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Structural Elements (structural + element)
Kinds of Structural Elements Selected AbstractsThe nurse's odyssey: the professional folktale in New Zealand backblocks nurses' stories, 1910,1915NURSING INQUIRY, Issue 2 2009Pamela J WoodArticle first published online: 12 MAY 200 Nurses have a long tradition of storytelling. Nurses in the New Zealand government's Backblocks Nursing Service, established in 1909 for settlers in remote rural areas, related narratives of personal experience in articles, conference papers and letters to their chief nurse that were published in the country's nursing journal. Analysis of the 16 stories published between 1910 and 1915 revealed 14 had a common storyline and structure. Structural elements included a call, arduous journey, arrival and reconnaissance, trial (difficult case or circumstance), resolution and homily. Using a literary folkloristics approach, this article argues that repetition of the story by nurses in different regions traditionalised it as a professional folktale, ,The nurse's odyssey'. It enabled nurses to debrief from difficult cases and write-into-being this new role and practice. Striking differences in the practice setting ensured the story's reportability, while clinical details connected writer and readers through a common professional aesthetic context and strengthened the story's credibility. For the chief nurse who was also a journal editor, publishing the stories allowed her to potentially attract nurses to the service while alerting them to its harsh realities, and show policy-makers the profession's value in meeting new health service needs. [source] Myosin-mediated cytoskeleton contraction and Rho GTPases regulate laminin-5 matrix assemblyCYTOSKELETON, Issue 2 2004Gregory W. deHart Abstract Laminin-5 is a major structural element of epithelial tissue basement membranes. In the matrix of cultured epithelial cells, laminin-5 is arranged into intricate patterns. Here we tested a hypothesis that myosin II-mediated actin contraction is necessary for the proper assembly of a laminin-5 matrix by cultured SCC12 epithelial cells. To do so, the cells were treated with ML-7, a myosin II light chain kinase inhibitor, or Y-27632, an inhibitor of Rho-kinase (ROCK), both of which block actomyosin contraction. Under these conditions, laminin-5 shows an aberrant localization in dense patches at the cell periphery. Since ROCK activity is regulated by the small GTPase Rho, this suggests that members of the Rho family of GTPases may also be important for laminin-5 matrix assembly by SCC12 cells. We confirmed this hypothesis since SCC12 cells expressing mutant proteins that inhibit RhoA, Rac, and Cdc42 assemble the same aberrant laminin-5 protein arrays as drug-treated cells. We have also evaluated the organization of the laminin-5 receptors ,3,1 and ,6,4 integrin and hemidesmosome proteins in ML-7- and Y-27632-treated cells or in cells in which RhoA, Rac, and Cdc42 activity were inhibited. In all instances, ,3,1 and ,6,4 integrin heterodimers, as well as hemidesmosome proteins, localize precisely with laminin-5 in the matrix of the cells. In summary, our results provide evidence that myosin II-mediated actin contraction and the activity of Rho GTPases are necessary for the proper organization of a laminin-5 matrix and localization of hemidesmosome protein arrays in epithelial cells. Cell Motil. Cytoskeleton 57:107,117, 2004. © 2004 Wiley-Liss, Inc. [source] Structural modeling and mutational analysis of yeast eukaryotic translation initiation factor 5A reveal new critical residues and reinforce its involvement in protein synthesisFEBS JOURNAL, Issue 8 2008Camila A. O. Dias Eukaryotic translation initiation factor 5A (eIF5A) is a protein that is highly conserved and essential for cell viability. This factor is the only protein known to contain the unique and essential amino acid residue hypusine. This work focused on the structural and functional characterization of Saccharomyces cerevisiae eIF5A. The tertiary structure of yeast eIF5A was modeled based on the structure of its Leishmania mexicana homologue and this model was used to predict the structural localization of new site-directed and randomly generated mutations. Most of the 40 new mutants exhibited phenotypes that resulted from eIF-5A protein-folding defects. Our data provided evidence that the C-terminal ,-helix present in yeast eIF5A is an essential structural element, whereas the eIF5A N-terminal 10 amino acid extension not present in archaeal eIF5A homologs, is not. Moreover, the mutants containing substitutions at or in the vicinity of the hypusine modification site displayed nonviable or temperature-sensitive phenotypes and were defective in hypusine modification. Interestingly, two of the temperature-sensitive strains produced stable mutant eIF5A proteins , eIF5AK56A and eIF5AQ22H,L93F, and showed defects in protein synthesis at the restrictive temperature. Our data revealed important structural features of eIF5A that are required for its vital role in cell viability and underscored an essential function of eIF5A in the translation step of gene expression. [source] Structural characterization of a novel branching pattern in the lipopolysaccharide from nontypeable Haemophilus