METHODS FOR PROCESSING EXPERIMENTAL DRYING KINETICS DATA

This paper provides a review of methods for processing the data obtained from drying kinetics rigs and pilot-plant trials. Different methods for fitting and smoothing drying curves are compared, aiming to generate curves that are usable in industrial design without losing vital information by oversmoothing. Generally, plots of drying rate need more smoothing than moisture content data. Special care is needed at low drying rates and moisture contents. It is shown that some popular methods of processing data, including use of smoothing programs or fitting to equations, may generate drying curves which are seriously in error. Recommendations are made for reliable methods of processing data; cubic splines have been found to be effective for moisture-time curves. It is important to retain the original raw experimental data as a cross-check, as smoothing can conceal valuable information.     

Measurement of hydrodynamic data of gas-phase polymerization reactors using non-intrusive methods

The hydrodynamic characteristics of polyethylene resins are studied in detail through a combination of different techniques in our laboratory. Computer Assisted Tomography is used to determine voidage distribution under different operating conditions. Radioactive particle tracking is used to determine the solid particle trajectories, the horizontal and vertical velocities of the solids and the residence time distribution of the solids. X-ray fluoroscopy is used to determine bubble frequency and velocity. All these techniques are then combined with the information obtained through monitoring pressure fluctuations in the fluidized bed columns. All experiments are performed in Plexiglas columns of diameters that vary between 10 and 30 cm in diameter. The materials used are polyethylene and air, respectively. The combination of these techniques provides the unique opportunity to study the fluidized bed systems in great detail. Unfortunately, all techniques cannot be implemented in a single experiment. As a result, the same experiment is repeated as many times as necessary to collect the required data. The column is moved from one imaging system to the next and the experiment is repeated under the same operating conditions. It is believed that the data collected can be used as if all the data were collected during the same test. This paper presents preliminary experimental results for each set of experiments along with the nature and limitations of each set of experimental data. The results from each different system are combined in an effort to describe the complex hydrodynamics of the bed. The incremental information obtained in each set of experiments compared to the macroscopic measurements (flow rate and pressure drop) is demonstrated.     

Accuracy and reproducibility of the electrochemical profiler

The electrochemical CV profiler (ECV) plays a key role in the characterisation of compound epitaxial structures. Epi suppliers and their customers need a procedure that ensures that the carrier concentration in any given layer lies within agreed limits. Carrier concentrations in optoelectronic device structures and HBTs are usually specified around ±20%, with tighter limits being applied to MESFET and HEMT structures. By understanding the factors that affect the accuracy and reproducibility of the ECV method, the standard deviation of the measurement, for uniformly doped epilayers, can be reduced to around 2%.     

Modernist Town Planning And Metropolitan Planning: Reflections From Gordon Stephenson

Gordon Stephenson died on March 29th this year, aged 88. We were fortunate enough to have spoken in depth with Stephenson late in 1995. We dedicate this piece to a person who was described in a recent obituary in The Australian (10.4.97) as “one of the great town planners of this century”.     

Optimal fluid control can normalize cardiovascular risk markers and limit left ventricular hypertrophy in thrice weekly dialysis patients

Increased hemodialysis frequency can make fluid overload easier to treat, although most patients are still treated thrice weekly. Chronic fluid overload is associated with left ventricular hypertrophy and elevated serum cardiac biomarkers, recognized as mortality risk factors. Serum cardiac troponin T (cTnT), N‐terminal prohormone brain natriuretic peptide (NT‐proBNP), left ventricular mass index by cardiac magnetic imaging, and ambulatory blood pressure was measured in 30 thrice weekly hemodiafiltration patients. Time‐averaged fluid overload (TAFO) was quantified by bioimpedance spectroscopy. In the study group, left ventricular hypertrophy was found to be 26% by cardiac magnetic resonance. Ambulatory blood pressure was 130 mmHg (112–151) requiring a low equivalent dose of medication of 0.25 units (0–1). Significantly, lower levels of left ventricular mass index (P < 0.05) were associated in those patients with TAFO <1 L or NT‐proBNP <1200 pg/mL or cTnT <0.1 ug/L. In the subgroups, 16 patients had normal cTnT (<0.03 ug/L), 16 patients had NT‐proBNP <400 pg/mL, and 20 patients had TAFO <1 L. Nine patients had both cTnT <0.03 ug/L and NT‐proBNP <400 pg/mL. Normally hydrated thrice‐weekly hemodiafiltration patients can have cardiac biomarker and TAFO levels indistinguishable from the normal healthy population. Obtaining TAFO by bioimpedance monitoring can offer a practical alternative to serum cardiac biomarkers.     

Escherichia coli biotransformation of daidzein fermentation products from soy‐based foods—relevance to food oestrogenicity‐based functionality

Oestrogenic isoflavones (e.g. daidzein) present in soy‐based foods are likely to be important in food functionality. Biotransformation of daidzein during fermentation‐based soy‐containing food manufacture forms three trihydroxy metabolites, 6‐ortho‐hydroxydaidzein (6‐OHD), 8‐ortho‐hydroxydaidzein (8‐OHD) and 3′‐ortho‐hydroxydaidzein (3′‐OHD) which alters the oestrogenicity of the final food product. We report that Escherichia coli (a key component of the gut microbiome) metabolism converts 8‐OHD to 6‐OHD with a likely concomitant increase in oestrogenicity. This means that the functionality of 8‐OHD‐containing soy‐based foods is altered by gut microbiome metabolism. This change in oestrogenicity‐based food functionality might have benefits for postmenopausal women, while being a feminising health risk for males and could add to the risk of oestrogen‐mediated precocious puberty in girls.     

Modifying the microstructure of low-fat yoghurt by microfluidisation of milk at different pressures to enhance rheological and sensory properties

The effects of microfluidisation of milk at different pressures, prior to heat treatment, on structural and sensory properties of low-fat stirred yoghurt, were investigated. Low-fat yoghurts prepared from microfluidised milk were compared with low-fat (1.5%) and full-fat (3.5%) control yoghurts made with homogenised (20/5 MPa) milk. The microstructure of low-fat yoghurts prepared with microfluidised milk consisted of smaller and more uniform fat globules, well incorporated into more interconnected fat-protein gel networks, compared with those of control yoghurts. This modification in microstructure caused significant changes in gel particle size, sensory profile and rheological behaviour. Microfluidisation increased the gel particle size, gel strength and viscosity; marked beneficial effects were found at higher pressures (50–150 MPa). Microfluidising milk at 50–150 MPa increased the gel strength by 171–195% and viscosity by 98–103%, creating low-fat yoghurts with creaminess and desirable texture properties similar to, or better than, full-fat conventional yoghurt.     

Synergy between synthetic aperture radar and other sensors for the remote sensing of the ocean

Over the last decades, satellite remote sensing has proved to be a valuable and effective tool for monitoring physical and biological ocean processes. However there are cases where data from one remote sensor alone cannot be interpreted unambiguously. In these situations the combination of data from different sensors can help to understand the observed processes due to the combined benefits of the various strengths and advantages of individual instruments. This paper illustrates the potential of synergy between synthetic aperture radar data and data from thermal and optical satellite sensors. Different aspects of oceanic and atmospheric fronts, eddies, upwelling, internal waves and surface films are imaged by the sensors and combined data give a broader picture of the physical processes involved. While the strengths of synergy are demonstrated in several examples, more frequent coincidence of data from existing and future sensors will be necessary before the benefits of synergy occur on an operational basis.