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A broadband, digital damper system for both transverse planes developed for the SNS accumulator ring has recently damped the first indications of the broadband 50–150 MHz e-p instability in a 1.2 MW neutron production beam. This paper presents details of the design and operation of the SNS damper system as well as results of active damping of the e-p instability in the SNS ring showing a reduction in power of betatron oscillation over the 10–300 MHz band of up to 70%. The spectral content of the beam during operation, with and without the damper system is presented and performance of the damper system is evaluated. [ABSTRACT FROM AUTHOR]

Bovine digital dermatitis (DD) is a severe infectious disease causing lameness in dairy cattle worldwide and is an important ruminant welfare problem that has considerable economic issues. Bovine DD is endemic in many regions worldwide and it is important to understand this major disease so that effective control strategies can be identified. There is substantial evidence that specific treponeme phylotypes play an important causative role in bovine DD. This review considers current research, including DD Treponema spp. investigations, associated DD pathobiology, and current and potential treatment and control options. Epidemiological data, alongside new microbiological data, help delineate important transmission routes and reservoirs of infection that allow effective interventions to be identified. Better on-farm housing hygiene, pasture access, routine footbathing and claw trimming with disinfected equipment need to be implemented to significantly reduce the incidence of DD. There is a paucity of peer reviewed research into both commonly used and novel treatments. In vitro antimicrobial susceptibility studies of DD treponemes and effective treatment of human treponematoses clearly indicate that antibiotics frequently selected for DD treatments are not the most efficacious. Whilst there are understandable concerns over milk withdrawal times in dairy cattle, more needs to be done to identify, license and implement more appropriate antibiotic treatments, since continued overuse of less efficacious antibiotics, applied incorrectly, will lead to increased disease recurrence and transmission. More research is needed into methods of preventing DD that circumvent the use of antibiotics, including vaccination and transmission blocking studies, to reduce or hopefully eradicate DD in the future. [ABSTRACT FROM AUTHOR]

A coasting hadron beam with an elliptical transverse profile, uniform charge density, and small transverse four-dimensional (4D) emittance could improve accelerator performance in several contexts. A phase space painting method to generate such a distribution is being tested in the Spallation Neutron Source (SNS) accumulator ring. A critical component of these efforts is to measure the 4D emittance of the beam during accumulation. The 4D emittance can be reconstructed from measured beam profiles in two ways: in the multi-optics method, the optics between a reconstruction and measurement location are varied; in the fixed-optics method, multiple measurement locations are used without modifying the optics. The fixed-optics method is faster but can lead to large uncertainty in the reconstructed 4D emittance. In this paper, we implement a variant of the multi-optics method using the four available wire-scanners near the SNS target. We also modify the wire-scanner region to reduce the uncertainty of the fixed-optics method. We then demonstrate the usefulness of the fixed-optics method by reconstructing the 4D emittance evolution during accumulation in the SNS ring. [ABSTRACT FROM AUTHOR]

Bovine digital dermatitis (BDD) is an infective foot disease commonly reported in dairy cattle where Treponema are considered as the primary causative infectious agents. There still remains little definitive information on the etiology of BDD in beef cattle suggesting further investigations are warranted. Beef BDD lesions ( n = 34) and healthy beef foot tissues ( n = 38) were analysed by PCR for three BDD-associated Treponema phylogroups and also for Dichelobacter nodosus and Fusobacterium necrophorum . Spirochete culture was attempted on all BDD lesion samples. One or more BDD-associated Treponema phylogroups were detected in 100% of beef BDD lesions. “ Treponema medium/Treponema vincentii -like”, “ Treponema phagedenis -like” and Treponema pedis spirochetes were identified in 27/34 (79%), 31/34 (91%) and 24/34 (71%) of BDD lesions, respectively. No BDD-associated treponeme DNA was amplified from beef healthy foot tissues. D. nodosus and F. necrophorum were present in 24/34 (71%) and 15/34 (44%) of lesions and 10/38 (26%) and 12/38 (32%) of healthy foot tissues, respectively. Twenty spirochetes were isolated from beef BDD lesions; 19 were representatives of the three BDD-associated Treponema phylogroups. One spirochete isolate shared less than 97% 16S rRNA gene similarity to the three cultivable BDD-associated Treponema phylogroups and therefore may represent a novel taxa of Treponema. Upon comparison, sheep contagious ovine digital dermatitis (CODD), dairy cattle and beef cattle BDD lesions appear to have extremely similar bacteriological data and therefore provides evidence of a shared etiopathogenesis posing concerns for cross-species transmission. [ABSTRACT FROM AUTHOR]

