939 resultados para Source-sink potential
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The visit highlighted the vital contribution of the inland fisheries sector to provision of basic food security within the uncleared area (farmers report very low consumption frequencies for all other fish or meat protein substitutes). A 30-mile system of Brackish water lagoons which demarcates the cleared and uncleared areas is the main source of retailed fish in the uncleared area. Second in importance is the inland tank fishery, where the bulk of production emanates from 17 major irrigation reservoirs. [PDF contains 29 pages]
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We develop a logarithmic potential theory on Riemann surfaces which generalizes logarithmic potential theory on the complex plane. We show the existence of an equilibrium measure and examine its structure. This leads to a formula for the structure of the equilibrium measure which is new even in the plane. We then use our results to study quadrature domains, Laplacian growth, and Coulomb gas ensembles on Riemann surfaces. We prove that the complement of the support of the equilibrium measure satisfies a quadrature identity. Furthermore, our setup allows us to naturally realize weak solutions of Laplacian growth (for a general time-dependent source) as an evolution of the support of equilibrium measures. When applied to the Riemann sphere this approach unifies the known methods for generating interior and exterior Laplacian growth. We later narrow our focus to a special class of quadrature domains which we call Algebraic Quadrature Domains. We show that many of the properties of quadrature domains generalize to this setting. In particular, the boundary of an Algebraic Quadrature Domain is the inverse image of a planar algebraic curve under a meromorphic function. This makes the study of the topology of Algebraic Quadrature Domains an interesting problem. We briefly investigate this problem and then narrow our focus to the study of the topology of classical quadrature domains. We extend the results of Lee and Makarov and prove (for n ≥ 3) c ≤ 5n-5, where c and n denote the connectivity and degree of a (classical) quadrature domain. At the same time we obtain a new upper bound on the number of isolated points of the algebraic curve corresponding to the boundary and thus a new upper bound on the number of special points. In the final chapter we study Coulomb gas ensembles on Riemann surfaces.
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The effectiveness of a vaccine is determined not only by the immunogenicity of its components, but especially by how widely it covers the disease-causing strains circulating in a given region. Because vaccine coverage varies over time, this study aimed to detect possible changes that could affect vaccine protection during a specific period in a southern European region. The 4CMenB vaccine is licensed for use in Europe, Canada, and Australia and is mainly directed against Neisseria meningitidis serogroup B. This vaccine contains four main immunogenic components: three recombinant proteins, FHbp, Nhba and NadA, and an outer membrane vesicle [PorA P1.4]. The allelic distribution of FHbp, Nhba, NadA, and PorA antigens in 82 invasive isolates (B and non-B serogroups) isolated from January 2008 to December 2013 were analyzed. 4CMenB was likely protective against 61.8% and 50% of serogroup B and non-B meningococci, respectively, in the entire period, but between 2012 and 2013, the predicted protection fell below 45% (42.1% for serogroup B isolates). The observed decreasing trend in the predicted protection during the 6 years of the study (X-2 for trend = 4.68, p=0.03) coincided with a progressive decrease of several clonal complexes (e. g., cc11, cc32 and cc41/44), which had one or more antigens against which the vaccine would offer protection.
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Broadband infrared luminescence centred at around 1300 nm with full-width at half maximum of about 342 nm was observed from transparent Ni2+-doped lithium-alumino-silicate glass-ceramics embedded with beta-eucryptite crystallines. The room temperature fluorescent lifetime was 98 mu s. The transparent glass-ceramics may have potential applications in a widely tunable laser and a super-broadband optical amplifier for optical communications.
