Structure-property relations in molded, nucleated isotactic polypropylene

The influence of molecular characteristics and nucleating agents on the morphology distribution and properties of injection molded isotactic polypropylene (iPP) is investigated using optical microscopy, X-ray diffraction and mechanical testing. To have better control over the thermo-mechanical history, instead of a reciprocating screw, a capillary rheometer is used to drive the melt into the simple rectangular mold. Molecular weight (MW), molecular weight distribution (MWD) and addition of ethylene via copolymerization all influence the thickness of the oriented shear layer, the crystallinity, the type and amount of crystal phases, and the lamellar thickness. The addition of a nucleating agent (DMDBS), dictates the crystallization process, and resulting morphology, and samples with an oriented morphology over the full thickness are created without changing other morphological features, by applying a thermal treatment to the melt prior to injection, which is based on the specific phase behavior of the iPP-DMDBS system. The thermally treated samples show a considerable improvement in mechanical properties.     

Controlled-release system for the insect growth regulator cyromazine

An encapsulation system designed to give long-lasting effectiveness of the insect growth regulator (IGR) cyromazine (Neporex) against Culex pipiens (Culicidae) mosquito larvae was developed. The main thrust of the research was to develop a simple method for preparing controlled-release formulations by means of an extrusion technique in combination with a supplementary coating and to study the release characteristics and effectiveness of the formulations. A series of formulations were prepared with low-density polyethylene (LDPE 600) for the matrix and with polyurea or one of four types of polyurethane for the coating. The rate of release of the active material from the controlled-release formulations was determined in an in vitro dissolution system. The biological activity of the controlled-release formulations was tested in vivo against C. pipiens larvae. Received: 3 August 2000 / Accepted: 22 December 2000     

Planktonic food web structure and potential carbon flow in the Lower River Rhine with a focus on the role of protozoans

Studies during the last two decades have revealed the importance of planktonic micro‐organisms in the aquatic matter flux. However, studies on the planktonic food web structure have mostly concentrated on lentic waters. In the present study the biomass partitioning of the major plankton groups (bacteria, algae, heterotrophic flagellates (HF), ciliates and metazoans) in a large river (Lower River Rhine) has been analysed for a complete annual cycle and calculations on potential carbon flow within the planktonic food web were conducted for the four seasons. The plankton biomass was dominated by phytoplankton followed by bacterioplankton. The zooplankton was dominated by HF, contributing more than 65% of the total zooplankton biomass in all seasons. A significant part of the HF biomass was contributed by large flagellates (> 20 µm). In accordance with the dominance of the HF and their high growth rates, this group contributed the largest part of the planktonic matter turnover within the zooplankton. The calculations suggest that the HF were able to consume between 11 and 65% of the seasonal mean bacterial production and that the HF consumed a larger amount of phytoplankton than both ciliates and metazoans. According to these calculations, only a small part of the total potential production of the phytoplankton as well as that of the total zooplankton was consumed by planktonic predators. Since the plankton abundance did not generally increase during the downstream passage, the present data suggest that a large part of the plankton production is lost by other means. The role of benthic predators has been discussed in this context. Copyright © 2005 John Wiley & Sons, Ltd.     

XRD profile analysis characterization of ultrafine grained Al–Mg alloys

The effect of impurities on the crystallite sizes and dislocation densities of ECAP-processed aluminum–magnesium alloys is studied by X-ray diffraction. It is shown that with increasing magnesium content the achievable reduction in crystallite size with ECAP eventually reaches a saturation state and a further reduction of the structural size seems unlikely. Simultaneously the dislocation density increases to a plateau level with increasing Mg content. In annealing experiments the microstructural stability of AlMg0.5 and the resulting changes are investigated by XRD profile analysis. It becomes evident that annealing leads to a moderate increase in crystallite size up to a temperature where accelerated crystallite growth begins. XRD results prior and after fatigue testing show an increase in crystallite size accompanied by a decrease in dislocation density.     

Accident scenarios of the TRIGA Mark II reactor in Vienna

The safety report of the TRIGA Mark II reactor in Vienna includes three accident scenarios and their deterministic dose consequences to the environment. The destruction of the cladding of the most activated fuel element, the destruction of all fuel elements and a plane crash were considered scenarios in that report. The calculations were made in 1978 with the software program named STRISK. In this paper, the program package PC Cosyma was applied on the TRIGA Mark II reactor in Vienna and the deterministic consequences of the scenarios to the environment were updated. The fission product inventories of all fuel elements were calculated with ORIGEN2. To get meteorological data of the atmospheric condition around the release area, a weather station was installed. The release parameters were taken from the safety report or were replaced by worst case parameters. This paper focuses on two accident scenarios: the destruction of the cladding of the fuel element with the highest activity content and the case of a large plane crash. The current accident scenarios show good agreement with the calculations from 1978, hence no technical modifications in the safety report of the TRIGA reactor Vienna were necessary. Even in the very worst case scenario – complete destruction of all fuel elements in a large plane crash – the expected doses in the Atominstitut's neighborhood remain moderate.     

The strength-of-weak-ties perspective on creativity: A comprehensive examination and extension.

Disentangling the effects of weak ties on creativity, the present study separated, both theoretically and empirically, the effects of the size and strength of actors' idea networks and examined their joint impact while simultaneously considering the separate, moderating role of network diversity. I hypothesized that idea networks of optimal size and weak strength were more likely to boost creativity when they afforded actors access to a wide range of different social circles. In addition, I examined whether the joint effects of network size, strength, and diversity on creativity were further qualified by the openness to experience personality dimension. As expected, results indicated that actors were most creative when they maintained idea networks of optimal size, weak strength, and high diversity and when they scored high on the openness dimension. The implications of these results are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A survey on handling computationally expensive multiobjective optimization problems using surrogates: non-nature inspired methods

Computationally expensive multiobjective optimization problems arise, e.g. in many engineering applications, where several conflicting objectives are to be optimized simultaneously while satisfying constraints. In many cases, the lack of explicit mathematical formulas of the objectives and constraints may necessitate conducting computationally expensive and time-consuming experiments and/or simulations. As another challenge, these problems may have either convex or nonconvex or even disconnected Pareto frontier consisting of Pareto optimal solutions. Because of the existence of many such solutions, typically, a decision maker is required to select the most preferred one. In order to deal with the high computational cost, surrogate-based methods are commonly used in the literature. This paper surveys surrogate-based methods proposed in the literature, where the methods are independent of the underlying optimization algorithm and mitigate the computational burden to capture different types of Pareto frontiers. The methods considered are classified, discussed and then compared. These methods are divided into two frameworks: the sequential and the adaptive frameworks. Based on the comparison, we recommend the adaptive framework to tackle the aforementioned challenges.