Flexible,Mechanically Stable,Porous Self-Standing Microfiber Network Membranes of Covalent Organic Frameworks: Preparation Method and Characterization

Covalent organic frameworks (COFs) show advantageous characteristics, such as an ordered pore structure and a large surface area for gas storage and separation, energy storage, catalysis, and molecular separation. However, COFs usually exist as difficult-to-process powders, and preparing continuous, robust, flexible, foldable, and rollable COF membranes is still a challenge. Herein, such COF membranes with fiber morphology for the first time prepared via a newly introduced template-assisted framework process are reported. This method uses electrospun porous polymer membranes as a sacrificial large dimension template for making self-standing COF membranes. The porous COF fiber membranes, besides having high crystallinity, also show a large surface area (1153 m² g⁻¹), good mechanical stability, excellent thermal stability, and flexibility. This study opens up the possibility of preparation of large dimension COF membranes and their derivatives in a simple way and hence shows promise in technical applications in separation, catalysis, and energy in the future.     

Influence of the Temperature on Coccolith-Containing Systems from Emiliania huxleyi Cultivations

Thermogravimetric analysis of a coccolith-containing biogenic broth showed a three-step degradation process. According to this system behavior, the biogenic broth was heated to specific temperatures and characterized in terms of its morphology, surface chemistry, and crystallinity. The elemental and organic composition of the treated samples was also evaluated and compared to the reference material. The presented results were acquired in an effort to exploit pretreatment scenarios for such a biogenic system that would improve and support a separation process.     

Abrasive wear of dental composite resins

Abrasive wear is a major problem in the application of dental composite resins. In this study the friction and wear behaviours of two types of dental composites: one containing relatively coarse filler particles and some microfillers (Estilux) and another containing only microfiller particles (Durafill), have been investigated by using a scratch testing machine. Experimental results show that the coefficients of friction in both composites are essentially constant for applied loads up to 20 N. The wear resistance of Durafill is better than Estilux. Under the same testing conditions, the size, shape and distribution of the filler particles are more important variables than applied load and sliding speed in controlling the wear mechanism. It is shown that for Estilux, plastic ploughing by the diamond indenter is the predominant mechanism. For Durafill, however, the formation and propagation of tensile cracks on the worn surface is the main wear mechanism. The effects of two different indenters, diamond and enamel, on the basic wear mechanisms are also discussed.     

Drugs, memory, and metamemory: A dose-effect study with lorazepam and scopolamine.

This experiment was designed to use the graded dose-related amnesia produced by the benzodiazepine lorazepam (1.0, 2.0 mg/70 kg, oral) and the anticholinergic scopolamine (0.3, 0.6 mg/70 kg, subcutaneous) as a tool to explore the cognitive and neurochemical mechanisms underlying metamemory in the judgment of learning paradigm, with a placebo-controlled independent groups design in healthy volunteers (n=12/group). Results provide evidence for a pharmacological dissociation between effects on memory versus metamemory (relative accuracy of item-by-item monitoring) across a range of levels of memory performance and suggest that the drugs selectively impair those aspects of metamnemonic monitoring that require participants' awareness of their overall current state of functioning (absolute accuracy of prospective item-by-item monitoring, prospective global monitoring) but not those that rely solely on assessment of individual item characteristics (relative accuracy of item-by-item monitoring). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A new ‘Tailor-made’ methodology for the mechanical behaviour analysis of rubber-like materials: II. Application to the hyperelastic behaviour characterization of a carbon-black filled natural rubber vulcanizate

The purpose of this paper is the modelling of the mechanical behaviour of an elastomeric material, through detailed experimental and numerical procedures, specific to large strains. The experimental technique is based on in-plane kinematics measurements using a speckle extensometer, from which the whole two-dimensional field of in-plane displacements is obtained by a digital image processing [Polymer (2002)]. This part of the work concerns the identification of the constitutive equation for a carbon black natural rubber (NR) vulcanizate. We start by quoting some theoretical considerations relative to rubber elasticity and stress-softening effect, which is the counterpart of the filler reinforcement. Then, we describe the experimental procedure and present data for both non-preconditioned and preconditioned samples. Next, the identification of the constitutive law parameters using a minimization algorithm is driven. Finally, we present the validation of the constitutive model, by its implementation into the finite element code SYSTUS and the numerical simulation of the response of a double edge notched tensile (DENT) specimen.     

PH3 residues in hazelnuts, soybeans and wheat following phosphine fumigation with non-constant concentrations

In model tests hazelnuts, soy beans and wheat were fumigated with phosphine (PH3) at non constant concentrations. The influence of different concentration characteristics on the fumigation and the decomposition of phosphine residues was investigated in accordance with the fumigation technique. At the beginning the concentration increases, and after attaining the maximum gradually decreases to zero. The level of residues during the fumigation as well as the behaviour of residues during the storage of the fumigated products was monitored with a gas chromatographic method. The residues correlate with the concentration of phosphine, they also pass through a peak. The rate of decomposition of residues which had been formed in the phase of increasing concentration is greater than the rate of residues of equal magnitude which had been formed during the decreasing phase. When the concentration is even the maximum residue occurs later than the maximum concentration; when there is a steep trend both maximums coincide. This behaviour can be explained by the sorption and diffusion of phosphine. A comparison is made with the phosphine concentration which occurs during fumigation in practice. The parameters which produce a constant concentration trend with only one maximum and a non constant trend with an often increasing and decreasing concentration are discussed. The different behaviour of residues in these cases is described. Conclusions are drawn for the practice of fumigation.     

Reliability aspects of microsensors and micromechatronic actuators for automotive applications

In modern cars microsensors and micromechatronic actuators play an essential and still increasingly important role as the interface between the vehicle with its complex functions of motor management, chassis systems, safety as well as comfort and convenience on the one hand and the respective electronic control units on the other hand. They have to fulfill their task in a harsh environment over the entire lifetime of an automobile. Therefore reliability aspects have moved more and more into the focus of engineering and research activities in microsystem technology. A methodical procedure is described that allows reliability issues to be approached efficiently. The implementation of the methodology is illustrated with real-life examples of reliability aspects of hot film mass air flow sensors, inertial sensors as well as piezoelectric actuators.