High‐energy‐resolution diced spherical quartz analyzers for resonant inelastic X‐ray scattering

A novel diced spherical quartz analyzer for use in resonant inelastic X‐ray scattering (RIXS) is introduced, achieving an unprecedented energy resolution of 10.53 meV at the Ir L₃ absorption edge (11.215 keV). In this work the fabrication process and the characterization of the analyzer are presented, and an example of a RIXS spectrum of magnetic excitations in a Sr₃Ir₂O₇ sample is shown.     

Effect of Bi‐content on hardness and micro‐creep behavior of Sn‐3.5Ag rapidly solidified alloy

In the present paper, the influence of 1, 3, 5 and 10 % Bi (weight %) as ternary additions on structure, melting and mechanical properties of rapidly solidified Sn‐3.5Ag alloy has been investigated. The effect of Bi was discussed based on the experimental results. The experimental results showed that the alloys of Sn‐3.5Ag, Sn‐3.5Ag‐1Bi and Sn‐3.5Ag‐3Bi are composed of two phases; Ag₃Sn IMC embedded in Sn matrix phase, which indicated that the solubility of Bi phase in Sn‐matrix was extended to 3 % as a result of rapid solidification. Bi precipitation in Sn matrix was only observed in Sn‐3.5Ag‐5Bi and Sn‐3.5Ag‐10Bi alloys. Also, addition of Bi decreased continuously the melting point of the eutectic Sn‐3.5Ag alloy to 202.6 °C at 10 % Bi. Vickers hardness of Sn‐3.5Ag rapidly solidified alloy increased with increasing Bi content up to 3 % due to supersaturated solid solution strengthening hardening mechanism of Bi phase in Sn matrix, while the alloys contain 5 and 10 % Bi exhibited lower values of Vickers hardness. The lower values can be attributed to the precipitation of Bi as a secondary phase which may form strained regions due to the embrittlement of Bi atom. In addition, the effect of Bi addition on the micro‐creep behavior of Sn‐3.5Ag alloy as well as the creep rate have been described and has been calculated at room temperature. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A correlation for crystallite size of undoped ZnO thin film with the band gap energy – precursor molarity – substrate temperature

Transparent conducting undoped zinc oxide thin films were deposited on glass substrate by ultrasonic spray and spray pyrolysis techniques. The thin films were deposited at different substrate temperatures ranging between 300 and 450 °C with various precursor molarities. The correlation between the structural and optical properties suggests that the crystallites sizes of the films are predominantly influenced by the band gap energy of the thin films. The data of the correlation is suspected of involving some experimental measurement errors and therefore discarded in the development of the present correlation. The coefficient of correction is equal to 0.01, indicating high quality representation of data based on Eq. (1). The correlation also indicates that the crystallites sizes of the films are predominantly influenced by the band gap energy and the precursor molarity of the thin films. The model proposed of undoped ZnO thin film with substrate temperature was investigated.     

A comparative study on structural and optical properties of ZnO and Al-doped ZnO thin films obtained by ultrasonic spray method using different solvents

Transparent conducting ZnO and Al doped ZnO thin films were deposited on glass substrate by ultrasonic spray method. The thin films with concentration of 0.1 M were deposited at 350 °C with 2 min of deposition time. The effects of ethanol and methanol solution before and after doping on the structural, optical and electrical properties were examined. The DRX analyses indicated that ZnO films have nanocrystalline nature and hexagonal wurtzite structure with (1 0 0) and (0 0 2) preferential orientation corresponding to ZnO films resulting from methanol and ethanol solution, respectively. The crystallinity of the thin films improved with methanol solution after doping to (0 0 2) oriented. All films exhibit an average optical transparency about 90%, in the visible range. The band gaps values of ZnO thin films are increased after doping from 3.10 to 3.26 eV and 3.27 to 3.30 eV upon Al doping obtained by ethanol and methanol solution, respectively. The electrical conductivity increase from 7.5 to 15.2 (Ω cm)⁻¹ of undoped to Al doped ZnO thin films prepared by using ethanol solution. However, for the methanol solution; the electrical conductivity of the film is stabilized after doping.     

Anisotropic Estimates for the Two-Dimensional Kuramoto–Sivashinsky Equation

We address the global solvability of the Kuramoto–Sivashinsky equation in a rectangular domain \([0,L_1]\times [0,L_2]\) . We give sufficient conditions on the width \(L_2\) of the domain, depending on the length \(L_1\) , so that the obtained solutions are global. Our proofs are based on anisotropic estimates.     

