A discharge flow mass-spectrometric study of the reaction between the NO3 radical and isoprene     

U. Wille  E. Becker  R. N. Schindler  I. T. Lancar  G. Poulet  G. Le Bras 《Journal of Atmospheric Chemistry》1991,13(2):183-193

The kinetics and mechanism of the reactionNO₃+CH₂=C(CH₃)–CH=CH₂productswere studied in two laboratories at 298 K in the pressure range 0.7–3 torr using the discharge-flow mass-spectrometric method. The rate constant obtained under pseudo-first-order conditions with excess of either NO₃ or isoprene was: k ₁=(7.8±0.6)×10^–13 cm³ molecule^–1 s^–1. The product analysis indicated that the primary addition of NO₃ occurred on both -bonds of the isprene molecule.  相似文献   

The Geoid Slope Validation Survey 2014 and GRAV-D airborne gravity enhanced geoid comparison results in Iowa     

Y. M. Wang  C. Becker  G. Mader  D. Martin  X. Li  T. Jiang  S. Breidenbach  C. Geoghegan  D. Winester  S. Guillaume  B. Bürki 《Journal of Geodesy》2017,91(10):1261-1276

Three Geoid Slope Validation Surveys were planned by the National Geodetic Survey for validating geoid improvement gained by incorporating airborne gravity data collected by the “Gravity for the Redefinition of the American Vertical Datum” (GRAV-D) project in flat, medium and rough topographic areas, respectively. The first survey GSVS11 over a flat topographic area in Texas confirmed that a 1-cm differential accuracy geoid over baseline lengths between 0.4 and 320 km is achievable with GRAV-D data included (Smith et al. in J Geod 87:885–907, 2013). The second survey, Geoid Slope Validation Survey 2014 (GSVS14) took place in Iowa in an area with moderate topography but significant gravity variation. Two sets of geoidal heights were computed from GPS/leveling data and observed astrogeodetic deflections of the vertical at 204 GSVS14 official marks. They agree with each other at a \({\pm }1.2\,\, \hbox {cm}\) level, which attests to the high quality of the GSVS14 data. In total, four geoid models were computed. Three models combined the GOCO03/5S satellite gravity model with terrestrial and GRAV-D gravity with different strategies. The fourth model, called xGEOID15A, had no airborne gravity data and served as the benchmark to quantify the contribution of GRAV-D to the geoid improvement. The comparisons show that each model agrees with the GPS/leveling geoid height by 1.5 cm in mark-by-mark comparisons. In differential comparisons, all geoid models have a predicted accuracy of 1–2 cm at baseline lengths from 1.6 to 247 km. The contribution of GRAV-D is not apparent due to a 9-cm slope in the western 50-km section of the traverse for all gravimetric geoid models, and it was determined that the slopes have been caused by a 5 mGal bias in the terrestrial gravity data. If that western 50-km section of the testing line is excluded in the comparisons, then the improvement with GRAV-D is clearly evident. In that case, 1-cm differential accuracy on baselines of any length is achieved with the GRAV-D-enhanced geoid models and exhibits a clear improvement over the geoid models without GRAV-D data. GSVS14 confirmed that the geoid differential accuracies are in the 1–2 cm range at various baseline lengths. The accuracy increases to 1 cm with GRAV-D gravity when the west 50 km line is not included. The data collected by the surveys have high accuracy and have the potential to be used for validation of other geodetic techniques, e.g., the chronometric leveling. To reach the 1-cm height differences of the GSVS data, a clock with frequency accuracy of \(10^{-18}\) is required. Using the GSVS data, the accuracy of ellipsoidal height differences can also be estimated.  相似文献   

Die Bewegung der Kontinente in der Wegenerschen Theorie     

Ludwig Becker 《International Journal of Earth Sciences》1939,30(3):304-308

Ohne Zusammenfassung  相似文献   

Field meeting at Sevenoaks,Kent: 10th July, 1948     

G. Austin Browne  F.G.S. 《Proceedings of the Geologists' Association. Geologists' Association》1949,60(4):274

  相似文献   

检测海洋弧菌的酶联免疫吸附试验研究   总被引：1，自引：0，他引：1  

张晓华  徐怀恕 《中国海洋大学学报(自然科学版)》1997,(3)

