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The southwest Indian Ocean (SWIO) recently experienced its most active, costliest and deadliest cyclone season on record (2018–2019). The anticipation and forecasting of natural hazards, such as tropical cyclones, are crucial to preparing for their impacts, but it is important to understand how well forecasting systems can predict them. Despite the vulnerability of the SWIO to tropical cyclones, comparatively little research has focused on this region, including understanding the ability of numerical weather prediction systems to predict cyclones and their impacts in southeast Africa. In this study, we evaluate ensemble probabilistic and high‐resolution deterministic forecasts of tropical cyclones in the SWIO from 2010 to 2020, using two state‐of‐the‐art global forecasting systems: one from the European Centre for Medium‐Range Weather Forecasts (ECMWF) and the other from the U.K. Met Office. We evaluate predictions of the track, assessing the location of the centre of each storm and its speed of movement, as well as its intensity, looking at maximum wind speeds and minimum central pressure, and discuss how the forecasts have evolved over the 10‐year period. Overall, ECMWF typically provides more accurate forecasts, but both systems tend to underestimate translation speed and intensity. We also investigate the impact of the Madden‐Julian Oscillation (MJO) on tropical cyclones and their forecasts. The MJO impacts where and when tropical cyclones form, their tracks and intensities, which in turn impacts forecast skill. These results are intended to provide an increased understanding of the ability of global forecasting systems to predict tropical cyclones in the SWIO, for the purpose of decision making and anticipatory action. [ABSTRACT FROM AUTHOR]

Precipitation efficiency refers to the amount of water that is lost from the atmosphere through precipitation compared to the available water vapor in the atmosphere. This metric plays a critical role in understanding precipitation patterns. However, calculating precipitation efficiency for extratropical cyclones can be challenging because cyclones are dynamic and move through the atmosphere as they evolve. To overcome this challenge, our study uses ERA5 reanalysis data to estimate precipitation efficiencies for 400 Southern Ocean cyclones, with a frame of reference that moves with the individual cyclones. Our findings indicate that at maximum intensity, average precipitation efficiencies reach a maximum of 60%/6 hr near the warm front where ascent rates are the largest. Typically, within 24–36 hr after cyclogenesis, all of the initial water vapor available within 500 km of a cyclone center is lost due to precipitation. However, a cyclone's precipitating phase is prolonged due to local evaporation and moisture flux convergence (MFC), which replenish the moisture lost via precipitation. Close to the cyclone center, MFC provides additional moisture from the environment into which cyclones are traveling. On average, this extends a cyclone's precipitation phase to over 60 hr after cyclogenesis. Thus, while moisture from the genesis location is quickly removed from the cyclone via precipitation, cyclones are replenished by moisture along their track, which doubles the timescale for a cyclone's precipitating phase. Plain Language Summary: Precipitation efficiency is a measure of how much water in the atmosphere falls as rain compared to how much is available to fall. In this study, we estimate how efficient precipitation is for 400 cyclones in the Southern Ocean. We find that when the cyclones are strongest, about 60% of the available water vapor turns into rain every 6 hr near the warm front of the cyclone where air is rising rapidly. Normally, within a day or two of a cyclone forming, all of the available water vapor in the cyclone gets turned into rain. However, the rain can persist for longer because cyclones pick up more moisture as they move, which gets turned into more rain. This can make the rain from a cyclone last on average for 60 hr, even after the initial moisture is all gone. Key Points: The initial moisture content of extratropical cyclones is removed via precipitation within 30 hr after cyclogenesisLocal evaporation and moisture flux convergence doubles the precipitating phase of extratropical cyclonesThe feeder airstream provides a continuous supply of moisture to cyclones in the developing stage of their evolution [ABSTRACT FROM AUTHOR]

The Tianshan orogenic belt, part of the Central Asian Orogenic Belt, offers an opportunity to examine the complexities of an orogenic system that records long‐term intracontinental deformation. The Tianshan have been reactivated multiple times since the Mesozoic, but the mechanisms and driving forces of these various orogenic events are not well constrained. Moreover, the spatial exhumation pattern of the entire Tianshan remains poorly studied. We present new zircon and apatite (U‐Th)/He and apatite fission track thermochronological data for samples from the northwestern part of the Chinese Western Tianshan. They indicate three distinctive phases of rapid cooling in the late Carboniferous‐early Permian, Late Triassic‐Early Jurassic, and Cretaceous. The first phase can be linked to uplift and exhumation related to the subduction/closure of the Paleo‐Asian Ocean, while the episodic cooling during the Late Triassic‐Early Jurassic (250–190 Ma) and Cretaceous (115–80 Ma) are interpreted as related to uplift and exhumation associated with strike‐slip deformation and Mesozoic clockwise or anticlockwise rotation of the Junggar basin. Our new data, in concert with a compilation of previously published data from elsewhere in the region, reveal that the Tianshan underwent a greater amount of exhumation in the southern section, and less exhumation took place to the north. All available data also support the notion that the exhumation process has been essentially the same in tectonic blocks along strike since late Paleozoic. During the Cenozoic, the Tianshan experienced large‐scale, rapid exhumation starting in the late Miocene (12–10 Ma) and not the early Miocene as has been previously proposed. Key Points: Pulsed exhumation episodes in the Tianshan orogenic belt are interpreted as the result of differential rotation of local crustal blocksThe late Paleozoic to Cenozoic regional exhumation was greatest in southwest Tianshan and lessened progressively to the north and eastNew data and regional compilation show that the late Oligocene deformation event was local and did not result in regional exhumation [ABSTRACT FROM AUTHOR]

