Polyoxometalates matrixed into surfactants: synthesis, characterizations, and conformations of surfactants

We synthesized two surfactant-encapsulated polyoxometalate (POM) clusters (SECs), (DODA)(15)[H(3)Mo(57)V(6)(NO)(6)O(189)(H(2)O)(12)(VO)(6)].13H(2)O (SEC-2, DODA: dimethyldioctadecyl ammonium) and (DODA)(12)[Eu(H(2)O)P(5)W(30)O(110)].28H(2)O (SEC-3). SECs were characterized in detail by elemental analysis, UV-Vis absorption spectroscopy, FTIR, 1H NMR, thermogravimetric analysis, Langmuir isotherms, and powdered X-ray diffractions. SEC-2 can form a stable monolayer at the air-water interface. SEC-2 and SEC-3 possess a layered structure with periodicities of 3.8 and 5.05 nm, respectively. Alkyl chains in SEC-2 are disordered, but SEC-3 is indicative of well-ordered alkyl chains. According to the simplified structural analysis for SEC-2 and SEC-3, DODAs occupy areas of 1.12 and 0.589 nm(2) on the surface of the POMs, which are characteristic of the liquid-like and crystalline-like phases for DODA, respectively. The different conformations of DODAs then lead to the different packing structures of SECs. This work is aiming to control the organizational structures of the POM-based materials by selecting the appropriate POMs.     

Molecular structure of Hf(BH4)4 investigated by quantum mechanical calculations and gas-phase electron diffraction

The structure of the gaseous hafnium tetrakis(tetrahydroborate) molecule, Hf(BH4)4, has been investigated by detailed quantum mechanical calculations and by analysis of its gas electron-diffraction (GED) pattern. The ground-state geometry possesses T symmetry with all of the triply-bridged BH4 groups twisted equally about the Hf...B-H axes. Salient structural parameters (ra distances, r angles) deduced from the GED pattern by the SARACEN method were: r(Hf...B) 231.4(2), r(Hf-Hb) 221.5(7), r(B-Hb) 127.6(5), r(B-Ht) 121(1) pm, Hf...B-Hb 69.4(3), Hb-B-Hb 108.4(4), Hb-B-Ht 110.6(3), B...Hf...B-Hb 166(1) degrees. A notable feature is the large magnitude of the Hf...B and Hf-Hb anharmonicity parameters, attributed to the fluxional hydrogen atom exchange process. The properties are compared with those of related tetrahydroborates..     

Random-wavelength solid-state laser

The spectral properties of a diode-pumped Yb:Y2O3 ceramic laser are reported. We show experimentally that the instantaneous emission wavelengths of the laser change randomly with time, whereas its emission has fixed well-defined transverse modes. The central wavelength of the laser emission also shifts prominently with the increase of intracavity light intensity. It is found that the spectral properties of the laser can be explained well based on the strong reabsorption of light in the gain medium.     

Diagnostics of laser-induced plasma with soft X-ray (13.9 nm) bi-mirror interference microscopy

X-ray interference microscopy diagnostics of a nanosecond-pulse pumped Al (Z=13) plasma are presented. A transient picosecond Ni-like Ag X-ray laser (13.9 nm) is used as the probe beam and a wavefront division bi-mirror interferometer is adopted as the diagnosis tool. From the fringe shifts, the two-dimensional plasma density profile at 1 ns after the peak of the heating pulse is deduced. Opposite fringe shifts during the plasma development are observed and possible explanations for this behavior are discussed. This study will contribute to the validation of 1D and 2D hydrodynamic codes as well as to the better understanding of the physics during the development of laser produced plasmas. PACS 41.50.+h; 41.85.Ew; 42.55.Vc     

Synthesis and photocatalytic properties of highly crystalline and ordered mesoporous TiO2 thin films

Highly crystalline and ordered mesoporous TiO2 thin films have been synthesized by stabilization of the mesostructure with confined carbon; the films exhibit 2.5% photoconversion efficiency for the water photolysis at zero-bias and Xe lamp illumination of 40 mW cm(-2).     

Zeolite nanoparticles with immobilized metal ions: isolation and MALDI-TOF-MS/MS identification of phosphopeptides

Metal-ion-immobilized zeolite nanoparticles have been applied for the first time to isolate phosphopeptides from tryptic beta-casein digest; the phosphopeptides enriched on the modified zeolite nanoparticles could be effectively identified by MALDI-TOF-MS/MS.     

Real solutions of the equation ϕ(X)=1/nJ n

For ann x n real matrixX, let ?(X)=X ο (X ^?1) ^T , where ο stands for the Hadamard (entrywise) product. SupposeA, B, C andD aren x n real nonsingular matrices, and among them there are at least one solutions to the equation ?(X)=1/nJ _n . An equivalent condition which enable $M = \left( {\begin{array}{*{20}c} A & B \\ C & D \\ \end{array} } \right)$ become a real solution to the equation ?(X)=1/2nJ _2n , is given. As applications, we get new real solutions to the matrix equation ?(X)-1/2nJ _2n by applying the results of Zhang, Yang and Cao [SIAM. J. Matrix Anal. Appl, 21 (1999), pp: 642–645] and Chen [SIAM. J. Matrix Anal. Appl, 22 (2001), pp:965–970]. At the same time, all solutions of the matrix equation ?(X)=1/4J ₄ are also given.     

The predicted barrier effects in the proximity of tall buildings

A ray model is developed and validated for the prediction of the insertion loss of barriers that are placed in front of a tall building in high-rise cities. The model is based on the theory of geometrical acoustics for sound diffraction at the edge of a barrier and multiple reflections by the barrier and fa?ade surfaces. It is crucial to include the diffraction and multiple reflection effects in the ray model, as they play important roles in determining the overall sound pressure levels for receivers located between the fa?ade and barrier. Comparisons of the ray model with indoor experimental data and wave-based boundary element formulation show reasonably good agreement over a broad frequency range. Case studies are also presented that highlight the significance of positioning the barrier relative to the noise-sensitive receivers in order to achieve improved shielding efficiency of the barrier.     

Magnetic alignment in nominally non-magnetic hexagonal metal hydrides: NMR

Powders of three hexagonal metal-hydrides or -deuterides are found to align in 4.4–8.3 T magnetic fields used for NMR. The field-alignment is unexpected, since all three systems have very small susceptibilities, as demonstrated by sharp NMR lines. The extent of alignment runs from nearly complete to barely detectable in ZrBe₂(H,D)_x, LuD₃, and YD₃, respectively. The preferred alignment direction in ZrBe₂(H,D)_x is with the crystallites’ c-axis perpendicular to B, while the c-axis and B tend to be parallel in LuD₃ and YD₃. The susceptibilities χ_|| and χ are determined from bulk magnetization measurements in aligned ZrBe₂H_1.4 powder. The alignment must be considered for proper analysis of NMR spectra in these and related materials.     

High precision measurement of the superallowed 0+ --> 0+ beta decay of 22Mg

The half-life, 3.8755(12) s, and superallowed branching ratio, 0.5315(12), for 22Mg beta decay have been measured with high precision. The latter depended on gamma-ray intensities being measured with an HPGe detector calibrated for relative efficiencies to an unprecedented 0.15%. Previous precise measurements of 0+ --> 0+ transitions have been restricted to the nine that populate stable daughter nuclei. No more such cases exist, and any improvement in a critical Cabibbo-Kobayashi-Maskawa unitarity test must depend on precise measurements of more exotic nuclei. With this branching-ratio measurement, we show those to be possible for T(z)=-1 parents. We obtain a corrected Ft value of 3071(9) s, in good agreement with expectations.