Regional and temporal characteristics of <Emphasis Type="Italic">bovine tuberculosis</Emphasis> of cattle in Great Britain     

Aristides Moustakas  Matthew R. Evans 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(3):989-1003

Bovine tuberculosis (TB) is a chronic disease in cattle that causes a serious food security challenge to the agricultural industry in terms of dairy and meat production. Spatio-temporal disease analysis in terms of time trends and geographic disparities of disease dynamics can provide useful insights into the overall efficiency of control efforts as well as the relative efficiency of different management measures towards eradication. In GB, Scotland has had a risk based surveillance testing policy under which high risk herds are tested frequently, and in September 2009 was officially declared as TB free. Wales have had an annual or more frequent testing policy for all cattle herds since January 2010, while in England several herds are still tested every 4 years except some high TB prevalence areas where annual testing is applied. Time series analysis using publicly available data for total tests on herds, total cattle slaughtered, new herd incidents, and herds not TB free, were analysed globally for GB and locally for the constituent regions of Wales, Scotland, West, North, and East England. After detecting trends over time, underlying regional differences were compared with the testing policies in the region. Total cattle slaughtered are decreasing in Wales, Scotland and West England, but increasing in the North and East English regions. New herd incidents, i.e., disease incidence, are decreasing in Wales, Scotland, West English region, but increasing in North and East English regions. Herds not TB free, i.e., disease prevalence, are increasing in West, North, and East English regions, while they are decreasing in Wales and Scotland. Total cattle slaughtered were positively correlated with total tests in the West, North, and East English regions, with high slopes of regression indicating that additional testing is likely to facilitate the eradication of the disease. There was no correlation between total cattle slaughtered and total tests on herds in Wales indicating that herds are tested frequent enough in order to detect all likely cases and so control TB. The main conclusion of the analysis conducted here is that more frequent testing is leading to lower TB infections in cattle both in terms of TB prevalence as well as TB incidence.  相似文献   

Erratum to: Groundwater Storage Changes: Present Status from GRACE Observations     

Jianli Chen  James S. Famiglietti  Bridget R. Scanlon  Matthew Rodell 《Surveys in Geophysics》2016,37(3):701-701

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Rock‐protecting seaweed? Experimental evidence of bioprotection in the intertidal zone          下载免费PDF全文

Matthew R. Gowell  Martin A. Coombes  Heather A. Viles 《地球表面变化过程与地形》2015,40(10):1364-1370

Biogeomorphological processes are an important component of dynamic intertidal systems. On rocky shores, the direct contribution of microorganisms, plants and animals to weathering and erosion is well known. There is also increasing evidence that organisms can alter rock breakdown indirectly, by moderating temperature and moisture regimes at the rock–air interface. These influences have been purported to represent mechanisms of bioprotection, by buffering microclimatic fluctuations associated with weathering processes such as wetting and drying and salt crystallization. However, virtually nothing has been done to test whether microclimatic buffering translates to differences in actual rock breakdown rates. Here we report a preliminary laboratory experiment to assess how an artificial canopy (chosen to represent seaweed) affects mechanical rock breakdown. Using a simplified and accelerated thermal regime based on field data from a rocky shore platform in southern England, UK, we find that breakdown (mineral debris release) of mudstone covered with a canopy is reduced by as much as 79% relative to bare rock after around 100 thermal cycles. Reduction in rock surface hardness (measured using an Equotip device) was also greater for bare rock (17%) compared to covered rock (10%) over this period. Measurements of salt crystal formation indicate that the mechanism driving these differences was a reduction in the frequency of crystallization events, via moisture retention and shading of the rock surface. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Evidence of biogeomorphic patterning in a low‐relief karst landscape          下载免费PDF全文

Adam C. Watts  Danielle L. Watts  Matthew J. Cohen  James B. Heffernan  Daniel L. McLaughlin  Jonathan B. Martin  David A. Kaplan  Todd Z. Osborne  Leda N. Kobziar 《地球表面变化过程与地形》2014,39(15):2027-2037

Patterned landscapes are often evidence of biotic control on geomorphic processes, emerging in response to coupled ecosystem processes acting at different spatial scales. Self‐reinforcing processes at local scales expand patches, while self‐inhibiting processes, operating at a distance, impose limits to expansion. In Big Cypress National Preserve (BICY) in southwest Florida, isolated forested wetland depressions (cypress domes) appear to be evenly distributed within a mosaic of short‐hydroperiod marshes and pine uplands. To test the hypothesis that the apparent patterning is regular, we characterized frequency distributions and spatial patterns of vegetation communities, surface and bedrock elevation, and soil properties (thickness and phosphorus content). Nearest neighbor distances indicate strongly significant wetland spatial overdispersion, and bedrock elevations exhibited periodic spatial autocorrelation; both observations are consistent with regular patterning. Bedrock elevations and soil P were clearly bimodal, suggesting strong positive feedbacks on wetland patch development. Soil‐surface elevations exhibited weaker bimodality, indicating smoothing of surface morphology by some combination of sediment transport, mineral reprecipitation, and organic matter production. Significant negative autocorrelation of bedrock elevations at scales similar to wetland spacing suggest the presence of distal negative feedbacks on patch expansion. These findings support the inference of regular patterning, and are consistent with the presence of local positive feedbacks among hydroperiod, vegetation productivity and bedrock dissolution. These processes are ultimately constrained by distal negative feedbacks, potentially induced by landscape scale limitations on the water volume required to enable this biogeomorphic mechanism. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Dating martian climate change     