Polar lows (PLs) are small, intense cyclones that form at high latitudes during the winter. Their high wind speeds and heavy precipitation can have substantial impacts on shipping, coastal communities and infrastructure. However, low‐resolution climate models poorly simulate PLs, which reduces the confidence in their future projections. In this study, Northern Hemisphere (NH) PLs are assessed for the first time in a high‐resolution (25 km) global atmosphere‐only climate model, N512 HadGEM3‐GA3, for both present‐day and future RCP8.5 climate scenarios. The representation of PLs is found to agree reasonably well with the NCEP‐CFS reanalysis. The number of NH PLs are projected to substantially decrease (by over 60%) by the end of the 21st century, which is largely due to an increase in atmospheric static stability. Large decreases in PL activity are found in the Norwegian Sea, north‐east Atlantic and north‐west Pacific Oceans. Smaller changes are found in regions of current PL activity, such as the Barents and Labrador Seas, while new regions of PL activity along the northern Russian coastline are found where the Arctic sea ice is projected to disappear. The spatial differences found in future PL activity could have a substantial impact on human activity in the Arctic region. Plain Language Summary: Polar lows (PLs) are small but intense storms that form during winter at high latitudes and affect regions such as Scandinavia, Northern Russia and Japan. Because of their strong winds and precipitation, PLs can cause damage to infrastructure, shipping and coastal communities. In this study, PLs are assessed for the first time in a high‐resolution (25 km) global climate model for both present climate conditions and a future climate scenario in the Northern Hemisphere. The number of PLs is found to substantially decrease by the end of the 21st century, mainly due to a reduction in vertical temperature differences in the atmosphere. However, new regions of PL activity are found over the Arctic Ocean where the sea ice is projected to retreat. Key Points: The present representation of Northern Hemisphere PLs in a high‐resolution global climate model is found in agreement with previous studiesThe number of PLs is found to decrease by 60% by the end of the 21st century in the RCP8.5 scenario, but new PL locations emergeThe decrease of PL activity in the future is attributed to an atmospheric static stability increase in a baroclinic instability reduction [ABSTRACT FROM AUTHOR]

Single crystal (U‐Th)/He dating has been undertaken on 21 detrital zircon grains extracted from a core sample from Ocean Drilling Project (ODP) site 1073, which is located ~390 km northeast of the center of the Chesapeake Bay impact structure. Optical and electron imaging in combination with energy dispersive X‐ray microanalysis (EDS) of zircon grains from this late Eocene sediment shows clear evidence of shock metamorphism in some zircon grains, which suggests that these shocked zircon crystals are distal ejecta from the formation of the ~40 km diameter Chesapeake Bay impact structure. (U‐Th/He) dates for zircon crystals from this sediment range from 33.49 ± 0.94 to 305.1 ± 8.6 Ma (2σ), implying crystal‐to‐crystal variability in the degree of impact‐related resetting of (U‐Th)/He systematics and a range of different possible sources. The two youngest zircon grains yield an inverse‐variance weighted mean (U‐Th)/He age of 33.99 ± 0.71 Ma (2σ uncertainties n = 2; mean square weighted deviation = 2.6; probability [P] = 11%), which is interpreted to be the (U‐Th)/He age of formation of the Chesapeake Bay impact structure. This age is in agreement with K/Ar, 40Ar/39Ar, and fission track dates for tektites from the North American strewn field, which have been interpreted as associated with the Chesapeake Bay impact event. [ABSTRACT FROM AUTHOR]

Despite ~50 Myr of continuous continent-continent collision, contractional structures in the Himalayan-Tibetan orogen are today limited to the northern and southern margins of the system, while extension dominates much of the interior. On the Tibetan Plateau, Cenozoic E-W extension has been accommodated by strike-slip faults and extensional grabens, while N-S extension at the Tibet-to-Himalaya transition has been accommodated by the South Tibetan fault system (STFS). The genetic relationship between N-S and E-W extension is disputed, although age constraints indicate temporal overlap of at least 7 Myr. In NW Bhutan the two intersect where the STFS basal detachment is cut by the Yadong cross structure (YCS), an extensional half graben that provides a rare opportunity to constrain relative timings. We report U-Pb zircon dates from four STFS footwall leucogranites consistent with episodic magmatism during the middle-late Miocene and in situ U(-Th)-Pb monazite and xenotime dates from three metasedimentary rocks ranging from late Oligocene to middle Miocene. We suggest that amphibolite facies footwall metamorphism was ongoing at the time the basal STFS detachment initiated as a ductile structure in the middle-late Miocene. Late-stage granitic intrusions may reflect footwall melting during extensional exhumation along the STFS, but post-metamorphic and post-intrusion fabrics suggest that most displacement occurred after emplacement of the youngest granites. Some of the oldest YCS-related fabrics are found in a deformed 14 Ma leucogranite, implying middle Miocene ductile deformation. This observation, along with evidence for subsequent brittle YCS deformation, suggests that N-S and E-W extensional structures in the area had protracted and overlapping deformation histories. [ABSTRACT FROM AUTHOR]

The ability of the High-Resolution Global Environmental Monitoring (HiGEM) climate model to represent high-impact, regional precipitation events is investigated in two ways. The first focuses on a case study of extreme regional accumulation of precipitation during the passage of a summer extratropical cyclone across southern England on 20 July 2007 that resulted in a national flooding emergency. The climate model is compared with a global numerical weather prediction (NWP) model and higher-resolution, nested limited-area models. While the climate model does not simulate the timing and location of the cyclone and associated precipitation as accurately as the NWP simulations, the total accumulated precipitation in all models is similar to the rain-gauge estimate across England and Wales. The regional accumulation over the event is insensitive to horizontal resolution for grid spacings ranging from 90-4 km. Secondly, the free-running climate model reproduces the statistical distribution of daily precipitation accumulations observed in the England-Wales precipitation record. The model distribution diverges increasingly from the record for longer accumulation periods, with a consistent under-representation of more intense multiday accumulations. This may indicate a lack of low-frequency variability associated with weather regime persistence. Despite this, the overall seasonal and annual precipitation totals from the model are still comparable to those from ERA-Interim. [ABSTRACT FROM AUTHOR]

