1,573 research outputs found

    Salt land survey, 1962 : report of a survey of soil salinity in the agricultural areas of Western Australia

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    IN Western Australia there are within the agricultural areas about one million acres of salt land, largely within the 14-25 inch rainfall area used for cereal and wool production. In March, 1962, farmers in 68 shires in the agricultural areas of Western Australia estimated that on their properties 305,270 acres of land previously cropped or sown to pasture had become salt affected. Of this total, 59,203 acres had gone salt in the seven years immediately before the survey

    Diversity of animal communities on southwestern rangelands: Species patterns, habitat relationships, and land management

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    The rangelands of the southwestern United States comprise a mosaic of biome types, including deserts, grasslands, chaparral, woodlands, forests, subalpine meadows, and alpine tundra. Taken together, these ecosystems support exceptionally high numbers of vertebrate and invertebrate animal species. Biogeographic patterns of mammal, bird, and reptile species across North America show trends of increasing species numbers for these vertebrate groups, and some invertebrate groups, occur in Texas, New Mexico, Arizona, and California, especially in the border region with Mexico. Underlying causes of the region\u27s high biodiversity are related to (1) the elevational variability inherent in the basin-and-range topography, with its concomitant range of climate conditions, (2) the diverse biogeographic history of the region, particularly with respect to the merging of major faunal groups during glacier retreats, and (3) the architectural variations in vegetation structure across the region\u27s component ecosystems. Climate dynamics and disturbance also play major roles in maintaining a habitat mosaic, promoting greater regional faunal diversity. Disturbances affect animal diversity at many scales, from individuals\u27 home ranges to continental species\u27 distributions. Human activities have generated new suites of disturbances (livestock grazing, timber harvesting, mining, agriculture, prescribed fires, construction of roads and buildings), many of which contribute to the habitat patchiness of the landscape. Studies have shown that these disturbances prove beneficial to some species and detrimental to others. Hence, local increases in biodiversity can be orchestrated by creating or maintaining habitat diversity and disturbance regimes. Such management strategies can be scaled up to regional landscapes, in which areas of intensive human land use and disturbance are interspersed with regions of little or no human interference. Historically, this has been accomplished at local or state levels on an ad hoc bases (i.e., crisis management), with little evidence of long-term, large-scale, regional planning or coordination. If faunal biodiversity is to be preserved and enhanced on southwestern rangelands, human activities must be managed in a fashion that integrates faunal biology, resource requirements, and movement patterns with landscape scale attributes. Therefore, the task of the modern land manager will be to balance carefully the various scales and intensities of human activities, for the purpose of promoting sustainable use of natural resources and assuring the maintenance or enhancement of biodiversity. Future regional planning for biodiversity attributes will clearly require extensive communication and close cooperation among concerned citizens, private landowners, scientists, and government land managers

    Spitzer IRAC Observations of Star Formation in N159 in the LMC

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    We present observations of the giant HII region complex N159 in the LMC using IRAC on the {\it Spitzer Space Telescope}. One of the two objects previously identified as protostars in N159 has an SED consistent with classification as a Class I young stellar object (YSO) and the other is probably a Class I YSO as well, making these two stars the youngest stars known outside the Milky Way. We identify two other sources that may also be Class I YSOs. One component, N159AN, is completely hidden at optical wavelengths, but is very prominent in the infrared. The integrated luminosity of the entire complex is L 9×106\approx 9\times10^6L_{\odot}, consistent with the observed radio emission assuming a normal Galactic initial mass function (IMF). There is no evidence for a red supergiant population indicative of an older burst of star formation. The N159 complex is 50 pc in diameter, larger in physical size than typical HII regions in the Milky Way with comparable luminosity. We argue that all of the individual components are related in their star formation history. The morphology of the region is consistent with a wind blown bubble $\approx 1-2Myr-old that has initiated star formation now taking place at the rim. Other than its large physical size, star formation in N159 appears to be indistinguishable from star formation in the Milky Way.Comment: 14 figure

    Structural Barriers to HIV Prevention and Services: Perspectives of African American Women in Low-Income Communities

