Development of low-loss lead-germanate glass for mid-infrared fiber optics: II. preform extrusion and fiber fabrication

For lead-germanate glass fibers, reducing the content of hydroxyl (OH) groups and the formation of metallic Pb species is essential to pave the way for their applications as low-loss mid-IR fiber optics since OH and metallic Pb species cause intense absorption and scattering loss, respectively, in the mid-IR spectral range. The first part of this study reported the optimization of the glass melting procedure to obtain low amount of OH while preventing formation of metallic Pb species in lead-germanate glass. Here, the second part of this study reports the investigation of the process conditions to fabricate low-loss lead-germanate glass fiber through further understanding of the co-effects of glass melting and heat treatment atmospheres on the formation of nano- and micron-scale metallic Pb species in both the as-produced and heat treated lead-germanate glasses. Finally, using this advance in knowledge, we successfully fabricated low-loss lead-germanate glass fibers with no presence of reduced metallic Pb particles by optimizing dehydration agent, glass melting, preform extrusion and fiber drawing conditions. The optimized fabrication conditions reduced the unstructured fiber loss by almost one order to <0.3 dB/m at 1.55 μm.     

Alteration of the Route to Menaquinone towards Isochorismate-Derived Metabolites

Chorismate and isochorismate constitute branch-point intermediates in the biosynthesis of many aromatic metabolites in microorganisms and plants. To obtain unnatural compounds, we modified the route to menaquinone in Escherichia coli. We propose a model for the binding of isochorismate to the active site of MenD ((1R,2S, 5S,6S)-2-succinyl-5-enolpyruvyl-6-hydroxycyclohex-3-ene-1-carboxylate (SEPHCHC) synthase) that explains the outcome of the native reaction with α-ketoglutarate. We have rationally designed variants of MenD for the conversion of several isochorismate analogues. The double-variant Asn117Arg–Leu478Thr preferentially converts (5S,6S)-5,6-dihydroxycyclohexa-1,3-diene-1-carboxylate (2,3-trans-CHD), the hydrolysis product of isochorismate, with a >70-fold higher ratio than that for the wild type. The single-variant Arg107Ile uses (5S,6S)-6-amino-5-hydroxycyclohexa-1,3-diene-1-carboxylate (2,3-trans-CHA) as substrate with >6-fold conversion compared to wild-type MenD. The novel compounds have been made accessible in vivo (up to 5.3 g L⁻¹). Unexpectedly, as the identified residues such as Arg107 are highly conserved (>94 %), some of the designed variations can be found in wild-type SEPHCHC synthases from other bacteria (Arg107Lys, 0.3 %). This raises the question for the possible natural occurrence of as yet unexplored branches of the shikimate pathway.     

Production of Particle‐Stabilized Nonspherical Emulsion Drops in Simple Shear Flow

Nonspherical drops are of interest in the formation of microcapsules in life sciences like food, pharmacy, and cosmetics, agro and fine chemicals as well as material sciences. Out of many systems, particle‐stabilized emulsion drops, so‐called Pickering emulsions, exhibit an interesting formulation. Systems with Pickering particles applied in an excess amount were investigated. During deformation, the particles fully covered the enlarged drop interfaces and prevented its relaxation to a spherical drop shape. Nonspherical drops could be produced in simple shear flow using an adequate process routine. The production in a simple device is a promising high‐throughput alternative to microfluidic devices.     

Vulnerability of bank filtration systems to climate change

Bank filtration (BF) is a well established and proven natural water treatment technology, where surface water is infiltrated to an aquifer through river or lake banks. Improvement of water quality is achieved by a series of chemical, biological and physical processes during subsurface passage. This paper aims at identifying climate sensitive factors affecting bank filtration performance and assesses their relevance based on hypothetical ‘drought’ and ‘flood’ climate scenarios. The climate sensitive factors influencing water quantity and quality also have influence on substance removal parameters such as redox conditions and travel time. Droughts are found to promote anaerobic conditions during bank filtration passage, while flood events can drastically shorten travel time and cause breakthrough of pathogens, metals, suspended solids, DOC and organic micropollutants. The study revealed that only BF systems comprising an oxic to anoxic redox sequence ensure maximum removal efficiency. The storage capacity of the banks and availability of two source waters renders BF for drinking water supply less vulnerable than surface water or groundwater abstraction alone. Overall, BF is vulnerable to climate change although anthropogenic impacts are at least as important.     

Segmentation and Restoration of Images on Surfaces by Parametric Active Contours with Topology Changes

In this article, a new method for segmentation and restoration of images on two-dimensional surfaces is given. Active contour models for image segmentation are extended to images on surfaces. The evolving curves on the surfaces are mathematically described using a parametric approach. For image restoration, a diffusion equation with Neumann boundary conditions is solved in a postprocessing step in the individual regions. Numerical schemes are presented which allow to efficiently compute segmentations and denoised versions of images on surfaces. Also topology changes of the evolving curves are detected and performed using a fast sub-routine. Finally, several experiments are presented where the developed methods are applied on different artificial and real images defined on different surfaces.     

A viability theory for digital businesses: Exploring the evolutionary changes of revenue mechanisms to support managerial decisions

The ongoing integration of Information Technology (IT) into various areas of our lives has led to a plethora of digital products and services. To survive competition in the long run, these offerings not only have to keep up with constant technological developments, but also have to adapt from a business point of view. Managers of these digital businesses have to especially focus on the design and evolution of their business’ revenue mechanisms to ensure the viability of their offerings. The related decisions are not trivial, as managers have to be aware of the relevant contextual factors and have to react quickly to changes in the environment. This paper proposes a viability theory for digital businesses described by 17 propositions that may guide managers in the design of revenue mechanisms and thereby support the evolution as well as the viability of a digital business.     

M?bius Strip Segmented into Flat Trapezoids: Design-Build Project by the Departments of Architecture and Mathematics of the Technische Universit?t Darmstadt

The M?bius strip trade fair stand was designed and built by students of the Faculty of Architecture of Darmstadt Technical University in collaboration with students of the Faculty of Mathematics. The project focused on two main issues: to introduce computer-driven parametric design and production strategies, techniques and technologies into architectural education, and to build and operate the final result. This required knowledge of different software packages and readiness to become familiar quickly with unknown data formats, flexibility in the time schedule and disposition to transport the material to the machinery. It introduced students to the possibilities of designing with parametric modeling software and familiarized them with the initial difficulties and ample payback in actual production.     

Low-level temporal coding impairments in psychosis: Preliminary findings and recommendations for further studies.

The authors investigated whether difficulties with temporal event coding, previously reported in patients with schizophrenia, are already present during first-episode psychosis (FEP). In this experiment, the subjective judgments of the simultaneity of visually presented stimuli were compared between 11 healthy controls, 9 patients with chronic schizophrenia (CSZ), and a sample of 11 FEP patients. Participants were asked to indicate whether 2 vertical bars appeared at the same time or at different times on a computer monitor. CSZ patients' thresholds were elevated, and the FEP sample showed higher thresholds relative to controls. Although preliminary, these findings indicate a generalized disturbance in event-structure coding at early stages of psychosis and question the specificity of its disturbance. Considering the proposed relationship between event-structure coding and the experience of time in general, this study recommends that future studies refocus on psychosis in general, rather than on schizophrenia as a particular case of abnormal temporal processing. In addition, it is suggested that the relevant psychopathology will be best determined by means of a comprehensive analysis of low-level temporal coding performance in different types of psychosis. (PsycINFO Database Record (c) 2011 APA, all rights reserved)