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51.
52.
大比例尺土壤保持服务制图分级方法研究 总被引:2,自引:1,他引:2
科学地编制生态系统服务空间分布图,有助于识别生态系统优先保护热点及空缺,能够为国土安全规划提供基础信息。但由于缺乏统一科学的生态系统服务分级方法,生态系统服务分布图的展示效果和制图效率都受到限制。不恰当的分级制图会误导决策者对生态系统服务空间分布特征的判断,增加生态保护决策的不确定性。以构建生态服务制图分级标准为目标,对我国6个典型县区的土壤保持服务数据展开1:25万比例尺制图分级案例研究。采用分级精度、面积均衡性、极差一致性、空间自相关一致性4个分级质量评价指标评价并比较了目前地图编制中常用的自然断点法、几何间隔法、累积比例法、等差法、分位数法5种分级算法的分级制图效果。结果表明,6个县区有相似的土壤保持服务分布特征:低值区覆盖面积大,高值区覆盖面积小。各县区土壤保持服务制图最优分级方法有差异:延庆区、丰满区最优分级方法为自然断点法;永靖县、天山区、安宁市最优分级方法为累积比例法;富阳区最优分级方法为几何间隔法。各分级方法中,累积比例法在6个县区综合制图效果最优或接近最优,适用性最好,能够较好的刻画各县区的土壤保持服务空间分布特征。本文提出的分级评价方法及其结果,可为生态系统土壤保持服务制图规范化和自动化提供科学依据。 相似文献
53.
Fabien Corblin Sbastien Tripodi Eric Fanchon Delphine Ropers Laurent Trilling 《Bio Systems》2009,98(2):91-104
Dynamical modeling has proven useful for understanding how complex biological processes emerge from the many components and interactions composing genetic regulatory networks (GRNs). However, the development of models is hampered by large uncertainties in both the network structure and parameter values. To remedy this problem, the models are usually developed through an iterative process based on numerous simulations, confronting model predictions with experimental data and refining the model structure and/or parameter values to repair the inconsistencies. In this paper, we propose an alternative to this generate-and-test approach. We present a four-step method for the systematic construction and analysis of discrete models of GRNs by means of a declarative approach. Instead of instantiating the models as in classical modeling approaches, the biological knowledge on the network structure and its dynamics is formulated in the form of constraints. The compatibility of the network structure with the constraints is queried and in case of inconsistencies, some constraints are relaxed. Common properties of the consistent models are then analyzed by means of dedicated languages. Two such languages are introduced in the paper. Removing questionable constraints or adding interesting ones allows to further analyze the models. This approach allows to identify the best experiments to be carried out, in order to discriminate sets of consistent models and refine our knowledge on the system functioning. We test the feasibility of our approach, by applying it to the re-examination of a model describing the nutritional stress response in the bacterium Escherichia coli. 相似文献
54.
Nickel Toxicity and Distribution in Maize Roots 总被引:5,自引:0,他引:5
Seregin I. V. Kozhevnikova A. D. Kazyumina E. M. Ivanov V. B. 《Russian Journal of Plant Physiology》2003,50(5):711-717
A new histochemical method for Ni determination has been developed and employed to study the pattern of Ni distribution in plant tissues. Two-day-old seedlings of maize (Zea mays L.) were transferred onto 15, 20, 25, and 35 M Ni(NO3)2 solutions in the presence of 3 mM Ca(NO3)2, and Ni localization in shoot and root tissues was investigated at days 2 and 7 of the incubation. Following two days of incubation, Ni was found in all root tissues, and its content increased with the period of exposure and from the tip to the root base. Independent of root region and tissue, Ni content in the protoplasts exceeded that in the cell walls. Ni penetrated the endodermal barrier and accumulated in the endodermis and pericycle to the highest concentration. Ni accumulation in the pericycle restricted root branching. Ni did not affect the final cell length, and the inhibition of root growth resulted from suppressed cell division. In the shoots, Ni content was below the level discerned by the dimethylglyoximine method; we therefore conclude that maize belongs to excluder plants, with their root systems functioning as a barrier limiting heavy metal intake by aboveground organs. The pattern of Ni transport differs from that of Cd and Pb; this difference stands for specific toxic effects of Ni, including an arrest of root branching. 相似文献
55.
