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Target Structure (target + structure)
Selected AbstractsA New Approach for Health Monitoring of Structures: Terrestrial Laser ScanningCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 1 2007H. S. Park Three-dimensional (3D) coordinates of a target structure acquired using TLS can have maximum errors of about 10 mm, which is insufficient for the purpose of health monitoring of structures. A displacement measurement model is presented to improve the accuracy of the measurement. The model is tested experimentally on a simply supported steel beam. Measurements were made using three different techniques: (1) linear variable displacement transducers (LVDTs), (2) electric strain gages, and (3) a long gage fiber optic sensor. The maximum deflections estimated by the TLS model are less than 1 mm and within 1.6% of those measured directly by LVDT. Although GPS methods allow measurement of displacements only at the GPS receiver antenna location, the proposed TLS method allows measurement of the entire building's or bridge's deformed shape, and thus a realistic solution for monitoring structures at both structure and member level. Furthermore, it can be used to create a 3D finite element model of a structural member or the entire structure at any instance of time automatically. Through periodic measurements of deformations of a structure or a structural member and performing inverse structural analyses with the measured 3D displacements, the health of the structure can be monitored continuously. [source] Structural seismic response analysis based on multiscale approach of computing fault,structure systemEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 4 2009T. Ichimura Abstract Structural safety for earthquake waves emitted from a nearby fault is a major concern. For a large complex structure, it might be desired to estimate its seismic response by analyzing a fault,structure system: a full three-dimensional model in which a source fault and a target structure are modeled so that fault processes, wave propagation and amplification processes, and resulting dynamic responses of the structure can be computed numerically. To analyze this fault,structure system, this paper proposes an efficient approach based on multiscale analysis, i.e. waves emitted from the source fault are computed in the entire system in the geological length-scale; then they are refined in a small part of the system that includes the structure, and the seismic response of the structure is accurately computed in the engineering length-scale. Using a long highway tunnel as an example, this paper examines the validity of the proposed approach. The usefulness and applicability of the proposed approach to estimate the structural seismic responses are discussed. Copyright © 2008 John Wiley & Sons, Ltd. [source] Biophysical characterization of the interaction of high-density lipoprotein (HDL) with endotoxinsFEBS JOURNAL, Issue 23 2002Klaus Brandenburg The interaction of bacterial endotoxins [lipopolysaccharide (LPS) and the ,endotoxic principle' lipid A], with high-density lipoprotein (HDL) from serum was investigated with a variety of physical techniques and biological assays. HDL exhibited an increase in the gel to liquid crystalline phase transition temperature Tc and a rigidification of the acyl chains of the endotoxins as measured by Fourier-transform infrared spectroscopy and differential scanning calorimetry. The functional groups of the endotoxins interacting with HDL are the phosphates and the diglucosamine backbone. The finding of phosphates as target groups is in accordance to measurements of the electrophoretic mobility showing that the zeta potential decreases from ,50 to ,60 mV to ,20 mV at binding saturation. The importance of the sugar backbone as further target structure is in accordance with the remaining negative potential and competition experiments with polymyxin B (PMB) and phase transition data of the system PMB/dephosphorylated LPS. Furthermore, endotoxin binding to HDL influences the secondary structure of the latter manifesting in a change from a mixed ,-helical/,-sheet structure to a predominantly ,-helical structure. The aggregate structure of the lipid A moiety of the endotoxins as determined by small-angle X-ray scattering shows a change of a unilamellar/inverted cubic into a multilamellar structure in the presence of HDL. Fluorescence resonance energy transfer data indicate an intercalation of pure HDL, and of [LPS],[HDL] complexes into phospholipid liposomes. Furthermore, HDL may enhance the lipopolysaccharide-binding protein-induced intercalation of LPS into phospholipid liposomes. Parallel to these observations, the LPS-induced cytokine production of human mononuclear cells and the reactivity in the Limulus test are strongly reduced by the addition of HDL. These data allow to develop a model of the [endotoxin]/[HDL] interaction. [source] A structural optimization method based on the level set method using a new geometry-based re-initialization schemeINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 12 2010Shintaro