Equação de referência do Teste do Degrau medida em distância para indivíduos saudáveis e sedentários

O teste de caminhada em seis minutos (TC6M) avalia a capacidade respiratória durante o exercício. Recentemente, o teste do degrau em seis minutos (TD6M) está sendo estudado como uma proposta para essa mesma avaliação. Diante do exposto, o desenvolvimento de uma equação de referência se torna importante. O objetivo desse estudo foi desenvolver uma equação de referência padrão para o Teste do Degrau em Seis minutos. Esse estudo foi do tipo transversal, em que foram selecionados 452 indivíduos. Após a aplicação dos critérios de inclusão/exclusão, foram selecionados 326 sujeitos saudáveis e sedentários com idade entre 20 e 80 anos. Para serem considerados saudáveis, os participantes não podiam ter história de doenças (exceto hipertensão arterial sistêmica ou diabetes mellitus em tratamento) e foram submetidos à radiografia de tórax, espirometria e eletrocardiograma, que deveriam ser normais. O nível de sedentarismo foi avaliado através do International Physical Activity Questionnaire (IPAQ). Foram coletados os seguintes dados demográficos: idade, peso e altura. Todos os indivíduos realizaram TD6M na sua própria cadência (autocadenciado) em um degrau de 16,5 cm de altura, 65 de largura e 30 cm de comprimento. O número de subidas e descidas foi contado por um pedômetro digital. Foram mensuradas a pressão arterial, a frequência cardíaca e a saturação de oxigênio, antes e depois do TD6M. A análise estatística foi realizada pelo software STATA 12.0, e as equações foram desenvolvidas pelo modelo estatístico de regressão linear múltipla. Como resultado, observou-se que os participantes apresentaram exames normais, sendo 135 homens e 191 mulheres. O IPAQ demonstrou 157 ativos, 114 irregularmente ativos e 40 inativos, sendo que 14 indivíduos não responderam. A análise da distância alcançada em relação à idade e à diferença da frequência cardíaca tanto para homens quanto para mulheres mostrou significância estatística, demonstrando a sua importância para o desenvolvimento das equações para cada gênero. Para mulheres: Distância (m) = 88,83 - [(FC final- FC inicial)* 0,23] (Idade *0,37); para homens: Distância (m)= 110,20 - [(FC final- FC inicial)*0,18] (Idade * 0,59). O estudo concluiu que as equações de referência desenvolvidas nesse estudo foram realizadas em uma população de indivíduos saudáveis e sedentários e pode ser usada como padrão de referência para o TD6M.

Shifts in the estuarine demersal fish community after a fishery closure in Puget Sound, Washington

Puget Sound is one of the largest and most ecologically significant estuaries in the United States, but the status and trends of many of its biological components are not well known. We analyzed a 21-year time series of data from standardized bottom trawl sampling at a single study area to provide the first assessment of population trends of Puget Sound groundfishes after the closure of bottom trawl fisheries. The expected increase in abundance was observed for only 3 of 14 species after this closure, and catch rates of most (10) of the abundant species declined through time. Many of these changes were stepwise (abrupt) rather than gradual, and many stocks exhibited changes in catch rate during the 3-year period from 1997 through 2000. No detectable change was recorded for either temperature or surface salinity over the entire sampling period. The abrupt density reductions that were observed likely do not reflect changes in demographic rates but may instead represent distributional shifts within Puget Sound.

