9,479 research outputs found

    A process yields large quantities of pure ribosome subunits

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    Development of process for in-vitro protein synthesis from living cells followed by dissociation of ribosomes into subunits is discussed. Process depends on dialysis or use of chelating agents. Operation of process and advantages over previous methods are outlined

    A 20 Thousand Solar Mass Black Hole in the Stellar Cluster G1

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    We present the detection of a 2.0(+1.4,-0.8)x10^4 solar mass black hole (BH) in the stellar cluster G1 (Mayall II), based on data taken with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope. G1 is one of the most massive stellar clusters in M31. The central velocity dispersion (25 kms) and the measured BH mass of G1 places it on a linear extrapolation of the correlation between BH mass and bulge velocity dispersion established for nearby galaxies. The detection of a BH in this low-mass stellar system suggests that (1) the most likely candidates for seed massive BHs come from stellar clusters, (2) there is a direct link between massive stellar clusters and normal galaxies, and (3) the formation process of both bulges and massive clusters is similar due to their concordance in the M_BH/sigma relation. Globular clusters in our Galaxy should be searched for central BHs.Comment: 4 pages, accepted in The Astrophysical Journal Letters, October 200

    Conquering the cattle plague: The global effort to eradicate rinderpest

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    The Global Effort to Eradicate Rinderpest

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    During the past 70 years, concerted efforts by the national veterinary services of affected countries from Senegal to China and Russia to South Africa—aided by international organizations—have brought the once-dreaded rinderpest virus to the point of extinction. In the near future, we can expect to see a global declaration of freedom from rinderpest, the first time this has been achieved for a livestock disease. The devastation wrought by rinderpest stimulated the founding of veterinary schools in many countries, and provided the basis for the development of the veterinary profession. The legacy of control programs in the past 20 years includes vaccine innovations and the development of new epidemiological and surveillance tools that are based on participatory techniques. Additionally, the benefits derived from eradication are many, ranging from increased confidence in livestock-based agriculture to increased food security, protected rural livelihoods, technically more proficient veterinary services, an opening of trade into lucrative markets in the Middle East, and the safeguarding of Africa’s wildlife heritage from a serious threat to its dwindling populations. As for the financial benefits of rinderpest eradication, describing them is constrained because of a general lack of studies on the subject, and the fact that programs covering multiple issues often did not clearly discern the rinderpest problem. This analysis attempts to present lessons learned from the experience gained in eradicating rinderpest, and explores the socioeconomic gains made as a result

    An Integral Field Study of Abundance Gradients in Nearby LIRGs

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    We present for the first time metallicity maps generated using data from the Wide Field Spectrograph (WiFeS) on the ANU 2.3m of 9 Luminous Infrared Galaxies (LIRGs) and discuss the abundance gradients and distribution of metals in these systems. We have carried out optical integral field spectroscopy (IFS) of several several LIRGs in various merger phases to investigate the merger process. In a major merger of two spiral galaxies with preexisting disk abundance gradients, the changing distribution of metals can be used as a tracer of gas flows in the merging system as low metallicity gas is transported from the outskirts of each galaxy to their nuclei. We employ this fact to probe merger properties by using the emission lines in our IFS data to calculate the gas-phase metallicity in each system. We create abundance maps and subsequently derive a metallicity gradient from each map. We compare our measured gradients to merger stage as well as several possible tracers of merger progress and observed nuclear abundances. We discuss our work in the context of previous abundance gradient observations and compare our results to new galaxy merger models which trace metallicity gradient. Our results agree with the observed flattening of metallicity gradients as a merger progresses. We compare our results with new theoretical predictions that include chemical enrichment. Our data show remarkable agreement with these simulations.Comment: Accepted for publication in ApJ. 26 pages, 18 figure

    Basal cell nuclear size in experimental oral mucosal carcinogenesis.

