Formation of Globular Clusters in Hierarchical Cosmology: ART and Science

We test the hypothesis that globular clusters form in supergiant molecular clouds within high-redshift galaxies. Numerical simulations demonstrate that such large, dense, and cold gas clouds assemble naturally in current hierarchical models of galaxy formation. These clouds are enriched with heavy elements from earlier stars and could produce star clusters in a similar way to nearby molecular clouds. The masses and sizes of the model clusters are in excellent agreement with the observations of young massive clusters. Do these model clusters evolve into globular clusters that we see in our and external galaxies? In order to study their dynamical evolution, we calculate the orbits of model clusters using the outputs of the cosmological simulation of a Milky Way-sized galaxy. We find that at present the orbits are isotropic in the inner 50 kpc of the Galaxy and preferentially radial at larger distances. All clusters located outside 10 kpc from the center formed in the now-disrupted satellite galaxies. The spatial distribution of model clusters is spheroidal, with a power-law density profile consistent with observations. The combination of two-body scattering, tidal shocks, and stellar evolution results in the evolution of the cluster mass function from an initial power law to the observed log-normal distribution. However, not all initial conditions and not all evolution scenarios are consistent with the observed mass function.Comment: 8 pages, invited review for conference "Globular Clusters, Guide to Galaxies", 6-10 March 2006, University of Concepcion, Chile, ed. T. Richtler, et a

The spectral function for Sturm-Liouville problems where the potential is of Wigner-von Neumann type or slowly decaying

We consider the linear, second-order, differential equation (∗) with the boundary condition (∗∗) We suppose that q(x) is real-valued, continuously differentiable and that q(x)→0 as x→∞ with q∉L1[0,∞). Our main object of study is the spectral function ρα(λ) associated with () and (). We derive a series expansion for this function, valid for λ⩾Λ0 where Λ0 is computable and establish a Λ1, also computable, such that () and () with α=0, have no points of spectral concentration for λ⩾Λ1. We illustrate our results with examples. In particular we consider the case of the Wigner–von Neumann potential

Higher derivatives of spectral functions associated with one-dimensional schrodinger operators

We investigate the existence and asymptotic behaviour of higher derivatives of the spectral function in the context of one-dimensional Schr¨odinger operators on the half-line with integrable potentials. In particular, we identify sufficient conditions on the potential for the existence and continuity of the n-th derivative, and outline a systematic procedure for estimating numerical upper bounds for the turning points of such derivatives. Explicit worked examples illustrate the development and application of the theory

Diversity of polycyclic triterpenoids in Rhodospirillum rubrum

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 22-24).Sedimentary rocks of all ages abound with geostable lipids of microbial origin, but many biomarkers lack known organismal sources and clear environmental contexts. Here we used Rhodospirillum rubrum, a metabolically versatile, genetically tractable c-Proteobacterium, to explore the diversity of its non-polar terpenoids as a function of growth condition and growth phase. We analyzed the nonpolar fraction of lipids extracted from R. rubrum grown under aerobic, anaerobic, heterotrophic and phototrophic conditions and detected a variety of bicyclic, tricyclic, tetracyclic and pentacyclic triterpenoids, derived from the enzymatic cyclization of squalene and produced in amounts comparable to diploptene. Identified compounds included bicyclic polypodatetraenes, malabaricatriene, euphadiene, adianane, and fernene. Prior to this work, malabaricatriene was an "orphan" biomarker suspected to have a microbial origin, yet it lacked a proven source. We observed similar patterns of polycyclic terpenoids in other hopanoid-producing c-proteobacteria, including Zymomonas mobilis, Rhodopseudomonas palustris, and Rhodomicrobium vannielii. The presence and relative abundance of polycyclic triterpenoids in R. rubrum varied with the growth stage (exponential versus early stationary phase) and growth condition (photoheterotrophic versus photoautotrophic growth). Since R. rubrum's genome contains a single squalene-hopene cyclase gene, the array of triterpenoids produced by it and other c-proteobacteria likely evolves from this enzyme performing low-fidelity cyclization. The observed diversity of sedimentary triterpenoids might therefore result from a select few squalene-hopene cyclase enzymes operating with varying specificity under a range of physiological and environmental conditions, rather than reflecting a great diversity of squalene-hopene cyclases.by Katherine Harris.S.M

Cloth in prehistoric societies. The social context of cloth in prehistory, with case studies from northern Italy and the Alpine region from the Neolithic to Bronze Age.

