Multi-mode photonic crystal fibers for VCSEL based data transmission

Quasi error-free 10 Gbit/s data transmission is demonstrated over a novel type of 50 micron core diameter photonic crystal fiber with as much as 100 m length. Combined with 850$ nm VCSEL sources, this fiber is an attractive alternative to graded-index multi-mode fibers for datacom applications. A comparison to numerical simulations suggests that the high bit-rate may be partly explained by inter-modal diffusion.Comment: Accepted for Optics Expres

Strategic Business Partnerships in the Consumer Technology Industry - A Case Study on Partner Selection Criteria and Their Influence on the Outcome of Value Constellations

Thesis purpose: To identify relevant criteria underlying the partner selection process in a leading company in the consumer technology industry, as well as to subsequently analyse the influences which those criteria have on overall outcome. The intention is to draw valid implications for future research as well as for actors in similar market environments. Methodology: The researchers of this paper have chosen to conduct exploratory research within the particular case company. An interpretivist epistemological position has been selected by orienting the emphasis on understanding the social world by specifically analysing participants in that world. A qualitative approach was chosen so that individual’s opinions, thoughts, perspectives and expressions can provide insight into this world so that findings can inductively establish justifiable theory. The focus is to assimilate reliability and validity into the qualitative research with little change of meaning other than playing down the salience of measurement issue. A highly interactive process was used as it would provide the researchers with an idyllic tool with which the necessary data can be accumulated. Theoretical perspectives: The main theories are based on previous literature of collaborative concepts, value constellations and business partnerships. This research study investigates important partner selection criteria in value constellations and discusses how these influence the outcome of such initiatives in the consumer technology industry. The chosen case company is seen as a good setting to examine the phenomena as it is one of the first companies to anticipate different expectations between business and private customers. Conclusions: This study contributed to a framework explaining the competitive advantages of value constellations. Namely ten key partner selection criteria and ten respective influences were empirically discovered in the focal company. Seven of these criteria were found to clearly correspond with the underlying theoretical framework of this thesis, whereas three criteria were not explicitly referred to as key criteria in standard literature, although their importance for the case company was found to be significantly high

Development of an outdoor wave basin to conduct long-term model tests with real vegetation for green coastal infrastructures

The demand for physical model tests with real vegetation is increasing due to the current trend to elucidate the performance and durability of green coastal infrastructures to ensure and promote ecosystem services. To address this demand, a new outdoor wave basin (OWB) was built in August 2017 at the Ludwig-Franzius-Institute in Hannover, Germany. This paper reviews the general characteristics and the ongoing development of the new OWB. First insights into the long-term development of the ecosystem services of different grass revetments are discussed in terms of their ecological value and safety standards of sea dikes. Focus is placed on the resistance and ecological value of different grass mixtures that are typically applied on sea dikes situated along the North Sea. Further research concepts are briefly described to highlight how experiments in the new OWB may contribute to the current understanding and design recommendations of green coastal infrastructures. The operation of the OWB enables the performance of long-term experiments over seasonal growth stages of coastal vegetation using either fresh or seawater with wave load stresses and varying sea water levels. The first conducted experiments with different grass revetment combinations mimic typical storm surge conditions with a constant wave load (with a duration of up to 10 hours every second week) on a natural dik

Effects of wave load on the long-term vegetation development and their resistance as grass revetments on sea dikes

Construction and design processes of revetments, sea dikes and estuarine dikes along the German coastline adhere the paradigm to protect and safeguard reliably the coastal hinterland from wave attack and storm surges. Following these standards coastal protection structures provide only poor ecosystem services in any proper design or maintenance approach. As a result, the EcoDike-project has been started with the aim to quantify and enhance the ecosystem services of revetments, sea dikes and estuarine dikes while preserving or possibly even enhancing the existing safety standards. Therefore, a profound understanding of the complex long-term interactions between wave load and vegetation development on sea dikes is inevitable. To achieve these objectives a typical seadike in prototype scale is tested under realistic and long-term wave loading in the new outdoor wave basin at the Ludwig-Franzius-Institute in Hannover (Germany)

Age an origin of the "Mexican Onyx" at San Antonio Texcala (Puebla, Mexico)

