Spatial averaging of oceanic rainfall variability using underwater sound: Ionian Sea rainfall experiment 2004

An experiment to evaluate the inherent spatial averaging of the underwater acoustic signal from rainfall was conducted in the winter of 2004 in the Ionian Sea southwest of Greece. A mooring with four passive aquatic listeners (PALs) at 60, 200, 1000, and 2000 m was deployed at 36.85 degrees N, 21.52 degrees E, 17 km west of a dual-polarization X-band coastal radar at Methoni, Greece. The acoustic signal is classified into wind, rain, shipping, and whale categories. It is similar at all depths and rainfall is detected at all depths. A signal that is consistent with the clicking of deep-diving beaked whales is present 2% of the time, although there was no visual confirmation of whale presence. Co-detection of rainfall with the radar verifies that the acoustic detection of rainfall is excellent. Once detection is made, the correlation between acoustic and radar rainfall rates is high. Spatial averaging of the radar rainfall rates in concentric circles over the mooring verifies the larger inherent spatial averaging of the rainfall signal with recording depth. For the PAL at 2000 m, the maximum correlation was at 3-4 km, suggesting a listening area for the acoustic rainfall measurement of roughly 30-50 km(2).     

Enhanced aqueous solubilization of tetrachloroethylene by a rhamnolipid biosurfactant

A rhamnolipid biosurfactant produced by Pseudomonas aeruginosa ATCC 9027 was isolated, purified and characterized in terms of its ability to mobilize and solubilize tetrachloroethylene (PCE) for potential use in surfactant-enhanced aquifer remediation (SEAR) applications. Using a drop volume method, the PCE-biosurfactant steady-state interfacial tension was determined and found to be ca. 10 mN/m which is not low enough to cause significant PCE nonaqueous phase liquid (NAPL) mobilization. It was observed that the biosurfactant partitioned significantly into PCE at aqueous concentrations higher than the critical micelle concentration (CMC). After accounting for rhamnolipid partitioning into the PCE phase, a weight solubilization ratio (WSR) of 1.2 g(PCE)/g(rhamnolipid) was determined and through this mechanism the biosurfactant significantly improved the apparent aqueous solubility of PCE.     

Hybrid Organic–Inorganic Halide Post-Perovskite 3-Cyanopyridinium Lead Tribromide for Optoelectronic Applications

2D halide perovskite-like semiconductors are attractive materials for various optoelectronic applications, from photovoltaics to lasing. To date, the most studied families of such low-dimensional halide perovskite-like compounds are Ruddlesden–Popper, Dion–Jacobson, and other phases that can be derived from 3D halide perovskites by slicing along different crystallographic directions, which leads to the spatially isotropic corner-sharing connectivity type of metal-halide octahedra in the 2D layer plane. In this work, a new family of hybrid organic–inorganic 2D lead halides is introduced, by reporting the first example of the hybrid organic–inorganic post-perovskite 3-cyanopyridinium lead tribromide (3cp)PbBr₃. The post-perovskite structure has unique octahedra connectivity type in the layer plane: a typical “perovskite-like” corner-sharing connectivity pattern in one direction, and the rare edge-sharing connectivity pattern in the other. Such connectivity leads to significant anisotropy in the material properties within the inorganic layer plane. Moreover, the dense organic cation packing results in the formation of 1D fully organic bands in the electronic structure, offering the prospects of the involvement of the organic subsystem into material's optoelectronic properties. The (3cp)PbBr₃ clearly shows the 2D quantum size effect with a bandgap around 3.2 eV and typical broadband self-trapped excitonic photoluminescence at temperatures below 200 K.     

Efficient Block Scheduling to Minimize Context Switching Time for Programmable Embedded Processors

Scheduling is one of the most often addressed optimization problems in DSP compilation, behavioral synthesis, and system-level synthesis research. With the rapid pace of changes in modern DSP applications requirements and implementation technologies, however, new types of scheduling challenges arise. This paper is concerned with the problem of scheduling blocks of computations in order to optimize the efficiency of their execution on programmable embedded systems under a realistic timing model of their processors. We describe an effective scheme for scheduling the blocks of any computation on a given system architecture and with a specified algorithm implementing each block. We also present algorithmic techniques for performing optimal block scheduling simultaneously with optimal architecture and algorithm selection. Our techniques address the block scheduling problem for both single- and multiple-processor system platforms and for a variety of optimization objectives including throughput, cost, and power dissipation. We demonstrate the practical effectiveness of our techniques on numerous designs and synthetic examples.     

Cross-linguistic studies of children's and adults' vowel spaces

This study examines cross-linguistic variation in the location of shared vowels in the vowel space across five languages (Cantonese, American English, Greek, Japanese, and Korean) and three age groups (2-year-olds, 5-year-olds, and adults). The vowels /a/, /i/, and /u/ were elicited in familiar words using a word repetition task. The productions of target words were recorded and transcribed by native speakers of each language. For correctly produced vowels, first and second formant frequencies were measured. In order to remove the effect of vocal tract size on these measurements, a normalization approach that calculates distance and angular displacement from the speaker centroid was adopted. Language-specific differences in the location of shared vowels in the formant values as well as the shape of the vowel spaces were observed for both adults and children.