研究建立中国对虾病原菌┐副溶血弧菌（Ｖｉｂｒｉｏｐａｒａｈａｅｍｏｌｙｔｉｃｕｓ）的间接酶联免疫吸附试验（ＥＬＩＳＡ）快速检测技术。间接ＥＬＩＳＡ技术中的副溶血弧菌的特异抗血清由家兔制备，羊抗兔ＩｇＧ用碱性磷酸酶标记，酶的底物为对磷酸基硝基苯。将该技术标准化后，测定了抗血清与１３株其它副溶血弧菌菌株及２９株其它弧菌标准菌株的交叉反应，并进行了苗期对虾样品中副溶血弧菌的检测  相似文献   

Fluid mud dynamics in the Weser estuary turbidity zone tracked by high-resolution side-scan sonar and parametric sub-bottom profiler   总被引：1，自引：0，他引：1  

Kerstin Schrottke  Marius Becker  Alexander Bartholomä  Burghard W. Flemming  Dierk Hebbeln 《Geo-Marine Letters》2006,26(3):185-198

Fluid mud in estuarine turbidity maximum zones (TMZ) can pose considerable navigation risks due to potentially substantial reductions in nautical depth, coupled with an inherent difficulty of detection by conventional echo-sounders. Despite intensive research efforts, however, our knowledge about the spatial and temporal dynamics of fluid mud is still not sufficient. In this study, the combined use of a side-scan sonar (Sportscan®, Imagenex) and a parametric sub-bottom profiler (SES-2000®, Innomar Technology GmbH) has proved successful for high-resolution fluid mud detection and volumetric quantification in an estuarine environment. In 2004 and 2005, repeated surveys were conducted in the navigation channel of the upper meso- to lower macrotidal Weser estuary TMZ (German North Sea coast) at different tidal stages and river discharges. Current velocity data were simultaneously collected by 1,200-kHz broadband ADCP (RDInstruments) measurements. Ground-truthing was carried out by means of grab sampling and gravity coring, adapted to fluid mud conditions. It was found that fluid mud occurrence in the Weser estuary is highly variable on time scales of a few hours and spatial scales of several metres. The riverbed is characterised by sand and mud deposits, and a complex morphology including subaqueous dunes and smooth bed deposits intermittently overlain by fluid mud. Thus, a continuous, coherent fluid mud body covering the entire TMZ riverbed was not observed. Rather, spatial distribution was patchy and highly dependent on suspended particulate matter (SPM) concentrations in the water column, as a result of which local fluid mud deposits varied in thickness from centimetres to metres. The formation of fluid mud was largely restricted to slack water, although slack-water conditions were not necessarily associated with large-scale fluid mud appearance. Advective SPM transport of resuspended fluid mud seems to be the most plausible explanation for the high spatial variability observed, even between two successive tides. The amount of fluid mud deposited and resuspended in the course of a tidal cycle can reach several 10s of tons even in small riverbed depressions.  相似文献   

Histochemistry as a tool for examining possible pathologic cause-and-effect relationships between heavy metal and inflammatory lesions in oysters, Crassostrea virginica     

C.Austin Farley 《Marine environmental research》1988,24(1-4)

Unexplained inflammatory lesions have been seen on many occasions in oysters (Crassostrea virginica) that have been examined by histopathologic methods. Application of the Mallory's hematin and the rubeanic acid methods for demonstration of copper in histologic sections revealed strong staining reactions in granules of some, but not all, granular hemocytes. These cells were clearly involved as constituents of acute inflammatory lesions characterized by infiltration of arteries, occlusion of veins, and diapedesis through external epithelia of the mantle and gastrointestinal tract. Heavily contaminated sites (i.e. Raritan Bay, New Jersey) showed strong staining reactions in a large number of animals examined. Control sites such as Great Bay, New Jersey, showed much lighter reactions. Seasonal sampling in the New Jersey sites revealed the most intense involvement in the late summer with apparent decreasing staining intensities in the fall. Other species of bivalve mollusks (Mytilus edulis and Mercenaria mercenaria) only showed significant staining reactions for heavy metal in kidney tissues with no evidence that heavily contaminated sites had higher levels. These results constitute preliminary evidence of a cause-and-effect relationship between a heavy metal contaminant (most probably copper) and inflammatory lesions in the oyster.  相似文献   