The aim of this thesis is to explore the social context of cloth from the Neolithic to Bronze Age (C.5500-1000BC) in the central Alpine region of Europe. The time spans from early farming to metal using societies and includes changes in the way cloth is produced and used. The Alpine region is a good place to study cloth as it includes waterlogged, frozen and salt environments where cloth is preserved. To achieve my aim I have reconsidered the definition of cloth as flexible, thin sheets of material that can be wrapped, folded, shaped and tied. The purpose of this is to approach the interrelated technologies of cloth types including animal skins, textiles, netting and twining. A further methodological concern is to investigate these cloth types in a holistic manner, as they would have existed in the societies, that is, throughout the whole sequence of production and use. I called this method the extended chame operatoire. To develop these stages in the production and use of cloth I investigate social contextual themes, including issues of time and place, the use of tools and equipment in relation to techniques and the social identity of participants in terms of gender, age and role. This approach is developed throughout the analysis of the extended chaine operatoire and applied more specifically to case studies of selected sites in the region. The cases studies include the waterlogged lake dwelling settlement of Homstaad Hornle IA, Lake Constance c. 3900 BC, the frozen Iceman from the Italian Alps, c. 3300 BC, the representation of cloth on the stelae from Sion, Swiss Valais c. 2800 BC, the waterlogged lake dwelling settlement of Molina di Ledro, Trentino c.2300-1500 BC and the salt preserved cloth artefacts from the Bronze Age salt mines in Hallstatt, Austria, c.1400 BC

Anomalous Charge Dynamics in the Superconducting State of Underdoped Cuprates

We present fermi liquid expressions for the low temperature behavior of the superfluid stiffness, explain why they differ from those suggested recently by Lee and Wen, and discuss their applicability to data on high-$T_c$ superconductors. We find that a consistent description requires a strong, doping dependent anisotropy, which affects states near the zone corners much more strongly than those near the zone diagonals

Star and cluster formation in extreme environments

Current empirical evidence on the star-formation processes in the extreme, high-pressure environments induced by galaxy encounters (mostly based on high-resolution Hubble Space Telescope observations) strongly suggests that star CLUSTER formation is an important and perhaps even the dominant mode of star formation in such starburst events. The sizes, luminosities, and mass estimates of the young massive star clusters (YMCs) are entirely consistent with what is expected for young Milky Way-type globular clusters (GCs). Recent evidence lends support to the scenario that GCs, which were once thought to be the oldest building blocks of galaxies, are still forming today. Here, I present a novel empirical approach to assess the shape of the initial-to-current YMC mass functions, and hence their possible survival chances for a Hubble time.Comment: 6 pages, LaTeX with Kluwer style files included; to appear in: "Starbursts - from 30 Doradus to Lyman break galaxies" (Cambridge UK, September 2004; talk summary), Astrophysics & Space Science Library, eds. de Grijs R., Gonzalez Delgado R.M., Kluwer: Dordrech

Managing diversity in organisations: practitioner and academic perspectives: report from a gender in management special interest group research event

Purpose - This report aims to provide a brief summary of the presentations made by researchers and practitioners at the Gender in Management Special Interest Group’s research event, Managing Diversity in Organisations: Practitioner and Academic Perspectives. Design/methodology/approach - The research seminar was chaired by Dr. Adelina Broadbridge (University of Stirling) and Dr. Gillian Maxwell (Glasgow Caledonian University), and featured five presentations related to diversity in organisations, with a focus on gender issues. Twenty-five delegates were in attendance. Findings - The academic research presented provided empirical evidence that women continue to face barriers to career progress in a number of industry sectors. The industry presentations provided examples of organisational efforts to improve diversity both among staff and customers. Research limitations/implications - More needs to be done to ensure that women enjoy career opportunities equal to those of men in a variety of industry sectors. Even in organisations where women are comparatively well represented, such as professional services firms, research indicates that they are disadvantaged in terms of career development and progress. Originality/value - This session provided a valuable opportunity for practitioners and academics to meet and share information regarding the state of diversity in today’s workplace

Thermodynamics as an alternative foundation for zero-temperature density functional theory and spin density functional theory

Thermodynamics provides a transparent definition of the free energy of density functional theory (DFT), and of its derivatives - the potentials, at finite temperatures T. By taking the T to 0 limit, it is shown here that both DFT and spin-dependent DFT (for ground states) suffer from precisely the same benign ambiguities: (a) charge and spin quantization lead to "up to a constant" indeterminacies in the potential and the magnetic field respectively, and (b) the potential in empty subspaces is undetermined but irrelevant. Surprisingly, these simple facts were inaccessible within the standard formulation, leading to recent discussions of apparent difficulties within spin-DFT.Comment: RevTeX, to appear in Phys. Rev.

Low-Loss All-Optical Zeno Switch in a Microdisk Cavity Using EIT

We present theoretical results of a low-loss all-optical switch based on electromagnetically induced transparency and the classical Zeno effect in a microdisk resonator. We show that a control beam can modify the atomic absorption of the evanescent field which suppresses the cavity field buildup and alters the path of a weak signal beam. We predict more than 35 dB of switching contrast with less than 0.1 dB loss using just 2 micro-Watts of control-beam power for signal beams with less than single photon intensities inside the cavity.Comment: Updated with new references, corrected Eq 2a, and added introductory text. 7 pages, 5 figures, 3 table