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51.
Steven W. Effler David A. Matthews Carol M. Brooks‐Matthews Mary Gail Perkins Clifford A. Siegfried James M. Hassett 《Journal of the American Water Resources Association》2004,40(3):737-754
ABSTRACT: The conspicuous shifts in summertime values of common measures of water qualify that have persisted for 10 years (1993 to 2002) in the Seneca River, New York, as a result of the zebra mussel invasion are documented. Resolution of patterns in time and space is supported by water quality monitoring that extends back to the late 1970s. Patterns are evaluated to describe the stability of impacts and quantify metabolic activity of the invader. The water quality impacts that have persisted unabated for 10 years since the invasion are the most severe documented for a river in North America. Changes in summer median conditions since the invasion include: (1) a 16‐fold decrease in chlorophyll concentration (Chi), (2) a 2.5‐fold increase in Secchi disc transparency, (3) a 17‐fold increase in soluble reactive phosphorus concentration, (4) a 3.7‐fold increase in total ammonia concentration, (5) a greater than 25 percent decrease in dissolved oxygen (DO) concentration, and (6) a decrease in pH of 0.55 units. The strength of these signatures has been driven by anthropogenic influences that include upstream nutrient loading and morphometric modifications of the river, and the functioning of Cross Lake, through which the river flows. This hypereutrophic lake sustains dense zebra mussel populations and related water quality impacts in the river downstream of the lake outflow by acting as a source of veligers and suitable food for this bivalve. Evidence is presented that levels of metabolic activity of the zebra mussel in this river have been resource limited, manifested through increased consumption of Chl and DO with increased delivery of these constituents in the lake's outflow. 相似文献
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Siegfried Greif 《Die Naturwissenschaften》1989,76(4):156-159
Although there exists a close causal relationship between R&D and patents the attempt to establish a real connection suffers from certain difficulties. By means of specific methods a correlation between patent applications and R&D expenditure could be achieved at the national economic level. A previously developed concordance between the International Patent Classification and the systematics of sectors of the economy opens the possibility for a more differentiated analysis of the relationship between R&D and patents. 相似文献
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Jose A. Nores MD Siegfried Rotmensch Roberto Romero Cecilia Avila Mona Inati John C. Hobbins 《黑龙江环境通报》1992,12(9):741-753
Atelosteogenesis type II is a lethal chondrodysplasia characterized by severe micromelia, spinal abnormalities, talipes equinovarus, and abducted thumbs and toes. We present a case diagnosed at 21 weeks of gestation in which antenatal sonographic and post-mortem radiological findings were correlated. The patient had a recurrence of this disorder in a subsequent pregnancy which was terminated at 15 weeks, supporting previous reports of an autosomal recessive inheritance pattern. The feasibility of diagnosing the following morphological features by prenatal ultrasonography is demonstrated: coronal clefts of the vertebral bodies, metaphyseal and epiphyseal abnormalities, spinal deviations such as cervical kyphosis and a horizontal sacrum, additional ossification centres in the pelvis, and preaxial deviation of the thumbs and toes. The differential diagnosis of this disorder from other skeletal dysplasias with similar features is discussed. 相似文献
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Siegfried Schneider 《Die Naturwissenschaften》1975,62(11):509-518
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