Enhancing ordering dynamics in solvent-annealed block-copolymer films by lithographic hard masks supports

We studied solvent-driven ordering dynamics of block copolymer films supported by a densely cross-linked polymer network designed as organic hard mask (HM) for lithographic fabrications. The ordering of microphase separated domains at low degrees of swelling corresponding to intermediate/strong segregation regimes was found to proceed significantly faster in films on a HM layer as compared to similar block copolymer films on silicon wafers. The ten-fold enhancement of the chain mobility was evident in the dynamics of morphological phase transitions and of related process of terrace-formation on a macroscale, as well as in the degree of long-range lateral order of nanostructures. The effect is independent of the chemical structure and on the volume composition (cylinder-/ lamella-forming) of the block copolymers. In-situ ellipsometric measurements of the swelling behavior revealed a cumulative increase in 1-3 vol. % in solvent up-take by HM-block copolymer bilayer films, so that we suggest other than dilution effect reasons for the observed significant enhancement of the chain mobility in concentrated block copolymer solutions. Another beneficial effect of the HM-support is the suppression of the film dewetting which holds true even for low molecular weight homopolymer polystyrene films at high degrees of swelling. Apart from immediate technological impact in block copolymer-assisted nanolithography, our findings convey novel insight into effects of molecular architecture on polymer-solvent interactions.Comment: This document is the unedited Author's version of a Submitted Work that was subsequently accepted for publication in Macromolecules, copyright \c{opyright} American Chemical Society after peer review. To access the final edited and published work see http://pubs.acs.org/doi/abs/10.1021/ma500561

Evolution in the Dust Lane Fraction of Edge-on L* Spiral Galaxies since z=0.8

The presence of a well-defined and narrow dust lane in an edge-on spiral galaxy is the observational signature of a thin and dense molecular disk, in which gravitational collapse has overcome turbulence. Using a sample of galaxies out to z~1 extracted from the COSMOS survey, we identify the fraction of massive disks that display a dust lane. Our goal is to explore the evolution in the stability of the molecular ISM disks in spiral galaxies over a cosmic timescale. We check the reliability of our morphological classifications against changes in restframe wavelength, resolution, and cosmic dimming with (artificially redshifted) images of local galaxies from SDSS. We find that the fraction of L* disks with dust lanes in COSMOS is consistent with the local fraction (~80%) out to z~0.7. At z=0.8, the dust lane fraction is only slightly lower. A somewhat lower dust lane fraction in starbursting galaxies tentatively supports the notion that a high specific star formation rate can efficiently destroy or inhibit a dense molecular disk. A small subsample of higher redshift COSMOS galaxies display low internal reddening (E[B-V]), as well as a low incidence of dust lanes. These may be disks in which the growth of the dusty ISM disk lags behind that of the stellar disk. We note that at z=0.8, the most massive galaxies display a lower dust lane fraction than lower mass galaxies. A small contribution of recent mergers or starbursts to this most massive population may be responsible. The fact that the fraction of galaxies with dust lanes in COSMOS is consistent with little or no evolution implies that models to explain the Spectral Energy Distribution or the host galaxy dust extinction of supernovae based on local galaxies are still applicable to higher redshift spirals. It also suggests that dust lanes are long lived phenomena or can be reformed over very short time-scales.Comment: 14 pages, 9 figures, 2 tables, accepted for publication by Ap

Polarized Proton Beams from Laser-induced Plasmas

We report on the concept of an innovative source to produce polarized proton/deuteron beams of a kinetic energy up to several GeV from a laser-driven plasma accelerator. Spin effects have been implemented into the PIC simulation code VLPL to make theoretical predictions about the behavior of proton spins in laser-induced plasmas. Simulations of spin-polarized targets show that the polarization is conserved during the acceleration process. For the experimental realization, a polarized HCl gas-jet target is under construction using the fundamental wavelength of a Nd:YAG laser system to align the HCl bonds and simultaneously circular polarized light of the fifth harmonic to photo-dissociate, yielding nuclear polarized H atoms. Subsequently, their degree of polarization is measured with a Lamb-shift polarimeter. The final experiments, aiming at the first observation of a polarized particle beam from laser-generated plasmas, will be carried out at the 10 PW laser system SULF at SIOM/Shanghai.Comment: 7 pages, 7 figure

UBVI Surface Photometry of the Spiral Galaxy NGC 300 in the Sculptor Group

We present UBVI surface photometry for 20.'5 X 20.'5 area of a late-type spiral galaxy NGC 300. In order to understand the morphological properties and luminosity distribution characteristics of NGC 300, we have derived isophotal maps, surface brightness profiles, ellipticity profiles, position angle profiles, and color profiles. By merging the I-band data of our surface brightness measurements with those of Boeker et al. (2002) based on Hubble Space Telescope observations, we have made combined I-band surface brightness profiles for the region of 0."02 < r < 500" and decomposed the profiles into three components: a nucleus, a bulge, and an exponential disk.Comment: 16 pages(cjaa209.sty), Accepted by the Chinese J. Astron. Astrophys., Fig 2 and 8 are degraded to reduce spac

