Error Estimates of Double-Averaged Flow Statistics due to Sub-Sampling in an Irregular Canopy Model     

Duman  Tomer  Bohbot-Raviv  Yardena  Moltchanov  Sharon  Shavit  Uri 《Boundary-Layer Meteorology》2021,179(3):403-422

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Stability and changes in astaxanthin ester composition from Haematococcus pluvialis during storage     

苗凤萍  耿亚洪  卢大炎  左进城  李夜光 《中国海洋湖沼学报》2013,31(6):1181-1189

In this paper, we investigated the effects of temperature, oxygen, antioxidants, and corn germ oil on the stability of astaxanthin from Haematococcus pluvialis under different storage conditions, and changes in the composition of astaxanthin esters during storage using high performance liquid chromatography and spectrophotometry. Oxygen and high temperatures （22-25~C） significantly reduced the stability of astaxanthin esters. Corn germ oil and antioxidants （ascorbic acid and vitamin E） failed to protect astaxanthin from oxidation, and actually significantly increased the instability of astaxanthin. A change in the relative composition of astaxanthin esters was observed after 96 weeks of long-term storage. During storage, the relative amounts of free astaxanthin and astaxanthin monoesters declined, while the relative amount of astaxanthin diesters increased. Thus, the ratio of astaxanthin diester to monoester increased, and this ratio could be used to indicate if astaxanthin esters have been properly preserved. If the ratio is greater than 0.2, it suggests that the decrease in astaxanthin content could be higher than 20%. Our results show that storing algal powder from H. pluvialis or other natural astaxanthin products under vacuum and in the dark below 4~C is the most economical and applicable storage method for the large-scale production of astaxanthin from H. pluvialis. This storage method can produce an astaxanthin preservation rate of at least 80% after 96 weeks of storage.  相似文献   

青藏粉土单向冻结冻胀率变化特性研究   总被引：6，自引：1，他引：5  

王永涛  王大雁  郭妍  雷乐乐  顾同欣 《冰川冻土》2016,38(2):409-415

开展了饱和青藏粉土在开放系统不同温度梯度条件下的单向冻结试验,对冻结过程中冻结深度和冻胀速率的发展变化过程进行了研究.结果表明：不同顶板温度下,土样均在25 h左右达到冻结稳定状态,之后冻结深度基本不再发生变化.土样冻结过程中,冻胀速率表现为快速减小、较小值保持稳定、快速增大、较大值保持稳定四个阶段.基于以上试验结果,对土样冻结过程中冻胀率的变化过程进行了研究,发现冻胀率随冻结深度的增加先减小后增加,冻胀率从减小变为增大的时刻就是冻结深度趋于稳定的时刻,而冻胀率快速增大的时刻为冻胀速率进入较大值保持阶段的时刻.冻胀率变化的内在机理为土样冻结过程中由冰透镜体分凝所导致的未冻区固结和已冻区冻胀共同作用的结果.  相似文献   

What feeds shelf-edge clinoforms over margins deprived of adjacent land sources? An example from southeastern Brazil     

Uri Schattner  Francisco José Lobo  Adrián López-Quirós  Jorge Luiz dos Passos Nascimento  Michel Michaelovitch de Mahiques 《Basin Research》2020,32(2):293-301

In southeastern Brazil, the Serra do Mar coastal mountain range blocks the sediment influx from arriving at a ca. 1,500 km long continental margin comprising Santos and Pelotas basins. Despite this deprivation, the margin accumulated a ca. 1 km thick sedimentary succession since the Mid-Miocene. Examination of seismic reflection and oceanographic data indicates that shelf-margin clinoform formation exhibits a regional variability, with major sigmoidal clinoforms developed in the transitional area between both basins. Laterally, poorly developed oblique clinoforms constitute isolated depocenters along the shelf margin. The continuous clinoform development in the transitional area is attributed to the major influence on sediment transport patterns of several ocean bottom currents flowing along the margin, such as the Brazil Coastal Current, the Brazil Current and the Intermediate Water Brazil Current. These currents erode, transport and distribute sediments across the shelf break and upper slope from distant sediment sources located either north or south of the study area. The progressive southward strengthening of the Brazil Current could be responsible for a major southward sediment redistribution from the northern Campos Basin, and/or for sediment entrainment from northward-induced transport by the Brazil Coastal Current, originally derived from the De la Plata Estuary. In the transition between Santos and Pelotas basins, the Intermediate Water Brazil Current splits forming the Santos Bifurcation, allowing for a continuous depositional process and clinoform generation. We suggest that ocean bottom currents may shape other shelf-edge ‘contouritic clinoforms’ in continental margins mainly constructed by along-strike sediment transport largely driven by long-term geostrophic currents.  相似文献   

