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Tree-Ring Dating of Two Log Buildings in Central Texas, USA
No full textTree-ring dating was used to develop construction scenarios for two log structures, the Draper and the Fuller buildings. in the Edwards Plateau region of Texas. The Draper building was constructed in 1902-3, and added onto in 1906. The dating of the Fuller building is less certain, but the structure probably was built in the 1860s or 1870s.This item is part of the Tree-Ring Research (formerly Tree-Ring Bulletin) archive. It was digitized from a physical copy provided by the Laboratory of Tree-Ring research at The University of Arizona. For more information about this peer-reviewed scholarly journal, please email the Editor of Tree-Ring Research at [email protected]
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Tree-Ring Chronologies from Nepal
No full textTen ring-width based chronologies from Nepal are described and the prospects for further dendroclimatic work there reviewed briefly. The initial results are encouraging, and more intensive subregional sampling is called for. All the cores examined showed distinct annual rings, and there was little evidence of double or missing rings, except juniper at some sites and in some Pinus roxburghii trees. Difficulty was encountered in dating Pinus wallichiana and Cupressus dumosa. Individual site chronologies of Cedros deodora, P. roxburghii and P. wallichiana were particularly promising, and of high elevation Abies spectabilis moderately so. Densitometric data are likely to be more useful for this species. The paucity of meteorological data in Nepal represents an obstacle to further dendroclimatic work there.This item is part of the Tree-Ring Research (formerly Tree-Ring Bulletin) archive. It was digitized from a physical copy provided by the Laboratory of Tree-Ring research at The University of Arizona. For more information about this peer-reviewed scholarly journal, please email the Editor of Tree-Ring Research at [email protected]
Millennium-Long Tree-Ring Chronology Reveals Megadroughts on the Southeastern Tibetan Plateau
No full textMillennium-aged trees are rare in natural forests. Herewe present an 1184-year-long tree-ring width chronology from living juniper trees in the Biru area on the southeastern Tibetan Plateau. Growthclimate response analysis shows that the Biru chronology is significantly and positively correlated with late-spring (May-June) Standardized Precipitation Evaporation Index (SPEI) (r = 0.67, n = 53, p < 0.01). The tree-ring chronology explains 44.5% of the total variance of SPEI during the period AD 1957-2010. Reconstruction of May-June SPEI shows that there was a two-century-long megadrought during the late 13th to late 15th Centuries, and a seven-decade-long megadrought during AD 1630s to 1690s. Comparisons with other moisture records in the region suggest that the two-century megadrought identified in our reconstruction might be a widespread phenomenon most likely reflecting a stage of reduced Southwest Asian Summer Monsoon. Our results provide new evidence on the megadrought events on the Tibetan Plateau for the last millennium
A survey of low-velocity collisional features in Saturn's F ring
No full textSmall (~50km scale), irregular features seen in Cassini images to be emanating from Saturn's F ring have been termed mini-jets by Attree et al. (2012). One particular mini-jet was tracked over half an orbital period, revealing its evolution with time and suggesting a collision with a local moonlet as its origin. In addition to these data we present here a much more detailed analysis of the full catalogue of over 800 F ring mini-jets, examining their distribution, morphology and lifetimes in order to place constraints on the underlying moonlet population. We find mini-jets randomly located in longitude around the ring, with little correlation to the moon Prometheus, and randomly distributed in time, over the full Cassini tour to date. They have a tendency to cluster together, forming complicated `multiple' structures, and have typical lifetimes of ~1d. Repeated observations of some features show significant evolution, including the creation of new mini-jets, implying repeated collisions by the same object. This suggests a population of ≲ 1 km radius objects with some internal strength and orbits spread over ±100 km in semi-major axis relative to the F ring but with the majority within 20 km. These objects likely formed in the ring under, and were subsequently scattered onto differing orbits by, the perturbing action of Prometheus. This reinforces the idea of the F ring as a region with a complex balance between collisions, disruption and accretion.Supplementary information available at http://www.maths.qmul.ac.uk/~attree/mini-jets
Looking at the Wood, Seeing the Trees and More: Australia-New Zealand Tree-Ring Science Conference, January 2025
No full textThe Australia-New Zealand Tree-Ring Conference was held January 21–23, 2025, at Waipapa Taumata Rau/University of Auckland, in Aotearoa/New Zealand. It was intended to provide an opportunity for the Australian and New Zealand dendrochronological researchers to meet, present current research, and discuss the challenges and opportunities in working with Southern Hemisphere tree species, but it was open to others outside of Australasia, including some keynote speakers. The meeting brought together many researchers from within and outside academia for the first time since the pandemic, and in addition to providing a look at current interesting and ongoing dendrochronology projects, it promoted camaraderie for this regional tree-ring community
Full waveform tomographic images of the peak ring at the Chicxulub impact crater