David P. Page  Matthew R. Balme  Monica M. Grady 《Icarus》2009,203(2):376-389

Geological evidence indicates that low-latitude polygonally-patterned grounds on Mars, generally thought to be the product of flood volcanism, are periglacial in nature and record a complex signal of changing climate. By studying the martian surface stratigraphically (in terms of the geometrical relations between surface landforms and the substrate) rather than genetically (by form analogy with Earth), we have identified dynamic surfaces across one-fifth of martian longitude. New stratigraphical observations in the Elysium-Amazonis plains have revealed a progressive surface polygonisation that is destructive of impact craters across the region. This activity is comparable to the climatically-driven degradation of periglacial landscapes on Earth, but because it affects impact craters—the martian chronometer—it can be dated. Here, we show that it is possible to directly date this activity based on the fraction of impact craters affected by polygon formation. Nearly 100% of craters (of all diameters) are superposed by polygonal sculpture: considering the few-100 Ma age of the substrate, this suggests that the process of polygon formation was active within the last few million years. Surface polygonisation in this region, often considered to be one of the signs of young, ‘plains-forming’ volcanism on Mars, is instead shown to postdate the majority of impact craters seen. We therefore conclude that it is post-depositional in origin and an artefact of thermal cycling of near-surface ground ice. Stratigraphically-controlled crater counts present the first way of dating climate change on a planet other than Earth: a record that may tell us something about climate change on our own planet. Parallel climate change on these two worlds—an ice age Mars coincident with Earth’s glacial Quaternary period—might suggest a coupled system linking both. We have previously been unable to generalise about the causes of long-term climate change based on a single terrestrial example—with the beginnings of a chronology for climate change on our nearest planetary neighbour, we can.  相似文献   

Calculation of single-scattering albedos: Comparison of Mie results with Hapke approximations     

G.B. Hansen 《Icarus》2009,203(2):672-676

The grain size of water ice can be determined from its near-infrared spectrum, which has numerous diagnostic absorption bands of different opacities. Models that have been used to determine water ice grain size from infrared spectra of icy outer Solar System objects have shown discrepancies in modeled grain size of a factor of two or more. Here the single-scattering albedo calculated using the commonly used Hapke model given by Roush [Roush, T.L., 1994. Icarus 108, 243-254] is compared with the exact calculation for spheres from a Mie series. An earlier approximation of single-scattering albedo called the Hapke “slab” model is also used in the comparison. All three models are implemented using the same optical constants for water ice at ∼110 K. Results are displayed for a large range of grain sizes from 1 μm to 1 mm. In general neither Hapke model can mimic the Rayleigh effects from particles sized near the wavelength of light that the Mie model predicts. For 10 μm particles, the slab model matches the Mie calculation quite well, but larger sizes are more discrepant. The Hapke/Roush model grain size needs to be ∼2.5 times larger to mimic the Mie results, and there are additional discrepancies in the continuum levels and band strengths. The Mie calculation for spheres is recommended for analysis of unknown remote sensing measurements, as it can mimic the spectra of oblate, prolate, and hollow particles given by equivalent sphere theories.  相似文献   

Stellar, brown dwarf and multiple star properties from hydrodynamical simulations of star cluster formation     

Matthew R. Bate 《Monthly notices of the Royal Astronomical Society》2009,392(2):590-616

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Evolution of the u-band luminosity function from redshift 1.2 to 0     

Matthew Prescott  Ivan K. Baldry  Phil A. James 《Monthly notices of the Royal Astronomical Society》2009,397(1):90-102

We produce and analyse u -band (  λ≈ 355  nm) luminosity functions (LFs) for the red and blue populations of galaxies using data from the Sloan Digital Sky Survey (SDSS) u -band Galaxy Survey ( u GS) and Deep Evolutionary Exploratory Probe 2 (DEEP2) survey. From a spectroscopic sample of 41 575 SDSS u GS galaxies and 24 561 DEEP2 galaxies, we produce colour magnitude diagrams and make use of the colour bimodality of galaxies to separate red and blue populations. LFs for eight redshift slices in the range  0.01 < z < 1.2  are determined using the  1/ V _max  method and fitted with Schechter functions showing that there is significant evolution in   M *  , with a brightening of 1.4 mag for the combined population. The integration of the Schechter functions yields the evolution in the u -band luminosity density (LD) out to   z ∼ 1  . By parametrizing the evolution as  ρ∝ (1 + z )^β  , we find that  β= 1.36 ± 0.2  for the combined populations and  β= 2.09 ± 0.2  for the blue population. By removing the contribution of the old stellar population to the u -band LD and correcting for dust attenuation, we estimate the evolution in the star formation rate (SFR) of the Universe to be  β_SFR= 2.5 ± 0.3  . Discrepancies between our result and higher evolution rates measured using the infrared and far-UV can be reconciled by considering possibilities such as an underestimated dust correction at high redshifts or evolution in the stellar initial mass function.  相似文献   