Phylogeographic structure is a product of a species' life history and dispersal patterns, geographic history, climatic history and chance. Comparative phylogeography, using carefully chosen model species, can highlight the relative contribution of each of these factors and identify common processes affecting communities. In this study we compare and contrast fine-scale phylogeographic patterns in two ground-dwelling species of water skink, Eulamprus heatwolei and Eulamprus tympanum, from the biogeographically well-characterized Tallaganda region in south-eastern Australia, and compare them against data from a number of invertebrate species from the same region. Using variation in mitochondrial sequence, we have uncovered dramatically different biogeographic histories for the two species, despite their marked behavioural and morphological similarity. Eulamprus tympanum shows an average corrected sequence divergence of 0.014 and patterns of geographic variation in haplotypes consistent with historical vegetational changes resulting from past glaciation cycles. In contrast, E. heatwolei shows an average divergence of only 0.0075, and geographic structure that reflects a recent and rapid colonization, perhaps following an ice age local extinction. These two contrasting patterns of variation have also been identified in invertebrate taxa as disparate as collembolans and spiders; these species show either deep structure, associated with local persistence, or little variation of structure, which we attribute to recent extinction and re-colonization. We argue that historical persistence versus extinction is a consequence of (often minor) differences in lifestyle and local habitat preference. [ABSTRACT FROM AUTHOR]

New U-Pb (titanite, apatite, rutile) and 40Ar/39Ar (hornblende, muscovite, biotite) data are linked with existing pressure-temperature-deformation paths to impose detailed temporal constraints on the juxtaposition and unroofing of domains in an extensive (>20,000 km2) region of exhumed lower crust in the East Lake Athabasca region of the western Canadian Shield. In the ∼200 m.y. between circa 1.9 Ga high-pressure granulite facies metamorphism and circa 1.7 Ga unconformable deposition of Athabasca basin sediments on the exhumed rocks, our analysis reveals at least three distinct phases of unroofing at different rates. Specifically, we distinguish (1) an early phase of extensional unroofing in the Chipman domain at rates of 1.5-2.0 km/m.y. from ∼1.0 GPa to ∼0.8 GPa associated with mafic magmatism and metamorphism, (2) an episode of regional contractional uplift and associated unroofing along the Legs Lake shear zone at circa 1850 Ma from 0.7-0.8 GPa to 0.4-0.5 GPa, and (3) a final period of extensional unroofing at rates of 0.2-0.3 km/m.y. from 0.4 to 0.5 GPa that culminated in transport of current exposures to near-surface conditions. The cooling patterns and retrograde assemblages are consistent with pauses between exhumational phases. The apparent convergence of disparate higher temperature histories in several deep crustal domains at circa 1.89-1.88 Ga implies their juxtaposition at 0.7-0.8 GPa conditions. Regional east directed thrusting of the deep crustal domains as a coherent unit at 1.85 Ga juxtaposed the granulites with middle crustal Hearne domain rocks at 0.4-0.5 GPa conditions. The detailed exhumational history allows correlation with changing regional tectonic regimes associated with the amalgamation of Laurentia. The temporal and spatial heterogeneity of exhumation patterns in the East Lake Athabasca region may be a common feature of the unroofing histories of lower crustal rocks. [ABSTRACT FROM AUTHOR]

The purpose of the investigation was to determine the effect of drinking a natural mineral dietary supplement (NMDS) on gingival health and dentinal hypersensitivity. The NMDS product was from a geothermal source and contained 3.6 mg l−1 of fluoride and other minerals. Sample selection included subjects with gingival inflammation and sensitivity as well as screening for exclusion factors. A double-blind randomized parallel approach was used. The investigation was a quasi-experimental pre/post-test design. The experimental group ingested and swished twice a day with the NMDS (1 l) and the control group followed the same regimen with a placebo containing de-ionized water (DIW). Clinical measurements of gingival inflammation and dentinal sensitivity were taken at baseline, 4 and 8 weeks. Gingival inflammation was measured using the Gingival Index. Dentinal hypersensitivity was measured using a tactile stimulus and an evaporative stimulus. After each stimulus was applied, the subjects rated the amount of discomfort on a visual analogue scale from 0 to 10. Each set of data was analysed usinganova and a post hoc probing technique to determine within- and between-group differences ( P = 0.05). The experimental and control groups ( n = 70) experienced a statistically significant decrease in tactile and evaporative sensitivity scores over time; however, the between-group differences were not significant. The gingival inflammation data were not statistically significant with regard to the within- and between-group differences. Therefore the NMDS and DIW were equally effective in reducing dentinal hypersensitivity and neither product effectively reduced gingival inflammation. [ABSTRACT FROM AUTHOR]

The distribution of detrital mineral cooling ages in modern sediments has been proposed as a proxy for long-term, catchment-averaged erosion rates in developing orogens. However, the applicability of this potentially valuable tool hinges on restrictive assumptions regarding a catchment's steady state thermal and topographic evolution. In this paper, we outline a method by which these assumptions can be tested through statistical comparisons of cooling age distributions for detrital minerals and the hypsometric curves for their source regions using cumulative synoptic probability density functions. Our approach is illustrated with new detrital muscovite 40Ar/39Ar dates from the Marsyandi River valley, in the central Nepalese Himalaya. One of three studied catchments (Nyadi Khola) showed the strong correlation of hypsometry and cooling ages expected for steady state conditions over the 11 to 2.5 Ma time frame. The pattern of mismatch between hypsometry and cooling age distribution in the other catchments suggests that spatially nonuniform and transient erosional processes may be responsible for departure from steady state. Cooling age distribution comparisons for samples collected from nearby localities, samples collected in different years, and different grain size fractions from the same sample were used to evaluate sampling fidelity over a range of spatial scales (200 to 2590 km2). We found that approximately 50 analyses from a single sediment sample adequately characterize the cooling age signal for tributary catchments with simple erosional histories. However, because of temporally and spatially transient erosion, a specific detrital sample is unlikely to adequately characterize the complex signal in trunk stream sediments that integrate information from several large tributaries. [ABSTRACT FROM AUTHOR]

