A biosensing method for detection of caffeine in coffee

A specific inhibition of 3′,5′‐cyclic phosphodiesterase (CPDE) from bovine heart by methylxanthines was used in combination with a pH electrode to develop a new biosensing method for the detection of caffeine in coffee. The potential response changes of the sensor were proportional to the concentration of caffeine in the range 0–4 mg ml⁻¹. The response time was about 2–4 min. The standard deviation of five measurements of a 0.2 mg ml⁻¹ caffeine solution was ±7.1 µg ml⁻¹. The electrode gave a detection limit of 0.6 mg l⁻¹ caffeine. The concentration of caffeine in espresso coffee was analysed. This model gave excellent correlation between observed and predicted caffeine values. This electrode exhibits advantages such as fast response, short conditioning time and low cost of the instrumentation used. We also expected to be able to perform the detection of caffeine in food and clinical analysis. © 1999 Society of Chemical Industry     

Manipulating microstructure and mechanical properties of CuO doped 3Y-TZP nano-ceramics using spark-plasma sintering

Nano-powder composites of 3Y-TZP doped with 8 mol% CuO were processed by spark-plasma sintering (SPS). A 96% dense composite ceramic with an average grain size of 70 nm was obtained by applying the SPS process at 1100 °C and 100 MPa for 1 min. In contrast to normal, pressureless, sintering during SPS reactions between CuO and 3Y-TZP were suppressed, the CuO phase was reduced to metallic Cu, while the 3Y-TZP phase remained almost purely tetragonal. Annealing after SPS results in grain growth and tetragonal to monoclinic zirconia phase transformation. The grain size and monoclinic zirconia phase content are strongly dependent on the annealing temperature. By combining the processing techniques studied in this work, including traditional pressureless sintering, properties of the composite ceramic can be tuned via manipulation of microstructure. Tuning the mechanical properties of dense 8 mol% CuO doped 3Y-TZP composite ceramic by utilising different processing techniques is given as an example.     

The influence of the die and floating plug geometry on the drawing process of tubing

Nowadays, the development of tube drawing process with a floating plug technique has moved our limit up to the production of thick-walled tubes; production of which still belongs to marginal techniques which are different from drawing of standard tubes. The submitted paper is basically a survey of research in fundamental characteristics of tube drawing with a floating plug with the aim to summarize some important results from the theory, which have not yet been published in any English publication. The purpose of this survey is to fill the gap in English literature to promote transfer and exploitation of knowledge. Research in fundamental characteristics was further developed and conditions under which it is possible to draw thick-walled tubes are defined. Confirmed possibility of thick-walled tubes drawing with support provided by a floating plug having negative overlap is the result of theoretical study and practical verification, which enables further moving of drawing process limit.     

MULSOPS: Multivariate Optimized Pit Shells Simulator for tactical mine planning

Abstract

Production planning, scheduling and allocation of resources in large-scale surface mining operations present a great challenge to mine planning engineers. Ore and waste extraction plans must be executed to achieve tactical objectives using appropriate tools. Many production planning and scheduling and resource allocation methods are based on trial and error, crisis management or subjective judgements with no detailed economic basis or mathematical rigour. In addition, these methods do not consider the random processes governing critical development and production variables. In this study, the authors develop a multivariate pit shell simulator, MULSOPS, which addresses these problems. Rigorous geometric formulations of the ellipsoidal approximations of the pit shells geometry, their expansions and sequential interactions are modeled to mimic material displacement dynamics in an open pit operation. Stochastic and numerical modeling techniques are used to provide solutions to the time-dependent geometric models in random multivariate states Under different production and economic paradigms, the geometric models are simulated to yield the source and characteristics of appropriate cuts. Combined production from successive exposed cuts provides periodic targets for tactical planning. Variance simulation is also used to provide analysts with sensitive stochastic variables for input data definition and tight production target tolerance. A numerical example is used to illustrate the use of MULSOPS for tactical planning in a typical open pit operation.     

