3,186 research outputs found

    Two Middle Holocene Marker Beds in Vertically Accreted Floodplain Deposits, Lower Fraser River, British Columbia

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    Drill cores obtained from the eastern Fraser Delta and adjoining Fraser River floodplain reveal two middle Holocene marker beds—a peat with an age of about 6000 14C yr BP and a tephra bed, identified as Mazama (6800 yr BP). These marker beds, in conjunction with 14C dates from the flood-plain sediments, indicate that the Fraser River floodplain aggraded in response to a rise in sea-level, between about 8000 and 2250 yr BP, and that aggradation kept pace with sea-level rise. The aggradational deposits form a sediment wedge consisting mainly of organic-rich silts and fine sands of overbank origin. The wedge extends at least 20 km into the lower Fraser River Valley. Preservation of the marker beds indicates considerable channel stability in the lower reaches of the Fraser River over about the last 7000 years.Des carottes recueillies dans la partie est du delta du Fraser et de la plaine d'inondation adjacente montrent deux lits repères datant du milieu de l'Holocène, un lit de tourbe datant d'à peu près 6000 BP et un lit de tephra, correspondant à l'éruption du mont Mazama (6800 BP). Ces lits repères, ainsi que les datations au radiocarbone obtenues dans les sédiments de crue, montrent que la plaine d'inondation du Fraser a progressé en réponse à une hausse du niveau marin survenue entre environ 8000 et 2250 BP et que l'aggradation suivait la hausse du niveau marin. L'accumulation de sédiments, de forme triangulaire, est composée principalement de limons riches en matière organique et de sables fins d'origine alluviale. Le triangle s'étend jusqu'à au moins 20 km dans la vallée inférieure du Fraser. La conservation des lits repères démontre la grande stabilité des biefs du Fraser inférieur depuis environ 7000 ans.Bohrkerne von dem ôstlichen Fraser-Delta und der angrenzenden Hochflutebene lassen zwei Betten aus dem mittleren Holozân erkennen, die als Anhalt dienen: ein Torfbett das auf etwa 6000 "1C Jahre v.u.Z. datiert wird und ein Tephra-Bett, das aus der Zeit des Ausbruchs des Mazamabergs stammt (6800 Jahre v.u.Z.). Die als Anhaltspunkt dienenden Betten weisen zusammen mit den von den Hochflutsedimenten gewonnenen 14C-Daten darauf hin, dass die Hochflut des Fraser-Flusses als Reaktion auf eine Anhebung des Meeresspiegels zwischen etwa 8000 und 2250 Jahren v.u.Z. zugenommen hat. und dass diese Zunahme der Hebung des Meeresspiegels entsprach. Die Akkumulationssedimente bilden einen Sedimentkeil, der vor allem aus organisch reichem Schlamm und feinem Sand alluvialer Herkunft besteht. Der Keil erstreckt sich mindestens 20 km in das TaI des unteren Fraser. Die Erhaltung der als Anhaltspunkte dienenden Betten beweist eine beachtliche Kanalstabilitât in den unteren Stillen des Fraser wâhrend ungefàhr 7000 Jahren