Whereas geologists have known for three-quarters of a century that there was significant crustal thickening in the central East Greenland Caledonides, the crucial role of extensional faulting during Caledonian orogenesis has only been recognized during the past decade. In this paper, new petrographic and thermobarometric observations are presented from migmatitic metasedimentary gneisses of the Forsblad Fjord region ( c. 72.5°N). Samples of the Krummedal Sequence, collected from the footwall of the upper of two significant splays of the main extensional fault system in the region—the Fjord Region Detachment (FRD)—enable us to establish a relative sequence of metamorphism. Our pressure ( P)–temperature ( T) results imply a clockwise loop in P–T space. As recorded by mineral assemblages in the Krummedal gneisses, prograde metamorphism involved a net increase of c. 4 kbar and 250 °C, with peak conditions of c. 10.5 kbar at 785 °C. Early burial and heating was followed by near-isothermal decompression of 4.5 kbar, a process which is attributed to roughly 18 km of tectonostratigraphic throw on the upper splay of the FRD. Combining data reported here with the published data, it is estimated that the approximate tectonostratigraphic throw along the lower splay of the FRD was c. 16 km. In situ U–Th–Pb-monazite electron microprobe dating suggests that the earliest phase of metamorphism recorded in the Krummedal Sequence gneisses of Forsblad Fjord occurred during the Caledonian orogeny. Furthermore, the combination of our new data with existing conventional TIMS U-Pb and 40Ar/39Ar data imply that: (1) movement along the uppermost splay of the FRD ( c. 425–423 Ma) occurred at maximum time-averaged slip-rates equivalent to c. 9 mm of vertical displacement per year; and (2) that the final stages of metamorphism occurred prior to c. 411 Ma, although part of this denudation was likely accommodated on overlying extensional structures that may have been active more recently. There is close agreement between our data and results from the Krummedal Sequence north of the field area (72.5°−74°N), and rocks of the Smallefjord Sequence (75°−76°N) that are suggested to correlate with the Krummedal Sequence. This leads us to infer that the events recorded in the Forsblad Fjord region are of orogen-scale significance. [ABSTRACT FROM AUTHOR]

Abstract The distribution of detrital mineral cooling ages in river sediment provides a proxy record for the erosional history of mountain ranges. We have developed a numerical model that predicts detrital mineral age distributions for individual catchments in which particle paths move vertically toward the surface. Despite a restrictive set of assumptions, the model permits theoretical exploration of the effects of thermal structure, erosion rate, and topography on cooling ages. Hypsometry of the source-area catchment is shown to exert a fundamental control on the frequency distribution of bedrock and detrital ages. We illustrate this approach by generating synthetic [sup 40] Ar/[sup 39] Ar muscovite age distributions for two catchments with contrasting erosion rates in central Nepal and then by comparing actual measured cooling-age distributions with the synthetic ones. Monte Carlo sampling is used to assess the mismatch between observed and synthetic age distributions and to explore the dependence of that mismatch on the complexity of the synthetic age signal and on the number of grains analysed. Observed detrital cooling ages are well matched by predicted ages for a more slowly eroding Himalayan catchment. A poorer match for a rapidly eroding catchment may result from some combination of large analytical uncertainties in the detrital ages and inhomogeneous erosion rates within the basin. Such mismatches emphasize the need for more accurate thermal and kinematic models and for sampling strategies that are adapted to catchment-specific geologic and geomorphic conditions. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau is a storehouse of excess gravitational potential energy accumulated through crustal thickening during India-Asia collision, and the contrast in potential energy between the Plateau and its surroundings strongly influences the modern tectonics of south Asia. The distribution of potential energy anomalies across the region, derived from geopotential models, indicates that the Himalayan front is the optimal location for focused dissipation of excess energy stored in the Plateau. The modern pattern of deformation and erosion in the Himalaya provides an efficient mechanism for such dissipation, and a review of the Neogene geological evolution of southern Tibet and the Himalaya shows that this mechanism has been operational for at least the past 20 million years. This persistence of deformational and erosional style suggests to us that orogens, like other complex systems, can evolve toward 'steady state' configurations maintained by the continuous flow of energy. The capacity of erogenic systems to self-organize into temporally persistent structural and erosional patterns suggests that the tectonic history of a mountain range may depend on local energetics as much as it does on far-field plate interactions. [ABSTRACT FROM AUTHOR]

The Nova Basin contains an upper Miocene to Pliocene supradetachment sedimentary succession that records the unroofing of the Panamint metamorphic core complex, west of Death Valley, California. Basin stratigraphy reflects the evolution of sedimentation processes from landslide emplacement during basin initiation to the development of alluvial fans composed of reworked, uplifted sections of the basin fill. 40Ar/39Ar geochronology of volcanic units in middle and lower parts of the sequence provide age control on the tectonic and depositional evolution of the basin and, more generally, insights regarding the rate of change of depositional environments in supradetachment basins. Our work, along with earlier research, indicate basin deposition from 11.38 Ma to 3.35 Ma. The data imply sedimentation rates, uncorrected for compaction, of ~100 m Myr-1 in the lower, high-energy part to ~1000 m Myr-1 in the middle part characterized by debris-flow fan deposition. The observed variation in sediment flux rate during basin evolution suggests that supradetachment basins have complex depositional histories involving rapid transitions in both the style and rate of sedimentation. [ABSTRACT FROM AUTHOR]

1. Snowshoe hare (Lepus americanus Erxleben) populations were studied in south-west Yukon during the low phase of the 10-year population cycle. Food availability and predator abundance were manipulated in a factorial design to determine the importance of each factor in hare dynamics during this phase. 2. Food was abundant during the low phase, and snowshoe hares were not food limited. 3. Survival of hares was higher than at any other phase of the cycle, and predators were scarce, but >75% of hare deaths resulted from predation. 4. Food addition resulted in higher hare densities and better body condition than on control sites. There were no observable effects of food addition on population rate of increase, recruitment, survival or age structure. 5. Mammalian predator reduction resulted in higher hare densities, higher survival, better body condition and an older age structure. Relative to control populations, recruitment was lower and population rates of increase similar. 6. The joint manipulation of food addition + predator reduction had greater positive effects on hare density and body condition than either single factor manipulation. Survival was better than on control sites, and the age structure was older than on control sites. Population rates of increase were similar, but recruitment was higher on the control areas. 7. We conclude that snowshoe hare dynamics at the low of the cycle are dominated by the interaction of food and predation. Risk of predation also had indirect effects on snowshoe hare age structure and body condition. [ABSTRACT FROM AUTHOR]

