Evaluation of the budget for silicic acid in Cascadia Basin deep water     

Tabitha A. Esther  Douglas E. Hammond  Susan L. Hautala  H. Paul Johnson  Richard J. Schwartz  Amelia N. Paukert 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(5):677-686

Between 2 and 3 km depth, North Pacific deep waters contain a plume of water with high silicic acid concentrations. The plume extends outward from Cascadia Basin (the Washington Margin), where waters can contain in excess of 200 μM off the coast of Oregon and Washington. To identify the source of the high Si concentrations in Cascadia Basin, we measured silicic acid and germanium concentrations in deep waters, and their fluxes from sediments using incubated cores. The mean flux of silicic acid into bottom waters is 0.81±0.05 mmol/m²-day, and the Ge/Si ratio of this flux is 0.7±0.1 μmol/mol. A box model, incorporating these results with hydrographic data, indicates that (1) no more than 5% of the silicic acid added to Basin deep waters can have a hydrothermal source (either hot or warm seeps), and (2) the total input of silicic acid to Basin deep waters is 0.06±0.02 Tmol/y. This input is nearly all from remineralized biogenic debris and should contribute about 0.5% of the 14 Tmol/y that are estimated to be necessary to maintain the North Pacific plume.  相似文献   

Multi-Wavelength Analysis of High-Energy Electrons in Solar Flares: A Case Study of the August 20, 2002 Flare     

Jana Kašparová  Marian KarlickÝ  Eduard P. Kontar  Richard A. Schwartz  Brian R. Dennis 《Solar physics》2005,232(1-2):63-86

A multi-wavelength spatial and temporal analysis of solar high-energy electrons is conducted using the August 20, 2002 flare of an unusually flat (γ₁ = 1.8) hard X-ray spectrum. The flare is studied using RHESSI, Hα, radio, TRACE, and MDI observations with advanced methods and techniques never previously applied in the solar flare context. A new method to account for X-ray Compton backscattering in the photosphere (photospheric albedo) has been used to deduce the primary X-ray flare spectra. The mean electron flux distribution has been analysed using both forward fitting and model-independent inversion methods of spectral analysis. We show that the contribution of the photospheric albedo to the photon spectrum modifies the calculated mean electron flux distribution, mainly at energies below ∼100 keV. The positions of the Hα emission and hard X-ray sources with respect to the current-free extrapolation of the MDI photospheric magnetic field and the characteristics of the radio emission provide evidence of the closed geometry of the magnetic field structure and the flare process in low altitude magnetic loops. In agreement with the predictions of some solar flare models, the hard X-ray sources are located on the external edges of the Hα emission and show chromospheric plasma heated by the non-thermal electrons. The fast changes of Hα intensities are located not only inside the hard X-ray sources, as expected if they are the signatures of the chromospheric response to the electron bombardment, but also away from them.  相似文献   

Secondary dispersion patterns of fluoride in the osor area,Province of Gerona,Spain     

M.O. Schwartz  G.H. Friedrich 《Journal of Geochemical Exploration》1973,2(2):103-114

The distribution of fluoride in spring and stream waters, stream sediments and soils of the Osor district, Province of Gerona, northeastern Spain, has been studied. Fluoride was determined by use of a fluoride-sensitive electrode. This potentiometric method has been found useful for geochemical exploration for fluorite because of its simplicity and high sensitivity.Investigations of the fluoride contents of natural waters and stream sediments resulted in the discovery of new fluorite mineralizations.Secondary dispersion patterns of soils have been studied. Different analytical procedures to extract the fluoride have been used. The application of the methods in geochemical exploration surveys is discussed.  相似文献   

Estimating historic lake stages from one‐time snapshot,the Shuttle Radar Topography Mission of 2000     

Kon Joon Bhang  Frank W. Schwartz  Seok‐Soon Park 《水文研究》2010,24(13):1834-1843

Lake studies play an important role in water management, ecology and other environmental issues. Monitoring lake stages is typically the first step on the lake studies. However, for the Prairie Pothole Region (PPR) of North America with millions of small lakes and potholes, onsite measurements for lake stages are almost impossible with the conventional gage stations due to the limited accessibility to lakes and the requirement of economical and human resources. To overcome this limitation, we employed the remote‐sensing approach to extract lake stages in PPR for bulk processing. To estimate lake stages, several image‐processing techniques were used with the Shuttle Radar Topography Mission (SRTM) data in January, 2000, a one‐time snapshot useful in historic lake level reconstruction. In this research, image processing techniques, for example, averaging, Fast Fourier Transform (FFT), Lee‐Sigma filtering were applied and masking with Canny Edge Detector (CED) and semi‐automated contouring were developed for lake stage estimation. In terms of simplicity, averaging might be useful if 1·5 m of the local bias for the study area in stage estimates. However, the FFT and Lee‐Sigma methods were slightly better than averaging. Masking with CED and semi‐automated contouring provided outstanding accuracy in the estimation. The masking and contouring methods provided ± 0·5 m of stage differences for relatively large lakes greater than 10 km² when compared with stage reading in spite of their calculation complexities and was shown as the best approaches among implemented methods in this study. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Cross-scale: multi-scale coupling in space plasmas     