    Spitzer Observations of the z=2.73 Lensed Lyman Break Galaxy, MS1512-cB58

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    We present Spitzer infrared (IR) photometry and spectroscopy of the lensed Lyman break galaxy (LBG), MS1512-cB58 at z=2.73. The large (factor ~30) magnification allows for the most detailed infrared study of an L*_UV(z=3) LBG to date. Broadband photometry with IRAC (3-10 micron), IRS (16 micron), and MIPS (24, 70 & 160 micron) was obtained as well as IRS spectroscopy spanning 5.5-35 microns. A fit of stellar population models to the optical/near-IR/IRAC photometry gives a young age (~9 Myr), forming stars at ~98 M_sun/yr, with a total stellar mass of ~10^9 M_sun formed thus far. The existence of an old stellar population with twice the stellar mass can not be ruled out. IR spectral energy distribution fits to the 24 and 70 micron photometry, as well as previously obtained submm/mm, data give an intrinsic IR luminosity L_IR = 1-2 x10^11 L_sun and a star formation rate, SFR ~20-40 M_sun/yr. The UV derived star formation rate (SFR) is ~3-5 times higher than the SFR determined using L_IR or L_Halpha because the red UV spectral slope is significantly over predicting the level of dust extinction. This suggests that the assumed Calzetti starburst obscuration law may not be valid for young LBGs. We detect strong line emission from Polycyclic Aromatic Hydrocarbons (PAHs) at 6.2, 7.7, and 8.6 microns. The line ratios are consistent with ratios observed in both local and high redshift starbursts. Both the PAH and rest-frame 8 micron luminosities predict the total L_IR based on previously measured relations in starbursts. Finally, we do not detect the 3.3 micron PAH feature. This is marginally inconsistent with some PAH emission models, but still consistent with PAH ratios measured in many local star-forming galaxies.Comment: Accepted for publication in ApJ. aastex format, 18 pages, 7 figure

    Testing XRF identification of marine washover sediment beds in a Coastal Lake in Southeastern Texas, USA

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    This study tests the ability of a novel approach to identifying washover beds in coastal lakes. Combined X-Ray Fluorescence (XRF) and cluster analysis was used to identify hurricane washover beds in sediment cores from Clam Lake on the McFaddin National Wildlife Refuge in southeastern Texas. The lake is known to contain washover beds from recent hurricanes, but the washover sediment has similar microfossil, loss-on-ignition and textural characteristics to non-washover sediment and is not readily distinguishable. Sediment cores taken from marshes surrounding the lake do contain visually-recognizable sandy washover beds of Hurricanes Ike, Rita, Carla and Audrey. XRF analysis of these washover beds, combined with cluster analysis, was used to construct elemental fingerprints with the potential to detect washover beds in the lake. Results are promising: multiple washover beds were detected in the lake and tentatively attributed to recent hurricanes. In some lake cores, washover beds likely to be present were not detected by the XRF/clustering technique; in other lake cores, up to nine washover beds were detected. The variation in the number of washover beds probably resulted from bio-turbation, identification of two or more washover beds in a single washover deposit, and washover beds resulting from smaller storms. Valuable outcomes of this study are; 1) it confirms the presence of washover beds in the lake; 2) it provides greater insight into the number, stratigraphic position and thickness of washover deposits; 3) it identifies periods of heightened and diminished overwash activity, and 4) it provides a means of estimating the contribution of washover deposition to sedimentation in the lake. An additional unexpected finding is that long-term sedimentation rates derived from the lake and marsh cores closely match the rate of local sea-level rise, suggesting that sea-level rise may drive sedimentation in the study area

    Roadkill scavenging behaviour in an urban environment

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    Roads can have negative impacts on wildlife through indirect effects such as fragmentation of habitat, or through direct effects such as fatal collisions with vehicles. Wildlife deaths on British roads number in the millions per year, so the resulting carcasses represent a substantial carrion biomass available as food for scavengers. By removing roadkill in urban areas, scavengers perform a valuable ecosystem service, but the rapid removal of these carcasses by scavengers could bias estimates of the impacts of roads on wildlife. In order to evaluate the scale and context of urban roadkill scavenging, we examined: (i) which species scavenge on roadkill in urban areas, (ii) the likelihood of roadkill being removed by scavengers, and (iii) whether spatial and temporal factors (habitat type and time of day) influenced the rate of removal. Camera traps baited with chicken heads as simulated ‘roadkill corpses’ were deployed in six residential and six parkland sites in the city of Cardiff, UK. Seven species were observed removing the roadkill, with corvids being the most common scavengers, responsible for 42% of removals. Of the 120 corpses, 90 (76%) were removed within 12 h. Time of day had a significant effect on the rate of removal, with the number of carcass removals peaking in the first few hours of daylight. Of roadkill placed at 9 am, 62% of carcasses had been removed after only 2 h. Removal of corpses by scavengers could mean that the actual number of road deaths is six times more than that observed during surveys

