Synthesis,structure, and properties of LaSrCuGaO5

The new brownmillerite-related compound, LaSrCuGaO₅, has been synthesized and characterized. It crystallizes in the orthorhombic non-centrosymmetric space group Ima2. The unit cell dimensions are a = 16.383(1) Å, b = 5.5293(7) Å, c = 5.3275(6) Å. The structure is related to perovskite but contains ordered oxygen vacancies within the two-dimensional gallium oxygen layers resulting in tetrahedral coordination of the gallium cations. Other important structural features include buckled copper-oxygen planes, and disorder of the lanthanum and strontium cations over the A-site. Accurate lattice constant measurements reveal an a-axis expansion of 0.17 Å when doped with strontium La_1–xSr_1+xCuGaO₅ (x_max = 0.13). Magnetic susceptibility measurements demonstrate that the compound remains paramagnetic to 4 K.     

Synthesis, characterization, and crystal structures of two strained cyclic diacetylenes and their precursors

The synthesis, characterization, and crystal structures of two novel strained cyclic diacetylenes are reported. A discussion is presented about the relative bond distances of the diacetylenes compared to a previously reported strained cyclic diacetylene to further determine the degree of aromaticity of that compound. 1,2:5,6:9,10:13,14-Tetrabenzo-3,7,11,15,17-pentadehydro[18] annulene (5) is triclinic, P ^–1, with = 9.489(5), b = 10.550(5), c = 12.155(6) Å, = 100.50(4), = 106.50(4), = 100.85(4)°. 1,2:5,6:9,10:13,14:17,18-Pentabenzo-3,7,11,15,19,23,25-heptadehydro[26]annulene (7) is triclinic, P ^–1, with a = 9.611(2), b = 10.388(3), c = 15.963(3) Å, = 88.67(2), = 76.25(1), = 68.69(2). In addition, two precursors of 5, 3 and 4 which have a helical twist, are reported. [1,2-ethynediyl-bis(2,1-phenylene-2,1-ethynediyl-2,1-phenylene-2,1-ethynediyl]bis[trimethyl-silane] (3) is monoclinic, P2₁/c, with a = 13.682(4), b = 9.787(2), c = 13.448(4) Å, = 112.37(2)°. 1,1-(1,2-ethynyldiyl)bis[2-[(2-ethynylphenyl)ethynyl]-benzene (4) is monoclinic, P2₁/n, with a = 15.951(3), b = 3.999(1), c = 18.168(4) Å, = 99.05(3)°.     

Current literature in mass spectrometry

In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of mass spectrometry. Each bibliography is divided into 11 sections: 1 Reviews; 2 Instrumental Techniques & Methods; 3 Gas Phase Ion Chemistry; 4 Biology/Biochemistry: Amino Acids, Peptides & Proteins; Carbohydrates; Lipids; Nucleic Acids; 5 Pharmacology/Toxicology; 6 Natural Products; 7 Analysis of Organic Compounds; 8 Analysis of Inorganics/Organometallics; 9 Surface Analysis; 10 Environmental Analysis; 11 Elemental Analysis. Within each section, articles are listed in alphabetical order with respect to author (4 Weeks journals - Search completed at 29th. June 2007).     

Excited electronic states and internal conversion in cyanocobalamin

Cyanocobalamin (CNCbl) is a paradigm system for the study of excited electronic states and biological cofactors including the B12 vitamers. The photophysics of CNCbl has been thoroughly investigated using both ultrafast spectroscopy and time dependent density functional theory (TD-DFT). Herewe review the spectroscopic and theoretical investigations of CNCbl with emphasis on the nature of S1, the lowest excited electronic state, and extend the spectroscopic measurements to include the ultraviolet region of the spectrum. Ultrafast transient absorption measurements in the visible αβ band region and in the midinfrared led to assignment of the S1 state to a ligand-to-metal charge transfer (LMCT) with lengthened axial bonds and a ~3 kcal/mol barrier for internal conversion to the ground state. The present measurements encompassing the γ band region of the spectrum provide further support for the assignment of the S1 state. The experiments are in good agreement with the results of TD-DFT calculations which confirm the expected lengthening of the axial bonds in S1 and account for the observed barrier for internal conversion back to the ground state.     

