PubMed | University of Western Ontario, Illinois State University, University of California at Los Angeles, Smithsonian Environmental Research Center and 3 more.
Type: | Journal: Scientific reports | Year: 2016
California has experienced a dry 21(st) century capped by severe drought from 2012 through 2015 prompting questions about hydroclimatic sensitivity to anthropogenic climate change and implications for the future. We address these questions using a Holocene lake sediment record of hydrologic change from the Sierra Nevada Mountains coupled with marine sediment records from the Pacific. These data provide evidence of a persistent relationship between past climate warming, Pacific sea surface temperature (SST) shifts and centennial to millennial episodes of California aridity. The link is most evident during the thermal-maximum of the mid-Holocene (~8 to 3ka; ka = 1,000 calendar years before present) and during the Medieval Climate Anomaly (MCA) (~1ka to 0.7ka). In both cases, climate warming corresponded with cooling of the eastern tropical Pacific despite differences in the factors producing increased radiative forcing. The magnitude of prolonged eastern Pacific cooling was modest, similar to observed La Nia excursions of 1(o) to 2C. Given differences with current radiative forcing it remains uncertain if the Pacific will react in a similar manner in the 21st century, but should it follow apparent past behavior more intense and prolonged aridity in California would result.
Whiteside J.H.,Brown University |
Olsen P.E.,Lamont Doherty Earth Observatory |
Eglinton T.I.,Woods Hole Oceanographic Institution |
Cornet B.,16921 Cielito Lindo Dr. |
And 2 more authors.
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2011
Triassic and Early Jurassic age lacustrine deposits of eastern North American rift basins preserve a spectacular record of precession-related Milankovitch forcing in the Pangean tropics in the wake of the end-Triassic extinction event (ETE). The abundant and well-preserved fossil fish assemblages from these great lakes show cyclical changes that track the permeating hierarchy of climatic cycles. To detail ecosystem processes correlating with succession of fish communities, bulk δ13C was measured through a 100ky series of precession-forced lake level cycles in the lower Shuttle Meadow Formation of the Hartford rift basin, Connecticut, that were deposited within 50ky after the ETE. The deep-water phase of one of these cycles, the Bluff Head Bed, has produced thousands of articulated fish. There are fluctuations in the bulk δ13Corg in the cyclical strata that reflect differing degrees of lake water stratification, nutrient levels, and relative proportion of algal vs. plant derived organic matter that trace fish community changes. Extrinsic changes in the global exchangeable reservoirs can be excluded as an origin of this variability because compound-specific δ13C of n-alkanes from plant leaf waxes in the same strata show no such variability. Although higher taxonomic levels of the fish communities responded largely by sorting of taxa by environmental forcing, at the species level the holostean genus Semionotus responded by in situ evolution, and ultimately extinction, of a species flock. Fluctuations at the higher frequency, climatic precessional scale are mirrored at lower frequency, eccentricity modulated scales, all following the lake-level hierarchical pattern. Thus, changes in lacustrine isotopic ratios amplify the Milankovitch climate signal that was already intensified by sequelae of the end-Triassic extinctions. The degree to which the ecological structure of modern lakes responds to similar environmental cyclicity is largely unknown, but similar patterns and processes are present within the Neogene history of the East African great lakes. © 2010 Elsevier B.V.
Walsh K.A.P.,Westminster School
Astronomy and Geophysics | Year: 2012
James Bradley, the third Astronomer Royal, made arguably some of the most important measurements in the history of science, yet he remains a relatively obscure figure. In the 250th year since his death, Kevin Walsh focuses on some of the events of 2012 that present particularly timely reminders of the greatness of Bradley's work and the extraordinary legacy he left. © 2012 Royal Astronomical Society.
Walsh K.A.P.,Westminster School |
Sharp P.,Westminster School
Physics Education | Year: 2011
Sir Nevil Maskelyne is remembered by many as the main rival to clockmaker John Harrison in the famous Longitude affair of the 18th century. However, his contributions to science go well beyond this often misreported drama; three of his many observations and developments are considered here in the year marking the 200th anniversary of his death. © 2011 IOP Publishing Ltd.