Abstract: Digital dermatitis (DD) is a major infectious lameness of dairy cattle and sheep considered to be caused by treponemes. The aim of this study was to identify antibiotics effective against DD treponemes that might be useful in the treatment of ruminant DD in the future or to identify antibiotics useful in isolation studies. Here, a microdilution method was used to identify in vitro antimicrobial susceptibility of treponemes cultured from DD lesions to eight relevant antibiotics. DD treponemes exhibited highest susceptibility to amoxicillin, azithromycin and gamithromycin. Unfortunately, amoxicillin whilst having potential for DD treatment in other animals (e.g. sheep) would require milk withhold periods in dairy cattle. DD treponemes were not particularly susceptible to two cephalosporins: cefalexin and ceftiofur, which do not require milk withhold. The bacteria demonstrated low susceptibility to trimethoprim and especially colistin suggesting these antimicrobials may be particularly useful in isolation of DD treponemes. The most promising high susceptibility results for macrolides indicate a rationale to consider veterinary licensed macrolides as DD treatments. Furthermore, given the DD treponeme antibiotic susceptibility similarities to established treatments for human treponematoses, identification of treponemacidal, long acting β-lactam analogues not requiring milk withhold may allow for development of a successful treatment for dairy cattle DD. [Copyright &y& Elsevier]

Abstract: Fluorite is one of the secondary minerals precipitated in pore spaces at the future nuclear waste repository site at Yucca Mountain, Nevada. The authors have conducted (U–Th)/He dating of this fluorite in an attempt to constrain the temperature and timing of paleo-fluid flux into the site. Repeated analysis of colourless fluorite yielded a weighted average age of 9.7±0.15Ma (2σ), younger than previously determined sanidine 40Ar/39 Ar ages (12.8Ma) for deposition of the tuff. Laboratory He-diffusion experiments conducted on the Yucca fluorite yield a preliminary He closure temperature (T c) of 90±10°C (cooling rate of 10°C/Ma) and previous studies have determined that the fluorite precipitated from warm fluids (65–80°C) at depths of <400m. However, minerals can experience partial He loss at temperatures well below the T c and therefore the (U–Th)/He age of 9.7Ma is interpreted to be a cooling age. This result implies that the last period of elevated temperature fluid circulation through the Yucca site was approximately 9.7Ma ago. It was observed that the purple coloured outer portion of the fluorite nodule yielded non-reproducible and invariably older ages than colourless fluorite. Several possible reasons are suggested. [Copyright &y& Elsevier]

On Earth, impact structures are rare in intertropical zones. Here we evaluate the 35–40 km diameter Velingara depression in Senegal as a candidate impact structure. The depression has a topographic relief of only 50 m and is essentially buried under modern sediments. For the first time, potential-field ground observations and a microstructural survey of detrital zircons for shock features were conducted at Velingara. A 15 mGal gravity low in a 10 km diameter central anomaly was found, while significant (100 nT) amplitude magnetic field anomalies were observed in the depression. Forward modeling was used to explain the crustal sources of the anomalies, arguing in favor of the presence of a buried impact structure. An electron backscatter diffraction survey of circa 5,000 detrital zircons from a sample of modern alluvium identified a single granular zircon; orientation data for the grain does not record the former presence of reidite, but does closely resemble grains with highly dispersed neoblast orientations that have only been reported from impact settings. Age determination by LA-ICP-MS indicates the unusual granular zircon recorded an age of ca. 550 Ma. Results of the geophysical data and zircon microstructural survey reported here are consistent with, but do not yet prove, an impact origin hypothesis for the Velingara structure. The difference in amplitude between the diameter of the depression, and that of the gravity anomaly remains puzzling. Several impact scenarios are considered, which include the subsequent evolution via surface processes of a 10-km crater into a larger depression, or a large-scale (d = 40 km) complex impact crater with a peculiar geophysical anomaly limited to its central region. • The Velingara depression (Senegal) shows a 10 km diameter 15 mGal low gravity anomaly. • A single granular zircon has been found in recent alluvium. • We suggest a hypervelocity meteorite impact origin for the Velingara depression. • The impact crater diameter ranges between 10 and 40 km. [ABSTRACT FROM AUTHOR]

