Artifacts caused by simplicial subdivision

We review schemes for dividing cubic cells into simplices (tetrahedra) for interpolating from sampled data to R/sup 3/, present visual and geometric artifacts generated in isosurfaces and volume renderings, and discuss how these artifacts relate to the filter kernels corresponding to the subdivision schemes.     

Mechanism for Salt Scaling

Over the past 60 years, concrete infrastructure in cold climates has deteriorated by "salt scaling," which is superficial damage that occurs during freezing in the presence of saline water. It reduces mechanical integrity and necessitates expensive repair or replacement. The phenomenon can be demonstrated by pooling a solution on a block of concrete and subjecting it to freeze/thaw cycles. The most remarkable feature of salt scaling is that the damage is absent if the pool contains pure water, it becomes serious at concentrations of a few weight percent, and then stops at concentrations above about 6 wt%. In spite of a wealth of research, the mechanism responsible for this damage has only recently been identified. In this article, we show that salt scaling is a consequence of the fracture behavior of ice. The stress arises from thermal expansion mismatch between ice and concrete, which puts the ice in tension as the temperature drops. Considering the mechanical and viscoelastic properties of ice, it is shown that this mismatch will not cause pure ice to crack, but moderately concentrated solutions are expected to crack. Cracks in the brine ice penetrate into the substrate, resulting in superficial damage. At high concentrations, the ice does not form a rigid enough structure to result in significant stress, so no damage occurs. The morphology of cracking is predicted by fracture mechanics.     

Poly(styrene-block-vinylpyrrolidone) beads as a versatile material for simple fabrication of optical nanosensors

A versatile platform for designing optical nanosensors is proposed. The "sensing chemistries" are entrapped into the poly(styrene-block-vinylpyrrolidone) nanobeads having the average size of 245 nm in aqueous media. Addressable staining into the core or the shell of the beads results in nanosensors for essential analytes such as dissolved oxygen, temperature, pH, chloride, and copper ions. Two immobilization procedures are developed: staining in the polystyrene core is performed from a tetrahydrofuran/water mixture (50:50 v/v) and staining in the poly(vinylpyrrolidone) shell is achieved by using the ethanol/water mixture (70:30 v/v). The oxygen and temperature indicators should be preferably immobilized into the core, whereas nanosensors for ions are manufactured by staining into the shell. In the case of the lipophilic pH indicators both procedures result in similar pKa values. The unique properties of the beads make them promising for sensing and imaging even in very complex media, multianalyte sensing, and monitoring of very fast processes.     

Computer-aided design and synthesis of nonpeptidic plasmepsin II and IV inhibitors

Plasmepsins (Plm) II (EC number: 3.4.23.39) and IV (EC number: 3.4.23.B14) are aspartic proteases present in the food vacuole of the malaria parasite Plasmodium falciparum and are involved in host hemoglobin degradation. Based on our established efficient synthetic sequence, a series of inhibitors for Plm II and IV has been synthesized bearing a 2,3,4,7-tetrahydro-1H-azepine scaffold as the core structural element. During the computational design cycle, thorough investigations were carried out in order to find a reasonable theoretical binding mode for Plm II and IV. The conformation of Plm II in the crystal structure (PDB code: 1LF2) provides a good starting geometry for our virtual screening approach. In contrast, the only available co-crystal structure for Plm IV of P. falciparum (PDB code: 1LS5) appears inappropriate for inhibitor design. Therefore, a homology model was constructed based on the Plm II 1LF2 structure. A combinatorial docking run using FlexX(c) suggested compounds which, after synthesis, turned out to exhibit affinities in the sub-micromolar range. The observed structure-activity relationships of the synthesized compounds confirm the assumed binding mode for Plm II and IV. The best-binding inhibitors designed for Plm II and IV are devoid of any inhibitory potency against human cathepsin D (EC number: 3.4.23.5).     

Ultrasensitive in situ tracing of the alkaloid dioncophylline A in the tropical liana Triphyophyllum peltatum by applying deep-UV resonance Raman microscopy

UV resonance Raman microspectroscopy was applied for a localization of the antiplasmodial naphthylisoquinoline alkaloid dioncophylline A in very low concentrations in different parts of the samples (e.g., in the roots) of the tropical liana Triphyophyllum peltatum. The application of resonance Raman microspectroscopy was characterized by a very high sensitivity and selectivity. It was possible to assign the resonance Raman spectra of dioncophylline A, dioncophylline C, and dioncopeltine A by means of a combination of NIR Raman spectroscopy and DFT calculations. The UV resonance Raman spectra of T. peltatum are very well resembled by the spectra of dioncophylline A, while they can be clearly distinguished from the spectra of dioncophylline C and dioncopeltine A. This distinction between the various naphthylisoquinolines was possible by the two modes at 1356 and 1613 cm-1. These two modes were assigned to C=C stretching and CH bending vibrations. The presented results of a highly sensitive and selective in situ localization of the active agent dioncophylline A in different parts of the plant material of T. peltatum are of high importance for the acquisition of new antimalarials and for plant science in general.     

Cross-modal evaluative priming: Emotional sounds influence the processing of emotion words.

Cross-modal priming occurs when a prime presented in one sensory modality influences responses to a target in a different sensory modality. Currently, demonstrations of cross-modal evaluative priming have been sparse and limited. In the present study, we seek to partially rectify this state of affairs by examining cross-modal evaluative priming from auditory primes to visual targets. Significant cross-modal priming effects were found, but only for negative primes. Results are discussed in terms of the negativity bias, and several suggestions are provided for using cross-modal evaluative priming to address theoretically important questions about emotion and cognition. (PsycINFO Database Record (c) 2011 APA, all rights reserved)