Intravesicular Genomic DNA Enriched by Size Exclusion Chromatography Can Enhance Lung Cancer Oncogene Mutation Detection Sensitivity

Extracellular vesicles (EVs) are cell-derived structures surrounded by a lipid bilayer that carry RNA and DNA as potential templates for molecular diagnostics, e.g., in cancer genotyping. While it has been established that DNA templates appear on the outside of EVs, no consensus exists on which nucleic acid species inside small EVs (<200 nm, sEVs) are sufficiently abundant and accessible for developing genotyping protocols. We investigated this by extracting total intravesicular nucleic acid content from sEVs isolated from the conditioned cell medium of the human NCI-H1975 cell line containing the epidermal growth factor (EGFR) gene mutation T790M as a model system for non-small cell lung cancer. We observed that mainly short genomic DNA (<35–100 bp) present in the sEVs served as a template. Using qEV size exclusion chromatography (SEC), significantly lower yield and higher purity of isolated sEV fractions were obtained as compared to exoEasy membrane affinity purification and ultracentrifugation. Nevertheless, we detected the EGFR T790M mutation in the sEVs’ lumen with similar sensitivity using digital PCR. When applying SEC-based sEV separation prior to cell-free DNA extraction on spiked human plasma samples, we found significantly higher mutant allele frequencies as compared to standard cell-free DNA extraction, which in part was due to co-purification of circulating tumor DNA. We conclude that intravesicular genomic DNA can be exploited next to ctDNA to enhance EGFR T790M mutation detection sensitivity by adding a fast and easy-to-use sEV separation method, such as SEC, upstream of standard clinical cell-free DNA workflows.     

Ketone-amine based suspensions for electrophoretic deposition of Al2O3 and ZrO2

Stable suspensions based on methylethylketone (MEK), n-butylamine and nitrocellulose were developed for the electrophoretic deposition (EPD) of Al₂O₃ and ZrO₂ powder. Deposits with a high green density, smooth surface and high deposition yield were obtained upon adding 10–15 vol.% n-butylamine in combination with 1 wt.% nitrocellulose. The influence of the reaction between MEK and n-butylamine, forming water and imines, on the electrophoretic deposition behaviour was investigated. Experimental results revealed that the zeta potential is not a straightforward indication of the stability of these suspensions, since the maximum absolute zeta potential did not correspond with a maximum suspension stability, due to the additional electrosteric stabilisation of the adsorbed charged nitrocellulose.     

On the Complexity of Mining Quantitative Association Rules

The discovery of quantitative association rules in large databases is considered an interesting and important research problem. Recently, different aspects of the problem have been studied, and several algorithms have been presented in the literature, among others in (Srikant and Agrawal, 1996; Fukuda et al., 1996a; Fukuda et al., 1996b; Yoda et al., 1997; Miller and Yang, 1997). An aspect of the problem that has so far been ignored, is its computational complexity. In this paper, we study the computational complexity of mining quantitative association rules.     

Production and characterization of ZrO<Subscript>2</Subscript> ceramics and composites to be used for hip prosthesis

Tetragonal ZrO₂ polycrystalline (TZP) ceramics with varying yttria and ceria content (2–3 mol%) and distribution (coated or co-precipitated), and varying second phase content Al₂O₃ were prepared and investigated by means of microstructural analysis, mechanical properties, and hydrothermal stability, and ZrO₂-based composites with 35–60 vol% of electrical conductive TiN particles were developed. The effects of stabilizer content and means of addition, powder preparation, sintering conditions, and grain size have been systematically investigated. Fully dense Y-TZP ceramics, stabilized with 2–3 mol% Y₂O₃, 2 wt% Al₂O₃ can be achieved by hot pressing at 1,450 °C for 1 h. The hydrothermal stability increased with increasing overall yttria content. The jet-milled TiN powder was used to investigate the ZrO₂–TiN composites as function of the TiN content. The experimental work revealed that fully dense ZrO₂–TiN composites, stabilized with 1.75 mol% Y₂O₃, 0.75 wt% Al₂O₃, and a jet-milled TiN content ranging from 35 to 60 vol% could be achieved by hot pressing at 1,550 °C for 1 h. Transformation toughening was found as the primary toughening mechanism. The decreasing hardness and strength could be attributed to an increasing TiN grain size with increasing TiN content, whereas the decreasing toughness might be due to the decreasing contribution of transformation toughening from the tetragonal to monoclinic ZrO₂ phase transformation. The E modulus increases linearly with increasing TiN content, whereas the hydrothermal stability increases with addition of TiN content.     

Influence of CaTiO3 impurity in SHS-TiN powder on the mechanical properties of ZrO2–TiN composites

Yttria-stabilised tetragonal polycrystalline ZrO₂-based composites with 40 vol.% TiN were hot pressed at 1450 °C for 1 h using a jet-milled thermally synthesized and a self-propagating high-temperature synthesis (SHS) TiN powder. The ZrO₂ phase of the SHS-TiN powder-based composites was found to be substantially coarser than for the jet-milled TiN powder-based ceramics and prone to spontaneous transformation to m-ZrO₂ and microcracking, due to the CaTiO₃ impurity in the SHS-TiN starting powder. In order to prove this, a set of experiments was performed to investigate the effect of the addition of CaO and TiO₂ on an yttria-stabilised tetragonal ZrO₂ polycrystalline (Y-TZP). The addition of 0.2 mol% of CaO to a Y-TZP ceramic was found to destabilise the t-ZrO₂ phase, whereas the addition of 1 mol% TiO₂ results in significant grain growth and the formation of less transformable t-ZrO₂. The CaTiO₃ impurity could be removed from the SHS-TiN powder by hot hydrochloric acid leaching, allowing to obtain a similar microstructure and mechanical properties as with conventional TiN powder.     