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We have recently shown that the transient receptor potential vanilloid type 1 (TRPV1), a non-selective cation channel in the peripheral and central nervous system, is localized at postsynaptic sites of the excitatory perforant path synapses in the hippocampal dentate molecular layer (ML). In the present work, we have studied the distribution of TRPV1 at inhibitory synapses in the ML. With this aim, a preembedding immunogold method for high resolution electron microscopy was applied to mouse hippocampus. About 30% of the inhibitory synapses in the ML are TRPV1 immunopositive, which is mostly localized perisynaptically (similar to 60% of total immunoparticles) at postsynaptic dendritic membranes receiving symmetric synapses in the inner 1/3 of the layer. This TRPV1 pattern distribution is not observed in the ML of TRPV1 knock-out mice. These findings extend the knowledge of the subcellular localization of TRPV1 to inhibitory synapses of the dentate molecular layer where the channel, in addition to excitatory synapses, is present.
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Lymphangioleiomyomatosis (LAM) is a rare lung-metastasizing neoplasm caused by the proliferation of smooth muscle-like cells that commonly carry loss-of-function mutations in either the tuberous sclerosis complex 1 or 2 (TSC1 or TSC2) genes. While allosteric inhibition of the mechanistic target of rapamycin (mTOR) has shown substantial clinical benefit, complementary therapies are required to improve response and/or to treat specific patients. However, there is a lack of LAM biomarkers that could potentially be used to monitor the disease and to develop other targeted therapies. We hypothesized that the mediators of cancer metastasis to lung, particularly in breast cancer, also play a relevant role in LAM. Analyses across independent breast cancer datasets revealed associations between low TSC1/2 expression, altered mTOR complex 1 (mTORC1) pathway signaling, and metastasis to lung. Subsequently, immunohistochemical analyses of 23 LAM lesions revealed positivity in all cases for the lung metastasis mediators fascin 1 (FSCN1) and inhibitor of DNA binding 1 (ID1). Moreover, assessment of breast cancer stem or luminal progenitor cell biomarkers showed positivity in most LAM tissue for the aldehyde dehydrogenase 1 (ALDH1), integrin-beta 3 (ITGB3/CD61), and/or the sex-determining region Y-box 9 (SOX9) proteins. The immunohistochemical analyses also provided evidence of heterogeneity between and within LAM cases. The analysis of Tsc2-deficient cells revealed relative over-expression of FSCN1 and ID1; however, Tsc2-deficient cells did not show higher sensitivity to ID1-based cancer inhibitors. Collectively, the results of this study reveal novel LAM biomarkers linked to breast cancer metastasis to lung and to cell stemness, which in turn might guide the assessment of additional or complementary therapeutic opportunities for LAM.
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Age of onset (AO) of Huntington disease (HD) is mainly determined by the length of the CAG repeat expansion (CAGexp) in exon 1 of the HTT gene. Additional genetic variation has been suggested to contribute to AO, although the mechanism by which it could affect AO is presently unknown. The aim of this study is to explore the contribution of candidate genetic factors to HD AO in order to gain insight into the pathogenic mechanisms underlying this disorder. For that purpose, two AO definitions were used: the earliest age with unequivocal signs of HD (earliest AO or eAO), and the first motor symptoms age (motor AO or mAO). Multiple linear regression analyses were performed between genetic variation within 20 candidate genes and eAO or mAO, using DNA and clinical information of 253 HD patients from REGISTRY project. Gene expression analyses were carried out by RT-qPCR with an independent sample of 35 HD patients from Basque Country Hospitals. We found suggestive association signals between HD eAO and/or mAO and genetic variation within the E2F2, ATF7IP, GRIN2A, GRIN2B, LINC01559, HIP1 and GRIK2 genes. Among them, the most significant was the association between eAO and rs2742976, mapping to the promoter region of E2F2 transcription factor. Furthermore, rs2742976 T allele patient carriers exhibited significantly lower lymphocyte E2F2 gene expression, suggesting a possible implication of E2F2-dependent transcriptional activity in HD pathogenesis. Thus, E2F2 emerges as a new potential HD AO modifier factor.