毛乌素沙地土地利用/土地覆被变化研究

毛乌素沙地是我国十二大沙漠之一，地处北方干旱半干旱区向亚湿润区过渡地带，长期以来，不合理的人类土地利用，结合当地脆弱的环境生态特征，引起了严重的现代荒漠化过程，是我国北方荒漠化研究的重点地区。本文着重从自然和人文学科密切合作的角度，对毛乌素沙地土地利用／土地覆被变化的内在作用机制进行了研究，得到以下主要结论： 1. 利用多年实地观测数据资料，考察了毛乌素沙地四种主要草地类型代表性植物群落地上生物量响应气候因子波动的变化规律，建立了植物地上生物量对气候因子的逐月回归模型，揭示出如下规律：①各种气候因子对不同类型草地以及同一类型不同生长阶段草地都产生不同的影响作用;②同一气候因子在植物不同生长阶段上，对生物量形成的重要性程度存在差异：③在植物生长期内，每个生长阶段的生物量都对后一时期的生物量产生显著影响，说明植物生长的连续性对于生物量的形成和积累是重要的;④在植物的凋枯期，各种气候因子基本上都不对生物量产生显著影响;⑤水分因子对毛乌素沙地几乎各种类型草地的生物量，都是重要的影响因子，毛乌素沙地降水状况在不同年份的显著波动对草地植物地上生物量的影响，不仅直接构成了土地覆被变化的重要组成部分，而且还影响到土地利用的方式、方法和后果。 2. 在考察毛乌素沙地草地地上生物量对气候因子变化的响应规律中，利用逐月动态回归建模方法改进了传统的累积气候因子回归建模方法。逐月回归模型与累积回归模型的比较显示，逐月动态回归模型的优势表现在三个方面：①可以提供累积回归模型无法揭示的作用规律;②模拟更加精确;③可以预测不同气候条件下群落地上生物量的变化范围。 3. 利用风速、降水和潜在蒸发等气象记录资料，建立了毛乌素沙地气候因子影响沙尘暴频率的作用模型，定量地考察了沙地各处气候因子对沙尘暴频率的影响作用。研究表明，气候因素是导致毛乌素沙地沙尘暴发生的主导原因，在沙地各处，气候因子可以解释沙尘暴频率分布格局总信息的比率分别为：乌审召83.6%，乌审旗77.5%，河南82.4%，鄂托克旗79.8%，新街73.1%，伊金霍洛旗82%。 4. 在定量考察气候因素对沙尘暴频率影响作用的基础上，对影响沙尘暴频率格局的自然和人为因素进行了定量分离，研究表明：人为影响因素对对沙尘暴发生起次要作用，解释沙尘暴频率分布格局信息的比率分别为：乌审召16.4%，乌审旗22.5%，河南17.6%，鄂托克旗20.2%，新街26.9%，伊金霍洛旗18%。 自然和人为因素影响作用的定量分离研究表明，毛乌素沙地人为因素的影响作用表现出空间上的差异性：①从方位上说，呈现自东向中、西部递减的梯度：②从地点上说，城镇附近人为影响作用远高于农村地区;③从土地利用方式上说，农垦种植业区域高于畜牧业区域。 5. 在实地观测基础上，建立了裸露沙面和植被覆盖沙面风蚀输沙率模型，定量考察了植被覆盖率与风蚀输沙率之间的关系。研究表明：当植被覆盖率达到60%以上，可以保护地表土壤使风蚀在大多数条件下不致发生;当覆盖率达到40%，可以使风蚀输沙大为减少;而当植被覆盖率低于10%，植被覆盖基本不能对地表土壤起到有效的防护作用。 6. 应用植被覆盖地表风蚀输沙率模型，考察了沙地不同风速条件下植被有效覆盖率。根据当地气象台站的多年气象记录，沙地最大风速在20m/s左右，这样的风速条件下，保证风蚀不致发生的植被有效覆盖率为65%左右;在沙地常见的大风风速14-16m/s下，植被有效覆盖率大致为50-55%;对于沙地一般的中等风速l0-12m/s．植被有效覆盖率为40%。植被覆盖对风蚀的影响作用也可以理解为，植被覆盖使沙粒起动风速发生了增大效应，研究表明：与裸露沙面沙粒起动风速4.5m/s对照，70%植被覆盖率使起动风速改变为15.4m/s;60%植被覆盖率使起动风速改变为12.1m/s;40%植被覆盖率使起动风速改变为8.Om/s;而在10%植被覆盖条件下，起动风速为5.Om/s，改变量很小，说明植被覆盖的保护作用极其有限。 7. 基于野外实地观测，比较了沙地五种常见植物种和二种人工防护材料防风效应上的差异。研究表明，防风效应由高到低的次序是，沙蒿>芨芨草>杨柴和牛心朴子>沙障>栅栏>旱柳;就乔、灌、草和人工材料而言，防风效应的次序是，灌木植被>草本植被>人工材料>乔木植被。植物和人工防护材料降低风速的比率与风速呈现二次函数关系，不同植物种或人工材料，降低风速比率都表现出不同的规律，在一般情况下，降低风速效应随着风速的增大而降低。 