767 research outputs found
Intersecting Branes in Matrix Theory
We construct BPS states in the matrix description of M-theory. Starting from
a set of basic M-theory branes, we study pair intersections which preserve
supersymmetry. The fractions of the maximal supersymmetry obtained in this way
are 1/2, 1/4, 1/8, 3/16 and 1/16. In explicit examples we establish that the
matrix BPS states correspond to (intersecting) brane configurations that are
obtained from the d=11 supersymmetry algebra. This correspondence for the 1/2
supersymmetric branes includes the precise relations between the charges.Comment: 11 pages, LaTeX, no figures, minor changes, shortened version to be
published in Physics Letters
Experimentele studie van het gedrag van natuurvriendelijke oeververdediging op niet tijgebonden bevaarbare waterlopen belast door scheepsgolven
Response of technical-biological bank protection to ship-generated wave actions – first results
River morphodynamics and sediment transportBank erosion and protectio
T-duality and Actions for Non-BPS D-branes
We employ T-duality to restrict the tachyon dependence of effective actions
for non-BPS D-branes. For the Born-Infeld part the criteria of T-duality and
supersymmetry are satisfied by a simple extension of the D-brane Born-Infeld
action.Comment: Latex, 11 page
Stereoelectronic effects on the binding of neutral Lewis bases to CdSe nanocrystals
Using P-31 nuclear magnetic resonance (NMR) spectroscopy, we monitor the competition between tri-nbutylphosphine (Bu3P) and various amine and phosphine ligands for the surface of chloride terminated CdSe nanocrystals. Distinct P-31 NMR signals for free and bound phosphine ligands allow the surface ligand coverage to be measured in phosphine solution. Ligands with a small steric profile achieve higher surface coverages (Bu3P = 0.5 nm(-2), Me2P-n-octyl = 2.0 nm(-2), NH2Bu = >3 nm(-2)) and have greater relative binding affinity for the nanocrystal (binding affinity: Me3P > Me2P -n-octyl similar to Me2P -n-octadecyl > Et3P > Bu3P). Among phosphines, only Bu 3 P and Me2P-n-octyl support a colloidal dispersion, allowing a relative surface binding affinity (K-rel) to be estimated in that case (K-rel = 3.1). The affinity of the amine ligands is measured by the extent to which they displace Bu3P from the nanocrystals (K-rel: H2NBu similar to N-n-butylimidazole > 4-ethylpyridine > Bu3P similar to HNBu2 > Me2NBu > Bu3N). The affinity for the CdSe surface is greatest among soft, basic donors and depends on the number of each ligand that bind. Sterically unencumbered ligands such as imidazole, pyridine, and n-alkylamines can therefore outcompete stronger donors such as alkylphosphines. The influence of repulsive interactions between ligands on the binding affinity is a consequence of the high atom density of binary semiconductor surfaces. The observed behavior is distinct from the self-assembly of straight-chain surfactants on gold and silver where the ligands are commensurate with the underlying lattice and attractive interactions between aliphatic chains strengthen the binding
Kortkruinig golfklimaat ter hoogte van de Halve Maan (haven Oostende): golfindringing voor een storm met T = 100 jaar en T = 1000 jaar
Studie golfimpact kaai 101 haven Oostende: deelrapport 1. Numerieke studie opwaartse golfkracht
Golfklimaat ter hoogte van de Halve Maan (haven Oostende): kort- en langkruinige golfkarakteristieken en reflectie-analyse
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