Structure Analysis

Une comptabilité en temps de travail se caractérise essentiellement par le fait que les flux de biens et services, au lieu d'être évalués aux prix du marché, sont évalués en quantité de travail, c'est-à-dire soit en heures de travail, soit en hommes-années. Si l'on passe provisoirement sous silence les débats théoriques, la mise en oeuvre concrète d'une telle comptabilité consiste à mettre en rapport des flux de biens et de services avec les quantités de travail qu'ils contiennent, en considérant comme incorporés non seulement le travail direct fourni au dernier stade du processus de production, mais également le travail indirect nécessaire pour produire les consommations intermédiaires et reproduire le capital fixe utilisé. L'intérêt des comptabilités sociales en temps de travail est d'être avant tout un instrument d'analyse structurelle du fonctionnement du système productif. On a ainsi pu comparer le nombre d'emplois correspondant au produit de chacune des 28 branches du Tableau d'échanges interindustriels avec l'évaluation de ce même produit en prix. Également, le modèle a permis de calculer le nombre d'emplois correspondant aux exportations et à la consommation des ménages.

Within the eastern Himalayan syntaxis, carbonatite-like dykes occur in granulite facies gneisses of the Greater Himalayan Crystallines. Most dykes are dolomitic and are associated with scapolite-bearing hornblendite and glimmerite, which are separated from the country rocks by a selvage of altered rocks containing minerals such as diopside, tremolite, K-feldspar, albite, and calcite. Only a few dykes are calcitic with alteration halos containing wollastonite, calcite, anorthite, diopside, and scapolite. Dolomitic dykes as wide as several tens of metres contain irregular xenoliths of granulitic gneiss.

We present a MOF-based metamodel for the SA/RT (Structured Analysis for Real-Time Systems) design method. The metamodel provides a well-defined interpretation of the SA/RT elements, allowing the designer to create unambiguous specifications of systems. The metamodel was designed to be easily combined with UML and UML tools, in order to provide support for creating, editing and manipulating SA/RT models in UML environments. The approach allowed us, to specify and implement automated model transformations both between SA/RT models and between SA/RT and UML models.

We report the effect of average A-site cation radius on the structural, magnetic and electrical properties of electron doped manganite La 0.7 Ce 0.3 MnO 3 thin films. A site cation radius hr A i is varied systematically by partially replacing La C3 ions by smaller Y C3 ions in the parent compound. The carrier doping, i.e. the fraction of tetravalent Ce atoms at the A-site was kept at 30%. A series of La 0.7Kx Y x Ce 0.3 MnO 3 (xZ0, 0.05, 0.1, 0.15 and 0.25) thin films were prepared under identical conditions by using pulsed laser deposition technique. Metal-insulator transition temperature (T p ) and the ferromagnetic Curie temperature (T c ) are found to be decreasing significantly with increasing yttrium concentration, i.e. decreasing hr A i. The resistivity (r) at T p increases by one order of magnitude when the yttrium concentration is increased from xZ0 to 0.25, while magnetization decreases with decreasing hr A i. Magnetoresistance as measured under field of 1 T is significant near T c . Structural analysis reveals the films are having single phase and c-axis lattice parameter decreasing linearly as hr A i decreases. There is no marked difference in surface morphology of samples with different yttrium concentration. From EDX the Y:Ce:Mn ratio were consistent within 5% of the nominal composition. q

Conventional methods for road and airport pavement analyses, such as BISAR and GAMES, were developed based on a cylindrical coordinate system. Because of the loading symmetry due to the assumption that a circular uniformly distributed load is acting on the pavement surface, it was useful to use a cylindrical coordinate system. However, depending on the magnitude of the tire load, several research reports on tire-pavement contact stresses have shown that the contact patch is predominantly rectangular and not circular in shape. Based on this observation and the fact that it may be difficult for most multi-layer linear elastic software packages to make use of the field measured tire-pavement contact stresses, which are rectangular in shape, this paper presents the development of a method for pavement structural analysis considering both uniform and non-uniform loads acting over a rectangular area. In this approach, three components of displacements, which satisfy Navier's equations, are expressed using Neuber-Papkovich functions.Worked examples for vertical and horizontal loads acting over rectangular area are presented in this paper. In order to verify the validity of the solutions obtained, the results are compared with those obtained from freeware GAMES software, which analyses loads acting over a circular area and is widely used in Japan and South Africa and a number of institutions in Australia, Europe and US.