The late-third-instar labial disc is comprised of two disc-proper cell layers, one representing mainly the ventral half of the anterior compartment (L-layer) and the other, the dorsal half of the anterior compartment and most, if not all, of the posterior compartment (M-layer). In the L-layer, Distal-less represses homothorax whereas no Distal-less-dependent homothorax repression occurs in the M-layer where Distal-less is coexpressed with homothorax. In wild-type labial discs, clawless, one of the two homeobox genes expressed in distal cells receiving maximum (Decapentaplegic+Wingless) signaling activity in leg and antennal discs, is specifically repressed by proboscipedia. A fate map, inferred from data on basic patterning gene expression in larval and pupal stages and mutant phenotypes, indicates the inner surface of the labial palpus, which includes the pseudotracheal region, to be a derivative of the distal portion of the M-layer expressing wingless, patched, Distal-less and homothorax. The outer surface of the labial palpus with more than 30 taste bristles derives from an L-layer area consisting of dorsal portions of the anterior and posterior compartments, each expressing Distal-less. Our analysis also indicates that, in adults and pupae, the anterior-posterior boundary, dividing roughly equally the outer surface of the distiproboscis, runs along the outer circumference of the inner surface of distiproboscis. 相似文献
56.
Michael?WangEmail author Hanjie?Lee John?Molburg 《The International Journal of Life Cycle Assessment》2004,9(1):34-44
Aim, Scope, and Background Studies to evaluate the energy and emission impacts of vehicle/fuel systems have to address allocation of the energy use and
emissions associated with petroleum refineries to various petroleum products because refineries produce multiple products.
The allocation is needed in evaluating energy and emission effects of individual transportation fuels. Allocation methods
used so far for petroleum-based fuels (e.g., gasoline, diesel, and liquefied petroleum gas [LPG]) are based primarily on mass,
energy content, or market value shares of individual fuels from a given refinery. The aggregate approach at the refinery level
is unable to account for the energy use and emission differences associated with producing individual fuels at the next sub-level:
individual refining processes within a refinery. The approach ignores the fact that different refinery products go through
different processes within a refinery. Allocation at the subprocess level (i.e., the refining process level) instead of at
the aggregate process level (i.e., the refinery level) is advocated by the International Standard Organization. In this study,
we seek a means of allocating total refinery energy use among various refinery products at the level of individual refinery
processes.
Main Features We present a petroleum refinery-process-based approach to allocating energy use in a petroleum refinery to petroleum refinery
products according to mass, energy content, and market value share of final and intermediate petroleum products as they flow
through refining processes within a refinery. The approach is based on energy and mass balance among refining processes within
a petroleum refinery. By using published energy and mass balance data for a simplified U.S. refinery, we developed a methodology
and used it to allocate total energy use within a refinery to various petroleum products. The approach accounts for energy
use during individual refining processes by tracking product stream mass and energy use within a refinery. The energy use
associated with an individual refining process is then distributed to product streams by using the mass, energy content, or
market value share of each product stream as the weighting factors.
Results The results from this study reveal that product-specific energy use based on the refinery process-level allocation differs
considerably from that based on the refinery-level allocation. We calculated well-to-pump total energy use and greenhouse
gas (GHG) emissions for gasoline, diesel, LPG, and naphtha with the refinery process-based allocation approach. For gasoline,
the efficiency estimated from the refinery-level allocation underestimates gasoline energy use, relative to the process-level
based gasoline efficiency. For diesel fuel, the well-to-pump energy use for the process-level allocations with the mass- and
energy-content-based weighting factors is smaller than that predicted with the refinery-level allocations. However, the process-level
allocation with the market-value-based weighting factors has results very close to those obtained by using the refinery-level
allocations. For LPG, the refinery-level allocation significantly overestimates LPG energy use. For naphtha, the refinery-level
allocation overestimates naphtha energy use. The GHG emission patterns for each of the fuels are similar to those of energy
use.