The Marañón Valley, located in the Eastern Cordillera of the northern Peruvian Andes, represents a 160-km-long section of the continental margin that was mainly active during the Paleozoic. A combination of whole rock geochemistry, and U-Pb, O and Hf isotope microanalysis of zircon on selected igneous rocks, reveals the timing and magmatic source variations along and across-strike of the Paleozoic proto-Andean margin. The igneous rocks exhibit a typical arc-related continental margin signature, with strong enrichment in LILE (e.g., Cs, Rb and Th), depletion of HFSE (e.g., Nb) and a negative Ti anomaly. The overlapping Hf-O isotopic compositions, together with similar inherited zircon ages, are consistent with the Lavasen Volcanics, the Esperanza Subvolcanic Complex and the Pataz Batholith sharing the same crustal source components, in about the same proportion. A genetic relationship is further supported by the strong depletion in Sr, Nb, Ta, Ti and Eu in the subvolcanic and volcanic rocks from the Esperanza Subvolcanic Complex and Lavasen Volcanics compared to the intrusive rocks from the Pataz Batholith, which is consistent with evolution of the erupted magmas by fractional crystallization. The new zircon U-Pb (LA-ICP-MS) age determinations, in combination with previously published geochronological data, suggest that the Pataz Batholith, the Esperanza Subvolcanic Complex and the Lavasen Volcanics were emplaced contemporaneously between ca. 342 Ma and 332 Ma. The new Mississippian U-Pb (zircon U-Pb LA-ICP-MS) age determination for the Lavador Pluton (336–332 Ma) and the Callangate-Enaben Pluton (341–337 Ma) suggest that magmatism was coeval with the emplacement of the Pataz Batholith. The Lavador Pluton is aligned with the main N-NW trend of the Pataz Batholith, and shares a similar range of Hf-O isotopic values (i.e., ε Hf (t) values from −5.3 to −1.3 and δ18O values from 6.4 to 7.1‰), and is therefore believed to represent a northern extension of the Pataz Batholith. The isotopic geochemistry and lithogeochemistry record in the Marañón Valley illustrates the regional scale tectonic switches that occurred during arc formation, from syn -collisional and compression in the Pataz-Parcoy district between ca. 342 Ma and 332 Ma, to post-collisional and extensional in the Montañitas district between ca. 332 Ma and 319 Ma. The delineation of the timing and location of tectonic regime switches in the Marañón Valley may provide a basis for future mineral exploration. • Long-lived magmatic activity in a compressional tectonic regime (ca. 342–332 Ma). • Juvenile magmatic input in extensional tectonic regime (ca. 332–321 Ma). • Intrusive and extrusive rocks at Pataz form a cogenetic magmatic suite. • Hf-O isotopes attest to a large contribution of older crustal material. [ABSTRACT FROM AUTHOR]