Yamasaki Abstract Structural optimization methods based on the level set method are a new type of structural optimization method where the outlines of target structures can be implicitly represented using the level set function, and updated by solving the so-called Hamilton,Jacobi equation based on a Eulerian coordinate system. These new methods can allow topological alterations, such as the number of holes, during the optimization process whereas the boundaries of the target structure are clearly defined. However, the re-initialization scheme used when updating the level set function is a critical problem when seeking to obtain appropriately updated outlines of target structures. In this paper, we propose a new structural optimization method based on the level set method using a new geometry-based re-initialization scheme where both the numerical analysis used when solving the equilibrium equations and the updating process of the level set function are performed using the Finite Element Method. The stiffness maximization, eigenfrequency maximization, and eigenfrequency matching problems are considered as optimization problems. Several design examples are presented to confirm the usefulness of the proposed method. Copyright © 2010 John Wiley & Sons, Ltd. [source] Adverse drug reactions to biologicsJOURNAL DER DEUTSCHEN DERMATOLOGISCHEN GESELLSCHAFT, Issue 6 2010Kathrin Scherer Summary The use of biologics has rapidly expanded since the introduction of the first diagnostic antibodies; they are now widely employed in oncology, autoimmune disorders, inflammatory diseases and transplantation medicine. Their widespread use has resulted in an increase in adverse drug reactions. Adverse effects result from both direct pharmacological actions and immunological actions, as well as through induction of a specific immune response. The nomenclature, particularly of the monoclonal antibodies, identifies the target structure and organ as well as the species of origin, which then helps predict their effects and antigenic properties. Depending on the extent of foreign protein, anti-allotypic or anti-idiotypic antibodies with or without neutralizing properties may be induced. Adverse drug reactions from biologics often depend on the target and may be explained by activation or inhibition of particular cytokine pathways. Adverse drug reactions are classified by their pathomechanism, which enhances understanding of the pathogenesis and facilitates both allergologic diagnostic measures and planning of premedication in future treatments. This review emphasizes immunostimulatory and hypersensitivity reactions. [source] Computerized Task-Based Exposure, Explicitness, Type of Feedback, and Spanish L2 DevelopmentMODERN LANGUAGE JOURNAL, Issue 2 2004Elena M. Rosa This study examined whether exposure to second/foreign language (L2) data under different computerized task conditions had a differential impact on learners' ability to recognize and produce the target structure immediately after exposure to the input and over time. Learners' L2 development was assessed through recognition and controlled-production tests containing old and new exemplars of the target structure. Adult learners of Spanish were exposed to past conditional sentences under 1 of 6 conditions premised on different degrees of explicitness. The degree of explicitness was manipulated by combining 3 features: (a) a pretask providing explicit grammatical information, (b) feedback concurrent to input processing, and (c) variation in the nature (i.e., implicit or explicit) of the feedback in those cases in which it was provided. The advantages of processing input under explicit conditions were evident (a) in production more than in recognition and (b) in new exemplars more than in old exemplars. [source] Technical Aspects of RadiofrequencyPAIN PRACTICE, Issue 3 2002M. Sluijter MD If the resulting current flows through a percutaneously introduced electrode, heat will be produced around the electrode because the body tissue acts as a resistor. RF can, therefore, be used to ablate nervous tissue in the treatment of chronic pain. This method has gained acceptance for percutaneous cordotomy and for the treatment of trigeminal neuralgia. For spinal pain, the method had little success initially, but since the introduction of small diameter instrumentation, the results have markedly improved. he mechanism of action of RF has not been challenged until recently even though there was awareness that some observations were not consistent with the heat concept. The formation of heat is not the only occurrence during RF treatment, however. The tissue surrounding the electrode is also exposed to the RF electric field. This exposure has a biological effect as has been demonstrated both in cells in a cell culture and in the exposure to RF of dorsal root ganglia, resulting in transsynaptal induction of early gene expression in the dorsal horn. The mode of action of RF is, therefore, uncertain at the moment. The method of pulsed RF is based on the concept that the production of heat has been a by-product of RF treatment and that the clinical effect is