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Estuaries provide critical nursery habitat for many commercially and recreationally important fish and shellfish species. These productive, diverse ecosystems are particularly vulnerable to pollution because they serve as repositories for non–point-source contaminants from upland sources, such as pesticide runoff. Atrazine, among the most widely used pesticides in the United States, has also been one of the most extensively studied. There has not, however, been a specific assessment of atrazine in marine and estuarine ecosystems. This document characterizes the presence and transformation of atrazine in coastal waters, and the effects of atrazine on marine organisms. Review of marine and estuarine monitoring data indicate that atrazine is chronically present in U.S. coastal waters at relatively low concentrations. The concentrations detected have typically been below acute biological effects levels, and below the U.S. EPA proposed water quality criteria for atrazine. While direct risk of atrazine impacts are low, uncertainty remains regarding the effects of long-term low levels of atrazine in mixture with other contaminants. It is recommended that best management practices, such as the use of vegetative buffers and public education about pesticide use, be encouraged in the coastal zone to minimize runoff of atrazine into marine and estuarine waters.
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玉米(Zea mays L.)是我国十分重要粮食、饲料和工业原料作物,种植区域覆盖我国大部分农业区。随着玉米品种改良和新栽培技术的应用,我国玉米产量大幅度增加。自1950s以来,我国玉米产量递增幅度为126kg/hm2/yr。在玉米产量提高过程中,单叶光合作用与产量之间存在什么样的关系?当代玉米品种的品质和养分利用效率如何?高密度种植条件下是否存在“根系拥挤”及如何调控等。为探讨上述科学问题,本研究选择中国北方常见的大田玉米品种,在高肥力自然光照条件下,探讨玉米高产优质栽培过程中生理生态特征的变化趋势,以指导科学育种和栽培。主要研究结果如下: 1)光合与产量的演变我国 1950s、1970s、1990s等不同年代推广的玉米品种中,当代品种叶片光合速率高且高值持续期长,光合色素叶绿素a、叶绿素b、类胡萝卜素等的含量高且持续时间长,与光合有关的蒸腾速率(E.)、细胞间隙CO2浓度(Ci.)、气孔导度(gs)等也有较大改良,中下部叶片尤其明显;在生育后期,当代品种具有更高的光合优势。老品种饱和光合速率(Psat)在灌浆期下降,并非RuBPCase 和PEPCase的活性降低,而是由于叶绿素含量和可溶性蛋白含量的降低。在花后期间,由于PS2功能的下降,造成了光合能力下降,而现代品种的PS2 功能在衰老前一致保持旺盛状态。 老品种光合特征对缺氮的反应表现更敏感。花后缺氮光合作用下降是非气孔限制的,因为气孔导度和胞间CO2浓度没有发生明显的变化。其主要原因是缺素造成老品种叶片早衰,叶绿素含量、可溶性蛋白含量、PEP羧化酶活性下降。现代品种表现较强的抗衰老能力,其N素利用效用高于老品种。我国玉米产量的大幅度提高在很大程度上应归功于叶片光合性能的改良。 随玉米品种更替,群体光合速率增强,群体光合衰减率降低,呼吸消耗所占总光合的百分率下降。灌浆期当代品种中下部叶片的群体光合速率明显高于老品种。种植密度是影响玉米群体光合速率的主要因素,在高中低三种密度条件下,当代品种均有较高的群体光合速率,表现出耐密性强、适应性广、源足库大、产量高的特点。 2)高油玉米的产量受到叶源大小和叶源活力的双重限制在 1.5 株/m2密度下,与普通玉米相比较,高油玉米单株籽粒产量显著低于普通玉米,产量构成中穗粒数差异不显著,千粒重较低(P<0.01);两类型玉米的单株库容量相当,高油玉米籽粒灌浆速率小,籽粒充实度低,单粒重对叶源相对减少(剪叶)或相对增多(疏库)的反应比普通玉米更为敏感,其产量受到同化产物供应(叶源)相对不足的限制。高油玉米授粉后的叶面积、叶面积持续期小,叶片含氮量和光合速率较低,说明高油玉米的产量受到叶源活力(光合速率)小和叶源数量少的双重限制。 3)我国北方玉米品种的个体产量潜力、氮素利用效率及籽粒与秸秆粗蛋白质含量在充分发挥个体生产潜力的低密度条件下,我国北方1990s 以来大面积种植的50个玉米主栽品种中,个体产量潜力和氮素利用效率高度正相关(P=0.01),而子粒千粒重与NUE 呈显著性负相关(P=0.002)。对玉米产量和氮素利用效率进行分层聚类,可将北方玉米品种划分为高产高NUE 型、低产低NUE 型和中间型,高产高NUE 型玉米品种相对较少,仅占24%。