High strength steel in fire

High-performance materials are necessary to meet the future demands of the construction industry, which is strongly influenced by a growing population and depletion of natural resources. Sustainable development is central to research and development into innovative structural materials, and requires solutions to be economically viable whilst equally providing a positive contribution towards environmental and social factors. High strength steels (HSS) have the potential to contribute towards such demands by reducing the weight of structures when employed in appropriate applications. Lighter structures require smaller foundations, shorter transportation and construction times and also lower CO2 emissions. A particular challenge related to the use of HSS in structures include increased likelihood of stability issues resulting from the reduction in section thickness, and limiting deflection and vibration criteria are also more likely to be critical. Nevertheless, when used appropriately, they can provide a sustainable solution. Their use in structural applications is further hindered by a lack of performance data and design guidance under fire conditions. This paper compares the mechanical properties, particularly strength and stiffness of HSS (yield strengths between 460-700 MPa) and mild steel (yields between 235-460 MPa) at elevated temperatures, through a critical review of published literature. Various alloying and processing routes used to achieve high yield strength are assessed. At the same time, the review considers available information on the strengthening mechanisms that can be utilised to retain the strength and/or stiffness of the material in the event of a fire. Using the information gathered, an extensive testing programme is developed which will enable design guidance for the fire design of HSS structures to be proposed.Engineering and Physical Sciences Research Council, TW

Glueball Interpretation of ξ\xi(2230)

On the basis of the results of $\xi(2230)\rightarrow\pi^{+}\pi^{-}, p\bar{p}$ and $K\bar{K}$, measured by the BES Collaboration in radiative J/$\psi$ decays, combined with the upper limit of Br($\xi\rightarrow p\bar{p}$)Br($\xi\rightarrow K\bar{K}$), measured by PS185 experiment, we argue that the distinctive properties of $\xi$(2230), the flavor-symmetric decays and the narrow partial decay widths to $\pi\pi$ and $K\bar{K}$ as well as its copious production in radiative J/$\psi$ decay, would strongly favor the glueball interpretation of $\xi$(2230).Comment: Latex file, no figure

Use and availability of medicinal resources in Ouro Verde de Goiás, Goiás State, Brazil

O objetivo do presente estudo foi realizar um levantamento etnobotânico das plantas medicinais usadas por comunidades rurais e urbanas no município de Ouro Verde de Goiás, situado na mesorregião do mato grosso goiano; eleger espécies nativas do bioma Cerrado potenciais para estudos farmacológicos com base na concordância de uso popular corrigida (CUPc); e avaliar se o conhecimento botânico e o cultivo de espécies medicinais em quintais podem ser afetados por classes de idade, gênero, escolaridade, local de nascimento e procedência rural/urbana do informante pelos testes Kruskal-Wallis (H) e Qui-quadrado (c 2). Foram selecionados 84 informantes por meio de amostragens aleatórias, sendo efetuadas entrevistas estruturadas. As fontes disponíveis de recursos medicinais foram: quintais, áreas antrópicas, matas de galeria e remanescentes de florestas estacionais. Foram registradas 98 espécies distribuídas em 45 famílias destacando-se em número as exóticas cultivadas. Nos quintais, foram catalogadas 78 espécies cultivadas, sendo 39,7% para remédios, e demais associações com a alimentação (39,7%) e a ornamentação (20,5%). Vinte espécies são adquiridas pelo extrativismo na vegetação do entorno, sendo todas nativas do bioma Cerrado, com exceção de Senna occidentalis, que é invasora. Duas espécies de florestas estacionais (Forsteronia refracta e Celtis iguanaea) apresentaram a CUPc > 50%, evidenciando consensos de uso popular. Verificou-se que 41% dos informantes da zona rural recorrem ao extrativismo na vegetação nativa, procura que é consideravelmente maior em relação aos informantes da zona urbana (16,7%). A quantidade de espécies citadas foi significativamente maior entre os informantes que tinham quintal. O número de espécies citadas e a presença de quintal independem do grau de escolaridade, gênero, local de nascimento, idade e zona de procedência rural ou urbana do informante.The goal of this study was to conduct an ethnobotanical survey of the medicinal plants used by rural and urban communities in the town of Ouro Verde de Goiás, situated in the mato grosso goiano meso-region of the state of Goiás; to pinpoint species native to the Cerrado biome with potential for pharmacological studies based on corrected popular use concordance (CUPc); and to determine if ethnobotanical knowledge of medicinal plants from backyards differed by age, gender, education, place of birth and rural versus urban setting of the informant. Statistical tests applied were Kruskal-Wallis (H) and Qui-square (c 2). Eighty-four informants were selected by random sampling and interviews were structured. The available sources of medicinal plants were: backyards, disturbed areas, gallery forests and deciduous dry forests. Ninetyeight species, distributed in 45 botanical families, were found, with cultivated exotics outnumbering native plants. In backyards, 78 species were cultivated, of which 39.7% were cited exclusively as medicinal, the remaining also being reported as food (39.7%) or ornamentals (20.5%). Twenty species were gathered from the surrounding vegetation, all of which are native to the Cerrado biome, except for Senna occidentalis which is weedy. Two species that occur in deciduous dry forest (Forsteronia refracta and Celtis iguanaea) had high CUPc (> 50%), showing consensus of popular use. Forty-one percent of rural area informants reported gathering medicinal plants from native vegetation, which is significantly more than those in urban areas (16.7%). The number of species cited by informants with cultivated backyards was significantly greater than those that did not. The number of medicinal plants cited by informants and the presence of a backyard did not differ significantly among informants from different classes of gender, education, place of birth and rural versus urban dwelling

