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

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

Ultrafast spin-lasers

The appeal of lasers can be attributed to both their ubiquitous applications and their role as model systems for elucidating nonequilibrium and cooperative phenomena. Introducing novel concepts in lasers thus has a potential for both applied and fundamental implications. Here we experimentally demonstrate that the coupling between carrier spin and light polarization in common semiconductor lasers can enable room-temperature modulation frequencies above 200 GHz, exceeding by nearly an order of magnitude the best conventional semiconductor lasers. Surprisingly, this ultrafast operation relies on a short carrier spin relaxation time and a large anisotropy of the refractive index, both commonly viewed as detrimental in spintronics and conventional lasers. Our results overcome the key speed limitations of conventional directly modulated lasers and offer a prospect for the next generation of low-energy ultrafast optical communication.Comment: 10 pages, 4 figure

Sorption and fractionation of dissolved organic matter and associated phosphorus in agricultural soil

Molibility of dissolved organic matter (DOM) strongly affects the export of nitrogen (N) and phosphorus (P) from oils to surface waters. To study the sorption an mobility of dissolved organic C and P (DOC, DOP) in soil, the pH-dependent sorption of DOM to samples from Ap, EB, and Bt horizons from a Danish agircultural Humic Hapludult was investigated and a kinetic model applicable in field-scale model tested. Sorption experiments of 1 to 72 h duration were conducted at two pH levels (pH 5.0 and 7.0) and six initial DOC concentrtions (0-4.7 mmol L-1). Most sorption/desorption occurred during the first few hours. Dissolved organic carbon and DOP sorption decreased strongly with increased pH and desorption dominated at pH 7, especially for DOC. Due to fractionation during DOM sorption/desorption at DOC concentrations up to 2 mmol L-1, the solution fraction of DOM was enriched in P indicating preferred leaching of DOP. The kinetics of sorption was expressed as a function of how far the solution DOC or DOP concentrations deviate from "equilibrium". The model was able to simulate the kinetics of DOC and DOP sorption/desorption at all concentrations investigated and at both pH levels making it useful for incorporation in field-scale models for quantifying DOC and DOP dynamics

Reviewing the Carbonation Resistance of Concrete

The paper reviews the studies on one of the important durability properties of concrete i.e. Carbonation. One of the main causes of deterioration of concrete is carbonation, which occurs when carbon dioxide (CO2) penetrates the concrete’s porous system to create an environment with lower pH around the reinforcement in which corrosion can proceed. Carbonation is a major cause of degradation of concrete structures leading to expensive maintenance and conservation operations. Herein, the importance, process and effect of various parameters such as water/cement ratio, water/binder ratio, curing conditions, concrete cover, super plasticizers, type of aggregates, grade of concrete, porosity, contaminants, compaction, gas permeability, supplementary cementitious materials (SCMs)/ admixtures on the carbonation of concrete has been reviewed. Various methods for estimating the carbonation depth are also reported briefl

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

A coupled hydrology-biogeochemistry model to simulate dissolved organic carbon exports from a permafrost influenced catchment

Funded by Natural Environment Research Council. Grant Number: NE/K000268/1 Natural Sciences and Engineering Research Council of CanadaPeer reviewedPublisher PD

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)