector magnetogram. Parameters \bar{|h_{c}|}, \bar{\rho_{free}}, and d_{Em} show higher correlation with the evolution of the solar cycle. The Pearson linear correlation coefficients between these three parameters and the yearly mean sunspot number are all larger than 0.59. Parameters \bar{\Delta\phi}, \bar{\Delta\psi}, \bar{|J_{z}|}, |\alpha_{av}|, and d_{E} show only weak correlations with the solar cycle, though the nonpotentiality and the complexity of active regions are greater in the activity maximum periods than in the minimum periods. All of the eight parameters show positive correlations with the flare productivity of active regions, and the combination of different nonpotentiality parameters may be effective in predicting the flaring probability of active regions.Comment: 20 pages, 5 figures, 4 tables, accepted for publication in Solar Physic

New polarimetric constraints on axion-like particles

We show that the parameter space of axion-like particles can be severly constrained using high-precision measurements of quasar polarisations. Robust limits are derived from the measured bounds on optical circular polarisation and from the distribution of linear polarisations of quasars. As an outlook, this technique can be improved by the observation of objects located behind clusters of galaxies, using upcoming space-borne X-ray polarimeters.Comment: Submitted to JCA

Observation of Orbitally Excited B_s Mesons

We report the first observation of two narrow resonances consistent with states of orbitally excited (L=1) B_s mesons using 1 fb^{-1} of ppbar collisions at sqrt{s} = 1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. We use two-body decays into K^- and B^+ mesons reconstructed as B^+ \to J/\psi K^+, J/\psi \to \mu^+ \mu^- or B^+ \to \bar{D}^0 \pi^+, \bar{D}^0 \to K^+ \pi^-. We deduce the masses of the two states to be m(B_{s1}) = 5829.4 +- 0.7 MeV/c^2 and m(B_{s2}^*) = 5839.7 +- 0.7 MeV/c^2.Comment: Version accepted and published by Phys. Rev. Let