Virtual geographic environments (VGE) are environments pertaining to the relationship between post-humans and 3-D virtual worlds. Post-humans are defined as a combination of humans in the real world with 3-D avatars in 3-D virtual worlds. Five types of space, namely Internet space, data space, 3-D graphical space, personal perceptual and cognitive space, and social space are used to explore the...

In this paper, we address two challenging issues underlying spatial cognitive simulation using software agents immersed in Virtual Geographic Environments (VGE). First, the way to describe virtual VGE models using accurate spatial decomposition approaches structured using graph theory techniques. Second, the use of graph abstraction techniques to realistically support advanced navigation and pa...

Cysteine cathepsins are lysosomal proteases involved in regulation of both normal cellular processes and disease. Biochemical studies with peptide substrates indicate that cathepsins have optimal activity at acidic pH and highly attenuated activity at neutral pH. In contrast, there is mounting evidence that cathepsins have biological roles in environments that have non-acidic pH. To further def...

A novel pH sensitive, colorimetric ionic liquid nanosensor based on phosphonium salts of fluorescein is reported. Herein, fluorescein salts of various stoichiometries were synthesized by use of a trihexyltetradecylphosphonium cation [TTP]+ in combination with dianionic [FL]2- and monoanionic [FL]- fluorescein. Nanomaterials derived from these two compounds yielded contrasting colorimetric respo...

A new type of viral-induced lysis system has recently been discovered for two unrelated archaeal viruses, STIV and SIRV2. Prior to the lysis of the infected host cell, unique pyramid-like lysis structures are formed on the cell surface by the protrusion of the underlying cell membrane through the overlying external S-layer. It is through these pyramid structures that assembled virions are relea...

Mycobacterium tuberculosis grows within the phagocytic vacuoles of macrophages, where it encounters a moderately acidic and possibly nutrient-restricted environment. Other mycobacterial species encounter acidic conditions in soil and aquatic environments. We have evaluated the influence of pH and divalent cation levels on the growth of M. tuberculosis and seven other mycobacterial species. In a...

A density functional theory (DFT) -based, combinatorial search for improved oxygen reduction reaction (ORR) catalysts is presented. A descriptor-based approach to estimate the ORR activity of binary surface alloys, wherein alloying occurs only in the surface layer, is described, and rigorous, potential-dependent computational tests of the stability of these alloys in aqueous, acidic environment...

Extremely halophilic microorganisms that accumulate KCl for osmotic balance (the Halobacteriaceae, Salinibacter) have a large excess of acidic amino acids in their proteins. This minireview explores the occurrence of acidic proteomes in halophiles of different physiology and phylogenetic affiliation. For fermentative bacteria of the order Halanaerobiales, known to accumulate KCl, an acidic prot...

Ambient pH strongly influences the synthesis of secreted enzymes, permeases and exported metabolites by a wide range of micro-organisms. For example, numerous microbes secrete acid phosphatase in acidic environments and alkaline phosphatase in alkaline environments. Only in the ascomycete Aspergillus nidulans, however, is characterization [ 1-51 of the pH-regulatory system sufficiently advanced...