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Spectra Shows (spectrum + shows)
Selected AbstractsReactive Imprint Lithography: Combined Topographical Patterning and Chemical Surface Functionalization of Polystyrene- block -poly(tert -butyl acrylate) FilmsADVANCED FUNCTIONAL MATERIALS, Issue 3 2010Joost Duvigneau Abstract Here, reactive imprint lithography (RIL) is introduced as a new, one-step lithographic tool for the fabrication of large-area topographically patterned, chemically activated polymer platforms. Films of polystyrene- block -poly(tert -butyl acrylate) (PS- b -PtBA) are imprinted with PDMS master stamps at temperatures above the corresponding glass transition and chemical deprotection temperatures to yield structured films with exposed carboxylic acid and anhydride groups. Faithful pattern transfer is confirmed by AFM analyses. Transmission-mode FTIR spectra shows a conversion of over 95% of the tert -butyl ester groups after RIL at 230,°C for 5 minutes and a significantly reduced conversion to anhydride compared to thermolysis of neat films with free surfaces in air or nitrogen. An enrichment of the surface layer in PS is detected by angle-resolved X-ray photoelectron spectroscopy (XPS). In order to demonstrate application potentials of the activated platforms, a 7,nm,±,1,nm thick NH2 -terminated PEG layer (grafting density of 0.9 chains nm,2) is covalently grafted to RIL-activated substrates. This layer reduces the non-specific adsorption (NSA) of bovine serum albumin by 95% to a residual mass coverage of 9.1,±,2.9,ng cm,2. As shown by these examples, RIL comprises an attractive complementary approach to produce bio-reactive polymer surfaces with topographic patterns in a one-step process. [source] Assessment of rainfall-runoff models based upon wavelet analysisHYDROLOGICAL PROCESSES, Issue 5 2007Stuart N. Lane Abstract A basic hypothesis is proposed: given that wavelet-based analysis has been used to interpret runoff time-series, it may be extended to evaluation of rainfall-runoff model results. Conventional objective functions make certain assumptions about the data series to which they are applied (e.g. uncorrelated error, homoscedasticity). The difficulty that objective functions have in distinguishing between different realizations of the same model, or different models of the same system, is that they may have contributed in part to the occurrence of model equifinality. Of particular concern is the fact that the error present in a rainfall-runoff model may be time dependent, requiring some form of time localization in both identification of error and derivation of global objective functions. We explore the use of a complex Gaussian (order 2) wavelet to describe: (1) a measured hydrograph; (2) the same hydrograph with different simulated errors introduced; and (3) model predictions of the same hydrograph based upon a modified form of TOPMODEL. The analysis of results was based upon: (a) differences in wavelet power (the wavelet power error) between the measured hydrograph and both the simulated error and modelled hydrographs; and (b) the wavelet phase. Power difference and wavelet phase were used to develop two objective functions, RMSE(power) and RMS(phase), which were shown to distinguish between simulated errors and model predictions with similar values of the commonly adopted Nash-Sutcliffe efficiency index. These objective functions suffer because they do not retain time, frequency or time-frequency localization. Consideration of wavelet power spectra and time- and frequency-integrated power spectra shows that the impacts of different types of simulated error can be seen through retention of some localization, especially in relation to when and the scale over which error was manifest. Theoretical objections to the use of wavelet analysis for this type of application are noted, especially in relation to the dependence of findings upon the wavelet chosen. However, it is argued that the benefits of localization and the qualitatively low sensitivity of wavelet power and phase to wavelet choice are sufficient to warrant further exploration of wavelet-based approaches to rainfall-runoff model evaluation. Copyright © 2006 John Wiley & Sons, Ltd. [source] Food additives characterization by infrared, Raman, and surface-enhanced Raman spectroscopiesJOURNAL OF RAMAN SPECTROSCOPY, Issue 3 2007Edyta Podstawka Abstract Fourier-transform infrared (FT-IR), Raman (RS), and surface-enhanced Raman scattering (SERS) spectra of , -hydroxy- , -methylobutanoic acid (HMB), L -carnitine, and N -methylglycocyamine (creatine) have been measured. The SERS spectra have been taken from species adsorbed on a colloidal silver surface. The respective FT-IR and RS band assignments (solid-state samples) based on the literature data have been proposed. The strongest absorptions in the FT-IR spectrum of creatine are observed at 1398, 1615, and 1699 cm,1, which are due to ,s(COOH) + ,(CN) + ,(CN), ,s(NH2), and ,(CO) modes, respectively, whereas