NONCOOPERATIVE MANAGEMENT OF THE NORTHEAST ATLANTIC COD FISHERY: A FIRST MOVER ADVANTAGE

The point of departure for this analysis is Bjørndal and Lindroos [2012], who developed an empirical bioeconomic model to analyze cooperative and noncooperative management of Northeast Atlantic cod. In their analysis, only constant strategies were analyzed for noncooperative games. In this paper, nonconstant strategies are considered. Moreover, the fishery in question is characterized by cooperative management. What may happen in the real world is that one nation breaks the cooperative agreement by fishing in excess of its quota. Often, it takes time for the other agent to detect this and respond. In this paper, we allow this kind of delayed response into a two‐agent noncooperative game so that, if country 2 exceeds its quota, there will be a time lag before this is detected by country 1; moreover, there may also be a delay until country 1 is able to respond. Results show that the outcome critically depends on the length of these two lags as well as initial conditions.     

Microwave Synthetic Routes for Shape-Controlled Catalyst Nanoparticles and Nanocomposites

The use of microwave irradiation for the synthesis of inorganic nanomaterials has recently become a widespread area of research that continues to expand in scope and specialization. The growing demand for nanoscale materials with composition and morphology tailored to specific applications requires the development of facile, repeatable, and scalable synthetic routes that offer a high degree of control over the reaction environment. Microwave irradiation provides unique advantages for developing such routes through its direct interaction with active reaction species, which promotes homogeneous heat distribution, increased reaction rates, greater product quality and yield, and use of mild reaction conditions. Many catalytic nanomaterials such as noble metal nanoparticles and intricate nanocomposites have very limited synthetic routes due to their extreme temperature sensitivity and difficulty achieving homogeneous growth. This work presents recent advances in the use of MW irradiation methods to produce high-quality nanoscale composites with controlled size, morphology, and architecture.     

Narcissistic Self‐Sorting in Self‐Assembled Cages of Rare Earth Metals and Rigid Ligands

Highly selective, narcissistic self‐sorting can be achieved in the formation of self‐assembled cages of rare earth metals with multianionic salicylhydrazone ligands. The assembly process is highly sensitive to the length of the ligand and the coordination geometry. Most surprisingly, high‐fidelity sorting is possible between ligands of identical coordination angle and geometry, differing only in a single functional group on the ligand core, which is not involved in the coordination. Supramolecular effects allow discrimination between pendant functions as similar as carbonyl or methylene groups in a complex assembly process.     

Nonlinear static behavior of a cantilever subjected to an inclined follower force

The nonlinear static behavior of a linearly elastic cantilever subjected to a nonconservative force of the follower type is formulated and examined. The formulation allows for finite rotations with small strains (the elastica). Exact solutions are found. The investigation is greatly facilitated by means of a phase plane analysis in which the phase plane variables are related to slope angle and bending moment. Some of the interesting and unusual effects occurring in this system are discussed and illustrated with a set of deflection curves for a typical case.Nomenclature x, y coordinates of a point on the deformed elastic axis - slope angle - s arc length - L length of beam (assumed constant) - x _L , y _L , _L values of x, y, at s=L - P applied force - constant angle between P and end tangent - angle between P and the horizontal - EI beam stiffness (assumed constant) - u, dimensionless variables defined by (7) and (8) - c ² load parameter defined by (10) - k, transformation parameters defined by (21) - F(, k), E(, k) elliptic integrals of the first and second kind - argument of elliptic integrals - ₀, ₁ values of at u=0 and u=1 - m, n positive integers - N mode number     

Suppression of silicon (001) surface reactivity using a valence-mending technique

It is experimentally shown that, by terminating dangling bonds on Si(001) with a monatomic layer of selenium, the chemical reactivity of the surface is suppressed. In the case of nickel silicidation, transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy reveal that Se passivation suppresses Ni silicidation by over 100 °C as compared to the bare Si(001) surface. The formation of Ni subsilicide (Ni₂Si) is not observed on Se-passivated Si(001). This interfacial silicidation appears to be linked with changes in electrical behavior of the interface between titanium and Se-passivated Si(001), which we reported previously.