Influence of larval outbreaks on the climate reconstruction potential of an Arctic shrub

Arctic shrubs have a strong potential for climate and environmental reconstructions in the chronically understudied regions of the high northern latitudes. The climate dynamics of these regions are important to understand because of large-scale feedbacks to the global climate system. However, little is known about other factors influencing shrub ring growth, possibly obscuring their climate signal. For example, as of yet we are not able to differentiate between herbivory or climatically induced growth depressions. Here, we use one of the most common Arctic shrubs, Alnus viridis as a test case to address this question. We sampled Alnus in Kobbefjord, Greenland, measured shrub-ring width and cell wall thickness and built site chronologies of each parameter. We analysed climate-growth relationships, tested their stability over time and employed a pointer-year analysis to detect growth depressions. We employed bootstrapped transfer function stability tests (BTFS) to assess the suitability of our shrub chronologies for climate reconstruction. Correlations with climate data showed strong significantly positive and stable correlations between summer temperature and ring-width with the exception of the recent decade. A climate reconstruction model failed stability tests, when the complete period of record was used for calibration and verification. Wood anatomy analysis uncovered the occurrence of unusual cell structure (very thin cell walls) in the exceptionally narrow ring of 2004, a recorded insect outbreak year in other parts of Greenland. When excluding the affected ring and a recovery period, the reconstruction model passed all tests, suggesting that the unusual 2004 ring was not climate driven, but rather the result of an insect attack. When combining anatomical analysis with traditional ring-width measurements, we move a step further in potentially distinguishing small rings caused by insect attacks from small rings formed in climatically challenging years. While this study does not provide unambiguous evidence, it does provide potential useful methodological combinations to enable more robust climate reconstructions in areas where climatic records are extremely sparse.     

Photosynthesis of herbaceous plants from nutrient-poor tropical forests

Photosynthetic characteristics, specific leaf mass, chlorophyll and total leaf nitrogen concentrations of four herbaceous plants (Dicranopteris linearis, Hanguana malayana, Pentaphragma ellipticum, Tacca integrifolia) from nutrient-poor tropical forests showed that all these plants were well-adapted to their natural growth environments. No photoinhibition was observed even in the understorey plants. This revised version was published online in June 2006 with corrections to the Cover Date.     

Personalized stent design for congenital heart defects using pulsatile blood flow simulations

Stent size selection and placement are among the most challenging tasks in the treatment of pulmonary artery stenosis in congenital heart defects (CHD). Patient-specific 3D model from CT or MR improves the understanding of the patient’s anatomy and information about the hemodynamics aid in patient risk assessment and treatment planning. This work presents a new approach for personalized stent design in pulmonary artery interventions combining personalized patient geometry and hemodynamic simulations. First, the stent position is initialized using a geometric approach. Second, the stent and artery expansion, including the foreshortening behavior of the stent is simulated. Two stent designs are considered, a regular stent and a Y-stent for bifurcations. Computational fluid dynamics (CFD) simulations of the blood flow in the initial and expanded artery models are performed using patient-specific boundary conditions in form of a pulsatile inflow waveform, 3-element Windkessel outflow conditions, and deformable vessel walls. The simulations have been applied to 16 patient cases with a large variability of anatomies. Finally, the simulations have been clinically validated using retrospective imaging from angiography and pressure measurements. The simulated pressure, volume flow and flow velocity values were on the same order of magnitude as the reference values obtained from clinical measurements, and the simulated stent placement showed a positive impact on the hemodynamic values. Simulation of geometric changes combined with CFD simulations offers the possibility to optimize stent type, size, and position by evaluating different configurations before the intervention, and eventually allow to test customized stent geometries and new deployment techniques in CHD.     

Research progress on monitoring vegetation water content by using hyperspectral remote sensing

植被含水量是陆地植被重要的生物物理特征, 其定量遥感反演有助于植被干旱胁迫的实时监测与诊断评估。该文系统综述了国内外利用高光谱遥感评估植被水分状况的4个常见植被水分指标——冠层含水量、叶片等量水厚度、活体可燃物湿度和相对含水量的概念及其遥感估算方法研究进展, 评述了植被含水量高光谱遥感估算各类方法的优缺点, 探讨了植被含水量高光谱遥感估算目前存在的问题, 并提出进一步的研究任务, 即服务于植被干旱胁迫的高光谱遥感监测、预警与评估。     

延展与解蔽—基于时空体验的景观与建筑的内外交互

基于时空关系与体验,探讨了景观与建筑的交接空间。对其建构方式与体验感知方式进行研究。基于戴维·哈维（David Harvey）的“时空压缩”以及希格弗莱德·吉迪恩（Sigfried Giedion）的“空间时间”理论,通过诠释“厚性”的概念,分析了景观与建筑空间交接的2种基本出发点：基于时空拉伸的“延展”,以及基于时空压缩的“解蔽”;通过案例研究,对其不同的空间组织方法与空间界定材料的使用方式进行解读,并论述与此对应的2种空间感知过程：“可推导性”与“瞬时生成性”;通过分析4个现当代景观实践案例,对景观设计在空间“内外交互”建构中所发挥的主动性与使用方法进行综合研究。最后,对时空建构的基本方法、综合使用等方面进行应用层面的分类与总结。     

