Alternating direction splitting for block Angular parallel optimization

We develop and compare three decomposition algorithms derived from the method of alternating directions. They may be viewed as block Gauss-Seidel variants of augmented Lagrangian approaches that take advantage of block angular structure. From a parallel computation viewpoint, they are ideally suited to a data parallel environment. Numerical results for large-scale multicommodity flow problems are presented to demonstrate the effectiveness of these decomposition algorithmims on the Thinking Machines CM-5 parallel supercomputer relative to the widely-used serial optimization package MINOS 5.4.This material is based on research supported by the Air Force Office of Scientific Research, Grants AFORS-89-0410 and F49620-1-0036, and by NSF Grants CCR-89-07671, CDA-90-24618, and CCR-93-06807. The work of the second author was supported partially by Grant 95.00732.CT01 from the Italian National Research Council (CNR).     

Excited states populated via nucleon transfer in the reaction32S +208Pb

The population strengths of excited states in nuclei produced via transfer reactions in the 185 MeV³²S +²⁰⁸Pb reaction have been investigated by heavy-ion- coincidence techniques. The cross sections extracted from the spectra, have been analyzed in the framework of the Complex WKB approximation theory.     

Br + Br2 atom exchange: an isotopically selective,laser-initiated,chemical study

The ratio of the Br + Br₂ halogen atom exchange rate, k₂, to the Br + HI reaction rate k₁, has been determined experimentally by using an isotopically selective, laser-initiated chemical reaction. At 294 K, k₂/k₁ = 4, and thus, k₂ = 4 × 10^?11 cm³ molecule^?1 s^?1.     

Low temperature crystallization behavior of TiO<Subscript>2</Subscript> derived from a sol–gel process

TiO₂ nanoparticles are widely used for many applications and an understanding of the crystallization behavior of TiO₂ is essential, so that heat treatment conditions can be optimized for particular applications. The effect of sol–gel synthesis conditions on the crystallization behavior of TiO₂ has, therefore, been investigated. Complete crystallization to the anatase phase (determined by XRD and TEM analysis) was achieved during drying of the synthesis product at 95 °C. The nanoparticles grew during heat treatment, reaching ∼10–15 nm in diameter with a heat treatment at 450 °C. Explanations are offered for the observed differences in the crystallization and particle growth behavior of TiO₂ synthesized under various conditions.     

Vibrational distributions of the CO(v) products of the C2H2 + O(3P) and HCCO + O(3P) reactions studied by FTIR emission

The C2H2 + O(3P) and HCCO + O(3P) reactions are investigated using Fourier transform infrared (FTIR) emission spectroscopy. The O(3P) radicals are produced by 193 nm photolysis of an SO2 precursor or microwave discharge in O2. The HCCO radical is either formed in the first step of the C2H2 + O(3P) reaction or by 193 nm photodissociation of ethyl ethynyl ether. Vibrationally excited CO and CO2 products are observed. The microwave discharge experiment [C2H2 + O(3P)] shows a bimodal distribution of the CO(v) product, which is due to the sequential C2H2 + O(3P) and HCCO + O(3P) reactions. The vibrational distribution of CO(v) from the HCCO + O(3P) reaction also shows its own bimodal shape. The vibrational distribution of CO(v) from C2H2 + O(3P) can be characterized by a Boltzmann plot with a vibrational temperature of approximately 2400 +/- 100 K, in agreement with previous results. The CO distribution from the HCCO + O(3P) reaction, when studied under conditions to minimize other processes, shows very little contamination from other reactions, and the distribution can be characterized by a linear combination of Boltzmann plots with two vibrational temperatures: 2320 +/- 40 and 10 300 +/- 600 K. From the experimental results and previous theoretical work, the bimodal CO(v) distribution for the HCCO + O(3P) reaction suggests a sequential dissociation process of the HC(O)CO++ --> CO + HCO; HCO --> H + CO.     

meso-Me2Si(1-indenyl)2ZrCl2/methylalumoxane catalyzed polymerization of the ethylene to ethyl-branched polyethylene

The meso ansa zirconocene with dimethylsilyl bridge, activated by methylalumoxane, catalyses the ethylene polymerization, producing ethyl-branched polyethylene. With respect to the polymers obtained with the previously investigated meso zirconocenes, we have found higher branching amount and lower molecular weight. The rapid β-H transfer from the growing chain to the coordinated monomer could account for both these features of the polymer. The investigation on the structural parameters of the complex, through X-ray diffraction analysis, and on the electrophilicity of the cationic center, through NMR experiments, suggests, as a possible rationalization of this behavior, the obstruction in the inward site.     

States of water,surface and rheological characterisation of a new biohydrogel as articular cartilage substitute

PVA based hydrogel was synthesised using, as crosslinking agent, trisodium trimetaphosphate (STMP) and its morphology was modified inducing a microporous structure to obtain potential substitutes for cartilage tissue. The hydrogel was characterised by Infrared Spectroscopy combined with Time of flight mass spectrometry (ToF‐SIMS) that confirmed the successful occurrence of crosslinking reaction, the hyphotised crosslinking arm and its homogeneous distribution. The mechanical spectra of the fully hydrated samples confirmed covalently crosslinked systems with a rheological behaviour similar to that of tibial cartilage. Further analysis in terms of water content measurements, thermal stability and cytotoxicity confirmed the applicability of such a hydrogel as cartilage substitute. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis of hydrophilic isotactic polypropylenes promoted by metallocene catalysts

In this paper, the synthesis of isotactic polypropylenes (i‐PP) modified with ? OH groups in sides (iPP‐OH), by combination of polyinsertion ansa‐metallocene catalysis and ring opening of propene oxide (PO), is described. i‐PP sequences interrupted by isolated ethylene/p‐methylstyrene units forms the backbone. This enchainment is obtained by controlled copolymerization of propene with ethylene and p‐methylstyrene comonomers in the presence of rac‐ethylenebis(1‐indenyl)zirconiumdichloride/methylalumoxane system. The metallation reaction of the p‐methyl group with sec‐BuLi generates an anionic center that can be reacted with PO. The iPP‐OH is the result of the monoaddition reaction of PO followed by hydrolysis with acidified methanol. By changing experimental conditions in the backbone synthesis, a tuned number of the functionalizable sites as well as polypropylene sequence lengths can be obtained. As a consequence, iPP samples with a different number of ? OH groups for the backbone can be synthesized after the PO monoaddition reaction. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 7008–7013, 2006