Spectroscopic studies on Co(II) and Cu(II) complexes of 6-amino-1-methyl-5-nitrosouracil and its 6-methylamine derivative

Four complexes are obtained during the reactions of 6-amino-1-methyl-5-nitrosouracil and its 6-methylamine derivative with Co(II) and Cu(II) ions. Theses complexes were characterized through their elemental, thermal analysis, infrared and 1H NMR spectroscopes. The obtained results indicate that, the exocyclic oxygen and nitrogen atoms are the most probable binding sites rather than ring nitrogen atoms. For cobalt complexes, the two pyrimidine bases act as bidentate ligands in the anionic form with the dissociation of iminic or N3 proton depending upon the nature of substituents on the pyrimidine ring. For copper complexes, the pyrimidine bases interact in the neutral form as monodentate ligands. Octahedral geometries are proposed for all of these complexes.     

Are Unsaturated Isocyanides so Different from the Corresponding Nitriles?

Simple unsaturated and cyclopropylic isocyanides are synthesized by an efficient and simple approach. These compounds with gradually increasing distance between the unsaturated moiety and the isonitrile group are studied by UV photoelectron spectroscopy and quantum chemical calculations, and also compared to the corresponding nitriles. The first photoelectron band of the unsaturated compounds is linked to removal of an electron from the HOMO, which corresponds to CC multiple-bond ionization in antibonding interaction with the π-isocyanide bond (in the same plane) for conjugated systems, or in antibonding interaction with the pseudo-π-CH(2) group for isolated systems. For the 1-ethenyl derivatives, both cyano and isocyano groups act as a π-electron acceptor from the vinyl group, but the isocyano π system is much more strongly destabilized (ionization energies (IEs) shift to smaller values) by vinyl (3.12 eV) than the cyano π system is (2.70 eV). In comparison with the 1-ethynyl derivatives, a less pronounced destabilization (2.69 eV) of π(NC) by the ethynyl system (1.86 eV for π(CN)), and nearly the same order of magnitude of the energetic gap between the total antibonding (π(CC)-π(NC)) and the total bonding (π(CC)+π(NC)) IEs for ethenyl and ethynyl compounds are noted. The huge values of these last-named data for H(2)C=CH-NC (3.85 eV) and for HC≡C-NC (4.04 eV) reflect the strong interaction between the unsaturated carbon-carbon moiety and the isocyanide group, and thus more efficient conjugation than for the corresponding nitriles.     

Pre-organization of the core structure of E-selectin antagonists

A new class of N-acetyl-D-glucosamine (GlcNAc) mimics for E-selectin antagonists was designed and synthesized. The mimic consists of a cyclohexane ring substituted with alkyl substituents adjacent to the linking position of the fucose moiety. Incorporation into E-selectin antagonists led to the test compounds 8 and the 2'-benzoylated analogues 21, which exhibit affinities in the low micromolar range. By using saturation transfer difference (STD)-NMR it could be shown that the increase in affinity does not result from an additional hydrophobic contact of the alkyl substituent with the target protein E-selectin, but rather from a steric effect stabilizing the antagonist in its bioactive conformation. The loss of affinity found for antagonists 10 and 35 containing a methyl substituent in a remote position (and therefore unable to support to the stabilization of the core) further supports this hypothesis. Finally, when a GlcNAc mimetic containing two methyl substituents (52 and 53) was used, in which one methyl was positioned adjacent to the fucose linking position and the other was in a remote position, the affinity was regained.     

Traceless chemical ligations from O-acyl serine sites

Chemical ligation via O- to N-acyl transfer of O-acylated serine containing peptides affords serine containing native peptides via 8- and 11-membered cyclic transition states opening the door to a wide variety of potential applications to peptide elaboration. The feasibility of these traceless chemical ligations is feasible as supported by computation.     

Intersubband resonant enhancement of the nonlinear optical properties in asymmetric (CdS/ZnSe) based quantum wells

In this work, the linear and nonlinear optical properties are studied theoretically in asymmetric (CdS/ZnSe/BeTe)/(ZnSe/BeTe) quantum wells. The electronic states are calculated using the envelope wave function approximation and the intersubband transition energies are studied as a function of CdS and ZnSe well thicknesses as well as doping concentration. The optimum parameters carrying out the transition energy 0.8 eV (1.55 μm wavelength) are given. Results are presented for the linear, the third order nonlinear optical absorption and the refractive index changes in the studied heterostructure. Results show that the changes in the linear and the third order nonlinear optical absorption as well as refractive index change are as important as the temperature is high, the nonlinear terms must be taken into consideration especially near the resonance.