due to exposure to the electric field. In pulsed RF, the generator output is interrupted to allow for the elimination of heat in the silent period. The early results have been encouraging, but the results of controlled, prospective studies are not yet available. Since there are now 2 almost diametrically opposed views on the mode of action of RF, it is difficult to give recommendations for treatment. The decision is easy for indications for which heat RF has traditionally been contraindicated such as the treatment of peripheral nerves and trigger points. When the application of heat carries a potential risk, for instance if the dorsal root ganglion is the target structure, the use of pulsed RF is also recommended. As for the medial branch the situation is controversial. Since there are controlled studies available showing the effect of heat lesions, it is recommended that the technique should not be changed until further studies have been completed. Finally, the equipment for RF treatment is described and safety issues are discussed. [source] The difference electron density: a probabilistic reformulationACTA CRYSTALLOGRAPHICA SECTION A, Issue 3 2010Maria Cristina Burla The joint probability distribution function P(E, Ep), where E and Ep are the normalized structure factors of the target and of a model structure, respectively, is a fundamental tool in crystallographic methods devoted to crystal structure solution. It plays a central role in any attempt for improving phase estimates from a given structure model. More recently the difference electron density ,q = ,,,p has been revisited and methods based on its modifications have started to play an important role in combination with electron density modification approaches. In this paper new coefficients for the difference electron density have been obtained by using the joint probability distribution function P(E, Ep, Eq) and by taking into account both errors in the model and in measurements. The first applications show the correctness of our theoretical approach and the superiority of the new difference Fourier synthesis, particularly when the model is a rough approximation of the target structure. The new and the classic difference syntheses coincide when the model represents the target structure well. [source] Molecular replacement: the probabilistic approach of the program REMO09 and its applicationsACTA CRYSTALLOGRAPHICA SECTION A, Issue 6 2009Rocco Caliandro The method of joint probability distribution functions has been applied to molecular replacement techniques. The rotational search is performed by rotating the reciprocal lattice of the protein with respect to the calculated transform of the model structure; the translation search is performed by fast Fourier transform. Several cases of prior information are studied, both for the rotation and for the translation step: e.g. the conditional probability density for the rotation or the translation of a monomer is found both for ab initio and when the rotation and/or the translation values of other monomers are given. The new approach has been implemented in the program REMO09, which is part of the package for global phasing IL MILIONE [Burla, Caliandro, Camalli, Cascarano, De Caro, Giacovazzo, Polidori, Siliqi & Spagna (2007). J. Appl. Cryst.40, 609,613]. A large set of test structures has been used for checking the efficiency of the new algorithms, which proved to be significantly robust in finding the correct solutions and in discriminating them from noise. An important design concept is the high degree of automatism: REMO09 is often capable of providing a reliable model of the target structure without any user intervention. [source] Design, synthesis, and characterization of a novel hemoproteinPROTEIN SCIENCE, Issue 2 2001Zhijin Xu Abstract Here we describe a synthetic protein (6H7H) designed to bind four heme groups via bis,histidine axial ligation. The hemes are designed to bind perpendicular to another in an orientation that mimics the relative geometry of the two heme a groups in the active site of cytochrome c oxidase. Our newly developed protein-design program, called CORE, was implemented in the design of this novel hemoprotein. Heme titration studies resolved four distinct KD values (KD1 = 80 nM, KD2 = 18 nM, KD3 , 3 mM, KD4 , 570 nM, with KD3 × K D4 = 1700); positive cooperativity in binding between the first and second heme, as well as substantial positive cooperativity between the third and forth heme, was observed. Chemical and thermal denaturation studies reveal a stable protein with native-like properties. Visible circular dichroism spectroscopy of holo-6H7H indicates excitonic coupling between heme groups. Further electrochemical and spectroscopic characterization of the holo-protein support a structure that is consistent with the predefined target structure. [source] The (Fo,Fc) Fourier synthesis: a probabilistic studyACTA CRYSTALLOGRAPHICA SECTION A, Issue 5 2008Rocco Caliandro (Fo,Fc) and (2Fo,Fc) Fourier syntheses are considered the most powerful tools for recovering the remainder of a structure and for correcting crystal structure models. A