The 2dF-SDSS LRG and QSO Survey: the spectroscopic QSO catalogue     

Scott M. Croom  Gordon T. Richards  Tom Shanks  Brian J. Boyle  Robert G. Sharp  Joss Bland-Hawthorn  Terry Bridges  Robert J. Brunner  Russell Cannon  Daniel Carson  Kuenley Chiu  Matthew Colless  Warrick Couch  Roberto De Propris  Michael J. Drinkwater  Alastair Edge  Stephen Fine  Jon Loveday  Lance Miller  Adam D. Myers  Robert C. Nichol  Phil Outram  Kevin Pimbblet  Isaac Roseboom  Nicholas Ross  Donald P. Schneider  Allyn Smith  Chris Stoughton  Michael A. Strauss  David Wake 《Monthly notices of the Royal Astronomical Society》2009,392(1):19-44

We present the final spectroscopic QSO catalogue from the 2dF-SDSS LRG (luminous red galaxy) and QSO (2SLAQ) survey. This is a deep,  18 < g < 21.85  (extinction corrected), sample aimed at probing in detail the faint end of the broad line active galactic nuclei luminosity distribution at   z ≲ 2.6  . The candidate QSOs were selected from SDSS photometry and observed spectroscopically with the 2dF spectrograph on the Anglo-Australian Telescope. This sample covers an area of 191.9 deg² and contains new spectra of 16 326 objects, of which 8764 are QSOs and 7623 are newly discovered [the remainder were previously identified by the 2dF QSO Redshift Survey (2QZ) and SDSS]. The full QSO sample (including objects previously observed in the SDSS and 2QZ surveys) contains 12 702 QSOs. The new 2SLAQ spectroscopic data set also contains 2343 Galactic stars, including 362 white dwarfs, and 2924 narrow emission-line galaxies with a median redshift of   z = 0.22  .
We present detailed completeness estimates for the survey, based on modelling of QSO colours, including host-galaxy contributions. This calculation shows that at   g ≃ 21.85  QSO colours are significantly affected by the presence of a host galaxy up to redshift   z ∼ 1  in the SDSS ugriz bands. In particular, we see a significant reddening of the objects in   g − i   towards the fainter g -band magnitudes. This reddening is consistent with the QSO host galaxies being dominated by a stellar population of age at least 2–3 Gyr.
The full catalogue, including completeness estimates, is available on-line at http://www.2slaq.info/ .  相似文献   

Three‐dimensional textural and compositional analysis of particle tracks and fragmentation history in aerogel     

Denton S. Ebel  Michael Greenberg  Mark L. Rivers  Matthew Newville 《Meteoritics & planetary science》2009,44(10):1445-1463

Abstract— We report analyses of aerogel tracks using (1) synchrotron X‐ray computed microtomography (XRCMT), (2) laser confocal scanning microscopy (LCSM), and (3) synchrotron radiation X‐ray fluorescence (SRXRF) of particles and their paths resulting from simulated hypervelocity impacts (1–2), and a single ～1 mm aerogel track from the Stardust cometary sample collector (1–3). Large aerogel pieces can be imaged sequentially, resulting in high spatial resolution images spanning many tomographic fields of view (‘lambda‐tomography’). We report calculations of energy deposited, and tests on aromatic hydrocarbons showing no alteration in tomography experiments. Imaging at resolutions from ～17 to ～1 micron/pixel edge (XRCMT) and to <100 nm/pixel edge (LCSM) illustrates track geometry and interaction of particles with aerogel, including rifling, particle fragmentation, and final particle location. We present a 3‐D deconvolution method using an estimated point‐spread function for aerogel, allowing basic corrections of LCSM data for axial distortion. LCSM allows rapid, comprehensive, non‐destructive, high information return analysis of tracks in aerogel keystones, prior to destructive grain extraction. SRXRF with LCSM allows spatial correlation of grain size, chemical, and mineralogical data. If optical methods are precluded in future aerogel capture missions, XRCMT is a viable 3D imaging technique. Combinations of these methods allow for complete, nondestructive, quantitative 3‐D analysis of captured materials at high spatial resolution. This data is fundamental to understanding the hypervelocity particle‐aerogel interaction histories of Stardust grains.  相似文献