Contradiction between strong lensing statistics and a feedback solution to the cusp/core problem

Standard cosmology has many successes on large scales, but faces some fundamental difficulties on small, galactic scales. One such difficulty is the cusp/core problem. High resolution observations of the rotation curves for dark matter dominated low surface brightness (LSB) galaxies imply that galactic dark matter halos have a density profile with a flat central core, whereas N-body structure formation simulations predict a divergent (cuspy) density profile at the center. It has been proposed that this problem can be resolved by stellar feedback driving turbulent gas motion that erases the initial cusp. However, strong gravitational lensing prefers a cuspy density profile for galactic halos. In this paper, we use the most recent high resolution observations of the rotation curves of LSB galaxies to fit the core size as a function of halo mass, and compare the resultant lensing probability to the observational results for the well defined combined sample of the Cosmic Lens All-Sky Survey (CLASS) and Jodrell Bank/Very Large Array Astrometric Survey (JVAS). The lensing probabilities based on such density profiles are too low to match the observed lensing in CLASS/JVAS. High baryon densities in the galaxies that dominate the lensing statistics can reconcile this discrepancy, but only if they steepen the mass profile rather than making it more shallow. This places contradictory demands upon the effects of baryons on the central mass profiles of galaxies.Comment: 8 pages, 3 figures. Largely improved compared with the version 1 to reflect the referees' reports, conclusions unchanged. Published in Research in Astronomy and Astrophysics (RAA

Preliminary Limits on the WIMP-Nucleon Cross Section from the Cryogenic Dark Matter Search (CDMS)

We are conducting an experiment to search for WIMPs, or weakly-interacting massive particles, in the galactic halo using terrestrial detectors. This generic class of hypothetical particles, whose properties are similar to those predicted by extensions of the standard model of particle physics, could comprise the cold component of non-baryonic dark matter. We describe our experiment, which is based on cooled germanium and silicon detectors in a shielded low-background cryostat. The detectors achieve a high degree of background rejection through the simultaneous measurement of the energy in phonons and ionization. Using exposures on the order of one kilogram-day from initial runs of our experiment, we have achieved (preliminary) upper limits on the WIMP-nucleon cross section that are comparable to much longer runs of other experiments.Comment: 5 LaTex pages, 5 eps figs, epsf.sty, espcrc2dsa2.sty. Proceedings of TAUP97, Gran Sasso, Italy, 7-11 Sep 1997, Nucl. Phys. Suppl., A. Bottino, A. di Credico and P. Monacelli (eds.). See also http://cfpa.berkeley.ed