籽粒粗蛋白质含量(CPC)与秸秆CPC 相关性不显著(P>0.05)。对籽粒和秸秆的CPC 进行分层聚类,将北方玉米品种划分为籽粒高秸秆低型、籽粒与秸秆双低型和籽粒与秸秆双高型,CPC 双高型品种相对较少,仅占20%。 4)玉米根系拥挤效应对产量影响的生理生态机制及其调控随玉米品种更替根系的空间分布呈“横向紧缩,纵向延伸”的特点。当代三类型玉米根系分布特性与株型、穗型相关。紧凑型品种根系分布深,下层根系所占比率大,适合密植,群体产量潜力大;平展大穗型品种根量多,分布较浅,在低密度下可获得较高的个体生产力,但不适合密植,群体产量潜力小。 “根系拥挤”显著影响玉米产量,减小根系横向伸展空间,下层土壤中的根系分配比率增多。在地上部充分生长条件下,紧凑型品种横向空间为30-50cm即可满足要求,平展型品种大于50cm;紧凑型品种对纵向空间受限制的反应更为敏感,平展型品种对横向空间受限制的反应更为敏感。“根系拥挤”影响根系活性、分布、氮素吸收利用和花后光合与14C同化物的分配。 在根系受限制条件下,增施肥料产量提高,根系总重增加,增加了根系在深层土壤(60-100cm)中的根系比率,显著增加了根系的TTC 还原量、SOD、CAT、POD活性。土壤加沙,根量减少,但根系TTC 还原量增加、产量提高,提高幅度以大穗型品种更为显著。 随种植密度增加耕层根系密度与群体产量同步增大,各类品种均在最高根系密度下获得最高产量。根系负荷的籽粒产量潜力三类型品种存在极大差异,在一定范围内增大种植密度,根系伸展空间减小,群体产量提高,紧凑大穗型品种产量最高,品种的耐密性是限制根系负荷籽粒产量潜力的主导因素。因此,培育株型紧凑、耐密性强、大穗玉米良种,采取有效的调控措施是玉米进一步高产的主攻方向。 5)我国夏玉米高产田的培创理论研究与实践相结合,2005 年在我国华北地区的山东莱州培创出籽粒实产21 042.9kg/hm2 ( 14% 含水量, 实收面积=45.7m×15.9m=726.63m2)的夏玉米高产纪录。主要采用以增加密度为保障的“群体结构性挖潜”和以提高整齐度为保障的“个体功能性挖潜”途径,生理生态指标包括:选用紧凑抗倒耐密植品种DH3719,种植密度102 030 株/hm2,收获密度98 610 株/hm2,花后具有较长的叶面积高值持续期,达60d以上,叶面积指数最大为6.53,收获2.59。上部叶片光合值对外界光强度变化敏感,其光合峰值出现时间提前,而后迅速衰减;中部叶片光合值的降低较慢,下部叶片变幅最小,可能是长期处于争光环境表现出的生态适应性。粒叶比0.32,经济系数0.542,单株产量216g,千粒重375.1g。
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In Cambodia, fish provide a major source of animal protein for rural households. Capture fisheries have declined and aquaculture has been identified as playing an important role in food and nutritional security and rural income generation. In 2011, WorldFish, in partnership with the Stung Treng Fishery Administration Cantonment and the Culture and Environment Preservation Association, aimed at improving the uptake of small-scale aquaculture by communities with limited experience in fish culture in Stung Treng Province in northeast Cambodia. The system was given the name “WISH ponds,” derived from the combination of the words "water" and "fish" to reflect the integration of fish cultivation with water for storage and vegetable growing. It was targeted towards households with limited space to construct large aquaculture ponds, such as peri-urban households. The study indicated that WISH ponds can create an important learning platform for communities to address challenges associated with small-scale aquaculture development by using scientific data generated and owned by the participants. Results from this 2011 study provided important insights into the challenges and constraints for introducing small-scale aquaculture into rural households in Cambodia. In mid-2013, WorldFish won a Feed the Future Partnering for Innovation grant, funded by the United States Agency for International Development, to build upon its successful engagement with communities in northeast Cambodia where WISH ponds had already been introduced and investigate scaling this technology to establish more WISH ponds in these communities.