influenzaeFEBS JOURNAL, Issue 14 2003Martin Månsson Structural analysis of the lipopolysaccharide (LPS) from nontypeable Haemophilus influenzae strain 981 has been achieved using NMR spectroscopy and ESI-MS on O -deacylated LPS and core oligosaccharide (OS) material as well as by ESI-MSn on permethylated dephosphorylated OS. A heterogeneous glycoform population was identified, resulting from the variable length of the OS branches attached to the glucose residue in the common structural element of H. influenzae LPS, l -,- d -Hepp -(1,2)-[PEtn,6]- l -,- d -Hepp -(1,3)-[,- d -Glcxp-(1,4)]- l -,- d -Hepp -(1,5)-[PPEtn,4]-,-Kdop -(2,6)-Lipid A. Notably, the O-6 position of the ,- d -Glcp residue was either substituted by PCho or the disaccharide branch ,- d -Galp -(1,4)- d -,- d -Hepp, while the O-4 position was substituted by the globotetraose unit, ,- d -GalpNAc-(1,3)-,- d -Galp -(1,4)-,- d -Galp -(1,4)-,- d -Glcp, or sequentially truncated versions thereof. This is the first time a branching sugar residue has been reported in the outer-core region of H. influenzae LPS. Additionally, a PEtn group was identified at O-3 of the distal heptose residue in the inner-core. [source] Structural analysis of the lipopolysaccharide from nontypeable Haemophilus influenzae strain 1003FEBS JOURNAL, Issue 3 2002Martin Månsson Structural analysis of the lipopolysaccharide (LPS) of nontypeable Haemophilus influenzae strain 1003 has been achieved by the application of high-field NMR techniques, ESI-MS, capillary electrophoresis coupled to ESI-MS, composition and linkage analyses on O-deacylated LPS,and core oligosaccharide material. It was found that,the LPS contains the common structural element of,H. influenzae, l -,- d -Hepp -(1,2)-[PEtn,6]- l -,- d -Hepp -(1,3)-[,- d -Glcp -(1,4)]- l -,- d -Hepp -(1,5)-[PP Etn,4]-,-Kdop -(2,6)-Lipid A, in which the ,- d -Glcp residue is substituted by phosphocholine at O-6 and an acetyl group at O-4. A second acetyl group is located at O-3 of the distal heptose residue (HepIII). HepIII is chain elongated at O-2 by either a ,- d -Glcp residue (major), lactose or sialyllactose (minor, i.e. ,-Neu5Ac-(2,3)-,- d -Galp -(1,4)-,- d -Glcp), where a third minor acetylation site was identified at the glucose residue. Disialylated species were also detected. In addition, a minor substitution of ester-linked glycine at HepIII and Kdo was observed. [source] Peptidoglycan structure and architectureFEMS MICROBIOLOGY REVIEWS, Issue 2 2008Waldemar Vollmer Abstract The peptidoglycan (murein) sacculus is a unique and essential structural element in the cell wall of most bacteria. Made of glycan strands cross-linked by short peptides, the sacculus forms a closed, bag-shaped structure surrounding the cytoplasmic membrane. There is a high diversity in the composition and sequence of the peptides in the peptidoglycan from different species. Furthermore, in several species examined, the fine structure of the peptidoglycan significantly varies with the growth conditions. Limited number of biophysical data on the thickness, elasticity and porosity of peptidoglycan are available. The different models for the architecture of peptidoglycan are discussed with respect to structural and physical parameters. [source] Two conserved structural components, A-rich bulge and P4 XJ6/7 base-triples, in activating the group I ribozymesGENES TO CELLS, Issue 12 2002Yoshiya Ikawa Background: The A-rich bulge of the group I intron ribozyme, a highly conserved structural element in its P5 peripheral region, plays a significant role in activating the ribozyme. The bulge has been known to interact with the P4 stem forming P4 XJ6/7 base-triples in the conserved core. The base-triples by themselves have also been identified as a distinctive element responsible for enhancing the activity of the ribozyme. Results: A weakly active variant of the Tetrahymena ribozyme lacking the P5 extension was dramatically activated by the addition of an A-rich bulge at the peripheral region, or by replacement of the original P4 XJ6/7 base-triples in the core structure with more stabilized isosteric ones. Biochemical analyses showed that the two methods of activation affect the ribozyme differently. Conclusions: The long-range interaction between the A-rich bulge and P4 or additionally stabilized P4 XJ6/7 base-triples can contribute dramatically to activation of the Tetrahymena ribozyme. Both improve the kcat value, which represents the rate of the limiting step of the ribozyme reaction when its binding site is saturated with GTP. However, the bulge or the modified base-triples gave a moderate reduction or considerable increase, respectively, to the Km(GTP) value. [source] Dynamic Hydrogels: Switching of 3D Microenvironments Using Two-Component Naturally Derived Extracellular Matrices (Adv. Mater.ADVANCED MATERIALS, Issue 6 20106/2010) The front cover image depicts a two-component extracellular matrix (ECM) in which one component acts as a stable structural element (which supports cell attachment and migration) and another component gels or dissolves reversibly (a modulatory component). Samuel K. Sia and co-workers show on p. 686 that by dynamically adding or removing crosslinks in the modulatory component, properties of the composite ECM, such as the ability of cells to migrate and the rate of