Two-dimensional thermal models of time-transitive crustal thickening and subsequent unroofing in large-scale overthrust terrains generate pressure-temperature-time (PTt) paths that generally resemble those produced by earlier one-dimensional instantaneous models, but that differ in detail. These differences in PTt path morphology are most pronounced proximal to major fault zones, where postthrusting geotherms are characterized by large temperature inversions in one-dimensional models but generally lack inversions in two-dimensional models. Tests using the two-dimensional fault model developed here indicate that (1) burial rate (proportional to dP/dt), not thrust fault geometry (dip angle), controls the topology of synthrusting PT paths, but plays only a minor role in determining the maximum temperature that rocks attain during the later, unroofing stage in their thermal histories; (2) normal ranges of thrusting and erosion rates and fault parameters result in PT paths with the usual sense (clockwise on conventional PT diagrams; counterclockwise in our diagrams); (3) the amount of heating and duration of heating following the end of thrusting are a function of the rate of unroofing (− dP/dt) during this period; (4) fast unroofing rates lead to the attainment of lower maximum temperatures after greater amounts of unroofing; (5) the initial thermal state of the lithosphere prior to thrusting has a profound effect on PT path morphologies and on the peak metamorphic conditions attained by samples; (6) for excess heat distributed across the entire lithosphere (e.g., due to increased background thermal gradients), a plot of peak temperatures experienced by metamorphic rocks versus structural depth (TMAX plot) closely represents the initial geotherm; (7) excess heat in the crust only (e.g., increased radioactive heating in a layer) yields a different result, with the TMAX plot corresponding to the initial geotherm only near the top of the hanging wall (TMAX plots for both (6) and (7) show no temperature inversion which exceeds the nominal uncertainties (±50 K) for geothermometric data); (8) shear heating can lead to significant temperature inversions at the fault zone if the frictional coefficient μ is 0.6 or greater; and (9) simultaneous thrusting and erosion produce PT loops significantly narrower than those resulting from sequential thrusting and erosion, suggesting that any formulation which fails to account for some degree of simultaneity between thrusting and erosion represents a far endmember model. Forward models like those presented here provide important guidelines for understanding the sensitivity of metamorphic PTt paths to various thermal, mechanical, and geometric factors related to tectonism, but they are generally inappropriate for reconstructing metamorphic thermal histories from actual petrologic and geochronologic data. Analytical inversion techniques that use a postthrusting thermal regime, consistent with two-dimensional forward models, and that integrate values of dP/dt, dT/dt, and radioactive heating rates extracted from suites of metamorphic rocks provide the best hope for furthering our understanding of the thermal evolution of metamorphic terrains. [ABSTRACT FROM AUTHOR]

Conventional thermobarometry and Gibbs' Method modeling have been used to obtain new information pertaining to the Mesozoic-Tertiary thermal evolution of the Ruby Mountains-East Humboldt Range and Wood Hills metamorphic complexes, northeastern Nevada. Kyanite-grade assemblages from Clover Hill, in the extreme northeastern part of the East Humboldt Range, were produced at temperatures of 780-810 K and depths in excess of 35 km; previously published geochronologic data suggest an Early Cretaceous or Late Jurassic age for this event. The Clover Hill area subsequently experienced a major unroofing interval prior to Late Cretaceous time, during which it was brought roughly 20 km closer to the surface. The lack of stratigraphic evidence for substantial Cretaceous erosion in the region and the topology of the pressure-temperature paths for the Clover Hill samples suggest that the unroofing mechanism may have been tectonic denudation related to the relaxation of large topographic gradients produced by crustal thickening in the hinterland of the Sevier orogen. Metamorphic rocks at Clover Hill and within the Wood Hills core complex equilibrated at 820-900 K and 500-640 MPa (18-24 km) in Cretaceous time, prior to 115 Ma. Other parts of the Ruby Mountains-East Humboldt Range metamorphic complex, presently structurally separated from the Clover Hill sequence, were intruded extensively by Late Cretaceous granitic magmas and attained substantially higher temperatures than the Clover Hill-Wood Hills block. Sillimanite-grade assemblages from these areas apparently underwent roughly 10 km of unroofing and 130 K of cooling prior to final equilibration at 820-920 K and 360-430 MPa (13-16 km) during Oligocene extension. [ABSTRACT FROM AUTHOR]

Neogene extension in the Death Valley region, SE California, has produced a variety of sedimentary basins. Diachronous movements on an array of strike-slip and normal fault systems have resulted in the uplift and preservation of older basins in modern ranges. One of the best exposed of these is the Nova basin on the western flank of the Panamint Mountains. The Nova basin includes over 2000 m of sedimentary and volcanic rocks deposited during denudation of the Panamint Mountains metamorphic core complex in late Miocene (?) - early Pliocene time. The principal growth structure for the basin was the Emigrant detachment, which initiated and moved at a low angle. Modern Panamint Valley, west of the range, developed as a consequence of Late Pliocene - Recent, kinematically linked movement on the right-slip, high-angle Hunter Mountain fault zone and the low-angle Panamint Valley detachment. Detailed mapping of the intersection between the Emigrant and Panamint Valley detachments demonstrates that segments of the earlier system remained active during development of Panamint Valley and, thus, during development of modern Basin and Range topography as well. These results indicate that large-scale extension in the Death Valley region, accommodated by movement on low- to moderate-angle normal fault systems and high-angle strike-slip fault systems, is a continuing process. Basin and Range topography in the Panamint Valley - Death Valley area was generated at least in part by displacements on low-angle detachments rather than high-angle normal faults. [ABSTRACT FROM AUTHOR]