Analytical study of the additives system in polyethylene

On the basis of standards of identification of substances in the additive system of polyethylene has been performed. Different methods for separation such as adsorption thin-layer chromatography, high-performance liquid chromatography with chemically bounded phases, and gas chromatography have been used. The fir al identification has been made with mass spectrometry. The substances have been extracted from polyethylene with hexane and chloroform.     

All-cellulose composites prepared from flax and lyocell fibres compared to epoxy–matrix composites

All-cellulose composites (ACCs) were prepared by partial dissolution in ionic liquid and compared to composites with epoxy matrix. Wide-angle X-ray diffraction and scanning electron microscopy were used to reveal differences in the structure of the composites. In tensile tests, lyocell-fibre based ACCs showed similar strength and stiffness, yet superior extensibility compared to lyocell-epoxy composites. However, when flax fibres were used, tensile properties clearly inferior to flax-epoxy were observed. Dynamic-mechanical and thermogravimetric analysis revealed a favourable behaviour for ACC in terms of more diffuse thermal softening and increased resistance to thermal degradation.     

Measurement of intrinsic properties of amyloid fibrils by the peak force QNM method

We report the investigation of the mechanical properties of different types of amyloid fibrils by the peak force quantitative nanomechanical (PF-QNM) technique. We demonstrate that this technique correctly measures the Young's modulus independent of the polymorphic state and the cross-sectional structural details of the fibrils, and we show that values for amyloid fibrils assembled from heptapeptides, α-synuclein, Aβ(1-42), insulin, β-lactoglobulin, lysozyme, ovalbumin, Tau protein and bovine serum albumin all fall in the range of 2-4 GPa.     

Evaluation of effect of paddle element stagger angle on the local velocity profiles in a twin-screw continuous mixer with viscous flow using Finite Element Method simulations

The effect of paddle element geometry, specifically a systematic change in stagger angle, on the velocity distribution of a Newtonian corn syrup was evaluated in the mixing region of a 2″ Readco continuous processor using 3D FEM simulations. Local velocities and regions of backflow were compared for three configurations of the paddle elements in the mixing region consisting of nine pairs of paddle elements with the central three being in a neutral (FLAT), staggered 45° forward (45F) or staggered 45° reverse (45R) configuration. The total material flow rate through the mixer was independent of the paddle element stagger but increased with screw speed when the mixer was operated with the barrel fully filled. The stagger angle variation caused only local disturbances in axial flow. The overall magnitudes of velocity were highest for the FLAT configuration followed by 45F and 45R. The local X and Y velocity components in the region of stagger showed no significant variation with paddle element stagger while the Z velocity component varied significantly in this region. Increased forward flow was seen for the 45F configuration while significant local backflow was seen for the 45R configuration at all positions of the paddle element rotation. The FLAT configuration had greater levels of pressure in the intermeshing region, suggesting a squeeze flow while there were not significant variations in pressure for the 45F and 45R configurations, suggesting a predominantly conveying/leakage flow in the axial direction. Variation in local flows is critical to good mixing.     

Design procedure of simple and accurate model of electric double layer capacitor (EDLC) targeting fast verification purposes of heat transfer simulations

From the macrostructure of electric double layer capacitor (EDLC) and from heat transfer point of view, the volumetric properties of EDLC act as surrounding anisotropy. The core of the supercapacitor is made of coil, which is composed of a number of turns. This coil is from the physical aspect represented as a anisotropic structure that has to be considered during the design of a 3D model. Such structure of capacitor’s core is then in axial direction geometrically and physically different comparing to radial direction. This results in diverse expression of thermal conductivities in the mentioned directions. Therefore, it is necessary to analytically determine axial and radial parts of heat conduction thus avoiding high degree of thermal model’s complexity. After mathematical analysis, this paper will also describe the procedure of design of the EDLC thermal simulation model. During development of EDLC thermal model, and for computational and simulation purposes, the CFD software, COMSOL 3.5a, has been used. The principal aim was to reach very close proximity of the simulation results as compared to measurements, and simultaneously achieve very low computational time. Targeting high degree of model’s accuracy, several alternatives of model complexity will be shown.