those of L -carnitine (at 1396/1586 cm,1 and 1480 cm,1) and HMB (at 1405/1555/1585 cm,1 and 1437,1473 cm,1) are associated with carboxyl and methyl/methylene group vibrations, respectively. On the other hand, the strongest bands in the RS spectrum of HMB observed at 748/1442/1462 cm,1 and 1408 cm,1 are due to methyl/methylene deformations and carboxyl group vibrations, respectively. The strongest Raman band of creatine at 831 cm,1 (,w(RNH2)) is accompanied by two weaker bands at 1054 and 1397 cm,1 due to ,(CN) + ,(RNH2) and ,s(COOH) + ,(CN) + ,(CN) modes, respectively. In the case of L -carnitine, its RS spectrum is dominated by bands at 772 and 1461 cm,1 assigned to ,r(CH2) and ,(CH3), respectively. The analysis of the SERS spectra shows that HMB interacts with the silver surface mainly through the COO,, hydroxyl, and CH2 groups, whereas L -carnitine binds to the surface via COO, and N+(CH3)3 which is rarely enhanced at pH = 8.3. On the other hand, it seems that creatine binds weakly to the silver surface mainly by NH2, and CO from the COO, group. Copyright © 2006 John Wiley & Sons, Ltd. [source] Polarized Raman scattering and phase transition studies of n -diethylenediammonium monohydrogenmonophosphate dihydrateJOURNAL OF RAMAN SPECTROSCOPY, Issue 12 2006S. Elleuch Abstract Polarized Raman scattering studies at room temperature were carried out on N -diethylenediammonium monohydrogenmonophosphate dihydrate single crystal samples, abbreviated N -DDHP. An assignment of the normal modes is proposed based on group theory analysis and correlations with previous data reported for other homologous hydrogen-bonded systems. A careful analysis of the vibrational spectra shows that the assignment of the fundamental vibrational modes can be done based on phosphate, organic and water group vibrations. In addition, differential scanning calorimetry measurement and a Raman spectroscopic study at several temperatures in the range 100,300 K are presented. The occurrence of a low-temperature phase transition near 220 K is well evidenced. From the temperature-dependence behavior of some internal and external modes, this transition is interpreted by an order,disorder transition which involves the structural modifications of both anion and cation groups. Copyright © 2006 John Wiley & Sons, Ltd. [source] Magnetic circular dichroism at transition metal L2,3 edges in D03 -type (Fe1- xMnx)3Al alloysJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2001Kazuo Soda We have measured magnetic circular dichroism (MCD) spectra at the transition-metal L2,3 edges in D03 -type (Fe1- xMnx)3Al in order to investigate their local magnetic moments. The analysis of the spectra shows that Fe has moments much larger than Mn, whose moment is ferromagnetically coupled with the Fe one. This does not lend support to the antiferromagnetic mechanism proposed for the reduction in magnetization as well as a large Mn moment predicted for x = 1/3. The evolution of satellites found in the Mn spectrum with x increased suggests that the change in the electronic state may result in the magnetization reduction. [source] Variability in red supergiant stars: pulsations, long secondary periods and convection noiseMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006L. L. Kiss ABSTRACT We study the brightness variations of galactic red supergiant stars using long-term visual light curves collected by the American Association of Variable Star Observers over the last century. The full sample contains 48 red semiregular or irregular variable stars, with a mean time-span of observations of 61 yr. We determine periods and period variability from analyses of power density spectra and time,frequency distributions. We find two significant periods in 18 stars. Most of these periods fall into two distinct groups, ranging from a few hundred to a few thousand days. Theoretical models imply fundamental, first and possibly second overtone mode pulsations for the shorter periods. Periods greater than 1000 d form a parallel period,luminosity relation that is similar to the long secondary periods of the asymptotic giant branch stars. A number of individual power spectra shows a single mode resolved into multiple peaks under a Lorentzian envelope, which we interpret as evidence for stochastic oscillations, presumably caused by the interplay of convection and pulsations. We find a strong 1/f noise component in the power spectra that is remarkably similar in almost all stars of the sample. This behaviour fits the picture of irregular photometric variability caused by large convection cells, analogous to the granulation background seen in the Sun. [source] Absorption Spectra of Human Skin In Vivo in the Ultraviolet Wavelength Range Measured by OptoacousticsPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2009Merve Meinhardt Knowledge of the optical properties of human skin in the ultraviolet range is fundamental for photobiologic research. However, optical properties of human