Conclusions We presented a refining-process-level-based method that can be used to allocate energy use of individual refining processes
to refinery products. The process-level-based method captures process-dependent characteristics of fuel production within
a petroleum refinery. The method starts with the mass and energy flow chart of a refinery, tracks energy use by individual
refining processes, and distributes energy use of a given refining process to products from the process. In allocating energy
use to refinery products, the allocation method could rely on product mass, product energy contents, or product market values
as weighting factors. While the mass- and energy-content-based allocation methods provide an engineering perspective of energy
allocation within a refinery, the market-value-based allocation method provides an economic perspective. The results from
this study show that energy allocations at the aggregate refinery level and at the refining process level could make a difference
in evaluating the energy use and emissions associated with individual petroleum products. Furthermore, for the refining-process-level
allocation method, use of mass — energy content- or market value share-based weighting factors could lead to different results
for diesel fuels, LPG, and naphtha. We suggest that, when possible, energy use allocations should be made at the lowest subprocess
level — a confirmation of the recommendation by the International Standard Organization for life cycle analyses.
Outlook The allocation of energy use in petroleum refineries at the refining process level in this study follows the recommendation
of ISO 14041 that allocations should be accomplished at the subprocess level when possible. We developed a method in this
study that can be readily adapted for refineries in which process-level energy and mass balance data are available. The process-level
allocation helps reveal some additional energy and emission burdens associated with certain refinery products that are otherwise
overlooked with the refinery-level allocation. When possible, process-level allocation should be used in life-cycle analyses. 相似文献
57.
58.
Kalyaneswar Mandal Brad L. Pentelute Valentina Tereshko Vilasak Thammavongsa Olaf Schneewind Anthony A. Kossiakoff Stephen B. H. Kent 《Protein science : a publication of the Protein Society》2009,18(6):1146-1154
We describe the use of racemic crystallography to determine the X‐ray structure of the natural product plectasin, a potent antimicrobial protein recently isolated from fungus. The protein enantiomers L ‐plectasin and D ‐plectasin were prepared by total chemical synthesis; interestingly, L ‐plectasin showed the expected antimicrobial activity, while D ‐plectasin was devoid of such activity. The mirror image proteins were then used for racemic crystallization. Synchrotron X‐ray diffraction data were collected to atomic resolution from a racemic plectasin crystal; the racemate crystallized in the achiral centrosymmetric space group P1 with one L ‐plectasin molecule and one D ‐plectasin molecule forming the unit cell. Dimer‐like intermolecular interactions between the protein enantiomers were observed, which may account for the observed extremely low solvent content (13%–15%) and more highly ordered nature of the racemic crystals. The structure of the plectasin molecule was well defined for all 40 amino acids and was generally similar to the previously determined NMR structure, suggesting minimal impact of the crystal packing on the plectasin conformation. 相似文献
59.
西藏南部岗巴地区白垩纪中期钙质超微化石带和Cenomanian-Turonian界线 总被引:6,自引:0,他引:6
我国西藏南部海相白垩系含有较丰富的钙质超微化石。文中着重研究岗巴地区两个剖面 (即剖面A ,B)Albian Santonian钙质超微化石的分布。根据标志种的存在 ,识别出 5个初现面事件 ,相应地建立 6个钙质超微化石带 ,自下至上是Prediscosphaeracretacea带 ,Eiffellithusturriseiffeli带 ,Lithraphiditesacutum带 ,Gartneragoobliquum带 ,Quadrumgartneri带 ,Lucianorhabduscayeuxii带。同时 ,通过洲际对比 ,建议以G .obliquum初现面作为划分本区Cenomanian和Turonian界线的标志。此外 ,Q .gartneri带和I .cayeuxii带之间缺失多个化石带 ,据此推测Turonian至Santonian期间本区可能存在沉积间断。 相似文献
60.
R. Balossino G. Pennati F. Migliavacca L. Formaggia A. Veneziani M. Tuveri 《Computer methods in biomechanics and biomedical engineering》2013,16(1):113-123
This work addresses the problem of prescribing proper boundary conditions at the artificial boundaries that separate the vascular district from the remaining part of the circulatory system. A multiscale (MS) approach is used where the Navier–Stokes equations for the district of interest are coupled to a non-linear system of ordinary differential equations which describe the circulatory system. This technique is applied to three 3D models of a carotid bifurcation with increasing stenosis resembling three phases of a plaque growth. The results of the MS simulations are compared to those obtained by two stand-alone models. The MS shows a great flexibility in numerically predicting the haemodynamic changes due to the presence of a stenosis. Nonetheless, the results are not significantly different from a stand-alone approach where flows derived by the MS without stenosis are imposed. This is a consequence of the dominant role played by the outside districts with respect to the stenosis resistance. 相似文献