Abstract The petrological information preserved in the trace element signature of titanite is a valuable complement to in situ U/Pb geochronology, and can be used to refine interpretations on the growth of this mineral. We present trace element and U/Pb isotopic compositions of titanite grains in five amphibolite- to granulite-facies samples from the east Albany-Fraser Orogen of Western Australia. Chondrite-normalised rare earth element (REE) abundance patterns discriminate between titanite populations and correlate with backscatter electron (BSE) zonation. In two samples, titanite REE composition correlates with proximity to garnet, and in one sample titanite composition correlates with gneissic compositional banding. The Dy/Yb ratio can be used as a geochemical indicator to link titanite growth to garnet growth. Titanite that crystallised in a garnet-bearing assemblage is HREE-depleted with Dy/Yb > 2, whereas titanite that crystallised in a garnet-free assemblage typically has flat HREE patterns with Dy/Yb < 2. The titanite grains investigated in this study have a wide range of Eu and LREE signatures, with no obvious correlation to mineralogy, lithology, or growth environment. Furthermore, the Th/U ratio is not uniquely diagnostic of metamorphic or magmatic titanite. For the five samples reported here, Eu, LREE and Th/U are useful to discriminate between titanite populations, but not necessarily as growth process indicators. By integrating the REE signatures with U/Pb data, the five new titanite U/Pb ages can be linked to a range of processes: magmatic titanite crystallisation, metamorphic titanite growth, garnet growth, and/or cooling through the closure temperature for Pb diffusion in titanite. Highlights • We report trace element and U/Pb data for titanites from the Albany-Fraser Orogen. • Titanite HREE depletion correlates with growth in a garnet-bearing assemblage. • The Dy/Yb ratio can be used as an indicator to link titanite and garnet growth. • Titanite U/Pb ages are attributed to magmatic or metamorphic growth, or cooling. [ABSTRACT FROM AUTHOR]

Cosmogenic exposure dating of Ca-rich minerals using 38 Ar on terrestrial rocks could be a valuable new dating tool to determine timescales of geological surface processes on Earth. Here, we show that advancement in analytical precision, using the new generation multi-collector ARGUSVI mass spectrometer on irradiated pyroxene and apatite samples, allows determination of cosmogenic 38 Ar abundances above background values, as well as discrimination of 38 Ar/ 36 Ar ratios (1 σ absolute precision of ±0.3%) from the non-cosmogenic background value. Four statistically significant cosmochron ( 38 Ar/ 36 Ar vs 37 Ar/ 36 Ar) diagrams could be constructed for southeast Australian pyroxene samples from the Mt Elephant scoria cone for which a combined apparent exposure age of 313 ± 179 ka (2 σ ) was obtained when using a 38 Ar production rate (Ca) of 250 atoms /g Ca/ yr. This exposure age overlaps within error with the known 40 Ar/ 39 Ar eruption age of 184 ± 15 ka (2 σ ). Although apatite shows much larger 38 Ar abundances than pyroxene, our modelling and analyses of unirradiated apatite suggest that apatite suffers from both natural and reactor-derived chlorogenic as well as natural nucleogenic contributions of 38 Ar. Hence, we suggest that cosmogenic 38 Ar exposure dating on irradiated Ca-rich (and eventually K-rich), but Cl-free, terrestrial minerals is a potential valuable and accessible tool to determine geological surface processes on timescales of a few Ma. Calculations show that with the new generation multi-collector mass spectrometers an analytical uncertainty better than 5% (2 σ ) can be achieved on samples with expected exposure ages of >4 Ma. [ABSTRACT FROM AUTHOR]

Titanite and apatite have Pb closure temperatures of ∼700 °C and 450–550 °C, respectively, allowing different points on a cooling trajectory to be determined. However, both phases typically accommodate moderate to significant quantities of common Pb. Understanding the thermal diffusivity of a specific isotopic system in different minerals along with their apparent U-Pb age allows modelling of regional cooling trends. Such cooling trends may provide key evidence for correct interpretation of the measured geochronometer. Specifically, thermal history reconstruction may address questions related to the interpretation of an isotopic date as the time of crystallization versus cooling, or alternatively, as a resetting age. In this work, a case study from metavolcanic rocks of the Karrat Group, West Greenland, is used to inform the U-Pb geochronology of common Pb bearing phases, thermal modelling, and also the regional geology. Magmatic apatite yields a reset U-Pb age of 1826 ± 9 Ma, whereas titanite yields a mean U-Pb age of 1768 ± 8 Ma. The apatite age is interpreted as the time of total resetting during a >485 °C event. In contrast, the titanite age is interpreted as the time of metamorphic crystallization, consistent with its REE chemistry. Thermal modelling indicates this metamorphic event did not exceed 452 °C. The resetting of the U-Pb system in magmatic apatite is interpreted as a response to the collision between the Rae Craton and the Superior Craton during the Trans-Hudson Orogeny. However, subsequent metamorphic titanite growth is interpreted as distal evidence of an event shared with the Nagssugtoqidian Orogen. The modelled thermal history implies over 100 million years of communal tectonic history between the Nagssugtoqidian and Rinkian Orogens. Of great significance is the fact that both apatite and titanite show distinctly different common Pb compositions. Apatite retains common Pb with a composition similar to ancient common Pb, whereas titanite retains common Pb with a lower 207 Pb/ 206 Pb ratio implying it was influenced also by Pb from recrystallized precursor U bearing minerals. The common Pb signature in minerals may assist in interpretation of the growth mechanism of the dated phase. [ABSTRACT FROM AUTHOR]