probabilistic approach has been applied to derive the formula for the variance for the expected value of the coefficient (Fo,Fc). This has allowed a better understanding of the features of the difference Fourier synthesis; in particular, a subset of well phased reflections has been separated from the subset of reflections best phased by the standard Fo Fourier synthesis. An iterative procedure, based on the electron-density modification of the difference Fourier map, has been devised which aims to improve phase and modulus estimates of the reflections with higher variance value, by using as lever arm the set of reflections with lower variance value. The new procedure (DEDM) has been implemented and verified on a wide set of test structures, the partial models of which were obtained by molecular replacement or by automatic model-building routines applied to experimental electron-density maps. Phase and modulus estimates of the difference Fourier syntheses improve in all the test cases; as a consequence, the quality of the difference Fourier maps also improves in the region where the target structure deviates from the partial model. A new procedure is suggested, combining DEDM with standard electron-density modification techniques, which leads to significant reduction of the phase errors. The procedure may be considered a starting point for further developments. [source] Visualisation of needle position using ultrasonographyANAESTHESIA, Issue 2 2006G. A. Chapman Summary Anaesthetists and intensivists spend a considerable proportion of their working time inserting needles and catheters into patients. In order to access deeper structures like central veins and nerves, they have traditionally relied on surface markings to guide the needle into the correct position. However, patients may present challenges due to anatomical abnormalities and size. Irrespective of the skill of the operator, there is the ever-present risk of needle misplacement with the potential of damage to structures like arteries, nerve bundles and pleura. Repeated attempts, even if ultimately successful, cause patient suffering and probably increase the risk of infection and other long term complications. Portable and affordable, high-resolution ultrasound scanners, has accelerated the interest in the use of ultrasound guidance for interventional procedures. Ultrasound guidance offers several advantages including a greater likelihood of success, fewer complications and less time spent on the procedure. Even if the target structure is identified correctly there is still the challenge to place the needle or other devices in the optimum site. The smaller and deeper the target, the greater the challenge and potential usefulness of ultrasound guidance. As a result of limited training in the use of ultrasound we believe that many clinicians fail to use it to its full potential. A lack of understanding, with regard to imaging the location of the needle tip remains a major obstacle. Needle visualisation and related topics form the basis for this review. [source] EDM,DEDM and protein crystal structure solutionACTA CRYSTALLOGRAPHICA SECTION D, Issue 5 2009Rocco Caliandro Electron-density modification (EDM) procedures are the classical tool for driving model phases closer to those of the target structure. They are often combined with automated model-building programs to provide a correct protein model. The task is not always performed, mostly because of the large initial phase error. A recently proposed procedure combined EDM with DEDM (difference electron-density modification); the method was applied to the refinement of phases obtained by molecular replacement, ab initio or SAD phasing [Caliandro, Carrozzini, Cascarano, Giacovazzo, Mazzone & Siliqi (2009), Acta Cryst. D65, 249,256] and was more effective in improving phases than EDM alone. In this paper, a novel fully automated protocol for protein structure refinement based on the iterative application of automated model-building programs combined with the additional power derived from the EDM,DEDM algorithm is presented. The cyclic procedure was successfully tested on challenging cases for which all other approaches had failed. [source] Cell-surface matrix proteins and sialic acids in cell-crystal adhesion; the effect of crystal binding on the viability of human CAKI-1 renal epithelial cellsBJU INTERNATIONAL, Issue 6 2003G. Kramer Objective To investigate the role of sialic acids and cellular matrix proteins as crystal-binding molecules in human calcium-oxalate nephrolithiasis. Materials and methods The well-defined human renal cancer cell line CAKI-1 was used a standard cell culture system. After enzymatic digestion of various cell surface molecules, the binding of ,2,6 (Sambucus nigra, SN-) and ,2,3 (Maackia amurensis, MA)-specific lectins to CAKI-1 cells was analysed. Simultaneously, the effect on adhesion and release of calcium oxalate monohydrate crystals was investigated (eight replicates). The effect of crystal adhesion on cell viability was assessed using Trypan blue exclusion (five replicates). Results Neuraminidase decreased MA-lectin binding of CAKI-1 