A Young Stellar Cluster in the Nucleus of NGC 4449

We have obtained 1-2 A resolution optical Echellette spectra of the nuclear star cluster in the nearby starburst galaxy NGC 4449. The light is clearly dominated by a very young (6-10 Myr) population of stars. For our age dating, we have used recent population synthesis models to interpret the observed equivalent width of stellar absorption features such as the HI Balmer series and the CaII triplet around 8500 A. We also compare the observed spectrum of the nuclear cluster to synthesized spectra of simple stellar populations of varying ages. All these approaches yield a consistent cluster age. Metallicity estimates based on the relative intensities of various ionization lines yield no evidence for significant enrichment in the center of this low mass galaxy: the metallicity of the nuclear cluster is about one fourth of the solar value, in agreement with independent estimates for the disk material of NGC 4449.Comment: 24 pages (incl. 7 figures), accepted by AJ, March 2001 issue revised version with minor changes and additions, one additional figur

HST/STIS Spectra of Nuclear Star Clusters in Spiral Galaxies: Dependence of Age and Mass On Hubble Type

(Abridged) We study the nuclear star clusters in spiral galaxies of various Hubble types using spectra obtained with STIS on-board HST. We observed the nuclear clusters in 40 galaxies, selected from two previous HST/WFPC2 imaging surveys. The spectra provide a better separation of cluster light from underlying galaxy light than is possible with ground-based spectra. To infer the star formation history, metallicity and dust extinction, we fit weighted superpositions of single-age stellar population templates to the spectra. The luminosity-weighted age ranges from 10 Myrs to 10 Gyrs. The stellar populations of NCs are generally best fit as a mixture of populations of different ages. This indicates that NCs did not form in a single event, but instead they had additional star formation long after the oldest stars formed. On average, the sample clusters in late-type spirals have a younger luminosity-weighted mean age than those in early-type spirals (log(age/yr) = 8.37+/-0.25 vs. 9.23+/-0.21). The average cluster masses are smaller in late-type spirals than in early-type spirals (log(M/Msun) = 6.25+/-0.21 vs. 7.63+/-0.24), and exceed the masses typical of globular clusters. The cluster mass correlates strongly with both the Hubble type of the host galaxy and the luminosity of its bulge. The latter correlation has the same slope as the well-known correlation between supermassive black hole mass and bulge luminosity. The properties of both nuclear clusters and black holes are therefore intimately connected to the properties of the host galaxy.Comment: AJ submitted (original submission Nov 30, 2005, present version includes changes based on referee recommendations). 69 pages, 16 figures, 7 table

Expression Pattern of Matrix Metalloproteinases in Human Liver

Peer Reviewe

Multi-density model of the ionised gas in NGC 253 using radio recombination lines

We have imaged the H92alpha (8.3 GHz), H75alpha (15 GHz), and H166alpha (1.4 GHz) Radio Recombination Lines (RRLs) from NGC 253 at resolutions of 4.5 pc (0.4"), 2.5 pc (0.2") and 53 pc (4.5") respectively. The H92alpha line arises from individual compact sources, most of which possess radio continuum counterparts. The line widths range from ~200 km/s for the sources near the radio nucleus to 70-100 km/s for the extranuclear ones. These lines are emitted by gas at a density ~10000 /cc. The remainder of the cm-wave RRLs arise in lower density gas (~500 /cc) with a higher area filling factor and with ten times highermass. A third component of higher density gas (>10000 /cc) is required to explain the mm-wave RRLs.Comment: Accepted by A&A; Changed to fit all figures within pag

Block Copolymer at Nano-Patterned Surfaces

We present numerical calculations of lamellar phases of block copolymers at patterned surfaces. We model symmetric di-block copolymer films forming lamellar phases and the effect of geometrical and chemical surface patterning on the alignment and orientation of lamellar phases. The calculations are done within self-consistent field theory (SCFT), where the semi-implicit relaxation scheme is used to solve the diffusion equation. Two specific set-ups, motivated by recent experiments, are investigated. In the first, the film is placed on top of a surface imprinted with long chemical stripes. The stripes interact more favorably with one of the two blocks and induce a perpendicular orientation in a large range of system parameters. However, the system is found to be sensitive to its initial conditions, and sometimes gets trapped into a metastable mixed state composed of domains in parallel and perpendicular orientations. In a second set-up, we study the film structure and orientation when it is pressed against a hard grooved mold. The mold surface prefers one of the two components and this set-up is found to be superior for inducing a perfect perpendicular lamellar orientation for a wide range of system parameters

The Quintuplet Cluster III. Hertzsprung-Russell diagram and cluster age

The Quintuplet, one of three massive stellar clusters in the Galactic center, is located about 30pc in projection from Sagittarius A*. Based on near-infrared K-band spectra we determine temperatures and luminosities for all stars in our sample and construct the Herztsprung-Russell diagram. We find two distinct groups: early-type OB stars and late-type KM stars, well separated from each other. By comparison with Geneva stellar evolution models we derive initial masses exceeding 8 solar masses for the OB stars, that are located along an isochrone corresponding to a cluster age of about 4 million years. In addition, we derive number ratios (e. g. N_WR/N_O) and compare them with predictions of population synthesis models. We find that an instantaneous burst of star formation at about 3.3 to 3.6\,Myr ago is the most likely scenario to form the Quintuplet cluster. The late-type stars in the sample are red giant branch (RGB) stars or red supergiants (RSGs) according to their spectral signatures. It is discussed if they could physically belong to the Quintuplet cluster. Furthermore, we apply a mass-luminosity relation to construct the initial mass function (IMF) of the cluster. We find indications for a slightly top-heavy IMF.Comment: 10 pages, 9 figures, 2 tables, accepted for publication in A&