Mcmanus M.D.,Westminster School |
Skinner J.B.B.,Westminster School |
Peter Hughes D.E.,Westminster School
Journal of Chemical Research | Year: 2011
By conductivity measurements, it has been shown that HCl, HBr and HI undergo addition to propanone and propanal to give gem-halogenohydrins. Chlorohydrins have been detected when HCl combined with aldehydes that do not undergo ketoenol tautomerism and 1,2,2,2-tetrachlorethanol has been identified when HCl combines with trichlo-roethanal (chloral). The formation of gem-chlorohydrins has been reported in the enzymic degradation of chlorinated hydrocarbons, but this is the first report that they can be formed by direct combination at room temperature. This reaction should, therefore, be considered as a typical property of the carbonyl group, similar to the addition of water and HCN.
Benet W.E.,Westminster School |
Lewis G.S.,Westminster School |
Yang L.Z.,Westminster School |
Peter Hughes D.E.,Westminster School
Journal of Chemical Research | Year: 2011
The Tollens test for aldehydes has been used for over 100 years but no reason has been given for adding sodium hydroxide to the silver nitrate before the solution is cleared with ammonia. In this paper, a mechanism is proposed which explains why the addition of alkali makes the test much more sensitive.
Cameron-Holford R.,Westminster School |
Ratneswaren T.,Westminster School |
Hughes D.E.P.,Westminster School
Journal of Chemical Education | Year: 2010
Kinetic study on the hydrolysis of diphenylbromomethane does not provide clear-cut evidence for the mechanism of the reaction. The reduction in the rate of the reaction by added bromide ions suggested that the reaction took place by a SN1 mechanism. A more detailed study of this common-ion effect, using conductivity to measure the rate of the reaction is described and gives stronger support to this mechanism. © 2010 The American Chemical Society and Division of Chemical Education, Inc.
Cho J.Y.,Hanseo University |
Choi J.W.,Westminster School |
Jang W.K.,Hanseo University
Asian Journal of Chemistry | Year: 2014
We proposed an additional optical algorism to improve the functionality of the conventional in situ glass inspection system of finding out real cracks in the glass boards of LCD and OLED. The modulated pulse laser output was used as an optical probe to investigate glass plates. Two parameters of the attenuated laser pulse counting and the decrease of transmitted optical power were used to modify crack detection algorism. Compared to that of the conventional in situ glass inspection method, the detecting accuracy of real cracks was increased with the additional laser inspection method. The technical parameters for analyzing glass defects were discussed such as pulse repetition rate of the incident laser, moving speed of glass board, and attenuation of the transmitted laser power. We also discussed the field adaptation factors of focal length, spot size and wavelength of the incident laser as well as the experimental field data of the laser inspection added system.
Kang W.,Westminster School |
Byun K.,Yonsei University |
Kang H.-G.,Westminster School
Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS | Year: 2015
This paper presents an algorithm for the detection of fiducial points in electrocardiogram (ECG) waves using iteration based adaptive thresholds. By setting the search range of the processing frame to the interval between two consecutive R peaks, the peaks of T and P waves are used as reference salient points (RSPs) to detect the fiducial points. The RSPs are selected from candidates whose slope variation factors are larger than iteratively defined adaptive thresholds. Considering the fact that the number of RSPs varies depending on whether the ECG wave is normal or not, the proposed algorithm proceeds with a different methodology for determining fiducial points based on the number of detected RSPs. Testing was performed using twelve records from the MIT-BIH Arrhythmia Database that were manually marked for comparison with the estimated locations of the fiducial points. The means of absolute distances between the true locations and the points estimated by the algorithm are 12.2 ms and 7.9 ms for the starting points of P and Q waves, and 9.3 ms and 13.9 ms for the ending points of S and T waves. Since the computational complexity of the proposed algorithm is very low, it is feasible for use in mobile devices. © 2015 IEEE.