Steven J. Schwartz  Timothy Horbury  Christopher Owen  Wolfgang Baumjohann  Rumi Nakamura  Patrick Canu  Alain Roux  Fouad Sahraoui  Philippe Louarn  Jean-André Sauvaud  Jean-Louis Pinçon  Andris Vaivads  Maria Federica Marcucci  Anastasios Anastasiadis  Masaki Fujimoto  Philippe Escoubet  Matt Taylor  Steven Eckersley  Elie Allouis  Marie-Claire Perkinson 《Experimental Astronomy》2009,23(3):1001-1015

Most of the visible universe is in the highly ionised plasma state, and most of that plasma is collision-free. Three physical phenomena are responsible for nearly all of the processes that accelerate particles, transport material and energy, and mediate flows in systems as diverse as radio galaxy jets and supernovae explosions through to solar flares and planetary magnetospheres. These processes in turn result from the coupling amongst phenomena at macroscopic fluid scales, smaller ion scales, and down to electron scales. Cross-Scale, in concert with its sister mission SCOPE (to be provided by the Japan Aerospace Exploration Agency—JAXA), is dedicated to quantifying that nonlinear, time-varying coupling via the simultaneous in-situ observations of space plasmas performed by a fleet of 12 spacecraft in near-Earth orbit. Cross-Scale has been selected for the Assessment Phase of Cosmic Vision by the European Space Agency.   相似文献   

Methods to calculate sedimentation rates of floodplain soils in the middle region of the Elbe River     

Frank Krüger  Ren Schwartz  Maritta Kunert  Kurt Friese 《洁净——土壤、空气、水》2006,34(3):175-187

This study presents different methods to quantify the historic and recent sedimentation of floodplain soils along the Elbe River. These methods include the comparison of surface elevations, the quantification of sedimentation with the aid of anthropogenic and geogenic tracers, sediment trap studies, and the calculation of load balances. Selected results from sites at the lower section of the middle Elbe River are presented and verified. The results show that several methods are suitable. In future work it should be possible, depending on the available soil and sediment data, to calculate sedimentation in Elbe River floodplain and the loss of retention volume for larger areas.  相似文献   

Numerical modelling of groundwater vulnerability: the example Namibia     

M. O. Schwartz 《Environmental Geology》2006,50(2):237-249

The UNSAT-H, HELP3 and MACRO4.3 computer codes, which have been developed for simulating the water balance of the unsaturated zone of soils and unconsolidated sediments, are also capable simulating water flow in low-porosity media such as fractured rock. The codes can be used to model the ability of rocks and overlying soils in the vadose zone to protect the groundwater in the uppermost aquifer. The net infiltration rates simulated by the different codes are compared against recharge determined by the chloride-balance method in Namibia. The dual-permeability code MACRO4.3 was found to produce more realistic estimates of net infiltration than the UNSAT-H and HELP3 codes, which are based on a single-permeability or effective-continuum method. The net infiltration rate together with the water storage in the unsaturated zone and the groundwater depth are used to calculate the residence time of pore water in the unsaturated zone. This parameter determines the intrinsic vulnerability of the aquifer.  相似文献   

Patterns of evolution of research strands in the hydrologic sciences   总被引：1，自引：0，他引：1  

F. W. Schwartz  Y. C. Fang  S. Parthasarathy 《Hydrogeology Journal》2005,13(1):25-36

This paper examines issues of impact and innovation in groundwater research by using bibliometric data and citation analysis.The analysis is based on 3120 papers from the journal Water Resources Research with full contents and their citation data from the ISI Web of Science. The research is designed to develop a better understanding of the way citation numbers can be interpreted by scientists. Not surprisingly, the most highly cited papers appear to be pioneers in the field with papers departing significantly from what has come before and to be effective in creating similar, follow-on papers. Papers that are early contributions to a new research strand that is highly influential will be on average highly cited. However, the importance of a research strand as measured by citations seems to fall with time. The citation patterns of some classic papers show that the activity in the topical area and impact of follow-on papers gradually decline with time, which has similarities with Kuhns ideas of revolutionary and normal science. The results of this study reinforce the importance of being a pioneer in a research strand, strategically shifting research strands, adopting strategies that can facilitate really major research breakthroughs.