8. 通过不同植物种防风效应的比较研究，对毛乌素沙地植被生态建设的实践有一定的指导意义。毛乌素沙地的植被建设中对植被类型和植物种类的选择，应该遵循如下原则：①选取防风固沙效应好的植物种类;②应该考虑植物水分供给与需求的平衡状况，实行适地适树;③植物防护效应应该与当地风蚀气候在时间上较好地匹配，在春季等风蚀严重季节，植被覆盖应该具有较好的防风效应。 9. 在现实中，各种影响风蚀的因素是同时发挥作用的。将风蚀影响因素分解为风速、湿润度和植被覆盖率（以及植被类型）三个方面，在此基础上，建立了风蚀影响因素的综合作用的概念模型和沙丘活动性指数定量模型。湿润程度低、风速高、植被覆盖率低的地区，是风蚀最为严重的地区;在湿润程度高、风速低、植被覆盖率高的地区，是风蚀最弱的地区;在其他地区，风蚀状况根据三个方面因素的综合状况来决定。 10. 利用风蚀影响因子综合作用的沙丘活动性指数模型，从空间、时间、植被类型变化角度，考察了毛乌素沙地的风蚀变化状况。得到如下结论：①随着空间变化，风速、降水等气候因素也随之存在差异，导致沙丘活动性指数的变化规律是，西北部鄂托克旗沙丘活动性最高，乌审旗次之，其他几个站差别不太显著，这是由各地降水、气温、沙粒粒径等因素共同决定;②随着时间的变化，气候、植被生长等方面的状况随之发生改变，导致沙丘活动性发生变化，春季最高，冬季次之，夏秋季最低：③随着沙丘植被覆盖类型的变化，沙丘活动性也发生显著变化，在一般情况下，乔木覆盖沙丘活动性>草本植物覆盖沙丘>灌木覆盖沙丘。 11. 在实地调查土地利用现实状况及其社会、经济和政策影响因素的基础上，建立了我国北方干旱半干旱区土地利用决策机制的概念模型，分析了与土地利用密切相关的农牧民一政府一环境科学家这三个社会群体对土地利用的立场和影响作用力上的差异，分析了毛乌素沙地土地利用的现状及其影响因素，探讨了现实中不可持续土地利用行为发生的社会、经济和政策原因。 12. 在实地调查基础上，分别利用产出一费用分析法和过程影响因素分析法，建立了毛乌素沙地土地利用经济收益的定量模型。产出一分析研究表明，无论是农垦种植业，还是草地畜牧业，农牧民从这两种土地利用方式都只能获得较低下的经济收益。造成这种状况的原因，主要在于两个方面：一是低下且不断处于波动之中的农牧业产品物价，二是沉重的农牧业税收。 13. 将影响农牧业产出的因素，划分为四个方面：土地面积（牲畜头数）、环境状况、管理水平和利用强度，在此基础上建立了定量的影响作用模型。研究表明：环境状况指数每增加0.1，农牧业经济收益增加26%;管理水平因子每提高0.1，农牧业经济收益增加12.7%;农牧业经济收益最优的土地利用强度在0.4左右，在此之前，随着利用强度的增加，经济收益随之增大，而在此之后，随着利用强度的增大，经济收益逐渐降低，当土地利用强度达到0.9左右时，呈现负的经济收益。 14. 毛乌素沙地实施土地资源可持续利用，必须从技术的革新和社会经济政策等因素的调整两条途径同时入手，二者缺一不可。通过改进和应用节水灌溉、风能光能利用、生物增产技术，尽可能地提高各种资源的利用效率;通过应用免耕或浅耕技术，尽量减轻土地利用对资源和环境的破坏;通过栽培、速生技术，提高植被建设的成效和速度。而通过税收、物价政策的调整，尽可能地提高农牧民经济收益增长的速度，减轻土地利用压力;通过政府与人民之间对话和合作机制的建立，让广大农牧民参与到土地利用的决策和管理的过程中去;通过土地利用管理政策、措施的调整和完善，调动农牧民保护资源的积极性和自觉性;通过激励机制的建立，引导农牧民土地利用向着可持续的方向发展。 15. 实现毛乌素沙地土地资源可持续利用的有效途径，在于这样几个方面：①建立和完善政府及其管理部门与人民之间有效的对话和合作机制，让广大农牧民参与到土地利用决策和管理的过程中去：②实行产业结构调整，转变片面追求经济增长的做法，制订适应当地自然条件和生态特征的发展模式;③降低农牧业税收、稳定并提高农牧业产品的物价，增加农牧民经济收入，减轻土地利用压力;④进一步改进和完善土地利用管理政策和法规;⑤建立有效激励机制，引导农牧民土地利用向着可持续的方向发展：⑥努力改进节水灌溉技术、生物增产技术，提高土地利用的科技水平：⑦改进环境保护和植被建设决策的科学性，提高植被建设的成效。