Abstract: Specification of a concurrent system using CAOS (Concurrent Action Oriented Specifications)(CAOS) as illustrated by Bluespec Inc.'s Bluespec System Verilog provides a high abstraction level, effective concurrency management through atomicity, and powerful compilation to efficient RTL hardware. In this paper, we present two algorithms that make CAOS to RTL synthesis power-aware and produce RTL that can be synthesized into hardware competitive in terms of power/area/slack trade-off against the well-known ...

Keywords: HIV-1 protease inhibitors; structure-based drug design; pyrrolidine-based inhibitors; crystallography; deviating binding modes Structure-based drug design is an integral part of industrial and academic drug discovery projects. Initial lead structures are, in general, optimized in terms of affinity using iterative cycles comprising synthesis, biological evaluation, computational methods, and structural analysis. X-ray crystallography commonly suggests the existence of a single well-defined state, termed binding mode, which is generally assumed to be consistent in a series of similar ligands and therefore used for the following optimization process. During the further development of symmetrically disubstituted 3,4-amino-pyrrolidines as human immunodeficiency virus type 1 protease inhibitors, we discovered that, by modification of the P1/P1′ moieties of our lead structure, the activity of the inhibitors towards the active-site mutation Ile84Val was altered, however, not being explainable with the initial underlying structure-activity relationship. The cocrystallization of the most potent derivative in complex with the human immunodeficiency virus type 1 protease surprisingly led to two different crystal forms (P2 1 2 1 2 1 and P6 1 22). Structural analysis revealed two completely different binding modes; the interaction of the pyrrolidine nitrogen atom with the catalytic aspartates remains as the only similarity. The study presented clearly demonstrates that structural biology has to escort the entire lead optimization process not to fail by an initially observed binding orientation.

One of the central problems in modern biology is to identify the complete set of interactions among the proteins in a cell. The structural interaction of proteins and their domains in networks is one of the most basic molecular mechanisms for biological cells. Structural evidence indicates that, interacting pairs of close homologs usually interact in the same way. In this article, we make use of both homology and inter-domain linker region knowledge to predict interaction between protein pairs solely by amino acid sequence information. High quality core set of 150 yeast proteins obtained from the Database of Interacting Proteins (DIP) was considered to test the accuracy of the proposed method. The strongest prediction of the method reached over 70% accuracy. These results show great potential for the proposed method.

An accepted assumption underlying application development is that the user is naive, with little understanding o f data processing . All the methods for handling the information system development process, from structured analysi s to prototyping, have in common a concern with user/developer communication, vet always under the assumption tha t users are alike in their capacity to understand dat a processing .

A search for noncanonical variants of the gypsy retrotransposon ( MDG4 ) in the genome of the Drosophila melanogaster strain G32 led to the cloning of four copies of the poorly studied 7411-bp gtwin element. Sequence analysis showed that gtwin belongs to a family of endogeneous retroviruses, which are widespread in the Drosophila genome and have recently been termed insect erantiviruses. The gtwin retrotransposon is evolutionarily closest to MDG4, as evident from a good alignment of their nucleotide sequences including ORF2 (the pol gene) and ORF3 (the env gene), as well as the amino acid sequences of their protein products. These regions showed more than 75% homology. The distribution of gtwin was studied in several strains of the genus Drosophila. While strain G32 contained more than 20 copies of the element, ten other D. melanogaster strains carried gtwin in two to six copies per genome. The gtwin element was not detected in D. hydei or D. virilis. Comparison of the cloned gtwin sequences with the gtwin sequence available from the D. melanogaster genome database showed that the two variants of the mobile element differ by the presence or absence of a stop codon in the central region of ORF3. Its absence from the gtwin copies cloned from the strain G32 may indicate an association between the functional state of ORF3 and amplification of the element.

Hydrocolloids and some of their mixtures were used to prepare spray-dried yogurt. Acetaldehyde retention and microbial viability were evaluated. Morphology was examined by scanning electron microscopy and the yield stress was evaluated, to assess the damage to the microstructure by the drying process. The yield stress displayed a significant irreversible decrease after spray drying and micrographs indicate that the microstructure of the yogurt was severely damaged by the drying process. Micrographs indicated that k-carrageenan and k-carrageenan-locust bean gum gave more protection to the casein matrix, leading to greater acetaldehyde retention (92% and 89%, respectively). Microbial viability was improved when pectin was used as the encapsulating agent.

