Second-harmonic generation imaging of metal nano-objects with cylindrical vector beams

We introduce an imaging technique based on second-harmonic generation with cylindrical vector beams that is extremely sensitive to three-dimensional orientation and nanoscale morphology of metal nano-objects. Our experiments and second-harmonic field calculations based on frequency-domain boundary element method are in very good agreement. The technique provides contrast for structural features that cannot be resolved by linear techniques or conventional states of polarization and shows great potential for simple and cost-effective far-field optical imaging in plasmonics.     

Study of the PM Gas-Phase Filter Artifact Using a Setup for Mixing Diesel-Like Soot and Hydrocarbons

The filter artifact is a significant source of error in gravimetric measurements of particulate matter (PM) exhaust. However, only a few studies on the subject exist. Results from these studies show a large discrepancy mainly because the experiments were performed using real diesel vehicle exhaust with varying exhaust composition. In this study, a setup for mixing diesel-like soot and hydrocarbon vapor was constructed for generating a stable exhaust aerosol with adjustable composition. The particle size distribution of the diesel-fueled soot generator (GMD [geometric mean diameter] adjustable between 27 and 164 nm) was found to represent “real” exhaust particulate emission. This setup was applied for studying the filter artifact on Teflon-coated glass fiber filters using pentadecane as the hydrocarbon vapor. Experiments were performed using particle and hydrocarbon concentrations of 130–700 μg/m³ and 10–12 ppm, respectively. It was found that the particle concentration of the aerosol affects the filter artifact. At lower particle concentrations, more hydrocarbon adsorption was detected. In the absence of particles, the adsorption was highest. Furthermore, filter soot load, corresponding to 0.13%–0.66% of the clean filter mass, was found to affect adsorption. Sooty filters adsorbed less vapor than clean filters. However, increasing the soot load resulted in more adsorption. Moreover, it was found that the backup filter serves as a reasonable estimate of the filter artifact only for low particle concentrations and filter soot loads. These results indicate that the filter soot load is an important parameter influencing the filter artifact, and therefore, it should be considered when performing gravimetric sampling. The setup was proven to be a unique tool for quantitative studies of the filter artifact.

Copyright 2012 American Association for Aerosol Research     

Crispatotrochus-mimicking coatings improve the flexural properties of organic fibres

This brief communication describes the application and utility of thin film coral-mimetic coatings to natural fibres and provides quantitative values for the actual enhancement of their flexural properties.     

Compositional failure-based semantic models for Basic LOTOS

A systematic analysis of trace- and failure-based compositional semantic models for Basic LOTOS is presented. The analysis is motivated by the fact that the weakest known equivalences preserving sufficient information for several typical verification tasks are failure-based, and the weakness of an equivalence can be advantageous for verification. Both the equivalences and the preorders corresponding to the semantic models are covered. The analysis yields in a natural way two compositional semantic models, which are particularly suited for the verification of a general class of liveness properties, a task which cannot be performed with most established models.     

Syntax-directed compression of program files

Parsing can be applied to compress source programs. A suitably encoded parse tree, together with the symbol table, constitutes a very compact representation of the program. The paper reports a Prolog implementation of the method, including automatic, syntax-directed, encoder and decoder generators. The test results show compression gains of 50–60 per cent.     

Chirality in surface nonlinear optics

The efficiency of second-harmonic generation from chiral surfaces and thin films is different for left- and right-hand circularly-polarized fundamental light. Such optical activity can occur in the electric-dipole approximation. However, to explain our results for chiral polymer films, magnetic contributions to the nonlinearity must be included. A technique that uses a quarter wave plate to continuously vary the polarization of the fundamental beam was used to determine the relative complex values of the components of the tensors that characterize the nonlinear interaction. The largest magnetic components were 20% of the largest electric components. Second-harmonic generation from achiral anisotropic surfaces can also lead to optical activity. This occurs if the orientation of the anisotropic sample makes an otherwise achiral experimental arrangement chiral. The effect occurs in the electric-dipole approximation and changes sign as the handedness of the setup is reversed.     

REPLICA MBTAC: multithreaded dual-mode processor

Prevailing trend in design of chip multiprocessors (CMP) has been that single-core processors are replicated. Therefore, they typically define asynchronous computational model, require heavily locality-aware memory allocation, and present high overheads in intercommunication. This kind of properties make parallel programming very challenging and prone to errors. We introduce our new dual-mode MultiBunched/Threaded Architecture with Chaining (MBTAC) processor core, the main building block of the REPLICA CMP. It provides a modern, sophisticated way for writing general purpose parallel programs backed up by native execution capabilities/realization of key concepts. These include support for cost-efficient machine instruction-level synchronization and uniform shared global memory for enabling easy-to-program memory allocation of data structures and data movement. MBTAC makes use of low-overhead thread-context switching solution; it has parallel computing savvy functional unit organization to exploit inter-thread instruction-level parallelism and highly efficient multioperations. To evaluate the goodness of our proposal, we implemented three MBTAC constellations featuring up to 2048 parallel threads on FPGA, compared it with respect to DLX and Intel’s Core i7 processors. The results point toward high performance in communication-intensive problems, simplified parallel programmability, and regular, implementation-friendly structure.     

Performance and programmability comparison of the thick control flow architecture and current multicore processors

The Journal of Supercomputing - Commercial multicore central processing units (CPU) integrate a number of processor cores on a single chip to support parallel execution of computational tasks....     

The comparison of particle oxidation and surface structure of diesel soot particles between fossil fuel and novel renewable diesel fuel

Conventional fossil diesel fuel and renewable diesel fuel based on hydrotreated vegetable oils (HVO) were compared regarding the oxidation characteristics of the generated soot particulate. The comparison was performed by utilizing a high-temperature oxidation tandem differential mobility analyser in which monodisperse soot aerosol was first selected and then heated in a high-temperature furnace. The particle size reduction caused by oxidation during the furnace treatment was then measured as a function of furnace temperature. The results indicate that soot oxidation is very similar between the studied fuels. This is supported by the obtained HR-TEM images and EELS-spectra which were practically indistinguishable between different fuels and engine conditions. The similar oxidation properties and surface structure between fossil and HVO-based diesel fuels imply that the oxidative aftertreatment devices designed for fossil diesel should work well also with the studied renewable diesel fuel.