Two optical coherence tomography systems detect topical gold nanoshells in hair follicles,sweat ducts and measure epidermis

Optical coherence tomography (OCT) is an established imaging technology for in vivo skin investigation. Topical application of gold nanoshells (GNS) provides contrast enhancement in OCT by generating a strong hyperreflective signal from hair follicles and sweat glands, which are the natural skin openings. This study explores the utility of 150 nm diameter GNS as contrast agent for OCT imaging. GNS was massaged into skin and examined in four skin areas of 11 healthy volunteers. A commercial OCT system and a prototype with 3 μm resolution (UHR‐OCT) were employed to detect potential benefits of increased resolution and variability in intensity generated by the GNS. In both OCT‐systems GNS enhanced contrast from hair follicles and sweat ducts. Highest average penetration depth of GNS was in armpit 0.64 mm ± SD 0.17, maximum penetration depth was 1.20 mm in hair follicles and 15 to 40 μm in sweat ducts. Pixel intensity generated from GNS in hair follicles was significantly higher in UHR‐OCT images (P = .002) and epidermal thickness significantly lower 0.14 vs 0.16 mm (P = .027). This study suggests that GNSs are interesting candidates for increasing sensitivity in OCT diagnosis of hair and sweat gland disorders and demonstrates that choice of OCT systems influences results.      

Zur Wandstruktur der großen Arterien der Vögel

Zusammenfassung Die Wandstruktur der großen Arterien des Schwans, der Drossel und des Stars wurde licht- und elektronenoptisch untersucht und eine Einteilung in elastische, muskuläre und Übergangsgefäße getroffen.Die Media der elastischen Gefäße besteht aus muskulo-elastischen Zylindersegmenten, die mit breiten Bindegewebslagen alternieren. Die Zylindersegmente bestehen aus plattenförmigen Lagen glatter Muskelzellen, die von elastischen Fasernetzen flankiert werden. Diese Zylindersegmente beginnen und enden in den Bindegewebslagen stark gegeneinander versetzt, so daß ein kulissenartig einander überlappendes Plattensystem entsteht. Die Bindegewebslagen bestehen neben kollagenen Fasern und Fibrozyten aus mehreren konzentrischen Lagen elastischer Fasernetze. Die elastischen Netze sind durch Verbindungsfasern zu einem dreidimensionalem, die ganze Gefäßwand durchsetzenden elastischen System verknüpft. In den Übergangsgefäßen sind die Bindegewebslagen zwischen den muskulo-elastischen Systemen weitgehend reduziert.Bindegewebige und muskuläre Wandbestandteile sind im muskulären Vogelgefäß weitgehend voneinander getrennt. Die Media besteht aus glatten Muskelzellen, die von elastischen Netzen zu Schichten zusammengefaßt werden, die Adventitia aus kollagenen Fasern, Fibrozyten und konzentrischen Lagen elastischer Fasernetze. Die glatten Gefäßmuskelzellen sind durch elastische Fasernetze zu muskulo-elastischen Einheiten zusammengefaßt. Die mechanischen Verknüpfungspunkte zwischen Muskelzellen und elastischen Fasern sind über die ganze Zelloberfläche verteilt.Die Gefäßbautypen sind durch eine Wandstärken-Lumenrelation gekennzeichnet. Sie beträgt im elastischen Gefäß 1:5 bis 1:6, im muskulären Gefäß 1:14 bis 1:16.

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The wall structure of large arteries in birds

Summary A classification of large arteries (elastic, muscular and intermediate type) in mute swan, trush and starling was undertaken with light and electron microscopy.The tunica media of elastic arteries consists of musculo-elastic cylindrical segments alternating with wide connective tissue layers. The former consists of smooth muscle cell layers, which are adjoined by a network of elastic fibers. These musculo-elastic cylinder segments overlap incompletely. The connective tissue layers consist of networks of elastic fibers concentrically arranged in addition to collagen fibers and fibrocytes. The elastic networks are joined by connecting elastic fibers, thus forming a three-dimensionalsystem. In the intermediate type of arteries the connective tissue layers between the musculo-elastic systems are greatly reduced.Connective tissue and muscular components of the wall of muscular arteries are almost completely separated. The tunica media is composed of smooth muscle cells sandwiched by networks of elastic fibers. The tunica adventitia is formed by concentric networks of elastic fibers, collagen fibers and fibrocytes.The arterial smooth muscle cells, together with networks of elastic fibers, form a musculoelastic unit. The points of mechanical attachment between smooth muscle cells and elastic fibers are scattered all over the cellular surface. The arterial types described above are characterized by a well-defined wall thickness/lumen ratio. This ratio is of the order of 1:5 to 1:6 for elastic arteries and 1:14 to 1:16 for muscular arteries.

Medizinische Dissertation unter Anleitung von Prof. Dr. Dr. H.-R. Duncker.