Preparation, Characterization and NO-CO Redox Reaction Studies over Palladium and Rhodium Oxides Supported on Manganese Dioxide

The catalytic activity of PdO/MnO2 and Rh2O3/MnO2 is investigated for NO-CO redox reaction. Supported catalysts are prepared by wet impregnation method. Among the tested catalysts, PdO/MnO2 shows higher activity for this reaction. Active metal dispersion on MnO2 enhances the selectivity for N2 over N2O in this reaction. The XRD substantiate the formation of MnO2 monophasic phase. SEM images show the formation of elongated particles. TEM images indicate nano-size rod-like morphologies. An increase in the catalytic activity is observed on supported Pd and Rh oxides on MnO2. Temperature programed desorption studies with NO and CO are undertaken to investigate the catalytic surface studies. © 2015 BCREC UNDIP. All rights reserve

Spectroscopic signatures of tetralayer graphene polytypes

Tetralayer graphene has recently become a new addition to the family of few-layer graphene with versatile electronic properties. This material can be realised in three distinctive stacking configurations, for which we determine spectroscopic signatures in angle-resolved photoemission spectroscopy (ARPES), dynamical optical conductivity, and Raman spectra of inter-band excitations. The reported library of spectral features of tetralayer graphenes can be used for the non-invasive identification of the stacking order realised in a particular film.Comment: Pages 11, figures

Symmetry of boundary conditions of the Dirac equation for electrons in carbon nanotubes.

We consider the effective mass model of spinless electrons in single wall carbon nanotubes that is equivalent to the Dirac equation for massless fermions. Within this framework we derive all possible energy independent hard wall boundary conditions that are applicable to metallic tubes. The boundary conditions are classified in terms of their symmetry properties and we demonstrate that the use of different boundary conditions will result in varying degrees of valley degeneracy breaking of the single particle energy spectrum

Predominant Golgi-residency of the plant K/HDEL receptor is essential for its function in mediating ER retention

Accumulation of soluble proteins in the endoplasmic reticulum (ER) of plants is mediated by a receptor termed ER RETENTION DEFECTIVE 2 (ERD2) or K/HDEL receptor. Using two gain-of-function assays and by complementing loss of function in Nicotiana benthamiana we discovered that compromising the lumenal N-terminus or the cytosolic C-terminus with fluorescent fusions abolishes its biological function and profoundly affects its subcellular localization. Based on the confirmed asymmetrical topology of ERD2 we engineered a new fluorescent ERD2 fusion protein that retains biological activity. Using this fusion, we show that ERD2 is exclusively detected at the Golgi apparatus, unlike non-functional C-terminal fusions which also label the ER. Moreover, ERD2 is confined to early Golgi compartments and does not show ligand-induced redistribution to the ER. We show that the cytosolic C-terminus of ERD2 plays a crucial role in its function. Two conserved Leucine residues that do not correspond to any known targeting motifs for ER-Golgi trafficking were shown to be essential for both ERD2 Golgi residency and its ability to mediate ER retention of soluble ligands. The results suggest that anterograde ER to Golgi transport of ERD2 is either extremely fast, well in excess of the bulk flow rate, or that ERD2 does not recycle in the way originally proposed

Imbibition in Disordered Media

The physics of liquids in porous media gives rise to many interesting phenomena, including imbibition where a viscous fluid displaces a less viscous one. Here we discuss the theoretical and experimental progress made in recent years in this field. The emphasis is on an interfacial description, akin to the focus of a statistical physics approach. Coarse-grained equations of motion have been recently presented in the literature. These contain terms that take into account the pertinent features of imbibition: non-locality and the quenched noise that arises from the random environment, fluctuations of the fluid flow and capillary forces. The theoretical progress has highlighted the presence of intrinsic length-scales that invalidate scale invariance often assumed to be present in kinetic roughening processes such as that of a two-phase boundary in liquid penetration. Another important fact is that the macroscopic fluid flow, the kinetic roughening properties, and the effective noise in the problem are all coupled. Many possible deviations from simple scaling behaviour exist, and we outline the experimental evidence. Finally, prospects for further work, both theoretical and experimental, are discussed.Comment: Review article, to appear in Advances in Physics, 53 pages LaTe

Enhanced Fluctuations of the Tunneling Density of States near the Bottom of a Landau Band Measured by a Local Spectrometer

We have found that the local density of state fluctuations (LDOSF) in a disordered metal, detected using an impurity in the barrier as a spectrometer, undergo enhanced (with respect to Shubnikov -de Haas and de Haas -van Alphen effects) oscillations in strong magnetic fields, v c t 1. We attribute this to the dominant role of the states near the bottom of Landau bands which give the major contribution to the LDOSF and are most strongly affected by disorder. We also demonstrate that in intermediate fields the LDOSF increase with field B in accordance with the results obtained in the diffusion approximation. PACS numbers: 73.23.Hk, 72.15.Gd, 73.20.Fz, 73.40.Ty Resonant tunneling through individual impurities has been identified and studied in vertical In this paper, we study the evolution with magnetic field of the LDOSF in a 3D disordered metal, a heavily doped semiconductor, and discuss the results from the point of view of the fluctuation and correlation properties of single-particle wave functions in disordered media. We have measured the fingerprint of the LDOSF, dn͑´͒, in the differential conductance G͑V ͒ dI dV ͑V ͒ in a broad range of magnetic fields, B, and analyzed its variance, ͗dG 2 ͘, and correlation parameters. In intermediate fields, v c t ϳ 1, we have detected an increase of the fluctuation magnitude, in agreement with the theoretically predicted behavior [11]: ͗͑dG͒ 2 ͘ B ͗͑͞dG͒ 2 ͘ B0 ഠ 1 1 ͑v c t͒ 2 . At higher fields, v c t 1, we have observed large 1͞B periodic oscillations in ͗dG 2 ͘. We conclude that LDOSF in strong fields are dominated by the states near the minimum of the Landau bands which play a distinguished role relative to the rest of the spectrum. Notably, the observed oscillations are significantly stronger than those in other oscillatory effects in metals, such as de Haas-van Alphen effect. The investigated structure consists of a 50 Å GaAs well imbedded between two 81 Å Al 0.33 Ga 0.67 As barriers. Each Si-doped GaAs contact consists of three layers: 4800 Å with nominal doping 10 18 cm 23 is followed by 4800 Å with 2 3 10 17 cm 23 , and the latter is separated from the barrier by an undoped spacer of 300 Å and 200 Å, for top and bottom contact, respectively. The lateral area of the nominally undoped quantum well is reduced to a 700 Å diameter disk using the ion bombardment technique At zero bias, the spectrometer level S is above the Fermi level m of the emitter with 3D metallic conduction. The alignment of S and m with increasing bias is registered as a step in IV . In the differential conductance G͑V ͒ shown in and its width is related to the energetic width of the spectrometer G Ӎ G max Ӎ 120 meV determined by the tunneling coupling between the impurity and the contacts. The values of G min,max depend on the transparencies of the two barriers, so that G max corresponds to the lower (collector) barrier and G min corresponds to the higher (emitter) barrier, G min ϳ 5 3 10 23 G max , as estimated from the value of G G . The relation between bias V and the energy scale of the spectrometer is established by the coefficientf b dE d͑eV ͒ 0.24, found for the selected 0031-9007͞00͞84(7)͞1563(4)$15.0