AQUEOUS DISPERSION RHEOLOGY OF EXTRUSION COOKED MAIZE

The effects of twin screw extrusion cooking of maize grits at different high moisture contents are described. Starch granules survive in the extrudate at high extrusion moisture or with a low shear screw configuration. The aqueous dispersion rheology of the milled extrudate and its dependence on shear rate and heat treatment is explained in terms of the starch swelling behaviour and solubility. These data resemble that of raw maize most closely for the low shear screw configuration. For the high shear configuration under similar conditions of moisture, temperature and mechanical energy dissipation, starch granules are not seen and the dispersion rheology is markedly different from that of raw maize.     

DISCOLORATION OF SUN-DRIED AND PROCESSED ELBERTA PEACHES DURING STORAGE

Discoloration of sun-dried 'Elberta' (Prunus persica) peaches during a 48 week storage period as affected by moisture content (15 and 17%) and temperature (4, 7, 10 and 20C) was investigated. In addition, the effect of rehydration to moisture contents of 20, 24 and 27% and resulphuring on the color of the processed fruit during storage for 100 days at 0 and 25C was studied. Drying fruit to 15% instead of 17% moisture content gave darker-colored fruit, and it did not improve color retention during storage. Storage at 20C decreased L* values, indicating darkening of the fruit, but the quality, correlated with chroma, was still acceptable for fruit obtained with most of the treatment combinations. Substantial losses of SO₂ occurred at 20C. Rehydration and resulphuring increased chroma and hue values of the fruit. Storage of processed fruit at OC was effective in preventing discoloration, irrespective of treatment, while discoloration took place at 25C.     

The Automated Underground: Computer-Aided Design of Boston's Central Artery Project

Computer applications related to under-ground construction are described as they are being applied to Boston's Central Artery/Third Harbor Tunnel Project. The project is currently one of the largest highway projects in the country. Computer applications include a geotechnical boring log management system, spreadsheets for tunnel analysis and design, finite-element studies of soil-structure interaction for a construction excavation problem, and software that draws flow nets. Each application is outlined, and problems and future improvements to the methods are discussed.     

Comparison of hyperspectral classification methods for the analysis of cerium oxide nanoparticles in histological and aqueous samples

Hyperspectral imaging (HSI) and classification are established methods that are being applied in new ways to the analysis of nanoscale materials in a variety of matrices. Typically, enhanced darkfield microscopy (EDFM)‐based HSI data (also known as image datacubes) are collected in the wavelength range of 400–1000 nm for each pixel in a datacube. Utilising different spectral library (SL) creation methods, spectra from pixels in the datacube corresponding to known materials can be collected into reference spectral libraries (RSLs), which can be used to classify materials in datacubes of experimental samples using existing classification algorithms. In this study, EDFM‐HSI was used to visualise and analyse industrial cerium oxide (CeO₂; ceria) nanoparticles (NPs) in rat lung tissues and in aqueous suspension. Rats were exposed to ceria NPs via inhalation, mimicking potential real‐world occupational exposures. The lung tissues were histologically prepared: some tissues were stained with hematoxylin and eosin (H&E) and some were left unstained. The goal of this study was to determine how HSI and classification results for ceria NPs were influenced by (1) the use of different RSL creation and classification methods and (2) the application of those methods to samples in different matrices (stained tissue, unstained tissue, or aqueous solution). Three different RSL creation methods – particle filtering (PF), manual selection, and spectral hourglass wizard (SHW) – were utilised to create the RSLs of known materials in unstained and stained tissue, and aqueous suspensions, which were then used to classify the NPs in the different matrices. Two classification algorithms – spectral angle mapper (SAM) and spectral feature fitting (SFF) – were utilised to determine the presence or absence of ceria NPs in each sample. The results from the classification algorithms were compared to determine how each influenced the classification results for samples in different matrices. The results showed that sample matrix and sample preparation significantly influenced the NP classification thresholds in the complex matrices. Moreover, considerable differences were observed in the classification results when utilising each RSL creation and classification method for each type of sample. Results from this study illustrate the importance of appropriately selecting HSI algorithms based on specific material and matrix characteristics in order to obtain optimal classification results. As HSI is increasingly utilised for NP characterisation for clinical, environmental and health and safety applications, this investigation is important for further refining HSI protocols while ensuring appropriate data collection and analysis.     

THE STOKES HYDRODYNAMIC RESISTANCE OF NONSPHERICAL PARTICLES

A review is presented of the motion of an isolated, nonspherical particle of general shape settling at small Reynolds numbers through an unbounded quiescent fluid—with a view towards establishing whether or not all particles ultimately attain a unique, time-independent terminal state, independently of their initial orientation and state of motion. Effects of inhomogeneities in internal mass distribution are incorporated into the analysis. Differences are pointed out between gravity and centrifugal settling rates for nonspherical particles. These arise from the tendency of such particles to adopt preferential orientations in a centrifugal field of force owing to variations in field strength over the length of the particle, ft is pointed out that Coriolis forces acting on both the fluid and particle in a centrifuge cause the particles to settle more slowly. Moreover, in the case of spherical particles, the particle path deviates from a purely radial trajectory. Effects of both translational and rotational Brownian motions on the mean settling velocities of submicron particles is discussed, again for generally-shaped particle. A detailed summary of the contents of this paper is provided at its conclusion.     

SYMBOLIC OPERATOR SOLUTIONS OF LAPLACE'S AND STOKES’ EQUATIONS PART II STOKES FLOW PAST A RIGID SPHERE

Symbolic operator methods are employed to derive a general solution of the Stokes' and continuity equations of low Reynolds number hydrodynamics for arbitrary flow past an immobile sphere. The novelty of the final working formula lies in the fact that the velocity and pressure fields are explicitly and directly expressed in terms of the prescribed velocity field and its derivatives at infinity. Hence, apart from these trivial differentiations, no further operations of any kind are required to effect a solution

The computational scheme is illustrated for the case of a rigid sphere embedded in a general undisturbed quadratic velocity field, of which Poiseuille flow in a circular tube is the pre-eminent example. Results obtained by this method accord with those obtained by other, more traditional, schemes requiring preliminary expansion of (certain functions of) the prescribed data into surface spherical harmonics.     

SYMBOLIC OPERATOR SOLUTIONS OF LAPLACE'S AND STOKES’ EQUATIONS PART I LAPLACE'S EQUATION

Symbolic operator techniques are employed to derive a general solution of Laplace's equation in the infinite space external to a sphere. This is done for the case where the function vanishes on the sphere surface and arbitrary continuous asymptotic boundary data are imposed at infinity, such data being prescribed in the form of a solution of Laplace's equation that is analytic at the origin. In contrast with other standard methods for solving Laplace's equation, e.g., Green's functions, eigenfunction expansions, etc., the novelty of the proposed method lies in the fact that the solution can be expressed in a completely explicit form, directly in terms of (radial derivatives of)the given “undisturbed” field at infinity

A reciprocal theorem is derived and used to demonstrate that certain integral properties of the field can be obtained directly from the prescribed data at infinity, without recourse to a detailed solution of the relevant boundary-value problem. This global symbolic operator technique is illustrated for ellipsoidal as well as spherical particles

The elementary scalar harmonic analysis of the present paper serves as an entré to a companion paper (Part II), concerned with the application of similar symbolic techniques to the solution of more difficult vector biharmonic boundary-value problems, relevant to hydrodynamic Stokes flows in the infinite region external to a particle.