No full text17/06/013 PDF version attached, OK to pub.Peak rings are a feature of large impact craters on the terrestrial planets and are generally believed to be formed from deeply buried rocks that are uplifted during crater formation. The precise lithology and kinematics of peak ring formation, however, remains unclear. Previous work has revealed a suite of bright inward-dipping reflectors beneath the peak ring at the Chicxulub impact crater and that the peak ring was formed from rocks with a relatively low seismic velocity. New 2D full-waveform tomographic velocity images show that the uppermost lithology of the peak ring is formed from a thin (~100-200 m thick) layer of low-velocity (~3000-3200 m/s) rocks. This low-velocity layer is most likely to be composed of highly porous, allogenic impact breccias. Our models also show that the change in velocity between lithologies within and outside the peak ring is more abrupt than previously realized and occurs close to the location of the dipping reflectors. Across the peak ring, velocity appears to correlate well with predicted shock pressures from a dynamic model of crater formation, where the rocks that form the peak ring originate from uplifted basement that has been subjected to high shock pressures (10-50 GPa), and lie above downthrown sedimentary rocks that have been subjected to shock pressures of < 5 GPa. These observations suggest that low-velocities within the peak ring may be related to shock effects and that the dipping reflectors underneath the peak ring might represent the boundary between highly-shocked basement and weakly-shocked sediments
Wake structure and kinematics in the vortex ring state
No full textHigh-resolution computational simulations of the vortical wake of a rotor operating both near to and within the vortex ring state have been conducted using Brown's vorticity transport model. The nonlinear vortex kinematics of the wake is exposed using three-dimensional visualizations of the simulated flow field. To reveal the vortex dynamics that underpin the highly unsteady flow within the vortex ring state, a rotor with just one blade was modeled. This blade was decoupled aerodynamically from the surrounding velocity field so that it acted merely as a source of trailed vorticity. The investigation identified a significant change in the dominant dynamics of the wake as it swapped fromthe tubular form that is characteristic of hover or very lowspeed descent into the toroidal geometry of the vortex ring state. Initial vortex 'pairing' leads to rotation of vortex filaments away from their original attitude. This phenomenon plays an important role in regulating the downwash that the rotor can produce and thus in precipitating the onset of the vortex ring state. The considerable and persistent coherence of the vortical structure of the wake when in the vortex ring state is revealed, despite these disturbances, as are themechanisms that lead to both small-scale and large-scale wake breakdown events. Simulations show the balance between the vortex pairing and short-wave instability modes to be different in the vortex ring state at high descent speed, where the wake lies above the rotor, compared to in the vortex ring state at low descent speed when the wake lies predominantly below the rotor. This yields subtle differences to the kinematics and structure of the wake in the two cases
C-clamp and pelvic packing for control of hemorrhage in patients with pelvic ring disruption
No full textBACKGROUND:
Exsanguinating hemorrhage is the major cause of death in patients with pelvic ring disruption.
AIMS:
The aim of this study was to document outcomes after the stabilization of pelvic ring injuries by a C-clamp and control of hemorrhage by pelvic packing. Physiological parameters were tested as prognostic factors.
SETTING AND DESIGN:
This was a retrospective study at a level I trauma center. The study period was from January 1996 to December 2007.
MATERIALS AND METHODS:
Fifty patients with pelvic ring disruption and hemorrhagic shock were analyzed. The pelvic rings were fixed by a C-clamp, and patients with ongoing hemorrhage underwent laparotomy and extra- and/or intra-peritoneal pelvic packing. Clinical parameters (heart rate, mean arterial pressure) and physiological parameters (lactate levels, hemoglobin, hematocrit) were documented at admission and at different time points during the initial treatment (1, 2, 3, 4, 6, 8, and 12h after admission).
RESULTS:
Within 12 h of admission, 16 patients died (nonsurvivors) due to hemorrhagic shock (n=13) or head injuries (n=3). In this group, 12 patients underwent laparotomy with pelvic packing. Thirty-four patients survived the first 12 h (early survivors) after fixation by a C-clamp and additional packing in 23 patients. Four of these patients died 12.3±7.1 days later due to multiple organ failure (n=3) or severe head injury (n=1). The blood lactate level at admission was significantly higher in the group of nonsurvivors (7.2±0.8 mmol/L) compared to the early survivors (4.3±0.5 mmol/L, P<0.05). While hemoglobin values improved within the first 2 h in nonsurvivors, lactate levels continued to increase.
CONCLUSION:
Pelvic packing in addition to the C-clamp fixation effectively controls severe hemorrhage in patients with pelvic ring disruption. Early sequential measurements of blood lactate levels can be used to estimate the severity of shock and the response to the shock treatment
A study of the ring opening metathesis polymerization of polycyclic aromatic monomers and cyclopentenes with well defined initiators
No full textThis thesis describes studies into the ring opening metathesis polymerisation (ROMP) of polycyclic aromatic monomers and cyclopentenes. Chapter 1 reviews general aspects of ring opening metathesis polymerisation of relevance to the themes of this thesis. Chapter 2 describes the synthesis of polycyclic aromatic monomers, the endo and the exo Diels-Alder adducts of acenaphthylene and cyclopentadiene. Chapter 3 reports a study on the polymerisation of these monomers using well defined initiators and classical catalyst systems. Chapter 4 describes the synthesis of a substituted cyclopentene. Chapter 5 reports an investigation of polymerisation of cyclopentene using a variety of well defined initiators of general formula M(=NAr)(- OR)(_2)(=CHR) where M=Mo or W. Chapter 6 presents a study on the polymerisation of a substituted cyclopentene, 4-methylcyclopentene, using a series of well defined initiators, and the characterisations of the polymers obtained using infrared, (^1)H, and (^13)C n.m.r. spectroscopy, differential scanning calorimetry, and gel permeation chromatography and an analysis of detailed microstructure with respect to meso/racemic configurations in the polymer chain. Finally, Chapter 7 summarises the conclusions and makes some suggestions for future work
Charles P. Ring, Jr., U.S. Marine Corps veteran-WWII
No full textCharles Ring is a United States Marine Corps veteran of World War II. He is being interviewed at Oakland University, Rochester, Michigan about his wartime experiences. This program is produced in conjunction with the Library of Congress
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