A brief review of the literature on structural analysis of interpersonal be-havior is followed by a proposal which draws heavily from prior models, especially those of Schaefer and of Leary. The proposed model goes be-yond previous ones in that it has a highly explicit ...

In this work, the structural effects of the Ca substitution in YBa2Cu307_~ (Ca-123) have been studied by X-ray single crystal structure analysis for the first time. The structure refinements of three single crystals show that at low Ca concentrations (< 11%) y3+ ions are substituted, while at higher concentrations Ca 2÷ also replaces Ba 2÷. Remarkably, no difference in the structural changes has been observed that are due to the apparent substitution for Ba 2+ with Ca 2+ in the more heavily doped samples. Changes in atomic parameters and bond lengths are observed upon Ca doping which are similar in Ca-124 and Ca-247 single crystals. In contrast to ceramic samples, our Ca-123 single crystals are not superconducting probably due to AI doping from the crucible. However, considering doped superconductors, the discussion of structural changes with doping is quite interesting as this work is the first structure refinement of Ca-123 single crystals.

A social network is a graph where people or organizations (depending on the application) are represented as nodes connected by edges that can refer to either tight social bonds or some common, shared aspect. The graph structure analysis and the statistical analysis of specific node/edge attributes can reveal important individuals, relationships, and clusters. New information continues to be collected and stored, and size and complexity of the semantic graphs overwhelm the human cognitive abilities. Hence, it is necessary to improve the computational mechanisms to analyze such volume of data. In this paper, we focus on analyzing the information from social networks, extracting relevant knowledge, and visualizing the facts resultant from the analysis.

. Three cDNA clones encoding timothy grass pollen profilin Phl p 11 were newly isolated. Comparison of the sequences of four cDNA clones, including a previously isolated clone, showed a low level of polymorphism. Isoelectrofocusing of highly purified timothy grass profilin indicated the existence of at least five isoforms. One recombinant profilin showed similar immunological properties to natural timothy grass profilin. Tertiary structure of Phleum pratense profilin was obtained by homology-based molecular modeling. q 1997 Elsevier Science B.V.

Intermediate conformations are crucial to our understanding of how proteins fold into their native structures and become functional. Conventional spectroscopic measurements of thermal denaturation transitions allow the detection of equilibrium intermediates but often provide little structural detail; thus, application of more informative techniques is required. Here we used small-angle X-ray scattering (SAXS) to study the thermal denaturation of four variants of Anabaena PCC 7119 flavodoxin, including the wild-type apo and holo forms, and two mutants, E20K/E72K and F98N. Denaturation was monitored from changes in SAXS descriptors. Although the starting and final points of the denaturation were similar for the flavodoxin variants tested, substantial differences in the unfolding pathway were apparent between them. In agreement with calorimetric data, analysis of the SAXS data sets indicated a three-state unfolding equilibrium for wild-type apoflavodoxin, a two-state equilibrium for the F98N mutant, and increased thermostability of the E20K/E72K mutant and holoflavodoxin. Although the apoflavodoxin intermediate consistently appeared mixed with significant amounts of either native or unfolded conformations, its SAXS profile was derived from the deconvolution of the temperature-dependent SAXS data set. The apoflavodoxin thermal intermediate was structurally close to the native state but less compact, thereby indicating incipient unfolding. The residues that foster denaturation were explored by an ensemble of equilibrium ϕ-value restrained molecular dynamics. These simulations pointed to residues located in the cofactor and partner-protein recognition regions as the initial sites of *Corresponding authors. denaturation and suggest a conformational adaptation as the mechanism of action in apoflavodoxin.

A new method to apply spatial two-dimensional power spectral density (2D PSD) analysis to the data measured with Particle Image Velocimetry (PIV) has been introduced. Applying the method to a set of the velocity vector fields characteristic turbulence length scales can be estimated. In this method the computation of 2D PSD has been performed to two kinds of pre-processed data. In the first set, the local average has been spatially subtracted (Spatial decomposition) and in the second set the time-average has been subtracted (Reynolds decomposition). In the computation of 2D PSD the 2D FFT with the variance scaling has been used.