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We present a map of the transformation of energy in China as a Sankey diagram. After a review of previous work, and a statement of methodology, our main work has been the identification, evaluation, and treatment of appropriate data sources. This data is used to construct the Sankey diagram, in which flows of energy are traced from energy sources through end-use conversion devices, passive systems and final services to demand drivers. The resulting diagram provides a convenient and clear snapshot of existing energy transformations in China which can usefully be compared with a similar global analysis and which emphasises the potential for improvements in energy efficiency in 'passive systems'. More broadly, it gives a basis for examining and communicating future energy scenarios, including changes to demand, changes to the supply mix, changes in efficiency and alternative provision of existing services. © 2012 Elsevier Ltd.
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Space heating accounts for a large portion of the world's carbon dioxide emissions. Ground Source Heat Pumps (GSHPs) are a technology which can reduce carbon emissions from heating and cooling. GSHP system performance is however highly sensitive to deviation from design values of the actual annual energy extraction/rejection rates from/to the ground. In order to prevent failure and/or performance deterioration of GSHP systems it is possible to incorporate a safety factor in the design of the GSHP by over-sizing the ground heat exchanger (GHE). A methodology to evaluate the financial risk involved in over-sizing the GHE is proposed is this paper. A probability based approach is used to evaluate the economic feasibility of a hypothetical full-size GSHP system as compared to four alternative Heating Ventilation and Air Conditioning (HVAC) system configurations. The model of the GSHP system is developed in the TRNSYS energy simulation platform and calibrated with data from an actual hybrid GSHP system installed in the Department of Earth Science, University of Oxford, UK. Results of the analysis show that potential savings from a full-size GSHP system largely depend on projected HVAC system efficiencies and gas and electricity prices. Results of the risk analysis also suggest that a full-size GSHP with auxiliary back up is potentially the most economical system configuration. © 2012 Elsevier Ltd.
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辐射传输研究是贯穿森林生态系统的纽带,太阳辐射为植物的生长发育提供光合能量、适宜的环境温度以及发育信息。一方面,气候变化使到达地面辐射能的质和量发生变化,影响到植被的生长发育,改变森林的结构,而森林结构的变化又会影响林冠内辐射能的分配和质量,这些变化会进一步影响到林下土壤温度,改变森林根系活性以及土壤营养转化的效率;连锁反应的结果有可能会使森林生态系统的生产力发生变化,改变碳素和氮素源库的调节方向,从而反馈影响地球气候系统。另一方面,人类作为生态系统的成员,必然需要森林生态系统为其提供更多的原材料和更好的生态服务功能,如何实现这些目标,就需要人类适度调整干预方式和频度,达到预期的目的。本文在建立适合于川西亚高山森林的叶面积测量技术、光照辐射模型和土壤温度变化模型的基础上,对川西亚高山地带森林生态系统的辐射传输特征进行了分析,并从森林结构的角度探讨了林分内的辐射分布以及对土壤温度的影响。主要成果如下: 1. 提出了一种照相法测量叶面积的方法。通过对摆放在平面上的叶片照相,利用投影变化,把非正射图像转化为正射图像,然后经过计算机图像处理得到每一片叶片的面积、周长、长度、宽度等信息。这种方法可使用户以任意方向和距离拍摄处于平面上的叶片,能同时处理大量的叶片,适于野外离体或活体叶片测量。叶片面积分辨率可调,分辨率可以与常用的激光叶面积仪相近甚至更高,而且叶片图像可以存档查询。 2. 提出一种模拟林内光照变化的模型。利用林冠半球照片,记录视点以上半球内的林冠构件空间分布,作为林冠子模型;天空辐射子模型采用国际照明委员会(CIE)的标准晴天和阴天以及插值模型。该模型能够模拟林下某一位点处的实时光斑变化。 3. 提出一种土壤温度变化模型。把土壤视为具有容量和阻力性质的结构,利用电阻和电容器件构建土壤能量分布模型。外界太阳辐射能经过植被以及其它一些能量分配器后进入土壤,其中有一部分转化为土壤势能,即土壤温度。