cells by 39% (P < 0.05) but elevated SN-lectin binding by 812% (P < 0.05). Simultaneously, crystal binding to CAKI-1 cells was increased by 28% (P > 0.05). Pretreatment with collagenase type I, trypsin and dispase II reduced crystal-binding by 61,74% (P < 0.05) with no effect on sialic acid-specific lectin-binding. However, only collagenase type I and dispase (ratio 4 : 1) were also able to release crystals from their receptor-binding sites (P < 0.05). An increase in the number of cell surface-bound crystals correlated significantly with a decrease in cell viability (P < 0.05). Conclusions ,2,3-linked sialic acids protect cells from crystal-binding. Much greater SN-lectin binding associated with only moderately increased crystal binding argues against ,2,6-linked sialic acids as a main target structure of crystals. In contrast, collagen type I, type IV and/or fibronectin seem to be potent crystal-binding molecules on human renal epithelial cells, with collagen type I involved in a potential second step of crystal,cell interaction. [source] Recent development and potential use of µ- and ,-opioid receptor ligands in positron emission tomography studiesDRUG DEVELOPMENT RESEARCH, Issue 12 2006Gjermund Henriksen Abstract Quantitative non-invasive imaging of target structures in the human central nervous system provided by positron emission tomography (PET) permits investigation of the relationship between molecular events and pharmacological effects in living humans. Due to their prominent role in opiate and stimulant drug misuse and dependence, as well as in nociceptive signaling, µ- and ,-opioid receptors are potential targets for advances in neuro(psycho)pharmacological treatment of these illnesses and syndromes. In this review, we describe recent developments in specific positron emitting radiopharmaceuticals for these opioid receptor subclasses. Implications for further advances and clinical applications of the labeled ligands are discussed. Drug Dev. Res. 67:890,904, 2006. © 2007 Wiley-Liss, Inc. [source] Postnatal innervation of the rat superior colliculus by axons of late-born retinal ganglion cellsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2002Elizabeth J. Dallimore Abstract Rat retinal ganglion cells (RGCs) are generated between embryonic day (E) 13 and E19. Retinal axons first reach the superior colliculus at E16/16.5 but the time of arrival of axons from late-born RGCs is unknown. This study examined (i) whether there is a correlation between RGC genesis and the timing of retinotectal innervation and (ii) when axons of late-born RGCs reach the superior colliculus. Pregnant Wistar rats were injected intraperitoneally with bromodeoxyuridine (BrdU) on E16, E18 or E19. Pups from these litters received unilateral superior colliculus injections of fluorogold (FG) at ages between postnatal (P) day P0 and P6, and were perfused 1,2 days later. RGCs in 3 rats from each BrdU litter were labelled in adulthood by placing FG onto transected optic nerve. Retinas were cryosectioned and the number of FG, BrdU and double-labelled (FG+/BrdU+) RGCs quantified. In the E16 group, the proportion of FG-labelled RGCs that were BrdU+ did not vary with age, indicating that axons from these cells had reached the superior colliculus by P0/P1. In contrast, for the smaller cohorts of RGCs born on E18 or E19, the proportion of BrdU+ cells that were FG+ increased significantly after birth; axons from most RGCs born on E19 were not retrogradely FG-labelled until P4/P5. Thus there is a correlation between birthdate and innervation in rat retinotectal pathways. Furthermore, compared to the earliest born RGCs, axons from late-born RGCs take about three times longer to reach the superior colliculus. Later-arriving axons presumably encounter comparatively different growth terrains en route and eventually innervate more differentiated target structures. [source] Synthesis of Amino-Bridged Oligosaccharide MimeticsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 5 2010Janna Neumann Abstract Synthesis of amino-bridged oligosaccharides using reductive amination opens rapid access to novel glycomimetic target structures as potential ligands for the receptor protein NKR P1 of natural killer cells. Emphasis was laid on fast and facile synthetic routes. The carbonyl building blocks were easily obtained by oxidation with Dess,Martin periodinane or iodoxybenzoic acid (IBX). For the required amino-functionalized units, reduction of azide precursors was advantageous, and generation of the novel oligosaccharides was achieved by subsequent reductive amination. The target saccharide structures feature a bridging nitrogen atom inserted between two non-anomeric positions as well as including one anomeric position. [source] Synthesis of Novel Di- and Trisaccharide Mimetics with Non-Glycosidic Amino BridgesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 7 2007Janna Neumann Abstract Synthesis of novel di- and trisaccharides using enzymatic glycosylation, Dess,Martin oxidation and reductive amination allows rapid access to the target structures. Thus, a novel class of glycomimetics was obtained having nitrogen inserted as bridging atom between two non-anomeric positions. Novel di- and trisaccharide mimetics were designed using N -acetylglucosamine as a basis structure. A third monosaccharide unit was attached via an unnatural sugar,sugar bond without participation of the anomeric center. Their synthesis, proceeding via oxidation, glycosylation and reductive amination, required only a few steps, thus allowing rapid access to the target structures. Generation of the novel pseudo-disaccharide was achieved by Dess,Martin oxidation and a subsequent reductive amination. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Enantioselective Butenolide Preparation for Straightforward Asymmetric Syntheses of ,-Lactones , Paraconic Acids, Avenaciolide, and Hydroxylated EleutherolEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 9 2006Stefan Braukmüller Abstract The naturally occurring ,-lactones (+)-methylenolactocin (13) and its enantiomer, (+)-protolichesterinic acid (14) and its enantiomer, (+)-rocellaric acid (15), and the methylene bis(,-lactone) (,)-avenaciolide (16) were synthesized with 95,98,% ees in very few steps. Enantiocontrol was imposed by the asymmetric dihydroxylation of trans -configured ,,,-unsaturated carboxylic esters (namely compounds 1i, 1j, and 1n) with AD mix-,® [for the levorotatory target structures, except for (,)-avenaciolide] or AD mix-,® [for the dextrorotatory target structures plus (,)-avenaciolide]. ,,,-Unsaturated carboxylic ester 1e required increased amounts of the oxidant and auxiliary to produce the hydroxy lactone R,R - 3e, a precursor of the naphtho-,-lactone (+)-9-hydroxyeleutherol (12; 96,% ee). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Human antibody response during sepsis against targets expressed by methicillin resistant Staphylococcus aureusFEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 2 2000Udo Lorenz Abstract The identification of target structures is a prerequisite for the development of new treatment options, like antibody based therapy, against methicillin resistant Staphylococcus aureus (MRSA). In this study we identified immunodominant structures which were expressed in vivo during sepsis caused by MRSA. Using human sera we compared the immune response of humans with MRSA sepsis with the immune response of normal individuals and asymptomatically colonized individuals. We identified and characterized four staphylococcal specific antigenic structures. One target is a staphylococcal protein of 29 kDa that exhibited 29% identity to secreted protein SceA precursor of Staphylococcus carnosus. The putative function of this protein, which was designated IsaA (immunodominant staphylococcal antigen), is unknown. The second target is an immunodominant protein of 17 kDa that showed no homology to any currently known protein. This immunodominant protein was designated IsaB. The third and fourth antigens are both immunodominant proteins of 10 kDa. One of these proteins showed 100% identity to major cold shock protein CspA of S. aureus and the other protein was identified as the phosphocarrier protein Hpr of S. aureus. The identified immunodominant proteins may serve as potential targets for the development of antibody based therapy against MRSA. [source] Near-surface models in Saudi ArabiaGEOPHYSICAL PROSPECTING, Issue 6 2007Ralph Bridle ABSTRACT A single-layer model of the near surface throughout the Kingdom of Saudi Arabia is available. While this simple model suffices for most areas and large subsurface structures, it fails in situations where the surface topography is complex, the base of weathering is below the datum, or where the time structural closure is less than the uncertainty in the static correction. In such cases, multiple-layered models that incorporate velocities derived from analysis of first arrivals picked from seismic shot records have proved to be successful in defining the lateral heterogeneity of the near surface. The additional velocity information obtained from this first-arrival analysis (direct as well as refracted arrivals) vastly improves the velocity,depth model of the near surface, regardless of the topography. Static corrections computed from these detailed near-surface velocity models have significantly enhanced subsurface image focusing, thereby reducing the uncertainty in the closure of target structures. Other non-seismic methods have been used either to confirm qualitatively or to enhance the layer models previously mentioned. Gravity data may be particularly useful in sandy areas to confirm general structure, while geostatistical modelling of vibrator base-plate attributes has yielded information that enhances the velocity field. In the global context, exploration targets of the oil and gas industry are seeking smaller and lower relief-time structures. Thus, near-surface models will need to enhance and integrate these methods, particularly in areas where the assumption of flat-lying near-surface layers cannot be met. [source] On the Scope of a Prins -Type Cyclization of Oxonium IonsHELVETICA CHIMICA ACTA, Issue 11 2004Georg Fráter The Prins cyclization of an aldehyde 1 with