skin in the ultraviolet spectral range have so far mainly been measured ex vivo. We have determined the absorption spectra of human skin in vivo in the wavelength range from 290 to 341 nm in 3 nm steps using laser optoacoustics. In this technique, optical properties are derived from the pressure profile generated by absorbed light energy in the sample. In a study on 20 subjects belonging to phototypes I,IV, we studied the optical properties at the volar and dorsal aspect of the forearm as well as on the thenar. Analysis of the measured absorption spectra shows that comparable skin areas,like different sides of the forearm,have qualitatively similar optical characteristics. Still, the optical properties may vary substantially within the same area, probably due to the skin structure and inhomogeneities. Comparison of the spectra from different skin sites indicates that the spectral characteristics of the stratum corneum and its chromophores play an important role for the optical properties of human skin in vivo in the ultraviolet B range. [source] Nanocrystalline boron-doped diamond films, a mixture of BCS-like and non-BCS-like superconducting grainsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 9 2010F. Dahlem Abstract Scanning tunneling topography and spectroscopy are performed below 100,mK on granular nanocrystalline boron-doped diamond (BDD) films. We found the superconductivity behavior to follow mainly the granular features of the BDD films. The temperature dependence of the local differential conductance spectra shows our nanocrystalline BDD films as made of grains with a supercondutivity either BCS-like or non-BCS-like. Such a distribution is not discernible in transport measurements, which present a sharp macroscopic superconducting transition at a temperature of a few Kelvins. Our local scanning tunneling microscopies also confirm the good coupling between these grains: only a few opaque interfaces are detected. Such a transparency of intergrain interfaces is responsible for a proximity effect in weakly superconductive grains and an inverse proximity effect in strongly superconducting grains. [source] Magnetic properties and structures of HDDR NdFeCoBNbZr alloysPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2004Fa-Zeng Lian Abstract The magnetic properties and the microstructures of HDDR magnet materials fabricated from the alloys with chemical composition of Nd14FebalCo15B6.5NbxZry (x = 0,0.25; y = 0,0.25) have been investigated. The variation of the magnetic properties of the magnets with HD temperature and DR temperature was studied. The results show that HD temperature and DR temperature affect the magnetic properties of HDDR magnet powders obviously. The analysis of XRD spectra shows that the process of HDDR technique is hydrogenation disproportionation desorption recombination. The addition of a small amount of Nb element is useful to improve the magnetic properties of HDDR magnetic powders. And the composite addition of a little Nb and Zr can further enhance the magnetic properties. The reasons for the enhancement of the magnetic properties by the composite addition of small amounts of Nb and Zr are analyzed. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Optical characterization of Zn0.97Mn0.03Se/ZnSe0.92Te0.08 type II multiple-quantum-well structuresPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 5 2007D. Y. Lin Abstract The optical characterization of type II Zn0.97Mn0.03Se/ZnSe0.92Te0.08 multiple-quantum-well structures have been studied using photoluminescence (PL), temperature-dependent PL, polarized PL, power-dependent PL, and photoreflectance (PR) in this study. The PL data reveal that the band alignment of the ZnMnSe/ZnSeTe system is type II. Comparing with the theoretical calculation based on the Schrodinger equation, the valence band offset is estimated to be 0.6 eV. From the power-dependent PL spectra, it is observed that the peak position of PL spectra shows a blueshift under different excitation power. The blueshift can be interpreted in terms of the band-bending effect due to spatially photoexcited carriers in a type II alignment. The thermal activation energy (EA) for quenching the PL intensity was determined from tem- perature-dependent PL spectra. The thermal activation energy was found to decrease as the thickness of ZnMnSe and ZnSeTe layers decreased. The polarized PL spectra exhibit a large in-plane polarization with the polarization degree up to 50%. The polarization does not depend on the excitation intensity as well as temperature. The large polarization is an inherent orientation of the interface chemical bonds. The higher transition features observed in PR spectra show a blueshift with the similar trend observed in the PL spectra as decreasing the thickness of ZnSeTe layer. This result provides a consistent evidence for the assumption that square-like well shapes were built in the ZnSeTe layers. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Reflectance and photoluminescence studies of InGaN/GaN multiple-quantum-well structures embedded in an asymmetric microcavityPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 7 2006D. Y. Lin Abstract Using reflectance (R) and photoluminescence (PL) measurements InGaN/GaN multiple-quantum-well (MQW) structures embedded in an asymmetric microcavity with different thickness of stacking pairs have been studied. The asymmetric microcavity structures are composed of a cavity sandwitched between the air/semiconductor interface and a mirror using distributed Bragg reflector (DBR). For the DBR with thinner AlN layers the high-reflectivity stop band locates at higher photon energy. The luminescence efficiency and the spectrum of InGaN/GaN multiple-quantum-well structures will be modified by the microcavity. A comparison of PL with R spectra shows that the emission efficiency can be enhanced by matching up the luminescence spectrum coming from the MQW and the high-reflectivity stop band. From the blue shift of the cavity modes as a function of incident angles the refractive index and cavity length can be determined. By measuring the PL spectra as a function of emission angle, it is found that the PL spectra were predominatly determined by microcavity resonances. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Influence of hydrogen intercalation on the local structure around Re ions in perovskite-type ReO3PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2005J. Gaidelene Abstract In-situ X-ray absorption spectroscopy at the Re L1 and L3 edges was used to study a modification of the local atomic and electronic structure around rhenium in perovskite-type ReO3 upon hydrogen intercalation. The analysis of both EXAFS and XANES parts of the X-ray absorption spectra shows an evidence of the charge disproportionation phenomenon in hydrogenated rhenium trioxide. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] 2-Hydroxyethylmethacrylate carrying uniform porous particles: preparation and electron microscopyPOLYMER INTERNATIONAL, Issue 1 2002A Tuncel Abstract Uniform macroporous particles carrying hydroxyl groups have been obtained in the size range 3,11.5,µm by seeded polymerization. For this purpose, uniform polystyrene particles in the size range 1.9,6.2,µm were used as seeds. The seed particles were successively swollen by dibutyl phthalate (DBP) and a monomer mixture comprising styrene, 2-hydroxyethylmethacrylate (HEMA) and a crosslinker. Two different crosslinkers, divinylbenzene (DVB) and ethylene glycol dimethacrylate (EGDMA), were tested. Size distribution properties together with bulk and surface structures of the particles have been characterized by both scanning and transmission electron microscopy. While EGDMA provides uniform particles with a non-porous surface, DVB produces uniform particles having a highly porous surface and interior. The comparison of FTIR and FTIR-DRS spectra shows that the HEMA concentration is higher on the particle surface than within the particle interior. Seed latex size and monomer/seed latex ratios are identified as the most important variables affecting the final particles. Different seed latexes have been tried; the result is that highly macroporous particles with a sponge-like pore structure both on the surface and in the particle interior have been obtained by use of the seed latex with the largest particles and the lowest molecular weight. An increase in the HEMA feed concentration leads to final particles with a non-porous surface and a crater-like porosity in the particle interior. The average pore size significantly decreases with increasing DBP/seed latex and monomer/seed latex ratios. © 2001 Society of Chemical Industry [source] Removal of N -methylpyrrolidone hydrogen-bonded to polyaniline free-standing films by protonation,deprotonation cycles or thermal heatingPOLYMER INTERNATIONAL, Issue 11 2001Eduardo A Ponzio Abstract Free-standing films of polyaniline (PANI), in an emeraldine base state, prepared by evaporation of polymer solutions in N -methylpyrrolidone (NMP) retain solvent even under dynamic vacuum drying as indicated by transmission Fourier transform infrared (FTIR) spectroscopy, where a band at 1670,cm,1 is clearly observed. Upon protonation,deprotonation cycles in aqueous media the weight of the dry base film decreases indicating gradual loss of NMP. Transmission FTIR spectra shows also the washing out of NMP with a clear decrease in intensity of the hydrogen-bonded >CO stretching band (1670,cm,1) of NMP. During this process the bands between 3500 and 3200,cm,1, assigned to >NH stretching in the PANI backbone, change intensity suggesting that intermolecular hydrogen-bonded >NH, with carbonyl oxygen of NMP, is replaced by free >NH. This is clear evidence of specific interaction of NMP with the emeraldine base. A similar loss of NMP is observed during heating but evidence of polymer degradation is also present. A mechanism is proposed to account for the loss of hydrogen-bonding