土壤温度的变化类似于电池的充放电过程。在已知模型参数的情况下,可以从太阳辐射计算土壤温度的变化。在模型参数未知的情况下,通过输入和输出值推算模型的参数,而模型参数中的时间常数与土壤组成和含水量有关,这样就可以知道土壤水分的变化情况。 4. 从王朗亚高山森林典型样地林分结构的测量获得林地三维结构图、树冠形态、叶面积密度等参数,这些参数输入到Brunner (1998)开发的tRAYci 模型中计算出一段时间内林分任意位置处的光照值。与林下辐射计测量值以及半球照片计算结果的比较,该模型基本上能够满足对林分光环境了解的要求。 5. 从川西亚高山森林生产力的角度,探讨了森林生产力研究的方法以及川西地区的研究历史和成果,发现了其中的一些规律和问题,特别是在叶面积测量上,还没有使用标准的叶面积指数定义。综合来看,川西地区针叶林叶面积指数(单位土地面积上植物冠层总叶面积的一半) 应在4-5 之间。降雨丰富的华西雨屏带是川西地区森林生产力最高的地区,而向西北森林生产力逐渐降低。川西地区云冷杉林森林生产力平均约为600 gDM m-2 a-1,但是根据辐射能计算的潜在生产力则达到1800 gDM m-2 a-1。实际与潜在森林生产力的巨大差异说明其它因子对生产力的影响。 6. 王朗亚高山3 个典型森林林分中,白桦林样地(BF) 林下草本以糙野青茅、牛至、紫菀等喜阳性物种为主,林下透光度较高;冷杉林样地(FF) 林下透光度最低,以喜阴性物种水金凤、蟹甲草、囊瓣芹等为主;而云杉林样地(SF)林分林龄最大,林下透光度介于冷杉林和白桦林之间,草本层仍然以喜阴性物种东方草莓、紫花碎米芥、酢浆草等为主。冷杉林和云杉林的灌木层也很丰富,卫矛属、五加属、茶藨子属、忍冬属植物很丰富,而在白桦林则以栒摘要子属、榛子属、鹅耳枥属等植物为主。藓类植物在云杉林中最丰富,并且形成毯状层,其它两个林分则很稀少。3 个样地林分结构与林下光环境有很强的相关性,从光环境特征可以在一定程度上推测林分的结构。各样地单纯从乔木层材积推算的NPP 排列顺序为BF>FF>SF,与林下辐射透射率和林分年龄的顺序相同,暗示辐射对群落演替过程的驱动作用。 7. 用半球照相法测得BF、FF 和SF 3 个样地的有效叶面积指数以SF 样地最高,BF 最低。如果考虑针叶树叶片在小枝上的丛聚分布,利用北方针叶林的数值进行校正,则SF 样地LAI 显著增加(达到89%),其它样地的LAI 基本不变甚至有所下降。校正后的数值与文献中地面测量的结果较相近,说明在使用半球照相法测量川西亚高山针叶林LAI 时必须加以校正。 8. 在3 个样地中,白桦、岷江冷杉和方枝柏种群为丛聚分布,紫果云杉在FF和SF 样地中基本上为随机分布。3 个物种出现丛聚分布的最短距离约为2m,在最短距离以内则为随机分布。最短距离可能与树冠大小有关,种子传播特征以及对光照的需求状况可能是造成这种分布格局类型的原因。 Radiative transfer plays a key role in forest ecosystems. Solar radiation providesenergy for photosynthesis, appropriate ambient temperature and development informationfor plants. However, quality and quantity of radiation reaching land surface are affected byweather and subsequently influence the growth and development of plants, which in turnchanges the budget of radiation in forest. Soil temperature changes with the variation ofradiation under forest canopy and influences the activity of roots and rate of nutrientturnover. Thus, any changes of radiation will induce chain reactions in the entireecosystem and display in the value of net primary productivity which will possibly shiftthe relationship between carbon source and sink at local or regional scale and feed back tothe global climate system. On the other hand, as a component of ecosystems, humanbeings of course need to demand more materials and better service from ecosystems. Forthese purpose, man must adapt their pattern and frequency of interference to ecosystems.This paper aims to research on the canopy structure, the radiation distribution and theirinfluence on soil temperature from the process of radiative transfer in subalpine forestecosystem of western Sichuan. The main results are: 1 Present a new photogrammetric method for leaf area. The main idea is to convertnon-vertically taken images of planar leaves to orthoimages through projectivetransformation. The resultant images are used to get leaf morphological parametersthrough image processing. This method enables users to take photos at almost anyorientation and distance if only the leaves are placed on same plane, and to processlarge quantity of leaves in a short time, which is suitable for field measurement. Theresolution of leaf area is adjustable to fit for special requirement. 2 A model using hemispherical photos combining with solar tracks and radiation courseis provided to simulate light variation in forest. The hemispherical photos of canopyrecord the real spatial distribution of each element of plants viewed from a point. Skyradiance is simulated with CIE standard clear sky or cloudy sky model. This modelcan be used to simulate real time light variation under canopy. 