diffusive transport, can be altered. [source] Dynamic Hydrogels: Switching of 3D Microenvironments Using Two-Component Naturally Derived Extracellular MatricesADVANCED MATERIALS, Issue 6 2010Brian M. Gillette This article describes fabrication of a two-component extracellular matrix (ECM) in which one component acts as a stable structural element and another component gels or dissolves reversibly (a modulatory component). Using a composite collagen-alginate ECM, reversible crosslinking of the alginate (the modulatory component) via application of calcium or citrate modulates cell mobility in a 3D collagen matrix (the structural component). [source] Second-order analysis and design of steel structures allowing for member and frame imperfectionsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2005J. X. Gu Abstract Conventional linear analysis is deficient in handling the design of slender frames since the effective length and other non-linear effects are difficult to assess accurately. Some proposed non-linear analyses cannot be directly employed for practical design since they are unable to re-produce the buckling curves of the basic structural element, a simple column under axial force, by a single element per member. This paper describes an advanced element, using the same physical significance as the advanced and second-order analysis proposed by a number of researchers and the BS5950(2000) and AS4100 (1995), for practical design of slender steel frames. The proposed element captures the physical behaviour of a structural member that the buckling strength of the member can be predicted using a single element per member and without assuming any effective length. Copyright © 2004 John Wiley & Sons, Ltd. [source] Stabilization of collagen by the plant polyphenolics Acacia mollissima and Terminalia chebulaJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008G. Krishnamoorthy Abstract The central role of collagen as the major structural fibrous protein in the mammalian extracellular matrix has motivated a significant effort toward the determination of its mechanical properties at all levels, ranging from single monomers and long-chain polymers to a structural element within a biological tissue. However, the stabilization of collagen against collagenolytic degradation finds significance in biomedical and industrial applications. Tannins are plant-derived polyphenols that have the ability to inhibit the collagenase activity at minimum concentration. The inhibitory effect of wattle (Acacia mollissima) and myrobalan (Terminalia chebula) on the action of collagenase against collagen was probed in this study. The kinetics of the inhibition of collagenase by wattle and myrobalan was deduced from the extent of hydrolysis of 2-furanacryloyl,L -leucyl,glycyl,L -prolyl,L -alanine. Both wattle and myrobalan tannin exhibited competitive modes of inhibition against collagenase. Circular dichroism studies of collagenase on treatment with wattle and myrobalan revealed changes in the secondary structure of collagenase. These results suggest that the tannins of A. mollissima and T. chebula extracts facilitated collagen stabilization through collagenase inhibition. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Inhibition of acetylcholinesterase by physostigmine analogs: Conformational mobility of cysteine loop due to the steric effect of the alkyl chainJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 2 2002Enrico Gavuzzo Abstract The effect of a series of physostigmine analogs on acetylcholinesterase activity was investigated. The second-order rate constant kon of the enzyme,inhibitor complex correlates with the conformational positioning of aromatic residues, especially Trp84, in the transition state complex. The van der Waals interactions are an important structural element of this conformational change. A transient mobility of the cysteine loop (Cys67,Cys94) was confined only to the presence of a significant steric effect. Even with this limitation, however, the steric effect seems to be an appropriate model for future tests on the "back door" hypothesis involving facilitated opening for faster product clearance. © 2002 Wiley Periodicals, Inc. J Biochem Mol Toxicol 16:64,69, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/jbt.10026 [source] Influence of "Alternative" C-terminal amino acids on the formation of [b3 + 17 + Cat]+ products from metal cationized synthetic tetrapeptides,JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 5 2004V. Anbalagan Abstract The aim of this study was to investigate the dissociation patterns, and in particular the relative abundance of [b3 + 17 + Cat]+, for peptides with C-termini designed to allow transfer of the ,OH required to generate the product ion, but not necessarily as the most favored pathway. Working with the hypothesis that formation of a five-membered ring intermediate, including intramolecular nucleophilic attack by a carbonyl oxygen atom, is an important mechanistic step, several model peptides with general sequence AcFGGX were synthesized, metal cationized by electrospray ionization and subjected to collision-induced dissociation (CID). The amino acid at position X was one that either required a larger ring intermediate (,-alanine, ,-aminobutyric acid and ,-amino- n -caproic acid