A great variety of color banded CaC03 is known as „Mexican Onyx“, and is extensively used for ornamental purposes. Within the San Antonio Texcala mining district an area of about 24.000 m2 is covered by a thick travertine crust with a calculated volume of at least 2,8 x 1061. It originates from warm waters that emerge on young fissures and faults. It seems to be likely that the travertine formation is related to the hydrothermal activity of the Transmexican Volcanic Belt and to the seismicity of this zone. The deposit is built up by different travertine varieties. The main lithotypes are: (1) dense crystalline laminated travertine; (2) ray crystal travertine; (3) shrub layer travertine; (4) irregular porous travertine; (5) travertine breccia. Textural variation seems to be related to water temperature/distance from the emergence point, rapid or slow degassing of CO, and bacterial influence. At the moment, a light green banded variety (native sulfur impurities) is mined. It is the facture fill of a morphological prominent fissure-ridge travertine. U/Th data indicate, that the travertine has been deposited since at least 52 + 5 ka

Experimental field estimation of organic nitrogen formation in tree canopies

The content of organic N has been shown in many studies to increase during the passage of rain water through forest canopies. The source of this organic N is unknown, but generally assumed to come from canopy processing of wet or dry-deposited inorganic N. There have been very few experimental studies in the field to address the canopy formation or loss of organic N. We report two studies: a Scots pine canopy exposed to ammonia gas, and a Sitka spruce canopy exposed to ammonium and nitrate as wet deposition. In both cases, organic N deposition in throughfall was increased, but only represented a small fraction (<10%) of the additional inorganic N supplied, suggesting a limited capacity for net organic N production, similar in both conifer canopies under Scottish summertime conditions, of less than 1.6 mmol Nm2 mth1 (equivalent to 3 kg N ha1 y1)

Entwicklung eines mikrofluidischen Analysesystems zum immunologischen Proteinnachweis

Die vorliegende Arbeit beschäftigt sich mit der Entwicklung eines kalibrier- und regenerierbaren, mikrofluidischen Analysesystems zur Point-of-Care-Diagnostik bakterieller Erkrankungen mithilfe des Serumproteins CRP (C-reaktives Protein). Die Konzentration von CRP im Blut eines Patienten steigt bei einer kritischen Entzündungsreaktion auf mindestens den 100-fachen Wert an und kann somit durch das hier entwickelte Analysesystem qualitativ bestimmt werden. Für die Detektion des Proteins wird ein massensensitiver Quarzsensor verwendet, an dessen Oberfläche CRP-spezifische Antikörperfragmente als Fängermoleküle immobilisiert werden. Für die Untersuchung einer Serumprobe wurde der Sensor in ein mikrofluidisches System aus dem Polymer PDMS (Polydimethylsiloxan) integriert. Ein weiterer Bestandteil des Analysesystems ist eine mit Beads gefüllte Affinitätschromatographiezelle, in der der nachzuweisende Analyt von anderen Serumproteinen gereinigt und für den Nachweis angereichert werden kann. Die Umsetzung des Analysesystems erfolgte zunächst in modularer Weise, indem für die Steuerung der Probelösung aktive elektromagnetische Ventile Verwendung fanden. Sowohl Sensor- als auch Affinitätschromatographiezelle wurden dabei charakterisiert und für ihren Einsatz in einem mikrofluidischen Analysesystem getestet. Die Komponenten mussten hierzu insbesondere auf ihre Wechselwirkungen mit den verwendeten Biomolekülen untersucht werden. Anschließend konnte aus den daraus gewonnenen Ergebnissen ein Lab-on-Chip- System realisiert werden. Für die Steuerung der Probelösung innerhalb dieses Systems kamen aktive pH-sensitive Hydrogel-Ventile zum Einsatz, die ebenso aus PDMS hergestellt und somit in das mikrofluidische Gesamtsystem integriert werden konnten. Die Hydrogel-Aktoren wurden dabei zuvor für ihren Einsatz in dem Analysesystem getestet. Mithilfe des in dieser Arbeit entwickelten Lab-on-Chip-Sytems ist die Möglichkeit gegeben, kritische CRP-Konzentrationen zu detektieren und somit entzündliche Erkrankungen zu diagnostizieren.This paper discusses the development of a calibratable and regeneratable microfluidic analysis system for point-of-care diagnostics of bacterial diseases with CRP (C-reactive protein). Serious inflammations cause the concentration of CRP in human’s blood to increase by the factor of 100 or more. This can be qualified by the developed analysis system. The detection of the protein can be achieved by using a mass sensitive quartz sensor. Immobilized CRP-specific antibody-fragments act as catching molecules on its surface. For analysing a serum-sample the sensor was integrated into a microfluidic system made of PDMS (polydimethylsiloxane). An additional component of the analysis system is the affinity chromatographic cell filled with beads which are used for cleaning the analyte from other serum proteins and thus concentrated for detection. The implementation of these analysis systems was developed in modular manner by controlling the test-solution with electromagnetic valves. Both the sensor and the affinity chromatographic cell were characterized and tested for application in microfluidic analysis system. All components had to be examinated due to their interactions with the used biomolecules. Afterwards the obtained results were utilized for realising a lab-on-chip-system. Active pH-sensitive hydrogel valves, also consisting of PDMS, were introduced for the regulation of the test-solution flow within the system. Therefore they fit into the rest of the whole analysing lab-on-chip concept. Before integration the hydrogel actors were tested for its use in the analysis system. The lab-on-chip-system described in this paper offers the opportunity to detect critical CRP-concentrations and can be used to diagnose inflammations