In this paper, seventeen different fish Antifreeze Proteins (AFPs) retrieved from Swiss-Prot database are analysed and characterized using In silico tools. Primary structure analysis shows that most of the AFPs are hydrophobic in nature due to the high content of non-polar residues. The presence of 11 cysteines in the rainbow smelt fish and sea raven fish AFPs infer that these proteins may form disulphide (SS) bonds, which are regarded as a positive factor for stability. The aliphatic index computed by Ex-Pasy's ProtParam infers that AFPs may be stable for a wide range of temperature. Secondary structure analysis shows that most of the fish AFPs have predominant α-helical structures and rest of the AFPs have mixed secondary structure. The very high coil structural content of rainbow smelt fish and sea raven fish AFPs are due to the rich content of more flexible glycine and hydrophobic proline amino acids. Proline has a special property of creating kinks in polypetide chains and disrupting ordered secondary structure. SOSUI server predicts one transmembrane region in winter flounder fish and atlantic cod and two transmembrane regions in yellowtail flounder fish AFP. The predicted transmembrane regions were visualized and analysed using helical wheel plots generated by EMBOSS pepwheel tool. The presence of disulphide (SS) bonds in the AFPs Q01758 and P05140 are predicted by CYS_REC tool and also identified from the three-dimensional structure using Rasmol tool. The disulphide bonds identified from the three-dimensional structure using the Rasmol tool might be correct as the evaluation parameters are within the acceptable limits for the modelled 3D structures.

The EF-hand family is a large set of Ca 2+ -binding proteins that contain characteristic helix-loop-helix binding motifs that are highly conserved in sequence. Members of this family include parvalbumin and many prominent regulatory proteins such as calmodulin and troponin C. EF-hand proteins are involved in a variety of physiological processes including cell-cycle regulation, second messenger production, muscle contraction, microtubule organization and vision.

We have developed new algorithms for efficient and flexible pattern-matching and pattern-discovery in multidimensional datasets. (A multidimensional dataset is simply any set of points in an N-dimensional space.) These algorithms could be used as the basis of new commercially exploitable applications for data compression, information retrieval and data mining or structural analysis of data. The new algorithms are particularly appropriate for use with databases in which each item in the database is represented as a multidimensional dataset, as is the case, for example, in computer-based music libraries and databases of audio data, databases of 2- and 3-dimensional molecular structures, computer-based image and video libraries and collections of graphs representing scientific results or financial data.

Abstract-Technology foresight deals with the necessity of anticipating the future to better adapt to new situations regarding innovations that directly affect business world. One widely spread methodology in technology foresight is Godet&apos;s Scenario Method, which includes a module (MICMAC) performing the so-called structural analysis. The goal of the structural analysis is to identify the most important variables in a system. To this end, it makes use of an influence matrix that describes the relations between the variables. This information is usually given by experts based on their own knowledge and experience. However, some of the information of the influence matrix may contain errors due to the subjective nature of the criteria and opinions of the experts. Here we propose a new analysis that follows a multi-objective approach and allows to measure the sensibility of the model versus possible errors at the input. The well-known NSGA-II algorithm has been used as a solver. The...

Some types of anodes that could replace the usual carbon anodes in aluminium production by the Hall-Heroult process are based on SnO 2. The present investigation deals with SnO 2-Sb 2 O 3-CuO ceramics having an SnO 2 content of 96%), Sb 2 O 3 and CuO being dopants. The ceramic pellets, thermally treated at 1400 C for 4 hours, were analysed by X-ray diffraction and IR spectroscopy. The structural analysis of the samples evidenced an SnO 2 (ss) type solid solution. All samples were electronically conductive (small negative values of the Seebeck coefficients), having an activation energy ranging within 0.02-0.3 eV. The anodic polarisation curves obtained with those anodes in an electrolyte of 88% Na 3 AlF 6 , 7% Al 2 O 3 and 5% CaF 2 were studied. The results were correlated with the microstructure of the investigated samples.

Secondary elements such as barriers, sidewalks, and diaphragms may increase the load carrying capacity of girder bridges. This in turn affects reliability. The objective of this study is to evaluate the potential benefit of secondary elements on the system reliability of girder bridges, if these elements are designed with the structural system to participate resisting vehicular live loads. Simple span,

Evolutionary Testing is an emerging methodology for automatically generating high quality test data. The focus of this paper is on presenting an approach for generating test cases for the unit-testing of object-oriented programs, with basis on the information provided by the structural analysis and interpretation of Java bytecode and on the dynamic execution of the instrumented test object. The rationale for working at the bytecode level is that even when the source code is unavailable, insight can still be obtained and used to guide the search-based test case generation process. Test cases are represented using the Strongly Typed Genetic Programming paradigm, which effectively mimics the polymorphic relationships, inheritance dependences and method argument constraints of object-oriented programs.