Time-Series Photometry of Stars in and around the Lagoon Nebula. I. Rotation Periods of 290 Low-Mass Pre-Main-Sequence Stars in NGC 6530

We have conducted a long-term, wide-field, high-cadence photometric monitoring survey of ~50,000 stars in the Lagoon Nebula \ion{H}{2} region. This first paper presents rotation periods for 290 low-mass stars in NGC 6530, the young cluster illuminating the nebula, and for which we assemble a catalog of infrared and spectroscopic disk indicators, estimated masses and ages, and X-ray luminosities. The distribution of rotation periods we measure is broadly uniform for 0.5 < P < 10 d; the short-period cutoff corresponds to breakup. We observe no obvious bimodality in the period distribution, but we do find that stars with disk signatures rotate more slowly on average. The stars' X-ray luminosities are roughly flat with rotation period, at the saturation level ($\log L_X / L_{\rm bol} \approx -3.3$). However, we find a significant positive correlation between $L_X / L_{\rm bol}$ and co-rotation radius, suggesting that the observed X-ray luminosities are regulated by centrifugal stripping of the stellar coronae. The period-mass relationship in NGC 6530 is broadly similar to that of the Orion Nebula Cluster (ONC), but the slope of the relationship among the slowest rotators differs from that in the ONC and other young clusters. We show that the slope of the period-mass relationship for the slowest rotators can be used as a proxy for the age of a young cluster, and we argue that NGC 6530 may be slightly younger than the ONC, making it a particularly important touchstone for models of angular momentum evolution in young, low-mass stars.Comment: 28 pages, 18 figures, Accepted for publication in ApJ. For a brief video explaining the key results of this paper, see http://www.youtube.com/user/OSUAstronomy#p/u/1/WarGh6GiWu

Energy-dependent tunneling from few-electron dynamic quantum dots

We measure the electron escape rate from surface-acoustic-wave dynamic quantum dots (QDs) through a tunnel barrier. Rate equations are used to extract the tunneling rates, which change by an order of magnitude with tunnel-barrier-gate voltage. We find that the tunneling rates depend on the number of electrons in each dynamic QD because of Coulomb energy. By comparing this dependence to a saddle-point-potential model, the addition energies of the second and third electron in each dynamic QD are estimated. The scale (similar to a few meV) is comparable to those in static QDs as expected

Kinematics of the Local Universe XIII. 21-cm line measurements of 452 galaxies with the Nan\c{c}ay radiotelescope, JHK Tully-Fisher relation and preliminary maps of the peculiar velocity field

This paper presents 452 new 21-cm neutral hydrogen line measurements carried out with the FORT receiver of the meridian transit Nan\c{c}ay radiotelescope (NRT) in the period April 2003 -- March 2005. This observational programme is part of a larger project aiming at collecting an exhaustive and magnitude-complete HI extragalactic catalogue for Tully-Fisher applications (the so-called KLUN project, for Kinematics of the Local Universe studies, end in 2008). The whole on-line HI archive of the NRT contains today reduced HI-profiles for ~4500 spiral galaxies of declination delta > -40&deg; (http://klun.obs-nancay.fr). As an example of application, we use direct Tully-Fisher relation in three (JHK) bands in deriving distances to a large catalog of 3126 spiral galaxies distributed through the whole sky and sampling well the radial velocity range between 0 and 8000 km/s. Thanks to an iterative method accounting for selection bias and smoothing effects, we show as a preliminary output a detailed and original map of the velocity field in the Local Universe

Application of the zero-range potential model to positron annihilation on molecules

In this paper we use a zero-range potential (ZRP) method to model positron interaction with molecules. This allows us to investigate the effect of molecular vibrations on positron-molecule annihilation using the van der Waals dimer Kr2 as an example. We also use the ZRP to explore positron binding to polyatomics and examine the dependence of the binding energy on the size of the molecule for alkanes. We find that a second bound state appears for a molecule with ten carbons, similar to recent experimental evidence for such a state emerging in alkanes with twelve carbons.Comment: 14 pages, 6 figures, to be published in Nuclear Instruments and Methods