Timepieces     

Goldstein BR 《Science (New York, N.Y.)》1993,259(5093):388-389

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Lungfish Neoceratodus forsteri: activities of ornithine-urea cycle and enzymes     

L Goldstein  P A Janssens  R P Forster 《Science (New York, N.Y.)》1967,157(786):316-317

The level of activity of the ornithine-urea cycle is low in the liver of the permanently aquatic Australian lungfish. The rate of incorporation of (14)C-bicarbonate into urea by liver slices was only 100th of that previously observed in the estivating African lungfish Protopterus dolloi. The activities of enzymes of the ornithine-urea cycle were similarly reduced. The low activity of this cycle in Neoceratodus is consistent with its exclusively aquatic nature.  相似文献   

The effect of nitrate and organic matter upon mobility of selenium in groundwater and in a water treatment process     

Oleh Weres  Harry R. Bowman  Aaron Goldstein  Emily C. Smith  Leon Tsao  Warren Harnden 《Water, air, and soil pollution》1990,49(3-4):251-272

Kesterson Reservoir in Merced County, California was formerly used as a storage and evaporation facility for Se-contaminated agricultural drain water. Very little Se entered the shallow aquifer below the ponds with percolating pond water. With few localized exceptions, most of the Se was removed from the water and retained in the first decimeter of soil, which was rich in decaying organic matter. Where it was present in groundwater, Se was nearly always associated with nitrate. Nitrate induces mildly oxidizing conditions (Eh ≈ 350 mV) and inhibits microbial fixation of Se. In the absence of nitrate, relatively reducing conditions prevail in the groundwater (Eh ≈ -50 mV), and Se is quickly removed. Selenate follows oxygen and nitrate in the order that soil microbes utilize electron acceptors. The process of Se removal from water by soil was reproduced in the laboratory, and the effect of nitrate was confirmed. This natural process might be applied to water treatment for Se removal. The deep water ecosystem at Kesterson Reservoir was highly productive. Vegetation growing in water treatment ponds should supply enough organic matter to maintain anaerobic conditions in the sediment. This process, including algae culture, was operated in an outdoor 79 cm column for 100 days. At percolation rates of 15 and 30 m yr^?1 Se removal averaged 94%, with an additional 2% converted to volatile compounds.  相似文献   

Influences of recovery from clear-cut, climate variability, and thinning on the carbon balance of a young ponderosa pine plantation   总被引：1，自引：1，他引：1  

Laurent Misson  Jianwu Tang  Ming Xu  Megan McKay  Allen Goldstein 《Agricultural and Forest Meteorology》2005,130(3-4):207-222

From 1999 to 2002, the variations in carbon flux due to management practices (shrub removal, thinning) and climate variability were observed in a young ponderosa pine forest originated from clear-cutting and plantation in 1990. These measurements were done at the Blodgett Forest Ameriflux site located in the Sierra Nevada Mountains of California. Thinning in spring 2000 decreased the leaf area index (LAI) by 34% and added 496 g C m⁻² of wood and leaf debris at the soil surface. Total ecosystem respiration was not significantly affected by thinning (1261 g C m⁻² in 1999 and 1273 g C m⁻² in 2000), while canopy photosynthesis decreased by 202 g C m⁻². As a result the ecosystem shifted from a net sink of CO₂ in 1999 (−201 g C m⁻²) to a small net source in 2000 (13 g C m⁻²). Woody and leaf debris resulting from thinning only accounted for maximum 1% and 7% of the total respiration flux, respectively. Thinning did not affect the relative proportion of the different components of respiration to an observable degree. Low soil water availability in summer 2001 and 2002 decreased the proportion of soil respiration to the total respiration. It also imposed limitations on canopy photosynthesis: as a result the ecosystem shifted from a sink to a source of carbon 1 month earlier than in a wetter year (1999). The leaf area index and biomass of the stand increased rapidly after the thinning. The ecosystem was again a sink of carbon in 2001 (−97 g C m⁻²) and 2002 (−172 g C m⁻²). The net carbon uptake outside the traditionally-defined growing season can be important in this ecosystem (NEE = −50 g C m⁻² in 2000), but interannual variations are significant due to differences in winter temperatures.  相似文献   

Watershed risk analysis model for TVA's Holston River basin     

C. W. Chew  J. Herr  R. A. Goldstein  F. J. Sagona  K. E. Rylant  G. E. Hausers 《Water, air, and soil pollution》1996,90(1-2):65-70

The Electric Power Research Institute has launched a research project to develop a conceptual risk analysis framework for watershed management of point and nonpoint source pollution. The research leads to the design of an engineering model to 1) process and translate water quality data (coliform, HOD, DO, suspended solids, temperature, sediment, etc.) into decision variables (suitability for water contact sports and swimming, fish spawning fish survival, human consumption of fish, and freedom from algal nuisance, etc.) and 2) predict water quality improvements from proposed management alternatives. Actual development of the model is being carried out with the Tennessee Valley Authority (TVA) for the Holston River watershed.The effort includes model construction by importation of GIS map files, stringing together existing watershed and reservoir models, calibration of the model, and selection of decision variables and water quality check points. The model calculates hydrology, waste load, water quality and suitability of fish habitats at headwaters. The base case results and improvements after best management alternatives will be compared to the data observed by TVA's River Action Team. The final product will be a user friendly tool that stakeholders can use to find a cost effective method of improving water quality, including market-based pollution trading.  相似文献   