Recent results obtained at IMEC on multicrystalline silicon solar cells

In order to optimize the efficiency of multicrystalline silicon solar cells, the influence of specific process steps and sequences were studied. Therefore clean-room high efficiency as well as industrial screen-printed cells were fabricated. Benefits are found in choosing a substrate with lower base resistivity, using front and rear oxide passivation, using hydrogen passivation for bulk and surfaces, the use of Si₃N₄ with a double function i.e. as an anti-reflection and passivation layer and the use of mechanical V-grooving. Efficiencies of 17% are found on 4 cm² clean-room fabricated cells and 15.2% has been obtained on 100 cm² V-grooved screenprinted industrial cells.     

Spatially separated atomic layer deposition of Al2O3, a new option for high‐throughput Si solar cell passivation

A next generation material for surface passivation of crystalline Si is Al₂O₃. It has been shown that both thermal and plasma‐assisted (PA) atomic layer deposition (ALD) Al₂O₃ provide an adequate level of surface passivation for both p‐ and n‐type Si substrates. However, conventional time‐resolved ALD is limited by its low deposition rate. Therefore, an experimental high‐deposition‐rate prototype ALD reactor based on the spatially separated ALD principle has been developed and Al₂O₃ deposition rates up to 1.2 nm/s have been demonstrated. In this work, the passivation quality and uniformity of the experimental spatially separated ALD Al₂O₃ films are evaluated and compared to conventional temporal ALD Al₂O₃, by use of quasi‐steady‐state photo‐conductance (QSSPC) and carrier density imaging (CDI). It is shown that spatially separated Al₂O₃ films of increasing thickness provide an increasing surface passivation level. Moreover, on p‐type CZ Si, 10 and 30 nm spatial ALD Al₂O₃ layers can achieve the same level of surface passivation as equivalent temporal ALD Al₂O₃ layers. In contrast, on n‐type FZ Si, spatially separated ALD Al₂O₃ samples generally do not reach the same optimal passivation quality as equivalent conventional temporal ALD Al₂O₃ samples. Nevertheless, after “firing”, 30 nm of spatially separated ALD Al₂O₃ on 250 µm thick n‐type (2.4 Ω cm) FZ Si wafers can lead to effective surface recombination velocities as low as 2.9 cm/s, compared to 1.9 cm/s in the case of 30 nm of temporal ALD Al₂O₃. Copyright © 2011 John Wiley & Sons, Ltd.     

On the reported experimental evidence for the quasi‐Fermi level split in quantum‐dot intermediate‐band solar cells

The reported experimental evidence for the quasi‐Fermi level split in quantum‐dot intermediate‐band solar cells is carefully examined. It is shown that the separation of the quasi‐Fermi level of the intermediate band from that of the conduction band is not consistent with the experimental results of the quantum efficiency and the luminescence intensity of the InAs/GaAs cells. The fact that the electroluminescence spectrum is too wide, extending much further than we expect on the basis of the measured quantum efficiency in the direction of increasing photon energies, indicates that the temperature of the optically active regions of the cell during the electroluminescence measurements is considerably higher than room temperature. The best agreement with the experimental results is achieved with a temperature of about 525 K. This temperature rise is probably a result of the heating effect of the relatively high forward current used in the luminescence experiments. It is argued that the lack of a quasi‐Fermi level split in this case is associated with the absence of a gap in the emission/absorption spectrum of sub‐bandgap photons. Copyright © 2011 John Wiley & Sons, Ltd.     

Elastic characterization of membranes with a complex shape using point indentation measurements and inverse modelling

The elasticity parameters of membranes can be obtained from tensile experiments on strips if adequate quantities of the material are available. For biomedical specimens, however, it is not always possible to harvest strips of uniform and manageable geometry suitable for tensile tests. A typical example is the human tympanic membrane. This small structure has a complex conical shape. In such case, elasticity parameters need to be measured in situ.A possible way to determine elasticity parameters of complex surfaces is the use of point indentation measurements. In this paper, this characterization procedure was applied on a scaled phantom model of the tympanic membrane. The model was built of natural latex rubber.In the characterization procedure, a point indentation is carried out on the membrane surface while forces and three-dimensional shapes are measured. Afterwards, a finite element simulation of the experiment is performed and parameters are found using an optimization routine. For validation purposes, the rubber was also subjected to a uniaxial tensile test.Several hyperelastic constitutive models are available to describe rubber-like behaviour. Among these, Mooney-Rivlin and Ogden models are the most popular. We used a low order Mooney-Rivlin and a higher order Ogden model to describe our experiments.Results show that there is a reasonable agreement between the tensile experiments output and the output of the inverse modelling of the indentation experiments.     

Another approach to form p+ emitter for rear junction n-type solar cells: Above 17.0% efficiency cells with CVD boron-doped epitaxial emitter

Epitaxial boron-doped emitters by CVD can provide a valuable alternative to the use of aluminum or diffused boron for the creation of p-type emitters. Compared to the traditional boron-diffused emitters for high-efficiency cells, epitaxial emitters need shorter process time, no boron skin removal step and have more opportunities to optimize the emitter doping profile. Our work proves that epitaxial emitters can be a good alternative for the p-type emitter. Very promising cell results with the highest cell efficiency of 17.0% on FZ material with LPCVD emitter and 16.7% on CZ material with APCVD emitter under 1 Sun have been achieved. Good fill factors have been obtained, which indicate good metal contacts are obtained on the epitaxial emitter. Cell results on n-type material are very encouraging and indicate a high potential of such epitaxial emitters for rear junction n-type solar cells.