to generate six-, seven- or nine- membered rings, respectively) to transfer ,OH, lacked a structural element required for nucleophilic attack (aminoethanol) or prohibited cyclization because of the inclusion of a rigid ring (p - and m -aminobenzoic acid). For Ag+, Li+ and Na+ cationized peptides, our results show that amino acids requiring the adoption of larger ring intermediates suppressed the formation of [b3 + 17 + Cat]+, while amino acids that prohibit cyclization eliminated the reaction pathway completely. Formation of [b3 , 1 + Cat]+ from the alkali metal cationized versions was not a favorable process upon suppression or elimination of the [b3 + 17 + Cat]+ pathway: the loss of H2O to form [M , H2O + Cat]+ was instead the dominant dissociation reaction observed. Multiple-stage dissociation experiments suggest that [M , H2O + Cat]+ is not [b4 , 1 + Cat]+ arising from the loss of H2O from the C-terminus, but may instead be a species that forms via a mechanism involving the elimination of an oxygen atom from an amide group. Copyright © 2004 John Wiley & Sons, Ltd. [source] Evidence for a role of the N-terminal domain in subcellular localization of the neuronal connexin36 (Cx36)JOURNAL OF NEUROSCIENCE RESEARCH, Issue 4 2002G. Zoidl Abstract The expression and functional properties of connexin36 (Cx36) have been investigated in two neuroblastoma cell lines (Neuro2A, RT4-AC) and primary hippocampal neurons transfected with a Cx36-enhanced green fluorescent protein (EGFP) expression vector. Transfected cells express Cx36-EGFP mRNA, and Cx36-EGFP protein is localized in the perinuclear area and cell membrane. Upon differentiation of cell lines, Cx36-EGFP protein was detectable in processes with both axonal and dendritic characteristics. Small gap junction plaques were found between adjacent cells, and electrophysiological recordings demonstrated that the electrical properties of these gap junctions were virtually indistinguishable from those reported for native Cx36. Mutagenesis of Cx36 led to the identification of a structural element that interferes with normal protein localization. In contrast, site directed mutagenesis of putative protein phosphorylation motifs did not alter subcellular localization. This excludes phosphorylation/dephosphorylation as a major regulatory step in Cx36 protein transport. © 2002 Wiley-Liss, Inc. [source] Tendon-defect and muscle-unloaded models for relating a rotator cuff tear to glenohumeral stabilityJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 6 2000Horng-Chaung Hsu Rotator cuff tear and glenohumeral instability are closely related. Any tear may disturb muscle force generation due to pain inhibition. In addition, a full-thickness tear may foster instability by removing a structural element constraining the joint. It was hypothesized that the loss of both dynamic force and static constraint with a rotator cuff tear will affect glenohumeral stability. In a tendon-defect model, dynamic and static elements of the joint were sacrificed. In a muscle-unloaded model, only the dynamic element was removed. The location and size of the defect were also investigated. The effect on instability of a small tendon defect was less than that of muscle unloading, implying that a patient with a small tear would have less instability than a patient with weak or nonfunctioning supraspinatus and infraspinatus muscles. On the other hand, with a larger tear the defect had a greater effect than muscle-unloading because sectioning of the glenohumeral and coracohumeral ligaments was included in the model. Clinically, such a defect in the front is critical for anterior stability because it might insult the important anterior capsule ligamentous complex. Orthopaedic surgeons should pay attention, therefore, to the effect of possible associated lesions of static constraints based on the size and location of the tear in addition to the dynamic stabilizer. [source] Rev response elements (RRE) in lentiviruses: An RNAMotif algorithm-based strategy for RRE predictionMEDICINAL RESEARCH REVIEWS, Issue 6 2002Elena A. Lesnik Abstract Lentiviruses (a sub-family of the retroviridae family) include primate and non-primate viruses associated with chronic diseases of the immune system and the central nervous system. All lentiviruses encode a regulatory protein Rev that is essential for post-transcriptional transport of the unspliced and incompletely spliced viral mRNAs from nuclei to cytoplasm. The Rev protein acts via binding to an RNA structural element known as the Rev responsive element (RRE). The RRE location and structure and the mechanism of the Rev-RRE interaction in primate and non-primate lentiviruses have been analyzed and compared. Based on structural data available for RRE of HIV-1, a two step computational strategy for prediction of putative RRE regions in lentivirus genomes has been developed. First, the RNAMotif algorithm was used to search genomic sequence for highly structured regions (HSR). Then the program RNAstructure, version 3.6 was used to calculate the structure and thermodynamic stability of the region of , 350 nucleotides encompassing the HSR. Our strategy correctly predicted the locations of all previously reported lentivirus RREs. We were able also to predict the locations and structures of potential RREs in