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    Background African American women are at a disproportionate HIV risk compared with other U.S. women. Studies show that complex structural and social determinants, rather than individual behaviors, place African American women at greater risk of HIV infection; however, little is known about women's views of what puts them at risk.AimsThis study sought to comprehend the perceptions of African American women living in low-income housing regarding the factors that influence both their personal sexual health behaviors and use of HIV prevention services. Methods We conducted seven focus groups with 48 African American women from 10 public housing communities in a small city in the southeastern United States. We analyzed the focus group transcripts using thematic data analysis to identify salient themes and points of interest related to the study aim. Results Women identified factors related to the health care system (trustworthiness of the health care system), the external environment (racism, classism, patriarchal structures, and violence/crime), as well as predisposing (health beliefs, stigma, and gender norms), enabling (agency to negotiate gendered power), and need (perceived HIV risk and perceptions of partner characteristics) features of individuals in the population. Conclusion African American women living in public housing are especially vulnerable to HIV infection due to intersectional discrimination based on racism, classism, gender power dynamics, and community conditions. Our findings confirm the need to develop HIV intervention programming addressing intersectional identities of those making up the communities they plan to address, and being informed by those living in the communities they plan to act on

    Phase transition behavior of the layered perovskite CsBi0.6La0.4Nb2O7 : a hybrid improper ferroelectric

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    We thank EPSRC for a PhD studentship to CALD (EP/P505097/1).The phase behavior of the layered perovskite CsBi0.6La0.4Nb2O7, of the Dion-Jacobson family, has been studied by high-resolution powder neutron diffraction between temperatures 25 < T < 850 °C. At ambient temperature this material adopts the polar space group P21am; this represents an example of hybrid improper ferroelectricity caused by the interaction of two distinct octahedral tilt modes. Within the limits of our data resolution the thermal evolution of the crystal structure is consistent with a first-order transition between 725 and 750 °C, with both tilt modes vanishing simultaneously, leading to the aristotype space group P4/mmm. This apparent ‘avalanche transition’ behavior resembles that seen in the related Aurivillius phase SrBi2Nb2O9.Publisher PDFOtherPeer reviewe

    N-terminal acetylation promotes synaptonemal complex assembly in C. elegans

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    N-terminal acetylation of the first two amino acids on proteins is a prevalent cotranslational modification. Despite its abundance, the biological processes associated with this modification are not well understood. Here, we mapped the pattern of protein N-terminal acetylation in Caenorhabditis elegans, uncovering a conserved set of rules for this protein modification and identifying substrates for the N-terminal acetyltransferase B (NatB) complex. We observed an enrichment for global protein N-terminal acetylation and also specifically for NatB substrates in the nucleus, supporting the importance of this modification for regulating biological functions within this cellular compartment. Peptide profiling analysis provides evidence of cross-talk between N-terminal acetylation and internal modifications in a NAT substrate-specific manner. In vivo studies indicate that N-terminal acetylation is critical for meiosis, as it regulates the assembly of the synaptonemal complex (SC), a proteinaceous structure ubiquitously present during meiosis from yeast to humans. Specifically, N-terminal acetylation of NatB substrate SYP-1, an SC structural component, is critical for SC assembly. These findings provide novel insights into the biological functions of N-terminal acetylation and its essential role during meiosis

    The ArDM experiment

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    The aim of the ArDM project is the development and operation of a one ton double-phase liquid argon detector for direct Dark Matter searches. The detector measures both the scintillation light and the ionization charge from ionizing radiation using two independent readout systems. This paper briefly describes the detector concept and presents preliminary results from the ArDM R&D program, including a 3 l prototype developed to test the charge readout system.Comment: Proceedings of the Epiphany 2010 Conference, to be published in Acta Physica Polonica

    Coupling to optical phonons in the one-dimensional t-J model: Effects on superconducting fluctuations and phase separation

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    The one-dimensional (1D) tt-JJ Holstein model is studied by exact diagonalization of finite rings using a variational approximation for the phonon states. Due to renormalization effects induced by the phonons, for intermediate electron-phonon coupling, the phase separation (PS) boundary, and with it the region of dominating superconducting fluctuations is shifted substantially to smaller values of J/tJ/t as compared to the pure tt-JJ model. Superconducting correlations are weakened through charge density wave interactions mediated by the phonons. Possible consequences for the high TcT_c oxides are discussed.Comment: 4 pages, Latex2
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