A simple and stable scale-similarity model for large Eddy simulation: Energy balance and existence of weak solutions

In averaging the Navier-Stokes equations, the problem of closure arises. Scale-similarity models address closure by (roughly speaking) extrapolation from the (known) resolved scales to the (unknown) unresolved scales. In a posteriori tests, scale-similarity models are often the most accurate but can prove to be unstable when used in a numerical simulation. In this report, we consider the scale-similarity model given by

. We prove it is stable (solutions satisfy an energy inequality) and deduce from that the existence of weak solutions of the model.     

Measurements of branching fraction, polarization, and charge asymmetry of B(+/-)-->rho(+/-)rho(0) and a search for B(+/-)-->rho(+/-)f(0)(980)

We measure the branching fraction (B), polarization (f(L)), and CP asymmetry (A(CP)) of B(+/-)-->rho(+/-)rho(0) decays and search for the decay B(+/-)-->rho(+/-)f(0)(980) based on a data sample of 231.8 x 10(6) Upsilon(4S)-->BB decays collected with the BABAR detector at the SLAC PEP-II asymmetric-energy B factory. In B(+/-)-->rho(+/-)rho(0) decays we measure B=(16.8+/-2.2+/-2.3) x 10(-), f(L)=0.905+/-0.042(-0.027)(+0.023), and A(CP)=-0.12+/-0.13+/-0.10, and find an upper limit on the branching fraction of B(+/-)-->rho(+/-)f(0)(980)(-->pi(+)pi(-)) decays of 1.9 x 10(-6) at 90% confidence level.     

Observation of B+ --> K0K+ and B0 --> K0K0

We report observations of the b --> d penguin-dominated decays B+ --> K0K+ and B0 --> K0K0 in 316 fb(-1) of e+ e- collision data collected with the BABAR detector. We measure the branching fractions B(B+ --> K0K+) = (1.61+/-0.44+/-0.09) x 10(-6) and B(B0 --> K0K0 = (1.08+/-0.28+/-0.11) x 10(-6) and the CP-violating charge asymmetry A(CP)(K0K+) = 0.10+/-0.26+/-0.03. Using a vertexing technique previously employed in several analyses of all-neutral final states containing kaons, we report the first measurement of time-dependent CP-violating asymmetries in B0 --> K(S)0K(S)0, obtaining S = -1.28(-0.73-0.16)(+0.80+0.11) and C = -0.40+/-0.41+/-0.06. We also report improved measurements of the branching fraction B(B+ --> K0 pi+) = (23.9+/-1.1+/-1.0) x 10(-6) and CP-violating charge asymmetry A(CP)(K0 pi+) = -0.029+/-0.039+/-0.010.     

Orientation of a nanocylinder at a fluid interface

A nanocylinder placed on a fluid interface can assume an end-on or side-on orientation, or it can immerse itself in the surrounding bulk phases. Any of these orientations can satisfy a mechanical force balance when the particle is small enough that gravitational effects are negligible. The orientation is determined by the surface energies of the fluid-solid, fluid-vapor, and vapor-solid surfaces. A comparison of the energy of each state allows phase diagrams to be defined in terms of the scaled aspect ratio x=2L/pir and the contact angle thetao, where L and r denote the nanocylinder length and radius, respectively. Line tension can also influence the orientations by changing the equilibrium contact angle theta and by increasing the energetic cost of the contact line. Phase diagrams accounting for positive line tensions Sigma are also constructed. These phase diagrams can be divided into two classes. In the first, over some range of x and Sigma, nanocylinders can be driven from side-on to end-on orientations with increasing Sigma. This transition terminates at a triple point where the side-on, end-on, and immersed energies are the same. In the second class, there is no triple point and, for a range of Sigma values, nanocylinders of all aspect ratios x prefer an end-on orientation. In all cases, for high enough Sigma, line tension drives a wetting transition similar to that already noted in the literature for spherical particles. The zero line tension predictions are compared favorably to experiment, in which functionalized gold nanowires made by template synthesis are spread at aqueous-gas interfaces, immobilized using a gel-fixation technique, and observed by scanning electron microscopy. The small aspect ratio particles (disks) were in an end-on configuration, while the longer nanowires were in a side-on orientation, in agreement with the theory.     