    The failures of ethnobotany and phytomedicine in delivering novel treatments for snakebite envenomation

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    Snakebite envenomation (SBE) is a high priority, neglected tropical disease. This devastating occupational health hazard disproportionately affects rural farming communities in tropical countries. This is exacerbated by the distribution and densities of venomous snakes, incidence of encounters and limited access to advanced healthcare, including antivenom. Before the development of antivenom, desperation and spiritual beliefs led patients to experiment with a wide range of traditional treatments. Many of these treatments still survive today, particularly in regions where access to healthcare is limited. Plants are a major source of bioactive molecules, including several lifesaving medications that are widely used to this day. However, much of the research into the use of traditional plant treatments for SBE are limited to preliminary analysis, or have focused on techniques used to confirm antibody efficacy that are not suitable for non-antibody containing treatments. Modern drugs are developed through a robust pharmaceutical drug discovery and development process, which applies as much to SBE as it does to any other disease. This review discusses specifically why research into ethnobotanical practices has failed to identify or develop a novel treatment for SBE, and proposes specific approaches that should be considered in this area of research in the future

    The Rest-Frame Optical Spectrum of MS 1512-cB58

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    Moderate resolution, near-IR spectroscopy of MS1512-cB58 is presented, obtained during commissioning of the the Near IR Spectrometer (NIRSPEC) on the Keck II telescope. The strong lensing of this z=2.72 galaxy by the foreground cluster MS1512+36 makes it the best candidate for detailed study of the rest-frame optical properties of Lyman Break Galaxies. A redshift of z=2.7290+/-0.0007 is inferred from the emission lines, in contrast to the z=2.7233 calculated from UV observations of interstellar absorption lines. Using the Balmer line ratios, we find an extinction of E(B-V)=0.27. Using the line strengths, we infer an SFR=620+/-18 Msun/yr (H_0=75, q_0=0.1, Lambda =0), a factor of 2 higher than that measured from narrow-band imaging observations of the galaxy, but a factor of almost 4 lower than the SFR inferred from the UV continuum luminosity. The width of the Balmer lines yields a mass of M_vir=1.2x10^10 Msun. We find that the oxygen abundance is 1/3 solar, in good agreement with other estimates of the metallicity. However, we infer a high nitrogen abundance, which may argue for the presence of an older stellar population.Comment: 14 pages, including 3 figures. Accepted for publication in ApJ Letter

    An unnecessary Russell’s Viper bite on the tongue due to live snake worship and dangerous first aid emphasise the urgent need for stringent policies

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    India suffers the highest incidence of snakebite envenomation (SBE) in the world. Rural commu-nities within India and other countries have long-held cultural beliefs surrounding snakes and SBE treatments, with snake statues present in numerous Hindu temples. While most cultural be-liefs are well respected and do not affect anyone, some people worship live venomous snakes without any safety precautions. Moreover, they practice various inappropriate first aid and tra-ditional treatments that exacerbate SBE-induced complications. We report an unusual case of SBE on the tongue of a patient who was bitten while worshipping Russell’s viper following the advice of an astrologer based on the appearance of a snake in the patient’s dream. Following the bite, the tongue was deeply incised by the priest as a first aid to mitigate SBE-induced complications. The patient suffered profuse bleeding and swelling of the tongue resulting in difficulties in intubating them. The patient regained consciousness after antivenom administration, intranasal ventilation, and blood removal from the mouth. The tongue underwent extensive surgery to restore movement and function. This report advises caution to those undertaking the extremely risky practice of worshipping live snakes and emphasises the urgent need to develop and enforce policies to miti-gate such actions and educate rural communities
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