The present paper is concerned with the development of an analytical model, based on Classical Lamination Theory, to predict the stiffness of twill in composites. A very simple yet quite general model is developed to obtain the elastic properties, i.e. extensional stiffness (A), extension±bending coupling stiffness (B) and bending stiffness (D). The model takes into account effects of the fabric structure by considering tow undulations and continuity along both the ®ll and warp directions. Various tow cross sections are possible and can be easily incorporated for a particular application. The model results in simple formulae for calculating in-plane and bending elastic constants, which can be used further in structural analysis.

In this work numerical structural analysis by the finite element method (FEM) is used in order to study the structural collapse of a Second World War (WWII) lattice tower. The study is divided into two different stages: a forensic pre-diagnostic stage (first) and pathologic analysis and diagnostic stage (second). In the first stage, the causes and the origin of the collapse are determined based on only on the symptoms. In the second stage the failure mechanics are established and these are proven. The entire FEM model is built through beam elements and the design of experiments (DOE) method was employed to limit the number of simulations required, significantly saving on the computational time needed to arrive at a diagnostic. Based on analytical results, it is concluded that the main variables in the structural collapse are: the corrosion of the wire ropes and the wind load. A buckling analysis, both linear and nonlinear, is also carried out to verify and to check that the collapse hypothesis for the communications tower is right. Finally the conclusions of this study are given.

The preparation of Ce(OH) 3 /CeO 2 nanostructures (NSs) through electrogeneration of base into anodic alumina membranes was studied. The effects of solvent (alcohol and/or water), Ce 3? partner anion nature (chloride or nitrate) and concentration, applied potential or current density in driving the morphology toward nanowires (NWs) and/or nanotubes (NTs) was described. The structural analysis performed by X-Ray Diffraction and Raman Spectroscopy allowed to evidence that the presence of Ce(IV) into the nanostructures strongly depends on the oxygen content in the growing environment.

Activity theory has been successfully applied in diverse schools of psychology with particularly extensive work in the fields of education, ergonomics, human factors and industrial-organizational psychology. However, existing efforts of translation and formulation in English suffer from certain limitations. These limitations include the blurring between Vygotsky's sociocultural theory of the development of mind and activity theory, the restriction of activity theory in its entirety to the version offered by Leont'ev, errors in the interpretation of some basic concept and terminology, reliance on studies that use obsolete methods, and failure to consider the Russian work in activity theory in its entirety. This last problem results in the omission of the recent advances in engineering psychology and educational psychology in the former Soviet Union that facilitates the application of activity theory to practical problems. This paper is a description of the evolution of basic theory, concepts and terminology relevant to practitioners-particularly in the field of ergonomics.

A pulsed time-of-flight laser range finder with a 1 GHz avalanche photo diode ͑APD͒ receiver and a laser pulser with ϳ35 ps pulse width has been developed and tested. The receiver channel is constructed using a silicon ASIC chip and a commercially available silicon APD placed on a hybrid ceramic susbstrate. The laser pulser utilizes a single heterostructure laser operating in Q-switching mode. It is shown that the single-shot precision of the complete laser range finder is ϳ2.1 mm ͑ value͒ at best. The nonaccuracy in the distance range of 0.5-34.5 m was ϳϮ2 mm excluding errors caused by the statistical variations and long-term instability. The single-shot precision is clearly better than the single-shot precision of the earlier laser range finders with ϳ100-200 MHz bandwidths. Also, two types of optics, coaxial and paraxial, were tested. The linearity of the coaxial optics was better, especially with a long ͑4 m͒ receiver fiber. Some possible applications of the laser range finder utilizing ps level pulses are, for example, fast three-dimensional vision in industrial environments and structure analysis of materials.