Late Miocene (12-5 Ma) extension around the edges of the Gulf of California has been alternatively attributed to 'Basin and Range' extension, back arc extension, or development of the Pacific-North America plate boundary. This extension was ENE directed and similar in structural style to extension in the Basin and Range province. Timing constraints permit nearly synchronous onset of this deformation in a belt extending SSE from northernmost Baja California to the mouth of the gulf. Where this extensional faulting continued through Pliocene time to the present, synchronous with motion on the modern transform plate boundary in the Gulf of California, no change in direction of extension can be resolved. Revised constraints on Pacific-North America plate motion support the development of this late Miocene extension as a component of Pacific-North America displacement that could not be accommodated by strike-slip displacement along the existing plate boundary west of the Baja California peninsula. This scenario implies that transfer of Baja California from the North America plate to the Pacific plate was a gradual process, beginning about 12-10 Ma, when motion of the Pacific plate relative to North America was partitioned into separate regimes of strike-slip and dip-slip displacement on opposite sides of Baja California. [ABSTRACT FROM AUTHOR]

One- and two-dimensional finite difference models are used to generate theoretical pressure-temperature-time (PTt) paths for rocks uplifted from deep and intermediate crustal levels during extension via ductile stretching of the entire lithosphere ('pure shear') and via movement of crustal blocks along rooted large-scale low-angle normal faults ('simple shear'). The temperature-time paths of rocks uplifted by these pure shear and simple shear mechanisms have similar morphologies, although rocks from pure shear settings reach their final depth at higher temperatures than do rocks uplifted by simple shear, and experience a greater amount of posttectonic cooling. The depth-temperature paths of rocks uplifted from deep crustal levels (30 km depth) via pure shear extension are often characterized by a period of nearly isothermal (high dP/dT) uplift during the early stages of extension. A modified pure shear extension model that includes enhanced heating in the lower lithosphere during extension generally produces PTt paths characterized by a more protracted period of nearly isothermal uplift. In contrast, simple shear uplift along low-angle normal faults produces almost linear depth-temperature paths with moderate dP/dT, and isothermal uplift is not observed. For a given initial geotherm, the single factor controlling the PTt paths of rocks unroofed below gently dipping normal faults that dip less than 30° is the rate at which unroofing takes place (unroofing rate is defined as the rate of uplift relative to the surface), and the syntectonic PTt paths are insensitive to fault dip or horizontal displacement rate. Current geothermometric and geobarometric techniques yield typical uncertainties in real pressure-temperature and temperature-time data of ±1 kbar and ±50°C. Thus it will be difficult to distinguish between these various extensional mechanisms on the basis of PTt data derived from a single sample or from a single structural level, although use of data from samples collected from a broad range of structural levels may improve resolution. Ultimately, the best prospect for distinguishing between simple shear and pure shear mechanisms through petrologic work lies in improving the precision of metamorphic pressure and temperature measurements to ±0.5 kbar and ±25°C. [ABSTRACT FROM AUTHOR]

The hanging wall of the Main Central Thrust (MCT) in Garhwal, India (roughly 79°N-80°E; 30°N-31°N), exhibits an inverted metamorphic gradient: sillimanite ± potassium feldspar assemblages near the top of the hanging wall, or Greater Himalayan sequence, are underlain by kyanite grade rocks near the fault. Textural relationships in pelitic samples from the Alaknanda and Dhauli river valleys indicate that the 'inversion' is the product of two distinct metamorphic events: an early Harrovian event (M1), which affected the entire Greater, Himalayan sequence and a later Buchan event (M2), the effects of which are most obvious in the upper part of the sequence. Rim thermobarometry, garnet inclusion thermobarometry, and thermodynamic modeling of garnet zoning reveal that the basal portions of the metamorphic sequence experienced peak M1 conditions of >900 K and >960 MPa (roughly 36 km depth) before following an 'erosion controlled' uplift path (e.g., England and Richardson, 1977). M2 metamorphic temperatures in the upper part of the sequence also exceeded 900 K, but maximum pressures (317-523 MPa) indicate paleodepths of only 12-19 km. Calculated pressure-temperature paths indicate that M2 was characterized by temperature increases of >80 K and roughly 5 km of tectonic burial We attribute M1 to tectonic burial of the Greater Himalayan sequence during the early stages of India-Eurasia collision. We believe that the uplift and cooling path of the sequence was interrupted in late Oligocene(?) - Miocene time by a second burial and heating event (M2) related to thrust imbrications in southern Tibet. This burial was coincident with the generation of leucogranites, which are abundant near the top of the Greater Himalayan sequence but are virtually absent near the MCT. Field relations do not constrain whether the leucogranites were derived from some presently unexposed portion of the Greater Himalayan sequence and were injected at their present structural level, or were melted in situ. If the granites were injected, then they may have provided some of the heat necessary for M2 metamorphism. Although our data suggest no direct relationship between the Main Central Thrust (as mapped in Garhwal) and metamorphism in the Greater Himalaya, anatectic melting of an unexposed portion of the Greater Himalayan sequence could have been associated with movement along a blind thrust with characteristics similar to the mapped MCT in central Nepal (cf. Le Fort, 1981). If the granites were produced by in situ M2 melting, then we must appeal to a heat source within the upper part of the Greater Himalayan sequence such as locally high concentrations of heat-producing elements (cf. Pinet and Jaupart, 1987). [ABSTRACT FROM AUTHOR]

The climactic phase of the Caledonian orogeny in Scandinavia involved collision of the Baltic and Greenland cratons in late Ordovician (?) to Silurian time. We infer that the collision resulted in large-scale subduction of the leading edge of the Baltic craton beneath an 'Andean-type' Greenland continental margin. Deep erosional levels in the Lofoten-Rombak area, Norway-Sweden (˜69°N) permit direct examination and evaluation of the structural evolution of a continental or A-type subduction zone. The early stages of collision involved en bloc underthrusting of the continental margin to depths of at least 30 km. During this process, deformational effects in the lower plate were restricted to its upper few hundred meters. Ultimately, en bloc A-type subduction should be limted by buoyancy effects. As convergence continued, the lower plate became involved in a series of imbricate thrusts with the same vergence as the intial subduction zone. The temporal and spatial relationships between these basement-involved thrusts are similar to those observed in foreland fold and thrust terrains. Field and geophysical data bearing on lower plate behavior elsewhere in the Caledonldes and in other collisional orogens suggest that the structural features observed in the Lofoten-Rombak area may be generally characteristic of A-type subduction in continent-continent collisional settings. [ABSTRACT FROM AUTHOR]

