RNA‐Cleaving Deoxyribozyme Sensor for Nucleic Acid Analysis: The Limit of Detection

Along with biocompatibility, chemical stability, and simplicity of structural prediction and modification, deoxyribozyme‐based molecular sensors have the potential of an improved detection limit due to their ability to catalytically amplify signal. This study contributes to the understanding of the factors responsible for the limit of detection (LOD) of RNA‐cleaving deoxyribozyme sensors. A new sensor that detects specific DNA/RNA sequences was designed from deoxyribozyme OA‐II [Chiuman, W.; Li, Y. (2006) J. Mol. Biol. 357, 748–754]. The sensor architecture allows for a unique combination of high selectivity, low LOD and the convenience of fluorescent signal monitoring in homogeneous solution. The LOD of the sensor was found to be ～1.6×10^?10 M after 3 h of incubation. An equation that allows estimation of the lowest theoretical LOD using characteristics of parent deoxyribozymes and their fluorogenic substrates was derived and experimentally verified. According to the equation, “catalytically perfect” enzymes can serve as scaffolds for the design of sensors with the LOD not lower than ～2×10^?15 M after 3 h of incubation. A new value termed the detection efficiency (DE) is suggested as a time‐independent characteristic of a sensor's sensitivity. The expressions for the theoretical LOD and DE can be used to evaluate nucleic acid and protein enzymes for their application as biosensing platforms.     

Test of fit for a Laplace distribution against heavier tailed alternatives

Over the last decade there has been a marked interest in a Laplace distribution and its properties and generalizations, especially in the framework of financial applications. Such an interest has led to a revision and discussion of available goodness-of-fit procedures for a Laplace distribution. Indeed, since most of the studies which employ the Laplace distribution are concerned with modelling heavy tailed patterns, the modern class of possible alternatives is way broader than just testing the Laplace vs. normal distribution. In this paper we propose a new test of fit for a Laplace distribution against deviations with heavier tails than that of the reference Laplace distribution. The proposed goodness-of-fit procedure is based on sample skewness and kurtosis and a robust L₁ estimator of scale about a sample median. The developed test statistic is shown to asymptotically follow a χ²-distribution with two degrees of freedom. Performance of the new goodness-of-fit test is illustrated by simulations and a case study.     

Low‐cost upscaling compatibility of five different ITO‐free architectures for polymer solar cells

Five different indium‐tin‐oxide free (ITO‐free) polymer solar cell architectures provided by four participating research institutions that all presented a laboratory cell performance sufficient for use in mobile and information and communication technology (ICT) were evaluated based on photovoltaic performance and lifetime tests according to the ISOS protocols. The comparison of the different device architectures was performed using the same active material (P3HT: PCBM) and tested against an ITO‐based reference device. The active area was 1 cm² and rigid glass or flexible polyester substrates were employed. The performance results were corroborated by use of a round robin methodology between the four participating laboratories (DTU/DK, ECN/NL, Frauenhofer ISE/DE, and the Holst Centre/NL), while the lifetime testing experiments were carried out in only one location (DTU). Five different lifetime testing experiments were carried out for a minimum of 1000 h: (1) shelf life (according to ISOS‐D‐1); (2–3) stability under continuous 1 sun illumination (1000 Wm^?2, AM1.5G) at low (37 ± 3°C) and high (80 ± 5°C) temperatures (according to ISOS‐L‐1 and ISOS‐L‐2); (4) stability under continuous low‐light conditions at 0.1 sun (100 Wm^?2, AM1.5G, 32°C) (according to ISOS‐LL); (5) continuous illumination (670 Wm^?2, AM1.5G) at high temperature (65°C) and high humidity (50% RH) (according to ISOS‐L‐3). Finally, the upscaling compatibility of these device architectures based on the device photovoltaic behavior, stability and scalability were identified and we confirm that an architecture that presents a high score in only one aspect of the solar cell performance is not sufficient to justify an investment in upscaling. Many will require further technical development. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 944‐954, 2013     

Physical Properties of La1−xEuxPO4,0 ≤ x ≤ 1, Monazite‐Type Ceramics

Synthetic La_1?xEu_xPO₄ monazite‐type ceramics with 0 ≤ x ≤ 1 have been characterized by ultrasound techniques, dilatometry, and micro‐calorimetry. The coefficients of thermal expansion and the elastic properties are, to a good approximation, linearly dependent on the europium concentration. Elastic stiffness coefficients range from 182(1) to 202(1) GPa for c₁₁ and from 53.8(7) to 61.1(4) GPa for c₄₄. They are strongly dependent on the density of the sample. The coefficient of thermal expansion at 673 K is 8.4(3)  × 10^?6 K^?1 for LaPO₄ and 9.9(3)  × 10^?6 K^?1 for EuPO₄, respectively. The heat capacities at ambient temperature are between 101.6(8) J·(mol·K)^?1 for LaPO₄ and 110.1(8) J·(mol·K)^?1 for EuPO₄. The difference between the heat capacity of LaPO₄ and the Eu‐containing solid solutions is dominated by electronic transitions of the 4f‐electrons at temperatures above 75 K.     

Characterization of Ni-Coated WS2 Nanotubes for Hydrodesulfurization Catalysis

A reactivity screening of new nano-hydrodesulfurization (HDS) catalysts was conducted using an ambient pressure flow reactor as well as ultra-high vacuum kinetics techniques. Thiophene was used as a probe molecule. Clean multiwall WS₂ nanotubes (INT-WS₂) as well as Ni- and Co-coated INT-WS₂ were considered. In addition, undoped MoS₂ and Re-doped nanoparticles with fullerene-like structures were studied. Commercial Ni and Co HDS catalysts from Haldor Topsoe (Denmark) as well as “nano MoS₂” from Impex Corp. (USA) were considered as reference materials. The lab-synthesized and commercial systems broke down thiophene into quite similar non-sulfur containing products, as identified by a gas chromatograph. The Ni and Co promoted catalysts showed similar thiophene conversion rates. Although the commercial catalysts had larger thiophene conversion rates than the laboratory-synthesized systems, the Re-doped nano-HDS catalyst showed quite low rates of formation of H₂S, an undesirable by-product.     

PolyHIPE: IPNs, hybrids, nanoscale porosity, silica monoliths and ICP-based sensors

Typical polyHIPE (porous polymers from high internal phase emulsions) have a cellular structure with volume fractions from 0.2 to 0.04, cell diameters from 15 to 25 μm and intercellular pore diameters from 0.5 to 10 μm. Unique interpenetrating polymer networks synthesized within the polyHIPE exhibited enhanced mechanical properties and an extended temperature range for damping. Hybrid polyHIPE that combine an inorganic polysilsesquioxane network with an organic polystyrene network exhibited superior high temperature mechanical properties and enhanced thermal stability. A nanoscale porosity in the cell walls, produced through the addition of a porogen to the HIPE, reduced the density and significantly enhanced the specific surface area. Porous silica monoliths with silica volume fractions of as low as 0.02 were produced through the pyrolysis of hybrid polyHIPE. PolyHIPE coated with an intrinsically conducting polymer exhibited reversible and repeatable changes in conductivity on exposure to acetone vapor, demonstrating their potential as sensor materials.