Open String/Open D-Brane Dualities: Old and New

We examine magnetic and electric near horizon regions of maximally supersymmetric D-brane and NS5-brane bound states and find transformations between near horizon regions with worldvolume dual magnetic and electric fluxes. These point to dual formulations of NCYM, NCOS and OD$p$ theories in the limit of weak coupling and large spatial or temporal non-commutativity length scale in terms of weakly coupled theories with fixed worldvolume dual non-commutativity based on open D-branes. We also examine the strong coupling behavior of the open D-brane theories and propose a unified web of dualities involving strong/weak coupling as well as large/small non-commutativity scale.Comment: 33 pages, Latex, 8 diagrams, added references and a remar

Complete precipitate dissolution during adiabatic shear localisation in a Ni-based superalloy

Whereas microstructure evolution in adiabatic shear bands have been thoroughly studied, reports on the stability of hardening precipitates during shear localisation are scarce. We report an atomic scale investigation of solute distribution in adiabatic shear bands in a precipitation strengthened Ni-Fe-based superalloy, showing that the hardening particles are completely dissolved. Temperature estimations indicate that peak temperatures in the shear band above the solvus limits of the precipitates are not unrealistic, and thus diffusion-assisted transformations during the severe plastic deformation cannot be ruled out

The distribution of O and N in the surface region of laser-patterned titanium revealed by atom probe tomography

Direct Laser Interference Lithography (DLIL) has shown to be a promising technique to chemically and physically alter the surface of titanium. In this work, atom probe tomography analysis was performed on DLIL-treated titanium to obtain the chemical composition of the surface in maxima and minima interference positions. The analysis revealed that a multilayer structure consisting of oxide/oxynitride is formed at both positions; however, the chemical composition is altered differently between the two. The observed difference is believed to be due to an uneven heating and temperature distribution, which is demonstrated by thermal simulations

How higher-spin gravity surpasses the spin two barrier: no-go theorems versus yes-go examples

Aiming at non-experts, we explain the key mechanisms of higher-spin extensions of ordinary gravity. We first overview various no-go theorems for low-energy scattering of massless particles in flat spacetime. In doing so we dress a dictionary between the S-matrix and the Lagrangian approaches, exhibiting their relative advantages and weaknesses, after which we high-light potential loop-holes for non-trivial massless dynamics. We then review positive yes-go results for non-abelian cubic higher-derivative vertices in constantly curved backgrounds. Finally we outline how higher-spin symmetry can be reconciled with the equivalence principle in the presence of a cosmological constant leading to the Fradkin--Vasiliev vertices and Vasiliev's higher-spin gravity with its double perturbative expansion (in terms of numbers of fields and derivatives).Comment: LaTeX, 50 pages, minor changes, many refs added; version accepted for publication in Reviews of Modern Physic

Detrital Zircons and Sediment Dispersal in the Eastern Midcontinent of North America

Results of detrital-zircon analyses (U-Pb ages and initial Hf values, εHft) of Mississippian–Pennsylvanian sandstones in the Michigan, Illinois, and Forest City basins are remarkably similar to data for coeval sandstones in the Appalachian basin, indicating dispersal of sediment from the Appalachian orogen through the Appalachian basin to the eastern Midcontinent during the late Paleozoic. The similarities of results include matches of the two most prominent age groups (1300–950 Ma and 490–350 Ma), as well as matches of the less abundant age groups. Comparisons of the data are from observations of probability density plots and multidimensional scaling of U-Pb age data and of εHft values. Despite the dominance of an Appalachian signature in all samples, some samples contain grains with ages that suggest intermittent additional sources. Four samples (three ranging in depositional age from Morrowan to Atokan–Desmoinesian in the Illinois basin, and one of Desmoinesian age in the Forest City basin), in addition to typical Appalachian age distributions, have prominent age modes between 768 and 525 Ma, corresponding in age to Pan-African/Brasiliano rocks in Gondwanan accreted terranes in the Appalachian orogen, suggesting intermittent dispersal from the Moretown terrane of the northern Appalachians. Sandstones in the Appalachian basin and those in the Midcontinent basins have very few grains with ages that correspond to the Alleghanian orogeny in the Appalachian orogen. Nevertheless, three sandstones each in the Illinois basin and Forest City basin with depositional ages of 312–308 Ma have a few zircon grains in the age range of 321 ± 5 to 307 ± 4 Ma. The nearly identical crystallization and depositional ages suggest reworking at the depositional sites of air-fall volcanic ash from the Alleghanian orogen, rather than fluvial transport from the orogen. The basal Pennsylvanian sandstones lap onto a regional unconformity around the northern rims of the Illinois and Forest City basins, suggesting sources for recycled grains. Along the northern edge of the Illinois basin, Ordovician sandstones beneath the unconformity may have contributed minor concentrations of Superior-age zircons in the basal Pennsylvanian sandstones. Basal Pennsylvanian sandstones in the Forest City basin lap onto Mississippian strata, suggesting possible recycling of zircons from eroded Mississippian sandstones

Evidence for constriction and Pliocene acceleration of east-west extension in the North Lunggar rift region of west central Tibet

This is the publisher's version, also available electronically from http://onlinelibrary.wiley.com/doi/10.1002/tect.20086/abstract;jsessionid=36D445F6B0A54FA5B74E359605FC0AD1.f04t02The active north trending North Lunggar rift in west central southern Tibet exposes an extensional metamorphic core complex bounded by an east dipping low-angle normal fault. Apatite and zircon (U-Th)/He thermochronology and thermal modeling of the North Lunggar rift document a minimum timing for rift inception at >10 Ma and rapid footwall exhumation between 5 and 2 Ma. Miocene footwall cooling and exhumation rates were initially slow to moderate at 400°C Ma−1 and 4–10 mm a−1. Footwall isotherms were significantly compressed during rapid exhumation resulting in an elevated transient geothermal gradient between 50 and 90°C km−1. The minimum magnitude of horizontal extension for the North Lunggar rift is 8.1–12.8 km; maximum is 15–20 km, less in the south at ~10 km. Mean Pliocene extension rate is 1.2–2.4 mm a−1 in the ~120° direction. Results for the North Lunggar rift are similar in magnitude, rate, and orientation of slip to the kinematically linked Lamu Co dextral strike-slip fault to the north. This suggests a state of constrictional strain during Pliocene time along this stretch of the Bangong-Nujiang suture from which the Lamu Co fault emanates. The onset of extension in this region may be explained by crustal thickening and gravitational orogenic collapse, followed by accelerated rifting resulting from localized crustal stretching and increased magmatic activity, potentially driven by the position and northward extent of underthrusting Indian lithosphere

Iron Age and Anglo-Saxon genomes from East England reveal British migration history

British population history has been shaped by a series of immigrations, including the early Anglo-Saxon migrations after 400 CE. It remains an open question how these events affected the genetic composition of the current British population. Here, we present whole-genome sequences from 10 individuals excavated close to Cambridge in the East of England, ranging from the late Iron Age to the middle Anglo-Saxon period. By analysing shared rare variants with hundreds of modern samples from Britain and Europe, we estimate that on average the contemporary East English population derives 38% of its ancestry from Anglo-Saxon migrations. We gain further insight with a new method, rarecoal, which infers population history and identifies fine-scale genetic ancestry from rare variants. Using rarecoal we find that the Anglo-Saxon samples are closely related to modern Dutch and Danish populations, while the Iron Age samples share ancestors with multiple Northern European populations including Britain