ability upon protonation which requires delocalization of the radical cations in the protonated films. © 2001 Society of Chemical Industry [source] Properties of Ionic Liquid Confined in Porous Silica MatrixCHEMPHYSCHEM, Issue 9 2010Manish Pratap Singh Abstract Porous silica matrices of different pore sizes with confined ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) [BMIM] [PF6] were prepared by sol-gel technique using a tetraethyl orthosilicate (TEOS) precursor with an aim to study the changes in physico-chemical properties of ionic liquid on confinement. It is found that on confinement 1) melting point decreases, 2) fluorescence spectra shows a red shift and 3) the vibrational bands are affected particularly those of imadazolium ring, which interacts more with the walls of the silica matrix. Preliminary theoretical calculations suggest that SiO2 matrix interact more with the heterocyclic group of [BMIM] cation than the tail alkyl chain end group resulting in significant changes in the aromatic vibrations. [source] Temperature Dependence of the Dielectric Properties and Dynamics of Ionic LiquidsCHEMPHYSCHEM, Issue 4 2009Johannes Hunger Abstract No solo dancers: The temperature dependence of dielectric spectra suggests that the lower-frequency relaxation dominating the dynamics of imidazolium-based room temperature ionic liquids cannot be solely due to independent rotational diffusion of the cations (see picture), but must also include cooperative motions of the surrounding particles. Dielectric spectra were measured for eight, mostly imidazolium-based, room temperature ionic liquids (RTILs) over a wide range of frequencies (0.2,,/GHz,89) and temperatures (5,,/°C, 65). Detailed analysis of the spectra shows that the dominant low frequency process centred at ca. 0.06 to 10 GHz (depending on the salt and the temperature) is better described using a symmetrically broadened Cole,Cole model rather than the asymmetric Cole,Davidson models used previously. Evaluation of the temperature dependence of the static permittivities, effective dipole moments, volumes of rotation, activation energies, and relaxation times derived from the dielectric data indicates that the low frequency process cannot be solely due to rotational diffusion of the dipolar imidazolium cations, as has been thought, but must also include other contributions, probably from cooperative motions. Analysis of the Debye process observed at higher frequencies for these RTILs is not undertaken because it overlaps with even faster processes that lie outside the range of the present instrumentation. [source] Enantiomers of 2-[(Acylamino)ethyl]-1,4-benzodiazepines, Potent ligands of ,-opioid receptor: Chiral chromatographic resolution, configurational assignment, and biological activityCHIRALITY, Issue 9 2001O. Azzolina Abstract Compounds 2a and 3a,e are racemic 2-[(acylamino)ethyl]-1,4-benzodiazepines, tifluadom analogs, with high affinity and selectivity towards the ,-opioid receptor. We describe the enantiomeric separation of all compounds through liquid chromatography with chiral stationary phases, as well as the resolution of the enantiomers of the most interesting compounds, 2a and 3a, by the semipreparative column Chiralpak AD. The configuration of the resolved enantiomers was investigated: the comparative study of CD and 1H NMR spectra shows that compounds (,)- 2a and (,)- 3a have the same absolute configuration of (+)-(S)-tifluadom. A study on the stereoselective interaction with opiate receptors is reported. Chirality 13:606,612, 2001. © 2001 Wiley-Liss, Inc. [source] Chemical and Electrochemical Behaviours of a New Phenolato-Bridged Complex [(L)MnIIMnII(L)]2+.EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 21 2006Dinuclear Mono-µ-Oxido [(L)MnIII(µ-O)MnIII/IV(L)]2+/3+ Species, Pathways to Mononuclear Chlorido [(L)MnII/III/IVCl]0/1/2+ Abstract The X-ray structure of a new dinuclear phenolato-bridged Mn2II complex abbreviated as [(L)MnMn(L)]2+ (1), where LH is the [N4O] phenol containing ligand N,N -bis(2-pyridylmethyl)- N, -salicylidene-ethane-1,2-diamine ligand, is reported. A J value of ,3.3 cm,1 (H = ,J,1·,2) was determined from the magnetic measurements and the 9.4 GHz EPR spectra of both powder and frozen acetonitrile solution samples were analyzed with temperature. The cyclic voltammetry of 1 displays a reversible anodic wave at E1/2 = 0.46 V vs. SCE associated with the two-electron oxidation of 1 yielding the dinuclear Mn2III complex [(L)MnMn(L)]4+ (2). The easy air oxidation of 1 gives the mono-,-oxido Mn2III complex [(L)Mn(, - O)Mn(L)]2+ (3). A rational route to the formation of the mixed-valence Mn2III,IV complex [(L)Mn(, - O)Mn(L)]3+ (4) starting from 1 by bulk electrolysis at EP = 0.75 V vs. SCE in the presence of one equiv. of base per manganese ion is also briefly reported. Addition of chloride ions to 1 led to the cleavage of the phenolato bridges to give the mononuclear MnII complex [(L)MnCl] (5). Cyclic voltammetry of 5 displays two reversible anodic waves at E1/2 = 0.21 and E1/2 = 1.15 V vs. SCE, assigned to the two successive one-electron abstractions giving the MnIII and MnIV species [(L)MnCl]+ (6) and [(L)MnCl]2+ (7), respectively. The electronic signatures from UV/Visible and EPR spectroscopy of the electrochemically prepared samples of 6 and 7 confirmed the respective oxidation states. For instance, 7 displays a broad and intense absorption band characteristic of a phenolato to MnIV charge-transfer transition at 690 nm (2000 M,1,cm,1) and its 9.4 GHz EPR spectrum shows a strong transition at g = 5.2 consistent with a rhombically distorted S = 3/2 system with a zero-field splitting dominating the Zeeman effect. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Electronic states in Cu2MnX (X = Al, In and Sn) Heusler alloy studied by XMCD and multiple scattering calculationsJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2001Shigeaki Uemura X-ray magnetic circular dichroism (XMCD) has been measured at Mn and Cu K-edge in Cu2MnX (X = Al, In, and Sn) Heusler alloy. The Mn K -edge spectrum shows a dispersion-type profile and the Cu K -edge resembles the Mn spectrum, which suggests that polarization of the p unoccupied bands originates commonly in Mn 3d states. To reproduce the observed spectrum by full multiple scattering calculations, Madelung potential has been taken into account. Charge redistribution is an important factor for the electronic structure in Cu2MnX Heusler alloy. [source] XANES study on the valence transitions in cerium oxide nanoparticlesJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2001Jing Zhang The aim of this work is the determination of Ce environment and valence state in cerium oxide nanoparticles prepared by the microemulsion method. X-ray absorption near-edge structure measurements at Ce L3 edge were performed on the nanoparticles as a function of annealing temperature, ranging from 298K to 873K under air condition. The experimental results support the conclusion that Ce ion, in the investigated systems, is in trivalence state when the annealing temperature is below 473K. As the temperature increases up to 623K, the XANES spectrum shows the coexistence of Ce3+ and Ce4+states. When the temperature is higher than 623K, the spectra become identical to that of CeO2 with a distinct double-peak structure, corresponding to the Ce4+ state. [source] Shock heating in the group atmosphere of the radio galaxy B2 0838+32AMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2008Nazirah N. Jetha ABSTRACT We present Chandra and radio observations, and analysis of Sloan Digital Sky Survey data, of the radio galaxy B2 0838+32A (4C 32.26) and its environment. The radio galaxy is at the centre of a nearby group that has often been identified with the cluster Abell 695, but we argue that the original Abell cluster is likely to be an unrelated and considerably more distant system. The radio source is a restarting radio galaxy and, using our Chandra data, we argue that the currently active lobes are expanding supersonically, driving a shock with Mach number 2.4+1.0,0.5 into the interstellar medium. This would be only the third strong shock round a young radio source to be discovered, after Centaurus A and NGC 3801. However, in contrast to both these systems, the host galaxy of B2 0838+32A shows no evidence for a recent merger, while the active galactic nuclei (AGN) spectrum shows no evidence for the dusty torus that would imply a large reservoir of cold gas close to the central black hole. On the contrary, the AGN spectrum is of a type that has been associated with the presence of a radiatively inefficient accretion flow that could be controlled by an AGN heating and subsequent cooling of the hot, X-ray emitting gas. If correct, this means that B2 0838+32A is the first source in which we can directly see entropy-increasing processes (shocks) driven by accretion from the hot phase of the interstellar medium. [source] Dependence of structural and optical properties of Zn1,xCdxO films on the Cd compositionPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 13 2004D. W. Ma Abstract Zn1,xCdxO alloy semiconductors have great latent applications in short wavelength optoelectronic devices. By the dc reactive magnetron sputtering technique, ternary single-phased Zn1,xCdxO (0 , x , 0.53) alloy crystalline films were prepared on glass and sapphire substrates. For x = 0, 0.20, 0.36, 0.53, the band-gaps of the Zn1,xCdxO alloy films were estimated as 3.28, 3.21, 3.11 and 2.65 eV, respectively. Photoluminescence spectrum shows that the near-band-edge energy of the Zn0.8Cd0.2O film has a red-shift of 0.14 eV from that of pure ZnO reported previously. The green-yellow emission in the photoluminescence spectrum is assumed to mainly related to electron transitions from the single ionized oxygen vacancies (Vo+) to Zn, Cd vacancies (VZn,, VC,d), or oxygen interstice (Oi,). (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | |||||||||||||||||||