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Structural Decay (structural + decay)

Distribution by Scientific Domains

Humanities and Social Sciences	60%

Selected Abstracts

GEOCHEMICAL AND ENGINEERING GEOLOGICAL PROPERTIES OF THE VOLCANIC TUFFS USED IN THE ETRUSCAN TOMBS OF NORCHIA (NORTHERN LATIUM, ITALY) AND A STUDY OF THE FACTORS RESPONSIBLE FOR THEIR RAPID SURFACE AND STRUCTURAL DECAY

ARCHAEOMETRY, Issue 2 2010
P. CICCIOLI
The geochemical and engineering geological properties of the tuffs used in the rock-cut cliff tombs of the Etruscan necropolis of Norchia were investigated to evaluate their susceptibility to different weathering agents and confirm their origin. For the first time, materials were characterized by X-ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT,IR), thermogravimetric analyses (TGA, DGA and DTG), scanning electron microscopy (SEM,EDS) and energy-dispersive X-ray fluorescence (ED,XRF), and their different origins confirmed. Tests of material properties indicate that both tuffs are poorly durable, but one of them is less susceptible to weathering. Although tombs made with the more resistant material show limited surface weathering, they undergo severe structural damage because of stress release and plant root infiltration. This, combined with the microclimatic conditions established inside river canyons, can trigger rock falls, leading ultimately to the complete destruction of these tombs. [source]

Organicism, Form and Structural Decay: Nielsen's Second Violin Sonata

MUSIC ANALYSIS, Issue 2 2002
Daniel Grimley
First page of article [source]

PUEBLO MISSION CHURCHES AS SYMBOLS OF PERMANENCE AND IDENTITY,

GEOGRAPHICAL REVIEW, Issue 3 2000
KEVIN S. BLAKE
ABSTRACT. The three Pueblo mission churches of San Esteban del Rey, Nuestra Señora de Guadalupe, and San José de Laguna are the most visually striking structures in the western New Mexico pueblos of Acoma, Zuni, and Laguna. Prime examples of "structures of permanence" on the landscape, the churches define local cultural identity. Church permanence and Pueblo identity are expressed in a five-part typology of visible characteristics: natural materials and hand labor, massive exterior form, adjoining cemeteries, syncretism of interior decorations, and structural decay and rebirth. Permanence must, however, be understood as an evolving condition, undergoing new representations as multicultural relationships evolve. [source]

Protein stability indicates divergent evolution of PD-(D/E)XK type II restriction endonucleases

PROTEIN SCIENCE, Issue 8 2002
Monika Fuxreiter
SC, stabilization center; PDB, Protein Data Bank Abstract Type II restriction endonucleases recognize 4,8 base-pair-long DNA sequences and catalyze their cleavage with remarkable specificity. Crystal structures of the PD-(DE)XK superfamily revealed a common ,/, core motif and similar active site. In contrast, these enzymes show little sequence similarity and use different strategies to interact with their substrate DNA. The intriguing question is whether this enzyme family could have evolved from a common origin. In our present work, protein structure stability elements were analyzed and compared in three parts of PD-(DE)XK type II restriction endonucleases: (1) core motif, (2) active-site residues, and (3) residues playing role in DNA recognition. High correlation was found between the active-site residues and those stabilization factors that contribute to preventing structural decay. DNA recognition sites were also observed to participate in stabilization centers. It indicates that recognition motifs and active sites in PD-(DE)XK type II restriction endonucleases should have been evolutionary more conserved than other parts of the structure. Based on this observation it is proposed that PD-(DE)XK type II restriction endonucleases have developed from a common ancestor with divergent evolution. [source]

"Natural restoration" can generate biological complexity

COMPLEXITY, Issue 2 2005
Emile ZuckerkandlArticle first published online: 16 DEC 200
Abstract Factor complexes engaged in transcriptional regulation of gene expression and their cognate DNA elements recurrently suffer mutational damage that can result in deadaptations in the mutual fit of interacting macromolecules. Such mutations can spread in populations by drift if their functional consequences are not severe. Mutational restorations of the damaged complexes may ensue and can take many forms. One of these forms would represent spontaneous increases in gene interaction complexity and correlated aspects of organismic complexity. In this particular mode of restoration, restabilization of a factor/factor/DNA complex occurs through the binding of an additional factor. Factors added under such circumstances to regulatory kits of individual genes are thought to be at the origin of a slow but persistent "complexity drive." This drive seems to be resisted in many forms whose developmental outcome has reached a finish line difficult to pass, but imposes itself along other lines of phylogenetic descent. In the process of restoration by an additional factor, the chances are significant that the original regulatory control of a target gene is not recovered exactly and that the restored gene expression has novel spatial, temporal, or quantitative characteristics. These new characteristics, which represent a functional transfer of the gene to a new domain of activity, may be selectable, even when the physicochemical properties of the gene product have remained largely unchanged. As a consequence of such activity transfers under quasi-constancy of the molecular properties of the protein encoded by the regulation's target gene, the activity domain originally covered by that target gene may be left at least in part functionally vacant. At that point, an unmodified duplicate of the target gene and of its original regulatory dependencies probably becomes in turn selectable. A causal link is therefore predicted between the regulatory specialization and selection of one of two duplicates and the regulatory maintenance and selection of the other. A conserved increase in gene number would result indirectly from the regulatory shift in paralogs, and the organism's complexity would be increased in this sense also, complexity as number of genes in addition to complexity as number of regulatory factors per gene. It is thus proposed that increased biological complexity, innovation in the gene regulatory network, and the development of a novel evolutionary potential can be the result, counterintuitively, of conservative forces that intervene when mutations play a survivable form of havoc with the system of gene regulation. Increasing complexity, then, could be seen as one of the side effects of "natural restoration." This phrase designates the mutational re-establishment in the gene whose regulation has been damaged of a functionally effective activity pattern, albeit, perhaps, with changes in its mode of expression in regard to location, time, and rate. The higher complexity, innovation in the gene regulatory network, of higher organisms,their very character of higher organisms,would to a significant extent be a side effect of episodes of natural selection aimed at functional restoration, not at complexity itself. Regulatory impairment, the point of departure of the process outlined, represents a controller gene disease. It thus may well be the case that molecular diseases, the effects on the individual of inheritable structural decay, are among the conditions of the evolution of higher organisms. © 2005 Wiley Periodicals, Inc. Complexity 11: 14,27, 2005 [source]