A Microfluidic Rectifier: Anisotropic Flow Resistance at Low Reynolds Numbers

It is one of the basic concepts of Newtonian fluid dynamics that at low Reynolds number (Re) the Navier-Stokes equation is linear and flows are reversible. In microfluidic devices, where Re is essentially always low, this implies that flow resistance in microchannels is isotropic. Here we present a microfluidic rectifier: a microscopic channel of a special shape whose flow resistance is strongly anisotropic, differing by up to a factor of 2 for opposite flow directions. Its nonlinear operation at arbitrary small Re is due to non-Newtonian elastic properties of the working fluid, which is a 0.01% aqueous solution of a high molecular weight polymer. The rectifier works as a dynamic valve and may find applications in microfluidic pumps and other integrated devices

Engineering glycan-binding proteins for the detection, analysis and treatment of cancer cells

Aberrant glycosylation in cancer cells can often lead to an increase in the exposure of unusual glycan structures. The presence of these structures can be exploited by engineering glycan-binding proteins as novel tools for the characterisation of glycoproteins bearing cancer-associated glycan structures. The carbohydraterecognition domain (CRD) of a rat serum mannose-binding protein (MBP) has been modified to mimic the glycan-specificity of a galactose-binding C-type lectin. Galactosebinding MBP (GalMBP) binds selectively to cancer-associated glycan structures on an array of glycans, including Lewis-type structures and T antigen. GalMBP binding to breast cancer cell lines has been demonstrated and GalMBP ligands on these cell lines have been purified on affinity columns of immobilised GalMBP. Analysis and purification of GalMBP ligands from MCF7 cell membranes led to the identification of a restricted population of high molecular weight glycoproteins. Proteomic and glycomic analysis of these glycoproteins by mass spectrometry showed that they are forms of CD98hc that bear glycans displaying heavily fucosylated termini, including Lewisx and Lewisy structures. Glycoproteomic analysis of a panel of commonly studied breast cancer cell lines reveals wide variations in the levels of Lewisx and the T antigen as well as the proteins that they are carried on. Proteins identified in multiple cell lines by GalMBP, including the mucin MUC-1 bearing T antigen and CD98hc, may represent common cancer-cell surface targets for GalMBP. The use of GalMBP as a proteomic tool for characterisation of glycoproteins bearing Lewisx has also been demonstrated on a panel of Hodgkin’s Reed-Sternberg cell lines. Identification of common protein carriers of Lewisx among different cell lines including CD98hc and ICAM-1 provides information about the likely role of these structures in the pathology of Hodgkin's Lymphomas and supports the previous finding that CD98hc is a novel protein carrier of Lewisx structures

Performance Evaluation of Market Timers

Previous investigators have shown that the Sharpe measure of the performance of a managed portfolio may be flawed when the portfolio manager has market timing ability. We develop the exact conditions under which the Sharpe measure will completely and correctly order market timers according to ability. The derived conditions are necessary, sufficient, and observable. We compare them to empirical estimates of actual market conditions, and find that the circumstances which can lead to a failure of the Sharpe measure do in fact occur. We show, however, that such failures can be greatly reduced by more frequent sampling.

Economic Evaluation of Positron Emission Tomography (PET) in Non Small Cell Lung Cancer (NSCLC), CHERE Working Paper 2007/6

Background: There are several perceived benefits from introducing positron emission tomography (PET) scanning into the staging of non small lung cancer (NSCLC). However, its greatest primary benefit is the role it can potential perform in reducing the number of unnecessary diagnostic examinations and futile surgeries. Objectives: To evaluate the economic impact and cost effectiveness of PET scanning in the management of potentially operable NSCLC patients using a cost-utility model. Methods: A literature review was conducted to find relevant studies and appropriate parameters to construct a decision model. Two strategies were compared. The first strategy was a conventional work up (CWU) consisting of an x-ray, a chest computer tomography (CT) scan and brochoscopy; the second strategy consisted of a CWU plus a whole body PET scan. These two strategies were applied to two sub-groups of NSCLC patients; those that had received a positive result on their CT scan and those that got a negative result on their CT scan. The cost-effectiveness of each strategy was dependent on a number of variables that were taken from a literature review. Costs were based on the Australian diagnostic related groups, a cost calculation for a chemotherapy course and values obtained from the literature. The life expectancy and utility scores were also taken from the literature and combined to create an incremental quality adjusted life year (QALY) value for PET for each of the patient groups. Results: The mean costs in CT negative and CT positive patients were lower in the CWU strategy, costing $A 20,427 and$A 23,578 per patient respectively compared to the PET strategy ($A 20,826 and$A 24,083 per patient respectively). The mean QALYs for both the CT positive and CT negative patients were higher in PET with 2.91 and 2.11 respectively compared to the CWU of 2.88 and 2.09. The incremental cost effectiveness ratio (ICER) for the CT negative strategy was $A 14,581 and$A 52,039 for the CT positive strategy. Conclusion: The PET strategy in CT negative and CT positive patients appears to be cost effective, however, there is much uncertainty surrounding this base result, particularly in CT positive patients.PET, non-small-cell lung cancer, economic evaluation

A Multi-Dimensional Trust Model for Heterogeneous Contract Observations

In this paper we develop a novel probabilistic model of computational trust that allows agents to exchange and combine reputation reports over heterogeneous, correlated multi-dimensional contracts. We consider the specific case of an agent attempting to procure a bundle of services that are subject to correlated quality of service failures (e.g. due to use of shared resources or infrastructure), and where the direct experience of other agents within the system consists of contracts over different combinations of these services. To this end, we present a formalism based on the Kalman filter that represents trust as a vector estimate of the probability that each service will be successfully delivered, and a covariance matrix that describes the uncertainty and correlations between these probabilities. We describe how the agents’ direct experiences of contract outcomes can be represented and combined within this formalism, and we empirically demonstrate that our formalism provides significantly better trustworthiness estimates than the alternative of using separate single-dimensional trust models for each separate service (where information regarding the correlations between each estimate is lost)

Efficient State-Space Inference of Periodic Latent Force Models

Latent force models (LFM) are principled approaches to incorporating solutions to differential equations within non-parametric inference methods. Unfortunately, the development and application of LFMs can be inhibited by their computational cost, especially when closed-form solutions for the LFM are unavailable, as is the case in many real world problems where these latent forces exhibit periodic behaviour. Given this, we develop a new sparse representation of LFMs which considerably improves their computational efficiency, as well as broadening their applicability, in a principled way, to domains with periodic or near periodic latent forces. Our approach uses a linear basis model to approximate one generative model for each periodic force. We assume that the latent forces are generated from Gaussian process priors and develop a linear basis model which fully expresses these priors. We apply our approach to model the thermal dynamics of domestic buildings and show that it is effective at predicting day-ahead temperatures within the homes. We also apply our approach within queueing theory in which quasi-periodic arrival rates are modelled as latent forces. In both cases, we demonstrate that our approach can be implemented efficiently using state-space methods which encode the linear dynamic systems via LFMs. Further, we show that state estimates obtained using periodic latent force models can reduce the root mean squared error to 17% of that from non-periodic models and 27% of the nearest rival approach which is the resonator model.Comment: 61 pages, 13 figures, accepted for publication in JMLR. Updates from earlier version occur throughout article in response to JMLR review

An Evaluation of Nutrient Trading Options in Virginia: A Role for Agriculture?

Water Quality Trading, offsets, nutrients, agriculture, BMPs, Environmental Economics and Policy,