Properties and production of F-doped silica glass

Fluorine-doped silica glass is an optical material with high transmission in the vacuum ultraviolet region, specifically at 157 nm. This feature, along with low thermal expansion and ease of polishing make it the material of choice for the photomask substrate for the 157 nm lithography node. We report the synthesis of fluorine-doped silica glass using various dopants. Characterization of the glasses was achieved by measuring vacuum UV and IR spectra and by refractive index measurements. Transmission and refractive index are both found to depend on fluorine concentration.     

Dendritic mRNAs encode diversified functionalities in hippocampal pyramidal neurons

Background  

Targeted transport of messenger RNA and local protein synthesis near the synapse are important for synaptic plasticity. In order to gain an overview of the composition of the dendritic mRNA pool, we dissected out stratum radiatum (dendritic lamina) from rat hippocampal CA1 region and compared its mRNA content with that of stratum pyramidale (cell body layer) using a set of cDNA microarrays. RNAs that have over-representation in the dendritic fraction were annotated and sorted into function groups.     

A numerical and experimental study of batch sedimentation and viscous resuspension

A suspension of non‐neutrally buoyant, large, nearly monodisperse spheres is studied both in batch sedimentation and in shear between concentric rotating cylinders. We apply a continuum constitutive equation based on the diffusive flux model augmented with buoyancy terms derived by Acrivos and coworkers and discretize the resulting equation set with the finite element method. We simulate batch sedimentation using this method and obtain a reasonable match with experiment. Next used two‐dimensional NMR imaging to measure the evolution of solid fraction profiles in the same suspension undergoing flow between rotating concentric cylinders with two different initial conditions. Here, both gravity‐induced and shear‐induced particle migration are significant. Under these conditions, we have found that simulating the correct initial condition is critical to matching the experimental results. When this is done, the model results compare well with the experiments. Copyright © 2002 John Wiley & Sons, Ltd.     

Endor and eseem study of the radical obtained by γ irradiation of a single crystal of ammonium tartrate

The radical obtained by γ irradiation of a single crystal of ammonium tartrate has been identified by paramagnetic resonance spectroscopies. The proton hyperfine coupling tensors have been obtained, from the angular dependence of the ENDOR transition frequencies. ESEEM spectra of the radical have been also obtained. The intensities of the ESEEM lines are related to the depth of the modulation, which has a dramatic angular dependence.     

On equality in an upper bound for the restrained and total domination numbers of a graph

Let G=(V,E) be a graph. A set S⊆V is a restrained dominating set (RDS) if every vertex not in S is adjacent to a vertex in S and to a vertex in V?S. The restrained domination number of G, denoted by γ_r(G), is the minimum cardinality of an RDS of G. A set S⊆V is a total dominating set (TDS) if every vertex in V is adjacent to a vertex in S. The total domination number of a graph G without isolated vertices, denoted by γ_t(G), is the minimum cardinality of a TDS of G.Let δ and Δ denote the minimum and maximum degrees, respectively, in G. If G is a graph of order n with δ?2, then it is shown that γ_r(G)?n-Δ, and we characterize the connected graphs with δ?2 achieving this bound that have no 3-cycle as well as those connected graphs with δ?2 that have neither a 3-cycle nor a 5-cycle. Cockayne et al. [Total domination in graphs, Networks 10 (1980) 211-219] showed that if G is a connected graph of order n?3 and Δ?n-2, then γ_t(G)?n-Δ. We further characterize the connected graphs G of order n?3 with Δ?n-2 that have no 3-cycle and achieve γ_t(G)=n-Δ.     

Ignition delay measurements of four component model gasolines exploring the impacts of biofuels and aromatics

This study explores the impacts of combinations of biofuel (ethanol, isobutanol and 2-methyl furan) and aromatic (toluene) compounds in a four component fuel blend, at fixed research octane number (RON) on ignition delay measured in an advanced fuel ignition delay analyzer (AFIDA 2805). Ignition delay measurements were performed over a range of temperatures from 400 to 725 °C (673 to 998 K) and two chamber pressures of 10 and 20 bar. The four component mixtures are compared to primary reference fuels at RON values of 90 and 100. The ignition delay measurements show that as the aromatic and biofuel concentrations increased, two stage ignition behavior was suppressed, at both initial chamber pressures. But both RON 100 (isooctane) and RON 90 reference fuels showed two stage ignition behavior, as did fuel mixtures with low biofuel and aromatic content. RON 90 fuels showed stronger two stage ignition behavior than RON 100 fuels, as expected. Depending on the type of biofuel in the mixture, the ignition delay at low chamber temperatures could be far greater than for the reference fuels. In particular, for the RON 100 mixtures at either 10 or 20 bar initial chamber pressure, the ignition delay at 400 °C (673 K) for the high level blend of 2-methyl furan and toluene (30 vol% of each) exhibited an ignition delay that was 10 times longer than for neat isooctane. The results show the strong non-linear octane blending response of these three biofuel compounds, especially in concert with the kinetic antagonism that toluene is known to display in mixtures with isooctane. These results have implications for the formulation of biofuel mixtures for spark ignition and advanced compression ignition engines, where this non-linear octane blending response could be exploited to improve knock resistance, or modulate the autoignition process.     

The One-Shot Method in SU2

For PDE-constrained optimization tasks the one-shot approach is well-suited. The solution of the state equation is augmented with an adjoint solver to provide approximate reduced derivatives that can be used in an optimization iteration to change the design. In this paper different one-shot strategies for SU2 are implemented and tested for aerodynamic shape optimization in the open-source multi-physics package SU2 to extend the choice of optimization algorithms. These include the application of the one-shot approach when considering additional constraints apart from the state equation. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

A comparison of direct thermal desorption with solvent extraction for gas chromatography-mass spectrometry analysis of semivolatile organic compounds in diesel particulate matter

Direct thermal desorption-gas chromatography-mass spectrometry (DTD-GC-MS) is a technique that is finding application in the characterisation of the semivolatile organic carbon fraction of ambient and combustion source particulate matter (PM) collected on filters. In this study, three DTD-GC-MS methods were assessed and compared to a conventional solvent extraction method for analysis of a mixture of target analytes in solution and of diesel PM collected on quartz filters. The target analytes included n-alkanes, hopanes, steranes and polycyclic aromatic hydrocarbons. This study showed that while the three DTD-GC-MS methods were generally comparable to the solvent extraction method, (1) the choice of calibration strategy and calibration materials has a significant impact on the measured accuracy of a method; (2) very large variations were seen in all methods for the more volatile compounds such as C₁₀ to C₁₃ n-alkanes and naphthalene; (3) accuracy, defined as difference from the known concentration of a liquid sample, ranged from 5% to 32%; (4) precision, defined as the relative standard deviation, ranged from 4% to 16%. The average difference of DTD-GC-MS results from the solvent extraction results for the diesel PM filters ranged from 20% to 40%. This difference was driven by the large number of target analytes present at relatively low concentrations (<25 pg/mm²) and their corresponding higher variability. Differences in performance among the compound classes were noted. Minimum detection limits for the DTD-GC-MS methods were on the order of 0.1 to 1 pg/mm² and were as good as or better than those obtained for the solvent extraction method.