By combining mild alkaline hydrolysis with quantitative 31 P NMR we have been able to arrive at a protocol for determining the various ester linkages and their relative contributions to the overall structure of wheat straw lignin. Additional information on the identity and location of these bonds was sought by the application of GC/MS and two-dimensional 13 C-1 H heterocorrelation NMR experiments. Milled straw lignin was found to contain about 12 ester units per 100 phenylpropane units. Approximately 77% of the carboxyl fraction of these ester bonds was found to be composed of p-coumaric acid while the rest was other aromatic acids bound to lignin via intra-and/or intermolecular ester bonds. In contrast, the hydroxyl fraction of the ester bonds was found to be almost exclusively aliphatic. A small fraction (about 1.6%) of the milled straw lignin units was found to be esterified through the phenolic hydroxyl groups of C-5 condensed phenolic units. The application of 13 C-1 H correlative NMR experiments revealed that acylation occurs only at the γ-position of the lignin side chain. Detailed studies of two-dimensional HOHAHA and HMQC experiments failed to show evidence for the presence of R-O-4 substructures in milled wheat straw lignin.

Nondestructive structural analysis of a series of β-d-(1→3, 1→6)-linked glucans (laminaran, curdlan, yeast glucan, scleroglucan, etc.) was performed using two-dimensional NMR spectroscopy. The relative ratios of H-1 at different AGUs provided the information about DPn and DB. The α-, and β-anomeric protons on reducing terminals were assigned at 5.02∼5.03 ppm (J 3.6∼3.7 Hz), and 4.42∼4.43 ppm (J 7.6∼7.9 Hz), respectively, whereas the H-1 protons of internal AGUs and β-(1→6)-branched AGUs appeared at 4.56∼4.59 ppm (J 7.6∼7.8 Hz), and 4.26∼4.28 ppm (J 7.6∼10.6 Hz), respectively, in a mixed solvent of 6:1 Me2SO-d6–D2O at 80°C. In the solvent, the OH peaks were eliminated from the spectra allowing the H-1 protons to appear clearly. In addition, the nonreducing terminal H-1 and H-1 at the AGU next to reducing terminal could be assigned at 4.45∼4.46 ppm (J 7.8∼7.9 Hz), and 4.51∼4.53 ppm (J 7.8 Hz), respectively. The DPn of the laminaran was 33 (polydispersity 1.12) and the DB was 0.07. The number of glucosyl units in the side chain of laminaran is more than one. The DPn and DB of the water-insoluble yeast glucan were 228 and 0.003, respectively. However the DPn of water soluble yeast glucan phosphate and curdlan was changed upon the number of freeze-drying processes and the content of water in the mixed solvent, respectively. And the DB of those were calculated as 0.02 and 0, respectively. The DB of scleroglucan was precisely calculated as 0.33, compared with the previously reported data. The H-1s at different AGUs of the various β-d-(1→3, 1→6)-linked glucans having different DB can be exactly assigned by their chemical shifts in the mixed solvent system. This NMR analysis can be effectively used to determine the DP and DB of polysaccharides in a simple and non-destructive manner.

There are many ancient masonry arch bridges still in use within the actual transportation. Some of these bridges are in need of special attention because they are subject to potentially destructive conditions, such as increased traffic loads and intense vibrations produced by their new functions, and these stresses are compounded by their age. To preserve these functional structures, structural assessment is necessary or, at least, highly recommended. However, many of the details of these structures are underground and are therefore hidden from view. In recent decades, ground-penetrating radar (GPR) has shown potential for internal bridge evaluation. The Roman Bibei bridge (Spain) was surveyed with GPR to analyse its inner state of conservation. The GPR survey was conducted using 250 and 500 MHz antennas. The interpretation and analysis of the GPR data were supported by finite-difference time domain numerical modelling based on the precise external geometry provided by threedimensional laser scanning methods. Both real and synthetic results reveal that GPR evaluation provides unknown structural details and possible modifications over time. The internal ring stone thickness was also measured, which represents valuable information for engineers to perform an exhaustive assessment of the load carrying capacity of the bridge.

Recently the Eurocode on Accidental Actions, officially referred to as EN 1991-1-7, has been completed. The code describes the principles and application rules for the assessment of accidental actions on buildings and bridges. The leading design principle is that local damage is acceptable, provided that it will not endanger the structure and that the overall load-bearing capacity is maintained during an appropriate length of time to allow necessary emergency measures to be taken. As measures to mitigate the risk various strategies are proposed like prevention of actions, evacuation of persons, physical protection of the structure and sufficient structural redundancy and ductility. The code makes a clear distinction between identified and unidentified accidental actions. For the identified accidental actions (impact, explosions) a structural analysis is proposed, the level of which may depend on the envisaged consequences of failure. It may vary from an analysis on the basis of stat...