Monazite within a granite intruding the Kalak Nappe Complex (Norway) provides an informative example of a complex age spectrum in which U–Th–Pb data scatters for ˜300 Ma along the Concordia curve. SIMS analyses yield 207 Pb/ 235 U ages (1σ) of 876 ± 18 to 633 ± 15 Ma, and petrographically constrained age groupings suggest dates of 856 ± 16 Ma for oscillatory zoned cores, 761 ± 32 Ma for patchy domains, and 647 ± 21 Ma for rims. A grid of LA-ICPMS spots across a single grain resolve 207 Pb/ 235 U ages (1σ) of 884 ± 23 to 564 ± 14 Ma, corroborating the spread in the SIMS dataset and highlighting its spatial relationship to BSE textures. Such Concordia patterns have led to diverse interpretations including prolonged growth or the influence of a variety of radiogenic-Pb mobility processes. In combination with U–Pb analyses, detailed chemical, EBSD, and Raman imaging are used to resolve the primary mechanism for this protracted age spread. The spread in monazite ages is not the result of deformation-induced radiogenic Pb loss because EBSD reveals that the grains are only weakly deformed and have no discernible microstructures. The age spread is not the result of thermally induced radiogenic Pb mobility either, as thermal diffusion time–temperature models fail to reproduce the observed age pattern, and even simplifications indicate diffusion domains that are vastly below the observed scale of dated domains. The age spread is not the result of metamictization as well-defined Raman peaks and the strong EBSPs indicate a well-ordered crystal structure. Younger monazite domains have smaller negative Eu/Eu* anomalies, elevated La N /Yb N ratios, and enhanced Th and U. The age distribution is primarily attributed to fluid-mediated element mass transfer driven by coupled substitution in the altered parts of monazite, consistent with the geochemical signatures in these domains. This process left the P–O framework of the original c. 850 Ma magmatic crystal intact, as confirmed by EBSD, but variably purged of its radiogenic-Pb cargo, as demonstrated by spatial interpolation of LA-ICPMS U–Pb data. In some instances, removal of radiogenic Pb appears complete, consistent with the correlation between texturally-defined age domains and well-known tectonothermal events, as inferred from dated intrusive rocks in the region. These results indicate the susceptibility of monazite to fluid alteration, which allows even a single monazite grain to record several tectonothermal events and potentially chart much of an orogens history. [ABSTRACT FROM AUTHOR]