Late Quaternary eolian dust in surficial deposits of a Colorado Plateau grassland: Controls on distribution and ecologic effects   总被引：1，自引：1，他引：1  

Richard L. Reynolds  Marith C. Reheis  Jason C. Neff  Harland Goldstein  James Yount 《CATENA》2006,66(3):251-266

In a semi-arid, upland setting on the Colorado Plateau that is underlain by nutrient-poor Paleozoic eolian sandstone, alternating episodes of dune activity and soil formation during the late Pleistocene and Holocene have produced dominantly sandy deposits that support grass and shrub communities. These deposits also contain eolian dust, especially in paleosols. Eolian dust in these deposits is indicated by several mineralogic and chemical disparities with local bedrock, but it is most readily shown by the abundance of titaniferous magnetite in the sandy deposits that is absent in local bedrock. Magnetite and some potential plant nutrients (especially, P, K, Na, Mn, and Zn) covary positively with depth (3–4 m) in dune-crest and dune-swale settings. Magnetite abundance also correlates strongly and positively with abundances of other elements (e.g., Ti, Li, As, Th, La, and Sc) that are geochemically stable in these environments. Soil-property variations with depth can be ascribed to three primary factors: (1) shifts in local geomorphic setting; (2) accumulation of relatively high amounts of atmospheric mineral dust inputs during periods of land-surface stability; and (3) variations in dust flux and composition that are likely related to changes in dust-source regions. Shifts in geomorphic setting are revealed by large variations in soil texture and are also expressed by changes in soil chemical and magnetic properties. Variable dust inputs are indicated by both changes in dust flux and changes in relations among magnetic, chemical, and textural properties. The largest of these changes is found in sediment that spans late Pleistocene to early Holocene time. Increased dust inputs to the central Colorado Plateau during this period may have been related to desiccation and shrinkage of large lakes from about 12 to 8 ka in western North America that exposed vast surfaces capable of emitting dust. Soil properties that result from variable dust accumulation and redistribution in these surficial deposits during the late Quaternary are important to modern ecosystem dynamics because some plants today utilize nutrients deposited as long ago as about 12–15 ky and because variations in fine-grained (silt) sediment, including eolian dust, influence soil-moisture capacity.  相似文献   

Xanthomatous keratitis, disseminated xanthomatosis, and atherosclerosis in Cuban tree frogs     

J L Carpenter  A Bachrach  D M Albert  S J Vainisi  M A Goldstein 《Veterinary pathology》1986,23(3):337-339

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Induction of high affinity nitrate and ammonium uptake systems in wheat     

Alan H. Goldstein  Andre D. Hunziker 《Journal of plant nutrition》2013,36(8):721-730

Abstract

The ability of 7 day old wheat seedlings to take up nitrate or ammonium from hydroponic solution was measured. Seedlings were grown under fully aerated hydroponic conditions. The growth solution consisted of either 0.5 mM CaSO₄ alone or in combination with high nitrate (5 mM NO₃ ^‐ ), high ammonium (2 mM NH₄ ⁺) or modified 1/10 Hoaglands solution with nitrate N only (14 mM) or ammonium N only (2 mM). After washing the roots for one hour in CaSO₄, nitrate or ammonium uptake was measured with an ion selective electrode. Plants grown in high nitrate were unable to take up nitrate from a 0.1 mM external solution. Those grown in CaSO₄ were able to take up nitrate at the same external concentration (flux = 10.2 +/‐ 3.0 μmol nitrate/g dry wtlbh). The same result was seen for plants grown in high ammonium vs those grown in CaSO₄ (flux = 21.0 +/‐ 10.0 μmol/g dry wtlbh). Similar results were obtained when modified Hoagland's solution was substituted for the high N solutions. These data indicate that wheat roots possess both high and low affinity nitrate and ammonium uptake systems. The data further indicate that, for a given ion, the high and low affinity systems do not operate simultaneously under high N conditions. The high affinity system is switched off in the range of 1 mM for both ionic forms of N. Developmental studies show that the expression of the high affinity trait is reversible and may be induced (repressed) by conditioning for 24 h in low (high) N media. Plants grown in high N solutions showed efflux of the ion under assay conditions. Neither ion interfered with the induction/repression of the high affinity trait for the other under the conditions used in this study.  相似文献   

Perspective: Educating Students for Composting Careers     

Jerome Goldstein 《Compost science & utilization》2013,21(1)

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Perspective: The Search for Quality     

Jerome Goldstein 《Compost science & utilization》2013,21(2)

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