a homoallylic alcohol 2, affording tetrahydro-2H -pyrans 4via the oxonium ion 3 as central intermediate, was conceptually transferred to (alk-3-enyloxy)acrylates 6, which form a related oxonium ion 7 upon treatment with acids (Scheme,1). The scope and utility of this modification of the Prins -type cyclization of oxonium ions is discussed exemplarily by means of the syntheses of ten tetrahydro-2H -pyran and tetrahydrofuran derivatives, featuring diverse substitution patterns as well as different degrees of molecular complexity. These target structures include (±)-ethyl (2RS)-2-[(2RS,4SR,6RS)- and (2SR,4RS,6SR)-2-tetahydro-4-hydroxy-6-methylpyran-2-yl]propanoate (23), (±)-ethyl [(2RS, 3RS)-tetrahydro-3-isopropenylfuran-2-yl]acetate (32), (±)-ethyl (2Z)-3-(tetrahydro-2,2-dimethylfuran-3-yl)acrylate (37), (±)-(3aRS,6RS, 7aRS)-octahydro-7a-methylbenzofuran-6-yl formate (42), (±)-ethyl (2RS,3RS,4aRS,8SR,8aRS)-hexahydro-2,5,5,8-tetramethyl-7-oxo-2H,5H -pyrano[4,3- b]pyran-3-carboxylate (48), and (±)-ethyl (2RS,3RS,6SR)-tetrahydro-6-(2-methoxy-2-oxoethyl)-3-methyl-2H -pyran-2-carboxylate (53) (see Schemes,3 and 5,8). Besides the stereochemistry and mechanistic details of this versatile oxonium-ion cyclization, the synthesis of suitable starting materials is also described. [source] A structural optimization method based on the level set method using a new geometry-based re-initialization schemeINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 12 2010Shintaro Yamasaki Abstract Structural optimization methods based on the level set method are a new type of structural optimization method where the outlines of target structures can be implicitly represented using the level set function, and updated by solving the so-called Hamilton,Jacobi equation based on a Eulerian coordinate system. These new methods can allow topological alterations, such as the number of holes, during the optimization process whereas the boundaries of the target structure are clearly defined. However, the re-initialization scheme used when updating the level set function is a critical problem when seeking to obtain appropriately updated outlines of target structures. In this paper, we propose a new structural optimization method based on the level set method using a new geometry-based re-initialization scheme where both the numerical analysis used when solving the equilibrium equations and the updating process of the level set function are performed using the Finite Element Method. The stiffness maximization, eigenfrequency maximization, and eigenfrequency matching problems are considered as optimization problems. Several design examples are presented to confirm the usefulness of the proposed method. Copyright © 2010 John Wiley & Sons, Ltd. [source] A Comparison of Echocardiographic Modalities to Guide Structural Heart Disease InterventionsJOURNAL OF INTERVENTIONAL CARDIOLOGY, Issue 6 2008PAUL A. HUDSON M.D. Percutaneous techniques to treat structural heart disease are rapidly evolving based on innovative interventions and the considerable advancement in image guidance technology. While two-dimensional transthoracic and transesophageal echocardiography have been integral to procedural planning and execution, intracardiac and three-dimensional echocardiography supply unique visualization of target structures with a potential improvement in patient safety and procedural efficacy. The choice of image guidance modality is based on specific differences between imaging systems, as well as other variables including cost, patient safety, operator expertise, and complexity of procedure. We will compare the adjunctive imaging tools for structural heart disease interventions, with a focus on intracardiac echocardiography and real-time three-dimensional transesophageal echocardiography. [source] Gene therapy approaches for Parkinson's diseaseJOURNAL OF NEUROCHEMISTRY, Issue 2003P. Aebischer The CNS delivery of glial cell line-derived neurotrophic factor (GDNF) for the treatment of Parkinson's disease constitutes one of the more promising clinical applications of neurotrophic factors. Crucial for clinical application will be the ability to deliver GDNF within the target structures, i.e. striatum and/or substantia nigra. We are developing both in vivo and ex vivo gene therapy approaches to reach this goal. We have shown in rodents that both lentiviral vectors coding for GDNF and polymer encapsulated cells genetically engineered to release GDNF are able to protect nigral dopaminergic neurons against various insults including axotomy and neurotoxins such as 6-hydroxydopamine. Even more important for clinical application is the ability to scale-up the technology to nonhuman primate application. Neurorestorative and/or neuroprotective properties of GDNF expression were demonstrated with both methods in various nonhuman primate models. [source] Influence of the frequency parameter on extracellular glutamate and ,-aminobutyric acid in substantia nigra and globus pallidus during electrical stimulation of subthalamic nucleus in ratsJOURNAL OF NEUROSCIENCE RESEARCH, Issue 2 2003François Windels Abstract High-frequency