Mask Formulas for Cograssmannian Kazhdan-Lusztig Polynomials

We give two constructions of sets of masks on cograssmannian permutations that can be used in Deodhar’s formula for Kazhdan–Lusztig basis elements of the Iwahori–Hecke algebra. The constructions are respectively based on a formula of Lascoux–Schützenberger and its geometric interpretation by Zelevinsky. The first construction relies on a basis of the Hecke algebra constructed from principal lower order ideals in Bruhat order and a translation of this basis into sets of masks. The second construction relies on an interpretation of masks as cells of the Bott–Samelson resolution. These constructions give distinct answers to a question of Deodhar.     

Relaxation effects during core ionization in metal—metal-bonded complexes

Using the ligand group shift model to calculate metal binding energies (BE's), comparisons of BE(calc) and BE(obs) values reveal a correlation between relaxation energy and the extent of metal—metal bonding. No significant difference in relaxation energy is detected between monometal complexes and the dipalladium complexes which contain a single MM bond. However, substantially larger relaxation energies (1–2 eV) relative to monometal complexes are found for multiply MM-bonded complexes. The magnitude of the additional relaxation energy is in the range expected on the basis of comparisons with other systems.     

Proton-hole states in 57Co studied with the 58Ni(d, 3He) 57Co reaction at 78 MeV

The ⁵⁸Ni(d, ³He)⁵⁷Co reaction was measured at a bombarding energy of 78 MeV. Energy levels up to 7.0 MeV excitation energy in ⁵⁷Co were studied. Angular distributions of the ³He particles, corresponding to transitions to the ground state and to 42 excited states in ⁵⁷Co, were analyzed in the range of θ_lab = 2.7° to 25°. Exact finite-range DWBA calculations were employed to extract l-values and spectroscopic factors. Shell-model calculations were carried out in an fp-shell model space. In addition, calculations of the energy levels in ⁵⁷Co were performed in the SU(6) particle-vibration model (PTQM). Satisfactory agreement is observed between the experimental results and both theoretical predictions.     

Semicrystalline blends of polyethylene and isotactic polypropylene: Improving mechanical performance by enhancing the interfacial structure

The low‐temperature mechanical behavior of semicrystalline polymer blends is investigated. Isotactic polypropylene (iPP) is blended with both Zeigler–Natta polyethylene (PE) and metallocene PE. Transmission electron microscopy (TEM) on failed tensile bars reveals that the predominate failure mode in the Zeigler–Natta blend is interfacial, while that in the metallocene blend is failure of the iPP matrix. The observed change in failure mode is accompanied by a 40% increase in both tensile toughness and elongation at −10 °C. We argue that crystallite anchoring of interfacially entangled chains is responsible for this dramatic property improvement in the metallocene blend. The interfacial width between PE and iPP melts is approximately 40 Å, allowing significant interfacial entanglement in both blends. TEM micrographs illustrate that the segregation of low molecular weight amorphous material in the Zeigler–Natta blend reduces the number and quality of crystallite anchors as compared with the metallocene blend. The contribution of anchored interfacial structure was further explored by introducing a block copolymer at the PE/iPP interface in the metallocene blend. Small‐angle X‐ray scattering (SAXS) experiments show the block copolymer dilutes the number of crystalline anchors, decoupling the interface. Increasing the interfacial coverage of the block copolymer reduces the number of anchored interfacial chains. At 2% block copolymer loading, the low‐temperature failure mode of the metallocene blend changes from iPP failure to interfacial failure, reducing the blend toughness and elongation to that of the Zeigler–Natta blend. This work demonstrates that anchored interfacial entanglements are a critical factor in designing semicrystalline blends with improved low‐temperature properties. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 108–121, 2000     

Electrical study of cathodic activation and relaxation of La0,80Sr0,20MnO3

The effect of cathodic activation of sprayed La_0.8Sr_0.2MnO₃ (LSM) films has been studied by electrochemical spectroscopy impedance (EIS). LSM powder was prepared by a citrate route and X-ray diffraction analyses show a complete LSM crystallization without La₂O₃ or La(OH)₃ as side products. Porosity and grain size estimated from scanning electronic microscopy gave values of 33% and 100 nm, respectively. EIS measurement was performed on a Pt/yttria-stabilized zirconia/LSM cell before and after a cathodic current load (300 mA/cm²) on LSM electrode. The relaxation process, which is time-dependent, has been investigated. A drastic decrease of the electrode resistance was noticed just after applying the cathodic current, but after 9 h at optimized valence configuration in air at 850 °C, the recorded polarization resistance gradually enhanced until it almost reached the initial value. The resulting diagrams have been fitted using a Gerischer associated with a resistor and constant phase elements. This simple method has permitted us to observe that only the electrode interfaces are modified by a cathodic activation and the microstructure remains nearly constant.     

Transition probabilities in 134Pr: a test for chirality in nuclear systems

Exited states in 134Pr were populated in the fusion-evaporation reaction 119Sn(19F,4n)134Pr. Recoil distance Doppler-shift and Doppler-shift attenuation measurements using the Euroball spectrometer, in conjunction with the inner Bismuth Germanate ball and the Cologne plunger, were performed at beam energies of 87 MeV and 83 MeV, respectively. Reduced transition probabilities in 134Pr are compared to the predictions of the two quasiparticle + triaxial rotor and interacting boson fermion-fermion models. The experimental results do not support the presence of static chirality in 134Pr underlying the importance of shape fluctuations. Only within a dynamical context the presence of intrinsic chirality in 134Pr can be supported.     

Understanding the polarity of ionic liquids

The polarities of a wide range of ionic liquids have been determined using the Kamlet-Taft empirical polarity scales α, β and π*, with the dye set Reichardt's Dye, N,N-diethyl-4-nitroaniline and 4-nitroaniline. These have been compared to measurements of these parameters with different dye sets and to different polarity scales. The results emphasise the importance of recognising the role that the nature of the solute plays in determining these scales. It is particularly noted that polarity scales based upon charged solutes can give very different values for the polarity of ionic liquids compared to those based upon neutral probes. Finally, the effects of commonplace impurities in ionic liquids are reported.     

Fullerol cluster formation in aqueous solutions: implications for environmental release

Here we report on the characteristics of fullerol in aqueous systems and examine those conditions that affect the physical state of fullerol in water. When dispersed in water fullerol forms polydisperse suspensions characterized by both small ( approximately 100 nm) and large associations (>500 nm). These clusters are charged with a point of zero net proton charge (PZNPC) of approximately pH 3. Though the size of fullerol clusters may be manipulated through changes in solution chemistry, principally pH, cluster formation cannot be entirely prevented through these means alone. The fullerol cluster structure is amorphous as revealed by X-ray diffraction analysis, which is in contrast to clusters of C(60) formed through dissolution in toluene and then introduced into water through sonication (SONnC(60)). The SONnC(60) clusters are crystalline with a structure similar to that of unreacted C(60) crystals.     

Di­methyl(2‐methyl­phenyl)­ammonium hydroxo­tris­(penta­fluoro­phenyl)­borate

In the title compound, [(CH₃)₂(C₇H₇)NH][(C₆F₅)₃B(OH)] or C₉H₁₄N⁺·C₁₈HBF₁₅O^?, the distorted tetrahedral borate anions are strongly hydrogen bonded to the substituted ammonium cations. The N?O separation in the N—H?O hydrogen bond is 2.728 (3) Å.