Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

Unique copolymers comprising propylene, ethylene and/or one or more unsaturated comonomers are characterized as having: at least one, preferably more than one, of the following properties: (i) 13C NMR peaks corresponding to a regio-error at about 14.6 and about 15.7 ppm, the peaks of about equal intensity, (ii) a B-value greater than about 1.4 when the comonomer content of the copolymer is at least about 3 wt%, (iii) a skewness index, S?ix?, greater than about -1.20, (iv) a DSC curve with a Tme that remains essentially the same and a Tmax that decreases as the amount of comonomer in the copolymer is increased, and (v) an X-ray diffraction pattern that reports more gamma-form crystals than a comparable copolymer prepared with a Ziegler-Natta catalyst. These polypropylene polymers are made using a nonmetallocene, metal-centered, heteroaryl ligand catalyst. These polymers can be blended with other polymers, and are useful in the manufacture of films, sheets, foams, fibers and molded articles.

Isotactic propylene copolymers, their preparation and use

Embodiments of the present invention relate to article comprising 1) a functionalized component, 2) tackifier, and 3) an olefin polymer comprising one or more C3 to C40 olefins, optionally one or more diolefins, and less than 5 mole % of ethylene having a Dot T-Peel of 1 Newton or more, a branching index (g′) of 0.95 or less measured at the Mz of the polymer; and an Mw of 100,000 or less; where the functional component is selected from the group consisting of functionalized polymers, functionalized oligomers and beta nucleating agents; and where the Gardner color of the adhesive does not change by more than 7 Gardner units when the adhesive has been heat aged at 180° C. for 48 hours as compared to the Gardner color of the unaged composition.

Polyolefin adhesive compositions and articles made therefrom

The present invention relates to plasticized polyolefin compositions comprising a polyolefin and a non-functionalized hydrocarbon plasticizer.

Plasticized polyolefin compositions

This invention provides a fuel oil composition comprising a major amount of a fuel oil and a minor amount of an additive comprising at least one fuel oil-soluble alkyl or alkoxy aromatic compound wherein at least one group independently selected from alkyl and alkoxy groups of 1 to 30 carbon atoms is attached to an aromatic nucleus and at least one carboxyl group and optionally one or two hydroxyl groups are attached to the aromatic nucleus; a process for the preparation of such a fuel oil composition; and the use of such a fuel oil composition as fuel in a compression-ignition engine for controlling wear rate in the fuel injection system thereof.

Fuel oil compositions

An adhesive blend is described that can include a semi-crystalline copolymer of propylene and at least one comonomer selected from the group consisting of ethylene and at least one C4 to C20 α-olefin, the copolymer having a weight average molecular weight (Mw) from about 15,000 to about 200,000; a melt index (MI) from about 7dg/min to about 3000 dg/min as measured by ASTM D 1238(B), and a (Mw/Mn) of approximately 2. Various production processes are also described. Also described are adhesive compositions and methods for making adhesive compositions having polymers or polymer blends with melt flow rates (MFRs) equal to and above 250 dg/min at 230NC. Certain specific embodiments of the invention involve the use of a free radical initiator, e.g., a peroxide.

Polypropylene-based adhesive compositions

Polyoxyalkylene esters, ethers, ester/ethers or mixtures thereof containing two C 10 -C 30 linear saturated alkyl groups and a polyoxy (C 1 -C 4 alkylene glycol group of molecular weight 200 to 5,000 have been found to be effective distillate fuel flow improvers, especially for narrow boiling distillates hitherto difficult to treat, they may also be used in combination with conventional additives such as ethyleneiunsatu- rated ester copolymers and nitrogen compounds such as diamides or amide/amine saits, ester/amides of dicarboxylic acids.

Flow improver additive for distillate fuels, and concentrate thereof

Distillate fuel is treated with additives whose structure match the crystal planes of the wax which crystallizes from the fuel to produce crystals below 4000 nanometres in size, suitable additive include novel sulpho-carboxylic materials particularly their esters and amine derivatives such as the amine salts and/or amides of ortho-sulpho benzoic acid.

Chemical compositions and use as fuel additives

The low temperature properties of a distillate petroleum fuel oil boiling in the range 120° C. to 500° C., are improved particularly the lowering of the cloud point by the addition of a polymer or copolymer of a n-alkyl vinyl or fumarate ester having at least 25 wt. % of n-alkyl groups of average number of carbon atoms from 14 to 18 with no more than 10 wt. % containing less than 14 carbon atoms and no more than 10 wt. % containing more than 14 carbon atoms.

Kenneth Lewtas

Papers

Polyolefin adhesive compositions and articles made therefrom

Polypropylene-based adhesive compositions

Flow improver additive for distillate fuels, and concentrate thereof

Chemical compositions and use as fuel additives

Middle distillate compositions with improved low temperature properties