3 Present a soil temperature model. Soil could be regarded as a body of resistor andcapacitor. Some of the budget of solar radiation in soil body is transformed into soilpotential energy, the soil temperature. Variation of soil temperature is driven by solarradiation, vegetation, soil properties, etc. This model has two parameters, one of whichis time constant and is related to soil water content. The inversed model can be used tosimulate the variation of soil water. 4 By using model tRAYci developed by Brunner (1998), the 3-D distribution of light inthree subalpine forest stands of Wanglang Nature Reserve has been simulated andvalidated with value of radiometers in these stands. This model can basically satisfythe need for understanding light regimes of these stands. 5 Present some principles and questions of NPP (net primary of productivity) researchesin western Sichuan. The standard leaf area index (LAI) defined by Chen and Black(1997) has not been used in this region. Total leaf area and projected leaf area indexare still used in NPP researches which may differ around 1-fold in magnitude. Thestandard LAI which is a half of total leaf area above unit land area should be between4 and 5 for typical subalpine coniferous forest of western Sichuan concluded fromliteratures. The maximum forest NPP occurs in West China rain belt and decreasesnorthwestwards. Average NPP of spruce-fir forest in western Sichuan is about600gDM m-2 a-1, which is below the potential NPP of 1800gDM m-2 a-1 based onmeasured radiation in this region. The significant difference between potential and realNPP suggests that other factors influence the growth of stands. 6 In the three subalpine forest stands of Wanglang Nature Reserve, herbage layer ofAbstractbirch stand (BF) with age of 40 is dominated by heliophytes of Deyeuxia scabrescens,Origanum vulgare, Aster tongoloa etc.. However, both of the other two stands aredominated by shade tolerent species, such as Impatiens noli-tangere, Impatiensdicentra, Cacalia deltophylla and Pternopetalum tanakae etc. in fir stand (FF) withage of 180 and Fragaria orientalis, Cardamine tangutorum and Oxalis corniculata etc.in spruce stand (SF) with age of 330. Shrub species in the latter two stands arerelatively rich, typical dominant genera being Euonymus, Acanthopanax, Ribes andLonicera. Birch stand has relatively sparse shrubs dominated by genera of Cotoneaster,Corylus and Carpinus. Mosses are significant only in spruce stand. The canopystructure controls the light regime of stand, which influence the composition of herblayers beneath the canopy. This light regime-community structure relationship can beused to infer the herb community from canopy structure. The NPP derived from timbervolume of arbor layer of the three stands decreases from BF to SF, which is in thesame order of transmitted total radiation under canopy and age of these stands,suggesting the driving effect of radiation in the succession of community. 