Method for generation of homogeneous multicellular tumor spheroids applicable to a wide variety of cell types

Multicellular tumor spheroids (MCTS) are used as organotypic models of normal and solid tumor tissue. Traditional techniques for generating MCTS, such as growth on nonadherent surfaces, in suspension, or on scaffolds, have a number of drawbacks, including the need for manual selection to achieve a homogeneous population and the use of nonphysiological matrix compounds. In this study we describe a mild method for the generation of MCTS, in which individual spheroids form in hanging drops suspended from a microtiter plate. The method has been successfully applied to a broad range of cell lines and shows nearly 100% efficiency (i.e., one spheroid per drop). Using the hepatoma cell line, HepG2, the hanging drop method generated well-rounded MCTS with a narrow size distribution (coefficient of variation [CV] 10% to 15%, compared with 40% to 60% for growth on nonadherent surfaces). Structural analysis of HepG2 and a mammary gland adenocarcinoma cell line, MCF-7, composed spheroids, revealed highly organized, three-dimensional, tissue-like structures with an extensive extracellular matrix. The hanging drop method represents an attractive alternative for MCTS production, because it is mild, can be applied to a wide variety of cell lines, and can produce spheroids of a homogeneous size without the need for sieving or manual selection. The method has applications for basic studies of physiology and metabolism, tumor biology, toxicology, cellular organization, and the development of bioartificial tissue. (C) 2003 Wiley Periodicals, Inc.

Super-fast scanning technique for phased array weather radar aplications

The authors present a super-fast scanning (SFS) technique for phased array weather radar applications. The fast scanning feature of the SFS technique is described and its drawbacks identified. Techniques which combat these drawbacks are also presented. A concept design phased array radar system (CDPAR) is used as a benchmark to compare the performance of a conventional scanning phased array radar system with the SFS technique. It is shown that the SFS technique, in association with suitable waveform processing, can realise four times the scanning speed and achieve similar accuracy compared to the conventional phased array benchmark.

Application of microencapsulated flavor to extrusion product

Flavoring is still a difficult problem in the snack food industry because of the high volatility of flavors and their instability under extrusion condition. Although postextrusion added flavor is commonly used, it suffers from numerous drawbacks. Flavor losses at the exit die because flash distillation is a critical issue and can only be minimized by controlling the pressure difference at the end of the barrel and the exit die, which, however, affects other desirable product characteristics. Residence time distribution (RTD), as an important intermediate process variable that among others controls the extent of reactions, can also be a major determinant on flavor retention during extrusion. Encapsulation of flavors is a promising alternative to enhance the retention of preextrusion added flavor during extrusion. The capsules should withstand high temperature and shear conditions in, the extruder barrel. Various encapsulation techniques and their encapsulated flavor characteristics are illustrated.

A new approach to the synthesis of nanocrystal conjugated polymer composites

A novel one pot process has been developed for the preparation of PbS nanocrystals in the conjugated polymer poly 2-methoxy,5-(2 ethyl-hexyloxy-p-phenylenevinylene) (MEH-PPV). Current techniques for making such composite materials rely upon synthesizing the nanocrystals and conducting polymer separately, and subsequently mixing them. This multi-step technique has two serious drawbacks: templating surfactant must be removed before mixing, and co-solvent incompatibility causes aggregation. In our method, we eliminate the need for an initial surfactant by using the conducting polymer to terminate and template nanocrystal growth. Additionally, the final product is soluble in a single solvent. We present materials analysis which shows PbS nanocrystals can be grown directly in a conducting polymer, the resulting composite is highly ordered and nanocrystal size can be controlled.

Slurry flow in mills with TCPL - An efficient pulp lifter for ag/sag mills

The difficulties associated with slurry transportation in autogenous (ag) and semi-autogenous (sag) grinding mills have become more apparent in recent years with the increasing trend to build larger diameter mills for grinding high tonnages. This is particularly noticeable when ag/sag mills are run in closed circuit with classifiers such as fine screens/cyclones. Extensive test work carried out on slurry removal mechanism in grate discharge mills (ag/sag) has shown that the conventional pulp lifters (radial and curved) have inherent drawbacks. They allow short-circuiting of the slurry from pulp lifters into the grinding chamber leading to slurry pool formation. Slurry pool absorbs part of the impact thus inhibiting the grinding process. Twin Chamber Pulp Lifter (TCPL) - an efficient design of pulp lifter developed by the authors overcomes the inherent drawbacks of the conventional pulp lifters. Extensive testing in both laboratory and pilot scale mills has shown that the TCPL completely blocks the flow-back process, thus allowing the mill to operate close to their design flow capacity. The TCPL performance is also found to be independent of variations in charge volume and grate design, whereas they significantly affect the performance of conventional pulp lifters (radial and curved). (c) 2006 Elsevier B.V. All rights reserved.

Approaches to environmental noise policy in Australia

Australia is a federation of six states and two territories. Legislation for environmental noise is the responsibility of each of the Australian states and territories. The Federal government has the responsibility for national issues such as aircraft noise and also to encourage harmonisation of the legislation and regulations among the states and territories. For some decades there has been a document on environmental noise produced by Standards Australia but it is up to each state or territory to call up part or all of this Standard. For general environmental noise some states use comparison with background as the criteria while others define the criteria levels based on land use zones. Both approaches have their advantages and drawbacks. This paper will compare and contrast the different legislation and regulations and discuss the issue of 'cross border' disputes.