Experimental (FT-IR, FT-Raman, 1H NMR) and theoretical study of magnesium, calcium, strontium, and barium picolinates

The experimental IR, Raman, and 1H NMR spectra of picolinic acid, as well as magnesium, calcium, strontium, and barium picolinates were registered, assigned and studied. Characteristic changes in the spectra of metal picolinates in comparison with the spectrum of ligand were observed, which lead to the conclusion that perturbation of the aromatic system of picolinates increases along with the series Mg-->Ca-->Sr-->Ba. Theoretical structures of beryllium and magnesium picolinates, as well as theoretical IR spectrum of magnesium picolinate were calculated in B3PW91/6-311++G(d, p) level. On the basis of calculated bond lengths in pyridine ring geometric, aromaticity indexes HOMA were calculated. The idea of these indexes is based on the fact that the essential factor in aromatic stabilization is the pi delocalization manifested in: planar geometry, equalization of the bond lengths and angles, and symmetry. The decidedly lower value of HOMA for magnesium picolinate (i.e. 0.545; 0.539) than that for beryllium picolinate (i.e. 0.998; 0.998) indicate higher aromatic properties of Be picolinate than of Mg picolinate. The comparison of theoretical and literature experimental structures of magnesium picolinate was done. The experimental structure contains two water molecules, so the calculations for hydrated magnesium picolinate were carried on, and the influence of coordinated water molecule on the structure of picolinates was discussed. The HOMAs for hydrated experimental and calculated Mg picolinate amount to 0.870; 0.743, and 0.900; 0.890, respectively, whereas for anhydrous structure, it is as described above, i.e. 0.545; 0.539. Thus, the calculations clearly showed that water molecules coordinated to the central atom weakens the effect of metal on the electronic system of ligand.     

Multidisciplinary characterization of novel emulsion polymers

A series of novel emulsion styrene‐butadiene copolymer blends were characterized using a multidisciplinary approach involving both analytical and rheological measurements. The blends were composed of 50/50 w/w high molecular weight (ca. 800,000 Da) ESBR and low molecular weight (ca. 200,000 Da) ESBR, each component having a different bound styrene level. When the difference in bound styrene between the two components was greater than 18%, a two phase co‐continuous morphology was observed by scanning probe microscopy, consistent with two glass transitions measured by temperature modulated DSC. Molecular weight and molecular weight distributions were characterized by both size exclusion chromatography and thermal field flow fractionation with multiangle light scattering detection. ThFFF was unique in its ability to detect ultra‐high molecular weight (> 10⁷ Da) fractions suggesting that traditional SEC often under‐estimates polymer molecular weight. Blending polymers of different molecular weights and styrene levels resulted in reduced molecular weight between entanglements which, based on rheological measurements, would be expected to improve processability.     

A Study of Porous and Surface Properties of Nickel-Molybdenum Catalyst Incorporated on Alumina Modified with Sodium and Magnesium Ions

A series of nickel-molybdenum samples supported on alumina modified with sodium or magnesium ions was studied by the BET method, differential thermal analysis (DTA) and IR spectroscopy to determine their surface properties, pore volume and distribution. Modification with sodium and magnesium ions causes a decrease of the surface area of the nickel-molybdenum catalysts. The decrease proceeds with increasing concentration of the modifying ions. Incorporation of these ions does not change the type of catalyst pores (the ink-bottle or bottle types), yet it affects the size and distribution of pores. It was found that sodium ions prevent from the formation of aluminum molybdate, while magnesium ions increase the thermal stability of the catalyst.     

Structure and Texture of Nickel-Molybdenum Catalysts on Alumina Support Modified with Fluoride or Chloride Ions

The performed study involves measurements of a specific surface area via a BET method, of the pore volume, FT-IR, and a derivatographic study of a series of Al₂O_3-supported nickel-molybdenum catalysts modified with fluoride and chloride ions. It was found that fluoride ions lead to a decrease in the specific surface area of catalysts, whereas chloride ions have a small effect on this parameter. Modification does not change the type of pores of the catalysts, yet it affects their size and increases concentration of OH groups adsorbed on the surface of the catalysts relative to the carrier and the unmodified catalyst. Addition of fluoride ions decreases the thermal stability of the catalyst, whereas chloride ions does not cause any change.