Single-Circulating Tumor Cell Whole Genome Amplification to Unravel Cancer Heterogeneity and Actionable Biomarkers

The field of single-cell analysis has advanced rapidly in the last decade and is providing new insights into the characterization of intercellular genetic heterogeneity and complexity, especially in human cancer. In this regard, analyzing single circulating tumor cells (CTCs) is becoming particularly attractive due to the easy access to CTCs from simple blood samples called “liquid biopsies”. Analysis of multiple single CTCs has the potential to allow the identification and characterization of cancer heterogeneity to guide best therapy and predict therapeutic response. However, single-CTC analysis is restricted by the low amounts of DNA in a single cell genome. Whole genome amplification (WGA) techniques have emerged as a key step, enabling single-cell downstream molecular analysis. Here, we provide an overview of recent advances in WGA and their applications in the genetic analysis of single CTCs, along with prospective views towards clinical applications. First, we focus on the technical challenges of isolating and recovering single CTCs and then explore different WGA methodologies and recent developments which have been utilized to amplify single cell genomes for further downstream analysis. Lastly, we list a portfolio of CTC studies which employ WGA and single-cell analysis for genetic heterogeneity and biomarker detection.     

EvaluatingWater Vapor Permeance Measurement Techniques for Highly Permeable Membranes

The cup method and dynamic moisture permeation cell (DMPC) method are two common techniques used to determine the water vapor permeation properties of a membrane. Often, ignoring the resistance of boundary air layers to the transport of water vapor results in the water vapor permeance of the membrane being underestimated in practical tests. The measurement errors are higher with highly permeable membranes. In this study, the two methods were simulated using COMSOL Multiphysics platform and the extent of the error was evaluated. Initial results showed that the error is equally high in both methods. With the correction for the still air gap, the cup method produces a relatively reduced error. In the DMPC method, reducing the error caused by the boundary air layer by increasing the sweep speed can produce higher instrument error. Highly accurate and precise instrument is needed for DMPC method; however, its error is still higher than that in the cup method. Simulations also show that lowering the test pressure is favorable to both methods.     

Rapid investment casting: direct and indirect approaches via fused deposition modelling

Investment casting (IC) offers an economical method for mass producing complex, shaped metal parts. However, high tooling cost and lead times associated with the fabrication of metal moulds for producing IC wax (sacrificial) patterns result in cost justification problems for customised single casting, small- and medium-quantity production. Rapid prototyping (RP) techniques can reduce the costs associated with single-part or small-quantity production as they can be applied to the fabrication of sacrificial IC patterns containing complex and intricate designs with significant cost and lead-time savings. In this project, a benchmark model is designed to assess the fused deposition modelling (FDM) process for creating sacrificial IC patterns. In addition, an indirect approach toward producing wax patterns via silicone rubber moulding is investigated. Cost and lead time comparisons between the two IC pattern production methods were carried out and presented. The dimensional accuracies of metal castings generated from the RP-produced patterns are also presented.     

A comparative study of different control strategies for indoor air humidity

There has been a rising concern in controlling the high indoor humidity of hot and humid countries. When an air-conditioned space experiences only part of its design heat load, its humidity tends to rise as a result of the air-conditioning system trying to control the indoor temperature by reducing its cooling capacity. In this study, the part-load dehumidification performances of three temperature control strategies are compared, namely, chilled water flow control, bypass air control and the variable air volume control. Coil simulations are employed to study the part-load performance of these control strategies. The coil model has been validated with experimental data to within ±6.5%. The relative humidity of a space depends of factors such as design sensible heat factor of the space, temperature control strategy employed and load condition experienced by the space. Simulation results have indicated that chilled water control strategy results in the highest indoor humidity throughout the range of conditions studied while variable air volume system provides highly effective dehumidification performance of the cooling coil. Bypass air control appears to be a good option for adoption as it is able to provide an acceptable humidity over a wide range of load conditions without having to affect the air movement within the space.     

Estimating wall deflections in deep excavations using Bayesian neural networks

In this study, a neural network algorithm has been used to model the soil-structure interaction behavior of deep excavations in clays. The hybrid evolutionary Bayesian back-propagation (EBBP) neural network was used in this study and utilizes the genetic algorithms and gradient descent method to determine the optimal parameters within a Bayesian framework to regularize the complexity of learning and to statistically reflect the uncertainty in data. The EBBP analysis was carried out on an extensive database of braced excavation performance from finite element analyses. Additional parametric studies indicate that the model gives logical and consistent trends. Back-analyses of some instrumented case histories from the literature also indicate that the trained neural network model gives reasonable predictions in comparison to the actual measured values. The trained model can serve as a simple and reliable prediction tool to enable estimates of maximum wall deflection for preliminary design of braced excavations in clay. The model is able to take into consideration various factors such as the wall stiffness, support stiffness, the in-situ stress state, non-homogeneous soil conditions, and the variation of soil properties with depth. An added advantage of this approach is that it provides meaningful error bars for the model predictions.     

An integrated experimental approach to link a laser digitiser, a CAD/CAM system and a rapid prototyping system for biomedical applications

This study is carried out to develop a direct link between a laser digitiser and a rapid prototyping system for biomedical applications. Two CAD/CAM systems, DUCT and Pro-Engineer, are investigated and the DUCT system is found to be more suitable for this purpose. A laser digitiser is used to capture three-dimensional surface data for the object. With the aid of the CAD/CAM system, the data can be manipulated in a number of ways for display, modification and enhancement. In addition, the object scanned by the laser digitiser can be physically produced relatively quickly and accurately using StereoLithography Apparatus (SLA), a leading rapid prototyping system. Feasible and practical solutions to the problems encountered in the CAD surface model construction are proposed and illustrated. Two case studies, a facial and a breast model, are presented. Results show that this integrated approach can be applied effectively in the biomedical field.     

Cusp error reduction under high speed micro/meso- scale milling with ultrasonic vibration assistance

In the conventional use of vibration assisted machining, vibratory motion is mostly applied to the continuous machining processes such as turning where the cutting speed is much lower than the vibration speed. Even the recent articles on vibration assisted milling processes are also quite limited to low spindle speed less than 3k RPM. This study investigates vibration assistance that is applied to the workpiece in a high speed micro/meso-scale intermittent milling system where the cutting speed is much higher than the vibration speed. In addition to this, the vibration effect is analyzed considering feed and cross-feed directional application separately, which gives an idea of a right vibration assistance direction for surface quality improvement. To validate this, a one-directional ultrasonic vibration assisted milling system with ultrasonic frequency at 40 kHz and with amplitudes of a few microns is designed and its effect on the machined surface quality is investigated at high spindle RPMs over 15k. As a result, cusp heights are found to be reduced with ultrasonic vibratory motion of cutting edge in high cutting speed. Furthermore, the machined surface quality clearly tells that feed directional vibration assistance is able to generate better surface quality with reduced wavy burrs than cross-feed directional vibration assistance.     

High frequency comparison with thermoelectric power sensors between INRIM and NMC

This paper describes the bilateral comparison carried out by two National Metrology Institutes, NMC from Singapore and INRIM from Italy. The subject of the comparison concerns the calibration of a new type of coaxial power sensors fitted with type N (up to 18 GHz) and 3.5 mm (up to 26.5 GHz) connector. This is the first international comparison of this kind in which the transfer standards are based on indirect heating thermocouples. Results show that the introduction of this type of transfer standard and the update of the measurement techniques of both institutes allowed a general reduction of the uncertainty with respect to that declared in the last Key Comparison in the field.