Estimation of waveguide phase error in silica-based waveguides

A new estimation method is proposed in order to clarify waveguide phase error factors. Using the proposed method, it is possible to analyze such factors as core size error and refractive index error, which cause optical phase error in waveguides. This method is applied to silica-based waveguides to estimate the waveguide phase error. This revealed an average core size error of 2.1×10^-3 μm and an average refractive index error of 1.9×10^-6. Finally, based on the measured phase error values, the optimum arrayed-waveguide grating (AWG) configuration is considered with a view to achieving low crosstalk     

Mitochondrial Fuel Dependence on Glutamine Drives Chemo-Resistance in the Cancer Stem Cells of Hepatocellular Carcinoma

Chemo-resistance hinders treatment of patients with hepatocellular carcinoma. Although there are many models that can be found in the literature, the root mechanism to explain chemo-resistance is still not fully understood. To gain a better understanding of this phenomenon, a chemo-resistant line, R-HepG2, was developed from a chemo-sensitive HepG2 line through an exposure of doxorubicin (DOX). The R-HepG2 exhibited a cancer stem cell (CSC) phenotype with an over-expression of P-glycoprotein (P-gp), conferring it a significant enhancement in drug efflux and survival. With these observations, we hypothesize that metabolic alteration in this drug-resistant CSC is the root cause of chemo-resistance. Our results show that, unlike other metabolic-reprogrammed CSCs that exhibit glycolytic phenotype described by the “Warburg effect”, the R-HepG2 was metabolically quiescent with glucose independence, high metabolic plasticity, and relied on glutamine metabolism via the mitochondria for its chemo-resistance Intriguingly, drug efflux by P-gp in R-HepG2 depended on the mitochondrial ATP fueled by glutamine instead of glycolytic ATP. Armed with these observations, we blocked the glutamine metabolism in the R-HepG2 and a significant reduction of DOX efflux was obtained. We exploited this metabolic vulnerability using a combination of DOX and metformin in a glutamine-free condition to target the R-HepG2, resulting in a significant DOX sensitization. In conclusion, our findings highlight the metabolic modulation of chemo-resistance in CSCs. We delineate the altered metabolism that drives chemo-resistance and offer a new approach to target this CSC through metabolic interventions.     

Explicit model predictive control of gas–liquid separation plant via orthogonal search tree partitioning

Solutions to constrained linear model predictive control (MPC) problems can be pre-computed off-line in an explicit form as a piecewise linear (PWL) state feedback defined on a polyhedral partition of the state space. This admits implementation at high sampling frequencies in real-time systems with high reliability and low software complexity. Recently, algorithms that determine an approximate explicit PWL state feedback solution by imposing an orthogonal search tree structure on the partition, have been developed, and it has been shown that they may offer computational advantages. This paper considers the application of an approximate approach to the design of an explicit model predictive controller for a two-input two-output laboratory gas–liquid separation plant, including experimental evaluation. The approximate explicit MPC controller achieves performance close to that of the conventional MPC, but requires only a fraction of the real-time computational machinery, thus leading to fast and reliable computations.     

Mechanical behavior of double-C60-end-capped poly(ethylene oxide)

Double-C₆₀-end-capped poly(ethylene oxide) (PEO) possesses good mechanical properties arising from a network-like structure due to the aggregation of C₆₀. The tensile strength is about 20 MPa, the elongation at break exceeds 640% and the fracture toughness is more than 110 MJ/m³. The material also possesses shape recovery ability. In contrast, single-C₆₀-end-capped PEO does not possess good mechanical properties.     

Miscibility and interactions in poly(methylthiomethyl methacrylate)/poly(vinyl alcohol) blends

Poly(methylthiomethyl methacrylate) (PMTMA) is miscible with poly(vinyl alcohol) (PVA) over the whole composition range as shown by the existence of a single glass transition temperature in each blend. The interaction between PMTMA and PVA was examined by Fourier transform infrared spectroscopy, solid-state nuclear magnetic resonance spectroscopy and X-ray photoelectron spectroscopy. The interactions mainly involve the hydroxyl groups of PVA and the thioether sulfur atoms of PMTMA, and the involvement of the carbonyl groups of PMTMA in interactions is not significant. The measurements of proton spin-lattice relaxation time reveal that PMTMA and PVA do not mix intimately on a scale of 1-3 nm, but are miscible on a scale of 20-30 nm. In comparison, we have previously found that PMTMA is miscible with poly(p-vinylphenol) and the two polymers mix intimately on a scale of 1-3 nm.     

Fibre management technique for optical device integration oncircuit board with hundreds of optical connections

The authors present a technique for fibre management on a circuit board, which utilises newly-developed, flexible optical fibre circuits and multifibre physical contact connectors. The technique achieves compact fibre wiring and easy fibre connection for hundreds of fibres on a circuit board. The authors have fabricated a compact 8×16 delivery and coupling switch board using the technique     

The influence of physical and chemical factors on the transport of E. coli through biological filters for wastewater purification

Transport studies of Escherichia coli were performed in laboratory columns over a period of 15 months. The effects of the filter media properties, effective grain size, specific surface area, pH and cation exchange capacity were examined for loading rates of 25 mm and 50 mm/day applied as 8 doses per day. Distilled water and two solutions of ionic strength 0.00725 and 0.097 M were applied to the columns. Physical factors were found to be the most important for the removal of E. coli. Reduced grain size, hydraulic loading rate and increased specific surface area of the grains significantly reduced transport of E. coli. Chemical factors such as pH, cation exchange capacity and wastewater ionic strength showed less significant effects. The results indicate that the chemical factors in biological wastewater filters have a minor influence on the removal of E. coli after a stabilizing period of three months. Minimum hydraulic retention time (time required for 10% breakthrough of a conservative tracer) was found to be the most relevant parameter for predicting bacterial removal in unsaturated filter systems. Correlation between observed data and a first order removal model, based on minimum retention time, was 0.70.     

Parallel Approximation Schemes for problems on planar graphs

 This paper describes a technique to obtain NC Approximations Schemes for the Maximum Independent Set in planar graphs and related optimization problems. The strategy consists in decomposing the graph into k-outerplanar subgraphs and solve for each k-outerplanar using tree contraction techniques. Received November 2, 1993/February 14, 1995