Effect of the Ca/P ratio on the dielectric properties of nanoscaled substoichiometric hydroxyapatite

Nanoscaled hydroxyapatite (n-HAp) was prepared by a wet chemical precipitation method, pressed to pellets and sintered at various temperatures between 900 and 1200°C. With input stoichiometries of Ca/P ratios between 1.4 and 2.0, compositions in the substoichiometric range of Ca/P between 1.45(1) and 1.62(3) were determined after preparation. After sintering, final values of the Ca/P ratio between 1.45(8) and 1.66(4) were found. Capacitances and dielectric losses were determined in the frequency range between 20 Hz and 1 MHz and dielectric constants calculated from the capacitances. Dependencies of the dielectric properties on the composition, as well as on sintering temperature and frequencies were investigated. The dielectric constants generally tend to increase with increasing Ca-content. Different behaviour was observed for low frequencies (below 10³ Hz) and for compositions far from the stoichiometric point of hydroxyapatite (Ca/P: 1.67). Comparable results were found for dielectric losses.     

In vitro inactivation of Chlamydia trachomatis by fatty acids and monoglycerides

The antichlamydial effects of several fatty acids and monoglycerides were studied by incubating Chlamydia trachomatis bacteria with equal volumes of lipid solutions for 10 min and measuring the reduction in infectivity titer compared with that in a control solution without lipid. Caprylic acid (8:0), monocaprylin (8:0), monolaurin (12:0), myristic acid (14:0), palmitoleic acid (16:1), monopalmitolein (16:1), oleic acid (18:1), and monoolein (18:1) at concentrations of 20 mM (final concentration, 10 mM) had negligible effects on C. trachomatis. In contrast, lauric acid (12:0), capric acid (10:0), and monocaprin (10:0) caused a greater than 10,000-fold (>4-log10) reduction in the infectivity titer. When the fatty acids and monoglycerides were further compared at lower concentrations and with shorter exposure times, lauric acid was more active than capric acid and monocaprin was the most active, causing a greater than 100, 000-fold (>5-log10) inactivation of C. trachomatis at a concentration of 5 mM for 5 min. The high levels of activity of capric and lauric acids and particularly that of monocaprin are notable and suggest that these lipids have specific antichlamydial effects. The mode of action of monocaprin was further studied by removal of the lipid by centrifugation before inoculation of Chlamydia onto host cells and by electron microscopy. The results indicate that the bacteria are killed by the lipid, possibly by disrupting the membrane(s) of the elementary bodies. A 50% effective concentration of 30 microgram/ml was found by incubation of Chlamydia with monocaprin for 2 h. The rapid inactivation of large numbers of C. trachomatis organisms by monocaprin suggests that it may be useful as a microbicidal agent for the prevention of the sexual transmission of C. trachomatis.     

Ecological networks: A spatial concept for multi-actor planning of sustainable landscapes

In this paper, we propose the ecological network concept as a suitable basis for inserting biodiversity conservation into sustainable landscape development. For landscapes to be ecologically sustainable, the landscape structure should support those ecological processes required for the landscape to deliver biodiversity services for present and future generations. We first show that in multifunctional, human-dominated landscapes, biodiversity conservation needs a coherent large-scale spatial structure of ecosystems. Theory and empirical knowledge of ecological networks provides a framework for the design of such structures. Secondly, ecological networks can bridge the paradox between reserve conservation (fixing nature in space and time) and development, which implies change. This is because ecological networks can change structure without losing their conservation potential. Thirdly, ecological networks facilitate stakeholder decision-making on feasible biodiversity goals. They help to focus on an effective spatial scale. We conclude that extending the ecological network concept with multifunctional indicators is a promising step towards sustainable landscape development and stakeholder decision-making.     

Theoretical and experimental properties of a binary linear beam-splitting element with a large fan angle

Abstract

Diffractive beam-splitting elements with a large fan angle of about 45° were realized as binary phase elements for application in a commercial laser device operating at the wavelength of 635 nm. The fan-out elements designated to split a laser beam into a line of 43 equal power spots were fabricated in silica by means of microstructuring techniques and replicated in acrylate by ultraviolet curing. Two different gratings have been designed using scalar unidirectional iterative methods, based on the iterative discrete on-axis and on the direct binary search algorithms. The optical properties of both gratings obtained by these scalar methods were compared with simulations based on rigorous electromagnetic calculations in order to verify and control the application-relevant specifications. The experimentally measured optical performance of the replicated fan-out elements is in good agreement with the theoretical predictions. The complete procedure for realizing the linear beam splitters, that is the design method, the fabrication of the master, and the replication process, will be presented. The optical properties and characteristic data of the replicas will be compared with scalar simulations as well as rigorous calculations; the results will be discussed.     

Diel activity and foraging mode of juvenile Arctic charr in fluctuating water flow

Streams fluctuate in water flow because of natural (e.g., rain) and human‐induced events (e.g., hydropeaking). Magnitude, frequency, and predictability of these events can have drastic consequences for fish populations. We studied how rapid modifications of water flow affect diel activity and foraging mode of juvenile Arctic charr Salvelinus alpinus in stream enclosures exposed to either stable (intermediate) or fluctuating (low vs. high) water flow. Under stable conditions, Arctic charr showed limited activity (9.4%). In fluctuating water flow, charr increased activity during low flow periods, especially during the first hours after the flow decreased, but ceased activity almost completely at high flow. Charr were mostly nocturnal, and more nocturnal at low than intermediate water flow. Fish were more mobile and swam faster during prey search and attacked prey at longer distances at low water flow. Activity and foraging mode differed between the first and second day after reduced water flow, suggesting that Arctic charr require time to adjust their foraging behaviour. This study demonstrates the importance of behavioural flexibility for population ecology in fluctuating environments such as regulated rivers.     

Integrated optical pickup system for axial dual focus

We propose an optical pickup that acquires data from both layers of a dual-layer digital versatile disk simultaneously. An adaptive optical element that uses liquid crystals creates two axial foci separated by a spacing of 55 mum, which is the distance between the two layers. The spacing between the foci can be varied by the adaptive element. The separation of the reflected light into TE and TM polarized light, corresponding to each of the layers, is made by dielectric gratings that are characterized by high aspect ratios. Electron-beam lithography and reactive ion etching techniques were used to produce the submicrometer structures. All fabricated elements were assembled in a pickup system, whose properties were measured.     

Multi-wavelength optical pickup with diffractive optical elements

Abstract

A novel, to our knowledge, multi-wavelength diffractive optical pickup is presented. The pickup enables multi-focus imaging and increases the data transfer rate considerably. Parallel reading of two or more memory layers is possible. The different spots can be controlled independently. The optical pickup consists of different diffractive optical elements (DOEs). The measured full-width at half-maximum (FWHM) spot intensity for the DOE-pickup is 0.76 μm—close to the diffraction limited predicted value of 0.71 μm—indicating good optical performance. The measured highest diffraction efficiencies of the realized DOEs are about 92%.