Stemflow Infiltration Hotspots Create Soil Microsites Near Tree Stems in an Unmanaged Mixed Beech Forest

In stemflow, rainfall is collected and channeled to a concentrated soil water input. It can constitute up to 30% of incident precipitation in some ecosystems. However, the size of the zone influenced by stemflow is unclear, and statistically representative measurement of stemflow (on and in between sites) is scarce. Therefore, whether stemflow creates hotspots of infiltration and potential impacts on forest soils remain subject to controversy. In this study, we investigated the areal dimension of infiltrating stemflow fluxes as well as effects on near-stem soils. We measured throughfall, stemflow and soil properties in high-resolution statistical designs on a mixed forest plot in Germany receiving moderate stemflow. From this data, we modeled the spatial distribution of net precipitation infiltration depth on the plot. Furthermore, we examined soil chemical and physical properties around tree stems to test for and assess a stemflow impact. Results show that stemflow infiltration areas are much smaller than typically assumed and constitute strong infiltration hotspots compared to throughfall. This is also mirrored in soil properties, which are significantly altered near stems. Here, accelerated soil formation and enhanced translocation processes indicate increased soil water fluxes due to high inputs. Additionally, altered soil hydraulic properties enable quicker soil water fluxes near stems. Our findings attest that even comparatively low stemflow fractions (of gross precipitation) can generate strong hotspots of water and matter inputs, which are impactful to subsequent hydrological and biogeochemical processes and properties. Trees shape their direct soil environment, thereby establishing pathways of preferential water flow connecting the canopy and the deeper subsurface

Microbial respiration and natural attenuation of benzene contaminated soils investigated by cavity enhanced Raman multi-gas spectroscopy

Soil and groundwater contamination with benzene can cause serious environmental damage. However, many soil microorganisms are capable to adapt and are known to strongly control the fate of organic contamination. Innovative cavity enhanced Raman multi-gas spectroscopy (CERS) was applied to investigate the short-term response of the soil micro-flora to sudden surface contamination with benzene regarding the temporal variations of gas products and their exchange rates with the adjacent atmosphere. 13C-labeled benzene was spiked on a silty-loamy soil column in order to track and separate the changes in heterotrophic soil respiration – involving 12CO2 and O2 – from the natural attenuation process of benzene degradation to ultimately form 13CO2. The respiratory quotient (RQ) decreased from a value 0.98 to 0.46 directly after the spiking and increased again within 33 hours to a value of 0.72. This coincided with the maximum 13CO2 concentration rate (0.63 μmol m−2 s−1), indicating the highest benzene degradation at 33 hours after the spiking event. The diffusion of benzene in the headspace and the biodegradation into 13CO2 were simultaneously monitored and 12 days after the benzene spiking no measurable degradation was detected anymore. The RQ finally returned to a value of 0.96 demonstrating the reestablished aerobic respiration