Purpose: This study sought to aggregate literature data on in vitro failure loads and failure modes of prefabricated fiber-reinforced composite (FRC) post systems and to compare them to those of prefabricated metal, custom-cast, and ceramic post systems. Materials and Methods: The literature was searched using MEDLINE from 1984 to 2003 for dental articles in English. Keywords used were (post or core or buildup or dowel) and (teeth or tooth). Additional inclusion/exclusion steps were conducted, each step by two independent readers: (1) Abstracts describing postand-core techniques to reconstruct endodontically treated teeth and their mechanical and physical characteristics were included (descriptive studies or reviews were excluded); (2) articles that included FRC post systems were selected; (3) in vitro studies, single-rooted human teeth, prefabricated FRC posts, and composite as the core material were the selection criteria; and (4) failure loads and modes were extracted from the selected papers, and failure modes were dichotomized (distinction was made between "favorable failures," defined as reparable failures, and "unfavorable failures," defined as irreparable [root] fractures). Results: The literature search revealed 1,984 abstracts. Included were 244, 42, and 12 articles in the first, second, and third selection steps, respectively. Custom-cast post systems showed higher failure loads than prefabricated FRC post systems, whereas ceramic showed lower failure loads. Significantly more favorable failures occurred with prefabricated FRC post systems than with prefabricated and custom-cast metal post systems. Conclusion: The variable "post system" had a significant effect on mean failure loads. FRC post systems more frequently showed favorable failure modes than did metal post systems. Int J Prosthodont 2004;17:476-482.

Since nearly all adult insects fly, the cuticle has to provide a very efficient and lightweight skeleton. Information is available about the mechanical properties of cuticle-Young's modulus of resilin is about 1 MPa, of soft cuticles about 1 kPa to 50 MPa, of sclerotised cuticles 1 -20 GPa; Vicker's Hardness of sclerotised cuticle ranges between 25 and 80 kgf mm 22 ; density is 1 -1.3 kg m 23 -and one of its components, chitin nanofibres, the Young's modulus of which is more than 150 GPa. Experiments based on fracture mechanics have not been performed although the layered structure probably provides some toughening. The structural performance of wings and legs has been measured, but our understanding of the importance of buckling is lacking: it can stiffen the structure (by elastic postbuckling in wings, for example) or be a failure mode. We know nothing offatigue properties (yet, for instance, the insect wing must undergo millions of cycles, flexing or buckling on each cycle). The remarkable mechanical performance and efficiency of cuticle can be analysed and compared with those of other materials using material property charts and material indices. Presented in this paper are four: Young's modulus-density (stiffness per unit weight), specific Young's modulus-specific strength (elastic hinges, elastic energy storage per unit weight), toughness-Young's modulus (fracture resistance under various loading conditions), and hardness (wear resistance). In conjunction with a structural analysis of cuticle these charts help to understand the relevance of microstructure (fibre orientation effects in tendons, joints and sense organs, for example) and shape (including surface structure) of this fibrous composite for a given function. With modern techniques for analysis of structure and material, and emphasis on nanocomposites and self-assembly, insect cuticle should be the archetype for composites at all levels of scale. q

A homologous series of new gemini cationic surfactants were synthesized and characterized using micro elemental analysis, FTIR, 1H-NMR and mass spectra. The surface activities of these amphiphiles were determined based on the data of surface tension. Critical micelle concentration, effectiveness of the surface tension reduction, efficiency of adsorption, maximum surface excess, minimum surface area and critical packing parameter were evaluated. The effect of cationic micelles on solubilization of anionic azo dye, sulforhodamine B (Acid Red 52) in aqueous micellar solution of the synthesized gemini cationic surfactants was studied at pH 6.9 ± 0.5 and 25 °C. The results showed that the solubility of dye rose with increasing surfactant concentration as a consequence of some association between the dye and the micelles. It was also observed that the aggregation of surfactant and dye takes place at a surfactant concentration below the CMC of the individual surfactant. The partition coefficients between the bulk water and surfactant micelles as well as the Gibbs energies of distribution of dye between the bulk water and surfactant micelles were calculated using a pseudo-phase model. The effect of the hydrophobic chain length of Gemini cationic surfactants on the distribution parameters was also reported. The results show favorable solubilization of dye in cationic micelles.