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Resumen Este artículo examina los temas de impacto e innovación en la investigación de las aguas subterráneas, mediante el uso de datos bibliométricos y del análisis de las referencias bibliográficas. El análisis se basó en 3120 artículos de la revista Water Resources Research, con el contenido completo y sus datos de referencias bibliográficas obtenidos de la Red de Ciencia ISI. La investigación se diseñó para desarrollar un entendimiento mayor de la forma en que la cantidad de citas bibliográficas puede ser interpretada por los científicos. No es sorprendente que los artículos más citados, parecen ser los pioneros en el campo, siendo artículos que divergen significativamente de lo que se ha hecho anteriormente, los cuales son efectivos creando de manera similar otros artículos seguidores. Los artículos que son contribuciones iniciales en una línea de investigación nueva, la cual es de alta influencia, serán en promedio citados muy frecuentemente. Sin embargo, la importancia de una línea de investigación, de acuerdo a su medida por las veces que es citada, parece disminuir con el tiempo. Las tendencias en cuanto a hacer citas bibliográficas de algunos artículos clásicos, muestran que la actividad en el área de actualidad, lo mismo que el impacto de los artículos seguidores, declinan con el tiempo gradualmente, lo cual muestra parecidos con las ideas de Kuhn acerca de la ciencia revolucionaria y la ciencia normal. Los resultados de este estudio refuerzan la importancia de ser un pionero en una línea de investigación, cambiando estratégicamente de líneas de investigación y adoptando estrategias que puedan facilitar verdaderos avances en investigaciones de trascendencia.

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Résumé Larticle examine les problèmes dimpact et dinnovation dans la recherche des eaux souterraines en utilisant les données bibliométriques et lanalyse des citations. Lanalyse a été faite sur 3120 articles parus dans Water Resources Research en tenant compte de leur texte complet et de toutes citations parues dans lISI Web de la Science. Le but de la recherche a été de mieux comprendre comment le nombre des citations peut être interprété par les scientifiques. Ce nest pas une surprise que les plus cités articles soient les articles-pionniers dans leurs domaines, qui sécartent dune manière significative de ce qui a été écrit auparavant et qui ont été suivi par des nouveaux articles. Les articles qui présentent une première contribution dans leur domaine et qui ont beaucoup influencé la recherche sont en général les plus cités. Il semble que la diminution de limportance dun domaine de recherche est aussi reflétée par le nombre de citations. Le modèle des citations des quelques articles classiques montre que lactivité dans le domaine ainsi que limpact sur les articles suivantes déclinent progressivement pendant le temps ce qui présente une analogie avec les idées de Kuhn sur la science normale et révolutionnaire. Le résultat de létude renforce une fois de plus limportance dêtre un pionnier dans un domaine, en faisant avancer la recherche dans le domaine respectif, en adoptant des stratégies qui peuvent créer des percées majeures dans la recherche.

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Microinstabilities and models of the solar wind     

D. P. Rowse  I. W. Roxburgh  S. J. Schwartz 《Solar physics》1981,74(1):179-185

The collision-dominated two-fluid plasma models of the solar wind are shown to become collisionless and subject to microinstabilities at a few solar radii. Assuming that once the plasma is unstable it stays close to marginal stability models of the solar wind are constructed including waves and proton heating. The resulting models have higher velocities and proton temperatures than the collision dominated two fluid models.Proceedings of the 14th ESLAB Symposium on Physics of Solar Variations, 16–19 September 1980, Scheveningen, The Netherlands.  相似文献   

Effects of seasonal breeding on productive performance of pastoral goat herds in northern Kenya: a longitudinal analysis of growth in kids and body weight development of does     

Ingo Hary  Horst-Jürgen Schwartz 《Journal of Arid Environments》2002,50(4):641

This paper investigates whether liveweight development of kids and dams can be improved by introducing a seasonal breeding regime in goat herds maintained under pastoral management in northern Kenya. The experimental treatment consisted of six consecutive mating seasons. Traits studied comprise relative growth rates of kids (g kg^−0·75 day⁻¹) from birth until 2 years of age, liveweight development of kids (kg) from birth until 2 years of age, and body weight development (kg) of does over a reproductive cycle of 1 year duration. No systematic effect of mating season on birth weights of kids could be detected, whereas the experiment succeeded in demonstrating that mating season has an impact upon body weight development of kids. The highest average preweaning weight gains were achieved by kids born in the period from October to May, while growth performance was seriously compromised when birth took place at the middle of the long dry season. However, the differences between mating season groups had almost completely disappeared by 1 year of age. The mating season treatment produced marked differences in weight development curves in does. During gestation, does were advantaged when they were mated just prior to the long rainy season, while the largest relative liveweight gains over the entire reproductive cycle were achieved by does mated during the short rains. It is concluded that seasonal breeding does not confer any major advantage in terms of liveweight production of young livestock, except that mating during the short dry season from December to January should be avoided. Similarly, a clear effect on body weights of does at the end of the reproductive cycle could only be observed when mating occurred during this period.  相似文献