Trends in CO2 emissions in Israel—an international perspective     

Moshe Yanai  Jean Koch  Uri Dayan 《Climatic change》2010,101(3-4):555-563

As a Party to the United Nations Framework Convention on Climate Change, Israel conducts a periodical inventory of greenhouse gases emissions. These data allowed the generation of time series of CO₂ emissions per capita and per GDP for the period 1990–2004. It was found that CO₂ emissions per capita increased dramatically from 1990 to 2000, reflecting the rapid economic growth that was initiated by the massive immigration wave at the beginning of the nineties. These emissions remained stable between 2000 and 2004, reflecting the economic stagnation caused by the uprising in the Palestinian Territories, as well as stagnation in the global economy. CO₂ emissions per GDP (CO₂ intensity) remained stable along the whole reviewed period. This stability can be explained by a shift in electricity consumption from the industrial sector towards the commercial and the residential sectors, corresponding to an increase in the standard of living in the same period. A comparison was held with countries considered as developed for many years represented by the five largest economies (G-5) and recently developed countries (RDCs). Although Israel exhibits emission levels within the range of the G-5 countries, it does not fit the patterns demonstrated by these countries. Trends observed in Israel resemble these observed in other RDCs, such as Spain or Greece, confirming the classification of Israel in this category.  相似文献   

Integrated analysis of policy options for protection of groundwater quality     

Noel D. Uri  Wen-Yuan Huang 《Environmental Geology》1990,15(3):233-241

This paper is directed at providing an integrated framework that a regional authority should use when assessing the potential impacts of any policy initiative directed at improving groundwater quality. In particular, a policy model is developed relying on three decision components (a farm-level production decisions model, a household decisions model and a regional policy decision model) where the objective is one of identifying the trade-offs that a regional authority will be confronted with as it strives to balance the preferences of farmers and households while endeavoring to maximize net economic welfare. The basic rule developed indicates that the regional authority must choose a policy whereby any increase (decrease) in regional income is just equal to the decrease (increase) in net benefits to households.The views expressed are those of the authors and do not necessarily represent the policies of the U.S. Department of Agriculture or the views of other U.S. Department of Agriculture staff members.  相似文献   

Footprint Estimation for Multi-Layered Sources and Sinks Inside Canopies in Open and Protected Environments     

Tomer Duman  Josef Tanny  Uri Dicken  Mario B. Siqueira  Gabriel G. Katul 《Boundary-Layer Meteorology》2015,155(2):229-248

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The location of deep salinity sources in the Israeli Coastal aquifer     

Uri Shavit  Alex Furman 《Journal of Hydrology》2001,250(1-4):63-77

The salinization process of the Israeli Coastal aquifer has led to an average concentration of about 200 mgCl/l with a significant number of discrete salinity plumes in the middle and southern regions. The salinity of these plumes is high (500–1000 mgCl/l) and is increasing rapidly. Geochemical evidence has suggested that the salinity source in the Be'er Tuvia plume (in the south part of the aquifer) is at the bottom of the aquifer. This paper describes a solution of the source inverse problem and its application in the Be'er Tuvia plume. A transient two-dimensional finite element model was solved and the source terms were computed at each node in a 14×14 km² area. An error analysis has shown that when no errors are introduced in the input data the reconstruction is perfect. The results of a sensitivity analysis are presented and the actual reconstruction errors are estimated. Applying the model in the Be'er Tuvia region indicates that a salinity source exists about 1 km to the west and 1.5 km to the north of the center of the salinity plume. This source is believed to be the plume source.  相似文献   

The geochemistry of groundwater resources in the Jordan Valley: The impact of the Rift Valley brines     

Efrat Farber  Avner Vengosh  Ittai Gavrieli  Amer Marie  Thomas D. Bullen  Bernhard Mayer  Amir Polak  Uri Shavit 《Applied Geochemistry》2007

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Environmental considerations in the fertilizer use decision   总被引：1，自引：0，他引：1  

Noel D. Uri 《Environmental Geology》1998,34(2-3):103-110

 The increase in the use of fertilizer in agricultural production has been associated with a substantial increase in agricultural productivity in the United States. This increase in fertilizer use has been driven by a variety of economic forces including variations in the price of output and changing relative factor prices. Associated with the increase in the use of fertilizer have been adverse environmental consequences that are not reflected in the costs and returns of agricultural production. That is, externalities exist whose cost need to be internalized. Because the use of fertilizer has been shown to respond to market forces, it is efficient to use the market to control the use of fertilizer. This can be done through, for example, the use of a fertilizer tax. Received: 31 December 1996 · Accepted: 13 May 1997  相似文献