A set of polymorphic microsatellite loci was identified for population and behavioural studies of the rainbow bee-eater ( Merops ornatus). Eight loci were newly isolated from a rainbow bee-eater genomic library enriched for GA-containing repeats, and six loci from those previously reported for the European bee-eater ( Merops apiaster). From these two sources, the seven most variable loci that amplified reliably were unlinked and in Hardy–Weinberg equilibrium, had five to 13 alleles (mean 7.7) and an expected heterozygosity of 0.60–0.86 (mean 0.73). [ABSTRACT FROM AUTHOR]

Objectives: To determine parameter combinations for effective drug delivery of intranasal spray steroids to the ostiomeatal complex (OMC) and maxillary sinus (MS) in patients with chronic rhinosinusitis (CRS)., Methods: Each patient's sinonasal cavity was reconstructed from computed tomography scans. Intranasal airflow and drug particle transport were simulated using computational fluid dynamic modeling. Airflow simulations were performed at 15 Pascal inhalation pressure. Intranasal spray particles of 1-100 μm were simulated at release speeds of 1, 5, and 10 m/s from 6 release locations (Bottom, Center, Top, Lateral, Lateral-Bottom, and Lateral-Top) at a nozzle insertion depth of 15 mm. Drug delivery simulations were performed in the head tilted forward position., Results: Maximal OMC deposition was 0.78%-12.44%, while maximal MS deposition was 0.02%-1.03% across all simulations. In general, particles between 6 and 10 μm had the best OMC (at 1 m/s particle velocity) and MS (at 10 m/s particle velocity) deposition. Particles ranging from 21 to 30 μm also had superior OMC deposition. The lateral and lateral-top spray release locations produced maximum OMC deposition, but no one release location demonstrated an increase in MS deposition., Conclusion: This preliminary study suggests that it is challenging to determine a common set of intranasal spray parameter combinations for effective drug delivery to the OMC and MSs. Although drug particle size and spray particle velocity seem to impact particle deposition patterns, spray release location appears to vary with anatomical differences between subjects, particularly when the MS is the target location for particle deposition. Laryngoscope, 133:1036-1043, 2023., (© 2022 The American Laryngological, Rhinological and Otological Society, Inc.)

Background In patients with obstructive hypertrophic cardiomyopathy, surgical myectomy (SM) is indicated for severe symptoms. We sought to compare long-term outcomes of patients with obstructive hypertrophic cardiomyopathy where SM was based on guideline-recommended Class I indication (Functional Class or FC ≥3 or angina/exertional syncope despite maximal medical therapy) versus earlier (FC 2 and/or impaired exercise capacity on exercise echocardiography with severe obstruction). Methods and Results We studied 2268 consecutive patients (excluding <18 years, ≥ moderate aortic stenosis and subaortic membrane, 56±14 years, 55% men), who underwent SM at our center between June 2002 and March 2018. Clinical data, including left ventricular outflow tract gradient, were recorded. Death and/or appropriate internal defibrillator discharge were primary composite end points. One thousand three hundred eighteen (58%) patients met Class I indication and 950 (42%) underwent earlier surgery; 222 (10%) had a history of obstructive coronary artery disease. Basal septal thickness, and resting and maximal left ventricular outflow tract gradient were 2.0±0.3 cm, 61±44 mm Hg, and 100±31 mm Hg, respectively. At 6.2±4 years after SM, 248 (11%) had composite events (13 [0.6%] in-hospital deaths). Age (hazard ratio [HR], 1.61; 95% CI, 1.26-1.91), obstructive coronary artery disease (HR, 1.46; 95% CI, 1.06-1.91), and Class I versus earlier SM (HR, 1.61; 95% CI, 1.14-2.12) were associated with higher primary composite events (all P <0.001). Earlier surgery had better longer-term survival (similar to age-sex-matched normal population) versus surgery for Class I indication (76 [8%] versus 193 [15%], P <0.001). Conclusions In patients with obstructive hypertrophic cardiomyopathy, earlier versus surgery for Class I indication had a better long-term survival, similar to the age-sex-matched US population.

Hypertrophic obstructive cardiomyopathy (HOCM) is one of the more common genetic disorders. The pathophysiology and natural history of the disease have been well studied. Left ventricular outflow tract obstruction (LVOTO) and systolic anterior motion (SAM) of the anterior mitral leaflet can result in sudden cardiac death, progressive heart failure and arrythmias. Surgical septal myectomy for HOCM is the standard of care and is routinely performed through a median sternotomy. Septal myectomy has also been performed using the trans-atrial, trans-mitral approach either directly or with robotic assistance. In cases with severe LVOT obstruction in the setting of only mild to moderate proximal septal hypertrophy, intrinsic problems with the mitral valve contribute. Typically, these are hypermobile papillary muscles and or excessive height of the anterior mitral leaflet. Combining septal myectomy with reorientation of hypermobile anteriorly positioned papillary muscles has shown to prevent SAM and thereby additionally decrease the subvalvular aortic outflow obstruction. Our extensive experience in both septal myectomy and robotic mitral valve repair has given us a different perspective in approaching the primary mitral regurgitation in HOCM patients where a combined septal myectomy, papillary muscle reorientation and complex mitral valve repair has been safely performed using the less invasive robotic-assisted approach.Our objective here is to discuss the technical aspects of the procedure., (© 2020 Wiley Periodicals LLC.)