four additional lentiviruses. © 2002 Wiley Periodicals, Inc. Med Res Rev, 22, No. 6, 617,636, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/med.10027 [source] Cleavage of the iron-methionine bond in c-type cytochromes: Crystal structure of oxidized and reduced cytochrome c2 from Rhodopseudomonas palustris and its ammonia complexPROTEIN SCIENCE, Issue 1 2002Silvano Geremia Abstract The three-dimensional structures of the native cytochrome c2 from Rhodopseudomonas palustris and of its ammonia complex have been obtained at pH 4.4 and pH 8.5, respectively. The structure of the native form has been refined in the oxidized state at 1.70 Å and in the reduced state at 1.95 Å resolution. These are the first high-resolution crystal structures in both oxidation states of a cytochrome c2 with relatively high redox potential (+350 mV). The differences between the two oxidation states of the native form, including the position of internal water molecules, are small. The unusual six-residue insertion Gly82-Ala87, which precedes the heme binding Met93, forms an isolated 310 -helix secondary structural element not previously observed in other c-type cytochromes. Furthermore, this cytochrome shows an external methionine residue involved in a strained folding near the exposed edge of the heme. The structural comparison of the present cytochrome c2 with other c-type cytochromes has revealed that the presence of such a residue, with torsion angles , and , of approximately ,140 and ,130°, respectively, is a typical feature of this family of proteins. The refined crystal structure of the ammonia complex, obtained at 1.15 Å resolution, shows that the sulphur atom of the Met93 axial ligand does not coordinate the heme iron atom, but is replaced by an exogenous ammonia molecule. This is the only example so far reported of an X-ray structure with the heme iron coordinated by an ammonia molecule. The detachment of Met93 is accompanied by a very localized change in backbone conformation, involving mainly the residues Lys92, Met93, and Thr94. Previous studies under typical denaturing conditions, including high-pH values and the presence of exogenous ligands, have shown that the detachment of the Met axial ligand is a basic step in the folding/unfolding process of c-type cytochromes. The ammonia adduct represents a structural model for this important step of the unfolding pathway. Factors proposed to be important for the methionine dissociation are the strength of the H-bond between the Met93 and Tyr66 residues that stabilizes the native form, and the presence in this bacterial cytochrome c2 of the rare six-residue insertion in the helix 310 conformation that increases Met loop flexibility. [source] Maximum-likelihood density modification using pattern recognition of structural motifsACTA CRYSTALLOGRAPHICA SECTION D, Issue 12 2001Thomas C. Terwilliger The likelihood-based approach to density modification [Terwilliger (2000), Acta Cryst. D56, 965,972] is extended to include the recognition of patterns of electron density. Once a region of electron density in a map is recognized as corresponding to a known structural element, the likelihood of the map is reformulated to include a term that reflects how closely the map agrees with the expected density for that structural element. This likelihood is combined with other aspects of the likelihood of the map, including the presence of a flat solvent region and the electron-density distribution in the protein region. This likelihood-based pattern-recognition approach was tested using the recognition of helical segments in a largely helical protein. The pattern-recognition method yields a substantial phase improvement over both conventional and likelihood-based solvent-flattening and histogram-matching methods. The method can potentially be used to recognize any common structural motif and incorporate prior knowledge about that motif into density modification. [source] Structure of native laccase B from Trametes sp.ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 3 2010AH28- Fungal laccases are oxidoreductases that belong to the multinuclear copper-containing oxidases. They are able to oxidize a wide range of substrates, preferably phenolic compounds, which makes them suitable for employment in the bioremediation of soil and water as well as in other biotechnological applications. Here, the structural analysis of natural laccase B (LacB) from Trametes sp. AH28-2 is presented. This structure provides the opportunity to study the natural post-translational modifications of the enzyme. The overall fold shows a high homology to those of previously analyzed laccases with known three-dimensional structure. However, LacB contains a new structural element, a protruding loop near the substrate-binding site, compared with the previously reported laccase structures. This unique structural feature may be involved in modulation of the substrate recognition of LacB. [source] Design of passive systems for control of inelastic structuresEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 6 2009Gian Paolo Cimellaro Abstract A design strategy for control of buildings experiencing inelastic deformations during seismic response is formulated. The strategy is using weakened, and/or softened, elements in a structural system while adding