The effect of surface hardening on the elastic shakedown of elliptical contacts

The effect of varying both the aspect ratio and the coefficient of friction of contacts with elliptical geometry on their elastic shakedown performance has been examined theoretically for surfaces with two types of subsurface hardness or strength profiles. In stepwise hardening the hard layer is of uniform strength while in linear hardening its strength reduces from a maximum at the surface to that of the core at the base of the hardened layer. The shakedown load is expressed as the ratio of the maximum Hertzian pressure to the strength of the core material. As the depth of hardening, expressed as a multiple of the elliptical semi-axis, is increased so the potential shakedown load increases from a level that is appropriate to a uniform half-space of unhardened material to a value reflecting the hardness of the surface and near-surface material. In a step-hardened material, the shakedown limit for a surface 'pummelled' by the passage of a sequence of such loads reaches a cut-off or plateau value, which cannot be exceeded by further increases in hardening depth irrespective of the value of the friction coefficient. For a linear-hardened material the corresponding plateau is approached asymptotically. The work confirms earlier results on the upper bounds on shakedown of both point and line contacts and provides numerical values of shakedown loads for intermediate geometries. In general, the case depth required to achieve a given shakedown limit reduces in moving from a transversely moving nominal line load to an axisymmetric point load.

Evolutionary trends of the mitochondrial lineage differentiation in species of genera Martes and Mustela

We compared partial sequences (402 bp) of the mitochondrial cytochrome b gene in 68 individuals of martens (Martes), weasels (Mustela) and their relatives from the Northern Hemisphere to identify the modes of geographic differentiation in each species. We then compared complete sequences (1140 bp) of the gene in 17 species of the family Mustelidae to know the spatial and temporal modes of speciation, constructing linearized trees with transversional substitutions for deeper lineage divergences and with transversions and transitions for younger lineages. Our data suggested that these lineages of Martes and Mustela differentiated in a stepwise fashion with five radiation stages from the generic divergences (stage I) to the intraspecific divergences (stage V), during the last 10 or 20 million years as the fossil evidence suggests. In the lineage of Martes, the first offshoots are of Martes flavigula, M. pennanti, and Gulo gulo (stage II), the second is M. foina (stage III), and the third are M. americana, M. martes, M. melampus, and M. zibellina (stage IV). The divergence of the lineages of Mustela is likely to have taken place concurrently with the radiations of the Martes. These divergence processes are attributable in part to the geographic allocation along the two continents, North America and Eurasia, as well as among peripheral insular domains, such as Taiwan and the Japanese Islands. In addition, the Eurasian continent itself was shown to have been involved in the species diversification in the martens and weasels.

From design characteristics to system requirements

This report presents the stepwise development of requirements for a process-based design support system aimed at improving the engineering design process. The starting point was the set of characteristics identified in three sources: models of design processes in prescriptive literature; empirical studies of design in descriptive literature; and a case-study in industry. All identified characteristics and derived requirements are listed in this report.