Biotite generates significant radiogenic Sr and is thus suitable for Rb–Sr dating, which can be achieved directly in thin section via laser ablation and provides a means to directly date growth of this important fabric-forming mineral or its cooling. In contrast, apatite has an extremely low Rb/Sr ratio and hence offers a useful tool to estimate source 87Sr/86Sr i. Plagioclase also contains significant Sr and may further assist in understanding the rocks Sr isotopic system. However, the fluid source of growing or recrystallizing apatite, plagioclase, and biotite need not be the same. Compounding the complexity, apatite may gain radiogenic Sr from biotite during recrystallization or dissolution–reprecipitation that accompanies metamorphism. In this contribution, we present a case study from the Kalak Nappe Complex in the Scandinavian Caledonides, Arctic Norway, where a combined geochronology program, critically supported by biotite Rb–Sr dating, helps to resolve the conspicuous inverted metamorphic field gradient found upwards through the nappe stack in this orogen. Apatite U–Pb ages of 417–413 Ma in the upper nappes are interpreted as cooling through the Pb retention zone. Such ages contrast with the suggestion of older, partially reset apatite ages in the lower nappes. Biotite Rb–Sr ages of c. 413 Ma in the upper nappes are similar to U–Pb ages of coexisting apatite but conspicuously different from c. 433 Ma biotite Rb–Sr ages in the lower nappes. Ages of c. 433 Ma are comparable to muscovite 40Ar/39Ar and titanite and monazite U–Pb ages throughout the complex and may directly date mineral growth at peak thermal conditions during the Scandian orogenic event. Apatite 87Sr/86Sr ratios also track the influence of metamorphism and imply more radiogenic signatures relative to relic plagioclase in samples which have greater overprinting in the upper nappes of the complex. Phase equilibrium modelling establishes Palaeozoic peak P–T conditions of 610–750 °C at <12 kbar in the upper nappes, comparable to peak conditions previously established for the lower nappes. Combined thermal modelling of the post-peak Scandian orogenic history based on published 40Ar/39Ar, paired with new Rb–Sr, and U–Pb data, implies a slower cooling pathway in the upper nappes relative to the lower nappes. We reconcile this thermal history with a geodynamic model of obduction of a hot back-arc, as represented by the Silurian Magerøy Nappe, onto the upper nappes of the Kalak Nappe Complex at c. 430 Ma. These results demonstrate that in-situ laser ablation Rb–Sr dating of biotite provides a powerful tool for resolving orogenic tectonothermal histories in orogens flushed with excess argon. [ABSTRACT FROM AUTHOR]

• An outbreak of an infectious dermatological disorder of unknown aetiology in a flock of yearling lambs was investigated. • Lesions occurred on the distal limb between the coronary band and carpel joint as a circular ulcerative dermatitis. • Treponema spp., Dichelobacter nodosus , Staphylococcus aureus, Dermatophilus congolensis and poxvirus screens were negative. • Fusobacterium necrophorum and Streptococcus dysgalactiae were detected in the majority of lesions examined. • An aetiology involving bacterial infection with F. necrophorum and S. dysgalactiae was implicated. Here we report an outbreak of an atypical, ulcerative dermatitis in North Country mule lambs, located in South Gloucestershire, UK. The lesions, which appeared to be contagious, occured between the coronary band and the carpal joint as a focal, well demarcated, circular, ulcerative dermatitis. Histopathological examination of the lesion biopsies revealed areas of ulceration, epidermal hyperplasia, suppurative dermatitis and granulation tissue. Clumped keratohyalin granules and intracellular keratinocyte oedema (ballooning degeneration) were evident within lesion biopsies, consistent with an underlying viral aetiology. A PCR-based microbiological investigation failed to detect bovine digital dermatitis-associated treponeme phylogroups, Dichelobacter nodosus , Staphylococcus aureus , Dermatophilus congolensis or Chordopoxvirinae virus DNA. However, 3 of the 10 (30 %) and 6 of 10 (60 %) lesion samples were positive for Fusobacterium necrophorum and Streptococcus dysgalactiae DNA, respectively. Contralateral limb swabs were negative by all standard PCR assays. To better define the involvement of F. necrophorum in the aetiology of these lesions, a qPCR targeting the rpoB gene was employed and confirmed the presence of F. necrophorum DNA in both the control and lesions swab samples, although the mean F. necrophorum genome copy number detected in the lesion swab samples was ∼19-fold higher than detected in the contralateral control swab samples (245 versus 4752 genome copies/μl, respectively; P < 0.001). Although we have not been able to conclusively define an aetiological agent, the presence of both F. necrophorum and S. dysgalactiae in the majority of lesions assayed supports their role in the aetiopathogenesis of these lesions. [ABSTRACT FROM AUTHOR]