A fully-automated pole-tip shape optimization tool, involving write head geometry construction, meshing, micromagnetic simulation and evaluation, is presented. Optimizations have been performed for three different writing schemes (centered, staggered
and shingled) for an underlying bit patterned media with an areal density of 2.12 Tdots/in$^2$ . Optimizations were performed for a single-phase media with 10 nm thickness and a mag spacing of 8 nm. From the computed write field and its gradient and the minimum energy barrier during writing for islands on the adjacent track, the overall write error rate is computed. The overall write errors are 0.7, 0.08, and 2.8 x 10$^{-5}$ for centered writing, staggered writing, and shingled writing.
Nanometric inclusions filled with nitrogen, located adjacent to FenN (n = 3 or 4) nanocrystals within (Ga,Fe)N layers, are identified and characterized using scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS
). High-resolution STEM images reveal a truncation of the Fe-N nanocrystals at their boundaries with the nitrogen-containing inclusion. A controlled electron beam hole drilling experiment is used to release nitrogen gas from an inclusion in situ in the electron microscope. The density of nitrogen in an individual inclusion is measured to be 1.4 +- 0.3 g/cm3. These observations provide an explanation for the location of surplus nitrogen in the (Ga,Fe)N layers, which is liberated by the nucleation of FenN (n> 1) nanocrystals during growth.
We present a sensitive 870 micron survey of the Extended Chandra Deep Field South (ECDFS) using LABOCA on the APEX telescope. The LABOCA ECDFS Submillimetre Survey (LESS) covers the full 30 x 30 field size of the ECDFS and has a uniform noise level o
f 1.2 mJy/beam. LESS is thus the largest contiguous deep submillimetre survey undertaken to date. The noise properties of our map show clear evidence that we are beginning to be affected by confusion noise. We present a catalog of 126 SMGs detected with a significance level above 3.7 sigma. The ECDFS exhibits a deficit of bright SMGs relative to previously studied blank fields but not of normal star-forming galaxies that dominate the extragalactic background light (EBL). This is in line with the underdensities observed for optically defined high redshift source populations in the ECDFS (BzKs, DRGs,optically bright AGN and massive K-band selected galaxies). The differential source counts in the full field are well described by a power law with a slope of alpha=-3.2, comparable to the results from other fields. We show that the shape of the source counts is not uniform across the field. The integrated 870 micron flux densities of our source-count models account for >65% of the estimated EBL from COBE measurements. We have investigated the clustering of SMGs in the ECDFS by means of a two-point correlation function and find evidence for strong clustering on angular scales <1. Assuming a power law dependence for the correlation function and a typical redshift distribution for the SMGs we derive a spatial correlation length of r_0=13+/-6 h^-1 Mpc.
The Large APEX Bolometer Camera, LABOCA, has been commissioned for operation as a new facility instrument t the Atacama Pathfinder Experiment 12m submillimeter telescope. This new 295-bolometer total power camera, operating in the 870 micron atmosphe
ric window, combined with the high efficiency of APEX and the excellent atmospheric transmission at the site, offers unprecedented capability in mapping submillimeter continuum emission for a wide range of astronomical purposes.
We present large scale 870 micron maps of the nearby starburst galaxies NGC253, NGC4945 and the nearest giant elliptical radio galaxy Centaurus A (NGC 5128) obtained with the newly commissioned Large Apex Bolometer Camera (LABOCA) operated at the APE
X telescope. Our continuum images reveal for the first time the distribution of cold dust at a angular resolution of 20 across the entire optical disks of NGC253 and NGC4945 out to a radial distance of 10 (7.5 kpc). In NGC5128 our LABOCA image also shows, for the first time at submillimeter wavelengths, the synchrotron emission associated with the radio jet and the inner radio lobes. From an analysis of the 870 micron emission in conjunction with ISO-LWS, IRAS and long wavelengths radio data we find temperatures for the cold dust in the disks of all three galaxies of 17-20 K, comparable to the dust temperatures in the disk of the Milky Way. The total gas mass in the three galaxies is determined to be 2.1, 4.2 and 2.8 x 10^9 solar masses for NGC253, NGC4945 and NGC5128, respectively. A detailed comparison between the gas masses derived from the dust continuum and the integrated CO(1-0) intensity in NGC253 suggests that changes of the CO luminosity to molecular mass conversion factor are mainly driven by a metallicity gradient and only to a lesser degree by variations of the CO excitation. An analysis of the synchrotron spectrum in the northern radio lobe of NGC5128 shows that the synchrotron emission from radio to the ultraviolet wavelengths is well described by a broken power law and that the break frequency is a function of the distance from the radio core as expected for aging electrons. We derive an outflow speed of ~0.5c at a distance of 2.6kpc from the center, consistent with the speed derived in the vicinity of the nucleus.
We consider two models with disorder dominated critical points and study the distribution of clusters which are confined in strips and touch one or both boundaries. For the classical random bond Potts model in the large-q limit we study optimal Fortu
in-Kasteleyn clusters by combinatorial optimization algorithm. For the random transverse-field Ising chain clusters are defined and calculated through the strong disorder renormalization group method. The numerically calculated density profiles close to the boundaries are shown to follow scaling predictions. For the random bond Potts model we have obtained accurate numerical estimates for the critical exponents and demonstrated that the density profiles are well described by conformal formulae.