passive energy dissipation devices (e.g. viscous fluid devices, etc.) in order to control simultaneously accelerations and deformations response during seismic events. A design methodology is developed to determine the locations and the magnitude of weakening and/or softening of structural elements and the added damping while insuring structural stability. A two-stage design procedure is suggested: (i) first using a nonlinear active control algorithm, to determine the new structural parameters while insuring stability, then (ii) determine the properties of equivalent structural parameters of passive system, which can be implemented by removing or weakening some structural elements, or connections, and by addition of energy dissipation systems. Passive dampers and weakened elements are designed using an optimization algorithm to obtain a response as close as possible to an actively controlled system. A case study of a five-story building subjected to El Centro ground motion, as well as to an ensemble of simulated ground motions, is presented to illustrate the procedure. The results show that following the design strategy, a control of both peak inter-story drifts and total accelerations can be obtained. Copyright © 2008 John Wiley & Sons, Ltd. [source] Inelastic spectra for infilled reinforced concrete framesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 15 2004Matja Abstract In two companion papers a simplified non-linear analysis procedure for infilled reinforced concrete frames is introduced. In this paper a simple relation between strength reduction factor, ductility and period (R,µ,T relation) is presented. It is intended to be used for the determination of inelastic displacement ratios and of inelastic spectra in conjunction with idealized elastic spectra. The R,µ,T relation was developed from results of an extensive parametric study employing a SDOF mathematical model composed of structural elements representing the frame and infill. The structural parameters, used in the proposed R,µ,T relation, in addition to the parameters used in a usual (e.g. elasto-plastic) system, are ductility at the beginning of strength degradation, and the reduction of strength after the failure of the infills. Formulae depend also on the corner periods of the elastic spectrum. The proposed equations were validated by comparing results in terms of the reduction factors, inelastic displacement ratios, and inelastic spectra in the acceleration,displacement format, with those obtained by non-linear dynamic analyses for three sets of recorded and semi-artificial ground motions. A new approach was used for generating semi-artificial ground motions compatible with the target spectrum. This approach preserves the basic characteristics of individual ground motions, whereas the mean spectrum of the whole ground motion set fits the target spectrum excellently. In the parametric study, the R,µ,T relation was determined by assuming a constant reduction factor, while the corresponding ductility was calculated for different ground motions. The mean values proved to be noticeably different from the mean values determined based on a constant ductility approach, while the median values determined by the different procedures were between the two means. The approach employed in the study yields a R,µ,T relation which is conservative both for design and performance assessment (compared with a relation based on median values). Copyright © 2004 John Wiley & Sons, Ltd. [source] Casualty occurrence mechanism in the collapse of timber-frame houses during an earthquakeEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 12 2004Junji Kiyono Abstract The collapse of timber-frame houses during an earthquake was analyzed by the 2-dimensional (2D) and 3-dimensional (3D) distinct element methods (DEM). The DEM is a numerical analysis technique in which positions of elements are calculated by solving equations of motion step by step. Both individual and group behavior can be simulated. The structure is modeled as an assembly of distinct elements connected by virtual springs and dashpots where elements come into contact. A timber-frame house with simple structural elements; beams, columns, floors, and a roof, was modeled. Injury to human bodies also was considered. Human bodies modeled as circles (2D) or rectangular parallelepipeds (3D) were placed on its floors. The maximum impact acceleration on the human body during an earthquake was calculated. Injury to humans in houses was assessed by the Chest-G index and Head Injury Criteria (HIC) widely used in automobile engineering. Copyright © 2004 John Wiley & Sons, Ltd. [source] Effects of column axial force , bending moment interaction on inelastic seismic response of steel framesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 12 2003Marina Como Abstract It is well known that axial force , bending moment interaction (N,M interaction) affects to a large extent the cyclic inelastic behaviour of structural elements, especially columns in framed structures, with reduction in bending capacity and loss of available ductility. A few studies have also shown that significant inelastic axial shortening affects the response of column elements subjected to medium,high levels of axial loads and cyclic bending. This paper is primarily