Recognizing of Ichthyophon and investigation of feeding and effects of water temperature, salinity and electrical conductivity on the population dynamic of Barbus grypus in the Dalaki and Helle river

This study was carried out for recognized ichthyophon and investigation of feeding and effects of water temperature, salinity and electrical conductivity on the population dynamic of Barbus grypus in the Dalaki and Helle river. In the study period, 2949 Barbus grypus was cached. The most of total length frequency was 200 to 300 mm and 2 to 3 years old. The oldest fish was8 years old with 756 mm total length. Fecundity was 950 upto 57400 oocyt per fish. Station no. 6 and 7 showed more temperature, fecundity and GSI than other stations. Females adulated before then males. Multiple stepwise regression of fecundity and RE (reproduction effort) showed significant correlation. Fishes of the upper parts of stream was more L than down stream stations. Condition factor of males was more than female, and for down stream stations was better than the other stations. Barbus grypus is omnivorous. Ichthyophon of Dalaki river include 4 family and 9 species that Capoeta capoeta intermadia was more than others species, but in the Helle river was 5 family and 9 species, that Liza abu zarudni was more than others.

Molecular phylogeny of the specialized schizothoracine fishes (Teleostei : Cyprinidae), with their implications for the uplift of the Qinghai-Tibetan Plateau

Molecular phylogeny of three genera containing nine species and subspecies of the specialized schizothoracine fishes are investigated based on the complete nucleotide sequence of mitochondrial cytochrome b gene. Meantime relationships between the main cladogenetic events of the specialized schizothoracine fishes and the stepwise uplift of the Qinghai-Tibetan Plateau are also conducted using the molecular clock, which is calibrated by geological isolated events between the upper reaches of the Yellow River and the Qinghai Lake. Results indicated that the specialized schizothoracine fishes are not a monophyly. Five species and subspecies of Ptychobarbus form a monophyly. But three species of Gymnodiptychus do not form a monophyly. Gd. integrigymnatus is a sister taxon of the highly specialized schizothoracine fishes while Gd. pachycheilus has a close relation with Gd. dybowskii, and both of them are as a sister group of Diptychus maculatus. The specialized schizothoracines fishes might have originated during the Miocene (about 10 MaBP), and then the divergence of three genera happened during late Miocene (about 8 MaBP). Their main specialization occurred during the late Pliocene and Pleistocene (3.54-0.42 MaBP). The main cladogenetic events of the specialized schizothoracine fishes are mostly correlated with the geological tectonic events and intensive climate shift happened at 8, 3.6, 2.5 and 1.7 MaBP of the late Cenozoic. Molecular clock data do not support the hypothesis that the Qinghai-Tibetan Plateau uplifted to near present or even higher elevations during the Oligocene or Miocene, and neither in agreement with the view that the plateau uplifting reached only to an altitude of 2000 in during the late Pliocene (about 2.6 MaBP).

Strategies to reduce the carbon footprint of consumer goods by influencing stakeholders

Consumer goods contribute to anthropogenic climate change across their product life cycles through carbon emissions arising from raw materials extraction, processing, logistics, retail and storage, through to consumer use and disposal. How can consumer goods manufacturers make stepwise reductions in their product life cycle carbon emissions by engaging with, and influencing their main stakeholders? A semi-structured interview approach was used: to identify strategies and actions, stakeholders in the consumer goods industry (suppliers, manufacturers, retailers and NGOs) were interviewed about carbon emissions reduction projects. Based on this, a summarising presentation was made, which was shared during a second round of interviews to validate and refine the results. The results demonstrate several opportunities that have not yet been exploited by companies. These include editing product choice in stores to remove products with higher carbon footprints, using marketing competences for environmental benefits, and bundling competences to create winewinewin business models. Governments and NGOs have important enabling roles to accelerate industry change. Although this work was initially developed to explore how companies can reduce life cycle carbon emissions of their products, these strategies and actions also give insights on how companies can influence and anticipate stakeholder actions in general. © 2012 Elsevier Ltd. All rights reserved.

Species identification of Chinese sturgeon using acoustic descriptors and ascertaining their spatial distribution in the spawning ground of Gezhouba Dam

This study has developed an improved subjective approach of classification in conjunction with Step wise DFA analysis to discriminate Chinese sturgeon signals from other targets. The results showed that all together 25 Chinese sturgeon echo-signals were detected in the spawning ground of Gezhouba Dam during the last 3 years, and the identification accuracy reached 90.9%. In Stepwise DFA, 24 out of 67 variables were applied in discrimination and identification. PCA combined with DFA was then used to ensure the significance of the 24 variables and detailed the identification pattern. The results indicated that we can discriminate Chinese sturgeon from other fish species and noise using certain descriptors such as the behaviour variables, echo characteristics and acoustic cross-section characteristics. However, identification of Chinese sturgeon from sediments is more difficult and needs a total of 24 variables. This is due to the limited knowledge about the acoustic-scattering properties of the substrate regions. Based on identified Chinese sturgeon individuals, 18 individuals were distributed in the region between the site of Gezhouba Dam and Miaozui reach, with a surface area of about 3.4 km(2). Seven individuals were distributed in the region between Miaozui and Yanshouba reach, with a surface area of about 13 km(2).