stimulation (HFS) of the subthalamic nucleus (STN) proves to be an efficient treatment for alleviating motor symptoms in Parkinson's disease (PD). However, the mechanisms of HFS underlying these clinical effects remain unknown. Using intracerebral microdialysis, we previously reported that HFS induces, in normal rats, a significant increase of extracellular glutamate (Glu) in the globus pallidus (GP in rats or GPe in primates) and the substantia nigra pars reticulata (SNr), whereas ,-aminobutyric acid (GABA) was increased only in the SNr. Bradykinesia can be improved by STN stimulation in a frequency-dependent manner, a plateau being reached around 130 Hz. The aim of the present study was to determine whether neurochemical changes are also frequency dependent. Electrical STN stimulation was applied at various frequencies (10, 60, 130, and 350 Hz) in normal rats. The results show that, for Glu, the amplitude of increase detected in GP and SNr is maximal at 130 Hz and is maintained at 350 Hz. No modifications of GABA were observed in GP whatever the frequency applied, whereas, in SNr, GABA increased from 60 to 350 Hz. Our results provide new neurochemical data implicating STN target structures in deep-brain-stimulation mechanisms. © 2003 Wiley-Liss, Inc. [source] Polygonal impact craters in Argyre region, Mars: Implications for geology and cratering mechanicsMETEORITICS & PLANETARY SCIENCE, Issue 10 2008T. ÖHMAN Such polygonal impact craters (PICs) are controlled by pre-existing target structures, mainly faults or other similar planes of weakness. In the Argyre region, Mars, PICs comprise , 17% of the total impact crater population (>7 km in diameter), and PICs are relatively more common in older geologic units. Their formation is mainly controlled by radial fractures induced by the Argyre and Ladon impact basins, and to a lesser extent by the basin-concentric fractures. Also basin-induced conjugate shear fractures may play a role. Unlike the PICs, ridges and graben in the Argyre region are mostly controlled by Tharsis-induced tectonism, with the ridges being concentric and graben radial to Tharsis. Therefore, the PICs primarily reflect an old impact basin-centered tectonic pattern, whereas Tharsis-centered tectonism responsible for the graben and the ridges has only minor influence on the PIC rim orientations. According to current models of PIC formation, complex PICs should form through a different mechanism than simple PICs, leading to different orientations of straight rim segments. However, when simple and complex PICs from same areas are studied, no statistically significant difference can be observed. Hence, in addition to enhanced excavation parallel to the strike of fractures (simple craters) and slumping along the fracture planes (complex craters), we propose a third mechanism involving thrusting along the fracture planes. This model is applicable to both simple and small complex craters in targets with some dominating orientations of structural weakness. [source] Involvement of Clusterin and the Aggresome in Abnormal Protein Deposits in Myofibrillar Myopathies and Inclusion Body MyositisBRAIN PATHOLOGY, Issue 2 2005I. Ferrer Myofibrillar myopathies (MM) are characterized morphologically by the presence of non-hyaline structures corresponding to foci of dissolution of myofibrils, and hyaline lesions composed of aggregates of compacted and degraded myofibrillar elements. Inclusion body myositis (IBM) is characterized by the presence of rimmed vacuoles, eosinophilic inclusions in the cytoplasm, rare intranuclear inclusions, and by the accumulation of several abnormal proteins. Recent studies have demonstrated impaired proteasomal expression and activity in MM and IBM, thus accounting, in part, for the abnormal protein accumulation in these diseases. The present study examines other factors involved in protein aggregation in MM and IBM. Clusterin is a multiple-function protein which participates in A,-amyloid, PrPres and ,-synuclein aggregation in Alzheimer disease, prionopathies and ,-synucleinopathies, respectively. ,-Tubulin is present in the centrosome and is an intracellular marker of the aggresome. Moderate or strong clusterin immunoreactivity has been found in association with abnormal protein deposits, as revealed by immunohistochemistry, single and double-labeling immunofluorescence and confocal microscopy, in MM and IBM, and in target structures in denervation atrophy. ,-Tubulin has also been observed in association with abnormal protein deposits in MM, IBM, and in target fibers in denervation atrophy. These morphological findings are accompanied by increased expression of clusterin and ,-tubulin in muscle homogenates of MM and IBM cases, as revealed by gel electrophoresis and Western blots. Together, these observations demonstrate involvement of clusterin in protein aggregates, and increased expression of aggresome markers in association with abnormal protein inclusions in MM and IBM and in targets, as crucial events related with the pathogenesis of abnormal protein accumulation and degradation in these muscular diseases. [source] | ||||||||||||||||||||||