aimed at evaluating the effects of column N,M interaction on the inelastic seismic response of steel frames. By considering the contemporaneous action of vertical loads, due to gravity, and of horizontal seismic excitation, it is shown that the progressive axial shortening of adjacent columns may differ substantially, thus inducing significant relative settlements at the ends of the connecting beams and, then, remarkable amplifications in beam plastic rotations. An evaluation of additional beam plastic rotations induced by column N,M interaction is carried out for real structures by investigating the inelastic response of steel frames designed according to European standards under horizontal and vertical earthquake excitations. Copyright © 2003 John Wiley & Sons, Ltd. [source] Torsional response of symmetric buildings to incoherent and phase-delayed earthquake ground motionEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 7 2003Ernesto Heredia-Zavoni Abstract This paper studies the effect of coherency loss and wave passage on the seismic torsional response of three-dimensional, multi-storey, multi-span, symmetric, linear elastic buildings. A model calibrated against statistical analyses of ground motion records in Mexico City is used for the coherency function. The structural response is assessed in terms of shear forces in structural elements. Incoherence and wave passage effects are found to be significant only for columns in the ground level of stiff systems. The increase of column shears in the ground level is much higher for soft than for firm soil conditions. For the torsionally stiff systems considered, it is found that incoherent and phase-delayed ground motions do not induce a significant rotational response of the structure. The use of a code eccentricity to account for torsion due to ground motion spatial variation is assessed. On firm soil, the use of a base shear along with an accidental eccentricity results in highly overestimated shear forces; however, for soft soil conditions, code formulations may result in underestimated shear forces. Copyright © 2003 John Wiley & Sons, Ltd. [source] Shaking table tests of 1:4 reduced-scale models of masonry infilled reinforced concrete frame buildingsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 6 2001Abstract Two models of masonry infilled reinforced concrete frame buildings were tested at the shaking table. Models were built in the reduced scale 1:4 using the materials produced in accordance to modelling demands of true replica modelling technique. The first model represented a one-storey box-like building and the second one the two-stories building with plan shaped in the form of a letter H. Models were shaken with the series of horizontal sine dwell motions with gradually increasing amplitude. Masonry infills of tested models were constructed of relatively strong bricks laid in weak mortar. Therefore, typical cracks developed and propagated along mortar beds without cracking of bricks or crushing of infill corners. Data collected from tests will be used in future evaluation, verification and development of computational models for prediction of in-plane and out-of-plane behaviour of masonry infills. The responses of tested models can be well compared with global behaviour of real structures using the modelling rules. The similarity of local behaviour of structural elements, e.g. reinforced concrete joints, is less reliable due to limitations in modelling of steel reinforcement properties. The model responses showed that buildings designed according to Eurocodes are able to sustain relatively high dynamic excitations due to a significant level of structural overstrength. Copyright © 2001 John Wiley & Sons, Ltd. [source] Using DNA sequencing electrophoresis compression artifacts as reporters of stable mRNA structures affecting gene expressionELECTROPHORESIS, Issue 21 2007Divya Kapoor Abstract The formation of secondary structure in oligonucleotide DNA is known to lead to "compression" artifacts in electropherograms produced through DNA sequencing. Separately, the formation of secondary structure in mRNA is known to suppress translation; in particular, when such structures form in a region covered by the ribosome either during, or shortly after, initiation of translation. Here, we demonstrate how a DNA sequencing compression artifact provides important clues to the location(s) of translation-suppressing secondary structural elements in mRNA. Our study involves an engineered version of a gene sourced from Rhodothermus marinus encoding an enzyme called Cel12A. We introduced this gene into Escherichia coli with the intention of overexpressing it, but found that it expressed extremely poorly. Intriguingly, the gene displayed a remarkable compression artifact during DNA sequencing electrophoresis. Selected "designer" silent mutations destroyed the artifact. They also simultaneously greatly enhanced the expression of the cel12A gene, presumably by destroying stable mRNA structures that otherwise suppress translation. We propose that this method of finding problem mRNA sequences is superior to software-based analyses, especially if combined with low-temperature CE. [source] Rational design of new CpG oligonucleotides that combine B cell activation with high IFN-, induction in