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    It has been suggested that the size of the nuclei of epithelial basal cells can be used in predicting the likelihood of malignant transformation of epithelium. This proposition was assessed in rat palatal epithelium after the carcinogen 4-nitroquinoline-1-oxide had been applied to the epithelium for varying periods of time. No consistent alterations in basal cell nuclear size, including area, perimeter, diameter and regularity of form were found with routine light microscopy as the epithelium passed through various stages of dysplasia to carcinoma. This finding casts doubt on the value of using a variation of basal cell nuclear size as a predictor of malignant transformation

    Condition-based maintenance for major airport baggage systems

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    Purpose: The aim of this paper is to develop a contribution to knowledge that adds to theempirical evidence of predictive condition-based maintenance by demonstrating how theavailability and reliability of current assets can be improved without costly capital investment,resulting in overall system performance improvements.Methodology: The empirical, experimental approach, technical action research (TAR), wasdesigned to study a major Middle-Eastern airport baggage handling operation. A predictivecondition-based maintenance prototype station was installed to monitor the condition of ahighly complex system of static and moving assets.Findings. The research provides evidence that the performance frontier for airport baggagehandling systems can be improved using automated dynamic monitoring of the vibration anddigital image data on baggage trays as they pass a service station. The introduction of low-endinnovation, which combines advanced technology and low-cost hardware, reduced assetfailures in this complex, high speed operating environment.Originality/Value: The originality derives from the application of existing hardware with thecombination of Edge and Cloud computing software through architectural innovation resultingin adaptations to an existing baggage handling system within the context of a time-criticallogistics system.Keywords: IoT, Condition-based maintenance, Predictive maintenance, Edge computing, IoT,Technical Action Research, Theory of Performance Frontiers,Case Stud

    Proper motions in Terzan 5: membership of the multi-iron sub-populations and first constrain to the orbit

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    By exploiting two sets of high-resolution images obtained with HST ACS/WFC over a baseline of ~10 years we have measured relative proper motions of ~70,000 stars in the stellar system Terzan 5. The results confirm the membership of the three sub-populations with different iron abudances discovered in the system. The orbit of the system has been derived from a first estimate of its absolute proper motion, obtained by using bulge stars as reference. The results of the integration of this orbit within an axisymmetric Galactic model exclude any external accretion origin for this cluster. Terzan 5 is known to have chemistry similar to the Galactic bulge; our findings support a kinematic link between the cluster and the bulge, further strengthening the possibility that Terzan 5 is the fossil remnant of one of the pristine clumps that originated the bulge.Comment: 25 pages, 14 figures, accepted for publication by Ap

    HST-NICMOS Observations of M31's Metal Rich Globular Clusters and Their Surrounding Fields: I. Techniques

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    We have obtained HST-NICMOS observations of five of M31's most metal rich globular clusters. These data allow photometry of individual stars in the clusters and their surrounding fields. However, to achieve our goals -- obtain accurate luminosity functions to compare with their Galactic counterparts, determine metallicities from the slope of the giant branch, identify long period variables, and estimate ages from the AGB tip luminosity, we must be able to disentangle the true properties of the population from the observational effects associated with measurements made in very crowded fields. In this paper we present a careful analysis of photometry in crowded regions, and show how image blending affects the results and interpretation of such data. Although this analysis is specifically for our NICMOS observations in M31, the techniques we develop can be applied to any imaging data taken in crowded fields; we show how the effects of image blending will even limit NGST. We use three different techniques to analyze the effects of crowding on our data, including the insertion of artificial stars (traditional completeness tests) and the creation of completely artificial clusters. They are used to derive threshold- and critical-blending radii for each cluster, which determine how close to the cluster center reliable photometry can be achieved. The simulations also allow us to quantify and correct for the effects of blending on the slope and width of the RGB at different surface brightness levels.Comment: AAS LaTeX v5.0, 18 pages. Submitted to the A

    An Empirical Measure of the Rate of White Dwarf Cooling in 47 Tucanae

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    We present an empirical determination of the white dwarf cooling sequence in the globular cluster 47 Tucanae. Using spectral models, we determine temperatures for 887 objects from Wide Field Camera 3 data, as well as 292 objects from data taken with the Advanced Camera for Surveys. We make the assumption that the rate of white dwarf formation in the cluster is constant. Stellar evolution models are then used to determine the rate at which objects are leaving the main sequence, which must be the same as the rate at which objects are arriving on the white dwarf sequence in our field. The result is an empirically derived relation between temperature (TeffT_{eff}) and time (tt) on the white dwarf cooling sequence. Comparing this result to theoretical cooling models, we find general agreement with the expected slopes between 20,000K and 30,000K and between 6,000K and 20,000K, but the transition to the Mestel cooling rate of Tefft0.4T_{eff} \propto t^{-0.4} is found to occur at hotter temperatures, and more abruptly than is predicted by any of these models.Comment: 10 pages, 16 figures, accepted for publication in Ap
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