Ecology of macrozoobenthic communities in two plateau lakes of Southwest China

Ecological studies on macrozoobenthos were conducted in two small plateau lakes in the Yunnan-Guizhou Plateau, Southwest China: Xingyun Lake (XL), a eutrophic lake whose main source of primary production was phytoplankton (Chl a=99.76 +/- 24.01 mu g/L), and Yangzong Lake (YL), a mesotrophic lake. Sampling was carried out from October 2002 to May 2004. Altogether 23 benthic taxa were identified in XL and 21 taxa in YL. The density of benthos in XL was much lower than that in YL, but the biomass was about equal in the two lakes, being 1 423 ind/m(2) and 8.71 g/m(2) in XL and 4 249 ind/m(2) and 8.60 g/m(2) in YL. The dominant species were Limnodrilus hoffmeisteri, Branchiura sowerbyi, Aulodrilus pluriseta and Chironomus sp. in XL and Limnodrilus hoffmeisteri, Aulodrilus pluriseta and Bellamya sp. in YL. Seasonal fluctuation occurred, showing richer species in summer and winter, but the density and biomass varied in different ways in the two lakes. Analyses on functional feeding groups indicate that collector-gatherers were predominant, but the relative abundances of other groups were different. Stepwise multiple regression analysis demonstrated that the water depth, conductivity and chlorophyll a were the key factors affecting macrozoobenthic abundance in the lakes.

Macrozoobenthic community of Fuxian Lake, the deepest lake of southwest China

Located in the Yunnan-Guizhou Plateau in southwest China, Fuxian Lake covers an area of 211 km(2), with maximum depth of 155 m. It is known to have a unique fauna, including 14 described endemic species. In order to describe the zoobenthic community of the lake more completely, the present study was conducted from August 2002 to August 2003. Altogether 62 benthic taxa, including 22 oligochaetes, 21 molluscs and 18 insects were identified, of which the dominant taxa belonged to Potamothrix, Procladius and Paraprososthenia. The standing stocks of benthos were much higher in the littoral (824 ind/m(2) in density, 3.72 g/m(2) in biomass) than in the profundal region (23 ind/m(2) in density, 0.10 g/m(2) in biomass). Species richness was greatest in summer and standing stocks were larger in spring and summer than in other seasons. Analyses of functional feeding groups indicated that collector-gatherers and scrapers were predominant in entire lake. Stepwise multiple regression analysis demonstrated that the water depth is the most important factor affecting the distribution of macrozoobenthos. (C) 2008 Elsevier GmbH. All rights reserved.

Morphological variability between wild populations and inbred stocks of a Chinese minnow, Gobiocypris rarus

Gobiocypris rarus, a small, native cyprinid fish, is currently widely used in research on fish pathology, genetics, toxicology, embryology, and physiology in China. To develop this species as a model laboratory animal, inbred strains have been successfully created. In this study, to explore a method to discriminate inbred strains and evaluate inbreeding effects, morphological variation among three wild populations and three inbred stocks of G. rarus was investigated by the multivariate analysis of eight meristic and 30 morphometric characters. Tiny intraspecific variations in meristic characters were found, but these were not effective for population distinction. Stepwise discriminant analysis and cluster analysis of conventional measures and truss network data showed considerabe divergence among populations, especially between wild populations and inbred stocks. The average discriminant accuracy for all populations was 82.1% based on conventional measures and 86.4% based on truss data, whereas the discriminant accuracy for inbred strains was much higher. These results suggested that multivariate analyses of morphometric characters are an effective method for discriminating inbred strains of G. rarus. Morphological differences between wild populations and inbred strains appear to result from both genetic differences and environmental factors. Thirteen characters, extracted from stepwise discriminant analysis, played important roles in morphological differentiation. These characters were mainly measures related to body depth and head size.