Continental terrace and Deep Plain offshore central California     

L. Austin Weeks  Robert K. Lattimore 《Marine Geophysical Researches》1971,1(2):145-161

Seismic-reflection profile investigations of the California continental terrace and Deep Plain, between 35°N and 39°N, support the hypothesis that the continental shelf and slope consist of alternating blocks of Franciscan and granitic-metamorphic basement overlain by varying thicknesses of younger sediments. North of 37°N, the seismic profiles confirm the distribution of turbidites shown by other workers. A significant proportion of the sediments on the middle and lower continental rise, south of 37°N, appears to be unrelated to the present Monterey deep-sea canyon system.Near 39°N the ridge which forms the topographic axis of the Delgada deep-sea fan consists of a thin cover of acoustically-transparent sediment unconformably overlying a thick sequence of turbidites; the southern part of this ridge is composed of well-defined short reflectors of highly variable dip. The ridge is incised by a steep-walled, flat-floored valley which follows a nearly straight course across its eastern flank. Among possible explanations for this pattern is uplift of the sea floor beneath the ridge.Our data and investigations of others indicate that acoustic basement north of 38°40N is at least 0.5 sec (two-way travel time) shoaler than it is south of Pioneer Ridge; when present, the ridge may represent as much as 0.5 sec additional basement relief. This structural pattern probably does not extend east of 127°40W, although the magnetic expression of the ridge persists to 127°W.Disappearance of the distinctive abyssal hills topography from west to east within the area of investigation usually can be attributed to burial by turbidites. Normal pelagic sediments form a veneer, rarely more than 0.15 sec thick, which conforms with the basement topography; some localities are devoid of discernible sediment.  相似文献   

Investigating the Functional Role of an Artificial Reef Within an Estuarine Seascape: a Case Study of Yellowfin Bream (<Emphasis Type="Italic">Acanthopagrus australis</Emphasis>)     

Matthew D. Taylor  Alistair Becker  Michael B. Lowry 《Estuaries and Coasts》2018,41(6):1782-1792

Estuaries contain mosaic habitats which support fish across different life stages. Artificial reefs represent a form of habitat enhancement which can provide additional structure for fishes and improve fishing opportunities, but the role of artificial reefs within the broader estuarine seascape has not been extensively studied. We used a VEMCO Positioning System (VPS) to monitor the fine-scale movements of yellowfin bream (Acanthopagrus australis, referred to as Bream), an estuarine predator and important recreational species. Fish were implanted with acoustic tags with accelerometer sensors (to measure relative fish activity), and their movements monitored on an artificial reef and adjacent habitats. Elevated activity patterns during crepuscular periods indicated that foraging was likely occurring over a large seagrass bed adjacent to the artificial reef system. Alternatively, lower activity was observed when fish were on the artificial reef, which may reflect the role of this habitat as a refuge, or that alternative foraging strategies were being employed. All fish exhibited a high degree of fidelity to the artificial reef on which they were tagged, and there was minimal movement among other reef groups within the array. There was extensive overlap in space use contours for smaller fish on the seagrass edge, but no overlap for larger fish that also tended to forage further afield. These findings have implications for the way in which artificial reefs support fish production, especially the importance of connectivity with other key habitats within the estuarine seascape.  相似文献   

The New CLOCIT Irradiation Facility for 40Ar/39Ar Geochronology: Characterisation,Comparison with CLICIT and Implications for High‐Precision Geochronology          下载免费PDF全文

Daniel Rutte  Tim A. Becker  Alan L. Deino  Steven R. Reese  Paul R. Renne  Robert A. Schickler 《Geostandards and Geoanalytical Research》2018,42(3):301-307

The Cadmium‐Lined Outer‐Core Irradiation Tube (CLOCIT) is a new irradiation facility for ⁴⁰Ar/³⁹Ar geochronology at the Oregon State University TRIGA^® reactor. We report fluence (i.e., time‐integrated flux) parameters from the first four CLOCIT irradiations and compare them with the existing Cadmium‐Lined Inner‐Core Irradiation Tube (CLICIT). CLOCIT provides an average neutron flux equivalent of 1.45–1.53 × 10^?4 J h^?1; about 55% of CLICIT. Radial fluence gradients were on the order of 0.2–4.2% cm^?1. A planar fit of J‐values results in residuals in the range of uncertainty in the J‐value, but systematic deviations resolve a non‐planar component of the neutron flux field, which has also been observed in CLICIT. Axial neutron fluence gradients were 0.6–1% cm^?1, compared with 0.7–1.6% cm^?1 for the CLICIT. Production rate ratios of interfering reactions were (⁴⁰Ar/³⁹Ar)_K = (4 ± 6) × 10^?4 and (³⁸Ar/³⁹Ar)_K = (1.208 ± 0.002) × 10^?2, (³⁶Ar/³⁷Ar)_Ca =  (2.649 ± 0.014) × 10^?4, (³⁸Ar/³⁷Ar)_Ca =  (3.33 ± 0.12) × 10^?5 and (³⁹Ar/³⁷Ar)_Ca =  (9.1 ± 0.28) × 10^?4, similar to the CLICIT values.  相似文献