7 The highest effective LAI of the three stands obtained by hemispherical photos is inplot SF and lowest in plot BF. After rectification of the clumping effect of leaves onshoot, the real LAI in plot SF increases significantly (89%) and approximate to theaverage LAI of coniferous forest in western Sichuan. Therefore, the LAI obtainedfrom hemispherical photos needs rectification for clumping effect. 8 Spatial distribution pattern for Betula platyphylla, Abies faxoniana and Sabinasaltuaria is clumpy, but Picea purpurea almost random in plot FF and SF. The shortestdistance for clumpy distribution for Betula platyphylla and Sabina saltuaria is 1.5m,and 2m for Abies faxoniana. And random pattern for these trees is exhibited within thisrange which almost coincides with the diameter of crown. Seed dispersalcharacteristics and light requirement may be the reason for different spatial pattern.
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Many efforts have been devoted to exploring novel luminescent materials that not contain expensive or toxic elements, or do not need a mercury vapor plasma source. In this paper, BPO4 and Li+-doped BPO4 powder samples were prepared by the Pechini-type sol-gel (PSG) process. The structure and optical properties of the resulting samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), photoluminescence (PL) excitation and emission spectra, kinetic decay, and X-ray photoelectron spectra (XPS), respectively. It was found that PSG -derived Li+-doped BPO4 annealed at 960 degrees C exhibited bright bluish-white emission centered at 416 nm. The luminescence decay curves analysis indicates that each sample has two kinds of lifetimes (5.9 ns and 0.529 ms) and two types of kinetic decay behaviors which can be fitted into a single-exponential function and a double-exponential function, respectively.
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Sedimentary basins in the Yellow Sea can be grouped tectonically into the North Yellow Sea Basin (NYSB), the northern basin of the South Yellow Sea (SYSNB) and the southern basin of the South Yellow Sea (SYSSB). The NYSB is connected to Anju Basin to the east. The SYSSB extends to Subei Basin to the west. The acoustic basement of basins in the North Yellow Sea and South Yellow Sea is disparate, having different stratigraphic evolution and oil accumulation features, even though they have been under the same stress regime since the Late Triassic. The acoustic basement of the NYSB features China-Korea Platform crystalline rocks, whereas those in the SYSNB and SYSSB are of the Paleozoic Yangtze Platform sedimentary layers or metamorphic rocks. Since the Late Mesozoic terrestrial strata in the eastern of the NYSB (West Korea Bay Basin) were discovered having industrial hydrocarbon accumulation, the oil potential in the Mesozoic strata in the west depression of the basin could be promising, although the petroleum exploration in the South Yellow Sea has made no break-through yet. New deep reflection data and several drilling wells have indicated the source rock of the Mesozoic in the basins of South Yellow Sea, and the Paleozoic platform marine facies in the SYSSB and Central Rise could be the other hosts of oil or natural gas. The Mesozoic hydrocarbon could be found in the Mesozoic of the foredeep basin in the SYSNB that bears potential hydrocarbon in thick Cretaceous strata, and so does the SYSSB where the same petroleum system exists to that of oil-bearing Subei Basin.