Dependence of dye regeneration and charge collection on the pore-filling fraction in solid-state dye-sensitized solar cells

Solid-state dye-sensitized solar cells rely on effective infiltration of a solid-state hole-transporting material into the pores of a nanoporous TiO 2 network to allow for dye regeneration and hole extraction. Using microsecond transient absorption spectroscopy and femtosecond photoluminescence upconversion spectroscopy, the hole-transfer yield from the dye to the hole-transporting material 2,2′,7,7′-tetrakis(N,N-di-p- methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD) is shown to rise rapidly with higher pore-filling fractions as the dye-coated pore surface is increasingly covered with hole-transporting material. Once a pore-filling fraction of ≈30% is reached, further increases do not significantly change the hole-transfer yield. Using simple models of infiltration of spiro-OMeTAD into the TiO2 porous network, it is shown that this pore-filling fraction is less than the amount required to cover the dye surface with at least a single layer of hole-transporting material, suggesting that charge diffusion through the dye monolayer network precedes transfer to the hole-transporting material. Comparison of these results with device parameters shows that improvements of the power-conversion efficiency beyond ≈30% pore filling are not caused by a higher hole-transfer yield, but by a higher charge-collection efficiency, which is found to occur in steps. The observed sharp onsets in photocurrent and power-conversion efficiencies with increasing pore-filling fraction correlate well with percolation theory, predicting the points of cohesive pathway formation in successive spiro-OMeTAD layers adhered to the pore walls. From percolation theory it is predicted that, for standard mesoporous TiO2 with 20 nm pore size, the photocurrent should show no further improvement beyond an ≈83% pore-filling fraction. Solid-state dye-sensitized solar cells capable of complete hole transfer with pore-filling fractions as low as ∼30% are demonstrated. Improvements of device efficiencies beyond ∼30% are explained by a stepwise increase in charge-collection efficiency in agreement with percolation theory. Furthermore, it is predicted that, for a 20 nm pore size, the photocurrent reaches a maximum at ∼83% pore-filling fraction. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spatial analysis for spring bloom and nutrient limitation in Xiangxi bay of three Gorges Reservoir

The spatial and temporal dynamics of physical variables, inorganic nutrients and phytoplankton chlorophyll a were investigated in Xiangxi Bay from 23 Feb. to 28 Apr. every six days, including one daily sampling site and one bidaily sampling site. The concentrations of nutrient variables showed ranges of 0.02-3.20 mg/L for dissolved silicate (Si); 0.06-2.40 mg/L for DIN (NH4N + NO2N + NO3N); 0.03-0.56 mg/L for PO4P and 0.22-193.37 mu g/L for chlorophyll a, respectively. The concentration of chlorophyll a and inorganic nutrients were interpolated using GIS techniques. The results indicated that the spring bloom was occurred twice in space during the whole monitoring period (The first one: 26 Feb.-23 Mar.; the second one: 23 Mar.-28 Apr.). The concentration of DIN was always high in the mouth of Xiangxi Bay, and PO4P was high in the upstream of Xiangxi Bay during the whole bloom period. Si seems no obvious difference in space in the beginning of the spring bloom, but showed high heterogeneity in space and time with the development of spring bloom. By comparing the interpolated maps of chlorophyll a and inorganic variables, obvious consumptions of Si and DIN were found when the bloom status was serious. However, no obvious depletion of PO4P was found. Spatial regression analysis could explained most variation of Chl-a except at the begin of the first and second bloom. The result indicated that Si was the factor limiting Chl-a in space before achieved the max area of hypertrophic in the first and second bloom period. When Si was obviously exhausted, DIN became the factor limiting the Chl-a in space. Daily and bidaily monitoring of Site A and B, representing for high DIN: PO4P ratio and low DIN:PO4P ratio, indicated that the concentration of Si was decreased with times at both site A and B, and the dramatically drop of DIN was found in the end monitoring at site B. Multiple stepwise regression analysis indicated that Si was the most important factor affect the development of spring bloom both at site A and B in time series.