plasmacytoid dendritic cellsEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 6 2003Gunther Hartmann Abstract Two different types of CpG motif-containing oligonucleotides (CpG ODN) have been described: CpG-A with high induction of IFN-, in plasmacytoid dendritic cells; and CpG-B with little induction of IFN-,, but potent activation of B cells. In this study, we demonstrate that CpG-A fail to activate B cells unless plasmacytoid dendritic cells are present. We identified a new set of CpG ODN sequences which induces high levels of IFN-, in plasmacytoid dendritic cells but remains capable of directly activating B cells. These new CpG ODN (termed CpG-C) are more potent stimulants of B cells than CpG-B due to their ability of directly and indirectly (via plasmacytoid dendritic cells) activating B cells. The sequence of CpG-C combines structural elements of both CpG-A and CpG-B. The most potent sequence, M362, contains a 5,-end ,TCGTCG-motif' and a ,GTCGTT-motif', both of which are present in CpG-B (ODN,2006); a palindromic sequence characteristic for CpG-A (ODN,2216); but no poly,G motif required for CpG-A. In conclusion, we defined the first CpG-containing sequences that potently activate both TLR9-expressing immune cell subsets in humans, the plasmacytoid dendritic cell and the B cell. CpG-C may allow for improved therapeutic immuno-modulation in vivo. [source] Enzymes in the acquired enamel pellicleEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 1 2005Christian Hannig The acquired pellicle is a biofilm, free of bacteria, covering oral hard and soft tissues. It is composed of mucins, glycoproteins and proteins, among which are several enzymes. This review summarizes the present state of research on enzymes and their functions in the dental pellicle. Theoretically, all enzymes present in the oral cavity could be incorporated into the pellicle, but apparently enzymes are adsorbed selectively onto dental surfaces. There is clear evidence that enzymes are structural elements of the pellicle. Thereby they exhibit antibacterial properties but also facilitate bacterial colonization of dental hard tissues. Moreover, the immobilized enzymes are involved in modification and in homeostasis of the salivary pellicle. It has been demonstrated that amylase, lysozyme, carbonic anhydrases, glucosyltransferases and fructosyltransferase are immobilized in an active conformation in the pellicle layer formed in vivo. Other enzymes, such as peroxidase or transglutaminase, have been investigated in experimental pellicles. Despite the depicted impact of enzymes on the formation and function of pellicle, broader knowledge on their properties in the in vivo -formed pellicle is required. This might be beneficial in the development of new preventive and diagnostic strategies. [source] 6-Deoxy-,- L -talopyranosides from Streptomyces sp.,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 16 2006Jens Bitzer Abstract Streptomyces sp. strain GöM1 was found to produce seven novel glycosides (2,8) containing the rare deoxysugar 6-deoxy-,- L -talose. The aglycones are small phenols, isovaleric acid or aromatic carboxylic acids. By precursor-directed biosynthesis, the yields of the compounds could be increased significantly. Feeding of 4-hydroxybenzoic acid led to the production of both acyl and aryl glycosides, and of compound 9 with both structural elements. Pyrrol-2-ylcarbonyl 6-deoxy-,- L -talopyranoside (6) shows remarkable growth inhibition of some parasites. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] A strategy for correlative microscopy of large skin samples: towards a holistic view of axillary skin complexityEXPERIMENTAL DERMATOLOGY, Issue 1 2008Katrin Wilke Abstract:, Knowledge about the structural elements of skin and its appendices is an essential prerequisite for understanding their complex functions and interactions. The hence necessary morphological description across several orders of scale not only requires the investigation at the light microscopic level but also ultrastructural investigation, ideally on the identical sample. For a correlative and multimodal observation one unique preparation protocol is mandatory. As a compromise between sample sizes of >500 ,m in diameter on the one hand and optimal preservation of antigenicity and morphology on the other, we developed a new preparation protocol that allows (i) 3D reconstruction of the resin-embedded sample by confocal light microscopy prior to (ii) direct immunolocalization of target proteins within selected sample planes by light and fluorescence microscopy or transmission electron microscopy. Alternatively, (iii) serial cryosections of the frozen sample can be taken for characterizing the sample in toto. With this unique approach we were able to fully demonstrate the structural complexity of axillary skin samples, increasing the structural resolution from 3D reconstruction of the whole gland up to ultrastructural investigations at the subcellular level. We could demonstrate that axillary sweat glands are not separately distributed, as has been assumed to date; instead, they seem to be intricately twisted into one another. This promotes the concept of a complex axillary sweat gland organ instead of single sweat gland entities. [source] | ||||||||||||||||||||||||||||||||||||||||||||||