Objective: To assess outcomes of concomitant ablation for atrial fibrillation (AF) in patients with preoperative AF undergoing septal myectomy for hypertrophic obstructive cardiomyopathy., Methods: From 2005 to 2016, 67 patients underwent concomitant ablation for AF and septal myectomy and had a follow-up beyond a 3-month blanking period. Ablation strategy (pulmonary vein isolation [PVI], modified Cox-maze III [CM-III], or Cox-maze IV [CM-IV]) was tailored to preoperative AF burden, with high AF burden defined as persistent AF or need for cardioversion. AF recurrence was analyzed as a time-related event and predictors of recurrence identified using a random forest methodology., Results: A total of 38 patients (57%) had low AF burden and 29 (43%) high burden. Patients with low AF burden most frequently underwent PVI (68%). Patients with high AF burden more frequently underwent CM-III (62%) or CM-IV (35%). Besides the preoperative AF burden, baseline characteristics were similar between patients receiving CM-III, CM-IV, and PVI. After surgery, the maximum provoked left ventricular outflow tract (LVOT) gradient decreased from 99 ± 34 to 18 ± 11mm Hg (P < .001). Eight patients (12%) required a permanent pacemaker. Cumulative AF recurrence at 1, 2, and 5 years was 11%, 22%, and 48%, respectively. Age, low preoperative resting LVOT gradient, and large left atrial diameter were predictors of AF recurrence., Conclusions: Surgical outcomes of concomitant ablation for AF and septal myectomy are good, although recurrence of AF by 5 years is frequent., (© 2020 Wiley Periodicals LLC.)

Barlow syndrome is a form of degenerative mitral valve (MV) disease found in a subset of patients with bileaflet prolapse. The hallmark of Barlow's disease includes excessive and billowing leaflet tissue caused by myxomatous tissue proliferation, elongated chordae, and pronounced annular dilatation. Surgical repair of patients with Barlow's disease is challenging due to the extent of the leaflet and annular abnormalities. Several techniques have been described to repair Barlow's MV including currently popular "non-resectional" approaches. Repair with neochordae has been associated with excellent results and includes the advantage of preserved leaflet mobility and a large surface of coaptation. We describe a simple approach to the use of neochordae to repair bileaflet prolapse in patients with Barlow syndrome and avoid systolic anterior motion., (© 2019 Wiley Periodicals, Inc.)

The aim of this study was to investigate advocacy actions of dental hygiene program alumni who had completed a Legislative Advocacy Project (LAP) when they were students in the undergraduate or graduate program. Five variables were assessed: participation, frequency, perceived barriers, engagement, and mentorship. Alumni of the undergraduate and graduate programs were compared regarding frequency of and barriers encountered to legislative advocacy actions. A descriptive-comparative research design was used with quantitative and qualitative analysis. A convenience sample of 157 alumni who had completed a seven-week LAP at Idaho State University between 2008 and 2013 were invited to complete a 52-item author-designed online questionnaire in 2015. The response rate was 41.4%. The results showed a significant difference for participation prior to and after the LAP (df=12, X 2 =28.28, p=0.005). Most respondents, however, did not participate in legislative actions. There was a significant difference between the two groups for two frequency items: subscribing to online listservs (p=0.001) and contacting political representatives or staff (p=0.003). The three greatest barriers were time, financial resources, and testifying. The analysis found a significant difference between the two groups for the barrier of interest in advocating (p=0.05). In the qualitative analysis, themes emerged about engagement factors (collective efforts and advocacy commitment) and mentorship (mentoring experiences). Advocacy actions after graduation improved, but implementation of actions was challenging due to competing barriers. The results of this study may be useful in identifying key components of advocacy education that should be part of training programs.

In species with a high male reproductive skew, competition between males for the top dominant position is high and escalated fights are common between competitors. As a consequence, challenges incur potentially high costs. Selection should favor males who time an alpha male challenge to maximize chances of a successful outcome minimizing costs. Despite the importance of alpha male replacements for individual males, we know little about the timing of challenges and the condition of the challenger. We investigated the timing and process of alpha male replacements in a species living in multi-male groups with high male reproductive skew, the crested macaque. We studied four wild groups over 6 years in the Tangkoko Reserve, North Sulawesi, Indonesia, during which 16 alpha male replacements occurred. Although unusual for cercopithecines, male crested macaques delayed their natal dispersal until they attained maximum body mass and therefore fighting ability whereupon they emigrated and challenged the alpha male in another group. Accordingly, all observed alpha male replacements were from outside males. Ours is the first report of such a pattern in a primate species living in multi-male groups. Although the majority of alpha male replacements occurred through direct male-male challenges, many also took place opportunistically (i.e., after the alpha male had already been injured or had left the group). Furthermore, alpha male tenures were very short (averaging ca. 12 months). We hypothesize that this unusual pattern of alpha male replacements in crested macaques is related to the species-specific combination of high male reproductive skew with a large number of males per group. Am. J. Primatol. 79:e22448, 2017. © 2015 The Authors. American Journal of Primatology Published by Wiley Periodicals, Inc., (© 2015 The Authors. American Journal of Primatology Published by Wiley Periodicals, Inc.)

Investigating which factors influence feeding competition is crucial for our understanding of the diversity of social relationships. Socio-ecological models differ in their predictions whether predation risk directly influences feeding competition and which factors exactly predict contest competition. We investigated feeding competition in Siberut macaques (Macaca siberu), a species endemic to Siberut Island (West Sumatra, Indonesia). Siberut macaques experience low predation risk, as major predators (felids, raptors) are absent. They are therefore appropriate subjects to test the prediction that low predation risk reduces feeding competition. To estimate contest potential, we quantified size, spatial distribution and density of food plants, and the availability of alternative resources. We recorded behavior in food patches using a modified focal tree method. Food patches, sorted by decreasing average feeding group size, included large trees (40% of focal plant observations), lianas/strangler (16%), medium trees (9%), small (palm) trees (20%), and rattan (15%). Most food patches were clumped but occurred at low densities relative to the area of average group spread. Thus, availability of alternative food patches was low. Although food patch characteristics indicate high contest potential, the observed aggression rate (0.13 bouts between adults/h) was low relative to other primates. Average feeding group size was small relative to total group size, and feeding group size matched crown volume. Perceived predation risk was low, based on spatial and feeding behavior of juveniles. Together, these results suggest that predation risk may influence feeding competition. Social and temporal factors (patch feeding time), but not ecological factors (fruit abundance in patch and forest, alternative resources) predicted aggression frequency in food patches. Overall, comparative data are still relatively scarce, and researchers should collect more data on group spread, sub-grouping, perceived predation risk, and aggression in food patches before we can draw final conclusions about the role of predation risk for feeding competition., (© 2015 Wiley Periodicals, Inc.)